JP2001157051A - Device and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress making wrong judgment for a black character and image quality deterioration being the result of it due to color slurring caused by the mechanical vibration of a scanning system at an image tip part, in an image forming device such as a color copying machine having a black character judging function. SOLUTION: At reading of a document image, parameter of a look-up table 117 of the black character judging part is switched between the image tip part and a regular area part to suppress image deterioration due to black character decision at the image tip part. More desirably, the output of the table 117 is switched gradually while moving to the regular area from the tip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and method suitable for a high-productivity color copying machine for performing black character determination processing. In particular, the image processing unit performs black character determination, separates a halftone dot, a halftone area, and a character / line drawing area, and changes the UCR (under color removal) and the spatial filter coefficient according to each of them, and outputs the number of output lines of the printer unit. The present invention relates to a copying machine which has a function of adaptively selecting an original, performs a sub-scanning of a document at high speed in an image scanner section, and performs repetitive scanning in a short time.

[0002]

2. Description of the Related Art In recent years, so-called digital color copiers have been developed in which a color original is color-separated and electrically read, and the obtained color image data is printed out on paper to copy a color image. There is something remarkable.

[0003] The image scanner of a color copier is
A CCD image sensor (hereinafter, referred to as a CCD), which is a three-line linear CCD having color filters of three primary colors of RGB and formed in parallel at a pitch of, for example, eight times the pixels, is used as an image reading element. Lamps and various fluorescent tubes are used as light sources for illuminating the original.

A read image of a document illuminated by illumination forms an image on the CCD by a lens. The image scanner unit has a sub-scanning driving unit such as a stepping motor, and the sub-scanning driving unit relatively moves the CCD and the document in a direction perpendicular to the main scanning direction of the CCD, that is, in the sub-scanning direction. Thus, the entire area of the document image is read.

In general, the sub-scanning by the stepping motor uses a trapezoidal drive or a rising and falling curve such as an S-shaped curve as a modification of the trapezoidal drive. In the sub-scanning image effective area for scanning original documents, the start-up is performed before the leading edge of the image. When the leading edge of the image is reached, the start-up is completed, and the sub-scanning feed at a steady speed is performed. When the end of the motor is reached, the motor is decelerated.

[0006] On the other hand, with the spread of these systems, the demand for printing quality of color images has been increasing. In particular, there has been an increasing demand for printing black characters and fine black lines more blackly and sharply.

That is, when a black document is subjected to color separation, each signal of yellow, magenta, cyan and black is generated as a signal for reproducing black. However, if printing is performed as it is based on the obtained signal, each color is superimposed by four colors. Therefore, a slight shift between the colors causes a color blur on a thin black line, and the original black does not look black or looks blurred, and the print quality is remarkably reduced.

On the other hand, color information such as black and other colors in an image signal and features of spatial frequency such as fine lines and halftone dots are extracted to detect areas such as black characters and color characters. In addition, there has been proposed a method in which the image is divided into a halftone image, a halftone image area, and the like, and a process corresponding to each area is performed. -203198).

[0009]

To date, color copiers have not been required to have higher productivity than monochrome copiers, and the situation is the same for image scanners.

However, recently, high productivity has been demanded for color copying machines, and accordingly, the productivity of the image scanner section of the copying machine, that is, the high sub-scanning speed and the high speed of sub-scanning, have been demanded. There is a need for repetitive performance. Meanwhile, cost reduction is also required.

Under the above-mentioned situation, it is necessary to improve the motor torque in order to increase the speed, and the cost cannot be increased, so that the diameter of the motor must be reduced. As a result, vibration increases. On the other hand, in a situation where rigidity is not required for a mechanical frame due to cost considerations, mechanical frames tend to be vulnerable to vibration.

As a result, mechanical vibrations affect the image captured by the image scanner unit. Here, first, three lines of CC used
In the case of D, since the positions of the RGB lines are apart from each other by, for example, 8 line pitches, color shift naturally occurs when there is mechanical vibration in the sub-scanning direction.

Second, in a color copying machine, so-called black character determination processing is performed in order to form a character / line image clearly in black and a halftone / halftone image with rich gradation and a natural beautiful image. The black character determination is vulnerable to the above-described color shift due to the determination algorithm.

Here, as a problem, erroneous determination of a black character due to mechanical vibration, which occurs when a color copying machine with high productivity is realized without cost, has become a problem. In particular, erroneous determination of black characters due to color misregistration due to vibration is made in a halftone / halftone image and a character / line image area.
One part is determined to be a black character, the area next to it is determined to be a halftone / halftone image, and one having a different UCR or filter is applied.

As a result, an unpleasant output-formed image such as a mottled pattern results. Therefore, color misregistration due to mechanical vibration must be reduced as much as possible, which is an urgent issue for today that requires high speed and low cost.

In particular, the mechanical vibration is remarkably generated at the leading end of image scanning (hereinafter referred to as leading end blur). The mechanical vibration at the tip of image scanning is characterized by the initial vibration of the motor itself due to the rapid start-up, the mechanical load, mechanical play, and the characteristics such as the natural frequency and rigidity of each part. This is caused by rapidly starting up a simple scanning mechanism. That is, even after optimizing the acceleration curve and optimizing the approach distance to the image front end after acceleration, the mechanical vibration and the resulting color shift amount at the image front end are large compared to the steady area. The prior art has a problem to be solved.

An object of the present invention is to provide an image forming apparatus and method capable of suppressing image quality deterioration due to erroneous determination of black characters in an output formed image, mainly due to the occurrence of color misregistration due to blur at the front end of the image. To provide.

[0018]

In order to achieve the above object, a first aspect of the present invention is to manage a scanning position of an image reading means for reading an image in a sub-scanning direction and to control the scanning position of the read image. A sub-scanning position management unit that outputs a scanning position in the sub-scanning direction; and a black character determination unit that separates a line component and a halftone dot component from the image read by the image reading unit and extracts characters and line drawings in the image. Means and first determining means for determining the thickness of the character / line drawing;
Second determining means for determining the outline of the line drawing, third determining means for determining the saturation of the character / line drawing, first determining means, second determining means, and third determining means And processing means for performing predetermined image processing based on the result of the determination in step (a) and the output of the sub-scanning position management means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the output of the sub-scanning position managing means is:
A signal for discriminating at least an image front end portion of the image and a steady region portion of the image is generated.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the processing means for performing the predetermined image processing comprises a look-up table, and a result of the determination by the first determining means. The determination result of the second determination unit, the determination result of the third determination unit, and the output of the sub-scanning position management unit are input to the look-up table.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the output signal of the look-up table controls a UCR, a printer line number, and a spatial filter.

According to a fifth aspect of the present invention, in the image forming apparatus according to the second aspect, the output of the sub-scanning position managing means is multi-valued, and the output from the leading end of the image to the steady area portion is output. Is switched smoothly.

