LU103267B1

LU103267B1 - Optical system, control system and light steering projector

Info

Publication number: LU103267B1
Application number: LU103267A
Authority: LU
Inventors: Dirk Maes; Dries Doornaert; Bart Maximus
Original assignee: Barco Nv
Priority date: 2024-03-21
Filing date: 2024-03-21
Publication date: 2025-09-22

Abstract

Current light steering architectures use individual phase modulators per color channel, or even two modulators per color channel when the phase modulators requires polarized light and the light from the laser source is unpolarized. While this offers the advantage that specific patterns can be generated for the individual color channels, it also increases the system complexity and cost. The invention reduces system complexity and cost by using a single spatial phase modulator to simultaneously or sequentially modulate the three primary colors and generate a white highlight image. In case where the phase modulator requires polarized light and the incoming light is unpolarized, a two-modulator architecture may be used, where each of two phase modulators modulates one of two polarization directions for the three primary colors and generate a white highlight image.

Description

D/BARUXR-019-DE Description

B220012

LU103267 -1-

BARCO NV

8500 Kortrijk, BE

Optical System, Control System and Light Steering Projector

TECHNICAL FIELD

The invention relates to an optical system, a control system for controlling the optical system and a light steering projector using the same.

TECHNICAL BACKGROUND

In recent years, so-called light steering projectors have been developed, in which in addition to a so-called baselight image a so-called highlight image are used to produce very realistic images.

DISCLOSURE OF THE INVENTION

Current light steering projector architectures use individual spatial phase modulators per color channel (i.e., per primary color), or even two spatial phase modulators per color channel when the spatial phase modulators require polarized light and the light from the laser source is unpolarized. While this offers the advantage that specific patterns can be generated for the individual color channels, it also increases the system complexity and cost.

The invention is based on the problem of reducing system complexity and cost of light steering projectors and systems employed therein.

The problem is solved by a light steering projector and systems therefor as disclosed herein. Surprisingly, it has turned out to be possible to use a single spatial

D/BARUXR-019-DE Description

B220012

LU103267 -2- phase modulator to simultaneously or sequentially modulate the three primary colors and generate a white highlight image. In case where the phase modulator requires polarized light and the incoming light is unpolarized a two-modulator architecture may be used, where each of two phase modulator modulates one of two polarization directions for the three primary colors and generate a white highlight image.

According to a first embodiment, an optical system for use in a light steering projector comprises a plurality of optical sub-systems, a first sub-system being an illumination sub-system for outputting light of three primary colors, wherein the illumination optical sub-system is operably connected to a second optical sub-system being an intermediate optical sub-system, the intermediate optical sub-system comprising one single spatial phase modulator and wherein the single spatial phase modulator is configured to simultaneously or sequentially modulate light from the illumination sub-system to generate a white highlight image.

According to a second embodiment, an optical system for use in a light steering projector comprises a plurality of optical sub-systems, a first sub-system being an illumination sub-system for outputting light of three primary colors, wherein the illumination optical sub-system is operably connected to a second optical sub-system being an intermediate optical sub-system, the intermediate optical sub-system comprising a single set of two spatial phase modulators, each spatial phase modulator modulating light of a different polarization, and wherein each of the two spatial phase modulators is configured to simultaneously or sequentially modulate light from the illumination sub-system to generate a white highlight image and

In this case, the optical system may further comprise a polarizing beam splitter splitting light from the illumination sub-system into two polarized light paths, each light path directed onto a different one of said two spatial phase modulators, and a broadband half-wave retarder in one of the two polarized light paths to change the polarization

D/BARUXR-019-DE Description

B220012

LU103267 -3- state in that one light path and realize a same polarization state of the light imaged on the intermediate highlight image on the intermediate image plane. in both the first and second embodiments, the system may further comprise a color- dependent optical path length compensator located on an optical path between the single spatial phase modulator and an intermediate image plane, said optical path length compensator configured to compensate at least two path lengths of light selected from the three primary colors for forming an intermediate highlight image on the intermediate image plane. Such path length compensator may appear as ong a compact unit or may appear in the form of separate sub-compensators for each color for which the optical path length shall be compensated.

A particular advantage of such embodiment is, that it not only facilitates a cost effective solution for light steering projectors employing a time sequential operation of light sources of different primary colors, but also for light steering projectors in which at least two, preferably three primary colors are simultaneous handled, so that light of two or even three different wavelengths is steered at the same time, which is made possible by the optical path length compensator, which ensures that highlights fall on the same location in an highlight image.

In this conjunction, the present invention also relates to white or multicolored light sources, i.e. three or more primary colors, optical sub-systems for projectors as well as methods of constructing and using white or multicolored light sources for optical sub-systems for projectors to generate highlights for projected or displayed images.

The present invention also relates to projectors able to present multicolored projected images with highlights, e.g. white highlights and methods of constructing and using such projectors. In particular, the present invention relates to a color dependent path length compensator and methods of constructing and using a color dependent path length compensator placed in an optical path between a single spatial phase modulator (e.g. for unpolarized light operation or optionally for polarized light operation) or a single set of two spatial phase modulators (polarized light operation) and an intermediate image plane. It is an object of the present invention that highlights for all colors fall together at the target image (intermediate

D/BARUXR-019-DE Description

B220012

LU103267 -4- image at the intermediate image plane), that have a "white" highlight pattern without or without a lot of color misconvergence. With only one spatial phase modulator (SPM) having more than one colored light incident simultaneously on the SPM, the highlights with different colors will emit under different angles per color, as diffraction is wavelength dependent and hence will land on different spots. The path length compensation is provided to counter this effect.

The present invention also relates to projectors or optical sub-systems suitable for use in a projector or projection apparatus namely for projecting multicolor images with highlights, e.g. white highlights (or multicolored highlights) as well as to methods of delivering multicolor images with highlights, e.g. white highlights (or multicolored highlights) for projection. In any implementation of the present invention, it may be that the PSF (Point Spread Function) (i.e., location, size and profile) has an illumination spot one will obtain when all the light is steered to the exact same location. With a point source, one would obtain a point result, but with real sources with the extend they have the point will become a "blob" with a certain

PSF. One can use the FWTM (Full Width at Tenth of Maximum) metric to indicate the size of the PSF, often expressed in percentage of the imager (spatial amplitude modulator) width or screen width. The PSF size can be with a range of 5-20% of the total image(r) width in accordance with this metric.

The PSF profiles and the highlight images for the at least two e.g. 3 primary colors can be a little bit different from each other, and, hence, don't produce a completely non-colored, or thus white, highlight image. In reality, there can be remaining color fringes around such "white" highlight images. These color fringes can be eliminated or reduced by a single or multiple imagers (which are spatial amplitude modulators), i.e. should be able to clean up such color fringes by applying small corrections different for each light color.

An illumination optical sub-system and a method of using an illumination optical sub- system, are described, e.g. having a single white laser light source or multicolored laser light sources for emitting laser light which is white or having at least two, e.g. three or more primary colors. The illumination optical sub-system can include an

D/BARUXR-019-DE Description

B220012

LU103267 -5- uniformizer such as a fiber. The uniformizer can be a common uniformizer for all laser light beams, e.g. light emitted by a single white laser light, or laser light of two, three or more primary colors. Alternatively, uniformizers can be individual color dependent uniformizers, e.g. individual fibers, each processing individual colored light beams. The illumination optical sub-system also include a common collimator for collimating or substantially collimating white light or three or more primary colored lights. Collimators can be individual collimators, each for processing an individual colored light beam. Multiple light beams of different colors exiting the individual collimators can be combined by a combiner such as by mirrors, e.g. including at least one primary color pass dichroic mirror such as a red pass dichroic mirror whereas other dichroic mirrors reflect one or two of the other primary colors such as green and blue. The illumination optical sub-system can deliver collimated or substantially collimated white light to an intermediate optical sub-system, for example, when the highlights are to be white.

An intermediate optical sub-system and a method of using an intermediate optical sub-system are aspects of the present invention. The intermediate optical sub- system can comprise a single spatial phase modulator, and a color dependent optical path length compensator. It should be noted that for sake of simplicity, in the claims only one optical path length compensator is mentioned, while more than one such compensator may be foreseen, as apparent for a skilled person.

A spatial phase modulator may have an array of individually addressable pixels, which form an adjustable grating displayed or published on the spatial phase modulator. The adjustable grating forms phase patterns, which steer the light, which is output from the spatial phase modulator. The single spatial phase modulator is controlled to apply phase shifts, which make up the phase patterns to steer light incident on the spatial phase modulator to a common target or image plane. The light steered by the single spatial phase modulator provides image areas of greater light intensity i.e. provide highlights, and image areas of less light intensity.

Accordingly, a major output of the single spatial phase modulator is steered light which is provided for forming an intermediate highlight image at an intermediate

D/BARUXR-019-DE Description

B220012

LU103267 -6- image plane. The intermediate highlight image can be provided on a static or dynamic diffuser such as a spinning diffuser or a diffuser with some movement such as a two-dimensional (2D) movement. The static or dynamic diffuser can be placed at (i.e. in the vicinity of) or in the intermediate highlight image plane. This will allow sufficient de-speckling though it will slightly increase the blurring of the image being processed. Furthermore, on ore, more intermediate highlight images can be provided in one or more intermediate image planes between the single spatial phase modulator or the single set of two spatial phase modulators and a spatial amplitude modulator or modulators. A diffuser such as a static or dynamic diffuser can be placed in each of these intermediate image planes. This is done for redundancy, for example to keep good speckle performance and a good laser classification even if one diffuser would fail.

The optical path length compensator is placed on an optical path between the single spatial phase modulator and the intermediate image plane or between the single set of two spatial phase modulators and the intermediate image plane. (With respect to the single set of two spatial phase modulators, each of these two spatial phase modulators will still process all three primary colors. It is not so that one color goes to one spatial phase modulator and two colors go to the other). Part of the light from the single spatial phase modulator or from the single set of two spatial phase modulators can be and usually is unsteered light.

Unsteered light is usually and mainly obtained by reflection from certain parts of the single set of two spatial phase modulators or of the single spatial phase modulator or on transmission through the single set of two spatial phase modulators or the single spatial phase modulator or from the other diffractive orders than the one used as steered light. This unsteered light is output by the single spatial phase modulator or by the single set of two spatial phase modulators but it is strictly speaking not “modulated light”. There is usually a much lower degree of “modulation” of the unsteered light compared to the modulation that is required to make the steered light. Any such “modulation” of the unsteered light is not deliberate. No programmed and adjustable highlights are made by the unsteered “modulated” light. Color- dependent unsteered light behavior is considered to be a negligible fluctuation of the

D/BARUXR-019-DE Description

B220012

LU103267 -7- “baseline light”, because of the blurring caused by the angular spread in the single spatial phase modulator. The modulation of the unsteered light is only a small effect and can be ignored.

Accordingly, the single spatial phase modulator modulates light received from the illumination sub-system and the modulated light is used to form an image with highlights on an intermediate image sub-system.

The following disclosure applies to each embodiment of the present invention, in particular to the embodiments of each of the figures, 9, 10, 11, 12 as well as the

RGB plus white segment explained by reference to Fig. 13:

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating which is a phase image, for instance a multiple of pixels with a different phase content that are published or displayed on a spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the specularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing linked to the pixel pitch of the spatial phase modulator (displaying or publishing any phase grating) has to be greater than the largest horizontal or vertical dimension of the steering target area increased with the size of the PSF. With such a minimum required path length the PSF of that color is as small as possible. A longer path length results in a wider PSF. The minimum path length is longer for blue than it is for green and even more than it is for red.

In a three-chip imager system or a single-chip imager system with white segment, the path length compensation has to be good to obtain overlapping highlight images at the intermediate image plane. In a three-chip system or in a single-chip system with white segment deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color. This is also mentioned with respect to Equations 5 and 6.

D/BARUXR-019-DE Description

B220012

LU103267 -8-

In a single-chip system without white segment, one may have the shortest path length for red and have a common blue/green path with the longer blue path length.

In this case, the green path length is longer than minimally required and the green

PSF will become larger. Path length compensation is then applied in this case which results in the green PSF being reduced in size.

A reason for wanting a minimum path length is to keep at least most of the light of the higher diffraction orders — which are leaving the spatial phase modulator under different angles than the diffraction order used for steering away from the intermediate highlight image. Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be directed to the spatial amplitude modulators. It should be noted that the word "directed" as used herein means that the light is guided to, relayed or emitted towards something. Were necessary, such directing may include some relay optics, as understood by a person skilled in the art. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not "guided" outside of the active target area, they will produce "ghost" illumination spots in the active area in areas where they are not always desired. The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and, hence, never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

A highlight relay optical sub-system can include one or more imagers e.g. one or more spatial amplitude modulators 28, e.g. at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c) and projecting the image from the at least one or greater than two spatial amplitude modulators, for example three spatial amplitude modulators 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c) and projecting the image from the at least one, or greater than two spatial amplitude modulators, for example three spatial amplitude modulators 28 onto a highlight image plane on a projection screen 33 via a projection lens 39. The

D/BARUXR-019-DE Description

B220012

LU103267 -9- highlight image can be added to a baseline image to provide final highlighted images, such as a highlighted multicolored baseline image such as video images.

The highlight image before being cast on the at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28, (e.g., imager, such as a DMD) is, due to the finite size of the PSF, resulting in a blurry highlighter image with, for instance, dark areas and bright areas. This is a very low-resolution, e.g. blurry, image, which will have a higher resolution in the final image that is made by the at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28. The highlighter path delivers a "configurable" but blurry illumination profile and the baseliner path delivers a (quasi-) uniform illumination profile (diffuse white illumination profile. These are combined or added together, and then the imager(s) (spatial amplitude modulators modulate that combined illumination profile. The final image arrives at the screen or wall, modulated at high resolution by the imagers (spatial amplitude modulators).

The highlight relay optical sub-system 40 can be provided for imaging the intermediate highlight image 14 onto the at least one or more spatial amplitude modulators, for example three spatial amplitude modulators in the highlight relay optical sub-system 40. One function of the at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28 can consist in modulating the intermediate highlight image 14 to clean-up the highlight image, e.g. to remove or adapt (“clean-up”) parts of the blurry highlight image that are misplaced in the projected highlighted image. Such a misplacement can be caused by the PSF (point spread function) of laser light being finite in size (i.e. is not a point of light).

The clean-up of the projected highlight image also includes generating the image with the desired color from the white highlight image. The at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28 can be part of the projection sub-system, e.g. further including prisms, and a projection lens 39. Accordingly, a set of one or more optical elements is provided to direct light from the intermediate image plane 14a to the at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28 and light incident on the at least one or more spatial amplitude modulators, for example three spatial

D/BARUXR-019-DE Description

B220012

LU103267 - 10 - amplitude modulators 28 can be modulated by the at least one or more spatial amplitude modulators, for example three spatial amplitude modulators 28and directed to a projection lens 39 for projection onto the projection screen 33.

A goal of the present invention is to reduce system complexity and cost, e.g. by use of a single spatial phase modulator, e.g. for unpolarized operation or optionally for polarized operation or a single set of two spatial phase modulators for polarized light operation. An example of such a system uses a single spatial phase modulator to simultaneously or sequentially modulate white light or three or more primary colors and to generate a white highlight image. In a case where the spatial phase modulator requires polarized light and the incoming light is unpolarized, the two spatial phase modulator may be used, wherein the single spatial phase modulator modulates one of two polarization directions for the at least two, e.g. three primary colors or white light and, thus, generating a white highlight image. Another example uses specific optical fibers that do not depolarize the incident light, i.e. using a polarization-maintaining optical fiber. One can put the already polarized light from the laser light sources through these fibers and use the single SPM also with that polarization, or use other homogenization methods like fly-eye lenses that also maintain the polarization.

A single spatial phase modulator for unpolarized light, e.g. preferably a piston based spatial phase modulator, may offer a number of advantages with regard to having less complexity in the optical path and better compactness. To achieve an acceptable PSF and to handle the required power, a larger device, e.g. a 0.98” (inch) device, would be advantageous.

Alternatively, a single two setup of spatial phase modulators, for polarized light operation e.g. LCOS spatial phase modulators, is within the scope of the present invention. Given the reduced (blue) power load on the individual spatial phase modulators, cooling and lifetime would be improved.

In particular, embodiments of the present invention use only a single spatial phase modulator for full color light steering can achieve significant cost savings. The light

D/BARUXR-019-DE Description

B220012

LU103267 - 11 - steering also becomes significantly more compact. Also, in a single-chip projector with light steering the present invention enables reduction in size of the PSF, e.g. minimization of the PSF size and offers compatibility with a white segment implementation. The embodiments that use a two spatial phase modulator or two spatial phase modulators for polarized operation have a reduced power load on each of the spatial phase modulators leading to longer lifetimes of this device.

Embodiments of the present invention provide light steering with minimal PSF especially for single-chip home theatre projectors.

Any of the embodiments of the present invention can have a control system which is configured to set the single spatial phase modulator to apply phase shifts, e.g. phase patterns so as to steer light to a common target or image plane. The light steered by the single spatial phase modulator provides image areas of greater light intensity and image areas of less light intensity i.e. provides highlights.

Any of the embodiments of the present invention can include one or more, two or more, such as three, spatial amplitude modulators. A spatial amplitude modulator or modulators is/are also controlled by the same or another control system to modulate light which is incident on the spatial amplitude modulator or modulators.

For example, the control system or systems is/are configured to control the single spatial phase modulator (for instance for, but not restricted to unpolarized light operation) or a single set of two spatial phase modulators (for polarized light operation when having an unpolarized input at the input) and/or spatial amplitude modulator or spatial amplitude modulators. Such a control system may comprise a data processor configured to deliver control signals to set, for example, pixels of the single spatial phase modulator to have a desired phase pattern. The data processor may, for example process image data to determine a desired light steering pattern and drive the single spatial phase modulator to steer light to achieve the desired light steering pattern.

D/BARUXR-019-DE Description

B220012

LU103267 „12 -

Such a control system may comprise a data processor configured to deliver control signals to set, for example, pixels of the spatial amplitude modulator or modulators for a desired amplitude pattern. The data processor may, for example process image data to determine a desired image, e.g. video image, by driving the spatial amplitude modulator or modulators to provide this image.

The single spatial phase modulator or single set of two modulators are preferably each illuminated by a light beam from a highly collimated light source; the control system being configured to set each of the spatial phase modulators to apply phase shifts so as to steer light to the intermediate image plane to provide a corresponding light field at the intermediate image plane. The corresponding light field includes areas of greater light intensity (highlight images) and areas of less light intensity; wherein it is desired that the light fields (highlight images) overlap and preferably at the intermediate image plane. Preferably, they are co-registered so that corresponding areas in the overlapping light fields are superposed. It is an object of the present invention that the highlights for all colors fall together at the target image (intermediate image), that provide a "white" highlight pattern without or without a lot of color misconvergence. With only one SPM, having more than one colored light incident simultaneously on the SPM, the highlights with different colors will emit under different angles per color, as diffraction is wavelength dependent and hence will land on different spots. The path length compensation is provided to counter this effect.

Where a component (e.g. an optical element, modulator, light source, lens, assembly, device, arrangement, etc.) is referred to above or in the description of the embodiments, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e. that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the present invention.

D/BARUXR-019-DE Description

B220012

LU103267 -13-

Specific examples of systems, methods and apparatus are described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described in the present application. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and/or acts with equivalent features, elements and/or acts; mixing and matching of features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments as described herein with features, elements and/or acts of other technology; and/or omitting combining features, elements and/or acts from described embodiments.

Various features are described herein as being present in “some embodiments” or as being “for example”. Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one or any combination of two or more of such features. All possible combinations of such features are contemplated by this disclosure even where such features are shown in different figures and/or described in different sections or paragraphs. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that “some embodiments” possess feature A and “some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features

A and B even if the descriptions of Features A and B are illustrated in different Figs. and/or described in different sentences, paragraphs or sections of this application (unless the description states otherwise or features A and B are fundamentally incompatible). It is therefore intended that the following appended claims are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred.

D/BARUXR-019-DE Description

B220012

LU103267 -14 -

Further details and advantages of the invention will become apparent from the following purely exemplary and non-limiting detailed description of embodiments in conjunction with the appended drawing, which comprises 13 figures.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 illustrates different path lengths resulting from different diffraction angles.

Figs. 2a, 2b, and 2¢ illustrate various embodiments of projectors according to embodiments of the present invention.

Fig. 2d illustrates a device for providing different path lengths such as longer path lengths for green and blue light compared to red.

Fig. 3 illustrates a blazed grating to simulate the effect of 2 PI scaling.

