Patent Grant
7438423
This invention generally relates to illumination systems. The invention is particularly applicable to illumination systems producing high contrast in projection systems.
Illumination systems typically include a light source and illumination optics for transferring light from the light source to a desired destination. Illumination systems are employed in various applications, such as projection displays and backlights for liquid crystal displays (LCD). The light source in an illumination system may, for example, include an arc lamp such as a mercury arc lamp, an incandescent lamp, a fluorescent lamp, a light emitting diode (LED), or a laser.
Projection systems typically include an active light valve for producing an image, an illumination system for illuminating the light valve, and optics for projecting and displaying the image typically on a projection screen. The illumination system in a projection system typically uses one or more white light sources, such as arc lamps. The illumination optics of the illumination system may include means for separating the white light into different colors, such as red, green, and blue.
It is often desirable to illuminate the light valve in such a way so as to display a projected image with high brightness, resolution and contrast.
Generally, the present invention relates to illumination systems. The present invention also relates to illumination systems employed in projection systems.
In one embodiment of the invention, an illumination system includes a plurality of discrete light sources. The output light intensity of each discrete light source can be individually controlled. The illumination system further includes an aperture stop that is positioned in a conjugate plane of the plurality of discrete light sources. The aperture stop has an opening. Light from the plurality of discrete light sources fills at least a portion of the opening and forms a first optical field at the aperture stop. The illumination system further includes a pixelated light modulator that has an active area capable of displaying a projectable image. The first optical field illuminates the active area and forms a second optical field at the active area. The first and second optical fields form a Fourier transform pair. The contrast ratio of the projectable image can be adjusted by selectively controlling the output intensity of one or more of the discrete light sources.
In another embodiment of the invention, an illumination system includes a two-dimensional array of independently operable light elements. The illumination system further includes a first optical transfer system. The first optical transfer system receives light from the light elements and illuminates an active area of a pixelated light modulator. The active area is capable of displaying a projectable image. Light from at least one light element illuminates the active area from a finite number of directions. Each pixel in the active area is illuminated by each light element. The contrast ratio of the projectable image can be controlled by adjusting the output intensity of one or more of the light elements.
In another embodiment of the invention, an illumination system includes a two-dimensional array of independently operable light sources. Each light source is capable of illuminating substantially the entire active area of a pixelated optical light modulator. Each light source emits light in different emission directions. Each emission direction is directed to a respective location in the active area. Each pixel in the active area is illuminated by an incident cone of light from the two-dimensional array of independently operable light sources. The cone has a cone angle and includes at least one light ray from each light source. The cone angle of at least one such cone of light can be controlled by adjusting the intensity of one or more of the independently operable light sources.
In another embodiment of the invention, an illumination system includes an extended light source that is capable of emitting light with adjustable two-dimensional intensity profile. The illumination system further includes a light modulator that has an active area capable of displaying an image. A point in the extended light source illuminates the entire active area from the same direction. The direction is different for different points in the extended light source. A contrast of the displayed image can be controlled by adjusting the two-dimensional intensity profile of the emitted light.
In another embodiment of the invention, a projection system includes a plurality of discrete light sources that are capable of illuminating the active area of a pixelated light modulator to form a projectable image having a contrast ratio. Each discrete light source illuminates substantially the entire active area. The projection system further includes a processor for controlling the output light intensity of each discrete light source individually. The processor further determines the contrast ratio that corresponds to each discrete light source. The processor further determines the average brightness of the projectable image. When the average brightness is less than a threshold value, the processor reduces the output light intensity of one or more discrete light sources that have low contrast ratios to increase the contrast ratio of the projectable image.
