CA1151455A - Device for projecting colour pictures onto a screen and display system incorporating such a device - Google Patents
Device for projecting colour pictures onto a screen and display system incorporating such a deviceInfo
- Publication number
- CA1151455A CA1151455A CA000360545A CA360545A CA1151455A CA 1151455 A CA1151455 A CA 1151455A CA 000360545 A CA000360545 A CA 000360545A CA 360545 A CA360545 A CA 360545A CA 1151455 A CA1151455 A CA 1151455A
- Authority
- CA
- Canada
- Prior art keywords
- screen
- cell
- image
- display
- making
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired
Links
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
- H04N9/3108—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 by using a single electronic spatial light modulator
Abstract
ABSTRACT OF THE DISCLOSURE
DEVICE FOR PROJECTING COLOUR PICTURES ONTO A SCREEN
AND DISPLAY SYSTEM INCORPORATING SUCH A DEVICE
The invention relates to devices making it possible to project onto a screen a magnified image formed on a small display cell.
It consists of inserting a filter formed from parallel, coloured bands placed at a point where a real image of the cell is formed on the optical path between the illumination source and the display screen.
It makes it possible to produce colour image or picture projection devices from a cell which only supplies a black and white image or picture.
DEVICE FOR PROJECTING COLOUR PICTURES ONTO A SCREEN
AND DISPLAY SYSTEM INCORPORATING SUCH A DEVICE
The invention relates to devices making it possible to project onto a screen a magnified image formed on a small display cell.
It consists of inserting a filter formed from parallel, coloured bands placed at a point where a real image of the cell is formed on the optical path between the illumination source and the display screen.
It makes it possible to produce colour image or picture projection devices from a cell which only supplies a black and white image or picture.
Description
~ ~5~4SS
BACKGROUND OF THE INVENTION
The present invention relates to devices for 5 projecting colour pictures onto a screen which make it possible on the basis of a small display cell to obtain an image or picture of desired size which can be observed with the naked eye under good conditions. It also relates to display systems 10 incorporating such a device.
It is known to produce devices based on liquid crystals making it possible to display mis-cellaneous information, particularly television pictures. However, the size of such devices is in 15 most cases due to the thermal phenomena used therein.
Such a device is for example described in Canadian Patent Application 302,627 filed by the Applicant Company on May 4, 1978 and entitled "Picture display device and television system using such a device".
In this known device, television pictures analysed in the form of lines forming a field are entered in a smectic liquid crystal layer using a mixed thermal - electrical effect. Each line is successively entered in the form of a more or less 25 diffusive structure along the line. The effect used makes it possible to realise devices of small size making it possible to project the picture entered this way in the device onto a screen. Generally, projection takes place by means of a so-called 30 schlieren optics making it possible to convert ~.
..
' '~ , ~ . ' ~:' ' ' `'~
1~L5~L55 variations in the diffusive power of the liquid crystal layer into variations in the brightness of the screen.
The aforementioned Canadian Patent Application also describes a variant making it possible to display a colour picture. For this purpose, the initial number of lines is multiplied by three by allocating a triplet of contiguous lines to each picture analysis line. A filtering layer formed from alternating red, green and blue lines superimposed on the aforementioned lines makes it possible to obtain the picture with the desired colours as a result of additive synthesis.
The image entered in this visual display cell can be observed in colour either at short distance or projected onto a screen. In the case where the picture is projected onto a screen, it is also possible to use three separate devices, each corres-ponding to a coloured primary and whereby the pictures are projected in superimposed manner onto the same screen.
In both cases, these devices are more complica-ted than a black and white device and in the case of projections using three devices, setting is also very difficult.
BRIEF SUMMARY OF THB INVBNTION
In order to obtain a colour projection device operating without complicated settings and at a cost which is substantially the same as that of a black and white device, the present invention proposes "~
.. ..
, .
. . . - .
,,: - -~5 ~
a device for projecting colour pictures onto a screen, of the type incorporating a visual display cell making it possible to display pictures in the form of a plurality of fields formed from interlaced parallel lines, a polychromatic light source making it possible to illuminate the said cell, and means making it possible to project the picture from the cell onto the screen, wherein the lines of the cell are grouped into line systems, each line of a line system making it possible to display in accordance with a grey scale pa~ng from black to white the infor~ation corresponding to a given separate colour and wherein the device also comprises means outside the display cell and placed on the optical path between the light source and the screen and optically connected to the cell, making it possible to filter the light passing by each line of the cell to obtain the gi~7en corres-ponding colour.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
_ _ ~ . . _ _ _ _ . ~ _ The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings, wherein show:
Fig l a first embodiment of a device according to the invention.