Fig. 4 illustrates the blazed grating as seen by the blue wavelength.

Along the y axis is phase difference in radians.

Fig. 5 illustrates the blazed grating as seen by the red wavelength. Along the y axis is phase difference in radians.

Fig. 6 illustrates an average steering efficiency of 2-, 3-, 4-, 8-pixel blazed gratings (for a MEM'S-piston based SMP with 15 non- equidistant retardation levels).

Fig. 7 illustrates unsteered light for 2-, 3-, 4-, 8-pixel blazed gratings (for a MEM’ piston based SPM with 15 non-equidistant retardation levels).

Fig. 8 illustrates matching PSF by reducing green and blue incident angles on the spatial phase modulator illumination.

D/BARUXR-019-DE Description

B220012

LU103267 - 15 -

Fig. 9 illustrates a single white laser light source, single fiber, single collimator, single spatial phase modulator (unpolarized) architecture.

Fig. 10 illustrates a single white laser light source, single fiber, single collimator, and a set of two spatial phase modulators (polarized) architecture.

Fig. 11 illustrates multiple (primary color RGB) laser light sources, multicolor (primary color) fiber, multiple (primary color) collimators, and single spatial phase modulator (unpolarized) architecture.

Fig. 12 illustrates multiple (primary color RGB) laser light sources, multicolor (primary color) fiber, multiple (primary color) collimators, and a set of two spatial phase modulators (polarized) architecture.

Fig. 13 shows the timing diagram for single spatial phase modulator single chip projection system with white segment.

DETAILED DESCRIPTION Definitions

An “imager” is any device that is operable to impart a desired image (an image may be any pattern) to a beam of light. A spatial light modulator, i.e. spatial amplitude modulator may be used as an imager. For example, in a cinema projector an imager may be used to modulate light incident from one or more light sources according to image data to project images according to the image data onto a screen. The images may be static or quasi static such as a presentation with slides or may be dynamic, e.g. a video. An “imaging engine” can include further optical elements such as a prism like a TIR prism and a projection lens.

D/BARUXR-019-DE Description

B220012

LU103267 - 16 -

A “digital mirror device” (“DMD”) comprises micro-mirrors that are tilted into 2 different positions. In a first position, they reflect the light to the screen via the projection lens, in the other position, they reflect the light to a light dump, e.g. inside the projector. The pixels do not alter the amplitude/ intensity of the beam, they only redirect it. On the screen these redirections make a difference of how much light arrives at each position on the screen and, hence, the amplitude of such light.

DMD’s are therefore spatial amplitude modulators. “Spatial amplitude modulator’ (SAM) means a type of spatial light modulator that is operable to controllably alter amplitude of light. Such a spatial amplitude modulator can be transmissive or reflective. Non-limiting examples of spatial amplitude modulators are liquid crystal panels (also called LCDs), liquid crystal on silicon (LCoS) devices, DMD. In accordance with embodiments of the present invention, a projector is provided with two spatial amplitude modulators, for instance one SAM modulating red light, and one SAM sequentially modulating green and blue light, therefore having two colored lights that are processed simultaneously by the single

SPM, i.e. the sequence for the single SPM is red+green, then red+blue.

A “spatial phase modulator” (SPM) is a type of spatial light modulator that is operable to controllably alter the phase of incident light. Such a “spatial phase modulator” is used to form a highlight image. Throughout this text, the word "image" in this context is to be interpreted as "illumination profile". Note that a spatial phase modulator will need a certain "steering distance" and a target or intermediate image plane to realize this "image" and it will be blurry. Contrary to SAMs, the image is not directly formed right after the light has gone through the SPM. Non-limiting examples of spatial phase modulators are LCoS devices, and deformable mirrors.

Embodiments of the present invention apply spatial phase modulators that have a pitch (i.e., a spacing between adjacent pixels in rows and/or columns). Such a spacing depends on the technology used. The pixels’ spacing can be 20um or less, e.g. 10 to 20pm.

A different and more preferable MEMS-based spatial phase modulator comprises mirrors on “pistons” that can move up or down. When a micro-mirror is moved up or

D/BARUXR-019-DE Description

B220012

LU103267 -17 - down perpendicular to a plane of the pixel micro-mirror array, it changes the distance that light needs to travel before it gets reflected, creating a variable “retardation” and, hence, a change of the phase of the light per pixel.

The “f-number” is a dimensionless number that can be used to characterize an optical system. f-number is a ratio of a focal length of the optical system to a diameter of an entrance pupil of the optical system.

A “highlight”, in reference to a projected light field (which may include an image), means a bright spot or area or pattern or zone. Highlights may include the brightest points in a light field.

A “highlighter light beam”, as used herein, includes a beam of light that is configured to produce a non-uniform light field or illumination field which includes one or more highlights at a target area. In a beam steering projector, the “images” are then illuminated by this “illumination field”. The target area may, for example, be a screen or image plane onto which the highlight beam is incident. The highlight beam may include areas having higher illumination intensities and areas having lower illumination intensities. For example, the highlighter light beam can be an almost uniform illumination field, just like the baseline light beam. This could be when there are no highlights in the image — like a fog scene. In that case, the highlighter light beam just contributes to the general brightness of the image everywhere in the image. The next scene could contain a highlight feature again and the beam steering is then immediately commanded to steer to provide a more suitable highlighter light beam.

The highlighter light beam can be combined with a baseline light beam.

A “baseline projector” refers to a conventional light valve projector design with conventional illumination and, thus, without light steering or highlighting. For example, imagers can be provided by DLP, LCD, and LCoS light valves.

D/BARUXR-019-DE Description

B220012

LU103267 - 18 - “Baseline light beam(s)” supply enough light to an imager, substantially uniformly distributed over the imager’s area, to project a desired image, without the potential addition of one or more highlighter light beams that can be modulated to supply extra light for highlights in specific regions of the projected image. A baseline light beam can provide uniform illumination as is used in a conventional projector without highlighting. There can be some deviation from a perfect uniform illumination because of optical variations (non-idealities). This can lead to a lower than 100% uniformity, i.e. a 90% uniformity or above. Typically, there is some roll-off to the corners of the image. There are measurement procedures to characterize this (i.e., measure illuminance on screen at 13 points and report the minimum value versus the central value). The baseline light beam is generated and used in a baseline illumination part before being combined with a highlighter light beam. “PSF” (Point Spread Function) (i.e., location, size and profile) for example refers to an illumination spot that one will obtain when multiple light beams especially when multiple light beams of different colors are steered to the exact same location. With a point source, one would obtain a point result, but with real sources the point will become a "blob" having a certain PSF value. One can use the FWTM (Full Width at

Tenth of Maximum) metric to indicate the size of the PSF, often expressed in percentage of the imager (spatial amplitude modulator) width or screen width.

According to this metric, the PSF size can be within a range of 5-20% (e.g. 10%) of the total image(r) width. “Modulate” means to vary a property of light, preferably intentionally or also by accident, as far as this application is concerned. Light can be modulated temporally or spatially or both. Example properties of light that may be modulated include any of, or any combination of amplitude (brightness or intensity), phase and polarization state. Spatial modulation of light can be achieved by selectively attenuating light at spatial locations (e.g., pixels) and/or by steering light. Light steering involves steering light that would otherwise illuminate some spatial locations to other spatial locations. Light steering may be achieved, for example, using variable lenses, variable mirrors or a variable array of micro-mirrors and/or spatial phase modulators.

A phase pattern applied by a spatial phase modulator may direct incident light to

D/BARUXR-019-DE Description

B220012

LU103267 - 19 - selected regions in an image plane. Interference between different parts of the directed light may result in some locations in the image plane having more light (i.e. constructive interference) and/or some locations in the image plane having less light (i.e. destructive interference). As a result of such interference, the phase pattern applied by the spatial phase modulator may effectively steer or direct incident light away from certain regions in the image plane and/or steer or direct the incident light so that light is concentrated in certain regions in the image plane.

An “Acceptance angle” for an optical system is a solid angle for which light rays entering the optical system with directions lying within in the solid angle will pass through the optical system. Solid angle may be measured in steradians. Solid angle is a valid and correct “unit” for acceptance angle, but the linear angle is often used to denote acceptance angle. For example, if it is said that the acceptance angle is i.e. 10°, this points to the radius angle of the solid angle cone. “Etendue” is a number that characterizes how "spread out" light is in area and angle.

From the point of view of an optical system the etendue may be defined as the area of an entrance pupil of the optical system times the acceptance angle (as defined herein) of the optical system. “Polarized, “unpolarized” and “partially polarized” light are discussed, for example, in “Projection Displays” by E. H. Stupp and M.S. Brennesholtz, Wiley, 1999, ISBN 0 47 198253 9, Appendix 4. In the present application, “Randomly polarized” light is used here as synonym for “unpolarized” light. There is no particular functional distinction between pseudo-random and full-random polarized light as far as this invention is concerned. Both would be problematic for prior art spatial phase modulators but would be suitable for use with piston-based spatial phase modulators and for use in the embodiments of the present invention. Full- and pseudo random polarized light can be treated as the same.

Embodiments if the present invention refer to a single spatial phase modulator, e.g. for un-polarized operation or optionally for polarized operation. Throughout the text reference is made to a single set of two spatial phase modulators that can be used

D/BARUXR-019-DE Description

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LU103267 - 20 - for polarized light operation. Such a set includes two and only two spatial light modulators each designed to work with light having one of two polarization directions. À single set of two spatial modulators is shown in Figs. 10 and 12 showing two spatial light modulators 26 in each figure. The polarization directions can be orthogonal to each other. With respect to the single set of two spatial phase modulators operating with three incident primary colors, each of these two spatial phase modulators of the set still process all three primary colors. It is not so that one color goes to one SPM and two colors go to the other. A single set of two spatial phase modulators is preferred.

A part of a projector creates a highlight which is a changeable illumination profile to a set of projection imagers, such as spatial amplitude modulators. A certain light flux can be distributed in various ways over the imager, such as a spatial amplitude modulator, going from a uniform distribution over its complete area to one or a number of concentrated “highlights”, which form a highlight image and can modify these highlights on a frame by frame basis, so that it can be synchronized with a moving video sequence provided on a baseline image. The “baseline image” is a part of the projector that creates a fixed illumination level with a substantially good uniformity over the whole imager (or spatial amplitude modulator) area. This part is the same as a conventional projector.

The light, after going through the one or more imagers (such as spatial amplitude modulator or modulators) is still accepted by a projection lens and is imaged on a projection screen. This means that the F-number of the illuminating light has to be equal or higher than the F-number of the projection optics.

For the terms steered and unsteered light, specularly reflected and non-diffracted light is unsteered light. Steered light is light that can get deflected away from the specular reflection direction as a consequence of the interaction with the diffraction grating displayed or published on the spatial phase modulator, which can then be redistributed or redirected so that one diffraction order is redistributed towards another location or other locations in the target image. The highlighter image has its designated illumination profile as produced for example with a phase grating.

D/BARUXR-019-DE Description

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LU103267 -21-

Redirection is normally in a direction different from that of the specular reflection.

Some -— rather rare — areas of the spatial phase modulator could still be instructed to mainly reflect the light along the specular reflection when it is the purpose to create a highlight target exactly on that line. Those zones will have a locally “flat” area in the phase grating image with constant spatial phase modulator values. Note that the amount of unsteered light has a fixed contribution from reflection on non-active optical interfaces on the spatial phase modulator, but also a varying contribution depending on the actual phase grating coming from non-optimal representations of the required retardation levels on the pixels (round-offs to a limited amount of driving levels, micro-mechanic tolerances, fringe fields at the pixel boundaries, etc.).

An “Uniformizer” is an optical component or optical system that creates a uniform illumination on an SPM (spatial phase modulator) or SAM (spatial amplitude modulator), the latter as an imager. Uniform illumination on a SPM can in the context of the present patent application be useful to spread out the power density evenly over the device which is better for reliability, and to create a more balanced and even steering performance from every part of it. Examples of uniformizers are a light pipe, a fiber (i.e. with rectangular core) or a set of fly-eye lens arrays. “White segment” with respect to any embodiment of the present invention, a single- chip system can be operated with a “white segment” which refers to an intermediate optical subsystem with one imager or projector type with one imager (a spatial amplitude modulator like a DMD) which operates in a color sequential manner. In addition to a sequence of primary colors, there is a white light output boost. In the present invention, the light steering system can work with well-collimated light sources, such as lasers. The color sequence can be made by turning on and off the lasers in sequence. It is included within the scope of the present invention, in addition to a sequence of colored lights, such as a sequence of primary color lights, to put on a number, such as two or three, lasers simultaneously during a certain fraction of a period of time (see Fig.13). In the present application, reference is made to the term “segment” in which the SPM and the SAM process this number, e.g. two or three, of colors simultaneously. This gives a white boost when three lasers, such as a red, a green and a blue laser, are on at the same time in that

D/BARUXR-019-DE Description

B220012

LU103267 -22- fraction of the period of time, i.e. “white segment”. The present invention includes other boosting segments or time periods, such as a cyan boost, yellow boost, magenta boost when two or more lasers are on simultaneously. In this boosting operation, a single SPM has to process two or more colors simultaneously. The single SPM sends out the colored light at different "diffraction" angles per colored light. Path length compensation is necessary to make sure that these colored steered lights fall on top of each other at an intermediate highlight image, without any or with only little color misconvergence.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Control system

This section deals with a control system which can be supplied alone or in combination with one or more optical sub-systems or with a complete projector.

Control systems, e. g. see elements 42 and 43 shown in Figs. 2a, 2b, 2c, are for controlling the spatial phase modulator or modulators (42) and/or for controlling the spatial amplitude modulator or modulators (43). These may be implemented using specifically designed hardware, configurable hardware, programmable data processors configured by the provision of software (which may optionally comprise “firmware”) capable of executing on the data processors, special purpose computers or data processors or microcontrollers that are specifically programmed, configured, or constructed to perform one or more steps in a method as explained in detail herein and/or combinations of two or more of these. The control system may be configured for controlling a projector as shown schematically in Figs. 2a, 2b, 2c. The control system may be configured for controlling an optical system, the optical system comprising an optical sub-system, wherein the optical sub-system comprises a spatial phase modulator. The spatial phase modulator can be configured to be operatively connected to an illumination sub-system which provides collimated white light or collimated lights of three primary colors which can combine to form white light supplied to the spatial phase modulator. The control system can be configured to control the operation of the spatial phase modulator to thereby provide phase patterns which steer the collimated white light to an area or areas of an image with

D/BARUXR-019-DE Description

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LU103267 -23- highlights which have higher brightness and another area or areas of the image with lower brightness, the image being transferred to a spatial amplitude modulator. The control system can be configured to control the operation of the spatial amplitude modulator to form a second image which is for projection via a projection lens. The control system can be adapted to calibrate the spatial phase modulator. The calibration can select from green having a primary wavelength range of 495-570 nm, red having a primary wavelength of 570 — 720 nm, and blue having a primary wavelength of 440 - 495 nm. As an example, the control system may use light with the dominant wavelengths derived from the ranges above, e.g. dominant wavelength or blue being 465 nm, the dominant wavelength for red being 639 nm, and the dominant wavelength for green being 530 nm. The control system may be implemented in different ways all, of which are included within the scope of the present invention. For example, the single spatial phase modulator can be calibrated for all primary colors using only green with a wavelength of 532 nm.

Examples of specifically designed hardware to implement the control system are logic circuits, application-specific integrated circuits (“ASICs”), large scale integrated circuits (“LSIs"), very large scale integrated circuits (“VLSIs”), and the like. Examples of configurable hardware are: one or more programmable logic devices such as programmable array logic (“PALS”), programmable logic arrays (“PLAs”), and field programmable gate arrays (“FPGAs”). Examples of programmable data processors are: microprocessors, digital signal processors (“DSPs”), embedded processors, graphics processors, math co-processors, general purpose computers, server computers, cloud computers, mainframe computers, computer workstations, and the like. For example, one or more data processors in a control circuit for a projector may implement methods as described herein by executing software instructions in a program memory accessible to the processors.

Sub-systems and methods therefor with phase modulation, light steering and color dependent path length compensation and a controller and a control method therefor.

This section deals with optical sub-systems to be commercialized either alone or in combination or as part of a projector.

D/BARUXR-019-DE Description

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LU103267 „24 -

Embodiments of the present invention provide ong or more optical sub-systems 20, 30, 40, 50 which can be used in any of the embodiments of the present invention, for example for use in a projector or projection apparatus shown schematically in Figs. 2a, 2b, 2c with a detail of a color dependent path length compensator 10 in Fig. 2d which can be used in any of the embodiments of the present invention. Some or all of the optical sub-systems 20, 30, 40, 50 can be combined together to form a projector or a projection apparatus or they can be used separately or in groups, e.g. for retro-fitting to other projectors.

One of the optical sub-systems can be an illumination optical sub-system 20 having a single white laser source or laser light sources of three or more primary colors for example red, green and blue lasers. It may also include one or more collimators and/or one or more uniformizers or mixers. The output of the Humination optical sub-system 20 can be a collimated or substantially collimated and/uniformized white beam or colored beams.

The illumination optical sub-system 20 can be operably connected to an intermediate optical sub-system 30 shown schematically in Figs. 2a, 2b, or 26. The intermediate optical sub-system 30 comprises a single spatial phase modulator 12 or a two spatial phase modulator 26, and one color dependent optical path length compensator 10, The path length compensator 10 is placed on an optical path 8 between the single spatial phase modulator 12 or two spatial phase modulator 26 and the intermediate image plane 14a, e.g. where a static or dynamic diffuser (e.g. spinning diffuser or diffuser with 2D movements, e.g. side to side) is placed. The static or dynamic diffuser can be placed at (i.e. in the vicinity of) or in the intermediate image plane. This will allow sufficient de- speckling though it will slightly increase the blurring of the image. Furthermore, two intermediate highlight images at one or more intermediate image planes can be provided. These one or more planes can be provided between the single spatial phase modulator or the single set of two spatial phase modulators and one or more spatial amplitude modulators. A (static or dynamic) diffuser can be placed in each of these one or more intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail.

D/BARUXR-019-DE Description

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LU103267 -25-

Outputs of the single spatial phase modulator 12 or two spatial phase modulator 26 is steered light (i.e. modulated light) and/or unsteered light, i.e. not modulated by the spatial phase modulator. The steered light and unsteered light are directed to the color dependent path length compensator 10. After path length compensation is complete, the output of the path length compensator 10 is path length compensated steered light for forming an intermediate highlight image 14 on an intermediate image plane 143. A static or dynamic diffuser (e.g., spinning diffuser or diffuser with 2d motion, e.g. side to side) can be provided at the intermediate image plane 14a.

Embodiments of the present invention shown in Figs. 2a, 2b and 2c can include a single spatial phase modulator 12 or a two spatial phase modulator 26 and have a control system 42 which is configured to set the spatial phase modulators 12, 26 to apply phase shifts, e.g. phase patterns so as to steer light to a common target or intermediate image plane 14a. The light steered by the spatial phase modulator 12, or the two spatial phase modulator 26, provide areas of greater light intensity and areas of less light intensity, i.e. provide highlights.

A highlight relay optical sub-system 40 has one or more spatial amplitude modulators 28. The highlight relay optical sub-system 40 is configured for relaying the intermediate highlight image 14 onto the one or more spatial amplitude modulators 28.

The highlight relay optical sub-system 40 can include one or more spatial amplitude modulators 28. The highlight image at this stage - before being cast on the one or more spatial amplitude modulators (e.g., imager, such as a DMD) is, due to the finite PSF size (typical PSF size in light steering of 10% of the image width, in the range of 5 to 20%, of the image width according to the metric given by FWTM (Full Width at Tenth of

Maximum) to indicate the size of the PSF, often expressed in percentage of the imager (spatial amplitude modulator) width or screen width..), a blurry illumination profile with, for instance, dark areas and bright areas. This is a very low-resolution, e.g. blurry, image, which will have a higher resolution in the final image that is made by the one or more spatial amplitude modulators. The highlight relay optical sub-system 40 can be provided for imaging the intermediate highlight image 14 onto the one or more spatial amplitude modulators 28. One function of the one or more spatial amplitude modulators 28 can be to modulate the intermediate highlight image to clean up the highlight image,

D/BARUXR-019-DE Description

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LU103267 - 26 - e.g. to remove (“clean up”) parts of highlights that are misplaced in the projected highlighted image. Such a misplacement can be caused by the PSF of laser light being finite in size (i.e. is not a point of light). Such a PSF of laser light having a size greater than a point of light, can result in a blurred image when made by steered light. The clean-up of highlights may also include generating the desired color from the white highlights, by removing or reducing the intensity of the colors that are unwanted or overrepresented. The one or more spatial amplitude modulators 28 can be part of a highlight image projection optical sub-system 50, e.g. further including a prism or prisms, and a projection lens 39 for projecting highlighted images onto a projection screen 33 via a projection lens 39.

