JP2000151937A - Image reader, method for discriminating read image and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the image reader where mis-discrimination for detecting a black letter caused by overshoot or the like in a scanning system is eliminated so as to enhance the image quality of a copy image by changing a threshold of a signal processing section to detect the black letter between an image tip area (an area where the scanning system is not yet stable at a prescribed speed) and its succeeding area, to provide the read image discrimination method and the storage medium. SOLUTION: The image reader is provided with an image read means 1, an image attribute discrimination means 2 that discriminates whether a pixel is a black/white pixel or a color pixel, an image component separate means 3 that separates a read image into a line component and a dot component, a scanning means 4, an area signal generating means 5 that generates a black letter area signal, a threshold revision means 6 that sets a threshold value for an astable area of a speed of a 1st mirror unit and a threshold area for a stable area, a black letter pixel discrimination means 7, and an image processing means 8 that outputs image data depending on the black letter pixel or the color pixel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, a read image judging method and a storage medium, and more particularly to an image reading apparatus and a read image judging method suitable for improving the quality of a copied image of a document. And a storage medium.

[0002]

2. Description of the Related Art In recent years, color image data obtained by digitally processing color image data and outputting it to a color printer to obtain a color image, and color reading of a color original by color separation and electrical reading. To magenta (M), cyan (C), yellow (Y), black (B
K) Color printing systems, such as so-called digital color copiers, which perform color image copying by printing and outputting on paper using four color toners, are remarkably developed. Further, with the spread of these, the demand for the printing quality of a color image is also increasing, and in particular, there is an increasing demand for printing black characters and black fine lines blacker and sharper.

That is, when a black document is subjected to color separation, signals of yellow, magenta, cyan, and black are generated as signals for reproducing black. Since the colors are reproduced by matching, a slight shift between colors causes color bleeding in a thin black line, and the black does not look black or appears blurred, thereby significantly lowering print quality. Therefore, when reading a document, a black character portion is extracted (black character determination), and the black character portion is subjected to a so-called black character process of forming a copy image using only black toner.

[0004] In addition, there has been a demand from copying machine users to shorten the copying time required for copying an original, and various measures have been taken.

FIG. 3 is a block diagram showing the internal structure of the color copying apparatus. In FIG. 3, reference numeral 201 denotes an image scanner which reads a document and performs digital signal processing. Reference numeral 202 denotes a printer unit which prints out an image corresponding to the document image read by the image scanner unit 201 on recording paper in full color. In the image scanner unit 201, reference numeral 200 denotes a mirror-thick plate, and a document 204 on a platen glass (hereinafter, platen) 203 is irradiated with light from a halogen lamp 205, and reflected light from the document is reflected by reflection mirrors 206 and 207. The light is led to form an image on a three-line sensor (hereinafter referred to as a sensor) 210 by a lens 209 and is sent to a signal processing unit 211 as full-color information red (R), green (G), and blue (B) components. The signal processing unit 211 performs predetermined signal processing, outputs an image signal to the printer unit 202,
The printer unit 202 forms a copy image of the document.

Incidentally, the halogen lamp 205, the reflection mirror 2
The first mirror unit 2061 with 06 has a speed v,
Second mirror unit 2071 having reflection mirror 207
Is driven by a motor (not shown) at a speed (1/2) v in a direction (hereinafter, a sub-scanning direction) perpendicular to an electrical scanning direction (hereinafter, a main scanning direction) of the line sensor, thereby scanning the entire surface of the document. I do.

FIG. 10 shows the relationship between the speed of the first mirror unit 2061 and time. The horizontal axis represents time, and the vertical axis represents the speed of the first mirror unit 2061. Also, 801
Shows the relationship between the speed of the first mirror unit 2061 and the time during the copying operation. t2 indicates the timing of starting the image data capture at the time of the copying operation.

Usually, a so-called acceleration time (0 → t) for accelerating the first mirror unit 2061 to the speed at the time of reading an image.
1) and the shorter the approach time (t2 → t3) from the end of acceleration to the start of image data capture, the shorter the time required for copying a document.

[0009]

However, the above-mentioned conventional control has the following problems. That is, as shown in FIG. 10, the overshoot of the first mirror unit 2061 is not completely eliminated at the start of image data capture t2 as shown in FIG. The original image cannot be accurately read in an area that is read during the period from time t2 to t3, and a black character portion cannot be accurately detected in this area.
There is a disadvantage that a portion to be copied by the color toner is generated, one character is partially copied, and the image quality is deteriorated as compared with a case where the image is simply copied with four color toners.

The present invention has been made in view of the above-described point, and a black character portion is formed between an image leading edge portion (a region where the scanning system is not stabilized at a predetermined speed) at the time of reading an original image and a region thereafter. An image reading apparatus, a read image determination method, and a storage that can improve erroneous determination of black character detection due to overshoot of a scanning system and improve the image quality of a copied image by changing a threshold value of a signal processing unit to be detected. The purpose is to provide a medium.

[0011]

According to the present invention, there is provided an image reading apparatus for reading an image by moving a scanning system relative to a document. Image attribute determining means for determining an attribute of an image read from a document based on a threshold, area signal generating means for generating an area signal every time the divided area obtained by dividing the entire surface of the document into at least one area is read, A threshold changing unit that changes a threshold of the image attribute determining unit for each area based on the signal.

