JPS62104379A - Digital copying device - Google Patents

Abstract

PURPOSE:To obtain an excellent copy of even an original where a halftone image and a binary image are both present and to facilitate the erasure of an optional area on the original by discriminating between the halftone image and binary image with respect to each area on the original and switching both automatically. CONSTITUTION:A signal outputted to a recording means is switched among a signal after halftone processing, a simply binary coded signal, and a specific- level signal automatically. The area decision means is equipped with the 1st decision means and the 2nd decision means. The 1st decision means decides the level of the output electric signal of an image read means with the 1st threshold level and decides whether the original image contains halftone information or not on the basis of the binary-coded signal and the 2nd decision means decides the level of the output electric signal of the image read means with the 2nd threshold level and decides whether the original image contains the halftone information or not on the basis of the binary-coded signal. When the specific-level signal is selected, respective picture elements of a recording image are recording picture elements or nonrecording picture elements irrelevantly to the original image.

Description

Detailed Description of the Invention [Field of JI Akira] The present invention provides a recording device that reads an original image, converts it into an electrical signal, processes the electrical signal, and converts one image information into binary information of recording/non-recording. The present invention relates to a digital copying device for use in a digital copying machine.

[Prior Art] Generally, in a digital copying apparatus, a C0D (charge-coupled device) image sensor or the like is used to read a document image in minute areas, that is, pixel by pixel, and an analog electrical signal obtained as the output of the image sensor is read. After performing A/D (analog/digital) conversion on the resulting digital signal and performing various processing on the resulting digital signal, the signal is supplied to a recording device to obtain a copy image.

By the way, in the printing apparatus used in this type of apparatus, it is difficult to change the density level for each printing pixel, so it is common to perform binary printing of printing/non-printing. However, since a document may also include halftone images such as photographs, it is necessary to reproduce halftone images. As methods for expressing halftones using a recording device that performs binary recording, methods such as the dither method, density pattern method, and submatrix method have been proposed, and if these methods are used, it is possible to reproduce halftone images. can.

However, when performing halftone processing, a relatively favorable copy image can be obtained when the original image density changes gradually, such as in a photograph, but when the original image density changes binaryly, such as with text, it is difficult to obtain a copy image. In this case, the outline of the copy image becomes blurred, making it difficult to read the characters, and light stains on the surface of the yK paper appear on the copy image, resulting in a significant deterioration in copy quality.

For original images such as text, without performing halftone processing,
Simple binary processing yields a good copy. Therefore, if a switch is provided to specify whether or not halftone processing is to be performed, the
A preferred copy mode can be selected.

However, there are many cases in which a single document, such as a pamphlet, contains both a half-tone image such as a photograph and a binary image such as text. In such a case, selecting the binary mode will reduce the quality of the photo, and selecting the halftone mode will reduce the quality of the text.

By the way, there is one more thing about this type of digital copying device.
There are two disadvantages. In other words, when reading an image in small pixel units using a line sensor or the like, if there is periodicity in density changes on the document, interference between the period (pitch) and the array pitch (sampling period) of the image reading sensor causes Moiré may occur on the recorded image.0 For example, when halftone dot printing is performed on a document, the density changes on the image have periodicity, so the period of this density change and the sampling period of the reading sensor Moiré occurs due to interference with the image.

For example, the resolution of one image reading sensor is 16 pixels/mm
In this case, dot printing with a density close to that resolution, that is, 133. Moire is likely to occur in the read signal when the density is in the range of II (approximately 10.5 pixels/mm) to 200 lines (approximately 16 pixels/mm). Of course, moire also occurs at other densities. However, the occurrence is particularly remarkable in the case of the above-mentioned density, and the fluctuation range of the signal due to this is large.

Halftone printing itself is a type of pseudo-halftone expression.

The density change in pixel units is a binary value of 110 (recording/non-recording). In halftone printing, the average density of the entire pixel set is changed in multiple steps by changing the pitch of the halftone dots and the size of the halftone dots, thereby expressing halftone density. Therefore, if the problem of moiré is not considered, when copying a halftone dot printed original image, the halftone dot image is reproduced in the recorded image by binary processing the signal.

A preferred copy can be made. However, in reality, moiré occurs in a document image to which halftone dots are applied at a specific density, as described above, resulting in a significant deterioration in copy quality.

On the other hand, when converting one image reading number multiple into a binary signal through halftone processing, the density of multiple pixels is averaged, the threshold level is changed, etc. in the process, so as a result, the copy image Moiré does not occur or its effect is reduced. In this case, the density of the copied image is represented by halftone dots, but the halftone dots on the copy are not direct reproductions of the halftone dots on the original, but are generated by halftone processing unique to copying machines. It is a point.

Therefore, if the original is a halftone-printed image or an image copied with halftone processing by a digital copying machine, it is a binary recording in pixel units, but it is better to select a copy mode that performs halftone processing. is preferred.

By the way, when copying, there are cases where it is desired to erase a specific area on the original from the copy image.

In such cases, conventionally, a piece of white paper cut to the same size as the portion of the document to be erased is pasted on the portion of the document to be erased, and then the document is placed in a copying machine and copies are made. However, cutting the paper to the specified size and pasting the paper onto the original is a hassle, and what's more, the border between the original and the paper pasted on top of it casts a shadow, which appears as a black line on the copy. In many cases, it is necessary to erase the lines with an eraser or the like.

By the way, when a character or figure is written with a thick line, there are cases where it is desired to obtain an image in which only the outline of the line is left and the inside of the line is erased (for example, a white outline). It has been known that a white image can be obtained by obtaining a blurred image and a sharp image through optical or electrical processing and calculating the exclusive OR of these two images. However, when this process is performed, the image becomes blurred. The corners are rounded. Inconveniences such as fine images being distorted occur.

Another method for obtaining a white image is to binarize the image signal using two different threshold levels, and then calculate the exclusive OR of the two binary image signals obtained. Are known. However, when this process is performed, defects such as thickening of the two images, which tend to cause unevenness in line thickness, occur.

[Object of the Invention] The present invention automatically determines whether each area on a document is a halftone image or a binary image, and is suitable even for a document containing a mixture of halftone images and binary images. The primary purpose is to obtain a copy. A second object of the present invention is to simplify the task of erasing any area on a document. A third object of the present invention is to eliminate the above-mentioned disadvantages in image processing such as whiteout.

[Structure of the Invention] In order to achieve the above-mentioned object, the present invention provides an area determining means for determining whether a document image is a halftone image by processing an electric signal obtained from an image reading means, and detecting the determination result. Accordingly, the signal output to a recording means such as a printer is automatically switched to one of a halftone processed signal, a simple binarized signal, and a signal at a predetermined level.

The area determination means includes a first threshold value that determines the level of the electrical signal output by the image reading means, and determines whether or not the original image includes halftone information based on the binarized signal. 1 determining means and a second threshold level for determining the level of the electrical signal output by the image reading means, and determining whether or not the original image includes halftone information based on the binarized signal. A second determining means is provided.

If you select a signal that has undergone halftone processing, the halftone density will be reproduced in the recorded image, if you select a signal that has undergone simple binarization processing, the density of the recorded image will be binary, and if you select a signal of a predetermined level, the density of the recorded image will be reproduced. , each pixel of the recorded image becomes a recorded pixel or a non-recorded pixel, regardless of the original image.

Therefore, for example, in the first operation mode, when the region determining means selects a halftone-processed signal when determining a halftone region, and selects a signal subjected to simple binarization processing when determining a binary region. By specifying this operation mode, the type of image being processed (intermediate Since the contents of the signal processing are automatically switched depending on the tone/binary density image, favorable copies can be obtained for both halftone density images and binary density images.

For example, in the second operation mode, when the area determining means selects a signal of a predetermined level when determining the area is in the halftone area, and selects a signal subjected to simple binarization processing when determining the area is in the binary area. By specifying this operating mode, the halftone areas on the original are erased and do not appear on the copy. That is, if the original includes a halftone area such as a photograph and a binary area such as text, the photograph will be erased on the copy in this mode.

