JP2004328677A - Color image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus in which costs can be reduced by a simple configuration by effectively utilizing an image storage memory 57 that is present in a color image processing apparatus, as a line buffer memory for line correction. <P>SOLUTION: The color image processing apparatus is provided with an input image processing part 53 for applying predetermined image processing to image data in each of colors read by an image sensor 22, the image storage memory 57 for storing the image data processed by the input image processing part 53, and a memory control part 55 for controlling the write/read of the image storage memory 55. The memory control part 55 stores the image data in the respective colors inputted from the image sensor 22 on the image storage memory 57, reads the image data in the respective colors from the same scan line from the image storage memory 57 at the same time and supplies the image data to the input image processing part 53. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image processing apparatus that performs predetermined image processing based on image data of a document read by a document reading unit.
[0002]
[Prior art]
A typical color image processing apparatus includes a light source for illuminating a document, a reflector for guiding light from the document to a detection surface of the image sensor, and an image sensor for detecting the reflected light and converting the reflected light into an electric signal. The main scanning of the document is achieved by electrical scanning in the image sensor, while the sub-scanning of the document is achieved by moving the light source and the reflecting mirror. An image signal scanned by the image sensor is input to an image processing unit.
[0003]
Image data output from the image processing unit is subjected to output image processing in the case of an electrophotographic copying machine, for example, and is input to a laser controller, where a drive signal to be supplied to a laser device is generated. The laser device irradiates a rotating photoconductor with a laser beam according to the drive signal. An electrostatic latent image corresponding to the original image is formed on the photoreceptor, and the electrostatic latent image is developed by the adhesion of the toner stored in the developing device, and the developed toner image is transferred to the surface of the recording sheet. You. Further, the toner image on the recording sheet is fixed by applying heat. Thereby, a document image is formed on the recording sheet.
[0004]
FIG. 5 is a block diagram for explaining an electrical configuration of a conventional image processing unit 50 in the color image processing apparatus. The image processing unit 50 includes a line correction processing unit 152, an input image processing unit 153, a compression processing unit 154, and a memory control unit 155 that controls writing and reading of image data to and from the image storage memory 157. .
The line correction processing unit 152 performs a line correction for correcting a temporal shift of the image signal of each color input from the image sensor 150. To perform this line correction, a high-speed line buffer memory 151 is used.
[0005]
[Patent Document 1] JP-A-6-125424
[0006]
[Problems to be solved by the invention]
However, the line buffer memory is a major factor in increasing the cost of the color image processing device. On the other hand, the image processing unit has a large-scale image storage memory used for storing image data.
Accordingly, the present invention provides a color image processing apparatus that can reduce the original line buffer memory and reduce costs by utilizing the image storage memory as a line buffer memory for performing line correction. Aim.
[0007]
Means for Solving the Problems and Effects of the Invention
2. A color image processing apparatus according to claim 1, wherein the image processing section performs predetermined image processing on image data of each color read by a document reading section, and performs image processing by the image processing section. An image storage memory that stores the read image data, and a memory control unit that controls writing and reading of the image storage memory, wherein the memory control unit is selected from colors of image data input from the document reading unit. The image data of two or more colors is stored in the image storage memory, and the image data of the two or more colors of the same scanning line is read out from the image storage memory at the same time and supplied to the image processing unit. is there.
[0008]
The document reading section has an image sensor extending in the main scanning direction, and reads the document by repeating the electrical main scanning and displacing the positional relationship between the image sensor and the document in the sub-scanning direction. is there.
According to this configuration, the memory control unit temporarily stores the image data of two or more colors input from the document reading unit in the image storage memory, and outputs the image data of two or more colors of the same scan line from the image storage memory. It can be read out at the same time and supplied to the image processing unit. As described above, since the role of the conventional line buffer memory is performed by the image storage memory, the line buffer memory can be reduced.
[0009]
Since the image storage memory is generally a large-scale memory and has a high-speed access method such as multi-bit / burst access, corresponding to this, image data for one scan is divided into a plurality of parts, and these divided parts are divided. It is possible to employ an embodiment in which the image data is written to the image storage memory in units of image data and the image data is read from the image storage memory.
