JPH0411458A - Picture reader - Google Patents

Abstract

PURPOSE:To prevent production of pseudo color without deteriorating resolution by applying band limit only to a color difference signal and outputting the result. CONSTITUTION:A C-signal component of a composite color video signal is subjected to band limit by a narrow band BPF 71 and the result is added to a Y signal, while C signal component of a Y/C separation output is extracted via a broad band BPF 81. Thus, the color blur of the monitored video image is reduced, a group delay of the BPF 81 is decreased, the transmission characteristic of the Y signal delay 73 is improved and a Y signal band and waveform distortion characteristic is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention enables color reading by reading an image original while switching between three primary colors such as R (red), G (green), and B (blue). The present invention relates to an image reading device.

[Summary of the invention]

The present invention reads an image document by sequentially emitting light sources of three primary colors while moving a line sensor including a plurality of light receiving cells arranged in a direction substantially perpendicular to the cell arrangement direction. By forming luminance signals and color difference signals from color component signals obtained based on line sequential color signals of each color, and outputting only the color difference signals after band limiting, it is possible to generate pseudo color signals without deteriorating resolution. This is to prevent this from occurring.

[Conventional technology]

As conventional image reading devices, there are known scanner devices that read an image original with an image sensor such as a CCD and output the obtained digital image data through a digital interface such as 5C3I or R3232C1GPTB. In order to output this read image in the form of visual expression, especially to display it on a monitor, it is necessary to use a computer device, etc., which results in a large-scale system and requires time for signal processing. Therefore, responsiveness is relatively poor. For this reason, conventional image reading devices such as scanner devices are unsuitable for use in presentations at exhibitions, lectures, and the like.

Therefore, the present applicant reads an image original, stores it in an image memory, and repeats it from the image memory in synchronization with a horizontal scanning signal and a vertical scanning signal of a television signal of a predetermined format, for example, a so-called NTSC television signal. For example, the specifications and drawings of Japanese Patent Application No. 183330, Japanese Patent Application No. 1-83696, and Japanese Patent Application No. 1-83697 describe an image reading device that outputs a video signal for displaying a still image by reading the image. It is proposed in According to such an image reading device, an original image can be visualized and displayed with good responsiveness in a short time.

[Problem to be solved by the invention]

By the way, when a color document is read by the above-mentioned image reading device, while a line sensor consisting of a plurality of light receiving cells arranged in the main scanning direction is moved in a sub-scanning direction that is approximately perpendicular to the main scanning direction, A light source of three primary colors, for example, R (red), G (green), and B (blue), is emitted sequentially, and an image original is read using the light of each of these colors.
A so-called line-sequential color one-way system can be considered. In this case, if the line sensor is continuously moved, R,
Since the position of the line sensor in the sub-scanning direction at each of the G and B light emission timings is shifted, there is a drawback that so-called false color or color shift occurs when reading an image original such as a fine striped pattern.

Therefore, it is conceivable to simply band-limit the color video signal using a low-pass filter (LPF) to lower the resolution and prevent the generation of false colors.
This is not preferable because the basic performance of resolution will deteriorate.

The present invention has been made in view of these points, and R
An object of the present invention is to provide an image reading device capable of preventing the generation of false colors without deteriorating resolution in the case of a line sequential reading method in which three primary colors such as , G, and B are switched and read line by line.

[Means to solve the problem]

The image reading device according to the present invention moves a line sensor including a plurality of light-receiving cells arranged in the main scanning direction in a sub-scanning direction substantially orthogonal to the main scanning direction, while emitting light sources of each of the three primary colors. A color image reading means for sequentially emitting light of each color and reading an image original using light of each color, and a luminance signal and a color difference signal from color component signals for each color obtained based on line sequential signals of each color from this color image reading means. The above-mentioned problem is solved by comprising means for forming a color difference signal, and means for band-limiting and outputting only this color difference signal.

[For production]

Since band limitation is applied only to the color difference signal and not to the luminance signal, pseudo colors can be reduced without deterioration of resolution.

〔Example〕

First, FIG. 1 is a block circuit diagram showing the basic configuration of essential parts of an embodiment of an image reading device according to the present invention.

In the main part configuration of the image reading device shown in FIG. 1, an R (red) signal r, a G (green) signal g, and a B (blue ) The signal is R, , for each line as described later.
Based on the R, G, and B line sequential signals read after G and B are switched, the timing is converted to correspond to the horizontal (H) synchronization signal and vertical (V) synchronization signal of the television video signal in a predetermined formant. This is the R, G, B component color signal. That is, when reading a color image original, a line sensor consisting of a plurality of light receiving cells arranged in the main scanning direction is moved in the sub-scanning direction, which is approximately perpendicular to the main scanning direction, to read R, G, By sequentially emitting light from each B color light source and irradiating the image document with each color of light, R, G, and B line sequential signals are obtained, and these are written in an image memory such as a frame memory. , R, G by reading in timing with the H synchronization signal and ■ synchronization signal of the predetermined format.
, B component color signals r, g, b.

