Liquid crystal cells – elements and systems – Liquid crystal system – Projector including liquid crystal cell
Patent
1996-03-08
1998-09-01
Sikes, William L.
Liquid crystal cells, elements and systems
Liquid crystal system
Projector including liquid crystal cell
349 8, 349 95, 353 31, 353 34, 359619, 359628, G02F 11335, G03B 2100, G03B 2126, G02B 2710
Patent
active
058017941
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a color display device and more particularly to a liquid crystal color display device.
DISCUSSION OF BACKGROUND
In order to generate video images of large dimensions, there is currently a trend towards the use of active liquid crystal matrices (LCD) in projection devices.
The projection of color images can be carried out either on the basis of three active matrices, each illuminated by one of the primary components, red, green or blue (R, G, B) or on the basis of a single three-color active matrix, in this case equipped with colored filters.
The incorporation of R, G, B colored filters into the structure of the screen (LCD) makes it possible to produce color image projection devices of simple design: monovalve projector since they consist of a source and a single LCD screen.
However, the presence of these colored filters leads to a low luminous yield related to the absorption and spatial distribution of these colored filters which divides the effective transmission of the LCD screen by three.
The cost of such a screen also remains high since it is necessary to implement extra masking levels to obtain these colored filters and to seek to increase the density of the image elements (pixels) required in the case of a color screen (as compared with a monochrome screen) if it is wished to produce them with reasonable dimensions (diagonal less than 6 inches).
To obviate these drawbacks, display screens are envisaged in which the colored filters are replaced by a diffracting grating capable, on the basis of a single white source, of dispersing the red, green, blue (R, G, B) chromatic beams in three different directions. It thus becomes possible, with the aid of arrays of lenses enabling the light of each chromatic range to be focused substantially on a pixel of the screen, to produce a three-color screen without colored filters, compatible with monovalve projection. Each lens corresponds with a dot, representative of an (R, G, B) triple of sub-pixels. FIG. 1 illustrates a display device according to this prior art. A source (S) of a certain extent generates white light comprising the chromatic components (R, G, B). These components are together sent via a collimator to the dispersive grating (RC) which then generates differently directed beams (R, G, B). An array of lenses (MLC) enables these beams to be focused on pixels of the active matrix (LCD). The spots (SR, SG, SB) are representative of the red, green and blue images of the source (S) in the various pixels which thus enable all of the light flux issuing from the source (S) to be concentrated in the active matrix. At the exit of the matrix, a field lens (L) makes it possible to converge the set of colored beams in a projection optic (PO). However, the chromatic dispersion used in this type of device generates a horizontal spreading of the beams, which then requires an increased aperture of the projection optic horizontally whereas the vertical aperture of this optic is not utilized. FIG. 2 illustrates this dispersion. For a lens whose cross section has dimensions h.sub.L and i.sub.L, if p represents the spacing separating two centers of sub-pixels, a horizontal spreading by p on each side of the image from the lens is obtained.
In order to make best use of the conventionally circular aperture of projection objectives, the invention proposes a display device which makes it possible to provide the best solution to this problem of the unsuitability of using a dispersive chromatic array coupled with a set of triples of sub-pixels with the geometry of the projection optics.
SUMMARY OF THE INVENTION
More precisely, the subject of the invention is a color display device comprising a light source (S) simultaneously emitting several ranges of chromatic components (R, G, B) and a spatial light modulator (LCD) comprising a set of triples of sub-pixels aligned along an axis x, each triple having a dimension sp.sub.x along this axis x, each sub-pixel corresponding to a chromatic component to be displayed, charac
REFERENCES:
patent: 4319322 (1982-03-01), Allain et al.
patent: 4451412 (1984-05-01), Loiseaux et al.
patent: 4576434 (1986-03-01), Huignard et al.
patent: 4847521 (1989-07-01), Huignard et al.
patent: 5052783 (1991-10-01), Hamada
patent: 5181054 (1993-01-01), Nicolas et al.
patent: 5206674 (1993-04-01), Puech et al.
patent: 5258969 (1993-11-01), Refregier et al.
patent: 5272496 (1993-12-01), Nicolas et al.
patent: 5323372 (1994-06-01), Puech et al.
patent: 5355187 (1994-10-01), Ogino et al.
patent: 5410421 (1995-04-01), Huignard et al.
patent: 5416617 (1995-05-01), Loiseaux et al.
patent: 5467206 (1995-11-01), Loiseaux et al.
Joubert Cecile
Lehureau Jean-Claude
Loiseaux Brigitte
"Thomson-CSF"
Malinowski Walter
Sikes William L.
LandOfFree
Color display device in which the area of a spherical lens equal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color display device in which the area of a spherical lens equal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color display device in which the area of a spherical lens equal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-275380