Further, when writing and reading of the image storage memory are simultaneously performed in time, data loss is likely to occur. In order to solve this problem, the transfer amount of write / read data of the image storage memory per unit time is set faster than the transfer amount of image data input from the document reading unit per unit time, and the memory control is performed. A buffer memory that absorbs a shift in the transfer amount of image data per unit time between the unit and the image storage memory, a time point at which the divided image data is written from the buffer memory to the image storage memory, It is preferable to provide a time difference between the time when the image data is read from the storage memory and the time when the image data is read out.
[0010]
In this case, in order that the writing to the image storage memory and the reading of the image data from the image storage memory do not overlap, the transfer amount of the write / read data of the image storage memory per unit time is input from the document reading unit. It is preferable that the transfer amount exceeds four times the transfer amount of the image data per unit time.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a schematic sectional view showing an internal configuration of a digital color copying machine 1 to which a color image processing apparatus of the present invention is applied.
The digital color copying machine 1 applies single-color toners of cyan (C), magenta (M), yellow (Y) and black (B) to paper based on color image data of a document read by a document reading unit 2. By overlapping, a full-color image can be formed by a so-called electrophotographic method.
[0012]
An original to be read by the original reading unit 2 is set on a contact glass 3 arranged on the upper surface of the digital color copying machine 1 so that the image faces downward. A cover 4 that can be opened and closed is disposed above the contact glass 3 so that the cover 4 can be opened and closed so that documents can be set one by one on the contact glass 3. I have.
The document reading unit 2 uses a light source 21 for illuminating the document set on the contact glass 3 from below, and a light receiving element such as a CCD for detecting reflected light from the document and converting it into an electric signal. The image sensor 22, first, second, and third reflecting mirrors 231 to 233 for guiding reflected light from the document to the detection surface of the image sensor 22, and forming an optical image of the document on the detection surface of the image sensor 22. A lens 24 for imaging. The scanning of the document is achieved by electrical scanning in the image sensor 22. This scanning direction is called a main scanning direction.
[0013]
The light source 21 and the first reflecting mirror 231 are held by a first holding member 251, and the second and third reflecting mirrors 232 and 233 are held by a second holding member 252. The two holding members 251 and 252 are movable along the lower surface of the contact glass 3 in the left-right direction (sub-scanning direction) in FIG. The first and second holding members 251 and 252 move in the same direction by the rotation of the stepping motor so that the speed of the second holding member 252 becomes half the speed of the first holding member 251. ing. With the movement of the light source 21 and the reflecting mirrors 231 to 233 accompanying the movement of the first and second holding members 251, 252, scanning of the document set on the contact glass 3 in the sub-scanning direction is achieved.
[0014]
On the detection surface of the image sensor 22, reading lines 22R, 22G, and 22B for detecting respective colors of red (R), green (G), and blue (B) are provided at predetermined intervals along the main scanning direction. (Eg, four lines).
The image sensor 22 outputs an RGB image signal based on each color component detected by each of the reading lines 22R to 22B, and outputs the output RGB image signal to an image processing unit 5 ( (See FIG. 2). The image processing unit 5 generates cyan (C), magenta (M), yellow (Y), and black (BK) image data based on the input RGB image signals, and It is provided to the laser scanning unit 6 (LSU) through the laser controller. The laser scanning unit 6 separately irradiates irradiation light based on the given image data toward the surface of the substantially cylindrical photoconductor 71 provided in the image forming unit 7.
[0015]
The image forming section 7 contains, in addition to the photoconductor 71, a main charger 72 for charging the surface of the photoconductor 71, and toners of respective colors of cyan, magenta, yellow, and black. The image forming apparatus includes developing devices 73C, 73M, 73Y, and 73BK for forming toner images of respective colors, and a cleaning device 73 for removing toner remaining on the surface of the photoconductor 71 after the transfer of the toner image.
