JP2000318206A - Image forming apparatus, image processor and method for correcting positional shift in printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To readily correct a positional shift in printing in a main scanning direction in terms of an image forming apparatus using a plurality of exposing light sources, an image processor and a method for correcting the positional shift in printing. SOLUTION: A beam detection sensor 212 detects an exposing light from a plurality of laser devices in a laser unit 114 at a predetermined position in a main scanning direction. A timer 500 measures a detection interval at a time when a predetermined laser device in the plurality of laser devices is turned on by a CPU 201 and another detection interval at a time when the other laser device is turned on after turning on the predetermined laser device. The CPU 201 generates position shift data by calculating the measured results of the timer 500 at a time when controlling the turning on or off of the laser devices. A pixel shift correcting section 307 generates a reference synchronism signal of a predetermined timing and a plurality of synchronism signals of which the phases are shifted corresponding to the number of laser devices with respect to the reference synchronism signal. A position shift in the main scanning direction is corresponding by using the plural synchronism signals and position shift data.

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, an image processing apparatus, and a printing position shift correcting method, and more particularly, to an image forming apparatus using a plurality of exposure light sources, and an image processing apparatus having the image forming apparatus. , And a print position shift correction method of the image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus provided with a printer using a plurality of exposure lasers and an image processing apparatus provided with the image forming apparatus and a scanner unit, a laser irradiation position is provided by providing a mechanical mechanism. The print position shift correction method of correcting the position shift of pixels in the main scanning direction on a photoconductor such as a rotating drum by moving the print position has been performed.

[0003]

However, in the above-mentioned prior art, a mechanical mechanism for correcting a pixel shift is very complicated and requires a high-precision mechanism, and an adjustment for performing an optimum correction is required. Was also difficult. Therefore, naturally, there is also a problem that the cost increases.

Accordingly, the present invention has been made in view of the above-mentioned problems, and has been made in view of the above-mentioned problems, and has no need for a complicated and high-precision mechanism, and is capable of easily correcting a pixel shift between a plurality of exposure light sources. It is an object to provide an apparatus, an image processing apparatus, and a print position shift correction method.

[0005]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a rotating photosensitive member that is exposed in a main scanning direction using a plurality of light sources; In an image forming apparatus for performing formation, position shift data representing a position shift in the main scanning direction of the latent image formed on the rotating photoconductor by the plurality of light sources with respect to a pixel at the same position in the main scanning direction. A synchronization data generating means for generating a plurality of read synchronization signals having different timings; and a position shift in the main scanning direction by each light source among the plurality of read synchronization signals based on the position shift data. And a correcting means for correcting the positional deviation in the main scanning direction by exposing the rotating photoconductor using an image signal synchronized with a synchronization signal optimal for correcting the positional deviation in the main scanning direction. .

[0006] The invention described in claim 2 is the invention according to claim 1.
, The shift data generating means includes: detecting means for detecting exposure by the plurality of light sources at a predetermined position in the main scanning direction; timer means for measuring time based on a detection output of the detecting means; Lighting control means for controlling lighting of the plurality of light sources with respect to pixels at the same position in the direction; and calculating means for calculating the position shift data by calculating a measurement result of the timer means when the lighting control is performed. An image forming apparatus comprising:

[0007] Further, the invention according to claim 3 is based on claim 2.
In the timer means, the interval of the detection output when the lighting control means turns on a predetermined light source among the plurality of light sources, the lighting control means to turn on a predetermined light source among the plurality of light sources And measuring another interval of the detection output when another light source is turned on, and the calculating means obtains a difference between the interval and the another interval.

[0008] The invention described in claim 4 is the first invention.
Wherein the synchronization generation means generates a reference synchronization signal at a predetermined timing and a plurality of synchronization signals phase-shifted by a phase corresponding to the number of the plurality of light sources with respect to the reference synchronization signal. A forming device is provided.

The invention described in claim 5 is the first invention.
Wherein the correction means selects the optimum synchronization signal, and synchronizes the image signal with the selected synchronization signal and outputs the image signal to each of the light sources.

