WO1998005996A1 - Solid optic color lcd projection system - Google Patents

Solid optic color lcd projection system Download PDF

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Publication number
WO1998005996A1
WO1998005996A1 PCT/US1997/011169 US9711169W WO9805996A1 WO 1998005996 A1 WO1998005996 A1 WO 1998005996A1 US 9711169 W US9711169 W US 9711169W WO 9805996 A1 WO9805996 A1 WO 9805996A1
Authority
WO
WIPO (PCT)
Prior art keywords
reflective
color
active matrix
mode active
dichroic
Prior art date
Application number
PCT/US1997/011169
Other languages
French (fr)
Inventor
Dean S. Irwin
Original Assignee
Spatialight, Inc.
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
Application filed by Spatialight, Inc. filed Critical Spatialight, Inc.
Publication of WO1998005996A1 publication Critical patent/WO1998005996A1/en

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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]
    • H04N9/3102—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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining

Definitions

  • This invention relates in general to liquid crystal display (LCD) projection systems and in particular, to a solid optic color LCD projection system.
  • Fig. 1 illustrates, as an example, a conventional color LCD projection system 100.
  • Light from a lamp 104 is collimated by collimating lens 105 into dichroic filters, 108 and 109, which are positioned so as to split the light into rays of blue, red and green colors.
  • Each color ray is directed to a corresponding one of three transmissive-mode active matrix LCDs, 101-103, which are driven by drive circuitry 150 so that they pass their corresponding color rays through pixels which are to be displayed by the LCD projection system 100 as that color.
  • the color rays passing through the selected pixels of the active matrix LCDs, 101-103 are recombined through dichroic filters, 110 and 111, and projected through projection lens 106 onto a display screen 107.
  • Each of the active matrix LCDs, 101-103 comprise an LCD panel, 114-116, a front polarizer, 117-119, and a back polarizer, 120-122, wherein front and back polarizers are crossed so that a fully turned on pixel appears trans issive, and a fully turned off pixel appears opaque to incident light.
  • the dichroic filter 108 functions as a blue dichroic mirror to reflect a blue portion of the light along an optical path 133 to the optical mirror 113, and pass the red and green portions along an optical path 132 to the dichroic filter 109.
  • the optical mirror 113 reflects the blue light to the active matrix LCD 101 which is driven by the drive circuitry 150 such that pixels to be displayed as blue by the LCD projection system 100 are activated so that the blue light only passes through the selected pixels.
  • the dichroic filter 109 functions as a red dichroic mirror to reflect the received red portion to the active matrix LCD 102 along an optical path 134, and pass the received green portion to the optical mirror 112 along an optical path 135.
  • the active matrix LCD 102 is driven by the drive circuitry 150 such that pixels to be displayed as red by the LCD projection system 100 are activated so that the red light only passes through such selected pixels.
  • the optical mirror 112 reflects the green light to the active matrix 103, which is driven by the drive circuitry 150 such that pixels to be displayed as green by the LCD projection system 100 are activated so that the green light only passes through such selected pixels.
  • the dichroic filter 110 functions as a red dichroic mirror to combine along an optical path 137, the blue light indicative of a blue pixel pattern received from the active matrix LCD 101 and the red light indicative of a red pixel pattern received from the active matrix LCD 102.
  • the dichroic filter 111 functions as a green dichroic mirror to combine along an optical path 138, the red and blue lights indicative of red and blue pixel patterns received along the optical path 137 from the dichroic filter 110 and the green light indicative of a green pixel pattern reflected by the optical mirror 112 from the active matrix LCD 103.
  • the resulting combined blue, red and green pixel patterns are thereupon projected onto the display screen 107 through the projection lens 106.
  • one object of the present invention is a color LCD projection system which does not need its reflective surfaces to be periodically aligned.
  • Another object is a color LCD projection system having a rugged construction capable of withstanding shock and vibration.
  • Another object is a color LCD projection system having a hermetic construction protecting its reflective surfaces from dust particles and moisture.
  • Still other objects include a color LCD projection system that is compact, lightweight, and low cost to manufacture.
  • one aspect is a solid optic color LCD projection system (e.g., 200 in fig. 2) having a solid glass structure (e.g., 222), embedded optical surfaces (e.g., 223-225), and attached active matrix LCDs (e.g., 226-228). Since the optical surfaces are fixedly positioned by embedding them in the solid glass structure, there is no need to periodically realign them, and expensive mechanical devices for conventionally doing so are unnecessary. Also, since the optical surfaces are hermetically sealed in the solid glass structure, they are protected from performance degrading dust particles and moisture. Further, since the active matrix LCDs are fixedly attached to the solid glass structure, the resulting color LCD projection system is a rugged construction resistant to shock and vibration.
  • the optical surfaces respectively function as a polarizing beamsplitter, and first and second dichroic reflectors which are embedded in the solid glass structure such that light entering the solid glass structure and passing through the polarizing beamsplitter is separated into first, second and third color light rays by the first and second dichroic reflectors.
  • the attached active matrix LCDs are preferably reflective-mode active matrix LCDs attached to the solid glass structure such that one active matrix LCD receives and reflects the first color light ray, another active matrix LCD receives and reflects the second color light ray, and another active matrix LCD receives and reflects the third color light ray.
