KR20050085620A - Scrolling color projection system incorporating electro-optic light modulator and rotating light-reflective element - Google Patents

Abstract

A method for color projection is provided in which light is generated from a light source and converted into a plurality of mutually different color bands including at least a first color, a second color, and a third color by directing the light from the light source onto at least three surface segments of a rotationally-symmetric element having an axis of rotation. By rotating the rotationally-symmetric element about the axis of rotation, the plurality of mutually different color bands are scrolled across a display- image-producing electro-optical light modulator panel such that at least three of the mutually different color bands including at least the first, second, and third colors are scrolling across the electro-optical light modulator panel at the same time.

Description

SCROLLING COLOR PROJECTION SYSTEM INCORPORATING ELECTRO-OPTIC LIGHT MODULATOR AND ROTATING LIGHT-REFLECTIVE ELEMENT}

The present invention relates to a color projection system, and more particularly to such a projection system incorporating a single electro-optical light modulator with a rotating light-reflective element.

The white light source is split into red, blue, and green sub-beams to separate and modulate by the corresponding color components of the incoming display signal, after which the modulated sub-beams are directed to a full color display for projection on a viewing screen. Color projected display systems that are recombined are known. Modulation of the sub-beams is commonly performed using three separate electro-optical light modulators, such as liquid crystal display (LCD) panels, one for each of the three sub-beams.

For example, in one type of color projection system described in US Pat. No. 5,532,763 to Janssen et al., All three sub-beams are modulated by a single LCD panel. This is accomplished by forming the sub-beams in a band-formed cross section and scrolling the bands sequentially over the LCD panel while synchronously addressing these portions of the panel illuminated by the bands with corresponding display signal information. Such a projection system is referred to herein as a single panel scrolling raster (SPSR) projector.

The simultaneous use of a significant portion of the red, blue, and green light available through a single light valve panel provides light efficiency comparable to the light efficiency of three panel systems using the same type of light-valve panels. By using only one panel, it eliminates the need to mechanically converge different color images formed on different panels, and reduces system cost.

Several scrolling means for such an SPSR system are disclosed, for example, in US Pat. No. 5,548,347 to Melnik et al. Systems using single-prism scrolling means are simple and compact, while multiple prism (separated or physically connected) scrolling means have better scroll-speed uniformity (for different color wide bands) than single-prism systems. And scroll-speed linearity (for each wide band). Systems using three physically separated prisms positioned in separate light paths provide better optical efficiency, but less compact, than systems using three physically connected prisms, as shown in FIG. 16 of the patent. Do.

An improved SPSR color projection system using only one moving part to achieve scrolling is disclosed in US Pat. No. 6,266,105 to Gleckman. In such a system, the illumination beam is not separated into separate color beams prior to scrolling, and the optical architecture is simple and compact. One rotationally-symmetrical element with reflective surface portions having different color reflection bands rotates about its axis, while light from the source is incident on the reflective surface and is reflected by the reflective surface portion into color components. This reflective surface portion reflects the desired color band into a relay lens that illuminates a defined portion of the surface of the element onto the light modulator panel. The color band reflected from the element is scrolled across one electro-optical light modulator panel by the rotation of the element. Driver electronics synchronously address the panel with the corresponding color component of the display information during scrolling.

Gleckman's rotationally-symmetrical elements have a cylindrical surface and the reflective portion includes a dichroic filter having a cylindrical curvature that matches the curvature of the surface of the element. This curvature can result in retroreflection when the incident light beam is perpendicular to the element's surface, resulting in the surface image onto the panel as well as the minimum color shift during rotation due to the angular sensitivity of the cut-off wavelength of the dichroic filter. Minimal aberration is guaranteed. In addition, such reflective elements, such as drums, used in the aforementioned retroreflective mode can be small cross sections (eg less than 40 mm in diameter), further reducing size and cost.

Using such reflective elements as scrolling means in an SPSR system eliminates the need to separate the white beam into sub-beams prior to scrolling, thereby enabling a smaller {less than 1.3 inch (3.3 cm) light modulator panel. This allows for smaller optical components. Thus, a simple and compact optical architecture is possible, leading to a compact projector with a small component count.

However, in the device disclosed by Gleckman, the color band reflected from the element is the same size as the light modulator panel. Using this or similar type of rotating element, the drum for the rotating element reflects on a transmissive color filter arranged in some combination of red / green / blue order. Light incident on the drum is reflected or transmitted through suitable optics such that color transitions are focused on the display device. As the drum rotates, the color scrolls down the device such that the color border moves down the panel to reach the bottom and another color border appears at the top. The red / green border comes after the blue / red border. As a result, there are at most two color patches, ie one color transition, on the panel at any given time.