Embodiments of the present invention shown in Figs. 2a, 2b and 2c include a spatial amplitude modulator 28 or modulators which is/are also controlled by the same control system (42) as used for the single spatial phase modulator 12 or for the single set of two spatial phase modulators 26 or is/are controlled by another control system (43) to modulate light which is incident on the spatial amplitude modulator 28 or spatial amplitude modulators.

The highlight image projection optical sub-system 50 is provided for taking a highlight image from the one or more spatial amplitude modulators 28 and projecting the image from the one or more spatial amplitude modulators 28 onto a highlight image plane, e.g. where a projection screen 33 is located via a projection lens 29.

An example is shown in Fig. 2c which shows a further embodiment wherein light is relaved in relay optics 41 from a white light source 31 to a combiner 34 along another optical path where i is combined with an intermediate highlight image 14 of the optical path. The optical path for the intermediate highlight image 14 is as above: using the sub-systems 20, 30, wherein the intermediate highlight image 14 is formed on an input to the combiner 34 which is in the intermediate image plane 14a. The path for the highlight images can be from an illumination sub-system 20 to an intermediate sub- system 30, wherein the intermediate image is formed on a further input to the combiner 34. The combined image will then be processed further via sub-systems 40, 50 to an imager, e.g. including one or more spatial amplitude modulators 28 (see Figs. 2a, 2b,

D/BARUXR-019-DE Description

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LU103267 - 27 - 26), one or more prisms, (not shown) and a projection lens 39 up to a projector screen 33.

As shown in Figs. 2c, 2d white laser light or a combination of three or more primary colors such as the red, blue and green light is/are modulated by the single spatial phase modulator 12. This light is modulated in the single spatial phase modulator 12 to generate steered light which is reflected by or emitted from the single spatial phase modulator 12 and which enters the color dependent path length compensator 10. The light with one primary color such as red light goes straight through the color dependent path length compensator via pass dichroic mirrors, i.e. red pass dichroic mirrors 1 and 2. The light having two other primary colors such as green light and blue light will be reflected by dichroic mirror 1, e.g. through an angle such as 90°. The light of one other primary color such as blue light will pass through a blue pass dichroic mirror 3 whereas light with yet another primary color such as the green light is reflected by it, e.g. through an angle such as 90°. The light of one other primary color such as blue light is reflected by mirrors 5 and 7, e.g. each through an angle such as 90°. Mirrors 5 and 7 do not need to be or are not dichroic mirrors. The light of one other primary color such as blue light passes through a blue pass mirror 9 but the light of yet another primary color such as green light will be reflected by this blue pass dichroic mirror 9, both blue and green lights arriving at the red pass dichroic mirror 2. The light other than red, such as green and blue light, will be reflected by the red pass dichroic mirror 2 to rejoin the red light on optical path 8 travelling towards the intermediate highlight image 14 and the intermediate image plane 14a. This will increase the path length of two of the primary colors such as the path length of green light and the path length of the blue light.

Further, by introducing the pass mirror for the one other primary color such as a blue pass dichroic mirror 3, the blue path can be elongated more than the green path. The blue and green paths will both be elongated compared with the red path, i.e. the path lengths of two primary colors are elongated compared to the third.

The path length differences which are wavelength dependent, are compensated for (at least partly) by the color dependent path length compensator 10 which is placed on the optical path 8 in between the single spatial phase modulator 12 and the intermediate highlight image 14. In any of the embodiments of the present invention, matching path lengths for red, green and blue light can be perfect (e.g. all have an exact compensation

D/BARUXR-019-DE Description

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LU103267 - 28 - for altering the path lengths for differences in wavelength dependent diffraction angles).

However, for any of the embodiments of the present invention this compensation does not need to be a perfect compensation. Instead, a defined difference in path length of at least one or some of red, green and blue light can be introduced which is/are not perfect compensations of path lengths for differences in wavelength dependent diffraction angles. If compensation is not perfect then the PSF of one or more of the colored laser lights such as the red or green (or optionally blue) light beams which are not perfectly compensated, will be a PSF that is increased in size which results in blurred highlights, and more “clean-up” being required using the one or more spatial amplitude modulator 28 of a highlight relay optical sub-system 40.

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as is displayed or published on a spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the specularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing linked to the pixel pitch of the spatial phase modulator (which is displaying or publishing a grating on the SPM) has to be greater than the largest horizontal or vertical dimension of the steering target area increased with the size of the

PSF. With such a minimum required path length the PSF of that color is as small as possible. À longer path length results in a wider PSF. The minimum path length is longer for blue than it is for green and even more for red. In a three-chip system or a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane. In a three-chip system, deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color. This is also mentioned with respect to Equations 5 and 6.

In a single-chip imager system without white segment, one may have the longest blue path length used for all colors. Alternatively, one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become

D/BARUXR-019-DE Description

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LU103267 -29- larger. À color dependent path length compensator 10 is used to reduce the path length differences and hence to reduce the size of the PSF e.g. for green light and especially for red light.

A reason for wanting a minimum path length is to keep the light of the higher diffraction orders — which are leaving the spatial phase modulator under different angles than the diffraction order used for steering away from the intermediate highlight image. Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be relayed to the spatial amplitude modulators. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not "guided" outside of the active target area, they will produce "ghost" illumination spots in the active area in areas where they are not always desired. The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and, hence, never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

Moreover, it is known in single-chip systems not to operate in a color sequential mode with only the pure primary colors. In order to boost the brightness, in accordance with an embodiment of the present invention it is beneficial to introduce a so called “white segment” where all three lights of primary colors are activated simultaneously forming white light. For example, Fig. 13 shows the timing diagram for single spatial phase modulator single chip (single spatial amplitude modulator) projection system with white segment. Also, other “boost schemes” are included within the scope of the present invention. Such boost schemes, for instance, provide a yellow, cyan and magenta boost by dedicating time segments to simultaneously operating two of the three or more laser sources. This boosts the secondary colors, and as a result also white brightness. At least all of these following options for additional segments are included within the scope of the present invention: RGBW, RGBY, RGBCMY, and RGBCMYW. Wherever there are two or more light beams of different colors incident on a single spatial phase modulator, path length compensation can be applied to the two or more light beams.

Without the path length compensations, this will only be possible if the illumination spots of the three primary colors are spatially separated (red, green and blue spots side by

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LU103267 - 30 - side). But as this limits the useful area on the spatial phase modulator that is available for each colored light, the angular spread in the illumination for a given beam quality of the laser source will further increase, resulting in a further increase in the size of the

PSF. Increase in size of the PSF results in a highlight image that is not so crisp but is blurry, which requires therefore a spatial amplitude modulator to “clean up the image”.

The highlight image at this stage - before being cast on the spatial amplitude modulator (e.g., imager, such as a DMD) is, due to the finite PSF, a blurry illumination profile with, for instance, dark areas and bright areas. This is a very low-resolution, e.g. blurry, image, which will have a higher resolution in the final image that is made by the spatial amplitude modulator.

Splitting light can be done not only on wavelength (e.g. splitting red, blue and green), but also by polarization. Polarization is usually not a preferred option, since it is simpler to work with unpolarized light. With polarized light all three colors would need to have the same polarization if the spatial phase modulator is polarization sensitive. Selection can be between the different wavelengths based on polarization if the single spatial phase modulator 12 can work with any polarization, e.g. it is the piston type spatial phase modulator supplied by Texas Instruments, USA, and where the laser light sources are polarized. Piston spatial phase modulators are described in

US2019/179134, US2019/179135, and US2020/209614, all of which are incorporated herein by reference. If the red incident light would have a different polarization than green and blue incident light for example, one could then deviate the path of green and blue with a polarizing beam splitter and combine it again with the same component.

Therefore, polarizing beam splitters can be an alternative to dichroic mirrors in making a path length compensator wherein a colored light is linked to a polarization state.

Color dependent path length differences to compensate for differences in diffraction angles

Following on from the above, this section deals with path length differences and how to compensate for them.

Referring to Fig. 1 and the intermediate optical sub-system 30 introduced above, when a defined phase grating 4 (to be published or displayed on a spatial phase

D/BARUXR-019-DE Description

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LU103267 -31- modulator) deviates a red beam with wavelength Ar with a certain angle Or a displacement D is created at a distance PLr. If the same phase grating is illuminated with a green beam with wavelength Ag, the green beam will be deviated to reach the displacement D with a different smaller angle ©c. It takes a longer path length PLe to achieve the same displacement D of the red beam. If it is assumed that the retardation is constant over all wavelengths (no dispersion), the relationship between the two diffraction angles is: (Equation 1) sin; = sin Bg + +

R

In order to achieve the same displacement D the following equation must be satisfied: (Equation 2) tan Og * PLp = tan 0ç * PLg

If it is assumed that the diffraction angles are small, the equations can be approximated by: . Ag (Equation 3) Og = Op x —

AR

(Equation 4) Or * PLp = 06* PLG

By substituting equation 4 in equation 3 the following is obtained: . AR (Equation 5) PL; = PLp * Te

G

In other words, aside from the small angle approximation, the image which is reproduced by the red beam at a distance of PLr can also be found when illuminating a phase grating with a green beam if the path length is scaled inversely proportionally to the wavelength ratio. Fig. 1 shows the color dependent different path lengths resulting from different diffraction angles for light of different wavelengths or colors, each to reach a displacement D.

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LU103267 -32-

The small angle approximation is quite accurate given the small angles that light steering typically works with (e.g. <4°) and the errors are e.g. < 0.2%. Given a typical

PSF size in light steering of 10% (in the range of 5 to 20%) of the image width, according to FWTM (Full Width at Tenth of Maximum) metric to indicate the size of the

PSF, often expressed in percentage of the imager (spatial amplitude modulator) width or screen width.

The effects on the reproduced highlights should be negligible.

Similarly, when the same phase grating is illuminated with a blue beam with wavelength

Ag the following equation applies with good approximation: (Equation 6) PLp = PLp * =

To compensate for such color-dependent path length differences, a color-dependent path length compensator 10 can be provided in an intermediate optical sub-system 30, namely in the optical path 8 between the spatial phase modulator 12 and an intermediate highlight image 14, e.g. a static or dynamic diffuser (e.g. a spinning diffuser). In the intermediate optical sub-system 30 the color dependent path length compensator 10 can be provided by a combination of dichroic mirrors 1, 2, located, in the optical path 8 between the spatial phase modulator and the intermediate highlight image 14, e.g. a static or dynamic diffuser (e.g., a spinning diffuser or diffuser with other 2D movements).

A color dependent path length compensator 10 is shown in Fig. 2d as an example of a path length compensator 10 in an intermediate optical sub-system 30. This color dependent path length compensator 10 can be used with any of the embodiments of the present invention, e.g. in any of the intermediate optical subsections 30. A color dependent path length compensator 10 can, for example, be constructed using dichroic mirrors, e.g. in a six-mirror color-dependent path length compensator 10, wherein some of the mirrors are dichroic. For example, in Fig. 2d mirrors 1, 2, 3 and 9 are dichroic and 5 and 7 are not. The present invention is not limited to such a color dependent path length compensator. For example, a first X-cube can be used to split a white beam into primary colors and then by moving tented mirrors path length differences can be

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LU103267 -33- compensated for, before recombining with a second X-cube. An X-cube is often a special arrangement of dichroic mirrors.

Implementation in a projection system with a three-chip spatial amplitude modulator - the effect of 2T] scaling (2 Pi scaling)

This section deals with the use of a three-chip spatial amplitude modulator which can be supplied alone or in combination with one or more optical sub-systems or with a complete projector.

Embodiments of the present invention provide one or more optical sub-systems (one or more of 20, 30, 40, 50) for use in a projection apparatus, wherein one optical sub- system is an illumination optical sub-system 20 having light sources of a single white source or three or more primary color light sources such as red, green and blue. The fHumination optical sub-system 20 can provide coliimated or substantially collimated fight to the intermediate optical sub-system 30, e.g. collimated white light. For example, the light output from the illumination optical sub-system 20 is preferably a uniformized and preferably collimated light beam, e.g. a uniformized and preferably collimated white fight beam.

The illumination optical sub-system 20 is operably connected to an intermediate optical sub-system 30, the intermediate optical sub-system 30 comprising a single spatial phase modulator 12 (controlled by the control system 42), Light from the single spatial phase modulator is steered i.e. modulated by the spatial phase modulator and/or is unsteered light, i.e. not modulated by the single spatial phase modulator. The steered or unsteered light is directed to a color dependent optical path length compensator 10, wherein outputs of the single spatial phase modulator 12 are phase patterns which produce steered light and are used, for example for forming an intermediate highlight image 14 at an intermediate image plane 14a.

The highlight image at this stage - before being cast on the spatial amplitude modulators (e.g. imager, such as a DMD) is, due to the finite PSF, a blurry illumination profile with, for instance, dark areas and bright areas. This is a very low-resolution, e.g. blurry, image, which will have a higher resolution in the final image that is made by the

D/BARUXR-019-DE Description

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LU103267 -34- spatial amplitude modulators. À highlight relay optical sub-system 40 is provided for imaging the intermediate highlight image 14 onto the imagers such as spatial amplitude modulators 28 (controlled by control system 43). The highlight relay optical sub-system 40 can comprise a set of one or more optical elements to relay the intermediate highlight image 14 from the intermediate image plane 14a to the spatial amplitude modulators 28.

A highlight image projection optical sub-system 50 can be provided for taking a highlight image from the spatial amplitude modulators 28 and projecting each highlight image from the one or more spatial amplitude modulators 28 onto a highlight image plane. For example, the images on the spatial amplitude modulators 28 are conveyed to a projector lens 39 whereby the light incident on the spatial amplitude modulators 28 can include baseline light as well as the highlight image and the modulation provided by the spatial amplitude modulators 28 can include cleaning up the highlight image. It can also include creating a baseline image, e.g. from video signals.

Embodiments of the present invention can be individual sub-systems one or more of which can be used in a projector such as a projector described above (see Figs. 2a, 2b, 2c, 2d) which receives multicolored light such as three or more primary color lights from an illumination optical sub-system 20. Modulation of the spatial phase modulator 12 provides steered light which is imaged as an intermediate highlight image 14, e.g. on a diffuser which can be a static diffuser or a dynamic diffuser such as a spinning diffuser or a moving diffuser in two dimensions. The static or dynamic diffuser can be placed at (i.e. in the vicinity of) or in the intermediate image plane. This will allow sufficient de- speckling though it will slightly increase the blurring of the image. Furthermore, two intermediate highlight images can be provided between the spatial phase modulator and a final spatial amplitude modulator and a (static or dynamic) diffuser can be placed in each of these intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail. The one or more intermediate highlight images 14 can be imaged onto spatial amplitude modulators 28, e.g. for projecting highlights as an addition to a final baseline video image. The one or more intermediate highlight images 14 can be relayed by a highlight relay optical sub-system 40 to one or more spatial amplitude modulators

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LU103267 -35- 28 (controlled by control system 43) where it/they can be added to a baseline illumination.

In accordance with embodiments of present invention, a projection system is provided with a highlight relay optical sub-system comprising, for example, three spatial amplitude modulators. If three primary colors are used then the laser sources of the three primary colors can be operated simultaneously, one primary color for each of three spatial amplitude modulators 28. For example, different phase patterns may be applied by three different spatial phase modulators 12. These different phase patterns can be optimized for the color and/or different calibration values could be applied that are optimized for the color. However, in the present invention only one spatial phase modulator is available for the steering of 3 color illumination profiles. For a three-imager projector (three spatial amplitude modulators) a single set of two spatial phase modulators can be used instead of a single spatial phase modulator. Each of the two

SPMs of the single set of two spatial phase modulators will create the highlight illumination profile (image) for the three incident colored lights simultaneously, at different angles, so that path length compensation between the colors is required.

For example, when the single spatial phase modulator is illuminated with white light, white highlights are provided in the intermediate images. The path length differences which are wavelength dependent are compensated for by the path length compensator 10 which is placed on the optical path 8 between the single spatial phase modulator 12 and the intermediate highlight image 14. In any of the embodiments of the present invention, matching path lengths for red, green and blue, do not need to be perfect, but instead a defined difference in path length (compared to perfect compensation for wavelength dependent diffraction) between red, green and blue lights can be tolerated.

If compensation is not perfect for the red or green or blue light, then the PSF of the red or green or blue light beams will be increased in size which results in more “clean-up” being required using one or more spatial amplitude modulators. In a three-chip system, deviations from an ideal compensation are less desirable. Next to an impact on PSF, the image size of the different color images will be different. At the edge of the image this will lead to PSFs of different colors not overlapping. Small errors can be compensated in the clean-up of the spatial amplitude modulators. Preferably, path length errors should be smaller than +/-5%.

D/BARUXR-019-DE Description

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LU103267 - 36 -

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as displayed or published on a single spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the secularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing which is linked to the pixel pitch of the single spatial phase modulator (seen as a grating) has to be greater than the largest horizontal or vertical dimension of the steering target area (intermediate highlight image) increased with the size of the

PSF. Atypical PSF size in light steering is 10% (in the range of 5 to 20%) of the image width, according to the FWTM (Full Width at Tenth of Maximum) metric to indicate the size of the PSF, often expressed in percentage of the imager (spatial amplitude modulator) width or screen width.

An aim is to capture one "steered" diffraction order in the target area (intermediate image) and have all the other steered diffraction orders - that would create undesired "ghost" illuminations - outside of that target area. The following formula is relevant: min_distance = target width x PLM_pitch/lambda where lambda is the wavelength. In reality the PSF size is not zero and the steering distance has to be increased because all the diffraction orders blur and become bigger and it is required that all of the light within the PSF size should fall outside of the target area (intermediate image).

With such a minimum required path length, the PSF of that color is as small as possible.

For the colored light a longer path length results in a wider PSF. The minimum path length is longer for blue than it is for green and even more for red. In a three-chip system or a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane. In a three-chip system, deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color.

This is also mentioned with respect to Equations 5 and 6.

D/BARUXR-019-DE Description

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LU103267 „37 -

For example, one may have the longest blue path length used for all colors, or one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become larger. A color dependent path length compensator 10 is used to reduce the path length differences and hence to reduce the size of the PSF, e.g. for green light and especially for red.

A reason for wanting a minimum path length is to keep (most of) the light of the higher diffraction orders — which are leaving the spatial phase modulator under different angles than the diffraction order used for steering away from the intermediate highlight image. (Most of) Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be relayed to the spatial amplitude modulators. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not "guided" outside of the active target area, they will produce "ghost" illumination spots in the active area in areas where they are not always desired.

The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and, hence, never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

Moreover, it is known in single-chip systems not to operate in a color sequential mode with only the pure primary colors. In order to boost the brightness, in accordance with an embodiment of the present invention it is beneficial to introduce a so called “white segment” where all three lights of primary colors are activated simultaneously forming white light. For example, Fig. 13 shows the timing diagram for single spatial phase modulator single chip (single spatial amplitude modulator) projection system with white segment. Also, other “boost schemes” are included within the scope of the present invention. Such boost schemes, for instance, provide a yellow, cyan and magenta boost by dedicating time segments to simultaneously operating two of the three or more laser sources. This boosts the secondary colors, and as a result also white brightness. So, at least all of these following options for additional segments are included within the scope of the present invention: RGBW, RGBY, RGBCMY, and RGBCMYW. Wherever there are two or more light beams of different colors incident on the single spatial phase modulator, path length compensation can be applied to the two or more light beams.

D/BARUXR-019-DE Description

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LU103267 - 38 -

Without the path length compensations, this will only be possible if the illumination spots of the three primary colors are spatially separated (red, green and blue spots side by side). But as this limits the useful area on the spatial phase modulator that is available for each colored light, the angular spread in the illumination for a given beam quality of the laser source will further increase, resulting in a further increase in the size of the

The highlight image at this stage - before being cast on the spatial amplitude modulators (e.g., imager, such as a DMD) is, due to the finite PSF, a blurry illumination profile with, for instance, dark areas and bright areas. This is a very low-resolution, e.g. blurry, image, which will have a higher resolution in the final image that is made by the spatial amplitude modulator.

Splitting light can be done not only on wavelength, but also on polarization type.

