WO1996021995A2 - Systeme de projection - Google Patents

Systeme de projection Download PDF

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Publication number
WO1996021995A2
WO1996021995A2 PCT/SE1996/000015 SE9600015W WO9621995A2 WO 1996021995 A2 WO1996021995 A2 WO 1996021995A2 SE 9600015 W SE9600015 W SE 9600015W WO 9621995 A2 WO9621995 A2 WO 9621995A2
Authority
WO
WIPO (PCT)
Prior art keywords
light
colour
projection
matrix
igd
Prior art date
Application number
PCT/SE1996/000015
Other languages
English (en)
Other versions
WO1996021995A3 (fr
Inventor
Stig Berglund
Original Assignee
Optica Nova Onab Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from SE9500149A external-priority patent/SE9500149D0/xx
Priority claimed from SE9502529A external-priority patent/SE9502529D0/xx
Priority claimed from SE9503107A external-priority patent/SE9503107D0/xx
Application filed by Optica Nova Onab Ab filed Critical Optica Nova Onab Ab
Publication of WO1996021995A2 publication Critical patent/WO1996021995A2/fr
Publication of WO1996021995A3 publication Critical patent/WO1996021995A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3141—Constructional details thereof
    • H04N9/315—Modulator illumination systems
    • H04N9/3164—Modulator illumination systems using multiple light sources
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/363—Image reproducers using image projection screens
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • G03B21/604—Polarised screens
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • G03B21/606—Projection screens characterised by the nature of the surface for relief projection
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • G03B21/62—Translucent screens
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/324—Colour aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/332—Displays for viewing with the aid of special glasses or head-mounted displays [HMD]
    • H04N13/337—Displays for viewing with the aid of special glasses or head-mounted displays [HMD] using polarisation multiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3102—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators
    • H04N9/3105—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators
    • H04N9/3108—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators by using a single electronic spatial light modulator
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/332—Displays for viewing with the aid of special glasses or head-mounted displays [HMD]
    • H04N13/341—Displays for viewing with the aid of special glasses or head-mounted displays [HMD] using temporal multiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/365—Image reproducers using digital micromirror devices [DMD]

Definitions

  • the invention relates primarily to a projection arrangement as stated in the preamble of the enclosed Claim 1.
  • One aspect of the invention thus relates to a projection arrangement for projection with coherent light sources to eliminate the visual impression of speckles in the image.
  • the arrangement includes an Image Generating Device (IGD) which can comprise a matrix of light valves with colour pixels.
  • IGD Image Generating Device
  • One of the drawbacks of the known projectors is that they offer deficient viewing ergonomics if, for instance, the projector is placed in a room at a position corresponding to half the width of a vertical wall onto which the picture is to be projected, and the projector furthermore is situated at a level corresponding to the viewer's eye level. In that case, the projected picture's centre will be situated at the corresponding height and width on the vertical projection surface, so that the projector or the viewer will obstruct the picture. It would therefore be desirable to offer a projection construction that provides a parallel shifting of the projected picture, so that the projector can be placed next to the ceiling, the floor and/or on a side wall.
  • the illumination arrangements have a common focal area, which in the orthogonal projection towards the respective image generating device primarily is situated in the centre of the respective IGDs, so that said deficient viewing ergonomics arise.
  • JP-62,280,8108 One way to reduce speckles in a laser ray is described in JP-62,280,818, showing an arrangement comprising an electro-optical element, an electrode and a lens system. JP-62,280,818, however, does not describe how this arrangement can be applied on projectors for moving pictures, as is the case for example on film, computers and similar media. Neither does it describe how the method can be applied for other purposes than for a fixed ray light source and thus not for continuously spread light sources. The arrangement in JP-62,280,818 appears furthermore to be more bulky than the present invention.
  • projection screens which are partly for use with spectrally broad- banded light and partly of the principally, in relation to the screen, centrally illuminated type.
  • Today's projectors with only one projection lens can generally be divided into two main categories.
  • the first category there are several IGDs which are each submitted to transillumination by one-coloured light with a different colour light for each IGD.
  • the light from the different IGDs is then linked together via a dichroical linking device consisting of dichroical mirrors, for example in the form of a dichroical prism.
  • a general purpose of the invention concerns an elimination of the visual impression of speckles in the picture, without obtaining the mentioned disadvantages with the moving parts, increased spectral band width or impaired resolution.