The surface of the substantially cylindrical transfer drum 75 contacts the surface of the photoconductor 71. The transfer drum 75 is formed such that its outer peripheral length is longer than the length of a sheet to be used. A transfer device 76 is provided in the transfer drum 75 at a position facing the photoconductor 71. In the digital color copying machine 1, the paper is wound around the transfer drum 75 rotating clockwise in FIG. 1, and passes through the transfer position (between the photoconductor 71 and the transfer drum 75) a plurality of times (for example, four times). Thus, the color toner images sequentially formed on the surface of the photoconductor 71 can be transferred one by one to the paper by the operation of the transfer device 76.
[0016]
Sheets to be used can be set in a sheet cassette 8 or a manual feed tray 9. In the digital color copying machine 1, sheets can be guided from the sheet cassette 8 and the manual feed tray 9 to the image forming unit 7. A branching paper transport path 10 is provided so as to be able to do so.
The paper cassette 8 is capable of storing a plurality of papers, and the stored papers can be sent out to the paper transport path 10 one by one by a pickup roller 81. On the other hand, the sheets set one by one on the manual feed tray 9 are sent out to a sheet transport path 10 by a sheet feeding roller 91.
[0017]
The sheet sent from the sheet cassette 8 or the manual feed tray 9 to the image forming unit 7 through the sheet conveyance path 10 is temporarily stopped when the leading end thereof reaches the registration roller 11. Then, the rotation of the registration roller 11 is adjusted so that the timing at which the one-color toner image formed on the surface of the photoreceptor 71 comes to a position facing the transfer drum 75 coincides with the timing at which the paper reaches the transfer position. Will be resumed. At this time, static electricity is applied to the surface of the transfer drum 75 by the discharge of the discharge device 12 arranged opposite to the surface of the transfer drum 75, and the paper sent from the registration roller 11 is transferred to the transfer drum 75 by the electrostatic force. It can be wound around. The sheet sent from the registration roller 11 is wound around the transfer roller 75 and moves to the transfer position, and the one-color toner image formed on the surface of the photoconductor 71 is transferred to the sheet.
[0018]
After the toner remaining on the surface of the photoreceptor 71 after the transfer of the toner image is collected by the cleaning device 73, the photoreceptor 71 is uniformly charged again by the main charger 72. On the charged surface of the photoconductor 71, an electrostatic latent image corresponding to a toner image (other than the one color) to be formed next is formed by irradiation light from the laser scanning unit 6. Toner is attached to the surface of the photoreceptor 71 on which the electrostatic latent image is formed by a developing device corresponding to the color to form a one-color toner image to be transferred to paper. Then, the toner image formed on the surface of the photoconductor 71 is wrapped around the transfer drum 75 and is again transferred to the sheet that has reached the transfer position.
[0019]
In this way, the paper is wound around the transfer drum 75 and passes through the transfer position four times, and each time the paper passes through the transfer position, a different color toner image is sequentially transferred to the paper, whereby cyan, magenta, yellow And black toner images of four colors are superimposedly transferred onto a sheet.
When the four color toner images are transferred to the sheet, the discharge device 12 discharges the static electricity on the surface of the transfer drum 75, and the sheet is separated from the transfer drum 75. Then, the toner adhered to the surface of the transfer drum 75 after the paper is separated is collected by the cleaning brush device 77.
[0020]
The toner image-transferred sheet separated from the transfer drum 75 is transported to the fixing device 14 on the surface of the rotating endless transport belt 13. Then, the sheet subjected to a predetermined fixing process by the fixing device 14 is discharged to a sheet discharge unit 17 disposed outside the apparatus via a conveying roller 15 and a discharge roller 16.
FIG. 2 is a block diagram for explaining an electrical configuration of the image processing unit 5.
The image processing unit 5 includes an input image processing unit 53, a compression processing unit 54, and a memory control unit 55 that controls writing and reading of image data to and from an image storage memory.
[0021]
The memory control unit 55 also has a function of performing line correction for correcting a time shift of the image signal of each color input from the image sensor 22. In order to perform this line correction, a small-capacity buffer memory 56 and an image storage memory 57 are used. The memory control unit 55 supplies a memory control signal to the image storage memory 57 and the buffer memory 56. The specific contents of the memory control will be described later in detail.
[0022]
Since the line correction cannot wait for the process, the memory control unit 55 determines whether the image storage memory 57 is accessed for another process during the line correction process. Must always be given priority. In some cases, access to other processes is restricted.
