Dot-sequential color display system

Abstract

A color display system includes a color light separator that separates incident white illumination light into red, green and blue wavelength bands to be directed to distinct color component sub-pixels (sometimes called dots) that are arranged in a dot-matrix, color triad arrangement (e.g., stripe or delta) to form individual picture elements (pixels) on a pixelated electronic image device (e.g., LCD of DMD). The entire picture is optically shifted from one set of color component sub-pixels to another in a 3-field sequence. As a result, the sets of red, green and blue color component sub-pixels appear to an observer as a single full-color image, thereby providing a dot sequential color display.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. application Ser. No. 09 / 681,184, filed Feb. 14, 2001, now allowed, and claims the benefit of provisional Application No. 60 / 182305, filed Feb. 14, 2000, the content of both of which in their entirety is hereby incorporated by reference.SUMMARY OF THE INVENTION [0002] There are many ways to produce a full color matrix-addressed display, but almost all methods require 3 independent elements of Red, Green and Blue coloration, so as to be able to mix (in the additive color method) each primary in variable ratios to be able to cover the entire color gamut. [0003] One method that does not need 3 simultaneous primary color elements is referred to as field-sequential color. In this method an imaging device is illuminated with just one color primary at a time. One can envision a color-wheel that filters the white light and allows passage of first red, then green, then blue light, to be directed onto the...

AI Technical Summary

Benefits of technology

[0004] Very recently the use of field-sequential color has been revived, with the Texas Instruments Digital Micromirror Device (DMD), wherein a single proprietary (expensive) DMD chip can be used with a quickly rotating color wheel to create 180 color fields per second and therefore 60 full-color frames per second. In order to alleviate the flickering effect of this sequential color display, the color wheel might rotate still faster, to provide 120 full-color frames per second.

[0014] Dot-sequential Color uses a single LCD (or DMD, etc.) imaging device at the desired final resolution, but creates 3 slightly displaced images over time, to make the equivalent of a full-color image with very low cost. We therefore exploit the ability of the human eye to synthesize three displaced color images into an equivalent higher resolution color image. Such a displacement may also be called ‘dithering’ or ‘dot dither’.

[0019] The preferred method of shifting the image of our device uses a simple tilted plate with a piezoelectric actuator. Another means of obtaining such a small image displacement uses a double-birefringence crystal and liquid crystal retarder which is switched between two polarization states to make a ‘solid state’ and reliable and fast-switching displacement control device.

[0022] Our chromatic separation also preferably uses a holographic grating, but as a compensating dispersion, and not as a microlens. We propose a better solution to putting RG and B wavelengths into spatially distinct pixel regions (RGB subpixels) and we furthermore propose a more economical method of displacing the image in time. Our display system and method provides high-efficiency illumination and a high-resolution image to the human eye.

Problems solved by technology

The major drawback of this type of display is that one-third of the light emanating from the display (in the case of a single-chip DMD, transmitted through the color wheel and reflected off of the micromirror elements) is used at any one time, and due to a ‘dead-band’ required between the color segments (to prevent any color cross-talk) this may be further reduced to around 30% light utilization efficiency.

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