Further, in the present invention, since the area determining means includes two determining means that process binarized signals at different threshold levels, it is possible to detect the presence or absence of halftone information for various types of original images. The judgment is reliable and the reliability is high.

In a preferred embodiment of the invention, the first threshold level is a fixed reference level for the binarization processing means and the second threshold level is a level lower in density than the first threshold level. , the second determining means has a pixel indicating the black corresponding level of the original image.

If a predetermined number or more of these appear consecutively in the main scanning direction and the sub-scanning direction of the image reading means, it is determined that the area is a halftone area.

According to this, all pattern areas having a size larger than a predetermined size are considered to be halftone images. Therefore, for example, if you fill in characters on a document with a low-density felt-tip pen, etc., the entire filled area will be considered a halftone area, so in the operation mode for erasing halftone images, any characters on the document will be erased neatly. can. Also, if there are characters written with thick lines with relatively high density, only the outline of the line is considered to be a binary image area, and the area inside it is considered to be a halftone image area, so halftone In the operation mode of erasing an area, only the outline remains and the inside thereof becomes unrecorded, so that an outline character pattern is obtained.

If the density of the area considered to be a binary image area is low, the binary recording signal indicating recording/non-recording obtained by reading the image of that area will be non-recording. The outline does not appear.

Further, in a preferred embodiment of the present invention, the first determination means processes the document reading signal to determine whether or not it contains a halftone dot, and if a halftone dot is detected, the first determination means is determined to be a halftone image. According to this, since the halftone image is subjected to halftone processing, the occurrence of moiré is suppressed and the copy quality is improved.

Other objects and features of the invention will become clear from the following description of an embodiment with reference to one drawing.

[Example code] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows one type of digital copying machine embodying the present invention. This copying machine is broadly divided into a scanner 1 at the top of the device and a printer 2 at the bottom of the device.

26 is a contact glass on which the original is placed.

The scanner 1 scans and reads an image of a document placed on a contact glass 26 . The sub-scanning is mechanical, and a carriage provided in the scanner moves to the right and left in FIG. 2 by driving the electric motor MT. Reflected light from the original is imaged on a fixed image reading sensor IO via various mirrors and lenses. The image reading sensor 10 is
It is a CCD line sensor, and in FIG. 2, a large number of reading cells are arranged in a direction perpendicular to the paper surface. In this example, when the copy magnification is 1.0, the resolution is 16 pixels per 1 mm of the original image. The main scan.

This is electrically performed by a COD shift register provided inside the image reading sensor 10. The main scanning direction is the direction in which the reading cells are arranged, that is, the direction perpendicular to the plane of the paper in FIG.

What is the signal obtained by reading the original image with scanner 1?

After being subjected to various processing as described later, it is sent to the printer 2. The printer 2 performs binary printing in accordance with the signal.

The printer 2 includes a laser writing unit 25. Photosensitive drum 3. Electric charger 24. Developing device 12° transfer charger 14. Separate charger 15. A fixing device 23 and the like are provided. Since this printer 2 has no particular differences from conventionally known general laser printers, only the operation will be briefly described.

The photosensitive drum 3 rotates clockwise in FIG. Then, the surface thereof is uniformly charged to a high potential by the energization of the electrification charger 24. This charged surface is irradiated with laser light modulated by a binary signal corresponding to the image to be recorded. The laser beam repeatedly scans the photosensitive drum 3 in the main scanning direction by one mechanical scan. The electrical potential of the charged surface of the photosensitive drum 3 changes when it is irradiated with laser light. Therefore, a change in the laser beam, that is, a potential distribution depending on the image to be recorded is generated on the surface of the photosensitive drum 3. This potential distribution is an electrostatic latent image.

When the portion on which the electrostatic latent image is formed passes through the developing device 12, toner is attached depending on the potential thereof, and the electrostatic latent image is developed into a toner image, that is, a visible image. This visible image overlaps the transfer paper fed from the paper feed cassette 4 or 5 to the photosensitive drum 3, and is transferred onto the transfer paper by the bias of the transfer charger 14. The transfer paper on which the image has been transferred passes through a fixing device 23 and is discharged onto a paper discharge tray 22 .

FIG. 1 shows the appearance of the operation panel of this digital copying machine.Referring to FIG. 1, this operation panel has copy magnification keys such as 5 and 5, like a general copying machine. 6 on the density key.
7 on the interrupt key. Numeric keypad KT, clear/stop key K
C, print start key KS, display DSP, etc.

In this example, a copy mode designation section is particularly provided. There are four mode keys K in the copy mode specification section.
l, to 2. 3 and 4, indicator lamps (light emitting diode indicators) Ll, L2 . L
3 and L4 are provided.

The mode key 1 is 0, which is the key that specifies the character mode.
When character mode is selected, the image is processed completely binary. That is, regarding the reading of JJK manuscripts.

With a certain threshold density as the boundary, areas with a lower density than that are considered as white (non-recording) pixels, and other areas are considered as recording pixels. Each reading pixel and recording pixel have a one-to-one correspondence. do. Therefore, high-quality copy images can be obtained for images with high resolution and no halftone density, such as characters.

Mode key 2 is a key for selecting photo mode.

When the photo mode is selected, the image is processed as including halftone information, and the density level information of the original image is also reflected in the copy image. however.

In this example, since the printer 2 can only perform binary recording (recording/non-recording) for each recording pixel, special halftone processing is performed to convert the multi-value signal into a binary signal. This type of halftone processing includes dithering, density patterning,
Although submatrix methods and the like are known, this example employs halftone processing using the submatrix method.

In photo mode, a good copy image can be obtained for multi-tone images such as photographs, but the resolution decreases due to halftone processing, making it unsuitable for reproducing binary images such as text. .

Mode key 3 is a key for selecting automatic separation mode. In the automatic separation mode, based on the image signal read by the scanner 1, it is automatically determined whether or not halftone information is included in both YK and K documents, and the signal processing is performed in a binary manner based on the determination result. automatically switches whether to perform halftone processing or halftone processing. When this mode is selected 1 For example, if a single document contains both photographs that contain halftone information and characters that do not contain halftone information, the processing will be switched during scanning, and halftones will be applied to the photographs. For each character, binary processing is performed.Therefore, the photograph is reproduced on the copy in a form that includes halftone information, and each character is recorded at high resolution.

Mode key 4 is a key for selecting magic erase mode. In the magic erase mode, if there is a thick line or the like in the original image, a copy image is obtained in which only the periphery of the line is left and the inside of the line is erased. Furthermore, if there is a pattern filled in with a thin felt-tip pen or the like, a copy image with that pattern erased can be obtained. The detailed operation will be described later.

3 shows the configuration of the electric circuit of the digital copying machine shown in FIG. 2. Referring to FIG. 3, the scanner 1 includes an image reading sensor 10. Scanning control section 20. Amplifier 30. A/D (analog/digital) converter 40, halftone processing section 50, binarization processing section 60. Area determination unit 70. Scraping control section 80. It is equipped with an output control section 90° motor driver MD, etc.

The scan control unit 20 exchanges signals with the printer 2, performs main scanning control, sub-scanning control, and generates various timing signals.The various timing signals are generated in synchronization with the scanning timing. Key reading control and display control other than copy mode designation on the operation panel shown in FIG. 1 are performed on the printer 2 side. Various status signals, print start signal.

Copy magnification signals and the like are transmitted from the printer 2 to the scan control unit 20.
sent to. The scan control unit 20 sends a scan synchronization signal, a status signal, etc. to the printer 2. By driving the motor MT, the scanner mechanically scans and performs sub-scanning.