According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, further comprising a sub-scanning origin detecting means for detecting a sub-scanning origin and a control means having a CPU. A parameter such as a document size and a magnification is given by the control means, and initialized by the control means receiving a signal from the sub-scan origin detection means,
The number of motor pulses from a motor driver for sub-scanning the image reading means is counted.

According to a seventh aspect of the present invention, a scanning position in the sub-scanning direction of the image reading means for reading an image is managed, a scanning position of the read image in the sub-scanning direction is output, and the image reading means reads the image. For the obtained image, a line component and a halftone dot component are separated, a black character determination for extracting a character / line drawing in the image is performed, a first determination for determining the thickness of the character / line drawing is performed, and the character Performing a second determination for determining the outline of the line drawing, performing a third determination for determining the saturation of the character / line drawing, and performing the first determination, the second determination, and the third determination; A predetermined image processing is performed based on the determination result and the output of the scanning position in the sub-scanning direction.

According to an eighth aspect of the present invention, in the image forming method according to the seventh aspect, the output of the scanning position in the sub-scanning direction is at least distinguished between an image leading end of the image and a steady area portion of the image. Generating a signal for performing the following.

According to a ninth aspect of the present invention, in the image forming method according to the seventh aspect, the predetermined image processing uses a look-up table, and a result of the first determination and a determination result of the second determination. And the output of the scan position in the sub-scanning direction and the output of the scan position in the sub-scanning direction are input to the look-up table.

According to a tenth aspect of the present invention, in the image forming method according to the ninth aspect, an output signal of the look-up table controls a UCR, a printer line number, and a spatial filter.

According to an eleventh aspect of the present invention, in the image forming method according to the eighth aspect, the output of the scanning position in the sub-scanning direction is multi-valued, It is characterized in that the output is switched smoothly.

According to a twelfth aspect of the present invention, in the image forming method of the seventh aspect, detection of the sub-scan origin and control by the CPU are further performed, and management of the scanning position in the sub-scanning direction is given by the control. Using parameters such as document size and magnification, initialization is performed by the control upon receiving the signal of detection of the sub-scanning origin, and a motor from a motor driver for sub-scanning the image reading means is used.
The number of pulses is counted.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a cross-sectional configuration of the image forming apparatus of the present embodiment. Reference numeral 201 denotes an image scanner unit, which reads a document and performs digital signal processing. 2
Reference numeral 00 denotes a printer unit, and an image scanner unit 201
Prints out an image corresponding to the original image read in full color on paper.

In the image scanner unit 201, a document 204 placed on a document table glass (platen) 203 is irradiated with light from a halogen lamp 205 by a document pressing plate 202. The reflected light from the original 204 is reflected by the mirror 20.
6,207, and a CCD image sensor (hereinafter referred to as CC) which is a three-line linear CCD by a lens 208.
(Referred to as D). The lens 208 is provided with an infrared cut filter 231.

The CCD 210 separates the light information from the document 204 into colors, reads the red (R), green (G), and blue (B) components of the full color information therefrom. send. Each color component reading sensor row of the CCD 210 is composed of 5000 pixels. As a result, 297 mm in the short direction of the A3 size document, which is the largest size of the documents placed on the platen glass 203, is read at a resolution of 400 dpi.

The halogen lamp 205 and the mirror 2
06 is the speed V, and the mirror 207 is (1/2) V
Then, the entire surface of the document 204 is scanned by mechanically moving in a direction perpendicular to the electrical operation direction of the CCD 210 (hereinafter referred to as a main scanning direction) (hereinafter referred to as a sub-scanning direction).

The standard white plate 211 includes the R, G, B sensors 2
Correction data of the read data at 10-1 to 210-3 is generated. The standard white plate 211 has a substantially uniform reflection characteristic with visible light, and has a white color when visible. Here, using this standard white plate 211, R,
The output data from the G and B sensors 210-1 to 210-3 is corrected.

The image signal processing unit 209 electrically processes the read signal, decomposes the signal into magenta (M), cyan (C), yellow (Y), and black (Bk) components. To the printer unit 200. In addition, for one document scan (scan) in the image scanner unit 201, one component among M, C, Y, and Bk is sent to the printer unit 200, and one document scan is performed by a total of four document scans. The printout is completed.

In the printer section 200, M, C, Y, and Bk image signals from the image scanner section 201 are sent to the laser driver 212. Laser driver 21
2 modulates and drives the semiconductor laser 213 according to the image signal. The laser light from the semiconductor laser 213 is
The photosensitive drum 217 is scanned via the mirror 214, the f-θ lens 215, and the mirror 216.

The developing device comprises a magenta developing device 219, a cyan developing device 220, a yellow developing device 221 and a black developing device 222. These four developing devices alternately contact the photosensitive drum 217 and are placed on the photosensitive drum 217. The formed M, C, Y, and Bk electrostatic latent images are developed with corresponding toner. Further, the transfer drum 223 is connected to the paper cassette 22.
4, or the paper supplied from the paper cassette 225 is wound around the transfer drum 223, and the toner image developed on the photosensitive drum 217 is transferred to the paper.

After the toner images for the four colors M, C, Y, and Bk are sequentially transferred in this manner, the paper passes through the fixing unit 226 and is discharged.

Next, the image scanner unit 201 according to the embodiment of the present invention will be described in detail.

FIG. 2 shows an external configuration of the CCD 210.
210-1 is a light receiving element array (photo sensor) for reading red light (R), and 210-2 and 21-3 are
A light receiving element array for reading wavelength components of green light (G) and blue light (B) in order. Each of the R, G, and B sensors 210-1 to 210-3 has an opening of 10 μm in the main scanning direction and the sub-scanning direction.

The three light receiving element rows having different optical characteristics are arranged on the same silicon chip so that the R, G, and B sensors are arranged in parallel with each other so as to read the same line of the document. Has a monolithic structure. By using a CCD having such a configuration, an optical system such as a lens is used in each color separation reading, thereby making it possible to simplify optical adjustment for each of R, G, and B colors. .

FIG. 3 is a sectional view when the CCD 210 is cut along the dotted line aa ^′ shown in FIG. A photo sensor 210-1 for reading R color and photo sensors 210-2 and 210-3 for reading visible information of G and B are arranged on a silicon substrate 210-5.

On the photo sensor 210-1 for R color,
R filter 21 that transmits the wavelength component of R color in visible light
0-7 are arranged. Similarly, the photo sensor 2 of G color
A G filter 210-8 is provided on 10-2, and a B filter 210-9 is provided on the B color photo sensor 210-3.
Is arranged. In addition, 210-6 is a flattening layer composed of a transparent organic film.

FIG. 4 is an enlarged view of the light receiving element indicated by reference numeral B in FIG. Each of the above sensors has a length of 10 μm per pixel in the main scanning direction. As described above, each sensor is used in the short direction (297 mm) of an A3 size document.
Has 5000 pixels in the main scanning direction so that can be read at a resolution of 400 dpi. Also, R,
The distance between the lines of the G and B sensors is 80 micrometers, and each line is separated by 8 lines for a resolution in the sub-scanning direction of 400 dpi.