  • a second purpose of one aspect of the invention is to reduce the visual impression of a pixel structure in the picture.
  • a third purpose of one aspect of the invention is thus to provide a design of a projector which has a lower weight and volume.
  • An aspect of the invention is based on a projection arrangement which includes a number of IGDs, for instance LCDs, or more generally SLMs (Spatial Light Modulators), for off-axis projection on a screen with one projection lens, which are illuminated by several, for instance, three differently coloured light sources that have possibly been obtained through colour separation of light from a single light source, a shared projection lens in the ray path after the out-put of the IGD, and a focusing illuminating optical system whereby the projection lens is situated in or at the shared focal area.
  • IGDs for instance LCDs, or more generally SLMs (Spatial Light Modulators)
  • SLMs Spatial Light Modulators
  • one aspect of the invented projection arrangement is mainly characterised in that the illumination arrangements' said shared focal area is situated, so that its optical orthogonal projection against the plane in which the IGD is located is substantially shifted from the centre of the IGD, whereby the projected picture obtains a parallel displacement, thus rendering the desired ergonomical advantage.
  • Laser diodes are the for this purpose best suited illumination sources because of their narrow spectral band width.
  • a particular advantage with such an arrangement is that the projection picture can be made particularly light-intensive and that a good function and viewing ergonomy are provided.
  • light is directed at different angles of incidence from the various illumination sources against the IGD.
  • the light first hits a positive microlens matrix with a positive lens for each of the different colour groups which together form an image spot and that focus the various colours towards separate negative tilted microlenses or microprisms, which focus the light through the middle of the respective colour pixel elements.
  • a tilted microlens is defined as a microlens that is deflecting a through the middle of the lens passing light ray, so that the deflection is different from the deflection that a light ray should have if the tangential surface at the middle of the lens were parallel to the plane of the microlens matrix itself.
  • the first matrix on the out-put side consists of positive microlenses collimating the from the pixel apertures coming light.
  • the second matrix consists of microprisms deflecting the light into the middle of the entrance pupil of the projection lens.
  • the two microlens matrices on the entrance side can be placed on either side of a sheet of glass.
  • the microprisms are having the same purpose as a very compact colour corrected field lens.
  • the second matrix with tilted microlenses on the in-put side may very well be affixed directly onto the substrate on the in-put side of the SLM. This is especially the case if the microlenses or microprisms are produced for example by etching. Techniques for etching of microlenses on glass exist. The same is true also for the first matrix on the out-put side of the SLM.
  • the latter matrix can moreover be the only one on the out-put side if the lens and prism operation is integrated into one and the same matrix with refractive or diffractive elements.
  • microlens matrices is also applicable on the projectors in the first category by instead using a positive microlens on the entrance side for each pixel.
  • the microlens array principle is combined with a field lens, which focuses the light on the out-put side of the IGD according to one of the invention's principles. It can be difficult to achieve a satisfactory colour correction in the field lens as it has to bring about big changes in the field angles. It is therefore advantageous to compensate the colour aberrations in the field lens with the prismatic elements in the microprism array.
  • One of the fundamental principles in achieving the purposes of one aspect of the invention is using time multiplexing possibly in combination with spatial multiplexing by, in one and the same IGD, using pixels dedicated to different colours - either by using a colour separation technology or by allowing light to be blocked in cells that do not have the colour for which the cell is dedicated.
  • time multiplexing refers to the fact that video information is divided up in time so that one picture is sent to the IGD in multiple in time separated partial pictures, where each of these partial pictures reproduce the picture information for a number of colours.
  • the ordinary colour systems for television are, for different, partly historical, reasons not very efficient. This is partly due to having to work with the at the time existing phosphors, which left large parts of the colour diagram uncovered. In particular, large parts of the green, more saturated colours are poorly reproduced. It is therefore a special purpose of one aspect of the invention to provide an improved colour reproduction. According to the C.I.E.
  • colour system from 1931 are the current colour co-ordinates according to both the European system EBU and the American NTSC, drawn up in a diagram, evidently completely insufficient for all saturated colours and especially in green, where the colour tolerance, however, is bigger.
  • Even with the transition to monochromatic illumination sources, which are known to represent maximal colour saturation and thus are on the borderline of the colour diagram according to C.I.E. can a great improvement be achieved. This is already possible using today's laser sources, which within the near future will be improved and less expensive.