The image reading sensor 10 includes a large number of reading cells, a CCD shift register, etc., like a general COD line sensor. When the scan control unit 20 outputs the sub-scanning synchronization signal, the signals accumulated in a large number of reading cells of the image reading sensor 10 are transferred to each bit of the CCD shift register at once. Thereafter, the signal of the CCD shift register is shifted in synchronization with the main scanning pulse signal, and the image signal held in the register appears as a serial signal at its output terminal one pixel at a time (a in Figure 3). (Hereinafter, signals generated from image signals are shown in parentheses).

The amplifier 30 amplifies one image signal (a), removes noise, etc., and the A/D converter 4o converts the analog image signal (a) into six analog image signals.
Convert to bit digital signal.

Although not shown in the drawings, the digital signal obtained by the A/D converter 40 is subjected to various conventional image processing such as shading correction, background removal, black and white conversion, etc. It is output as a digital image signal (b) of bits, that is, 64 gradations.

This digital image signal (b) is applied to the halftone processing section 50 and the binarization processing section 60.

The halftone processing section 50 processes a 6-bit digital image signal (b
) into a binary signal (d) containing halftone information using the submatrix method.

A circuit for performing halftone processing using the submatrix method is well known, and since no special circuit is used in this embodiment, the specific configuration and operation will be omitted. Note that, in addition to the submatrix method, halftone processing may be performed using a dither method or a density pattern method.

The binarization processing unit 60 performs MTF correction on the input 6-bit digital image signal (b), compares the correction result with a predetermined fixed threshold level THI, and generates two short signals according to their magnitude. Output number (e). Therefore, the processing performed here is simple binarization processing, and the signal (e) does not include information on the halftone density of the original image.

Furthermore, the binarization processing unit 60 outputs a 6-bit digital image signal (C1) and a 1-bit binary image signal (C2) to the area determination unit 70. The 1-image signal (C1) is subjected to MTF correction. The signal (C2
) is the same as the binary image signal (e) output by the binarization processing unit 60, except for the signal timing.

As will be described later, the area determination unit 70 is a circuit that determines whether or not the JJK manuscript image includes image tone information, and outputs a binary signal (f) according to the determination result to the output control unit 90. .

The operation control unit 80 sends mode signals (g: in detail, g1eg2rg3 and g4
) is given to the output control section 90. Also.

The energization of the display lamps L1 to L4 is controlled according to the mode signal.

The output control unit 90 outputs a binary image signal ( d) Selectively output the binary image signal (e) output by the binarization processing unit 60 or a signal at a predetermined level (white level). This signal (h) is given to the printer 2 as a recording signal. The printer 2 modulates the laser beam according to this binary signal and performs recording.

FIG. 4 shows the configuration of the area determination section 70 shown in FIG. 3. Fourth
Referring to the figure, the area determination section 70 includes a first determination section 71.
It consists of a second determination section 72 and an OR gate 73. 1st
A 6-bit image signal (C1) is applied to the determination section 71, and a 1-bit binary image signal (C2) is applied to the second determination section 72.
is applied.

The region determining section 70 outputs the logical sum (f) of the signal (Q) output from the first determining section 71 and the signal (r) output from the second determining section 72 .

The first determination unit 71 includes the binarization circuit 110. Y delay circuit 12
0. It consists of an X delay circuit 130 and an AND circuit 140.

Note that in this specification, the symbol X or X is used to indicate the main scanning direction of the scanner, and the symbol y is used to indicate the sub-scanning direction.
Or use the symbol Y. Further, "1" of the binary image signal corresponds to the black pixel level.

"0" corresponds to the white pixel level.

The details of the configuration of the first determination section 71 are shown in FIG. 5, and examples of signal waveforms and timing of each section are shown in FIGS. 6a and 6b.

Details of the first determination section will be explained with reference to FIG. 5.

The binarization circuit 110 includes a digital comparator 111° pull-up circuit 112 and a switch circuit 113. Digital comparator 111 compares the value of the digital signal applied to its 6-bit input terminal A with the value of the digital signal applied to the other 6-bit input terminal B, and outputs the comparison result.

In other words, if A≧B, the signal (j) becomes “1” (corresponds to high level H, and the same goes for 2 and below); otherwise, the signal (j) becomes “O” (corresponds to low level L, and the same goes for 2 and below). Become.

Each switch of the switch circuit 113 is set so that the value of the input terminal B of the comparator 111 becomes a predetermined threshold value TH2. This threshold TH2 can be varied, but is usually set to a fairly low density level, as shown in Figure 6b. In this example, the threshold value TH1 used by the binarization processing section 60 is set to the center level (32) of the density gradation.

In other words, the binarization circuit 110 determines the black level even for pixels whose density is considerably lower than the normal black pixel determination level.

The Y delay circuit 120 is a circuit that processes the signal (j) output from the binarization circuit 110 and delays the timing of the signal by a predetermined pixel in the X direction, that is, in the sub-scanning direction, and delays the timing of the signal by a predetermined amount of pixels in the X direction, that is, in the sub-scanning direction. Output. In FIG. 5, a signal jn represents a signal obtained by delaying the signal j by n pixels in the y direction, and is the same as the signal j3 in terms of the amount of delay. By delaying the signal for each pixel in the X direction, signals from multiple pixels adjacent to each other in the X direction can be extracted as parallel signals. In other words, this circuit can also be regarded as a serial-parallel conversion circuit.

The operation will be described with reference also to FIG. 6a, which shows the operation timing of the Y delay circuit 120.

The input signal (j) is latched by the latch 121 by a clock pulse t2 output at a timing for each pixel in the X direction. That is, the signal (j) applied to the input terminal DI of the latch 121 appears at its output terminal Q1, and its state is maintained. By clock pulse t3, latch 1
The states of the output terminals Q1 to Q6 of 21 are stored in each bit of a RAM (read/write memory) 123 at timing for each pixel in the X direction.

The memory address to store is specified by address signal t1. The content of this address signal t1 is updated for each pixel in the X direction, and the same content (value) is set for pixels located at the same position in the X direction. That is, the signal t1
corresponds to the pixel position in the X scanning direction. In this example, since the number of pixels in the X direction is 4096, the signal t1 is a 12-bit parallel signal.

The stored contents of the RAM 123 are read out pixel by pixel in the X scanning direction by the clock pulse t3.

The data read is the data previously stored at the current X-direction position. If we pay attention to the connection between the data line Di-D6 of the RAM 123 and the latch 121, R
AM123 data line bits 1, 2, 3, 4, 5
and 6 are bit 2 of the input terminal of the latch 121, respectively.
, 3, 4, 5, 6, and 7, shifted by one bit.

Therefore, a signal (j) input at a certain timing is latched into bit 1 of the latch 121, and stored in bit 1 of the RAM L 23 before the next pixel data is set in the latch 121. and.

At a timing delayed by one pixel in the X direction, RAM L23
is read out from bit 1 of the latch 121 and applied to the bit 2 input terminal D2 of the latch 121. This signal is latched into bit 2 of the latch 121 at the timing when a pixel signal appearing delayed by one pixel in the X direction is latched into bit 1 of the latch 121 at its X position.

Thereafter, by repeating this operation, the signal is transferred to latch 1.
Bits 3, 4, 5, 6 and 7 of 21 have a timing of
The data is transferred sequentially every time one pixel is advanced in the direction. That is, when the signal is latched to bit 7 of latch 121, bits 6, 5, 4, 3, 2, and 1 of latch 121 have 1, 2, and 3 bits in the X direction, respectively, than the signal of bit 7.
, 4, 5, and 6 pixels are present. As a result, signals of seven pixels adjacent to each other in the X direction at a predetermined X position are obtained at the output terminals Q1 to Q7 of the latch 121 at the same timing.

Note that the latch 122 is used to adjust the timing of sending a signal to a circuit connected to the output of the Y delay circuit 120. Therefore, signal jO-36 is approximately the same as the signal output by latch 121.

In addition, in FIG. 6a, the symbol JlyJ2+...B
l, B2. B3... and At, A2. It should be noted that the signals indicated by A3 . . . represent changes in each pixel in the X direction, and are different from the signals output by the latch 122.