The invention described in claim 6 is the first invention.
6. An image processing apparatus comprising: the image forming apparatus according to any one of claims 5 to 5; and an image reading unit that generates an image signal to be provided to the image forming apparatus.

According to a seventh aspect of the present invention, there is provided a method for correcting a print position shift of an image forming apparatus for forming an image based on a latent image obtained by exposing a rotating photosensitive member in a main scanning direction using a plurality of light sources. A plurality of pixels having different timings, each of which includes positional deviation data representing a positional deviation in the main scanning direction of the latent image formed on the rotating photoconductor by the plurality of light sources with respect to a pixel at the same position in the main scanning direction. Generating a read synchronizing signal, and an image synchronized with an optimum synchronizing signal for correcting a positional shift in the main scanning direction due to each light source among the plurality of read synchronizing signals based on the positional shift data. A correction step of exposing the rotating photoconductor using a signal to correct the positional deviation in the main scanning direction. That.

[0012] The invention described in claim 8 is the same as in claim 7.
In the generating step, the lighting of the plurality of light sources is controlled for pixels at the same position in the main scanning direction, and exposure by the plurality of light sources is detected by a detection unit at a predetermined position in the main scanning direction, The output interval of the detection means when a predetermined light source is turned on among the plurality of light sources and the output of the detection means when another light source is turned on after turning on a predetermined light source among the plurality of light sources. A print position shift correction method is provided, wherein another interval is measured and a difference between the interval and the another interval is obtained.

The invention according to claim 9 is the same as the invention according to claim 7.
Wherein the generating step generates a reference synchronization signal at a predetermined timing and a plurality of synchronization signals phase-shifted by a phase corresponding to the number of the plurality of light sources with respect to the reference synchronization signal. A shift correction method is provided.

According to a tenth aspect of the present invention, in the seventh aspect, in the correcting step, the optimal synchronization signal is selected, and the image signals are synchronized with the selected synchronization signal respectively. And a print position shift correction method characterized in that the print position error is output.

[0015]

According to the present invention having the above-described structure, a print position shift in the main scanning direction between a plurality of exposure light sources can be corrected without providing a mechanical mechanism.

[0016]

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

FIG. 1 is a sectional view for explaining an example of the configuration of a digital copying machine to which the present invention can be applied.
It is configured to perform image processing on an image signal generated by the sensor to form an image. The present invention can be applied to an image forming apparatus that does not have such an image reading unit, whereby a high-quality image in which a print position shift has been corrected can be obtained.

In FIG. 1, an original is placed at a predetermined position on an original platen glass 101. The original illumination lamp 102 is formed of, for example, a halogen lamp, and
The original placed on 1 is exposed. Scanning mirror 103, 1
Reference numerals 04 and 105 are housed in an optical scanning unit (not shown), and guide reflected light from the document to the CCD unit 106 while reciprocating. The CCD unit 106 is a coupling lens 107 for coupling the reflected light from the original to the CCD, for example, the linear image sensor 1 composed of a color CCD.
08, CC driving linear image sensor 108
It comprises a D driver 109 and the like.

The image signal output from the linear image sensor 108 is converted into, for example, 8-bit digital data and then input to the controller 139. Also,
The photosensitive drum 110 is discharged by the pre-exposure lamp 112 in preparation for image formation. The charger 113 is a photosensitive drum 1
10 is uniformly charged. Reference numeral 114 denotes a laser unit serving as an exposure unit, which includes four semiconductor lasers, and controls the photosensitive drum 110 based on image data processed by a controller unit 139 that performs image processing and control of the entire apparatus. Exposure to form an electrostatic latent image.

At this time, one of these semiconductor lasers exposes an odd first line, one exposes an even first line, one exposes an odd second line, and the other exposes the other. One exposes an even number of second lines. It is assumed that the irradiation position of each semiconductor laser on the pixel at the same position in the main scanning direction has a position shift in the main scanning direction as described later.

