JP2009184145A - Image forming apparatus and image forming apparatus controlling program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly grasp intervals of a plurality of laser beams without deteriorating image quality. <P>SOLUTION: The image forming apparatus includes a first scanning time measuring means, a second scanning time measuring means and a sub-scanning direction light beam interval calculating means. The first scanning time measuring means has two light beam detecting means arranged side by side in a main scanning direction so that edges on the starting side of a main scanning direction of detection regions of the means become non parallel to each other, and measures scanning times detected by the two light beam detecting means when one light beam is scanned-brought in. The second scanning time measuring means measures the scanning times detected by the two light beam detecting means when another light beam is scanned-brought in. The calculating means operates a deviation (scanning time deviation) of the scanning times respectively measured by the first and second scanning time measuring means, corrects the scanning time deviation according to a difference between a scanning speed of the light beam at an image carrier surface and a scanning speed of the light beam at the light beam detecting means, and calculates the interval in a sub-scanning direction orthogonal to the main scanning direction of two light beams by the scanning time deviation after corrected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and an image forming apparatus control program. The present invention relates to a multi-beam type image forming apparatus having a function of writing on a medium and a control program thereof.

  More specifically, a technique for detecting a gap (pitch) deviation between the plurality of light beams in an image forming apparatus that simultaneously scans the image carrier with a plurality of light beams in parallel in the main scanning direction and records a plurality of lines simultaneously. About.

  An image forming apparatus that forms an image of one line in the main scanning direction according to image data, and forms an image for one page by repeating image formation for each line in the main scanning direction in the sub-scanning direction. Are known.

  As an example, in an electrophotographic image forming apparatus, a laser beam modulated in accordance with image data is scanned by a polygon mirror or the like in the main scanning direction of the image carrier, and is rotated in the sub-scanning direction in parallel therewith. An image is formed on the image carrier (photosensitive drum) by the laser beam. In this case, the laser beam is modulated with image data on the basis of a clock signal (pixel clock) called a dot clock.

In addition, in order to perform image formation at high speed or with high resolution, a light source such as two or three or more laser diodes (LD) is provided, and image data is generated using laser beams from the plurality of light sources. There is known a method in which image formation for one page is performed by repeating image formation for each of a plurality of lines in the main scanning direction in the sub-scanning direction. Such a multi-beam type image forming apparatus is described in, for example, Patent Document 1 below. Various multi-beam image forming apparatuses are described in, for example, the following Patent Documents 1 and 2.
Japanese Unexamined Patent Publication No. 63-124664 JP 7-72399 A

  However, as described above, when scanning a plurality of laser beams at the same time, the intervals (pitch) of the plurality of laser beams are shifted, which may affect faithful image formation.

Here, Patent Document 1 described above describes a technique related to a general multi-beam image forming apparatus, but no consideration is given to a deviation in the interval between a plurality of laser beams.
Further, in Patent Document 2 described above, control is performed so as to detect an interval deviation between a plurality of laser beams and keep the interval deviation constant.

By the way, in the interval deviation correction of a plurality of laser beams proposed in Patent Document 2, the interval is detected from the difference in scanning time of the two laser beams by the light beam detecting means.
In this case, FIG. 10 shows a state where the photosensitive drum 161 is exposed as a plan view. In FIG. 10, a semiconductor laser 151 as a plurality of light sources for generating a plurality of laser beams, a collimator lens 152 and a cylindrical lens 153 for optically correcting various laser beams, and a polygon mirror 154 for scanning the laser beams in the main scanning direction. The optical system includes an fθ lens 155 that optically corrects a scanning angle, a cylindrical lens 156 that optically corrects, a mirror 157 for detecting a horizontal synchronizing signal, and a sensor 158 for detecting a horizontal synchronizing signal. Yes. The sensor 158 also serves as a sensor (light beam detection means) that detects the interval between a plurality of laser beams.

  A plurality of laser beams scanned as described above are scanned on the photosensitive drum 161 as an image carrier, and the rotation of the photosensitive drum 161 is scanned in the sub-scanning direction. A latent image corresponding to the laser beam is formed. In the case of a color image forming apparatus, the exposure units 150 shown here are arranged for the number of colors.

  Here, there is a problem that the scanning speed a at the end on the photosensitive drum 161 and the scanning speed a 'by the sensor 158 are detected as different. This is because the laser beam from the mirror 157 is configured to be perpendicularly incident on the sensor 158 in order to prevent malfunction due to irregular reflection of light.

  When the sensor 158 is tilted so that the scanning speed a and the scanning speed a ′ coincide with each other (when the sensor 158 is installed so as to have a detection surface parallel to the photosensitive drum 161), irregular reflection of light, etc. Therefore, the sensor 158 rarely makes an erroneous detection, which causes a larger problem that a correct control signal cannot be generated.

  That is, in the method of the above-mentioned Patent Document 2, when a laser beam is incident vertically to prevent malfunction of the sensor 158, the detection surface of the sensor 158 is not parallel to the surface of the photosensitive drum 161. For this reason, the inventors of the present application have found that there is a problem that the interval between the plurality of laser beams cannot be accurately detected due to the difference between the scanning speed a and the scanning speed a ′. . In this case, there is a problem that the image quality is deteriorated.

  The present invention has been made in order to solve the above-described problem, and is capable of accurately grasping the interval between a plurality of laser beams without deteriorating the image quality, and capable of realizing image formation with good image quality. It is an object to realize an apparatus and an image forming apparatus control program.

