JPH04346576A - Color document reading 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]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color document reading device capable of selectively outputting color image data and monochrome image data.

0002

[Background Art] In recent years, document reading devices have become colorized, and there is a desire for one that can faithfully reproduce color.However, at the same time, there are still many black and white documents, and selective output of black and white image data is desired. .

An example of the above-mentioned conventional color document reading device will be described below with reference to the drawings.

FIG. 3 shows a block diagram of a conventional document reading device. In FIG. 3, 100R, 100G,
100B is an A/D converter that reads a document and converts the color-separated RGB signals into A/D. Reference numeral 101 indicates a background removal unit for removing the background component of the original, and reference numeral 102 indicates a CCM (computer color matching) table, which performs color correction and complementary color conversion. A color data selector 103 selects a color signal to be output. 104 is a data selector that selects data to be output based on a mode select signal; 105 is an averaging circuit that adds RGB data and averages it to 1/3 to create monochrome image data; 106 is an averaging circuit that multiplies monochrome image data; 107 is a monochrome threshold setting circuit for converting color image data into multi-values;
08 is a threshold selector that selects a threshold value in accordance with a mode select signal; 109 is a multi-value conversion circuit that multi-values the image data selected by the selector 104 using the threshold value selected by the threshold selector 108; be.

The operation of the conventional color document reading device configured as described above will be explained below.

First, a mode select button (not shown)
When the color mode is selected by the color mode select signal, the data selector 104 selects the data from the color data selector 103 and transfers it to the multi-value conversion circuit 109, and the threshold selector 108 selects the data from the color threshold. The threshold data from the value setting circuit 107 is transferred to the multi-value conversion circuit 109. That is, the RGB signals obtained by reading the original and color-separating the original are sent to the A/D converters 100R and 100.
The Y, M, C, and BK density data are converted into digital data in each of G and 100B, the background is removed in the background removal unit 101, and color correction and complementary color conversion are performed in the CCM table 102.The Y, M, C, and BK density data are transferred one color at a time to the data selector. The signal is inputted to the multi-value conversion circuit 109 via the color threshold setting circuit 104, and multi-value conversion is performed using the threshold value from the color threshold setting circuit 107.

On the other hand, when the monochrome mode is selected by the mode select button, the data selector 104 is activated by the averaging circuit 10 in response to the monochrome mode select signal.
Select the data from 5 and transfer it to the multi-value conversion circuit 109,
The threshold selector 108 selects the threshold data from the monochrome threshold setting circuit 106 and transfers it to the multi-value conversion circuit 109. That is, the R, G, and B signals obtained by reading the original and color-separating the original are sent to the A/D converters 100R, 100G,
Each of the 100B is converted into digital data, and an averaging circuit 105 performs averaging processing to add RGB data to 1/3, and the monochrome image data is inputted to a multi-value conversion circuit 109 via a data selector 104. , is multi-valued using the threshold value from the monochrome threshold setting circuit 106 (see Japanese Patent Laid-Open No. 1-296775).

[0008]

[Problems to be Solved by the Invention] However, when this conventional method is applied to a device that outputs image data to a CRT, it is possible to read the original and color-separate linear R, G, B
Since monochrome image data from the signal is obtained by adding and averaging R, G, and B data, it is not suitable for human visual characteristics.

[0009] Also, in order to display on a CRT, R, G, B
Since the data must be averaged and output after gamma correction, for example, to obtain accurate monochrome image data with 256 gradations, 16 bits are required at the input of the gamma correction circuit, so monochrome image data is created. The circuit that does this requires 16 bits of output, and has the problem of becoming a large circuit.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems of the conventional color document reading device, and an object of the present invention is to provide a color document reading device having a simple configuration and capable of expressing appropriate monochrome shading in accordance with human visual characteristics. It is something to do.

[0011]

[Means for Solving the Problems] The present invention reads an image and separates it into R (red), G (green), and B (blue) colors.
, B video signal, and the R, G, B output video signals of this γ correction means are approximately 0.30:0.5.
Signal addition means for weighted addition in a ratio of 9:0.11;
The apparatus further includes a signal switching means for selecting one of the R, G, and B output video signals of the γ correction means and the black and white video signal produced by the signal addition means.

