JPH08186725A - Picture processor - Google Patents

Abstract

PURPOSE: To prevent a peripheral void accompanying an edge processing by detecting the edge part of a black character plotted on a colored base. CONSTITUTION: Analog picture data read by a CCD image sensor are passed through A/D conversion, shading correction, monochromatic/full-color correction and a variable magnification processing, etc., and inputted to an HVC conversion part 1100 as RGB picture data R, G and B57-50 . The HVC conversion part 1100 generates brightness signals V7-0 and saturation data W7-0 from input signals. An area discrimination part 1500 performs the edge detection of pictures from the derivation of the brightness signals V7-0 , refers to the saturation data W7-0 , and at the time of judging the edge part of black, replaces the respective color data of the cyan(C), magenta(M) and yellow(Y) of the picture element with the data of a lowest density among the data of the C, M and Y colors of the peripheral picture element. Also, the value of the black(BK) color data is replaced with the data of the high density for a prescribed amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a digital color copying machine.

[0002]

2. Description of the Related Art Conventionally, RGB image data read by an image reader is obtained by color conversion into four color image data of cyan (C), magenta (M), yellow (Y), and black (BK). A full-color digital copying machine that develops the above-mentioned four-color toners on a copy paper based on image data, detects black characters in an original image as MTF correction, and detects BK data for the detected portion. Edge enhancement is performed using edge components, and C, M, and Y data are
Edge removal is performed using the lightness edge component. As a result, the black character portion is reproduced with a single color of BK data, and the quality of the image reproduced on the copy paper is improved.

[0003]

However, when the peripheral portion of black characters is drawn on a colored background, if the C, M, and Y data are edge-removed by the lightness edge component, the amount of data to be removed is too large. As shown in FIG. 69A, white spots appear around the black characters on the document. In general, the determination as to whether or not an image in a document is black characters is performed as follows. A character basically consists of two elements, an "edge part" and a "solid fill" part sandwiched between the edge parts. In the case of thin line characters, only the edges are available. That is, the character determination is achieved by performing the edge determination. The black determination is made based on the values of the saturation data _W7-0 . Specifically, when the value of the saturation data _W7-0 is less than or equal to a predetermined reference value, it is determined to be black. By the above character and black determination, the black image at the edge portion can be determined to be a black character. However, the character (edge) only determination and black determination, the value of the brightness signal V _{7 to 0} is low, black and chroma value data WS _{7 to 0} is low (e.g., dark blue or dark green) character May be erroneously discriminated as the edge part of. Also,
If the pixels forming the halftone image are erroneously determined to be the edges of black characters and edge enhancement is performed, moire occurs. Further, in the case of the electrophotographic image processing apparatus, as shown in FIG. 70A, the toner is excessively attached to the rising portion of the edge and the toner is faint in the falling portion of the edge with reference to the sheet passing direction of the copy paper. Such a phenomenon occurs.

A first object of the present invention is to provide an image processing apparatus which more reliably determines a black character and performs an appropriate edge enhancement process as MTF correction. Also,
A second object is to provide an image processing device that performs appropriate MTF correction according to the type of image. A third object of the present invention is to provide an image processing apparatus that eliminates excessive toner sticking at the rising edge of the edge and toner fading at the falling edge of the edge, which occurs with the sheet passing direction as a reference.

[0005]

In the first image processing apparatus of the present invention, the reading means for reading the RGB image data of the document, and the RGB image data read by the reading means are cyan (C) and magenta (M). , Yellow (Y), black (BK) color data (hereinafter, each color data is C
They are called data, M data, Y data, and BK data. ), A HVC conversion unit for obtaining the brightness data V and the saturation data W of each pixel in the original from the RGB image data of the original read by the reading unit, and HV.
Determination means for determining whether or not the pixel is an edge portion pixel from the brightness data V of each pixel in the document obtained by the C conversion means, and determining whether or not the pixel is black based on the saturation data W. Of the C, M, and Y data of each peripheral pixel in a predetermined matrix whose center pixel is a pixel determined to be a black edge portion by the determination unit, the lowest density data is the C, M, and Y of that pixel. C, M, Y to replace M, Y data
The data replacement means and the BK data replacement means for replacing the value of the BK data of the pixel in the black edge portion detected by the detection means with the high-density data by a predetermined amount.

Further, in the second image processing apparatus, the R of the original is read.
A reading unit that reads GB image data, and the RGB image data read by the reading unit is color data of cyan (C), magenta (M), yellow (Y), and black (BK) (hereinafter, each color data is C Data, M data,
They are called Y data and BK data. ) Is obtained by the HVC conversion means for obtaining the brightness data V and the saturation data W of each pixel in the document from the RGB correction image data of the document read by the reading means, and the HVC conversion means. The brightness data V of each pixel in the original document is used to determine whether the pixel is an edge pixel, and the saturation data W is used to determine whether the pixel is black. In the predetermined matrix having the pixel determined to be the pixel of the edge portion as the central pixel, the lightness data V obtained by the HVC conversion means is less than the predetermined value, and the saturation data W is not less than the predetermined value. A detection unit that detects a pixel that is present and that is not determined to be an edge portion by the determination unit, a counting unit that counts the number of pixels detected by the detection unit, and a counting unit. If the count value exceeds a predetermined value, and a misjudgment correcting means for invalidating the determination result for the pixel in which the determination means determines that the pixel of an edge portion of the black.

Further, in the third image processing apparatus, the R of the original is
A reading unit that reads GB image data, and the RGB image data read by the reading unit is color data of cyan (C), magenta (M), yellow (Y), and black (BK) (hereinafter, each color data is C Data, M data,
They are called Y data and BK data. ) Is obtained by the HVC conversion means for obtaining the brightness data V and the saturation data W of each pixel in the document from the RGB correction image data of the document read by the reading means, and the HVC conversion means. The brightness data V of each pixel in the original document is used to determine whether the pixel is an edge pixel, and the saturation data W is used to determine whether the pixel is black. Of the C, M, and Y data of the pixel determined to be the edge portion and the peripheral pixels in a predetermined matrix having the pixel as the center pixel, the lowest density data is the C, M, and Y data of the pixel. C, M, Y data replacing means for replacing with BK data replacing means for replacing the value of the BK data of the pixel determined to be a black edge portion by the determining means with high density data by a predetermined amount, and HVC Converter From the value of the brightness data V obtained by the above, in the predetermined matrix, the target pixel in which the difference between the value of the brightness data V of all the peripheral pixels and the value of the brightness data V of the target pixel is a predetermined value or more is determined. The isolated pixel detecting means for detecting as an isolated pixel, the counting means for counting the number of isolated pixels detected by the isolated pixel detecting means in a predetermined matrix different from the above, and the count value by the counting means are proportional to And an edge emphasis amount adjusting means for reducing the data replacement amount of the BK data replacement means.

Further, in the fourth image processing apparatus, the R of the original is read.
A reading unit that reads GB image data, a photoconductor, a developing unit that forms a toner image on the photoconductor based on the read RGB image data, and a toner image that is formed on the photoconductor in a predetermined direction. The transfer means for transferring the paper to the paper conveyed by the transfer means, the transfer means for transferring the paper to the transfer means in a predetermined direction, and the rising portion of the edge with reference to the direction in which the transfer means transfers the paper to the transfer means. A detection unit that detects a pixel and a pixel corresponding to a falling portion of the edge, a pixel immediately preceding the pixel at the rising portion of the edge detected by the detection unit in the sheet passing direction, and a falling portion of the edge. 1 in the paper feed direction of pixels in
A correction data addition unit that adds predetermined correction data to the next pixel is provided.

Further, in the fifth image processing apparatus, the R of the original is
A reading unit that reads GB digital image data, and the RGB image data that is read by the reading unit is color data of cyan (C), magenta (M), yellow (Y), and black (BK) (hereinafter, each color data is C data, M data, Y data, and BK data), and a HVC conversion unit that obtains the brightness data V and the saturation data W of each pixel in the original from the read RGB image data. Then, it is determined from the brightness data V of each pixel in the document obtained by the HVC conversion means whether or not the pixel is an edge pixel, and from the saturation data W whether or not the pixel is black. An area information input unit for inputting monochromatic / monochrome area information in synchronization with the reading of the image data of the document by the determination unit and the reading unit, and an area information input unit. With respect to the pixel determined to be the black edge portion of the full-color original from the input by the determination unit and the determination result by the determination unit, among C, M, and Y data of peripheral pixels in a predetermined matrix having the pixel as a central pixel, Based on the C, M, Y data replacing means for replacing the lowest density data with the C, M, Y data of the pixel concerned, and the input by the area information input means and the judgment result by the judging means, the black edge portion or monochrome of the full color original document. The BK data of the pixel determined to be the black edge portion of the document is emphasized by the lightness edge component, and the BK data of the pixel determined to be the color edge part of the full-color document or the edge part of the monocolor document is output as it is. The color edge portion of the full-color original or the mono-color original is determined based on the BK data emphasizing means, the input by the area information inputting means, and the judgment result by the judging means. Of pixels determined as an edge portion C, M, Y data highlighted in density edge component, and outputs C of pixels determined as an edge portion of the monochrome document, M, Y data as C,
And M and Y data emphasizing means.

[0010]

In the first image processing apparatus of the present invention, from the RGB image data read by the reading means, C, M, and
The Y data replacing means replaces the lowest density data of the C, M, Y data of the peripheral pixels in the predetermined matrix having the pixel as the center pixel with the C, M, Y data of the pixel, and BK. BK of the pixel by the data replacement means
Replace the data with a high amount by a predetermined amount. This prevents white spots from occurring around the black edge portion of the full-color document.

In the second image processing apparatus, the brightness data V is equal to or less than the predetermined value and the color is within the predetermined matrix centered on the pixel determined to be the black edge portion by the determination unit. The counting means counts the number of pixels whose frequency data W is equal to or larger than a predetermined value and which is determined not to be an edge portion by the determining means. Here, when the count value by the counting means is a predetermined number or more,
Cancel the judgment made by the judging means. This prevents the color boundary line from cyan to yellow from being erroneously determined to be a black edge portion.

Further, in the third image processing apparatus, the brightness data values of all the peripheral pixels in the predetermined matrix whose central pixel is the pixel judged to be the black edge portion by the judging means, When the difference from the value of the brightness data V of the pixel is equal to or more than a predetermined value, the target pixel is detected as an isolated pixel, and the number of the isolated points in a predetermined matrix different from the above is counted by the counting means, In proportion to this count value, the data replacement amount by the BK data replacement means is reduced by the edge emphasis amount adjustment means.

Further, in the fourth image processing apparatus, the detecting means detects the rising portion and the falling portion of the edge with reference to the direction in which the conveying means conveys the sheet to the transfer means. The correction data addition means adds predetermined correction data to the pixel immediately preceding the pixel in the sheet passing direction at the rising portion of the edge detected by the detection means and the pixel immediately after the falling portion.

Further, in the fifth image processing apparatus, the black edge portion, the color edge portion of the full-color original, the edge portion of the mono-color original, the monochrome original based on the input by the area information input means and the judgment result by the judging means. The values of the C, M, Y, and BK data are replaced according to each of the edge portions of.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image processing apparatus of this embodiment will be described below in the following order with reference to the accompanying drawings. (A) Configuration of image processing apparatus (a-1) Configuration of copying machine main body (a-2) Operation panel (b) Description of each processing in the read signal processing unit 20 (b-1) A / D conversion unit (b) -2) Shading correction section (b-2-1) Peak value hold circuit (b-2-2) Reciprocal conversion processing (b-3) Line correction section (b-3-1) Line correction processing (b- 3-2) Interpolation processing (b-4) AE processing section (b-4-1) Histogram generation section (b-4-2) Original size detection section (b-4-3) AE processing section (b-5) Magnification / movement processing unit (b-5-1) Reduction interpolation unit (b-5-2) Magnification / movement processing unit (b-5-2-1) Magnification / reduction processing (b-5-2-2) Moving process (b-5-2-3) Image repeat (b-5-3) Enlargement interpolation part (b-6) Image interface part (b-7) HVC conversion part (b-7-1) HVC conversion (b -7-2) Image quality monitor function (b-8) Density conversion unit (b-9) UCR / BP processing unit (b-10) Color correction unit (b-11) Area discrimination unit (b-11-1) Character (Edge) judgment (b-11-1-1) First order differential filter (b-11-1-2) Second order differential filter (b-11-1-3) Edge judgment (b-11-2) Judgment of black (b-11-3) Extraction of black character misjudgment area (b-11-4) Judgment of halftone dot area (b-11-5) Other judgment (b-12) MTF correction part (b-12-1) MTF correction when full color standard mode is set (b-12-1-1) Black edge part (b-12-1-1-1) BK printing process (b-12 -1-1-2) During C, M, Y printing process (b-12-1-2) Color edge part (b-12-1-3) Highlight flat part (b-12-1-4) Non-edge part (b-12-2) MTF correction when full color photo mode is set (b-12-2-1) Black edge part and color edge part (b-12-2-2) Flat highlight part (b- 12-2-3) Non-edge part (b-12-3) MTF correction when mono color standard mode is set (b-12-3-1) Edge part (b-12-3-2) Flat highlight part ( b-12-4) MTF correction when mono-color photo mode is set (b-12-4-1) Edge part (b-12-4-2) Highlight flat part (b-12-5) Monochrome standard mode setting Hour (b-12-5-1) Edge part (b-12-5-2) Highlight flat part (b-12-6) Monochrome photo mode setting MTF correction at fixed time (b-12-7) Description of MTF correction unit 1600 (b-13) γ correction unit

(A) Configuration of image processing apparatus (a-1) Configuration of copying machine main body FIG. 1 is a schematic configuration diagram of a digital color copying machine used in this embodiment. The digital color copying machine includes an image reader unit 100 for reading a document image and an image reader unit 1.
The copying unit 200 that reproduces the image data read by 00 is roughly divided. In the image reader unit 100, the scanner 10 includes an exposure lamp 12 that illuminates a document.
And a rod lens array 1 that collects the reflected light from the original
3, and a contact-type C that converts the condensed light into an electric signal
A CD color image sensor 14 is provided. The CCD color image sensor 14 has R (red), G (green) and B
It is composed of three lines of CCDs arranged at predetermined intervals for reading digital image data of each component of (blue). When reading a document image, the scanner 10 is driven by the motor 11 and moves in the direction of the arrow (sub-scanning direction). First, after reading the data of the white plate 16 for shading correction, the scanner 10 is placed on the platen 15. The placed document is scanned. The image of the document surface illuminated by the exposure lamp 12 is photoelectrically converted by the CCD image sensor 14.
R, G, B 3 obtained by the CCD image sensor 14
The multivalued electrical signal of color is an 8-bit gradation of Y (yellow), M (magenta), C (cyan), and BK (black) that has been subjected to shading correction and line correction in the read signal processing unit 20. After being converted into data and subjected to MTF correction, γ correction, etc., the synchronization buffer memory 30
Is stored.

Next, in the copying section 200, the printer head section 31 D / A converts the inputted gradation data to generate a semiconductor laser drive signal, and the semiconductor laser is caused to emit light by this drive signal. This semiconductor laser is always in a weak light emitting state in order to improve the rising response at the time of light emission. The weak light emitted by the semiconductor laser at this time is called bias light.

The printer head unit 3 corresponding to the gradation data
The laser beam emitted from the laser beam No. 1 exposes the photosensitive drum 41, which is rotationally driven, via the reflecting mirror 37. The photosensitive drum 41 is irradiated by the eraser lamp 42 before being exposed for each copy, and is uniformly charged by the charging charger 43. When exposed in this state, an electrostatic latent image of the original is formed on the photosensitive drum 41. Only one of the C (cyan), M (magenta), Y (yellow), and BK (black) toner developing devices 45a to 45d is selected to develop the electrostatic latent image on the photosensitive drum 41. To do. The developed toner image is transferred by the transfer charger 46 onto the copy paper wound around the transfer drum 51. The fur brush 47 collects the toner transferred to the outside of the transfer drum.

The above printing process is repeated for four colors of Y (yellow), M (magenta), C (cyan) and BK (black). At this time, the scanner 1 is synchronized with the operations of the photosensitive drum 41 and the transfer drum 51.
0 repeats the scan operation. After that, the copy paper is separated from the transfer drum 51 by operating the separation claw 47, passes through the fixing device 48 and the toner image is fixed, and is then discharged to the paper discharge tray 49. The copy paper is fed from the paper cassette 50, and the chucking mechanism 52 on the transfer drum 51 chucks the front end of the copy paper to prevent misalignment during transfer.

(A-2) Operation Panel FIG. 2 is a front view of the operation panel 25 provided in the copying machine of this embodiment. The operation panel 25 includes a display unit 71.
When the user presses the image quality monitor selection key 77, the display unit 71 displays four types of image forming conditions, such as masking coefficient, shapeness, γ curve, and color balance, in addition to the normal display such as the number of copies and the copy magnification. indicate. In this case, as will be described later, the copying machine displays one of eight images formed based on the image forming condition displayed on the display unit 71.
Print out on a sheet of copy paper. The above four types of image forming conditions can be changed by operating the image quality selection keys 74a to 74d. The user presses the print key 73 after selecting a desired image number from the above eight images actually printed out by using the ten-key 72, thereby printing out the desired image forming condition (that is, image quality). Can be obtained. The key 75 is a key for entering the serviceman mode, and when this mode is selected, the LED 75a lights up. The serviceman mode is a mode for setting the HVC conversion coefficients a ₁ , a ₂ , and a ₃ used in the HVC conversion unit 1000 as described later. The negative / positive reversal key 76 is used when reversing a document reproduced on a copy sheet.

(B) Description of each process in the read signal processing unit 20 The following is a brief description of each process executed in the read signal processing unit 20 included in the digital color copying machine. After this schematic description, each process will be described in detail.

Next, FIGS. 3 and 4 are processing block diagrams of the read signal processing section 20. CCD image sensor 1
The analog image data OSR1 and 2, OSG1 and 2, OSB1 and 2 read by 4 are input to the A / D conversion unit 300. The A / D converter 300 converts the input signal into 8-bit digital image data R _17-10 , G
_17-10, the shading correction section 40 is converted into B _17-10
Output to 0.

The shading correction section 400 corrects variations in read data due to uneven illumination of the original by the exposure lamp 12. First, the data of a plurality of lines in the main scanning direction of the uniform white plate 16 is read. With respect to the read data of a plurality of lines, the data of pixels arranged on the same line in the sub-scanning direction is compared. Here, the brightest (white) data for each pixel is the data for shading correction. As a result, defective data caused by contamination of the white plate 16 such as ink splattering can be deleted, and accurate shading correction can be performed. Further, in the shading correction unit 400 of the present embodiment, output data having more bits than input data is used in the reciprocal conversion process executed when calculating the shading correction data. Thereby, more accurate shading correction is realized. The respective components R _{27 to 20} , G _{27 to 20} and B ₂₇ to 20 of the RGB image data which have been subjected to the shading correction are input to the next inter-line correction unit 500.

The CCD image sensor 14 is provided with 3-line CCDs at predetermined intervals for reading RGB image data (see FIG. 8). Below, RGB
Each component of the image data will be simply referred to as R data, G data, and B data. The inter-line correction unit 500 uses the R data and G
The data is temporarily stored in the memory and delayed by a predetermined time to correct the deviation from the B data caused by the predetermined interval. In the copying machine of this embodiment, attention is paid to the fact that the maximum size of the copy paper on which an image is formed is specified as A3, and the number of effective dots in one line is controlled according to the copy magnification. This suppresses an increase in the memory capacity required to correct the above deviation. Further, the inter-line data interpolation processing is executed to correct a finer deviation in the read data. The data in which the deviation is corrected is input to the AE processing unit 600 and the scaling / moving processing unit 800 as well.

