JPS62161256A - Picture reader - Google Patents

Abstract

PURPOSE:To attain reading with high resolution by binarizing a signal read by the 2nd picture element array and ANDing it with a signal read by the 1st picture element array in case of the high definition picture. CONSTITUTION:A photosensitive picture element array with a small picture element pitch in a read section reads a black/white picture and 3-array of the photosensitive picture element arrays having a large picture element pitch read R, G, B picture respectively. Then the maximum values of the both are compared and when the difference is larger than a reference level, it is discriminated that the picture is a high definition picture. Then the signal read in color is binary-coded and ANded with a signal read by the photosensitive picture element array with a smaller picture element pitch, then the high definition picture is processed by 7 colors K, G, B, C, M, Y, K and the line density is much improved.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is a method for reading images on a document using a photosensitive pixel row formed by arranging a plurality of photosensitive pixels in a row that generates electric charge in response to an optical signal. The present invention relates to an image reading device that performs.

"Prior Art" Solid-state imaging using a CCD array, etc. is used in a device that reads an image on a document, converts it into an electrical signal and stores it, or performs predetermined signal processing and records the image on paper. devices are widely used. Among these, a conventional solid-state image sensor used for reading color images will be explained with reference to the drawings.

FIG. 11 shows a plan view of essential parts of an array of color solid-state image sensors.

This solid-state image sensor has photosensitive pixels 9 that generate electric charge in response to optical signals arranged in a row, and color filters in three colors: cyan (C), green (G), and yellow (Y). They are arranged alternately. As a result, each color is read, and the image signals thus obtained are processed and recorded.

An image reading device using such a solid-state image sensor is described in, for example, Japanese Patent Laid-Open No. 86361/1983.

In the case of this image reading device, the reading pixels are substantially composed of a set of three C, G, and Y pixels. Therefore, there is also a drawback that the pixel size S in the column direction becomes relatively large.

Further, FIG. 12 shows a block diagram of another type of image reading device.

This image reading device uses a dichroic prism, which receives reflected light 1 from the surface of a document through a lens 2, separates it into lights using a prism 3, and sends it to CCD arrays 4 to 6, which perform photoelectric conversion for each color. Make it incident. C.C.
The structure of the D array is similar to that shown in FIG. 8, but without color filters. Therefore, compared to the one shown in FIG. 11, the pixel size S in the column direction is reduced to one-third, which has the advantage of improved resolution.

Such an image reading device is disclosed in Japanese Patent Application Laid-Open No. 59-1619, for example.
It is described in Publication No. 70.

However, in this case, since the reflected light from the original is divided into three parts using a prism, the amount of light is significantly attenuated, and there is also the problem that the amount of light irradiated onto the original must be increased.

For example, considering blue light, which has the lowest sensitivity due to the characteristics of a CCD sensor, its sensitivity is as shown in Figure 13.
This results in approximately one-fifth of the sensitivity to white light. That is, RSG has a relative sensitivity of 0.9, B has a relative sensitivity of 0.5, and a total of 2
．． 3, and the case of only B is 0.5, so the ratio is about 5
It will be 1 to 1.

Assuming that the specific transmittance of the dichroic prism is 0.7, reading a blue image requires 1/(0,2XO,7) times, or 7 times, the amount of light compared to reading a white image. .

"Problems to be Solved by the Invention" However, it is not practical to increase the amount of light illuminating the document in this way, and it is also undesirable because it increases the power consumption and heat generation of the reading device. On the other hand, in order to increase the substantial amount of light received by the photosensitive pixel, it is possible to increase the area of the photosensitive pixel, but this inevitably results in a decrease in resolution.

If we focus on the content of the original image, for example, if it contains text or line drawings, high resolution is required, but there is little requirement for precision in the density and color tone of individual lines. .

On the other hand, for color photographs, etc., the read signals are required to be processed in multiple gradations so that the shades of color can be reproduced as faithfully as possible, but text and line drawings do not require any resolution.