The signal output from the Y delay circuit 120 includes the signal output from the X delay circuit 13.
Applied to 0. The X delay circuit 130 is composed of one shift register, as shown in FIG. signal(
k) is applied to the serial data input terminal of the shift register. Signals (kl, 2., 3., 4., 5., 6, and 7) are output from the parallel data terminals Q1 to Q7 of this shift register. This shift register (130) shifts data one bit at a time every time a clock pulse t4, which is output every time the scanning position in the X direction changes pixel by pixel, appears. The signal appears at bit 1 of the output terminal at the primary pixel timing (X direction) (
kl), bits 2, 3, 4 each time the pixel timing changes
, 5.6 and 7 in sequence.

That is, 1. For example, when the signal of the pixel located at N in the pixel coordinates in the X direction appears as the signal (kl), each signal (
k6. 5. 4. 3. 2. The position of the pixel appearing in (kl) is the same in the X direction as in (kl), and the position of the pixel appearing in (kl) is N+1. N+2. N+3°N+4. N+5 and N+6
It is. That is, the signals (kl~7) are signals of seven pixels located at pixel positions adjacent to each other in the X direction, and these are obtained at the same timing. Therefore, the X delay circuit 130 can also be regarded as a serial-to-parallel conversion circuit for serial pixel signals.

The signals (jO to j6 and 1 to 7) output from the Y delay circuit 120 are applied to the AND circuit 140. The AND gate 141 outputs 1 when all the signals (jO to j6) are 1, and outputs O at other times. Therefore,
The signal (jlo) output from the AND gate 141 is
The position in the X direction is the same.

Seven pixels adjacent to each other in the X direction are all at black level (TH2
becomes 1 when This signal is.

The shift register 143 moves a predetermined number of pixels (
1 pixel) and applied to the AND gate 144 as a signal (jll).

The AND gate 142 outputs 1 when all the signals (kl~7) are 1, and outputs 0 otherwise. Therefore, the signal (k 10
) becomes 1 when all seven pixels adjacent in the X direction and at the same position in the X direction are at the black level (with respect to TH2). The AND gate 144 has a signal (J41) and a signal (k
10), that is, outputs a signal (Q).

In other words, regarding the pixel of interest at that time, when the seven pixels in the X direction and the seven pixels in the Q is determined to be 1). The reason why the shift 1 register 143 is provided to shift the signal (jll) in the X direction with respect to the signal (jlO) is to adjust the timing of the seven pixels in the X direction and the seven pixels in the X direction.

That is, the signal (jO to j6) is the signal (k
), in order to obtain the signal (k4) corresponding to the center pixel in the X direction and the signal (jll) at the corresponding X position, the signal is changed by one pixel (4 pixels in this example) in the (jlo) is being shifted. In other words, since many micropatterns are generally close to circular, it is preferable to arrange the pixel of interest at the center pixel of the pixel group forming the ``10'' pattern.

See Figure 6b. Note that in this figure, only the X direction is shown for easy understanding. Since the digital image signal (C1) is 6 bits, it contains 64 levels of density gradation information. In this example.

Each part (C1l, (:12) of the signal (CI) shown in the figure indicates a signal obtained by reading a halftone image such as a photograph,
(C13) shows a signal obtained by reading a background (i.e., white) image, and (C14) shows a signal obtained by reading characters written with relatively thick lines (i.e., binary density pixels).

(C15) shows the signal obtained by reading characters written in relatively thin lines, and (C16, C17) shows the signals obtained by reading the dirt on the manuscript.

In the binarization circuit 110, the low density level TH2 is set as the threshold level and the signal is binarized, so the obtained image signal (j) has a very low image density. Even in this case, all the parts where the image exists correspond to black pixels. On the other hand, in the signal (e) output from the binarization processing unit 60 with the intermediate level 32 set as the threshold value, in the halftone image, parts with low density correspond to white pixels, and parts with low density correspond to white pixels. Only dark areas correspond to black pixels.

The signal (k10) becomes 1 only when the black of the image signal appears for 7 consecutive pixels in the X direction, that is, only when the pattern is larger than a predetermined size.
11, C12, C14), the signal (klO) is 1
However, other parts (C13, C15, C16, C17
) is 0. Normally, this signal (k 10)
Since the halftone processed signal (d) and the binarized signal (6) are selected according to the The other parts correspond to the halftoned signal (d).

E and F correspond to the binarized signal (e). Here, C, D, and E are parts of the same character, but D and E (each 6 pixels in the X direction) corresponding to the outline part do not reach 7 pixels, which is the criterion for determining halftone information. , each part (C16, C
17) is binarized with respect to the threshold level THI, so dirt on the document is not output as a copy image.

The second determination section 72 will be explained with reference to FIG.

Simply put, the second determining section 72 is a circuit that determines the presence or absence of a halftone pattern. The signal C processed by this circuit
2 is the signal CI simply binarized with respect to the fixed threshold level THI, and unless timing etc. are considered, it can be considered to be the same as the signal (e) output by the binarization processing section 6°. I don't mind.

The second determination unit 72 includes an XY delay circuit 15o, a mesh detection circuit 160. It consists of a first area detection circuit 17o, a second area detection circuit 180, and a third area detection circuit 190. The XY delay circuit 150 processes the signal (C2) and outputs the signal (mij), and the mesh detection circuit 160 processes the signal (C2) and outputs the signal (mij).
mij) and outputs the signal (n), the first area detection circuit 170 processes the signal (n) and outputs the signal (p), and the second area detection circuit 180 processes the signal (p). The third area detection circuit 190 processes the signal (q) and outputs a signal (r).

FIG. 7a shows the configuration of the XY delay circuit 150.

Referring to FIG. 7a, this circuit includes Y delay circuit 151
and an X delay circuit. The configuration of Y delay circuit 151 is the same as Y delay circuit 120 shown in FIG. However, since a signal corresponding to the signal (k) is not required, only seven output terminals of the latch 122 are used. In other words, the signal (m
11 to m17) correspond to seven pixels that are the same in the X direction and adjacent to each other in the Y direction.

The X delay circuit consists of six 7-bit latches 152, 153 .
It consists of 154, 155, 156 and 157. The latch 152 is connected to the signal (m11 to m17) output by the Y delay circuit.
) and latch 153, 154. 155, 156
and 157 are latches 152, 153, 154, respectively.
, 155 and 156 output signals (m21 to m27)
, (m31-m37).

(m41-m47), (m51-m57) and (m6
1 to m67) are latched in synchronization with clock pulse t4. Therefore, each signal (m21.m31.m41.m51
．． m61 and m71) respectively convert the signal (nil) to
The signals are delayed by 1, 2, 3 degrees, 4.5, and 6 pixels in the direction.

In other words, the XY delay circuits 150 are adjacent to each other.
The signals mij of each pixel of a 7×7 pixel matrix composed of 7 rain elements in the X direction and 7 box elements in the y direction are all output at the same timing.

FIG. 7b shows a specific configuration of the mesh detection circuit 160. Referring to FIG. 7b, this mesh detection circuit 1
60, a first mesh detection circuit MS1, a second mesh detection circuit MS2. Third mesh detection circuit MS3. It consists of a fourth mesh detection circuit MS4 and a data selector 168. A signal mij output from the xy delay circuit 150 is applied to each mesh detection circuit MS1 to MS4.

The fourth mesh detection circuit MS4 consists of gates 161, 162, 163, 164, 165° 166 and 167, as shown in the figure. In the figure, mij indicated by a symbol with an overline indicates a signal obtained by inverting the logic of the signal indicated by a symbol without an overline. Therefore, although not shown, a large number of inverters are inserted between the output terminal of the XY delay circuit 150 and the input terminal of the mesh detection circuit 160. For convenience, in this specification, underlines are used instead of overlines.