  • a method of forming a solid reflective-mode color LCD projection system comprises the steps of: forming a solid glass structure with embedded dielectric and dichroic coatings such that the solid glass structure resembles the joinder of four glass cubes wherein a first glass cube is formed by joining two prisms with a dielectric coating between the joining faces, a second glass cube is formed by joining two prisms with a first dichroic coating between the joining faces, a third glass cube is formed by joining two prisms with a second dichroic coating between the joining faces, and a fourth glass cube is formed as a glass cube, wherein the first and second glass cubes are joined by optical cement such that the dielectric and first dichroic coatings lie in parallel planes, the second and third glass cubes are joined by optical cement such that the first and second dichroic coatings lie in parallel planes, and the second and fourth glass cubes are joined by optical cement such that the fourth glass cube is attached to a free square face of
  • Fig. 1 illustrates, as an example, a conventional color LCD projection system
  • Fig. 2 illustrates, as an example, a color LCD projection system utilizing aspects of the present invention
  • Fig. 3 illustrates, as an example, a blow-up exemplifying a method of constructing the color LCD projection system of fig. 2, utilizing aspects of the present invention
  • Figs. 4 and 5 respectively illustrate, as examples, a glass cube and a glass prism used in constructing the color LCD projection system of fig. 2, utilizing aspects of the present invention.
  • Fig. 2 illustrates a color LCD projection system 200 including a lamp 104, a collimating lens unit
  • the lamp 104, the collimating lens unit 105, the projection lens unit 106, and the drive circuitry 150 are generally constructed and operate the same as their identically referenced counterparts in the conventional color LCD projection system 100 of fig. 1.
  • a display screen 107 is commonly used with the color LCD projection system 200, and is also generally constructed and operates the same as its identically referenced counterpart of fig. 1.
  • the solid optic structure 220 functions similarly to the combination of the active-matrix LCDs 101-103, dichroic filters 108-111, and optical mirrors 112-113 of the conventional color LCD projection system 100 of fig. 1, in that it also processes the light received from the lamp 104 through the collimating lens unit 105, and provides red, blue and green light rays respectively indicative of red, blue and green pixel patterns to the projection lens unit 106 for projection onto the display screen 107.
  • the solid optic structure 220 is a substantially different construction which avoids the various problems of the conventional color LCD projection system 100 of fig. 1.
  • the solid optic structure 220 avoids the necessity of periodically aligning its optical surfaces, is less sensitive to shock and vibration, is more resistant to contaminating dust, dirt and moisture, is more compact, and is cheaper to manufacture than its conventionally formed counterpart of fig. 1.
  • the solid optic structure 220 is formed of a solid glass structure 222, embedded optical surfaces 223-225, red, blue and green color corrector coatings 229-231, and attached reflective-mode active matrix LCDs 226-228.
  • the optical surfaces 223-225 are formed as three parallel coatings embedded in the solid optic structure 220 and angled at forty-five degrees with respect to light received from the lamp 104 through the collimating lens unit 105.
  • the optical coating 223 is a dielectric coating functioning as a polarizing beamsplitter
  • the optical surface 224 is a dichroic mirror coating functioning as a reflector for the red portion of the light and a transmitter for the blue and green portions of the light
  • the optical surface 225 is another dichroic mirror coating functioning as a reflector for the blue portion of the light and a transmitter for the remaining green portion of the light.
  • the reflective-mode active matrix LCDs 226-228 are attached to the solid optic structure 220 and positioned such that the active matrix LCD 226 receives and reflects back the red light reflected by the dichroic coating 224, the active matrix LCD 227 receives and reflects back the blue light reflected by the dichroic coating 225, and the active matrix LCD 228 receives and reflects back the green light transmitted through the dichroic coating 225.
  • the drive circuitry 150 drives the active matrix LCDs 226-228 in generally the same manner as their respective counterparts in the conventional color LCD projection system 100 of fig. l.
  • the active matrix LCD 226 is driven such that pixels to be displayed as red by the LCD projection system 200 are activated so that the red light only passes and is reflected back through such selected pixels
  • the active matrix LCD 227 is driven such that pixels to be displayed as blue by the LCD projection system 200 are activated so that the blue light only passes and is reflected back through such selected pixels
  • the active matrix LCD 228 is driven such that pixels to be displayed as green by the LCD projection system 200 are activated so that the green light only passes and is reflected back through such selected pixels.
  • the red, blue and green corrector coatings 229-231 are optionally formed on the solid glass structure 222 at the attachment points respectively for the active matrix LCDs 226-228, so as to correct for by filtering out all but the red, blue and green light rays being received and reflected by the active matrix LCDs 226-228.
  • the blue reflecting dichroic coating 225 is transraissive to the green light indicating a green pixel pattern received from the active matrix LCD 228, and is reflective to the blue light indicating a blue pixel pattern received from the active matrix LCD 227.
  • the red reflecting dichroic coating 224 is transmissive to both the green light and the blue light received from the blue reflecting dichroic coating 225, and is reflective to the red light indicating a red pixel pattern received from the active matrix LCD 226.
  • the optical paths between the dielectric coating 223 and each of the active matrix LCDs 226-228 should be the same length.
  • the pixels of the active matrix LCDs 226-228 may be selectively controlled by the drive circuitry 150 to various shades of a gray scale, and that corresponding pixels of the active matrix LCDs 226- 228 may be jointly activated to form colors in combination of red, blue and green.
  • Fig. 3 illustrates a blow-up exemplifying one method of constructing the solid optic structure 220 and in particular, the solid glass structure 222 which is formed by first forming four glass cubes 301-304, then joining the four glass cubes 301-304 together with optical cement.
