JPH0411495A - Video equipment - Google Patents

Abstract

PURPOSE:To form high quality video equipment by attaining color conversion by three-dimensional information with a small table memory for color- conversion. CONSTITUTION:A new color difference which is color-converted is outputted to a sampled color difference signal in a digital data processor 107. Then, outputs (R-Y)', (B-Y)' and (G-Y)' of the processor 107 and luminance Y stored in a memory 106 are inputted and RGB data are prepared in a photographic data converting circuit 108. The photographic data prepared here are transmitted to a photographic processing part 112. In the processing part 112, the data are density-corrected by look-up data, thereafter, are data-converted so as to match the driver IC of a line head 113, are transmitted to the line head 113 and are photographically printed by one line. Thus, data conversion and photographic printing are repeated and the photographic printing of the whole screen is executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention mainly relates to a color printing device using a video signal as an input source;
It relates to video equipment such as video projectors and color television receivers.

[Prior Art] As a color conversion processing method for recent video equipment, 1.NT
The output signal R has a conversion table for each of the input signals R (red), G (green), and B (blue) demodulated from the SC signal.

How to determine G' and B'.

That is, R' = tr (R) G' = tg (G) B' = tb (B) t is conversion table 2, input signal R (red) demodulated from the NTSC signal
, G (green), and B (blue) and has a conversion table and determines the output signals R' and G'B°.

That is, (R', G', B') = trgb(R, G, B)
t had a conversion table.

[Problems to be Solved by the Invention] In the method of Prior Art 1, if input and output are 8 bits, a 256-byte conversion table is required for each color. Three colors have the advantage of being able to perform color conversion with a small amount of memory (768 bytes), but since they are converted using one-dimensional information such as R゛ is information only for R and G' is information only for G, there are certain The problem was that flexible color conversion such as emphasizing a specific color could not be performed.

Furthermore, although the method of Prior Art 2 is flexible and allows desired color conversion, if each color is 8 bits, a huge table memory of about 16.7 million x 3 bytes is required, making it difficult to put it into practical use. Was.

The present invention solves the above-mentioned problems, and its purpose is to provide high-quality, low-cost video equipment by realizing ideal color conversion with a small amount of table memory for color conversion. .

[Means for solving the problem] At least a composite video signal (hereinafter NTS
It is written as C signal. ) input means, demodulation processing means for outputting a luminance signal component and two color difference signal components from the NTSC signal, and an analog-to-digital converter (hereinafter referred to as an A/D converter) for quantizing the color difference signal component or the NTSC signal. ) and digital data processing means for performing image processing on the quantized digital data (color difference signal components), and the digital data processing means performs table conversion of the color difference signal components to perform color conversion. The present invention is characterized in that nonlinear data is written in the first stage table through a two-stage table when color difference signal components are converted into tables.

[Example] A full color gradation recording device was created as an example of video equipment using the present invention. The input image signal is an NTSC signal, a line head is used, and the recording density is 6.0 dat/m.
m, the number of pixels is 480 in the main scanning direction and 64 in the sub-scanning direction.
There are 0 pieces. Recording screen size is approximately 80mm x 112mm
It is.

FIG. 1 shows a schematic diagram of a system according to the present invention.

101 is an NTSC signal, 102 is a synchronous processing circuit, 103
104 is a Y/C separation circuit, 104 is a chroma demodulation circuit, 105 is an A/D converter, 106 is a memory, 107 is a digital data processing means, 108 is a printing data conversion circuit, 109 is a sampling clock generation circuit, and 110 is a memory address. 111 is a central processing unit CPU; 112 is a printing processing unit having a look-up table; 113 is a line head having a drive circuit; and 114 is a printing mechanism.

The input NTSC signal 101 is sent to the Y/C separation circuit 10
3 and is separated into a luminance signal (Y signal) and a carrier color signal (C signal). The chroma signal is further processed by the chroma demodulation circuit 1.
04 and is converted into two color difference signals (RY and BY signals). - On the other hand, the NTSC signal 101 is also input to a synchronization processing circuit 102, which outputs a horizontal synchronization signal and a vertical synchronization signal. Horizontal synchronization signal and vertical synchronization signal are CPU11
1 is input to the print processing section 112.

