JPH05336341A - Image processor - Google Patents

Abstract

PURPOSE:To discriminate between an original surface and an external frame from a copied image and to suppress the relief of a mask portion at a center part by replacing the image signal within a mask range by the signal showing & prescribed density which is higher than a non-recording level. CONSTITUTION:This image processor is provided with a mask processing means 50A including a means 51 generating the gate signal showing a mask range and a means 53 replacing the image signal within the mask range shown by the signal in response to the gate signal by the signal showing prescribed density which is higher than a non-recording level. The mask processing means 50A replaces the image signal within the mask range by the signal showing prescribed density which is higher than the non-recording level. Further, by being provided with a means 53E selecting and setting the recording density of a mask area, a mask density selection for clarifying the discrimination between an original surface and an external frame more and a mask density selection for suppressing the relief of a mask portion at a center part more are possible. In this case, preferably, the density selections of the recording density of an external mask area and the center part mask area are performed separately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, like a digital copying machine or a facsimile, reads original image information with an image reading device such as a CCD, converts it into digital image data, processes the image data, and finally The present invention relates to an image processing device for outputting to a recording device such as a printer.

[0002]

2. Description of the Related Art When copying an original such as a book such as a thick book as shown in FIG. 16, even if the original (book) is pressed by a pressing plate, the pressing plate cannot reach the contact glass because of the thickness of the original. Since it is far from the glass, the outside of the original becomes solid black on the copy as shown by the diagonal lines in FIG. Further, there is a problem in that the floating of the document due to the binding portion (central portion) between the pages also stains the central portion in black on the copy, impairing the aesthetics of the copy. In addition, the toner is wastefully consumed.

In order to prevent this unnecessary solid black or black stains, in an analog copying machine, there is a method of erasing the latent image of the stain portion by providing a light source different from the light source for forming a latent image on the photoconductor. Known (for example, Japanese Patent Laid-Open No. 2-103)
064 publication). Further, in the digital copying machine, the image signal is converted into an electric signal and the electric signal is masked to prevent stains (shaded lines in FIG. 17) on the outside of the document and the binding portion (central portion) (for example, Japanese Patent Laid-Open No. 61-61). 276476). The prevention of stains on the outside of the original is called frame erasing, and the prevention of stains on the bound portion (central portion) is called center erasing.

FIG. 18 shows an example of a mask processing circuit for erasing the seed frame in a digital copying machine. LGAT
The E and FGATE signals are mask signals in the main scanning direction and the sub scanning direction as shown in FIG. In the example shown in FIG. 19, the recording sheet and the LGATE and FGATE are closely aligned, but when masking the outside of the recording sheet, it is sufficient to make the LGATE and FGATE as long as desired. On the contrary, it may be shortened when it is held inside the recording sheet. FIG. 20 is a time chart showing the state of this type of image mask. In FIG. 20, LSYNC is a line synchronization signal for each raster scan line. This L
By changing the gate width and gate position of GATE and FGATE, a mask can be applied at a desired position, which enables frame erasing and center erasing.

[0005]

However, in the conventional mask processing, since the whitest level is given to the pixels of the mask portion, the black stain disappears, but the distinction between the original background and the outer frame is distinguished from the copied image. If the center erasure is performed when the background of the original has a certain density, on the contrary, there is a problem that the masked part is clearly lifted and unnatural.

Further, particularly in the case of center erasing, there is a possibility that the necessary image information remaining in the central portion of the document of the book will also be erased.

Therefore, the first object of the present invention is to improve the unnaturalness of the frame erasing and the center erasing as much as possible, and the second object thereof is to avoid the disappearance of the document image information as much as possible. And

[0008]

According to a first image processing apparatus of the present invention, an image reading means (100) for optically reading document image information and outputting an image signal; Means for setting a mask range for masking the outer frame, means for setting a mask range for masking the central portion of the original, and mask processing means for processing image signals within the mask range separately from those outside the range Image signal processing means including
00,400); and an image recording means (200) for recording an image on a recording medium based on the image signal output by the image signal processing means (300,400); and generating a gate signal representing a mask range. Means (51), and means (53 / 53-1, 53-2) for replacing the image signal in the mask range represented by the gate signal with a signal representing a predetermined density higher than the non-recording level in response to the gate signal. And a mask processing means (50A in FIG. 3 / 50B in FIG. 6);

The second image processing apparatus of the present invention is an image reading means (100) for optically reading document image information and outputting an image signal; for masking the outer frame of the document with respect to the image signal. Image signal processing means including means for setting the mask range, means for setting the mask range for masking the central portion of the original, and mask processing means for processing image signals within the mask range separately from those outside the range. (300,400); and image recording means (20) for recording an image on a recording medium based on the image signal output by the image signal processing means (300,400).
0); in the image processing device, means for generating a gate signal representing a mask range for masking the central portion.
(51), means (61) for detecting whether or not the image signal conforms to the set passage condition, and a mask in the central portion when the image signal conforms to the passage condition in response to the detection and the gate signal Mask processing means (50c in FIG. 8) including means (62, 53H, 53A) for interrupting the image signal output when the image signal is not output even within the range.