If we call an image like the former a high-definition image and an image like the latter a high-gradation image, it would be unreasonable to process both images using the same image reading device under the same conditions. It can be said.

Note that methods for determining and processing whether an image on a document is a high-definition image or a high-gradation image are described in, for example, Japanese Patent Laid-Open Nos. 59-156069 and 59-11067.
It is stated in the No.

However, both are intended for reading devices for monochrome images, and do not mention reading color images.

The present invention has been made with attention to the above points, and an object of the present invention is to provide the following image reading device.

(2) If the original is a high-definition image, it should be read at high resolution, and if the original is a high-gradation image, it should be read at high gradation.

2. Reading a color image requires several times the amount of light compared to reading a black and white image.

However, color images generally do not require as high resolution as black and white images. Therefore, the area of a photosensitive pixel for reading a color image is made larger than the area of a photosensitive pixel for reading a monochrome image, so that color images can be read with a lower amount of light.

"Means for Solving the Problems" The image reading device of the present invention includes a reading section including a plurality of photosensitive pixel rows formed by arranging a plurality of photosensitive pixels that generate charges in response to optical signals; and a signal processing section that processes a signal obtained by reading the projected image of the document onto the reading section, in which at least one of the photosensitive pixel rows of the reading section is a pixel in the column direction of the photosensitive pixels constituting it. pitch,
The pixel pitch in the column direction is selected to be smaller than the pixel pitch in the column direction of the photosensitive pixels in the other photosensitive pixel columns, and the photosensitive pixel column with the small pixel pitch is the first pixel column, and the photosensitive pixel column with the large pixel pitch is the second pixel column. A color filter having a predetermined spectral transmittance is disposed in each photosensitive pixel constituting the second pixel column when the pixel column is arranged as a column. a comparison and determination circuit that compares the signal obtained by reading with the second pixel column and determines whether the image is a high-definition image or a high-gradation image, and from the determination result,
If the image is a high-definition image, the signal read by the second pixel row is binarized and the logical product is calculated with the signal read by the first pixel row. If the image is a high-gradation image, The present invention is characterized in that a selection circuit is provided which converts the signal read by the second pixel column into a halftone image signal and outputs it to a subsequent circuit.

"Operation" In this way, a plurality of photosensitive pixel columns are provided, and the pixel pitch in the column direction of at least one of them is selected to be smaller than that of the other pixel columns. By comparing the read signal of the photosensitive pixel row with the small pixel pitch and the read signal of other photosensitive pixel rows, it is possible to determine whether the image is a high-definition image or a high-gradation image.

Then, color reading is performed using the photosensitive pixel row with the larger pixel pitch, and a halftone output button is determined from the signal.

On the other hand, in the case of high-definition image processing, the signals read in color are each binarized and then ANDed with the signals read by a photosensitive pixel array with a smaller pixel pitch. For example, KSG, B5C5M, Y
, can be processed in seven colors, and the line density can be extremely high.

"Embodiment" (Explanation of Block Diagram) FIG. 1 is a plan view of essential parts showing an embodiment of an image reading apparatus of the present invention, and FIG. 2 is a block diagram showing the overall configuration thereof.

In FIG. 2, this image reading device includes a reading R12 in which, for example, four photosensitive pixel rows 11 are provided on a substrate 10, and a signal processing unit 13 that processes signals read by this reading unit 12.
It has

Each photosensitive pixel row 11 includes a pixel row W for reading a black and white image, a pixel row R for reading a red (,R) image,
Pixel row G for reading green (G) pixel Q and blue (B
) pixel row B for reading images.

The signals read in each photosensitive pixel column are sent to the buffer amplifier 14.
The signal is then transferred to the signal processing section 13 via.

When reading an image on a document, its projected image is not read simultaneously by these photosensitive pixel arrays.