Y signal and color difference signal (RY, B-Y) are sent to A/D converter 1
05 is input.

Luminance and color difference signals for one frame (640 pixels in the horizontal scanning line direction)
The CPU 111 sends a control signal to the sampling clock generation circuit 109 and the memory address control unit so that the data is sampled (480 dots in the vertical direction). The sampling clock generation circuit 109 generates a sampling clock according to the control signal of the CPU 111, and
/D converter 105. The luminance and color difference signals converted into digital data by the A/D converter 105 are stored in the memory 106.
It will be written once again.

The digital data processing means 107 performs color conversion on the sampled color difference signal and outputs a new color difference.

The print data conversion circuit 108 outputs the outputs (RY)', (B-Y)' (G-Y) of the digital data processing means 107.
)'' and Y stored in the memory 106, and enter RG
Create B data using the following formula.

R' = Y+ (RY)'G' = Y+ (G-Y)'B'' = Y+ (B-Y)' The created print data is sent to the print processing section 112. After density correction using an up-table, the data is converted to match the driver IC of the line head 113 and sent to the line head 113.
One line is printed.

In this way, data conversion and printing are repeated to print the entire screen. The above is an outline of the system.

Next, the digital data processing means 107 of the present invention is shown in FIG.
This will be explained using FIG.

FIG. 2 is a diagram showing the relationship between the three attributes of color, brightness, hue, and saturation, and digital data such as luminance (Y) and two color differences (R-Y, B-Y). Lightness (L) corresponds to brightness, and hue is expressed as an angle (H) counterclockwise from the point acr)B-Y axis mapped on the RY-B-Y plane. Saturation (S) can be expressed as the distance from the origin to a. Therefore, lightness (L), hue (H), and saturation (S) are Y, RY
, B-Y is expressed by the following formula.

L=Y ・・・・・・・・・(Formula 1)%Formula%(3
) Among these, the digital data processing unit 107 is characterized in that it ignores the brightness information (Y) since it is brightness information, and performs color conversion by focusing on two pieces of information: hue and saturation. In other words, since only the color information is converted, the amount of table required can be reduced compared to the conventional conversion of R, G, and B. For example, R,
In the case of 8 bits each for G and B, the conventional method uses 224 x 3
A byte table was required, but in this example, R-Y, B
- Since only Y data is converted, color conversion is possible using 216 x 3 bytes and sunset memory. FIG. 3(a) shows one embodiment of the digital data processing section 107 shown in FIG.

R-Y, B-Y color difference data from memory 106 (8 each
bit) points to the address of the color conversion table RAM 301 and the data bus ((RY)", (B-Y)', (G-
Y)') is output. The contents of the color conversion table were determined according to steps 1 to 5 below.

1. Perform equation 2) for the inputs of RY and B-Y to determine the input hue angle.

2. Perform 2) for the inputs of RY and BY to obtain the input saturation.

3. Obtain the output hue angle (Ho) from FIG. 3(b).

4. Obtain the output saturation (SO) from FIG. 3(c).

5. From the output hue angle (Ho) and output saturation (So), calculate the following formula %
(Formula %) Figure 3 (b) and (C) are human skin (hue angle around 140 degrees)
, green (around 225 degrees f&), and blue sky (around 320 degrees). The above is the digital data processing section 10
However, special color conversion is also possible by devising the contents of the table.

Next, referring to FIG. 4.5, an embodiment will be described in which the color conversion table memory is further reduced to 192 bytes as shown in FIG. 3(a) and the image quality is maintained at the same level. One possible way to reduce memory is to simply lower the resolution of input color differences. For example, both RY and BY have a resolution of 1/2 (in Fig. 3(a), the lower 1 bit of RY and BY is ignored).
If you do this, the table size will be reduced to 1/4 of 48 bytes. However, in this method, as shown in Figure 4 (a), when an ), it is large when the saturation is low, which causes harmful effects on human skin. Therefore, we adopted a method of changing the resolution depending on the color difference value. As can be seen from Fig. 4 (b), this takes advantage of the property that the hue error etc. decreases even if the resolution is low (the higher the saturation, the higher the color difference value), and when the color difference value is small, the resolution 1/1, medium size 1/2, large size 1/4. FIG. 4(C) is a diagram showing the hue error, etc. at this time, and the hue error was at most ±1 degree, and the saturation error was also small at about 3%. Moreover, when the saturation is low, the error is 0, so delicate hues such as skin tones are not affected. With this method, the amount of table memory is reduced to approximately 48 bytes, and the same level of image quality as in the case of a resolution of 1/1 can be achieved. FIG. 5(a) is a more specific example of the method described above. Each color difference data R-Y, B-Y (8 bits each) from the memory 106 is stored in the first table 501.
．． 502 addresses and each data bus (7 bits each) is output.