Next, a description will be given of a density reproduction method in the printer unit 200 of the image forming apparatus according to the present embodiment.

In this embodiment, in order to reproduce the density of the printer, the lighting time of the semiconductor laser 213 is controlled according to the image density signal by a well-known PWM (pulse width modulation) method. As a result, an electrostatic latent image having a potential corresponding to the laser lighting time is formed on the photosensitive drum 217. Subsequently, in the developing devices 219 to 222, the latent image is developed with an amount of toner corresponding to the potential of the electrostatic latent image, thereby performing density reproduction.

FIG. 5 is a timing chart showing the control operation of the density reproduction in the printer section 200 of this embodiment. Reference numeral 10201 denotes a printer pixel clock;
It corresponds to the resolution of dpi. Printer pixel clock 10
201 is made of a laser driver 212. Also,
A 400-line triangular wave 10202 is generated in synchronization with the printer pixel clock 10201. In addition, 400 line triangular wave 1
The cycle of 0202 is the same as the cycle of the printer pixel clock 10201.

The 40 sent from the image signal processor 209
M, C, 256 gradations (8 bits) at a resolution of 0 dpi
The Y and Bk image data and the 200-line / 400-line switching signal are transmitted in synchronization with the above-described printer pixel clock 10201.
Synchronization is performed on 201.

The 8-bit digital image data (M,
C, Y, and Bk image data) are converted into an analog image signal 10203 by a D / A converter (not shown).
The analog image signal 10203 is compared with the above-described 400-line triangular wave 10202 in an analog manner.
A line PWM output 10204 is generated.

The digital pixel data changes from 00H (H indicates hexadecimal) to FFH, and the 400 line PWM output 10
Reference numeral 204 denotes a pulse width corresponding to these values. Also,
One cycle of the 400-line PWM output 10204 is 63.5 μm on the photosensitive drum.

In the laser driver 212, 400 lines P
In addition to the WM output 10204, the printer pixel clock 10
In synchronization with 201, a 200-line triangular wave 10
Also make 205. 200-line triangular wave 10205 and 400d
By comparing the pi analog image signal 10203 with the pi analog image signal 10203, a 200-line PWM output 10206 is generated. 20
The 0-line PWM output 10206 is, as shown in FIG.
A latent image is formed on the photosensitive drum at a period of 7 μm.

In the density reproduction with 200 lines and the density reproduction with 400 lines, the minimum reproducibility unit for density reproduction of the 200 lines is 127 μm, which is twice as large as that of the 400 lines. However, in terms of gradation, 400 lines that reproduce the density in units of 63.5 μm are more suitable for high-resolution image recording.

As described above, the 200-line PWM recording is suitable for gradation reproduction, and the 400-line PWM recording is excellent in terms of resolution.
Switching between M and 400-line PWM is performed.

The signal for performing the above switching is shown in FIG.
And is input from the image signal processing unit 209 to the laser driver 212 in pixel units in synchronization with a printer pixel clock 10201 corresponding to a resolution of 400 dpi.

200/400 line switching signal 1020
When 7 is a logic low (hereinafter referred to as L level),
400 line PWM output 10204 is selected and 200 lines /
When the 400-line switching signal 10207 is logic high (hereinafter, referred to as H level), the 200-line PWM output 10206 is selected.

The merged signal of the 400-line PWM output and the 200-line PWM output selected as described above becomes the laser drive signal 10208.

Next, the image signal processing section 209 will be described.

FIG. 6 is a block diagram showing a flow of an image signal in the image signal processing unit 209 of the image scanner unit 201 according to the present embodiment.

In FIG. 6, an image signal output from the CCD 210 is input to an analog signal processing unit 101,
Then, after gain adjustment and offset adjustment, A / D
The converter 102 converts each color signal into 8-bit digital image signals R1, G1, and B1. Thereafter, the R1, G1, and B1 are input to the shading correction unit 103, and are subjected to known shading correction using a read signal of the standard white plate 211 for each color.

The clock generator 121 generates a clock for each pixel. Also, main scanning address counter 1
At 22, the clock from the clock generator 121 is counted, and a one-line pixel address output is generated.

After that, the decoder 123 decodes the main scanning address from the main scanning address counter 122, and outputs a CCD drive signal for each line such as a shift pulse or a reset pulse, or a one-line read signal from the CCD. Signal, HSYNC indicating the effective area of the
Generate The main scanning address counter 122
It is cleared by the HSYNC signal and starts counting the main scanning addresses of the next line.

As shown in FIG. 2, since the light receiving sections 210-1, 210-2, 210-3 of the CCD 210 are arranged at a predetermined distance from each other, the line delay circuit 104, FIG. At 105, a spatial shift in the sub-scanning direction is corrected. Specifically, in the sub-scanning direction with respect to the B signal, the R and G signals are line-delayed in the sub-scanning direction to match the B signal.

The input masking section 106 includes a CCD 210
R, G, B filters 210-7, 210-8, 210
This is a part that converts the reading color space determined by the spectral characteristics of −9 to the NTSC standard color space, and performs a matrix operation as shown in the following equation.

[0065]

(Equation 1)

The light quantity / density conversion unit (LOG conversion unit) 107 is constituted by a look-up table ROM.
4 and B4 luminance signals are converted into C0, M0 and Y0 density signals. The line delay memory 108 includes ucr, which is generated from the R4, G4, and B4 signals by a black character determination unit 113 described later,
The image signals C0, M0, and Y0 are delayed by a line delay until a determination signal such as filter or sen. As a result, the C1, M1, and Y1 image signals and the black character determination signal for the same pixel are input to the masking UCR circuit 109 at the same time.

The masking UCR circuit 109 extracts a black signal (Bk) from the inputted three primary color signals of C1, M1, and Y1, and further performs an operation of correcting color turbidity of a recording color material in the printer unit 200. And Y2, M2, C2, Bk2
Are sequentially output with a predetermined bit width (8 bits) at each reading operation.

The main scanning magnification changing circuit 110 performs enlargement / reduction processing of the image signal and the black character determination signal in the main scanning direction by a known interpolation operation. Further, the spatial filter processing unit (output filter) 111 switches between edge enhancement and smoothing processing based on a 2-bit filter signal from the LUT 117 as described later.

Y4, M4, C processed as described above
4 and Bk4, and a sen signal, which is a signal for switching between 200 lines and 400 lines, are sent to the laser driver 212, and the printer unit 200 performs density recording by PWM.

FIG. 7 shows the image signal processing unit 209 shown in FIG.
5 is a timing chart showing the timing of each control signal in FIG.

In FIG. 7, a VSYNC signal is an image valid section signal in the sub-scanning direction. In a section of logic "1", an image is read (scanned) and sequentially.
The output signals of (C), (M), (Y) and (Bk) are formed. The VE signal is an image valid section signal in the main scanning direction, takes the timing of the main scanning start position in the section of logic "1", and is mainly used for line counting control of line delay.

