JP2006259005A - Optical scanner, image forming apparatus, and method for detecting scanning line inclination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner capable of detecting an inclination characteristic of scanning lines quickly and with high accuracy, suppressing deterioration of optical characteristics, and dealing with color deviation in a job. <P>SOLUTION: In an optical path, there are arranged laser beam detectors P1K, P2K for detecting a laser beam emitted from a light source 10. On the basis of the detection information from these laser beam detectors, the inclination of scanning lines on a photoreceptor 20 face is detected. On the basis of the arithmetic result of the inclination quantity and direction of the scanning lines, the inclination of the scanning lines are compensated. To be concrete, for example, a scanning imaging lens 17K is rotated around a position a prescribed quantity away from the optical axis in the subscanning direction, thereby compensating the inclination of the scanning lines. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical scanning device that forms a latent image on the surface of an image carrier, an image forming device such as a copying machine, a printer, a facsimile, or a plotter having the optical scanning device, and a scanning line tilt detection method.

  Japanese Patent Application Laid-Open No. 2003-337294 discloses a plurality of folding mirrors for guiding a laser beam corresponding to each color to a photoreceptor around an axis that is perpendicular to the main scanning correspondence direction and parallel to the reflecting surface of the folding mirror. The optical element having a mechanism for adjusting the scanning speed of the laser beam uniformly and correcting the scanning line position of the laser beam in the sub-scanning corresponding direction is perpendicular to the main scanning corresponding direction and perpendicular to the sub-scanning corresponding direction. An optical scanning device capable of adjusting the scanning speed uniformity with high accuracy and obtaining an image with good absolute position accuracy by providing a scanning line tilt adjusting mechanism for the laser beam displaced about the axis, and an image equipped with the optical scanning device A forming apparatus has been proposed.

In a color image forming apparatus such as a color laser printer, information on a plurality of different colors is separately obtained by a light scanning unit using a plurality of scanning imaging lenses for a plurality of photosensitive members rotated by a driving mechanism. Writing with a laser beam (scanning beam) to form an electrostatic latent image, each of these electrostatic latent images is visualized as a different color image by a plurality of visualization means, and superimposed on a transfer material. There is a tandem type color image forming apparatus that transfers and obtains a color image.
Each of the optical scanning means emits a laser beam from a semiconductor that is driven and controlled in accordance with the image information signal of each color to be read. The laser beam is condensed on a uniformly charged photoreceptor surface via an optical component such as a polygon mirror and a lens and scanned in the main scanning direction.
Image signals corresponding to a plurality of scanning beams having a predetermined interval are written on the rotating photosensitive member surface, and an electrostatic latent image is formed.

In the optical scanning device used in such a tandem type color image forming apparatus, color shift occurs when the amount of scanning beam scanning line and the direction of the scanning beam differ among the plurality of optical scanning devices for each color. The image quality is degraded.
In addition, if the timing of writing the electrostatic latent image formed on the photosensitive member is not accurately adjusted for each color, it may cause color misregistration due to resist misregistration.
Furthermore, since the components are arranged so that the laser beam toward the photoconductor passes through different paths, the scanning imaging lens is thermally deformed due to the environmental temperature in which the color image forming apparatus is installed and the temperature rise in the apparatus. However, the position of the scanning beam is likely to fluctuate. This is particularly true for resin lenses.

  Such a shift in scanning position is detected and corrected periodically at the start-up of the apparatus or between jobs by a registration position shift detection pattern (toner pattern or toner mark) recorded on the transfer body. ing.

JP 2003-337294 A

By the way, in this type of color image forming apparatus, the scanning position may further fluctuate due to heat generated by the fixing device and the polygon motor accompanying the continuous printing operation. However, there is a problem that the color shift gradually increases.
In the conventional method of detecting a positional deviation by forming a toner pattern on a transfer body at the time of starting up the apparatus or between jobs, the inclination of the scanning line is detected. I couldn't.
Further, the method of detecting a positional deviation by forming a toner pattern on the transfer body has a problem that the line width is different and the quality of the toner image (pattern image) is likely to vary due to humidity, so that the detection accuracy is low. Further, in the configuration of Patent Document 1, since one end of the optical element is fixed and the inclination of the scanning line is adjusted, the amount of change in the optical axis height at the other end is large, and the optical characteristics, particularly the laser beam diameter (peak light amount). 1 / e ² ) deteriorated.

  The present invention has an optical scanning device that can detect the inclination characteristic of a scanning line quickly and with high accuracy, can suppress deterioration of optical characteristics, and can cope with color misregistration during a job, and the optical scanning device. The main object of the present invention is to provide an image forming apparatus and a scanning line tilt detection method.

  In order to achieve the above object, according to the first aspect of the present invention, an optical scanning device for forming a latent image by scanning a laser beam emitted from a light source onto a surface of an image carrier by deflection scanning means and a scanning imaging optical system. A plurality of laser beam detecting means for detecting the laser beam are arranged in a scanning optical path, and a scanning line inclination detecting means for detecting the inclination of the scanning line on the surface of the image carrier based on detection information from the laser beam detecting means. It has the means.

  According to a second aspect of the present invention, the optical scanning device according to the first aspect includes a plurality of the light sources.

In the invention according to claim 3, in the optical scanning device according to claim 1 or 2,
An optical scanning apparatus comprising: a scanning line inclination correcting unit that corrects the inclination of the scanning line based on a calculation result of an inclination amount and an inclination direction of the scanning line by the scanning line inclination detecting unit.

  According to a fourth aspect of the present invention, in the optical scanning device according to the third aspect, the scanning line inclination correcting unit moves the scanning imaging lens of the scanning imaging optical system from the optical axis by a predetermined amount in the sub-scanning direction. An optical scanning device characterized in that the tilt of a scanning line is corrected by turning around a distant position.

  According to a fifth aspect of the present invention, in the optical scanning device according to any one of the first to fourth aspects, the laser beam detecting means comprises two light receiving elements for detecting a laser beam, and the two systems At least one of the light receiving elements has two light receiving areas that are non-parallel to each other in the region through which the laser beam passes, and the two light receiving elements are arranged in the main scanning direction so that adjacent edges are parallel to each other. It is characterized by being arranged adjacent to each other.

  According to a sixth aspect of the present invention, in the optical scanning device according to the fifth aspect, the scanning line inclination detecting unit measures time intervals of a plurality of pulse signals output from the laser beam detecting unit, and And an arithmetic means for calculating an inclination amount and an inclination direction of the scanning line.