The output of the first table 501 is input to the address (upper 7 bits) of the second table 503, and the output of the first table 502 is input to the address (lower 7 bits) of the second table 503. The second table outputs new color difference data (8 bits) according to the input. The content of the second table is determined in the same way as the color conversion table shown in FIG. 3(a). The contents of the first table correspond to the means for changing the resolution according to the value of the input color difference shown in FIG. 4(C), and are nonlinear as shown in FIG. 5(b). Since the output of this first table indicates the address of the second table, simple color conversion can be realized by changing the contents of this first table. For example, if you want the entire image to be brightly colored, the content shown in FIG. 5(c) may be used.

Since the first table has a capacity of at most 256×2 bytes (when inputting 8 bits), it is possible to have a plurality of first tables and switch between them.

In this example, by changing the color difference resolution to 1/1.1/2.1/4 depending on the size of the color difference, the resolution is originally 19.
We have shown an example where the memory required for 2 bytes can be converted to 48 bytes and color conversion can be done using 1/4 of the memory.
If you change it to 8, you can achieve 12 bytes. In this case, the hue error etc. will be slightly larger, so it may be determined based on the characteristics required by each video device.

[Effects of the Invention] As described above, the present invention makes it possible to perform color conversion using three-dimensional information (each color difference signal) with a small amount of table memory for color conversion. This has the effect that color correction etc. can be performed freely and high quality video equipment can be provided. Furthermore, since parts that require complicated calculations are made into tables, logic circuits for calculations are not required, and an inexpensive video device can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing a system according to the present invention. 101... 102... 103... 104... 105... 106... 107... NTSC signal synchronous processing circuit Y/C separation circuit Chroma demodulation circuit A/D converter memory Digital data processing Means 108... Print data conversion circuit 109... Sampling clock generation circuit 110...
. . . Memory address control unit 111 . FIG. 3(a) is a diagram showing one embodiment of the digital data processing section. 301...Color conversion table RAM FIG. 3(b) is a diagram showing the relationship between the input hue angle and the output hue angle. FIG. 3(c) is a diagram showing the relationship between input saturation and output saturation. FIG. 4(a) is a diagram explaining hue error and saturation error. FIG. 4(b) is a diagram showing the relationship between hue error, saturation error, and the size of color difference. FIG. 4(c) is a diagram showing the relationship between the hue error, the saturation error, and the size of the color difference when the resolution of the color difference is changed depending on the size of the color difference. FIG. 5(a) is an application example of FIG. 3(a) and an embodiment of FIG. 4(C). 501...First table 502...First table 503...Second table FIG. 5(b) is a diagram showing the contents of the first table. FIG. 5(c) is a diagram showing another example of the first table. Applicant Seiko Epson Corporation Agent Patent Attorney Kizobe Suzuki 1 person Figure 2 Figure 3 (Q) Input hue angle Figure 3 (b) Figure 3 (C) Figure 1-Y Figure 4 (Q) Figure r4 (b) Figure 4 (c) Figure 5 Figure 5 (b) Line 5”j (c)

Claims (2)

[Claims] (1) In a video device, at least a composite video signal (hereinafter referred to as an NTSC signal) input means, a demodulation processing means for outputting a luminance signal component and two color difference signal components from the NTSC signal, and the color difference signal component or the NTSC signal an analog-to-digital converter (hereinafter referred to as an A/D converter) that quantizes the quantized digital data (color difference signal component), and a digital data processing means that performs image processing on the quantized digital data (color difference signal component), A video device characterized in that the means performs table conversion of color difference signal components to perform color conversion. (2) The video equipment according to claim 1, wherein nonlinear data is written in the first stage table through a two-stage table when color difference signal components are converted into tables.