These color signals r, g, and b are transmitted to the resistance matrix circuit 2.
1 at a predetermined ratio, the luminance (Y
) signal y is obtained. That is, resistance matrix circuit 2
If the addition ratio of each signal determined by each resistance value of 1 is α, β, and γ, the Y signal y is as follows: y=αr+βg+1 b (1). Here, the normal luminance signal y in NTSC system 2 is
Approximately, the ratios should be α=0.30, β-0.59, and r=0.11, and y=0.30r+0.59g+0.11b·-(2). The Y signal y from this resistance matrix circuit 21 is
The polarity of the signals is inverted by an inverter amplifier 23 and sent to adders 24 and 25, respectively. Each of these adders 24 or 25 is constructed by connecting resistors having the same resistance value in parallel. In the adder 24, the inputted R signal r is sent through a unit gain buffer amplifier 26, and the Y signal y is subtracted from the R signal r to produce an R-Y color difference signal (ry). is obtained.

In the adder 25, the human-powered B signal is sent via a unit gain buffer amplifier 28, and the Y signal y is subtracted from the B signal to obtain a B-Y color difference signal (b-y). The R-Y color difference signal (ry) from the adder 24 is passed through a low-pass filter (LPF) 41 to the B-Y color difference signal (ry) from the adder 25.
The color difference signals (by) are each sent to the color adjustment circuit 30 via the LPF 42. These LPF41.4
2, band limitation is performed to prevent the above-mentioned false color from occurring. In addition, the color adjustment circuit 3G includes
The Y signal y from the resistance matrix circuit 21 is transmitted to the LPF
The signal is supplied via a delay circuit 43 having a delay time corresponding to the amount of group delay of the signal by 41 (or 42).

The color adjustment circuit 30 generates an R, G, B combo similar to that input to the circuit of FIG. 1 based on these Y signal y and each color difference signal (ry) and (by). This is for forming two-tone color signals r, g, and b (however, the color difference components are band-limited). That is,
The R-Y color difference signal (ry) from the LPF 41 is sent to the unit gain buffer amplifier 31 and inverter amplifier 32 of the color adjustment circuit 30, and the BY color difference signal (b-y) from the LPF 42 is sent to the unit gain buffer amplifier 31 and inverter amplifier 32 of the color adjustment circuit 30. The signal is sent to a buffer amplifier 33 and an inverter amplifier 34. The Y signal y from the delay circuit 43 is sent to a unit gain buffer amplifier 44 and an inverter amplifier 38 of the color adjustment circuit 30. R-Y color difference signal (ry
) is sent to the adder 35 and added to the Y signal y from the buffer amplifier 44 to obtain a red (R) component signal r, which is sent to the buffer amplifier 4 with unity gain.
6. Next, the inverter amplifier 32
(y-r) is the polarity-inverted R-Y color difference signal from
and the polarity inverted B-Y color difference signal (y-b) from the inverter amplifier 33 are added by the adder 36.
(2y-r-b) is obtained, which is sent to the addition H37 and added to the polarity inverted Y signal -y from the inverter amplifier 33 to become (y-r-b), which is the green (G) component. The signal g is taken out via a buffer amplifier 47 with unity gain. Next, the B-Y color difference signal (b-y) from the buffer amplifier 34 is sent to the adder 3
5, it is added to the Y signal y from the buffer amplifier 44, resulting in a blue (B) component signal, which is extracted via the buffer amplifier 48 with unity gain.

In this way, RSG and B component color signals r, g, and b are obtained.

According to the above configuration, the R, G, and B lines can be read in sequence, which may cause false colors.
The G, B component color signals r, g, b are expressed as luminance (
Separate into Y) component and color difference (C) component, band limit is applied only to color difference (C) component by LPF41.42,
R, (1
By forming a B component color signal, false colors (or color shifts) can be reduced without deteriorating the resolution of the monitored video.

Next, the overall schematic configuration of an image signal reading device to which the above-described embodiment of the present invention is applied will be described with reference to FIG.

In FIG. 2, an image reading head 2 for reading an image original CD placed on an original placing table I includes a light source 3
, a multi-lens array 4 and a CCD line sensor LS are provided so that light #3 irradiates the image original CD and reflected light from the image original GD is received by the line sensor LS via the multi-lens array 4. It has become.