The nine input terminals of the gate 161 receive the signal m44°,
Concave, 2, 2, 2, 1, 11, 5 and 1 are applied, and the nine input terminals of the gate 162 receive signals, m24 and m24. m33. m35. m42. m46. m53
．． m55 and m64 are applied to the 17 input terminals of gate 163, and signal m44. Yutan, 2U, 2■・工U
・1 average・m 31. m37. m 41. m 47
．． m 51. m57. m62. m66, m
73°2B and m75 are applied, 17 of gate 166
The input terminals have a signal of 1, m13. m 14
．． m 15. m22#m26. m31. m37.
m41. m47. m51. m5? , m62. m66゜m
73. m74 and m75 are applied.

Before explaining the operation of mesh detection circuit 160, halftone printing will be considered. In FIG. 8, halftone dots were printed with the same halftone dot pitch. Three types of density (reflectance of 10% and 30%)
and 50%) of the image.

The hatched area is the printed (black) area, and the rest is the background (white).Although not shown, the density is 70.
% and 90%, the concentration is 10% and 30%, respectively.
% and the black/white state is reversed.

Referring to FIG. 8, it can be seen that when the density is 50%, there are parts where adjacent dots are in contact with each other and parts where they are apart. In addition, due to the relationship between the scanner and the document when reading the document, the tilt between the halftone dot array direction and the scanner's scanning directions x and y is not constant, and the diameter of the recorded dots also changes. do.

The presence or absence of such halftone dots needs to be determined by the second determining section 72.

Referring to FIG. 8, it can be seen that in any case, in the halftone printed original image, there are black dots on a white background or white dots on a black background. Therefore, in the mesh detection circuit 160.

For each pixel of interest, it is detected whether it corresponds to one of these dots.

The fourth mesh detection circuit MS4 is shown in FIG.

The center pixel of the 7×7 pixel matrix, that is, the pixel of interest M44
(the pixel corresponding to the signal m44) and the surrounding pixels indicated by the symbol O or Δ, it is clear that the pixel of interest M44 is a black dot (there is a black pixel in the white pixel group) and a white dot ( It is detected whether there is a white pixel in the black pixel group. That is, if the pixel of interest M44 is 1 (black pixel) and the pixels indicated by the symbol O are all 0 (white pixels), the gate 161 outputs a signal indicating that there is a black dot, and the gate 162 outputs a signal indicating that there is a black dot.
If 44 is 0 and all the pixels indicated by symbol ∘ are 1, it outputs 0, that is, a signal indicating that there is a white dot, and in game 1-163, if the target pixel M44 is 1 and all the pixels indicated by symbol Δ are 0, it is 0, that is, black. Outputs a signal indicating the presence of a dot.

If the pixel of interest M44 is 0 and all the pixels indicated by the symbol Δ are 1, the gate 166 outputs a signal indicating that there is a white dot.

Any one of gates 161, 162, 163 and 166
When outputs a signal indicating the presence of black dots or white dots, 1. In other words, there is a signal indicating the presence of a dot.

Otherwise 0. In other words, there is a signal indicating no dots.

It is output as n4 from the fourth mesh detection circuit MS4.

Here, for the pixel of interest M44, two types of arrangement patterns are referred to: the pixel group at the position of the symbol ○ and the pixel group at the position of the symbol Δ, because of changes in the halftone dot pitch and dot diameter. This is to accommodate this and increase detection accuracy.

First mesh detection circuit MSI, second mesh pressure detection circuit M
S2 and the third mesh detection circuit MS3 have the same configuration as the fourth mesh detection circuit MS4. However, the signals mij and 1 applied to the respective input terminals are MS4
It is different from That is, each mesh detection circuit MSI~
MS4 differs in the position of the pixel used to determine the presence or absence of a dot. This change in conditions is set in advance for each copy magnification, especially in anticipation of a dot-like change due to a change in copy magnification.

Referring to FIG. 7b, a copy magnification signal line is connected to the selection terminal S of the data selector 168. Therefore, when the copy magnification changes, each mesh detection circuit MSI to M S4ffi outputs a signal n according to the change.
l, n2. One of n3 and n4 is selectively output from data selector 168 as signal n. That is, in this embodiment, the conditions for dot detection are automatically changed using the copy magnification as a parameter.

FIG. 10a shows an example of the positional relationship between dots and pixels when reading a halftone image, and FIG. 10b shows an arrangement of signals obtained by binarizing each pixel signal in FIG. 10a using a threshold value THI.

In addition, in these drawings, the pixel pitch is 1/16
(am/pixel), and the halftone dot pitch is 1/5 (+
am/pixel), and the values of the x and y coordinates in FIG. 10a and FIG. 10b correspond to each other.

In this example, if we look at the pixel at coordinates (15, 4), the pixel of interest is 1, and the nine pixels indicated by the symbol 0 in Figure 9 are all 0, so for this pixel, the dot It is determined that there is.

Basically, as described above, the mesh detection circuit 160 outputs a signal n indicating the presence or absence of halftone dots, but the positional relationship between pixels and halftone dots changes in various ways.

Furthermore, processing described later is performed.

FIG. 7c shows a specific configuration of the first area detection circuit 170. To put it simply, the first area detection circuit 170 detects a predetermined pixel matrix (referred to as a first area) consisting of W pixels in the X direction (for example, 8 pixels) and W pixels in the y direction as shown in FIG. Then, it is determined whether one or more dots exist in this first area. The signal p is 1. when a dot is present. Set to 0 if it does not exist.

Referring to FIG. 7c, this circuit 170 includes a read-only memory ROMI, a counter CNI, a CN2° flip-flop FFI, FF2 . Read/write memory RAM 1
, Game) Gl, G2. G3. G4. G5, G6. There are inverters v1 and IV2.

The operation timing of the circuit of FIG. 7C is shown in FIG. 12a. Counter CNI counts clock pulses t4 and
Count up for each pixel in the direction.

When the count value reaches 15, the carry terminal CY becomes high level H.
become. The signal obtained by inverting this signal is the preset terminal LD.
Therefore, when the next clock pulse appears, the data at the input terminals D1 to D4 are set in the counter. In FIG. 12a, the preset data is 8.

Therefore, the counter CNI operates as an N-ary counter that counts up every time the clock pulse t4 appears. The value of N can be arbitrarily set within the range of 1 to 16 depending on the values applied to the data input terminals D1 to D4. On the signal line Qx, a signal that goes to a low level L appears for one cycle every N clock pulses t4.

On the other hand, the signal n output for each pixel in the X direction is applied to the flip-flop FFI via the OR gate G1, and t
It is latched into the FFI in synchronization with 4.

When the signal line Qx is at a high level H, the signal latched in the flip-flop FFI is applied from its output terminal Q to one input terminal of the OR gate G1 via the AND gate G2.

Therefore, when the signal n becomes 1, the output terminal Q of the flip-flop FFI maintains the (H) state until the signal line Qx becomes a low level L. That is, when the counter CNL is set to an octal counter, the first
As shown in Figure 2a, after the signal n for a certain first pixel appears as signal 01 in the Q of FF1, the signal 01
The logical sum of and the next signal n appears on the FFI Q as the signal o2, and by repeating the same, when the signal line Qx becomes low level, all of the signals n for 8 pixels continuous in the X direction are The result of calculating the logical sum, that is, the signal o7 is
Obtained in Q of FF1.

When the signal 07 appears, the primary clock pulse t
When the signal P4 arrives, the signal is latched by the flip-flop FF2, and the latched signal is output as the signal P. Further, the signal outputted by the FF2 is stored in the read/write memory RAM1 in synchronization with the clock pulse t5. The signal t6 specifying the address of memory RAM 1 is
The value is updated every N pixels in the X direction to a value corresponding to the position in the X direction.

Note that the signal t6 is unrelated to the pixel position in the y direction.

Therefore, data for one line in the X direction is stored in the memory RAMI.

Furthermore, at the timing of the clock pulse t41, the data stored in the previous line (the position where the relative coordinate in the y direction is -1) is read out from the memory RAM 1, and the data is sent to one of the OR gates G4 via the AND gate G5. Applied to the input terminal.