  According to a seventh aspect of the present invention, in the optical scanning device according to any one of the first to sixth aspects, the optical scanning device includes a plurality of optical scanning devices, and other light is applied to the scanning line of the arbitrary optical scanning device. The inclination of the scanning line is corrected so as to match the scanning line of the scanning device.

  According to an eighth aspect of the present invention, in the optical scanning device according to the fourth aspect, the scanning imaging lens is within a range in which the rotation angle of the scanning imaging lens and the amount of change in scanning line tilt are substantially proportional. It is characterized by rotating.

  According to a ninth aspect of the present invention, in the optical scanning device according to the fourth aspect, the angle at which the scanning imaging lens is rotated is such that the variation in the diameter of the laser beam focused on the image carrier is before and after the rotation. The angle is equal to or less than ± 10%.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to ninth aspects, wherein a latent image is formed on an image carrier by optical scanning, and the latent image is visualized to obtain a desired recorded image. The optical scanning device described in 1 is used.

  According to the eleventh aspect of the present invention, the detection of the scanning line inclination of the optical scanning device for forming a latent image by scanning the laser beam emitted from a plurality of light sources onto the image carrier surface by the deflection scanning means and the scanning imaging optical system. In the method, a plurality of laser beam detecting means are arranged in the optical path of the optical scanning device, and the inclination of the scanning line on the surface of the image carrier is detected based on detection information from the laser beam detecting means. .

According to the first, second, tenth, or eleventh aspects, the inclination of the scanning line can be detected quickly and with high accuracy.
According to the invention described in claim 3 or 10, the inclination of the scanning line can be detected quickly and with high accuracy, and the inclination of the scanning line can be easily corrected.
According to the invention described in claim 4, the inclination of the scanning line can be corrected with high accuracy.
According to the invention described in claim 5, 6 or 10, it is possible to detect the inclination of the scanning line with high accuracy without affecting the detection accuracy even if the light quantity of the laser beam is changed.
According to the seventh or tenth aspect of the present invention, a plurality of (color) scanning lines are matched, and high-precision optical scanning is possible.
According to the invention described in claim 8 or 10, the processing of the calculating means for calculating the inclination of the scanning line can be performed easily and at high speed.
According to the ninth or tenth aspect of the present invention, the detection accuracy of the laser beam is not deteriorated, and the image is not deteriorated.

A first embodiment of the present invention will be described below with reference to FIGS.
First, the optical scanning device 32 according to the present embodiment will be described with reference to FIG. In the figure, reference numeral 10 denotes a light source for emitting a laser beam, 11 denotes a laser transmitting member (window) disposed in an optical housing, which will be described later, 12 denotes a polygon mirror as deflection scanning means (optical deflector), and 14 denotes scanning connection. A first lens (hereinafter also referred to as a “scanning lens”) constituting an fθ lens group of the image lens, a liquid crystal deflecting element 15 for correcting a scanning line, 16 a mirror, and 17 constituting an fθ lens group. Second lens (hereinafter also referred to as “scanning imaging lens”), 19 is a half mirror (semi-transparent mirror), 20 is a photosensitive member, 21 is an intermediate transfer belt, 22 to 24 are detection units as color misregistration detection means, P1 indicates a laser beam detector on the upstream side as a laser beam detector, and P2 indicates a laser beam detector on the downstream side as a laser beam detector.
The first lens 14, the liquid crystal deflecting element 15, the mirror 16, the second lens 17, and the like constitute a scanning imaging optical system.
For color machines, it has a scanning imaging optical system (scanning imaging lens) for four colors of yellow, magenta, cyan, and black (hereinafter abbreviated as Y, M, C, and K), and a laser beam corresponding to each color is photosensitive. It shows a state of focusing on the body.

The light source 10 shown in FIG. 1 has four sets of “light source devices” including a semiconductor laser, a coupling lens, and a cylindrical lens. Each light source device is a light source corresponding to each color (Y, M, C, K). Therefore, a plurality of (four) light sources are provided substantially.
The light beam emitted from each semiconductor laser is converted into a light beam form (parallel light beam or weak divergent or convergent light beam) suitable for the subsequent optical system by the coupling lens, and converged in the sub-scanning direction by the cylindrical lens. A line image that is long in the main scanning direction is formed in the vicinity of the deflection reflection surface of the polygon mirror 12 serving as the deflection scanning means.
Each of the four semiconductor lasers in the light source emits a light beam for writing each color component image of Y, M, C, and K. A surface emitting laser may be used as a semiconductor laser that can be an element of the light source or the light source itself.

The deflected light beams for the four colors deflected in the same direction by the rotation of the polygon mirror 12 are transmitted through the first lens 14 constituting the fθ lens group of the scanning imaging lens. The light beam (for example, the position of the upper end of the lens) for writing the K (black) component image is reflected by the mirror 16K, passes through the second lens 17K constituting the fθ lens group, and branches (transmitted and reflected) by the half mirror 19K. Then, one transmitted light beam is condensed as a light spot on the drum-shaped photoconductive photoconductor 20K that forms the actual state of the surface to be scanned, and optically scans the photoconductor 20K in the direction of the arrow.
The other reflected light beam forms an image on laser beam detectors P1K (upstream scanning side) and P2K (downstream scanning side) that detect the laser beam, and scans these light receiving portions. The laser beam detectors P1K and P2K are mounted and fixed on the fixing substrates B1 and B2, respectively.

The material of the first lens 14 and the second lens 17K of the fθ lens group is an aspherical shape made of a plastic material that is easy and low in cost. Specifically, polycarbonate, which has low water absorption, high transmittance, and excellent moldability can be used. A synthetic resin mainly composed of polycarbonate is preferred.
Similarly to the above, the light beams for writing the respective color component images of Y (yellow), M (magenta), and C (cyan) are reflected by the mirror, transmitted through the lens, transmitted through the half mirror, and reflected to form a drum shape. An image is formed as a light spot on the photoconductive photoreceptor, and each color is scanned in the same arrow direction. By this optical scanning, an electrostatic latent image of a color component image corresponding to each photoconductor is formed. In FIG. 1, the optical elements corresponding to the colors other than K are not labeled, but the components with “K”, which is an abbreviation for black, are optically attached to Y, M, and C. It is arranged at the same position.

