JP5817471B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method.

  2. Description of the Related Art Conventionally, there is known an image forming apparatus that forms an image by reflecting a laser beam by a polygon mirror (rotating polyhedron) and performing exposure scanning on a photosensitive member. The polygon mirror is formed such that the shape seen from the direction of the rotation axis forms a regular polygon, and the laser beam is deflected on a plurality of surfaces forming each side of the regular polygon. However, it is difficult to accurately form the polygon mirror in the shape of a regular polygon, which causes a problem that the writing position is shifted by the laser beam due to non-uniformity of each side.

  As a method for solving this problem, a technique is known in which each surface of a polygon mirror is specified, and a main scanning offset value is assigned to each surface, thereby adjusting a deviation of a writing position generated between the surfaces. Yes.

  Japanese Patent Laid-Open No. 2004-228688 aims to reduce horizontal synchronization sensors in an opposed scanning optical system including a first scanning station corresponding to a first laser light source and a second scanning station corresponding to a second laser light source. The horizontal synchronization sensor is provided only in the first scanning station, and based on the detection result of the horizontal synchronization sensor, output of two image data of the image data for the first laser light source and the image data for the second laser light source is performed. Techniques for controlling are disclosed.

  As described above, by giving a main scanning offset value to each surface of the polygon mirror, it is possible to adjust the deviation of the writing position that occurs between each surface, but in order to give a main scanning direction offset value It is necessary to correctly specify each surface of the polygon mirror. However, there is a case where each surface is mistaken, and in this case, a main scanning offset value to be set to a surface different from the surface is set for a predetermined surface, and this causes a decrease in image quality. There was a problem.

  The present invention has been made in view of the above, and an object thereof is to provide an image forming apparatus and an image forming method capable of stably forming a high-quality image.

  In order to solve the above-described problems and achieve the object, the present invention is an image forming apparatus having a light source for irradiating laser light and a plurality of surfaces, and deflecting the laser light by the plurality of surfaces. A rotating polyhedron for scanning, a light receiving unit that receives the laser light deflected by each surface of the rotating polyhedron, and the light receiving unit that receives the laser light from each of two adjacent surfaces that are two adjacent surfaces of the rotating polyhedron. A scanning period measuring unit that measures a time difference between light receiving timings, an algorithm that identifies a reference plane set in advance from the plurality of surfaces of the rotating polyhedron based on the time difference obtained from the rotating polyhedron, and the time difference Obtained from each of the two adjacent surfaces of the rotating polyhedron by the scan period measuring unit in the first storage unit that stores the features indicated by An algorithm specifying unit for specifying the algorithm associated with a feature indicated by a plurality of the time differences; the algorithm specified by the algorithm specifying unit; and the time difference obtained from the rotating polyhedron by the scanning period measuring unit; A second reference surface specifying unit for specifying the reference surface, each surface of the rotating polyhedron, and an adjustment amount of a writing position written by a laser beam deflected by each surface in association with each other. Based on the reference surface specified by the storage unit, the reference surface specifying unit, the surface specifying unit for specifying each surface of the rotating polyhedron, and in the second storage unit, specified by the surface specifying unit And a control unit that controls irradiation of the laser light applied to each surface based on the adjustment amount associated with each surface.

  An image forming method executed by an image forming apparatus, the image forming method executed by the image forming apparatus, the image forming apparatus having a light source for irradiating a laser beam and a plurality of surfaces, Based on the rotation polyhedron that deflects and scans the laser light by a plurality of surfaces, a light receiving unit that receives the laser light deflected by each surface of the rotation polyhedron, and the time difference obtained from the rotation polyhedron, the rotation polyhedron A first storage unit that stores an algorithm for specifying a reference plane set in advance from the plurality of surfaces and a feature indicated by the time difference, each surface of the rotating polyhedron, and deflection by each surface A second storage unit that stores the adjustment amount of the writing position written by the laser beam in association with each other, and the light receiving unit receives the laser beam from each of the two adjacent surfaces of the rotating polyhedron. A plurality of characteristics obtained from each of the plurality of adjacent two faces of the rotating polyhedron in the scanning period measuring step from a plurality of characteristics stored in the first storage unit and a scanning period measuring step for measuring the time difference between the mings Corresponding to the feature indicated by the plurality of time differences obtained from each of the plurality of adjacent two faces of the rotating polyhedron in the scanning cycle measuring step in the first storage unit. The reference plane is specified based on an algorithm specifying step for specifying the attached algorithm, the algorithm specified in the algorithm specifying step, and the time difference obtained from the rotating polyhedron by the scanning period measurement unit The reference plane specifying step, and the reference plane specifying step A surface specifying step for specifying each surface of the rotating polyhedron based on the determined reference surface, and the adjustment associated with each surface specified in the surface specifying step in the second storage unit And a control step of controlling the irradiation of the laser beam applied to each surface based on the amount.

