Computer graphics processing and selective visual display system – Display driving control circuitry – Intensity or color driving control
Reexamination Certificate
2000-03-03
2004-02-24
Bella, Matthew C. (Department: 2672)
Computer graphics processing and selective visual display system
Display driving control circuitry
Intensity or color driving control
Reexamination Certificate
active
06697084
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a tone display method of a display device using the “subfield method”, such as a plasma display panel (PDP), digital mirror device (DMD) and the like which has a binary memory and displays plural binary images repeatedly in time, with half-tone moving images weighted individually.
BACKGROUND AND BRIEF DESCRIPTION OF THE PRIOR ART
The conventional subfield method is used in a display device having a binary (ON/OFF) memory in order to display half-tone images as shown in Japanese Kokai Patent Application No. Hei 4 [1992]-195,087, the contents of which are incorporated herein by reference and which corresponds to U.S. Pat. No. 5,317,334.
FIGS. 29 and 30
illustrate such a display method with
FIG. 31
showing one DMD element and a rotary color filter used to display the red, green and blue colors in order to realize color display and to display 8-bit, 256-tone TV images.
As shown in
FIG. 31
, there is provided a lamp
13
which directs light through a disk-shaped color filter
12
to a DMD
11
with light being reflected from the DMD
11
through a projecting lens
14
. The DMD
11
is a collection of minute mirrors, each of which mirrors can be turned ON (lit or angled to pass light through lens
14
) or OFF (unlit or angled not to pass light through lens
14
) to create a display in well known manner. The mirrors of the DMD are controlled by a DMD control driver (c) from data collected in a memory (a) under control of a data format unit (b) at very high speed.
In the above described conventional 8-bit example, each image field (each field) comprises eight binary sub-images (subfields or sf) as shown in
FIGS. 29 and 30
. For the duration of each subfield as shown in
FIG. 29
, a weight corresponding to the brightness of one color when the subfield alone is ON is applied. In the case of the embodiment shown in
FIG. 31
, this weight corresponds to the time when a mirror of DMD
11
is ON or corresponds to the number of ON pulses during this time duration. In the example shown in
FIGS. 29 and 30
, the subfields have weights (brightness) of “1”, ‘2’, “4”, “8”, “16”, “32” and “128” according to the binary scheme. That is, the subfields have durations of “1”, ‘2’, “4”, “8”, “16”, “32”, “64” and “128” times the unit time duration “t”. As shown in
FIG. 30
, the pixels of the DMD display the half tone by a combination of certain subfields that are turned ON. For example, the brightness corresponding to “173” can be obtained by turning on the following subfields: subfield No. 8 having a weight of “128”, subfield No. 6 having a weight of “32”, subfield No. 4 having a weight of “8”, subfield No. 3 having a weight of “4” and subfield No. 1 having a weight of “1”. In the following explanation and with reference to the figures, subfield No. 1, subfield No. 2, etc. are denoted as “1sf”, “2sf”, etc.
For a still picture, the line of sight is nearly fixed. Consequently, for the various pixels, integration of the subfields can be carried out normally, so that there is no degradation in image quality. By adopting this driving method, it is also possible to display the tone for mirrors and other elements for which only the binary states of ON/OFF can be obtained.
A problem with the above described prior art display method using the conventional subfield method, as set forth in the reference “Pseudo shadow-like noise observed on pulse width modulated moving image display” (Japanese Title), which is synonymous with “New Category Contour Noise Observed in Pulse-Width-Modulated Moving Images” (English Title), Television Gakkai Gijutsu Hokoku, Vol. 19, No. 2, IDY95-21, pp. 61-66, is that pseudo shadow-like noise unique to moving images is observed and the image quality deteriorates. This is a disadvantage and is caused by the fact that, for moving images, the eyes must follow the images. Therefore, the time integration region of the eyes varies in space (i.e., when the line of sight moves at a speed equal to movement of plural pixels within one field of display period, integration of the subfields is carried out striding over plural pixels instead of within a single pixel). Consequently, it is impossible to obtain a normal image and the image quality degrades.
FIG. 36
is a diagram illustrating the aforementioned problem with respect to the extreme case of the tone display method shown in
FIGS. 29 and 30
. Pixel A and pixel B are set adjacent to each other and display tone
127
and
128
in the tone display method shown in
FIGS. 29 and 30
. That is, pixel A is ON for 1sf-7sf and is OFF only for 8sf while pixel B is OFF for 1sf-7sf and is ON only for 8sf. In
FIG. 36
, the pixel direction is the vertical direction and the subfields direction is the horizontal direction. That is, the vertical direction in
FIG. 36
indicates the movement of the viewpoint in space, while the horizontal direction indicates the movement of the viewpoint in time. In this case, assuming the viewpoint does not move from pixel A (arrow c), the integration value of one field of pixel A becomes tone
127
as displayed. However, when the viewpoint moves from pixel A to pixel B at the speed of two pixels in one field (arrow a), the integration values of pixel A and pixel B can both be taken as tone
255
. Also, when the viewpoint moves from pixel B to pixel A at a speed of two pixels in one field (arrow b), the integration values of pixel A and pixel B can both be taken as tone
0
.
As shown in
FIG. 32
, in order to make quantitative measurement of the actual degree of degradation in the image quality, the image of a moving ramp waveform as viewed when the conventional subfield method is used for display is simulated on a computer. In this simulation method, the integration over time of the eyes in the case of movement to the left side at a speed of 8 pixels during each field display period is computed.
The ramp waveform should be a straight oblique line. However, in the conventional method, as the line of sight changes in the pixels form “127” to “128” and form “63” to “64”, significant noise appears at these sites where new bits appear in the binary display. For the actual images, this leads to pseudo shadow-like degradation in the image quality.
As explained above, for tone quality using the conventional subfield method, when the image is viewed as the image moves, there may be unnatural appearances with a significant difference in brightness between pixels which should have little difference in brightness, this presenting a problem.
When the conventional subfield method is adopted to solve the aforementioned problem, it has been proposed that division of the subfields should be finer and the duration of each subfield should be approximately equal to the shortest subfield (“1t” in the tone display method shown in FIGS.
29
and
30
). However, an increase in the number of subfields leads to an increase in memory requirement and an increase in power consumption. Consequently, when fine division into subfields is utilized randomly, the cost is increased significantly. As a result, there is a demand for a tone display method which can prevent degradation in the image quality of moving images without increasing cost by suppressing an increase in the number of subfield divisions.
A major purpose of this invention is to solve the aforementioned problems of the conventional technology by providing a tone display method characterized by preventing degradation in image quality of moving images without increasing cost when the subfield method is utilized.
SUMMARY OF THE INVENTION
In order to solve the problem as described hereinabove, there is first provided a tone display method wherein the time band corresponding to one prescribed color within one frame/field includes plural time-shared time bands. Time segments corresponding to the time-shared time bands are set. Each of the time segments includes one or several subfields. The tone of the prescribed one color is displayed by appropriately setting the various subfields to ON/OFF. The time segments have a mixture of the s
Hitomi Hisakazu
Kunzman Adam J.
Ohmae Hideki
Bella Matthew C.
Brady III Wade James
Brill Charles A.
Cunningham G. F.
Telecky , Jr. Frederick J.
LandOfFree
Tone display method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tone display method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tone display method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3282496