These electrostatic latent images are visualized with a corresponding color toner by a developing device, which will be described later, and transferred onto the intermediate transfer belt 21. At the time of transfer, the color toner images are superimposed on each other to form a color image.
This color image is transferred onto a sheet-like recording medium and fixed. The intermediate transfer belt 121 after the color image transfer is cleaned by a cleaning device (not shown).
As described above, the optical scanning device shown in FIG. 1 uses the polygon mirror 12 of the deflection scanning means to transmit the light beams emitted from the plurality of light source devices corresponding to two or more color component images constituting the color image in the same direction. The first lens 14 which deflects and scans each of the deflected light beams and transmits the deflected light beam in common for each color, and each scanning image forming means (meaning an optical scanning device for each color). The second lens 17 performs optical scanning by individually condensing toward the scanned surface (photoconductor) 20 corresponding to each color component image. Therefore, this is an optical scanning device having four scanning imaging means (optical scanning devices) corresponding to the respective color components.

Immediately after the first lens 14, a liquid crystal deflecting element 15 is disposed as an optical element having a function of correcting the scanning line. The liquid crystal deflecting element 15 is an element that can be finely adjusted by electrically controlling the emission direction of the laser beam locally arbitrarily.
Reference numerals 22, 23, and 24 denote detection units that constitute “color misregistration detection means” on the intermediate transfer belt 21. The detection units 22, 23, and 24 condense a light beam from another light source with a condensing lens to irradiate a fixed position of the intermediate transfer belt 21, and form an image of reflected light on the light receiving element by the lens. ing. When color misregistration detection is performed, a detection pattern 21a is written to each of the three portions at both ends and the center in one scan by each light flux, visualized for development, and transferred to the intermediate transfer belt 21.
At this time, the detection patterns 21a for the respective colors are formed on the intermediate transfer belt 21 at equal intervals in the sub-scanning direction. In these toner patterns for detection, a shift in the sub-scanning registration position is detected by each detection unit of the color shift detection means.

  Next, the arrangement relationship between the laser beam detectors P1K and P2K will be described with reference to FIG. The optical deflector, which is a deflection scanning means, is composed of a polygon mirror 12 and a rotation drive unit (not shown) including a motor. The polygon mirror 12 is disposed in a space 4 that is sealed by the polygon mirror cover 2, and a high-temperature air flow accompanying the high-speed rotation of the polygon mirror 12 is caused by the laser transmitting member 11 to cause an internal sealed space 3 (optical housing) of the optical housing 1. 1 and the optical housing upper cover 1a). By shielding, the temperature distribution in the main scanning direction of the first lens 14 is reduced and reduced.

The laser beam detector P (P1K, P2K) is arranged outside (in the optical path) the image area in the main scanning direction, and at least an area where the light receiving element (reference numeral D) detects the laser beam from the end of the image area. It is arranged so as to be substantially perpendicular to the optical axis within a range of 10 mm.
If it is arranged outside 10 mm or more, the optical characteristics (field curvature, magnification error) of the scanning imaging element (scanning lens 14 and the like) are reduced, and the variation in the diameter and scanning time of the laser beam incident on the light receiving element. This is because the detection accuracy of the laser beam detector P deteriorates.

In order to further improve the detection accuracy, it is more preferable that the 10 mm region (range) is 5 mm or less. The temperature fluctuation of the magnification error in the main scanning direction due to the scanning imaging element within 10 mm is set to be equal to or smaller than that in other regions.
As will be described later, since the position of the scanning beam in the sub-scanning direction is detected at the scanning time interval in the main scanning direction, fluctuations in magnification error in the main scanning direction (especially changes with time due to temperature fluctuations) directly affect detection accuracy. This is because if the magnification error fluctuation is larger than that of the image area, the relationship between the accuracy of the image and the detection unit is reversed to cause a problem. In other words, if the variation in the detection region is large, there is a risk that it will be recognized as an abnormal variation even if the variation in the image portion is small.
On the other hand, if the design is forcibly designed so that the optical characteristics do not deteriorate even when the distance is 10 mm or more, the scanning lens 14 and the optical housing 1 are increased in size, leading to a cost increase.

Here, two laser beam detectors P are disposed at both ends, but it is preferable to provide a plurality of laser beam detectors P in order to improve detection accuracy. In that case, it is more preferable to arrange densely (concentrated) in a portion where the inclination of the scanning line seems to be large.
The “scanning line” here is a movement trajectory of the laser beam on the surface to be scanned, and needs to be on a straight line with respect to a direction orthogonal to the sub-scanning direction. Since main scanning is performed, it is not strictly orthogonal to the sub-scanning direction. Actually, the laser beam is scanned with an inclination with respect to the sub-scanning direction (scanning line inclination).

The inclination of the scanning line often occurs due to the optical characteristics and mounting orientation of the scanning imaging lens. In the case of a lens or optical housing using a plastic material, which is a low-cost material, the temperature environment of the optical scanning device As a result of the change, the optical characteristics and the mounting posture fluctuate, and the inclination amount of the scanning line in the initial operation may fluctuate and increase.
On the other hand, a device that obtains a final image by superimposing a plurality of (color) scanning lines as in a color image forming apparatus does not necessarily need to be orthogonal to the sub-scanning direction. Even if it is tilted, color shift is not recognized on the image if the other scanning lines are tilted in the same manner (indicating that the tilt direction and tilt amount are the same).
However, even in that case, it is preferable that the inclination amount of the scanning line is 500 μm or less (per 300 mm of main scanning). This is because when the thickness is 500 μm or more, the magnification error becomes large, which causes a problem.

Based on FIG. 3, the structure and detection signal of the laser beam detector P will be described. FIG. 4A shows the configuration of the detector, and FIG. 4B shows the output waveform. In the figure, reference numeral 219 is a detector, PD1 is a first light receiving element, PD2 is a second light receiving element, D is a maximum element width (full width in the main scanning direction), and H is an effective detection height in the sub scanning direction. , Θ is the angle of the light receiving element inclined side, AMP is an amplifier, and CMP is a comparator.
The light receiving element PD1 of the first system and the light receiving element PD2 of the second system are arranged adjacent to each other in the main scanning direction, and both are divided into two light receiving areas formed non-parallel to each other in the area where the laser beam passes. The respective regions are arranged adjacent to each other with the light receiving elements PD1 and PD2, and the adjacent edge portions are linearly formed in parallel with each other.
The angle between the two light receiving regions of each light receiving element is arranged with an angle θ (0 <θ <90 °). The angle θ is preferably 30 ° to 60 °. The figure and the next figure (FIG. 4) show an example of 45 °, which is the most preferable example.