The third image processing apparatus of the present invention is an image reading means (100) for optically reading document image information and outputting an image signal; for masking the outer frame of the document with respect to the image signal. Image signal processing means including means for setting the mask range, means for setting the mask range for masking the central portion of the original, and mask processing means for processing image signals within the mask range separately from those outside the range. (300,400); and image recording means (20) for recording an image on a recording medium based on the image signal output by the image signal processing means (300,400).
0); in the image processing apparatus, means (51) for generating a gate signal representing the mask range, means (71) for detecting the background level of the original, and an image signal within the mask range in response to the gate signal. To the image signal representing the background level of the document (53D, 53A) including mask processing means (Fig. 14).
50D);

[0011]

According to the first image processing apparatus, the mask processing means
(50A in FIG. 3 / 50B in FIG. 6) replaces the image signal in the mask range with a signal representing a predetermined density higher than the non-recording level, so that, for example, the predetermined density is slightly higher than the standard original background density. When set to, the distinction between the original background and the outer frame can be identified from the copied image, and the difference between the recording density of the central mask area and the recording density of the original image area outside the mask area is small, and the mask of the central area is small. Lifting of parts is suppressed. In the embodiment of the first image processing apparatus (FIGS. 3 and 6),
Since a means (53E) for selectively setting the recording density of the mask area is provided, in order to more clearly select the mask density for making the distinction between the background of the original document and the outer frame clearer, and to further suppress the lifting of the mask portion in the central portion. It is possible to select the mask density. In the preferred embodiment (FIG. 6), the print densities of the outer frame mask area and the central mask area are set to the mask density selection circuit 53.
-1 and 53-2 are selected separately.

According to the second image processing apparatus, the mask processing means (50c in FIG. 8) detects whether or not the image signal meets the set passing condition, and when the image signal meets the passing condition. Even when the image signal is not output even within the central mask range, the image signal output is blocked, so that the original image is extracted as much as possible from the passage condition, for example, black stain due to floating of the pressure plate or the original is removed as much as possible. By setting to be excluded, it is possible to obtain a copy with the omission of the original image and the black stain as little as possible. In one embodiment (a in FIG. 9) of the second image processing apparatus, within the mask range in the central portion, the density is a threshold that makes it difficult to visually recognize the original image due to black stains caused by the pressure plate and the original being lifted. As a value, it is detected whether or not the density level of the image signal is higher (61A), and if it is higher than that, the image signal is output as it is if the image signal is blocked. Another example
In (b of FIG. 9), it is detected whether or not the average value of the image signal is equal to or more than the threshold corresponding value (61B), and if it is greater than or equal to, the image signal remains as it is if the image signal is not blocked. Output. In another embodiment (FIG. 10), image edges are detected (66,6
7) Pass the image signal when the sharpness of the image edge is more than the threshold value. In yet another embodiment (FIG. 13), the average value of the image signal is detected by detecting whether or not the average value of the image signal is equal to or more than the threshold corresponding value (61D), and the average value of the image signal is calculated. An image signal is output when it is below a threshold value and there is an image edge.

According to the third image processing apparatus, the mask processing means (50D in FIG. 14) detects the original background level and replaces the image signal within the mask range with the image signal representing the original background level. The area automatically becomes the background density of the original, and a copy can be obtained in which there is substantially no rise in the mask area.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the outline of the internal mechanism of a digital copying machine embodying the present invention. The internal mechanism includes a scanner unit 100 and a printer unit 200. Although the scanner unit 100 and the printer unit 200 are often integrated as shown in the figure, they are sometimes separated and connected only electrically.

The contact glass 1 of the scanner section 100 on which a document (not shown) is placed is a light source 2a, 2b.
The reflected light (original image) from the read original is illuminated by C through the mirrors 3, 4, 5, 6, 7 and lens 8.
An image is formed on the light receiving surface of the CD image sensor 9. Light source 2
(2a, 2b) and mirror 3 are contact glasses 1
The lower surface of the parallel to the contact glass 1 in the sub-scanning direction (see FIG.
Mounted on a moving body 10 that moves in
The mirrors 4 and 5 are mounted on a traveling body 11 that moves in the sub-scanning direction at a speed of 1/2 in conjunction with the traveling body 10.
The main scanning direction is performed by solid-state scanning of the CCD image sensor 9, the original image is read by the CCD image sensor 9, and the entire surface of the original is scanned by moving the optical system as described above. In this embodiment, the reading density is set to 16 pixels / mm for both the main scanning and the sub-scanning, and it is possible to read a document of A3 size (297 mm × 420 mm). Reference numeral 39 is a document pressure plate for pressing the document.