The AE processing section 600 detects the document size,
ACS (abbreviation of Auto Color Selection) and AE processing are executed. Here, the detection of the document size is to detect the existence range of the document placed on the platen 15 in units of one line in the main scanning direction (see FIG. 17). The ACS is to determine whether the document is full color or monochrome based on the ratio of monochrome pixels in the document. The AE process is a process of determining the background level of the original so that the brightest color in the original becomes white (gradation level 255). When this is applied to a full-color original, it is reproduced on the copy paper. The image looks faded overall. Therefore, in the copying machine of this embodiment, the ACS
Based on the result of (3), the background level of the original is determined, and the AE process for the full-color original is prohibited.

The scaling / move processing unit 800 deletes unnecessary area data, reduces interpolation processing, reduces, and _scales the input R _{37 to 30} data, G _{37 to 30} data, and B ₃₇ to ₃₀ data. , Enlargement output, image repeat and enlargement interpolation processing are executed. The unnecessary areas include two areas, that is, an area where no original exists on the original table and an area generated by reducing the original image. The unnecessary area is executed based on the result of the original size detection by the AE processing unit 600. For example, in order to reduce the size of the original document to 50%, the image data of the original document is read using a scanner with a reading density of 200 dpi instead of the scanner with a reading density of 400 dpi, and the image data obtained by the reading is 4
Printing should be done at a density of 00 dpi. However, actually, the image data obtained by reading with a scanner of 400 dpi is thinned out in half, and the printing process is performed at a density of 400 dpi. In this case, the data of the thin line is erased and the quality of the reproduced image deteriorates. Therefore, the interpolation process is executed with a size according to the reduction rate. This prevents the quality of the reproduced image from deteriorating. Further, when enlarging a document, if the data is simply padded, the image is severely deteriorated, such as the noticeable edge rattling. Therefore, when enlarging the original, smoothing processing is performed on the image data according to the enlargement ratio. This prevents the deterioration of the image at the time of enlargement. When the user presses the image quality monitor selection key 77 on the operation panel, a part of the original image is image-repeated eight times and output.

In the image interface unit 1000, the R, G, and B data (R
-VIDEO _{7 to 0} , G-VIDEO _{7 to 0} , B-VIDEO _{7 to 0} ) and internal data (R _{67 to 60} , G _{67 to 60} , B _{67 to 60} ) are selected and combined by fitting. It also generates a timing signal when transmitting image data to the RGB interface or printer interface.

In the HVC converter 1100 shown in FIG. 4, C
RGB data (R _57-50 , G) obtained by actually reading a color patch by the CD color image sensor 14.
_{57 to 50} , B _{57 to 50} ) and the color patch RGB data stored in the ROM, based on the brightness signal (V
_7-0), the color difference signal (WR _{8 to 0,} to generate a WB _7-0), further generates the chroma data (W _7-0) and the hue signal (H _7-0) from the color difference signals. This corrects the variations in the reading characteristics of each CCD element. In addition, the HVC conversion unit 110
0 includes an image quality control circuit 1103. Image quality control circuit 11
03, different image forming conditions (masking coefficient, shapeness, γ curve, and Color balance).

The density correction unit 1200 changes the RGB data (R) that changes in proportion to the amount of light reflected from the original by the exposure lamp.
_67~60, G _67~60, a B _{from 67 to 60),} data that changes in proportion to the concentration (DR _7~0, DG _7~0, converted to DB _{7 to 0).} Further, the negative / positive inversion unit 1250 receives the -NEGA signal (negative / positive inversion signal) which is the editing area signal, and when it is "L", DR _7-0 , DG _7-0 , DB _7-0 , DV.
Inverted output (negative output) of ₇ to _0, and when it is "H", pass it through as it is.

The UCR / BP processing unit 1300
The minimum value of the data of R _7-0 , DG _7-0 , DB _7-0 (MIN
(DR, DG, DB)), assume that this is a black color, treat a certain proportion as BK data, and add black toner by the printer (BP processing) operation and C according to the BK data added above. Undercolor removal (UCR processing) is performed to reduce the amounts of M, Y color materials.

The color correction unit 1400 executes a predetermined masking calculation process to match the color reproduction of the original and the copy. This is because the spectral characteristics of the color separation filter provided for each read pixel of the CCD image sensor 14 has an unnecessary transmission area indicated by hatching in FIG. 46 also has unnecessary absorption components indicated by diagonal lines in FIG.

The area discrimination unit 1500 executes the discrimination processing of the black character portion in the document image and the discrimination processing of the halftone dot area. The black character discrimination can be roughly divided into detection of a character (edge) portion, detection of black, and detection of a region that is apt to be erroneously detected as black. The detection of the character (edge) portion is performed using a differential filter. The black color is detected based on the saturation value. In the case of the copying machine of the present embodiment, the erroneous determination that occurs when the R, G, and B data slightly shifts due to the vibration of the CCD color image sensor 14 when reading the image data is smoothed to the saturation data. It is prevented by applying. Further, in order to prevent a character having low lightness and low saturation from being erroneously determined to be a black character, a solid portion is discriminated. Even if it is determined to be a black character, the above-described determination to be a black character is canceled for a portion determined to be a solid color portion.
As a result, accurate black character discrimination is realized.

The MTF correction unit 1600 has a region discrimination unit 15
The most suitable edge enhancement process and smoothing process are performed on the pixel data based on the type of pixels and the printing status of the document recognized by the area determination result of 00. In particular, when copying in the full color standard mode, by not performing edge enhancement on C, M, Y data in the black edge portion and using the minimum value of C, M, Y data as image data, C, M , The Y data fine protruding lines are erased (see FIG. 68 (a)). Also, when copying in the mono color standard mode or photo mode, BK
Edge emphasis is not performed during the print processing of. This allows
It prevents the edge portion of the color character from being blackened.
Further, the laser light emission duty ratio is changed in one cycle of the pixel clock according to the type of pixel recognized by the area discrimination unit 1500. Here, the light emission duty ratio means the ratio of the laser light emission period in the case where a period in which the laser light is not emitted is provided during one cycle of the pixel clock. In the case of a halftone dot pixel, the light emission duty ratio is set to 100% in order to prevent the occurrence of moire. In the case of pixels other than halftone dots, the light emission duty ratio is set to, for example, 80% in order to make noise between lines inconspicuous. Further, a predetermined value is added to the pixel data of the rising and falling portions of the edge, and when the toner image formed on the photoconductor drum 41 is transferred onto the copy paper, the toner is excessively attached and rises at the rising portion of the edge. Corrects toner fading in the falling part.

The γ correction unit 1700 changes the γ curve of the image data (VIDEO ₃₇ to ₃₀ ) after MTF correction according to the user's preference and outputs data of desired image quality. The user operates the image quality selection key 74c provided on the operation panel 25 to operate the γ curve switching signal G
A ₂ to ₀ can be changed.

(B-1) A / D conversion section The A / D conversion section 300 converts the input signal into 8-bit digital image data R _17-10 , G _17-10 , B _17-10 and shading. Output to the correction unit 400. FIG. 5 shows A
6 is a configuration diagram of a / D conversion unit 300. FIG. The CCD image sensor 14 operates according to a predetermined CCD drive signal output from the clock signal generator 301, and has R, G, B analog image data OSR1 and OSG2 proportional to the amount of reflected light of the original image from the exposure lamp 12. And 2, OSB
Output 1 and 2. Where OSR1, OSG1, O
SB1 is analog image data of even dots, and O
SR2, OSG2, OSB2 are analog image data of odd dots. Each image data of R, G, B is R-
A / D conversion unit 307, G-A / D conversion unit 308, B-A
It is input to the / D conversion unit 309. The configurations and processing contents of the A / D conversion units 307 to 309 are the same. Here, regarding the A / D conversion processing, the B-A / D conversion unit 309
Will be explained. In the A / D conversion unit 309, the A / D
Processing units 310 and 311 are provided for performing optimization processing of each image data of odd-numbered dots and even-numbered dots before conversion. The configurations and processing contents of the optimization processing units 310 and 311 are the same. Here, the optimization process will be described using the even-dot data optimization processing unit 311.
The even-dot analog image data OSB2 input to the even-dot data optimization processing unit 310 has the reset noise removed by the sampling and holding circuit 302, the signal amplified by the VCA circuit 303, and the predetermined DC signal by the clamp circuit 304. Adjusted to the level.

Here, the level of the above processing is set according to the control voltage of the VG2B, VC2B, etc. from the D / A converter 305. The SCLK signal is a sampling pulse for the sampling and holding circuit. -BKH
The D signal (here, "-" added to the front of the signal means that it is an inverted signal of the signal BKHD. The same applies to all signals below), and the analog SW is switched. , VCA circuit 303 is a signal for temporarily clamping the DC level to 0V in order to amplify the signal. -CLAMP signal is used in the feedback ramp circuit 3
DC to the control voltage of the D / C converter 305 by 04
This is a clamp pulse for clamping the level.

The image data of the odd-numbered dots and the even-numbered dots which have been subjected to the optimization processing by the respective optimization processing units 310 and 311 are combined into continuous image data by switching switching by the OSSEL signal. The combined image data is sent to the A / D converter 30 via the buffer 312.
6 and is converted into 8-bit digital image data. The ADCK signal is a sampling pulse of the A / D converter.

(B-2) Shading Correction Unit The shading correction unit 400 corrects variations in read data due to uneven illumination of the original by the exposure lamp 12 and the like. First, the data of a plurality of lines in the main scanning direction of the uniform white plate 16 is read. The data of the read plural lines is compared with the data of the pixels arranged on the same line in the sub-scanning direction. Here, the brightest (white) data for each pixel is the data for shading correction. As a result, defective data caused by contamination of the white plate 16 such as ink splattering can be deleted, and accurate shading correction can be performed. Further, in the shading correction unit 400, output data having more bits than input data is used in the reciprocal conversion processing executed when calculating the shading correction data. Thereby, more accurate shading correction is realized.

FIG. 6 is a block diagram of the shading correction unit 400. The 8-bit digital image data of R _{17 to 10} , G _{17 to 10} , and B ₁₇ to 10 output from the A / D conversion unit 300 are respectively the R-correction unit 401 and the G-correction unit 40.
2, input to the B-correction unit 403. Thus R
_17-10 , _G17-10 , and _B17-10 image data are read independently from each of the three-line CCDs provided for reading RGB digital image data by independently performing shading correction. Shading correction can be performed appropriately. Correction units 401 to 403
Has the same configuration and processing content. Hereinafter, the shading correction of this embodiment will be described using the B-correction unit 403.

(B-2-1) Peak value hold circuit Data B ₁₇ to 10 obtained by the CCD image sensor 14 reading the predetermined first line of the white plate 16 in the main scanning direction.
Is input, the peak value hold circuit 404 stores the data in the shading memory 405 as it is. The peak value hold circuit 404 is the second plate of the white plate 16.
The data is sequentially read after the first line stored in the shading memory 405 in synchronization with the input of the image data of the line, and the data value is compared for each corresponding pixel. Then, the value of brighter (white) data is held and the data is stored in the shading memory 405. The same processing is performed on the data of the third and fourth lines.
In this way, by storing the value of the brightest (white) data of each pixel among the data of a plurality of lines of the white plate 16 as the data for shading correction, defective data due to ink or dust adhering to the white plate 16 is stored. Remove the effect of.

The -SHWR signal input to the peak value hold circuit 404 maintains "H" except when reading the data for shading correction. When the value of the −SHWR signal is “H”, data input to the peak value hold circuit 404 is prohibited. As a result, the data stored in the shading memory 405 retains its value. On the other hand, when the data for shading correction is input to the peak value hold circuit 404, the -SHWR signal is switched to "L". -The value of the SHWR signal is "
During the L ″ period, the peak value hold circuit 404 compares the read shading correction data with the data of the corresponding pixel stored in the shading memory 405, and outputs a larger value data to the shading memory 405. Data of value 0 is stored as an initial value in the shading memory 405.
As described above, the data of the first line is stored in the shading memory as it is. When the data of the second and subsequent lines is input, the data of the corresponding pixel is read from the shading memory 405 and the comparison process is executed. The -SHWR signal returns to "H" again when the CCD image sensor 14 starts reading the image data of the original image, prohibits the data input, and holds the data stored in the shading memory 405.

(B-2-2) Inverse conversion processing The shading correction data stored in the shading memory 405 is input to the next inverse conversion table 406. The reciprocal conversion table 406 executes the arithmetic processing shown in the following “Equation 1” on the 8-bit input data Din to obtain 1
2-bit reciprocal conversion data Dout is output.

## EQU1 ## Dout = 255 × Q / Din (However, if Din ≧ 4, Dout = 1.) Here, Dout is 12-bit data even though the value of Din is different. This is to prevent the value of the reciprocal conversion data D _{out from} becoming the same value due to the slight difference, and to maintain the shading correction accuracy at a constant level. The graph of FIG. 7 shows the relationship between Din and Dout. When the value of Din is extremely low, for example, Din = 255
The value of Dout sharply increases below × Q / 4. In order to prevent an error in shading correction caused by this, the reciprocal conversion table 406 has a Dout value of 4 (1
When it is equal to or greater than FFF in hexadecimal, the value of Dout is forcibly converted to 1 (400 in hexadecimal) to invalidate the shading correction.

The shading correction is executed by multiplying the data B ₁₇ to _{10 of the} original image by the reciprocal data obtained by the above " _Formula 1" in the multiplier 407. This calculation is shown in the following "Equation 2".

[ _Formula 2] B _{27 to 20} = B _{17 to 10} × Dout = B _{17 to 10} × 255 × Q / Din In the calculation of the above " _Formula 2", the data value of B ₁₇ to 10 is 255 ×
The value is normalized to the value of Q. The coefficient Q is a value determined for each of R, G, and B according to the spectral distribution of the white plate 16 for shading correction in order to correct the white balance. This is because the shading correction plate 16 provided in the copying machine is completely white (R = 255, G = 25).
5, B = 255), but a case in which the color is biased to any one of R, G, and B, for example, a case where it is slightly greenish (R = 200, G = 242, B = 211) It is a thing. In the above case, the value of each Q of R, G and B is Q _R =
200/255, Q _G = 242/255, Q _B = 211 /
255. The value of the coefficient 255 shown in the above “Equation 2” is the coefficient X that determines the background level, and the background level can be changed by changing this value to, for example, 240. In the copying machine of this embodiment, the AE shown in FIG.
In the processing unit 600, a process of changing the value of the coefficient 255 according to the ratio of monochrome pixels in the entire document, that is, an AE process is executed.

(B-3) Line-to-line correction section As shown in FIG.
8 lines of 3 line CCD to read GB image data
It is provided at intervals of 0 μm. In the case of the copying machine of this embodiment, the width of one pixel is 10 μm, and the CC of the above three lines is used.
D is provided at intervals of 8 lines.
Therefore, the G component (G data) is read by 8 lines and the R component (R data) is read by 16 lines before the B component (B data) of the RGB image data. Actually, the preceding line number changes depending on the moving speed of the scanner 10 in the sub-scanning direction. That is, the number obtained by multiplying the copy magnification Y in the sub-scanning direction (8 × Y line, 16 × Y line)
Is the actual number of preceding lines. Interline correction unit 50
With 0, the R data and the G data are temporarily stored in the memory and delayed at a predetermined timing to correct the deviation from the B data. When the copy magnification is doubled, the data shift between the lines is doubled, and the memory capacity required to correct the shift is doubled. The line-to-line correction unit 500 pays attention to the maximum size of copy paper on which an image is formed is A3, and controls the number of effective dots in one line according to the copy magnification. Specifically, if the copy magnification is doubled,
Reduce the range read by one line to 1/2. This suppresses an increase in the memory capacity required to correct the above deviation. Further, by executing the interpolation processing of the inter-line data, a finer deviation of the read data is corrected.

(B-3-1) Interline Correction Processing FIG. 9 shows an interline correction processing section 501 and an interpolation processing section 50.
It is a block diagram of 2. The image data R _{27 to 20} and G _{27 to 20} input from the shading correction unit 400 are input to the field memories 503 and 505. The field memories 503 to 505 have a capacity of 256K × 8 bits. The R, G, B image data is 8-bit digital data. When the maximum size of the document read by the CCD image sensor 14 is A3 and the resolution is 400 dpi, the data amount for one line in the main scanning direction is about 5 kbits. Therefore, 51 lines of image data can be stored in one field memory. When the read document is enlarged (Y times) in the sub-scanning direction and printed out, the image data of each line of the document is repeatedly read Y times, and the data amount in the sub-scanning direction is padded to Y times. Here, as described above, the R data is 1 with respect to the B data.
It is preceded by 6 × Y lines and the G data is preceded by 8 × Y lines with respect to the B data. To correct this shift, the field memories 503 to 505 are 8 × Y.
It is required to be able to store data for lines. However, as described above, the field memories 503 ...
The 505 can store only 51 lines of data. That is, Y = 51/8 = 6.375 as it is.
This means that you can only increase the copy magnification up to twice. Therefore, the line-to-line correction processing unit 501 pays attention to the fact that the maximum size of printable copy paper is specified in advance (A3 in many copying machines), and the magnification X in the main scanning direction.
The range in which the document is read by the image scanner is limited in proportion to the reciprocal of (where X ≧ 1). As a result, the data amount for one line in the main scanning direction becomes about 5k / X bits, and the field memory stores 256k / about 5k × (1 /
X) ≈51 × X lines of data can be stored. In this way, the interline correction unit 500 increases the maximum copy magnification value without increasing the memory.

FIG. 10 shows the -FIFOEN signal, -FRES1 signal, -F input to the interline correction processing unit 501.
7 is a time chart showing a RES2 signal, a −FRES3 signal, and R, G, B data input / output to / from the line correction processing unit 501. The -TG signal is a trigger signal output in synchronization with the reading cycle t of the CCD image sensor 14 for one line in the main scanning direction. The -FIFOEN signal is a signal that becomes "L" within the reading range determined by the copy magnification in the main scanning direction. -FR
The ES1 signal is a write start signal input to the field memories 503 and 505, and has a cycle T = {INT.
It rises at (8 × Y) +1} × t. -The FRES2 signal is applied to the field memories 503 and 50.
5 is a read start signal, and is a signal having a cycle T synchronized with the -FRES1 signal. Field memory 50
3 and 505 start writing data in synchronization with the rising edge of the -FRES1 signal. Then, after the lapse of the period T, the signal is read in synchronization with the rising edge of the -FRES2 signal. Also, the -FRES2 signal is used in the field memory 5
It acts as a write start signal for 04. The field memory 504 writes the data output from the field memory 503 in synchronization with the rising edge of the -FRES2 signal. -FRES3 signal is the above-FRES1 and -FRES
It is a signal of a cycle T which is advanced by a reading period t for one line with respect to two signals. Here, the reason why the -FRES3 signal is advanced by the reading period t for one line is that the interpolation processing in the next interpolation processing unit 502 is performed to match the green component G data of the RGB image data.

(B-3-2) Interpolation processing-The rising of the FRES1 to 3 signals, that is, the period T is I
It is converted into an integer by the NT function and synchronized with the TG signal. Therefore, the output of the data from the field memories 503 to 505 can be adjusted only in the unit of the period t (that is, the copy magnification ⅛). In the interpolation processing unit 502, when the copy magnification has a decimal part, the line-to-line correction processing unit 501 could not correct {8 × Y-INT (8 × Y)}.
Compensate for the data shift of the line.

In the interline correction processing unit 501, the R data is output after being delayed by 2T-t. The G data is delayed by T and then output. However, in reality, R,
The G and B image data are offset from each other by 8 × Y lines. Due to the fractional part generated by this 8 × Y, the R data is a ₁ = {8 × Y-INT (8 ×
Y)} precedes. On the other hand, B data precedes G data by b ₁ = [1- {8 × Y-INT (8 × Y)}]. FIG. 11 shows the deviation of the data regarding the read position between the R _{27 to 20} data output from the field memory 504, the G _{27 to 20} data output from the field memory 505, and the B _{2 to 20} data.

As shown in FIG. 9, the R data is branched into two signals. The data flowing through one branch is delayed by one line by the line memory 507. Here, when the data of the m-th line is represented by R _m , the R _m data is input to the multiplier 506. The data of R _{m + 1} is input to the multiplier 508. The multiplier 506 executes the following operation of “Equation 3”.