  • Much of the documentation is, however, already registered with the old basic colours, and one would like to reproduce this documentation with compatibility. There is the possibility to extrapolate by elongating the vector from the white point in the diagram in order to reproduce colours, which according to the registered values are close to the limiting triangle, with points that are outside.
  • the improvement that is possible by using monochromatic colours can according to one aspect of the invention's principle, be improved further by using more than three colours.
  • the principle for metamerics are the sense of seeing and the brain thus constituted that the brain cannot make out the difference between two stimuli, even if they are physically different, but sees the same colour nuance although the spectral division is different. and it is therefore possible to reproduce one single, subjective impression in many different ways. Every imaginable colour impression is theoretically defined to the colour (consequently not considering the intensity) of a point in a two-dimensional colour diagram, because of which two parameters are enough for the colour information. Ordinary television, of course, transfers information for each pixel through one intensity parameter and two colour parameters.
  • a disadvantage with the known projectors is then that they have a severely limited colour dynamics (gamut) . This largely depends on the fact that only three colours are used to generate the picture wherefore it is impossible to with good efficiency reproduce colours of down to 400 nm and up to 700 nm. Should one expand the number of colours in a projector in the first category, one would have to, using today's technology, expand the number of IGDs with as many as the number of colours, thus making this kind of projector even more expensive. Should one expand the number of colours in a projector in the second category, one would, using the existing technology, worsen the already poor light efficiency.
  • the one IGD is illuminated with different time multiplexed illumination sources of different colours.
  • the illumination sources are directed in correlation with the picture information to the IGD so that the information of a certain colour is generated via the IGD when said colour illuminates the IGD.
  • the one IGD is used for both spatial and time multiplexing.
  • the time multiplexing is generated in the manner stated above, while the spatial multiplexing is generated by colour separation implementing microlens matrices according to the above stated two principles. It is in this way possible to produce a picture using, for instance, a gamut between six primary colours with, for example, three colour pixels which each are transilluminated by two colours that are close in the spectrum and are sequentially alternated in time.
  • the received signal's gamut is designated G c .
  • the display's gamut is designated G d . All three gamut areas are supposed to have a mainly shared achromatic point x n and y n .
  • the received signal supposedly has the colour co-ordinates x c and y c located within G c .
  • the colour co-ordinates for the received signal's dominant colour is calculated as the point where a line through the points x n ,y n and x c ,y c crosses the edge of G r and is designated x b and y b .
  • the colour co-ordinates X bc y bc Ior tne point of the edge of G c which makes up the point of intersection between the edge of G c and a line through the achromatic point x detox,y n and the point x c ,y c in the colour diagram is calculated.
  • the colour's excitation potential p re is determined as:
  • the relative light intensities are not distinctly determined but can be chosen freely from a metametrical area with combinations of primary colours that render the same colour co-ordinates x r ,y t . It is therefore possible to divide the by the different colours generated gamut into a number of non-overlapping triangles, which are limited by the points of the different light sources in the colour diagram. Every point in the picture can thereby, at a certain point in time, be represented by light from a maximum of all three light sources which generate the triangle in which the point's colour co-ordinates, or expanded colour co-ordinates, are located. Generally speaking, will the number of triangles equal the number of different-coloured illumination sources minus two.
  • At least three light sources can be used in order to represent a given point pO with the coordinates (xO,yO) in the colour diagram.
  • the luminous flux ⁇ 0 in lumen is maximised for the point pO (or the inverse of the luminous flux is minimised for said point) .
  • n the total number of light sources
  • G c is a convex polygon where the corners are given by the primary colour co-ordinates, which are determined by the camera. This facilitates the calculation of the point x bcfYb c which simply can be calculated as the intersection of two straight lines. To facilitate the calculation of the point x b ,y b it could be suitable to approximate the edge of G r nG d with a number of straight lines, which together form a polygon G rr .
  • the point x bc ,y bc can formally be calculated as:
  • the point x b ,y b can be calculated analogously.
  • the visual impression of speckles in the picture is eliminated by placing a dispersive window (a despeckelator) for example based on the PDLC-technology described in the article "Field Controlled Light Scattering From Nematic Microdroplets" by the authors J.W. Doane, N.A. Vaz, B-G Wu and S. Zu er; Applied Physics Letters 48, 269 (1986).
  • a dispersive window a despeckelator
  • the light will reach the eye from one picture point with an in time varying phase-relationship and one gets an in time varying speckle pattern that is integrated by the eye as a speckle-free image.
