O
`Umted States Patent
`
`[19]
`
`Kikinis
`
`IIIIIIIMIlIIIMIIIII
`
`USOOS632545A
`
`[11] Patent Number:
`
`5,632,545
`
`[45] Date of Patent:
`
`May 27, 1997
`
`[54] ENHANCED VIDEO PROJECTION SYSTEM
`
`[75]
`
`Inventor: Dan Kikinis’ Sarawga‘ Calif‘
`
`[73] Assignee: Lextron Systems, Inc, Saratoga, Calif,
`-
`
`[21] AppL No.: 686,809
`
`[22]
`
`Filed:
`
`Jul. 26, 1996
`
`Int. Cl.‘5 .................................................... G033 21/14
`[51]
`[52] US. Cl.
`................................. 353I31; 353/84: 353/88;
`353/94
`[58] Field of Search ........... 353/31, 33. 37.
`353/84. 88, 94; 359/48, 49; 348fl40
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,287,131
`2/1994 Lee .......................................... 353/84
`5,359,345 10/1994 Hunter ................ 359/48
`
`3’1995 Nakano 6t 31. m.
`. 3533].
`$398,086
`. 353/31
`5,481,320
`1/1996 Konomaetal.
`............................... 353/31
`9/1996 Mead et a].
`$555,035
`Primary Examiner~William Dowling
`Anome); Agent, or Finn—Donald R. Boys
`
`[57]
`
`ABSTRACT
`
`A c010; 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 projectable
`to provide a full-color video display with superimposed
`color spots rather then side-by-slde color spots. In a pre-
`fen'ed embodiment the color beams are red, green, and blue.
`
`4,368,963
`
`1/1983 Stolov ...................................... 353/84
`
`3 Claims, 1 Drawing $1196!
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`115
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`111
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`100
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`101
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` HID Controller
`LCD Controller
`for 3 l-IID lamps,
`with Live Video
`lZVDC in
`Capability
`Fan Control
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`System Overview
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`

`US. Patent
`
`May 27,1997
`
`5,632,545
`
`101
`
`100 System
`
`120
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`115
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`131
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`Overview
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`Fig.1
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`LCDController
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`‘thLiveVideoCapability
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`HIDControllerfor3HIDlamps,
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`136
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`130
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`XLNX-1 001
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`

`

`5,632,545
`
`1
`ENHANCED VIDEO PROJECTION SYSTEM
`
`FED 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 difierent systems available for video
`projections. Such systems include, but are not necessarily
`limited to, color Liquid Crystal Display (LCD) projectors,
`Cathode Ray Tube (CKI') 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 difliculty 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 (TFT-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 regrlar Television sets (TV’5) is still rather high. The
`brightness availability is still marginal, so, in a living room,
`which will typically have large windows, daylight viewing
`may not be eflective 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 when
`What is clearly needed are better projection systems and
`better methods, crossing traditional media boundaries.
`One simple way to ofier 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 of. This fact
`dictates that most light is converted 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; a 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.
`Each beam passes through a color filter before being pro-
`wssed 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.
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`2
`In various embodiments, assuming projectors of relatively
`equal cost, by using a triple monochrome LCD structure
`instead of a color AM-LCD, and pro-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 IED projection systems. A
`further advantage in quality is provided because the recom-
`bination of three video-controlled color beams allows super-
`position of color spots (or nibbles) in a final display.
`
`BRIE7 DESCRIPTION OF THE DRAWING
`FIGURES
`
`1 is a generalized topology example showing
`FIG.
`arrangement and connectivity of elements in an embodiment
`of the present invention.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`The present invention in various embodiments differs
`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 circuitry 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 its very definition it must abstrb 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.
`v
`
`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
`of each pixel superimposed, instead 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.
`Ligrt 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 sub-unit 131, which acts as a heat containment
`system, exchanging the 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 blaclrlng out the non-active areas of the
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`5,632,545
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`3
`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.
`
`After passing through the active regions 117—119, the
`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 skillin the anthatthere are number ofways thebeam
`combination may be done, and a number of ways the 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.
`Avideo signal for the system is 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 manner 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 12A 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.
`It will be apparent to those with skill in the art that there
`are many alterations that might be made in the embodiments
`
`4
`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 sorts of light sources that may be used in practicing
`embodiments of the invention. There are many ways
`adequate controllers may be implemented as well. Othu-
`design difierences will become apparent to those with skill
`in the art. The invention is limited in scope only by the
`claims which follow.
`What is claimed is:
`
`1. A video projector system 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;
`a number of individual color films 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 plawd 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 pro-
`jection on a surface to provide a video display;
`whm‘ein each beam passes through a color filter before
`being processed by a liglreswitching matrix.
`2. The video projection system of claim 1 wherein the
`light-shutter matrices are monochrome LCD arrays.
`3. The video projector system of claim 1 wherein three
`light sotn'ces provide three beams. and red, green, and blue
`filters are used to provide red, green, and blue beams to an
`LCD matrix system.
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