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`US005287131A
`
`United States Patent [19]
`5,287,131
`Lee
`Feb. 15, 1994
`[45] Date of Patent:
`
`[11] Patent Number:
`
`[54] COLOR LCD SYSI'EM OF PROJECTION
`TYPE
`
`2172733 9/1986 United Kingdom .
`2218842 11/1989 United Kingdom .
`
`[75]
`
`Inventor:
`
`Jongeheon Lee, Kyunggi, Rep. of
`Korea
`
`[73] Assignee:
`
`Samsung Electron Devices Co., Ltd”
`Kyunszi. Rep. of Korea
`
`Primary Examiner—William A. Cuchlinski, Jr.
`Assistant Examiner—William C. Dowling
`Attorney, Agent. or Firm—Christie, Parker & Hale
`
`[57]
`
`ABSTRACT
`
`[21] Appl. No: 981,861
`
`[22] Filed:
`
`Nov. 25, 1992
`
`Foreign Application Priority Data
`[30]
`Dec. 30, 1991 [KR] Rep. of Korea .................... 91.25223
`
`Int. Cl.’ .............................................. 6038 21/00
`[51]
`[52] US. Cl. ........................................ 353/31; 353/84;
`353/88
`[58] Field of Search ....................... 353/30, 31, 94, 88,
`353/122, 89, 97; 359/66, 68, 69
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,090,219 5/1978 Ematofl' et a1. ....................... 358/59
`1/1983 Stolov .................. 353/31
`4,368,963
`
`..... 353/94
`4,919,518 4/1990 Ogino et a1.
`
`4,928,123 5/1990 Takafuji ..........
`353/122
`
`4,969,731 11/1990 Ogino et a].
`..... 353/31
`......................... 353/31
`5,144,462 9/1992 Otsuka et al.
`FOREIGN PATENT DOCUMENTS
`
`478186 4/1992 European Pat. Off.
`8701495
`3/1987 PCT Int'lAppl.
`.
`
`.
`
`A projection color liquid crystal display (LCD) system
`uses a large reflecting liquid crystal (LC) panel as a
`screen. The system includes three unicolor light sources
`for emitting lights of the colors red, green and blue,
`respectively, the light sources being disposed remote
`from the screen; three light shutters for permitting the
`red, green, and blue light beams to successively and
`periodically pass to the screen; and three diffusing
`lenses for diffusing the respective beam which is passing
`to the screen. Each respective light shutter permits the
`passage of a corresponding light beam. The color driv-
`ing signal corresponding to the light beam from the
`image controlling circuit is applied to the driver to
`drive the LC panel. As a result, the red, green and blue
`light beams are successively reflected from the reflec-
`tion type LC panel according to the color driving sig-
`nal. Since the reflecting frequency of successive three
`color light beams is under 1/30 of a sec and, a person
`who is looking at the front side of the screen recognizes
`successive three color light beams as the composite
`color screen.
`
`10 Claims, 4 Drawing Sheets
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`XLNX-1004
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`US. Patent
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`Feb. 15, 1994
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`Sheet 1 of 4
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`5,287,131
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`XLNX-1 004
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`

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`US. Patent
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`Feb. 15, 1994
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`Sheet 2 of 4
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`5,287,131
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`XLNX-1004
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`US. Patent
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`Feb. 15, 1994
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`Sheet 3 of 4
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`5,287,131
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`XLNX-1004
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`FIG.3
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`

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`US. Patent
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`Feb. 15, 1994
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`Sheet 4 of 4
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`5,287,131
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`92LornaYo:
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`Fm
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`XLNX-1004
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`

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`I
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`5,287,131
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`COLOR LCD SYSTEM OF PROJECTION TYPE
`
`FIELD OF THE INVENTION
`
`The present invention relates to a color liquid crystal
`display (LCD) of the projection type and, more particu-
`larly to a color LCD system of the projection type
`which can optionally modulate a color and brightness
`ofthe LCD by appropriate modulation of the respective
`intensity of the colors red, green and blue projected
`onto a display in accordance with the use of a reflection
`type LCD as a screen.
`BACKGROUND OF THE INVENTION
`
`image projection system
`A conventional color
`grantedin U.S. Pat. No. 4,368.963 as illustratedin FIG
`
`5
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`IO
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`15
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`25
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`30
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`35
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`This color”image projection system includes a large
`screen 1. three lenses 2, three identical liquid crystal
`panels 3, three color filters 4, 5 and 6, respectively of the
`colors red. green and blue. three white light sources 7
`and three reflectors 8.