  • Glass cube 304 is a conventionally formed glass cube such as depicted in fig. 4.
  • Glass cubes 301-303 are each formed from two half-cube glass prisms, such as depicted in fig. 5, with an optical surface preformed on a diagonal face of one of the two prisms.
  • the glass cube 301 is formed by first forming the dielectric coating 223 on the diagonal face 311 of the glass prism 222-2, then joining together at their diagonal faces, glass prisms 222-1 and 222-2 with optical cement, so that glass cube 301 functions as a polarizing beamsplitter.
  • the glass cube 302 is formed by first forming the dichroic coating 224 on the diagonal face 312 of the glass prism 222-3, then joining together at their diagonal faces, glass prisms 222-3 and 222-4 with optical cement, so that glass cube 302 functions as a red dichroic reflector.
  • the glass cube 301 is formed by first forming the dielectric coating 223 on the diagonal face 311 of the glass prism 222-2, then joining together at their diagonal faces, glass prisms 222-1 and 222-2 with optical cement, so that glass cube 301 functions as a polarizing beamsplitter.
  • the glass cube 302 is formed by first forming the dichroic coating 224 on the diagonal face 312 of the glass
  • 303 functions as a blue dichroic reflector.
  • the formed glass cubes 301-304 are joined together with optical cement to form the solid glass structure 222.
  • Optical cement is used throughout the forming of the solid glass structure 222, because its index of refraction matches that of glass and as a consequence, the resulting structure 222 appears as a solid optic glass structure.
  • the embedded optical surfaces 223-225 are positioned so as to be parallel to one another. For examples, square faces, 314 and 315, of the glass cubes, 301 and 302, are optical cemented together, and square faces, 316 and 317, of the glass cubes, 302 and 303, are optical cemented together.
  • the glass cube 304 is optical cemented to the glass cube 302 on a square face 318 of the glass cube 302.
  • Color corrector coatings 229-231 are respectively formed on faces 319-321 of the solid glass structure 222, and reflective-mode active matrix LCDs 226-228 attached by optical cement to the solid glass structure 222 respectively over the color corrector coatings 229-231.
  • the color corrector coating 229 is a red color corrector since red light passes through it
  • the color corrector coating 230 is a blue color corrector since blue light passes through it
  • the color corrector coating 231 is a green color corrector since green light passes through it.
  • the active matrix LCD 226 is positioned so as to receive the red light reflected by the dichroic coating 224, the active matrix LCD 227 is positioned so as to receive the blue light reflected by the dichroic coating 225, and the active matrix LCD 228 is positioned to receive the green light transmitted by the dichroic coating 225.
  • the collimating lens unit 105 may also be formed as part of the solid optic structure 220 by attaching it to the appropriate face of the solid glass structure 222. In such a case, the lamp 104 will be positioned at a predetermined distance from the attached collimating lens unit 105.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal (AREA)
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Abstract

A color LCD projection system (200) comprises a lamp (104), a collimating lens unit (105), a solid optic structure (220), drive circuitry (150), and a projection lens unit (106). The solid optic structure (220) includes a solid glass structure (222) having embedded optical surfaces (223-225) which separate the lamp light into red, blue and green rays of polarized light. Three reflective-mode active matrix LCDs (226-228) are attached to the solid glass structure (222) to receive the red, blue and green rays of polarized light from the optical surfaces (223-225) and are driven by the drive circuity (150) to generate red, blue and green pixel patterns and to reflect them back to the optical surfaces (223-225). The optical surfaces (223-225) combine the reflected back red, blue and green pixel patterns and direct the combined pixel patterns to the projection lens unit (106) for projecting the patterns onto a display screen (107) employed with the color LCD projection system (200).

Description

SOLID OPTIC COLOR LCD PROJECTION SYSTEM
FIELD OF THE INVENTION This invention relates in general to liquid crystal display (LCD) projection systems and in particular, to a solid optic color LCD projection system.
BACKGROUND OF THE INVENTION
Fig. 1 illustrates, as an example, a conventional color LCD projection system 100. Light from a lamp 104 is collimated by collimating lens 105 into dichroic filters, 108 and 109, which are positioned so as to split the light into rays of blue, red and green colors. Each color ray is directed to a corresponding one of three transmissive-mode active matrix LCDs, 101-103, which are driven by drive circuitry 150 so that they pass their corresponding color rays through pixels which are to be displayed by the LCD projection system 100 as that color. The color rays passing through the selected pixels of the active matrix LCDs, 101-103, are recombined through dichroic filters, 110 and 111, and projected through projection lens 106 onto a display screen 107. Each of the active matrix LCDs, 101-103, comprise an LCD panel, 114-116, a front polarizer, 117-119, and a back polarizer, 120-122, wherein front and back polarizers are crossed so that a fully turned on pixel appears trans issive, and a fully turned off pixel appears opaque to incident light.
In one example, the dichroic filter 108 functions as a blue dichroic mirror to reflect a blue portion of the light along an optical path 133 to the optical mirror 113, and pass the red and green portions along an optical path 132 to the dichroic filter 109. The optical mirror 113 reflects the blue light to the active matrix LCD 101 which is driven by the drive circuitry 150 such that pixels to be displayed as blue by the LCD projection system 100 are activated so that the blue light only passes through the selected pixels. The dichroic filter 109, on the other hand, functions as a red dichroic mirror to reflect the received red portion to the active matrix LCD 102 along an optical path 134, and pass the received green portion to the optical mirror 112 along an optical path 135. The active matrix LCD 102 is driven by the drive circuitry 150 such that pixels to be displayed as red by the LCD projection system 100 are activated so that the red light only passes through such selected pixels. The optical mirror 112 reflects the green light to the active matrix 103, which is driven by the drive circuitry 150 such that pixels to be displayed as green by the LCD projection system 100 are activated so that the green light only passes through such selected pixels.