Further, the CLOCK signal is a pixel synchronizing signal, transfers image data at the rising timing of “0” → “1”, and supplies it to the A / D converter 102 and the signal processing units of the black character determination unit 113 described above. In addition, it is used to transmit an image signal and a 200/400 line switching signal to the laser driver 212.

Next, the black character determination section will be described.

(Explanation of Edge Detecting Unit) Signals R4, G4, B4 masked by input masking unit 106
Is input to the edge detection unit 115 of the black character determination unit 113, and calculates the luminance signal Y according to the following equation. FIG. 8 is a block diagram showing an internal configuration of the edge detection unit 115, and FIG. 9 shows a detailed configuration of the luminance calculation circuit 250.

Y = 0.25R + 0.5G + 0.25B (2) In FIG. 9, the input color signals R, G, and B are multiplied by multipliers 301, 302, and 303 with coefficients of 0. 25,
After multiplication by 0.5 and 0.25, adders 304 and 30
5, and the luminance signal Y is calculated according to the above equation (2).

The luminance signal Y corresponds to the FIFOs 401 to 401 shown in FIG.
A known Laplacian filter 403 to 406 is extended to three lines delayed by one line by 402.
To Thereafter, the direction in which the absolute value a of the edge amount, which is the output of the filter, takes the minimum value among the four directions shown in FIG. 10 is determined, and the determined direction is defined as the edge min direction. The edge min direction detection shown in FIG.
This is performed by the n-direction detector 251.

Next, an edge min direction smoothing unit 252 performs a smoothing process on the edge min direction obtained by the edge min direction detection unit 251.
By this processing, only the direction having the largest edge component can be stored, and the other directions can be smoothed.

That is, in the halftone dot portion having a large edge component in a plurality of directions, the edge component is smoothed by the above-described processing, and the feature is reduced. On the other hand, the edge component exists only in one direction. With respect to the character / thin line, the effect is obtained that the feature is preserved.

By repeating the above process as necessary, the line component and the halftone dot component can be more effectively separated, and cannot be detected by the conventional edge detection method.
It is also possible to detect a character component existing in a halftone dot.

Thereafter, the edge detection circuit 253 shown in FIG.
Is applied to the above-mentioned Laplacian filters 403 to 406, those whose absolute value of the edge amount is equal to or smaller than a are removed, and only those whose absolute value is equal to or larger than a are output as logic "1".

FIG. 11 shows an example of edge detection, in which image data (a) relating to luminance data Y is generated as an edge detection signal as shown in (b).

The edge detecting section 115 further expands the above-mentioned determination signal by a signal expanded by a block size of 7 × 7, 5 × 5, 3 × 3 and an output expressed by five codes of no expansion and no edge. The signal “edge” (3 bits) is output from the edge detection unit 115. Here, the expansion of the signal refers to performing an OR operation on the signal values of all the pixels in the block.

(Description of Saturation Determining Section) FIG. 12 is a block diagram showing a detailed configuration of the saturation determining section 116 constituting the black character determining section 113. Here, the input signal R
The maximum value max (R, G, B) and the minimum value min (R, G, B) are extracted by the maximum value detection unit 601 and the minimum value detection unit 602 for 4, G4, and B4, respectively.

Thereafter, in the next LUT (look-up table) 603, a saturation signal Cr is generated by threshold values Cr_BK, Cr_COL, and Cr_W that divide the data into regions as shown in FIG. Note that the saturation determination unit 1 shown in FIG.
The output signal “col” from 16 is black when the data enters the area BK shown in FIG. 13, intermediate when entering the GRY (between white and black), and white when entering the COL. Is 2
It is represented by a bit code.

(Explanation of Character Thickness Determining Unit) FIG. 14 is a block diagram showing the configuration of the character thickness determining unit 114 constituting the black character determining unit 113. 14, a red signal R4, a green signal G4, and a blue signal B4, which are outputs from the input masking circuit 106, are input to the minimum value detection unit 2011. The minimum value detection unit 2011 calculates the minimum value MINRGB of the input RGB signal.

Next, MINRGB is input to the average value detection unit 2012, and the average value of MINRGB of 5 × 5 pixels near the target pixel is input.
AVE5 and the average value AV of MINRGB of 3x3 pixels
Find E3.

AVE5 and AV are sent to the character / halftone detection unit 2013.
E3 is input, and by detecting the density of the target pixel for each pixel and the amount of change between the target pixel and the average density in the vicinity thereof, it is determined whether the target pixel is part of a character or a halftone area. Make a determination.

FIG. 15 is a block diagram showing the internal configuration of the character / halftone detecting unit 2013. In FIG. 15, in the character / halftone detection circuit, first, the AV
Add an appropriate offset value OFST1 to E3, and obtain the obtained value and AVE
5 is compared with the comparator 2031. In the comparator 2032, the output from the adder 2030 and
Compare with the appropriate limit value LIM1. After that, the output value from each comparator is input to the OR circuit 2033.

In the OR circuit 2033, when AVE3 + OFST1> AVE5 (3) or AVE3 + OFST1> LIM1 (4), the output signal BINGRA becomes logic "H". That is, when the character / halftone detection circuit causes a density change near the pixel of interest (character edge portion), or
When the vicinity of the target pixel has a density equal to or higher than a certain value (inside of a character and a halftone portion), the character / halftone region signal BINGRA becomes logic “H”.

On the other hand, FIG. 16 shows a detailed configuration of the halftone dot area detection unit 2014. In FIG. 16, in order to detect a halftone dot area, first, the MI detected by the minimum value detection circuit 2011 is detected.
An appropriate offset value OF in the adder 2040 is added to NRGB.
ST2 is added, and the obtained result is compared with AVE5 in the comparator 2041. In the comparator 2042, the output from the adder 2040 and the appropriate limit value LIM2
Compare with

Thereafter, each output value is output to the OR circuit 20.
43, and when MINRGB + OFST2> AVE5 (5) or MINRGB + OFST2> LIM2 (6), the output signal BINAMI from the OR circuit 2043 becomes logic "H". Then, using the BINAMI signal, the edge direction detection circuit 2044 obtains the edge direction of each pixel.

FIG. 17 shows the rules for detecting the edge direction in the edge direction detection circuit 2044. That is, when the eight pixels in the vicinity of the target pixel satisfy any of the conditions (0) to (3) shown in FIG. 17, any one of the 0th to 3th bits of the edge direction signal DIRAMI is logic “H”. "become.

Further, in FIG. 16, in the next stage of the opposite edge detection circuit 2045, 5 pixels × 5 pixels surrounding the pixel of interest.
Edges facing each other are detected in the area of five pixels. As shown in FIG. 18, a rule for detecting the opposite edge in a coordinate system in which the DIRAMI signal of the target pixel is A33 is shown below.