  According to the present invention, it is possible to stably form a high quality image.

FIG. 1 is a block diagram illustrating a main configuration of the image forming apparatus. FIG. 2A is a diagram for explaining a shift in the writing position of a five-sided polygon. FIG. 2-2 is a diagram for explaining a shift in the writing position of the five-sided polygon. FIG. 3 is a diagram illustrating a data configuration of the algorithm storage unit. FIG. 4 is a diagram for explaining each algorithm. FIG. 5 is a diagram illustrating a data configuration of the main scanning offset value storage unit. FIG. 6 is a flowchart showing the image forming process. FIG. 7 is a flowchart showing detailed processing in the surface identification processing (step S104). FIG. 8A is a diagram illustrating a scanning cycle measurement result obtained by a four-sided polygon mirror. FIG. 8-2 is a diagram illustrating a scan period measurement result obtained by a five-sided polygon mirror. FIG. 9 is a block diagram illustrating a main configuration of an image forming apparatus according to another example.

  Hereinafter, embodiments of an image forming apparatus and an image forming method will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a main configuration of an image forming apparatus 1 according to the first embodiment. The image forming apparatus 1 includes an LD (laser diode) driver 101, an LD 102, a polygon mirror 105, an fθ lens 106, a photoreceptor 108, a horizontal synchronization sensor 110, and a writing position adjustment unit 120. .

  An LD (laser diode) driver 101 receives an image signal and a writing clock and controls the LD 102 based on these signals. Specifically, the LD driver 101 generates a modulation signal corresponding to the image signal and outputs this modulation signal to the LD 102. Furthermore, image writing by a laser beam is controlled based on a main scanning offset value output from a writing position adjusting unit 120 described later.

  The LD 102 irradiates a laser beam modulated by an image signal under the control of the LD driver 101. The laser beam irradiated by the LD 102 is reflected by the polygon mirror 105 and is irradiated to the photoconductor 108 and the horizontal synchronization sensor 110 via the fθ lens 106. Although omitted here, it is assumed that a plurality of lenses other than the fθ lens 106 are arranged in the optical path from the LD 102 to the photoconductor 108.

  In the above configuration, the laser modulated by the image signal is scanned in the main scanning direction of the photoconductor 108 by the high-speed rotation of the polygon mirror 105, so that optical writing is performed line by line, and the photoconductor 108 is electrostatically charged. A latent image is formed. Thereafter, the electrostatic latent image is developed with toner to become a visible image, and is transferred onto a recording sheet. The sheet on which the unfixed toner image is transferred is then conveyed to a fixing unit (not shown). In the fixing unit, the unfixed toner image is fixed.

  On the other hand, the horizontal synchronization sensor 110 is disposed beside the photosensitive member 108, that is, in an area outside the area where effective image writing is performed. When the horizontal synchronization sensor 110 receives the laser beam deflected by each polygon surface, the horizontal synchronization sensor 110 outputs a synchronization detection signal indicating that the laser beam has been received to the writing position adjustment unit 120. The horizontal synchronization sensor 110 is specifically a photodiode integrated with a photodiode, a phototransistor, or a peripheral circuit thereof.