The printer section 200 comprises a laser writing system, an image reproducing system and a paper feeding system. The laser writing system includes a laser output unit 21, an imaging lens 22 and a mirror 23. Laser output unit 21
A polygonal mirror (polygon mirror) that rotates at a high speed and a constant speed by a laser diode, which is a laser light source, and an electric motor is provided inside. The laser light output from the laser writing system is the photosensitive drum 24 of the image reproducing system.
Is irradiated. Around the photosensitive drum 24, a charging charger 25, an eraser 26, a developing unit 27, a transfer charger 28, a separation charger 29, a separation claw 30, a cleaning unit 31, etc. are provided. A beam sensor (not shown) that generates a main scanning synchronization signal (MSSYNC) is arranged near the one end of the photosensitive drum 24 at a position where the laser beam is emitted.

The image reproduction process in the printer section 200 will be briefly described. The peripheral surface of the photosensitive drum 24 is
The charging charger 25 uniformly charges the battery to a high potential. When the peripheral surface is irradiated with laser light, the potential of the irradiated portion is lowered. The laser light is on / off controlled according to black / white of recording / reproduction, and the lighting pulse width of the laser diode is changed according to the gradation level by PWM to control the irradiation area. The potential distribution corresponding to the recorded image, that is, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 24 by the irradiation of the laser light or the irradiation area. When the portion on which the electrostatic latent image is formed passes through the developing unit 27, toner adheres according to the level of the potential, and the electrostatic latent image becomes a visualized toner image. The recording sheet 32 is fed from the cassette to the portion where the toner image is formed at a predetermined timing and overlaps the toner image. This toner image is transferred to the recording sheet 32 by the transfer charger 28, and then separated from the photosensitive drum 24 by the separation charger 29 and the separation claw 30. The separated recording sheet 32 is conveyed by a conveyor belt 34, heated and fixed by a fixing roller 35 having a built-in heater, and then ejected to an ejection tray 36.

In this embodiment, the laser printer 200 has two paper feeding systems. One of the paper feed systems is provided with an upper paper feed cassette 33a and a manual paper feed tray 33c. The upper paper feed cassette 33a or the manual paper feed tray 33c is provided.
The recording sheet 32a set in the
Fed by. The other sheet feeding system is provided with a lower sheet feeding cassette 33b, and the recording sheet 32b in the lower sheet feeding cassette 33b is fed by a sheet feeding roller 37b. Then, the recording sheet 32 fed from any one of the sheet feeding rollers is temporarily stopped while being in contact with the registration roller 38, and is fed to the photosensitive drum 24 at a timing synchronized with the progress of the recording process. Each sheet feeding system has a recording sheet 32 stored in a cassette 33a, 33b.
Sensors (not shown) for detecting the sizes of a and 33b are provided respectively.

The line sync signal, which is the reference for the copying operation, is
Normally, when the laser beam scans with polygon rotation based on the rotation of the polygon motor, an optical sensor is installed at the position immediately before the scanning starts, and the signal obtained by detecting the beam is synchronized with the image clock (strictly speaking, the clock (Synchronized with detection). This detection signal (PMSYNC) is set as a cycle and C
A drive signal for the CD image sensor 9 is created.

FIG. 2 shows an outline of the configuration of the electrical equipment section of the digital copying machine shown in FIG. The electrical component section mainly scans a document and outputs an image signal, a scanner section 100, an image processing section 300 that processes the image signal, a printer section 200 that records based on the image signal, and inputs and displays various processing modes. The operation display unit 500 and the control unit 400 for controlling these units and the like.

As described above, the CCD image sensor 9
An image signal read at a sampling density of 6 pixels / mm is amplified to a predetermined voltage amplitude which is an amplifier 101,
After that, the A / D conversion circuit 102 converts the digital data into several gradations (256 gradations in this embodiment) per pixel.
Then, in the shading correction circuit 103, the light sources 2a, 2b
Shading correction for correcting unevenness in illuminance, sensitivity variations among the elements of the CCD image sensor 9, and the like. Reference numeral 103 is a sensor driver.

After that, the spatial filter circuit 301 of the image processing unit 300 performs MTF correction for increasing the resolution of characters and line characters,
Smoothing processing for removing noise such as photographs is performed. Then, the output modulation circuit 302 performs γ correction in consideration of γ characteristics of the printer, halftone expression processing in consideration of tone reproduction of the printer, and code data (PWM in the embodiment) corresponding to a write signal (PWM in the embodiment) created by the printer unit 200. In the embodiment, it is converted into a code indicating a PWM pulse width and a phase and is output from the output circuit 303 to the printer unit 200. The processing / editing circuit 304 includes the mask processing circuit 50, and the circuit 304 performs various processing and editing processing including the mask processing on the code data. This processing will be described later.