This line sensor LS is configured by, for example, 1728 CCD light receiving cells arranged in a straight line along the main scanning direction, and for example, in the main scanning direction (vertical direction on the display screen) with respect to the image original GD. When reading one line, the light source 2 sequentially emits light corresponding to RlG and B of the three primary colors, so that the image signals of the three primary colors are transmitted line-sequentially (in this case, the line is vertical to the screen). direction). The output from the line sensor LS of the image reading head 2 is amplified by the amplifier 5 and
It is sent to the D converter 6 and the R signal, G signal, and B signal are sent to 1 in this order.
Each line is converted into digital image data of, for example, 8 bits per pixel.

This digital image data is processed by the shading correction circuit 7.
The unevenness in the gradation expression characteristics caused by unevenness in the light amount of the light source 3, unevenness in the sensitivity of the line sensor LS, etc. is corrected. The output from the shading correction circuit 7 is M
The signal is sent to the TF correction circuit 8 and subjected to MTF correction, that is, contour enhancement correction. The output from the MTF correction circuit 8 is output after timing adjustment is performed by a data buffer 9 such as a so-called FIFO, and is stored in an image memory 10. Here, digital image data obtained from the line sensor LS via the amplifier 5 and A/D converter 6 is sent to the light amount detection circuit 11, so that
The amount of light from the light source 3 is detected and supplied to the system control circuit 12, and the system control circuit 12
Based on this light amount detection signal, the light source drive circuit 13 is controlled so that the light source 3 has an appropriate amount of light. The system control circuit 12 also controls a line sensor drive circuit 14, a motor drive circuit 15, etc., and the line sensor drive circuit 14 reads and drives the line sensor LS in the image reading head 2, and controls the motor drive circuit 15. rotates the motor 16 that moves the image reading head 2 in the sub-scanning direction.

Next, digital image data r for each color of R, G, and B
, g, and b are stored in the image memory 10 so that writing/reading is controlled by control signals from a memory control circuit 18. That is, at the time of writing, since the light-receiving cell arrangement direction (main scanning direction) of the line sensor LS is the vertical direction of the screen, the line sensor LS is moved in the horizontal direction (sub-scanning direction) for each vertical line. (scan), each line of R and GXB is sequentially written. When reading from the image memory 10, the memory control circuit 18 uses a predetermined television signal format (
For example, the R, G,B
digital image data r, g, b are read out in parallel and output.

The R, G, and B digital image data r, g, and b read out from the image memory 10 are converted into analog signals (also shown as r, g, and b) by the D/A converter 19, respectively. It is sent via the buffer 20 to the circuit section for preventing false colors as described above, but in this specific example, masking processing (color correction or color correction processing) as described later is also performed at the same time. Therefore, the signals are first sent to resistance matrix circuits 21 and 22 for forming two types of brightness (Y) signals y and y2, respectively.

The luminance signal y1 from the resistance matrix circuit 21 has its polarity inverted by the inverter amplifier 23 to become -yl, and is sent to the adders 24 and 25. The analog R image signal r from the buffer 20 is supplied to the adder 24 via a unit gain buffer amplifier 26, and an RY color difference signal (ry+) is obtained from the adder 24. This R-Y
The color difference signal (ry+) is a low pass filter (LPF) 41
The signal is supplied to the color adjustment circuit 30 via. Also,
The adder 25 is supplied with the analog B image signal from the buffer 20 via a unit gain buffer amplifier 27, and the adder 25 receives the B-Y color difference signal (b-
yl) is obtained. This B-Y color difference signal (by+) is L
The signal is supplied to the color adjustment circuit 30 via the PF 42. Furthermore, the luminance signal y2 from the resistance matrix circuit 22 is passed through the unit gain buffer amplifier 28 to each of the above-mentioned LPFs.
The signal is sent to the color adjustment circuit 30 through a delay circuit 43 such as a delay line having a delay time equal to the signal delay time at 41.42. This color adjustment circuit 30
is based on these color difference signals (r-yl), (by+) and luminance signal y2, r = r+y2 )'+ g'=23'+ (rfb+yz) b""' b+ Y z Y + ・・
・R, G, B signals like (3) r+, g', b'
is formed to perform masking processing.

This allows masking processing (color correction, color correction processing)
can be performed by analog linear calculation using resistance addition of input analog signals at a predetermined ratio, and with a relatively simple circuit configuration, masking calculation with higher precision than digital calculation can be realized. In addition, as described in the explanation of Fig. 1, only the color difference signals from each adder 24.25 are subjected to band limiting processing by LPF41.42 to lower the resolution, and the luminance signal is simply delayed and not band limited. Therefore, deterioration in the resolution of the luminance component can be suppressed even if the generation of the above-mentioned pseudo colors is prevented.

