JP4541940B2 - Image forming apparatus, light beam position correcting method and program - Google Patents

Description

  The present invention relates to an image forming apparatus such as a digital copying machine or a printer, a beam position correcting method and a program used in the image forming apparatus.

  In an electrophotographic image forming apparatus using a so-called negative / positive process method in which an electrostatic latent image is formed by irradiating a laser beam on a photosensitive member, and this is developed with toner to form an image. In general, a multi-beam scanning method in which a photosensitive member is scanned with two or more light beams is used for the purpose of increasing the density and the writing speed (see, for example, Patent Document 1).

Also, laser light detection means are provided on the write start side and end side, the passing time between the two points is measured by the count number of a predetermined clock, and the write clock frequency is matched with the initially stored reference count number Has been proposed (see, for example, Patent Document 2). In Patent Document 2, two beam detection sensors are provided, and the passing time interval of each sensor is measured by counting with a pixel clock, and writing is performed so that the count value and a preset reference count value coincide with each other. The image frequency is changed and the magnification (absolute magnification) is corrected.
JP 2002-137450 A Japanese Patent No. 3548210

When two or more light beams are emitted from independent laser light sources, if the oscillation wavelength of each laser light source is different, a transmissive optical element (such as a lens) that exists in the optical path from the light source to the photoconductor Due to the wavelength dependency of the refractive index, there is a problem that the main scanning magnification differs for each beam emission light source. As in Patent Document 2, two beam detection sensors are provided, and the passage time interval of each sensor is measured by counting with a pixel clock, and the count value and a preset reference count value coincide with each other. Thus, if the method of changing the writing image frequency and correcting the magnification (absolute magnification) is applied to each laser light source, even if the oscillation wavelength differs for each light source, the main scanning magnification for each beam Can be matched. However, this method has a problem in that the configuration is complicated because it is necessary to provide beam detecting means and correcting means for each of the plurality of laser light sources.
Therefore, in the present invention, when the oscillation wavelength of each laser light source of two or more light beams is different and the main scanning magnification on the photosensitive member is different for each beam emission light source, the laser light detection means is provided for each light source. An object of the present invention is to enable correction of the main scanning magnification for each beam without providing it.

At the same time sensitive in a first aspect of the present invention, includes a first light source and the second light source, the first light beam from said first light source and the second light beam from said second light source by scanning the body, it said on the photoreceptor to an image forming device for forming a latent image, first made by the oblique line pattern by the horizontal line pattern by the first beam and the second beam Pattern forming means for forming a first pattern in the first pattern, and a second pattern composed of a horizontal line pattern by the second beam and an oblique line pattern by the first beam, and the first pattern in the first pattern A first interval that is an interval in a sub-scanning direction between a horizontal line pattern by the second beam and an oblique line pattern by the second beam, a horizontal line pattern by the second beam in the second pattern, and the first Beam by a second distance, which is the sub-scanning direction of the spacing between the oblique line pattern, a measuring means for measuring a predetermined position in the main scanning direction, wherein said measured first interval and the first predetermined the difference between the value, based on a difference between the measured second of said first predetermined value and interval, and having a an adjustment means for adjusting the main scanning magnification.

According to a second aspect of the present invention, in the apparatus according to the first aspect, the adjusting means determines a main scanning magnification based on a difference between the measured first interval and the measured second interval. It is characterized by adjusting.

According to a third aspect of the present invention, in the apparatus according to the first or second aspect, the adjustment of the main scanning magnification by the adjusting means is performed by changing the number of pixels necessary for the magnification adjustment among the pixels constituting the scanning line to one pixel. It is characterized by being performed by increasing or decreasing the width.

According to a fourth aspect of the present invention, in the apparatus according to any one of the first to third aspects, the main scanning magnification is adjusted by the adjusting means so that the temperature change near the light source becomes equal to or greater than a second predetermined value. It is characterized by being executed when

According to a fifth aspect of the present invention, in the apparatus according to any one of the first to fourth aspects, the measuring unit includes a light emitting unit that emits light, and light from the light emitting unit is predetermined on the photoconductor. A light receiving means for receiving the light reflected at the position, and the light receiving means also serves as a reflected light intensity detecting means for setting an image forming process condition of the image forming apparatus.