Fig 2 a variant of the device of Fig l.
Fig 3 a second embodiment of a device according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to a first embodiment of a projecting device according to the invent~n shown in Fig l, the ~ O
picture to be projected is entered in a liquid crystal display device lOl shown in a greatly simplified manner and having a system of lines forming a field seen in the drawing by the end of the lines. This devîce has therefore three times as many lines as there are lines in the field according to which the picture is analysed. By an electronic processing of the video signal representing the picture, it is possible to separate the three components corresponding to the red, green and blue signals. The picture is then displayed on device lOl in the form of triplets of contiguous lines, each corresponding to a line of different colour as in the device which has a screen formed from coloured filter-ing lines incorporated into the device. However, thepresent device lOl does not have filtering lines and the displayed in picture is consequently a black and white picture.
For the purpose of illumi~ting the screen, a light source 102 emits a beam of light which is collected by a first lens 103 which, in the present embodiment, focuses it in the vicinity of the surface of deviating mirror 104. This mirror directs the light beam towards an objective 105 making it possible to illuminate cell lOl by a substantially parallel and homogeneous light beam.
The light is reflected by display device 101 towards objective 105, this taking place in specular manner by reflection on the heating electrodes when the liquid crystal is not diffusive and in accordance . J
.
: . ` , 5~ ~ 5 with a l~be of variable shape as a function of the liquid crystal used and which will be considered as su~stantially Lambertian for the purposes of the description.
Objectives 105 collects the light reflected by display device 101 and forms therefrom a picture on a slide 106.
In their passage between objective 105 and slide 106, the rays reemitted by device 101 in a specular manner pass through a focusing point located in the centre of a diaphragm 107. This point substantially corresponds to the image of the light source 102 given by optical elements 103, 104, 101 and 105.
Diaphragm 107 enables it to eliminate the light rays from the retrodiffusion lobe corresponding to the point where the liquid crystal is diffusive.
In this way, the desired schlieren optics are produced for the purpose of obtaining a good contrast.
Slide 106 on which is formed the image of device 101 forms a coloured filter constituted by bandscorresponding to the lines of device 101. Thus, the image of each line of device 101 is superimposed on one of the bands of slide 106. These bands are coloured red, g~en and blue and are grouped in such a way as to form triplets corresponding to the triplets de~ined hereinbefore in the display device 101. T.hus, the light reemitted in black and white by one line of a triplet of device 101 is filtered by the corresponding band of slide 106, which colours 5~ 55 it in accordance with the corresponding primary.
The image of device 101 formed in the plane of slide 106 is thus seen in colours by transparency through said slides. A projection objective 104 then makes 5` it possible to project onto a screen 109 the image coloured by slide 106.
It is easy to obtain such a slide 106 by photographing a large dimension coloured image reproducing the necess~y filter bands. The design of such a large size image presents no difficulties~
It can for example be photographed by using a re-production caption stand, so that there is a negligible distortion. If it is desired to use a simpler optical device for forming this slide, the distortions intro-duced can be accepted and they are then compensatedduring the design of the large scale image.
Slide 106 can also be located on the lighting beam of device 101. For this purpose, it is necessary that the optics illuminating device 101 form on the surface of the latt~r an image of slide 106 in such a way that the lines of the device are illuminated by the corresponding bands.
A variant using this positioning of the filter-ing slide, as well as a device 101 for use by trans-parency is partly shown in Fig 2.
Slide 106 is illuminated by a source 102 bymeans of a parallel light beam obtained via a lens 203. An objective 205 forms the image of slide 105 on the rear face of the display device 101 in such a way that the image of the coloured bands of the slide .
iP~
coincides with the display lines of the device.
Thus, these display lines are illuminated by the light of colour corresponding to that which it is necessary to display and it is possible to directly form the image of the other face of the device 101 on a screen. The optical device necessary for forming this image comprises for example a pro-jection objective and a diaphragm for forming schlieren optics.
According to another variant shown in Fig 3, the system is identical to that of Fig 1 from light source 102 to diaphragm 107 inclusive. However, instead of forming an intermediate image on a slide and then projecting it onto a white screen, the image is directly projected by means of a projection objective 308 onto a specially coloured screen 309.