## EQU3 ## Rx × R _m Here, Rx is a coefficient obtained by the following "Equation 4".

Equation 4] _{256: 1 = Rx: 1-} a 1 = Rx: 1- {8 × Y-INT (8 × Y)} ∴Rx = 256 [1- {8 × Y-INT (8 × Y)} Further, the computing unit 508 executes the computation shown in the following “Equation 5”.

## EQU00005 ## (1-Rx) .times.R.sub.m _{+ 1} where Rx is the coefficient obtained by the above "Equation 4".

The data output from the arithmetic units 506 and 508 are added in the adder 509. By executing the above calculation, the interpolation process for the decimal part of the copy magnification for the R data is achieved.

Similarly, as shown in FIG. 9, B data is also branched into two signals. The data flowing through one branch is delayed by one line by the line memory 511. Where m-th
When the line data is represented by B _m , B _m data is input to the calculator 510. B _{m + 1} data is input to the arithmetic unit 512. The computing unit 510 executes the following computation of "Equation 6".

(1−Bx) × B _m Here, Bx is a coefficient obtained by the following “Equation 7”.

Equation 7] 256: 1 = 255-Bx: 1-b 1 = 255-Bx: 8 × Y-INT (8 × Y) ∴Bx = 256 [1- {8 × Y-INT (8 × Y)} Further, the computing unit 512 executes the computation shown in the following “Equation 8”.

## EQU00008 ## Bx.times.B.sub.m _{+ 1} where Bx is a coefficient obtained by the above "expression 7".

The data output from the arithmetic units 510 and 512 are added by the adder 513.
By executing the above calculation, the interpolation processing for the decimal part of the copy magnification for B data is achieved. As described above, by performing the interpolation process of the R and B data with the G data as a reference, it is possible to set the copy magnification in units of 1/2024 times. The R _{37 to 30} data, G _{37 to 30} data, and B _{37 to 30} data which have been subjected to the above-mentioned interpolation processing by the interpolation processing unit 502 are respectively the scaling / movement processing unit 80.
It is output to 0 and is input to the AE processing unit 600.

(B-4) AE Processing Unit The AE processing unit 600 detects the document size, ACS (Auto
(Abbreviation of Color Selection), AE processing is executed. The detection of the document size means to detect the existing range of the document placed on the platen 15 in units of one line in the main scanning direction.
In the copying machine according to the present embodiment, the boundary line between the original and the original is detected by making the original cover a color having a predetermined uniform density. The ACS refers to obtaining the ratio of monochrome pixels in the document from the detected document size, and determining whether the document is a full-color document or a monochrome document from the calculated ratio. The AE process is a process for correcting the background level of the original so that the brightest color of the original is reproduced as white (tone level 255) on the copy paper. However, when this AE processing is applied to a full-color original, the image reproduced on the copy paper will appear to be entirely faded. Therefore, the AE processing unit 600 executes the AE processing based on the result of the determination by the ACS. Figure 12 shows AE
3 is a block diagram showing the configuration of a processing unit 600. FIG. The histogram generation unit 602 uses the monochrome 256 in the original image.
Obtain a histogram of gradation data. Document size detector 6
At 50, the document size is detected. The line data monitor unit 700 stores and monitors data for one line of RGB image data, and monitors the exposure lamp 12 and the CCD sensor 1.
Detects a signal reading error due to a problem such as 4.

(B-4-1) Histogram Generating Unit FIG. 13 is a diagram showing the configuration of the histogram generating unit 602. The histogram generation unit 602 receives the input R
Of the pixel data obtained by appropriately thinning out all the pixel data of _{37 to 30} , G _{37 to 30} , and B _{37 to 30} , a histogram for the gradation data of monochrome pixels is obtained. The histogram obtained by the histogram generation unit 602 is used when obtaining the ratio of monochrome pixels in the document in the AE process described later. Pixel data in the main scanning direction is thinned by the main scanning 1/16 dot thinning circuits 603 to 603.
At 05. The main scanning 1/16 dot thinning circuits 603 to 605 output the data in the main scanning direction once every 16 dots to the A of the histogram memories 606 to 608.
Output to the DR terminal. As a result, the amount of data in the main scanning direction is thinned out to 1/16. The thinning of the data in the sub-scanning direction is performed by the V direction counter 616, the comparator 617, and the NAND gate 619. Comparator 617
Indicates that the count output from the V direction counter 616 is output from the histogram memory control unit 618 as Vdot _{7 to 0.}
When it is equal to, an "L" signal is output. The V-direction counter 616 resets the count value when the comparator 617 outputs an “L” signal to the −CLR terminal. N
The AND gate 619 outputs from the main scanning direction synchronization signal −HD, the sub scanning direction synchronization signal −VD, and the comparator 617.
When the "L" signal is input, the "L" signal is input to the -CS terminals of the histogram memories 606 to 608. As a result, the data amount in the sub-scanning direction is 1 / (Vd
ot _{2 to 0} )). In addition, R _37-30 , G
The determination as to whether or not each of the data _{37 to 30} and B _{37 to 30} is monochrome pixel data is performed by the minimum value detection unit 612,
Maximum value detector 613, calculator 614, and comparator 615
Done in. This judgment is made by R,
This is performed by utilizing the fact that there is almost no difference between the G and B image data. The minimum value detection unit 612 receives R, G, and
B The data having the smallest value among the respective data is output. The maximum value detection unit 613 outputs the data having the largest value among the R, G, and B data that are simultaneously input. Calculator 6
14 finds the difference between the two and outputs it. Comparator 61
5 is the reference value SREF output from the histogram memory control unit 618 as the difference value obtained by the calculator 614.
If it is smaller than ₁₇ to 10, it is determined that the pixel is a monochrome pixel, and the signal of "L" is set to the histogram memory 60.
It outputs to -WE terminal of 6-608. Where SREF
_If the value of _{17 to 10} is set to a relatively large value, even if the background of the original is color, a histogram is created and the background color can be intentionally set to a high key. The histogram memories 606 to 608 count the frequency of each gradation data of the pixel data determined to be a monochrome pixel among the pixel data obtained by appropriately thinning out. For example, after initialization by the CPU 1, -CS terminal and -W
When both "L" signals are input to the E terminal, the histogram memory 606 outputs the frequency value of the pixel data value input to the ADR terminal as RAE _{15 to 10} from the Dout terminal. The adder 609 adds 1 to the input frequency value and then inputs this value to the Din terminal of the histogram memory 606. Similar operations are performed in the histogram memories 607 and 608. As described above, the histogram generation unit 602 generates a histogram for monochrome pixels included in the original image. FIG. 14 is a histogram generated for a certain document. Here, the gradation level m = 0 is black, and m = 255 is white. A in the figure
As will be described later, the data in the range is excluded when obtaining the ratio of monochrome pixels in the document. This is because the original pressing plate of the copying machine of this embodiment is a mirror surface pressure plate and the area other than the original is read as "black".

(B-4-2) Document Size Detection Unit The document size detection unit 650 is a CCD before the copying operation is executed.
The existence range of the document placed on the platen 15 is detected by the unit of one line in the main scanning direction by the preliminary scan performed by the image sensor 14 (see FIG. 16). In the copying machine according to the present embodiment, the boundary line between the original and the original is detected by making the original cover a color having a predetermined uniform density. As shown in FIG. 16, the preliminary scan is performed on the area (A3) corresponding to the maximum document size. This document size detection unit 65
The size of the document detected as 0 is used when obtaining the ratio of monochrome pixels in the document in the AE process described later. FIG. 15 is a diagram showing the configuration of the document size detection unit 650. The document size detecting section 650 outputs document size data SZD _7-0 to the CPU 1 based on the input image data of R _97-90 , G _97-90 , B _97-90 . The NAND gate 654 outputs an "H" SZON signal when it is determined that the input R _{97 to 90} , G _{97 to 90} , and B ₉₇ to ₉₀ are original pixel data. To the NAND gate 654, the −HD signal that switches from “H” to “L” within the readable range of the document and the comparison result signal output from the comparison unit 653 are input. The comparing unit 653 receives the input R _{97 to 90} , G _{97 to 90} , B
_97-90 5: 6: shading data S _{7 to 0} obtained by mixing in a ratio of 5, the following cases document background level SREF _{7 to 0,} and outputs a comparison result signal of "L". The shading data S _{7 to 0} are inputted _R 97~90, G 97~90, B
_This is _data obtained by multiplying ₉₇ to ₉₀ by × 5, × 6, × 5 by the multiplier 651 and then multiplying by 1/16 by summing them by the calculator 652. The shift register circuit 655 to which the SZON signal is input extracts the value of the SZON signal for every 4 dots and outputs it to the AND gate 656. The AND gate 656 outputs the signal of "H" only when all the SZON signals become "H". This is because the original area is 16
It means that dots (about 1 mm) or more are continuously detected. This makes it possible to prevent erroneous determination of the document size. In response to the value of the signal output from the AND gate 656 switching from “L” to “H”, DF
As shown in the time chart of FIG. 16, F659 is "
The VCLKEN signal of "H" is output. Further, in response to the end of the original area and the value of the SZON signal being switched to "L", the D-FF 659 outputs the VCLKEN signal of the VCLKEN signal as shown in the time chart of FIG. Switch the value to “L.” VCL of the original background area by the VCLKEN signal
When the K signal is enabled, the AND gate 658 causes LA
The STCK signal is output. The LASTCK signal is disabled according to the trailing edge of the VCLKEN signal on the trailing end side of the main scanning area of the original area, and the main scanning address HA _C to ₀ at the trailing end portion of the original area is latched in the D-FF 660. Further, the LASTCK signal is the flip-flop 6
A FIRSTCK signal is generated at 64, and the D-FF 66 is cleared by the -TG signal at the beginning of one line.
Change the output of 1 to "H". That is, when the first LASTCK signal on one line rises, FIRSTCK
The signal also rises. D-FF with this FIRSTCK signal
The main scanning address latched by 661 becomes the original area head address. D-FF660 and D-FF661
The address latched in is output from the AND gate 665 at the next rise of the -TG signal on the line.
It is latched again by the D-FF 662 and D-FF 663 by the signal of "H", and the original size address signal
_C-0 and FIRSTSZ _C-0 ). CPU1
Latches again to read these signals −
The TG signal is temporarily disabled by the -TGSTP signal, and the necessary address signal is selected and read by SZSEL1, 0. Selector 667 receives input SZ
If SEL0 and SEL0 are "0", the lower 8 bits of the document trailing edge address are selected, SZSEL0 is "0", SZSE
L1 is if "1", selects the most significant 5 bits of the original rear end address, C it as a document size data SZD _{7 to 0}
Output to PU1. Further, the selector 667 is an SZSE
If L0 is "1" and SZSEL1 is "0", the lower 8 bits of the document leading edge address are selected, and SZSEL0 and SZSEL1 are selected.
If There "1", selects the most significant 5 bits of the original tip address and outputs the original size data SZD _{7 to 0} in the CPU 1. The CPU 1 repeatedly recognizes the original area in the sub-scanning direction by repeatedly executing the data reading operation.

Here, the inside of the document is 0 and the outside is 1 on the bitmap memory corresponding to the positions of the document in the main scanning direction and the sub scanning direction from the sequentially detected leading and trailing end addresses of the main scanning.
As the original size data SZD ₇ to ₀ is written (Fig. 1
7). The bitmap memory is provided in the CPU 1. Next, it is determined whether the change points 1 → 0 and 0 → 1 in the bitmap memory exist as continuous lines in the sub-scanning direction. At this time, if discontinuity is detected, the change point of the main scanning address 1 → 0, 0 → 1 is corrected from the change information of the preceding and following lines. This is done for the purpose of correcting the address information that is mistakenly detected in the binding portion of the book original, where the original floats from the glass surface of the original, is read in black, or the edge of the original is dirty. In this way, after all the change points from 1 to 0 or 0 to 1 on the bit map memory are determined and corrected, the CPU 1 sequentially synchronizes with the start of the copy operation based on the bit map information. Determine the original valid area.

The image size data SZD _7-0 of the document effective area determined by the CPU 1 is sent to a scaling / movement control circuit 801 of a scaling / movement processing unit 800 described later. The scaling / movement control circuit 801 generates a DCLR1 signal of "H" in the area other than the original area and "L" in the area of the original based on the sent data of the effective area of the original, which is unnecessary for image processing. Areas that are not visible. As a result, as shown in FIG. 17, even if the document is placed obliquely, the outside of the area can be masked according to the document arrangement. Note that -TGS
TP signal and -SZCS signal, CPU 1 is SZD _{7 to 0}
It is turned on when it is difficult to read the signal. The -OE2 signal is a sword signal of the CPU 1.

(B-4-3) AE processing The CPU 1 performs shading before based on the histogram of the monochrome pixels generated by the histogram generation unit 602 and the size of the document sheet detected by the document size detection unit 650. The coefficient value X of the background level described in the description of the correction unit 400 is determined. 18 to 2
0 is a flowchart of the AE process executed by the CPU 1. After the completion of the preliminary scan (step S600), the total number of dots outside the document area is calculated from the document size calculated by the document size detection unit 650 (step S60).
1). Next, the total number of dots of the maximum document size (A3) is multiplied by the thinning rate in the main scanning direction and the sub scanning direction to obtain the total number of dots Tn that can be stored in each of the histogram memories 606 to 608, and The number of dots outside the area Un is obtained by multiplying the number of dots in the area other than the original size detected by the size detection unit 650 by the thinning rate in the main scanning direction and the sub scanning direction (step S602). Next, the histogram memories 606-6
08, total frequency RSn, GSn,
BSn is checked, and the maximum value Sn = MAX (RSn, RSn,
GSn, BSn) is calculated (step S603). Based on the total dot number Tn, the out-of-region dot number Un, and the maximum value Sn thus obtained, the ratio BKn = (Sn-Un) / (Tn-U of monochrome pixels in the original image
n) is calculated (step S604). Here, the reason why Un is subtracted from the values of Sn and Tn is that the pixel data outside the region is read as "black" data close to zero. When the value of the ratio BKn thus obtained is equal to or smaller than the predetermined threshold value TH1 (NO in step S605), it is determined that the original is color, and the coefficient value X of the background level is set to 255. (Step S606). If the value of BKn is greater than or equal to the predetermined threshold value TH1 (YES in step S605), it is determined that the original document is a monochrome document, and the distribution of the histogram is analyzed as described below.

The CPU 1 has a frequency RS (m), GS (m), BS (m) of each gradation level from 255 to a certain level LV1 for each histogram data of R, G, B respectively.
(However, the relationship of 255 ≧ m ≧ LV1 is satisfied) is checked (step S607). Next, the frequency RS of each gradation level
(M), GS (m), BS (m) from each total frequency RPn,
RPn, GPn, BPn obtained by obtaining GPn, BPn
The maximum value Pn = MAX (RPn, GPn, BPn) of the monochrome original is calculated from the maximum value Pn.
Hn = Pn / (Sn-Un) is calculated (step S60)
8). If the value of the background ratio WHn is larger than the predetermined threshold value TH2 (YES in step S609), R, G,
For each B, the grayscale levels RX, GX, and BX having the maximum values that first appear in the grayscale value 255 are checked (step S61).
0). When all of the gradation levels RX, GX, BX are present (YES in step S611), the minimum value MIN (RX, GX, BX) among them is calculated, and the calculated minimum value is related to the background level. The value is set to X (step S61)
2). Here, the minimum value MIN (RX,
(GX, BX) is used because if the background level is set for each of R, G, and B, the color balance other than the background is lost. In addition, when one of the R, G, and B histogram curves does not have a maximum value from the original document (step S611).
NO), the value of the background ratio WHn is a predetermined threshold value TH2.
If it is smaller than the above (NO in step S609), it is determined that the background level of the original is 255 or more, or the original is a photograph or the like with no background (step S61).
4), the coefficient value of the background level is set to X = 255 (step S615). Even when RX, GX, and BX are present, the coefficient value is set to X = 255 when the photo mode is set (YE in step S613).
S).

When the standard mode is set, AE processing is executed (YES in step S616). As will be described later, the value of the coefficient P is set to 1 when executing the AE processing (step S617). When the exposure level is manually set (NO in step S616), the value of the coefficient P is determined according to the set values of 1 to 7 (step S618), as will be described later using "Table 1". ). In this case, the values of the coefficient X are all set to 255. As described in the description of the shading correction unit 400, since the shading correction plate 16 is not necessarily an ideal white color, this spectral distribution ratio is replaced with the R, G, and B sensitivity ratios of the CCD image sensor 14. The value is RN: GN: BN
And Assuming that the sensitivity of the shading correction plate 16 in the G wavelength region is WH1 and the minimum value of the copy density gradation dynamic range is WH2, for the desired value 255 × Q of the reciprocal conversion table for shading correction, 9 ”to obtain Q for each of R, G and B (step S619).

Equation 9] _{Q R = P × (RN /} GN) × 10 WH1-WH2 × (255 /
X) Q _G = P × 1 × 10 ^WH1-WH2 × (255 /
X) Q _B = P × (BN / GN) × 10 ^WH1-WH2 × (255 /
X) The coefficient P is a coefficient used when the background level is manually set, and is set to 1 when the AE process is executed. When the background level is manually set, the coefficient value X of the background level is set to 255. The following "Table 1" shows the value of the coefficient P and the value of the coefficient X at the time of AE processing and when the background level is manually set. As shown, there are seven levels of background levels that can be set manually. The setting value is centered around 4, 3 → 2 →
The value of the coefficient P is set so that the lower the value, the more the background is blown,
The value of the coefficient P is set so that the background is covered more as it becomes 5 → 6 → 7.

[Table 1] Q _R, Q _G obtained in step S619, based on the respective values of Q _B, R, G, downloads the converted data for each B to the inverse conversion table 406 (step S6
20). By the above AE processing, the background of the original is optimally processed so that the color balance of the reproduced copy does not differ from the original even if the original is a photograph or chromatic color.

In the above AE processing, the coefficient value X of the background level is
And the coefficient P is changed to optimize the shading correction, but the present invention is not limited to this, and for example, the background removal level UDC used in the γ correction unit 1700 shown in FIG. 73.
_It may be performed by changing ₇ to ₀ and the inclination correction value GDC ₇ to ₀ . In this case, the background removal level UDC _{7 to 0} and the inclination correction value GDC _{7 to 0} are the LOG shown in the following " _Equation 10".
It is determined based on the correction formula.

[ _Expression 10] UDC _7-0 =-(255 / DMAX) x lo
g (X / 255) GDC _7-0 = {255 / (255-UDC _7-0 )} x 1
28 However, the desired value 255 × Q for shading correction is
Set as X = 255.

Furthermore, the achromatic color ratio of the original document obtained during the analysis of the histogram data is a signal indicating whether the original document is a color original document or a monochrome original document. Therefore, if the achromatic color ratio of the original is used for identifying the original, the ACS operation can be performed as a full-color PPC.
If the original is a monochrome original, it is possible to execute the print processing by using only BK toner. In this case, it is possible to save the toner consumption amount and speed up the print processing. You can Further, even if the background of the original is color, the background can be intentionally skipped. This is S
This is realized by increasing the level of REF _{7 to 0} to widen the range treated as an achromatic color, and histogram the R, G, B data within the widened range. In this case, it is not necessary to obtain the achromatic color ratio, but the analysis of the histogram may be executed to detect the document background level X. Furthermore, in order to obtain the coefficient value X of the original background level, the maximum maximum value is detected from the histogram of the R, G, B data, but the average gradation level and the maximum and minimum values are obtained. The coefficient value X may be obtained from the average brightness of the document and the gradation dynamic range.