On the other hand, the counter CN2 operates as an N-ary counter that counts up every time the clock pulse t7 appears. Clock pulse t7 is a sub-scanning synchronization pulse that is output every time the pixel position in the y direction changes. Other operations are the same as for counter CNI.

Therefore, the signal line Qy is normally at a high level H, and becomes a low level L once every N pixels in the y direction. If a high level H is applied even once to the data terminal of the flip-flop FF2 while the signal line Qy is at a high level, the logical sum of it and the input signal is stored in the FFI and the memory R.
Since the AMI is held, the signal P becomes high level H.

That is, when the signal line Qy becomes low level L, F
The result of calculating the logical sum of all the signals (for example, 07) output by F1 is output as the signal p. In other words, NX
For a predetermined pixel matrix consisting of an array of N (for example 8x8), that is, for each first area, if there is a signal n of 1 in at least one pixel therein, the signal p becomes 1.
become.

At other times, P becomes O. This signal p indicates the presence or absence of a dot in the first area detection circuit, that is, the presence or absence of a halftone dot.

On the other hand, the data terminals D1 to D4 of the counter CNI are connected to the data terminals D5 to D8 of the read-only memory ROMI, and the data terminals D1 to D4 of the counter CN2 are connected to the data terminals D5 to D8 of the read-only memory ROMI.
It is connected to data terminals D1 to D4 of OMI. A copy magnification signal is applied to the address terminal of the memory ROMI. The read-only memory ROM1 stores in advance information on the size of the first area associated with each copy magnification.

For example, in this example, when the copy magnification is 1.0, the first
Since the area size is 8×8 pixels, 8 is output to the 4-bit output terminals D1 to D4 of the first group of ROMI, and 8 is also output to the 4-bit output terminals D5 to D8 of the second group. In this case, counters CNI and CN2 are set to 8 at the time of presetting, and 8, 9, 10, 11
, 12, 13°, 14.15, 8, 9.10, etc., so it operates as an octal counter. When the copy magnification is different, the counting range of the counters CNI and CN2 changes, and thereby the size (number of pixels) of the first area changes.

FIG. 7d shows the configurations of the second area detection circuit 180 and the third area detection circuit 190. First, the second area detection circuit 180 will be explained.

Briefly speaking, in the second area detection circuit 180.

As shown in FIG. 11, the second area is made up of four first areas: two first areas that are continuous with each other in the X direction, and two first areas that are continuous with each other in the y direction. Assuming an area, it is determined whether or not there are three or more first areas in which dots are detected (signal P is 1) in this second area.

If three or more dots are detected in the first area, the signal q is
to indicate that a halftone dot has been detected.

The reason for performing such second area detection processing is to prevent the following erroneous detection. In other words, if there is a missing dot on the document side due to a printing error or a dot detection error on the copying machine side due to a reading error, etc., at the stage of signal p, the halftone dots are actually It may be determined that there are no points.

Further, when the image is not a halftone dot image, at the stage of the signal P, for example, a part of a character or dirt on the background may be detected as a single dot, and it may be erroneously determined to be a halftone dot area.

The operation timing of the second area detection circuit 180 is set to 12b.
This will be explained with reference to FIG. 7d and FIG. 12b shown in the figure.

181 is a data selector, 182 and 183 are latches,
184 is a read/write memory. Data selector 181
．． The latch 182 and read/write memory 184 are circuits that delay the signal p output for each first area in the X direction by a pixel corresponding to the first area. Signals from two first areas adjacent to each other in the direction are obtained at the same timing.

The latch 183 receives the signal output by the latch 182.

This is a circuit that delays the signals in the X direction by a pixel corresponding to the first area, and the signals output from the latch 182 to the output terminals Q1 and Q2 of the latch 183 to the output terminals Q1 and Q2 of the first area, respectively. A signal delayed in the X direction appears. Therefore, the signals p for each of the four first nilia included in the second area are obtained at the output terminals Q1 and Q2 of the latch 182 and the output terminals Q1 and Q2 of the latch 183 at the same timing.

That is, the signals p in the first areas El, E2, E3, and E4 in FIG. 11 are 183-Ql, respectively.

182-Ql, 183-02 and 182-02. These four signals are connected to gates G11. G12.
G13. Processed in G14 and G15, a signal q is generated. If three or more of the four signals are 1, the signal q becomes 1.

For example, in FIG. 11, El, E2. If three or more Ps in E3 and E4 are 1, the signal q output to the first area E4 becomes 1.

In addition, in Fig. 12b, Po, P1+ P3tp4
．． ... indicates the signal P output for each first area,
qO* qly . . . indicates a signal q output for each first area, po-1, Pi-1゜p2-1 .
. . . indicate signals obtained by delaying Pot P1*P2, . . . in the X direction by the number of pixels in one first area, respectively. For example, ql.

PI 1+P1. It is determined by four signals p2 1 and p2.

Next, the third area detection circuit 190 will be explained.

Roughly speaking, in the third area detection circuit 190, the eleventh
As shown in the figure, four first areas that are continuous in the X direction are assumed to be third areas, and at least one of the third areas has halftone dots.

This third area is determined to be a halftone area, and the signal r is set to 1.

The third area detection process is performed to prevent moire. That is, due to the scanning method and structure, there is a greater risk of moire occurring in the pressure side in the main scanning direction than in the sub-scanning direction.In the sub-scanning direction, there is no moire or it is not noticeable. .

In the main scanning direction, the reading resolution is generally 16 pixels/m
Moiré occurs when the halftone dot pitch is approximately 1 to 3 mm. When the amplitude of the read signal decreases due to moire, the accuracy of dot detection decreases, and errors may occur in dot detection. Therefore, if there is no risk of moire occurring, this third area detection process is unnecessary.

Note that in this embodiment, the number of pixels in the X direction in the third area is 3.
2 and the reading resolution is 16 pixels/mm, so the pitch of the third area is 2 mm.

Referring to FIG. 7d, the third area detection circuit 190:
It consists of a shift register 191 and an OR gate 192. The shift register 191 shifts the signal q for each number of pixels in the X direction in the first area in synchronization with the clock pulse t8.

When the signal q becomes 1 at least once in the four first areas that are continuous in the X direction, the signal r becomes 1 for all the first areas that make up the third area, including that first area. Set. In other words, in FIG. 11, when the signal q becomes 1 in the first area E6 in the third area, the signal r also becomes 1 in the other first areas El, E2A, and E5 that make up the third area. Becomes 1.

Next, the operation control section 80 and output control section 90 shown in FIG. 3 will be explained. FIG. 13 shows the operation control section 80 and the output control section 9.
0 configuration is shown.

The operation control unit 80 presses the mode key Kl, 2. 3°K4
．． Signal processing circuit 81. Pull-up circuit (resistor) 822
Display driver 832 display lamp Ll.

L2. It consists of L3 and L4. The signal processing circuit 81 reads the state of 4 on the mode key Kl- and outputs the mode signal g.
l* g2p Output g3 and g4.

That is, when the mode key Kl is turned on, each mode signal g1
1g2+g3 and g4 become 1,0°0 and 0 respectively, and when you turn on the mode key 2, each mode signal gl
+ g2v g3 and g4 become 0, 1.0 and 0, respectively, and when 3 is turned on in the mode key, each mode signal glyg2yg3 and g4 becomes O, 0, 1 and 0, respectively.
, and when you turn on 4 in the mode key, each mode signal g
lyg2*g3 and g4 are 0, 0.0 and l, respectively
become. When no mode key is pressed, each mode signal maintains its previous state. In the initial state.

Each mode signal gl*g2+g3 and g4 is 1
．． It becomes O, o and 0.

The display driver 83 controls the display lamps LL, L2 . Activate L3 and L4.