According to a sixth aspect of the present invention, a first light source and a second light source are provided, and the first light beam from the first light source and the second light beam from the second light source are simultaneously exposed. by scanning the body, said a light beam position correction method Ru used in the image forming device for forming a latent image on a photosensitive member, an oblique line according to the first and the second beam and the horizontal line pattern by the beam a first pattern composed of a pattern to form a second pattern constituted by the oblique line pattern by the horizontal line pattern first beam by the second beam, the first pattern A first interval which is an interval in a sub-scanning direction between a horizontal line pattern by the first beam and an oblique line pattern by the second beam, and a horizontal line pattern by the second beam in the second pattern A second distance, which is the sub-scanning direction of the spacing between the slanting line pattern by the first beam, was measured at a predetermined position in the main scanning direction, wherein said measured first interval and the first predetermined The main scanning magnification is adjusted based on a difference between the values and a difference between the measured second interval and the first predetermined value .

According to a seventh aspect of the present invention, a first light source and a second light source are provided, and the first light beam from the first light source and the second light beam from the second light source are simultaneously sensitized. by scanning the body, a program to be executed by a computer of an image forming device for forming a latent image on the photosensitive member, and the oblique line pattern by the horizontal line pattern by the first beam and the second beam a first pattern formed in a second pattern formation process for forming a second pattern constituted by the oblique line pattern by the horizontal line pattern first beam by the beam, the first A first interval which is an interval in a sub-scanning direction between a horizontal line pattern by the first beam and an oblique line pattern by the second beam in the pattern of the second pattern, and the second in the second pattern. A second distance, which is the sub-scanning direction of the spacing between the oblique line pattern by the horizontal line pattern and the first beam by the beam, a measurement process of measuring a predetermined position in the main scanning direction, the measured first intervals and the difference between the first predetermined value, said, the adjustment process and the difference, based on, to adjust the main scanning magnification of the measured second of said first predetermined value and interval A program to be executed by a computer of an image forming apparatus .

According to the first, second, sixth, and seventh inventions, the oscillation wavelength of each light source of two or more light beams is different, and the main scanning magnification on the photosensitive member is different for each beam emission light source. However, it is possible to correct the main scanning magnification for each beam without providing light detection means for measuring the passage time interval on the writing end side. In addition, according to the first, second, sixth, and seventh aspects of the present invention, it is possible to accurately detect the positional deviation of the light beam by drawing a simple pattern.

According to the third aspect of the present invention, the adjustment can be made in finer steps compared to the case where the main scanning magnification is adjusted by changing the write clock frequency.
According to the invention of claim 4 , even when the oscillation wavelength changes due to the temperature change of the light source and the main scanning magnification on the recording medium changes, the main scanning magnification for each beam can be corrected.

According to the invention of claim 5 , the main scanning magnification can be corrected without providing a dedicated detection means for setting the image forming process condition.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a block diagram showing a configuration of an image forming apparatus according to the first embodiment of the present invention. FIG. 1B is a configuration diagram around the photosensitive drum 12.
In FIG. 1A, two laser beams (beam 0, beam 1) emitted from two laser diodes LD0 and LD1 are scanned in a main scanning direction by a polygon mirror 10 that rotates at a constant speed, and passes through a lens 11. Thus, an image is formed on the surface of the photosensitive drum 12, and an electrostatic latent image is formed on the photosensitive drum 12. Thereafter, a transfer material on which an image has been transferred through a known image forming process by toner development, toner transfer unit 24 (FIG. 1B), and the like is output.

  The synchronization detector 13 includes a photoelectric conversion element and a signal waveform shaping circuit, detects the beams 0 and 1 from the LD0 and LD1, and sends a detection signal to the synchronization detection signal separation circuit 14. The synchronization detection signal separation circuit 14 separates the detection signal into the synchronization detection signals of LD0 and LD1, and sends them to the memory control circuit 15. The memory control circuit 15 reads the line memory 16 to which image data is input in synchronization with the synchronization detection signal, and outputs the image data to the PWM circuits 17 and 18 (CH0, CH1).

  Since the main scanning writing position is based on the synchronization detection signal, even if the oscillation wavelengths of LD0 and LD1 are different and the refraction angles at the lens 12 are different, they are hardly affected. The PWM circuits 17 and 18 send PWM signals to the LD drivers 19 and 20 (CH0 and CH1) based on the received image data. The PWM signal is output in synchronization with the video clock signal. The video clock signal can be set independently by LD0 and LD1. The LD drivers 19 and 20 supply the drive current to the LD0 and LD1 when receiving the “ON” signal of the PWM signal and the offset current when receiving the “OFF” signal. LD0 and LD1 output beams 0 and 1 according to on / off.

