JP2022067671A - Image formation apparatus - Google Patents

Abstract

To provide an image formation apparatus which can reduce the occurrence of an irregular pitch by correcting the inclination for each light source at a main-scanning position.SOLUTION: An image formation apparatus comprises: an image formation unit 10 which forms an image by scanning a plurality of light beams emitted from a plurality of light sources according to image data in the main-scanning direction in an image carrier (photoreceptor 200); a modulation unit (control unit 20) which applies frequency modulation to each light source according to a main scanning interval at the plurality of main-scanning positions of the plurality of light beams; and a control unit 20 which causes the plurality of light sources to emit light on the basis of the modulation result by the modulation unit.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus.

Conventionally, an image forming apparatus such as a laser printer or a digital copying machine is equipped with an image writing unit that scans a photoconductor using a semiconductor laser emitted from a light source.

In the above image forming apparatus, a phenomenon that the forming position of the image formed on the photoconductor may shift may occur.
Therefore, a configuration for correcting a partial magnification shift caused by polygon jitter is disclosed (see, for example, Patent Document 1).
Further, a configuration for correcting a partial magnification shift caused by the characteristics of the fθ lens is disclosed (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2012-226501 Japanese Unexamined Patent Publication No. 2004-338336.

By the way, in recent years, in an image forming apparatus, high-speed and high-density image recording is required, and a plurality of lines of images are written on a photoconductor by one scan using laser beams emitted from a plurality of light sources. Image formation is performed in the above image formation, and one page of image formation is performed by repeating the above image formation in the sub-scanning direction. In a configuration using a plurality of light sources, the inclination (main scanning interval) of each light source at the main scanning position on the photoconductor changes. As a result, the main scanning magnification changes for each light source, so that pitch unevenness occurs in the output image.
However, the configurations described in Patent Documents 1 and 2 are all configured to correct the partial magnification deviation generated by a mechanism other than the light source, and do not take into consideration the partial magnification deviation generated for each light source.
It is also conceivable to correct the inclination of each light source by correcting the main scanning beam pitch (main pitch) by shifting the light emission timing of each light source. In this case, the main scanning beam pitch is measured using a photodiode to determine the light emission timing. However, since the inclination of each light source at the main scanning position changes depending on the lens accuracy and mechanical adjustment accuracy of the fθ lens, the effect of the main pitch correction is lost, and as a result, there is a problem that pitch unevenness occurs in the output image.

An object of the present invention is to provide an image forming apparatus capable of correcting the inclination of each light source at the main scanning position to reduce the occurrence of pitch unevenness.

The invention according to claim 1 has been made in order to achieve the above object.
In the image forming apparatus
An image forming unit that forms an image by scanning a plurality of light rays emitted from a plurality of light sources according to image data in the main scanning direction on the image carrier.
A modulation unit that applies frequency modulation to each of the light sources according to the main scan interval at a plurality of main scan positions of the plurality of rays.
A control unit that emits light from the plurality of light sources based on the modulation result of the modulation unit, and
It is characterized by having.

The invention according to claim 2 is the image forming apparatus according to claim 1.
Provided is a storage unit that stores the main scanning interval at the main scanning positions of the plurality of light rays measured by the measuring unit arranged so as to correspond to the plurality of main scanning positions in the production process or the frequency modulation rate of each light source. It is characterized by.

The invention according to claim 3 is the image forming apparatus according to claim 2.
The modulation unit calculates the frequency modulation rate of each light source based on the main scanning interval stored in the storage unit, and applies frequency modulation to each light source based on the calculated frequency modulation rate of each light source. It is characterized by that.

The invention according to claim 4 is the image forming apparatus according to claim 2 or 3.
The measuring unit is characterized by being a camera or a sensor.

The invention according to claim 5 is the image forming apparatus according to claim 4.
In the measuring unit, a plurality of cameras or sensors are fixedly arranged so as to correspond to the plurality of main scanning positions, or one camera or sensor is movably arranged to move to the plurality of main scanning positions. It is characterized by that.

The invention according to claim 6 is the image forming apparatus according to any one of claims 1 to 5.
The modulation unit calculates the frequency modulation rate of each light source based on the approximate straight line of the main scan interval at the plurality of main scan positions, and frequency-modulates each light source based on the calculated frequency modulation rate of each light source. It is characterized by applying.

According to the present invention, it is possible to correct the inclination of each light source at the main scanning position and reduce the occurrence of pitch unevenness.