If the device is changed so that all three colors are preferably in the same area on the panel at once, it is clear that all three color components will be viewed exactly at the same time and will produce a better viewing image. Therefore, in the preferred embodiment of the device disclosed herein, all three colors appear as separate bars at once, scrolling together over the panel. For example, if the red field deviates from scrolling the bottom of the panel, here the new red field appears on top in the same way as in the scrolling color architecture of Philips, except that the scrolling color band is provided by a rotating element such as a drum. In this architecture, the scrolling color or the color generated by the light is reflected through the rotating prism.

1 is a perspective view of a reflective color drum according to one embodiment of the present invention;

FIG. 2A is a schematic cross sectional view of a portion of one embodiment of the reflective segment of the drum of FIG. 1; FIG.

FIG. 2B is a schematic cross sectional view of a portion of another embodiment of the reflective segment of the drum of FIG. 1; FIG.

FIG. 2C is a schematic cross sectional view of a portion of another embodiment of the reflective segment of the drum of FIG. 1; FIG.

3 is a schematic diagram of one embodiment of a color projection system of the present invention including the color drum of FIG. 1 and including a telephoto lens set, three relay lenses, and two polarizing beam splitters (PBSs).

Thus, according to one aspect of the invention, a light source; A rotation-symmetry element having a rotation axis and a plurality of surface segments capable of providing light from the light source as a plurality of different color bands including at least a first color, a second color and a third color; A first optical circuit arranged to direct light from the light source to the surface segment; A display-image generating electro-optical light modulator panel; A second optical circuit arranged to direct light from the surface segment onto the light modulator panel, the mutually comprising at least a first color, a second color, and a third color when the rotationally-symmetrical element is rotating about an axis of rotation; An apparatus is provided for color projection, wherein at least three of the different color bands simultaneously scroll across the electro-optical light modulator panel.

According to another aspect of the invention, there is provided a color projection method, wherein light is generated from a light source and at least a first color, a second color by sending light from the light source onto at least three surface segments of a rotation-symmetrical element having an axis of rotation. And a color projection method that is converted into a plurality of different color bands including a third color. By rotating the rotation-symmetrical element about the axis of rotation, a plurality of different color bands scroll simultaneously across the electro-optical light modulator panel, wherein at least three of the different color bands including at least the first, second and third colors simultaneously. Scroll across the display-image-generating electro-optical light modulator panel.

The present invention will now be described with reference to the drawings with respect to a limited number of preferred embodiments.

1 is a reflective color drum 10 of the present invention having 18 dichroic color segments 11 with a rotation axis X and a circumference of 20 degrees each, red / green / blue (R / Reflects red, green, and blue light in the order of G / B), which sequence illustrates in perspective form an exemplary embodiment of the reflective color drum 10 repeated six times on the cylindrical surface 12 of the drum. do. Other embodiments may use the red / blue / green order. In theory, there may be as few as six or nine color segments, or conversely, there may be more than 18 segments. The exact number depends on the desired rotational speed of the drum and the desired addressing speed of the electro-optical light modulator.

Reflective segment 11 will be used to reflect light of reflective color onto the display-image generating electro-optical light modulator panel, which panel in this embodiment is a reflective LCD panel (RLCD) 72 (in FIG. 3). Can be seen).

The dark band 14 located between the color segments 11 prevents the illumination of the RLCD during the time period in which the pixel is returning to the "off" state. The addition of one or more white segments interspersed with color segments can eventually increase the light output of the system by up to 50%. Typically, one white segment can be added to each RGB group of segments 11, resulting in a 24-segment deformation of the drum of FIG. 1 with, for example, a repeating color segment sequence.

Segment 11 forms each dichroic filter on a separate thin flexible substrate such as, for example, a plastic sheet (eg, 80 μm thick) or a glass sheet (eg, 50 μm thick), and then forms the sheet in an appropriate size. By dividing into segments 11, for example. The segment 11 is then bent to conform to the drum surface and attached, for example using an adhesive.

Preferably, the flexible sheet is a plastic selected from low temperature plastics such as polycarbonate and polyester or high temperature plastics such as polyimide (eg KAPTON®). Suitable dichroic coating deposition methods include sputtering (for low temperature plastics) and thermal deposition (for high temperature plastics).