  • the angle spread has a standard deviation of about 0.15 degrees in order for one ray in to the despeckelator to obtain a standard deviation of about 90 degrees to the eye. If one varies the angle spread in the despeckelator with a frequency of about 60 Hz, the eye integrates all speckle patterns to a uniformly lit surface. By using a finite distance between the despeckelator and the IGD, one also obtains a certain broadening of the pixel apertures in the IGD. This causes a reduction or an elimination of the pattern of the pixel frames. It is therefore correct to say that the despeckelator also functions as a depixelator.
  • the screen In order to reduce light reflection from surrounding illumination sources on the screen and the resulting poor contrast in the picture, it is possible to coat the screen with a light-absorbing layer on which a filter is placed (for instance a thin-film filter), which has high reflectance for the wavelengths where the light that passes the IGD has a high intensity, and which has a high transmission for the wavelengths where this light has low intensity.
  • a filter for instance a thin-film filter
  • the illumination sources are very narrow-banded.
  • a filter be designed as a filter between two bands with high transmission between the blue and green colours, and between the green and red colours.
  • the screen shaped as a diffuser with a light-absorbing coating on which the thin- film coating is applied.
  • the irregular or diffuse surface is shaped so that its Fourier transform mainly renders a significant spectrum with considerably higher frequencies than the frequencies which are obtained at Fourier transformation of the on the picture projected pixel structure. It is obviously of great significance that the light which reaches the screen is reflected as efficiently as possible before reaching the eyes of the viewers.
  • This is possible to achieve by designing the screen with microfacets or DOEs onto which a light-absorbing coating is applied, together with the above mentioned filter which mainly reflects the narrow light bands from the projector.
  • the microfacets or the DOEs are designed so that light is reflected back within an angular area in which the viewer's eyes are likely to be.
  • the screen will, of course, not have uniform qualities, since the angle of incidence of the light varies across the screen, and the viewer's eyes will be directed in different angular positions in relation to different parts of the screen.
  • Within each pixel on the screen there are a number of facets with both vertical and horizontal randomly tilted angles. The distributions of the tilted angles is calculated in consideration to incidence and the desired angular area for reflected light, and the number of mirror elements is chosen in consideration to the diffraction, so that an even distribution of light is obtained.
  • the diffusor can very well be modelled with micro-facets according to the above described principle. It is of course possible that the screen is 17 manufactured with its irregular surface in a light absorbing material, at which the coating with the light absorbing layer can be omitted.
  • the screen When the projector is positioned asymmetrically in relation to the projection screen, then the screen itself will be asymmetric with regard to the light spread distribution. This is for example the case when the projector is placed in connection to a normal to the screen emerging from a corner of the screen. To be able to use the one and the same screen with the projector placed in connection to each one of the corners of the screen, it is possible to model the screen such that it is possible to turn the screen upside down to be able to place the screen in connection to the diametrically opposite corner. A screen structure for the remaining two corners can be applied on the other side of the screen.
  • a six-colour projector can be designed with three IGDs, where each IGD is illuminated by two colours, and where colour separation, on the analogy of the one shown in figure 5, is used.
  • the advantage of not having to resort to time multiplexing makes it possible to chose low power illumination sources and also results in a better colour saturation, since the illumination sources shine without interruption. The latter can be of significance to the life of the illumination sources, since intermittent light in all probability cause a faster wear.
  • Fig. 1 schematically depicts a projector for 3-D projection.
  • Figs. 2 to 4 schematically depict different alternative positions of the polarisation-twisting window in 3-D projectors.
  • Fig. 5 shows the principle for a colour separation technology in an LCD-projector.
  • Fig. 6 schematically illustrates how one expands the of the camera given gamut to a realistic gamut.
  • Fig. 7 schematically illustrates how one expands the of the camera given gamut to a, with a polygon approximated, realistic gamut.
  • Fig. 8 schematically depicts the make of a IGD with a despeckelator / depixelator.
  • Fig. 9 shows a cross section of one part of the projection screen.
  • Fig. 10 shows in a diagram how the diffuse reflectance, with the help of thin-film technology, is designed in the case of narrow-banded illumination sources.
  • Fig. 11 schematically shows the design of a reflecting screen with microlenses as the foundation for the in figure 9 illustrated coating.
  • Fig. 12 schematically depicts a six-colour projector where both spatial and time multiplexing are used.
  • Fig. 13 illustrates an example of the division of a six- colour gamut in four colour triangles.