According to another aspect of the present invention, there is provided an image reading means which constitutes the scanning system and reads an image from an original, and a line component based on an image signal read by the image reading means. An image component separating unit that separates a halftone dot component; a black character pixel determining unit that determines whether each pixel is a black character pixel based on the determination result of the image attribute determining unit and the separation result of the image component separating unit; Image processing means for performing predetermined processing on the image signal belonging to the attribute,
The black character pixel determination unit outputs a determination result to the image processing unit.

According to a third aspect of the present invention, the image attribute determining means determines whether each pixel is a monochrome pixel or a color pixel based on an image signal read by the image reading means. It is characterized by the following.

In order to achieve the above object, the present invention according to claim 4 is characterized in that the area signal generating means generates a black character area signal based on the sub-scanning of the scanning system.

According to a fifth aspect of the present invention, in the present invention, the threshold value changing means sets a threshold value for the unstable area in an unstable area where the scanning speed of the scanning system is not stable in the image attribute determination. And outputting a threshold value for a stable area to the image attribute determining means in a stable area where the scanning speed of the scanning system is stable.

In order to achieve the above object, according to the present invention, the image component separating means is characterized in that a halftone dot component having a large edge component in a plurality of directions smoothes the edge component. Characters / thin lines in which an edge component exists only in one direction are preserved.

According to another aspect of the present invention, the image processing means outputs image data represented only by black data in the case of a black character pixel, and outputs the image data in the case of a color pixel. It is characterized in that image data separated into colors is output.

In order to achieve the above object, the present invention according to claim 8 is characterized in that the threshold value changing means can change a threshold value for each of the regions only for the image component separating means.

In order to achieve the above object, according to a ninth aspect of the present invention, the threshold value changing means can change the threshold values of both the image attribute determining means and the image component separating means for each area. It is characterized by the following.

To achieve the above object, the present invention is characterized in that the present invention is applicable to a copying apparatus.

To achieve the above object, the present invention according to claim 11 is a read image determining method applied to an image reading apparatus for reading an image by moving a scanning system relative to a document. An image attribute determining step of determining an attribute of an image read from a document based on a threshold, and an area signal generating step of generating an area signal every time the divided area obtained by dividing the entire surface of the document into at least one area is read; A threshold value changing step of changing a threshold value of the image attribute determining step for each area based on the area signal.

In order to achieve the above object, according to the present invention, there is provided an image reading step for reading an image from a document by constituting the scanning system, and detecting a line component based on an image signal read in the image reading step. An image component separation step of separating a halftone dot component; a black character pixel determination step of determining whether each pixel is a black character pixel based on the determination result of the image attribute determination step and the separation result of the image component separation step; An image processing step of performing predetermined processing on the image signal belonging to the attribute, wherein the black character pixel determination step outputs a determination result to the image processing step.

In order to achieve the above object, according to a thirteenth aspect of the present invention, in the image attribute determining step, it is determined whether each pixel is a monochrome pixel or a color pixel based on the image signal read in the image reading step. It is characterized by the following.

In order to achieve the above object, the invention according to claim 14 is characterized in that in the area signal generating step, a black character area signal is generated based on the sub-scanning of the scanning system.

According to another aspect of the present invention, in the threshold value changing step, a threshold value for the unstable region is set in the image attribute determination in an unstable region where the scanning speed of the scanning system is not stable. And outputting a threshold value for a stable area to the image attribute determining step in a stable area where the scanning speed of the scanning system is stable.

In order to achieve the above object, according to the present invention, in the image component separating step, a halftone dot component having a large edge component in a plurality of directions is smoothed by the edge component, and the image component separating step is characterized by the following. Characters / thin lines in which an edge component exists only in one direction are preserved.

In order to achieve the above object, according to the present invention, in the image processing step, in the case of a black character pixel, image data represented only by black data is output,
In the case of a color pixel, image data separated into toner colors is output.

In order to achieve the above object, the present invention according to claim 18 is characterized in that, in the threshold value changing step, a threshold value can be changed for each of the regions only in the image component separating step.

In order to achieve the above object, according to the present invention as set forth in claim 19, in the threshold changing step, both thresholds of the image attribute determining step and the image component separating step can be changed for each area. It is characterized by the following.

In order to achieve the above object, the present invention is characterized in that the present invention is applicable to a copying apparatus.

In order to achieve the above object, the present invention according to claim 21 executes a read image determining method applied to an image reading apparatus which performs image reading by moving a scanning system relative to a document. A computer-readable storage medium storing a program, wherein the read image determination method includes: an image attribute determination step of determining an attribute of an image read from a document based on a threshold; A region signal generating step of generating a region signal each time the divided region is read, and a threshold changing step of changing a threshold of the image attribute determining step for each region based on the region signal. .

[0032]

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments of the present invention,
Although a copying apparatus is shown as an example of application of the present invention, it is needless to say that the present invention is not limited to this and can be applied to various other apparatuses.

FIG. 3 is a block diagram showing the internal structure of the color copying apparatus according to the embodiment of the present invention. The color copying apparatus according to the embodiment of the present invention includes an image scanner unit 20.
1. The printer generally includes a printer unit 202. The image scanner unit 201 includes a mirror-thick plate 200, a platen glass (hereinafter, platen) 203, a first mirror unit 2061 having a halogen lamp 205 and a reflection mirror 206, a second mirror unit 2071 having a reflection mirror 207,
A three-line sensor (hereinafter C) comprising a lens 209 and a CCD
CD sensor) 210, signal processing unit 211, standard white plate 5
102 is provided. The printer unit 202 includes a laser driver 212, a semiconductor laser 213, a polygon mirror 214, an f-θ lens 215, a mirror 216, a photosensitive drum 217, a magenta developing device 219, and a cyan developing device 22.
The image forming apparatus includes a rotary developing device 218 having 0, a yellow developing device 221 and a black developing device 222, a transfer drum 223, paper cassettes 224 and 225, and a fixing unit 226.

