Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-03-20
2001-11-13
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S692000, C345S102000
Reexamination Certificate
active
06317112
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to display systems, and more particularly to a miniature display system in which a ferroelectric liquid crystal (FLC) spatial light modulator is positioned directly on top of and controlled by a specifically written (i.e. addressed) very-largescale-integration (VLSI) silicon integrated circuit (IC) backplane.
In the field of miniature displays and especially those using spatial light modulators, it is well known that stationary and moving images, either monochrome or color, may be sampled and both color separated and gray scale separated. These separations may be digitized forming digitized images which correspond to the given images. These digitized images are used by devices in this field to create visual images that can be used for a direct visual display, a projected display, a printer device, or for driving other devices that use visual images as their input. The present invention provides a novel spatial light modulator using novel data sequencing schemes which may be used to produce a direct view miniature display or a projected display, or for driving a printer or other devices that use visual images as their input.
One of the ongoing challenges facing the manufacture of miniature display systems is providing smaller and smaller displays with higher and higher resolution. The combination of these two factors dictates smaller and smaller pixel sizes in order to achieve smaller displays with higher resolution. Miniature displays which are small enough to be mounted onto a helmet or displays small enough to be supported by a pair of eyeglasses will find a wide variety of uses if they can provide adequate resolution and brightness in a small, low-power package at a low cost. Conventional display technologies such as CRTs are difficult to miniaturize and therefore do not hold much promise in this field. Alternatively, new displays based on VLSI integrated circuits are currently being developed. Examples of these miniature displays in the prior art include digital micromirror devices, active-matrix electroluminescent displays, and active-matrix liquid crystal displays. However, each of these prior art devices has significant limitations in resolution, brightness, compactness, lumination efficiency, or color capability. Furthermore, because of various physical restrictions on systems of these types, the smallest pixel pitch that to applicant's knowledge has been achievable thus far has been a pitch much greater than 10 microns. As will be seen hereinafter, the present invention provides a display capable of providing smaller pixels, for example with a pitch on the order of 10 microns or less, with higher resolution in a bright, full color capable display. As will also be seen, the present invention provides for unique data ordering schemes, and a unique method of illuminating the display, as well as other features which will become apparent.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, a system for producing modulated monochrome or color light having gray scale is disclosed. The system includes an active matrix liquid crystal spatial light modulator having light modulating means including (i) a layer of liquid crystal material which is designed to switch between ON and OFF states and (ii) active matrix means including VLSI circuitry for dividing the layer of liquid crystal material into an array of individual liquid crystal pixels and for causing each of the pixels of liquid crystal material to modulate light individually by switching between the ON and OFF states in a way that depends upon the data with which the VLSI circuitry is written. The VLSI circuitry of the active matrix means includes an array of sub circuits, each of which is dedicated to and defines a specific one of the pixels. The system also includes illumination means having a light source for directing light from the source into the pixel-divided layer of liquid crystal material in a specific way. And finally, the system includes means for writing the VLSI circuitry with preselected data in accordance with a particular data ordering scheme such that the circuitry, in response to the data, causes the pixels of liquid crystal material to individually switch between their ON and OFF states and therefore modulate light from the source in a way which, depending upon the data, produces a specific overall pattern of gray scale light.
The particular data ordering scheme is such that the data writing means writes each of the subcircuits and therefore each of the pixels with preselected data in a predetermined successive order, timewise, so that none of the subcircuits includes buffer circuitry, thereby reducing the complexity of the array of subcircuits. The preselected data is digital data divided into individual digital data commands, one for each of the subcircuits and therefore each of the pixels. Each digital data command establishes, during any given time frame, the length of time its associated pixel is in its ON and OFF state during a given time frame and each of the given time frames is divided into a first plurality of subframes and a second plurality of subframes for purposes of obtaining gray scale. The illumination means includes means for maintaining the intensity of light directed from the light source into the pixel-divided layer of liquid crystal material substantially constant during the first plurality of subframes and means for directing light of variable intensities from the light source into the pixel-divided layer of liquid crystal material during the second plurality of subframes. Each of the digital data commands establishes whether its associated pixel is in its ON or OFF state during each subframe of any given frame.
In one embodiment of the present invention, the first plurality of subframes is a plurality of subframes of unequal lengths of time and the time periods of the first plurality of subframes, if arranged in order timewise, increase by a factor of two. The second plurality of subframes is a plurality of subframes of equal lengths of time and each of the different intensities of light directed into the pixel divided layer double from subframe to subframe when the subframes of equal length are arranged in a particular order. Furthermore, each of the digital data commands comprises a series of binary bits, one for each of the subframes, each binary bit establishing whether its associated pixel is in its ON or OFF state during its associated subframe.
In another feature of the present invention, each of the frames includes an additional blackout subframe after each of the second plurality of subframes of equal time periods. Also, each of the digital data commands includes a binary bit associated with each of the blackout subframes for maintaining its associated pixel in an OFF state during its associated blackout subframe. Each of the blackout subframes is sufficiently long to allow all of the pixels written during each immediately previous subframe of equal time period to respond fully and to allow the illumination means to switch the intensity of the light source before the writing means begins writing the pixels in the next subframe of equal time period.
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Handschy Mark A.
Meadows Michael R.
Morrison Bryan T.
Anyaso Uchendu O.
Crouch Robert G
Displaytech, Inc.
Saras Steven
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