It is a figure which shows the schematic structure of the image forming apparatus which concerns on this embodiment. It is a functional block diagram which shows the control structure of the image forming apparatus which concerns on this embodiment. It is a figure which shows the schematic structure of the image writing part. It is a figure which shows an example of the light emission timing of each light source in the case of printing a straight line at three places of the front edge, the center, and the rear edge of a paper in the main scanning direction. It is a figure which shows an example of how the printing position gradually shifts in the case which prints a straight line at three places of the front edge, the center, and the rear edge of a paper in the main scanning direction. It is a figure which shows an example of the structure which measures the inclination of each light source at a plurality of main scanning positions using a CCD camera. It is a figure which shows an example of the structure which measures the inclination of each light source at a plurality of main scanning positions using a photodiode. It is a figure which shows an example of the light-receiving timing in each photodiode when measuring the inclination of each light source in the configuration of FIG. 7.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The image forming apparatus 1000 according to the present embodiment is used as, for example, a laser printer, a digital copying machine, or the like, and as shown in FIGS. 1 and 2, an image forming unit 10, a control unit 20, a storage unit 30, and the like are used. Is configured with.

The image forming unit 10 includes a plurality of image writing units 100 provided for each of the colors cyan, magenta, yellow, and black, and a photoconductor (image) such as a photoconductor drum provided corresponding to the image writing unit 100. The carrier) 200, the charging unit 210 that charges the photoconductor 200, and the developing unit 220 that visualizes an electrostatic latent image into an image by the developing agent by supplying a developing agent to the photoconductor 200 irradiated with light. An intermediate transfer belt 300, a transfer roller 400 that transfers an image of a developer onto the paper P, and a fixing portion 500 that fixes an image of the developer transferred by the transfer roller 400 to the paper P. To.

The image forming unit 10 forms an image by irradiating (scanning) a plurality of laser beams (light rays) emitted from a plurality of light sources 1 (see FIG. 3) in the photoconductor 200 in the main scanning direction according to the image data. do. Specifically, first, the image forming unit 10 forms a toner image with the photoconductor 200 exposed to the laser light emitted from the image writing unit 100, and transfers the toner image onto the intermediate transfer belt 300. .. Next, the image forming unit 10 presses the toner image transferred to the intermediate transfer belt 300 against the paper P by the transfer roller 400 to transfer the toner image, and heats and pressurizes the paper P by the fixing unit 500 to obtain the toner image. Is fixed on the paper P. Then, the image forming unit 10 performs an image forming process by transporting the paper P by a paper ejection roller (not shown) or the like and ejecting the paper to a tray (not shown).

As shown in FIG. 3, the image writing unit 100 irradiates the photoconductor 200 charged by the charging unit 210 with the laser beam L to expose the photoconductor 200 (electrostatic latency on the photoconductor 200). Form an image). The image writing unit 100 causes a light source 1 that emits a laser beam L, a deflector 2 that deflects the laser beam L emitted from the light source 1, and a laser beam L deflected by the deflector 2 onto the photoconductor 200. The fθ lens 3 for condensing, the reflection mirror 4 that reflects the laser light L transmitted through the fθ lens 3 toward the photoconductor 200, and the synchronization detection mirror that reflects a part of the laser light L deflected by the deflector 2. 5 and a light receiving element 6 that receives the laser light L reflected by the synchronization detection mirror 5 are provided.

The light source 1 is a laser diode (LD) that emits a laser beam L. The laser beam L emitted from the light source 1 is applied to the deflector 2.

The deflector 2 includes a polygon mirror having a polygonal prism shape whose side surface is a mirror surface, and a motor that applies rotational power to the polygon mirror to rotate the polygon mirror. The deflector 2 deflects the laser beam L emitted from the light source 1 in a direction corresponding to rotation. Then, the deflector 2 irradiates the peripheral surface of the photoconductor 200 with the deflected laser beam L via the fθ lens 3. At this time, since the deflector 2 irradiates the laser beam L at different positions in the longitudinal direction of the photoconductor 200 according to the rotation position, the laser beam L in the main scanning direction (longitudinal direction of the photoconductor 200 in FIG. 3). Allows scanning of.

The fθ lens 3 focuses the laser beam L deflected by the deflector 2 on the photoconductor 200 and forms an image.
The reflection mirror 4 reflects the laser beam L transmitted through the fθ lens 3 toward the photoconductor 200.

The synchronization detection mirror 5 reflects a part of the laser beam L deflected by the deflector 2 and transmitted through the fθ lens 3, and the reflected laser beam L is incident on the light receiving element 6.
The light receiving element 6 is an optical sensor that detects the laser beam L reflected by the synchronization detection mirror 5. Then, the control unit 20 of the image forming apparatus 1000 provided with the image writing unit 100 adjusts the timing of the writing position to the photoconductor 200 based on the detection signal detected by the light receiving element 6.