Polarization is not always a preferred option, since it is simpler to work with unpolarized light. With polarized light, all three colors would need to have the same polarization if the spatial phase modulator is polarization sensitive. Selection can be between the different wavelengths based on polarization if the spatial phase modulator can work with any polarization, e.g. is for example of the piston type spatial phase modulator supplied by Texas Instruments, USA, and where the laser light sources are polarized. Piston based spatial phase modulators are described in US2019/179134, US 2019/179135,

US2020/209614 which are incorporated by reference. If then red incident light would have a different polarization than green and blue incident light for example, one could then deviate the path of green and blue with a polarizing beam splitter and combine it again with the same component. Therefore, polarizing beam splitters can be an alternative to dichroic mirrors in the construction of color-based path length compensators if the polarization state is linked to the light color.

As described above, the diffraction grating displayed or published on the surface of the spatial phase modulator introduces the same phase pattern for all three or more primary colors. Practical spatial phase modulators will usually do, or often do, introduce a more or less fixed retardation (not taking into account dispersion effects) for a certain drive level. In accordance with embodiments of the present invention, the retardation relative to the wavelength of the light will be different for the three primary colors.

D/BARUXR-019-DE Description

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LU103267 -39-

In a system with three spatial phase modulators, this is dealt with during the calibration of the spatial phase modulators, such that a certain input value to a spatial phase modulator driver will result in a 2T] (2 Pi) retardation for the wavelength with which it is used.

On the other hand, the single spatial phase modulator can only be calibrated for a single wavelength. Assuming that the calibration is carried out for the green wavelength for example, then the retardation in red light will be smaller than the targeted (smaller than the perfect value) retardation while the retardation in blue light will be larger than targeted (larger than the perfect value) retardation. For example, if the target 21T retardation is in green light, then there will be 2112 retardation in red and 2115

R B retardation in blue again ignoring dispersion.

When there is only one spatial phase modulator, a preferred or a most preferred arrangement is that the spatial phase modulator is calibrated to achieve the desired retardation at a wavelength intermediate between blue and red (shown as lambda or

Ab). . 2 (Equation 7) M= —z— at ar

For example, in a system with A8=465 nm and Ar=639 nm, calibration of the spatial phase modulator is carried out for A=538 nm. For example, one could have a green wavelength Az=530 nm. The light intermediate between blue and red will cause a phase mismatch.

To estimate the impact of the phase mismatch, the response of a blazed grating can be studied (see Fig. 3). This can apply to any of the embodiments of the present invention.

Fig. 3 shows a collimated incoming light beam 19, e.g. from the illumination optical sub- system 20, the incoming light 19 being incident on a single spatial phase modulator 12 which is modelled by a blazed grating in transmissive mode. Instead of a transmissive blazed grating, a reflective spatial phase modulator could be modelled. Due to the

D/BARUXR-019-DE Description

B220012

LU103267 - 40 - surface of the single spatial phase modulator 12 and the blazed grating having a periodic structure, steered light 15 will be dependent upon the wavelength of the incoming light, and the steered light 15 from the single spatial phase modulator 12 will exit the single spatial phase modulator 12 at a first angle (alpha) which steers this steered light 15 to a beam steering target, e.g. forming a highlight. The single spatial phase modulator 12 will also produce lesser steered light 17 at higher orders and angles. The dimensions of relay optics can be provided that prevents the higher order steered light from reaching an intermediate image. Unsteered light 16 will leave the spatial phase modulator 12 in a constant manner, i.e. is not modulated.

For example, a 4-pixel blazed grating can be produced by a spatial phase modulator with pixel size of 10.8 micron, which is calibrated for the intermediate wavelength of 538 nm. At the nominal wavelength this grating shows steps of 27/4, going from -2.36 Rad to +2.36 Rad. The same grating seen by the blue wavelength (see Fig. 4) shows steps of 2171/4, going from -2.76 Rad to +2.76 Rad. And when seen by the red wavelengths the steps of 2T7/4 go from -1.99 Rad to +1.99 Rad (see Fig. 5).

Assuming an idealized phase pixel the steering angle can be modelled, as well as the steering efficiency and the amount of unsteered light for different blazed gratings. 3 3 3 c c c

D ‚© 2 ‚© c oO oO oO = — = = = o 8 © © © ° © © o = D P D © D © = © c D c D c D © S 5 2 5 2 5 2 zs |2 2 2 2 2 2 2 mn = 0 D © 0 D © D 3pix 06841 082° 0.6357 0.028€ 094° 06836 00004 113° 06357 0.0421 4pix 0.8107 062° 07504 0.0227 070° 0.8101 0.0002 0.85° 0.7505 0.0374 gpix 00497 031° 0.8757 0.0182 035° 0.9489 0.0002 042° 08757 0.0334

D/BARUXR-019-DE Description

B220012

LU103267 - 41 - 16pix 0.9872 0.15° 09094 0.0174 0.18° 0.9864 0.0002 0.21° 0.9094 0.0325

Table 1: Effect on steering efficiency and unsteered light of 2PI scaling for blazed gratings (continuous addressing or thus infinite amount of driving bits assumed)

From table 1, one can see that the steering angle (alpha) scales with wavelength and, therefore, the path length differences discussed earlier can result in the intermediate color images overlapping each other for the three colors. The choice of the intermediate wavelength results in balanced efficiency losses between the blue and red lights. There is a reduction in steering efficiency of around 7% in blue and red. Table 1 also shows that there is an increase in the amount of unsteered light in blue and red. For the 2-pixel blazed grating blue and red show 6% unsteered light, for shallower blazed grating the amount of unsteered light is reduced.

This data, including gratings with larger diffraction angles than the 2-pixel grating is represented in the graphs of Figs. 6 and 7. Fig. 6, shows average steering efficiency of 2-, 3-, 4-, 8-pixels blazed gratings (for a MEMS piston based spatial phase modulator with 15 non-equidistant retardation levels). Fig. 7 illustrates unsteered light for 2-, 3-, 4-, 8 pixels blazed gratings (for a MEM’S piston-based SPM with 15 non-equidistant retardation levels).

The x-axis denotes the normalized diffraction angle (1 denotes diffraction angle = wavelength/pitch).

Fig. 7 shows the unsteered light for 2, 3, 4, 8 pixels blazed gratings (for a MEM’S-piston based spatial phase modulator with 15 non-equidistant retardation levels).

Implementation in a projection system with a single-chip spatial amplitude modulator

This section deals with use of a single-chip spatial amplitude modulator, which can be supplied alone or in combination with one or more optical sub-systems or with a complete projector.

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LU103267 „42 -

In a projection system with a single spatial amplitude modulator, the laser sources of three primary colors will be operated sequentially, i.e. each color having a time segment when it is applied to the single spatial amplitude modulator. In this case, if the single spatial phase modulator is fast, different phase patterns may be applied in each of the time segments that are optimized for the color that is activated at that point in time and/or different calibration values could be applied that are optimized for the color that is activated at that point in time.

This sequential operating mode with phase patterns and calibration optimized for each color brings a number of advantages. Firstly, the highlight patterns can be different for each colored light. The 2[] scaling can be exact for each of the colored lights. Matching

PSFs (see further) is not required.

In principle, the phase patterns for each color can now also be optimized to bring the intermediate images for red, green and blue to overlap in the same position (i.e. intermediate highlight image 14 at the intermediate image plane 14a). However, the minimal path length is determined by the color with the smallest diffraction angle which is blue. The other colors will not have the advantage of the larger diffraction angle they achieve. As a result, the size of the point spread function (PSF) of green and especially red will grow larger than what could be achieved at their respective minimal path lengths, for a given angular spread in the illumination angles (as defined by the beam quality of the laser source). Color dependent path length compensation using compensator 10 can be used to reduce PSF size.

Therefore, also in a projection system with a single-chip spatial amplitude modulator, the implementation of the path length compensator, will reduce or remove path length differences. A path length compensator 10 as shown in Fig. 2d and, e.g. functioning by means of dichroic mirrors, is useful to minimize the PSF size in green light and especially in red light. The present invention is not limited to this type of color- dependent path length compensators.

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as published or displayed on the single spatial phase modulator, inside of the steering target dimensions

D/BARUXR-019-DE Description

B220012

LU103267 - 43 - (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the secularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing linked to the pixel pitch of the single spatial phase modulator (seen as a grating) has to be greater than the largest horizontal or vertical dimension of the steering target area increased with the size of the PSF. With such a minimum required path length the PSF of that color is as small as possible. À longer path length results in a wider PSF. As stated above, the minimum path length is longer for blue than it is for green and even more for red.

An aim is to capture one "steered" diffraction order in the target area (intermediate image) and have all the other steered diffraction orders - that would create undesired "ghost" illuminations - outside of that target area. The following formula is relevant: min_ distance = target width x PLM_pitch/lambda where lambda is the wavelength. In reality the PSF size is not zero and the steering distance has to be increased because all the diffraction orders blur and become bigger and it is required that all of the light within the PSF size should fall outside of the target area (intermediate image).

In a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane.

Deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color. This is also mentioned with respect to Equations 5 and 6.

In a single-chip system without white segment, one may have the longest blue path length for all colors. Alternatively, one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become larger. Use of the color dependent path length compensator 10 reduces the path length differences and hence reduces the PSF size, e.g. for green.

D/BARUXR-019-DE Description

B220012

LU103267 - 44 -

A reason for wanting a minimum path length is to keep (most of) the light of the higher diffraction orders — which are leaving the single spatial phase modulator under different angles than the diffraction order used for steering away from the intermediate highlight image. (Most of) Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be relayed to the spatial amplitude modulator. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not "guided" outside of the active target area, they will produce "ghost" illumination spots in the active area in areas where they are not always desired. The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and, hence, never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

Moreover, it is known in single-chip systems not to operate in a color sequential mode with only the pure primary colors. In order to boost the brightness, in accordance with an embodiment of the present invention it is beneficial to introduce a so called “white segment” where all three lights of primary colors are activated simultaneously forming white light. For example, Fig. 13 shows the timing diagram for single spatial phase modulator single chip (single spatial amplitude modulator) projection system with white segment. Also, other “boost schemes” are included within the scope of the present invention. Such boost schemes, for instance, provide a yellow, cyan and magenta boost by dedicating time segments to simultaneously operating two of the three or more laser sources. This boosts the secondary colors, and as a result also white brightness. So, at least all of these following options for additional segments are included within the scope of the present invention: RGBW, RGBY, RGBCMY, and RGBCMYW. Wherever there are two or more light beams of different colors incident on a single spatial phase modulator, path length compensation can be applied to the two or more light beams

Without the path length compensations, this will only be possible if the illumination spots of the three primary colors are spatially separated (red, green and blue spots side by side). But as this limits the phase modulator that is available for each colored light, the angular spread in the illumination for a given beam quality of the laser source will further increase, resulting in a further increase in the size of the PSF. Increase in size of the

PSF results in a highlight image that is not so crisp but is blurry, which requires

D/BARUXR-019-DE Description

B220012

LU103267 - 45 - therefore a spatial amplitude modulator to “clean up the image”. The highlight image at this stage - before being cast on the spatial amplitude modulator (e.g., imager, such as a DMD) is, due to the finite PSF, a blurry illumination profile with, for instance, dark areas and bright areas. This is a very low-resolution, e.g. blurry, image, which will have a higher resolution in the final image that is made by the spatial amplitude modulator.

With the path length compensation, it is possible to have each of the primary colors illuminate the full useful or active area of the single spatial phase modulator, and to use a common phase pattern to steer white highlights during this “white segment”. This is similar to the three-chip spatial amplitude modulator system applying a mid-wavelength 2]] calibration during these “white or secundary color segments”.

Hence, for projectors with a single-chip spatial amplitude modulator, operating with a white segment, the system with the path length compensations brings a double advantage on the PSF, for example to minimize the PSF on green and especially red by enabling shorter path lengths than blue and to minimize the PSF by enabling the use of the full area of the PLM for each of the primary colors.

In a color sequential system with white segment included, it is preferable that the PSF’s are approximately matched between the three primary colors.

Matching PSFs

This section relates to how the PSF influences the generation of images which can be applied to any embodiment of the present invention.

Preferably, the three color lights delivered by the illumination optical sub-system to the spatial phase modulator each produce a point spread function (PSF) that is similar in size and in shape.

Given the path length differences, the angular spread of the light incident on the spatial phase modulator 12 preferably scales proportionally to the wavelength.

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LU103267 - 46 -

If the red incident angle on the spatial phase modulator 12 is defined to be between 0 and +/- BR the aim for the green incident angle on the spatial phase modulator 12 is to be between 0 and +/- BG. . Ag (Equation 8) BG = PR =* Te

R

Similarly, the aim for the blue incident angle on the spatial phase modulator 12 is to be between 0 and +/- BB. Therefore, (Equation 9) BB = BR +2

R

In any of the embodiments of the present invention, this requirement does not have to be met perfectly. The clean-up in the spatial amplitude modulator of the highlights can deal with some degree of differences in PSF shapes for each colored light. In that case, the light steering is preferably adapted such that the highlight is fully encompassed by the color with the smallest PSF. However, to minimize the light waste in the other colors a more or less matching PSF is most favorable.

White laser light source and common fiber uniformization

This is an embodiment that is illustrated in Fig. 9. It can be used individually or in combination with any of the other illustrated sub-systems or in a projector.

Fig. 9 illustrates an illumination optical sub-system 20, suitable for use in a projection apparatus. The illumination optical sub-system 20 in Fig. 9, shows a single white laser light source 16, a single common uniformizer such as a single common fiber 18, a single common collimator 22, a single spatial phase modulator 12 (controlled by control system 42 as shown in Figs. 2a, 2b, 2c and also in Fig. 9 but not shown in Fig. 9). The fHumination optical sub-system 20 can comprise a single while laser source of combined fight sources 16-B (blue), 16-G (green, 16-R (red), i.e. three or more primary color light source. The illumination optical sub-system 20 can provide collimated or substantially

D/BARUXR-019-DE Description

B220012

LU103267 - 47 - collimated light to an intermediate optical sub-system 30. The illumination optical sub- system 20 includes a white light source 16, which, for example is a laser diode array (LDA) of laser diodes emitting light of the primary colors. The iliumination optical sub- system 20 is operably connected to the intermediate optical sub-system 30 whereby the intermediate optical sub-system 30 comprises a single spatial phase modulator 12 {controlled by control system 42 as shown in Figs. 2a, 2b, 2c and also in Fig. 9 but not shown in Fig. 9), and a color dependent optical path length compensator 10, wherein an output of the spatial phase modulator 12 is for generating steered light which forms an intermediate highlight image 14 on an intermediate image plane 14a. In addition, a control system (not shown in Fig. 9 but shown in Figs. 2a, 2b, 2c) can be configured to control the operation of the spatial phase modulator 12 to thereby provide phase patterns which steer the collimated white light to an area or areas of an image with highlights which have higher brightness and another area or areas of the image with lower brightness, the image being transferred to a spatial amplitude modulator. The control system can be configured to control the operation of the spatial amplitude modulator to form another image which is for projection via a projection lens. The control system can be adapted to calibrate the spatial phase modulator. The calibration can select from green having a primary wavelength range of 495 - 570 nm, red having a primary wavelength of 570 - 720 nm, and blue having a primary wavelength of 440 - 495 nm. As an example, the control system may use light with the dominant wavelengths derived from the ranges above, e.g. dominant wavelength or blue being 465 nm, the dominant wavelength for red being 639 nm, and the dominant wavelength for green being 530 nm. The control system may be implemented in different ways all, of which are included within the scope of the present invention. For example, the spatial phase modulator can be calibrated for all primary colors at an intermediate wavelength of 538 nm.

A highlight relay optical sub-system 40 has a set of optical components such as lenses and mirrors for imaging the intermediate highlight image 14 onto a spatial amplitude modulator 28.

The path between white light source and the diffuser 14a or between the white light source and the spatial amplitude modulator 28 can be folded to reduce length.

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LU103267 - 48 -

The spatial amplitude modulator 28 can be as shown in any of Figs. 2a, 2b, 2c in sub- system 40 and can be controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also to be included in Fig. 9 but not shown in Fig. 9.

A highlight relay optical sub-system 40 for relaying and imaging the intermediate highlight image 14 onto a spatial amplitude modulator 28 can be provided (see any of

Figs. 2a, 2b, 2c, controlled by control system 42 not shown in Fig. 9). Color-dependent optical path length compensator 10 (for RGB beams) is placed in optical path 8 between the spatial phase modulator 12 and the intermediate highlight image 14, for example on a static or moving diffuser, e.g. spinning diffuser or diffuser with 2D motion (e.g. side to side, or rotate). The static or dynamic diffuser can be placed at (i.e. in the vicinity of) or in the intermediate image plane 14a. This will allow sufficient de-speckling though it will slightly increase the blurring of the image. Furthermore, intermediate highlight image 14 can be provided on intermediate image planes 14a, respectively can be provided between the spatial phase modulator or modulators and a final spatial amplitude modulator. A (static or dynamic) diffuser can be placed in or at each of these intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail although it will slightly increase the blurring of the highlight image.

A highlight image projection optical sub-system 50 (e.g. as shown in any of the Figs. 2a, 2b, 2¢) can be provided for taking a highlight image from the spatial amplitude modulator (controlled by control system 43 as shown in Figs. 2a, 2b, 2c) and projecting the image from the spatial amplitude modulator onto a projection screen 33. The highlight image can be added to a baseline image already projected on the projection screen 33, e.g. a multicolored baseline image such as a video image to provide highlights in video images.

Referring again to Fig. 9, an illumination optical sub-system 20 can include white collimated light from a single white laser source 16. The single white laser source 16 can contain red, green and blue lasers 16-R, 16-G, 16-B, respectively producing colored laser beams. Light from the white laser source 16 is introduced into a common uniformizer. For example, light from the white laser source 16 is introduced into a single common fiber 18 for uniformization and mixing of the light from the individual lasers 16-

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LU103267 - 49 -

R, 16-G, and 16-B. As an alternative to fiber uniformization, also uniformization with a micro-lens fly-eye integrator can be used.

For example, light beams from the red, green and blue lasers 16-R, 16-G, and 16-B can be combined with a combiner such as a dichroic mirror combiner (not shown) and can be focused together at an entrance of an uniformizer such as uniformizing fiber 18. The uniformizing fiber 18 can have a rectangular cross-section. The focusing can be achieved by a common focusing lens, i.e. common to the light beams from the red, green and blue lasers 16-R, 16-G, and 16-B (not shown). N.B. it is included within the scope of the present invention that the focusing lens may combine optical elements that are common to light beams from the red, green and blue lasers with other optical elements that are for each individual light beam color.

Alternatively, a focusing lens for each colored light can be provided and then the different colored light beams can be combined by a combiner such as dichroic mirrors placed in the converging light beams (not shown). The cross-section of the light beams before the common focusing lens can be tailored to obtain an as good as possible matching of the PSF as discussed above, namely, cross-section blue < cross-section green < cross-section red. Ideally, CSg/A\B=CSe/AG=CSr/Ar (with CS meaning cross- section)

Light from the exit of the common fiber 18 (common to the light beams from the red, green and blue lasers 16-R, 16-G, 16-B) is imaged with any required magnification by common collimation optics 22 to subsequently illuminate such as evenly illuminate the spatial phase modulator 12 with white light. The illumination optical sub-system 20 can provide collimated or substantially collimated light to the intermediate optical sub- system 30. The illumination can be incident on the spatial phase modulator 12 at a small angle e.g. 5 to 25°. This angle can be in either vertical (along the direction of the smallest dimension of the active area) or horizontal (along the direction of the longest dimension of the active area) direction. The vertical direction is much preferred as this minimizes the angle required to separate ingoing and outgoing light beams. The outgoing light beam is directed to wavelength dependent path length compensator 10, for example using dichroic mirrors as described with reference to Fig. 2d. The wavelength dependent path length compensator 10 is installed to introduce the path

D/BARUXR-019-DE Description

B220012

LU103267 - 50 - length differences required for compensation of the path lengths in the green and blue paths. If dichroic mirrors are used these dichroic mirrors can be installed perpendicular to the outgoing beam direction. Since these path deviations can only be introduced at the point where the incoming and outgoing beams are separated, preferably they are introduced as close as possible to the intermediate image.

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as published or displayed on a spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the secularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing linked to the pixel pitch of the spatial phase modulator (seen as a grating) has to be greater than the largest horizontal or vertical dimension of the steering target area increased with the size of the PSF. With such a minimum required path length the PSF of that color is as small as possible. À longer path length results in a wider PSF. The minimum path length is longer for blue than it is for green and even more for red.

In a three-chip system or a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane. In a three-chip system, deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color. This is also mentioned with respect to Equations 5 and 6.