  In the present embodiment, the misalignment correction is performed by detecting the main scanning misalignment of the beams 0 and 1 output from the LD0 and LD1 on the photosensitive drum 12, and the pattern used in this correction control is used. FIG. 3 shows (1) and pattern (2). Each pattern is output at the main scanning writing end position on the photosensitive drum. In FIG. 3, the pattern (1) includes a horizontal line pattern 30 drawn by the beam from LD0 and an oblique line pattern 31 drawn by the beam from LD1 and having an inclination of 45 °. The pattern (2) includes an oblique line pattern 31 with an inclination of 45 ° drawn by the beam from LD0 and a horizontal line pattern 30 drawn by the beam from LD1. Both pattern (1) and pattern (2) are arranged so that the relative positions are the same when there is no deviation in the main scanning positions of the beams from LD0 and LD1.

  Returning to FIG. 1, after the toner is attached to the electrostatic latent image formed on the surface of the photosensitive drum by the beams 0 and 1 to be visualized, the reflected light intensity at the central scanning center of the pattern is detected by the pattern detection sensor 21. Read. The reflected light intensity varies depending on the presence or absence of toner, that is, the presence or absence of a pattern. The pattern detection sensor 21 includes a light emitting unit, an optical system that obtains a desired measurement aperture diameter on the surface of the photosensitive drum, a light receiving unit (photodiode), and an amplifying unit that amplifies the current output from the light receiving unit. The light receiving unit receives light reflected by the light emitting unit on the photosensitive drum. The output signal voltage corresponding to the light reception of the light receiving unit from the pattern detection sensor 21 is input to the comparator 22 and converted into a binary digital voltage value by comparing with the reference voltage.

  The aperture diameter of the pattern detection sensor 21 on the photosensitive drum surface is, for example, 100 μm. Since the photosensitive drum 12 rotates at a constant speed, the aperture of the pattern detection sensor 21 passes the pattern in the vertical direction. At this time, the output of the comparator 22 has an output waveform as shown on the right side of the patterns (1) and (2) in FIG. In this output waveform, the falling intervals T01 and T10 change according to the main scanning position shift caused by the difference in the oscillation wavelength of LD0 and LD1 on the photosensitive drum 12 of the beam. This is corrected by the control unit 23. Correction is performed by changing the main scanning magnification.

FIG. 2 is a flowchart showing the correction control process in the control unit 23.
In FIG. 2, a pattern (1) is first drawn (S1). Next, the falling interval T01 of the output waveform of the comparator 22 is measured by counting with a clock having a frequency eight times the video clock (S2).
When the oscillation wavelengths of LD0 and LD1 are different and the main scanning position of the pattern is shifted,
The falling interval of the comparator output waveform is
In pattern (1),
When the LD0 horizontal line pattern is shifted, the falling interval T01 of the comparator output waveform remains unchanged.
When the LD1 diagonal line pattern is shifted to the right, the falling interval T01 of the comparator output waveform increases.
When the LD1 diagonal line pattern is shifted to the left, the falling interval T01 of the comparator output waveform decreases.
In pattern (2),
When the LD1 horizontal line pattern is shifted, the falling interval T10 of the comparator output waveform remains unchanged.
When the LD0 diagonal line pattern is shifted to the right, the falling interval T10 of the comparator output waveform increases.
When the LD0 diagonal line pattern is shifted to the left, the falling interval T10 of the comparator output waveform decreases.
It becomes.

  Therefore, the falling intervals T01 and T10 are compared with appropriate values (S3) (S4), and the main scanning magnification is changed by changing the frequency of the video clock signal corresponding to each LD from the difference (S5) ( S6). The frequency of the video clock signal is changed by changing the ratio between the frequency division number and the multiplication number of the reference clock.