That is, the present invention as a means for solving the problems is as described below.
(1) The invention according to claim 1 is an image forming apparatus for simultaneously scanning a plurality of light beams on the image carrier in parallel with the main scanning direction to simultaneously record a plurality of lines, and two light beam detecting means Are arranged side by side in the main scanning direction so that the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are not parallel to each other, while one light of the plurality of light beams is arranged. A first scanning time measuring means for causing only the beam to scan and enter each of the two light beam detecting means, and measuring a scanning time in which the light beam is detected by the two light beam detecting means; and the first scanning time Only one light beam different from the light beam scanned by the measuring means is scanned and incident on each of the two light beam detecting means, and the scanning time for detecting the light beam by the two light beam detecting means is set. Measurement The second scanning time measuring means, and the scanning time deviations (scanning time deviations) respectively measured by the first and second scanning time measuring means are calculated, and the scanning speed of the light beam on the surface of the image bearing member is calculated. The scanning time deviation is corrected according to the difference in the scanning speed of the light beam in the light beam detecting means, and the first and second scanning time measuring means are selectively selected based on the corrected scanning time deviation, respectively. An image forming apparatus comprising: a sub-scanning direction light beam interval calculating unit that calculates an interval in a sub-scanning direction orthogonal to the main scanning direction between two scanned light beams.

  (2) In the invention according to claim 2, the correction of the scanning time deviation is based on a difference in scanning speed generated according to an angle formed between a light receiving surface of the image carrier and a detection surface of the light beam detecting means. The image forming apparatus according to claim 1, wherein the image forming apparatus is executed by a correction coefficient.

  (3) The invention according to claim 3 is the second 2 arranged side by side in the main scanning direction so that the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are parallel to each other. One light beam detection means and one light beam of the plurality of light beams are scanned and incident on each of the second two light beam detection means, and the second two light beam detection means make the light A scanning time measuring means for calculating a correction coefficient for measuring a scanning time during which the beam is detected, and the correction of the scanning time deviation is performed between the light receiving surface of the image carrier and the detection surface of the light beam detecting means. In the case of being parallel, the correction coefficient obtained by the ratio of the scanning time measured by the second two light beam detecting means to the scanning time actually measured by the second two light beam detecting means Executed, characterized The image forming apparatus according to claim 1, in which.

  (4) The invention described in claim 4 is an image forming apparatus control program for controlling an image forming apparatus for simultaneously recording a plurality of lines by simultaneously scanning a plurality of light beams on the image carrier in parallel with the main scanning direction. The two light beam detectors are arranged side by side in the main scanning direction so that the edges on the start end side or the end side in the main scanning direction of the respective light beam detection regions are not parallel to each other. First scanning time measurement in which only one of the light beams is scanned and incident on each of the two light beam detecting means, and the scanning time for detecting the light beam by the two light beam detecting means is measured. Only one light beam different from the light beam scanned by the first scanning time measuring means is caused to scan and enter each of the two light beam detecting means, and the two light beam detecting means A second scanning time measuring means for measuring a scanning time at which the light beam is detected; and a deviation of the scanning time (scanning time deviation) measured by each of the first and second scanning time measuring means to calculate the image carrying The scanning time deviation is corrected according to the difference between the scanning speed of the light beam on the body surface and the scanning speed of the light beam in the light beam detecting means, and the first and second scans are performed based on the corrected scanning time deviation. A computer is operated as a sub-scanning direction light beam interval calculating unit that calculates an interval in a sub-scanning direction orthogonal to the main scanning direction between two light beams selectively scanned by the time measuring unit, respectively. This is an image forming apparatus control program.

As described above, according to the present invention, the following effects can be obtained.
The present invention relates to an image forming apparatus that simultaneously scans a plurality of light beams on the image carrier in parallel in the main scanning direction and simultaneously records a plurality of lines. While the start edge side or the end edge side in the main scanning direction are arranged side by side in the main scanning direction so that they are not parallel to each other, only one of the plurality of light beams is detected by the two light beams. The first scanning time is measured as a scanning time in which the light beams are detected by the two light beam detecting means, and only one other light beam is measured for each of the two light beam detecting means. The scanning time when the light beam is detected by the two light beam detecting means is measured as a second scanning time, and the deviation of the scanning time measured for each of them (first scanning) And the second scanning time difference = scanning time deviation), and the scanning time deviation according to the difference between the scanning speed of the light beam on the surface of the image carrier and the scanning speed of the light beam in the light beam detecting means. And the interval in the sub-scanning direction perpendicular to the main scanning direction of the two light beams selectively scanned by the first and second scanning time measuring units based on the corrected scanning time deviation. Is calculated.

  According to the image forming apparatus having this configuration, the two light beam detection units are arranged side by side in the main scanning direction so that the edges on the start end side or the end side in the main scanning direction of the respective light beam detection regions are not parallel to each other. Therefore, the distance between the edges changes along the sub-scanning direction orthogonal to the main scanning direction.

  Therefore, in the case where only one light beam is detected by the two light beam detection means, the rising interval time during which the light beam is detected by each light beam detection means varies depending on the scanning position in the sub-scanning direction. Become. Here, when the rising interval time is measured for each of the two light beams to be compared, the difference in the interval time in each light beam becomes a value correlated with the interval in the sub-scanning direction of each light beam. A change in the time difference indicates a deviation of the optical axis in the sub-scanning direction (change in the light beam interval in the sub-scanning direction).

  Then, the scanning time deviation is corrected in accordance with the difference between the scanning speed of the light beam on the surface of the image carrier and the scanning speed of the light beam in the light beam detecting means, and the first and the second are corrected based on the corrected scanning time deviation. Since the interval in the sub-scanning direction orthogonal to the main scanning direction of the two light beams selectively scanned by the two scanning time measuring means is calculated, the detection surface is not parallel to the image carrier surface. When the laser beam is incident perpendicularly to the detection surface of the light beam detection means using the light beam detection means, the difference between the scanning speed a and the scanning speed a ′ occurs as described above. It becomes possible to accurately detect the interval.

  Then, the scanning time deviation is corrected in accordance with the difference between the scanning speed of the light beam on the surface of the image carrier and the scanning speed of the light beam in the light beam detecting means, and the first and the second are corrected based on the corrected scanning time deviation. Since the interval in the sub-scanning direction orthogonal to the main scanning direction of the two light beams selectively scanned by the two scanning time measuring means is calculated, the detection surface is not parallel to the image carrier surface. When the laser beam is incident perpendicularly to the detection surface of the light beam detection means using the light beam detection means, the difference between the scanning speed a and the scanning speed a ′ occurs as described above. It becomes possible to accurately detect the interval.

