Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Patent
1993-08-04
1997-11-11
Hjerpe, Richard
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
345 55, 345147, 345108, 345 84, G09G 510
Patent
active
056869398
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to spatial light modulators, and more particularly to circuits for driving such modulators. The invention is particularly though not exclusively suitable for use with the type of spatial light modulator which has become known as a deformable mirror device or DMD.
For a background description of several types of spatial light modulator reference may be made to HUIGNARD, J. P., "Spatial Light Modulators and their Applications", J. Optics (Paris), 1987, Vol. 18, No. 4, pp 181-186. By way of example another type of spatial light modulator is described in THOMAS, R. N. et. al. "The Mirror-Matrix Tube: A Novel Light Valve for Projection Displays", IEEE Transactions on Electron Devices, Vol. ED-22, No. 9, September 1975, pp 765-775.
The deformable mirror device is a particular type of spatial light modulator and comprises a micro-mechanical array of electronically addressable mirror elements, the elements corresponding to pixels. Each pixel mirror element is capable of mechanical movement in response to an electical input. Such movement is in practice more often a deflection rather than a deformation but the term deformable mirror device has now become accepted as the description of this class of devices. They may be digitally addressed in which case they can be referred to as digital mirror devices. The expression DMD covers all of these.
For a description of current DMD technology reference is made to HORNBECK, L. J., "Deformable-Mirror Spatial Light Modulators" Proc. SPIE Critical Reviews Series, Vol. 1150, 6-11 August 1989, San Diego, Calif., U.S.A., pp 86-102. This paper contains many references to earlier work and attention is drawn particularly to references 3, 9, 14 and 23 of that paper. Further details of the construction of the devices is found in BOYSEL, R. M., "A 128.times.128 frame-addressed deformable mirror spatial light modulator" Optical Engineering, Vol. 30, No. 9, September 1991, pages 1422-1427. Attention is also drawn to reference 1 in that paper which is an earlier publication by Boysel et al. It has been proposed that DMDs should be usable as projection displays, see e.g. HORNBECK, L. J., et al., "Deformable Mirror Projection Display", SID 80 Digest, pp 228-229 (Abstract of presentation delivered Jul. 20, 1980 at SID Symposium), and U.S. Pat. No. 4,680,579.
The construction and manufacture of DMDs is further described in U.S. Pat. No. 4,615,595 and U.S. Pat. No. 4,566,935 and European Patent Application EP-A-0 391 529, all of Texas Instruments Incorporated.
The following description assumes a knowledge of the above-noted prior documents, all of which are hereby incorporated by reference.
A DMD may comprise an area array of deflectable mirrors, used to modulate the light in an optical projector. There is one mirror for each picture point or pixel and each mirror is approximately 20 microns square. It is termed digital because each mirror has two positions, an "on" and an "off" position. In the "on" position, incoming light is directed through the projection lens to the display screen, and in the "off" position, light is deflected away from the projection lens, so that no light reaches the screen.
The "on" and "off" positions of each mirror are controlled by two deflection electrodes, which exert an electrostatic attraction on the mirror according to which of the electrodes has been charged with the necessary bias. In addition, there is a common bias applied to all the mirrors, to hold them in their "on" or "off" positions after the potential on the deflection electrodes has leaked away. Therefore the sequence for applying new positional information to each mirror is as follows. Just before the change, the potential on each deflection electrode could be equal, especially if some time has elapsed since the previous change, but the mirrors will remain locked in their previous position because of the common mirror bias. New potentials are now applied to all the deflection electrodes over a relatively short period of approximately 60 to 80 micro
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Chau, Wk, Wong, Sem, Wang J. "A Critical Analysis of Dithering Aloorithms for Image Processing". IEEE Region X Conference on Computen & Com Systems pp. 309-313, 1990 Sep..
Anastassiou, D. "Error Diffusion Coding for A/D Conversion". IEEE Trans Circuits & System 36(9):1175-1186 Sep. 1989.
Hornbeck, L.J., "Deformable-Mirror Spatial Light Modulators" Proc. SPIE Critical Review Series, vol. 1150, 6-11 Aug. 1989, San Diego, California, U.S.A. pp. 86-102.
Boysel, R.M., "A 128 + 128 frame-addressed deformable mirror spatial light modulator" Optical Engineering, vol. 30, No. 9, Sep. 1991, pp. 1422-1427.
Hornbeck, L.J., et al., "Deformable Mirror Projection Display", SID 80 Digest, pp. 228-229 (Abstract of presentation delivered Jul. 20, 1980 at SID Symposium), and United States Patent US-A-4,680,579.
Huignard, J.P., "Spatial Light Modulators and their Applications", I. Optics (Paris), 1987, vol. 18, No. 4, pp. 181-186.
Thomas, R.N. et al. "The Mirror-Matrix Tube: A Novel Light Valve for Projection Displays", IEEE Transactions on Electron Devices, vol. ED-22, No. 9 Sep. 1975, pp. 765-775.
Gillespie John
Millward John David
Chang K.
Hjerpe Richard
Rank Brimar Limited
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