This is because when the angle θ is smaller than 30 °, the variation of T1 with respect to the scanned laser beam is reduced, and the detection sensitivity is deteriorated. On the other hand, when the angle exceeds 60 °, the effective detection height H in the sub-scanning direction with respect to the entire width D of the light receiving surface in the main scanning direction decreases, and in order to secure the necessary effective detection height H, the entire width D of the light receiving surface increases. Therefore, there is a problem that the light receiving surface enters the image area, or it is necessary to set a wide effective area of the scanning optical system, and there is a problem that the scanning lens becomes long.
It is preferable that the height H in the sub-scanning direction and the total width D of the light receiving surface are set to H = 1 to 3 mm and D = 5 mm or less, respectively, without causing the above problem. Note that 45 ° is most preferable because the above problem can be distributed and allowed in a balanced manner.

If one of the two light receiving regions is formed perpendicular to the laser beam scanning direction, the sensor output timing does not change even when the laser beam is shifted in the sub-scanning direction, which is suitable for obtaining a horizontal synchronization signal.
Reference numeral 219 (220 in FIG. 13) in FIG. 3 represents the detector shown in the light receiving surface shape and circuit block diagram of the laser beam detector P1K (or P2K) in FIG. In the present embodiment, the detector denoted by reference numeral 219 and the laser beam detector P1K (or P2K) are handled in the same way. A laser beam detector having this function is mounted and fixed on the fixing substrate B1 or B2.
After the output signals of the light receiving elements PD1 and PD2 are subjected to current-voltage conversion and voltage amplification by the amplifiers AMP1 and AMP2, respectively, voltage comparison is performed by the comparator CMP, and the output signal level of the AMP2 becomes lower than the output signal level of the AMP1. Sometimes outputs a signal.
Thus, since the cross point of AMP1 and AMP2 is detected, even if the light quantity of a laser beam changes, a highly accurate detection which does not affect a detection accuracy is attained. Therefore, the interval between the adjacent portions of the two light receiving elements is set smaller than the spot size of the beam passing therethrough.

FIG. 3B is a timing chart of the output signal of the laser beam detector when the laser beam L1 passes through the light receiving elements PD1 and PD2. Two pulses are output by the passage of the laser beam L1, and the time interval T1 from the fall to the fall of the two pulses depends on the sub-scanning position where the laser beam L1 is scanned.
When the time interval between the two laser beams is T1, the sub-scanning position P of the laser beams can be obtained from the following equation (1).
P = (v × T1) / tan θ Formula (1)
Here, v represents the speed of the scanned laser beam.
When a plurality of laser beams for each color are scanned at the same time, only one laser beam is scanned only when scanning the laser beam detector, and the other laser beams are attenuated to such an extent that they are not detected only at that time. Or extinguish.
This is because if a plurality of laser beams scan the light receiving portion of the laser beam detector, the detection value outputs an incorrect result.

  In order to detect the inclination of the scanning line, when the laser beam detectors 219 are arranged at at least two positions on both ends in the main scanning direction, the laser beam for scanning one laser beam detector is L1, and the other laser beam detector is Assuming that the laser beam to be scanned is L1 ′ and the pulse time interval T1 ′ at that time, T1 in equation (1) can be replaced with T1 ′ for calculation.

In the above case, for example, if the scanning characteristic changes due to jitter of the polygon mirror 12, even if the same part of the light receiving surface is scanned, it is measured as a different scanning time, and it is mistakenly assumed that the scanning position in the sub-scanning direction has changed. There is a risk.
Therefore, by providing a circuit that averages the number of scans by the polygon mirror 12 by the following number, the influence of jitter on the polygon mirror 12 can be reduced.
The number of scans of the laser beam is C [times], the rotation speed of the polygon mirror 12 is N [rpm], the number of faces of the polygon mirror 12 is M [surface], and the non-image formation time from the end of image formation to the start of the next image formation Is set to satisfy the equation (2).
C <(N × M × T) / 60 Formula (2)
By obtaining T1 information when scanning an arbitrary specific surface of the polygon mirror 12, the right side of the above equation is expressed as (N × T) / 60.
It is good.

As a method for obtaining information on a specific surface, a method that does not count data according to the number of surfaces, that is, in the case of six surfaces, an arbitrary one surface is assumed to be a first surface and a specific surface is obtained. What is necessary is just to take the method which does not count the data of the 5th surface. In this way, there is an advantage of further reducing the influence of jitter.
In order to reduce the influence of jitter on the polygon mirror 12, at least C must be set to two or more times and an averaging process must be performed. Considering the influence of electrical noise, the accuracy increases as the number of scans increases.
However, the increase in the number of scans is the non-image formation time (printing) between the image formation in the image forming device (the time during which the light source of the optical scanning device is controlled to emit light based on the image signal) and the next (page) image formation. It is preferable to set the number of times of scanning within (between pages) or less. The reason is that by detecting the laser beam immediately after the image formation is completed, it is possible to correct the inclination of the scanning line during the immediately subsequent image formation based on the result.
Therefore, more preferably, in the left side of the equation (2), it is preferable to set “C + F” as the number of times of scanning corresponding to the time until the inclination correction of the scanning line is completed. Since the detection of the laser beam is set as the non-image forming time, the detection of the laser beam in the image area is not hindered.

The fixing substrates B1 and B2 to which the laser beam detectors P1K and P2K are fixed are shown as separate members. However, when the temperature is exposed to a high temperature of 50 ° C. or higher, or the laser beam arranged in each color portion When the temperature difference between the detectors is 5 ° C. or more, the fixing substrates B1 and B2 are preferably arranged on the same substrate.
If the temperature fluctuates, accurate detection cannot be performed due to the movement of the laser beam detector and the movement of the relative positional relationship, so the thermal expansion coefficient of the fixing substrates B1 and B2 is 1.0 × 10 ⁻⁵ / ° C. The effect of temperature fluctuations is virtually eliminated. Furthermore, in order to eliminate the influence of electrical noise generated between the plurality of laser beam detectors, the fixing substrates B1 and B2 are preferably non-conductive.
Specifically, glass (thermal expansion coefficient 0.5 × 10 ⁻⁵ / ° C.), ceramic material (alumina: thermal expansion coefficient 0.7 × 10 ⁻⁵ / ° C., silicon carbide: thermal expansion coefficient 0.4 × 10 ⁻⁵ / ° C.) is preferred. In the case of an aluminum alloy (thermal expansion coefficient 2.4 × 10 ⁻⁵ / ° C.), the laser beam detection accuracy deteriorates due to temperature fluctuation.