The dichroic filter 110 functions as a red dichroic mirror to combine along an optical path 137, the blue light indicative of a blue pixel pattern received from the active matrix LCD 101 and the red light indicative of a red pixel pattern received from the active matrix LCD 102. The dichroic filter 111 functions as a green dichroic mirror to combine along an optical path 138, the red and blue lights indicative of red and blue pixel patterns received along the optical path 137 from the dichroic filter 110 and the green light indicative of a green pixel pattern reflected by the optical mirror 112 from the active matrix LCD 103. The resulting combined blue, red and green pixel patterns are thereupon projected onto the display screen 107 through the projection lens 106.
One problem with such conventional color LCD projection systems is that the reflective surfaces of the dichroic mirrors, 108-111, and optical mirrors, 112 and 113, must be carefully aligned in several axes, thus necessitating the addition of expensive mechanical devices for precisely aligning such surfaces. Complicating such alignment problems are the possibility of exposing the color LCD projection system to mechanical shock and vibration, as well as the possibility of exposing the various elements of the projection system to different temperatures. Another problem with such conventional color LCD projection systems is that reflections from the surfaces degrade significantly when they are dirty or dusty.
OBJECTS AND SUMMARY OF THE INVENTION Accordingly, one object of the present invention is a color LCD projection system which does not need its reflective surfaces to be periodically aligned.
Another object is a color LCD projection system having a rugged construction capable of withstanding shock and vibration.
Another object is a color LCD projection system having a hermetic construction protecting its reflective surfaces from dust particles and moisture.
Still other objects include a color LCD projection system that is compact, lightweight, and low cost to manufacture.
These and additional objects are accomplished by the various aspects of the present invention, wherein, briefly stated, one aspect is a solid optic color LCD projection system (e.g., 200 in fig. 2) having a solid glass structure (e.g., 222), embedded optical surfaces (e.g., 223-225), and attached active matrix LCDs (e.g., 226-228). Since the optical surfaces are fixedly positioned by embedding them in the solid glass structure, there is no need to periodically realign them, and expensive mechanical devices for conventionally doing so are unnecessary. Also, since the optical surfaces are hermetically sealed in the solid glass structure, they are protected from performance degrading dust particles and moisture. Further, since the active matrix LCDs are fixedly attached to the solid glass structure, the resulting color LCD projection system is a rugged construction resistant to shock and vibration.
The optical surfaces respectively function as a polarizing beamsplitter, and first and second dichroic reflectors which are embedded in the solid glass structure such that light entering the solid glass structure and passing through the polarizing beamsplitter is separated into first, second and third color light rays by the first and second dichroic reflectors. The attached active matrix LCDs are preferably reflective-mode active matrix LCDs attached to the solid glass structure such that one active matrix LCD receives and reflects the first color light ray, another active matrix LCD receives and reflects the second color light ray, and another active matrix LCD receives and reflects the third color light ray. In another aspect of the present invention, a method of forming a solid reflective-mode color LCD projection system, comprises the steps of: forming a solid glass structure with embedded dielectric and dichroic coatings such that the solid glass structure resembles the joinder of four glass cubes wherein a first glass cube is formed by joining two prisms with a dielectric coating between the joining faces, a second glass cube is formed by joining two prisms with a first dichroic coating between the joining faces, a third glass cube is formed by joining two prisms with a second dichroic coating between the joining faces, and a fourth glass cube is formed as a glass cube, wherein the first and second glass cubes are joined by optical cement such that the dielectric and first dichroic coatings lie in parallel planes, the second and third glass cubes are joined by optical cement such that the first and second dichroic coatings lie in parallel planes, and the second and fourth glass cubes are joined by optical cement such that the fourth glass cube is attached to a free square face of the one of two prisms forming the second glass cube which is joined to the first glass cube; attaching a first reflective-mode active matrix LCD to the solid glass structure such that the first reflective-mode active matrix LCD receives light passing through the dielectric coating and reflecting off the first dichroic coating; attaching a second reflective-mode active matrix LCD to the solid glass structure such that the second reflective-mode active matrix LCD receives light passing through the first dichroic coating and reflecting off the second dichroic coating; and attaching a third reflective-mode active matrix LCD to the solid glass structure such that the third reflective-mode active matrix LCD receives light passing through the first and second dichroic coatings . Additional objects, features and advantages of the various aspects of the present invention will become apparent from the following description of its preferred embodiments, which description should be taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates, as an example, a conventional color LCD projection system;
Fig. 2 illustrates, as an example, a color LCD projection system utilizing aspects of the present invention;
Fig. 3 illustrates, as an example, a blow-up exemplifying a method of constructing the color LCD projection system of fig. 2, utilizing aspects of the present invention; and
Figs. 4 and 5 respectively illustrate, as examples, a glass cube and a glass prism used in constructing the color LCD projection system of fig. 2, utilizing aspects of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 2 illustrates a color LCD projection system 200 including a lamp 104, a collimating lens unit
105, a solid optic structure 220, a projection lens unit
106, and drive circuitry 150. The lamp 104, the collimating lens unit 105, the projection lens unit 106, and the drive circuitry 150 are generally constructed and operate the same as their identically referenced counterparts in the conventional color LCD projection system 100 of fig. 1. A display screen 107 is commonly used with the color LCD projection system 200, and is also generally constructed and operates the same as its identically referenced counterpart of fig. 1.