Next, the R, G, B signals (r'
, g', b") are R, G, B signal output terminals 51.5 via the R, G, B line driver (amplifier) 50.
2.53 respectively. Further, the R, G, and B signals from the color adjustment circuit 30 are added and combined at a predetermined ratio by the resistance matrix circuit 60 to become a luminance (Y) signal. The polarity of this Y signal is inverted by an inverter amplifier 61 and sent to adders 62 and 63, respectively.
The adder 63 subtracts the Y signal from the B signal (b'') from the color adjustment circuit 30 to obtain the B-Y color difference signal.Adder 62
The R-Y color difference signal from is sent to the modulator 66, and the adder 6
The BY color difference signal from 3 is sent to the modulator 67, so that the subcarrier of phase 90e from the subcarrier generation circuit 68 is the R-Y color difference signal, and the subcarrier of phase 0° is the B-Y color difference signal. Equilibrium modulated. By mixing these modulated output signals in an adder 69, a carrier color signal, a so-called chroma (C) signal, whose subcarriers are quadrature two-phase modulated (orthogonal double modulation) with each color difference signal is obtained. This C signal is a narrow band BPF (band pass filter)
71 and a broadband BPF 81.

The BPF 71 is a narrow band filter that has a pass band of, for example, about IMHz and limits the signal component to 0.5 MHz or less in order to form a C (chroma) signal component of a composite color video signal. . That is, the Y (luminance) signal from the resistance matrix circuit 60 is sent to the adder 75 via the delay circuits 73 and 74, and the BPF 7
1 to form a composite color video signal, and this composite color video signal is taken out from an output terminal 77 via a driver amplifier 76. Here, the delay times of the delay circuits 73 and 74 are set according to the group delay amount of the BPF 71. On the other hand, the BPF 81 is provided for outputting the C signal when separating and extracting the Y signal and the C signal, and has a pass band of, for example, about 3 MHz or more, and a signal component of at least 1.5 MHz. This is a wideband filter that can pass the . The output from this BPF 81 is taken out from the output terminal 83 via the driver amplifier 82, and the Y signal that forms a pair with this is taken out from the output terminal 85 from the delay circuit 73 via the driver amplifier 84. It has become. That is, since the group delay amount of the BPF 81 is small, the Y signal is taken out from the delay circuit 73 with a delay time corresponding to this.

In this way, the C signal component of the composite color video signal is band limited by the narrow band BPF 71 and added to the Y signal, but the C signal component in the case of Y/C separated output is added to the Y signal via the wide band BPF 81. Since the Y-signal delay section (delay circuit 73) is taken out, it is possible to reduce color smearing (color stains) in the monitored image, and also to reduce the amount of group delay of the BPF 81, improving waveform transmission characteristics in the Y signal delay section (delay circuit 73). However, the band and waveform distortion characteristics of the Y signal are improved.

〔Effect of the invention〕

As is clear from the above explanation, according to the image reading device according to the present invention, the line sensor is moved with respect to the color image original, and each color is switched and read, and the line sequential signal is obtained from the line sequential signal of each color. By forming a luminance signal and a color difference signal based on a color component signal, and outputting a band-limited signal only for the color difference signal, it is possible to prevent the occurrence of false colors without deteriorating resolution.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing essential parts of an embodiment of an image reading device according to the present invention, and FIG. 2 is a block circuit diagram schematically showing a specific example of the overall configuration of the image reading device according to the present invention. . 3.61...Inverter amplifier 4.25.62
．． 63.69.75...Adder O...1.・
Color adjustment circuit 1.42...LPF (low pass filter) 3
．． 73.74...Delay circuit LS...Line sensor CD...Image original ■......Original table 2... Image reading head 3...
...Light source 6...A/D converter 10...Image memory 12...System control circuit 15...
... Motor drive circuit 16 ... (head feeding) motor 18 ...
...Memory control circuit 19...D/A converter

Claims (1)

[Claims] A line sensor consisting of a plurality of light-receiving cells arranged in the main scanning direction is moved in the sub-scanning direction substantially orthogonal to the main scanning direction, and a light source of each of the three primary colors is sequentially emitted. a color image reading means for reading an image original using light of each color; and a color component signal for each color obtained based on line sequential signals of each color from the color image reading means to form a luminance signal and a color difference signal. and means for band-limiting and outputting only the color difference signal.