(B-5) _{Magnification} / Movement Processing Unit In the magnification / movement processing unit 800, unnecessary area data is input to the input R _{37 to 30} data, G _{37 to 30} data, and B ₃₇ to ₃₀ data. Deletion, reduction interpolation processing, reduction, equal magnification, enlargement output, image repeat, and enlargement interpolation processing. The unnecessary areas include two areas, that is, an area where no original exists on the original table and an area generated by reducing the original image. The unnecessary area is executed based on the result of the original size detection by the AE processing unit 600. For example, to reduce the original to 50%,
Originally, the image data of the original is read by using a scanner of 200 dpi instead of the scanner of reading density of 400 dpi, and the image data obtained by reading is read by 400 dpi.
Printing should be done at a density of i. But actually 40
Data obtained by thinning out image data obtained by reading with a 0 dpi scanner is used. In this case, the data of the thin line is erased and the quality of the reproduced image deteriorates. Therefore, the interpolation process is executed with a size according to the reduction rate. This prevents the quality of the reproduced image from deteriorating. Further, when enlarging a document, if the data is simply padded, the image is severely deteriorated, such as the noticeable edge rattling. The enlargement interpolation unit performs smoothing processing according to the enlargement magnification. This prevents the deterioration of the image at the time of enlargement. When the user presses the image quality monitor selection key 77 on the operation panel, a part of the original image is image-repeated eight times and output.

FIG. 21 shows the configuration of the scaling / movement processing unit 800 to which R data, G data, and B data are input. The out-of-region erase unit 805 erases the image data of an unnecessary region from the input image data Din ( _R37 to ₃₀ , _G37 to ₃₀ , _B37 to ₃₀ ). Here, the unnecessary area is
As shown in FIG. 22A, it refers to a portion other than the original sheet placed on the original table glass 15. The value of the read data in this unnecessary area is black data, which causes deterioration of copy quality. The data in this unnecessary area is executed based on the output of the DCLR1 signal output from the scaling / movement control circuit 801. The DCLR1 signal is switched based on the -TG signal which is a horizontal synchronizing signal and the VCLK signal which is a synchronizing signal of image data. The control circuit 801 detects the end of image data by the VCLK signal. Then, the data read until the synchronization signal of the next line rises by the -TG signal is judged as the data of the unnecessary area, and the out-of-area erase section 8
05 is executed to erase data.

(B-5-1) Reduction Interpolation Unit The reduction interpolation unit 806 interpolates sequentially input pixel data using the data of pixels before and after it. The data of R _{37 to 30} , G _{37 to 30} , and B _{37 to 30} from which the data of the unnecessary area is erased by the out-of-area erase unit 805 are input to the reduction interpolation unit 806. The reason why the reduction interpolation unit 806 executes the interpolation process is as follows. Generally, reduction of a document image is executed by thinning out image data. For example, in order to reduce the read document image to half and output it, the data amount is halved by thinning out every other image data. As shown in FIG. 23A, when an image read by a CCD image scanner that reads image data at 400 dpi is reduced to half, originally, FIG.
It is necessary to read the image data of the original image with a 200 dpi image scanner and print out with 400 dpi as shown in FIG. However, in reality, FIG.
As shown in, the reading resolution is changed by using the pixel data at a predetermined position among the image data obtained when the image data of the original is read at 400 dpi. However, when the original image is halftone dots, moire occurs when the reduction ratio is increased. Moreover, since the data is simply thinned out, the resolution of the image decreases in proportion to the reduction rate. In general, in the case of a monochrome binary image, the existence of each monochrome pixel is not established.
% Is rare, and the ratio of white pixels is usually large. In such a case, if data is simply thinned out, data loss will occur. In order to mitigate the influence of this data loss, the reduction interpolation unit 806 performs a predetermined interpolation process together with the data before and after it. The computing unit 807 executes the computation shown in the following “Equation 11”.

## EQU11 ## W = a.y + (1-a). (X + z) / 2 Here, the value of the coefficient a is the value of the magnification X in the main scanning direction. Also, x is the value of the (n + 1) th data. y
Is the value of the nth data. z is the value of the (n-1) th data. W obtained by the above equation is a value of the n-th image data which is interpolated based on the copy magnification in the main scanning direction.

(B-5-2) Magnification / Movement Processing Unit The image data subjected to the above-mentioned interpolation processing by the calculator 807 is inputted to the next magnification memory 1 and 2. The signals input to the scaling memories 1 and 2 are as follows. WCK
The (write clock) signal is a signal which is used when writing data and whose period is controlled by the copy magnification. The RCK (read clock) signal is a signal that is used when reading data and whose period is controlled by the copy magnification. -WE (write enable) signals 1 and 2 are signals for prohibiting data writing. -RE (read enable) signals 1 and 2 are signals that prohibit reading of data. -WRST (write address reset)
Signals 1 and 2 and -RRST (read address reset) signals 1 and 2 are signals that are output when data reading from the scaling memory is started. Magnification / movement control circuit 80
1 outputs a -WE signal to either one of the scaling memories 1 and 2, while outputting a -RE signal to the other scaling memory, and scales either scaling memory 1 or 2. While writing the data in the memory, the data stored in the other scaling memory is read out.

The scaling movement processing unit 803 uses the above WCK.
The scaling processing is executed by changing the cycle of the signal / RCK signal and the duty ratio of the rising pulse. Also,
Image movement is executed by changing the phases of the -WE signal and the -RE signal. In addition, -WRST signal and R
The phase of the RST signal is changed to control the repeat position of the image.

(B-5-2-1) Magnification / Magnification Processing FIGS. 24 to 26 show input data Din, WCK signal and RCK when outputting read data by enlarging / reducing the read data.
The timing relationship between the signal and the output data Dout is shown. (I) Same Size Output FIG. 24 is a diagram showing the timing relationship of the above signals when the read image is outputted at the same size. In this case WCK signal and R
The CK signal is set to have the same cycle t _c and a predetermined duty ratio d as the input timing of each pixel data. The scaling memory 1 sequentially stores the image data Din in synchronization with the rising edge of the pulse of the WCK signal while the -WE1 signal is "L". Next, waiting for the -RE1 signal to switch to "L", the image data stored in the memory is sequentially output in synchronization with the rising pulse of the RCK signal. The same applies to the scaling memory 2. By executing the writing and reading of the data at such a timing, the same size image data is output. Note that, as described above, data is not written to the scaling memory 2 while data is being written to the scaling memory 1. When data write permission is given to one of the scaling memories,
Only data can be read into the other scaling memory.

(Ii) Enlarged Output In FIG. 25, the read image is multiplied by X in the main scanning direction (where X> 1).
FIG. 3 is a diagram showing a timing relationship of each of the above signals in the case of outputting the signals. In this case, the WCK signal is set to have a cycle t _c and a duty ratio d. On the other hand, the RCK signal is set to have a cycle t _c × X and a duty ratio of d / X. Note that FIG. 25 is a diagram showing a case where X = 2. The procedure for writing and reading data to and from the variable-magnification memory is the same as in the case of equal-magnification output described with reference to FIG. However, the cycle of the RCK signal when reading data from the scaling memory is multiplied by X. This means that the data Dout is padded X times and output. By executing the writing and reading of the data at such timing, the data Dout enlarged X times in the main scanning direction is output. Here, the value of the magnification X may include a minority part. This is because unlike the case of reducing the image as described below, the timing of reading data is only extended in proportion to the value of the magnification X in the main scanning direction.

(Iii) Reduced output In FIG. 26, the read image is multiplied by X in the main scanning direction (where X <1.
Is. FIG. 4 is a diagram showing a timing relationship of the above signals when the signals are output as a signal. In this case, the WCK signal has a cycle t
_c / X and duty ratio d × X are set. On the other hand, RC
The K signal is set to have a cycle t _c and a duty ratio d. Note that FIG. 26 shows the case where X = 1/2. The writing and reading of data to and from the variable-magnification memory are the same as the case of equal-magnification output described with reference to FIG. But,
The cycle of the WCK signal at the time of writing data in the scaling memory is multiplied by X. This is the data D, as shown.
_This means that in is decimated to half and the data is read into the variable-magnification memory. The data stored in the variable-magnification memory is read out by using the RCK signal having the same cycle and duty ratio as in the case of equal-magnification output, so that the data Dout reduced to X times in the main scanning direction is obtained.
Is output.

(B-5-2-2) Movement processing In the control circuit 801, -WE1,2 signals and -RE1,
The movement processing of the output data is executed by controlling the phases of the two signals. Here, the movement of output data refers to FIG.
As shown in (a) and (b), it means moving an image of a read document on the copy paper left and right. FIG.
(A) shows the scaling / movement control unit 801 to the scaling memory 1
2 shows the waveforms of -WRST1 and -RRST2 and the waveforms of -WRST2 and -RRST1 that are input to the input terminals 2 and 2.
FIG. 28B shows the waveform of each signal (Din, -WE1, -WE2, -RE1, -RE2, Dout) output in synchronization with the waveform of (a).
To move the data of the read original image to the right on the copy paper and output it, as shown in FIG. 28B, -RE1
And delay the timing of switching -RE2 to "L". By delaying the timing, the timing of reading data from the scaling memory is delayed. As a result, the original image formed on the copy paper is moved to the right as a whole. Further, in order to move the read original image to the left on the copy paper and output it, the timing of switching the -WE1 and 2 signals to "L" is delayed as shown in FIG. 28 (c). The variable-magnification memory writes the line data input after the −WE1 and 2 signals are switched to “L” from the start address. When the data thus written is read out at a normal timing, an image moved to the left side is formed on the copy paper. To move the read original image up and down on the copy paper, the original reading start time of the CCD image sensor 14 and the development start timing of the copy paper are adjusted. Detailed description of this process is omitted.

(B-5-2-3) Image repeat The variable magnification / movement control circuit 801 controls the output of the -WRST1 and 2 signals and the -RRST1 and 2 signals, and thus
As shown in FIG. 9, image repeat is performed in which the image of the read document is output multiple times on one copy sheet. For example, to output the same image data twice at equal intervals on one line in the main scanning direction, as shown in FIG.
It suffices to output the 1 and 2 signals once each at the beginning and in the middle of the reading of the line. The scaling memory outputs the stored data from the first address in response to the output of the -RRST signal. As a result, the same image data is repeatedly output twice on one line in the main scanning direction. By repeating this for each line of the read image data, image repeat is realized. When the user presses the image quality monitor selection key 77, a part of the image of the document is image-repeated eight times and output.

The data read from the variable-magnification memory 1 or 2 at any of the timings shown in FIGS. 24 to 26 is changed by the out-of-area erase unit 808 to white data of the unnecessary area. Here, the unnecessary area refers to FIG.
As shown in (b), for example, the area that occurs when the size of the original paper is A3 and this is reduced to A4 for output. The data in this area is changed to white data because the unnecessary area is painted in black when A3 size copy paper is selected as the copy paper when making a reduction copy from A3 to A4, This is to prevent it from becoming unsightly.

(B-5-3) Enlargement Interpolation Unit The enlargement interpolation unit 804 executes an interpolation process on the input data according to the enlargement ratio. This is because when the read image is enlarged, the image is significantly deteriorated, for example, the rattling of the edge portion is conspicuous if the read data is simply padded. The enlargement interpolation unit 804 uses the outside area erase unit 8
The image data output from 08 is input to smoothing filters 809 to 816. Smoothing filter 80
9 to 916, appropriate weighting factors are given to the pixel of interest in the center of the pixel row and the adjacent pixels outside thereof in accordance with the enlargement ratio. Smoothing filter 80
9 to 816 correspond to the enlargement magnifications x1 to x8 in order. For example, in the filter 809 having a magnification of × 1, only the pixel of interest is the processing target, and the value of the weighting factor is set to 1. That is, the smoothing filter 809 outputs the input image data as it is to the selector 818. The main scanning magnification detection circuit 817 inputs R to the scaling memory.
An integer value of the copy magnification X in the main scanning direction is obtained from the cycle and duty ratio of the CK signal, and the obtained magnification value is selected by the selector 818.
To enter. The selector 818 outputs the data from the smoothing filter corresponding to the input magnification value as output data D _out .

(B-6) Image Interface Unit The R _{47 to 40} data, G _{47 to 40} data, and B _{47 to 40} data output from the scaling / movement processing unit 800 are input to the image interface unit 1000. In the image interface unit 1000, R, G, and B data (R-VIDEO _{7 to 0} , G-VIDEO _{7 to 0} , B-VIDEO _{7 to 0} ) input from the outside.
And R _{47 to 40} data, G _{47 to 40} data, and B _{47 to 40} data are selected and inset-combined. It also generates a timing signal for transmitting image data to the RGB interface or printer interface.

(B-7) HVC conversion section The HVC conversion section 1100 shown in FIG.
GB Data _{(R 57~50, G 57~50, B} 57~50) from the brightness signal (V _{7 to 0),} the color difference signal (WR 7~0, WB _7~0) generates a further color difference signals To generate saturation data ( _W7-0 ) and a hue signal ( _H7-0 ). When the user presses the serviceman mode setting key 75, the preset color patch is read, and the actually read R patch is read.
The above data is obtained based on the value of GB data. This corrects the variations in the reading characteristics of each CCD element.

(B-7-1) HVC conversion The input RGB data is input to the arithmetic unit 1101. The computing unit 1101 executes the respective conversion formulas shown in the following "Equation 12" to calculate the brightness signal ( _V7-0 ), the color difference signal ( _WR7-0 ,
Output WB ₇ to ₀ ).

## EQU12 ## V = a ₁ .R + a ₂ .G + a ₃ .B (provided that a ₁ + a ₂ + a ₃ = 1 is satisfied.) WR = (R−V) / (1-a ₁ ) WB = ( coefficient values of B-V) / (1- a 3) above a _1, a ₂ in the case of normal TV of the RGB image data, a ₁ = 0.3, is set to about a ₂ = 0.1 .
This means that the mixing ratio of RGB image data is 3: 6: 1. This mixing ratio slightly changes depending on the characteristics of the CCD image sensor and the color characteristics of the lens of the reduction optical system. For example, in the CCD image sensor 14 used in the copying machine of this embodiment, a ₁ = 0.35 and a ₂ = 0.55. The coefficient values of a ₁ and a ₂ are determined according to the flowchart shown in FIG. First, after the user presses the serviceman mode setting key 75 (step S1
If YES at 100), the color patch is placed on the platen glass 15. Wait for the print key 73 to be pressed, then CC
The RGB data of the color patch is read by the D image sensor 14 (step S1111). The value of the lightness V of the actual color patch is read from the standard value stored in advance (step S1112). RG read after this
From the B image data and the value of the brightness V, using the method of least squares, a
The values of ₁ and a ₂ are determined (step S1113). Wait for the user to press the serviceman mode setting key 75 again (YES in step S1114), and then the LED
After turning off 75a, it returns to the normal mode (step S1115).

Color difference signal (WR
_{7 to 0} , WB _{7 to 0} ) are represented by orthogonal coordinate axes of the hue plane in the color space, as shown in FIG. The saturation signal W _7-0 is obtained by inputting the color difference signals (WR _7-0 , WB _7-0 ) to the calculator 1102. The calculator 1102 executes the following calculation of "Equation 13" and outputs the saturation signals _W7-0 .

[Equation 13] W = (WR ² + WB ² ) ^1/2

(B-7-2) Image quality monitor function The HVC conversion unit 1100 includes the arithmetic units 1101 and 1
In addition to 102, an image quality control circuit 1103 for controlling an image quality (masking coefficient, sharpness, γ curve, color balance) adjustment signal selected by the user's operation of the image quality adjustment keys 74a to 74d is provided. Image quality control circuit 1103
Is a circuit for controlling execution of the image quality monitor function described below.

In the full-color copying machine, it is difficult for the user to know under what image forming conditions a desired image is obtained. However, it is uneconomical to set different image forming conditions each time one copy is made and repeat this until a desired image quality copy is obtained. The copying machine of this embodiment has an image quality monitor function that can easily obtain a desired image by simply selecting a desired image from a plurality of images actually printed out. Specifically, the operation panel 2
In response to the pressing of the image quality monitor setting key 77 provided on the No. 5, first, a part of the image on the document surface is first shown in FIG.
As shown in, the image is repeated to eight, and different masking coefficients, sharpness (edge enhancement / smoothing level), γ curve, and color balance (background removal / tilt correction level) are set for each. . The user selects an image having a desired image quality from the printed out images and inputs the number of the corresponding image from the ten-key pad 72 provided on the operation panel 25. The image quality control circuit 1103 outputs image forming condition data corresponding to the input number (masking correction coefficient switching signals MA _{2 to 0} , shapeness switching signals SH _{2 to 0} , γ curve switching signals GA _{2 to 0} , color balance switching). Signal CO
₂ to ₀ ) is output to the corresponding processing unit.

The scaling / movement processing section 800 responds to the depression of the image quality monitor setting key 77 by shifting the image data of a part of the document to 8
Repeat image times. FIG. 34 shows the image quality control circuit 11
03 shows the circuit configuration of 03. The main scanning counter 1104 reset by the -TG signal, which is a line trigger signal in the main scanning direction, starts counting in synchronization with the VCLK signal. The count output of the main scanning counter 1104 is the P output of the comparators 1105, 1106, 1107, 1108, respectively.
Input to the terminal. XE _{C to} 0, XF _{C to} 0, XG _C to 0, 0 are input to the Q terminals of the comparators 1105 to 1108, respectively. The XE _{C to 0} , XF _{C to 0} , and XG _{C to 0} are count values in the main scanning direction corresponding to the repeat points of the image repeat executed by the magnification / move processing unit 800 (see the lower part of FIG. 35). ). Each comparison unit 1105-1
Reference numeral 108 outputs a signal of "L" when the count value input from the main scanning counter 1104 matches the count value input from the Q terminal. The NAND gate 1109 is a counter pulse signal of “L” (hereinafter, CP) when the signal of “L” is input from any of the comparison units.
A signal) is output to the monitor area counter 1111 via the delay circuit 1110. Monitor area counter 1
In 111, the inputted CP signal is used as a clock signal to output a NUM _2-0 signal. The monitor area counter 1111 is designated with the identification number of the image to be image-repeated by the LD _2-0 signal which is the load data. The countdown signal is the monitor area counter 11
Set whether to up-count or down-count 11.

Switching of the image identification number in the main scanning direction is performed by C
It is performed by the reference values (XE _C-0 , XF _C-0 , XG _C-0 , 0) of the comparators 1105 to 1108 which generate the P signal,
The image identification number in the sub-scanning direction is switched by the countdown signal input to the monitor area counter 1111 and LD _2-0.
This is done by changing the value of the signal. For example,
When the value of the LD _2-0 signal is 5, the monitor area counter 1111 is set to 5 as the initial value of the image identification number. When the down count is set by the count down signal, the monitor area counter 111
1 outputs the value 4 counted down corresponding to the input of the first "L" CP signal as the value of the NUM _2-0 signal. Hereinafter, the monitor area counter 1111 is "L".
Corresponding to the input of CP signal of 4 → 3 → 2 → 1
The UM _2-0 signals are repeatedly output. The countdown signal causes the monitor area counter 1111 to count up in synchronization with the output of the second image in the sub-scanning direction. Here, if the value of the LD _2-0 signal is set to 3, the monitor area counter 1111 displays 4 → 5 → 6.
→ 7 NUM _2-0 signals are output (see FIG. 35). NUM _{2 to 0} output from the monitor area counter 1111
The signals are selectors 1114, 1117, 112, respectively.
0, 1123. Selector 1114,111
Selection signals MSEL0 to MSEL3 are input to the S terminals of 7, 1120 and 1123, respectively. Each MSEL
Normally, "H" is set to 0 to 3, and selectors 1114, 1117, 1120, 1123 are set to this.
Is a fixed value M _{2 to 0} , S _{2 to 0} , G input to the B terminal.
_{2 to 0} and C ₂ to ₀ are output from the Y terminal, respectively.