The LD driver circuit 201 energizes the LD 202, and modulated laser light is emitted from the LD.

The control unit 400 includes a CPU 401 and a ROM 4
02, RAM 403, I / O port 404, etc., and controls the entire copying machine.

As described above, the image signal for which the image processing has been completed is sent to the printer section 200, but it is wasteful of toner to form an image on the photosensitive drum 24 in a portion beyond the range of the recording sheet. Although it is preferable to form an image on the entire surface of the recording sheet, the appearance of the copied image is improved by prohibiting recording around the recording sheet (the edge portion), or at the moment when the recording sheet contacts the photosensitive drum 24. In some cases, the toner on the photoconductor is not scraped off by the leading edge of the recording sheet. Further, as shown in FIGS. 16 and 17, when copying a book original, it is necessary to erase the frame and erase the center. In such cases,
It is necessary to mask the image signal in the range corresponding to the recording sheet, and this processing is performed by the mask processing circuit 50 of the processing / editing circuit 304. In the present embodiment, the masking process (50) of the image signal is performed by the processing / editing circuit 304, but the present invention is not limited to this, after shading correction, after spatial filtering, or after the image signal is transferred to the printer unit 200. May be

The mask processing for frame erasing and center erasing according to the present invention will be described. The range of the frame erasure and the center erasure when copying a book original is input by the operator through the operation display unit 500, and as shown in FIG. 5, the addresses P1, P2, Q1, Q2, Q3 and Q4 are set. The CPU 401 recognizes it. As a result, the mask range is determined. Regarding the determination of the mask range, details are omitted, but even if the operator does not specify the method, the method is executed when the copy operation is started without closing the original pressure plate 39, and the original size is detected after the operator instructs the mask range. There is a method of automatically determining the size of the document and a method of detecting the size of the document as well as the range of the black area around the document and in the center.

A first example of the mask processing circuit 50 (50 in FIG. 3)
A): FIG. 3 shows a configuration of a first example 50A of the mask processing circuit 50 included in the processing / editing circuit 304. Two mask signals ML for erasing the frame and erasing the center generated by the mask signal generation circuit 51 based on the address setting and the like.
The AND gate 52 takes the logical product of GATE and MFGATE to mask the image data. That is, MLGAT
When both the E signal and the MFGATE signal are active, the image data passes through the AND gate group 53.
When either the GATE signal or the MFGATE signal is non-active, the image data does not pass through the first AND gate group 53A, all the bits are "0" and are at the whitest level.

Here, the second AND is used in order to replace the mask target pixel with the level of a predetermined value without setting it to the whitest level.
A gate group 53B, a third AND gate group 53C and a data selector 53E are added. In contrast to the first AND gate group 53A, the second AND gate group 53B is different in that an OR gate is used for the signal line of the lower second bit of the image data, and the third AND gate group 53C is different from the lower third bit of the image data. The difference is that an OR gate is used for the signal line. In the mask area (the output of the AND gate 53D = “L”), all bits indicating the whitest level of the first AND gate group 53A are 0 (= “L”).
Of the second AND gate group 5
3B outputs image data showing a recording density of 2 in decimal notation, and the third AND gate group 53C outputs image data showing a recording density of 4 in decimal notation. Outside the mask area (AND
When the output of the gate 53D = “H”), all the AND gate groups 53A to 53B output the same image data, that is, input image data.

In response to the mask density designation input by the operator via the operation display unit 500, the CPU 401 generates a density selection signal designating an AND gate group (one of 53A to 53B) and gives it to the data selector 53E. , The data selector 53E is the AN designated by the density selection signal.
The output data of the D gate group (one of 53A to 53B) is
Output as masked image data. That is, the operator sets the mask density level by the operation display unit 5
It is input via 00. In addition, D7 to 0 is the CPU 40
1 is a data bus, A2 to 0 are register addresses in the mask signal generation circuit 51, WR is a write signal, and CS
Is a select signal.

FIG. 4 shows an outline of the configuration of the mask signal generation circuit 51. This circuit includes a decoder 511 and a register 51.
2a to 512f, X counter 513, Y counter 51
4, Comparators 515a to 515f, JK flip-flops 516a to 516c, and the like. CPU
Addresses P1, P2, Q1, Q2, Q recognized by 401
3 and Q4 correspond to registers 512a to 51, respectively.
Written in 2f. The X counter 513 is a counter in the main scanning direction and counts up with the pixel clock CLK starting from the line synchronization signal LSYNC. The Y counter 514 is a counter in the sub-scanning direction and counts up for each line (LSYNC) starting from the assertion of FGATE (a signal indicating the length of the recording sheet in the sub-scanning direction, FIG. 19). When the X counter 513 reaches P1, it is asserted and when it reaches P2, it is negated. This signal is ML
It is GATE. SF is asserted when the Y counter 514 reaches Q1 and negated when it reaches Q4.
The GATE signal is a signal for erasing the frame. Also Y
The CMASK signal, which is asserted when the counter 514 reaches Q2 and is negated when the counter 514 reaches Q3, is a signal for erasing the center. Unlike other mask signals, the CMASK signal has a logic of masking with "H". The signal obtained by ANDing the SFGATE signal and the CMASK signal (negative) is MFGATE. FIG. 5 shows the correlation between these signals, that is, the mask gate signal and the designated area.