Based on FIG. 4, the scanning line inclination detection method in the present embodiment will be described in detail.
FIG. 4A shows a main part in which the laser beam detector is laid out by the optical scanning device. The light receiving parts 41 and 42 are the light receiving parts of the laser beam detectors P1K and P2K shown in FIG.
In this example, the laser beam scans the light receiving unit 41 on the upstream side in the main scanning direction, and a signal shown in the output of the light receiving unit 41 in FIG. A scanning time T41 corresponding to the sub-scanning position of the laser beam is measured by a counter measurement unit (not shown).
Next, when the laser beam scans the light receiving unit 42, a signal shown in the output of the light receiving unit 42 in FIG. 4B is output, and another counter measurement (not shown) corresponding to the scanning time T42 corresponding to the sub-scanning position of the laser beam is output. Measure by means.

The measured scanning times T41 and T42 are output to the control means 50 as the scanning line inclination detecting means shown in FIG. 11, and the sub-scanning position is calculated according to the above equation (1). The control unit 50 is a microcomputer having an I / O interface 51, a CPU 52 as a calculation unit, a RAM 53, a ROM 54, and the like, and can also serve as a main controller of a color image forming apparatus described later. The counter measuring means may be provided separately, but the CPU 52 may also serve.
Note that since v and θ in the expression (1) are substantially constant during image formation and when a laser beam is detected, only the time intervals T41 and T42 are used in actual calculation. This is suitable for shortening the calculation time.

Next, the scan line tilt calculating means (control means 50) calculates the scan line tilt amount from the results of the scan times T41 and T42.
The scanning line inclination amount is the difference between the scanning times T41 and T42, and the calculation of “T41−T42” is performed.
For example, even when the arrangement or posture of the optical element changes due to the influence of temperature fluctuation or the like and the scanning line moves in parallel, the difference is calculated, so that it is possible to detect (discriminate) whether the movement is parallel or tilted. .
Further, the inclination direction of the scanning line is determined based on the sign “T41-T42”. When the two light receiving region portions formed non-parallel are arranged so as to spread toward the upstream side in the sub-scanning direction (example shown in the figure)
(1) When “T41−T42” is a plus (+) sign, the scanning line tilts in the upward direction with respect to the horizontal direction (example shown in the figure).
(2) When “T41−T42” is a minus (−) sign, it is determined that there is a scanning line inclination in the upward left direction with respect to the horizontal.
When the two light receiving area portions of the laser beam detector are arranged so as to extend toward the downstream side in the sub-scanning direction, the scanning line tilt directions are opposite to each other.

On the other hand, when “T41−T42” is within the detection error of the laser beam detector, it is determined that “T41 = T42” and it is determined that there is no inclination of the scanning line. The detection error of the laser beam detector is a value corresponding to a difference between T41 and T42 of 10 μm or less as a result of calculation by the calculation means when the detection accuracy of the light receiving unit and the error component related to the electric circuit are included. In this case, it is determined that there is no inclination of the scanning line.
The detection of the scanning line inclination is performed individually for each color scanning line, and the laser beam detectors are arranged at the same position for each color. Therefore, all the calculation formulas can be the same, and the calculation means is not provided for each color by sharing the timing within the calculation means so that the detection timing of the scanning line of each color is sequentially detected for each color. , It becomes possible to share one arithmetic means.
Thereby, there is an effect of reducing (cost reduction) the counter and the arithmetic circuit.

As for the inclination of the scanning line, a value corresponding to the scanning position of the laser beam at the time of shipment from the factory or at the start of correction is stored in advance in the storage means (for example, the ROM 54) as reference time interval information. By calculating the difference between the detected time interval and the reference time interval, the amount of parallel movement of the scanning line can be detected.
By adjusting the laser beam lighting start timing so as to become a reference time interval according to the result, it is possible to correct the sub-scanning registration position fluctuation due to the parallel movement of the scanning line.
The optical system shown in FIG. 1 is a so-called one-side scanning system in which the main scanning direction is the same for each color with respect to the polygon mirror 12, but is an opposed scanning system that performs main scanning on both sides facing the polygon mirror 12. In this case, the main scanning direction is reversed with the polygon mirror 12 interposed therebetween.

For this reason, it is preferable to arrange the laser beam detector P so as to be upside down from the example shown in FIG. 4, that is, as shown in FIG. As shown in FIG. 6, the same fixing substrate B can be used upside down so as not to increase the types of fixing substrates on which the laser beam detector P is mounted even in the reverse direction.
In that case, it is provided so that the attachment position is equally divided (L) with respect to the center of the light receiving region in the sub-scanning direction. Further, the middle of the first and second light receiving portions that are substantially orthogonal to the main scanning direction is equally arranged (W) with respect to the attachment position, so that one of the opposed scanning systems is arranged as shown in FIG. As shown in FIG. 6B, the other side (opposite side) can be easily installed at an optically equivalent position simply by turning the fixing substrate B upside down. In FIG. 6, reference symbol Ba denotes a screwing hole.
Note that a variation in magnification error can be detected by measuring the scanning time T43 from the output of the light receiving unit 41 and the output of the light receiving unit 42 by another measuring unit (not shown) (or the CPU 52 of the control unit 50).

The scanning time T43 is the scanning time between the laser beam detectors in the main scanning direction, and since the light receiving portion uses a portion perpendicular to the main scanning direction, the scanning time is constant regardless of the sub-scanning position. Therefore, it is suitable for measuring fluctuations in the scanning time (magnification error) in the main scanning direction.
Further, the falling edge of the scanning time T43 (or the first falling edge of the scanning time T41) can be used as a main scanning synchronization signal. Specifically, it can be achieved by starting writing of an image after a predetermined time after detecting the falling signal of the scanning time T3.
Although the waveform fall is described here, it is not particularly limited to the fall, and it is a matter of course that the same effect can be obtained even with a rise waveform in which the entire waveform is inverted.
Based on the detection result, it is possible to form a high-quality color image with little color misregistration by feeding back and correcting to the adjusting means (control means 50) for adjusting the image signal corresponding to each color.
In the feedback correction, control is performed so that another scanning imaging lens is rotated with respect to the scanning imaging lens of the reference color set in advance.