The input image processing unit 53 corrects a color conversion function for converting RGB image data into cyan (C), magenta (M), and yellow (Y) image data, a light source, and variations in reading sensitivity of the image sensor 22. It realizes various functions such as a shading correction function, an input γ correction function for converting image data subjected to shading correction into image data having a gradation characteristic proportional to the document density, and image enlargement / reduction.
[0023]
When storing the image data in the image storage memory 57, the compression processing unit 54 compresses the image data in order to compress the image data before storing the image data. Is unnecessary.
The output image processing unit 55 performs filter processing for performing edge enhancement processing or smoothing processing on image data, output γ adjustment for correcting γ characteristics of an output engine, and halftone processing such as dither processing and error diffusion processing. .
[0024]
The functions of the input image processing unit 53, the compression processing unit 54, and the memory control unit 55 described above are performed by a computer in a single-chip ASIC mounted on the digital color copier 1 by a predetermined image processing. This is realized by executing a program.
The function of the output image processing unit 58 is also realized by executing a predetermined image processing program in a computer mounted on the digital color copying machine 1. This computer may or may not be the same as the computer in the ASIC.
[0025]
The output image data of the output image processing unit 58 is sent to the laser controller 59, where a driving signal to be supplied to the laser scanning unit 6 is generated, and the laser scanning unit 6 irradiates a laser beam according to the driving signal. .
Hereinafter, the flow of processing in the image processing unit 5 will be described.
Light emitted from the light source 21 is reflected on the document, and the reflected light is reflected by the reflecting mirrors 231 to 233 and is incident on the detection surface of the image sensor 22. Then, an RGB image signal based on each color component (RGB) detected on each reading line (red reading line 22R, green reading line 22G, blue reading line 22B) of the image sensor 22 is sent from the image sensor 22 to the memory control unit 55. Is entered.
[0026]
First, the memory control unit 55 performs a line correction for correcting a shift of the input RGB image signal of each color. That is, each of the RGB image signals is shifted in accordance with the distance between the reading lines 22R, 22G, and 22B (the distance corresponding to four lines). For example, a green (G) image signal is delayed by four lines with respect to a red (R) image signal, and a blue (B) image signal is delayed by four lines with respect to a green (G) image signal. (The image signal of the red (R) is delayed by 8 lines), the memory control unit 55 converts the image signals of the red (R) and green (G) out of these colors. By accumulating them in the image storage memory 57, delaying the green (G) image signal by four lines and the red (R) image signal by eight lines, and reading them simultaneously with the blue (B) image signal, The deviation of each image signal can be eliminated.
[0027]
In this embodiment, since the two color image signals before the line correction are stored in the image storage memory 57, the number of dedicated line buffer memories can be reduced as compared with a configuration in which a dedicated line buffer memory is separately provided.
Each of the RGB image signals after the line correction is provided to the input image processing unit 53. The input image processing unit 53 first quantizes each of the red, green, and blue RGB image signals into cyan, magenta, and yellow image data (for example, 256 gradations). For the image data generated in this way, for example, the optical system such as the light source 21 has different light distribution characteristics between the center and the end in the main scanning direction (the luminance at both ends in the main scanning direction decreases). Characteristic), shading correction processing for correcting sensitivity variations of the read lines 22R, 22G, and 22B for each read pixel, and input gamma correction processing for providing a gradation characteristic proportional to the density of a document. In addition, processing for enlarging or reducing image data in the sub-scanning direction, processing for enlarging or reducing in the main scanning direction, and the like are performed.
[0028]
The image data after the input image processing is stored in the image storage memory 57 via the memory input image processing unit 6 after being subjected to data compression processing by the compression processing unit 54. The compressed image data stored in the image storage memory 57 is read out and decompressed by the memory input image processing unit 6 at a predetermined timing, and then subjected to output image processing by the output image processing unit 58. Then, it is sent to the laser scanning unit 6.
The output image processing includes, for example, filter processing (so-called edge enhancement processing and smoothing processing) and intermediate value processing (so-called error diffusion processing and dither processing). At the time of output image processing, black generation processing is performed by extracting only the same component (level) from cyan, magenta, and yellow and replacing it with a black component. Thereby, black (BK) image data is added to the image data provided to the laser scanning unit 6.
[0029]
Next, the contents of the line correction processing of the present invention will be described in detail with reference to FIGS. Hereinafter, RGB color, CMY color, and the like will be described as XYZ colors.
FIG. 3 is a time chart for explaining the line correction timing. The numbers indicate line numbers.
FIG. 3A illustrates a main scanning reference signal indicating a break of a scanning period of the image sensor 22, and FIG. 3B illustrates XYZ image data input from the image sensor 22 to the memory control unit 55. I have.
[0030]
This image sensor 22 has a structure with a delay width of 4 lines. Therefore, the Y color input image data is input four lines later than the X color input image data,
The Z color input image data is input four lines later than the Y color input image data. Therefore, the Z color input image data is input after a total of eight lines behind the X color input image data. The hatched portion in FIG. 3B indicates that no memory transfer is performed because no image data is input.
[0031]
FIG. 3C is a diagram showing the timing of writing the X-color and Y-color image data from the memory control unit 55 to the image storage memory 57, and FIG. FIG. 9 is a diagram showing the timing of reading image data of X color and Y color into the image data.
As can be seen from FIG. 3C, in writing the image data, the image data sequentially input from the image sensor 22 is written in real time. However, as shown in FIG. 3D, in the image data reading, the reading is performed when the XYZ color data for the same line is accumulated and stored. During this reading, the X-color and Y-color image data are temporarily stored in the image storage memory 57. That is, the image storage memory 57 plays a role as a conventional line buffer memory dedicated to line correction.
[0032]
The image storage memory 57 is a large-capacity memory usually composed of a DRAM or the like, and when data reading and writing occur simultaneously, data skipping or omission may occur. Therefore, in the embodiment of the present invention, in order to avoid such a situation, a method is devised so that data reading and writing to the image storage memory 57 do not occur at the same time.
FIG. 4 is an enlarged view showing one main scanning period. FIG. 4A shows a main scanning reference signal and a main scanning effective section signal indicating a period during which image data is effectively extracted from the image sensor 22 in the main scanning period.
[0033]
FIG. 4B shows a timing A for writing image data from the memory control unit 55 to the buffer memory 56 and a timing B for writing image data from the buffer memory 56 to the image storage memory 57. FIG. 4C shows a timing C for reading image data from the image storage memory 57 to the buffer memory 56 and a timing D for reading image data from the buffer memory 56 to the memory control unit 55. The line number of the image data written to the image storage memory 57 and the line number of the image data read from the image storage memory 57 at the same time are not necessarily the same. For example, the X color data written in FIG. 4B is the image data of the ninth line, and the X color data read almost simultaneously in FIG. 4C is the image data of the first line.
[0034]
These timings A to D are all controlled by a memory control signal input from the memory control unit 55 to the buffer memory 56 and the image storage memory 57.
Specifically, the memory control unit 55 delays the image data read timing D from the buffer memory 56 to the memory control unit 55 by a predetermined time t with respect to the image data write timing A from the memory control unit 55 to the buffer memory 56. ing.
Also, as shown in FIG. 4B, the memory control unit 55 divides one line of image data written from the memory control unit 55 into the buffer memory 56 into 1, 2, 3,. In. Here, N is an integer of 1 or more (for example, N = 8). The period of each of these divided image data is T. Then, these divided image data are written into the image storage memory 57 and read out from the image storage memory 57 for each division unit (that is, for each period T).
[0035]
In this case, it is preferable to set u <T / 4, where u is the time during which each divided image data is transferred to the image storage memory 57. That is, it is preferable that the transfer amount of the data to the image storage memory 57 per unit time be faster than four times the transfer amount of the original image data per unit time. This means that during the period T of the input image data, the writing and reading of the X color to and from the image storage memory 57 must be performed, and the writing and reading of the Y color overlap with the writing and reading of the X color. This is because writing to and reading from the image storage memory 57 must be performed.