Gate signal MLGA shown in FIGS. 4 and 5.
Since TE and MFGATE are applied to the AND gate 53D shown in FIG. 3, the output of the AND gate 53D is 1 (= “H”) inside the document areas A1 and A2 shown in FIG. 5, and 0 (= “” outside). L "), and therefore the original area A1,
The image data of A2 is the first AND gate group 53A to 53.
It is directly output through one of C and the data selector 53E. Outside the manuscript areas A1 and A2, when the density selection signal designates the first AND gate group 53A, the data selector 53E outputs its output. In this case, as in the conventional mask processing (FIG. 18), The image data indicates the whitest level. However, if the concentration selection signal is 2A
10 when the ND gate group 53B is designated
The image data indicating the density of 2 in binary notation is selected by the data selector 53.
E is output, and the density 2 is recorded outside the document areas A1 and A2. When the density selection signal designates the third AND gate group 53C, the data selector 53E outputs the image data indicating the density 4 in decimal notation, and the original area A
The outside of 1 and A2 is a record of density 4.

A second example of the mask processing circuit 50 (50 in FIG. 6)
B): According to the mask processing circuit 50A shown in FIG. 3, the outside of the original areas A1 and A2 is printed with the density specified by the operator, and the frame erase and the center erase (entire mask area) are recorded with the same density. Become. By the way, a mask density for increasing or decreasing the density contrast with the background of the original is set in the frame portion (recording paper edge), and the right edge of the original area X and the center portion (between X and Y in FIG. 5) are set. It may be preferable to set the mask densities separately for the frame portion and the center portion, such as setting a mask density having a small contrast with the density at the left end of Y (which is darker than the background density). A mask processing circuit 50B adapted to this is shown in FIG. In this example, the mask density selection circuit 1 (53-1) having the same configuration as the mask density selection circuit 53 shown in FIG.
A mask density selection circuit 2 (53-2) in which the D gate 53D is replaced with a NAND gate 53N is provided, and the former (5
The density selection signal 1 for specifying the mask density of the frame portion (recording paper edge) is given to 3-1), and the density selection signal 2 for specifying the mask density of the center portion is given to the latter (53-2).
Further, since MLGATE and CMASK are given to the NAND gate 53N of the mask density selection circuit 2 (53-2), the mask density selection circuit 2 (53-2) receives an image input to it in a region outside the center portion. The data (the same as the output of the data selector 53E in FIG. 3) is output as it is, but in the center portion, in response to the density selection signal 2,
Recording density 0 (whitest level), recording density 2 or recording density 4
Is output. That is, the mask density of the center portion is determined by the density selection signal 2. This density selection signal 2 also
In response to the center mask density designation input by the operator via the operation display unit 500, the CPU 401 causes the data selector (5) of the mask density selection circuit 2 (53-2) to operate.
3E equivalent).

A third example of the mask processing circuit 50 (50 in FIG. 8).
C): According to the mask processing circuits 50A and 50B shown in FIGS. 3 and 6 described above, the original areas A1 and A2
The outside of is a record of the density specified by the operator. By the way, the range of frame erasing and center erasing for a thick book (original) is as shown in FIG. 7 when viewed in the sub-scanning direction. From the transition of the background level (center part in FIG. 7), it can be seen that the background is black on the outside and center of the document. Normally, an image as transmission information does not exist outside the document, but an image as transmission information may exist in the center portion.
In particular, the closer to Q2 and Q3, the higher the possibility that image information exists. Therefore, it is preferable to avoid leakage of image information as much as possible, but when determining the positions of Q2 and Q3, if the width (between Q2 and Q3) is wide, the image information is lost, and conversely, if it is narrow, scumming remains. .. The part of the uncertain area shown in FIG. 7 is an area in which it is desired to save the image information but there is background stain, and the image information cannot be saved in the area where the background density is higher than a certain value (TH) (dark).