(1) A11, A21, A31, A41, A5
Bit0 of one of A22, A32, A42 and A33
Is "H" and A33, A24, A34, A44, A15,
Any of bit1 of A25, A35, A45, and A55 is “H”. (2) A11, A21, A31, A41, A51, A22, A3
2. Any one of bit1 of A42 and A33 is “H”, and A33, A24, A34, A44, A15, A25, A3
5. Any one of bit0 of A45 and A55 is “H” (3) A11, A12, A13, A14, A15, A22, A
23, A24, or A33 bit2 is “H” and A33, A42, A43, A44, A51, A52, A5
3. Any one of bit3 of A54 and A55 is “H”. (4) A11, A12, A13, A14, A15, A22, A
23, A24, or A33 bit3 is “H” and A33, A42, A43, A44, A51, A52, A5
3, any bit2 of A54 and A55 is "H" When any one of the above conditions (1) to (4) is satisfied, EAAMI is set to "H" (facing edge detection circuit 2045).
If the opposite edge is detected at
AMI becomes “H”).

The expansion circuit 2046 expands the EAAMI signal by 3 pixels × 4 pixels. If there is a pixel whose EAAMI is “H” in 3 × 4 pixels near the target pixel, the EAAMI of the target pixel is obtained.
Replace the AMI signal with “H”. Further, the contraction circuit 204
7 and an expansion circuit 2048 to remove an isolated detection result in an area of 5 × 5 pixels to obtain an output signal EBAMI. Here, the contraction circuit 2047 is a circuit that outputs “H” only when all the input signals are “H”.

Next, the counting unit 2049 determines the number of pixels for which the output signal EBAMI of the expansion circuit 2048 is “H”.
Count in a window of appropriate size. In the present embodiment, an area of 5 pixels × 64 pixels including the target pixel is referred to. FIG. 19 shows the shape of the window.

In FIG. 19, the sample points in the window are 9 points every 4 pixels in the main scanning direction and 5 points in the sub-scanning direction.
There are a total of 45 points for the line. For one pixel of interest,
By moving the window in the main scanning direction, nine windows (1) to (9) in FIG. 19 are prepared. That is, 5 pixels × 64 around the pixel of interest
This means that the pixel area has been referred to.

Here, in each window, EB
The AMI is counted, and when the number at which EBAMI becomes “H” exceeds an appropriate threshold, the dot area detection unit 2014 of FIG.
Outputs the dot area signal AMI as logic "H".

By the processing in the dot area detection circuit 2014, a dot image detected as a set of isolated points in the BINGRA signal can be detected as an area signal. The detected character / halftone area signal BINGRA and halftone area signal AMI are output to the OR circuit 2015 in FIG.
An R operation is performed, and as a result, a binary signal PICT of the input image is generated. The PICT signal is output from the area / size determination circuit 201
6, and the area size of the binarized signal is determined.

Here, a set of isolated points will be simply described.

The above-described image area determination is performed on a binary image by binarizing the image at a certain density. In this case, the dots and lines are determined to be halftones having characters and areas. But,
When a halftone image is simply binarized, an aggregate of fine points is generated by dots which are components of the halftone dot.

Therefore, it is determined whether or not a dot is a halftone image by determining whether or not a set of isolated points exists in a region having a certain area. In other words, a region where a certain number of dots are present in a certain region is a halftone image, and even if a pixel of interest is a part of a dot, if there is no dot around it, the pixel of interest is a part of a character. Is determined.

FIG. 20 shows an area / size determination circuit 201.
FIG. 6 is a block diagram showing an internal configuration of No. 6; In FIG. 20, there are a plurality of pairs of a contraction circuit 2081 and an expansion circuit 2082, and the sizes of the regions to be referred to are different. The input PICT signal is input to the contraction circuit 2081 after being line-delayed according to the size of the contraction circuit. In the present embodiment, seven types of contraction circuits having a size from 23 pixels × 23 pixels to 35 pixels × 35 pixels are prepared.

The signal output from the contraction circuit 2081 is
The signal is input to the expansion circuit 2082 after the line delay.
In the present embodiment, seven types of expansion circuits having a size from 27 pixels × 27 pixels to 39 pixels × 39 pixels are prepared corresponding to the output of the contraction circuit, and the output signal PICT_FH from each expansion circuit is obtained. .

Regarding the output signal PICT_FH, when the pixel of interest is a part of a character, the PI
The output of CT_FH is determined. FIG. 22 shows how the output of PICT_FH is determined. For example, if the PICT signal is present in a strip shape having a width of 26 pixels, the output will be all 0 if a contraction of a size larger than 27 × 27 is performed, and after performing a contraction of a size smaller than 25 × 25, When the expansion according to the size of PICT is performed, a band-like output signal PICT with a width of 30 pixels
_FH is obtained.

Thereafter, by inputting the output signal PICT_FH to the encoder 2083, the image area signal ZONE_P to which the target pixel belongs is obtained. FIG. 23 is a diagram showing an encoding rule of the encoder 2083.

By the above-described processing, a photographic image or a halftone image in which the PICT signal is “H” in a wide area is defined as area 7 (maximum value), and the area size is smaller than the maximum value. A (thin) character or line image is defined as a multivalued image area according to its size (thickness). In the present embodiment, the ZONE signal has three bits, and the character size is represented in eight levels. Here, it is assumed that the thinnest character is 0, and the thickest character (including an area other than the character) is 7.

The ZONE correction unit 2084 shown in FIG.
As shown in FIG. 1, ZO line-delayed by multiple FIFOs
It has an average value calculation unit 2110 to which the NE_P signal is input, and the average value calculation unit 2110 calculates an average value of 10 pixels × 10 pixels. The ZONE_P signal has a larger signal value as the character is thicker, and has a smaller signal value as the character is thinner. Therefore, the output of the average value calculator 2110 becomes a corrected ZONE signal as it is.

Here, it is desirable that the block size to be used for correction is determined according to the size of the block size for judging the character thickness. By performing the subsequent processing using the above-mentioned corrected ZONE signal, even in the part where the character / line thickness changes rapidly, the determination of the thickness changes smoothly, and the image quality deteriorates due to the change in black character processing. But,
More improved.

Here, as described above, the area where the ZONE signal is in the stage 7 can be regarded as a halftone area, and the area exists in the halftone area or the halftone area from the ZONE signal and the edge signal. It is possible to distinguish a character / line to be used from a character / line in another area. Hereinafter, a method for distinguishing the above will be described.

FIG. 24 is a diagram showing an algorithm for detecting characters in halftone / halftone. First, in the 5 × 5 expansion processing 2111, a 5 × 5
The expansion processing is performed in the block of. 5 × 5 expansion processing 2111
By this, for the halftone dot region that is likely to be incomplete detection,
The detection area is corrected.

Next, in the 11 × 11 erosion process 2112, the output signal of the 5 × 5 expansion process 2111 is
An 11 × 11 block contraction process is performed. 5 × 5 above
The signal FCH obtained by the expansion processing 2111 and the 11 × 11 reduction processing 2112 is a signal obtained by reducing the PICT signal by 8 pixels.