The components of the above components will be described in detail. The image scanner unit 201 reads a document and performs digital signal processing. The printer unit 202 is a unit that prints out an image corresponding to the original image read by the image scanner unit 201 on recording paper in full color. In the image scanner section 201, the mirror-surface thick plate 2
The original 204 on the platen 203 with the “00” closed is irradiated with the light of the halogen lamp 205, and the reflected light from the original is guided to the reflection mirrors 206 and 207, forms an image on the CCD sensor 210 by the lens 209, and becomes full color. The information is sent to the signal processing unit 211 as red (R), green (G), and blue (B) components. Standard white plate 5102
Is the CCD sensor 210 when the halogen lamp 205 is used.
Used for the correction data of the read data.

Incidentally, the halogen lamp 205, the reflection mirror 2
The first mirror unit 2061 with 06 has a speed v,
Second mirror unit 2071 having reflection mirror 207
Is driven by a motor (not shown) in a direction (hereinafter, a sub-scanning direction) perpendicular to an electrical scanning direction (hereinafter, a main scanning direction) of the CCD sensor 210 at a speed (１ ／) v, so that the entire surface of the original is Scan.

When the original is a color image, the signal processing unit 211 electrically processes the read signal to obtain each component of magenta (M), cyan (C), yellow (Y), and black (BK). And sends it to the printer unit 202.
In addition, for one document scan (scan) in the image scanner unit 201, one component among M, C, Y, and BK is sent to the printer unit 202, and one printout is performed by a total of four document scans. Is completed. When the original is a black and white image, the signal processing unit 211 electrically processes the read signal and sends a black (BK) component signal to the printer unit 202.

The M, C, Y, and BK image signals sent from the image scanner unit 201 are transmitted to the laser driver 21.
Sent to 2. The laser driver 212 modulates and drives the semiconductor laser 213 according to the image signal. The laser light is reflected by a polygon mirror 214, an f-θ lens 215, and a mirror 21.
6 and scans over the photosensitive drum 217. The rotary developing device 218 includes a magenta developing device 219 and a cyan developing device 22.
0, a yellow developing device 221 and a black developing device 222. The four developing devices are alternately in contact with the photosensitive drum 217, and are formed on the photosensitive drum 217.
Is developed with the corresponding toner. Transfer drum 2
23 winds the paper fed from the paper cassette 224 or 225 and transfers the toner image developed on the photosensitive drum 217 to the paper. Thus, M, C, Y,
After the four colors BK are sequentially transferred, the sheet passes through the fixing unit 226 and is discharged.

FIG. 14 shows the structure of the CCD sensor 210 used in this embodiment. Here, 210-1, 210-
Reference numerals 2 and 210-3 denote light receiving element arrays for sequentially reading R, G, and B wavelength components. The three light receiving element rows having different optical characteristics are monolithically formed on the same silicon chip so that the R, G, and B sensors are arranged in parallel with each other to read the same line of the document. I have.

FIG. 13 is an enlarged view of the light receiving element. Each sensor has a length of 10 μm per pixel in the main scanning direction.
Each sensor measures 400 mm in the short direction (297 mm) of the A3 document.
There are 5000 pixels in the main scanning direction so that the image can be read at a resolution of dpi. The distance between the lines of the R, G, and B sensors is 80 μm, and each line is separated by 8 lines for a sub-scanning resolution of 400 lpi. Further, in each line sensor, an optical filter is formed on the sensor surface in order to obtain predetermined R, G, B spectral characteristics.
Note that the above numerical values are merely examples, and the present invention is not limited to these numerical values.

Referring to FIG. 7 and FIG.
The spectral characteristics of the R, G, and B line sensors will be described. Each of the line sensors R, G, and B has an optical filter formed on the sensor surface in order to obtain predetermined spectral characteristics. FIG.
Are the characteristics of the conventionally used R, G, B filters. As can be seen from this figure, the conventional R, G, B
8 has sensitivity to infrared light of 700 nm or more, the lens 209 is provided with the infrared cut filter shown in FIG.

FIG. 2 is a block diagram showing the configuration (flow of image signals) of the signal processing section 211 in the image scanner section 201 of the color copying apparatus according to the embodiment of the present invention shown in FIG. The signal processing unit 211 includes an analog signal processing unit 4001, a shading correction unit 4002 having a line memory 4003, a coefficient memory 4006, and a multiplier 4007, delay elements 401 and 402, log converters 403, 404, and 405, a masking and UCR circuit 406. , Sub-scanning address counter 420, decoder 42
01, edge detection unit 108, saturation detection unit 4009, AN
D gate 1001, decoder 4008, CPU 417,
RAM / ROM 418, main scanning address counter 419
It has.