The control unit 20 includes a CPU, RAM, and the like. The CPU reads out various processing programs stored in the storage device such as the storage unit 30 and expands them in the RAM, and centrally controls the operation of each unit of the image forming apparatus 1000 according to the expanded program.
For example, the control unit 20 applies frequency modulation to each light source 1 according to the main scanning interval (inclination) at a plurality of main scanning positions of the plurality of light rays. That is, the control unit 20 functions as the modulation unit of the present invention.
Further, the control unit 20 causes a plurality of light sources 1 to emit light based on the modulation result.

The storage unit 30 stores a program that can be read by the control unit 20, a file used when the program is executed, and the like. As the storage unit 30, a large-capacity memory such as a hard disk can be used.

In this embodiment, as shown in FIG. 4A, four light sources 1 (LD1 to LD4) are arranged at equal intervals in the main scanning direction. For example, as shown in FIG. 4 (B), when printing straight lines at three locations of the front end, the center, and the rear end of the paper P in the main scanning direction, the light emission timings are as shown in FIG. 4 (A). The light emission of the light sources 1 (LD1 to LD4) is repeatedly controlled in the sub-scanning direction. In the example shown in FIG. 4A, light emission is controlled in order from the light source 1 on the rear end side in the main scanning direction (that is, in the order of LD4 → LD3 → LD2 → LD1). The reference numeral X2 in the figure indicates the distance between the light sources 1 adjacent to each other in the main scanning direction, and indicates the light emission time of each light source 1. That is, each light source 1 is controlled to emit light (scan) for a time corresponding to the distance between adjacent light sources 1. Further, the reference numeral X1 in the drawing indicates the distance between the light source 1 (LD1) on the front end side in the main scanning direction and the light source 1 (LD4) on the rear end side in the main scanning direction, and also indicates the distance between the light source 1 (LD4) on the rear end side in the main scanning direction. It shows the time difference between the timing when the light source 1 (LD4) of the above starts light emission and the timing when the light source 1 (LD1) on the tip side in the main scanning direction starts light emission.

In the configuration of the image forming apparatus 1000 according to the present embodiment, the inclination of each light source 1 at the main scanning position changes depending on the lens accuracy and mechanical adjustment accuracy of the fθ lens, so that the front end, the center, and the rear end of the paper P in the main scanning direction are changed. In the case where a straight line is printed at three locations, as shown in FIG. 5, even if the straight line is printed at the tip, the printing position may shift at the center or the rear end and the straight line may not be printed.
Therefore, in the present embodiment, in order to suppress the occurrence of pitch unevenness as described above, the inclination (main scanning interval) of each light source 1 at a plurality of main scanning positions is measured in the production process, and the measured inclination (main scanning interval) is measured. Frequency modulation is applied to each light source 1 according to the above (the frequency modulation rate of each light source 1 is changed), and a plurality of light sources 1 are made to emit light based on the modulation result.

As an example of the method of measuring the inclination (main scanning interval) of each light source 1 at a plurality of main scanning positions in the production process, a method using a camera (CCD camera) can be mentioned. The CCD camera (camera) functions as the measuring unit of the present invention.
Specifically, as shown in FIG. 6, a plurality of CCD cameras 40 are fixedly arranged so as to correspond to the front end, center, and rear end positions in the main scanning direction when viewed from the image writing unit 100, and each main camera 40 is fixedly arranged. The inclination (main scanning interval) of each light source 1 at the scanning position is measured.

Further, as another example, a method using a sensor (photodiode) can be mentioned.
Specifically, as shown in FIG. 7, a plurality of sensor substrates 50 are fixedly arranged so as to correspond to the positions of the front end, the center, and the rear end in the main scanning direction when viewed from the image writing unit 100, and each main is fixedly arranged. The inclination (main scanning interval) of each light source 1 at the scanning position is measured. Each sensor substrate 50 is provided with a pair of photodiodes PD1 and PD2. The photodiodes (sensors) PD1 and PD2 function as the measuring unit of the present invention.
Here, the light emitted from the light source 1 (LD4) on the rear end side in the main scanning direction is incident on the photodiode PD1 on the front end side in the main scanning direction until it is incident on the photodiode PD2 on the rear end side in the main scanning direction. The time is A (see FIG. 8A), and after the light emitted from the light source 1 (LD4) on the rear end side in the main scanning direction is incident on the photodiode PD1 on the front end side in the main scanning direction, it is on the front end side in the main scanning direction. When the time until the light emitted from the light source 1 (LD1) is incident on the photodiode PD2 on the rear end side in the main scanning direction is B (see FIG. 8B), the inclination between LD1 and LD4 (main scanning). Interval) X1 can be calculated using the following equation (1). Further, the slope (main scanning interval) X2 between adjacent LDs can be calculated using the following equation (2).
X1 = BA ... (1)
X2 = X1 / 3 ... (2)