The correction of the scanning time deviation is executed by a correction coefficient based on the difference in scanning speed that occurs according to the angle formed by the light receiving surface of the image carrier and the detection surface of the light beam detecting means.
A second two light beam detectors arranged in the main scanning direction so that edges at the start side or the end side of the light beam detection region in the main scanning direction are parallel to each other; and a plurality of light beams One of the two light beams is scanned and incident on each of the second two light beam detecting means, and a correction coefficient calculation for measuring a scanning time for detecting the light beam by the second two light beam detecting means And a scanning time measuring means, the scanning time deviation is corrected when the light receiving surface of the image carrier and the detection surface of the light beam detecting means are parallel to each other. This is executed with a correction coefficient obtained by a ratio between the scanning time measured by the means and the scanning time actually measured by the second two light beam detecting means.

  Accordingly, it is possible to accurately grasp the intervals between the plurality of laser beams without degrading the image quality, and to realize image formation with a good image quality.

  The best mode (embodiment) for carrying out the present invention will be described below in detail with reference to the drawings. The image forming apparatus to which the present embodiment is applied is a multi-beam type image forming in which a plurality of laser beams from a plurality of light sources are scanned in the main scanning direction of the image carrier and a plurality of lines are exposed in parallel. Device.

  Hereinafter, the electrical configuration of the first embodiment of the multi-beam image forming apparatus 100 of the present embodiment will be described in detail with reference to FIG. In this embodiment, the basic configuration requirements of the image forming apparatus 100 that uses a plurality of laser beams for exposure without degrading the image quality will be mainly described. Therefore, it is common for an image forming apparatus, and well-known constituent elements are omitted.

In the following embodiments, an image forming apparatus using two laser beams L1 and L2 as a plurality of laser beams will be described as a specific example.
[First embodiment]
A control unit 101 is configured by a CPU or the like to control each unit of the image forming apparatus 100. An image processing unit 110 executes predetermined image processing according to image data. Reference numeral 120 denotes a laser control circuit that controls light emission of the laser in accordance with image data and predetermined command data. A laser driving circuit 130 drives the light source based on the control of the laser control circuit 120. Reference numeral 140 denotes a print engine that forms an image by exposure, and includes an exposure unit 150 that scans with a plurality of laser beams, and a process unit 160.

FIG. 2 is an explanatory diagram schematically showing a part of the periphery of the laser control circuit 120, the laser driving circuit 130, and the exposure unit 150 as a partial perspective view.
In FIG. 2, the exposure unit 150 has a semiconductor laser 151a and a semiconductor laser 151b as a plurality of light sources for generating a plurality of laser beams. The semiconductor laser 151a and the semiconductor laser 151b are driven by a laser driving circuit 130 to generate laser beams L1 and L2 according to image data.

The laser beam L1 from the semiconductor laser 151a is incident on one input surface of the beam combining prism 152p.
The laser beam L2 from the semiconductor laser 151b is incident on the other input surface of the beam combining prism 152p via the beam interval adjusting unit 152c. Then, the laser beam L1 and the laser beam L2 are combined into two laser beams with a predetermined interval.

  The beam interval adjusting unit 152c is a plate-like optical element having a predetermined thickness, and the vertical position of the laser beam is changed by taking a forward or backward tilt posture. The beam interval adjusting unit 152c is driven by a beam interval adjusting circuit 180.

  The plurality of laser beams L1 and L2 include a collimator lens 153a and a cylindrical lens 153b that optically correct the laser beam, a polygon mirror 154 that scans the laser beam in the main scanning direction, and an optical correction of the scanning angle. Fθ lens 155, a cylindrical lens 156 for optical correction, a mirror 157 for detecting a horizontal synchronizing signal, and a sensor 158 for detecting a horizontal synchronizing signal.

  The sensor 158 includes, for example, a plurality of light receiving elements (light beam detecting means) 158a, 158b, 158c, and 158d as shown in FIG. In FIG. 3, it is assumed that the height of the sub-scanning direction is such that L1 and L2 can be received for measuring the distance between the laser beams L1 and L2.

  Here, when the laser beams L1 and L2 scan in the horizontal direction on the paper surface, the light receiving element 158a and the light receiving element 158c included in the sensor 158 have a longitudinal direction in a direction perpendicular to the laser beams L1 and L2.

  Further, the two light receiving elements 158b and 158d included in the sensor 158 are arranged side by side in the main scanning direction so that the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are not parallel to each other. It is installed. The light receiving elements 158b and 158d are arranged not to be parallel to each other so as to have an angle β.

  That is, in this case, when the edges of the light beam detection areas of the light receiving elements 158b and 158d on the start end side in the main scanning direction are not parallel to each other, the light beam detection areas of the light receiving elements 158b and 158d are terminated in the main scanning direction If the edges are non-parallel to each other, it is conceivable.

  In addition to this, the edge on the start side in the main scanning direction of the light beam detection region of the light receiving element 158b and the edge on the end side in the main scanning direction of the light beam detection region of the light receiving element 158d are not parallel to each other. In this case, it is also conceivable that the edge on the end side in the main scanning direction of the light beam detection region of the light receiving element 158b and the edge on the start side in the main scanning direction of the light beam detection region of the light receiving element 158d are not parallel to each other. .

  In the following description of the embodiment, the two light receiving elements 158b and 158d included in the sensor 158 are arranged such that the edges on the start end side in the main scanning direction of the respective light beam detection regions are not parallel to each other. A specific example is a case where the time T1 and time T2 that are arranged side by side in the main scanning direction and that cross these are measured.

  The sensor 158 is configured to have light receiving elements 158a and 158c for generating a horizontal synchronization signal in addition to the light receiving elements 158b and 158d for adjusting the laser beam interval.

  A plurality of laser beams scanned as described above are scanned on the photosensitive drum 161 as an image carrier, and the rotation of the photosensitive drum 161 is scanned in the sub-scanning direction. A latent image corresponding to the laser beam is formed. In the case of a color image forming apparatus, the exposure units 150 shown here are arranged for the number of colors.