The solid optic structure 220 functions similarly to the combination of the active-matrix LCDs 101-103, dichroic filters 108-111, and optical mirrors 112-113 of the conventional color LCD projection system 100 of fig. 1, in that it also processes the light received from the lamp 104 through the collimating lens unit 105, and provides red, blue and green light rays respectively indicative of red, blue and green pixel patterns to the projection lens unit 106 for projection onto the display screen 107.
However, the solid optic structure 220 is a substantially different construction which avoids the various problems of the conventional color LCD projection system 100 of fig. 1. In particular, the solid optic structure 220 avoids the necessity of periodically aligning its optical surfaces, is less sensitive to shock and vibration, is more resistant to contaminating dust, dirt and moisture, is more compact, and is cheaper to manufacture than its conventionally formed counterpart of fig. 1.
The solid optic structure 220 is formed of a solid glass structure 222, embedded optical surfaces 223-225, red, blue and green color corrector coatings 229-231, and attached reflective-mode active matrix LCDs 226-228. The optical surfaces 223-225 are formed as three parallel coatings embedded in the solid optic structure 220 and angled at forty-five degrees with respect to light received from the lamp 104 through the collimating lens unit 105. The optical coating 223 is a dielectric coating functioning as a polarizing beamsplitter, the optical surface 224 is a dichroic mirror coating functioning as a reflector for the red portion of the light and a transmitter for the blue and green portions of the light, and the optical surface 225 is another dichroic mirror coating functioning as a reflector for the blue portion of the light and a transmitter for the remaining green portion of the light.
The reflective-mode active matrix LCDs 226-228 are attached to the solid optic structure 220 and positioned such that the active matrix LCD 226 receives and reflects back the red light reflected by the dichroic coating 224, the active matrix LCD 227 receives and reflects back the blue light reflected by the dichroic coating 225, and the active matrix LCD 228 receives and reflects back the green light transmitted through the dichroic coating 225. The drive circuitry 150 drives the active matrix LCDs 226-228 in generally the same manner as their respective counterparts in the conventional color LCD projection system 100 of fig. l. In particular, the active matrix LCD 226 is driven such that pixels to be displayed as red by the LCD projection system 200 are activated so that the red light only passes and is reflected back through such selected pixels, the active matrix LCD 227 is driven such that pixels to be displayed as blue by the LCD projection system 200 are activated so that the blue light only passes and is reflected back through such selected pixels, and the active matrix LCD 228 is driven such that pixels to be displayed as green by the LCD projection system 200 are activated so that the green light only passes and is reflected back through such selected pixels. The red, blue and green corrector coatings 229-231 are optionally formed on the solid glass structure 222 at the attachment points respectively for the active matrix LCDs 226-228, so as to correct for by filtering out all but the red, blue and green light rays being received and reflected by the active matrix LCDs 226-228.
The blue reflecting dichroic coating 225 is transraissive to the green light indicating a green pixel pattern received from the active matrix LCD 228, and is reflective to the blue light indicating a blue pixel pattern received from the active matrix LCD 227. The red reflecting dichroic coating 224, on the other hand, is transmissive to both the green light and the blue light received from the blue reflecting dichroic coating 225, and is reflective to the red light indicating a red pixel pattern received from the active matrix LCD 226. The dielectric coating 223, acting as a polarizing beamsplitter, thereupon receives the red, blue and green lights respectively indicating red, blue and green pixel patterns from the red reflecting dichroic coating 224, and reflects the polarized light to the projection lens unit 106 for projection onto the display screen 107. To ensure proper synchronization of the red, blue and green pixel patterns being displayed on the display screen 107, the optical paths between the dielectric coating 223 and each of the active matrix LCDs 226-228 should be the same length.
Although not elaborated upon, it is to be understood that the pixels of the active matrix LCDs 226-228 may be selectively controlled by the drive circuitry 150 to various shades of a gray scale, and that corresponding pixels of the active matrix LCDs 226- 228 may be jointly activated to form colors in combination of red, blue and green.
Fig. 3 illustrates a blow-up exemplifying one method of constructing the solid optic structure 220 and in particular, the solid glass structure 222 which is formed by first forming four glass cubes 301-304, then joining the four glass cubes 301-304 together with optical cement. Glass cube 304 is a conventionally formed glass cube such as depicted in fig. 4. Glass cubes 301-303, on the other hand, are each formed from two half-cube glass prisms, such as depicted in fig. 5, with an optical surface preformed on a diagonal face of one of the two prisms.
The glass cube 301 is formed by first forming the dielectric coating 223 on the diagonal face 311 of the glass prism 222-2, then joining together at their diagonal faces, glass prisms 222-1 and 222-2 with optical cement, so that glass cube 301 functions as a polarizing beamsplitter. The glass cube 302 is formed by first forming the dichroic coating 224 on the diagonal face 312 of the glass prism 222-3, then joining together at their diagonal faces, glass prisms 222-3 and 222-4 with optical cement, so that glass cube 302 functions as a red dichroic reflector. The glass cube
302 is formed by first forming the dichroic coating 225 on the diagonal face 313 of the glass prism 222-5, then joining together at their diagonal faces, glass prisms 222-5 and 222-6 with optical cement, so that glass cube
303 functions as a blue dichroic reflector.