Next, the attitude control of the scanning imaging lens for correcting the inclination of the scanning line will be described in detail including the conventional problems.
The scanning imaging lens 17K described with reference to FIG. 1 is formed by molding using a plastic material. However, the scanning imaging lens made of a plastic material is susceptible to changes in optical characteristics due to the influence of changes in temperature and humidity. Further, the inclination of the scanning line is also changed by changing the mounting posture.
For this reason, for example, when printing several tens of color images continuously, the temperature inside the apparatus rises due to the continuous operation of the image forming apparatus, and the inclination of the scanning line of the optical scanning apparatus for each color gradually changes. There is a problem that the deviation becomes obvious.
In particular, in the case where the optical housing is a molding material made of a plastic material, the resin fluidity at the time of molding varies in each part, so that the influence of thermal expansion strain at the time of temperature rise differs. As a result, the temperature expansion or contraction is similar and does not expand or contract, and the entire optical housing is curved, or the portion where the scanning imaging lens is placed is inclined, and the inclination of the scanning line greatly fluctuates. There are specific problems.

In the optical housing, glass fiber or the like is mixed in the plastic material in order to improve the mechanical strength. Therefore, the variation in fluidity at the time of molding is remarkable, and the change in the inclination of the scanning line tends to be large.
The amount of inclination of the scanning line includes an amount generated by the optical scanning device itself and an amount generated by factors other than the optical scanning device, for example, the inclination of the scanning line due to the inclination of the rotation axis of the photosensitive member in the sub-scanning direction. Since the accumulation of each factor is manifested as an image color misregistration, in this embodiment, factors other than the optical scanning device can be corrected by the optical scanning device.

FIG. 7 shows a scanning imaging lens unit 100 in which a scanning imaging lens 17K, which is a long lens that is longer in the main scanning direction than in the sub-scanning direction, is formed integrally with the scanning line inclination correction means. In the optical scanning device.
The inclination of the scanning line can be changed by rotating around the optical axis of the scanning imaging lens 17K (indicated by reference numeral γ in FIG. 7). The inclination of the scanning line can be arbitrarily changed and the state is maintained.
On the other hand, the bending of the scanning line (curvature in the sub-scanning direction) can be corrected by the rotation (indicated by the symbol β in FIG. 7) in the direction orthogonal to the optical axis of the scanning imaging lens 17K.

The scanning imaging lens unit 100 includes a shape holding unit 102 and a scanning line inclination correction unit 103 of the scanning imaging lens 17K.
The shape holding means 102 functions as a means for correcting the shape of the scanning imaging lens 17K when the scanning imaging lens 17K undergoes deformation such as warping due to a local temperature change. A lower sheet metal member 102A on which the lens 17K is placed and can be positioned, an upper sheet metal member 102B that can hold the upper surface of the scanning imaging lens 17K, and upper and lower each disposed at both longitudinal ends of the scanning imaging lens 17K. And an interval holding member 102C to which the side metal plate members 102A and 102B are attached.

The material of the sheet metal members 102A and 102B is preferably an inexpensive thin steel plate having a high Young's modulus and good workability. An aluminum alloy plate has a low Young's modulus and cannot have a function for maintaining the shape. The material of the spacing member 102C is preferably a metal member having a smaller thermal expansion than the scanning imaging lens 17K made of a plastic material. This is because the thermal expansion of the resin is large and the accuracy of maintaining the interval cannot be maintained with high accuracy.
Further, the spacing member 102C is set to be equal to or lower (thin) the height (thickness) of the scanning imaging lens 17K in the sub-scanning direction. As a result, the scanning imaging lens 17K is sandwiched at both ends in the sub-scanning direction by the lower and upper sheet metal members 102A and 102B, and is held with its deformation suppressed when warping occurs. .

A protruding piece 102A2 is formed on the front end edge of the central portion in the longitudinal direction of the lower sheet metal member 102A, that is, on the edge on the emission side of the scanning light on one side in the optical axis direction, and the protruding piece 102A2 has the above-mentioned β An adjustment screw 104 for adjusting the tilt in the direction is fastened to a fixed portion of the optical housing 1.
Thus, the inclination of the scanning imaging lens 17K in the direction orthogonal to the optical axis can be adjusted to correct the bending of the scanning line.
As shown in FIG. 8, one end of a U-shaped plate spring 107 spanned between the upper base metal member 102B and the support base 106 provided in a part of the optical housing 1 is fastened. It is attached. The plate spring 107 supports the upper sheet metal member 102B, and rotates the shape holding means 102 including the lower sheet metal member 102A, the upper sheet metal member 102B, and the spacing member 102C with the spherical tip of the reference pin 108 as a fulcrum. It is supported so as to be movable in the sub-scanning direction.

The leaf spring 107 has a degree of freedom only in each of the β and γ directions and restricts others, and thus has a side effect other than correction of the inclination or bending of the scanning line and is a preferable structure.
The shape holding means 102 has a longitudinal center portion of the scanning imaging lens 17K placed on a reference pin 108 provided on the support base portion 106 side of the optical housing, and is separated from the optical axis G by a predetermined amount Y in the sub-scanning direction. It is possible to incline in the γ direction with the position as a fulcrum.
When the scanning line inclination correcting unit 103 is rotated in the γ direction, the inclination of the scanning line can be corrected. By rotating around a position that is a predetermined amount Y apart from the optical axis G instead of the fulcrum, it is possible to moderate (dull) the amount of change in the scan line inclination with respect to the rotation angle. Even if it rotates, the influence on the amount of inclination of the scanning line is suppressed as much as possible.