  • Fig. 14 schematically illustrates a six-colour projector with two IGDs with three-colour separation in each of the IGDs.
  • Fig. 15 illustrates a preferred manner of choosing polarisation directions at the use of 3-D projectors.
  • Fig. 16 schematically illustrates the make of a 3-D three colour projector, where an off-axis field lens is used to direct the light into the projection lens.
  • Fig. 17 schematically illustrates a detailed study of an IGD with condensor, despeckelator/depixelator and field lens.
  • Figs. 18 to 21 illustrate different placements of the projector in relation to the projection screen.
  • Fig. 1 schematically depicts a projector for 3-D projection.
  • the laser diode light sources 2R, 2G, 2B can beside a number of laser diodes in the colours red, green and blue also include light distributing optics in the form of for example diffractive optical elements (DOE) so that an even illumination of the IGD IK is obtained via the condensor C.
  • the light in the green colour generally incides with an angle W against the IGD IK.
  • the light in the red and the green colour incide with the angles El and E2 in relation with the to the green colour whereby one in the IGD IK obtains the colour separation described below in connection with figure 5.
  • Via the connections V and H to the unit Ul picture information comes in with right and left stereo pictures.
  • the unit Ul is simplified to give only the necessary alternation impulses to the polarisation alternating window LI.
  • the projector has here been depicted in projection that could be a side projection. The projector can however be designed so that similar conditions also apply at vertical projection.
  • the light from the illumination sources have been given the average incident angle W onto the IGD IK in order to simplify the focusing of light to the projection lens 7.
  • the angle W can be chosen within the interval 0 to AW degrees, where the angle AW is an average angle for the light that leaves the IGD IK.
  • the light from each of the light sources 2R, 2G and 2B can be either collimated after the passage through the condensor C, or convergent with angle of convergence CW that is in the interval 0 to OW degrees, where OW is the angle of convergence that the light has when it leaves the IGD IK.
  • OW is the angle of convergence that the light has when it leaves the IGD IK.
  • FIGs. 2 to 4 schematically illustrate different alternative ways to place the polarisation-twisting window LI in 3-D projectors.
  • the illumination source is designated with L, the IGD with 1, the projection lens with 7 and the projection screen with 11.
  • the arrangement in figure 2 corresponds principally with the one in figure 1, with placement of the polarisation-twisting window LI between the IGD and the projection lens 7.
  • In figure 3 has the polarisation-twisting window LI been placed immediately after the projection lens 7.
  • Figure 4 represents a case of the illumination source generating polarised light for which the direction can be altered by a polarisation- twisting window between the illumination source L and the IGD 1.
  • Fig. 5 very schematically depicts a section of the IGD according to one aspect of the invention where colour separation is used, i.e. the different colours R, G and B are separated in the dedicated light valves 1R, 1G and IB in an SLM 1.
  • Green light is here thought of as inciding orthogonally against the IGD, i.e. the angle W in figure 1 is 0, while red light incides with the angle E2 and blue light with the angle El.
  • the light in the different colours first come in to a microlens matrix 322, with positive microlenses 94 with an effective focal length that is considerably larger than the distance A between the matrices 322 and 323, and at the same time considerably shorter than the distance B between the matrix 322 and the SLM 1.
  • a negative microlens each i.e. the microlenses 19R, 19G and 19B in a second microlens matrix 323 and are then focused to a light valve each, i.e. the valves 1R, 1G and IB in an LCD matrix 1, whereby light in the three different colours hit the light-directing, possibly with diffractive structures colour corrected combinations 7R, 7G and 7B of microlenses and microprisms in the matrices 21 and 22.
  • the microlenses in the matrix 21 have an effective focal length equivalent to the distance between the LCD matrix 1 and the matrix 21.
  • the negative microlens 19G can be an ordinary on-axis lens.
  • the lenses 19R and 19B can be made out of a combination of prismatic parts and negative lenses, i.e. tilted negative lenses. In the general case, when the angle W in figure 1 is not zero, all the negative lenses in matrix 323 are tilted. It is certainly possible to shape the lenses 94 as well as the lenses 19R, 19G and 19B, as diffractive optical elements.
  • the two matrices 21 and 22 can at advantage be combined into one matrix, either as refractive elements, which is especially suitable when the illumination sources have a spectrally narrow band width, or as diffractive optical elements.