After forming the glass cubes 301-304, the formed glass cubes are joined together with optical cement to form the solid glass structure 222. Optical cement is used throughout the forming of the solid glass structure 222, because its index of refraction matches that of glass and as a consequence, the resulting structure 222 appears as a solid optic glass structure. In joining the glass cubes 301-303 together, the embedded optical surfaces 223-225 are positioned so as to be parallel to one another. For examples, square faces, 314 and 315, of the glass cubes, 301 and 302, are optical cemented together, and square faces, 316 and 317, of the glass cubes, 302 and 303, are optical cemented together. The glass cube 304 is optical cemented to the glass cube 302 on a square face 318 of the glass cube 302.
Color corrector coatings 229-231 are respectively formed on faces 319-321 of the solid glass structure 222, and reflective-mode active matrix LCDs 226-228 attached by optical cement to the solid glass structure 222 respectively over the color corrector coatings 229-231. The color corrector coating 229 is a red color corrector since red light passes through it, the color corrector coating 230 is a blue color corrector since blue light passes through it, and the color corrector coating 231 is a green color corrector since green light passes through it. The active matrix LCD 226 is positioned so as to receive the red light reflected by the dichroic coating 224, the active matrix LCD 227 is positioned so as to receive the blue light reflected by the dichroic coating 225, and the active matrix LCD 228 is positioned to receive the green light transmitted by the dichroic coating 225.
Optionally, the collimating lens unit 105 may also be formed as part of the solid optic structure 220 by attaching it to the appropriate face of the solid glass structure 222. In such a case, the lamp 104 will be positioned at a predetermined distance from the attached collimating lens unit 105.
Although the various aspects of the present invention have been described with respect to a preferred embodiment, it will be understood that the invention is entitled to full protection within the full scope of the appended claims.

Claims

What is claimed is;
1. A color LCD projection system comprising: a solid glass structure; a polarizing beamsplitter, and first and second dichroic reflectors embedded in said solid glass structure such that light entering said solid glass structure and passing through said polarizing beamsplitter is separated into first, second and third color light rays by said first and second dichroic reflectors; and first, second and third reflective-mode active matrix LCDs attached to said solid glass structure such that said first reflective-mode active matrix LCD receives and reflects said first color light ray, said second reflective-mode active matrix LCD receives and reflects said second color light ray, and said third reflective-mode active matrix LCD receives and reflects said third color light ray.
2. The color LCD projection system as recited in claim 1, wherein said polarizing beamsplitter, said first and second dichroic reflectors, and said first, second and third reflective-mode active matrix LCDs are positioned such that a first color portion of said light passing through said polarizing beamsplitter is reflected by said first dichroic reflector to said first reflective-mode active matrix LCD as said first color light ray, a second color portion of said light passing through said polarizing beamsplitter and said first dichroic reflector is reflected by said second dichroic reflector to said second reflective-mode active matrix LCD as said second color light ray, and a third color portion of said light passing through said polarizing beamsplitter, said first dichroic reflector and said second dichroic reflector is passed to said third reflective-mode active matrix LCD as said third color light ray.
3. The color LCD projection system as recited in claim 1, further comprising: a light source; and a collimating lens for directing light emanating from said light source to enter said solid glass structure and pass through said polarizing beamsplitter embedded in said solid glass structure.
4. The color LCD projection system as recited in claim 3, wherein said collimating lens is attached to said solid glass structure.
5. The color LCD projection system as recited in claim 1, further comprising a projection lens positioned so as to receive said first, second and third color light rays reflected respectively back by said first, second and third reflective-mode active matrix LCDs.
6. The color LCD projection system as recited in claim 5, wherein said polarizing beamsplitter, said first and second dichroic reflectors, and said first, second and third reflective-mode active matrix LCDs are positioned such that said first color ray reflected by said first reflective-mode active matrix LCD is directed to said projection lens by reflecting off said first dichroic reflector and said polarizing beamsplitter, said second color ray reflected by said second reflective-mode active matrix LCD is directed to said projection lens by reflecting off said second dichroic reflector, passing through said first dichroic reflector, and reflecting off said polarizing beamsplitter, and said third color ray reflected by said third reflective-mode active matrix LCD is directed to said projection lens by passing through said second and first dichroic reflectors and reflecting off said polarizing beamsplitter.
7. The color LCD projection system as recited in claim 6, wherein first, second and third light paths respectively of said first, second and third color rays reflected from said first, second and third reflective-mode active matrix LCDs back to said polarizing beamsplitter, are equal in length.
8. The color LCD projection system as recited in claim 5, further comprising a driving circuit for selectively activating pixels of said first, second and third reflective-mode active matrix LCDs such that pixels corresponding to pixels to be projected in said first color by said projection lens are activated on said first reflective-mode active matrix LCD, pixels to be projected in said second color by said projection lens are activated on said second reflective-mode active matrix LCD, and pixels to be projected in said third color by said projection lens are activated on said third reflective-mode active matrix LCD.
9. The color LCD projection system as recited in claim 1, further comprising first, second and third color corrector coatings respectively interposed between said first, second and third reflective-mode active matrix LCDs and the glass substrate where said first, second and third reflective-mode active matrix LCDs are respectively attached to said glass substrate.