When rotating around the optical axis G, the amount of change in the inclination of the scanning line is sensitive, so it is necessary to provide a high-resolution drive mechanism for the rotation mechanism, which requires a complicated mechanism and high-precision parts, which increases costs. There is also a problem of becoming.
Specifically, the predetermined amount Y is preferably in the range of 3 to 10 mm from the above problem. The scanning line inclination correcting unit 103 is disposed on one side in the longitudinal direction of the shape holding unit 102 and includes a drive source 109 using a stepping motor.
As shown in FIG. 9, a lead screw 109A is formed on the output shaft of the drive source 109, and a nut 110 is attached to the lead screw 109A. The nut 110 is provided with an adjustment lever 112 that supports a swing fulcrum shaft on a drive source support bracket 111 installed on the support base 106.
As a result, as indicated by an arrow in FIG. 9, the adjustment lever 112 swings according to the direction in which the nut 110 moves in the axial direction of the lead screw 109A according to the rotation direction of the lead screw 109A. The swing end of the adjustment lever 112 can be interlocked with the support pin 102 </ b> C <b> 1 provided on the spacing member 102 </ b> C by pressing from above. As a result, according to the swinging state of the adjusting lever 112, it is possible to incline in the γ direction with a position away from the optical axis G by a predetermined amount Y in the sub scanning direction as a fulcrum, and the inclination of the scanning line can be corrected.
As shown in FIG. 11, the inclination of the scanning line is corrected by driving the drive source 109 by the number of steps corresponding to the adjustment amount by the control means 50.
Therefore, strictly speaking, the scanning line inclination correcting means is composed of a rotation mechanism indicated by reference numeral 103 and a control means 50.

FIG. 10 shows the amount of change in the inclination of the scanning line with respect to the rotation angle of the scanning imaging lens.
The inclination of the scanning line does not change constantly depending on the rotation angle, but the range of constant change is limited by the optical characteristics of the scanning imaging lens and the effective range in the sub-scanning direction.
Therefore, in the present embodiment, the inclination of the scanning line is changed within a range (between θ1 and θ2) in which the processing of the calculation means is in a simple substantially proportional relationship.
The amount of change in the inclination of the scanning line at this time secures a rotation angle range corresponding to 500 μm at the maximum. The “substantially proportional relationship” refers to a relationship in which the amount of change at an arbitrary angle in the range of the rotation angles θ1 to θ2 is a linear approximation in the least square method and the correlation coefficient r is 0.8 or more.
On the other hand, turning the scanning imaging lens causes a side effect such that the beam spot diameter (1 / e ^{2 of the} peak light amount) on the surface of the photosensitive member deteriorates. Change) is within ± 10%. If it is ± 10% or more, the detection accuracy of the laser beam detector is deteriorated to cause a problem, and the image (particularly gradation and resolution) when used as an image forming apparatus is deteriorated.

The scanning imaging lens unit described above is arranged for each color, and correction is performed so that the scanning line corresponding to an arbitrary color is adjusted to adjust the inclination direction and the amount of inclination of the scanning line so as to match other scanning lines. Execute.
In addition, when the inclination of the scanning line is corrected, the inclination of the scanning line due to the inclination of the photosensitive member is detected in advance, and the correction is performed including the inclination amount stored in the storage unit. Factors other than the scanning device can be corrected by the optical scanning device.
In addition, as described above, in the case of a plastic scanning imaging lens or optical housing, the inclination of the scanning line changes in temperature (temperature rise in the optical scanning device due to elapsed time, air current in the image forming apparatus, and heat source). Therefore, the inclination of the scanning line is constantly detected and monitored while the optical scanning device is operating to determine whether it is necessary to correct the inclination of the scanning line.

It should be noted that the laser beam is turned on only when the temperature fluctuates greatly (when the temperature fluctuation amount exceeds a predetermined value), and the laser beam is turned off and the laser beam detector is turned off otherwise. Power supply can also be saved by shutting off the power supply.
In addition, since the inclination of the scanning line can be detected only by the laser beam detector in the optical scanning device, there is no need to visualize the detection pattern with toner on the intermediate transfer belt as in the prior art, and the toner consumption Can be reduced as much as possible to contribute to resource saving.

FIG. 12 shows a color image forming apparatus (color laser printer) equipped with the optical scanning device of this embodiment. An optical scanning device 32 in which the configuration shown in FIG. 1 is housed in a single optical housing is disposed in a color image forming device 33.
The optical scanning device 32 includes four photoconductors 20Y, 20M, 20C, and 20K (hereinafter, subscripts Y, M, C, and K are appropriately added to the reference numerals, Y: yellow, M: magenta, and C: cyan). , K: shall be distinguished as a portion corresponding to the color of black.) Are arranged above the image forming units arranged in parallel.
This is a tandem type color image forming apparatus in which a plurality of photoconductors 20Y, 20M, 20C, and 20K are arranged in parallel. An optical scanning device 32, a developing device 25, a photoconductor 20, an intermediate transfer belt 21, a fixing device 31, and a paper feed cassette 30 are laid out in order from the top of the device.
On the intermediate transfer belt 21, photosensitive members 20Y, 20M, 20C, and 20K corresponding to the respective colors are arranged at equal intervals in the parallel order. The photoreceptors 20Y, 20M, 20C, and 20K are formed to have the same diameter, and members are sequentially arranged around the photoreceptors according to an electrophotographic process.

The photoconductor 20Y will be described as an example. A charging charger (not shown), a laser beam LY based on an image signal emitted from the optical scanning device 32, a developing device 25Y, a transfer charger (not shown), a cleaning device (not shown), and the like. Are arranged in order. The same applies to the other photoconductors 20M, 20C, and 20K. That is, in this embodiment, the photoconductors 20Y, 20M, 20C, and 20K are to be scanned surfaces set for the respective colors, and the laser beams LY, LM, LC, and LK are emitted from the optical scanning device 32 for each color. Are provided to correspond to each.
The photoconductor 20Y uniformly charged by the charging charger rotates in the direction of arrow A, thereby sub-scanning the laser beam LY, and an electrostatic latent image is formed on the photoconductor 20Y. Further, a developing device 25Y that supplies toner to the photoconductor 20Y is disposed downstream of the irradiation position of the laser beam LY by the optical scanning device 32, and yellow toner is supplied. The toner supplied from the developing device 25Y adheres to the portion where the electrostatic latent image is formed, and a toner image is formed. Similarly, M, C, and K monochromatic toner images are formed on the photoreceptors 20M, 20C, and 20K, respectively.

An intermediate transfer belt 21 is disposed further downstream in the rotational direction than the position where the developing device 25 of each photoconductor 20 is disposed. The intermediate transfer belt 21 is wound around a plurality of rollers 26, 27, and 28, and is moved and conveyed in the direction of arrow B by driving a motor (not shown).
By this conveyance, the intermediate transfer belt 21 is sequentially moved to the photoreceptors 20Y, 20M, 20C, and 20K. The intermediate transfer belt 21 sequentially superimposes and transfers the single color images developed by the photoreceptors 20Y, 20M, 20C, and 20K to form a color image.
Thereafter, the transfer paper is conveyed from the paper feed tray 30 in the direction of arrow C, and the color image is transferred by the transfer roller 29. The transfer paper on which the color image is formed is fixed by the fixing device 31 and then discharged as a full-color image.