`In this projection system, light from the light sources
`7 passes through the corresponding filters 4. 5 and 6 and
`a liquid crystal (LC) panel 3, resulting in its incidence
`into the respective lenses 2.
`Since the respective lenses 2 are focused in the same
`place onto the screen 1, the mixture of the three colored
`composites projected on the screen via the lenses 2
`creates a multicolor image.
`For example, if the composite portions of an image or
`picture must be in the color red. the light intensity is
`modulated by connecting the variable frequency and/or
`amplitude voltage source 31 to the LC panel 3 and
`varying the applied voltage and the frequency of the
`applied volatge.
`Behind the LC panel 3 is disposed the red filter 4,
`which is made of red transparent glass or plastic. The
`color filters 4, 5 and 6 could alternatively be disposed in
`front of the LC panel 3 or even in front of the lenses 2.
`Behind the light sources 7, there are reflectors 8 for
`improving light efficiency. Light from each of the
`sources 7 passes through a respective filter and through
`a liquid crystal panel 3. Each respective lens magnifies
`and projects all of the energized port ions of the liquid
`crystal panel onto the screen. By such manner, the mix-
`ture of the three colored composites on the screen cre-
`ates a multicolor image or picture with high resolution.
`However, in the case of a conventional projection
`system, due to the close distance between the sources 7
`and the LC panels 4, 5 and 6. in order to raise the bright-
`ness, a cooling device is needed because heat generated
`from the source 7 has an influence over the LCD char-
`acteristics. However, difficulties in the technology of 55
`this device result in a limitation in the light intensity.
`' Accordingly, the light intensity cannot be suitably mod-
`ulated, so that there are difficulties in the modulation of
`the brightness. Thus, a conventional system has a defi-
`nite disadvantage of reducing the brightness on the 60
`screen.
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`45
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`50
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`SUMMARY OF THE INVENTION
`
`Accordingly, an object of the present invention is to
`provide a projection type color liquid crystal display of 65
`new structure which provides an improved brightness
`using a liquid crystal (LC) panel capable of displaying
`any kind of data on a screen.
`
`2
`To achieve this object, the present invention pro-
`poses a color LCD system of the projection type includ-
`mg:
`a plurality of unicolor light sources;
`a plurality of light shutters disposed in front of the
`respective corresponding ‘light source to permit
`the
`unicolor light from the light source to alternatively and
`periodically pass therethrough;
`a plurality of diffusing lenses disposed in front of the
`respective corresponding light shutter to project inci-
`dent unicolor light beams to a common screen; and
`a reflecting liquid crystal panel screen disposed at a
`predetermined distance apart from the diffusing lens in
`order to selectively reflect the light beams according to
`information to be displayed of the saline color as that of
`the unicolor light beam projected through the diffusing
`lens.
`
`According to the present invention. the frequency of
`the being alternately passed and blocked by a light
`shutter is such that the respective unicolor light which
`is successively projected produces an illusion of the
`composite color light due to the afterimage phenome-
`non.
`
`Also each respective shutter is such that. when there
`are it different unicolor light sources the light passes
`with a frequency of l/n, and the light is cut off or
`blocked during the rest of the time, i.e. l- l/n.
`Further, the same effect as that of the above could be
`obtained even when a white light source is selected
`instead of the above unicolor light source and color
`filters corresponding to the white light source are dis-
`posed between the light shutter and the white light
`source.
`
`The color filter and the light shutter corresponding
`thereto can be substituted for a negative plate provided
`with a unicolor light beam passing part and blocking
`part capable of using the light filter as the shutter.
`The above respective light shutter is driven by the
`successive inducement with the LC panel.
`When the successive driving frequency of the light
`shutter and LC panel is under 1/30 sec, the repective
`unicolor beam of red, green and blue light which is
`successively projected is recognized as the projection of
`one color light beam. According to the present inven-
`tion, the light source and the LC panel are sufficiently
`separated from each other, so that it is possible to in-
`crease respective unicolor light source or the white
`light source intensity enough to obtain the improved
`brightness.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Further advantages and other objects of the present
`invention will be apparent in the following detailed
`descriptionin connection with the accompanying draw-
`ings, in which:
`FIG. 1Is a schematic sectional view of the first em-
`bodiment of a projection color liquid crystal display
`LCD system of the present invention;
`FIG 2 is a schematic sectional view of the second
`embodiment of a projection color LCD system of the
`present invention;
`FIG. 3'is a plan View of a shutter used as a light filter
`of the present invention; and
`FIG. 4'IS a schematic sectional view of a conventional
`color image projection system.