The arrangement of the segments 11 and the selection of the adjacent layers should preferably be such that light of wavelengths outside the reflecting band is considerably absorbed or scattered at an angle outside the collection angle of the relay system.

2A is a schematic cross-sectional view of a portion of one possible embodiment of the reflective segment 11 of the drum of FIG. 1. The thin sheet 122 supports the dichroic filter layer 123 and is adhered to the drum surface 120 by an adhesive layer 121. Layers 121 and 122 will usually be light transmissive. In addition, the drum surface 120 should be light-absorbing (eg, black matte) or light-scattering. Alternatively, or in addition, layer 121 and / or layer 122 may be light-absorbing or light-scattering, such as by adding pigment or scattering particles to the layer. Light that is not reflected by filter layer 123 will be absorbed or scattered by the underlying structure.

FIG. 2B is a cross section similar to the cross section of FIG. 2A with a quarter wave foil 124 and an antireflective layer 125 formed on the dichroic filter layer 123. This arrangement allows the use of simple shortened foils with a bandwidth that matches the bandwidth of the filter, so that a broad band quarter wave plate as shown in FIG. 3 can be omitted.

FIG. 2C shows an alternative embodiment of the reflective segment 11 of the drum in which the transparent dichroic filter layer 128 replaces the reflective dichroic filter layer 123 in the FIG. 2A embodiment. The reflection is provided by, for example, a vaporized aluminum coating 126, and the quarter wave foil 127 inserted between the reflective layer 126 and the filter layer 128 is once incident light, reflected light (dichroic). The light reflected by the filter does not change polarization, and therefore is rejected by the following PBS), changing the polarization of the incident light from P to S by passing the light into the layer twice once.

FIG. 3 is a schematic diagram of one embodiment of a color projection system of the present invention incorporating a color drum 58 similar to that shown in FIG. 1, with reflective dichroic filter segments on its surface, wherein two of the filter segments (60) And 62) can be seen in FIG. 3. Illumination from a source 38, preferably a high intensity source such as a high intensity discharge (HID) lamp, such as a UHP lamp, is made uniform and rectangular by the integrated plates 40a and 40b, and then flat PCS (polarization conversion). System 42 is converted into P type polarized light.

The first optical circuit 100 directs light from the light source 38 to the surface of the rotating drum 58. The telephoto lens sets 44, 46, and 48 produce telecentric P illumination beams in the PBS 50 and the quarter wave foil 54 formed in this embodiment on the surface of the PBS 50. Form. The telephoto lens set reduces the length of the optical path between the PCS 42 and the PBS 50. Alternatively, a simpler lens system with at least one lens element can be used.

This P-beam is passed to the cylindrical lens 56 via a polarizing beam splitter (PBS) 50 and a wide band quarter-wave foil 54, which is subjected to retroreflection (i.e., light Sent at right angles to the surface of the drum). Light is focused onto the surface of the rotating drum 58 at an angle of incidence. This eliminates color shifts that might otherwise occur due to the angle dependence of the color reflection band of the dichroic filter. The telecentricity of the incident beam ensures the same angle of incidence across the drum surface.

After reflection by the drum 58, the second optical circuit 200 directs light from the surface segment onto the light modulator panel. P type polarized light is converted to S type by quarter wave foil 54, and is thus reflected by the reflective surface 52 of PBS 50 to relay lenses 64 and 66, such lens 64. And 66) allow the filter to image onto the RLCD 72.

Lens 56, 64, and 66 relay systems are of sufficient quality so that the filter segments accurately image on the RLCD with no or minor overlap of the segments and avoid color mixing or at least maintain color mixing at an acceptable level. Should be Whereas lens 56 is a cylindrical lens, lenses 64 and 66 can be symmetric in the axial direction, such as shaped spheres, and have the advantage of reducing the length of the light path.

Reflective surface 70 of PBS 68 reflects light from relay lenses 56, 64, and 66 to the RLCD, which emits light from, for example, video input 37 applied by driver electronics 36. The display image is generated by changing the light according to the display signal of the. The RLCD reflects the image through the PBS 68 to the projection lens 74 to project to the viewer. The bright LCD R72 converts S light back to P light for projection by the projection lens 74.

The telecentricity of the reflected beam is preserved by the reflective surface 52 of the PBS 50, the relay lenses 64 and 66, and the reflective surface 70 of the PBS 68, so that each pixel of the LCD has a PBS (68). Ensure the same angle of incidence over As a result, there is little or no color, brightness, or contrast change over the image generated by the RLCD 72.