D/BARUXR-019-DE Description

B220012

LU103267 -51-

In a single-chip system without white segment, one may have the longest blue path length used for all colors. Alternatively, one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become larger. A color dependent path length compensator 10 is used to reduce the path length differences and hence to reduce the size of the PSF, e.g. for green light.

The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and hence never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

Moreover, it is known in single-chip systems not to operate in a color sequential mode with only the pure primary colors alone. In order to boost the brightness, in accordance with an embodiment of the present invention it is beneficial to introduce a so called “white segment” where all three lights of primary colors are activated simultaneously forming white light. For example, Fig. 13 shows the timing diagram for single spatial phase modulator single chip (single spatial amplitude modulator) projection system with white segment. Also, other “boost schemes” are included within the scope of the present invention. Such boost schemes, for instance, provide a yellow, cyan and magenta boost by dedicating time segments to simultaneously operating two of the three or more laser sources. This boosts the secondary colors, and as a result also white brightness. So, at least all of these following options for additional segments are included within the scope of the present invention: RGBW, RGBY, RGBCMY, and

RGBCMYW. Wherever there are two or more light beams of different colors incident on

D/BARUXR-019-DE Description

B220012

LU103267 „52 - a single spatial phase modulator, path length compensation can be applied to the two or more light beams.

The spatial phase modulator 12 can be a single spatial phase modulator, if the spatial phase modulator does not require polarized light for its operation. For a single spatial phase modulator for unpolarized light a piston based spatial phase modulator is preferred. To achieve an acceptable PSF and to handle the required power, a 0.98” (inch) device would be advantageous.

White laser light source with common fiber uniformization and two spatial phase modulator (polarized light)

This is an embodiment that is illustrated in Fig. 10. It can be used individually or in combination with any of the other illustrated sub-systems or in a projector.

Referring to Fig. 10, an illumination optical sub-system 20, having light sources 16, e.g. 18-B (blue), 16-G (green), 16-R (red) of three or more primary colors, The illumination optical sub-system 20 can provide collimated or substantially collimated light to an intermediate optical sub-system 30. The illumination optical sub-system 20 is operably connected to an intermediate optical sub-system (30). Referring to Fig. 10, a single set of two spatial phase modulators 26 for polarized operation (controlled by control system

D/BARUXR-019-DE Description

B220012

LU103267 -53- 42 as shown in Figs. 2a, 2b, 2c and also to be understood as included in Fig. 10 but not shown in Fig. 10) can be used with a polarizing beam splitter 24 for spatial phase modulators that work with polarized light. For example, a broadband half wave retarder 27 can be installed in one of the two polarized light paths to obtain the same incident polarization on the single set of two spatial phase modulators 26 as the incident light.

The single set of two spatial phase modulators 26 can be used, that by design, work with orthogonal polarization directions. The polarizing beam splitter 24 splits the incoming light over the single set of two spatial phase modulators and also combines the outgoing beams of the single set of two spatial phase modulators. The combined outgoing beam is again unpolarized.

The intermediate optical sub-system 30 comprises the single set of two spatial phase modulators 25 for polarized light operation and a color dependent optical path length compensator 10, wherein an output of the single set of two spatial phase modulators 26 is steered light for forming an intermediate highlight image 14 on an intermediate image plane 14a. A highlight relay optical sub-system 40 is provided for imaging the intermediate highlight image 14 onto one or more spatial amplitude modulators (e.g., as shown in any of Figs. 2a, 2b, 2c).

In addition a control system (not shown in Fig. 10 but shown in Figs. 2a, 2b, 2c) can be configured to control the operation of the single set of two spatial phase modulators 26 for polarized light operation to thereby provide phase patterns which steer the collimated white light to an area or areas of an image 14 with highlights which have higher brightness and another area or areas of the image with lower brightness, the image being transferred to a spatial amplitude modulator 28. The control system can be configured to control the operation of the single set of two spatial modulators 28 for polarized light operation to form another image which is for projection via a projection lens. The control system can be adapted to calibrate the single set of two spatial modulators 26 for polarized light operation. The calibration can select from green having a primary wavelength range of 495 -570 nm, red having a primary wavelength range of 570 - 720 nm, and blue having a primary wavelength range of 440 - 495 nm. As an example, the control system may use light with the dominant wavelengths derived from the ranges above, e.g. dominant wavelength or blue being 465 nm, the dominant wavelength for red being 639 nm, and the dominant wavelength for green being 530

D/BARUXR-019-DE Description

B220012

LU103267 - 54 - nm. The control system may be implemented in different ways all, of which are included within the scope of the present invention. For example, the single set of two spatial phase modulators 25 for polarized light operation can be calibrated for use with all primary colors by using only green with a wavelength of 532 nm.

A highlight image projection optical sub-system (as shown in any of Fig. 2a, 2b, 2c) can be provided for taking a highlight image from the spatial amplitude modulator 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also in Fig. 10 but not shown in Fig. 10) and projecting the image from the spatial amplitude modulator 28 onto a highlight image plane. The highlight image can be added to a bassline video image to provide highlights, such as a multicolored baseline image such as a video image.

Accordingly, one projecior makes a standard video image, and one projector makes highlight images. The two images are then projected on the same projection screen and are coinciding there. Preferred embodiments of the present invention are hybrid projectors with blurry but configurable highlight images superimposed on uniform baseline illumination, which are combined in the projector before being brought to the

SAMs that make the final high-resolution image with a much better resolution.

Referring again to Fig. 10, an illumination optical sub-system 20 can include white collimated light from a single white laser source 16. The single white laser source 16 can contain red, green and blue lasers 16-R, 16-G, and 16-B, respectively. Light from the white laser source 16 is introduced into a common uniformizer. For example, light from the white laser source 16 is introduced into a single common fiber 18 for uniformization and mixing of the light from the individual lasers 16-R, 16-G, and 16-B.

An alternative to fiber uniformization, uniformization with a micro-lens fly-eye integrator can be used.

For example, light beams from the red, green and blue lasers 16-R, 16-G, 16-B can be combined together by means of a combiner (not shown), such as a dichroic mirror combiner (not shown), and can be focused together at an entrance of an uniformizer such as uniformizing fiber 18. The uniformizing fiber 18 can have a rectangular cross- section. The focusing can be achieved by a common focusing lens (not shown). N.B. it is included within the scope of the present invention that the focusing lens may combine

D/BARUXR-019-DE Description

B220012

LU103267 -55- optical elements that are common to light beams from the red, green and blue lasers with other optical elements that are for each individual light beam color.

The cross-section of the light beams before the focusing lens can be tailored to obtain an as good as possible matching of the PSF as discussed above, namely, cross-section blue < cross-section green < cross-section red. Ideally, CSg/\g=CSc/Ac=CSr/Ar (with CS meaning cross-section).

Light from the exit of the common fiber 18 is imaged with any required magnification by common collimation optics 22 to subsequently evenly illuminate the single set of two spatial phase modulators 26 for polarized light operation, with white light. The

Humination optical sub-system 20 can provide coliimated or substantially collimated white light to the intermediate optical sub-system 30. The illumination, that is collimated or substantially collimated white light, can be incident on the single set of two spatial phase modulators 26 for polarized light operation, at a small angle (e.g. 5 to 25°). The active area (the area of the addressable pixels elements) of the single set of two spatial phase modulators 26 for polarized light operation is rectangular in shape. This incident angle can be in either vertical (along the direction of the smallest dimension of the active area of the single set of two spatial phase modulators 26 for polarized light operation), or horizontal (along the direction of the longest dimension of the active area) direction. The vertical direction is much preferred as this minimizes the angle required to separate ingoing and outgoing light beams. In the outgoing light beam, wavelength dependent path length compensator 10, for example using dichroic mirrors as described with reference to Fig. 2, is installed to introduce the path length differences required for compensation of the path lengths in the green and blue paths. If dichroic mirrors are used, these dichroic mirrors can be installed perpendicularly to the outgoing beam direction.

Since these path deviations, i.e. the path length differences required for compensation of the path lengths of the differently colored light beams, can only be introduced at the point where the incoming and outgoing beams are separated, preferably they are introduced as close as possible to the intermediate image 14.

D/BARUXR-019-DE Description

B220012

LU103267 - 56 -

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as published or displayed on a spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the specularly reflected or undeflected transmitted zero order) fall outside of the same steering target, namely the intermediate highlight image. For this, the diffraction order spacing which is linked to the pixel pitch of the spatial phase modulator (seen as a grating) has to be greater than the largest horizontal or vertical dimension of the steering target area (i.e. intermediate highlight image) increased with the size of the

PSF (. With such a minimum required path length for a light color, the PSF of that color is as small as possible. À longer path length results in a larger, i.e. wider PSF. The minimum path length is longer for blue than it is for green and even more for red. An aim is to capture one "steered" diffraction order in the target area (intermediate image) and have all the other steered diffraction orders - that would create undesired "ghost" illuminations - outside of that target area. The following formula is relevant: min_ distance = target width x PLM_pitch/lambda where lambda is the wavelength. In reality the PSF size is not zero and the steering distance has to be increased because all the diffraction orders blur and become bigger and it is required that all of the light within the PSF size should fall outside of the target area (intermediate image).

In a three-chip system or a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane. In a three-chip system, deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color. This is also explained with respect to Equations 5 and 6.

In a single-chip system without white segment, one may have the longest blue path length used for all colors. Alternatively, one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become larger. The color dependent optical path length compensator 10 can be applied which will reduce the size of the green PSF for example.

D/BARUXR-019-DE Description

B220012

LU103267 - 57 -

A reason for wanting a minimum path length is to keep at least most of the light of the higher diffraction orders — which are leaving the single set of two spatial phase modulators adapted for polarized operation, under different angles than the diffraction order used for steering away from the intermediate highlight image. Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be relayed to the spatial amplitude modulator or modulators. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not "guided" outside of the active target area (the intermediate highlight image), they will produce "ghost" illumination spots in the active area of the intermediate highlight image in areas where they are not always desired. The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and hence never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

Moreover, it is known in single-chip systems not to operate in a color sequential mode with only the pure primary colors. In order to boost the brightness, in accordance with an embodiment of the present invention it is beneficial to introduce a so called “white segment” where all three lights of primary colors are activated simultaneously forming white light. For example, Fig. 13 shows the timing diagram for single spatial phase modulator single chip (single spatial amplitude modulator) projection system with white segment. Also, other “boost schemes” are included within the scope of the present invention. Such boost schemes, for instance, provide a yellow, cyan and magenta boost by dedicating time segments to simultaneously operating two of the three or more laser sources. This boosts the secondary colors, and as a result also white brightness. So, at least all of these following options for additional segments are included within the scope of the present invention: RGBW, RGBY, RGBCMY, and RGBCMYW. Wherever there are two or more light beams of different colors incident on a single spatial phase modulator, path length compensation can be applied to the two or more light beams.

Without the path length compensations, this will only be possible if the illumination spots of the three primary colors are spatially separated (red, green and blue spots side by side). But as this limits the useful area on the spatial phase modulator that is available

D/BARUXR-019-DE Description

B220012

LU103267 - 58 - for each colored light, the angular spread in the illumination for a given beam quality of the laser source will further increase, resulting in a further increase in the size of the

A white LDA can be used with any of the embodiments of the present invention. The

LDA can have 2 legs of red light lasers with each leg holding 10, 20 or 30 lasers, e.g. 3x10 lasers. These two legs can be combined on polarization, to minimize the overall etendue. For instance, further the white LDA contains one leg of green light lasers holding 3x10 lasers. The green light is combined with the red light by means of a dichroic mirror that passes the red light and reflects the green light. It further contains one leg of blue laser holding 3x6 lasers. The blue light is combined with the green and red light by means of a dichroic mirror that passes red and green light and reflects blue light. A single common focusing lens couples the combined red, green and blue beams into a common fiber.

Figs. 2a, 2b, 2c, controlled by control system 42 not shown in Fig. 10). Color-dependent optical path length compensator 10 (for RGB beams) is placed in optical path 8 between the spatial phase modulator 12 and the intermediate highlight image 14, for example on a static or moving diffuser, e.g. spinning diffuser or diffuser with 2D motion (e.g. side to side, or rotate). The static or dynamic diffuser can be placed at (i.e. in the vicinity of) or in the intermediate image plane 14a. This will allow sufficient de-speckling though it will slightly increase the blurring of the image. Furthermore, two intermediate highlight images 14 can be provided on two intermediate image planes 14a, respectively can be provided between the spatial phase modulator or modulators and a final spatial amplitude modulator. A (static or dynamic) diffuser can be placed in or at each of these

D/BARUXR-019-DE Description

B220012

LU103267 -59- intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail, although it will slightly increase the blurring of the highlight image.

A highlight image projection optical sub-system 50 (see any of Figs. 2a, 2b, 2c) can be provided for taking the final highlight image from the spatial amplitude modulator 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also in Fig. 10 but not shown in Fig. 10), illuminated by the intermediate highlight image 14 or the combined intermediate highlight image (fig 2c) and projecting the image from the spatial amplitude modulator 28 onto a highlight image plane on a projection screen 33 via a projection lens 39. The highlight image can be added to a baseline image to provide highlighted images, such as a multi-colored baseline image such as a video image.

Multiple (e.g. three) primary color light sources, such as laser light sources (R, G, B), multiple individual (R, G, B) fiber uniformization, multiple individual (R, G, B) collimators, single spatial phase modulator (used for unpolarized light).

This is an embodiment that is illustrated in Fig. 11. It can be used individually or in combination with any of the other illustrated sub-systems or in a projector. This embodiment is for use with a single spatial phase modulator adapted for unpolarized light operation but a single set of two spatial phase modulators, adapted for polarized light operation is included in the embodiment of Fig. 12. At least two light beams of different colors are incident on the spatial phase modulator or modulators at the same time.

Referring to Fig. 11, this embodiment has at least two separate color beams such as three primary color beams, e.g. from RGB (red, green, blue) laser light sources 36-R, 36-G, 36-B, multicolor individual uniformization, e.g. provided by individual fibers (38-R, 38-G, 38-B, multicolored, individual collimators, 32-R, 32-G, 32-R, and a single spatial phase modulator (for operation with unpolarized light).

In Fig. 11, the illumination optical sub-system 20 has individual colored laser light sources each producing a light beam having at least one color of at least two colors. In

D/BARUXR-019-DE Description

B220012

LU103267 - 60 - particular, the light sources emit three light beams having three primary colors, such as red, green and blue, i.e. 36-R (red), 36-G (green), 36-B (blue). A beam from each laser light source is fed to an individual, uniformizer such as individual fibers 38-R (red), 38-G (green), and 38-B (blue). As an alternative to the fiber uniformization, also uniformization with a micro-lens fly-eye integrator can be implemented (not shown).

Individual collimation optics 32-R (for red), 32-G (for green), 32-B (for blue) can be provided per laser light color such as per primary-colored laser sources. The illumination optical sub-system 20 can provide collimated or substantially collimated light from individual color dependent collimators 32-R, 32-G, and 32-B to the intermediate optical sub-system 30. Individual primary-colored beams are provided such as red, green and blue collimated beams can be combined by reflecting off mirrors 35 and at least one dichroic mirror 37 which passes one primary color such as red and is reflective for green and blue, a dichroic mirror 47 which passes one of the other primary colors, such as blue and reflects green, and the remaining primary color blue is reflected from mirror 35. These colored light beams are combined into a single white beam for delivery to the single spatial phase modulator 12. For a single spatial phase modulator for use with unpolarized light, a piston based spatial phase modulator is preferred. To achieve an acceptable PSF and to handle the required power, a 0.98” (inch) device would be advantageous.

Dichroic mirror 37 can be provided to reflect two of the primary colors such as the blue and green light beams, e.g. through an angle of 90°. The remaining primary color such as red passes through the red pass dichroic mirror 37 which reflects the other primary colors such as blue and green light beams, e.g. through 90°. The green light beams are reflected by dichroic mirror 37 and dichroic mirror 47. Blue light beams are passed by dichroic mirror 47 and reflected by mirror 35. These blue and green light beams join with the red light beam which passes through the red pass dichroic mirror 37.

Referring to Fig. 11, optical sub-systems 20, 30, 40, 50 are provided for use either individually or in any combination in a projection apparatus (see Figs. 2a, 2b, 2c for such a projection apparatus). One of the optical sub-systems is an illumination system

D/BARUXR-019-DE Description

B220012

LU103267 - 61 - 20 comprising at least two color sources, e.g. three primary color sources such as R, G,

B light sources 36-B (blue), 36-G (green), 36-R (red). The illumination optical sub- system 20 can provide collimated or substantially collimated light to a single spatial phase modulator 12 of an intermediate optical sub-system 30 (i.e. working with unpolarized light). À further example of use with polarized light, uses specific optical fibers that do not depolarize the incident light, i.e. using a polarization-maintaining optical fiber, one can put the already polarized light from the laser light sources through these fibers and use the single SPM also with that polarization, or use other homogenization methods like fly-eye lenses that also maintain the polarization. The illumination optical sub-system 20 is operably connected to the intermediate optical sub- system (30) whereby the intermediate optical sub-system 30 comprises the single spatial phase modulator 12 (controlled by control system 42 as shown in Figs. 2a, 2b, 2c and to be understood as included in Fig. 11 but not shown in Fig. 11) and color- dependent optical path length compensator 10 (for example as shown in Fig. 2d).

Outputs of the spatial phase modulator 12 are steered and unsteered light whereby the steered light is for forming an intermediate highlight image 14 on an intermediate image plane 14a. A highlight relay optical sub-system 40 is provided for relaying and imaging the intermediate highlight image 14 onto one or more spatial amplitude modulators 28 (see any of Figs. 2a, 2b, 2c, controlled by control system 42 not shown in Fig. 11).

Color-dependent optical path length compensator 10 (e.g. for RGB beams) is placed in optical path 8 between the single spatial phase modulator 12 and the intermediate highlight image 14, for example on a static or moving diffuser, e.g. spinning diffuser or diffuser with 2D motion (e.g. side to side). The static or dynamic diffuser can be placed at (i.e., in the vicinity of) or in the intermediate image plane 14a. Being placed in the vicinity of the intermediate image plane 14a will allow sufficient de-speckling though it will slightly increase the blurring of the image. Furthermore, two intermediate highlight images 14 can be provided on two intermediate image planes 14a, respectively can be provided between the single spatial phase modulator and a final spatial amplitude modulator. A (static or dynamic) diffuser can be placed in each of these intermediate image planes. This is done for redundancy, for example to keep good speckle performance and a good laser classification even if one diffuser would fail.

D/BARUXR-019-DE Description

B220012

LU103267 „62 -

A highlight image projection optical sub-system 50 (see any of Figs. 2a, 2b, 2c) can be provided for taking an intermediate highlight image 14 from the at least one or more, for example three, spatial amplitude modulators 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also in Fig. 11 but not shown in Fig. 11) and projecting the image from the spatial amplitude modulator 28 or modulators onto a highlight image plane on a projection screen 33 via a projection lens 39. The highlight image can be added to a baseline image to provide highlighted images, such as a multicolored baseline image forming a video image.

Individual light beams of primary colors from red, green and blue lasers 36-R, 36-G, and 36-B can each be focused at an entrance of an individual uniformizer. Each uniformizer processes light of one primary color such as individual uniformizing fibers 38-R (red), 38-G (green), 38-B (blue). Each or any fiber 38-R, 38, G, 38-B can have a rectangular cross-section.

The focusing can be achieved by individual (i.e., one per color) focusing lenses (not shown). The individual cross-sections of the light beams before the individual focusing lenses with in this case the same focal length can be tailored to obtain an as good as possible matching of the PSF as discussed above namely, cross-section blue < cross- section green < cross-section red. Ideally, CSB/\?B=CSG/)\2G=CSR/R (with CS meaning cross-section). Since the focusing lens and the fiber are individual and color- specific, there are multiple options to match the PSF. One may adapt the power of the focusing lens as well as the cross section of the fiber for each colored light while leaving the cross-section of the light beams identical. For example, light beams from the red, green and blue lasers 36-R, 36-G, 36-B can be focused together each at an entrance of an uniformizer such as uniformizing fiber 38-R, 38, G, 38-B. The different colored light beams can be combined by a combiner such as dichroic mirrors placed in the converging light beams.