Therefore, the mask processing circuit 50C shown in FIG.
Is to extract the image information of the uncertain region as much as possible. The mask processing circuit 50c normally applies an image mask in an uncertain region (CMASK = H in FIG. 7), but sets a pass condition and masks a pixel satisfying the condition even in the uncertain region. Absent. That is, the image data is output as it is. The image data is input to the condition setting circuit 61 that determines the passage condition in the uncertain region, and when the condition is not satisfied, the condition setting circuit 61 outputs "H" to the NAND gate 62 to indicate the uncertain region. In cooperation with the indicated CMASK = H, the AND gate 53H is supplied with L for instructing the cutoff. When the passing condition is satisfied, the condition setting circuit 61 outputs the passing instruction signal L, which causes the output of the NAND gate 62 to become H and MLGATE and SFGATE (a signal for erasing the frame, "H" between Q1 and Q4) are given. The output of the AND gate 53H becomes H, and the AND gate group 53A outputs the input image data as it is. Therefore, when CMASK is active and the image data does not satisfy the pass condition, the image mask is applied even if both MLGATE and SFGATE are active. Conversely, when CMASK is active and the pass condition is satisfied by the image data, an uncertain region (CMASK = In (H), the mask is not applied and the image data is reproduced.

Next, several examples of the condition setting circuit 61 are shown in FIGS. 9A, 9B, 11 and 13.

(1) Condition setting circuit 61 shown in (a) of FIG.
The condition A is that the image data itself is below a certain density value TH (FIG. 7) as a passage condition. When the image data is A and TH is B, the two are compared by the comparison circuit 64, and when A> B, H is output to instruct the cutoff, and otherwise, L is output to instruct the passage.

(2) Condition setting circuit 61 shown in FIG. 9B.
The condition B is that the average value including not only the image data itself but also its surroundings is TH or less as a passing condition. In the condition setting circuit 61A, when the image data exceeds TH, the information is masked and cannot be saved. However, by smoothing it with an average value, leakage is prevented. The smoothing filter 65 for calculating the average value smoothes, for example, in units of 3 × 3 pixel matrix, as shown in FIG. The center is the target pixel, and the target pixel and its adjacent pixels are multiplied by 1 and summed, and the result is 1/9 to obtain an average value. Further, as shown in FIG. 10B, the area to be smoothed may be increased in 5 × 3 pixel matrix units. The larger this area is, the more the pixel of interest is prevented from leaking when it contains transmission information (original image information). However, the larger the smoothing area, the more complicated the process and the larger the circuit.

(3) The condition setting circuit 61C shown in FIG.
Edge extraction filter 6 instead of using density as a pass condition
6, the change in density is detected, and the place where the change in density is large is passed as transmission information. The comparison circuit 67 is
The edge sharpness obtained by the filter calculation is compared with the threshold value EDG, and when the sharpness is smaller than the EDG, H that indicates a cutoff is output, and when the sharpness is larger than the EDG, an L that indicates a passage is output. The edge extraction filter 66 multiplies the pixel of interest by a positive coefficient and the adjacent pixel by a negative coefficient in pixel matrix units, for example, as shown in FIG. Since the sum of the coefficients is 0, the added value is small when the density does not change, and the numerical value increases by ± when the density changes greatly. In FIG. 12A, a positive coefficient is multiplied by 2 and a negative coefficient is multiplied by −1/2. In FIG. 12B, a positive coefficient is 8 and a negative coefficient is −2.
The case where 1 is applied is shown. It should be noted that if it is limited that the transmission information is always blacker than the background, only the + side edge needs to be extracted, but the + side edge and the − side edge are adjacent to each other where there is information. Therefore, only the + value or the-value may be used instead of the absolute value.

(4) The condition setting circuit 61D shown in FIG.
Condition setting circuit 61B (b in FIG. 9) and condition setting circuit 61C
(FIG. 11) is combined. The passing condition is that the average value output of the smoothing filter 65 is TH or less and the edge detection value of the edge extracting filter 66 is EDG or more. The condition setting circuit 61D satisfies this passing condition. At this time, L which instructs the passage is output.

The third mask processing circuit 50 described above is used.
According to the example (50C in FIG. 8), the outer frame portion represents data representing the whitest level, and the inner frame portion (center) represents data representing the whitest level if the input image data is not satisfied when the passing condition is satisfied. However, the mask density selection circuits 53 and 53-2 shown in FIGS. 3 and 6 may be used together to output data representing a predetermined density in the outer frame portion. Further, the inner frame portion may output data representing a predetermined density if the passage condition is not satisfied.

For example, by replacing the AND gate group 53A and the AND gate 53H of FIG. 6 with the mask density selection circuit 53 shown in FIG. 3, data representing a predetermined density is output in the outer frame portion and the passage condition is passed in the inner frame portion. If the value does not satisfy the condition, data representing the predetermined density is output.

A condition setting circuit 61 and a NAND gate 62 shown in FIG. 8 are added to the mask processing circuit 50B shown in FIG. 6, and the AND gate 5 of the mask selection circuit 1 (53-1) is added.
By giving SFGATE to 3D instead of MFGATE and giving the output of the NAND gate 62 to the NAND gate 53N of the density selection circuit 2 (53-2), data representing a predetermined density is output in the outer frame portion. When the passage condition is not satisfied, the frame portion outputs data representing the predetermined concentration, and the predetermined concentrations of the outer frame portion and the inner frame portion can be set or selected separately.