  • refractive elements which is especially suitable when the illumination sources have a spectrally narrow band width
  • diffractive optical elements In the case of the light valves 1R, 1G and IB being dispersive, for instance of the PDLCD-type, there is no need for a polariser or an analyser. The light transmission will hereby be three times as efficient.
  • Fig. 6 schematically illustrates how one expands the of the camera given gamut G c into a realistic gamut G r during reproduction with a 6-colour display with the gamut G d .
  • CIE designates the CIE colour diagram.
  • x and y designate the co-ordinates in the CIE.
  • a colour c in the camera's gamut G c is expanded to the colour r in the realistic gamut G r .
  • Fig. 7 schematically depicts how one expands the of the camera given gamut G c into a with a polygon approximated realistic gamut G rr .
  • a colour c in the camera's G c is expanded to the colour r in the with a polygon approximated realistic gamut G rr .
  • Fig. 8 schematically illustrates the design of an IGD with a despeckelator/depixelator.
  • the light valves in the IGD are designated with IV
  • the from figure 5 integrated matrices 21 and 22 are designated with MM
  • the despeckelator window is designated with 88 where a light distribution with the standard deviation of DV is obtained.
  • VA alternating voltage device
  • VD DC device
  • the angle DV is chosen so that the standard deviation of the phase changes amounts to at least 90 degrees.
  • the frequency of the phase changes should amount to at least 60 Hz.
  • the despeckelator window also will broaden the visual impression of the pixel aperture and will also therefore function as a depixelator. Because the light from different parts of the IGD incides with different angles on the window 88, it would be suitable to divide it into different segments with between themselves varying values on both the direct current component VD and the alternating current component VA.
  • the light valves 1R, 1G, IB in the matrix IV are constituted by dispersive elements, for example dispersive liquid crystals over which the alternating voltage VA superimposes the information-carrying supply voltage VD, the light valves can also provide a light spreading with the standard deviation DV.
  • Fig. 9 shows a cross section of a part of the projection screen 11, where the filter layer is designated with 41, the diffuser layer, which can be made from microfacets is designated with 42 and the foundation layer is designated with 43.
  • Fig. 10 shows how the diffuse reflection factor for the screen is to be optimally designed, using thin-film technology.
  • the axis r is graduated in a diffuse reflection factor while the axis 1 is graduated in wavelength, with the wavelengths in the illumination wavelengths R, G, B marked.
  • the curve 8 shows the diffuse reflection factor, which is obtained by, for example, coating a diffuse light-absorbing surface with a thin-film filter which transmits between the colours B and G, respectively G and R.
  • the curve 8 could therefore also show the reflection factor of the thin-film filter, where the axis r is graduated in a reflection factor. Because the main part of the surrounding light which hits the screen, and which is located between the colours B and G, respective G and R, will be absorbed, the contrast of the picture will be considerably greater.
  • the transmission curve 8 be designed so that mainly only the projected light wavelengths are reflected, while light with wavelengths outside of these mainly are absorbed by the screen.
  • the relation between the reflection factor at the illumination wavelengths R, G and B, and the reflection factor for any wavelength between the illumination wavelengths R, G and B be larger than 1,4. If the spectral band width of the illumination sources is relatively small, it is possible to obtain an obvious improvement of contrast through the absorption of a considerable amount of the surrounding light into the projection screen 11.
  • Fig. 11 shows schematically the principle for design of a projection screen with microfacets illustrated.
  • the facets 45 which have been covered with an absorbing layer and then with a reflecting layer as illustrated in figure 9, basically cover a pixel on the screen and reflect light in such a way that all viewers are able to see this pixel.
  • Light which is reflected against mirror 45a obtains a different direction from the light which is reflected against mirror 45b.
  • the number of mirrors and the distribution of angles is calculated with the diffraction in consideration, so that an even distribution of light is obtained to all presumptive viewers' eyes.
  • Fig. 12 schematically illustrates a six-colour projector where both time and spatial multiplexing are being used.
  • the projector is mainly designed as the projector described in figure 1, with the following additions:
  • the six illumination sources with the appurtenant light distributing optics are grouped in three groups: 2r, 2R; 2g, 2G and 2b, 2B.
  • the illumination sources in each group chosen so that they are spectrally close.
  • Light in each group is linked together with the help of dichroical mirrors 5a, 5b and 5c, so that the light in each group will incide towards the condensor C with the same angle relations.