When focusing on a specific portion of the projected image that has the same width as the pixel row 11, that portion moves at a constant speed in the direction of arrow 16 in the figure. Each photosensitive pixel row 11 sequentially reads this and photoelectrically converts it. Therefore, in order to simultaneously process the output signals of the photosensitive pixel columns that read the same portion of the projected image, it is necessary to provide a memory that delays the output signal of the photosensitive pixel column that was read first by a certain period of time.

(Reading Unit) FIG. 1 shows an example of arrangement for mounting four photosensitive pixel columns and such a memory 15 on one substrate.

Here, the pixel row W is called the first photosensitive pixel row, and the pixel row R
, G, and B will be referred to as the second photosensitive pixel array. Each pixel column is indicated by the symbols W, R, G, and B in the figure. In this example, the size parameters of the relationship between each photosensitive pixel and the photosensitive pixel rows were set as follows. The size parameters (vertical and horizontal dimensions) of a single photosensitive pixel are shown in an enlarged view in FIG.

a W= b w= 7 [μrr+) ac=bc=2
xaw=14 [μm] dwc=28 Ct-tm'
) Dl=bc+dwc=42 [μm) D2=14
Cμm] D3=56Cμm] That is, the pixel pitch aw in the column direction of the pixel column w0:)g and the pixel size bw in the direction orthogonal to the column direction are both equal, and these are different from other pixel columns R and G. , B is selected to be I, which is half the pixel pitch aC and pixel size bc. Furthermore, the relationship between each photosensitive pixel column is as follows when compared with the pixel size bc of the second photosensitive pixel column.

Distance between pixel row W and pixel row R; Di bc=28 Cμm)=(2XbC) Distance between pixel row R and pixel row G; D2-bc=0 Distance between pixel row G and pixel row B; D3-bc=42 Cpm] = (3xbc) Assuming that the projected image moves in the direction of the arrow 16 explained in FIG. Desired.

Memory for pixel row R: (Di/bc)-1=2 (book) Memory for pixel row G; ((DI+D2)/bc)-1=3 (book) Memory for pixel row daily use; ((D1+D2+D3)/bc ) - 1 = 7 (Book) In the final stage of each memory 15, a shift register is provided for latching the signal for l life, and in the example shown in the figure, 1 is added to the result of the above equation. This means that the added memory has been allocated.

The signals read from each photosensitive pixel column are transferred to the signal processing section 13 via the buffer amplifier 14, as described above.

In addition, in this embodiment, the number of effective photosensitive pixels in the pixel row W is 4.
The number of pixels was 800, and the number of effective photosensitive pixels in the pixel rows R, G, and B was 2400 pixels. Therefore, when viewing a document with a width of 300 mm when viewed in the column direction of the photosensitive pixel column, the pixel column W is 15 dots/m.
m, pixel rows R and G.

B can be read at a resolution of 3 dots/mm.

Further, in this case, the magnification of the lens system that forms the projected image on the reading unit was selected to be a reduction ratio of 7/((1/16)×100O)=0.112.

(Recording of Read Signals) FIG. 4 is a longitudinal cross-sectional view of an apparatus for recording read images on recording paper using image signals obtained by the image reading apparatus.

In this device, an original is placed on the platen glass 20 on the top surface, and an irradiation lamp 21, a mirror 22, a lens 23,
The image on the document is read by the reading section 12 and the signal processing section 13. The irradiation lamp 21, the mirror 22, and the lens 23 are driven by a known full-rate/half-rate mirror scan mechanism to project an image of the original onto the reader 912.

In the case of this device, the projected image moves at a constant speed in the direction of the arrow 16, and is moved from below the reading unit 12 to the pixel arrays BSG, R, W.
Read them in order.

The signal processing unit 13 converts the signals read in this way into yellow (Y), magenta (M), and cyan (C) suitable for printing.
) and black (K) signals, and these signals are sent to the optical writing heads 25Y, 25M, 25C, and 25Ki, respectively:
(Send.

