Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1997-10-15
2001-06-05
Cuchlinski, Jr., William A. (Department: 3661)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S084000, C345S087000, C345S089000, C345S182000
Reexamination Certificate
active
06243072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an apparatus and method for improving image quality and in particular to an apparatus and method for converting binary images to grey-scale or color images and displaying those images.
2. Background of the Related Art
It has been known that when a person views a rapidly cycled through sequence of binary images, the person may, if the rate and duration of images is proper, temporally integrate such that that sequence of binary images and the sequence in turn appears to be grey-scale images. This integration phenomenon is of particular interest with the arrival of high speed binary displays. Such devices are used, for example, in projection display systems, head-up displays and head mounted displays. There exist small fast high resolution displays which are essentially binary in nature such as the Digital Mirror Device (DMD), made by Texas Instruments, as well as actively addressed ferroelectric liquid crystal devices. These technologies are both capable of producing many thousands of binary images per second, depending on the number of pixels per frame, etc. . . . .
FIG. 1A
shows a series of binary images
105
which could be viewed by a person in the manner described above. Each frame F
1
-Fm will be comprised of a series of bits that are either
1
(ON) or
0
(OFF). That is, the series F
1
-Fm of frames as well as each individual frame is actually a series of bits which must eventually be displayed in order to make it possible for the person viewing the binary images to perform the integration discussed above.
FIG. 1A
further shows pixels Pj in general, and P
1
-P
4
, in particular, as representative pixels. As each frame F
1
-Fm is displayed for a time t, some of the pixels Pj will be a logical 1 and some will be a logical 0. In order for a person to view images produced by frames F
1
-Fm, a display device is required.
A problem with the above approach is that a display device which displays the group of binary images
105
must be capable of responding in the time t (which relates to the frame rate 1/t). This places a limitation on which displays can be used. Namely, only those display devices can be used which have response rates at least as great as 1/t Hz or frames per second. However, the integration process requires that t be small, otherwise the display would appear to flicker and not appear to provide a grey-scale.
Currently, there are a variety of display devices which might be used to output the above discussed subframes. Liquid crystal on silicon (LCOS) devices which have been designed as displays (or spatial light modulators) have used pixel designs which can be categorized as being either “dynamic” or “static”. A static pixel design has a memory element at each pixel, which can store the pixel data indefinitely without the need for periodic refresh cycles. This is analogous to SRAM (static random access memory) in computer memory. A dynamic pixel stores data capacitively and requires a periodic refresh to compensate for leakage of the stored charge, analogous to DRAM (dynamic random access memory).
Both of these types of displays share the property that as the array of pixels is addressed in sequence, row-at-a-time, the liquid crystal begins to update to the new data immediately once the row is addressed. It happens that a reasonably high resolution displays, such as 1024 by 1024 pixels, the electronic refresh time is comparable or longer than the liquid crystal switching time. For example, if data is supplied to the display through 32 data wires running at 50M bits/sec, such an array of pixels takes approximately 690 microseconds to update. The liquid crystal switches in approximately 100 microseconds. It is valid, therefore, to view the display as being updated in a sweeping motion across its area.
Some applications require that the data on all of the display be simultaneously valid before it can be usefully viewed. Examples of such applications include most coherent applications such as optical correlators, optical beam steerers etc. . . . , and display applications where precise synchronization with other parts of the system, such as an illuminated source, is required.
SUMMARY OF THE INVENTION
An object, therefore, of the invention is to improve image quality from binary display devices.
Another object of the invention is to provide a method of achieving grey-scale images produced using binary display devices.
Another object of the invention is to provide a method and apparatus for reducing the data rate requirement for generation of time sequential grey-scale images on a display device.
Another object of the invention is to provide a method and apparatus for displaying subframes to allow a person to perform temporal integration of the stream of images.
One advantage of the invention is that it makes it possible to observe grey-scale images using a binary display device.
Another advantage of the invention is that it can be used to produce colored grey-scale images.
Another advantage of the invention is that it can utilize liquid crystal display devices.
Another advantage of the invention is that it significantly reduces the time interval during which the displayed data is changing by avoiding the row by row updating of the pixels.
Another advantage of the invention is that it is only limited by the switching time of the pixels.
Another advantage of the invention is that it can be used with static as well as dynamic type display systems.
One feature of the invention is that it provides grey-scale images by rapidly cycling through a sequence of binary images or subframes.
Another feature of the invention is that in one embodiment the ON pixels in the least significant frame is displayed at approximately half their full duration but no change in their output or ON intensity.
Another feature is that the non-attenuated subframes are grouped together to reduce the rate at which the display device outputs subframes.
Another feature of the invention is that in another embodiment the ON pixels in the least significant frame is displayed at approximately half their full or ON intensity.
Another feature of the invention is that it can utilize pixel buffers or a frame/image buffer.
These and other objects advantages and features are achieved by the provision of a method for displaying a grey-scale image on a display unit with a plurality of pixels, comprising the steps of: receiving a group of subframes to be displayed at a first rate; attenuating the least significant subframes within the group of subframes to yield attenuated subframes; combining unattenuated subframes to yield fewer unattenuated subframes; increasing the duration of the attenuated subframes; and displaying the unattenuated subframes and the attenuated subframes at a correspondingly reduced rate to achieve visual integration.
These and other objects, advantages and features are also achieved by the provision of a method for displaying a grey-scale image on a display unit with a plurality of pixels, comprising the steps of: receiving a group of subframes to be displayed at a first rate; attenuating the intensity of pixels of least significant subframes within the group of subframes to yield a series of attenuated subframes, the series including one or more of the subframes; combining pairs of unattenuated subframes to yield a shorter series of unattenuated subframes; increasing the duration of the series of attenuated subframes; and displaying the series of unattenuated subframes and the series of attenuated subframes at a rate sufficiently high to achieve visual integration.
These and other objects, advantages and features are also achieved by the provision of a method for displaying a grey-scale image on a display unit with a plurality of pixels, comprising the steps of: receiving a group of subframes to be displayed at a first rate; combining subframes other than the least significant bit subframes to yield a reduced number of subframes; and displaying the reduced number of subframes and the least signific
Cuchlinski Jr. William A.
Fleshner & Kim LLP
Marc-Coleman Marthe Y.
Regents of the University of Colorado
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