Although high quality images are desirable, the glass type is preferred for PBS 68, since the reflective surface 70 can be made more optically flat than for the polymer type, but PBS is preferred for conventional (MacNeille). ) Or a lightweight polymer type ("A Recent Advance in Reflective Polarizer Technology" by D. Wortman at the 1997 International Display Research Conference, cited herein).

The wide band quarter-wave foil may be, for example, a single layer foil, an achromatic stack of single non-short foils, or a single layer of polymer liquid crystal of the type described in US Pat. No. 5,506,704 to Broer et al.

The present invention has been described in terms of a limited number of embodiments. Other embodiments, variations of the embodiments, and technically recognized equivalents will be apparent to those skilled in the art and are included within the scope of the invention as set forth in the appended claims.

For example, instead of a drum, the rotationally-symmetrical element may be an element with a small face such as a polyhedron with multiple faces with a polygonal cross section. The element may also have its reflective surface segments or small sides inclined with respect to the axis of rotation as in the case of a cone-shaped element to direct reflected light away from the path of incident light.

Instead of forming reflective segments on the substrate and attaching the substrate to the segments, the segments can be formed directly on the surface of the element, such as by depositing the segments through a mask.

Instead of converting from P type polarization to S type and then converting back to P type for projection, the polarization type can be reversed, i.e. from S type to P type and back to S type. Can be.

Finally, additional embodiments of the invention may be made in which the surface segments are transparent instead of reflective. Modifications using transmissive segments can be easily realized using, for example, flat or conical color wheels, or hollow drums with internal reflective elements, for example.

As mentioned above, the present invention is used in color projection systems and, in particular, projection systems incorporating a single electro-optical light modulator with rotating light-reflective elements.

Claims (20)

As a color projection system, A light source; A rotation-symmetry element having a rotation axis and a plurality of surface segments capable of providing light from the light source as a plurality of different color bands including at least a first color, a second color and a third color; A first optical circuit arranged to direct light from the light source to the surface segment; An electro-optical light modulator panel for producing a display-image; A second optical circuit arranged to direct light from the surface segment onto the light modulator panel, wherein the rotationally-symmetric element is rotating at least around the first, second, and third colors when the rotationally symmetrical element is rotating about an axis of rotation; A second optical circuit for causing at least three of said different color bands to scroll across said electro-optical light modulator panel simultaneously; Including, color projection system. The color projection system of claim 1, wherein the surface segment is a curved surface segment. The color projection system of claim 2, wherein the curvature of the surface segment matches the curvature of the element surface. The color projection system of claim 1, wherein the surface segment is a cylindrically curved surface segment. The color projection system of claim 1, wherein the surface segment of the surface comprises a dichroic filter. 6. The color projection system of claim 5, wherein the dichroic filter is formed on a support, the support adhered to a surface of the element. 6. The color projection system of claim 5 wherein the dichroic filter has a color reflection band. 6. The color projection system of claim 5 wherein the dichroic filter has a color transmission band. The color projection system of claim 1, wherein the first optical circuit comprises a cylindrical lens. The color projection system of claim 1 comprising a light integrator for integrating light from the light source into a telecentric beam. The color projection system of claim 1 comprising a polarizing element for converting light from the light source into polarized light of P type. The color projection system of claim 1 comprising a polarizing element for converting light from the light source into polarized light of S type. The color projection system of claim 1, wherein the first optical circuit comprises a telephoto lens set. As a color projection method, Generating light from the light source; Sending light from the light source onto at least three surface segments of a rotation-symmetrical element having an axis of rotation, thereby allowing a plurality of mutually different light including at least a first color, a second color, and a third color; Converting to a color band; By rotating the rotation-symmetrical element about the axis of rotation such that at least three of the different color bands including at least the first, second and third colors scroll simultaneously across the display-image generating electro-optical light modulator panel, Scrolling the plurality of different color bands across the electro-optical light modulator panel; Including, color projection method. 15. The method of claim 14, wherein the curvature of the surface segment matches the curvature of the element surface. 15. The method of claim 14, wherein the surface segment is a cylindrically curved surface segment. 15. The method of claim 14, wherein the surface segment of the surface comprises a dichroic filter. 15. The method of claim 14, comprising using a cylindrical lens to direct light from the light source to the surface segment. 15. The method of claim 14, comprising using a light integrator for integrating light from the light source into a telecentric beam. 15. The method of claim 14, comprising using a polarizing element to convert light from the light source into polarized light.