This screen is coloured in a series of red, green and blue bands forming triplets in much the same way as for slide 106. These bands are located on the screen in such a way that the images of the display lines of device 101 are formed thereon. In this way, each band illuminated in white light only reflects the colour corresponding to the line used for illuminat-ing it. Thus, the image is coloured directly on the screen. In another variant where the cell 101 is positioned closer to objective 105, the latter makes it possible to directly project the image onto the screen.
These devices for projecting coloured images or pictures onto a screen can be used in all display , ~. . . ;
~5 ~S S
systems where it is desired to have a large picture from a small display cell. It is in particular pointed out that screen 309 in Fig 3 can be observed both by transparency and by reflection. When observing by transparency, the complete device can be placed in a case providing the equivalent of a display system equipped with a cathode tube. The visual analogy with the system of so-called autoconvergent tubes with aligned cathodes shows that the image or picture quality of this system is very good.
Finally, in the case where screen 309 is transparent and is observed from behind, the complete device of Fig 3 is equivalent to that part of the device of Fig 1 limited to the system terminated by the slide.
.
BACKGROUND OF THE INVENTION
The present invention relates to devices for 5 projecting colour pictures onto a screen which make it possible on the basis of a small display cell to obtain an image or picture of desired size which can be observed with the naked eye under good conditions. It also relates to display systems 10 incorporating such a device.
It is known to produce devices based on liquid crystals making it possible to display mis-cellaneous information, particularly television pictures. However, the size of such devices is in 15 most cases due to the thermal phenomena used therein.
Such a device is for example described in Canadian Patent Application 302,627 filed by the Applicant Company on May 4, 1978 and entitled "Picture display device and television system using such a device".
In this known device, television pictures analysed in the form of lines forming a field are entered in a smectic liquid crystal layer using a mixed thermal - electrical effect. Each line is successively entered in the form of a more or less 25 diffusive structure along the line. The effect used makes it possible to realise devices of small size making it possible to project the picture entered this way in the device onto a screen. Generally, projection takes place by means of a so-called 30 schlieren optics making it possible to convert ~.
..
' '~ , ~ . ' ~:' ' ' `'~
1~L5~L55 variations in the diffusive power of the liquid crystal layer into variations in the brightness of the screen.
The aforementioned Canadian Patent Application also describes a variant making it possible to display a colour picture. For this purpose, the initial number of lines is multiplied by three by allocating a triplet of contiguous lines to each picture analysis line. A filtering layer formed from alternating red, green and blue lines superimposed on the aforementioned lines makes it possible to obtain the picture with the desired colours as a result of additive synthesis.
The image entered in this visual display cell can be observed in colour either at short distance or projected onto a screen. In the case where the picture is projected onto a screen, it is also possible to use three separate devices, each corres-ponding to a coloured primary and whereby the pictures are projected in superimposed manner onto the same screen.
In both cases, these devices are more complica-ted than a black and white device and in the case of projections using three devices, setting is also very difficult.
BRIEF SUMMARY OF THB INVBNTION
In order to obtain a colour projection device operating without complicated settings and at a cost which is substantially the same as that of a black and white device, the present invention proposes "~
.. ..
, .
. . . - .
,,: - -~5 ~
a device for projecting colour pictures onto a screen, of the type incorporating a visual display cell making it possible to display pictures in the form of a plurality of fields formed from interlaced parallel lines, a polychromatic light source making it possible to illuminate the said cell, and means making it possible to project the picture from the cell onto the screen, wherein the lines of the cell are grouped into line systems, each line of a line system making it possible to display in accordance with a grey scale pa~ng from black to white the infor~ation corresponding to a given separate colour and wherein the device also comprises means outside the display cell and placed on the optical path between the light source and the screen and optically connected to the cell, making it possible to filter the light passing by each line of the cell to obtain the gi~7en corres-ponding colour.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
_ _ ~ . . _ _ _ _ . ~ _ The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings, wherein show:
Fig l a first embodiment of a device according to the invention.
Fig 2 a variant of the device of Fig l.
Fig 3 a second embodiment of a device according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to a first embodiment of a projecting device according to the invent~n shown in Fig l, the ~ O
picture to be projected is entered in a liquid crystal display device lOl shown in a greatly simplified manner and having a system of lines forming a field seen in the drawing by the end of the lines. This devîce has therefore three times as many lines as there are lines in the field according to which the picture is analysed. By an electronic processing of the video signal representing the picture, it is possible to separate the three components corresponding to the red, green and blue signals. The picture is then displayed on device lOl in the form of triplets of contiguous lines, each corresponding to a line of different colour as in the device which has a screen formed from coloured filter-ing lines incorporated into the device. However, thepresent device lOl does not have filtering lines and the displayed in picture is consequently a black and white picture.