The developing unit 115 is detachable and replaceable, so that the user can easily set it at a predetermined position in the apparatus. It is filled with a developer that develops a black developing color. The pre-transfer charger 119 causes the photosensitive drum 1
A high voltage is applied to the toner developed on 10 to increase the charge density of the toner, thereby increasing the transfer efficiency and facilitating the separation of the paper. The transfer paper stored in the paper feed units 120, 122, and 124 is supplied to each of the paper feed rollers 121, 123,
The photosensitive drum 1 is fed into the apparatus by being driven, and temporarily stopped at the position where the registration roller 126 is disposed.
The timing for starting writing with the image formed on the image 10 is taken, and the image is re-fed.

The transfer drum 127 causes the photosensitive drum 11
The toner image developed to 0 is transferred to the fed transfer paper. The transfer paper after the transfer operation is separated from the photosensitive drum 110 by the separation charger 128. The toner remaining on the photosensitive drum 110 without being transferred is collected by the cleaner 111. The transfer sheet on which the transfer process has been completed is transferred to the fixing device 130 by the transfer belt 129, and is fixed by, for example, heat. By the flapper 131, the transfer path of the transfer sheet having completed the fixing process is changed to the discharge tray 1
32 or the direction in which the intermediate tray 137 is arranged.

The transfer paper having undergone the fixing process is inverted (multiplexed) or non-inverted (both sides) and fed to the intermediate tray 137 by the feeding rollers 133 to 136. The transfer paper placed on the intermediate tray 137 is again conveyed by the re-feed roller 138 to the position where the registration roller 126 is provided. The controller unit 139 includes a microcomputer, an image processing unit, and the like, which will be described later, and performs the above-described image forming operation in accordance with an instruction from the operation panel 140.

FIG. 2 is a block diagram of the controller 139 in the digital copying machine according to the present invention.

The CPU 201 is a processing unit for controlling the entire image processing apparatus. The CPU 201 sequentially reads programs from a read-only memory 203 (ROM) that stores control procedures (control programs) for the apparatus main body, loads the programs into the RAM 204, and executes them. . An address bus and a data bus of the CPU 201 are connected to each load via a bus driver / address decoder circuit 202. A random access memory (RAM) 204 is a memory device used by the CPU 201 as a main storage device, and is used as storage of input data and a work storage area.

The I / O port 205 controls an interface function with various external devices. That is, the I / O port 205 is provided with an operation panel 140 for displaying the state of the apparatus using liquid crystal and LEDs by inputting a key by an operator, and motors 207 for driving a paper supply system, a conveyance system, and an optical system. ,
The clutches 208, the solenoids 209, and the paper detection sensors 210 for detecting paper being conveyed are connected to loads in the apparatus, and transmit and receive various signals. Further, the developing device 115 is provided with a remaining toner detection sensor 211 for detecting the remaining amount of toner in the developing device, and an output signal thereof is input to the I / O port 205.

The image processing unit 206 includes the CCD unit 106
The image signal output from is input to perform image processing to be described later, and the laser unit 114 according to the image data.
Output a control signal. The laser beam output from the laser unit 114 irradiates and exposes the photosensitive drum 110, and at the same time, the light emission state is detected by the beam detection sensor 212 in the non-image area, and the output signal is input to the I / O port 205. The high voltage controller 215 controls the high voltage applied to the photosensitive drum 110 by the pre-transfer charger 119.

FIG. 3 is a block diagram of the image processing unit 206 in the digital copying machine according to the present invention.

The image signal converted into an electric signal by the CCD unit 106 is first corrected for variations between pixels by a shading circuit 301,
In 02, data thinning processing is performed at the time of reduced copy, and data interpolation is performed at the time of enlarged copy. Next, in the filter circuit 303, for example, 2 × 5 × 5 windows
The next differentiation is performed to emphasize the edges of the image.

Since the image data is luminance data, the γ conversion circuit 304 performs data conversion by table search in order to convert the image data into density data to be output to a printer. The image data converted into the density data is input to the binarization processing unit 305. Here, multivalued data is converted to binary data by, for example, the ED method (error diffusion method). 2
The image data converted into the value is separated by the line separation unit 306 into a first odd line, a first even line, a second odd line, and a second even line.

The pixel shift correction unit 307 includes the line separation unit 3
The four types of image signals output from the unit 06 are synchronized with the four types of image signals by using a readout synchronization signal of image data whose optimum timing has been selected by the processing described later. Outputs as

FIG. 4 is an explanatory diagram showing in detail a pixel shift in the digital copying machine according to the present invention.