  In the above configuration, the image processing unit 110 is an image processing unit that performs various types of image processing necessary for image formation. In this embodiment, in order to perform simultaneous exposure with a plurality of light sources, It has a function of outputting image data for each line in parallel.

Hereinafter, the first operation (first embodiment) of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG. 4 and the explanatory diagram of FIG.
First, at the time of factory shipment adjustment, at the elapse of a predetermined time after the start of use, at the time of periodic inspection, etc., an operation of adjusting the laser beam interval is started by an instruction from the control unit 101 (start in FIG. 4).

  Here, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151a to generate the first laser beam L1 (step S401 in FIG. 4), and the polygon mirror The laser beam L1 scans on the photosensitive drum 161 by the rotational reflection of 154. Further, the laser beam L1 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L1 in FIG. Then, the time T1 across the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180 (step S402 in FIG. 4).

  Therefore, in the first embodiment, the light receiving element 158b and the light receiving element 158d are configured so that the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are not parallel to each other. The two light beam detectors arranged side by side in the main scanning direction ”. Further, the beam interval adjusting circuit 180 constitutes “first scanning time measuring means” in the claims.

  Then, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151b to generate the second laser beam L2 (step S403 in FIG. 4), and the polygon mirror 154. The laser beam L2 scans on the photosensitive drum 161 by the rotational reflection. Further, the laser beam L2 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L2 in FIG. Then, a time T2 across the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180 (step S404 in FIG. 4). That is, the beam interval adjusting circuit 180 constitutes “second scanning time measuring means” in the claims.

  Here, the beam interval adjustment circuit 180 obtains the difference ΔT = (T2−T1) between T1 and T2 (step S405 in FIG. 4). In the prior art (the above-mentioned Patent Document 2), the beam interval is obtained directly from T2-T1.

  However, as described above, when the surface of the photosensitive drum 161 and the light receiving surface of the sensor 158 are not parallel, the laser beam scanning speed differs, an error occurs in the detection result, and an accurate laser beam interval is measured. Will cause problems.

  FIG. 5 is a drawing in which the scanning of the laser beam on the surface of the photosensitive drum 161 and the scanning of the laser beam on the light receiving surface by the sensor 158 are schematically overlapped at the same position. Actually, the sensor 158 receives the reflected light from the mirror 157, but the angle can be equivalently shown as shown in FIG.

  Here, when the scanning speed of the laser beam on the surface of the photosensitive drum 161 is V (scanning speed a in FIG. 2) and the angle formed between the surface of the drum 161 and the light receiving surface of the sensor 158 is θ, the sensor 158 The scanning speed V ′ on the light receiving surface is V ′ = V · cos θ (scanning speed a ′ in FIG. 2). That is, on the light receiving surface of the sensor 158, the speed is cos θ times slower than the speed on the photosensitive drum surface. Therefore, T1 and T2 are actually measured as a time that is cos θ times longer than the original time.

  When the distance between the light receiving element 158b and the light receiving element 158d is D, the laser beam scanning time Torg on the photosensitive drum surface is Torg = D / V. On the other hand, the laser beam scanning time T on the light receiving surface of the sensor 158 is T = D / V ′ = D / (V · cos θ) = Torg / cos θ.

  That is, the measured T is in a state including an error of 1 / cos θ as compared with the original Torg. As will be described later, since the laser beam interval is proportional to T (Torg), an error is included in the laser beam interval to be controlled as it is. If θ is 25 °, cos θ = 0.906, and an error of about 10% occurs.

Since this θ is a value determined by the design of the optical system, it is only necessary to correct the measured values of the scanning times T1 and T2 based on this θ.
That is, the scanning time is corrected using the correction coefficient α = 1 / cos θ.
The corrected measurement value Tnew is Tnew = T / α = (Torg / cos θ) · cos θ = Torg, and the same measurement value as the laser beam scanning time on the drum surface can be obtained.

  The beam interval adjustment circuit 180 corrects as described above, obtains T2new and T1new, and calculates ΔTnew = T2new−T1new = (T2 / α) − (T1 / α) (step S406 in FIG. 4). .

  The beam interval adjusting circuit 180 uses this ΔTnew to refer to the angle β (FIG. 3) formed by the light receiving element 158b and the light receiving element 158d, and for the laser beam interval H, H = (ΔTnew / 2) / tan Calculate as (β / 2) (step S407 in FIG. 4).

  Alternatively, the beam interval adjusting circuit 180 uses ΔT and α to refer to the angle β (FIG. 3) formed by the light receiving element 158b and the light receiving element 158d, and for the laser beam interval H, H = ((ΔT / 2 ) / Α) / tan (β / 2) (step S407 in FIG. 4). That is, the beam interval adjusting circuit 180 constitutes “sub-scanning direction light beam interval calculating means” in the claims.

  Then, the beam interval adjusting circuit 180 uses a stepping motor (not shown) or the like so as to eliminate the difference between the laser beam interval H thus obtained and the original laser beam interval Horg. Is tilted by a predetermined angle to make H and Horg coincide with each other (step S408 in FIG. 4).

  Here, the laser beam interval H is adjusted by tilting a plate-like optical element as the beam interval adjusting unit 152c as shown in FIG. 6 to shift the optical path using light refraction. In this case, another element may be used, or a method of moving the semiconductor laser 151a or 151b with an actuator or the like may be used.

  By doing as described above, the laser beam interval H becomes closer to the original laser beam interval Horg, and the error can be reduced. Accordingly, it is possible to accurately grasp the intervals between the plurality of laser beams without degrading the image quality, and to realize image formation with a good image quality.

  Note that the sensor 158 of this embodiment has a configuration in which light receiving elements 158a and 158c for generating a horizontal synchronizing signal are combined in addition to the light receiving elements 158b and 158d for adjusting the laser beam interval. That is, by adding the light receiving element portion of the present embodiment to the sensor 158 for generating the horizontal synchronization signal of the existing image forming apparatus, it is substantially unnecessary to add new parts. On the contrary, it is not necessary to provide the light receiving elements 158a and 158c in the sensor 158 only for the adjustment of the laser beam interval of the present embodiment.