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`XLNX-1004
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`3
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`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`5,287,131
`
`FIG. 1 describes the first embodiment of a projection
`color liquid crystal display LCD system of the present
`invention.
`
`5
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`4
`tional system, increasing considerably the light source
`intensity does not have an influence over the LC panel
`characteristic, resulting in good brightness. Further, the
`respective light source could be easily controlled and
`the respective color could be easily corrected. Also, a
`cooling device for cooling the LC panel is not necessary
`any more.
`FIG. 2 describes the second embodiment of the pro-
`jection color LCD system of the present invention.
`The second embodiment of FIG. 2 is nearly the same
`as the first embodiment of FIG. 1. The same reference
`numbers therebetween are given to the same parts.
`Description of the same parts will be omitted.
`The difference between the first and second embodi-
`ments is that, in the second embodiment, a white light
`source is used as the light source and so, in order to
`obtain the respective light beams of the colors red,
`green and blue, filters of the colors red 2811, green 286,
`and blue 288 are dispom between the focusing lenses
`15R, ISG, 15B and the light shutters 14R, l‘G, MB.
`Thus, each respective light beam from the color fil-
`ters 28R, 28G, 288 is controlled through the same path
`5 that of the first embodiment so as to be projected
`onto the LC panel 11, from which the light beam is
`selectively reflected to display any kind of characters
`and graphic information in color.
`FIG. 3 describes an example of the shutter 90 used as
`the red light filter and the light shutter corresponding to
`the color filter shown in FIG. 2.
`The shutter 90 used as the red light filter includes a
`negative plate provided with a light beam passing part
`91 corresponding to the color filter through which only
`the red light can pass and a light beam cutting part 92
`through which the light beam can not pass.
`The area ratio of the light beam passing part 91 to
`cutting part 92 is 1:2. Namely, in case of choosing the
`light source number of n, the area ratio of the light beam
`passing part to cutting part is l:n— 1.
`Accordingly, when the negative plate shown in FIG.
`3 is rotated one revolution, the red light beam passes
`during the frequency of i while the light beam cuts off
`during the frequency of 1. instead of this manner, the
`shutter can also be used as the light filter of the colors
`green and blue could be easily provided.
`While the shutter used as the light filter such as the
`above is mechanically formed, those skilled in the art
`could easily use it electronically, optically and the like.
`The number of the light source and the kind of the
`corresponding color would not be restricted within this
`embodiment of the present invention. The change of the
`number of the light source is easily performed by those
`skilled in the art.
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`This embodiment discloses three light sources capa-
`ble of emitting three colors of light: red, green and blue;
`and three lenses and light shutters corresponding to
`each of the light sources. However, the technical idea of lo
`the present invention would not be restricted within
`that and a system can be provided having two colors,
`four colors or more colors as necessary.
`This system shown in FIG. 1 is such that three uni-
`color light sources 16R. 166, 163, c.g. three lamps
`which emit three sources of the lights red, green and
`blue are connected to a lamp voltage controlling circuit
`1. so as to change the light intensity emitted from a
`respective light source.
`In front of the three unicolor sources are focusing
`lenses 15R, 156, 158 for focusing the light emitted from
`the respective light source and behind the three uni-
`color sources, reflectors 17R, 17G, 17]! are disposed
`corresponding thereto. However, the focusing lenses
`are not essential in the present invention.
`Light shutters 14R, MG, 148 are disposed in front of
`the respective focusing lens 15R, ISO, 153. A light
`shutter controlling circuit 19 which successively per-
`mits a respective unicolor light beam connected to a
`respective light shutter 14R, I‘G, MB to pass there-
`through during the frequency of i and to cut off during
`the frequency of I is connected to respective light shut-
`ter 14R, MG, MB. At that time, the successive operat-
`ing frequency t of respective light shutter 14R, “G,
`"B is under l/30 see.
`In the meantime, diffusing lenses 1211. 126, 12B each
`having a determined projection angle and focusing dis-
`tance to project a respective successive unicolor light
`beam through the light shutter are disposed in front of
`the respective light shutters 14R, MG. 14B.
`Also, a large liquid crystal LC panel 11 serving as a
`screen is disposed remote from the diffusing lenses 12R,
`126, 128. This LC panel is formed in the reflection type
`reflecting the light when the driving voltage is applied
`to the corresponding picture element.
`The LC panel 11 is successively connected to a liquid
`crystal display LCD driver 20 to drive the panel; an
`image controlling circuit 21 to supply a driving signal
`based on a color information of respective color with
`the driver 20; and a frame inducing circuit 22 to induce
`the respective light shutter MR. 140, 143 and image
`controlling circuit 21.