The main scanning intervals at the main scanning positions of the plurality of rays measured by the measuring unit (CCD camera 40 or photodiodes PD1 and PD2) in the production process are stored in the storage unit 30.
When the main scanning interval is stored in the storage unit 30, the control unit 20 calculates the frequency modulation rate of each light source 1 based on the main scanning interval stored in the storage unit 30, and each of the calculated light sources. Frequency modulation is applied to each light source 1 based on the frequency modulation factor of 1.

In the present embodiment, the main scanning interval of each light source 1 is measured at a plurality of main scanning positions (tip, center, and rear end positions in the main scanning direction) by a measuring unit (CCD camera 40 or photodiodes PD1 and PD2). After that, the control unit 20 calculates the frequency modulation factor of each light source 1 based on the approximate straight line of the main scan interval at the plurality of measured main scan positions, and each light source is based on the calculated frequency modulation factor of each light source. Frequency modulation is applied to 1.
As a result, the frequency modulation factor can be calculated without measuring the information at many main scanning positions, so that the cost and time required for the measurement can be reduced.

As described above, the image forming apparatus 1000 according to the present embodiment scans a plurality of light rays emitted from the plurality of light sources 1 according to the image data in the image carrier (photoreceptor 200) in the main scanning direction. The image forming unit 10 that forms an image, the modulation unit (control unit 20) that performs frequency modulation on each light source 1 according to the main scanning intervals at the plurality of main scanning positions of the plurality of rays, and the modulation result by the modulation unit. A control unit 20 for emitting a plurality of light sources 1 based on the above is provided.
Therefore, according to the image forming apparatus 1000 according to the present embodiment, the inclination of each light source 1 at the main scanning position can be corrected, so that the occurrence of pitch unevenness can be reduced.

Further, the image forming apparatus 1000 according to the present embodiment is a plurality of light rays measured by a measuring unit (CCD camera 40 or photodiodes PD1 and PD2) arranged so as to correspond to a plurality of main scanning positions in a production process. A storage unit 30 for storing the main scan interval at the main scan position is provided.
Therefore, according to the image forming apparatus 1000 according to the present embodiment, information for correcting the inclination of each light source 1 can be acquired and stored in advance, so that the inclination of each light source 1 can be easily corrected. be able to.

Further, according to the image forming apparatus 1000 according to the present embodiment, the modulation unit calculates the frequency modulation rate of each light source 1 based on the main scanning interval stored in the storage unit 30, and the calculated light source 1 of each light source 1. Frequency modulation is applied to each light source 1 based on the frequency modulation factor.
Therefore, according to the image forming apparatus 1000 according to the present embodiment, the inclination of each light source 1 can be easily corrected, so that the occurrence of pitch unevenness can be easily reduced.

Further, according to the image forming apparatus 1000 according to the present embodiment, the measuring unit is a camera (CCD camera 40) or a sensor (photodiodes PD1 and PD2).
Therefore, according to the image forming apparatus 1000 according to the present embodiment, it is possible to acquire information for correcting the inclination of each light source 1 with a simple configuration, so that the inclination of each light source 1 can be easily corrected. can.

Further, according to the image forming apparatus 1000 according to the present embodiment, the measuring unit is fixedly arranged so that a plurality of cameras or sensors correspond to a plurality of main scanning positions.
Therefore, according to the image forming apparatus 1000 according to the present embodiment, it is possible to sufficiently secure the measurement accuracy of the main scanning intervals of the plurality of light rays, so that the inclination of each light source 1 can be corrected with high accuracy.

Further, according to the image forming apparatus 1000 according to the present embodiment, the modulation unit calculates the frequency modulation factor of each light source 1 based on the approximate straight lines of the main scanning intervals at the plurality of main scanning positions, and the calculated light sources. Frequency modulation is applied to each light source 1 based on the frequency modulation rate of.
Therefore, according to the image forming apparatus 1000 according to the present embodiment, the frequency modulation factor can be calculated without measuring the information at many main scanning positions, so that the cost and time required for the measurement can be reduced. can.

Although the present invention has been specifically described above based on the embodiment of the present invention, the present invention is not limited to the above embodiment and can be changed without departing from the gist thereof.