  The writing position adjustment unit 120 adjusts the deviation of the writing position due to the laser beam deflected by each surface of the polygon mirror 105. Here, with reference to FIGS. 2-1 and 2-2, a shift in the writing position of the pentahedral polygon as the polygon mirror 105 will be described. In the present embodiment, the polygon mirror 105 having five surfaces will be described. However, the number of surfaces of the polygon mirror 105 is not limited to the embodiment.

  As shown in FIG. 2A, for convenience of explanation, each surface of the polygon mirror 105 is referred to as one surface (1) to five surfaces (5). FIG. 2B is a diagram illustrating timing at which a synchronization detection signal is output from the horizontal synchronization sensor 110 based on the laser beam deflected by each surface of the polygon mirror 105 illustrated in FIG. In FIG. 2B, the synchronization detection signal actually obtained is indicated by a solid line, and the synchronization detection signal to be obtained from an ideal regular pentagonal polygon mirror is indicated by a dotted line. The timing t1 when the synchronization detection signal generated by the laser beam deflected on one surface of the polygon surface is output and the timing when the synchronization detection signal generated by the laser beam deflected on the two surfaces of the polygon surface is detected. Is t2. Further, the time difference between the timing t1 and the timing t2 is set to cnt12. Note that the measurement of the time difference between the timings when the synchronization detection signals generated by the laser beams deflected by the two adjacent polygon surfaces are detected is referred to as scanning period measurement.

  In a polygon mirror having five surfaces, ideally, the time differences cnt12, cnt23, cnt34, cnt45, and cnt51 with respect to two adjacent polygon surfaces should all be the same, but in practice, FIG. As shown in -2, the time difference value varies. The writing position adjustment unit 120 performs a process of adjusting the deviation of the writing position caused by this variation.

  The writing position adjustment unit 120 includes a scanning period measurement unit 121, an algorithm storage unit 122, an algorithm specification unit 123, a main scanning offset value storage unit 124, a main scanning registration control unit 125, and a writing position adjustment unit 120. And a control unit 126 for controlling the whole.

  The scanning cycle measurement unit 121 performs scanning cycle measurement based on the synchronization detection signal input from the horizontal synchronization sensor 110. Specifically, when the synchronization detection signal is input, the scanning cycle measurement unit 121 defines the synchronization detection signal input first as a temporary 1 signal obtained from the temporary surface of the polygon surface. The scanning cycle measuring unit 121 defines the synchronization signals that are subsequently input as temporary 2 signals to temporary 5 signals obtained from the temporary 2 surfaces to the temporary 5 surfaces of the polygon surface. Then, the scanning cycle measuring unit 121 calculates a time difference (provisional cnt12, provisional cnt23, provisional cnt34, provisional cnt45, provisional cnt51) for each of two adjacent polygon surfaces of the polygon mirror 105.

  FIG. 3 is a diagram illustrating a data configuration of the algorithm storage unit 122. The algorithm storage unit 122 stores information that is referred to when the algorithm specifying unit 123 specifies an algorithm used when determining the reference plane of the polygon mirror 105. Specifically, the algorithm storage unit 122 corresponds to the feature indicated by the scan period measurement result obtained from the polygon mirror 105 and the algorithm for specifying a preset reference plane from a plurality of faces of the polygon mirror 105. A number of them are stored.

  The characteristic indicated by the result of scanning period measurement is specifically the characteristic indicated by five time differences obtained by scanning period measurement. In the present embodiment, the algorithm storage unit 122 has a time difference in a plurality of time differences (provisional cnt12, provisional cnt23, provisional cnt34, provisional cnt45, provisional cnt51) obtained as a result of the measurement as a feature indicated by the result of the scanning cycle measurement. The minimum value of the time difference is detected in a plurality of time differences obtained as a result of measurement, or the same time difference is continuously detected in the plurality of time differences obtained as a result of measurement. Two features are remembered. In the present embodiment, when the difference between the count values as the time difference is within ± 5 counts, it is determined that the time differences are the same.