The invention may be more completely understood and appreciated in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
a and 2b show two exemplary cross-sectional intensity profiles for the extended light source of
a-4e show exemplary light cones according to the invention;
a-6c show schematic front-view of exemplary light assemblies in accordance with different embodiments of the invention;
a and 8b show exemplary illumination directions according to the invention;
a and 17b show schematic front-view of exemplary light sources in accordance with different embodiments of the invention;
The present invention generally relates to illumination systems. The invention is also applicable to projection systems that include an illumination system where it is desirable to display a projected image with high contrast and brightness. The invention is particularly applicable to projection systems that include a liquid crystal display (LCD) or a digital micro-mirror device (DMD) for producing a projectable image.
In the specification, a same reference numeral used in multiple figures refers to the same or similar elements having the same or similar properties and functionalities.
An advantage of the invention is that the light intensity profile of the illumination system can be dynamically controlled to optimize the contrast and/or brightness of each or a sequence of projected images depending, for example, on an overall brightness of the projected image. For example, the illumination system can be dynamically controlled to provide maximum brightness for a bright projected image, such as an outdoor day scene, and provide optimum contrast for a relatively dark projected image, such as a night scene.
According to one aspect of the invention, extended light source 115 emits light in different emission directions such as directions denoted by rays 112A, 112B, and 112C. The two-dimensional intensity profile of extended light source 115, for example, in the xy-plane, can be controlled by electronics 105 along one or more directions in the xy-plane. For example, the intensity profile can be controlled by electronics 105 along directions A1-A2 and B1-B2, as schematically illustrated in
Referring back to
Illumination system 100 may further include other components not explicitly shown in
Light modulator 130 can be any light modulator that is capable of displaying an image. For example, light modulator 130 may be a Microelectromechanical system (MEMS) such as a digital micro-mirror device (DMD). A DMD typically includes an array of tiltable micro-mirrors. The tilt of each mirror can be independently controlled by, for example, an electrical signal. The tilting of each mirror (or pixel) allows the mirror to act as a fast and precise light switch. As a result, a DMD can act as a spatial light modulator digitally modulating an incident light to, for example, display an image when illuminated with an incident light. An example of a DMD is a Digital Light Processor™ (DLP™) available from Texas Instruments Company, Dallas, Tex.
Further examples of light modulator 130 include a grating light valve (GLV) discussed, for example, in U.S. Pat. No. 5,841,579, or a liquid crystal display (LCD). An LCD type modulator 130 can, for example, be optically transmissive or reflective, such as a high temperature polysilicon (HTPS) LCD or a liquid crystal on silicon (LCoS) display, respectively. In a typical LCD, a thin film of a liquid crystal fills a gap between two substrates made of, for example, glass or plastic. Polarizing sheets are usually placed on one or both sides of the substrates to polarize the light entering and exiting the liquid crystal. The sides of the substrates facing the liquid crystal are typically coated with patterned conductive electrodes that define an array of liquid crystal cells or pixels. Application of an electric field to the electrodes across a cell can affect optical transmission or reflection properties of the cell by changing the orientation of the liquid crystal molecules in the cell. The ability to affect optical properties of individual pixels allows the LCD to display an image when illuminated with an incident light.
In general, light modulator 130 can be any electronically addressable or switchable device capable of forming an image. In some applications, light modulator 130 may display a static image that can, for example, be refreshed, changed, or otherwise updated as a function of time depending on the particular application.
Contrast ratio of a light modulator is usually defined as the ratio of luminance or brightness between “white” (or “on”) and “dark” (or “off” or “black”) states in an active area of the modulator. There are different methods for measuring contrast ratio, such as sequential and ANSI (American National Standards Institute) contrast. In a sequential contrast ratio measurement, contrast ratio of a modulator, such as modulator 130, is typically determined by measuring the brightness of active area 140, for example, at or near the center of the area, with the entire active area displaying “white” (“on” state), followed by making a similar measurement with the entire active area displaying “black” (“off” or “dark” state). Contrast ratio is the ratio of the two measured values for brightness.