For the purpose of illumi~ting the screen, a light source 102 emits a beam of light which is collected by a first lens 103 which, in the present embodiment, focuses it in the vicinity of the surface of deviating mirror 104. This mirror directs the light beam towards an objective 105 making it possible to illuminate cell lOl by a substantially parallel and homogeneous light beam.
The light is reflected by display device 101 towards objective 105, this taking place in specular manner by reflection on the heating electrodes when the liquid crystal is not diffusive and in accordance . J
.
: . ` , 5~ ~ 5 with a l~be of variable shape as a function of the liquid crystal used and which will be considered as su~stantially Lambertian for the purposes of the description.
Objectives 105 collects the light reflected by display device 101 and forms therefrom a picture on a slide 106.
In their passage between objective 105 and slide 106, the rays reemitted by device 101 in a specular manner pass through a focusing point located in the centre of a diaphragm 107. This point substantially corresponds to the image of the light source 102 given by optical elements 103, 104, 101 and 105.
Diaphragm 107 enables it to eliminate the light rays from the retrodiffusion lobe corresponding to the point where the liquid crystal is diffusive.
In this way, the desired schlieren optics are produced for the purpose of obtaining a good contrast.
Slide 106 on which is formed the image of device 101 forms a coloured filter constituted by bandscorresponding to the lines of device 101. Thus, the image of each line of device 101 is superimposed on one of the bands of slide 106. These bands are coloured red, g~en and blue and are grouped in such a way as to form triplets corresponding to the triplets de~ined hereinbefore in the display device 101. T.hus, the light reemitted in black and white by one line of a triplet of device 101 is filtered by the corresponding band of slide 106, which colours 5~ 55 it in accordance with the corresponding primary.
The image of device 101 formed in the plane of slide 106 is thus seen in colours by transparency through said slides. A projection objective 104 then makes 5` it possible to project onto a screen 109 the image coloured by slide 106.
It is easy to obtain such a slide 106 by photographing a large dimension coloured image reproducing the necess~y filter bands. The design of such a large size image presents no difficulties~
It can for example be photographed by using a re-production caption stand, so that there is a negligible distortion. If it is desired to use a simpler optical device for forming this slide, the distortions intro-duced can be accepted and they are then compensatedduring the design of the large scale image.
Slide 106 can also be located on the lighting beam of device 101. For this purpose, it is necessary that the optics illuminating device 101 form on the surface of the latt~r an image of slide 106 in such a way that the lines of the device are illuminated by the corresponding bands.
A variant using this positioning of the filter-ing slide, as well as a device 101 for use by trans-parency is partly shown in Fig 2.
Slide 106 is illuminated by a source 102 bymeans of a parallel light beam obtained via a lens 203. An objective 205 forms the image of slide 105 on the rear face of the display device 101 in such a way that the image of the coloured bands of the slide .
iP~
coincides with the display lines of the device.
Thus, these display lines are illuminated by the light of colour corresponding to that which it is necessary to display and it is possible to directly form the image of the other face of the device 101 on a screen. The optical device necessary for forming this image comprises for example a pro-jection objective and a diaphragm for forming schlieren optics.
According to another variant shown in Fig 3, the system is identical to that of Fig 1 from light source 102 to diaphragm 107 inclusive. However, instead of forming an intermediate image on a slide and then projecting it onto a white screen, the image is directly projected by means of a projection objective 308 onto a specially coloured screen 309.
This screen is coloured in a series of red, green and blue bands forming triplets in much the same way as for slide 106. These bands are located on the screen in such a way that the images of the display lines of device 101 are formed thereon. In this way, each band illuminated in white light only reflects the colour corresponding to the line used for illuminat-ing it. Thus, the image is coloured directly on the screen. In another variant where the cell 101 is positioned closer to objective 105, the latter makes it possible to directly project the image onto the screen.
These devices for projecting coloured images or pictures onto a screen can be used in all display , ~. . . ;
~5 ~S S
systems where it is desired to have a large picture from a small display cell. It is in particular pointed out that screen 309 in Fig 3 can be observed both by transparency and by reflection. When observing by transparency, the complete device can be placed in a case providing the equivalent of a display system equipped with a cathode tube. The visual analogy with the system of so-called autoconvergent tubes with aligned cathodes shows that the image or picture quality of this system is very good.