  Further, in the algorithm storage unit 122, each feature is associated with an algorithm. FIG. 4 is a diagram for explaining each algorithm. First, algorithm 1 will be described. Algorithm 1 is associated with the feature that the maximum time difference is detected. The algorithm 1 determines the time difference (count value) of the l-th scanning cycle counted from the maximum value of the detected plurality of time differences (provisional cnt12, provisional cnt23, provisional cnt34, provisional cnt45, provisional cnt51) as a reference time difference. Of the time difference, the surface corresponding to the synchronization detection signal at the earlier timing is determined as the reference surface. In the present embodiment, the first time difference counted from the maximum value, that is, the time difference that becomes the maximum value is determined as the reference time difference.

  For example, as shown in the upper part of FIG. 4, when the provisional cnt23 is detected as the maximum value, the provisional cnt23 is set as a reference time difference, and the provisional two signals that are synchronization detection signals at the earlier timing of the cnt23 as the reference time difference. 2 are determined as reference planes. In the present embodiment, the reference surface is one surface, and the subsequent surfaces are 2 to 5 in order.

  Next, algorithm 2 will be described. Algorithm 2 is associated with the feature that the minimum value of the time difference is detected. Algorithm 2 determines the time difference of the m-th scanning cycle counted from the minimum value of a plurality of detected time differences as the reference time difference, and determines the surface corresponding to the synchronization detection signal at the earlier timing among the reference time differences as the reference surface. It is. In the present embodiment, the first time difference counted from the minimum value, that is, the time difference that becomes the minimum value is determined as the reference time difference.

  For example, as shown in the middle part of FIG. 4, when the provisional cnt 34 is detected as the minimum value, the provisional cnt 34 is set as a reference time difference, and the provisional 3 is a synchronization detection signal at an earlier timing of the provisional cnt 34 as the reference time difference. The provisional three surfaces corresponding to the signals are determined as reference surfaces.

  Next, algorithm 3 will be described. Algorithm 3 is associated with the feature that the same time difference is detected n times in succession. Algorithm 3 determines the time difference of the nth scanning cycle among the same n time differences that are consecutive as the reference time difference, and determines the surface corresponding to the synchronization detection signal at the earlier timing out of the reference time differences as the reference surface. is there. In the present embodiment, the second time difference among the two consecutive time differences is determined as the reference time difference.

  For example, as shown in the lower part of FIG. 4, when the temporary cnt51 and the temporary cnt12 have the same time difference, the temporary cnt12 obtained following the temporary cnt51 corresponds to the second one, so that cnt12 is set as the reference time difference. The Then, a temporary surface corresponding to a temporary 1 signal that is a synchronization detection signal at an earlier timing among the temporary cnt12 as a reference time difference is determined as a reference surface.

  Returning to FIG. 1, the algorithm specifying unit 123 determines which feature stored in the algorithm storage unit 122 matches the result of the scanning cycle measurement obtained by the scanning cycle measuring unit 121 and determines that they match. Identify the algorithm associated with the feature.

  FIG. 5 is a diagram illustrating a data configuration of the main scanning offset value storage unit 124. The main scanning offset value storage unit 124 stores information referred to by the main scanning registration control unit 125 to determine a main scanning offset value for controlling the irradiation timing of the laser beam. Specifically, the main scanning offset value storage unit 124 stores the surface No that specifies the polygon surface and the main scanning offset value that should be given to the laser beam scanned by each surface in association with each other.

  Returning to FIG. 1, the main scanning registration control unit 125 identifies the reference plane from a plurality of time differences obtained by the scanning period measurement unit 121 using the algorithm identified by the algorithm identification unit 123. Further, the main scanning registration control unit 125 refers to the main scanning offset value storage unit 124 at the time of image formation, identifies the main scanning offset value corresponding to each surface based on the identified reference surface, and identifies the identified main scanning. The offset value is output to the LD driver 101. Thereby, in the LD driver 101, the irradiation of the laser beam to be deflected by each surface can be controlled by the main scanning offset value set for each surface.