ANSI-contrast is measured by providing a 16 box (pixel) checkerboard display made up of alternating “white” and “black” pixels. The luminance of the “white” state is obtained by measuring and adding the brightness at the centers of the eight “white” pixels. Similarly, the luminance of the “black” state is obtained by measuring and adding the brightness at the centers of the eight “black” pixels. ANSI-contrast is the ratio of the two luminance values.
According to one aspect of the invention, the contrast ratio of an image displayed in active area 140 can be controlled by adjusting the two-dimensional intensity profile of the emitted light. For example, referring again to
One advantage of the present invention is that for a given light modulator and/or light source, the contrast ratio and/or brightness of a displayed image can be improved or optimized by adjusting the two-dimensional intensity profile of extended light source 115.
Illumination system 100 may be advantageously employed in a front or rear projection system to provide improved contrast, resolution, and brightness. An image formed by the projection system may be real or virtual, in which case, a viewer may be able to view the image directly or, for example, with an eyepiece.
In one embodiment of the invention, each independently operable light source in light source 315 illuminates substantially the entire active area 340. For example, independently operable light source 315C illuminates substantially the entire active area 340. Furthermore, each independently operable light source emits light in different emission directions. For example, light source 315A emits light in different emission directions such as light rays 318A and 318B emitted along emission directions A and B, respectively; light source 315B emits light in different emission directions such as light rays 316A and 316B emitted along emission directions A and B, respectively; and light source 315C emits light in different emission directions such as light rays 317A and 317B emitted along emission directions A and B, respectively. In addition, each emission direction is directed to a respective location in active area 340, meaning that all rays emitted in a given direction by light source 315 illuminate active area 340 in a respective location. For example, rays 316A, 317A, and 318A which are emitted along direction “A” converge to a same location in active area 340, such as pixel 341A. As another example, rays 316B, 317B, and 318B which are emitted along direction “B,” where direction “B” is different than direction “A,” converge to a different location in active area 340, such as pixel 341B.
Each pixel in the active area 340 is illuminated by an incident light cone that has a cone angle and includes at least one light ray emitted from each independently operable light source in two-dimensional array of light sources 315. For example, pixel 341C in active area 340 is illuminated by light cone 320. Light cone 320 has a cone angle β.
Cone angle β of light cone 320 can be controlled by adjusting the output light intensity of one or more of the independently operable light sources in two-dimensional array of light sources 315. For example, by modifying the output light intensity of one or more of the independently operable light sources 315, light cone 320 can change to light cone 350 with a cone angle γ, where γ is smaller than β.
In general, the contrast ratio of a light modulator decreases as the cone angle of an incident light cone illuminating the modulator increases. In the case of an LCD modulator, this decrease is typically due to the dependence of the liquid crystal material retardance on the incident angle of an incident light ray. Such dependence reduces the contrast ratio by increasing the brightness of a pixel in the dark state. Light leakage in the polarizing sheets (or other components such as polarizing beam splitters) at oblique incident angles can also contribute to contrast degradation.
In the case of a DMD modulator, the decrease in the contrast ratio is believed to be, at least in part, due to optical diffraction effects. In all light modulators, stray or scattered light originating, for example, from an imperfect lens surface can also reduce the contrast ratio.
One advantage of the present invention is that the contrast of an image displayed by light modulator 330 can be increased by adjusting the output light intensities of the individual light sources in two-dimensional array of light sources 315 so that one or more cone angles of incident light cones in active area 340 are reduced which can, for example, result in improved image contrast.
Furthermore, in one embodiment of the invention, the output intensity of one or more light sources that do not significantly affect the size of the cone angle of an incident light cone may be increased to further improve the contrast ratio and/or brightness of an image. Such light sources can, for example, be light sources that contribute incident light rays that are located in the inner parts of an incident light cone.
Illumination system 300 may further include other components not explicitly shown in
Illumination system 300 may be advantageously employed in a front or rear projection system to provide improved contrast, resolution, and brightness.