10. A method of forming a solid reflective- mode color LCD projection system, comprising the steps of: forming a solid glass structure with embedded dielectric and dichroic coatings such that said solid glass structure resembles the joinder of four glass cubes wherein a first glass cube is formed by joining two prisms with a dielectric coating between the joining faces, a second glass cube is formed by joining two prisms with a first dichroic coating between the joining faces, a third glass cube is formed by joining two prisms with a second dichroic coating between the joining faces, and a fourth glass cube is formed as a glass cube, wherein said first and second glass cubes are joined by optical cement such that said dielectric and first dichroic coatings lie in parallel planes, said second and third glass cubes are joined by optical cement such that said first and second dichroic coatings lie in parallel planes, and said second and fourth glass cubes are joined by optical cement such that said fourth glass cube is attached to a free square face of the one of two prisms forming said second glass cube which is joined to said first glass cube; attaching a first reflective-mode active matrix LCD to said solid glass structure such that said first reflective-mode active matrix LCD receives light passing through said dielectric coating and reflecting off said first dichroic coating; attaching a second reflective-mode active matrix LCD to said solid glass structure such that said second reflective-mode active matrix LCD receives light passing through said first dichroic coating and reflecting off said second dichroic coating; and attaching a third reflective-mode active matrix LCD to said solid glass structure such that said third reflective-mode active matrix LCD receives light passing through said first and second dichroic coatings.
11. The method as recited in claim 10, further comprising, before said first reflective-mode active matrix LCD attaching step, the step of attaching a first color corrector to said solid glass structure such that said first color corrector receives light passing through said dielectric coating and reflecting off said first dichroic coating, and said first reflective-mode active matrix LCD attaching step comprises the step of attaching said first reflective- mode active matrix LCD to said first color corrector such that said first reflective-mode active matrix LCD receives light passing through said first color corrector, and passing through said dielectric coating and reflecting off said first dichroic coating.
12. The method as recited in claim 10, further comprising, before said second reflective-mode active matrix LCD attaching step, the step of attaching a second color corrector to said solid glass structure such that said second color corrector receives light passing through said first dichroic coating and reflecting off said second dichroic coating, and said second reflective-mode active matrix LCD attaching step comprises the step of attaching said second reflective- mode active matrix LCD to said second color corrector such that said second reflective-mode active matrix LCD receives light passing through said second color corrector, and passing through said first dichroic coating and reflecting off said second dichroic coating.
13. The method as recited in claim 10, further comprising, before said third reflective-mode active matrix LCD attaching step, the step of attaching a third color corrector to said solid glass structure such that said third color corrector receives light passing through said first and second dichroic coatings, and said third reflective-mode active matrix LCD attaching step comprises the step of attaching said third reflective-mode active matrix LCD to said third color corrector such that said third reflective-mode active matrix LCD receives light passing through said third color corrector, and passing through said first and second dichroic coatings.
AMENDED CLAIMS
[received by the International Bureau on 18 November 1997 (18.11.97); original claims 1, 3, 9 and 11-13 amended; new claim 14 added; remaining claims unchanged (5 pages)]
1. A color LCD projection system comprising: a solid glass structure comprising a plurality of triangular shaped prism attached together to form the solid glass structure; a polarizing beamsplitter coating sandwiched between a first and second prism of the solid glass structure, a first dichroic coating sandwiched between a third and fourth prism of the solid glass structure, and a second dichroic coating sandwiched between a fifth and sixth prism of the solid glass structure such that light entering said solid glass structure and passing through said polarizing beamsplitter is separated into first, second and third color light rays by said first and second dichroic coatings; and first, second and third reflective-mode active matrix LCDs attached to said solid glass structure such that said first reflective-mode active matrix LCD receives and reflects said first color light ray, said second reflective-mode active matrix LCD receives and reflects said second color light ray, and said third reflective-mode active matrix LCD receives and reflects said third color light ray.
2. The color LCD projecuon system as recited in claim 1, wherein said polarizing beamsplitter, said first and second dichroic reflectors, and said first, second and third reflective-mode active matrix LCDs are positioned such that a first color portion of said light passing through said polarizing beamsplitter is reflected by said first dichroic reflector to said first reflective-mode active matrix LCD as said first color light ray, a second color portion of said light passing through said polarizing beamsplitter and said first dichroic reflector is reflected by said second dichroic reflector to said second reflective-mode active matrix LCD as said second color light ray and a third color portion of said light passing through said polarizing beamsplitter, said first dichroic reflector and said second dichroic reflector is passed to said third reflective-mode active matrix LCD as said third color light ray. are activated on said first refiectrve-mode active matrix LCD, pixels to be projected in said second color by said projection lens are activated on said second reflective-mode active matπx LCD, and pixels to be projected in said third color by said projection lens are activated on said third reflective- mode active matπx LCD
9 The color LCD projection system as recited in claim 1, further comprising first, second and third color corrector coatings respectively interposed between said first, second and third reflective-mode active matrix LCDs and the solid glass structure , where said first, second and third reflective-mode active matπx LCDs are respectively attached to said solid glass structure
10 A method of forming a solid reflectrve-mode color LCD projection system, compπsing the steps of
forming a solid glass structure with embedded dielectnc and dichroic coatings such that said solid glass structure resembles the joinder of four glass cubes wherein a first glass cube is formed by joining two pnsms with a dielectirc coating between the joining faces, a second glass cube is formed by joining two pnsms with a first dichrioic coating between the joining faces, a third glass cube is formed by joining two pnsms with a second dichroic coating between the joining faces, and a fourth glass cube is formed as a glass cube, wherein said first and second glass cubes are joined by optical cement such that said dielectnc and first dichroic coatings lie in parallel planes, said second and third glass cubes are joined by optical cement such that said first and second dichroic coatings e in parallel planes, and said second and fourth glass cubes are joined by optical cement such that said fourth glass cube is attached to a free square face of the one of two pnsms forming said second glass cube which is joined to said first glass cube,
attaching a first reflective-mode active matπx LCD to said solid glass structure such that said first reflective-mode active matπx LCD receives light passing through said dielectirc coating and reflecting off said first dichroic coating,
attaching a second reflective-mode active matrix LCD to said solid glass structure such that said second reflective-mode active matπx LCD receives light passing through said first dichroic coating and reflecting off said second dichroic coating, and
3. The color LCD projection system as recited in claim 1 , further compπsing' a light source, and a collimating lens for directing light emanating from said light source to enter said solid glass structure and pass through said polarizing beamsphtter, said polarizing beamsplitter being embedded in said solid glass structure.