[Second Embodiment]
Hereinafter, the second operation (second embodiment) of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG.

  In the first embodiment described above, the sensor 158 receives the laser beam vertically on the light receiving surface, and when the angle formed between the surface of the drum 161 and the light receiving surface of the sensor 158 is θ, The scanning speed V ′ was assumed to be V ′ = V · cos θ (scanning speed a ′ in FIG. 2).

  However, when the angle at which the sensor 158 receives the laser beam changes, an error occurs in the calculation using θ in the first embodiment described above. Therefore, the interval between the laser beams deviates from the intended state, and the image quality is deteriorated.

  Therefore, in this second embodiment, the angle corresponding to θ in the first embodiment is measured regardless of the deviation of the angle at which the light receiving surface of the sensor 158 receives the laser beam, and the laser beam interval is accurately determined. The purpose is to prevent image quality deterioration by controlling.

First, at the time of factory shipment adjustment, at the elapse of a predetermined time after the start of use, at the time of periodic inspection, etc., an operation of adjusting the laser beam interval is started by an instruction from the control unit 101 (start in FIG. 7).
Here, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151a to generate the first laser beam L1 (step S701 in FIG. 7), and the polygon mirror The laser beam L1 scans on the photosensitive drum 161 by the rotational reflection of 154.

  Further, the laser beam L1 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L1 in FIG. Then, the time T1 across the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180 (step S702 in FIG. 7).

  The sensor 158 includes, for example, a plurality of light receiving elements (light beam detecting means) 158a, 158b, 158c, and 158d as shown in FIG. In FIG. 3, it is assumed that the height of the sub-scanning direction is such that L1 and L2 can be received for measuring the distance between the laser beams L1 and L2.

  In the sensor 158 of the second embodiment, in addition to the light receiving elements 158b and 158d for adjusting the laser beam interval, the light receiving elements 158a and 158c are also used for adjusting the laser beam interval.

  Here, the two light receiving elements 158b and 158d included in the sensor 158 are arranged in the main scanning direction such that the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are not parallel to each other. It is arranged. The light receiving elements 158b and 158d are arranged not to be parallel to each other so as to have an angle β.

  Also, here, the two light receiving elements 158a and 158c included in the sensor 158 are arranged in the main scanning direction so that the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are parallel to each other. They are arranged side by side.

  That is, in this case, when the edges of the light beam detection areas of the light receiving elements 158a and 158c on the start side in the main scanning direction are parallel to each other, the light beam detection areas of the light receiving elements 158a and 158c are located on the end side in the main scanning direction. A case where the edges are parallel to each other is conceivable.

  In addition to this, the edge on the start side in the main scanning direction of the light beam detection region of the light receiving element 158a and the end edge on the end side in the main scanning direction of the light beam detection region of the light receiving element 158c are parallel to each other. In addition, there may be a case where the edge on the end side in the main scanning direction of the light beam detection region of the light receiving element 158a and the edge on the start side in the main scanning direction of the light beam detection region of the light receiving element 158c are parallel to each other.

  In the following description of the second embodiment, the two light receiving elements 158a and 158c included in the sensor 158 are parallel to each other in the main scanning direction start edge side of each light beam detection region. A specific example is a case where the time t1 that is arranged side by side in the main scanning direction and crosses these is measured.

  Then, the time t1 crossing the light receiving element 158a and the light receiving element 158c is measured by the beam interval adjusting circuit 180 as the time T1 crossing the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180. It is measured (step S702 in FIG. 7).

  Therefore, in the second embodiment, the light receiving element 158a and the light receiving element 158c are configured so that “the edges on the start end side or the end side in the main scanning direction of the respective light beam detection regions are parallel to each other”. 2nd light beam detection means "arranged side by side in the main scanning direction. In addition, the beam interval adjusting circuit 180 may be configured such that “one of the plurality of light beams is scanned and incident on each of the second two light beam detectors to detect the second two light beams. The correction coefficient calculating scanning time measuring means for measuring the scanning time during which the light beam is detected by the means is configured.

  Further, in the second embodiment, when the light receiving surface of the sensor 158 is parallel to the photosensitive surface of the photosensitive drum 161, it is generated when the laser beam crosses the light receiving element 158a and the light receiving element 158c of the sensor 158. The time t0 to be obtained is obtained in advance.

  Then, from the time t1 when the laser beam actually crosses the light receiving element 158ab and the light receiving element 158c of the actual device and the above t0, the beam interval adjusting circuit 180 obtains the correction coefficient α ′ (step in FIG. 7). S703). Here, α ′ = t1 / t0.

  The correction coefficient α ′ matches the correction coefficient α of the first embodiment when the light receiving surface of the sensor 158 has a predetermined angle. The correction coefficient α ′ is an appropriate correction coefficient according to the actual angle of the light receiving surface of the sensor 158 when the light receiving surface of the sensor 158 is different from a predetermined angle.

  Here, the correction coefficient α ′ is obtained from t1 and t0 in parallel with the T1 measurement. However, when measuring T2 described later, the correction coefficient is calculated from t2 (= t1) and the above t0. α ′ may be obtained.

  Then, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151b to generate the second laser beam L2 (step S704 in FIG. 7), and the polygon mirror 154. The laser beam L2 scans on the photosensitive drum 161 by the rotational reflection. Further, the laser beam L2 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L2 in FIG. Then, a time T2 across the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180 (step S705 in FIG. 7).

Here, the beam interval adjusting circuit 180 obtains the difference ΔT = (T2−T1) between T1 and T2 (step S706 in FIG. 7).
In the prior art (the above-mentioned Patent Document 2), the beam interval is obtained directly from T2-T1. However, as described above, when the surface of the photosensitive drum 161 and the light receiving surface of the sensor 158 are not parallel, the laser beam scanning speed differs, an error occurs in the detection result, and an accurate laser beam interval is measured. Will cause problems.