Finally, in the case where screen 309 is transparent and is observed from behind, the complete device of Fig 3 is equivalent to that part of the device of Fig 1 limited to the system terminated by the slide.
.
Claims (6)
1. A device for projecting colour pictures onto a screen, of the type incorporating a visual display cell making it possible to display pictures in the form of a plurality of fields formed from interlaced parallel lines, a polychromatic light source making it possible to illuminate the said cell, and means making it possible to project the picture from the cell onto the screen, wherein the lines of the cell are grouped into line systems, each line of a line system making it possible to display in accordance with a grey scale passing from black to white the information corresponding to a given separate colour and wherein the device also comprises means outside the display cell and placed on the optical path between the light source and the screen and optically connected to the cell, making it possible to filter the light passing by each line of the cell to obtain the given corres-ponding colour, said projection means incorporating means for focusing the polychromatic radiation emitted by the source and spatial filtering means located at the convergence point of said radiation in order to form schlieren optics.
2. A device according to claim 1, wherein the filtering means comprise a transparent screen formed by parallel filter bands and located at a point where a real image of the display cell is formed, the image of the lines coinciding with the bands.
3. A device according to claim 2, wherein the transparent screen coincides with the projection screen.
4. A device according to claim 2, wherein the location for the transparent screen corresponds to a location where an intermediate real image of the display cell is formed and wherein it also comprises means making it possible to project the image of the thus illuminated transparent screen onto the display screen.
5. A device according to claim 1, wherein the filtering means comprise a transparent screen formed by parallel filters bands and positioned between the light source and the display cell and means making it possible to form the image of said transparent screen on the display cell, the image of the bands coinciding with the lines of the cell.
6. A device according to claim 1, wherein the filtering means coincide with the projection screen and wherein the latter has a system of coloured, paral-lel, retrodiffusive bands, the image of the lines on said screen coinciding with said coloured bands.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7923599 | 1979-09-21 | ||
| FR7923599A FR2466071A1 (en) | 1979-09-21 | 1979-09-21 | DEVICE FOR PROJECTING COLOR IMAGES ON A SCREEN, AND VISUALIZATION SYSTEM COMPRISING SUCH A DEVICE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1151455A true CA1151455A (en) | 1983-08-09 |
Family
ID=9229906
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000360545A Expired CA1151455A (en) | 1979-09-21 | 1980-09-17 | Device for projecting colour pictures onto a screen and display system incorporating such a device |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0026129B1 (en) |
| JP (1) | JPS5679591A (en) |
| AT (1) | ATE4362T1 (en) |
| CA (1) | CA1151455A (en) |
| DE (1) | DE3064421D1 (en) |
| FR (1) | FR2466071A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4613207A (en) * | 1984-05-08 | 1986-09-23 | Manchester R & D Partnership | Liquid crystal projector and method |
| JPH01201622A (en) * | 1988-02-06 | 1989-08-14 | Sharp Corp | Liquid crystal display device |
| JPH05203908A (en) * | 1991-06-07 | 1993-08-13 | Hughes Aircraft Co | Single light valve full color projection display device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3912386A (en) * | 1974-06-14 | 1975-10-14 | Rca Corp | Color image intensification and projection using deformable mirror light valve |
| FR2284237A1 (en) * | 1974-09-06 | 1976-04-02 | Thomson Csf | COLOR IMAGE TELEPROJECTION AND TELEPROGRAPHY DEVICE |
| US4031542A (en) * | 1976-03-08 | 1977-06-21 | Westinghouse Electric Corporation | Projection color television system |
-
1979
- 1979-09-21 FR FR7923599A patent/FR2466071A1/en active Granted
-
1980
- 1980-09-09 DE DE8080401284T patent/DE3064421D1/en not_active Expired
- 1980-09-09 AT AT80401284T patent/ATE4362T1/en not_active IP Right Cessation
- 1980-09-09 EP EP80401284A patent/EP0026129B1/en not_active Expired
- 1980-09-17 CA CA000360545A patent/CA1151455A/en not_active Expired
- 1980-09-22 JP JP13087180A patent/JPS5679591A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5679591A (en) | 1981-06-30 |
| FR2466071B1 (en) | 1982-10-01 |
| DE3064421D1 (en) | 1983-09-01 |
| FR2466071A1 (en) | 1981-03-27 |
| ATE4362T1 (en) | 1983-08-15 |
| EP0026129B1 (en) | 1983-07-27 |
| EP0026129A1 (en) | 1981-04-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |