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`USOOS779334A
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`United States Patent
`
`[19]
`
`[11]
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`Patent Number:
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`5,779,334
`
`Kikinis
`
`[45] Date of Patent:
`
`*Jul. 14, 1998
`
`[54] ENHANCED VIDEO PROJECTION SYSTEM
`
`[75]
`
`Inventor: Dan Kikinis. Saratoga. Calif.
`
`[73]
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`[*1
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`[2 l]
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`[22]
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`[631
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`151]
`[52]
`15 8]
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`[56]
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`Assignee: Lextron Systems, Inc. Saratoga. Calif.
`
`Notice:
`
`The term of this patent shall not extend
`beyond the expiration date of Pat. No.
`5.632.545.
`
`Appl. No.: 780,351
`Filed:
`Jan. 8, 1997
`
`Related US. Application Data
`
`Continuation—in-pan of Ser No. 686.809. Jul. 26, 1996.
`
`Int. Cl.°
`G03B 21/28
`US. Cl. ..............
`.. 353/31: 353/84
`
`Field of Search
`353/31. 33. 34.
`353/84; 349/5. 7. 3. 61
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4.368963
`5,135,3(1)
`
`1/1983 Stolor
`8/1992 Toide el al.
`
`353/84
`................................. 349/8
`
`5.287.131
`5.394.204
`5.398.086
`5.481.320
`5.632545
`
`2/1994 Lee
`2/1995 Shigeta el al.
`3/1995 Nakanoetal.
`1/1996 Konuma et a1.
`5/1997 Kik'mis
`
`353/31
`. 353/31
`
`..
`353/31
`.
`. 353/31
`
`353/31
`
`Primary Examiner—William Dowling
`Attorney, Agent. or F[rm—Donald R. Boys
`
`[57]
`
`ABSTRACT
`
`A color video projector system has separate light sources for
`producing separate beams of light which are passed each
`first through color filters to provide separate color beams
`before being processed by video-controlled light shutter
`matrices and then combined into a single beam projeetable
`to provide a full-color video display with superimposed
`color spols rather then side-by-side color spots. In a pre—
`ferred embodiment the color beams are red. green. and blue.
`In another aspect of the invention a single white—light source
`is used. and the beam of white light is split by a prism system
`into separate color beams. which are redirected to impinge
`as parallel beams on a monochrome LCD array. The LCD
`array is switched by a controller driven in accordance with
`a video signal. and the emerging beams are recombined and
`focused on a surface to produce a dynamic color image.
`
`14 Claims. 2 Drawing Sheets
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`136
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`131
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`116
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`111
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`100
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` System Overview
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`XLNX-1001
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`US. Patent
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`Jul. 14, 1998
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`Sheet 1 of 2
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`5,779,334
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`US. Patent
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`Jul. 14, 1998
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`Sheet 2 of 2
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`5,779,334
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`1
`ENHANCED VIDEO PROJECTION SYSTEM
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`CROSS-REFERENCE TO RELATED APPLICATIONS
`The present application is a continuation—in-part appli-
`cation of prior application 08/686309. filed Jul. 26. 1996.
`which is incorporated herein in its entirety by reference.
`
`FIELD OF THE INVENTION
`
`The present invention is in the area of video projection
`display. and pertains more particularly to such displays using
`Liquid Crystal Displays.
`
`BACKGROUND OF THE INVENTION
`
`There are many different systems available for video
`projections. Such systems include. but are not necessarily
`limited to. color Liquid Crystal Display (LCD) projectors.
`Cathode Ray Tube (CRT) projectors. micro-mirror projec-
`tors and so forth. There are also back projection systems
`available, that project on the back of translucent or trans—
`parent material. and are viewed from the opposite direction.
`but they use generally the same technology as the systems
`already mentioned. In general. however. all of these display
`systems are rather expensive and have difficulty proving
`satisfactory light levels.
`Less expensive units than those mentioned above have
`recently become available. mostly based on small active
`matrix color LCD‘s (AM-LCD’s) or thin-film transistor
`LCD‘s ('I'Fr-LCD’S). These systems are a partial solution to
`the problems besetting projection display technology. but
`resolution and brightness are still limited. and cost compared
`to regular Television sets ('l'V's) is still rather high. "lhe
`brightness availability is still marginal. so. in a living room.
`which will typically have large windows. daylight viewing
`may not be effective due to strong ambient light. Of course
`curtains can be closed. or a special windowless TV room can
`be built. but cost and ease of use sufler.
`
`What is clearly needed are better projection systems and
`better methods. crossing traditional media boundaries.
`One simple way to offer more brightness is to use brighter.
`better lamps. This allows more light to be projected. The
`problem. however. with brighter. more powerful lamps is
`that the lamps generate a lot of heat. requiring noisy high
`speed fans. and at the same time drastically reduce the useful
`life of LCD’s used in such projection schemes by thermally
`loading the LCD's to the maximum allowable. and some-
`times beyond This is true partly because in a conventional
`color AM—LCD only 2-5% of light is transmitted when a cell
`is on. and near 0% when the LCD cell is 05. This fact
`dictates that most light is convened into heat in the LCD.
`
`SUMMARY OF THE INVENTION
`
`In a preferred embodiment of the present invention a
`video projector system is provided comprising individual
`light sources. one each for each color to be projected.
`adapted to provide each a separate light beam; a lens system
`in the path of the separate light beams. adapted for focusing
`the beams; is number of individual color filters equal to the
`number of beams. in the colors to be projected. and placed
`one each in each beam path; a light-shutter matrix system
`comprising a number of equivalent switching matrices equal
`to the number of beams and placed one each in the beam
`paths; a video controller adapted for controlling the light-
`shutter matrices; and an optical combination system adapted
`for combining the several beams into a single composite
`beam for projection on a surface to provide a video display.
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`Each beam passes through a color filter before being pro—
`cessed by a light-switching matrix.
`In a preferred embodiment the light-shutter matrices are
`monochrome LCD arrays and three light sources provide
`three beams. Red. green. and blue filters are used to provide
`red. green. and blue beams to an LCD matrix system.
`In various embodiments. assuming projectors of relatively
`equal cost. by using a triple monochrome LCD structure
`instead of a color AM-LCD. and pre—coloring of light. more
`light output can be achieved than in conventional systems.
`Systems according to embodiments of the invention are also
`less expensive than conventional color LCD systems.
`because the monochrome LCDs used are less expensive than
`color LCDS. and because alignment of components is less
`critical than in conventional LCD projection systems. A
`further advantage in quality is provided because the recom-
`bination of three videocontrolled color beams allows super-
`position of color spots (or nibbles) in a final display.
`In another embodiment of the invention a single white
`light beam is focused on a prism system which splits the
`white light beam into separate color beams. which are in turn
`directed as parallel beams on cells of a monochrome LCD
`array. The LCD array is switched by a controller following
`a video signal. and the emerging beams are recombined and
`focused on a screen to form a dynamic video image.
`Video projection systems according to embodiments of
`the present
`invention are capable of providing sharper
`images than conventional systems with less expensive and
`less complicated apparatus. and with considerably less need
`to dispose of waste heat from light sources.
`
`BRIEF DESCRIPTION OF THE DRAWING
`FIGURES
`
`FIG. 1 is a diagrammatical representation of an enhanced
`video projector system according to an embodiment of the
`present invention.
`FIG. 2 is a diagrammatical representation of an enhanced
`video projector system according to another embodiment of
`the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`invention in various embodiments differs
`The present
`from the prior art in that a color AM-LCD array. as described
`above in the Background section. is not used. When a color
`AM—LCD array is used in video projection systems. the light
`typically first has to pass through a polarization filter. then
`through the glass and circuin of the LCD matrix as well as
`the actual chambers containing the LCD material. The light
`then passes through a second set of circuitry and glass.
`through a second polarization filter. and finally through the
`color filter. Since a color filter is essentially a band pass filter
`for light. and typically the scheme used is Red/Green/Blue
`(RGB). by it's very definition it must absorb most of the
`energy reaching it. Also. the color filter contains nibbles of
`each color next to each other. and must be precisely aligned
`when attached to the glass. in order to provide that the LCD
`cell and the Filter nibble match.
`
`In embodiments of the present invention. the apparatus is
`arranged in a distributed manner. Light from light sources.
`typically lamps. is first colored and otherwise prepared into
`three single color beams. which then pass each through a
`monochrome LCD array. The three color beams are then
`optically recombined with a mirror and prism system in such
`a Way that they form a single beam having light of all colors
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`5.779.334
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`of each pixel superimposed. instwd of side by side in each
`pixel. as is typical in the art. Superposition of the color dots
`in the pixels projected and displayed provides for true and
`brighter color.
`FIG. 1 is an elevation view showing a typical implemen—
`tation in a preferred embodiment of the present invention.
`Light for the projector is generated in this embodiment by
`three High intensity Discharge (HID) lamps 132—134. which
`are controlled by controller 130. which also controls a fan
`136 for cooling the light sources. The lamps are provided in
`a separate subunit 131. which acts as a heat containment
`system. exchangingthe heat via fan 136 to the outside. rather
`than in the box. Light leaves heat containment system 131
`via heat filter glass 123.
`After leaving the heat containment and light source unit.
`the three light beams produced are focused by a condenser
`lens system 115. and then passed through color RGB filters
`112—114. The position and order of the color filters is
`arbitrary. as long as one is red. one is green. and one is blue.
`On the first glass of LCD unit 120. which comprises three
`monochrome LCD arrays 117. 118. and 119. there is an
`optional metal mask 116 blacking out the non-active areas of
`the LCD. An aluminum process can be used for the mask.
`similar to a process known in the art for making connections
`on the active matrix of the LCD.
`
`the
`After passing through the active regions 117—119.
`separate beams get combined into a single beam by mirror
`and prism system 111. then the combined beam is focused
`and projected onto a surface 101. It will be apparent to those
`with skill in the art that there are a number of ways the beam
`combination may be done. and a number of ways lens
`system 110 may be fashioned and used to project the final
`display on a screen or wall or other surface. The projection
`system is useful as well for backside projection.
`A video signal for the systemis delivered from outside via
`link 125 into a controller 122. A great variety of different
`signal formats are known and can be implemented. both
`analog and digital. or any combination of several signals can
`be used. Controller 122 controls the three monochrome
`matrices 117. 118. and 119. In one embodiment the LCD unit
`is built from three separate pieces of glass. each containing
`only one monochrome set. A mounting frame is then used to
`align those in front of mirror and prism system 111.
`In some embodiments of the invention. chip—on-glass
`technology is used to implement most of LCD controller 122
`on glass. reducing wiring and handling issues.
`In embodiments of the present invention the color filter
`always precedes the LCD arrays. and the filters are imple-
`mented in such a manna that each color filter covers all
`pixels of its own color in a contiguous manner. This feature
`allows more light
`than in the prior art. partly because
`monochrome LCD cells absorb much less light than do color
`lCD’s. and also allows much cheaper manufacturing cost
`than prior art systems. since no precise alignment between
`color filter and LCD is required.
`A control link 124 is provided between controllers 122
`and 130. and this link is used in some embodiments for some
`limited variable control of light output from each of the three
`light sources individually.
`FIG. 2 is a diagrammatical representation of another
`embodiment of the present invention. In the embodiment of
`FIG. 2 a single white-light source 233 is used. and a single
`beam is passed through heat filter glass 123 to condenser
`lens system 115. From lens system 115 the collirnated
`white-light beam is directed to a prism system 211 where the
`white light is split into three beams. red. green. and blue
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`(RGB). Mirrors 213 and 215 cooperate in directing two
`beams back toward monochrome LCD array 120. while the
`third beam is directed straight ahead into the LCD array.
`Since the white (or near white light) contains energy in all
`colors of visible light. splitting out the three colors for the
`LCD array results in no significant loss of light energy for
`each color.
`
`After passing through monochrome LCD array 120.
`which in this embodiment is controlled by controller 122
`just as described for the first embodiment above with referral
`to FIG 1.
`the colors are recombined by another prism
`system 217 and mirrors 219 and 221. The recombined beam
`is then focused and directed by lens system 119 to a screen
`101 to provide a dynamic color image. Compensation filters
`may be mounted to compensate for differences in light
`efficiency for the system.
`It will be apparent to those with skill in the art that there
`are many alterations that might be made in the embodiments
`described without departing from the spirit and scope of the
`invention. For example. there are many ways to implement
`light shutter devices besides LCD‘s. There are similarly
`many sons of light sources that may be used in practicing
`embodiments of the invention. There are many ways
`adequate controllers may be implemented as well. Other
`design differences will become apparent to those with skill
`in the an. The invention is limited in scope only by the
`claims which follow.
`What is claimed is:
`l. A video projector system comprising:
`a source projecting parallel beams of light of different
`colors;
`
`a light-shutter matrix system comprising a number of
`equivalent switching matrices equal to the number of
`beams and placed one each in the beam paths;
`a video controller adapted for controlling the light- shutter
`matrix system; and
`an optical combination system adapted for combining the
`separate beams after the light—shutter matrix system
`into a single composite beam for projection on a
`surface to provide a video display.
`2. The system of claim 1 wherein the source projeaing
`parallel beams of light comprises three white—light sources
`producing three parallel beams of white light through three
`color filters.
`3. The system of claim 2 wherein the three color filters
`comprise one each of red. green. and blue filters.
`4. The system of claim 1 wherein the source projecting
`parallel beams of light comprises a single whitevlight source
`projecting a white beam on a prism system adapted to
`separate the white beam into three color beams. and a
`redirection apparatus for directing the color beams into
`parallel paths to the light shutter matrix system
`5. The system of claim 4 wherein the three color beams
`produced by the prism system are one each of red. green. and
`blue beams.
`6. The video projection system of claim 1 wherein the
`light—shutter matrix system comprises a monochrome LCD
`array.
`7. A method for projecting a dynamic color
`comprising steps of:
`a) providing separate parallel beams of colored light;
`b) directing the separate color beams on separate cells of
`a monochrome LCD array;
`0) switching the monochrome matrix by action of a video
`signal through an LCD controller;
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`image.
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`5.779.334
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`d) recombining the beams of colored light into a single
`beam: and
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`e) focusing the recombined beam on a surface to provide
`a dynamic color image.
`8. The method of claim 7 wherein the separate beams of
`colored light comprise beams of red. green and blue light.
`9. A method for projecting a dynamic color
`image.
`comprising steps of:
`a) directing a beam of white light on a prism system:
`b) splitting the beam of white light into separate beams of
`colored light by action of the prism system:
`c) directing the separate beams of colored light onto a
`monochrome LCD matrix having as many cells as the
`separate beams of colored light;
`(1) switching the monochrome matrix by action of a video
`signal through an LCD controller;
`e) recombining the beams of colored light into a single
`beam; and
`f) focusing the recombined beam on a surface to provide
`a dynamic color image.
`10. The method of claim 9 wherein in step b) the beam of
`white light is split into three color beams. one red. one green.
`and one blue.
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`11. A video projector system comprising:
`a source projecting a beam of white light;
`a splitter adapted to split the beam of white light into
`separate parallel beams of light of dilferent colors:
`a light—shutter matrix system comprising a number of
`equivalent switching matrices equal to the number of
`beams of light of different colors and placed one each
`in each beam pram;
`a video controller adapted for controlling the light-shutter
`matrix system; and
`an optical combination system adapted for combining the
`separate beams after the light-shutter matrix system
`into a single composite beam for projection on a
`surface to provide a video display.
`12' The video projector system of claim ll wherein the
`splitter divides the beam of white light into three separate
`beams of colored light. one red. one green. and one blue.
`13. The video projcaor system of claim 11 wherein the
`splitter is an apparatus comprising prisms.
`14. The video projection system of claim ll wherein the
`light-shutter matrix system comprises a monochrome LCD
`array.
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`XLNX-1001
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