In the invention, a cone generally refers to a plurality of light rays defining an inclusion angle, referred to as a cone angle. A general light cone according to the invention is shown in
Other exemplary light cones are shown in
c shows a cone 402 having a rectangular base 413, an inclusion solid angle α3, and exemplary outermost rays 402A, 402B, and 402C. Cross-section 422 is a cross-section of the cone in the xy-plane at a different location along the z-axis. As can be seen, cross-section 422 has an arbitrary profile. Another exemplary cone is schematically shown in
As yet another example,
In general, the base of a cone or other cross-sections of the cone in the xy-plane can have any two-dimensional shape that may be desirable in a particular application. Exemplary shapes include a circle, an ellipse, a polygon such as a quadrilateral, a rhombus, a parallelogram, a trapezoid, a rectangle, a square, or a triangle, or any other shape that may be advantageous in a given application. For example, referring back to
The exemplary cones shown in
Referring back to
In one preferred embodiment of the invention, each light source in two-dimensional array of light sources 315 is an LED.
The independently operable light sources in array 315 can be arranged in any form of an array that may be desirable in an application. Examples include rectangular, triangular, hexagonal, circular, or any other suitably configured arrays.
In one embodiment of the invention, the individual light sources can be of different types. For example, some of the light sources can be LEDs and some others can be arc lamps, and still some other light sources in the array can be OLEDs. Furthermore, the emission spectra of the light sources can be different. For example, in an array of independently operable LEDs, different LEDs can emit different color light such as white, green, red, and blue.
Extended light source 710 is centered on an optical axis 716 and includes a two-dimensional array 715 of independently operable light elements, such as light elements 715A and 715B. Each light element emits a cone of light characterized by an output light intensity, a cone angle, and a central ray that propagates along a direction. For example, light element 715B emits a cone of light 703 that has a cone angle α7, exemplary outermost rays 705A and 705B, and a central ray 705C that propagates along a direction 704.
First optical transfer system 720 receives light emitted by light source 710 from its input face 721, transfers the received light to its output face 722, and delivers the transmitted light from its output face to pixelated light modulator 730.
According to one embodiment of the invention, light from at least one light element that is transmitted by first optical transfer system 720 illuminates pixelated light modulator 730 from a finite number of directions, where the finite number of directions is at least two. For example, first optical transfer system 720 receives cone of light 703 from its input face 721, transmits the received light to its output face 722 and delivers the transmitted light to modulator 730 along two directions 717 and 719. For example, rays 716A and 716B originate from cone 703, exit output face 722, and propagate towards modulator 730 along direction 717. Similarly, rays 718A and 718B originate from cone 703, exit output face 722, and propagate towards modulator 730 along direction 719.
According to one embodiment of the invention, directions 717 and 719 are rotationally symmetric about optical axis 716 as described in reference to the schematics shown in
As shown in
Referring back to
In general, light rays in a light cone, such as light rays in light cone 703 from light element 715B can exit output face 722 of first optical transfer system 720 along a finite number of directions. An example is shown schematically in
Referring back to
First optical transfer system 720 can include one or more optical components such as a lens, a micro lens array, a light homogenizer, an optical filter, a color wheel, a mirror, or any other optical component that may be used in first optical transfer system 720 to transfer light to light modulator 730 according to the invention.
An exemplary first optical transfer system 720 is optical transfer system 1300 shown schematically in
Another exemplary first optical transfer system 720 is optical transfer system 1400 shown schematically in
Optical transfer system 1400 further directs lights rays emitted by array 715 so that light rays emitted in a same direction are directed to substantially a same location in active area 740. For example, light rays 1431, 1432, and 1433 are emitted by different light elements along a same direction 1480. Optical transfer system 1400 redirects these light rays so that they converge substantially to a same point 1491 in active area 740.