FIG. 25 is a diagram specifically showing a state of processing by the above algorithm. In FIG. 25, by combining the FCH signal, the ZONE signal and the edge signal,
Edges in a white background and edges in halftone / halftone can be distinguished, without emphasizing halftone components even in halftone images, and portions where black character processing is unnecessary such as edges of photographs 3 shows that black character processing can be performed without processing.

(Explanation of Sub-scanning Position Management Unit) Next, the sub-scanning position management unit 131 will be described.

The sub-scanning position management means 131 outputs an n-bit pos signal to the LUT 117. In the present embodiment, the pos signal has 2 bits.

FIG. 28 is an explanatory diagram for explaining the state of image reading in the image scanner section.

The sub-scanning motor 135 is controlled by a control unit 132 such as a CPU after being initialized by receiving a signal from a sub-scanning origin detecting unit 133 formed of a photo sensor. First, after being accelerated and reaching a predetermined speed according to the magnification, it reaches the tip of the image effective area via the approach area. After scanning at a constant speed to the end of the image effective area, the motor is decelerated from the end of the image and stopped. Thereafter, a back scan operation (not shown) is performed to return to the original position.

With respect to the above operation, mechanical vibration and color shift due to the vibration will be described. The upper half of FIG. 28 is a diagram for explaining color misregistration due to mechanical vibration, in which the horizontal axis is a sub-scanning position, and the measured value of the color misregistration amount between R and G on the vertical axis is plotted. It is.

In the above measurement, a line of about 100 dpi consisting of a single black color as shown in FIG. 29 is read in the sub-scanning direction along the color misregistration measurement line in FIG.
The positions of the B edges are compared, and the difference between them is obtained.
FIG. 28 shows a result of calculating RG as a difference between R and G, and a pixel shift occurs as shown in FIG. RB and GB are not shown, but show the same tendency and value as RG.

Due to the above-described color misregistration, the black character judging unit judges that a portion which is originally a black line is colored, and a black character erroneous judgment occurs. The black character determination unit has a certain degree of tolerance for the color shift, but erroneous determination frequently occurs when the color shift exceeds a certain amount.

Next, the relationship between the sub-scanning operation and the color misregistration will be described.

As shown in FIG. 28, mechanical vibration occurs in response to motor acceleration, and the amount of color misregistration greatly increases. Although the acceleration is completed and the vehicle reaches the approaching region, mechanical vibrations start to attenuate, but the vibrations are still large, and thus the amount of color misregistration is also large. Next, the amount of color misregistration is reduced to reach the leading edge of the image.

The color misregistration due to mechanical vibration in the image front end region is the front end blurring which is a problem in the present invention. Originally, if the motor was accelerated sufficiently slowly and the approach distance was long enough, the tip blur should not be a problem.However, according to the demand for improving the productivity of the copier, the time required for repeated scanning time Since the interval is limited, a problem of tip blur occurs.

The above-mentioned tip shake will be described in detail as follows.

In a copying machine of 40 cpm, the period of the time of the repetitive scanning is 1.5 seconds. letter size 21
Assuming that an original of 5.9 mm is read by an image scanner with a scanning speed of 200 mm / s, the read time of the image effective area is 1.08 seconds. Therefore, 1.5-1.
08 = 0.42, and in the remaining 0.42 seconds, acceleration, approach, deceleration, back scan, and stop before the next acceleration must all be performed.

Subsequently, after passing the image leading edge region, a steady region is formed. In this region, as shown in FIG. 28, the vibration amplitude is small and the color shift is small.

FIG. 30 is an explanatory diagram of the output signal pos of the sub-scanning position management means 131.

As shown in FIG. 30, the sub-scanning position management means 1
31 is first initialized at the sub-scan origin by the control unit 132 which has received the signal from the sub-scan origin detection unit 133. It is determined that the position is 0 in the leading edge area of the image, and the pos signal 0
Is output. Next, at position1, pos signal 1, positi
The pos signal 2 is output at on2, and when the steady area is reached, po
The pos signal 3 is output at sition3.

Positions 1 and 2 are signals indicating a transitional state from the tip region to the steady region. position0,
Since the widths of 1, 2, and 3 differ depending on the magnification, the document size, and the like, the control unit determines which signal of position 0, 1, 2, or 3 is to be generated with respect to the pulse count from the motor driver 134. 132 to sub-scanning position management means 1
It is controlled by setting to 31. This is because if the magnification and the document size are different, the acceleration curve, the approach distance, and the steady speed change, so that the state of mechanical vibration also changes.

The pos signal generated as described above is input to the LUT described below.

(Description of LUT) Next, the LUT 117 constituting the black character determination unit 113 shown in FIG. 6 will be described. LUT
Reference numeral 117 denotes an input of the output pos from the sub-scanning position management unit 131 in addition to the signals determined by the character thickness determination unit 114, the edge detection unit 115, and the saturation determination unit 116 in FIG. According to a table as shown in FIGS.
r, "filter", and "sen", which are signals for controlling masking UCR coefficients, spatial filter coefficients, and printer resolution, respectively.

In the tables shown in FIGS. 30 to 34, the meanings of each signal and its value are as follows: sen-0: 200 line, 1: 400 line filter-0: smoothing, 1: strong edge enhancement, 2: medium edge Enhancement, 3: weak edge enhancement ucr-0 to 7: more black to less black FCH-0: edge of image, 1: not edge of image The characteristics of the tables shown in FIGS. ) To (7).

(1) Multi-valued black character processing is possible according to the character thickness. (2) Since a plurality of edge area ranges are prepared, it is possible to select a black character processing area according to the character thickness. it can. In the present embodiment, the widest area is processed even for the thinnest characters.

(3) Black character processing is performed with a difference in the degree of processing between the edge of the character and the inside of the character to realize a smoother change in the amount of black.

(4) Characters in halftone / halftone are distinguished from characters in a white background for processing.

(5) Character edge, character interior, halftone dot /
The coefficients of the spatial filter are changed for each halftone image. Also, the coefficient is changed for the character edge according to the thickness.

(6) The resolution of the printer is changed according to the thickness of the character.

(7) Masking UC for color characters
Except for the R coefficient, the same processing is performed for black characters.

FIG. 34 shows the position in FIG.
3 (constant region). FIG.
This corresponds to position 0 (tip region) of 0. FIG. 32 corresponds to position 1 in FIG. FIG. 33 corresponds to position 2 in FIG.

As described above, corresponding to positions 0 to 3 in FIG. 30, LUTs as shown in FIGS.
The output of 117 changes.

In the present embodiment, in the position 0 image front end region, an erroneous determination is assumed in the saturation determination due to color misregistration, so that output is not performed based on the input col. As the position changes from position 1 to position 3, the influence of the col signal is increased.

Needless to say, not only the processing in the present embodiment but also various processing methods using various combinations with respect to the input signal are conceivable.