The function of the main part will be described in detail.
Reference numeral 7 controls the apparatus in each mode based on a control program stored in the apparatus (RAM / ROM 418) or supplied from outside the apparatus. RAM / ROM 418
Is added to the CPU 417, and temporarily stores data and stores control programs and the like. CCD sensor 210
The image signal output from the analog signal processing unit 400
1 and 8bi in the analog signal processing unit 4001.
After being converted into a digital image signal of t, the digital image signal is input to the shading correction unit 4002. The main scanning address counter 419 is reset at the rising edge of HSYNC, counts up at the timing of the CLK signal, and
3-bit main scanning address (X address) AX12-A
Generate X0.

The sub-scanning address counter 420 has a VSY
It is reset in the section of "0" of the NC signal, counted up at the timing of the HSYNC signal, and generates 13-bit sub-scanning addresses (Y addresses) AY12 to AY0. The decoder 4008 includes a main scanning address counter 41
The main scanning address from No. 9 is decoded to generate a line-by-line CCD drive signal such as a shift pulse or a reset pulse. The decoder 4201 decodes the sub-scanning address from the sub-scanning address counter 420 and outputs a black character area signal at a predetermined timing. Note that the shading correction unit 4002, the delay elements 401, 402, l
og converters 403, 404, 405, edge detector 10
8. The detailed functions of the saturation detector 4009, AND gate 1001, masking and UCR circuit 406 will be described later.

FIG. 1 is a functional block diagram showing a configuration of a main part of a color copying apparatus according to an embodiment of the present invention and corresponding to the claims. The main parts of the color copying apparatus according to the embodiment of the present invention include an image reading unit 1, an image attribute determining unit 2, an image component separating unit 3, a scanning unit 4, an area signal generating unit 5, a threshold changing unit 6, a black character pixel. It comprises a judgment means 7 and an image processing means 8. The configuration shown in FIG. 1 shows a configuration of a main part corresponding to the claims in the color copying apparatus, and illustrations of an analog signal processing unit, a shading correction unit, and the like are omitted.

The function of each section will be described in detail. The image reading means 1 reads an image from a document. Image attribute determination means 2
Is determined based on an image signal read by the image reading means 1 with a threshold value that allows the change of whether each pixel is a monochrome pixel or a color pixel. The image component separating means 3 smoothes the edge component of the halftone component having a large edge component in a plurality of directions based on the image signal read by the image reading means 1 to reduce the feature thereof, and reduces the edge component in only one direction. The character / thin line where is present preserves its characteristics. The scanning unit 4 moves relatively to the document and performs scanning / sub-scanning. Area signal generating means 5
Generates a black character area signal based on the sub-scanning of the scanning means 4.

The threshold changing means 6 outputs a threshold value for the unstable area to the image attribute determining means 2 in an area where the scanning speed of the scanning system is not stable, and outputs a threshold value for the stable area in an area where the scanning speed of the scanning system is stable. Is output to the image attribute determining means 2.
The black character pixel determining means 7 determines whether each pixel is a black character pixel based on the attribute determination result of the image attribute determining means 2 and the component separation result of the image component separating means 3. Image processing means 8
Outputs image data represented only by black data in the case of a black character pixel, and outputs color-separated image data of four toners in the case of a color pixel. In FIG. 1, the image reading unit 1 and the scanning unit 4 are shown in different configurations, but the image reading unit 1 and the scanning unit 4 are included in a scanning system.

The correspondence between the components in the claims and the components in the color copying apparatus according to the embodiment of the present invention is as follows. The image reading unit corresponds to the image reading unit 1 (CCD sensor 210), and the image attribute determining unit is the image attribute determining unit 2 (the saturation detecting unit 400).
9), the image component separating means is the image component separating means 3
(Edge detecting unit 108), and the scanning system is the scanning unit 4
(First mirror unit 2061, second mirror unit 2
071), the area signal generating means corresponds to the sub-scanning address counter 420, and the area signal generating means 5 (decoder 420)
Corresponding to 1), the threshold changing means is a threshold changing means 6 (CPU
417), the black character pixel determining means corresponds to the black character pixel determining means 7 (AND gate 1001), and the image processing means corresponds to the image processing means 8 (masking and UCR circuit 40).
This corresponds to 6).

FIG. 9 is a block diagram showing a configuration of the analog signal processing section 4001 in the signal processing section 211 of the color copying apparatus according to the embodiment of the present invention shown in FIG. The analog signal processing unit 4001 includes a sample and hold unit (S / H unit) 4101, a clamp circuit 4106, a variable amplifier 4103, a clamp circuit 4102, an A / D converter 4105, and a voltage control circuit 4104. Here, since the processing circuits for R, G, and B are all the same, a circuit for one color is shown.

The function of each unit will be described in detail together with the operation.
The image signal output from the CCD sensor 210 is sampled and held by a sample and hold unit (S / H unit) 4101 to stabilize the waveform of the analog signal. C
PU 417 is connected via a voltage control circuit 4104 to
The variable amplifier 4103 and the clamp circuit 4102 are controlled so that the image signal can fully utilize the dynamic range of the A / D converter 4105. A / D converter 4105
Converts an analog image signal into an 8-bit digital image signal.

The 8-bit digital image signal is subjected to shading correction by known shading correction means in the shading correction section 4002.
When reading shading data, the CCD sensor 210
The CPU 417 stores a read signal for one line from the standard white plate 5102 in the line memory 4003 and multiplies the read data of each pixel recorded in the line memory 4003 to 255 levels with respect to the read signal from A coefficient is obtained for each pixel, and this is stored in the coefficient memory 4006 for one line. Then, at the time of actual document reading, a multiplication coefficient corresponding to the pixel is read from the coefficient memory 4006 in synchronization with the output of each pixel by the line reading of the CCD sensor 210, and the
Shading correction is performed by applying to each pixel signal from the sensor 210.