The masking coefficient setting key 74 is selected by the user.
When a is pressed, MSEL0 is switched to "L" and the NUM input to the A terminal of the selector 1114 is entered.
₂ to ₀ are output as MA ₂ to ₀ from the Y terminal. That is, in this case, the masking coefficient switching signal MA is displayed on the copy paper.
_The image of which the values of _{2 to 0} are switched to 4 → 3 → 2 → 1 is repeated four times, and the masking coefficient switching signal M is sent to the next stage.
An image in which four images in which the values of A _{2 to 0} are switched to 4 → 5 → 6 → 7 are image-repeated is printed out. After that, when the user inputs, for example, the sixth image identification signal, the fixed values M _{2 to 0} are updated to 6. Subsequently, when the user presses the shapeness setting key 74b, the value of MSEL1 is switched to "L" and NUM _{2 to 0} input to the A terminal of the selector 1117.
Is output as SH _2-0 from the Y terminal. In this case, on the copy paper, the values of the shapeness switching signals SH _{2 to 0} are changed from 4 →
The image switched from 3 → 2 → 1 is repeated four times, and the values of the sharpness switching signals SH _{2 to 0} are changed to 4 →
The image in which four images that have been switched in the order of 5 → 6 → 7 are repeated is printed out. At this time, selector 1
From the selectors 1114, 1120 and 1123 other than 117, fixed values M _{2 to 0} , G _{2 to 0} and C ₂ to ₀ are output from each Y terminal. Note that the fixed values M _{2 to 0} are the updated values 6
Is. After that, when the user inputs, for example, a second image identification signal, the fixed values S _{2 to 0} are updated to 2. Similarly, when the γ curve setting key 74c or the color balance setting key 74d is pressed,
On the copy paper, four images in which the values of the γ-curve switching signals GA _{2 to 0} or the color balance switching signals CO _{2 to 0} are switched to 4 → 3 → 2 → 1 are image repeated, and the γ-curve switching is performed in the next stage. Signal GA _{2 to 0} or color balance switching signal C
An image in which four images in which the values of O _{2 to 0} are switched to 4 → 5 → 6 → 7 is image-repeated is printed out. Thereafter, the fixed value G _2-0 or C _2-0 is updated according to the input of the image identification number by the user. With the above processing, the user can quickly obtain a print with desired image quality.

The contents set by the four types of image adjustment switching signals will be described below. The masking coefficient switching signal MA _2-0 switches the masking coefficient and adjusts the tint of the copy, as described in the section of the color correction section described in the section below. As shown in FIG. 36, this is performed by obtaining the coefficient by a method such as the least square method so that the original color difference between the original and the copy is eliminated. With respect to the coefficient, six other kinds of coefficients are set so as to rotate the color circulation of the reproduced copy clockwise or counterclockwise. Next "Table 2"
Indicates the relationship between the values of MA _{2 to 0} and the masking coefficient to be set.

[Table 2] Normally, the original color of 5R is the masking coefficient switching signal M
When the value of A _{2 to 0} is 4, the masking coefficient is set so that the color of the copy also becomes 5R. Masking coefficient switching signal M
As the value of A _2-0 decreases from 3 → 2 → 1, 5Y
The masking coefficient is set so as to be reproduced to the side (clockwise) (to rotate the color circulation diagram). On the contrary, as the masking coefficient switching signals MA ₂ to ₀ increase in the order of 5 → 6 → 7, the masking coefficient is set so as to be reproduced on the 5RP side. The masking coefficient switching signals MA _{2 to 0}
When the value of is 0, the masking coefficient for sepia color is set. That is, as described in the color correction unit 1400, when the -SEPIA signal is "L", the sepia color coefficient in the masking coefficient selection block is selected so that the values of the masking coefficient switching signals MA ₂ to 0 become 0. .

The sharpness switching signals SH ₂ to SH ₀ are signals for adjusting the sharpness of the image. This is the edge emphasis amount coefficient as described in the explanation of the MTF correction unit 1600,
Adjust the image sharpness by changing the smoothing filter size. The following "Table 3" indicates the value of the edge emphasis coefficient ED _{7 to 0} with respect to the value of SH _{2 to 0,} the relationship between the size SD _{7 to 0} of the smoothing filter.

[Table 3] As you can see, when the value of SH _2-0 becomes smaller than 4,
The edge emphasis coefficient switching block is selected so that the value of the edge emphasis coefficient ED _{7 to 0} becomes large. SH _{2 ~ 0}
If the value of 4 is 4 or less, the data not subjected to the smoothing filter is set to SD ₇ to ₀ and selected by the smoothing filter switching block. On the other hand, as SH _7-0 becomes larger, ED _7-0 becomes smaller and the filter having a larger smoothing filter size is designated as filter 1. As a result, the smaller the SH ₂ to ₀ , the sharper the image,
The larger the value, the smoother (blurred) the image.

The .gamma.-curve switching signals _GA.sub.2-0 are signals for selecting .gamma.-curves, and as described in the .gamma. When the value of GA _{2 to 0} is 4, the input and output data are set to be the same for both the adjustment of brightness and contrast. For the light / dark adjustment, a shadow type curve is selected when the value of GA _{2 to 0} is large, and a highlight type curve is selected when the value is small. In contrast adjustment, the highlight shadow type is selected when GA ₂ to ₀ is large, and the halftone emphasis type is selected when GA ₂ to ₀ is small.

CO _{2 to 0} are for adjusting three types of color balance, image saturation and copy density. For color balance adjustment, CR adjustment, MG adjustment, YB adjustment
There are adjustments. Taking the C-R adjustment as an example, when the value of CO _{2 to 0} becomes larger than 4, the inclination correction level GDC ₇ to ₀ ,
For C toner development, make it larger than 128 (slope = 1), and
By making it smaller than 128 for Y development, the cyan density of the image data is emphasized more than the magenta and yellow densities. On the contrary, CO
_When the value of _2-0 becomes smaller than "4", GDC
₇ to ₀ is made smaller than 128 (slope = 1) for C toner development and larger than 128 for M and Y development, and the red density is strengthened by making the cyan density of image data weaker than magenta and yellow density. . Similarly, for M-G adjustment and Y-B adjustment, GDC ₇ to ₀ during C, M, and Y development are adjusted as shown in "Table 4". As shown, in the C-R adjustment, when the amount of C is increased by Δ, the respective values of M and Y are increased by −Δ / 2. That is, C, M, Y without changing the amount of toner adhered to the copy paper per unit area
Adjust the toner adhesion amount.

[Table 4] To display, when the value of the CO _{2 to 0} is 4, which a developing process is also a GDC _{7 to 0} = 128, at the time of the BK developing, not variable remains _GDC 7~0 = 128. This adjustment is operating the color circulation as shown in FIG. Saturation adjustment, when the value of CO _{2 ~ 0} becomes larger than 4,
GDC ₇ to ₀ is made smaller than 128 at the time of C, M, and Y development, and is made larger than 128 at the time of BK development. This weakens the density of the chromatic color component (C, M, Y) and strengthens the density of the achromatic color component (BK). When the value of CO _{2 to 0} becomes smaller than “4”, the reverse process is performed. This adjustment is operating the color cycle shown in FIG. What is important in color balance adjustment is not to change the density of the entire copy, that is, the amount of toner adhered to the copy paper per unit area. This is because when the amount of toner attached per unit area changes, not only the density of the entire document changes before and after image adjustment, but also the fixing temperature changes and gloss changes, and toner fixing failure occurs. This is because. At this time, the other parameter, that is, the background removal level UDC ₇ to 0 remains 0. In addition, copy density adjustment can be performed with C, M, Y, B
It is operated regardless of the K developing process. CO _{2 to 0} is 4
If it is larger than, it becomes thicker, and if it is smaller, it becomes thinner.

(B-8) Density Correcting Section The density correcting section 1200 is an RGB data (R _{67 to 60} , G) that changes in proportion to the amount of light reflected from the original by the exposure lamp.
_{67 to 60} , B ₆₇ to ₆₀ ) are converted into data (DR _{17 to 10} , DG _{17 to 10} , DB ₁₇ to ₁₀ ) that change in proportion to the concentration.
FIG. 39 is a diagram showing the configuration of the density conversion unit 1200.
The input data of R _67-60 , G _67-60 , B _67-60 is
These are respectively input to the LOG tables 1201 to 1203. The LOG tables 1201 to 1203 are the same table and are the tables shown in FIG. In the LOG tables 1201-1203, the density data (DR _17-10 , D ₁₇₎ obtained by executing the conversion process shown in the following "Equation 14" is executed.
G _17-10 and DB _17-10 ) are output.

## EQU14 ## DR =-(255 / DMAX) × LOG (R
/ 255) DG = − (255 / DMAX) × LOG (G / 255) DB = − (255 / DMAX) × LOG (B / 255) where DMAX is the maximum reflection density value.

Further, the RGB data (R _{67 to 60} ,
G _{67 to 60} and B _{67 to 60} ) in the weighting unit 1204:
It is weighted with a ratio of 6: 5, mixed in the next addition unit 1205, and then input to the LOG table 1206. L
DVs ₁₇ to 10 output from the OG table 1206 are signals representing the density level in mono color.

Next, the negative / positive reversing unit 1250 is operated by -NEG.
DR when A signal (negative-positive inversion signal) is "L"
_17-10 , DG _17-10 , DB _17-10 , and DV _17-10 are inverted output (negative output), and when "H", they are passed through as they are. The -NEGA signal is sent to the operation panel 2 by the user.
5 is an optional signal which is set by the negative / positive reversing key 76 provided on the No. 5. It is held at "H" during normal copying.

(B-9) UCR / BP processing section Each color data of cyan (C), magenta (M), yellow (Y) and black (BK) necessary for full color reproduction is
It is created for each scan by the frame sequential method, and full color is reproduced by a total of four scans. Here, the reason why black is also printed is that even if cyan, magenta, and yellow are superimposed to reproduce black, it is difficult to reproduce clear black due to the influence of the spectral characteristics of each toner. Therefore, in the copying machine of this embodiment, the reproducibility of black is improved and full color is realized by the subtractive color mixture method using the data Y, M, and C and the black printing using the black data K.

The UCR / BP processor 1300 uses the DR
_27-20 , DG _27-20 , DB _27-20 minimum data (M
IN (DR, DG, DB) is calculated, it is assumed that it is a black color, a certain ratio thereof is treated as BK data, and a process of adding black toner by the printer (hereinafter, this process is referred to as BP).
Called processing. ), And C, according to the BK data added above.
Undercolor removal processing (hereinafter, this processing is referred to as UCR processing) for reducing the amounts of M and Y color materials is executed.

FIG. 41 is a diagram showing the structure of the UCR / BP processing unit 1300. Input density data D
The data of R _{27 to 20} , DG _{27 to 20} , and DB ₂₇ to 20 are input to the minimum value detection circuit 1301. The minimum value detection circuit 1301 determines the minimum value (MIN (DR, DG, DB)) of the input data of DR _{27 to 20} , DG _{27 to 20} , and DB _{27 to 20} , as shown in FIG. Detect and output.
In the next difference circuit 1302, the background level X data (represented by BPC in the figure) sent from the CPU 1 is subtracted from the minimum value (MIN (DR, DG, DB).
At the time of CR processing, this data is 0.

The saturation signals W _{7 to 0} calculated by the HVC converter 1100 are input to the UCR table 1303. Also input to the UCR table 1303 -CMY / K
The signal is set to "L" during the C (cyan), M (magenta), and Y (yellow) printing process, and switched to "H" during the BK (black) printing process. The UCR table 1303 stores UCR coefficient data α during UCR processing.
In addition to outputting (W), the BP coefficient data β (W) is output during BP processing. FIG. 43 shows the UCR table. If the scanned image is achromatic (black and white), reproducing the image with black toner alone will reduce the amount of toner adhesion,
I see black tightly. Therefore, when the value of the saturation signal W _{7 to 0} signal is small, the UCR table 1303 increases the values of α (W) and β (W) to be output so that both the undercolor removal amount and the black addition amount are set. To increase. On the other hand, when the read image is chromatic (color), if the α (W) and β (W) values are too large, a muddy color is reproduced. Therefore, when the value of the saturation signal W _{7 to 0} is large, the UCR table 13
03 sets the output α (W) and β (W) values to be small. By changing the α (W) and β (W) values to be output according to the magnitude of the saturation signals W _{7 to 0 in} this manner, more appropriate UCR / BP processing is executed.

Α output from the UCR table 1303
(W) or β (W) is input to the calculator 1304. The computing unit 1304 uses the MIN (D
Each data of R, DG, and DB is multiplied by α (W) / 256, and the undercolor removal amount (the amount shown by the broken line in FIG. 42B) is output to the subtractors 1305 to 1307. Subtractor 1305
In ～1307, "number 15" in the following is executed, C0 _{7 to 0} has been subjected to UCR processing, M0 _{7 to 0,} Y0 _{7 to 0} is output.

[Equation 15] C0 = DR-MIN (DR, DG, DB) ×
α (W) / 256 M0 = DG-MIN (DR, DG, DB) × α (W) /
256 Y0 = BR-MIN (DR, DG, DB) × α (W) /
256

On the other hand, the computing unit 1304 executes the following computation of "Equation 16" during the BP processing. That is, MIN (DR, D
(G, DB) data is multiplied by β (W) / 256, and the black toner amount BK to be added (see FIG. 42B) is output.

BK = (MIN (DR, DG, DB) -k)
× β (W) / 256

(B-10) Color Correction Section The spectral characteristic of the color separation filter provided for each read pixel of the CCD image sensor 14 has an unnecessary transmission area indicated by hatching in FIG. Further, the C, M, and Y color toners used on the printer side also have unnecessary absorption components indicated by hatching in FIG. The color correction unit 1400 executes a predetermined masking calculation process to match the color reproduction of the original and the copy. In the color correction unit 1400, the UCR-processed C
0 _7-0 , M0 _7-0 , Y0 _7-0 and its nonlinear term {(C0 + M0) / 2)} ² , {(M0 + Y0) /
2)} ² , {(Y0 + C0) / 2)} ² , and the constant term is further matrix-calculated as shown in the following "Equation 17" to obtain C, M, Y data. The color correction unit 1400 matches the color reproducibility of the original and the copy by this processing.

[Equation 17] Masking coefficients c11 to c17, m21 to m27, y3
Each coefficient of 1 to y37 is determined by the following procedure. First, the CCD image scanner 14 is caused to read the test chart to form a test print. Then, the output test print is read by the CCD image sensor 14. Here, the read data of the test chart is compared with the read data of the actually printed test print, and the value of each coefficient is determined so that the difference between the two data is minimized. Specifically, the masking coefficients c11 to c17 are set during cyan image formation. Masking coefficients m21 to m27 are set during magenta image formation. At the time of yellow image formation, the masking coefficients y31 to y37 are set.

FIG. 44 is a diagram showing the structure of the color correction unit 1400. An inputted C0 _{7 to 0,} M0 _{7 to 0,} the data of Y0 _{7 to 0,} respectively, is input to the multiplier 1409 to 1411, is input to the calculator 1402 to 1404. The arithmetic units 1402-1404 have C0,
Data is input in the order of M0, Y0, and M0,
Data is input in the order of Y0 and C0. Arithmetic unit 1402
At 1404, the average value of the data input to the A terminal and the data input to the B terminal is calculated and output. The respective data output from the arithmetic units 1402-1404 are input to the X terminals of the next arithmetic units 1405 to 1407. Each of the arithmetic units 1405 to 1407 calculates the square of the input data by 2
The value divided by 56 is output to the multipliers 1412 to 1414. The color correction control unit 14 is provided in each of the multipliers 1409 to 1414.
From 01, masking coefficients c11 to c17, m21 to m2
7, y31 to y37 are input. Each multiplier 1409-
The multiplication result of 1414 is input to each of the terminals A to F of the arithmetic unit 1415. Further, the constant term data is directly input to the G terminal from the color correction control unit 1401 in the calculator 1415. The computing unit 1415 uses the value obtained by subtracting the constant term data D from the data total value of A to F as the next selector 141.
6 is output. That is, by the above processing, the above "Equation 17"
Matrix calculation is performed.

At the time of forming each of cyan, magenta and yellow images, the color correction unit 1401 simultaneously provides eight types of masking coefficients, such as a masking coefficient that intentionally changes the hue balance, in addition to the masking coefficient determined by the above-described procedure. The masking coefficient can be set. Which data of these coefficients is to be output as the masking coefficient is determined by the masking coefficient switching signals MA ₂ to ₀ and the sepia area signal -SEP.
It switches in real time (every 1 dot) by IA.

The color correction unit 1401 outputs a "H" -CMY / K signal in the BK (black) printing process, and "L" in the other (cyan, magenta, and yellow) printing processes.
Output the -CMY / K signal. Selector 1416
Corresponds to the input of "H" -CMY / K signal and BK
_7-0 data is output to the next selector 1417. On the other hand, the data from the calculator 1415 is output to the next selector 1417 in response to the input of the "L" -CMY / K signal.

The color correction control section 1401 switches the coefficient (MM) according to the image forming process (C, M, Y, BK) of the printer according to the mono color reproduction color data input by the user through the operation panel. _{7 to 0} : C ₁₈ , M ₁₈ , Y ₁₈ , BK
₁₈ ) is output to the multiplier 1408. The multiplier 1408 is
The above-mentioned coefficient M is added to the density data DV17 to 10 for mono color.
Selector 14 for mono color data by multiplying M ₇ to ₀
Output to 17.

Further, the color correction control section 1401 has a mono-color area (-COLMONO) signal and an monochrome area (-BK) which are edit area signals having attributes for each pixel.
(MONO) signal is input. The −COLMONO signal and the −BKMONO signal are input to the OR gate 1418. When both the -COLMONO signal and the -BKMONO signal are "L", that is, the pixel data is data in the full color mode area, the OR gate 1418 outputs the "L" signal to the selector 1417. In this case, the selector 1417 outputs the full color data input from the selector 1416 as VIDEO7-0 signals.

However, the -COLMONO signal and -BK
When either one of the MONO signals is "H", that is, when the pixel data is data in the mono color mode area or the monochrome mode area, the OR gate operates as the selector 1
The "H" signal is output to the S terminal of 417. in this case,
The selector 1417 outputs the _monocolor data input to the multiplier 1408 as a VIDEO _7-0 signal.

(B-11) Area Discriminating Section FIGS. 47 and 48 show an area discriminating section 1500 for executing the discrimination processing of the black character portion in the original image and the discrimination of the halftone dot area.
It is a figure which shows the structure of. The black character determination is roughly divided into "character (edge) determination", "black determination", "black character erroneous determination area extraction", and the MTF correction unit 160 described later.
When it is 0, it is classified into four processes of "generation of black edge reproduction signal" which is executed to improve the reproducibility of black characters. Less than,
The four processes will be described.

(B-11-1) Judgment of Character (Edge) A character basically consists of two elements, "edge portion" and "solid painting" sandwiched between the edge portions. Further, in the case of a thin line character, only the edge is provided. That is, the character determination is achieved by performing the edge determination.

The lightness signals V _{7 to 0} generated by the HVC conversion section 1100 are input to the line memory 1502 via the N / P inversion section 1501. The N / P inversion unit 1501
When the input -NEGA signal is "L", the input data is inverted and output. Here, the −NEGA signal is an optional signal set by the user using the negative / positive inversion key 76 of the operation panel 25.

The data read from the line memory 1502 is input to the primary differential filter 1503 in the main scanning direction and the primary differential filter 1504 in the sub-scanning direction, each of which is composed of a 5 × 5 matrix, and also to the secondary differential filter 1508. Is entered. Here, both the first-order differential filter and the second-order differential filter are used for edge determination because each filter has the following features.
FIG. 49A shows the lightness distribution of five lines having different thicknesses, and the line becomes thicker toward the right in the figure. FIG. 49 (b) is a diagram showing the results of the first-order differentiation of the above lines. Further, FIG. 49 (c) is a diagram showing a second-order differentiation result of each line. As understood from the figure, the first-order differential filter outputs a higher detection value than the second-order differential filter at the edge portion of the thick line (width of 4 dots or more). On the other hand, the secondary differential filter outputs a higher detection value than the primary differential filter at the edge portion of the thin line (width less than 4 dots). That is, the primary differential filter is suitable for detecting a thick edge portion having a width of 4 dots or more, and the secondary differential filter is suitable for detecting an edge portion of a thin line having a width of less than 4 dots. In the area discriminating unit 1500 of this embodiment, paying attention to the feature of each filter, when the differential value of one of the primary differential filter and the secondary differential filter exceeds a predetermined threshold value, the edge portion It is determined that This maintains a constant edge detection accuracy regardless of the line thickness.