`_
`Thus, at the same time when the light beam of the
`colors red, green and blue is successively projected
`from the respective light shutters 14R, 146, 148 onto
`the LC panel 11, the color driving signal corresponding
`to the light beam from the image controlling circuit 21
`is applied to the driver 20 to drive the LC panel 11.
`As a result, the light beams of the colors red, green
`and blue are successively reflected from the reflection
`type LC panel 11 according to the color driving signal.
`Since the reflecting frequency t of successive three
`color light beams is under l/30 sec, a person who is
`looking at the front side of the screen recognizes and
`three successive color light beams as the composite
`color screen.
`In this system. since the LC panel is formed remote
`from the light source distinct from that of a conven-
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`The projection color LCD system of the present
`invention can be applied in high quality professional
`devices, as multicolor data and graphic screens associ-
`ated with computers, radar apparatus, advertising dis-
`plays, apparatus for providing theatre backgrounds, and
`in many other art areas where an image or picture pro-
`jection system may be used.
`It is understood that the above description is for the
`purpose of describing the. various embodiments of the
`invention, and those skilled in this art will recognize
`that various modification and changes can be made
`without departing from the scope of the invention,
`which scope is to be determined by the following claims
`and the equivalents to which the elements thereof are
`entitled.
`What is claimed is:
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`XLNX-1004
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`5,287,131
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`5
`l. A color LCD system of a projection type compris-
`ins
`a reflecting liquid crystal panel screen;
`a plurality of unicolor light sources;
`a plurality of light shutters, one disposed in front of 5
`each corresponding light source to permit the uni-
`color light from the corresponding light source to
`alternately pass therethrough and be blocked
`thereby; and
`a plurality of diffusing lenses, one disposed in front of 1°
`each corresponding light shutter to project an inci-
`dent unicolor light beam to the reflecting liquid
`crystal panel screen, the screen being disposed at a
`predetermined distance from the diffusing lenses in
`order to selectively reflect the light beams accord-
`ing to information to be displayed.
`2. The color LCD system of claim 1, further compris-
`ing a plurality of focusing lenses for focusing the uni-
`color light emitted from each light source, each lens
`being disposed between a corresponding unicolor light
`source and light shutter.
`3. The color LCD system of claim 1, wherein the
`light shutters alternate between positions where light
`passes through and light is blocked such that the light
`from each light source is on the panel screen alternately
`and successively, so that due to an afterimage phenome-
`non, an illusion that the respective unicolor lights which
`alternately pass to the panel screen from composite
`color light.
`4. The color LCD system of claim 1, further compris-
`ing n different sources each having a different unicolor
`light.
`5. The color LCD system of claim 3. further compris-
`ing it different light sources each having a different
`unicolor light, wherein each light shutter has a ratio of
`light passing to light blocking of l to (n— l).
`6. The color LCD system of claim 1, further compris-
`ing means for synchronizing each of the light shutters
`
`15
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`20
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`25
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`6
`with an application of color display information for the
`liquid crystal panel.
`7. A color LCD system of a projection type compris-
`mg:
`a reflecting liquid crystal panel screen;
`a plurality of white light sources for emitting light;
`a plurality of focusing lenses for focusing the light
`emitted from each corresponding light source;
`a plurality of color filters for filtering only a specific
`color light corresponding to the respective focus.
`ing lens;
`a plurality of light shutters for periodically permitting
`passage of incident light beams of the specific color
`light corresponding to a respective one of the color
`filters, such passage of each specific color light
`being successive; and
`a plurality of diffusing lenses. each disposed in front
`of a respective corresponding light shutter to
`project incident unicolor light beams to the reflect-
`ing liquid crystal panel screen, the screen being
`disposed at a predetermined distance apart from
`the diffusing lens in order to selectively reflect the
`light beams according to information to be dis-
`played of the same color as that of the unicolor
`light beam projected through the diffusing lens.
`8. The color LCD system of claim 7. wherein the
`respective light shutter and color filter comprises a
`shutter used as a light filter having one body and the
`shutter used as the light filter comprises a plate pro
`vided with a light beam passing part and a light beam
`blocking part.
`9. The color LCD system of claim 8, wherein each of
`the shutters being used as the light filter has a frequency
`under 1/30 sec and, if the number of shutters used as the
`light filters is n, an area of the light beam passing part of
`the plate is l/n of an area of the whole plate.
`10. The color LCD system of claim 9, wherein the
`D
`O
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`O
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`shutters are formed one of optically and electronically.
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`XLNX-1004
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