Light beams from the exit of the uniformizers such as from the individual fibers 38 are imaged with any required magnification by individual collimation optics 32-R (red), 32-G (green), 32-B (blue) to subsequently evenly illuminate the single spatial phase modulator 12 in the intermediate optical sub-system 30 with white light. The illumination

D/BARUXR-019-DE Description

B220012

LU103267 - 63 - optical sub-system 20 can provide collimated or substantially collimated white light to the intermediate optical sub-system 30. The illumination can be incident on the single spatial phase modulator 12 at a small angle e.g. 5 to 25°. This angle can be in either vertical (along the direction of the smallest dimension of the active area) or horizontal (along the direction of the longest dimension of the active area) direction. The vertical direction is much preferred as this minimizes the angle required to separate ingoing and outgoing light beams. In the outgoing light beam, path length compensator 10, e.g. using dichroic mirrors, is installed to introduce the path length differences required for compensation of the path lengths in the green and blue paths. If dichroic mirrors are used these dichroic mirrors can be installed perpendicular to the outgoing beam direction.

Since these path deviations can only be introduced at the point where the incoming and outgoing beams are separated, they are preferably introduced as close as possible to the intermediate highlight image 14.

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as published or displayed on a spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the secularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing linked to the pixel pitch of the spatial phase modulator (seen as a grating) has to be greater than the largest horizontal or vertical dimension of the steering target area increased with the size of the PSF. With such a minimum required path length the PSF of that color is as small as possible. A longer path length results in a wider PSF. The minimum path length is longer for blue than it is for green and even more for red. In a three-chip system or a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane. In a three-chip system, deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color. This is also mentioned with respect to Equations 5 and 6.

D/BARUXR-019-DE Description

B220012

LU103267 - 64 -

In a single-chip system without white segment, one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become larger. Color dependent path length compensation can be used to reduce the size of the PSF for green, for example.

A reason for wanting a minimum path length is to keep (most of) the light of the higher diffraction orders — which are leaving the single spatial phase modulator under different angles than the diffraction order used for steering away from the intermediate highlight image. (Most of) Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be relayed to the spatial amplitude modulator or modulators. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not "guided" outside of the active target area, they will produce "ghost" illumination spots in the active area in areas where they are not always desired. The path length is configured to make sure that these "ghost" illuminations never arrive in the intermediate highlight image and hence never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

D/BARUXR-019-DE Description

B220012

LU103267 - 65 -

The spatial phase modulator 12 can be a single spatial phase modulator, if the spatial phase modulator does not require polarized light for its operation. As a single spatial phase modulator for unpolarized light, a piston based spatial phase modulator is preferred. To achieve an acceptable PSF and to handle the required power, a 0.98” (inch) device would be advantageous. À further example of use with polarized light, uses specific optical fibers that do not depolarize the incident light, i.e. using a polarization-maintaining optical fiber, one can put the already polarized light from the laser light sources through these fibers and use the single SPM also with that polarization, or use other homogenization methods like fly-eye lenses that also maintain the polarization.

The individual primary-color beams such as red, green and blue collimated beams can be combined with at least one dichroic mirror 37 into a single white beam, that is then modulated by a single spatial phase modulator 12 operating with unpolarized light. The use of two or two spatial phase modulators 26 operating with polarized light after the incoming beam has been split in two polarizations, is described with reference to Fig. 12. This configuration is less preferable as it increases the system complexity and cost.

However, it still takes advantage of using only two spatial phase modulators to modulate the three primary color beams.

D/BARUXR-019-DE Description

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LU103267 - 66 -

Returning to Fig. 11 in this embodiment, the fiber cross-sections can be scaled for each colored light to deliver a smaller angular spread of the incident light on the single spatial phase modulator 12, i.e. for shorter wavelengths, in order to achieve matching PSF’s for the three colors.

An optical sub-system 20 is provided for use in a projection apparatus, the optical sub- system 20 comprising optical sub-elements such as light sources 36, uniformizers (fibers) 38 and collimators 32). The light sources 36-B (blue), 36-G (green), 36-R (red) emit light beams for 2 or more primary colors. The illumination optical sub-system 20 can provide collimated or substantially collimated (white light) light to an intermediate optical sub-system 30. The illumination optical sub-system 20 is operably connected to the intermediate optical sub-system 30 comprising path 8, color dependent path length compensator10, single spatial phase modulator 12, intermediate highlight image 14, and intermediate image plane 14a. An output of the single spatial phase modulator 12 is steered light for forming the intermediate highlight image 14 on an intermediate image plane 14a. Another output is unsteered light 16 (see Fig. 3). A highlight relay optical sub-system 40 is provided for casting the intermediate highlight image 14 onto a spatial amplitude modulator 28 (see any of Figs. 2a, 2b, 20).

In addition a control system 42 (not shown in Fig. 11 but shown in Figs. 2a, 2b, 2c) can be configured to control the operation of the single spatial phase modulator 12 to thereby provide phase patterns which steer the collimated white light to an area or areas of the image 14 with highlights which have higher brightness and another area or areas of the image with lower brightness, the image being transferred to a spatial amplitude modulator or modulators. The control system can be configured to control the operation of the single spatial amplitude modulator to form another image which is for projection via a projection lens. The control system can be adapted to calibrate the single spatial phase modulator. The calibration can select from wavelengths such ass green having a primary wavelength range of 495-570 nm, red having a primary wavelength of 570-720 nm, and blue having a primary wavelength of 440 - 495 nm.

As an example, the control system may use light with the dominant wavelengths derived from the ranges above, e.g. dominant wavelength or blue being 465 nm, the dominant wavelength for red being 639 nm, and the dominant wavelength for green being 530

D/BARUXR-019-DE Description

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LU103267 - 67 - nm. The control system may be implemented in different ways all, of which are included within the scope of the present invention. For example, the spatial phase modulator can be calibrated for all primary colors using an intermediate wavelength of 538 nm.

A highlight image projection optical sub-system 50 (see any of Figs. 2a, 2b, 2c) can be provided for taking a highlight image from the spatial amplitude modulator 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also in Fig. 11 but not shown in

Fig. 11) and projecting the image from the spatial amplitude modulator 28 through a projection lens onto a highlight image plane such as a projection screen 33. The highlight image can be added to a baseline image to provide highlights, e.g. highlights on a multicolored baseline image such as a video image.

Figs. 2a, 2b, 2c, controlled by control system 42 not shown in Fig. 11). Color-dependent optical path length compensator 10 (for white light as provided by RGB beams) is placed in optical path 8 between the single spatial phase modulator 12 and the intermediate highlight image 14, for example on a static or moving diffuser, e.g. spinning diffuser or diffuser with 2D motion (e.g. side to side, or rotate). The static or dynamic diffuser can be placed at (i.e., in the vicinity of) or in the intermediate image plane 14a.

This will allow sufficient de-speckling though it will slightly increase the blurring of the image. Furthermore, two intermediate highlight images 14 can be provided on two intermediate image planes 14a, respectively can be provided between the spatial phase modulator or modulators and a final spatial amplitude modulator. A (static or dynamic) diffuser can be placed in or at each of these intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail although it will slightly increase the blurring of the highlight image.

A highlight image projection optical sub-system 50 (see any of Figs. 2a, 2b, 2c) can be provided for taking an intermediate highlight image 14 from the spatial amplitude modulator 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also in

Fig. 11 but not shown in Fig. 11) and projecting the image from the spatial amplitude modulator 28 onto a highlight image plane on a projection screen 33 via a projection

D/BARUXR-019-DE Description

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LU103267 - 68 - lens 39. The highlight image can be added to a baseline image to provide highlighted images, such as a multicolored bassline image such as a video image.

Further details of this embodiment can be taken from Fig. 12 and the relevant description thereof.

Multiple (e.g. three) primary color laser light sources (R, G, B), multiple individual primary color fibers (R, G, B), multiple individual primary color collimators (R, G, B), and two spatial phase modulators (for polarized light operation).

This is an embodiment that is illustrated in Fig. 12. It can be used individually or in combination with any of the other illustrated sub-systems or in a projector.

Referring to Fig. 12, this embodiment has a number of separate primary colors, e.g.

RGB laser light sources 36-R, 36-G, 36-B, multicolor individual uniformization, e.g. provided by individual per color fibers (38-R, 38-G, 38-B), multicolored, individual per color collimators, (32-R, 32-G, 32-R), and a two or two spatial phase modulators 26 for use with polarized light. Uniformization with a micro-lens fly-eye integrator can be implemented alternatively (not shown).

Another example uses specific optical fibers that do not depolarize the incident light, i.e. using a polarization-maintaining optical fiber; one can put the already polarized light from the laser light sources through these fibers and use the single SPM also with that polarization, or use other homogenization methods like fly-eye lenses that also maintain the polarization.

Accordingly, Fig. 12 illustrates an optical sub-system 20 provided for use in a projection apparatus, comprising multicolor primary color laser light sources (red green blue 36-R, 36-G, 36-B), individual multicolor primary color fibers (38-R, 38-G, 38-B), individual multicolor primary collimators (32-R, 32-G, 32-B), and in intermediate optical sub- system 30 comprising a single set of two spatial phase modulators 26 (for polarized light operation). The illumination optical sub-system 20 can provide coliimated or substantially collimated light to the intermediate optical sub-system 30. The illumination optical sub-system 20 is operably connected to the intermediale optical sub-system 30.

D/BARUXR-019-DE Description

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LU103267 - 69 -

Referring to Fig. 12, a single set of two spatial phase modulators 26 is controlled by control system 42 as shown in Figs. 2a, 2b, 2c and also operating within the embodiment of Fig. 12 but not shown in Fig. 12. The single set of two spatial phase modulators 26 can be used with a polarizing beam splitter 24 for those spatial phase modulators that work with polarized light. For example, a broadband half wave retarder 27 can be installed in one of two light paths to obtain the same incident polarization on the single set of two spatial phase modulators (controlled by control system 42 as shown in Figs. 2a, 2b, 2c and also operating within the embodiment of Fig. 12 but not shown in Fig. 12). The single set of two spatial phase modulators 26 can be used, that by design, work with orthogonal polarization directions. The polarizing beam splitter 24 splits and distributes the incoming light over the single set of two spatial phase modulators 26 via the two light paths and also combines the outgoing beams of the single set of two spatial phase modulators 26. The combined outgoing beam is unpolarized.

The intermediate optical sub-system 30 comprises the single set of two spatial phase modulators 26 and color dependent optical path length compensator 10, wherein an output of the single set of two spatial phase modulators 26 is for forming an intermediate highlight image 14 on an intermediate image plane 14a. A highlight relay optical sub-system 40 can be provided (see Figs. 2a, 2b, 2c) for casting the intermediate highlight image 14 onto a spatial amplitude modulator 28, e.g. by using relay optics. The single set of two spatial phase modulators 26 is controlled by control system 42 as shown in Figs. 2a, 2b, 2c and for use in the embodiment of Fig. 12 but not shown in Fig. 12) and the color-dependent optical path length compensator 10 (for example as shown in Fig. 2d), wherein outputs of the single set of two spatial phase modulators 26 are steered and unsteered light whereby the steered light is for forming an intermediate highlight image 14 on an intermediate image plane 14a.

À highlight image projection optical sub-system 50 (see any of Figs. 2a, 2b, 2¢) can be provided for taking a highlight image from the spatial amplitude modulator 28 (controlled by control system 43 as shown in Figs. 2a, 2b, 2c and also for use in the embodiment in

Fig. 12 but not shown in Fig. 12) and projecting the image from the spatial amplitude modulator 28 onto a highlight image plane, e.g. a projection screen 33 via a projection lens 39. The highlight image can be added to a baseline image to provide highlights

D/BARUXR-019-DE Description

B220012

LU103267 - 70 - when the multicolored image is projected, e.¢. a multicolored baseline image such as a video image.

Referring again to Fig. 12, the illumination optical sub-system 20 can provide white collimated light from a plurality of color laser light sources. Each laser light source can contain primary-color lasers such as red, green and blue lasers 36-R, 36-G, and 36-B, respectively. Individual light beams from the red, green and blue lasers 36-R, 36-G, 36-

B, respectively, are introduced into individual uniformizers. For example, light from each of the red, green and blue lasers 36-R, 36-G, 36-B is introduced into individual uniformizers such as individual fibers 38-R, 38-G, 38-B for uniformizing and mixing of the light from the primary color individual lasers such as red, green and blue 36-R, 36-

G, 36-B- lasers. An alternative to fiber uniformization, also uniformization with a micro- lens fly-eye integrator can be used.

Primary colored light beams from the red, green and blue lasers 36-R, 36-G, and 36-B can be focused each at an entrance of an uniformizer such as one of uniformizing fibers 38-R, 38-G, and 38-B, respectively. Each uniformizing fiber 38-R, 38-G, 38-B can have a rectangular cross-section. The focusing can be achieved by individual focusing lenses (not shown). Output from each focusing lens for each colored light can be provided to the individual uniformizer such as an individual fiber 38-R, 38-G, and 38-B. The cross- section of the light beams before combining can be tailored to obtain an as good as possible matching of the PSF.

The RGB beams are then collimated in individual color specific collimators 32-R, 32-G, and 32-B. The different primary colored light beams which are output from individual collimators 32-R, 32-G, 32-B, respectively can be combined by a combiner such as a combiner having dichroic mirrors placed in the converging light beams. For example, the output from the collimators can be combined in one collimated light beam by using dichroic mirrors 37, 47 and regular mirror 35. Individual primary-colored beams such as red, green and blue collimated beams can be combined by reflecting off mirrors 35 and at least one dichroic mirror 37 (e.g. dichroic mirror 37) passes one primary color such as red and is reflective for green and blue, a dichroic mirror 47 passes one of the other primary colors, such as blue and reflects green, and the remaining primary color blue is reflected from mirror 35) to form a single collimated white beam for delivery to the single

D/BARUXR-019-DE Description

B220012

LU103267 -71- spatial phase modulator 12. Dichroic mirror 37 can be provided to reflect two of the primary colors such as the blue and green light beams, e.g. through an angle of 90°.

The remaining primary color such as red passes through the red pass dichroic mirror 37 which reflects the other primary colors such as blue and green light beams, e.g. through 90°. The green light beams are reflected by dichroic mirror 37 and dichroic mirror 47.

Blue light beams are passed by dichroic mirror 47 and reflected by mirror 35. These blue and green light beams join with the red light beam which passes through the red pass dichroic mirror 37.

For each primary color there is a minimum required path length that enables to keep only a maximum of one diffraction order for any grating such as published or displayed on a spatial phase modulator, inside of the steering target dimensions (dimensions of the intermediate highlight image) and have the other diffraction orders (except for the specularly reflected or undeflected transmitted zero order) fall outside of the same steering target of the intermediate highlight image. For this, the diffraction order spacing linked to the pixel pitch of the single set of two spatial phase modulators 26 (seen as a grating) has to be greater than the largest horizontal or vertical dimension of the steering target area increased with the size of the PSF. With such a minimum required path length, the PSF of that color is as small as possible. A longer path length results in a wider PSF. The minimum path length is longer for blue than it is for green and even more for red. In a three-chip system or a single-chip system with white segment, the path length compensation has to be perfect to obtain overlapping highlight images at the intermediate image plane.

D/BARUXR-019-DE Description

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LU103267 -72-

In a three-chip system, deviations smaller than +/-5% can be acceptable. “Perfect” compensation in this case means a path length variation for each light color that is inversely proportional to the dominant wavelength of the (laser) light used for that color.

This is also mentioned with respect to Equations 5 and 6.

In a single-chip system without white segment, the longest blue path length can be used for all colors. Alternatively, one may have the shortest path length for red and have a common blue/green path with the longer blue path length. In this case, the green path length is longer than minimally required and the green PSF will become larger. By using color dependent path length compensation, the PSF of the green beam can be reduced.

A reason for wanting a minimum path length is to keep the light of the higher diffraction orders — which are leaving the single spatial phase modulator or single set of two spatial phase modulators under different angles than the diffraction order used for steering away from the intermediate highlight image. Light of higher diffraction orders of the phase modulation falls outside of the active target area (intermediate highlight image size) that will be relayed to the spatial amplitude modulators. The spatial separation of light of such higher/other diffraction orders is only big enough after a certain minimum path length. If lights of these higher diffraction orders are not “guided” outside of the active target area, they will produce “ghost” illumination spots in the active area in areas where they are not always desired. The path length is configured to make sure that these “ghost” illuminations never arrive in the intermediate highlight image and hence never as “ghost” illumination spots on the final imagers (spatial amplitude modulators).

Moreover, it is known in single-chip systems not to operate in a color sequential mode with only the pure primary colors. In order to boost the brightness, in accordance with an embodiment of the present invention it is beneficial to introduce a so called “white segment” where all three lights of primary colors are activated simultaneously forming white light. For example, Fig. 13 shows the timing diagram for single spatial phase modulator single chip (single spatial amplitude modulator) projection system with white segment. Also, other “boost schemes” are included within the scope of the present invention. Such boost schemes, for instance, provide a yellow, cyan and magenta boost by dedicating time segments to simultaneously operating two of the three or more laser sources. This boosts the secondary colors, and as a result also white brightness. So, at

D/BARUXR-019-DE Description

B220012

LU103267 -73- least all of these following options for additional segments are included within the scope of the present invention: RGBW, RGBY, RGBCMY, and RGBCMYW. Wherever there are two or more light beams of different colors incident on a single spatial phase modulator, path length compensation can be applied to the two or more light beams.

Since these path deviations can only be introduced at the point where the incoming and outgoing beams are separated, preferably they are introduced as close as possible to the intermediate highlight image 14.

The cross-section of the RGB light beams before combining can be tailored to obtain an as good as possible matching of the PSF as discussed above, namely cross-section blue < cross-section green < cross-section red. Ideally, CSg/Ap=CSc/Ac=CSr/\r (with

CS meaning cross-section). With regard to matching the PSF, tailoring the cross-section is one option but tailoring the focus lens and/or the fiber cross section is an alternative.

The fiber cross-sections can be scaled for each colored light to deliver a smaller angular spread of the incident light on the single set of two spatial phase modulators 26 i.e. for shorter wavelengths, in order to achieve matching PSF ’s for the three colors.

In addition a control system 42 (not shown in Fig. 12 but shown in Fig. 2a, 2b, 2c) can be configured to control the operation of the single set of two spatial phase modulators 26 to thereby provide phase patterns which steer the collimated white light to an area or

D/BARUXR-019-DE Description

B220012

LU103267 „74 - areas of an image with highlights which have higher brightness and another area or areas of the image with lower brightness, the image being cast on a spatial amplitude modulator or modulators. The control system can be configured to control the operation of the spatial amplitude modulator or modulators to form a second image which is for projection via a projection lens. The control system can be adapted to calibrate the single set of two spatial phase modulators 26. The calibration can be selected from green having a primary wavelength range of 495 - 570 nm, red having a primary wavelength of 570 — 720 nm, or blue having a primary wavelength of 440 - 495 nm. As an example, the control system may use light with the dominant wavelengths derived from the ranges above, e.g. dominant wavelength or blue being 465 nm, the dominant wavelength for red being 639 nm, and the dominant wavelength for green being 530 nm. The control system may be implemented in different ways all, of which are included within the scope of the present invention. For example, the single set of two spatial phase modulators 26 can be calibrated for all primary colors using an intermediate wavelength of 538 nm followed by color-dependent optical path length compensation in compensator 10, e.g. for primary colors red and blue.

A highlight relay optical sub-system 40 for relaying and casting the intermediate highlight image 14 onto a spatial amplitude modulator 28 can be provided (see any of

Figs. 2a, 2b, 2c, controlled by control system 42 not shown in Fig. 12). Color-dependent optical path length compensator 10 (for RGB beams) is placed in optical path 8 between the single set of two of separate spatial phase modulators 26 and the intermediate highlight image 14, for example imaged on a static or moving diffuser, e.g. spinning diffuser or diffuser with 2D motion (e.g. side to side, or rotate). The static or dynamic diffuser can be placed at (i.e., in the vicinity of) or in the intermediate image plane 14a.

Being placed in the vicinity of the intermediate image plane 14a will allow sufficient de- speckling, though it will slightly increase the blurring of the image. Furthermore, two intermediate highlight images 14 can be provided on two intermediate image planes 14a, respectively which can be provided between the single set of two spatial phase modulators 26 and a final spatial amplitude modulator. A (static or dynamic) diffuser can be placed in or at each of these intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail although it will slightly increase the blurring of the highlight image.

D/BARUXR-019-DE Description

B220012

LU103267 -75-

Light from the exit of the individual fibers 38 (38-R, 38-G, 38-B) is imaged with any required magnification by collimation optics 32 (32-R, 32-G, 32-B), to subsequently evenly illuminate the single set of two spatial phase modulators 26 with polarized white light. The illumination optical sub-system 20 can provide collimated or substantially collimated light to the intermediate optical sub-system 30. The illumination can be incident on the single set of spatial phase modulators 26 at a small angle e.g. 5 to 25°.