As shown in FIG. 13, light receiving sections (light receiving element arrays) 210-1, 210-2, 210 of the CCD sensor 210 are provided.
Since -3 is arranged at a fixed distance, the delay elements 401 and 402 correct the spatial shift in the sub-scanning direction. Specifically, the R and G signals for reading the original in the sub-scanning direction with respect to the B signal are delayed in the sub-scanning direction to match the B signal. log converters 403, 404, 4
05 is constituted by a look-up table ROM,
The luminance signal is converted to a density signal. The determination as to whether each pixel is a black character pixel is made by any known method. Here, the edge detection unit 108 and the saturation detection unit 40 are used.
For example, a method configured by using the method of No. 09 will be described.

FIG. 12 shows a color saturation detecting section 4009 comprising a window comparator in the signal processing section 211 of the color copying apparatus according to the embodiment of the present invention shown in FIG.
FIG. 3 is a block diagram showing the configuration of FIG. The saturation detection unit 4009 determines whether each pixel is a monochrome pixel or a color pixel based on the 8-bit R, G, and B image signals. Saturation detector 4009
Are arithmetic units 621, 622, 623, a register 601,
602, 603, 604, 605, 606, comparators 607, 608, 609, 610, 611, 612,
A 6-input AND gate 613 is provided.

The function of each unit will be described in detail together with the operation.
In the arithmetic units 621, 622, and 623, the input R,
G × 128 / R, B × 128 based on G and B image signals
/ G, R × 128 / B, and outputs the operation result to the next-stage comparators 607, 608, 609, 610, 61
1, 612. Comparators 607, 608,
The outputs 609, 610, 611, and 612 become 1 only when A> B is satisfied with respect to the inputs A and B.

Now, the registers 601, 602, 603,
RGL, RGH, GBL, GBH, BRL, and BRH are assigned to 604, 605, and 606 by the CPU 417, respectively.
When the following values are written, RGL <G × 128 / R <RGH and GBL <B × 128 / G <GBH and BRL <R × 128 / B <BRH are established for the input signals R, G, and B. The output of the saturation detection unit 4009 is "1" only when the operation is performed, and is "0" otherwise. That is, when each pixel is determined to be an achromatic pixel, that is, a monochrome pixel, the output of the AND gate 613 becomes “1”, and when each pixel is determined to be a chromatic pixel, that is, a color pixel, AND
The output of the gate 613 becomes “0”.

In this embodiment, the first mirror unit 20
T1 to t shown in FIG.
In the two periods, the threshold value of the saturation detection unit 4009 is adjusted to the following values, and the R, G, and B signals are set to 70H <G × 128 / R <90H and 70H <B × 128 / G <90H and When 70L <R × 128 / B <90H is satisfied, each pixel is determined to be a monochrome pixel, and the first pixel is determined.
After t2 when the speed of the mirror unit 2061 is stabilized, the saturation detection unit 40 including the window comparator is used.
The threshold of 09 is adjusted to the value shown below, and R, G, B
When the signal satisfies 60H <G × 128 / R <A0H and 60H <B × 128 / G <A0H and 60L <R × 128 / B <A0H, each pixel is determined to be a monochrome pixel.

FIG. 4 is a block diagram showing the configuration of the edge detecting unit 108 of the color copying apparatus according to the embodiment of the present invention shown in FIG. The edge detection unit 108 includes a luminance calculation circuit 301, an edge min direction detection unit 302, an edge min direction smoothing unit 303, and an edge unit 304.

FIG. 5 is a block diagram showing a detailed configuration of the luminance calculating circuit 301 in the edge detecting section 108 of the color copying apparatus according to the embodiment of the present invention shown in FIG. The luminance calculation circuit 301 includes multipliers 401, 402, 4
03, adders 404 and 405 are provided.

FIG. 6 is an explanatory diagram for explaining the processing in the edge min direction detecting section 302 in the edge detecting section 108 of the color copying apparatus according to the embodiment of the present invention shown in FIG. The edge min direction detection unit 302
IFO (First In First Out) 50
1, 502, Laplacian filters 503, 504, 5
05, 506.

The function of each unit will be described in detail together with the operation.
The signals R, G, and B for which the shading correction and the spatial shift in the sub-scanning direction have been corrected are input to the edge detection unit 108, and the luminance signal Y is calculated by the luminance calculation circuit 301 according to the following equation.
Is calculated.

Y = 0.25R + 0.5G + 0.25B (1) The color signals R, G,
B is multiplied by each coefficient 0.25, 0.5, 0.25 in multipliers 401, 402, 403, and then added to adder 4
04 and 405 are added to calculate the luminance signal Y according to the above equation (1).

Next, the input luminance signal Y is represented by F in FIG.
3 delayed by one line each by IFOs 501-502
A known Laplacian filter 50 extended to the number of lines
The direction in which the absolute value a of the edge amount, which is the output value of the filter, takes the minimum value among the four directions is determined, and the direction is defined as the edge min direction. This is the edge min direction detection unit 302 in FIG.