(B-11-1-1) Primary Differential Filter The data read from the line memory 1502 shown in FIG. 47 is a primary differential filter 1503 in the main scanning direction consisting of a 5 × 5 matrix and 1 in the sub scanning direction. It is input to the next derivative filter 1504. As the primary differential filter 1503 in the main scanning direction, the filter shown in FIG. 50 is used. The primary differential filter 1504 in the sub-scanning direction is shown in FIG.
The filter shown in is used. Each first derivative filter 15
The differential results obtained by 03 and 1504 are input to the next computing units 1505 and 1506, and their absolute values are obtained. Here, the absolute value of the first-order differentiation result is obtained by the first-order differentiation filter 150 shown in FIGS.
This is because there are negative coefficients in 3 and 1504. 1
The absolute value of the first-order differentiation result by the second-order differentiation filters 1503 and 1504 is averaged by the next computing unit 1507. The reason for obtaining the average value in this way is to take into consideration the first-order differential results in both the main scanning direction and the sub-scanning direction. The average value FL ₁₇ to 10 thus obtained
Are the edge determination comparators 1521, 1 shown in FIG.
It is input to each of 524, 1526 and 1528.

(B-11-1-2) Secondary Differential Filter The data read from the line memory 1502 shown in FIG. 47 is also input to the secondary differential filter 1508. Two
As the second derivative filter 1508, the filter shown in FIG. 52 is used. The absolute value FL ₂₇ to 20 of the second derivative D _{7 to 0} is calculated by the computing unit 1509. This is because there is a negative coefficient in the filter as in the first derivative filter. The absolute values FL _{27 to 20} are input to the edge determination comparators 1522, 1523, 1525 and 1527 shown in FIG. 48, respectively. The second-order differential results D _{7 to 0} are input to the VMTF table 1512. FIG. 59 is a diagram showing the VMTF table 1512. V
The MTF table 1512 is used to input the second derivative result D
Brightness edge components VMTF ₇ to ₀ corresponding to ₇ to ₀ are output.

(B-11-1-3) Edge Judgment The edge judgment comparator 1521 shown in FIG. 48 uses the first-order differential results FL _17-10 and the first edge reference level ED.
Compare with Gref _17-10 . Here, the first derivative result FL
_{When 17} to 10 are larger than the first edge reference level EDGref ₁₇ to 10, the "L" signal is output. Also,
The edge discrimination comparator 1522 is a second derivative FL
₂₇ to 20 are compared with the second edge reference level EDGref ₂₇ to 20. Here, when the second derivative result is larger than the second edge reference level EDGref ₂₇ to 20, "
It outputs a signal of L ″. Edge judgment comparator 152
The determination results in 1 and 1522 are the AND gate 15
33 is input. When the AND gate 1533 receives the "L" signal from at least one of the edge determination comparators 1521 and 1522, the AND gate 1533 outputs the "L" -EG signal indicating the edge portion.

(B-11-2) Black Judgment Black judgment is performed based on the values of the saturation data W _{7 to 0} . That is, when the value of the saturation data _W7-0 is less than or equal to a predetermined reference value, it is determined to be black. However, the saturation data W
A value of _{7 to 0} may be a large value even though it is a black pixel. For example, the CCD image sensor 14
When the phase of each of the R, G, and B data is slightly shifted as shown in the upper part of FIG. 53 due to the vibration at the time of reading the image data of the above, it is shown in the lower part of FIG. As described above, the value of the saturation data W _{7 to 0} becomes large. In this case, if black is determined based on the above criteria, it is erroneously determined to be a color pixel. In the present embodiment, first, the saturation data W ₇ to ₀ obtained by the HVC conversion unit 1100 is input to the line memory 1514 to form 3 × 3 matrix data, and then the smoothing filter 1515 shown in FIG. 54 is used. Apply smoothing processing. The saturation data _WS7-0 subjected to the smoothing processing is changed to a gentle value as shown in the lower part of FIG. This avoids the above erroneous determination.

Saturation data W subjected to smoothing processing
S _{7 to 0} are the saturation determination comparator 1529 shown in FIG.
In it is compared to the chroma reference data WREF _{7 to 0.}
The value of saturation data WS _{7 to 0} is the saturation reference data WR.
When it is smaller than the value of EF _{7 to 0} , this saturation data WS
Pixels with _7-0 are determined to be black. in this case,
The comparator 1529 outputs the “L” −BK signal to the OR gate 1537.

The saturation reference data WREF _{7 to 0}
Is the lightness data V input to the line memory 1502.
It is obtained by inputting ₇ to ₀ into the WREF table 1513. WR
As shown in FIG. 55, the EF table 1513 shows that when the brightness data V ₇ to ₀ is brighter than a predetermined value, WREF.
_The feature is that the value of _{7 to 0} is reduced in proportion to the brightness. This is because the black pixels caused by the erroneous determination are conspicuous in the bright areas.

As described above, the pixel for which the character (edge) determination and the black determination are performed is the pixel of the edge portion (-EG signal is "L") and the black pixel (-BK signal is "").
If the LBK signal is "L") and the -BKEGEN signal is "L", the OR gate 1537 outputs the "L" -BKEG signal, which means that the pixel is a black edge portion.

[0115] (b-11-3) black characters only erroneously extracted the character determination region (edge) determined and black determination, low value of the brightness signal V _{7 to 0,} chroma values of the data WS _{7 to 0} Characters (for example, dark blue or dark green) may be erroneously determined as an edge portion of a black character. Further, as shown in FIG. 56, in the adjacent portions of the images corresponding to the opposite colors such as cyan and yellow, the values of the saturation data W _{7 to 0} are once lowered at the transition portions of the colors. That is, there is a portion where the color changes to black at the color transition portion. If only the character (edge) determination and the black determination are made, this portion is erroneously determined to be the edge portion of the black character. If it is erroneously determined to be an edge portion, a black line will be drawn instead of transition between cyan and yellow colors. Such a case is likely to occur when blue letters are printed on a yellow background on a magazine cover or the like.

In this embodiment, in order to solve the above-mentioned problems, a solid portion is discriminated as the extraction processing of the black character erroneous discrimination area. And, even when it is determined that the black character,
The determination is canceled for the portion determined to be this solid portion. As a result, more reliable black character determination is realized.

The solid-colored portion is a non-edge portion, is a pixel in the color mode area, and is further characterized in that pixels having a low lightness are present at a certain level or more within a predetermined range. Based on this feature, the determination of the color solid portion is executed as follows. The third edge reference level EDGref _37-30 and the value of the fourth edge reference level _EDGref 47~40 1 derivative filter results FL _{from 17 to 10} and the secondary differential filter results FL _{twenty-seven to twenty} is in the edge determination comparator 1523 and 1524 OR gate 1 if lower than
534 means that it is a pixel in the non-edge portion "
Outputs a -BETA1 signal of L ". When the value of the chroma data WS _{7 to 0} is a predetermined reference value WREF _{twenty-seven to twenty} smaller in the saturation determination comparator 1530, the comparator 1530, this part color data _If the value of the brightness data V _17-10 is smaller than a predetermined reference value Vref _17-10 , the brightness determination comparator 1531 outputs "L".
The -VL ₁ signal of is output. The OR gate 1538 has the -BETA1 signal, the -COL signal, and the -L signal of "L", respectively.
In response to the input of the VL ₁ signal, the pixel outputs the “L” -CAN signal, which means that the pixel is a non-edge portion, a pixel in the color mode area, and a pixel with low lightness. This part is considered to be a chromatic flat part of the non-background part. The next counter 1542 is "L" -CA.
The number of N signals is counted in 9 × 9 pixel units. The count judgment comparator 1543 outputs "L" -BKE when the count result data Cnt _{15 to 10} input from the counter 1542 is smaller than the reference value Cntref ₇ to _0.
Output GON signal.

The OR gate 1544 is connected to the above-mentioned BKEG.
The signal and the -BKEGON signal are input. Above BKE
The G signal is delayed by the delay circuit 1541 so that the signals for the same pixel are input to the OR gate 1544. Even when the "L" -BKEG signal indicating the determination result of the black edge portion is input to the OR gate 1544, the color data exists within the predetermined range and is equal to or larger than the predetermined reference value. When it is determined that the color is a solid portion, the "H" -BKEGON signal is input, the determination of the black edge portion is canceled, and the "H" -PAPA signal is output. In this embodiment, the edge emphasis processing is executed only when black characters are drawn on an achromatic background. Further, when the pixel determined to be a solid portion within the predetermined range does not satisfy the predetermined reference value, the determination of the black edge portion is maintained and the "-PAPA" signal of "L" is output.

(B-11-4) Discrimination of halftone dot area As shown in FIG. 47, the data output from the line memory 1502 is input to the white halftone dot detection filter 1510 and the black halftone dot detection filter 1511. As shown in FIG. 57, each of the filters surrounds the pixel of interest X and is arranged in two directions in eight directions.
The target pixel is at a certain level (AMIRE
Greater than F _7-0 ) in all directions (white dots)
If the pixel of interest is larger than the eight surrounding pixels in order to make it an isolated point, it is determined to be a white dot (−WAMI = “L”), and When all are small, it is determined as a black dot (-KAMI = "L").

Specifically, the white halftone dot detection filter 1510 shown in FIG. 47 satisfies each conditional expression shown in the following "Equation 18" and all the conditional expressions shown in the following "Equation 19". Only in this case, the "L" -WAMI signal is output.

X- (a ₁₁ + a ₂₂ ) / 2> AMIREF _{7 to 0} X- (a ₃₁ + a ₃₂ ) / 2> AMIREF _{7 to 0} X- (a ₅₁ + a ₄₂ ) / 2> AMIREF _{7 to 0} X _{- (a 53 + a 43)} / 2> AMIREF 7~0 X- (a 55 + a 44) / 2> AMIREF 7~0 X- (a 35 + a 34) / 2> AMIREF 7~0 X- (a 15 + a _{24) / 2> AMIREF 7~0 X-} (a 13 + a 23) / 2> AMIREF 7~0

X> a ₂₂ X> a ₃₂ X> a ₄₂ X> a ₄₃ X> a ₄₄ X> a ₃₄ X> a ₂₄ X> a ₂₃

Further, the black halftone dot detection filter 1511 satisfies each conditional expression shown in the following "Equation 20", and the following "Equation 2" is satisfied.
"L" only when all the conditional expressions shown in "1" are satisfied
-KAMI signal is output.

Equation 20] _{X- (a 11 + a 22)} / 2 <AMIREF 7~0 X- (a 31 + a 32) / 2 <AMIREF 7~0 X- (a 51 + a 42) / 2 <AMIREF 7~0 X _{- (a 53 + a 43)} / 2 <AMIREF 7~0 X- (a 55 + a 44) / 2 <AMIREF 7~0 X- (a 35 + a 34) / 2 <AMIREF 7~0 X- (a 15 + a _{24) / 2 <AMIREF 7~0 X-} (a 13 + a 23) / 2 <AMIREF 7~0

X <a ₂₂ X <a ₃₂ X <a ₄₂ X <a ₄₃ X <a ₄₄ X <a ₃₄ X <a ₂₄ X <a ₂₃

White and black halftone dot detection filters 1510 and 1
The -WAMI signal and the -KAMI signal output from 511 are counters 1550 and 1 shown in FIG. 48, respectively.
551 is input. Counters 1550 and 1551
Counts the number of “L” signals of each signal in the 41 × 9 pixel matrix. Each counter 1550 and 1551
The counter value output from the maximum value detection circuit 1552
Is input to In the maximum value detection circuit 1552, the larger input counter value is used as the number of halftone dots (Amicn).
It is output as _t7-0 ). Amicnt _{7 to 0} are input to the four halftone dot number determination comparators 1553 to 1556. In each of the comparators 1553 to 1556, FIG.
As shown in FIG.
NTREF _17-10 , CNTREF _27-20 , CNTREF _37-30 ,
It is binarized by CNTREF _47-40 ). In each of the comparators 1553 to 1556, Amicnt ₇ to ₀ are halftone dot determination reference levels (CNTREF _{17 to 10} and CNTREF
_27~20, CNTREF _37~30, CNTREF _47~40) signal "L" is greater than (-AMI0, -AMI1, -
AMI2, -AMI3) is output.

(B-11-5) Other discrimination: The lightness data V ₇ to ₀ are input to the lightness judgment comparator 1532 shown in FIG. 48, and the second lightness reference level VRE is inputted.
Compare with F _27-20 . Here, the brightness signal V _{7 to 0} is the case of a value greater than the second lightness reference level VREF _{27 to 20,} and outputs a -VH1 signal of this portion is meant to be a highlight portion "L". Further, as in the case of black determination, the non-edge portion is determined. Results FL _{17 to} 10 of the first derivative filter and result F of the second derivative filter
L ₂₇ to ₂₀ are edge determination comparators 1527 and 152
7th edge reference level EDGref _{77-70 in 8}
And the eighth edge reference level EDGref 87 to ₈₀ , the OR gate 1536 outputs the -BETA2 signal of "L", which means that the pixel is a non-edge pixel. The OR gates 1539 are -L of "L".
With respect to the input of the H1 signal and the −BETA2 signal, the “L” signal indicating that the relevant portion is the highlight flat portion is output. This signal is delayed by the delay circuit 1546 and output as the -HLIGHT signal.

Also, the results of the first order differential filter FL _17-10
And the results FL _{27 to} 20 of the second-order differential filter are input to the edge determination comparators 1525 and 1526, and are compared with the fifth edge reference level EDGREF _{57 to 50} and the sixth edge reference level EDGREF ₆₇ to 60. From 1535, the -EG2 signal of "L" meaning that it is an edge portion is output. -EG
The two signals are delayed by the delay circuit 1545, and -MAMA
It is output as a signal.

(B-12) MTF Correction Section FIGS. 60 and 61 are diagrams showing the configuration of the MTF correction section 1600. The MTF correction unit 1600 includes the area determination unit 15
Area discrimination result by 00 (-AMI0-AMI3,-
Types of pixels recognized by MAMA, -PAPA, -EDG, -HLIGHT, and status signals (MODE,
Based on the print status recognized by -CMY / K, -BKER, -COLER, pixel data (MVIDEO)
_{7 to 0} or VIDEO ₇ to ₀ ), the most suitable edge enhancement processing and smoothing processing are executed. Also, the laser light emission duty ratio is changed in one cycle of the pixel clock in accordance with the recognized pixel type. Here, the light emission duty ratio means the ratio of the laser light emission period in the case where a period in which the laser light is not emitted is provided during one cycle of the pixel clock. Further, a predetermined value is added to the pixel data at the rising and falling portions of the edge, and when the toner image formed on the photoconductor drum 41 is transferred onto the copy paper, the toner is excessively attached and risen at the rising portion of the edge. Corrects toner fading in the falling part.

The MTF correction unit 1600 recognizes the color of the toner currently undergoing print processing from the -CMY / K signal. -CM
When Y / K = “L”, it is recognized that the print processing is performed for the C (cyan), M (magenta), and Y (yellow) toners. Also, -CMY / K = "
In the case of H ", it is recognized that the printing process is performed on the BK (black) toner.
Full color standard mode (-BKER = "H",-COLER = "H", MODE = "H") from three signals of E, -BKER, -COLER,
Full color photo mode (-BKER = "H",-COLER = "H", MODE = "
L "), mono color standard mode (-BKER =" H ",-COLER =" L ", MOD
E = "H"), Mono-color photo mode (-BKER = "H",-COLER = "L",
MODE = "L"), monochrome standard mode (-BKER = "L",-COLER = "
L ", MODE =" H "), or monochrome photo mode (-BKER =" L ",-
Recognize which mode (COLER = "L", MODE = "L") is set. Further, based on the area discrimination result, the type of pixel to be printed is the flat highlight portion (-HLIGHT = "
L ") pixel, non-edge part (-HLIGHT =" H ",-EDG =" H ",-PAPA ="
H ") pixel, color edge part (-HLIGHT =" H ",-EDG =" L ",-PAPA ="
H ") pixels and black edges (-HLIGHT =" H ",-EDG =" L ",-PAPA
Recognize which pixel is "L"). The MTF correction unit 1600 will be described below based on the configuration diagrams shown in FIGS. 60 and 61, after describing the MTF correction that is performed on various pixels when the above modes are set.

(B-12-1) Full color standard mode setting (-BK
MTF correction in ER = "H",-COLER = "H", MODE = "H") Table 5 below shows the signal level of each data input to the MTF correction parameter control unit 1601 when the full color standard mode is set. And the printing status that the level of each signal means,
In this case, DMPX0, DMPX1, DMPX5 and DMPX output from the MTF parameter controller 1601.
Each signal level of 6 is displayed.

[Table 5]

(B-12-1-1) Black edge part (-HLIGHT = "H",-EDG
= "L",-PAPA = "L") (b-12-1-1-1) BK printing process (-CMY / K = "H") BK (black) when full color standard mode is set
During the toner printing process of,
Normal image data SD ₇ to ₀ have brightness edge component VMTF
_The data obtained by adding ₇ to ₀ is output as VIDEO ₃₇ to 30. Here, the use of lightness edge component VMTF _{7 to 0} instead of density edge component DMTF _{7 to 0,} since the direction of lightness edge component is sensitive to the image edge from the background than density edge component Is. Here, when pixels form a halftone image, the amount of edge enhancement (values of the lightness edge components VMTF _{7 to 0} ) is limited according to the degree (density of halftone dots). This prevents the occurrence of moire when the halftone image is edge-emphasized.

(B-12-1-1-2) Printing process of C, M, Y (-CM
Y / K = “L”) For the pixels in the black edge portion in the C, M, and Y print processing, edge enhancement is not performed, and the data of the smallest value in the 5 × 5 or 3 × 3 pixel matrix MIN _{7 ~ 0} for VIDEO
_Output as ₃₇ to 30. Thus, by setting the minimum value data in the predetermined matrix as C, M, and Y image data, C, M shown in the portion surrounded by the broken line in FIG.
68. The fine protruding line of M and Y data is erased, and FIG.
The state is changed to the state surrounded by the broken line in (b). In order to erase the fine protruding line of the C, M, Y data shown in the portion surrounded by the broken line in FIG. 68 (a), the minimum value data MIN ₇ to ₀ in the predetermined matrix is used. For the reason. Conventionally, in order to erase the minute protruding line, data obtained by subtracting the edge detection result (FL _{17 to 10} or FL ₂₇ to _{20 in} this embodiment) from the value of each image data of C, M and Y is C and M. , Y for each image data. However, in the above-mentioned conventional copying machine, the value of CMY data around the edge portion of the black character becomes 0, and as shown in FIG. 69 (a), there is a problem that white spots occur around the edge portion of the black character. It was Therefore,
In this embodiment, by using the minimum value data MIN ₇ to ₀ in the predetermined matrix, only the value of each image data of C, M and Y inside the black character is set to 0 as shown in FIG. 68 (b).
To As a result, as shown in FIG. 69 (b), it is possible to print black characters with no white spots and with edge enhancement.

(B-12-1-2) Color edge part (-HLIGHT = "H",-EDG
"=" L ",-PAPA =" H ") As described above, in the area discrimination 1500 of the present embodiment, the processing of" (b-11-3) Extraction of black character erroneous discrimination area "is executed and the color character And the edge part of a black character are distinguished. The MTF correction unit 1600 does not _perform edge enhancement on the pixels of the color edge portion when the full-color standard mode is set and performs normal pixel data SD ₇ to VI on the VI edge without _performing edge enhancement.
_Output as DEO _37-30 . Moreover, C, M, during the printing process of the Y outputs data obtained by adding the density edge component data DMTF _{7 to 0} in the pixel data SD _{7 to 0} as VIDEO _{37 to 30.} The MTF correction unit 1600 cancels the edge enhancement during the BK printing process on the pixel data of the edge portion of the color character. This eliminates a black border around the edge-enhanced character.