This angle can be in either vertical (along the direction of the smallest dimension of the active area) or horizontal (along the direction of the longest dimension of the active area) direction. The vertical direction is much preferred as this minimizes the angle required to separate ingoing and outgoing light beams. In the outgoing light beam, path length compensator 10, e.g. using dichroic mirrors, is installed to introduce the path length differences required for compensation of the path lengths in the different primary colors such as green and blue paths compared to the remaining primary color red. If dichroic mirrors are used these dichroic mirrors can be installed perpendicular to the outgoing beam direction.

Embodiment comprising method steps

An embodiment of the present invention relates to method comprising steps S1-S13 are as follows:

A method 100 for obtaining a highlight image in an optical system, the optical system having an optical path, the system comprising: a singie spatial phase modulator or a single set of two spatial phase modulators and color-dependent optical path length compensator located on the optical path between the single spatial phase modulator or the single set of two spatial phase modulators and an intermediate image plane, and one or more spatial amplitude modulators. The single spatial phase modulator can be a single set of two spatial phase modulators, e.q. for polarized light operation, A further example of use with polarized light, uses specific optical fibers that do not depolarize the incident light, i.e. using a polarization- maintaining optical fiber, one can put the already polarized light from the laser light sources through these fibers and use the single SPM also with that polarization, or use other homogenization methods like fly-eye lenses that also maintain the polarization.

D/BARUXR-019-DE Description

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LU103267 - 76 -

The method 100 comprising the following steps:

ST: generating collimated white light and, optionally, uniformized and collimated white fight; 32: receiving collimated white light (optionally uniformized) at the single spatial phase modulator or the single set of two spatial phase modulators;

S3: the single spatial phase modulator or the single set of two spatial phase modulators phase modulating the collimated white light (optionally uniformized) to form phase patterns; 34: the phase patterns forming steered light; 35: relaying or directing the steered light to the color dependent optical path length compensator;

SE: the path length compensator compensating for at least two path lengths of primary colors;

ST: outpuiting from the path length compensator an intermediate highlight image. The intermediate highlight image at this stage - before being cast on the spatial amplitude modulator (2.g., imager, such as a DMD) is, due to the finite PSF, a blurry illumination profile with, for instance, dark areas and bright areas. This is a very low-resolution, &.¢g. blurry, image, which will have a higher resolution in the final image that is made by one or more spatial amplitude modulators. 88: the optical system further comprises a combiner, the combiner combines or overlays the intermediate highlight image with an intermediate image of another optical path to form a combined intermediate image:

S9: the combined intermediate image or the intermediate highlight image in an intermediate image plane being cast onto the one or more spatial amplitude modulators;

D/BARUXR-019-DE Description

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LU103267 -77-

S10: the one or more spatial amplitude modulators cleaning up (= increasing the resolution of by removing artefacts) the intermediate highlight image or the combined intermediate image, to form the final highlight image: 311: the intermediate image of the another optical path being a uniform baseline intermediate image, 2.9. a diffuse white light;

S12: the one or more spatial amplitude modulators forming the final highlight image for projecting onto a final highlight image plane, wherein the final highlight image plane is on a projection screen or on a wall, and 513: the final highlight image is projecied through a projection lens to the projection screen or on the wall,

Optional steps are:

S14: optionally the intermediate image at the intermediate image plane is provided by a static or dynamic diffuser {e.q., 2D moving or spinning diffuser). The static or dynamic diffuser can be placed at (i.e., in the vicinity of) or in the intermediate image plane. This will allow sufficient de-speckling though it will slightly increase the blurring of the image.

Furthermore, two intermediate highlight images can be provided at one or more intermediate image planes between the single spatial phase modulator or the single set of two spatial phase modulators and one or more spatial amplitude modulators. À (static or dynamic) diffuser can be placed at each of these one or more intermediate image planes. This is done for redundancy, to for example keep good speckle performance and a good laser classification even if one diffuser would fail.}

S15: optionally calibrating the single spatial phase modulator or the single set of two spatial phase modulators with a wavelength, e.g. with a wavelength intermediate between blue and red. 516: wherein the optical system optionally has a single set of two spatial phase modulators functioning with a polarizing beam splitter. A first of the single set of two spatial phase modulators operates with one polarized direction while the other spatial

D/BARUXR-019-DE Description

B220012

LU103267 - 78 - phase modulator operates with a polarized direction orthogonal to the polarized direction of the first spatial phase modulator. The polarizing beam splitter splits incoming unpolarized light over the two spatial phase modulators and combines outgoing beams from the single set of two, e.g. two, spatial phase modulators to form a single outgoing beam, whereby the single outgoing beam is unpolarized.

S17: optionally the spatial phase modulator is a single spatial phase modulator generating a white highlight image.

S18: dichroic mirrors optionally combining individual primary-color (red, green and blue) collimated beams into a single white beam.

S19: optionally the spatial phase modulator is a single spatial phase modulator to modulate three or more primary colors, wherein the first primary color light incident on the single spatial phase modulator has a first wavelength, a second primary color light incident on the single spatial phase modulator has a second wavelength, a third primary color light incident on the single spatial phase modulator has a third wavelength, and the single spatial phase modulator is calibrated at a fourth wavelength intermediate between the third and second wavelengths.

Besides the aspects set forth in the appended claims, the present invention has also the following enumerated aspects:

Aspect 1: An optical system for use in an optical projection apparatus, the optical system comprising: a plurality of optical sub-systems, a first sub-system being an illumination optical sub-system having a single white light source or light sources of three or more primary colors, that, when combined, appear to the human eye to be white even when a sequential color scheme is used and the beams coming from different primary color sources are outputted in a time sequential manner, wherein the illumination optical sub-system is operably connected to a second optical sub-system being an intermediate optical sub-system, the intermediate optical sub-system comprising a single spatial phase modulator or a single set of two spatial

D/BARUXR-019-DE Description

B220012

LU103267 -79- phase modulators, and a color-dependent optical path length compensator which is located on an optical path between the single spatial phase modulator or the single set of two spatial phase modulators and an intermediate image plane, wherein each spatial phase modulator is configured for at least a part of a frame time (for creating an image) to simultaneously modulate a light beam coming from the illumination optical sub-system containing more than one primary color wavelengths (for example: a single imager projector with a yellow boost segment in the color sequence, so that it is only yellow = red + green which are provided to each spatial phase modulator at the same time; in that case, blue light does not need to be path length compensated; or a two-imager projector, still with one single spatial phase modulator, for which there will only be i.e. red & green and then red & blue simultaneous single spatial phase modulator illumination, in case of which no path length compensation between green and blue is necessary), wherein the at least one spatial phase modulator is configured to output steered light for direction or relay to the path length compensator which is configured to compensate at least two path lengths of light selected from the primary colors, the output from the path length compensator being for forming an intermediate highlight image on the intermediate image plane.

Note that there can be applications that have only maximum two different primary colors delivered simultaneously to the spatial phase modulator(s) and therefor only need one path length compensation between these two simultaneously available primary color wavelengths. With regard to primary color wavelengths a typical example is blue 465nm, green 532nm, and red 640nm. Of course, other wavelengths are possible depending on the color gamut requirements or desires.

As set out above, a basic idea of the invention is to either use a single spatial phase modulator to simultaneously or sequentially modulate at least three primary colors comprised in white light or, in case where the phase modulator requires polarized light and the incoming light is unpolarized, using a two-modulator architecture comprising two single spatial phase modulators, wherein each phase modulator modulates one of two polarization directions for the three primary colors and generate a white highlight image.

D/BARUXR-019-DE Description

B220012

LU103267 - 80 -

For sake of simplicity, in the following the singular form "the spatial phase modulator" is used, which in case of two spatial phase modulators means that each spatial phase modulator of the two spatial phase modulators is configured or used to handle its respective portion of polarized light. 2. The optical system according to aspect 1, further comprising a third optical sub- system being a highlight relay optical sub-system having one or more spatial amplitude modulators and wherein the highlight relay optical sub-system is configured to direct the intermediate highlight image on the intermediate image plane, onto each spatial amplitude modulator. 3. The optical system according to aspect 2, wherein the intermediate highlight image, before being cast on the one or more spatial amplitude modulators, is a blurry image with dark areas and bright areas, which will have a higher resolution in the final image that that is realized after modulation by each spatial amplitude modulator. 4. The optical system according to aspect 2 or aspect 3, further comprising a combiner configured to combine or overlay the intermediate highlight image with another intermediate image of another optical path to form a combined intermediate image. 5. The optical system according to aspect 4, wherein the intermediate image of the another optical path is a substantially uniform baseline intermediate image. 6. The optical system according to aspect 5, wherein the substantially uniform baseline intermediate image can vary in intensity depending on the image content, by a modulation of the light source (via its driver) that provides the light for this baseline intermediate image. 7. The optical system according to one of aspects 4 to 6, wherein the optical system is configured to relay the combined intermediate image to the one or more spatial amplitude modulators.

D/BARUXR-019-DE Description

B220012

LU103267 - 81 - 8. The optical system according to aspect 7, wherein the optical system is configured to project the final highlight image through a projection lens to the final highlight image plane on a projection screen or a wall. 9. The optical system according to any of the aspects 1 to 8, wherein one or more static or dynamic diffuser(s) is/are located at or in one or more intermediate image plane(s). 10. The optical system according to any previous aspect, further comprising a common collimator configured to collimate light from the single white light source or from the light sources of three or more primary colors. 11. The optical system according to any of the aspects 1 to 10, further comprising individual collimators each configured to collimate one of the light sources of three or more primary colors. 12. The optical system according to aspect 11, wherein the individual collimators each comprise a plurality of lenses or lens groups and one lens or lens group is common to the three or more primary colors. 13. The optical system according to any previous aspect, wherein the illumination optical sub-system has a uniformizer configured to uniformize light from the single white light source or the light sources of three or more primary colors. 14. The optical system according to any of the aspects 1 to 13, wherein the illumination optical sub-system has an individual uniformizer for the single white light source or individual uniformizers for each of the light sources of three or more primary colors. 15. The optical system according to any of the aspects 1 to 13, wherein the illumination optical sub-system has a common uniformizer configured to uniformize light from the single white light source or the light sources of three or more primary colors. 16. The optical system according to any of the aspects 1 to 15, wherein the intermediate optical sub-system has the single set of two spatial phase modulators and a polarizing beam splitter splitting two polarized light paths from light incident on the single set of

D/BARUXR-019-DE Description

B220012

LU103267 - 82- two spatial phase modulators, and a broadband half-wave retarder in one of the two polarized light paths being connected to one of the single set of two spatial phase modulators to change the polarization state in that one light path and realize a same polarization state of the light imaged on the intermediate highlight image on the intermediate image plane. 17. The optical system according to any of the aspects 1 to 15, wherein the intermediate optical sub-system has the set of two spatial phase modulators configured to function with orthogonal polarization directions, and wherein a polarizing beam splitter is configured to split incoming light over the single set of two spatial phase modulators and to combine outgoing beams from the single set of two spatial phase modulators to form outgoing, light whereby the outgoing light is unpolarized. 18. The optical system according to any of the aspects 1 to 15, wherein the spatial phase modulator is configured for simultaneously or sequentially modulating the three or more primary colors, or a hybrid mix of a simultaneous and sequential modulation.

Example: a red, green, blue, yellow color sequence has sequential color modulation and one subframe where there is simultaneous red + green light being processed. Another example is a red, green, blue, white color sequence. 19. The optical system according to any previous aspect, wherein the single set of two spatial phase modulators requires polarized light and the incoming light from the illumination optical sub-system is unpolarized light, and the incoming light is split into two polarized paths distributed over the set of two spatial phase modulators, wherein each spatial phase modulator of the single set of two spatial phase modulators is configured to modulate one of two polarization directions for the light simultaneously containing more then one primary colors. A typical way of doing this is to split the unpolarized light into two beams with orthogonal polarization state, then put a half wave plate retarder in one of these beams to make the polarization states in the two “legs” equal, and then use the same SPM working with that same polarization state. And then at the end, the two beams are combined on the same intermediate plain by each with a slight different angle of incidence upon that plane.

D/BARUXR-019-DE Description

B220012

LU103267 - 83 - 20. The optical system according to any of the aspects 2 to 19, wherein the highlight relay optical sub-system has three spatial amplitude modulators, each spatial amplitude modulator being configured to modulate light from a respective one of each of the light sources of three primary colors, and the optical system is configured to simultaneously operate the three light sources and to simultaneously illuminate the single spatial phase modulator or the single set of two spatial phase modulators with light from the three light sources. 21. The optical system according to any previous aspect, wherein the single spatial phase modulator or the single set of two spatial phase modulators is tuned to achieve optimal steering efficiency for a wavelength intermediate between blue and red. 22. The optical system according to any of the aspects 1 to 21, wherein the color dependent optical path length compensator is configured to reduce the size of the PSF in green and red. 23. The optical system according to aspect 22, wherein the optical system is configured to have the light of each of the primary colors illuminating a substantially full active area of the single spatial phase modulator. 24. The optical system according to aspect 23, wherein the different phase patterns applied in each of the time segments comprise a common phase pattern applied to steer white highlights during a time segment with simultaneous illumination of a spatial phase modulator by more than one primary colors. 25. The optical system according to any previous aspect, wherein light sources of three or more primary colors are lasers comprising red, green and blue lasers which are directed at an entrance to an uniformizer and a mixer. 26. The optical system according to aspect 25, wherein the uniformizer and mixer is a fiber. 27. The optical system according to aspect 26, wherein the fiber is a single fiber.

D/BARUXR-019-DE Description

B220012

LU103267 - 84 - 28. The optical system according to aspect 26 or 27, wherein the fiber is a fiber with a rectangular core section or a rectangular core section with rounded corners. 29. The optical system according to any of the aspects 26 to 28, wherein the illumination sub-system has a combiner configured to combine the light of red, green and blue lasers; and wherein the red, green and blue lasers are focused together at the entrance of the uniformizer. Note that if instead of a fiber uniformizer, a set of fly eye lenses is used, the light does not have to be focused at the entrance. 30. The optical system according to aspect 29, wherein the combiner comprises dichroic mirrors. 31. The optical system according to aspect 29 or 30, wherein light beams of the red, green and blue lasers are configured to be focused by a focusing lens per color light beam to create red, green and blue converging laser beams. 32. The optical system according to aspect 29 or 30, wherein light beams from the red, green and blue lasers are configured to be focused by a common focusing lens. 33. The optical system according to aspect 32, wherein a combiner is provided to combine the converging laser beams. 34. The optical system according to aspect 33, wherein the combiner comprises dichroic mirrors. 35. The optical system according to aspect 34, wherein a cross-section of the light beams is set with cross-section blue < cross-section green < cross-section red before the common focusing lens. 36. The optical system according to aspect 35, wherein a cross-section of the light beams is set to CSB/A’B=CSG/A>G=CSR/A*R with CS meaning cross-section of. Note that if the SPM is LCOS based, the diffraction angle of steered light coming from a

D/BARUXR-019-DE Description

B220012

LU103267 - 85 - phase grating scales with a factor (Delta n) / lambda versus the wavelength lambda instead of just with the factor 1/lambda like in the case of the MEMS based phase modulator. Delta n is the birefringence of the liquid crystal material and the value of it varies a bit when the wavelength goes from red to blue. This factor should be taken into account for steering distance calculations and then also for the cross section calculations. Lambda needs to be substituted by (lambda / Delta n) in this kind of formulas. 37. The optical system according to any of aspects 25 to 36, wherein an output of the uniformizer and mixer to the common collimation optics is configured to evenly illuminate the single spatial phase modulator or the single set of two spatial phase modulators with white light. 38. The optical system according to any of the aspects 25 28 or 30 to 37, wherein the uniformizer is a micro-lens fly-eye integrator. 39. The optical system according to any of the previous aspects, wherein the illumination optical sub-system comprises a plurality of colored laser sources, each of which is configured to introduce light into an individual fiber for uniformization and individual collimation optics to form individual red, green and blue collimated beams. 40. The optical system according to aspect 39, wherein the illumination optical sub- system is configured to combine the individual red, green and blue collimated beams into a single white beam by dichroic mirrors. 41. The optical system according to aspect 40, wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to operate with unpolarized light to modulate the single white beam. 42. The optical system according to aspect 40, wherein two spatial phase modulators of the single set of two spatial phase modulators are configured to operate with polarized light to modulate the single white beam after the single white beam has been split into two polarizations.

D/BARUXR-019-DE Description

B220012

LU103267 - 86 - 43. The optical system according to aspect 26, wherein a fiber cross-section for each fiber is scaled per light color, to deliver a smaller angular spread of light incident on the single spatial phase modulator or single set of two spatial phase modulators for light with shorter wavelengths. 44. The optical system according to any of the previous aspects, wherein the path length compensator is configured to provide path length compensation set at a monochromatic wavelength i.e. the dominant wavelength per color of light emitted by lasers of each primary color. 45. The optical system according to any of the aspects 1 to 43, wherein path length compensator is configured to provide optical path length compensation set at a center wavelength of light of each primary color emitted by a laser diode array (LDA). 46. The optical system according to any previous aspect, the intermediate optical sub- system having a single spatial phase modulator or the single set of two spatial phase modulators, wherein the first primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a first wavelength, a second primary color light incident on the spatial phase modulator or the single set of two spatial phase modulators has a second wavelength, a third primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a third wavelength, and the single spatial phase modulator or the single set of two spatial phase modulators is configured to represent phase gratings with a phase range (0 - 21) calibrated for a fourth wavelength intermediate between the lowest and highest wavelengths. Note that the 0 to 21 reference in this case is not referring to an angle in geometrical sense, but to the phase value range. Phase 21 means that the

SPM pixel can modulate the wave front so that it undergoes a retardation of a full wavelength (e.g. 532nm for green). Practically, a good choice for the 4th wavelength can be found following the formula 2/lambda_4 = 1/lambda_blue + 1/ lambda_red.

Because red and blue are always the outer wavelengths.

D/BARUXR-019-DE Description

B220012

LU103267 - 87 -

In the following, the numbering of the aspects is not consecutive, i.e. some numbers are not used, for example numbers 47 to 51. 52. À method for use with an optical projection system, the optical system comprising: a plurality of optical sub-systems, a first sub-system being an illumination optical sub- system having a single white light source or light sources of three or more primary colors, the illumination optical sub-system being operably connected to a second optical sub-system being an intermediate optical sub-system, the intermediate optical sub- system comprising a single spatial phase modulator or a single set of two spatial phase modulators, and a color dependent optical path length compensator located on an optical path between the single spatial phase modulator or the single set of two spatial phase modulators and an intermediate image plane, the method comprising: outputting from the illumination optical sub-system collimated white light, and the intermediate optical sub-system receiving the collimated white light and being incident on the single spatial phase modulator or the single set of two spatial phase modulators, the single spatial phase modulator or the single set of two spatial phase modulators, modulating the white light from the single white source or modulating the light from light sources of three or more primary colors and outputs from the single spatial phase modulator or from the single set of two spatial phase modulators is steered light which is directed to the path length compensator, which compensates two or more path lengths selected from the three or more primary colors, the output from the path length compensator forming an intermediate highlight image on the intermediate image plane. 53. The method according to aspect 52, wherein the optical system further comprises a third optical sub-system being a highlight relay optical sub-system having one or more spatial amplitude modulators and directing or relaying the intermediate highlight image on the intermediate image plane onto the one or more spatial amplitude modulators. 54. The method according to aspect 53, wherein the intermediate highlight image, before being cast on the one or more spatial amplitude modulators, is a blurry image with dark areas and bright areas, which will have a higher resolution in the final image that is made by the one or more spatial amplitude modulators.

D/BARUXR-019-DE Description

B220012

LU103267 - 88 - 55. The method according to aspect 53 or 54, wherein the optical system further comprises a combiner which combines or overlays the intermediate highlight image with an intermediate image of another optical path to form a combined intermediate image. 56. The method according to aspect 55, wherein the intermediate image of the other optical path is a uniform baseline intermediate image. 57. The method according to aspect 55 or 56, wherein the combined intermediate image is relayed to the one or more spatial amplitude modulators. 59. The method according to aspect 58, wherein the final highlight image plane is on a projection screen or an on wall and the final highlight image is projected through a projection lens. 61. The method according to aspect 60, wherein one or more static or dynamic diffuser(s) is/are located at or in one or more intermediate image planes. 62. The method according to any of the aspects 52 to 61, wherein the optical system further comprises a common collimator for collimating light from the single white light source or the light sources of three or more primary colors. 63. The method according to any of the aspects 52 to 61, wherein the optical system further comprises individual collimators, each collimating one of the light sources of three or more primary colors. 64. The method according to aspect 63, wherein the individual collimators each comprise a plurality of lenses or lens groups and one lens or lens group is common to the three or more primary colors. 65. The method according to any of the aspects 52 to 64, wherein the illumination optical sub-system has a uniformizer, the uniformizer uniformizing light from the single white light source or the light sources of three or more primary colors.

