JPH0411496A - Imaging device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to a recording device that uses a video signal as an input source.

[Prior Art] Conventionally, devices for printing video signals have performed color conversion in order to improve color reproducibility and color expression.

There are two main methods.

(1) R (red), G (
The method shown in FIG. 4(a) performs one-dimensional transformation on each of the green) and B (blue) signals. That is, R''=Tr (R) G'=Tg (G) B'=Tb (B) Tr, Tg, and Tb are each one-dimensional conversion tables.

In this case, since there is no need to refer to other colors during color conversion, basically one A/D converter is sufficient.

(2) R (red), G (
The method shown in FIG. 4(b) performs three-dimensional transformation using green) and B (blue) signals. That is, (R', G', B') = Trgb (R, G,
B) Trgb is a three-dimensional conversion table.

In this case, three A/D converters are required, and each A/D converter samples an RGB signal.

[Problems and objects to be solved by the invention] However, in conventional example (1), since the conversion is one-dimensional, there is a problem that flexible color conversion such as emphasizing or converting a specific color cannot be performed. there were.

Furthermore, in conventional example (2), it is possible to perform the desired color conversion, but if each color is 8 bits, it requires a huge memory space of about 16.7 million x 3 bytes, making it difficult to put it into practical use. Ta.

The present invention is intended to solve the above-mentioned problems, and its purpose is to provide a high-quality recording device that enables desired color conversion with a simple system configuration.

[Means for Solving the Problems] A recording device of the present invention includes an NTSC signal input means and the N
Y/C separation means inputs the TSC signal and separates the Y signal and C signal; inputs the C signal and separates color difference signals (R-Y signal, B signal
-Y signal); and a color difference demodulation means for outputting the R-Y,
- color difference selection means for inputting the Y signal and outputting one of them; at least two A/D converters for inputting the Y signal and the output of the color difference selection means and performing quantization;
a color conversion processing section that inputs the R-Y signal and B-Y signal quantized by the converter and performs desired color conversion; and the A/D
It is characterized by comprising print data generation means for generating print data using the luminance signal quantized by the converter and the output of the color conversion processing section, and printing the image output by the print data generation means. .

[Example] A full color gradation recording device using the present invention was created. The input image signal is an NTSC signal and a line head is used.
The recording density is 6.0 dat/mm in the main scanning direction, 7.2 dat/mm in the sub-scanning direction, and the number of pixels is 480 in the main scanning direction.
760 in the sub-scanning direction.

The recording screen size is approximately 80 mm x 106 mm.

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 color difference demodulation circuit, 105 is a color difference selection circuit, 106 and 107 are each an A/D converter, 108
is a video memory, 109 is a color conversion processing unit, and 110 is RG.
B output circuit, 111 is a sampling clock generation circuit, 112
113 is a memory address control unit; 113 is a central processing unit CPU;
114 is a print processing unit having a look-up table;
15 is a line head having a drive circuit, and 116 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 chroma signal (C signal). The chroma signal is further processed by the chroma demodulation circuit 1.
04 and is converted into a color difference signal (RY, BY signal). On the other hand, the NTSC signal 101 is also input to a synchronization processing circuit 102, which outputs a horizontal synchronization signal (H synchronization) and a vertical synchronization signal (V synchronization). The H synchronization signal and the V synchronization signal are input to the CPU 113 and the print processing section 114.

The luminance signal is input to A/D converter 106.

The color difference signals (R-Y, B-Y) are input to the color difference selection circuit 105, which selects one of them, and then input to the A/D converter 107.

According to the NTSC signal standard, the maximum luminance signal component is approximately 4.2M.
Contains frequency components up to Hz, color difference signal components are approximately 1.5
Contains frequencies up to MHz.

According to the sampling theorem, a band-limited analog signal is
Complete restoration can be achieved by sampling at a frequency that is more than twice that band, so for a luminance signal, a sampling frequency of 4.2 x 2 = 8.4 8.4 MHz or more is required.
If it is a color difference signal, it will be 1.5×2=3.03MHz or more. There is a big difference in the required sampling frequencies for both, and there is no need to sample at the same frequency.

The frequency of the sampling clock of the luminance signal (f s) is set to 910 times the horizontal synchronization frequency (f h) or the color carrier frequency (f
sc) shall be 4 times.

fs=910fh=4fsc Since fs is about 14.2 MHz, the above-mentioned condition of the sampling frequency of the luminance signal is fully satisfied. The luminance signal is for one frame (760 dat in the horizontal scanning line direction, 48 dat in the vertical direction)
0dat) The CPU 113 sends a control signal to the sampling clock generation circuit 111 and the memory address control unit 112 so that the sampling clock is sampled. On the other hand, the color difference signal is 1 fs
Since it is sufficient to sample at a frequency of /4, that is, fsc (=3.58MHz), the color difference selection circuit 105 is switched at a frequency of 1/4 of fs, and R-Y, at a frequency of 1/2 of fs. B-Y same color difference signals are sampled alternately. This relationship will be explained using FIG. 2. Numbers are repeatedly assigned to each rising edge of fs from the first phase to the fourth phase. Let fs(P) be a waveform obtained by dividing fs (rising at the 1st and 3rd phases and falling at the 2nd and 4th phases), and let fs(SW) be the waveform that rises at the 2nd phase of fS and falls at the 4th phase. A falling waveform. The color difference selection circuit 105 has fs(SW
), select the L level period R-Y signal, and select the H level period B.
-Select Y signal. It is assumed that the A/D converters 106 and 107 operate at the rising edge of the clock, and when the A/D converter 107 is operated at fs(P), the A/D converter 10
7 alternately quantizes and outputs the RY signal and the BY signal every time fs(P) rises.