For example, in the above embodiment, the measuring unit (CCD camera 40 or photodiodes PD1 and PD2) measures the main scanning intervals at the main scanning positions of a plurality of rays and stores them in the storage unit 30. Not limited. For example, instead of the main scanning interval, the frequency modulation factor of each light source 1 may be stored in the storage unit 30. In this case, the control unit 20 may calculate the frequency modulation factor of each light source 1 based on the main scanning interval measured by the measurement unit, and store the calculated frequency modulation factor in the storage unit 30.

Further, in the above embodiment, a configuration in which a plurality of cameras (CCD camera 40) or sensors (sensor substrates 50 (photodiodes PD1, PD2)) are fixedly arranged so as to correspond to a plurality of main scanning positions is exemplified. Although explained, it is not limited to this. For example, one camera (CCD camera 40) or a sensor (sensor substrate 50 (photodiodes PD1, PD2)) may be movably arranged at a plurality of main scanning positions.
However, in the case of a configuration in which one camera (CCD camera 40) or a sensor (sensor substrate 50 (photodiodes PD1, PD2)) is movably arranged at a plurality of main scanning positions, it is necessary to move the sensor to the measurement position with high accuracy. .. Therefore, a configuration in which a plurality of cameras (CCD camera 40) or sensors (sensor substrates 50 (photodiodes PD1, PD2)) are fixedly arranged so as to correspond to a plurality of main scanning positions is better in terms of ensuring measurement accuracy. It is more preferable because it is advantageous.

Further, in the above embodiment, the main scanning interval for each light source 1 is measured at three locations, that is, the front end, the center, and the rear end in the main scanning direction of the paper, but the present invention is not limited to this. Since the frequency modulation factor of each light source 1 can be calculated from the approximate straight line as long as it is measured at at least two points, any configuration may be used as long as it is configured to measure at least two points. However, it is more preferable that the number of measurement points is large because the measurement accuracy can be improved as the number of measurement points is increased.
It should be noted that each measurement point may be arranged at any interval as long as the distance between adjacent measurement points is known, and it is not always necessary to arrange them at equal intervals.

Further, in the above embodiment, the configuration using the four light sources 1 (LD1 to LD4) is illustrated and described, but the present invention is not limited thereto. Any configuration may be used as long as it uses at least two or more light sources 1. For example, a configuration using two light sources 1 or a configuration using eight light sources 1 may be used.

In addition, the detailed configuration of each device constituting the image forming apparatus and the detailed operation of each device can be appropriately changed without departing from the spirit of the present invention.

1000 Image forming device 10 Image forming unit 100 Image writing unit 1 Light source 2 Deflection device 3 fθ lens 4 Reflective mirror 5 Synchronous detection mirror 6 Light receiving element 200 Photoreceptor (image carrier)
210 Charging unit 220 Developing unit 300 Intermediate transfer belt 400 Transfer roller 500 Fixing unit 20 Control unit (modulation unit)
30 Storage unit 40 CCD camera (Measurement unit: Camera)
50 Sensor board PD1, PD2 photodiode (measurement unit: sensor)
L Laser light (ray)

Claims (6)

An image forming unit that forms an image by scanning a plurality of light rays emitted from a plurality of light sources according to image data in the main scanning direction on the image carrier.
A modulation unit that applies frequency modulation to each of the light sources according to the main scan interval at a plurality of main scan positions of the plurality of rays.
A control unit that emits light from the plurality of light sources based on the modulation result of the modulation unit, and
An image forming apparatus comprising. Provided is a storage unit that stores the main scanning interval at the main scanning positions of the plurality of light rays measured by the measuring unit arranged so as to correspond to the plurality of main scanning positions in the production process or the frequency modulation rate of each light source. The image forming apparatus according to claim 1. The modulation unit calculates the frequency modulation rate of each light source based on the main scanning interval stored in the storage unit, and applies frequency modulation to each light source based on the calculated frequency modulation rate of each light source. The image forming apparatus according to claim 2, wherein the image forming apparatus is characterized in that. The image forming apparatus according to claim 2 or 3, wherein the measuring unit is a camera or a sensor. In the measuring unit, a plurality of cameras or sensors are fixedly arranged so as to correspond to the plurality of main scanning positions, or one camera or sensor is movably arranged to move to the plurality of main scanning positions. The image forming apparatus according to claim 4. The modulation unit calculates the frequency modulation rate of each light source based on the approximate straight line of the main scan interval at the plurality of main scan positions, and frequency-modulates each light source based on the calculated frequency modulation rate of each light source. The image forming apparatus according to any one of claims 1 to 5, wherein the image forming apparatus is applied.

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