Next, an edge min direction smoothing unit 3
In step 03, a smoothing process is performed on the min direction of the edge obtained by the edge min direction detection unit 302. By this processing, only the direction having the largest edge component can be stored, and the other directions can be smoothed. That is, a halftone dot component having a large edge component in a plurality of directions has its feature reduced by smoothing the edge component, while the feature of a character / thin line having an edge component in only one direction is preserved. The effect is to increase. By repeating this processing as necessary, the line component and the halftone dot component are more effectively separated, and the character component existing in the halftone dot, which cannot be detected by the conventional edge detection method, is also detected. It becomes possible. Then, the Laplacian filters 503-
Multiplied by 506, the edge value whose absolute value is equal to or smaller than the predetermined value a is removed, and only the edge value equal to or larger than a is output from the edge unit 304 as “1”.

Next, the AND gate 1001 in FIG. 2 determines whether each pixel is a black character pixel based on the determination results of the edge detection unit 108 and the saturation detection unit 4009, that is, each pixel is a black and white pixel and If the pixel has an edge in one direction, the pixel is determined to be a black character pixel, and "1" is output. Otherwise, "0" is output.

The masking and UCR circuit 40 shown in FIG.
Reference numeral 6 denotes a circuit obtained by adding a processing function for determining a black character to a known masking and UCR circuit.
For the pixel whose output of 01 is "0", normal masking and UCR processing, that is, image data separated into four colors of toner is output, and the output of the AND gate 1001 is "1".
The image data composed of only the black data is output for the pixel of.

Next, an actual copying operation in the color copying apparatus according to the embodiment of the present invention configured as described above will be described.

FIG. 11 shows the image scanner unit 201 of the color copying apparatus according to the embodiment of the present invention shown in FIG.
FIG. 5 is an operation timing chart of each unit at the time of a copying operation in FIG.
The VSYNC signal is an image valid section signal in the sub-scanning direction.
Are sequentially formed (C), (M), (Y), and (BK) output signals are formed. VE is an image valid section signal in the main scanning direction, and takes a timing of a main scanning start position in a section of “1”. The CLK signal is a pixel synchronization signal, and is 0 →
The image data is transferred at the rising timing of 1.

When the operator places a document on the platen 203 and starts a copy operation from an operation unit (not shown), the CPU 417 reads the register 6 of the saturation detection unit 4009.
01 to 606 (the first mirror unit 20)
The threshold value is set for the region 61 in which the speed is not stable. Next, the CPU 417 controls a motor (not shown) to
The mirror unit 2061 is moved to start the original image reading operation.

Next, the decoder 4201 decodes the sub-scanning address output from the sub-scanning address counter 420 and compares it with VSYNC as shown in FIG. 11 for several lines (here, shown in FIG. 10 (t3 -T2) A black character area signal that rises with a delay (a period corresponding to time) is output. The CPU 417 inputs the black character area signal output from the decoder 4201 to the interrupt terminal, and responds to the rising edge of the black character area signal to cause the saturation detection unit 4
A threshold for a stable area (an area where the speed of the first mirror unit 2061 is stable) is set in the registers 009 to 606 of 009, and the image reading operation on the entire surface of the document is ended.

In the embodiment of the present invention, the saturation detecting section 40
The method of changing the threshold value of black character determination by changing the register setting value of the value 09 has been described. However, the method of changing the threshold value of the edge detection unit 108, the method of changing the absolute value “a” of the edge amount in the present embodiment, , Saturation detector 4009
A method of changing the threshold value of both the edge detection unit 108 and the edge detection unit 108, and a method of changing the threshold value in other black character determination methods are also effective.

As described above, according to the color copying apparatus of the embodiment of the present invention, the CCD sensor 210 (image reading means 1) for reading an image from a document, and each pixel is monochrome based on the read image signal. Saturation detection unit 4009 that determines whether a pixel is a pixel or a color pixel (image attribute determination unit 2)
For a halftone dot component having a large edge component in a plurality of directions, the edge component is smoothed to reduce its characteristics, and a character / thin line having an edge component in only one direction is stored in the edge detection unit 108. (Image component separating unit 3), a first mirror unit 2061 and a second mirror unit 2071 (scanning unit 4) that move relative to the document and scan the document, and sub-scanning from the sub-scanning address counter 420 A decoder 4201 (area signal generating means 5) for decoding an address to generate a black character area signal, and a threshold value for an unstable area in an area where the speed of the first mirror unit 2061 is not stable, are set. CPU 417 (threshold changing means 6) for setting a threshold for a stable area in an area where the speed is stable;
And an AND gate 1001 (black character pixel determination means 7) for determining whether each pixel is a black character pixel based on the determination result of the color detection unit 4009 and image data represented by only black data in the case of a black character pixel. In the case of a color pixel, since it has a masking and UCR circuit 406 (image processing means 8) for outputting image data separated into four colors of toner, the following operations and effects are achieved.

In the above configuration, when the start of the copy operation is instructed, the first mirror unit 2061 moves to start the original image reading operation. The decoder 4201 is
The sub-scanning address output from the sub-scanning address counter 420 is decoded, and a black character area signal is output to the CPU 417. The saturation detection unit 4009 determines whether each pixel is a monochrome pixel or a color pixel based on the image signal, and outputs the determination result to the AND gate 1001. Further, the edge detection unit 108 smoothes a halftone dot component having a large edge component in a plurality of directions, saves a feature of a character / thin line having an edge component in only one direction, The result of the separation is output to an AND gate 1001.