Another exemplary first optical transfer system 720 is optical transfer system 1600 shown schematically in
Homogenizer 1650 is designed to homogenize light received from two-dimensional array of independently operable light elements 715. For example, homogenizer 1650 homogenizes light received from light element 715A, where by homogenizing it is meant that light exiting homogenizer 1650 has a more uniform spatial intensity distribution than light entering homogenizer 1650. Examples of known light homogenizers may be found in U.S. Pat. Nos. 5,625,738 and 6,332,688; and U.S. Patent Application Publication Nos. 2002/0114167, 2002/0114573, and 2002/0118946.
Homogenizer 1650 has an input face 1651, an optical rod 1653 and an output face 1652. Input face 1651 may or may not be parallel to output face 1652. In general, output face 1652 may have a shape that is different than the shape of active area 740. For example, output face 1652 may be a trapezoid and active area 740 may be a square. In some applications, output face 1652 and active area 740 may have the same shape, such as a rectangle or a square.
Input face 1651, output face 1652, and a cross-section of optical rod 1653 can have any shape such as a rectangle, a trapezoid, a square, an ellipse or any other shape that may be desirable in an application. Input face 1651, output face 1652, and a cross-section of optical rod 1653 can have different shapes. For example, input face 1651 can be a circle, while output face 1652 can be a square. A cross-section of optical rod 1653 can be different at different locations along the optical rod. For example, optical rod 1653 may be tapered along its length along optical axis 716. The sides of a cross-section of optical rod 1653 may be straight or curved. An example of a tapered optical rod is described in U.S. Pat. No. 6,332,688.
Homogenizer 1650 can have any three-dimensional shape, for example, a polyhedron, such as a hexahedron. A portion of or the entire homogenizer 1650 can be solid or hollow. Homogenizer 1650 may homogenize an input light by any suitable optical method such as reflection, total internal reflection, refraction, scattering, or diffraction, or any combination thereof.
Another exemplary first optical transfer system 720 is optical transfer system 1700 shown schematically in
Optical transfer system 1700 further includes an aperture stop 1705 positioned at or near lens array 1704. In the embodiment shown in
Referring back to
Referring back to
Second optical transfer system 750 can include one or more optical components such as a lens, a micro lens array, a polarizer, a color combiner, a mirror, a Fresnel lens, or any other optical component that may be used in second optical transfer system 750 to project an image displayed by light modulator 730 (or 1030) onto screen 760 according to the invention.
An exemplary second optical transfer system 750 is optical transfer system 1500 shown schematically in
Illumination system 1101 includes an extended light source 1110, a first optical transfer system 1120, an aperture stop 1130, a second optical transfer system 1150 and a pixelated light modulator 1160. Extended light source 1110 includes a plurality of discrete light sources 1115, such as discrete light source 1111. Each of the discrete light sources can be controlled individually, meaning that, for example, the output intensity of each discrete light sources can be controlled independent from other discrete light sources. In some applications, it may be advantageous to control different subsets of plurality of discrete light sources 1115 as discrete groups as described in more detail in reference to
a shows a front view schematic of a plurality of discrete light sources 1215 similar to light sources 1115 in
b shows a front view schematic of a plurality of discrete light sources 1250 in accordance to one embodiment of the invention. Plurality of discrete light sources 1250 includes 16 discrete light segments numbered from 1 to 16. Each light segment is individually controlled by, for example, a dedicated electronics circuitry. For example, electronics 1212 controls the output light intensity of light segment 12, and electronics 1209 controls the output light intensity of light segment 9.
Referring back to
According to one embodiment of the invention, the plurality of discrete light sources 1115 may include different size light sources. For example, referring to
Aperture stop 1130 has an open area 1140 that is optically transmissive. Opening area 1140 may be in the form of a square, circle, ellipse, trapezoid, or any other shape that may be suitable in an application. Furthermore, the size of opening 1140 can be controlled, for example, manually or electronically.