A second embodiment will be described based on FIG. Note that the same parts as those in the above embodiment are denoted by the same reference numerals, and unless otherwise specified, description of the configuration and functions already described is omitted, and only the main part will be described (the same applies to other embodiments below).
FIG. 4A shows the configuration of the detector, and FIG. 4B shows the output waveform. In the figure, reference numeral 220 denotes a detector.
In the present embodiment, the light receiving element PD1 of the first system is divided into two light receiving areas in the laser beam passing area, although it is one light receiving element as in the configuration of FIG. On the other hand, the light receiving element PD2 of the second system has only one light receiving region in the laser beam passing region.
Even in this case, the adjacent edges of the light receiving elements PD1 and PD2 are formed in parallel to each other. Therefore, PD2 has a substantially triangular shape.
In the case of the configuration shown in the figure, the detection signal output from the comparator is one pulse for one laser beam scan, and the pulse width (T1 or T1 ′) depends on the sub-scan scan position. Since the calculation formula is the same as that of Formula (1), it is omitted.

FIG. 14 shows a third embodiment.
As shown in FIG. 2A, the first light receiving element PD1 and the second light receiving element PD2 are divided into two elements to form two light receiving regions. Each light receiving region is electrically connected, and each is treated as if it were one light receiving element.
Therefore, signal processing is exactly the same as in FIG. In FIG. 14B, only the first light-receiving element PD1 is divided into two elements as described above, and is electrically connected. The light receiving element PD2 of the second system may have a triangular shape as shown in FIG. 3, but in order to avoid an extremely short output time from the light receiving element PD2 when the scanning line is shifted upward. As shown in the figure, it is also a good method to form a trapezoidal shape.
In addition, when the amount of light in the image area and the amount of light necessary for the laser beam detector are different, it is possible to prevent a decrease in detection accuracy by adjusting the output of the light source only when detecting by the laser beam detector. .

1 is a perspective view of an optical scanning device according to a first embodiment of the present invention. It is a figure which shows the arrangement | positioning relationship of the laser beam detector in an optical housing. It is a figure which shows the structure and output waveform of a laser beam detector. It is a figure which shows the detection method of a scanning line inclination. It is a figure which shows the arrangement | positioning state of the laser beam detector in the case of a counter scanning system. It is a figure which shows the board | substrate for fixation which is not influenced by the arrangement state of a laser beam detector. It is a perspective view of a scanning imaging lens unit. It is sectional drawing of a scanning image formation lens unit. It is a figure which shows the structure and operation | movement of a scanning line inclination correction means. It is a graph which shows the relationship between the rotation angle of a scanning image formation lens, and the inclination variation | change_quantity of a scanning line. It is a control block diagram. 1 is a schematic front view of an image forming apparatus. It is a figure which shows the structure and output waveform of the laser beam detector in 2nd Embodiment. It is a figure which shows the structure and output waveform of the laser beam detector in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light source 12 Polygon mirror as a deflection scanning means 17 Scanning imaging lens (2nd lens)
20 Photoconductor as image carrier 50 Control means as scanning line tilt detection means 52 CPU as calculation means
103 Scanning line inclination correction means PD1, PD2 Light receiving element

Claims (11)

In an optical scanning device that forms a latent image by scanning a laser beam emitted from a light source onto a surface of an image carrier by a deflection scanning unit and a scanning imaging optical system,
A plurality of laser beam detecting means for detecting the laser beam are arranged in a scanning optical path, and scanning line inclination detecting means for detecting the inclination of the scanning line on the image carrier surface based on detection information from the laser beam detecting means. An optical scanning device comprising: The optical scanning device according to claim 1,
An optical scanning device comprising a plurality of the light sources. The optical scanning device according to claim 1 or 2,
An optical scanning apparatus comprising: a scanning line inclination correcting unit that corrects the inclination of the scanning line based on a calculation result of an inclination amount and an inclination direction of the scanning line by the scanning line inclination detecting unit. The optical scanning device according to claim 3.
The scanning line inclination correction means corrects the inclination of the scanning line by rotating the scanning imaging lens of the scanning imaging optical system about a position separated from the optical axis in the sub-scanning direction by a predetermined amount. An optical scanning device. The optical scanning device according to any one of claims 1 to 4,
The laser beam detecting means comprises two light receiving elements for detecting the laser beam, and at least one of the two light receiving elements has two light receiving regions that are non-parallel to each other in the region through which the laser beam passes. The two systems of light receiving elements are arranged adjacent to each other in the main scanning direction so that adjacent edges are parallel to each other. The optical scanning device according to claim 5,
The scanning line inclination detecting unit has a calculating unit that measures time intervals of a plurality of pulse signals output from the laser beam detecting unit and calculates an inclination amount and an inclination direction of the scanning line based on the time interval. An optical scanning device characterized by comprising: The optical scanning device according to any one of claims 1 to 6,
An optical scanning device comprising a plurality of optical scanning devices, wherein the inclination of the scanning line is corrected so as to match the scanning line of another optical scanning device with respect to the scanning line of an arbitrary optical scanning device. The optical scanning device according to claim 4.
An optical scanning device characterized in that the scanning imaging lens is rotated within a range in which the rotation angle of the scanning imaging lens and the amount of change in scanning line tilt are substantially proportional. The optical scanning device according to claim 4.
An optical scanning device characterized in that the angle at which the scanning imaging lens is rotated is equal to or less than an angle at which fluctuations in the diameter of the laser beam focused on the image carrier are within ± 10% before and after the rotation. In an image forming apparatus that forms a latent image on an image carrier by optical scanning and obtains a desired recorded image by visualizing the latent image.
An image forming apparatus using the optical scanning device according to claim 1. In a method of detecting a scanning line inclination of an optical scanning device that forms a latent image by scanning laser beams emitted from a plurality of light sources onto a surface of an image carrier by a deflection scanning unit and a scanning imaging optical system.
A plurality of laser beam detecting means are arranged in the optical path of the optical scanning device, and the inclination of the scanning line on the surface of the image carrier is detected based on detection information from the laser beam detecting means. Detection method.

Images