The CPU 417 sets a threshold value for the unstable region in the registers 601 to 606 of the saturation detecting unit 4009 in the image leading end region (the region where the speed of the first mirror unit 2061 is not stable). In a stable area (an area in which the speed of the first mirror unit 2061 is stable), the CPU 417 stores the stable signal in the registers 601 to 606 of the saturation detection unit 4009 at the rising edge of the black character area signal output from the decoder 4201. Set the threshold for the region.

The AND gate 1001 is connected to the edge detector 1
08 and the determination result of the saturation detection unit 4009, it is determined whether each pixel is a black character pixel, that is, each pixel is a black and white pixel, has an edge in one direction, and the black character area signal is “1”.
Is determined to be a black character pixel. If it is determined that the pixel is a black character pixel, “1” is output to the masking and UCR circuit 406 otherwise. The masking and UCR circuit 406 outputs image data of only black data in the case of a black character pixel, and outputs image data of four color toners in the case of a color pixel.

That is, in the embodiment of the present invention, the image leading end portion (first mirror unit 2
By changing the threshold value of the signal processing unit (registers 601 to 606 of the saturation detection unit 4009) for detecting a black character portion between an area in which the speed is not stable at a predetermined speed (061) and an area thereafter. This has the effect of eliminating erroneous determination of black character detection due to overshoot or the like of the unit 2061 and improving the image quality of a copied image.

In the embodiment of the present invention, in addition to the effect of improving the image quality of a copied image as described above, a halftone component having a large edge component in a plurality of directions is Characters / thin lines that have edge components in only one direction are preserved by smoothing the edge components and reducing their characteristics, so that line components and halftone dot components are more effectively separated. There is also an effect that a character component existing in a halftone dot, which cannot be detected by the edge detection method described above, can be detected.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and a computer (or CPU or MPU) of the system or the apparatus executes the program code stored in the storage medium. Needless to say, this can also be achieved by executing the reading.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

The functions of the above-described embodiments are implemented when the computer executes the readout program codes, and the OS or the like running on the computer is actually executed based on the instructions of the program codes. It goes without saying that a part or all of the above-described processing is performed, and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0081]

As described above, claims 1 to 5,
According to the image reading device of the present invention, the leading edge of the image at the time of reading the original image (the area where the scanning system including the light source for the original illumination and the reflection mirror is not stable at a predetermined speed) and the subsequent portions are read. By changing the threshold value of the signal processing unit for detecting the black character portion between the region and the region, it is possible to eliminate the erroneous determination of the black character detection caused by the overshoot of the scanning system and to improve the image quality of the copied image. There is.

According to the image reading apparatus of the sixth aspect, it is possible to improve the image quality of a copied image, similarly to the image reading apparatuses of the first to fifth and seventh to tenth aspects. In addition to the effect, a halftone dot component having a large edge component in a plurality of directions smoothes the edge component to reduce its feature, and a character / thin line having an edge component in only one direction preserves its feature. Therefore, the line component and the halftone dot component are more effectively separated, and there is also an effect that a character component existing in a halftone dot, which cannot be detected by the conventional edge detection method, can be detected.

According to the read image determination method of the present invention, it is preferable that a scanning system including a light source for document illumination, a reflection mirror, and the like be used when a document image is read. By changing the threshold value of the signal processing unit for detecting a black character portion between the region where the speed is not stable) and the subsequent region, erroneous determination of black character detection due to overshoot of the scanning system and the like is eliminated, and copying is performed. There is an effect that the image quality of an image can be improved.

According to the read image judging method according to the sixteenth aspect, the eleventh to fifteenth and the seventeenth to second aspects are described.
Similarly to the read image determination method described in No. 0, in addition to the effect that the image quality of the copied image can be improved, a halftone dot component having a large edge component in a plurality of directions is smoothed by the edge component. Characters / thin lines that have reduced features and have edge components in only one direction preserve the features, so line components and halftone components are more effectively separated, and can be detected by conventional edge detection methods. There is also an effect that a character component existing in a halftone dot can be detected.

According to the storage medium of the present invention, the read image judging method is read out from the storage medium and executed by the image reading apparatus, and the image leading end portion when reading the original image (the original illumination light source and the reflection mirror, etc.) ), The threshold of the signal processing unit for detecting a black character portion is changed between the region where the scanning system is not stable at a predetermined speed) and the region thereafter. This has the effect of eliminating erroneous determinations and improving the image quality of the copied image.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of a main part of a color copying apparatus according to an embodiment of the present invention and corresponding to the claims.

FIG. 2 is a block diagram illustrating a configuration of a signal processing unit of the color copying apparatus according to the embodiment of the present invention.

FIG. 3 is a configuration diagram showing an internal structure of the color copying apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an edge detection unit of the color copying apparatus according to the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a luminance calculation circuit of the color copying apparatus according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a process in an edge min direction detection unit of the color copying apparatus according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a spectral sensitivity characteristic of the visible line sensor according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a spectral sensitivity characteristic of the visible line sensor according to the embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of an analog signal processing unit of the color copying apparatus according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a relationship between speed and time of a first mirror unit of the color copying apparatus according to the embodiment of the present invention.

FIG. 11 is a timing chart showing the timing of each section during a copying operation in the image scanner section of the color copying apparatus according to the embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration of a saturation detection unit of the color copying apparatus according to the embodiment of the present invention.

