Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1999-02-26
2001-06-26
Brier, Jeffery (Department: 2672)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C345S156000
Reexamination Certificate
active
06252581
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color image signal generator used for a video game machine. More particularly, the present invention relates to a color image signal generator arranged to generate red, green and blue image signals for each pixel in accordance with red, green and blue image data and with brightness data. The present invention also relates to a storage medium for storing programs to control such a color image signal generator.
2. Description of the Related Art
A conventional video game machine may incorporate many electronic components and units for enabling a player (or players) to enjoy a video game by the video game machine. Among these units may be a color image signal generator arranged for generating red, green and blue image signals (analog signals) based on red, green and blue image data supplied from a look-up table incorporated in the video game machine.
Typically, the look-up table may be made up of a RAM (random access memory). The red, green and blue image data from the look-up table are converted into corresponding red, green and blue analog signals by digital-to-analog converters (D/A converters).
The analog image signals from the color image signal generator are supplied to a display unit. As a result, desired characters (each of which is made up of plural “objects”) are visually presented on the screen of the display unit.
Disadvantageously, the memory of the conventional look-up table has not been put to effective use. Specifically, the bit number of a memory in general is eight (8) bits or sixteen (16) bits. Color image data are made up of three kinds of data, namely, red, green and blue image data. Thus, supposing that the look-up table is of 16-bit and five (5) bits are used for each color, one bit in the look-up table remains to be unused.
For avoiding the above problem, the applicant of the present application once proposed a color image signal generator shown in
FIG. 6
of the accompanying drawings. The illustrated signal generator includes a look-up table
51
, buffers
52
Ra-
52
Rd,
52
Ga-
52
Gd and
52
Ba-
52
Bd, three-state gates
53
Ra-
53
Rd,
53
Ga-
53
Gd and
53
Ba-
53
Bd, amplifiers
54
R,
54
G and
54
B, and resistors Rra-Rrh, Rga-Rgh and Rba-Rbh.
The resistors Rra, Rga and Rba may have a resistance of 1600&OHgr;, the resistors Rrb, Rgb and Rbb may have a resistance of 800&OHgr;, the resistors Rrc, Rgc and Rbc may have a resistance of 400&OHgr;, the resistors Rrd, Rgd and Rbd may have a resistance of 200&OHgr;, the resistors Rre, Rge and Rbe may have a resistance of 800&OHgr;, the resistors Rrf, Rgf and Rbf may have a resistance of 400&OHgr;, the resistors Rrg, Rgg and Rbg may have a resistance of 200&OHgr;, and the resistors Rrh, Rgh and Rbh may have a resistance of 100 &OHgr;.
The look-up table
51
outputs 4-bit red image data, 4-bit green image data and 4-bit blue image data in parallel. The 4-bit red image data are supplied to the buffers
52
Ra-
52
Rd. Similarly, the 4-bit green image data are supplied to the buffers
52
Ga-
52
Gd, while the 4-bit blue image data are supplied to the buffers
52
Ba-
52
Bd.
The look-up table
51
also outputs 4-bit brightness data together with the three color image data. The brightness data are supplied to the three-state gates
53
Ra-
53
Rd,
53
Ga-
53
Gd and
53
Ba-
53
Rd via their control terminals. As is shown, the input terminals of the respective three-state gates
53
Ra-
53
Rd,
53
Ga-
53
Gd and
53
Ba-
53
Bd are grounded.
It is now supposed that the combination of the four resistors Rra-Rrd in parallel has an equivalent resistance of R
1
, while the combination of the four resistors Rre-Rrh in parallel has an equivalent resistance of R
2
. In this instance, the output voltage from the buffers
52
Ra-
52
Rd is divided into two lower voltages in accordance with the ratio of R
1
to R
2
, and only one of the lower voltages is supplied to the amplifier
54
R. The supplied data are amplified by the amplifier
54
R and then output as analog red image signals.
Similarly, analog green image signals are obtained from the amplifier
54
G, while analog blue image signals are obtained from the amplifier
54
B.
According to the color image signal generator shown in
FIG. 6
, the look-up table
51
can be used effectively. Supposing that the look-up table
51
is a 16-bit memory, 12 bits may be used for the three kinds of image data (4 bits for each color) and the remaining 4 bits may be used for the brightness data. In this way, it is possible to use all of the 16 bits of the look-up table
51
, thereby enabling provision of sixty five thousand five hundred and thirty six (65536) colors in total.
However, the color image signal generator of
FIG. 6
has been found disadvantageous in the following points.
Specifically, the signal generator of
FIG. 6
is an analog circuit using the resistors Rra-Rrh, Rga-Rgh and Rba-Rbh for example. In general, analog circuits tend to have constraints on designing freedom. Further, it is difficult to generate accurate color image signals with the use of an analog circuit. Referring to the signal generator of
FIG. 6
, the buffers
52
Ra-
52
Rd,
52
Ga-
52
Gd and
52
Ba-
52
Bd are TTL (transistor-transistor-logic) circuits. In this case, the high-level output voltage from these buffers will unfavorably vary due to variations in load. Thus, it becomes difficult to maintain an accurate image signal level in accordance with the combination of the image data and the brightness data.
Still further, when the resistances of the resistors Rra-Rrh, Rga-Rgh and Rba-Rbh are increased, the delay time in signal transmission will become longer. On the other hand, when the above resistances are decreased, the power consumption of the color image signal generator tends to become unduly larger or the input voltage to the amplifiers
54
R,
54
G and
54
B may decrease. Additionally, in the signal generator of
FIG. 6
, the variable range of image signals based on the brightness data is unfavorably limited, so that it cannot be expected to obtain satisfactory results of fade-in or fade-out.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention is to provide a color image signal generator which eliminates or reduces the above-described problems.
Another object of the present invention is to provide a video game machine incorporating such a color image signal generator.
Still another object is to provide a storage medium advantageously used in such a color image signal generator.
According to a first aspect of the present invention, there is provided a color image signal generator for generating red, green and blue analog image signals based on first red, green and blue image data and on first brightness data, each of the first red, green and blue image data having a predetermined first bit number, the first brightness data having a predetermined second bit number, the color image signal generator comprising:
a brightness data modifier for providing second brightness data based on the first brightness data, the second brightness data having a predetermined third bit number which is greater than the second bit number;
a data multiplier arranged to multiply the second brightness data with the first red, green and blue image data for output of second red, green and blue image data, each of the second red, green and blue image data having a fourth bit number which is greater than the first and the third bit numbers; and
a digital-to-analog converter for converting predetermined top bits of each of the second red, green and blue image data into analog signals.
With such an arrangement, the second brightness data (digital data) are multiplied with the first image data (digital data) before the data multiplier converts the second image data (digital data) into analog data. Thus, all of the bits of a look-up table are advantageously utilized, while accurate color image signals can be generated.
According to a preferred embodiment, the first bit number is equal to the second bit number.
The brightness data modi
Bednarek Michael D.
Blackman Anthony
Brier Jeffery
Capcom Co.. Ltd.
Pittman Shaw
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