  FIG. 5 is a drawing in which the scanning of the laser beam on the surface of the photosensitive drum 161 and the scanning of the laser beam on the light receiving surface by the sensor 158 are schematically overlapped at the same position. Actually, the sensor 158 receives the reflected light from the mirror 157, but the angle can be equivalently shown as shown in FIG.

  Here, when the scanning speed of the laser beam on the surface of the photosensitive drum 161 is V (scanning speed a in FIG. 2) and the angle formed between the surface of the drum 161 and the light receiving surface of the sensor 158 is θ, the sensor 158 The scanning speed V ′ on the light receiving surface is V ′ = V · cos θ (scanning speed a ′ in FIG. 2). That is, on the light receiving surface of the sensor 158, the speed is cos θ times slower than the speed on the photosensitive drum surface. Therefore, T1 and T2 are actually measured as a time that is cos θ times longer than the original time.

  When the distance between the light receiving element 158b and the light receiving element 158d is D, the laser beam scanning time Torg on the photosensitive drum surface is Torg = D / V. On the other hand, the laser beam scanning time T on the light receiving surface of the sensor 158 is T = D / V ′ = D / (V · cos θ) = Torg / cos θ.

  That is, the measured T is in a state including an error of 1 / cos θ as compared with the original Torg. As will be described later, since the laser beam interval is proportional to T (Torg), an error is included in the laser beam interval to be controlled as it is.

Since this θ is a value determined by the design of the optical system, it is only necessary to correct the measured values of the scanning times T1 and T2 based on this θ.
However, the above explanation is based on the assumption that the laser beam is incident perpendicularly to the light receiving surface of the sensor 158 and that an error in scanning time is caused only by the above-described θ.

Actually, the laser beam is not necessarily incident on the light receiving surface of the sensor 158 perpendicularly or at a predetermined angle due to an attachment error of the sensor 158 or the like.
Therefore, in the second embodiment, the scanning time is corrected using the correction coefficient α ′ = t1 / t0. The corrected measurement value Tnew is Tnew = T / α ′ = (Torg / (t1 / t0)) · (t1 / t0)) = Torg, and the correct measurement value is the same as the laser beam scanning time on the drum surface. It will be obtained.

  The beam interval adjustment circuit 180 corrects as described above to obtain T2new and T1new, and calculates ΔTnew = T2new−T1new = (T2 / α ′) − (T1 / α ′) (step in FIG. 7). S707).

  The beam interval adjusting circuit 180 uses this ΔTnew to refer to the angle β (FIG. 3) formed by the light receiving element 158b and the light receiving element 158d, and for the laser beam interval H, H = (ΔTnew / 2) / tan It is calculated as (β / 2) (step S708 in FIG. 7).

  Alternatively, the beam interval adjusting circuit 180 refers to the angle β (FIG. 3) formed by the light receiving element 158b and the light receiving element 158d using ΔT and α ′, and for the laser beam interval H, H = ((ΔT / 2) / α ′) / tan (β / 2) (Step S708 in FIG. 7).

  Then, the beam interval adjusting circuit 180 uses a stepping motor (not shown) or the like so as to eliminate the difference between the laser beam interval H thus obtained and the original laser beam interval Horg. Is tilted by a predetermined angle to make H and Horg coincide with each other (step S709 in FIG. 7).

  Here, the laser beam interval H is adjusted by tilting a plate-like optical element as the beam interval adjusting unit 152c as shown in FIG. 6 to shift the optical path using light refraction. In this case, another element may be used, or a method of moving the semiconductor laser 151a or 151b with an actuator or the like may be used.

  By doing as described above, the laser beam interval H becomes closer to the original laser beam interval Horg, and the error can be reduced. Accordingly, it is possible to accurately grasp the intervals between the plurality of laser beams without degrading the image quality, and to realize image formation with a good image quality. In the second embodiment, even if the light receiving surface of the sensor 158 is deviated from a predetermined angle, an appropriate correction is made by the correction coefficient α ′ without being affected by the deviation. It becomes possible to do.

  In the second embodiment, the relationship between the sensor 158 and the incident angle of the laser beam is not strictly fixed, and the angle at the time of attachment is not a predetermined angle. Even if the mounting angle of the sensor 158 is deviated due to the change, an appropriate correction is made by the correction coefficient α ′, so that an effect such as no error is obtained.

[Third embodiment]
Hereinafter, the second operation (third embodiment) of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG.

  In the first embodiment described above, the sensor 158 receives the laser beam vertically on the light receiving surface, and when the angle formed between the surface of the drum 161 and the light receiving surface of the sensor 158 is θ, The scanning speed V ′ was assumed to be V ′ = V · cos θ (scanning speed a ′ in FIG. 2).

  However, when the angle at which the sensor 158 receives the laser beam changes, an error occurs in the calculation using θ in the first embodiment described above. Therefore, the interval between the laser beams deviates from the intended state, and the image quality is deteriorated.

  Therefore, in the third embodiment, the angle corresponding to θ in the first embodiment is measured regardless of the deviation of the angle at which the light receiving surface of the sensor 158 receives the laser beam, and the laser beam interval is accurately determined. The purpose is to prevent image quality deterioration by controlling.

First, at the time of factory shipment adjustment, when a predetermined time elapses after the start of use, at the time of periodic inspection, etc., an operation of adjusting the laser beam interval is started by an instruction from the control unit 101 (start in FIG. 9).
Here, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151a to generate the first laser beam L1 (step S901 in FIG. 9), and the polygon mirror The laser beam L1 scans on the photosensitive drum 161 by the rotational reflection of 154.

  Further, the laser beam L1 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L1 in FIG. Then, the time t1 across the light receiving element 158a and the light receiving element 158c is measured by the beam interval adjusting circuit 180 (step S902 in FIG. 9).

  Therefore, in the third embodiment, the light receiving element 158a and the light receiving element 158c are configured so that “the edges on the start side or the end side in the main scanning direction of the respective light beam detection regions are parallel to each other”. 2nd light beam detection means "arranged side by side in the main scanning direction. In addition, the beam interval adjusting circuit 180 may be configured such that “one of the plurality of light beams is scanned and incident on each of the second two light beam detectors to detect the second two light beams. The correction coefficient calculating scanning time measuring means for measuring the scanning time during which the light beam is detected by the means is configured.