[0036]
The timing of writing these divided image data to the image storage memory 57 is, for example, when each divided image data is accumulated in the buffer memory 56 as shown in FIG. For example, if the first divided image data accumulates in the buffer memory 56, the first divided image data is burst-transferred to the image storage memory 57 at high speed. The second divided image data is stored in the buffer memory 56. If accumulated, the second image data is burst-transferred to the image storage memory 57 at a high speed. As described above, since writing and reading of data to and from the buffer memory 56 overlap with each other in time, the memory capacity of the buffer memory 56 needs to be a capacity that can store at least two divided image data per color. Therefore, in the case of two colors, the capacity needs to be able to store a total of four divided image data.
[0037]
As described above, the memory control unit 55 delays the image data read timing D from the buffer memory 56 to the memory control unit 55 by a predetermined time t with respect to the image data write timing A to the buffer memory 56.
As described above, the memory control unit 55 delays the image data read timing D from the buffer memory 56 to the memory control unit 55 by a predetermined time t with respect to the image data write timing A to the buffer memory 56. As shown in (c), the time point C at which the image data is read from the image storage memory 57 is later than the time point B at which the image data is written into the image storage memory 57 by the time t.
[0038]
Thus, reading and writing of image data to and from the image storage memory 57 can be performed alternately.
In FIG. 4 described above, the memory transfer control for the X color has been described. However, similar memory transfer control is performed not only for the X color but also for the Y color. However, it is necessary to adjust the transfer time between the memory transfer for the X color and the memory transfer for the Y color so that reading and writing of image data to the image storage memory 57 do not occur at the same time.
[0039]
With the above memory control, reading and writing of image data to the image storage memory 57 can be prevented from occurring at the same time, so that image data to be written to the image storage memory 57 and image data to be output from the image storage memory 57 can be stored. Missing can be reliably prevented.
It should be noted that the present invention is not limited to the contents of the above embodiments, and various changes can be made within the scope of the present invention.
[0040]
For example, the digital color copying machine may have a scanner function. That is, the image data stored in the image storage memory 57 is not limited to the configuration in which the image data is sent to the laser scanning unit 6 after the output image processing in the output image processing unit 58. The information may be sent to an external device (for example, a personal computer) connected to the device 1.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an internal configuration of a digital color copying machine 1 to which a color image processing apparatus of the present invention is applied.
FIG. 2 is a block diagram for explaining an electrical configuration of an image processing unit 5;
FIG. 3 is a time chart for explaining a line correction process performed by a memory control unit 55;
4 is an enlarged time chart for explaining the timing of writing and reading image data to and from an image storage memory 57. FIG.
FIG. 5 is a block diagram for explaining an electrical configuration of a conventional image processing unit.
[Explanation of symbols]
1 Digital color copier
2 Document reading section
5 Image processing unit
22 Image Sensor
53 input image processing unit
54 Compression processing unit
55 Memory control unit
56 buffer memory
57 Image storage memory
58 Output image processing unit

Claims (4)

An image processing unit that performs predetermined image processing on image data of each color read by the document reading unit;
An image storage memory for storing image data subjected to image processing by the image processing unit;
A memory control unit that controls writing and reading of the image storage memory,
The memory control unit stores the image data of two or more colors selected from the colors of the image data input from the document reading unit in the image storage memory, and reads the two or more colors of the same scan line from the image storage memory. A color image processing apparatus for reading out color image data at the same time and supplying it to the image processing unit. The image processing apparatus according to claim 1, wherein the memory control unit divides the image data for one scan into a plurality of pieces, writes the image data into the image storage memory in units of the divided image data, and reads the image data from the image storage memory. 2. The color image processing apparatus according to 1. The transfer amount per unit time of the writing and reading data of the image storage memory is set faster than the transfer amount per unit time of the image data input from the document reading unit,
The memory control unit, between the image storage memory, further comprising a buffer memory that absorbs a shift in the amount of image data transferred per unit time,
The color memory according to claim 2, wherein the memory control unit provides a time difference between a time point at which the divided image data is written from the buffer memory to the image storage memory and a time point at which the image data is read out from the image storage memory. Image processing device. 4. The transfer amount of write / read data of the image storage memory per unit time exceeds four times the transfer amount of image data input from a document reading unit per unit time. Color image processing device.

Images