On the other hand, in the masking UCR processing circuit 109, the UCR control signal ucr output from the LUT 117
Thus, the generation and output masking of the black signal Bk are performed.

FIG. 27 shows a masking UCR calculation expression in the masking UCR processing circuit 109.

First, the minimum value MINC of C1, M1, Y1
MY is obtained, and Bk1 is obtained by equation (2101). Next, masking of 4 × 8 is performed by equation (2102), and C2, M2, Y2, and Bk2 are output. The above equation (2
102), coefficients m11 to m84 are masking coefficients determined by the printer used, and coefficients k11 to k8.
4 is a UCR coefficient determined by the UCR control signal ucr.

For a halftone / halftone image (ZONE signal is 7), the UCR coefficients are all 1.0, but for the thinnest characters (ZONE signal is 0), a single Bk color is output. UCR coefficients are set as follows. Further, for an intermediate thickness, the UCR coefficient is determined so that the change in tint according to the thickness is smoothly connected, and the amount of Bk is controlled.

In the spatial filter processing unit 111, 5
Two filters of pixel × 5 pixels are prepared, and the output signal of the first filter is connected to the input of the second filter. Four types of filter coefficients, namely, smoothing 1, smoothing 2, edge enhancement 1, and edge enhancement 2, are prepared.
The coefficient is switched for each pixel by the filter signal from the UT 117. Further, by using two filters, edge enhancement is performed after smoothing to realize moiré-reduced edge enhancement. By combining two types of edge enhancement coefficients, a higher-quality image output can be achieved. Making it possible.

As described above, according to the present embodiment, when the thickness of a character / line drawing portion in an image is determined and image processing is performed by combining the outline information and saturation information of the character / line drawing, By correcting the thickness judgment signal so that the thickness of characters and lines changes continuously, smoother thickness judgment is possible even in areas where characters and lines change rapidly, and black reproduction High quality can be realized.

The following embodiment can be carried out in addition to the above embodiment.

1) In the above embodiment, the pos signal is 2
Although the number of bits is four, if the number of bits is increased, the change can be controlled more smoothly and more finely in accordance with the position of the sub-scan.

2) In the above embodiment, as shown in FIG. 6, an RGB signal is used as an input to the black character determination unit 113. However, the present invention is not limited to using an RGB signal. May be input to the black character determination unit 113.

3) In the above embodiment, the black character determination unit 1
The input to the thickness determination unit 114 of the characters constituting
The GB signal is used. However, the present invention is not limited to the RGB signals. For example, as shown in FIG.
An L (luminance) signal may be obtained through 0, and the subsequent processing may be performed using the obtained L signal. Note that FIG.
7, the same reference numerals are used for the same components of the character thickness determination unit shown in FIG.

4) The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device.

5) It goes without saying that the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0155]

As described above, according to the present invention, in an image forming apparatus such as a color copying machine having a black character judging function, a color shift caused by a mechanical vibration of a scanning system at a leading end of an image. , It is possible to suppress the erroneous determination of black characters and the resulting deterioration in image quality.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image processing apparatus according to an embodiment.

FIG. 2 is an external configuration diagram of a CCD 210 of the present embodiment.

FIG. 3 is a cross-sectional view when the CCD 210 is cut along a dotted line aa ′ shown in FIG. 2 of the present embodiment.

FIG. 4 is an enlarged view of a light receiving element indicated by reference numeral B shown in FIG. 2 of the present embodiment.

FIG. 5 is a timing chart illustrating a control operation of density reproduction in the printer unit according to the embodiment.

FIG. 6 is a block diagram illustrating a flow of an image signal in an image signal processing unit 209 of the image scanner unit 201 according to the present embodiment.

FIG. 7 illustrates an image signal processing unit 209 illustrated in FIG. 6 according to the present exemplary embodiment.
5 is a timing chart of each control signal in FIG.

FIG. 8 is a block diagram illustrating an internal configuration of an edge detection unit 115 according to the embodiment.

FIG. 9 is an explanatory diagram of a detailed configuration of a luminance calculation circuit 250 according to the present embodiment.

FIG. 10 is a diagram showing a FIFO and a Laplacian of the present embodiment;
FIG. 4 is an explanatory diagram illustrating a state of a line delay caused by a filter.

FIG. 11 is an explanatory diagram illustrating an example of edge detection according to the embodiment;

FIG. 12 is a block diagram illustrating a detailed configuration of a saturation determination unit that forms the black character determination unit according to the embodiment.

FIG. 13 is an explanatory diagram illustrating data conversion characteristics in the LUT of the present embodiment.

FIG. 14 is a block diagram illustrating a configuration of a character thickness determination unit 114 included in the black character determination unit 113 according to the present embodiment.

FIG. 15 illustrates a character / halftone detection circuit 2013 according to the present embodiment.
FIG. 2 is a block diagram showing an internal configuration of the device.

FIG. 16 is a block diagram illustrating a detailed configuration of a halftone dot area detection unit 2014 according to the present embodiment.

FIG. 17 is an explanatory diagram showing a rule of edge direction detection in the edge direction detection circuit 2044 of the present embodiment.

FIG. 18 is an explanatory diagram showing rules for detecting an opposite edge according to the embodiment;

FIG. 19 is a diagram illustrating a shape of a window in a counting unit 2049 according to the present embodiment.

FIG. 20 is an area size determination circuit 201 according to the present embodiment.
FIG. 6 is a diagram showing an internal configuration of the sixth embodiment.

FIG. 21 is a block diagram illustrating a configuration of a zone correction unit 2084 of the present embodiment.

FIG. 22 shows a PICT_FH according to the character size according to the present embodiment.
FIG. 4 is an explanatory diagram showing how to determine the output of the scalar.

FIG. 23 is an explanatory diagram showing an encoding rule of the encoder 2083 of the embodiment.

FIG. 24 is a diagram showing an algorithm for detecting characters in halftone / halftone according to the present embodiment.

FIG. 25 is an explanatory diagram specifically showing a state of processing by the algorithm shown in FIG. 23 of the present embodiment.

FIG. 26 is an explanatory diagram showing a modification of the character thickness determination unit according to the embodiment.

FIG. 27 is an explanatory diagram showing a masking UCR calculation expression of the present embodiment.

FIG. 28 is an explanatory diagram illustrating a relationship between a sub-scanning position and a color shift amount according to the present embodiment.

FIG. 29 is an explanatory diagram of color misregistration amount measurement according to the present embodiment.

FIG. 30 is an explanatory diagram of an output of the sub-scanning position management means of the embodiment.