A fourth example of the mask processing circuit 50 (5 in FIG. 14)
0D): As shown in FIG. 7, the background level of the document is not always the signal level "0" (whitest level),
May have some concentration. It is good for masking to "0" on the outside of the original, that is, for erasing the frame, but for center erasing in the middle of the original, and as in the third example (50C in FIG. 8), the mask (inner frame) It is unnatural that the background of the mask is whiter than the surroundings when the original image information in the inside is reproduced. This is usually
This is because it is preferable that there is a slight difference in density between the background of the original and the outside of the original, and conversely, it is preferable that there is no difference in density between the background after the mask at the center and the background of the original. Especially CMASK = H
When the width of the (inner frame) is narrowed, the background level before and after the mask rises as the CMASK becomes narrower, and the gap with the mask range becomes conspicuous.

A fourth example for improving this is shown in FIG. This is CMASK = H (inner frame) in relation to the center erase
The background level immediately before is held, and the held background signal is output to the mask (inner frame) portion. The background level and image data detected by the background detection circuit 71 are input to the selector 72, and either data (background level or image data) is output by the output signal from the NAND gate 62. That is, image data other than CMASK = H (inner frame) is selected. CMASK =
When the passage condition is not satisfied within H (inner frame) (output of the condition setting circuit 61 = H), the held background level signal is selected, and when the passage condition is satisfied (condition setting circuit 6).
When the output of 1 = L), the image data is selected. The selected signal is masked by the logical product of MLGATE and SFGATE. That is, in the manuscript areas A1 and A2 and the inner frame area between them, the output of the selector 72 is the AND gate group 5
3A, the data indicating the whitest level is output in the outer frame area.

FIG. 15 shows the structure of the background detection circuit 71. The background detection circuit 71 receives C from the assertion of SFGATE.
The background level is detected until MASK is asserted.
First, the DF / F 712 is preset before assertion of SFGATE. Then, during the assertion period of SFGATE, the comparison circuit 713 determines the one having the smallest value (density value) within the MLGATE assertion range, the selector 711 selects the background image signal, and the DF / F 712 is used as a mask portion. It is held as a background image signal. It should be noted that although the detection period is also provided between the assertions of CMASK, the background level between the CMASKs is actually high, so there is no problem in detection. Since the actual operation is not affected after the negation of CMASK, the background image signal may or may not be held or updated. In order to obtain the value immediately before the assertion of CMASK, instead of SFGATE, a signal to be asserted one line or several lines before CMASK is asserted (the number of lines required to detect the background) may be created and input to the preset of the DF / F 712.

Although the masking target pixel is set to the whitest level for erasing the outer frame, the present invention is not limited to this, and the first pixel shown in FIG.
It may be replaced with a certain predetermined level as in the example. For example, the AND gate group 53A and the AND gate 53D in FIG. 13 are replaced by the mask density selection circuit 53 shown in FIG. 3, and the AND gate 53D is replaced with MLGATE and SF.
Try to give GATE.

The third example shown in FIG. 8 and the fourth example shown in FIG.
In the example, the image data used by the condition setting circuit 61 to determine whether or not the passing condition is satisfied does not have to be the image data at the stage of actually masking. For example, the mask processing described above may be performed after the image processing is completed, and the determination of the pass condition therefor may be performed immediately after the shading correction 103 or after the spatial filter processing 301. However, the image data for determination and the image data to be masked have the same physical position on the document.

[0049]

The first image processing apparatus (50A in FIG. 3/50 in FIG. 6)
According to B), the image signal in the mask range is replaced with a signal representing a predetermined density higher than the non-recording level, and therefore, by setting the predetermined density slightly higher than the standard original background density, the original background It is possible to distinguish between the outer frame and the outer frame from the copied image, and the difference between the recording density of the central mask area and the recording density of the original image area outside the mask area is small, and the lifting of the central mask portion is suppressed. ..

According to the second image processing apparatus (50c in FIG. 8),
The passage condition is set to remove the original image as much as possible, for example, to eliminate the black stains caused by the pressure plate or the floating of the original document as much as possible, so that the original image does not leak and the black stains are as small as possible. You get a copy.

According to the third image processing apparatus (50D in FIG. 14), the mask area is automatically set to the background density of the original, and a copy in which the mask portion is not substantially lifted can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of the structure of a mechanical portion according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an electric component section of the digital copying machine shown in FIG.

3 is a block diagram showing a configuration of a first example of the mask processing circuit 50 shown in FIG.

4 is a block diagram showing a configuration of a mask signal generation circuit 51 shown in FIG.

FIG. 5 is a plan view showing a relationship between original areas A1 and A2, an outer frame area and an inner frame area on a recording medium, and a mask gate signal.

6 is a block diagram showing a configuration of a second example of the mask processing circuit 50 shown in FIG.