The optical writing head is composed of a light emitting diode array or the like, and forms an electrostatic latent image corresponding to each color on the outer periphery of the photosensitive drum 26. This electrostatic latent image is developed by a developing device 27, and the toner of each color adhered to the outer periphery of the light drum 26 is transferred onto recording paper by a transfer device 28. Note that the recording paper 29a is stored in the paper feed tray 29 according to its size, and is then sent out by the feed roller 31 to pass through a large number of guide slopes 32 and guide rollers 3.
3 and then passes through a transfer machine 28 provided for each color.

Then, when the transfer of the four colors is completed, the image passes through the fixing @ 34 and is ejected to the ejection tray 35.

In this way, the image read by the reading section 12 is recorded on the recording paper.

(Flow of Signal Processing) FIG. 5 illustrates the flow of signal processing operation of the image reading device of the present invention.

First, in the reading section, a black and white image is read using a photosensitive pixel array with a small pixel pitch (step 2). These signals are grouped into 4×4 matrix blocks (step ■), and the maximum value of the signals within them is determined (
Step ■).

On the other hand, three rows of photosensitive pixel rows with a large pixel pitch allow
Red (R), green (G), and blue (B) images are read (step 2).

These signals are grouped into 2x2 matrix blocks for each color and averaged (step ■).
, the maximum value of which is detected (step ■).

Then, the two maximum values are compared to obtain the difference. If this difference is larger than a preset reference level, it is determined that the image has a significant difference in shading in some parts and is a high-definition image (step (2)).

This discrimination result is sent to the discrimination data memory, and a selection signal is output (step ■).

On the other hand, the color reading signals from the three photosensitive pixel rows R, G, and B are averaged into a 2×2 matrix block (step ■), and the signals are cyan (C) and magenta (M). , yellow (Y), and black (K), and the signal level is corrected and output (step ■).

This signal is converted into a halftone pattern for high-gradation image processing (step O) and sent to the output selection section.

On the other hand, another color reading signal from the three photosensitive pixel rows is
The two portions are binarized for each color (step ■).

Next, in the same way as the color conversion described above, in the color discrimination circuit, the binarized R and GSB signals are converted into binarized C5 signals.
M5Y, is converted into a signal (step 0).

Further, the signal read in the pixel row W to be binarized (Step 0) is ANDed with the selection signal output from the discrimination data memory (Step Q).

The output of this AND circuit and the output of the previous color discrimination circuit are ANDed (step 2) and input to the output selection circuit.

This signal is used for high-definition image processing.

The output selection circuit selects and outputs either a signal for high-gradation image processing or high-definition image processing based on the selection signal output from the discrimination data memory (step [
phase]).

(Description of Processing Circuit) FIG. 6 is a block diagram of the signal processing section 13 that processes the signal read by the reading section 12.

The reading unit 12 corrects the signal input time difference using the predetermined number of memories 15 described above. That portion is illustrated as a time difference correction circuit 41.

Since the signals read by the reading section 12 for each color are analog signals, the A/D converter 42 converts the signals into, for example, 8
Convert to bit digital signal. Then, a shading correction circuit 43 corrects signal distortion due to variations in reading sensitivity in the column direction of the photosensitive pixel array and sensitivity of individual photosensitive pixels. As a result, signals of 6 bits for each color, that is, 64 density steps are output.

Here, the signal read in the pixel row W is input to a circuit 44 that detects the maximum value within the 4×4 block. The maximum value is stored in memory 45.

In addition, the signals read by the pixel rows R and GSB are divided into two parts, one of which is input to the circuit 46 that averages within the 2×2 block, and the other is input to the circuit 46 that averages the signal within the 2×2 block. The 2-line delay buffer 47 for adjustment is manually input.The averaged 3-wave signal within the 2×2 block is detected by the detection circuit 48, and its value is detected by the detection circuit 48. It is stored in the memory 49. Both memories 45.
The difference between the data stored in 49 is calculated by a subtracter 51 and compared with a constant reference value 52 in a comparison circuit 53.