D/BARUXR-019-DE Description

B220012

LU103267 - 89 - 66. The method according to any of the aspects 52 to 65, wherein the illumination optical sub-system has an individual uniformizer which uniformizes light from the white light source or has individual uniformizers which each uniformize light from the light sources of three or more primary colors. 67. The method according to any of the aspects 55 to 65, wherein the illumination optical sub-system has a common uniformizer which uniformizes light from the single white light source or the light sources of three or more primary colors. 68. The method according to any of the aspects 52 to 67, wherein the intermediate optical sub-system has the single set of two spatial phase modulators and a polarizing beam splitter splitting two polarized light paths from light incident on the single set of two spatial phase modulators, and a broadband half-wave retarder in one of the two polarized light paths being connected to one of the single set of two spatial phase modulators to change the polarization state in that one light path and realize a same polarization state of the light imaged on the intermediate highlight image on the intermediate image plane. 69. The method according to any of the aspects 52 to 67, wherein in the intermediate optical sub-system there is the set of spatial phase modulators functioning with orthogonal polarization directions, and wherein a polarizing beam splitter splits incoming light over the single set of two spatial phase modulators and combines outgoing beams from the single set of two spatial phase modulators to form a single outgoing beam, whereby the single outgoing beam is unpolarized. 70. The method according to any of the aspects 52 to 67, wherein in the intermediate optical sub-system there is the set of spatial phase modulators which simultaneously or sequentially modulates the three or more primary colors and the highlight image projection optical sub-system to generate a white highlight image, or which perform a hybrid mix of a simultaneous and sequential modulation. 71. The method according to any of the aspects 52 to 70, wherein the single set of two spatial phase modulators requires polarized light and incoming light from the

D/BARUXR-019-DE Description

B220012

LU103267 - 90 - illumination optical sub-system is unpolarized, wherein each spatial phase modulator of the single set of two spatial phase modulators modulates light with one of two polarization directions for the light simultaneously containing more than one primary colors and the highlight image projection optical sub-system generates a white final highlight image. 72. The method according to any of aspects 52 to 71, wherein the highlight relay optical sub-system has three spatial amplitude modulators, each spatial amplitude modulator modulates light from a respective one of the light sources of three primary colors; and wherein the three light sources are operated simultaneously and the spatial phase modulator is illuminated with light from three light sources. 73. The method according to any of the aspects 52 to 72, wherein the single spatial phase modulator or the single set of two spatial phase modulators is calibrated with a wavelength intermediate between blue and red. 74. The method according to any of the aspects 52 to 73, wherein the highlight relay optical sub-system has a single spatial amplitude modulator and the light sources of the three primary colors are operated sequentially in time segments, each time segment being for one of the three primary colors or for a simultaneous combination of two or three primary colors, the single spatial phase modulator or the single set of two spatial phase modulators provides different phase patterns applied in each of the time segments. Note that in a pure sequential operation there is never a moment of steering two different wavelengths and an optical path length compensator is not needed to make the highlights fall on the same location in the highlight image, or to care about the fact that these highlights have to fall on the same location. 77. The method according to any of the aspects 52 to 76, wherein the color-dependent optical path length compensator reduces the size of the PSF for green light beams and red light beams. 79. The method according to any of aspects 74 to 78, wherein the different phase patterns applied in each of the time segments comprise a common phase pattern

D/BARUXR-019-DE Description

B220012

LU103267 - 91 - applied to steer white highlights during a time segment with simultaneous illumination of the spatial phase modulator by more than one primary colors. 80. The method according to any of the aspects 52 to 79, wherein light sources of three or more primary colors are lasers comprising red, green and blue lasers which are directed at an entrance to an uniformizer and mixer. 81. The method according to aspect 80, wherein the uniformizer and mixer is a fiber. 82. The method according to aspect 81, wherein the fiber is a single fiber. 83. The method according to aspect 81 or 82, wherein the fiber is a fiber with a rectangular fiber core section or a rectangular core section with rounded corners. 84. The method according to any of the aspects 80 to 83, wherein the illumination sub- system has a combiner which combines the light of red, green and blue lasers and the red, green and blue lasers are focused together at the entrance of the combiner. 85. The method according to aspect 84, wherein the combiner comprises dichroic mirrors. 86. The method according to aspect 84 or 85, wherein light beams of the red, green and blue light lasers are focused by a focusing lens per color light beam to create red, green and blue converging laser beams, respectively. 87. The method according to aspect 84 or 85, wherein light beams from the red, green and blue lasers are focused with a common focusing lens. 88. The method according to aspect 86, wherein a combiner is provided to combine the converging laser beams. 89. The method according to aspect 88, wherein the combiner comprises dichroic mirrors.

D/BARUXR-019-DE Description

B220012

LU103267 - 92- 90. The method according to aspect 87, wherein a cross-section of the light beams is set with cross-section blue < cross-section green < "cross-section red in front of the common lens. 91. The method according to aspect 90, wherein a cross-section of the light beams is set to CSB/\?B=CSG/\2G=CSR/A2R wherein CS means cross-section. 92. The method according to any of aspects 80 to 91, wherein an output of the uniformizer and mixer to common collimation optics evenly illuminates the single spatial phase modulator or the single set of two spatial phase modulators with white light. 93. The method according to any of the aspects 66 to 92, wherein the uniformizer is a micro-lens fly-eye integrator. 94. The method according to any of the aspects 52 to 93, wherein the illumination optical sub-system comprises a plurality of colored laser sources, and wherein light from each source of the plurality of colored laser sources is introduced into an individual fiber for uniformization and individual collimation optics to form individual red, green and blue collimated beams. 95. The method according to aspect 94, wherein the individual red, green and blue collimated beams are combined by dichroic mirrors into a single white beam. 96. The method according to aspect 95, wherein the single white beam is modulated by a single spatial phase modulator operating with unpolarized light or with polarized light. 97. The method according to aspect 95, wherein the single white beam is modulated by two phase modulators operating with polarized light after the single white beam has been split in two polarizations. 98. The method according to any of the aspects 52 to 96, wherein a single spatial phase modulator is a piston based spatial phase modulator

D/BARUXR-019-DE Description

B220012

LU103267 - 93- 99. The method according to any of the aspects 81 to 98, wherein a fiber cross-section for each fiber is scaled per light color to deliver an angular spread of light incident on the single spatial phase modulator or the single set of two spatial phase modulators for each light color, the spread being dependent on the wavelength. Note that this translation from cross section to angular spread on the SPM will have to happen via the different collimator optics, which will thus need to have a different magnification per color. 100. The method according to any of the aspects 52 to 99, wherein the one or more optical path length compensators provide path length compensation set at a monochromatic wavelength of light emitted by lasers of each primary color. 101. The method according to any of the aspects 52 to 100, wherein the one or more optical path length compensators provide optical path length compensation set at a center wavelength of light of each primary color emitted by a laser diode array (LDA). 102. The method according to any of the aspects 52 to 101, wherein the in the intermediate optical sub-system there is the single spatial phase modulator or the single set of two spatial phase modulators which operates as a diffraction grating with a phase range (0 - 2[]) - reformulate like aspect 50 ?! , wherein the first primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a first wavelength, a second primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a second wavelength, a third primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a third wavelength, and the single spatial phase modulator or the single set of two spatial phase modulators is calibrated at a fourth wavelength intermediate between the third and second wavelengths. 103. The method according to any of the aspects 71 to 100, wherein in the intermediate optical sub-system there is the single spatial phase modulator to modulate the three or more primary colors, wherein the first primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators or the single set of

D/BARUXR-019-DE Description

B220012

LU103267 - 94 - two spatial phase modulators has a first wavelength, a second primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a second wavelength, a third primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a third wavelength, and the single spatial phase modulator or the single set of two spatial phase modulators is calibrated at a fourth wavelength intermediate between the third and second wavelengths. 104. An optical system comprising a single spatial phase modulator or a single set of two spatial phase modulators and a color-dependent optical path length compensator located on an optical path between the single spatial phase modulator or the single set of two spatial phase modulators and an image plane, the optical system being configured to receive light from a single white light source or simultaneously or time sequentially light from light sources of three or more primary colors; wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to modulate the light from source(s) and to output steered light directed to the optical path length compensator configured to compensate one or more path lengths of light of three primary colors; and wherein the optical path length compensator is configured to have its output forming a highlight image at an image plane. 105. The optical system according to aspect 104, further comprising a combiner configured to combine or to overlay the intermediate highlight image with an intermediate image of another optical path to form a combined intermediate image. 106. The optical system according to aspect 105, wherein the intermediate image of the another optical path is a uniform baseline intermediate image. The baseline light source may be dimmed depending on the content of the image. 107. The optical system according to aspect 105 or 106, wherein optical system is configured to relay the combined intermediate image to the one or more spatial amplitude modulators.

D/BARUXR-019-DE Description

B220012

LU103267 -95- 111. The optical system according to any of the aspects 104 to 110, wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to receive collimated light from the single white light source or collimated light from the light sources of three or more primary colors. 112. The optical system according to any of the aspects 104 to 111, wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to receive uniformized light from the single white light source or light from the light sources of three or more primary colors. 113. The optical system of any of the aspects 104 to 111, the optical system comprising the single set of two spatial phase modulators and a broadband half-wave retarder installed in one of two polarized light paths. 114. The optical system of any of the aspects 104 to 111, wherein the single set of two spatial phase modulators work with orthogonal polarization directions; and wherein a polarizing beam splitter is configured to split incoming light over the single set of two spatial phase modulators and to combine outgoing beams from the single set of two 0 spatial phase modulators to form a single outgoing beam, whereby the single outgoing beam is unpolarized. 115. The optical system according to any of the aspects 104 to 112, wherein the single spatial phase modulator is configured to simultaneously and/or sequentially modulate the light of three or more primary colors to generate a white highlight image 116. The optical system according to any of the aspects 104 to 115, wherein the single set of two spatial phase modulator requires polarized light and incoming light to the single set of two spatial phase modulators is unpolarized; wherein each spatial phase modulator of the single set of two spatial phase modulators is configured to modulate light of a different one of two polarization directions for the light simultaneously containing more then one primary color.

D/BARUXR-019-DE Description

B220012

LU103267 - 96 - 117. The optical system according to any of the aspects 104 to 116, wherein the single spatial phase modulator or the single set of two spatial phase modulators is calibrated with a wavelength intermediate between blue and red. 119. The optical system according to aspect 118, wherein the optical system is configured to optimize the phase patterns for the color that is activated in the time segment. 120. The optical system according to aspect 119, wherein the optical system is configured to optimize the phase patterns to bring intermediate images for red, green and blue to overlap in the same position. 121. The optical system according to any of the aspects 118 to 120, wherein the one or more color-dependent optical path length compensators are configured to reduce the size of the point spread function (PSF) in green and red. 122. The optical system according to aspect 121, wherein the optical system is configured to have the light of each of primary colors illuminating a substantially full active area of the single spatial phase modulator or the single set of two spatial phase modulators. 123. The optical system according to aspect 122, wherein the optical system is configured to have the different phase patterns applied in each of the time segments comprise a common phase pattern applied to steer white highlights during a time with simultaneous illumination of a spatial phase modulator by more than one primary color. 124. The optical system according to any of the aspects 104 to 123, wherein light sources of three or more primary colors are lasers comprising red, green and blue lasers. 125. The optical system according to any of the aspects 104 to 124, wherein the spatial phase modulator is a piston based spatial phase modulator.

D/BARUXR-019-DE Description

B220012

LU103267 „97 - 126. The optical system according to any of the aspects 104 to 125, wherein the one or more color-dependent optical path length compensators are configured to provide path length compensation set at a monochromatic wavelength of light emitted by lasers of primary colors. 130. A control system for controlling an optical system, the optical system comprising an optical sub-system, the optical sub-system comprising a single spatial phase modulator or a single set of two spatial phase modulators, wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to be operatively connected to an illumination sub-system which provides collimated white light to the single spatial phase modulator or the single set of two spatial phase modulators, and wherein the control system is configured to control the operation of the single spatial phase modulator or the single set of two spatial phase modulators to thereby provide phase patterns which steer the collimated white light to an area or areas of an image with highlights which have higher brightness and another area or areas of the image with lower brightness, the image being transferred to one or more spatial amplitude modulators, wherein the control system is configured to control the operation of the single spatial amplitude modulator or the single set of two spatial phase modulators to form a second image which is for projection via a projection lens.

Together with an optical path length compensator this allows to steer the highlights as “white highlights” with a minimum of color fringes or discrepancies. 131. The control system according to aspect 130, wherein the control system is adapted to calibrate the single spatial phase modulator or the single set of two spatial phase modulators. 132. The control system according to aspect 130 or 131, wherein the control system is configured to calibrate the single spatial phase modulator or the single set of two spatial phase modulators with a value to achieve a desired retardation at a wavelength intermediate between blue and red. 133. The control system according to aspect 132, wherein the control system is adapted to calibrate the single spatial phase modulator or the single set of two spatial phase

D/BARUXR-019-DE Description

B220012

LU103267 - 98- modulators at a dominant wavelength for blue of 465 nm, or at a dominant wavelength for red of 639 nm, and/or at a dominant wavelength for green of 532 nm, or the control system is adapted to calibrate the single spatial phase modulator or the single set of two spatial phase modulators at a value selected from green having a primary wavelength range of 495 - 570 nm, red having a primary wavelength of 570 - 720 nm, and blue having a primary wavelength of 440 - 495 nm, or the single spatial phase modulator is calibrated for all primary colors using only green with a wavelength of 530 to 532 nm. 134. The control system according to any of the aspects 130 to 133, configured to control the single spatial phase modulator or the single set of two spatial phase modulators , the control system comprising a data processor configured to deliver control signals to a set of pixels of the single spatial phase modulator or the single set of two spatial phase modulators to obtain a desired phase pattern, wherein the data processor is configured process image data to determine a desired light steering pattern and drive the signal spatial phase modulators or the single set of two spatial phase modulators to steer light to achieve the desired light steering pattern.

Claims

D/BARUXR-019-DE Claims B220012 LU103267 -1- CLAIMS

1. An optical system for use in a light steering projector, the optical system comprising a plurality of optical sub-systems, a first sub-system being an illumination sub-system for outputiing light of three primary colors, wherein the illumination optical sub-system is operably connected to a second optical sub-system being an intermediate optical sub-system, the intermediate optical sub-system comprising one single spatial phase modulator and wherein the single spatial phase modulator is configured to simultaneously or sequentially modulate light from the illumination sub-system to generate a white highlight image.

2. An optical system for use in a light steering projector, the optical system comprising a plurality of optical sub-systems, a first sub-system being an illumination sub-system for outputting light of three primary colors, wherein the illumination optical sub-system is operably connected to a second optical sub-system being an intermediate optical sub-sysiem, the intermediate optical sub-system comprising a single set of two spatial phase modulators, each spatial phase modulator modulating light of a different polarization, and wherein each of the two spatial phase modulators is configured to simultaneously or sequentially modulate light from the illumination sub-system to generate a white highlight image and

3. The optical system according to claim 2, further comprising a polarizing beam splitter splitting light from the illumination sub-system into two polarized light paths, each light path directed onto a different one of said two spatial phase modulators, and a broadband half-wave retarder in one of the two polarized light paths to change the polarization state in that one light path and realize a same polarization state of the light imaged on the intermediate highlight image on the intermediate image plane.

D/BARUXR-019-DE Claims B220012 LU103267 -2-

4. The optical system according to one of claims 1 to 3, further comprising a color- dependent optical path length compensator located on an optical path between the single spatial phase modulator and an intermediate image plane, said optical path length compensator configured to compensate at least two path lengths of light selected from the three primary colors for forming an intermediate highlight image on the intermediate image plane.

5. The optical system according to one of claims 1 to 4, wherein each spatial phase modulator is configured to output steered light to the color-dependent optical path length compensator.

6. The optical system according to one of claims 1 to 5, further comprising a combiner configured to combine or overlay the intermediate highlight image with a second intermediate image from a second optical path to form a combined intermediate image, said second intermediate image being in particular a uniform baseline intermediate image.

7. The optical system according to claim 6, wherein the optical system is configured to direct the combined intermediate image to at least one spatial amplitude modulator,

8. The optical system according to one of claims 1 to 7, further comprising at least one static or dynamic diffuser located at or in an intermediate image planes.

9. The optical system according to one of claims 1 to 8, wherein each spatial phase modulator is tuned to achieve steering efficiency for a wavelength intermediate between blue and red.

10. The optical system according to one of claims 1 to 9, wherein the path length compensator is configured to reduce the size of the PSF of green and red light.

11. The optical system according to one of claims 1 to 10, the optical system being configured to have the light of each of the primary colors illuminating a substantially full

D/BARUXR-019-DE Claims B220012 LU103267 -3- active area of the single spatial phase modulator or of one of the two spatial phase modulators.

12. The optical system according to of claims 1 to 11, wherein the illumination sub- systems is configured to operate light sources of three primary colors sequentiaily in time segments, each time segment being for one of the three primary colors; and wherein each spatial phase modulator is configured to apply different phase patierns in each of the time segments.

43. An optical system comprising a single spatial phase modulator or a single set of two spatial phase modulators and a single white light source or light sources of three or more primary colors, wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to modulate the white light from the single white source or to modulate the light from light sources of three or more primary colors and to output steered light.

14. The optical system according to claim 13, further comprising a combiner configured to combine or to overlay the intermediate highlight image with an intermediate image of another optical path to form a combined intermediate image, said the intermediate image of the another optical path being in particular a uniform baseline intermediate image. 45, The optical system according to claim 14, wherein optical system is configured to direct the combined intermediate image to at least one spatial amplitude modulator.

18. The optical system according to one of claim s13 to 15, further comprising & color-dependent optical path length compensator located on an optical path between the single spatial phase modulator or the single set of two spatial phase modulators and an image plane, the optical path length compensator configured to receive steered light from the single spatial phase modulator or the single set of two spatial phase modulators and to

D/BARUXR-019-DE Claims B220012 LU103267 -4- compensate one or more path lengths of light of three primary colors in order to output a highlight image at the image plane.

17. The optical system according to 16, wherein the optical path length compensator is configured to provide path length compensation at a monochromatic wavelength of light emitted by lasers of primary colors.

18. The optical system according to claim 16 or 17, wherein the optical path length compensator is to provide optical path length compensation at a center wavelength of light of each primary color emitted by a laser diode array.

19. The optical system according to any of claims 12 to 16, wherein the single spatial phase modulator or the single set of two spatial phase modulators is configured to operate as a diffraction grating between a start and finish operational angle (0 - 277), wherein the first primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a first wavelength, a second primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a second wavelength, a third primary color light incident on the single spatial phase modulator or the single set of two spatial phase modulators has a third wavelength; and the single spatial phase modulator or the single set of two spatial phase modulators is calibrated at a fourth wavelength intermediate between the third and second wavelengths.

20. A control system for controlling an optical system, in particular an optical system according to one of claim 1 to 19, the optical system comprising optical sub-systems, one of the optical sub-systems comprising a single spatial phase modulator or a single set of two spatial phase modulators configured to be operatively connected to an illumination sub-system which provides light to the single spatial phase modulator or the single set of two spatial phase modulators, and wherein the control system is configured to control the operation of the single spatial phase modulator or the single set of two spatial phase modulators to provide phase patterns for steering the light to highlight certain areas of an image, the image being transferred to at least one spatial amplitude modulator, wherein the control system is further configured to control the operation of

D/BARUXR-019-DE Claims B220012 LU103267 -5- the at least one spatial amplitude modulator to form a second image which is for projection via a projection lens.

21. The control system according to claims 20, further comprising a data processor configured lo deliver control signals to the single spatial phase modulator or the single set of two spatial phase modulators to obtain a desired phase pattern, wherein the data processor is configured process image data to determine a desired light steering pattern and drive the single spatial phase modulator or the single set of two spatial phase modulators to steer light to achieve the desired light steering pattern.

22. A light steering projector comprising an optical system according to any of the claims 1 to 19 and/or a control system according to any of the claims 20 or 21.

23. The projector according to claim 22, comprising red, green and blue lasers as light sources, which are directed at an entrance of an uniformizer and/or mixer.