In FIG. 2, if T01 is larger than the appropriate value (S3, YES), the main scanning magnification of CH1 (LD1) is lowered (S5), and then the pattern (2) is drawn (S7). If T01 is smaller than the appropriate value (S4, YES), the main scanning magnification of CH1 is increased (S6), and then the pattern (2) is drawn (S7). After drawing the pattern (2) (S7), the falling interval T10 of the comparator output waveform is measured (S8). If T10 is larger than the appropriate value (S9, YES), the main scanning magnification of CH0 (LD0) is lowered (S10), and the process ends. If T10 is smaller than the appropriate value (S11, YES), the main scanning magnification of CH1 is lowered (S6), and the process ends.
In this way, it is possible to correct a main scanning position shift caused by a difference in oscillation wavelength between LD0 and LD1.

  Although the present embodiment has been described for the case where two light beams are scanned simultaneously, even when the number of beams is three or more, the present embodiment can be applied by increasing the number of combinations of detection patterns.

FIG. 4 is a flowchart showing another processing method of correction control.
First, the pattern (1) is drawn (S21), and the falling interval T01 is measured (S22). Next, a pattern (2) is drawn (S23), and the falling interval T10 is measured (S22). Then, T01 and T10 are compared (S25) (S26). If T01 is smaller than T10 (S25, YES), the CH1 main scanning magnification is lowered (S27), and the process ends. If T01 is larger than T10 (S26, YES), the main scanning magnification of CH1 is increased (S28), and the process ends.
According to the above, since the LD1 side is corrected on the basis of the main scanning position of LD0, the main scanning absolute magnification of the LD0 side deviates, but the main scanning position deviation between LD0 and LD1 can be corrected.

Next, a second embodiment of the present invention will be described.
In the present embodiment, in the image forming apparatus of the first embodiment, the PWM circuits 17 and 18 further set the write pulse period to 15/16 or 17/16 based on the pulse period increase / decrease signal from the write control circuit. It has a function.

  In the correction control in this case, first, the falling intervals T01 and T10 are compared with appropriate values, and the pulse period of the PWM signal transmitted to each LD is increased or decreased from the difference. The number of pulses whose period has been increased or decreased is inserted as many as necessary to change the main scanning magnification with respect to the length of one line. That is, in the correction control flow of FIG. 2, the main scanning magnification is changed by setting only the necessary number of pixels in one line as pixels with increased or decreased pulse periods. In other words, the main scanning magnification adjustment is performed by increasing or decreasing the width of one pixel among the pixels constituting the scanning line by increasing or decreasing the width of one pixel. Compared with the case of changing, it is possible to adjust in fine steps.

FIG. 3 shows a third embodiment of the present invention. The parts corresponding to those in FIG.
In the present embodiment, a temperature sensor 25 is further provided in the vicinity of the light source LD (LD0, LD1) in FIG. 1 according to the first embodiment. Since the oscillation wavelength of the LD changes with the temperature rise of the LD, the main scanning position deviation correction is performed when the temperature change near the light source becomes a predetermined value or more.

FIG. 6 is a flowchart showing the correction control process according to the present embodiment.
In FIG. 6, first, the initial temperature T0 detected by the temperature sensor 25 is acquired (S31). Thereafter, the detected temperature T is acquired every predetermined time (S32). Then, it is determined whether or not the absolute value of T-T0 is greater than 5 ° C. (S33), and if it is greater, main scanning position deviation correction is performed (S34). Then, the process returns to S32 with T0 as the latest T, and thereafter the same processing is repeated.

Next, a fourth embodiment of the present invention will be described.
In this embodiment, in the image forming apparatus of FIG. 1, the light receiving unit of the pattern detection sensor 21 for detecting the main scanning position deviation is used as a reflected light intensity sensor used for setting image forming process conditions (bias voltage, light amount). It is intended to be used for both purposes.
This eliminates the need to provide a dedicated reflection intensity detection sensor for setting image forming process conditions.

  Note that the program for the CPU of the control unit 23 to execute the processes shown in the flowcharts of the drawings constitutes a program according to the present invention. As a recording medium for recording the program, a semiconductor storage device, an optical and / or magnetic storage device, or the like can be used. By using such a program and recording medium in a system having a configuration different from that of each of the above-described embodiments and causing the CPU to execute the program, substantially the same effects as those of the present invention can be obtained.

