Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2002-02-04
2004-06-29
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S581000, C345S582000, C345S088000, C345S690000
Reexamination Certificate
active
06756991
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a color signal adjustment device that adjusts first through third color signals according to lookup tables and to an image display apparatus using the same.
BACKGROUND ART
An image display apparatus like a projector has a color signal adjustment device for correcting non-linear input-output characteristics (gamma characteristics) of a display device, such as a liquid crystal panel. The color signal adjustment device utilizes lookup tables for correction of the input-output characteristics. Each lookup table represents a mapping of linear tone values of each color signal, red (R), green (G), or blue (B) to non-linear tone values for correction of the gamma characteristics.
FIG. 10
is a block diagram schematically illustrating the structure of a prior art color signal adjustment device. The prior art color signal adjustment device
300
includes three address selector circuits
310
R,
310
G, and
310
B corresponding to respective color signals R, G, and B and three RAMs
320
R,
320
G, and
320
B, as well as one data selector
330
. Lookup tables corresponding to the color signals R, G, and B are respectively stored in the three RAMs
320
R,
320
G, and
320
B.
The first address selector
310
R selects either an R color signal RI or an address signal AD supplied via an external address bus (not shown) as an input address signal in response to a first address selection signal SLTR and supplies the selected input address signal to the RAM
320
R. In a similar manner, the second address selector
310
G selects either a G color signal GI or the address signal AD as an input address signal in response to a second address selection signal SLTG and supplies the selected input address signal to the RAM
320
G. The third address selector
310
B selects either a B color signal BI or the address signal AD as an input address signal in response to a third address selection signal SLTB and supplies the selected input address signal to the RAM
320
B.
The data selector
330
selects one of output color signals RO, GO, and BO read from the three RAMs
320
R,
320
G, and
320
B in response to the first through the third address selection signals SLTR, SLTG, and SLTB, and supplies the selected output color signal as reading data RD to an external data bus. Writing data WD is supplied to the three RAMS
320
R,
320
G, and
320
B via an external data bus.
Read-write signals WRR, WRG, and WRB are supplied to control the reading and the writing operations from and into the respective RAMs
320
R,
320
G, and
320
B. In the reading process of the respective RAMs
320
R,
320
G, and
320
B, data corresponding to the input address signals are read and output as the respective output color signals RO, GO, and BO.
During the operation of the image display apparatus, the respective color signals RI, GI, and BI are selected in the first through the third address selectors
310
R,
310
G, and
310
B as the input address signals into the RAMS
320
R,
320
G, and
320
B. Corresponding data are read from the lookup tables stored in the RAMs
320
R,
320
G, and
320
B and are output as the output color signals RO, GO, and BO.
The lookup tables for the respective colors are stored into the RAMs
320
R,
320
G, and
320
B of the corresponding colors according to an exemplified procedure discussed below.
The procedure first stores the lookup table for the color R into the RAM
320
R of the color R. The procedure selects the address signal AD supplied via the address bus in the first address selector
310
R as the input address signal into the RAM
320
R. The procedure then writes the writing data WD supplied via the data bus at the address in the RAM
320
R specified by the address signal AD. At this moment, the output of the RAM
320
R is generally cut off, and the output color signal RO is fixed to either a high level or a low level by a connected terminal resistance (not shown). Alternatively a variation in data at the address may be output directly.
In the same manner as that for the RAM
320
R of the color R, the procedure stores the lookup table for the color G into the RAM
320
G of the color G by selecting the address signal AD in the second address selector
310
G as the input address signal into the RAM
320
G of the color G. Like the RAMs
320
R and
320
G of the colors R and G, the lookup table for the color B is stored into the RAM
320
B of the color B by selecting the address signal AD in the third address selector
310
B as the input address signal into the RAM
320
B of the color B.
As described above, the lookup tables for the respective colors are sequentially stored into the three RAMs
320
R,
320
G, and
320
B of the corresponding colors.
Storage of the lookup tables for the respective colors into the RAMs
320
R,
320
G, and
320
B of the corresponding colors is generally carried out in the course of initializing the image display apparatus.
In some cases, however, it is required to rewrite and update the lookup tables for the respective colors stored in the RAMs
320
R,
320
G, and
320
B of the corresponding colors during the operation of the image display apparatus. For example, there may be a requirement of rewriting the lookup tables to adjust the contrast, the brightness, and the color tone.
During the operation of the image display apparatus, lookup tables are generally written in a blanking period. The lookup tables stored in the RAMs
320
R,
320
G, and
320
B are sequentially rewritten as mentioned above. It accordingly takes a relatively long time to complete the rewriting operation. The rewriting may thus be performed during the display. The rewriting during the display causes output of specific data intrinsic to the rewriting operation, for example, high-level data or low-level data in the above example. This disadvantageously causes superimposition of noise on the displayed image.
One applicable procedure to prevent superimposition of noise does not use the lookup table for display only in the course of rewriting the lookup table. In this case, however, the displayed image during the rewriting of the lookup table is defined by color signals without gamma correction and adjustment of the contrast or brightness. This disadvantageously changes the color tone of the displayed image.
The object of the present invention is thus to solve the drawbacks of the prior art technique discussed above and to provide a technique that enables lookup tables to be rewritten without causing superimposition of noise in a displayed image or a variation in color tone of the displayed image during operation of an image display apparatus.
DISCLOSURE OF THE INVENTION
At least part of the above and the other related objects is attained by an image display apparatus of the present invention, which includes: a color signal adjustment module that adjusts first through third color signals corresponding to first through third colors expressing a color image; an image display module that displays a color image defined by first through third output color signals from the color signal adjustment module; and an adjustment control module that controls the color signal adjustment module. The color signal adjustment module has: first through fourth RAMs available as lookup tables for adjusting color signal levels; an address selection module that replaceably allocates the first through the third color signals and a predetermined address signal to input address signals of the first through the fourth RAMs, in response to a preset selection signal from the adjustment control module; and a data selection module that selectively outputs at least three output signals among output signals from the first through the fourth RAMs as the first through the third output color signals corresponding to the first through the third colors, in response to the preset selection signal.
During the normal operation, the first through the third lookup tables corresponding to the first through the third color signals are allocated to three RAMs selected among the first through the fourth
Bella Matthew C.
Oliff & Berridge, plc
Rahmjoo Mike
Seiko Epson Corporation
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