Computer graphics processing and selective visual display system – Display driving control circuitry
Reexamination Certificate
1999-11-10
2002-05-07
Chang, Kent (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
C345S696000
Reexamination Certificate
active
06384816
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to image display apparatus in which high resolution images are displayed by shifting pixels based on an optical wobbling operation.
It is known in image display apparatus using a liquid crystal display device or the like to improve resolution of the liquid crystal display device by performing a pixel shifting operation called “wobbling” where the optical axis of light from the liquid crystal display device is wobbled in predetermined directions.
A technique for improving resolution has been disclosed, for example, in Japanese patent application laid open No. 4-63332, in which two sets each consisting of a liquid crystal panel for controlling the direction of polarization and a quartz plate are used for a displaying liquid crystal panel and at the same time four frame memories are employed therefor. A 4-point pixel shift is effected by causing an image to shift horizontally by ½ pixel pitch through one set of the polarizing direction control liquid crystal panel and quartz plate and causing the image to shift vertically by ½ pixel pitch through the other set of polarizing direction control liquid crystal panel and quartz plate. In other words, one frame is composed of four fields with dividing image signals into four images, and each divided image is stored to a frame memory. These are then synthesized as displayed at respective positions by allowing a straight propagation through the two sets of liquid crystal panels for a first filed, by shifting horizontally by ½ pixel pitch for a second field, by shifting vertically by ½ pixel pitch for a third field, and by shifting ½ pixel pitch both horizontally and vertically for a fourth field. A high-definition image based on the 4-point pixel shift is thereby displayed.
Further, a disclosure has been made in Japanese patent application laid open No. 7-36054 with respect to an optical apparatus achieving high resolution by two-dimensional 4-point pixel shift, provided with two sets of one-dimensional 2-point pixel shifting devices each consisting of a liquid crystal phase modulation device and a birefringence medium. These are combined into a lamination with rotating one of the devices about the optical axis of incidence through 90 degrees with respect to the other to perform four times of pixel shift vertically and horizontally within one frame or one field.
The prior techniques as described above are both related to performance of 4-point pixel shift to attain a quadruple resolution by shifting horizontally, vertically and obliquely by ½ pixel pitch the pixels of a rectangularly arrayed liquid crystal display device having horizontal pixel pitch P
x
and vertical pixel pitch P
y
.
The following problem then occurs if the above described 4-point pixel shift system is simply applied to a liquid crystal display device having pixels disposed in a delta-array of the generally used type as shown in
FIG. 1
, so as to perform the 4-point pixel shift as shown in FIG.
2
. In particular, a frequency band diagram of
FIG. 3
results when changes in frequency band are considered in the case of effecting the above described 4-point pixel shift system. Referring to FIG.
3
: the transverse axis represents the frequency band in a horizontal direction; the vertical axis represents the frequency band in a vertical direction; the black small circle represents the origin (zero frequency); and white small circles represent the sampling frequencies of the liquid crystal display device. Here, from the sampling theorem where information obtained by sampling is to possess its frequency band only up to ½ of the sampling frequency, the original frequency band of the liquid crystal display device without performing pixel shift, as indicated by the darker dotted region “a”, is extended to the frequency band of the lighter dotted region “b” upon performance of 4-point pixel shift as the above. In thus extended frequency band, as can be seen from
FIG. 3
, while the frequency band is increased in the vertical and oblique directions, the frequency band in the horizontal direction is not increased at all even after the performance of 4-point pixel shift, resulting in a problem that the horizontal resolution is not improved.
SUMMARY OF THE INVENTION
The present invention has been made to eliminate the above problems in the case of applying 4-point pixel shift system of the conventional liquid crystal display device to a liquid crystal display device having delta-array. It is an object of the invention to provide an image display apparatus having 4-point pixel shift system capable of increasing frequency band and improving resolution in both horizontal and vertical directions.
To solve the above problems, there is provided an image display apparatus in accordance with a first aspect of the invention, including: a display device having pixels disposed in a delta-array; pixel position transition means for repeatedly making a transition of pixel positions of the display device respectively to each of positions at four points; and image transition means for making a transition of image signals in synchronization with the pixel position transition means so as to display images corresponding to the pixel positions on the display device. The pixel positions at the four points are: a first pixel position serving as standard; a second pixel position shifted from the standard, first pixel position in a horizontal direction by approximately ½ of horizontal pixel pitch P
x
; a third pixel position shifted from the standard, first pixel position in the horizontal direction by approximately ¾ or approximately ¼ of horizontal pixel pitch P
x
and in a vertical direction by approximately ½ of vertical pixel pitch P
y
; and a fourth pixel position shifted from the standard, first pixel position in the horizontal direction by approximately ¼ or approximately ¾ of horizontal pixel pitch P
x
and in the vertical direction by approximately ½ of vertical pixel pitch P
y
.
Of the pixel positions changed by the pixel position transition means: the third pixel position {circle around (3)} is thus determined as shown in
FIG. 4
to be shifted from the first, standard pixel position {circle around (1)} horizontally by approximately ¾ of horizontal pixel pitch P
x
and vertically by approximately ½ of vertical pixel pitch P
y
; and the fourth pixel position {circle around (4)} is determined to be shifted from the first, standard pixel position {circle around (1)} horizontally by approximately ¼ of horizontal pixel pitch P
x
and vertically by approximately ½ of vertical pixel pitch P
y
. As shown in
FIG. 6
, the original frequency band of the liquid crystal display device without performing pixel shift as indicated by the darker dotted region “A” is thereby extended to the frequency band of region “B” which is lightly dotted. The frequency band is increased in both the vertical and horizontal directions. It is thereby possible to double the resolution not only in the vertical direction but also in the horizontal direction.
Further, resolution in the vertical and horizontal directions can be similarly doubled also by inverting the third pixel position {circle around (3)} and the fourth pixel position {circle around (4)} as shown in
FIG. 5A
, i.e., by determining the third pixel position {circle around (3)} to be the position shifted from the standard, first pixel position {circle around (1)} by approximately ¼ of horizontal pixel pitch P
x
in the horizontal direction and by approximately ½ of vertical pixel pitch P
y
in the vertical direction and determining the fourth pixel position {circle around (4)} to be the position shifted from the standard, first pixel position {circle around (1)} by approximately ¾ of horizontal pixel pitch P
x
in the horizontal direction and by approximately ½ of vertical pixel pitch P
y
in the vertical direction. Furthermore, as shown in
FIG. 5B
, a
Armstrong Westerman & Hattori, LLP
Chang Kent
Olympus Optical Co,. Ltd.
Patel Nitin
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