  Further, in the third embodiment, when the light receiving surface of the sensor 158 is parallel to the photosensitive surface of the photosensitive drum 161, it is generated when the laser beam crosses the light receiving element 158a and the light receiving element 158c of the sensor 158. The time t0 to be obtained is obtained in advance.

  Then, from the time t1 when the laser beam actually crosses the light receiving element 158ab and the light receiving element 158c of the actual device and the above t0, the beam interval adjusting circuit 180 obtains the correction coefficient α ′ (step in FIG. 9). S903). Here, α ′ = t1 / t0.

  The correction coefficient α ′ matches the correction coefficient α of the first embodiment when the light receiving surface of the sensor 158 has a predetermined angle. The correction coefficient α ′ is an appropriate correction coefficient according to the actual angle of the light receiving surface of the sensor 158 when the light receiving surface of the sensor 158 is different from a predetermined angle.

  Here, the correction coefficient α ′ is obtained from t1 and t0 by the laser beam L1, but the correction coefficient α ′ may be obtained from t1 and t0 by the laser beam L2.

  Further, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151a to generate the first laser beam L1 (step S904 in FIG. 9), and the polygon mirror 154. The laser beam L1 scans on the photosensitive drum 161 by the rotational reflection.

  Further, the laser beam L1 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L1 in FIG. Then, the time T1 across the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180 (step S905 in FIG. 9).

  Then, the laser control unit 120 and the laser drive circuit 130 that have received an instruction from the control unit 101 drive the semiconductor laser 151b to generate the second laser beam L2 (step S906 in FIG. 9), and the polygon mirror 154. The laser beam L2 scans on the photosensitive drum 161 by the rotational reflection. Further, the laser beam L2 is reflected by the mirror 157 at the end, and enters the sensor 158. At this time, a plurality of light receiving elements constituting the sensor 158 are traversed as indicated by L2 in FIG. Then, a time T2 across the light receiving element 158b and the light receiving element 158d is measured by the beam interval adjusting circuit 180 (step S907 in FIG. 9).

Here, the beam interval adjusting circuit 180 obtains the difference ΔT = (T2−T1) between T1 and T2 (step S908 in FIG. 9).
In the prior art (the above-mentioned Patent Document 2), the beam interval is obtained directly from T2-T1. However, as described above, when the surface of the photosensitive drum 161 and the light receiving surface of the sensor 158 are not parallel, the laser beam scanning speed differs, an error occurs in the detection result, and an accurate laser beam interval is measured. Will cause problems.

  FIG. 5 is a drawing in which the scanning of the laser beam on the surface of the photosensitive drum 161 and the scanning of the laser beam on the light receiving surface by the sensor 158 are schematically overlapped at the same position. Actually, the sensor 158 receives the reflected light from the mirror 157, but the angle can be equivalently shown as shown in FIG.

  Here, when the scanning speed of the laser beam on the surface of the photosensitive drum 161 is V (scanning speed a in FIG. 2) and the angle formed between the surface of the drum 161 and the light receiving surface of the sensor 158 is θ, the sensor 158 The scanning speed V ′ on the light receiving surface is V ′ = V · cos θ (scanning speed a ′ in FIG. 2). That is, on the light receiving surface of the sensor 158, the speed is cos θ times slower than the speed on the photosensitive drum surface. Therefore, T1 and T2 are actually measured as a time that is cos θ times longer than the original time.

  When the distance between the light receiving element 158b and the light receiving element 158d is D, the laser beam scanning time Torg on the photosensitive drum surface is Torg = D / V. On the other hand, the laser beam scanning time T on the light receiving surface of the sensor 158 is T = D / V ′ = D / (V · cos θ) = Torg / cos θ.

  That is, the measured T is in a state including an error of 1 / cos θ as compared with the original Torg. As will be described later, since the laser beam interval is proportional to T (Torg), an error is included in the laser beam interval to be controlled as it is.

Since this θ is a value determined by the design of the optical system, it is only necessary to correct the measured values of the scanning times T1 and T2 based on this θ.
However, the above explanation is based on the assumption that the laser beam is incident perpendicularly to the light receiving surface of the sensor 158 and that an error in scanning time is caused only by the above-described θ.

Actually, the laser beam is not necessarily incident on the light receiving surface of the sensor 158 perpendicularly or at a predetermined angle due to an attachment error of the sensor 158 or the like.
Therefore, in the third embodiment, the scanning time is corrected using the correction coefficient α ′ = t1 / t0. The corrected measurement value Tnew is Tnew = T / α ′ = (Torg / (t1 / t0)) · (t1 / t0)) = Torg, and the correct measurement value is the same as the laser beam scanning time on the drum surface. It will be obtained.

  The beam interval adjusting circuit 180 corrects as described above to obtain T2new and T1new and calculates ΔTnew = T2new−T1new = (T2 / α ′) − (T1 / α ′) (step in FIG. 9). S909).

  The beam interval adjusting circuit 180 uses this ΔTnew to refer to the angle β (FIG. 3) formed by the light receiving element 158b and the light receiving element 158d, and for the laser beam interval H, H = (ΔTnew / 2) / tan Calculated as (β / 2) (step S910 in FIG. 9).

  Alternatively, the beam interval adjusting circuit 180 refers to the angle β (FIG. 3) formed by the light receiving element 158b and the light receiving element 158d using ΔT and α ′, and for the laser beam interval H, H = ((ΔT / 2) / α ′) / tan (β / 2) (Step S910 in FIG. 9).

  Then, the beam interval adjusting circuit 180 uses a stepping motor (not shown) or the like so as to eliminate the difference between the laser beam interval H thus obtained and the original laser beam interval Horg. Is inclined by a predetermined angle to make H and Horg coincide with each other (step S911 in FIG. 9).