That is, the mode signals gl+g2*g3 and g4 are respectively 1. O, O and 0, the 1 display lamp L1 is energized, and 0, 1 . O and O energize the indicator lamp L2, and 0, 0.1 and 0.

The indicator lamp L3 is energized, and if it is 0, 0.0 and 1, it is 1.
Turn on indicator lamp L4.

Mode signals g1wg2-g3 output by the operation control unit 80
and g4 are applied to the output control section 90.

Next, the output control section 90 shown in FIG. 13 will be explained. This output control section 90 consists of data selectors 91 and 92 and OR gates 93 and 94.

Data selectors 91 and 92 are selection control terminals A.

When B is 0,0, the input terminal CO is selected, when it is 1.0, the input terminal C1 is selected, when it is 0,1, the input terminal C2 is selected, and when it is 1,1, the input terminal C3 is selected, The signal applied to the selected input terminal is output to the output terminal Y. The input terminals CO, CI, C2 and C3 of the data selector 91 have a signal e, a signal e, a signal d and a fixed level L, respectively.
(0) is applied. Input terminal C of data selector 92
A signal e and a signal d are applied to input terminals CO and C2 of the data selector 92, respectively, and a signal selected by the data selector 91 is applied to input terminals CO and C3 of the data selector 92.

Therefore, the contents of the signals output by the output control section 90 are as shown in Table 1 below.

Table 1 However, operation modes 1, 2, 3, and 4 are character modes (gl, g2.g3.g4 = 1, 0, 0.0), respectively.
, photo mode (gl, g2.g3.g4=0.1.O
, O), automatic separation mode (gl, g2.g3.g4=
0.0,1. O) and magic race mode (gl,
g2. g3. g4=o, 0, 0.1).

In other words, if you press 1 on the mode key to specify the character mode, regardless of whether the original image is halftone or not, the image data is simply binarized using the fixed threshold value THI (e
) is sent to the printer as one image data, and if you press 2 on the mode key to specify photo mode, the 0 image data will be converted into binary data processed by halftone processing using the submatrix method, regardless of whether the original image is halftone or not. Signal (d) is sent to the printer as image data.

Also, if you press 3 on the mode key to specify automatic separation mode, the image signal is selected according to the result of determining whether the original image contains halftone information, that is, the signal (f), and the halftone image is selects the signal (d) that has undergone halftone processing and outputs it to the printer, and for a binary image, selects the signal (e) that has undergone simple binarization processing and outputs it to the printer. Here, even if the halftone-printed image is a character or the like, it is determined as having halftone information as described above and is subjected to halftone processing.

When you press 4 on the mode key to specify magic erase mode, a signal is selected according to the result of determining whether the original image contains halftone information, that is, the signal (f), and if there is halftone information, the signal is selected at low level L, That is, a signal at the white pixel level is selected and output to the printer, and if there is no halftone information, a signal (e) subjected to simple binarization processing is selected and output to the printer.

Here, the operation of the magic erase mode will be explained in an easy-to-understand manner.

In the magic erase mode, all pixels in an area determined to have halftone information are replaced with a signal (low level L) corresponding to a white pixel and output to the printer. In other words, all images in the halftone area are erased. In areas determined to have no halftone information, a signal subjected to simple binarization processing is output to the printer.

In the actual copy operation, the following things are realized in this magic erase mode.

Here, as shown in FIG. 14a, the character string ha A B C#l, tr pq, written with relatively thin lines,
Assume that there is an image as a manuscript that includes the characters #RPI written in a thick line and the characters ``u, a4 x y z''6.For example, if you want to erase the part with the characters II pqrat, you can All you need to do is fill it in with a thin felt-tip pen, etc.The character string of II Pqr1' is a binary image, but when you fill it in, the spaces between the lines are colored, and the entire area becomes one relatively large area. This is determined by the first determination unit 71 in the area determination unit 70. That is, in this determination unit 71, as described above, the
x7 pixel matrix) has a density equal to or higher than the threshold value TH2, that portion is regarded as a halftone area.

For areas considered to be halftone areas, white pixels are recorded (not recorded) regardless of the content of the original image (in this case, the characters l#Pqru) and its density, so II PqrIt. The characters and the marks that filled them in are erased. In this case, other ``ABC''
The characters 'XYZ' and 'XYZ' are processed as a binary image and appear on the copy image (see Figure 14b).

On the other hand, regarding the characters rz Rtr written in thick lines,
Magic erase mode erases all but one outline without special filling.

That is, since an area larger than a predetermined size is determined to be a halftone area, the portion written with a thick line is regarded as a halftone area and is erased as described above. however.

From the outline of the thick line, that is, from each pixel located furthest outside the line among the pixel group corresponding to the thick line.

A portion having a width in the X direction or up to the 6th pixel in the X direction is determined to be a binary region. The portion determined to be a binary region is subjected to binarization processing using a threshold value THI, and the result is output as an image signal. As a result, only the outline of the line appears black on the copy (see Figure 14b); in other words, in Magic Erase mode, all characters written with thick lines are converted to so-called white characters (or patterns). Ru.

Note that even when filling in with a thin felt-tip pen or the like as described above, the outline of the area is processed as a binary area. However, if the density is lower than the threshold level THI, the result of the binarization process will be a white pixel. In other words,
By using a writing instrument with a low density for filling,
Outlines can also be erased.

For example, if there are characters written using a thin felt-tip pen or the like from the beginning, all of them are erased.

Here, the characteristics of the blank copy obtained by this embodiment will be explained. The blank copy obtained by this embodiment is not limited to characters but also symbols.

Any pattern having a thickness greater than a predetermined value, such as a single line figure, a picture, etc., can be processed. In addition, in this embodiment, the outline remaining by whitening is recorded by a binary image signal, and its width is constant (6 pixels in the X direction and 6 pixels in the X direction), so there is no blur and a sharp It becomes an image.

Methods for obtaining this type of white copy have been proposed in the past, but in this method, a blurred image and a sharp image are obtained respectively, whether optically, electrically, or logically. Since the result is obtained by exclusive OR of , blurring occurs in the white pattern. One image with rounded corners becomes thicker. Inconveniences such as small parts being crushed cannot be avoided.

In addition, the image signal can be divided into two levels using two threshold levels: high and low.
A method has also been proposed in which two types of digitized signals are obtained and the result is obtained by exclusive ORing them, but even with this method, there are disadvantages such as uneven line thickness and two images becoming thick. There is.

Furthermore, in the above two conventional methods, since exclusive OR is used, the character 2 formed by thin lines or thin lines
All figures and the like are also subjected to whiteout processing, and the lines in the whiteout image are thicker than in the original. In other words, conventional whiteout processing is similar to border processing.

On the other hand, in the embodiment described above, the outline process is performed only on images having a thickness greater than a predetermined thickness, so that thin line parts that do not require the outline process are recorded as in the original. Furthermore, since the outline of the original image remains as a blank copy, the size of the pattern does not change, and phenomena such as blurring of the image and rounding of the corners of the pattern do not occur.

The thickness of the lines of the pattern obtained by whitening is
In this embodiment, the configuration of pixels processed by the first determination unit 71 (
It can be changed arbitrarily by changing the number of pixels).

FIG. 15a shows a modification of the mesh detection circuit and the first area detection circuit, and FIG. 15b shows the operation timing of the first area detection circuit 170B.

This will be explained with reference to each episode. The mesh detection circuit 160B has the same configuration as the fourth mesh detection circuit MS4 shown in FIG. 7b.

In the first area detection circuit 170B, the circuit that generates the signal Qx is changed to a gate 171, and the circuit that generates the signal QY is changed to a gate 172. Three input terminals of the gate 171 are applied with the lower three bits QXO, QXI, and Qx2 of a signal indicating the position in pixel units in the X direction, and three input terminals of the gate 172 are applied with the position in pixel units in the y direction. The lower 3 bits of the signal QyOy Qyl and Qy
2 is applied.