First optical transfer system 1120 images plurality of discrete light sources 1115 in a plane that substantially coincides with or is substantially close to the plane of aperture 1130. The formed image is a first optical field 1145 that fills at least a portion of aperture opening 1140. In one embodiment of the invention, first optical field 1145 substantially fills the entire aperture opening 1140. Optical field 1145 and plurality of discrete light sources 1115 form a conjugate pair, meaning that, for example, optical field 1145 lies in an image plane of plurality of discrete light sources 1115.
One advantage of the present invention is dynamic apodization, meaning that by individual control of discrete light sources in plurality of discrete light sources 1115, the effective shape and/or size of aperture stop 1130 can be dynamically controlled resulting in improved brightness and/or contrast of a projected image.
First optical transfer system 1120 can include one or more optical components such as a lens, a micro lens array, a light homogenizer, an optical filter, a color wheel, a mirror, a Fresnel lens, or any other optical component that may be suitably used in first optical transfer system 1120 to image plurality of discrete light sources 1115 onto aperture opening 1140.
Pixelated light modulator 1160 has a pixelated active area 1170, including pixels such as pixel 1171, that is capable of forming an image. Second optical transfer system 1150 transfers first optical field 1145 onto active area 1170, thus forming a second optical field 1165 in the plane of active area 1170 or pixelated light modulator 1160. According to one embodiment of the invention, first optical field 1145 and second optical field 1165 form a Fourier transform pair, meaning that, in general, every point in optical field 1145 illuminates substantially the entire active area 1171 from a finite number of directions, preferably one or two directions. Furthermore, all light rays from first optical field 1145 that propagate along a same direction converge substantially at a respective point in active area 1170.
Second optical field 1165 may illuminate a portion of active area 1170, a situation that is sometimes referred to as an underfill. Second optical field 1165 may illuminate an area extending beyond active area 1170, a situation that is sometimes referred to as an overfill. According to one embodiment of the invention, the size of second optical field 1165 is substantially the same as the size of active area 1170, meaning that there is minimized or no overfill or underfill.
Second optical transfer system 1150 can include one or more optical components such as a lens, a micro lens array, a light homogenizer, an optical filter, a color wheel, a mirror, a Fresnel lens, or any other optical component that may be suitably used in second optical transfer system 1150 to receive first optical field 1145 and form a second optical field 1165 at modulator 1160 where the two optical fields form a Fourier transform pair.
An exemplary first optical transfer system 1120 and second optical transfer system 1150 is shown in
Referring back to
Projection display 1100 may be a rear projection system, in which case, projection screen 1190 is a rear projection screen. Projection display 1100 may be a front projection system, in which case, projection screen 1190 is a front projection screen.
Third optical transfer system 1180 can include one or more optical components such as a lens, a micro lens array, a polarizer, a color combiner, a mirror, a Fresnel lens, an aperture stop, or any other optical component that may be suitably used in third optical transfer system 1180 to project an image displayed by light modulator 1160 onto screen 1190. An example of third optical transfer system 1180 is shown in
Projection display 1100 further includes a processor 1103 for measuring and storing the contrast ratio corresponding to each discrete light source. This can be done by, for example, turning off all but one of the discrete light sources, and measuring the contrast ratio in active area 1170 corresponding to “on” light source. Such a measurement can be made for each light source resulting in an electronically stored look-up table ranking the discrete light sources from having the worst or smallest contrast ratio to the best or highest contrast ratio.
Processor 1103 can also measure an average brightness of a projectable image formed in active area 1170 where the projectable image can, for example, be projected onto projection 1190 by third optical transfer system 1180. The measured average brightness can be used by processor 1103 to increase the contrast ratio and/or brightness of the projectable image by adjusting the output intensity of one or more discrete light sources. For example, when the average brightness is lower than a threshold value signaling a relatively dark image such as a night scene, processor 1103 may reduce the output intensity of or completely turn off one or more of the independent light sources that have the lowest corresponding contrast ratios. The affected discrete light sources can be in the outer part of the plurality of discrete light sources 1115, in the inner part, or in general positioned at different locations in the extended light source 1110. An advantage of the invention is that the output intensity of a discrete light source can be controlled individually to improve the contrast ratio and/or brightness of a projectable image regardless of the location of the discrete light source. At the same time, processor 1103 can increase the output intensity of one or more discrete light sources that have corresponding high contrast ratios. Therefore, the brightness and contrast of a relatively dark projectable image may be increased.