  Here, the laser beam interval H is adjusted by tilting a plate-like optical element as the beam interval adjusting unit 152c as shown in FIG. 6 to shift the optical path using light refraction. In this case, another element may be used, or a method of moving the semiconductor laser 151a or 151b with an actuator or the like may be used.

  By doing so, the laser beam interval H can be brought close to the original laser beam interval Horg, and the error can be reduced. Accordingly, it is possible to accurately grasp the interval between the plurality of laser beams without degrading the image quality, and to realize image formation with a good image quality. In the third embodiment, even if the light receiving surface of the sensor 158 is deviated from a predetermined angle, an appropriate correction is made by the correction coefficient α ′ without being affected by the deviation. It becomes possible to do.

  In the third embodiment, the relationship between the sensor 158 and the incident angle of the laser beam is not strictly fixed, and the angle at the time of attachment is not a predetermined angle. Even if the mounting angle of the sensor 158 is changed due to a change, an appropriate correction is made by the correction coefficient α ′, so that an effect such as no error is obtained.

[Other Embodiments]
In the above embodiment, the beam interval adjusting circuit 180 has the functions of the first scanning time measuring unit, the second scanning time measuring unit, and the sub-scanning direction light beam interval calculating unit. You may make it comprise with the circuit which carried out.

The functions of the first scanning time measuring unit, the second scanning time measuring unit, and the sub-scanning direction light beam interval calculating unit may be configured by the control unit 101.
In the above embodiment, an electrophotographic image forming apparatus using a laser beam has been described. However, the present invention is not limited to this. For example, each embodiment of the present invention can be applied to various image forming apparatuses such as a laser imager that exposes photographic paper using a laser beam, and good results can be obtained.

Further, the present invention can be applied even when a light source other than the semiconductor laser (LD) is used as the light source.
For the laser beam synthesis, elements other than the beam synthesis prism 152p used in the embodiment may be used. In addition, for the laser beam interval adjustment, an element other than the beam interval adjustment unit 152c used in the embodiment can be used.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention. 1 is a configuration diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention. It is explanatory drawing which shows the structure of the sensor of the image forming apparatus of one Embodiment of this invention. 4 is a flowchart illustrating an operation state of the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation state of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation state of the image forming apparatus according to the embodiment of the present invention. 10 is a flowchart illustrating an operation state of the image forming apparatus according to the second embodiment of the present invention. It is explanatory drawing which shows the structure of the sensor of the image forming apparatus of one Embodiment of this invention. 10 is a flowchart illustrating an operation state of the image forming apparatus according to the second embodiment of the present invention. It is explanatory drawing explaining the laser beam detection of an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Control part 110 Image processing part 120 Laser control circuit 130 Laser drive circuit 140 Print engine 150 Exposure unit 160 Process unit 180 Beam interval adjustment circuit

Claims (4)

An image forming apparatus that simultaneously scans an image carrier with a plurality of light beams in parallel in the main scanning direction to simultaneously record a plurality of lines.
The two light beam detecting means are arranged in the main scanning direction so that the edges of the respective light beam detection regions on the start end side or the end side in the main scanning direction are not parallel to each other. A first scanning time measuring unit that scans / incides one of the light beams into each of the two light beam detecting units, and measures a scanning time during which the two light beam detecting units detect the light beam;
One light beam different from the light beam scanned by the first scanning time measuring means is scanned and incident on each of the two light beam detecting means, and the light beams are detected by the two light beam detecting means. Second scanning time measuring means for measuring the scanning time
The scanning time deviation (scanning time deviation) measured by the first and second scanning time measuring means is calculated, and the scanning speed of the light beam on the surface of the image carrier and the scanning of the light beam by the light beam detecting means are calculated. The scanning time deviation is corrected according to the difference from the speed, and the two light beams selectively scanned by the first and second scanning time measuring units based on the corrected scanning time deviation, respectively. Sub-scanning direction light beam interval calculating means for calculating an interval in the sub-scanning direction orthogonal to the main scanning direction;
An image forming apparatus comprising: The correction of the scanning time deviation is executed by a correction coefficient based on a difference in scanning speed generated according to an angle formed between a light receiving surface of the image carrier and a detection surface of the light beam detection unit.
The image forming apparatus according to claim 1. A second two light beam detection means arranged in the main scanning direction so that the edges on the start side or the end side in the main scanning direction of each light beam detection region are parallel to each other;
A scanning time in which one light beam of the plurality of light beams is scanned and incident on each of the second two light beam detectors, and the light beams are detected by the second two light beam detectors. A correction coefficient calculation scanning time measuring means for measuring
Further comprising
The correction of the scanning time deviation includes the scanning time measured by the second two light beam detecting means when the light receiving surface of the image carrier and the detecting surface of the light beam detecting means are parallel, and actually Is executed by a correction coefficient obtained by a ratio with a scanning time measured by the second two light beam detecting means.
The image forming apparatus according to claim 1. An image forming apparatus control program for controlling an image forming apparatus for simultaneously scanning a plurality of light beams on the image carrier in parallel in the main scanning direction and simultaneously recording a plurality of lines.
The two light beam detecting means are arranged in the main scanning direction so that the edges of the respective light beam detection regions on the start end side or the end side in the main scanning direction are not parallel to each other. A first scanning time measuring unit that scans / incides one of the light beams into each of the two light beam detecting units and measures a scanning time during which the two light beam detecting units detect the light beam,
One light beam different from the light beam scanned by the first scanning time measuring means is scanned and incident on each of the two light beam detecting means, and the light beams are detected by the two light beam detecting means. Second scanning time measuring means for measuring the scanning time,
The scanning time deviation (scanning time deviation) measured by the first and second scanning time measuring means is calculated, and the scanning speed of the light beam on the surface of the image carrier and the scanning of the light beam by the light beam detecting means are calculated. The scanning time deviation is corrected according to the difference from the speed, and the two light beams selectively scanned by the first and second scanning time measuring units based on the corrected scanning time deviation, respectively. Sub-scanning direction light beam interval calculating means for calculating an interval in the sub-scanning direction orthogonal to the main scanning direction;
An image forming apparatus control program for operating a computer as a computer program.

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