Therefore, the signal Qx is at a low level L for one out of eight consecutive pixels in the X direction, and is at a high level H during the other periods. Similarly, the signal Qy is 8 consecutive in the y direction.
The low level is set to L at a rate of 1 pixel, and the high level is set to H during the other periods.

Therefore, in this example, the detection conditions of the mesh detection circuit are fixed, and the size of the first area is fixed to 8×8 pixels.

In the above embodiment, the operation mode is not changed unless the mode key Kl~ is changed to 4, but the mode can be arbitrarily programmed and specified for each position on the document using the numeric keypad, for example. The control device may automatically change the mode for each scanning position while reading the document.

Furthermore, in the embodiment, in the magic erase mode, the portion determined to be a halftone area is erased, and the portion determined to be a binary image area is recorded.

Conversely, a configuration may be adopted in which only the determined portion is recorded in the halftone area. In that case, you may output a simple binarized signal instead of a halftone processed signal for the part determined to be a halftone area. If you do this, the part filled in with a felt-tip pen etc. will be copied. According to this, only the filled areas can be selectively copied.

This type of configuration change can be made using the data selector 9 shown in FIG.
This can be done by simply changing the connection between each input terminal of 1 and each signal line.

[Effects] As described above, according to the present invention, each area of the original image determines whether the halftone image is a binary image and automatically switches between halftone processing and binarization processing. Even for an original in which tone images and binary images such as characters are mixed, both images of photographs and characters can be clearly copied. Furthermore, since it is provided with an operation mode for erasing a specific area, it is possible to easily erase any image on a document, and image processing such as whitening is also possible.

In particular, since a plurality of different types of determination circuits are provided to determine the presence or absence of halftone information, the determination accuracy is high.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an operation panel of one type of copying machine embodying the present invention. FIG. 2 is a front view showing a mechanical section of a copying machine equipped with the operation panel shown in FIG. 1. FIG. 3 is a block diagram showing the electrical circuit of the copying machine of FIG. 2. FIG. 4 is a block diagram showing the area determining section of FIG. 3. FIG. 5 is an electrical circuit diagram showing the first determination section 71 of FIG. 4. 6a and 6b are timing charts showing the operation of the circuit of FIG. 5. FIG. FIGS. 7a, 7b, 7c, and 7d are electrical circuit diagrams showing the configuration of the second determination section 72 shown in FIG. 4. FIG. 8 is a plan view showing an enlarged image printed with halftone dots at three different densities. FIG. 9 is a plan view showing the arrangement of pixels used by the mesh detection circuit 160 to determine the presence or absence of dots. FIG. 10a is a plan view showing a part of a halftone-printed image;
FIG. 10b is a plan view showing the binary code obtained by reading the image in FIG. 10a. FIG. 11 shows the first area assumed by the first determination unit 72,
FIG. 3 is a plan view showing the configuration of a second area and a third area. FIGS. 12a and 12b are timing charts showing the operations of the first area detection circuit 170 and the second area detection circuit 180, respectively. FIG. 13 is an electrical circuit diagram showing the configuration of the operation control section 80 and the output control section 90. FIG. 14a is a plan view showing an example of an original image, and FIG. 14b is a plan view showing a copy image obtained from the original shown in FIG. 14a. FIG. 15a is a block diagram showing a modification of the mesh detection circuit and the first area detection circuit, and FIG. 15b is a timing chart showing the operation of the first area detection circuit of FIG. 15a. 1: Scanner 2: Printer (recording means) 3:
Photosensitive drum 10: Image reading sensor (image reading means) 40: A/D converter 50: Halftone processing section (halftone processing means) 60: Binarization processing section (binarization processing means) 70: Area determination Section (Area Judgment Means) 71: First judgment section 72: Second judgment section 80: Operation control section 90: Output control section (control means) 11
0: Binarization circuit 120: Y delay circuit 130: X delay circuit 140: AND circuit 150: XY delay circuit 160: Mesh detection circuit 170: First area detection circuit 180: Second area detection circuit 190; Third area 2. to the detection circuit Kl; 3. 4: Mode key (operation mode designation means) '9i9 Entai 14a [%14b[] 1A, 10a mouth 10b procedure Ariguchi Seiatsu: (J9i January 7, 1985 1, Incident display 1985 Patent Application No. 245036 2
, Title of the invention Digital copying device 3, Relationship with the person making the amendment Patent applicant address 1-3-6 Nakamagome, Ota-ku, Tokyo Name
(674) Ricoh Co., Ltd. Representative Hama 1
) Hiro 4, Agent 103 Te1.038646052
Address: 2-27-6 Higashi Nihonbashi, Chuo-ku, Tokyo
No. 5, Detailed explanation of the invention in the specification to be amended, and Drawing 6, Contents of the amendment (,) The following pages and lines in the detailed description of the invention in the specification: (b) Drawings Figures 7d and 10a are corrected as shown in the attached sheet. 7. List of attached documents

Claims (9)

[Claims] (1) Image reading means that scans a document image and outputs an electric signal according to the image density for each minute area of the image; Processes the electric signal outputted by the image reading means and according to the level of the signal. halftone processing means for outputting a binary signal containing halftone information; a halftone processing means for processing the electrical signal output by the image reading means, comparing the level of the signal with a predetermined fixed reference level; Binarization processing means for outputting a binary signal; a level of the electric signal outputted by the image reading means is determined by a first threshold level, and the original image has halftone information based on the binary signal; a first determining means for determining whether or not the original image contains halftone information; and a second threshold level for determining whether the original image contains halftone information. a second determining means for determining whether or not the second determining means includes; a recording means for performing binary recording on a predetermined recording medium according to an input electrical signal; and the area determining means control means for applying any one of a signal output by the halftone processing means, a signal output from the binarization processing means, and a signal at a predetermined level to the recording means according to the determination result; Digital copying equipment. (2) The first threshold level is a fixed reference level of the binarization processing means, and the second threshold level is set to a lower level in terms of density than the first threshold level. , a digital copying apparatus according to claim (1). (3) The first determination means detects whether the arrangement of black level pixels or white level pixels of the original image is in the form of a halftone dot, and if it is in the form of a halftone dot, it is determined that there is halftone information. A digital copying apparatus according to scope (2). (4) The first determination means includes a serial-to-parallel conversion means for simultaneously outputting signals of a plurality of pixels adjacent to each other in the main scanning direction and the sub-scanning direction of the image reading means; a pixel detection means that processes a signal output from the pixel detection means and determines for each pixel whether or not the pixel of interest and its surrounding pixels are arranged in a halftone pattern; 3. The digital copying apparatus according to claim 3, further comprising: first area detection means for determining the presence or absence or number of pixels for which a halftone pattern has been detected within one area. (5) The first determining means processes the signal output from the first area detecting means to determine the presence or absence of a halftone pattern in a second area formed by a plurality of sets of the first areas. 2-area detection means. A digital copying apparatus according to claim (4). (6) The first determination means processes the signal output from the second area detection means to determine the presence or absence of a halftone pattern in a third area that is a plurality of sets of the first areas. 3 area detection means.
) The digital copying device described in item 2. (7) The second determination means processes the binary signal determined based on the second threshold level, and determines whether the pixel indicating the black corresponding level of the original image is in the main scanning direction of the image reading means and The digital copying apparatus according to claim 2, wherein the digital copying apparatus determines that halftone information exists if it appears consecutively in the sub-scanning direction a predetermined number or more times. (8) In the first operation mode, the control means applies a signal output from the halftone processing means to the recording means when the area determination means determines that there is halftone information, and when the area determination means determines that there is halftone information, When making a determination, a signal output from the binarization processing means is applied to the recording means; in a second operation mode, when the area determining means determines that halftone information is present, a signal of a predetermined level is applied to the recording means; and applying the signal output from the binarization processing means to the recording means when determining that there is no halftone information.
Section 1), Section (2), Section (3), Section (4), Section (5)
), (6) or (7). (9) The digital copying apparatus according to claim (1), wherein the predetermined level corresponds to a white level of an image.