FIG. 31 is an LUT 11 corresponding to position 0 in the present embodiment.
FIG. 7 is an explanatory diagram showing contents of input / output correspondence of No. 7;

FIG. 32 shows an LUT 11 corresponding to position 1 of the present embodiment.
FIG. 7 is an explanatory diagram showing contents of input / output correspondence of No. 7;

FIG. 33 is an LUT 11 corresponding to position 2 of the present embodiment.
FIG. 7 is an explanatory diagram showing contents of input / output correspondence of No. 7;

FIG. 34 is an LUT 11 corresponding to position 3 of the present embodiment.
FIG. 7 is an explanatory diagram showing contents of input / output correspondence of No. 7;

[Explanation of symbols]

 Reference Signs List 101 analog signal processing unit 102 A / D converter 103 shading correction unit 104 line delay circuit 105 line delay circuit 106 input masking unit 107 light intensity / density conversion unit (LOG conversion unit) 108 line delay memory 109 masking UCR circuit 110 main scanning Magnification circuit 111 Spatial filter processing unit (output filter) 113 Black character determination unit 114 Character thickness determination unit 115 Edge detection unit 116 Saturation determination unit 117 LUT (look-up table) 121 Clock generation unit 122 Main scanning address / Counter 123 Decoder 131 Sub-scanning position management unit 132 Control unit 133 Sub-scanning origin detection unit 134 Motor driver 135 Motor 200 Printer unit 201 Image scanner unit 202 Original platen plate 203 (Platen) 204 Document 205 Halogen lamp 206 Mirror 207 Mirror 208 Lens 209 Image signal processing unit 210 CCD image sensor 210-1 R sensor 210-2 G sensor 210-3 B sensor 210-5 Silicon substrate 210-6 Transparent Organic film 210-7 R filter 210-8 G filter 210-9 B filter 211 Standard white plate 212 Laser driver 213 Semiconductor laser 214 Polygon mirror 215 f-θ lens 216 Mirror 217 Photosensitive drum 219 Magenta developing device 220 Cyan developing device 221 Yellow developing device 222 Black developing device 223 Transfer drum 224 Paper cassette 225 Paper cassette 226 Fixing unit 231 Infrared cut filter 250 Luminance calculation circuit 251 Edge min direction Detector 252 Smoothing unit in edge min direction 253 Edge detection circuit 301 Multiplier 302 Multiplier 303 Multiplier 304 Adder 305 Adder 401 FIFO 402 FIFO 403 Laplacian filter 404 Laplacian filter 405 Laplacian filter 406 Laplacian filter 601 Maximum Value detection unit 602 Minimum value detection unit 603 LUT (lookup table) 2010 Lab conversion unit 2011 Minimum value detection unit 2012 Average value detection unit 2013 Character / halftone detection unit 2014 Halftone dot region detection unit 2015 OR circuit 2016 Area / Size determination circuit 2030 Adder 2031 Comparator 2032 Comparator 2033 OR circuit 2040 Adder 2041 Comparator 2042 Comparator 2043 OR circuit 2044 G direction detection circuit 2045 Opposite edge detection circuit 2046 Expansion circuit 2047 Contraction circuit 2048 Expansion circuit 2049 Count section 2081 Contraction circuit 2082 Expansion circuit 2083 Encoder 2084 ZONE correction section 2101 Masking UCR calculation equation 2102 Masking UCR calculation equation 2110 Average value calculation section 21115 × 5 expansion processing 2112 11 × 11 reduction processing 10201 printer pixel clock 10202 400-line triangular wave 10203 analog image signal 10204 400-line PWM output 10205 200-line triangular wave 10206 200-line PWM output 10207 200-line / 400-line switching signal 10208 Laser drive signal

Continued on the front page F term (reference)

Claims (12)

[Claims] A sub-scanning position managing unit that manages a scanning position of an image reading unit that reads an image in a sub-scanning direction and outputs a scanning position of the read image in a sub-scanning direction; For the scanned image,
Black character determining means for separating a line component and a halftone dot component to extract a character / line drawing in the image, first determining means for determining the thickness of the character / line drawing, and determining a contour of the character / line drawing A second determination unit that performs the determination, a third determination unit that determines the saturation of the character / line image, a determination result obtained by the first determination unit, the second determination unit, and the third determination unit; An image forming apparatus comprising: processing means for performing predetermined image processing based on an output of the sub-scanning position management means. 2. The image forming apparatus according to claim 1, wherein the output of the sub-scanning position management unit generates a signal for distinguishing at least a leading edge of the image from a steady area of the image. An image forming apparatus comprising: 3. The image forming apparatus according to claim 1, wherein the processing means for performing the predetermined image processing comprises a look-up table, wherein a result of the determination by the first determination means and a value of the second The determination result by the determination means and the third
An image forming apparatus, wherein the judgment result of the judgment means and the output of the sub-scanning position management means are input to the look-up table. 4. The image forming apparatus according to claim 3, wherein an output signal of said look-up table is used as a UC.
An image forming apparatus for controlling R, the number of lines of a printer, and a spatial filter. 5. The image forming apparatus according to claim 2, wherein the output of the sub-scanning position management means is multi-valued, and the output is smoothly switched from the leading end of the image to the steady area. An image forming apparatus comprising: 6. An image forming apparatus according to claim 1, wherein a sub-scan origin detecting means for detecting a sub-scan origin is provided.
The sub-scanning position management unit further includes a control unit having a PU, and the sub-scanning position management unit is given parameters such as a document size and a magnification by the control unit, and is initialized by the control unit that receives a signal from the sub-scanning origin detection unit. An image forming apparatus for counting the number of motor pulses from a motor driver for causing the image reading means to perform sub-scanning. 7. A scanning position in a sub-scanning direction of an image reading unit that reads an image is output, and a scanning position of the read image in a sub-scanning direction is output.
A line component and a halftone dot component are separated, a black character determination for extracting a character / line drawing in the image is performed, a first determination for determining a thickness of the character / line drawing is performed, and a contour of the character / line drawing is determined. A second determination is performed, and a third determination is performed to determine the saturation of the character / line image. The determination results of the first determination, the second determination, the third determination, and the sub-determination are performed. An image forming method, wherein predetermined image processing is performed based on an output of a scanning position in a scanning direction. 8. The image forming method according to claim 7, wherein the output of the scanning position in the sub-scanning direction generates a signal for discriminating at least an image front end of the image and a steady area portion of the image. An image forming method. 9. The image forming method according to claim 7, wherein the predetermined image processing uses a look-up table to determine a result of the first determination and a determination of the second determination. An image forming method, wherein a result, a result of the third determination, and an output of a scanning position in the sub-scanning direction are input to the look-up table. 10. The image forming method according to claim 9, wherein an output signal of said look-up table is used as a UC.
An image forming method comprising controlling R, the number of lines of a printer, and a spatial filter. 11. The image forming method according to claim 8, wherein the output of the scanning position in the sub-scanning direction is multi-valued, and the output is smoothly switched from the leading end of the image to the steady area. An image forming method comprising: 12. The image forming method according to claim 7, further comprising detecting a sub-scan origin and controlling by a CPU, wherein the control of the scanning position in the sub-scan direction is performed by a document size, magnification, and the like given by the control. Initialization is performed by the control that receives the signal of the detection of the sub-scanning origin using the above parameters, and the number of motor pulses from the motor driver for sub-scanning the image reading unit is counted. Image forming method.