1 is a block diagram illustrating an image forming apparatus according to a first embodiment of the present invention. It is a flowchart which shows a position shift correction control process. It is a block diagram explaining performing the positional deviation correction of a light beam using a horizontal line pattern and a diagonal line pattern, and these patterns. It is a flowchart which shows the other process of position shift correction control. It is a block diagram which shows the image forming apparatus by the 3rd Embodiment of this invention. It is a flowchart which shows the correction control process in the case of performing position shift correction by the temperature by 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Photosensitive drum 16 Line memory 17, 18 PWM circuit 19, 20 LD driver LD0, LD1 Laser light source 21 Pattern detection sensor 22 Comparator 23 Control part 25 Temperature sensor 30 Horizontal line pattern 31 Diagonal line pattern

Claims (7)

By a first and second light sources to scan the first light beam and second light beam simultaneously with the photoreceptor above in from the second light source from the first light source, an image forming device for forming a latent image on said photosensitive member,
A first pattern constituted by a horizontal line pattern by the first beam and an oblique line pattern by the second beam; a horizontal line pattern by the second beam; and an oblique line pattern by the first beam. A second pattern to be formed, pattern forming means for forming,
A first interval which is an interval in a sub-scanning direction between a horizontal line pattern by the first beam and an oblique line pattern by the second beam in the first pattern; and the second beam in the second pattern. Measuring means for measuring , at a predetermined position in the main scanning direction , a second interval that is an interval in the sub-scanning direction between the horizontal line pattern by and the oblique line pattern by the first beam ;
The main scanning magnification is adjusted based on the difference between the measured first interval and the first predetermined value and the difference between the measured second interval and the first predetermined value. an image forming apparatus comprising: the adjusting means for the. The adjusting means includes
The image forming apparatus according to claim 1, wherein a main scanning magnification is adjusted based on a difference between the measured first interval and the measured second interval. Adjustment of the main scanning magnification by the adjusting means is
3. The image forming apparatus according to claim 1, wherein the number of pixels required for magnification adjustment among the pixels constituting the scanning line is increased or decreased by increasing or decreasing the width of one pixel. Adjustment of the main scanning magnification by the adjusting means is
4. The image forming apparatus according to claim 1 , wherein the image forming apparatus is executed when a temperature change in the vicinity of the light source becomes equal to or greater than a second predetermined value. 5. The measuring means includes
Comprising a light emitting means for emitting light, light receiving means for receiving light light is reflected at a predetermined position on the photosensitive member from the light emitting means, a light receiving means, the image forming process conditions of the image forming apparatus the image forming apparatus according to claim 1, any one of 4, characterized in that also serves as the reflected light intensity detecting means for setting. By a first and second light sources to scan the first light beam and second light beam simultaneously with the photoreceptor above in from the second light source from the first light source, wherein on the photosensitive member to a light beam position correction method Ru used in the image forming device for forming a latent image,
A first pattern constituted by a horizontal line pattern by the first beam and an oblique line pattern by the second beam; a horizontal line pattern by the second beam; and an oblique line pattern by the first beam. A second pattern to be formed,
A first interval which is an interval in a sub-scanning direction between a horizontal line pattern by the first beam and an oblique line pattern by the second beam in the first pattern; and the second beam in the second pattern. Measuring a second interval, which is an interval in the sub-scanning direction, between the horizontal line pattern by and the oblique line pattern by the first beam at a predetermined position in the main scanning direction ,
The main scanning magnification is adjusted based on the difference between the measured first interval and the first predetermined value and the difference between the measured second interval and the first predetermined value. And a light beam position correcting method. By a first and second light sources to scan the first light beam and second light beam simultaneously with the photoreceptor above in from the second light source from the first light source, a program for causing a computer to execute an image forming device for forming a latent image on said photosensitive member,
A first pattern constituted by a horizontal line pattern by the first beam and an oblique line pattern by the second beam; a horizontal line pattern by the second beam; and an oblique line pattern by the first beam. A second pattern to be formed , and a pattern forming process for forming
A first interval which is an interval in a sub-scanning direction between a horizontal line pattern by the first beam and an oblique line pattern by the second beam in the first pattern; and the second beam in the second pattern. A measurement process for measuring at a predetermined position in the main scanning direction , a second interval that is an interval in the sub-scanning direction between the horizontal line pattern by and the oblique line pattern by the first beam ;
The main scanning magnification is adjusted based on the difference between the measured first interval and the first predetermined value and the difference between the measured second interval and the first predetermined value. and adjustment process of the program to be executed by a computer of the image forming apparatus.

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