4. The color LCD projection system as recited in claim 3, wherein said collimating lens is attached to said solid glass structure
5 The color LCD projection system as recited in claim 1 , further comprising a projection lens positioned so as to receive said first, second and third color light rays reflected respectively back by said first, second and third reflective-mode active matπx LCDs
6. The color LCD projection system as recited in claim 5, wherein said polarizing beamsplitter, said first and second dichroic reflectors, and said first, second and third reflective-mode active matπx LCDs are positioned such that said first color ray reflected by said first refective-mσde active matrix LCD is directed to said projection lens by reflecting off said first dichroic reflector and said polarizing beamsphtter, said second color ray reflected by said second reflective-mode active matrix LCD is directed to said projection lens by reflecting off said second dichroic reflector, passing through said first dichroic reflector and reflecting off said polarizing beamsplitter, and said third color ray reflected by said third reflective-mode active matrix LCD is directed to said projection lens by passing through said second and first dichroic reflectors and reflecting off said polarizing beamsplitter
7 The color LCD projection system as recited in claim 6, wherein first, second and third light paths respectively of said first, second and third color rays reflected from said first, second and third reflective-mode active matπx LCDs back to said polarizing beamsplitter, are equal in length
8 The color LCD projection system as recited in claim S, further comprising a driving circuit for selectively activating pixels of said first, second and third reflective-mode active matπx LCDs such that pixels corresponding to pixels to be projected in said first color by said projection lens attaching a third reflective-mode active matrix LCD to said solid glass structure such that said third reflective-mode active matrix LCD receives light passing through said first and second dichroic coatings
11. The method as recited in claim 10, further comprising , before said first reflective- mode active matrix LCD attaching step, the step of attaching a first color corrector to said solid glass structure such that said first color corrector receives light passing through said dielectric coating and reflecting off said first dichroic coating, and said first reflective-mode active matrix LCD attaching step comprises the step of attaching said first reflective-mode active matrix LCD to said first color corrector such that said first reflective-mode active matrix LCD receives light passing through said dielectric coating, reflecting off said first dichroic coating, and passing through said first color corrector.
12. The method as recited in claim 10, further comprising , before said second reflective- mode active matrix LCD attaching step, the step of attaching a second color corrector to said solid glass structure such that said second color corrector receives light passing through said first dichroic coating and reflecting off said first dichroic coating, and said second reflective-mode active matrix LCD attaching step comprises the step of attaching said second reflective-mode active matrix LCD to said second color corrector such that said second reflective-mode active matrix LCD receives light passing through said first dichroic coating, reflecting off said second dichroic coating, and passing through said second color corrector.
13. The method as recited in claim 10, further comprising , before said third reflective- mode active matrix LCD attaching step, the step of attaching a third color corrector to said sohd glass structure such that said third color corrector receives light passing through said first and second dichroic coatings, and said third reflective-mode active matrix LCD attaching step comprises the step of attaching said third reflective-mode active matrix LCD to said third color corrector such that said third reflective-mode active matrix LCD receives light passing through said first and second dichroic coatings, and passing through said third color corrector.
14. A color LCD projection system comprising: a sohd glass structure comprising a plurality of triangular shaped prism attached together to form the solid glass structure; a polarizing beamsphtter coating sandwiched between a first and second prism of the sohd glass structure, a first dichroic coating sandwiched between a third and fourth prism of the sohd glass structure, and a second dichroic coating sandwiched between a fifth and sixth prism of the sohd glass structure such that light entering said sohd glass structure and passing through said polarizing beamsphtter is separated into first, second and third color light rays by said first and second dichroic coatings; first, second and third reflective-mode active matrix LCDs attached to said sohd glass structure such that said first reflective-mode active matrix LCD receives and reflects said first color hght ray, said second reflective-mode active matrix LCD receives and reflects said second color light ray, and said third reflective-mode active matrix LCD receives and reflects said third color hght ray; and first, second and third color corrector coatings respectively interposed between said first, second and third reflective-mode active matrix LCDs and the solid glass structure where the first, second and third reflective-mode active matrix LCDs are respectively attached to said sohd glass structure.
PCT/US1997/011169 1996-06-27 1997-06-27 Solid optic color lcd projection system WO1998005996A1 (en)

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