If the average brightness of a projectable image in active area 1170 is higher than a threshold value signaling a bright image such as an outdoor day image, processor 1103 may keep all discrete light sources 1115 on, and may even increase the output intensities of one or more of the discrete light sources.
An advantage of the present invention is that processor 1103 can measure a contrast ratio for each discrete light source for any given active area 1170 and any given plurality of light sources 1115. For example, the output intensity of a particular discrete light source that has a corresponding low contrast ratio can be reduced regardless of where the discrete light source is located in extended light source 1110. Processor 1103 can be part of electronics 105 (see
Each illumination system in
According to one embodiment of the invention, light emitted by each light element illuminates substantially the entire active area of a corresponding light modulator. For example, all light emitted from light element 1801A illuminates substantially the entire active area 1851. Furthermore, according to one embodiment of the invention, the illumination is along a same direction. For example, light emitted from light element 1801A illuminates active area 1851 along direction 1810A as exemplified by light rays 1811 and 1812, light emitted from light element 1801B illuminates active area 1851 along direction 1810B, and light emitted from light element 1801C illuminates active area 1851 along direction 1810C. Furthermore, according to one embodiment of the invention, directions 1810A, 1810B, and 1810C are different from one another as shown in
According to one embodiment of the invention, all light rays that are emitted along a same direction by a two-dimensional array of independently operable light elements converge substantially to a same location in the active area of a corresponding light modulator.
Each of the three exemplary illumination systems shown in
Projection system 1800 further includes a color combiner 1860 for combining and superimposing images formed by the three light modulators.
Paths of images formed by the different light modulators are schematically shown in color combiner 1860. In particular, ray path 1861 shows the general propagation path for an image formed by illumination system 1801, ray path 1862 shows the general propagation path for an image formed by illumination system 1802, and ray path 1863 shows the general propagation path for an image formed by illumination system 1803. Although the ray paths are shown to be slightly offset relative to one another, this is done for ease of illustration. In general, images formed by the illumination systems substantially overlap and superimpose to form a colored image having high resolution.
Projection system 1800 further includes a projection lens system 1870 and a projection screen 1880. Projection lens system 1870 typically includes multiple lenses (for example, five in
Projection system 1800 may be a rear projection system, in which case, projection screen 1880 is preferably a rear projection screen. Projection system 1800 may be a front projection system, in which case, projection screen 1880 is preferably a front projection screen.
Each illumination system in
Furthermore, each light element in an illumination system has a dedicated lens from a corresponding first lens array and a dedicated lens from a corresponding second lens array. For example, light element 2001C has dedicated lens 2020C from first lens array 2020 and dedicated lens 2030C from second lens array 2030. The three illumination systems share the same field lens 2005 and the same reflective light modulator 2050, where reflective light modulator 2050 has an active area 2051 capable of displaying an image. Light modulator 2050 is preferably a DMD such as a DLP.
In the exemplary embodiment shown in
According to one embodiment of the invention, light emitted by each light element illuminates substantially the entire active area of the light modulator. For example, all light emitted from light element 2001A illuminates substantially the entire active area 2051. Furthermore, according to one embodiment of the invention, light rays from a given light element illuminate active area 2051 along a same direction, where the direction of illumination is different for different light elements in the same two-dimensional array of independently operable light elements.
According to one embodiment of the invention, all light rays that are emitted along a same direction by a two-dimensional array of independently operable light elements converge substantially to a same location in active area 2051 of light modulator 2050.