Reference numeral 401 denotes a main scanning synchronization signal for synchronizing the main scanning. In this embodiment, the portion indicated by 402 is generated by the exposure laser on the first even line. The image signal 403 is the main scanning synchronization signal 40
1 and the portion indicated by 404 is image data for one pixel. Now, assuming that an image is formed using the image signal 403 with respect to the four exposure lasers in the laser unit 114, four exposure lasers (for the first even line, the first odd line, and the second even line) are formed. (For the line and for the second odd-numbered line), there is a physical displacement, so that the formed image has a displacement in the main scanning direction.

That is, the vertical line 408 on the photosensitive drum becomes a straight line having a width of one pixel extending in the sub-scanning direction unless there is physical displacement, but the first odd-numbered line of pixels 412 has the first line.
The pixel shift of the amount indicated by 405 occurs with respect to the pixel 411 of the even line, the pixel 413 of the second even line has the pixel shift of amount 406 with respect to the pixel 411 of the first even line, and the second odd number The pixel 414 on the line has a pixel shift amount of 407 from the pixel 411 on the first even-numbered line.

Hereinafter, a method of correcting a print position shift in a digital copying machine according to the present invention will be described in detail with reference to FIGS. 5, 6, and 7.

FIG. 5 is a block diagram for explaining a method of detecting a pixel shift (print position shift in the main scanning direction) and a method of correcting the print position shift.

In FIG. 5, a beam detection sensor 212 is a well-known optical sensor, and is arranged so that a plurality of light beams (laser beams) output from the laser unit 114 can be detected at predetermined positions in the main scanning direction. Is done.
The CPU 201 controls the lighting of a plurality of lasers in the laser unit 114 for pixels at the same position in the main scanning direction as described below, and at this time, the light beams output from each laser are detected by the beam detection sensor 212, Timer 5
00 measures a time interval based on the detection output as described later, and further, the CPU 201 calculates the measurement result to generate displacement data as described later.

First, of the four exposure lasers, control is performed so that only the first even-line exposure laser is turned on.
The output from the beam detection sensor 212 (sensor output 1) is as shown in FIG. Portions 611 and 612 are portions where the beam detection sensor 212 has detected a beam from the first even-line exposure laser.
The sensor output 1 of the beam detection sensor 212 is a timer 500
The main scanning period T1 when only the first even-line exposure laser is turned on is measured in accordance with the intervals 611 and 612.

Next, as shown in FIG. 6B, first, only the first even-line exposure laser is turned on, and after the beam detection sensor 212 detects the beam indicated by 611, the first even-line exposure is performed. Is controlled so that the first laser for exposing the first odd-numbered line is turned on. At this time, the beam detection sensor 212 detects a beam from the first odd line exposure laser as indicated by 622.
In the sensor output 2 from the beam detection sensor 212,
The portion indicated by 611 is a detection signal by the first even line exposure laser, and the portion indicated by 622 is by the first odd line exposure laser.

The sensor output 2 is also input to the timer 500, and the main scanning period T2 is measured according to the intervals 611 and 622. The portion indicated by 622 has a phase shift of t1 with respect to the portion indicated by 612.

Similarly, as shown in FIG. 6C, first, only the first even-line exposure laser is turned on, the beam detection sensor 212 detects the beam indicated by 611, and then the first even-line exposure is performed. Is controlled so that the laser for exposing is turned off and the laser for exposing the second even-numbered line is turned on. At this time, the beam detection sensor 212 detects the beam from the second even-line exposure laser as indicated by 632.
In the sensor output 3 from the beam detection sensor 212,
A portion 611 is a detection signal by the first even-line exposure laser, and a portion 632 is a detection signal by the second even-line exposure laser.

The sensor output 3 is also input to the timer 500, and the main scanning period T3 is measured according to the intervals 611 and 632. The portion indicated by 632 has a phase shift of t2 with respect to the portion indicated by 612.