0012

[Operation] In the present invention, an image is read and separated into R, G, and B colors, and the R, G, and B video signals, which have been γ-corrected by the γ-correction means, are converted into approximately 0.30:0.59 by the signal addition means. The signals are weighted and added at a ratio of 0.11, and the signal switching means selects and outputs one of the R, G, and B output video signals of the γ correction means and the black and white video signal produced by the signal addition means. As a result, when selecting a monochrome video signal, a video signal capable of expressing appropriate monochrome gradation matching human visual characteristics can be obtained with a simple configuration.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a color document reading device according to an embodiment of the present invention. In Figure 1, 1 indicates R''' and G'' which are obtained by reading the image and separating the colors.
', B''' color image sensor outputting signals, 2
is an A/D converter that converts the output signal of the color image sensor 1 from analog to digital; 3 is an A/D converter that converts the output signal of the color image sensor 1 from analog to digital; 3 is an A/D converter that converts the R", G", and B" signals from the A/D converter 2 into R', G', B'
4 is a CRT-γ as an example of a γ correction means for correcting the voltage-luminance characteristics of the CRT for the R', G', and B' signals color-corrected by the color correction circuit 3;
correction circuit; 5, 6, and 7 are multipliers with coefficients a, b, and c as multiplication coefficients; 8 is output d, e of multipliers 5, 6, and 7;
, f to create a luminance signal (hereinafter referred to as Y signal); 9 is a mode switch for the operator to select a reading mode; 10 is a CRT-γ correction circuit based on the signal from mode switch 9; This is a signal switching device as an example of a signal switching means for selecting the R, G, and B signals from adder 8 and the Y signal from adder 8.

FIG. 2 is a standard luminous efficiency curve diagram illustrating the Y signal output from the adder 8.

The operation of the color document reading device configured as described above will be explained below.

First, a document is read by the color image sensor 1 and color-separated into R''', G''', and B'.
When the R'', G'', and B'' signals are input to the A/D converter 2 and converted into digital signals, the color correction circuit 3 performs predetermined 3×3 color correction masking. Masking calculation processing is performed using coefficients to determine the color and CR of the original.
R optimized so that the colors displayed on T are the same
', G', and B' signals are input to the CRT-γ correction circuit 4. The CRT-γ correction circuit 4 inputs R, G, and B signals whose voltage-luminance characteristics of the CRT have been corrected to the multipliers 5, 6, and 7 and the signal switch 10.

Multipliers 5, 6, and 7 each have d≈R×0
．． 30, multiplies e≒G×0.59 and f≒B×0.11, and adder 8 performs these additions to obtain Y=d+e.
+f=R×0.30+G×0.59+B×0.11 is output.

Next, before starting reading, the operator selects and sets a desired mode from among the color mode and monochrome mode with the mode switch 4. When the color mode is selected with the mode switch 4, the signal switch 10 outputs the R, G, and B signals from the CRT-γ correction circuit 4 by switching them dot-sequentially.

Further, when the black and white mode is selected by the mode switch 4, the Y signal from the adder 8 is output. At this time, the Y signal is a mixture of signals with color distribution approximately as shown in the standard luminous efficiency curve diagram shown in FIG. 2, and is suitable for human visual characteristics. And this Y
Since the signal is calculated from the CRT-γ corrected R, G, and B signals, the bit precision of the calculation is, for example, in the case of 256 gradations, the output of the adder 8 only needs 8 bits, so the circuit that creates the black and white video signal can be made small.

Here, in this embodiment, R of the γ correction means,
G, B output video signals are practically 0.30:0.59:0
．． As an example of a signal addition means for performing weighted addition with a ratio of 11, the Y signal was calculated using multipliers 5, 6, 7 and adder 8, but it is of course possible to use other means to perform the same function. .

As described above, the mode switch 4 allows the operator to set the reading mode, and the multipliers 5, 6, 7 and adder 8 are provided after the CRT-γ circuit 4 to create the Y signal. When the mode switch 4 is set to black and white mode, by selecting the Y signal, appropriate monochrome shading can be expressed that matches human visual characteristics.

[0023]

As described above, the present invention provides a signal addition means for producing a black and white video signal after the γ correction means, and a signal switching means after that, so that the R and R of the output of the γ correction means can be adjusted.
By making the G and B signals and the output of the signal addition means selectable, it is possible to obtain a color original reading device with a simple configuration that can express monochrome shading suitable for human visual characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a color document reading device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the operation in the same embodiment.

FIG. 3 is a block diagram of a conventional color document reading device.

[Explanation of symbols]

1 Color image sensor 2
A/D converter 3
Color correction circuit 4 CR
T-γ correction circuit 5, 6, 7 Multiplier 8 Adder

Claims (1)

[Claims] Claim 1: Read the image to read R (red), G (green), and B.
(Blue) A color image sensor that obtains R, G, and B video signals separated into colors, a γ correction means that γ corrects the R, G, and B video signals, and R, G, and B outputs of this γ correction means. Signal addition means for weighting and adding video signals substantially in a ratio of 0.30:0.59:0.11, and R, G, B output video signals output from the γ correction means or from the signal addition means. 1. A color document reading device comprising: signal switching means for selecting a black and white video signal to be output.