The discrimination data memory 54 receives the output signal from the comparison circuit 53.
Selection of output of multiplexer 55 and AND gate 5
A selection signal 54a for opening and closing 6 is created.

On the other hand, the output of the two-line delay buffer 47 is converted into Y, M, and C colors by a color discrimination table 58 and input to an AND gate 59. The output of the AND gate 59 is input to the multiplexer 55 and becomes a signal for high-gradation image processing.

(Color conversion/color correction circuit) The color conversion/correction circuit 57 converts the manual signals read by the red, green, and blue color filters into cyan, magenta, and cyan colors suitable for printing.
This circuit converts the signal into yellow and black signals, and further adjusts the signal level to correct the color difference with the original due to unnecessary absorption components of the color material of the recording device.

These circuits manually input a 6-bit signal for each color, but each color outputs a 4-bit signal.

(Operation of Halftone Processing Circuit) FIG. 7 shows a conceptual diagram of data processing at the halftone processing stage.

In the figure, a human input signal 61 on which high-gradation image processing is performed is converted into a 4×47) IJ Fuchs halftone pattern 62 for each pixel. Specifically, we prepare a threshold value corresponding to each pixel of the 4x4 matrix, compare this with the signal level of the human input signal, and select the output button 63 as shown in the figure.
get. The numbers written in the human input signal 61 are examples of the signal levels, and the numbers written in the IJ socks 2 for halftone processing are the threshold values. When the input signal 61 is larger than this threshold value, a white dot is selected as the output button 63, and when it is smaller than this threshold value, a black dot is selected as the output button 63. This process reproduces an image with 16 gradations and 4096 colors. The resolution is 3 when the halftone processing button size is 1 dot.
It becomes dot/mm.

FIG. 8 shows a more specific block diagram of the halftone processing section.

One set of these circuits is provided to process signals for each color of yellow, magenta, cyan, and black, which were previously converted and output by the color conversion/color correction circuit 57.

The circuit includes a ROM (read-only memory) element 66 that stores threshold values for conversion to halftone bangs, two counters 64 and 65 for readout control, and a human input signal and a threshold value. and a comparator 67 that compares the two and outputs the intermediate tone.

The ROM element 66 stores threshold values for the 4×4 matrix halftone pattern shown in FIG.
The signals are addressed by the check signal CK and the horizontal synchronizing signal H, read out in order, and sent to the comparator 67. The comparator compares the human input signal and the threshold value 1 in the manner shown in FIG. 7, and the output button 63 shown in the figure is obtained.

Either the signal for high-gradation image processing or the signal for high-definition image obtained in this way is sent to the multiplexer 5.
By selecting and outputting in step 5, it is possible to record the read image with high image quality.

Moreover, in the case of high-definition image processing, the signals read in color are each binarized and then ANDed with the signals read by a photosensitive pixel array with a smaller pixel pitch. N,G,BSC,MSY
, can be processed in seven colors, and the line density can be extremely high.

As a result, the high-definition image is 21! of 16 dots/mm!
It is possible to record in 7 colors (R, GXBSY, M, C, K), and the high gradation image is 4 dots/mm, 16 gradations, 40
It is possible to record in 96 colors.

However, the 4 d o t 7 mm of a high gradation image (
Direct is the size of the halftone dot as one dot.

More specific example of signal processing> Of the above signal processing, the image discrimination method will be explained in more detail.

FIG. 9 is a graph showing the spectral reflectance characteristics of an original, and the description will be given by taking, for example, a case where the original is magenta.

In Fig. 10, the horizontal axis shows the photosensitive pixels No. 1 to No. 28.
The spectral reflectance or read signal level is plotted on the vertical axis.

Here, the reflectance distribution in the main scanning direction of the original (direction parallel to the rows of photosensitive pixel rows) is as shown in Figure 10a, with a line image (high-definition image) on the left and a higher-order image on the right. It is assumed that the image contains a tone image.

In this case, the level of the signal read by the pixel row W is as shown in the figure, and the level of the signal read by the pixel rows R, G, and B is as shown in c, d, and e of the figure, respectively.