FIG. 13 is an explanatory diagram showing an enlarged configuration of a light receiving element of a CCD sensor of the color copying apparatus according to the embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a configuration of a CCD sensor of the color copying apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 image reading means 2 image attribute determining means 3 image component separating means 4 scanning means 5 area signal generating means 6 valid / invalid determining means 7 image processing means 108 edge detecting section 210 CCD sensor 406 masking and UCR circuit 417 CPU 420 subscanning address counter 1001 AND gate 2061 First mirror unit 4009 Saturation detector 4201 Decoder

Claims (21)

[Claims] 1. An image reading apparatus for reading an image by moving a scanning system relatively to a document, comprising: an image attribute determining means for determining an attribute of an image read from the document based on a threshold; Area signal generating means for generating an area signal each time the divided area divided into at least one area is read, and threshold changing means for changing a threshold of the image attribute determining means for each area based on the area signal An image reading apparatus, comprising: 2. An image reading means constituting the scanning system and reading an image from a document, an image component separating means for separating a line component and a halftone component based on an image signal read by the image reading means, A black character pixel determining unit that determines whether each pixel is a black character pixel based on the determination result of the determining unit and the separation result of the image component separating unit, and an image processing unit that performs a predetermined process on an image signal belonging to a predetermined attribute. 2. The image reading device according to claim 1, wherein the black character pixel determination unit outputs a determination result to the image processing unit. 3. The image reading apparatus according to claim 1, wherein the image attribute determining unit determines whether each pixel is a monochrome pixel or a color pixel based on an image signal read by the image reading unit. . 4. An image reading apparatus according to claim 1, wherein said area signal generating means generates a black character area signal based on sub-scanning of said scanning system. 5. The threshold changing unit outputs a threshold value for an unstable region to the image attribute determining unit in an unstable region where the scanning speed of the scanning system is not stable, so that the scanning speed of the scanning system is stable. The image reading apparatus according to claim 1, wherein a threshold value for a stable area is output to the image attribute determination unit in a stable area. 6. A character / thin line in which a halftone dot component having a large edge component in a plurality of directions smoothes the edge component to reduce its characteristic, and the edge component exists only in one direction. The image reading apparatus according to claim 2, wherein the feature is stored. 7. The image processing means outputs image data represented only by black data in the case of a black character pixel, and outputs image data separated into toner colors in the case of a color pixel. The image reading device according to claim 2. 8. The apparatus according to claim 2, wherein the threshold value changing unit is capable of changing a threshold value for each of the regions only for the image component separating unit. Image reading device. 9. The image processing apparatus according to claim 2, wherein the threshold value changing unit is capable of changing both threshold values of the image attribute determining unit and the image component separating unit for each of the regions.
The image reading device according to claim 6. 10. The image reading apparatus according to claim 1, wherein the image reading apparatus is applicable to a copying apparatus. 11. A read image determining method applied to an image reading apparatus for reading an image by moving a scanning system relative to a document, wherein the attribute of the image read from the document is determined based on a threshold value. An attribute determining step, an area signal generating step of generating an area signal each time the divided area obtained by dividing the entire surface of the document into at least one area is read, and a threshold value of the image attribute determining step based on the area signal is set for each area. And a threshold value changing step of changing the threshold value to a threshold value. 12. An image reading step of configuring the scanning system to read an image from a document, an image component separating step of separating a line component and a halftone component based on the image signal read in the image reading step, A black character pixel determination step of determining whether each pixel is a black character pixel based on the determination result of the determination step and the separation result of the image component separation step, and an image processing step of performing a predetermined process on an image signal belonging to a predetermined attribute 12. The read image determination method according to claim 11, further comprising: outputting a determination result to the image processing step in the black character pixel determination step. 13. The read image determination according to claim 11, wherein the image attribute determination step determines whether each pixel is a monochrome pixel or a color pixel based on the image signal read in the image read step. Method. 14. The read image determination method according to claim 11, wherein in the area signal generating step, a black character area signal is generated based on sub-scanning of the scanning system. 15. In the threshold changing step, a threshold value for an unstable area is output to the image attribute determining step in an unstable area where the scanning speed of the scanning system is not stable, and the scanning speed of the scanning system is stabilized. 15. The read image determination method according to claim 11, wherein a threshold value for a stable area is output to the image attribute determination step in a stable area. 16. In the image component separating step, a halftone dot component having a large edge component in a plurality of directions smoothes the edge component to reduce its characteristic, and a character / thin line in which the edge component exists only in one direction. 16. The read image determination method according to claim 12, wherein the feature is stored. 17. In the image processing step, in the case of a black character pixel, image data represented only by black data is output, and in the case of a color pixel, image data separated into toner colors is output. The read image determination method according to any one of claims 12 to 16. 18. The apparatus according to claim 12, wherein in the threshold value changing step, a threshold value can be changed for each of the regions only in the image component separating step. Read image determination method. 19. The apparatus according to claim 12, wherein, in the threshold value changing step, both threshold values of the image attribute determining step and the image component separating step can be changed for each of the regions. 18. The read image determination method according to any one of 17. 20. The read image determination method according to claim 11, wherein the read image determination method is applicable to a copying apparatus. 21. A storage medium readable by a computer storing a program for executing a read image determination method applied to an image reading apparatus for reading an image by moving a scanning system relative to a document, The read image determination method includes an image attribute determination step of determining an attribute of an image read from a document based on a threshold, and generating an area signal each time the divided area obtained by dividing the entire surface of the document into at least one area is read A storage medium comprising: an area signal generating step; and a threshold changing step of changing a threshold value of the image attribute determining step for each area based on the area signal.