  • the video signal for each picture from the unit Ul is in the unit CU divided into two pictures with information respectively for the colours in the illumination sources 2R,2G,2B and 2r,2g,2b, so that when a picture changes from one colour group to an other are the illumination sources activated or deactivated via the connections 3 or 4.
  • the division of colours in the different illumination sources is for the main part of the, by the six colours defined, gamut not entirely unique, i. e. there are a great number of combinations of the six light colours which are represented by one single point in the colour diagram. It is therefore possible to, as shown in figure 13, divide the, by the six colours defined, gamut into four non-overlapping triangles Gl, G2, G3 and G4, which are limited by the six illumination sources' 2R, 2G, 2B, 2r, 2g and 2b points 3A, 3a, 3B, 3b, 3C and 3c in the C.I.E. colour diagram CIE.
  • x and y are the designations for the co-ordinates in the C.I.E. colour diagram CIE.
  • Every point, for instance CP, in the picture will thereby, at a certain point in time, uniquely be determined by light from a maximum of all three illumination sources which define the triangle, for instance G2, in which the colour co-ordinates or the expanded colour co-ordinates of the point are located.
  • the number of triangles equal the number of different-coloured illumination sources minus two.
  • Fig. 14 schematically depicts a six-colour projector with two IGDs and with three-colour separation in each of the IGDs. It is, from the illumination sources 2R, 2G, 2B and 2r, 2g, 2b up to the IGDs IK and 2K respectively, designed in the same way as the device in figure 1, with the difference that the condensor is shown as if its optical axis were coinciding with the normal of the midpoint of the IGD.
  • the light spectrum for the light sources in the groups 2R,2G,2B and 2r,2g,2b are mainly disjoint.
  • the light from the IGD IK is linked via the dichroic prism DS into a device on the whole equivalent to the one described in figure 1.
  • a unit CE On the output of the unit Ul is a unit CE, where colour expansion is performed in the case of the , via V and H or VH, incoming signal to the unit Ul has been registered with a smaller gamut than the projectors potential gamut.
  • the unit U2 which divides picture information from the unit CE into two partial images in consideration to the colour contents, one via Jl for the illumination sources 2r,2g,2b and one via J2 for the illumination sources 2R,2G,2B.
  • CC designates schematically a connection on the unit CE, by means of which the value of the colour expansion factor k re can be determined.
  • Fig. 15 demonstrates a preferred manner of choosing polarisation directions at the use of 3-D projectors.
  • RE designates the right eye
  • LE designates the left eye in a pair of glasses.
  • the polarisation in the two glasses have the directions RP and LP, oriented in the angles RA respectively LA, which are given the values 45 respectively 135 degrees, or 135 respectively 45 degrees.
  • the projected light naturally has the corresponding polarisation directions for right-, respectively left-registered pictures.
  • Fig. 16 schematically illustrates the design of a 3-D three colour projector, where an off-axis field lens FL is used to direct the light into the projection lens 7.
  • the design is in other respects the same as illustrated in figure 1, with the difference that the condensor is shown as if its optical axis were coinciding with the normal of midpoint of the IGD.
  • the field lens may very well be combined with the prismatic matrix 21 in figure 5, whereby means to colour means to colour correction of the colours from the light sources 2R,2G,2B are given.
  • Fig. 17 schematically illustrates a detailed study of an IGD with condensor C, despeckelator/depixelator 88 and field lens FL.
  • the matrix ML can either consist of only positive microlenses or a combination of positive microlenses and microprisms with little prismatic angle, where the prisms are used to correct the colour aberrations originating in the field lens as well as to, together with the field lens, contribute to the light deflection.
  • Figs. 18 to 21 illustrate four different positions of the projector 10 in relation to the projection screen 11 and 11' .
  • the screen can be used for projection on booth sides 11 and 11' .
  • the projector 10 is positioned at a corner with the symbol HI.
  • the side 11' of the screen is used, then the projector 10 is positioned at the corner indicated with the symbol H2.
  • the symbols HI and H2 are indicated with Hi' and H2 ' respectively when they are on the back side of the screen.
  • Optically orthogonal' relates to planes or lines, that would be mathematically orthogonal if no plane mirrors were in-between them.