(B-12-1-3) Highlight flat part (-HLIGHT = "
L ") In the flat part of the highlight, the FSD ₇ to ₀ that has been subjected to smoothing processing without edge enhancement is used as the image data VIDEO.
_Used as _37-30 . This makes noise in the highlight part inconspicuous.

(B-12-1-4) Non-edge part (-HLIGHT = "H",-EDG
"H",-PAPA = "H") In the non-edge portion, that is, in the solid-colored portion, the edge enhancement is not performed, and the normal pixel data SD ₇ to ₀ is output as VIDEO ₃₇ to 30.

(B-12-2) When full-color photo mode is set (-BK
MTF correction in ER = "H",-COLER = "H", MODE = "L") Table 6 below shows the signal level of each data input to the MTF correction parameter control unit 1601 when the full color photographic mode is set. , The print statuses indicated by the signal levels and the signal levels of DMPX0, DMPX1, DMPX5, and DMPX6 output from the MTF parameter control unit 1601 in this case are displayed.

[Table 6]

(B-12-2-1) Black edge part (-HLIGHT = "H",-EDG
= "L",-PAPA = "L") and color edge (-HLIGHT = "H",-EDG = "
L ",-PAPA =" H ") When the full-color photo mode is set, the density edge component data D is _added to the data FSD ₇ to _{0 that} has been smoothed so as not to impair the gradation characteristics of the halftone pixel.
Pixel data VIDEO obtained by adding MTF ₇ to _0
Output as ₃₇ to 30. By executing such edge enhancement processing, appropriate edge enhancement is realized without destroying the gradation characteristics.

(B-12-2-2) Highlight flat part (-HLIGHT = "
L ") In the highlight area, edge enhancement is not performed during C, M, Y, and BK printing processing, and FSD that has been subjected to smoothing processing.
₇ to ₀ are output as pixel data VIDEO ₃₇ to 30. This makes noise in the highlight part less noticeable.

(B-12-2-3) Non-edge part (-HLIGHT = "H",-EDG
= "H",-PAPA = "H") For non-edge parts, that is, solid parts, C, M, Y,
The edge enhancement processing is not performed during the BK printing processing, and the smoothed FSD ₇ to ₀ are output as VIDEO ₃₇ to 30. This maintains the gradation characteristics of the photographic image.

(B-12-3) Mono color standard mode setting (-BK
MTF correction in ER = "H",-COLER = "L", MODE = "H") Table 7 below shows the signal level of each data input to the MTF correction parameter control unit 1601 when the mono color standard mode is set. And the print statuses that the respective signal levels mean and the respective signal levels of DMPX0, DMPX1, DMPX5 and DMPX6 output from the MTF parameter control unit 1601 in this case are displayed.

[Table 7]

(B-12-3-1) Edge part (-HLIGHT = "H", -EDG = "
L ") During the BK printing process in the mono color standard mode, the normal pixel data SD ₇ to ₀ are output as VIDEO ₃₇ to ₃₀ without _performing edge enhancement. Also, during the C, M, Y printing process. Is the normal pixel data SD _7-0 added with the density edge component data DMTF _7-0.
Output as ₃₇ to 30. This prevents the edge portion of the color character from being blackened.

(B-12-3-2) Highlight flat part (-HLIGHT = "
L ") and non-edge part (-HLIGHT =" H ", -EDG =" H ") In the highlight flat part, edge enhancement processing is not performed during C, M, Y, and BK printing processing, and smoothing processing is performed. The applied FSD ₇ to ₀ are output as VIDEO ₃₇ to _30. This makes noise in the highlight portion inconspicuous.
Further, the edge enhancement is not performed on the non-edge portion, that is, the solid color portion, the edge enhancement processing is not performed during the printing processing of C, M, Y, and BK, and the smoothed FSD is performed.
₇ ~ ₀ is output as VIDEO ₃₇ ~ ₃₀ .

(B-12-4) Mono-color photo mode setting (-BK
MTF correction in ER = "H", -COLER = "L", MODE = "L") Table 8 below shows the signal level of each data input to the MTF correction parameter control unit 1601 when the mono-color photo mode is set. And the print statuses that the respective signal levels mean and the respective signal levels of DMPX0, DMPX1, DMPX5 and DMPX6 output from the MTF parameter control unit 1601 in this case are displayed.

[Table 8]

(B-12-4-1) Edge part (-HLIGHT = "H", -EDG = "
L ") When the mono-color photographic mode is set, smoothed data FSD ₇ to ₀ is used as pixel data so as not to impair the gradation characteristics of the halftone pixel. The density edge enhancement component DMTF is added to the data FSD ₇ to ₀ only during the printing process of M and Y.
It is performed by adding ₇ to ₀ . By doing so, it is possible to prevent the edge portion of the color character from being blacked.

(B-12-4-2) Highlight flat part (-HLIGHT = "
L ") and non-edge part (-HLIGHT =" H ", -EDG =" H ") In the highlight flat part, edge enhancement processing is not performed during C, M, Y, and BK printing processing, and smoothing processing is performed. The applied FSD ₇ to ₀ are output as VIDEO ₃₇ to _30. This makes noise in the highlight portion inconspicuous.
For the non-edge part, that is, the solid part, C,
The edge enhancement processing is not performed during the M, Y, and BK printing processing, and the smoothed FSD ₇ to ₀ are set to VIDE.
_Output as O _37-30 .

(B-12-5) Monochrome standard mode setting (-BKER
MTF correction in "L", MODE = "H") The following Table 9 shows the signal level of each data input to the MTF correction parameter control unit 1601 when the monochrome standard mode is set and the print meaning of each signal level. The situation and D output from the MTF parameter control unit 1601 in this case
The signal levels of MPX0, DMPX1, DMPX5, and DMPX6 are displayed.

[Table 9]

(B-12-5-1) Edge part (-HLIGHT = "H", -EDG = "
L ") When the monochrome standard mode is set, normal data SD ₇ to ₀ is used as pixel data, and edge emphasis is performed by changing the lightness edge component VMTF ₇ to ₀ into the data SD ₇ to ₀ during the BK printing process. Edge addition is not performed during C, M, and Y print processing.

(B-12-5-2) Highlight flat part (-HLIGHT = "
L ") and non-edge part (-HLIGHT =" H ", -EDG =" H ") In the highlight flat part, edge enhancement processing is not performed during C, M, Y, and BK printing processing, and smoothing processing is performed. The applied FSD ₇ to ₀ are output as VIDEO ₃₇ to _30. This makes noise in the highlight portion inconspicuous.
For the non-edge portion, the edge enhancement processing is not performed during the printing processing of C, M, Y, and BK, and the normal data SD is used.
₇ ~ ₀ is output as VIDEO ₃₇ ~ ₃₀ .

(B-12-6) MTF correction in monochrome photography mode setting The following table 10 shows the signal level of each data input to the MTF correction parameter control section 1601 and each signal level in the monochrome photography mode setting. And the signal levels of DMPX0, DMPX1, DMPX5, and DMPX6 output from the MTF parameter control unit 1601 in this case are displayed.

[Table 10]When set to monochrome photography mode, the gradation of the halftone pixel
In order not to damage the characteristics, the image data is
Data FSD with smoothing processing_{7 ~ 0}Use
It The edges are emphasized with the smoothing process described above.
Data FSD_{7 ~ 0}Concentration edge component data DMTF_{7 ~ 0}
Is done by adding. Highlight flat area and non-edge area
Then, make sure not to impair the gradation characteristics of the halftone pixel.
Therefore, smoothing processing was applied as image data.
Data FSD _{7 ~ 0}To use.

(B-12-7) Description of MTF Correction Unit 1600 Next, based on the configuration of the MTF correction unit 1600 shown in FIGS. 60 and 61, the MT executed by the MTF correction unit 1600 will be described.
The F correction will be described. The MTF correction parameter control unit 1601 has the -AM0 signal to the -AMI3 signal of 1 bit each, -HLI from the area discrimination unit 1500 described above.
GHT signal, -EDG signal, -PAPA signal, -MAM
A signal and are input. Further, the control unit 1601 is provided with a 1-bit MODE signal, -CMY / K signal, -BKE.
The R signal and the -COLER signal are input. MODE
The signal is a signal indicating the type of document, and is "L" in the photo mode and "H" in the normal mode. The CMY / K signal is a status signal indicating the printing status, and is “L” during the printing process for the C (cyan), M (magenta), and Y (yellow) toners, and the BK (black) toner. Is "H" during the printing process. The -BKER signal is a signal that requests signal processing to be executed in the monochrome mode. The -COLER signal is a 1-bit signal that requests signal processing in the mono color mode. -BKER signal and -COLE
The R signal is an area signal. The MTF correction parameter control unit 1601 uses the values of the eight types of input signals as described above to perform DMP as shown in Tables 5 to 10 above.
In addition to outputting X0 to DMPX6, LIMOS is output as shown in "Table 11" below.

[Table 11] The LIMOS signal is a signal for changing the light emission duty ratio of the laser diode with respect to the image data. Here, the light emission duty ratio means the ratio of the laser light emission period in the case where a period in which the laser light is not emitted is provided during one cycle of the pixel clock. Further, changing the light emission duty ratio of the laser diode means providing a non-light emitting period of a predetermined ratio in one cycle of the pixel clock. FIG. 62
Is the non-100% light emission duty generated corresponding to the value of the image data sent in synchronization with the pixel clock.
FIG. 3 is a diagram showing the LD drive signal and the LD drive signal whose light emission duty ratio is limited to 80% by a limiting pulse.
In this embodiment, the light emission duty ratio is set to 100% when LIMOS = “L”. Also, LIMOS = ""
In the case of "H", the light emission duty ratio is set to 80%.
As shown, in the case of MODE = "H", that is, the edge part (-MAMA = "L") when the standard mode is set.
And L for the pixel of the halftone dot part (-AMI0 = "L")
Set IMOS = "L". This improves the reproducibility of the edge portion and the halftone dot portion. On the other hand, when the standard mode is set, the non-edge portion and the photo mode are set to L
A non-light emitting period is provided with IMOS = “H”. As a result, line-to-line noise generated in the main scanning direction is made inconspicuous.

MODE signal, -CMY / K signal, -BK
The ER signal and the -COLER signal are directly input to the NAND gate 1602, and the -PAPA signal is inverted and then input to the NAND gate 1602. The NAND gate 1602 to which these five signals are input is D
The MPX7 signal is output to the S terminal of the selector 1603.
The NAND gate 1602 has a MODE signal, -CMY /
K signal, -BKER signal and -COLER signal are "H"
And only when the -PAPA signal is "L", "L"
The signal of is output. That is, the AND gate 1602 outputs the signal of “L” to the selector 160 only when the full color standard copy mode is set and the BK printing process of the black edge portion is performed.
Output to the S terminal of 3. The selector 1603 outputs the density data VIDEO ₇ to ₀ in response to the input of the “H” signal, and outputs the brightness data MVIDEO subjected to the masking process in response to the input of the “L” signal.

Masking is applied to the A terminal of the selector 1603.
Processed image data MVIDEO _{7 ~ 0}Is C, M, Y,
Input in the order of K, and the density converted VID is input to the B terminal
EO_{7 ~ 0}Data is input in the order of C, M, Y, K. SE
The data output from the lector 1603 is 5 ×
Line memory 1604 for forming 5 matrix data
Laplacian filter 1605 via smoothing
Filters 1607 to 1609, 5 × 5 matrix minimum value
Detection filter 1612, 3 × 3 matrix minimum value detection filter
Filter 1613 and printer edge correction unit 1615
Entered in.

The Laplacian filter 1605 is shown in FIG.
The filter shown in FIG. 3 converts the data of the pixel of interest located in the center into the emphasis data. Laplacian filter 16
The data output from 05 is the next DMTF table 16
It is input to 06. The DMTF table 1606 is shown in FIG.
The density edge component data DMTF is executed by performing the conversion shown in FIG.
Outputs ₇ to ₀ . ．

Smoothing filters 1607 to 1609
Inputs the input data to 300 dpi and 20 dpi, respectively.
It is a filter that smoothes to 0 dpi and 100 dpi, and for example, the filters shown in FIGS. 65 to 67 are used. Each data that has been smoothed by each filter is input to the smoothing filter control unit 1610 together with the data that has not been smoothed. The smoothing filter control unit 1601 includes an HVC conversion unit 1100.
The sharpness switching signals SH ₂ to SH ₀ to be output are input. The sharpness switching signals _SH2-0 are signals set by the image quality control circuit 1103 shown in FIG. The smoothing filter control unit 1610 is configured to smooth the data and the smoothing filter 16 that are not smoothed according to the values of the input sharpness switching signals SH _{2 to 0.}
Corresponding data is selected from the data smoothed by 07 to 1609 and output as SD ₇ to ₀ . Further, the sharpness switching signals SH _{2 to 0} are the eight types of edge enhancement coefficient ED output from the edge enhancement coefficient control unit 1611.
_7-0 can be switched in real time (every 1 pixel), and multiple sharpness can be changed up to 8 areas at the same time.

5 × 5 matrix minimum value detection filter 16
12 and 3 × 3 matrix minimum value detection filter 1613
Is a filter that outputs the minimum value of the data in the matrix when the target pixel is arranged in the center of each matrix. Minimum value detection filters 1612 and 1613
The minimum value data output from is input to the selector 1614. The selector 1614 has a filter selection signal FS.
Depending on the value of EL2, one of the input minimum value data is selected and output as MIN _7-0 . The value of the filter selection signal FSEL _{7 to 0} are determined experimentally. In this way, if the minimum value data in the predetermined pixel matrix is used as the data of the target pixel, the thin line character portion will be deleted. That is, the fine protruding line of the C, M, Y data shown in the portion surrounded by the broken line in FIG. 68A is erased, and the state is changed to the state shown in the portion surrounded by the broken line in FIG. 68B. . Data MIN of the minimum value in a predetermined matrix is used to erase the fine protruding line of C, M, Y data shown in the portion surrounded by the broken line in FIG.
The reason for using ₇ to ₀ is as follows. Conventionally, there is a copying machine which uses data obtained by subtracting the edge detection result FL _{17 to 10} or FL ₂₇ to ₂₀ from the value of CMY data as C, M, and Y image data in order to erase the fine protruding line. . However, in the above conventional copying machine, the CMY data value around the edge portion of the black character becomes 0,
As shown in FIG. 69 (a), white spots occur around the edge portion of the black character. Therefore, in this embodiment, by using the minimum value data MIN ₇ to ₀ in the predetermined matrix, only the value of the CMY data inside the black character is set to 0 as shown in FIG. 68 (b). As a result, as shown in FIG. 69 (b), it is possible to print black characters with no white spots and with edge enhancement.

The printer edge correction unit 1615 executes an edge correction process in consideration of the printing characteristics that occur when the toner image formed on the photosensitive drum is transferred onto a copy sheet. Here, the printing characteristics, for example, at the edge portion of the character, while the same amount of toner should be attached to both ends of the edge, while a large amount of toner is attached to the print start position, On the contrary, it means that the toner becomes faint at the end portion of the edge. This occurs when the degree of rising or falling of the edge is large and the value of the pixel data before rising, which is the base, is considered to be almost zero. On the other hand, the edge correction is performed by adding the data in the hatched area to the data in the edge portion having the predetermined data value, as shown in FIG. In FIG. 70B, the solid line shows the amount of toner attached to the sheet before correction, and the dotted line shows the amount of toner attached to the sheet after correction. As shown
After the correction, too much toner is attached at the rising portion of the edge, and toner blurring at the falling portion is reduced.

FIG. 71 shows the printer edge correction unit 1615.
FIG. When the data of the central pixel is represented by (L), the subtractor 1650 obtains a value obtained by subtracting the (L) th data from the data of the (L + 1) th pixel. Further, the subtractor 1651 obtains a value obtained by subtracting the (L) -th data from the (L-1) -th data. Comparator 1
When the difference obtained by the subtracter 1650 is larger than the predetermined reference values REF ₁₇ to 10, 653 outputs a signal of "L" to the S ₀ terminal. Further, the comparator 1654 outputs an “L” signal to the S ₁ terminal when the difference obtained by the subtractor 1651 is larger than the predetermined reference values REF ₂₇ to 20. Further, the comparator 1652 compares the (L) th data with the reference values REF ₃₇ to 30. Here, when the value of the (L) th data is smaller than the reference value REF ₃₇ to ₃₀ , the "L" signal is output to the S ₂ terminal. When “L” is input to the three terminals of S ₂ , S ₁ and S ₀ , the pixel is in the valley of the edge as shown in FIG. 72 (b) and the data is less than the predetermined value. I understand. in this case,
The selector 1655 ADD the addition data PD ₇ to ₀ .
_Output as ₁₇ to 10. Further, the signal of "H" to the terminal of S ₁ is entered, if the signal of "L" to the terminals of the S ₀ and S ₂ are input, the pixel is an edge as shown in FIG. 72 (a) It can be seen that the pixel is the rising portion and is equal to or less than the predetermined value. In this case, the selector 1655 outputs the addition data PD _17-10 as ADD _17-10 . Also, the "H" signal is input to the terminal of S ₀ , and S ₁ and S ₂
When “L” is input to the terminal of
As shown in (c), it is the trailing edge of the edge,
It can be seen that the number of pixels is less than or equal to the predetermined value. in this case,
The selector 1655 _ADDs the addition data PD ₂₇ to 20.
_Output as ₁₇ to 10. The selector 1655, S ₂ terminal, the signal input to the S ₁ terminal and S ₀ terminal the data of all values 0 if other than the above combinations ADD _{from 17 to 10}
Output as

Further, the MTF correction executed by the MTF correction unit 1600 will be described based on the configuration of the MTF correction unit shown in FIG. As described above, the selectors 1616 and 1617 shown in the figure are suitable from the data of the lightness edge component data VMTF _{7 to 0} , the density edge component data DMTF _{7 to 0} or the edge emphasis amount 0 according to the type of the pixel in the printing process. Data is selected and output as edge emphasis component data USM _7-0 . DMPX0 and DMPX1 output from the MTF correction parameter control unit 1610 are input to the selector 1616 and the selector 1617, respectively. DMPX0 and DMPX1 are output as shown in "Table 5" to "Table 10" described above according to the type of pixel in the printing process in each mode setting.

In addition, the selector 1622 and the selector 16
23 is an edge emphasis coefficient E based on the halftone dot discrimination results -AMI0 to -AMI3 input from the area discrimination unit 1500.
D ₇ to ₀ are suppressed and output. The edge enhancement coefficients ED _{7 to 0} input to the D terminal of the selector 1622 are signals set by the CPU 1 and control the degree of edge enhancement (sharpness). Further, the coefficient ED ₇ to ₀ signals are respectively set to 1 to A terminal to C terminal of the selector 1623.
Data that has been multiplied by / 4, 2/4, and 3/4 is input. DMPF2 and DMPX3 are input to the selector 1622 from the MTF correction parameter control unit 1601,
DMPX4 is input to the selector 1623. DMP
X2 to DMPX4 are -A as shown in the following "Table 12".
It is output based on the values of MI0 to -AMI3. -AM
If all I0~-AMI3 is "H", i.e., if it is determined not to be a halftone image area determination unit 1500, the arithmetic unit edge emphasis coefficient ED _{7 to 0} as it ED _17-10 1618 Output to. As described above, in the area discriminating unit 1500, -AMI0, -AMI1, -AMI2, -AMI3 increases as the degree of halftone dots increases.
Are sequentially switched to "L" and output. In the MTF correction parameter control unit 1601, the A terminal to
The data input to the C terminal is selected and output.