The sampling clock generation circuit 109 generates sampling clocks fs, f according to the control signal of the CPUI 11.
5 (P), a color difference switching signal fs (SW) is generated and sent to the A/D converters 106 and 107 and the color difference selection circuit 105. The luminance and color difference signals quantized by the A/D converters 106 and 107 are once written into the video memory 108. Data sampled in this manner requires only 1/2 the amount of video memory compared to conventional example (2).

The color conversion processing unit 109 performs two-dimensional table conversion on the two sampled color difference signals, and outputs three new color difference signals.

In other words, two color difference signals are input and second-order matrix transformation is performed to obtain three new color difference signals.

FIG. 3 shows this situation.

The three attributes of color are brightness, hue, and saturation1, and two color difference signals (R-Y, B-Y) express hue and saturation, so two-dimensional table conversion is required. It is possible to perform desired color conversion as much as possible. Compared to performing three-dimensional conversion using R and GlB in conventional example (2), the amount of tables can be significantly reduced. For example, R,G
, B in the case of 8 bits each, conventional example (2) required a table of 224×3 bytes, but in this embodiment, a table of 216×3 bytes was required.
Desired color conversion is possible with a small amount of memory of 3 bytes.

The RGB output circuit 110 inputs the output (RY)'(B-Y)',(G-Y)'' of the color conversion processing unit 109 and the Y input stored in the video memory 106, and outputs the RGB
Convert to data.

R"=Y+ (RY)'G' = Y0 (G-Y) 'B' = Y+ (B-Y)" However, as mentioned above, the color difference signal has only 1/4 the data amount of the luminance signal. Therefore, for the four luminance signals Y, the same (RY)', (B-Y)', and (G-Y)' are used to output RGB data.

In other words, the color difference signal is padded four times and used.

The created print data is sent to the print processing section 114. The print processing unit 114 prints the line head 11 after gamma conversion.
The data is converted so as to be compatible with the No. 5 driver IC, and sent to the line head 115, where it is printed in the main scanning direction.

Data conversion and printing are repeated in this way to print the entire screen.

We have talked about NTSC signal input, but the input signal is Y
/C separate signals may also be used, and the signal flow is exactly the same except that in that case, Y/C separate signal input is required and a Y/C separation circuit is not required.

The color conversion processing section in the embodiment can be configured as a custom IC and hardware, but if the data bus is configured so that it can be directly read by the CPU, the color conversion process can also be performed by software calculation.

In the embodiment, the same color difference signals are used for the four pixels, but a horizontal low-pass filter may be inserted in consideration of aperture distortion and the like.

[Effects of the Invention] As described above, according to the present invention, it is possible to perform desired color conversion with a simple system configuration, and to provide a recording device with high image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing a system according to the present invention. FIG. 2 is a diagram for explaining sampling of color difference signals. FIG. 3 is a diagram for explaining color conversion in this embodiment. FIG. 4(a) is a diagram for explaining color conversion of conventional example (1). FIG. 4(b) is a diagram for explaining color conversion of conventional example (2). 101...NTSC signal 102...Synchronization processing circuit 103...Y/C separation circuit 104...Color difference demodulation circuit 105...Color difference selection circuit 106.107...A/D converter 108
... Video memory 109 ... Color conversion processing section 110 ... RGB output circuit 111 ... Sampling clock generation circuit 112
... Memory address control unit 113 ... CP
U 114...Print processing section 115...Rhein Rad 116...Print mechanism and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizo Suzuki 1 person Line head Figure 1 W, 1 phase 2 Phase 3 Phase 4 Phase (1st phase) Figure 2 Figure 3 Figure 4 (a) Figure 4 (b)

Claims (1)

[Claims] a composite video signal (hereinafter referred to as an NTSC signal) input means, a Y/C separation means for inputting the NTSC signal and separating a luminance signal (Y signal) and a chroma signal (C signal), and inputting the C signal and inputting a color difference signal. color difference demodulation means for outputting (RY signal, BY signal); color difference selection means for inputting the RY and BY signals and outputting either; and the Y signal and the color difference selection means. two analog-to-digital converters (hereinafter referred to as A/D converters) that input the output of the A/D converter and perform quantization;
a color conversion processing section that inputs the R-Y signal and B-Y signal quantized by the D converter and performs desired color conversion;
It is characterized by comprising print data generation means for generating print data using the luminance signal quantized by the D converter and the output of the color conversion processing section, and printing the image output by the print data generation means. A printing device.