Each of the three exemplary illumination systems shown in
Projection system 2000 further includes a color combiner 2060 shared by the three illumination systems for compact and efficient redirecting of light from different light elements to light modulator 2050. Ray paths in color combiner 2060 are schematically shown in
Projection system 2000 further includes a total internal reflection (TIR) prism 2070 for compact and effective redirecting of light. TIR prism 2070 includes a first prism 2071, a second prism 2072, an input face 2074, an exit face 2075, and a low index area 2073, such as air, for separating prism 2071 from prism 2072.
A ray of light 2081 entering first prism 2071 from input face 2074 suffers total internal reflection at the interface between first prism 2071 and low index area 2073 at point 2085, and propagates toward light modulator 2050 as light ray 2082. Light ray 2082 is incident on a pixel in active area 2051. If the pixel is in an “on” state, incident light ray 2082 is reflected back as ray 2083 that exits TIR prism 2070 from exit face 2075 and propagates towards projection lens system 2090. If, on the other hand, the pixel is in an “off” state, incident light ray 2082 is reflected as ray 2084 away from projection lens system 2090. Ray 2084 is typically trapped by a light trap not shown in
Projection system 2000 further includes a projection lens system 2090 and a projection screen 2095. Projection lens system 2090 typically includes multiple lenses (for example, five in
Projection system 2000 may be a rear projection system, in which case, projection screen 2095 is preferably a rear projection screen. Projection system 2000 may be a front projection system, in which case, projection screen 2095 is preferably a front projection screen.
Projection system 2000 further includes a processor 2024, similar to processor 1103 of
All patents, patent applications, and other publications cited above are incorporated by reference into this document as if reproduced in full. While specific examples of the invention are described in detail above to facilitate explanation of various aspects of the invention, it should be understood that the intention is not to limit the invention to the specifics of the examples. Rather, the intention is to cover all modifications, embodiments, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4458303 | Berns | Jul 1984 | A |
| 5442414 | Janssen et al. | Aug 1995 | A |
| 5625738 | Magarill | Apr 1997 | A |
| 5841579 | Bloom et al. | Nov 1998 | A |
| 5969876 | Kreitzer et al. | Oct 1999 | A |
| 5978142 | Blackham et al. | Nov 1999 | A |
| 6301057 | Kreitzer | Oct 2001 | B1 |
| 6332688 | Magarill | Dec 2001 | B1 |
| 6417971 | Moskovich | Jul 2002 | B1 |
| 6547400 | Yokoyama | Apr 2003 | B1 |
| 6644814 | Ogawa et al. | Nov 2003 | B2 |
| 6882331 | Wu | Apr 2005 | B2 |
| 6935749 | Kato | Aug 2005 | B2 |
| 7052138 | Matsui | May 2006 | B2 |
| 20020114167 | Schmidt et al. | Aug 2002 | A1 |
| 20020114573 | Schmidt et al. | Aug 2002 | A1 |
| 20020118946 | Wagner | Aug 2002 | A1 |
| 20020196414 | Manni et al. | Dec 2002 | A1 |
| 20050018141 | Hosaka | Jan 2005 | A1 |
| 20050022487 | Ryan et al. | Feb 2005 | A1 |
| 20060187415 | Slobodin | Aug 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 829 747 | Mar 1998 | EP |
| 2005-189472 | Jul 2005 | JP |
| 10-2003-0045433 | Jun 2003 | KR |
| 10-2004-0009312 | Jan 2004 | KR |
| WO 9633483 | Oct 1996 | WO |
| WO 0192980 | Dec 2001 | WO |
| WO 0203687 | Jan 2002 | WO |
| WO 02069030 | Sep 2002 | WO |
| WO 02097323 | Dec 2002 | WO |
| WO 2003077013 | Sep 2003 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20070046898 A1 | Mar 2007 | US |