  • Optically parallel' relates to planes or lines, that would be mathematically parallel if no plane mirrors were in-between them.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Liquid Crystal (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Overhead Projectors And Projection Screens (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Projection Apparatus (AREA)

Abstract

L'invention concerne un système de projection à l'aide de sources d'illumination cohérentes, doté d'un organe générateur d'image (1K, 2K) pouvant comprendre une matrice (1, 1V) de préférence un modulateur spatial de lumière (SLM), doté de modulateurs de lumière pour pixels de couleur (1R, 1G, 1B), plusieurs fenêtres (88) à éléments dispersifs étant disposées à proximité de l'organe générateur d'image (1K, 2K), et une dispersion optique avec une déviation standard (DV) pouvant être assurée au moyen d'une tension alternative (VA) superposée sur une tension d'alimentation (VD) sur la fenêtre.
PCT/SE1996/000015 1995-01-14 1996-01-12 Systeme de projection WO1996021995A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9500149A SE9500149D0 (sv) 1995-01-14 1995-01-14 Färg-TV-projektor
SE9502529A SE9502529D0 (sv) 1995-07-10 1995-07-10 Digital TV- och multimedia-projektor
SE9503107A SE9503107D0 (sv) 1995-07-10 1995-09-08 Digital HDTV- och multimedia-projektor

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WO1996021995A2 true WO1996021995A2 (fr) 1996-07-18
WO1996021995A3 WO1996021995A3 (fr) 1996-09-19

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PCT/SE1996/000019 WO1996021883A2 (fr) 1995-01-14 1996-01-12 Ecran de projection
PCT/SE1996/000017 WO1996021997A2 (fr) 1995-01-14 1996-01-12 Projection en relief
PCT/SE1996/000015 WO1996021995A2 (fr) 1995-01-14 1996-01-12 Systeme de projection
PCT/SE1996/000018 WO1996021992A2 (fr) 1995-01-14 1996-01-12 Procede de reproduction d'images avec un nombre accru de couleurs
PCT/SE1996/000016 WO1996021996A2 (fr) 1995-01-14 1996-01-12 Separation de la lumiere en pixels couleur dans un dispositif de projection

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PCT/SE1996/000019 WO1996021883A2 (fr) 1995-01-14 1996-01-12 Ecran de projection
PCT/SE1996/000017 WO1996021997A2 (fr) 1995-01-14 1996-01-12 Projection en relief

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PCT/SE1996/000018 WO1996021992A2 (fr) 1995-01-14 1996-01-12 Procede de reproduction d'images avec un nombre accru de couleurs
PCT/SE1996/000016 WO1996021996A2 (fr) 1995-01-14 1996-01-12 Separation de la lumiere en pixels couleur dans un dispositif de projection

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DE19924519A1 (de) 1999-04-12 2000-10-19 Deutsche Telekom Ag Verfahren und Vorrichtung zur Reduktion der Speckelsbildung an einem Projektionsschirm
ATE225947T1 (de) * 1999-04-12 2002-10-15 Deutsche Telekom Ag Verfahren und vorrichtung zur reduktion der speckelbildung an einem projektionsschirm
JP2001339742A (ja) * 2000-03-21 2001-12-07 Olympus Optical Co Ltd 立体映像プロジェクション装置、及びその補正量演算装置
JP4123939B2 (ja) 2001-12-13 2008-07-23 ソニー株式会社 スクリーンおよびその製造方法ならびに画像表示システム
JP4111011B2 (ja) 2002-03-14 2008-07-02 ソニー株式会社 投影用スクリーン
US7597447B2 (en) 2004-07-14 2009-10-06 Honeywell International Inc. Color correcting contrast enhancement of displays
DE102007011560A1 (de) * 2007-03-02 2008-09-04 Seereal Technologies S.A. Vorrichtung zur Minimierung der verbeugungsbedingten Dispersion in Lichtmodulatoren
DE102007011561B4 (de) * 2007-03-02 2016-03-17 Seereal Technologies S.A. Einrichtung zur Korrektur der Wellenlängenabhängigkeit in beugungsbasierten optischen Systemen
CN108227353B (zh) * 2016-12-14 2020-12-22 中强光电股份有限公司 光源模块以及投影装置

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Also Published As

Publication number Publication date
WO1996021883A2 (fr) 1996-07-18
WO1996021883A3 (fr) 1996-09-12
WO1996021997A3 (fr) 1996-09-12
WO1996021996A2 (fr) 1996-07-18
WO1996021997A2 (fr) 1996-07-18
WO1996021992A3 (fr) 1996-09-19
WO1996021996A3 (fr) 1996-09-12
WO1996021995A3 (fr) 1996-09-19
WO1996021992A2 (fr) 1996-07-18

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