Here, if we pay attention to regions A and B, pixel rows R1G, B
The average value of the signals read by is shown by the broken line in the figure. In reality, the average value for a total of 4 pixels is taken, including 2 pixels in the sub-scanning direction (direction perpendicular to the pixel row), but for the sake of explanation, the average value for 2 pixels is taken. Proceed with the explanation. It goes without saying that in the case of four pixels, the accuracy of discrimination is improved.

Now, looking at area A, as shown in figure f,
It can be seen that the difference between the maximum signal (1M W) read from the pixel row W and the maximum value MC of the average residue of the signals read from the pixel examples R, G, and B is larger than the reference value S.

As a result, the image in area A is determined to be a high-definition image.

In addition, for area B, as shown in FIG.
The difference between the average value of the signals read at and the maximum value MC is calculated. This is smaller than the reference value S.

Therefore, the image in this area can be determined to be a high-gradation image.

In this way, signal processing is automatically switched for each area of the image, making it possible to perform high-quality recording.

"Variation" The image reading device of the present invention is not limited to the above embodiments.

The colors of the color filters arranged in each photosensitive pixel column may be a combination of cyan, yellow, and green, for example.

Further, the number of photosensitive pixel columns can be freely changed.

"Effects of the Invention" The image reading device of the present invention described above automatically determines whether the image is a high-definition image or a high-gradation image based on the signal obtained by reading the image on the document. Since the information is determined and processing is performed accordingly, it is possible to obtain a read signal that allows recording of higher image quality.

[Brief explanation of drawings]

FIG. 1 is a plan view of the main parts of a reading section showing an embodiment of the image reading device of the present invention, FIG. 2 is a block diagram showing an overview of the image reading device of the present invention, and FIG. FIG. 4 is a cross-sectional view of a recording device suitable for implementing the image reading device of the present invention, FIG. 5 is a flowchart explaining the operation of the image reading device of the present invention, and FIG. 6 is a diagram showing the operation of the image reading device of the present invention. A block diagram of a signal processing circuit suitable for implementation, FIG. 7 is a conceptual diagram of its halftone processing,
Figure 8 is a block diagram of the halftone processing part, Figure 9 and 10
11 is a plan view of essential parts showing an example of a conventional reading section, and FIG. 12 is an example of another conventional reading section. The main block diagram, FIG. 13, is a graph showing the relative sensitivity of these photosensitive pixels. 11...Photosensitive pixel row, 12...Reading unit, 13...Signal processing unit. Applicant Fuji Xerox Co., Ltd. Representative Patent Attorney Ume Yamauchi
Male figure 1 figure 2 figure,
01shi 14 Figure 3 Figure 4 Figure 7 Shiriki Figure 8 Figure 67 Figure 9

Claims (1)

[Claims] 1. A reading section equipped with a plurality of photosensitive pixel rows formed by arranging a plurality of photosensitive pixels that generate charges in response to optical signals, and processing signals obtained by reading the projected image of the document onto this reading section. At least one of the photosensitive pixel columns of the reading section has a pixel pitch in the column direction of the photosensitive pixels constituting it, which is equal to the pixel pitch in the column direction of the photosensitive pixels of the other photosensitive pixel columns. When the photosensitive pixel row with the smaller pixel pitch is selected as the first pixel row and the photosensitive pixel row with the larger pixel pitch is selected as the second pixel row, the second pixel row is configured. Each photosensitive pixel has
A color filter having a predetermined spectral transmittance is disposed, and the signal processing section receives a signal obtained by reading with the first pixel column and a signal obtained by reading with the second pixel column. and a comparison/judgment circuit that determines whether the image is a high-definition image or a high-gradation image by comparing the images. and the signal read at the exit of the first pixel row, and if the image is a high gradation image, the signal read at the second pixel row is converted into a halftone image signal and output to the subsequent circuit. An image reading device characterized by being provided with a selection circuit.