Similarly, as shown in FIG. 6D, first, only the first even-line exposure laser is turned on, and after the beam detection sensor 212 detects the beam indicated by 611, the first even-line exposure is performed. Is controlled so that the laser for exposing is turned off and the laser for exposing the second odd-numbered line is turned on. At this time, the beam detection sensor 212 detects the beam from the second odd line exposure laser as indicated by 642.
In the sensor output 4 from the beam detection sensor 212,
The portion indicated by 611 is a detection signal by the first even line exposure laser, and the portion indicated by 642 is by the second odd line exposure laser.

The sensor output 4 is also input to the timer 500, and the main scanning period T4 is measured according to the intervals 611 and 642. The portion indicated by 642 has a phase shift of t3 with respect to the portion indicated by 612.

The CPU 201 controls each of the main scanning periods T1, T
From 2, T3, and T4, the shift amount of each of the remaining exposure lasers with respect to the first even-line exposure laser is calculated. For example, the phase shift t1 between the first even-line exposure laser and the first odd-line exposure laser is calculated from T1−T2 = t1. Similarly, a phase shift t2 (= T1−T2) between the first even-line exposure laser and the second even-line exposure laser
3) and a phase shift t3 (= T1-T4) between the first even-line exposure laser and the second odd-line exposure laser is calculated.

FIG. 7 is a timing chart showing in detail the image data reading synchronization signal generated by the pixel shift correcting section 307 in the digital copying machine according to the present invention.

The pixel shift correcting section 307 delays the basic image data read synchronizing signal SSy shown in FIG. 7A and the basic image data read synchronizing signal SSy by a quarter period, as shown in FIGS. The four types of read synchronizing signals FSy1, FSy2, FSy3, and FSy4 shown in FIG. 7E and the basic image data read synchronizing signal SSy are advanced by a quarter period, respectively, as shown in FIGS. 7F to 7I. Read synchronizing signals DSy1, DSy2, DSy3, DSy4
Has been generated.

Here, in FIG. 7, the arrows attached to the rising edges of the respective synchronizing signals indicate the image data reading start timings by the respective image data reading synchronizing signals SSy, FSy1 to 4 and DSy1 to 4. The image data of the first even-line exposure laser is read out in synchronization with the basic image read-out synchronization signal SSy.

The CPU 201 is generated in the pixel shift correction unit 307 from the phase shifts t1, t2, and t3 of each exposure laser with respect to the first even line exposure laser calculated by the method described with reference to FIG. Of the image data reading synchronization signals SSy, DSy1 to 4 and FSy1 to 4 which are most suitable for the correction. The pixel shift correction unit 307 outputs a synchronization signal of the selected optimal timing to the CPU.
When instructed by 201, the image signals of the respective exposure lasers are synchronized with the optimum synchronization signal, and the synchronized image signals are output to the laser unit 114.

The four semiconductor lasers in the laser unit 114, which have physically different irradiation positions, are driven by these phase-corrected image signals. Therefore, according to the present embodiment, a print position shift between a plurality of exposure lasers with respect to a pixel at the same position in the main scanning direction is easily corrected without requiring a complicated and high-precision mechanical mechanism. Can be improved.

[0051]

As described above, according to the present invention, there is provided an image forming apparatus provided with a plurality of exposure light sources, an image processing apparatus provided with the image forming apparatus, and a method of correcting a printing position shift of the image forming apparatus. For example, it is possible to easily and optimally correct the printing position shift between the respective light sources for exposure without requiring a complicated and high-precision mechanism, so that it is not necessary to perform a difficult adjustment for performing the correction, and the cost of the apparatus is increased. There is an effect that it does not come.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a digital copying machine to which the present invention can be applied.

FIG. 2 is a block diagram showing a configuration of a controller unit in the digital copying machine according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of an image processing unit in the digital copying machine according to the present invention.

FIG. 4 is an explanatory diagram illustrating a pixel shift in the digital copying machine according to the present invention.

FIG. 5 is a block diagram for explaining a pixel shift detecting method and a print position shift correcting method in the digital copying machine according to the present invention.

FIG. 6 is a timing chart for explaining generation of scanning direction shift data used for correcting a print position shift in the digital copying machine according to the present invention, and illustrates a beam detection output.