[Table 12] Calculator 1618 outputs the data obtained by multiplying the edge emphasis coefficient ED _{from 17 to 10} to the amount of edge enhancement USM _{7 to 0} as the edge enhancement amount USM _{from 17 to 10.}

DMPX5 and DMPX6 output from the MTF correction parameter control unit 1601 are input to the selector 1626 and the selector 1627, respectively. Here, the image data used for printing is output from the normal pixel data SD _{7 to 0} , the smoothed data FSD _{7 to 0} , and the selector 1614 shown in FIG. The selected data MIN ₇ to ₀ is output as VIDEO ₁₇ to 10. DMPX5
And DMPX6 are output as shown in "Table 5" to "Table 10" described above according to the type of pixel in the printing process in each mode setting.

The adder 1624 determines the edge emphasis amount USM.
₁₇ to ₁₀ are added to the pixel data VIDEO ₁₇ to 10, and this is output as VIDEO ₂₇ to 20. The adder 1628 is
Addition data ADD ₁₇ to 10 output from the printer edge correction unit 1615 are added to VIDEO ₂₇ to ₂₀ , and this is added to V
_Output as IDEO _{37 ~ 30} . As I explained before,
The addition data ADD _{17 to 10} are data to be added to the pixel data at the rising or falling edge portion.

(B-12) γ correction section Image data after MTF correction (VIDEO _{37 to 30} )
Is input to the γ correction unit 1700 shown in FIG. 73. The γ correction unit 1700 changes the γ curve according to the preference of the user, changes it to data of desired image quality, and outputs it. VI
The _{DEOs 37 to 30} are input to the γ correction table 1702 together with the γ curve switching signals GA ₂ to ₀ . γ curve switching signal G
A _{2 to 0} are signals set by the image quality control circuit 1103 shown in FIG. The γ correction table 1702 can switch eight kinds of gradation curves in real time by using the γ curve switching signals GA ₂ to ₀ as BANK signals of the table. These eight types of gradation curves are shown in FIGS. 74 and 75. FIG. 74 shows a gradation curve corresponding to the values of the γ curve switching signals GA _{2 to 0} when the brightness adjustment mode is set. Also,
FIG. 75 shows a gradation curve corresponding to the γ curve switching signals GA ₂ to ₀ when the contrast adjustment mode is set. In the γ correction table 1702, the data Dout ₇ to ₀ corresponding to the data Din ₇ to _{0 of} VIDEO ₃₇ to 30 is converted into VIDEO according to the gradation curve selected by the γ curve switching signals GA ₂ to ₀ .
_Output as _47-40 . The VIDEO _{47 to 40} output from the γ correction table 1702 are the operation units 1703 and 17
In 04, the operation shown in the following "Equation 22" is performed.

[ _Equation 22] VIDEO _{77 to 70} = (VIDEO _{47 to 40} -U
DC _7-0 ) x GDC _7-0 / 128 (However, if the value exceeds 256, VIDEO
_77-70 = 256. ) Here, the background removal data UDC _7-0 and the inclination correction data GDC _7-0 are CO _{2-0 as} shown in the following "Table 13".
There are eight types of data output by the color balance control unit 701 corresponding to.

[Table 13] FIG. 76 is a graph showing the relationship between VIDEO ₄₇ to ₄₀ and VIDEO ₇₇ to ₇₀ when the values of CO _{2 to 0} are 1 to 7, respectively. As shown in FIG. 77, the background removal data UDC ₇ to ₀ are removed from the VIDEO ₄₇ to ₄₀ , and the inclination is corrected by the inclination correction data GDC _{7 to 0} .

[0160]

According to the first image processing apparatus of the present invention, the C, M, and
Since the Y data is replaced by the C, M, Y data replacement means, the peripheral portion of the black character is not blank and more appropriate edge enhancement can be executed. Further, in the second image processing apparatus, in a document, the value of the brightness signal V _{7 to 0} is low, an erroneous determination for the chroma value of the data WS _{7 to 0} is low (e.g., dark blue or dark green) character Can be prevented.
Further, in the third image processing apparatus, the halftone dot degree of the document is determined based on the count value of the isolated pixels in the predetermined matrix, and the BK data of the BK data replacement unit is proportional to the count value. By reducing the replacement amount, it is possible to prevent moire caused by edge enhancement. Further, in the fourth image processing apparatus, it is possible to eliminate excessive toner sticking to the rising part of the edge and toner blurring to the falling part of the edge with respect to the direction in which the carrying part carries the sheet to the transfer part. . Further, in the fifth image processing apparatus, based on the input by the area information input means and the determination result by the determination means, it is possible to execute the appropriate edge enhancement processing according to the type of the document.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the configuration of a digital color copying machine of this embodiment.

FIG. 2 is a front view of an operation panel 25.

FIG. 3 is a processing block diagram of a read signal processing unit 20.

FIG. 4 is a processing block diagram of a read signal processing unit 20.

5 is a configuration diagram of an A / D conversion unit 300. FIG.

6 is a configuration diagram of a shading correction unit 400. FIG.

FIG. 7 is a graph showing the relationship between 8-bit input data Din and 12-bit reciprocal conversion data Dout output from the reciprocal conversion table 406.

FIG. 8 is a diagram showing a configuration of a CCD image sensor 14.

FIG. 9 is an inter-line correction processing unit 501 and an interpolation processing unit 5
It is a block diagram of 02.

FIG. 10 is input to the interline correction processing unit 501-
FIFOEN signal, -FRES1 signal, -FRES2 signal, -FRES3 signal, and line-to-line correction processing unit 501
4 is a time chart showing R, G, B data input / output to / from.

FIG. 11: R output from the field memory 504
_27-20 and data, G _27-20 data output from the field memory 505 is a diagram showing a deviation of the data relating to the reading position of the B _{2 to 20} data.

FIG. 12 is a block diagram showing a configuration of an AE processing unit 600.

FIG. 13 is a diagram showing a configuration of a histogram generation unit 602.

FIG. 14 is a diagram showing a density histogram of a document.

FIG. 15 is a diagram showing a configuration of a document size detection unit 650.

FIG. 16 is a diagram showing a relationship between a document placed on a platen glass and each signal in the document size detection unit 650.

FIG. 17 is a diagram showing a relationship between a document placed on a platen glass and a DCLR1 signal output from a scaling / movement processing circuit 801.

FIG. 18 is a flowchart of AE processing executed by the CPU 1.

FIG. 19 is a flowchart of AE processing executed by the CPU 1.

FIG. 20 is a flowchart of AE processing executed by the CPU 1.

FIG. 21 shows a configuration of a scaling / movement processing unit 800 to which R data, G data, and B data are respectively input.

22A shows a portion other than the original sheet placed on the original platen glass 15, and FIG. 22B shows a blank portion generated by reducing the original.

23 (a) shows read data D1, D2, ... At a density of 400 dpi, (b) shows read data D1 ', D2', ... At a density of 200 dpi, and (c).
Is read data D1 ″, D when the data read at 400 dpi is thinned to half and used as 200 dpi.
2 ", ...

FIG. 24 is a diagram showing a timing relationship of the above signals when outputting a read image at a normal size.

FIG. 25 shows the read image X times in the main scanning direction (where X>
FIG. 3 is a diagram showing a timing relationship of each of the signals in the case of outputting (1).

FIG. 26 shows a read image multiplied by X in the main scanning direction (where X <
It is 1. FIG. 4 is a diagram showing a timing relationship of the above signals when the signals are output as a signal.

27A and 27B are diagrams showing left and right movement of an image of a read document.

FIG. 28A shows -WRST1 and -R input to the scaling memories 1 and 2 from the scaling / movement control unit 801.
The waveform of RST2 and the waveforms of -WRST2 and -RRST1 are shown, and (b) shows each signal (Din, -WE1, -WE2, -RE1, -RE2, which is output in synchronization with the waveform of (a). Dout) waveform is shown, and (c) is a diagram showing a waveform when the timing of switching the -WE1 and 2 signals to "L" is delayed.

FIG. 29 is a diagram showing an image repeat in which an image of a read document is output multiple times on one copy sheet.

FIG. 30 is a time chart showing the timing of each signal when performing image repeat.

[Fig. 31] Fig. 31 is a diagram illustrating processing blocks that configure the HVC conversion unit 1100.

FIG. 32: Lightness signal (V _7-0 ), color difference signal (WR _7-0 ,
A ₁ to be used in determining the WB _{7 to 0),} a flowchart when determining the coefficient values of a _2.

FIG. 33 is a diagram showing color difference signals (WR _{7 to 0} , WB ₇ to ₀ ) by orthogonal coordinate axes of the hue plane in the color space.

FIG. 34 is a diagram showing a circuit configuration of an image quality control circuit 1103.

FIG. 35 is a diagram showing a relationship between an image printed out on a copy sheet by an image quality monitor function and each signal in the image quality control circuit 1103.

FIG. 36 is a value of a masking coefficient switching signal MA _2-0 ,
It is a figure which shows the relationship with color circulation.

FIG. 37 is a diagram showing the relationship between the values of color balance switching signals CO ₂ to CO ₂ and color circulation.

FIG. 38 is a diagram showing a state of color circulation when performing saturation adjustment.

FIG. 39 is a diagram showing a configuration of a density conversion unit 1200.

[FIG. 40] LOG tables 1201-1203

FIG. 41 is a diagram showing a configuration of a UCR / BP processing unit 1300.

42A and 42B are diagrams for explaining the UCR / BP processing.

FIG. 43 is a diagram showing a UCR table.

FIG. 44 is a diagram showing a configuration of a color correction unit 1400.

FIG. 45 is a diagram showing a spectral characteristic of a G filter.

FIG. 46 is a diagram showing spectral characteristics of M toner.

FIG. 47 is a diagram showing a structure of a region discriminating unit 1500.

FIG. 48 is a diagram showing a configuration of a region discriminating unit 1500.

49 (a) is a diagram showing the lightness distribution of five lines having different thicknesses, FIG. 49 (b) is a diagram showing the first-order differentiation result of each line in FIG. 49 (a), and FIG. 2 of each line in a)
It is a figure which shows a secondary differentiation result.

FIG. 50 is a diagram showing a primary differential filter 1503 in the main scanning direction.

FIG. 51 is a diagram showing a primary differential filter 1504 in the sub-scanning direction.

FIG. 52 is a diagram showing a second derivative filter 1508.

FIG. 53 shows a case where the values of the saturation data W _{7 to 0} become large even though the pixel is a black pixel because the phases of the R, G, and B data are slightly shifted. It is the figure which overlapped and represented _WS7-0 obtained by smoothing _W7-0 .

FIG. 54 is a diagram showing a smoothing filter 1515.

FIG. 55 is a diagram showing a WREF table.

FIG. 56 is a diagram showing RGB image data and saturation data W _{7 to 0} , and color difference signals WR and WB in an area that is likely to be erroneously discriminated as a black character.

57 is a diagram illustrating a white halftone dot detection filter 1510 and a black halftone dot detection filter 1511 that surrounds a target pixel X. FIG.
It is a figure which shows the position of two pixels before and behind a direction.

FIG. 58 is a four-step halftone dot determination reference level (C
NTREF _17-10 , CNTREF _27-20 , CNTREF _37-30 ,
It is a figure which shows the relationship between CNTREF _47-40 ) and -AMI0-AMI3.

FIG. 59 is a diagram showing a VMTF table.

FIG. 60 is a diagram showing the configuration of an MTF correction unit 1600.

FIG. 61 is a diagram showing a configuration of an MTF correction unit 1600.

FIG. 62 is an LD drive signal having a light emission duty ratio of 100% generated corresponding to the value of image data sent in synchronization with a pixel clock, and an LD having a light emission duty ratio limited to 80% by a limiting pulse. It is a figure which shows a drive signal.

FIG. 63 is a diagram showing a Laplacian filter 1605.

FIG. 64 is a diagram showing a DMTF table 1606.

FIG. 65 is a diagram showing input 400 dpi data of 300
This is a smoothing filter that smoothes to a level equivalent to dpi.

FIG. 66 is a flow chart showing the input data of 400 dpi to 200
This is a smoothing filter that smoothes to a level equivalent to dpi.

FIG. 67: Inputting 400 dpi data into 100
This is a smoothing filter that smoothes to a level equivalent to dpi.

FIG. 68 (a) shows that the C, M, Y data slightly protrude from the Bk data, and (b) shows
It is a figure which shows the relationship of each data when the protrusion of the said data is deleted by making the value of C, M, and Y data into predetermined minimum value _MIN7-0 .

69A shows an image reproduced on a copy sheet when the relationship between Bk data and C, M, Y data is shown in FIG. 69A, and FIG. 69B shows the above relationship. In the case of 69 (b), it represents an image reproduced on the copy paper.

FIG. 70A is a diagram when correction data indicated by diagonal lines is added to the edge portion of the image data, and FIG.
Indicates the amount of toner attached to the sheet before correction with a solid line, and the amount of toner attached to the sheet after correction with a dotted line.

71 is a diagram showing a configuration of a printer edge correction unit 1615. FIG.

72A shows a case where PDs ₇ to ₀ are added to the image data of the rising edge portion of the edge, and FIG. 72B shows the PD data to the image data of the portion between the edges and the valley of the edge.
₁₇ to ₁₀ are added, and (c) shows a case where PDs ₂₇ to ₂₀ are added to the image data of the trailing edge of the edge.

FIG. 73 is a diagram showing a configuration of a γ correction unit 1700.

FIG. 74 is a diagram showing a γ correction table in the brightness adjustment mode.

FIG. 75 is a diagram showing a γ correction table in the contrast adjustment mode.

FIG. 76 is a graph showing the relationship between VIDEO ₄₇ to ₄₀ and VIDEO ₇₇ to ₇₀ when the values of CO _{2 to 0} are 1 to 7 respectively.

77 is a diagram showing changes in the graph when the background removal data UDC ₇ to ₀ is removed and the inclination is corrected by the inclination correction data GDC ₇ to ₀ for the _{VIDEOs 47} to _40. FIG.

[Explanation of symbols]

 Reference numeral 100 ... Image reader unit 600 ... AE processing unit 1100 ... HVC conversion unit 1400 ... Color correction unit 1500 ... Region discrimination unit 1600 ... MTF correction unit

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 17, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Fig. 68

[Correction method] Change

[Correction content]

FIG. 68 is a diagram showing a relationship between Bk data and C, M, Y data at the time of edge enhancement of a black character.

Claims (5)

[Claims] 1. A reading unit for reading RGB image data of an original, and color data of cyan (C), magenta (M), yellow (Y), black (BK) (hereinafter referred to as RGB image data read by the reading unit). , The color correction means for converting the respective color data into C data, M data, Y data, and BK data), and the brightness data V of each pixel in the original from the RGB image data of the original read by the reading means. And HVC conversion means for obtaining the saturation data W, and it is judged from the brightness data V of each pixel in the document obtained by the HVC conversion means whether or not the pixel is an edge pixel, and the saturation data W Determining means for determining whether or not the pixel is black, and C of each peripheral pixel in a predetermined matrix having the pixel determined to be a black edge portion by the determining means as a central pixel. M, of the Y data, the most low levels of data, of the pixel C, M, C replacing the Y data, M, and Y data replacing means, the pixels of an edge portion of the black detected by the detecting means B
Replace the value of K data with high density data by a predetermined amount B
An image processing apparatus comprising: K data replacement means. 2. Reading means for reading RGB image data of an original, and color data of cyan (C), magenta (M), yellow (Y), and black (BK) (hereinafter referred to as RGB image data read by the reading means). , The color correction means for converting the respective color data into C data, M data, Y data, and BK data), and the brightness data V of each pixel in the original from the RGB image data of the original read by the reading means. And HVC conversion means for obtaining the saturation data W, and it is judged from the brightness data V of each pixel in the document obtained by the HVC conversion means whether or not the pixel is an edge pixel, and the saturation data W And a predetermined matrix whose center pixel is a pixel determined to be a black edge portion pixel by the determination means, Detection means for detecting a pixel for which the brightness data V obtained by the VC conversion means is less than or equal to a predetermined value, the saturation data W is at least a predetermined value, and the determination means has determined that the pixel is not an edge portion; Counting means for counting the number of pixels detected by the means, and when the count value by the counting means is greater than or equal to a predetermined value, the determination result for the pixel determined to be the pixel of the black edge portion by the determination means is displayed. An image device apparatus comprising: an erroneous determination correction unit that invalidates. 3. A reading unit for reading RGB image data of an original, and color data of cyan (C), magenta (M), yellow (Y), black (BK) (hereinafter referred to as RGB image data read by the reading unit). , The color correction means for converting the respective color data into C data, M data, Y data, and BK data), and the brightness data V of each pixel in the original from the RGB image data of the original read by the reading means. And HVC conversion means for obtaining the saturation data W, and it is judged from the brightness data V of each pixel in the document obtained by the HVC conversion means whether or not the pixel is an edge pixel, and the saturation data W Determining means for determining whether or not the pixel is black, a pixel determined to be a black edge portion by the determining means, and a circumference in a predetermined matrix having the pixel as a central pixel. Among the C, M, Y data of the pixel, C, M, Y data replacing means for replacing the lowest density data with the C, M, Y data of the pixel, and the judging means judges that it is a black edge portion. Based on the value of the brightness data V obtained by the HVC conversion means and the BK data replacement means for replacing the value of the BK data of the selected pixel with high density data by a predetermined amount, the brightness of all peripheral pixels in a predetermined matrix. In a predetermined matrix different from the above, an isolated pixel detection unit that detects the target pixel whose difference between the value of the data V and the value of the brightness data V of the target pixel is a predetermined value or more as an isolated pixel, Counting means for counting the number of isolated pixels detected by the isolated pixel detecting means, and the data replacement amount of the BK data replacing means are reduced in proportion to the count value by the counting means. The image processing apparatus characterized by comprising a Tsu di enhancement amount adjustment means. 4. A reading unit for reading RGB image data of an original, a photoconductor, a developing unit for forming a toner image on the photoconductor based on the read RGB image data, and a developing unit formed on the photoconductor. A transfer unit that transfers the toner image to a sheet that is transported in a predetermined direction, a transport unit that transports the sheet to the transfer unit in a predetermined direction, and a direction in which the transport unit transports the sheet to the transfer unit, Detection means for detecting a pixel corresponding to the rising edge portion of the edge and a pixel corresponding to the falling edge portion of the edge, and a pixel immediately preceding the pixel at the rising edge portion of the edge detected by the detection means in the sheet passing direction. And a correction data adding unit that adds predetermined correction data to a pixel that is one pixel behind the pixel at the trailing edge of the edge in the sheet passing direction. Processing equipment. 5. A reading means for reading RGB digital image data of an original, and color data of cyan (C), magenta (M), yellow (Y), black (BK) for the RGB image data read by the reading means ( Hereinafter, color correction means for converting each color data into C data, M data, Y data, and BK data), and lightness data V and saturation of each pixel in the document based on the read RGB image data. Based on the HVC conversion unit that obtains the data W and the brightness data V of each pixel in the document that is obtained by the HVC conversion unit, it is determined whether or not the pixel is an edge pixel, and from the saturation data W, the pixel is determined. Area information input for inputting area information of mono-color / monochrome in synchronization with reading of image data of an original by the reading means For the pixel determined to be the black edge portion of the full-color original document based on the step, the input by the area information input unit, and the determination result by the determination unit, C of the peripheral pixel in the predetermined matrix having the pixel as the central pixel, Of the M and Y data, the lowest density data is replaced with the C, M, and Y data of the pixel concerned.
The BK data of the pixel determined to be the black edge portion of the full-color original document or the black edge portion of the monochrome original document based on the M / Y data replacement means, the input by the area information input means, and the determination result by the determination means is defined as the lightness edge component. Based on the BK data emphasizing means that outputs the BK data of the pixels which are emphasized and are determined to be the color edge portion of the full-color original or the edge portion of the monocolor original, and the determination result by the input and the determination means by the area information input means, The C, M, and Y data of the pixels determined to be the color edge portion of the full-color original document or the edge portion of the mono-color original document are emphasized by the density edge component, and the C, M, and Y data of the pixels determined to be the edge portion of the monochrome original document. An image processing apparatus comprising: C, M, Y data emphasizing means for outputting M, Y data as it is.