FIG. 7 is a graph showing a transition of background density in the sub-scanning direction and a mask gate signal for setting a frame erasing range and a center erasing range when a thick book is copied.

8 is a block diagram showing a configuration of a third example of the mask processing circuit 50 shown in FIG.

9 is a block diagram showing two examples of the condition setting circuit 61 shown in FIG.

10 is a plan view showing a pixel matrix of a smoothing processing unit in the smoothing filter 65 shown in FIG. 9B, where FIG. 10A shows a 3 × 3 pixel matrix and FIG.
Indicates a 5 × 3 pixel matrix, and coefficient values are shown in the squares.

11 is a block diagram showing a third example of the condition setting circuit 61 shown in FIG.

12 is a plan view showing a pixel matrix of an edge extraction processing unit of the edge extraction filter 66 shown in FIG. 11, and coefficient values for edge extraction calculation are shown in a square.

13 is a block diagram showing a fourth example of the condition setting circuit 61 shown in FIG.

14 is a block diagram showing a configuration of a fourth example of the mask processing circuit 50 shown in FIG.

15 is a block diagram showing a schematic configuration of a background detection circuit 71 shown in FIG.

FIG. 16 is an external perspective view showing how a thick book is copied by a copying machine.

FIG. 17 is a plan view showing a recording sheet after copying a thick book with the copying machine shown in FIG.

FIG. 18 is a block diagram showing an example of a mask processing circuit 50P included in a conventional digital copying machine.

FIG. 19 is a state diagram showing the positional relationship between the gate width defined by the LGATE and FGATE signals shown in FIG. 18 and the recording sheet.

FIG. 20 shows the LGATE signal and FGA shown in FIG.
It is a time chart which shows the relationship between a TE signal and image data.

[Explanation of symbols]

9: CCD image sensor 24: Photoreceptor drum 39: Document pressure plate 50, 50A, 50B, ...: Mask processing circuit 51: Mask signal generation circuit 53, 53-1, 53-2: Mask density selection circuit 61, 61A 61D: condition setting circuit 64, 67, 713: comparison circuit 65: smoothing filter 66: edge extraction filter 71: background detection circuit 72, 711: selector 100: scanner unit 200: printer unit 300: image processing unit 304: processing Editing circuit 400: control unit 401: CPU 500: operation display unit 712: DF / F

Claims (6)

[Claims] 1. An image reading means for optically reading original image information and outputting an image signal; means for setting a mask range for masking an outer frame of the original with respect to the image signal and a central portion of the original. Image signal processing means including means for setting a mask range for masking and image processing means for processing image signals within the mask range separately from those outside the range; and an image signal output by the image signal processing means. An image recording device for recording an image on a recording medium based on the above; a device for generating a gate signal representing a mask range, and an image within the mask range represented by the gate signal in response to the gate signal. An image processing apparatus comprising: a mask processing unit including a unit that replaces a signal with a signal representing a predetermined density higher than a non-recording level. 2. Image reading means for optically reading original image information and outputting an image signal; means for setting a mask range for masking the outer frame of the original with respect to the image signal and central portion of the original Image signal processing means including means for setting a mask range for masking and image processing means for processing image signals within the mask range separately from those outside the range; and an image signal output by the image signal processing means. An image processing device comprising an image recording means for recording an image on a recording medium on the basis of the :, a means for generating a gate signal representing a mask range for masking the central portion, the image signal conforming to a set passage condition Means for detecting whether or not to do so, and when the image signal meets the passage conditions in response to the detection and the gate signal, the image signal is output even within the mask range in the central portion. An image processing apparatus comprising: a mask processing unit including a unit that shuts off an image signal output when the determination result is negative. 3. The means for detecting whether or not the passing condition is met detects whether or not the image signal has a recording density lower than a specified threshold value and whether the image signal has a high recording density or not. Item 2. The image processing device according to item 2. 4. The means for detecting whether or not the pass condition is satisfied is suitable if the average value of the image signal of the pixel of interest and the image signal of the peripheral pixels is lower than the specified threshold. The image processing apparatus according to claim 2, wherein it is determined that the recording density is high. 5. The image processing apparatus according to claim 2, wherein the means for detecting whether or not the passage condition is met is an edge detecting means, and it is detected that the edge is a match and the edge is not an edge. 6. Image reading means for optically reading original image information and outputting an image signal; means for setting a mask range for masking the outer frame of the original with respect to the image signal and central portion of the original Image signal processing means including means for setting a mask range for masking and image processing means for processing image signals within the mask range separately from those outside the range; and an image signal output by the image signal processing means. An image recording device for recording an image on a recording medium based on the following: a device for generating a gate signal representing a mask range, a device for detecting a document background level, and a device for responding to the gate signal. An image processing apparatus comprising: mask processing means including means for replacing an image signal within a mask range with an image signal representing a background level of a document.