FIG. 7 is a timing chart showing an image data reading synchronization signal generated by a pixel shift correction unit in the digital copying machine according to the present invention.

[Explanation of symbols]

 114 Laser unit 201 CPU 202 Bus driver / address decoder circuit 205 I / O port 212 Beam detection sensor 307 Pixel shift correction unit 500 Timer

Claims (10)

[Claims] 1. An image forming apparatus for forming an image based on a latent image obtained by exposing a rotating photosensitive member in a main scanning direction by using a plurality of light sources, wherein said image forming apparatus includes: Displacement data generating means for generating displacement data representing displacement in the main scanning direction of the latent image formed on the rotating photoreceptor by a plurality of light sources; and synchronization for generating a plurality of read synchronization signals having different timings. Generating means, based on the displacement data, the rotationally-sensitive light using an image signal synchronized with an optimal synchronization signal for correcting the displacement in the main scanning direction due to each light source among the plurality of readout synchronization signals. An image forming apparatus comprising: a correcting unit configured to correct the positional deviation in the main scanning direction by exposing a body. 2. The apparatus according to claim 1, wherein the shift data generating means includes: detecting means for detecting exposure by the plurality of light sources at a predetermined position in the main scanning direction; and measuring time based on a detection output of the detecting means. Timer means, a lighting control means for controlling lighting of the plurality of light sources for pixels at the same position in the main scanning direction, and calculating a measurement result of the timer means when the lighting control is performed. An image forming apparatus comprising: a calculation unit configured to generate the displacement data. 3. The apparatus according to claim 2, wherein the timer means includes an interval of the detection output when a predetermined light source is turned on by the lighting control means, and the plurality of light sources by the lighting control means. Measuring another interval of the detection output when the other light source is turned on after turning on the predetermined light source, and wherein the calculating means obtains a difference between the interval and the another interval. Image forming device. 4. The synchronization generating means according to claim 1, wherein the synchronization generating means includes: a reference synchronization signal at a predetermined timing; and a plurality of synchronization signals phase-shifted by a phase corresponding to the number of the plurality of light sources with respect to the reference synchronization signal. An image forming apparatus characterized by generating. 5. The image according to claim 1, wherein the correction unit selects the optimal synchronization signal, and outputs the image signal to each of the light sources in synchronization with the selected synchronization signal. Forming equipment. 6. An image processing apparatus comprising: the image forming apparatus according to claim 1; and an image reading unit that generates an image signal to be provided to the image forming apparatus. 7. A print position shift correction method for an image forming apparatus for forming an image based on a latent image obtained by exposing a rotating photosensitive member in a main scanning direction using a plurality of light sources, wherein the same position in the main scanning direction is provided. Generating position shift data representing a position shift in the main scanning direction of the latent image formed on the rotating photoconductor by the plurality of light sources with respect to the pixels, and a plurality of read synchronization signals having different timings Based on the displacement data, the rotating photoconductor is rotated using an image signal synchronized with an optimal synchronization signal for correcting the displacement in the main scanning direction due to each light source among the plurality of readout synchronization signals. A correcting step of correcting the positional shift in the main scanning direction by exposing the print medium. 8. The method according to claim 7, wherein in the generating step, lighting of the plurality of light sources is controlled for pixels at the same position in the main scanning direction, and the plurality of light sources are controlled at predetermined positions in the main scanning direction. Exposure was detected by the detecting means, and an output interval of the detecting means when the predetermined light source among the plurality of light sources was turned on and the other light source was turned on after turning on the predetermined light source among the plurality of light sources. And measuring another interval of the output of said detecting means at the time, and calculating a difference between said interval and said another interval. 9. The method according to claim 7, wherein in the generating step, a reference synchronization signal at a predetermined timing and a plurality of synchronization signals phase-shifted by a phase corresponding to the number of the plurality of light sources with respect to the reference synchronization signal are generated. A print position deviation correcting method. 10. The printing method according to claim 7, wherein in the correcting step, the optimum synchronization signal is selected, and the image signal is output to the light sources in synchronization with the selected synchronization signal. Position shift correction method.