  Note that the features indicated by the results of the scanning cycle measurement and the algorithms corresponding to the features are specified in advance by the designer of the image forming apparatus 1 in accordance with the characteristics of the polygon mirror 105, and for example, this is the It is assumed that the algorithm storage unit 122 is set in advance before the shipment. Similarly, the main scanning offset value corresponding to each surface of the polygon mirror 105 is also specified in advance by the designer in accordance with the characteristics of the polygon mirror 105, and this is, for example, a point in time before shipment of the image forming apparatus 1. In this case, the main scanning offset value storage unit 124 is set in advance. These values can be appropriately updated at a timing after shipment, for example, when the polygon mirror 105 is replaced.

  FIG. 6 is a flowchart showing image forming processing by the image forming apparatus 1 according to the present embodiment. In the image forming apparatus 1, when an operation of a polygon motor (not shown) for driving the polygon mirror 105 is started (step S100), the LD 102 is turned on under the control of the LD driver 101 (step S102). Next, a surface specifying process for specifying the reference surface of the polygon mirror 105 is performed (step S104). Thereafter, image formation is performed (step S106). In image formation, the main scanning registration control unit 125 adjusts the deviation of the writing position by giving a main scanning offset value corresponding to each surface specified by the surface specifying process. Thus, the image forming process is completed.

  FIG. 7 is a flowchart showing detailed processing in the surface identification processing (step S104). In the surface specifying process (step S104), first, the scanning cycle measurement unit 121 performs scanning cycle measurement based on the synchronization detection signal input from the horizontal synchronization sensor 110 (step S110). Next, the algorithm specifying unit 123 determines which feature stored in the algorithm storage unit 122 matches the feature indicated by the scan cycle measurement result obtained by the scan cycle measuring unit 121 (step S112). That is, the algorithm specifying unit 123 specifies the feature indicated by the scanning cycle dispute result obtained by the scanning cycle measuring unit 121. Next, the algorithm specifying unit 123 specifies an algorithm associated with the previously specified feature in the algorithm storage unit 122 (step S114). Next, the main scanning registration control unit 125 specifies a reference surface from a plurality of surfaces of the polygon mirror 105 using the specified algorithm (step S116). Thus, the surface specifying process is completed.

  As described above, in the image forming apparatus 1 according to the present embodiment, the scanning period is measured based on the synchronization detection signal obtained according to the light deflected by the polygon mirror 105, and the feature indicated by the result is specified. Since the reference plane of the polygon mirror 105 is specified using an algorithm suitable for the feature, the reference plane can be specified more accurately. Therefore, in the image forming apparatus 1 according to the present embodiment, each surface can be identified and a main scanning offset value corresponding to each surface can be assigned based on the reference surface, which is caused by a mistake in the surfaces. There is no deviation in the writing position, and a high-quality image can be formed stably.

  Furthermore, in the image forming apparatus 1 according to the present embodiment, the polygon mirror 105 has five reflecting surfaces that reflect the laser light. As described above, the number of reflection surfaces of the polygon mirror is preferably an odd number, and more preferably a prime number.

  FIG. 8A is a diagram illustrating a scanning cycle measurement result obtained by a four-sided polygon mirror as an example other than a prime number. FIG. 8-2 is a diagram illustrating a scan period measurement result obtained by a five-sided polygon mirror as an example of a prime number.

  For example, as a result of scanning cycle measurement, a predetermined value A and a value B lower than A may be detected alternately as a time difference. In such a case, as shown in FIG. 8A, in the four-sided polygon mirror, a pattern in which the value of A and the value of B are alternately continued is obtained. For this reason, there is no difference between the detection results of cnt12 and cont34 and the detection results of cnt23 and cnt41, and even when the algorithm suitable for the characteristics of the scan period measurement result is used as described above, the reference plane of the polygon mirror is used. Is difficult to identify.

  On the other hand, as shown in FIG. 8B, in the polygon mirror having a prime number of faces, since the number of faces is a prime number, the value of A or B is continuous at cnt12 and cnt51. Become. For this reason, it is possible to specify the reference plane of the polygon mirror by using an algorithm that focuses on the point where the value A or the value B continues. That is, by using a polygon mirror having a prime number of faces, the reference plane of the polygon mirror can be specified with higher accuracy.

  In the embodiment, for convenience of explanation, a configuration in which a laser beam irradiated from one LD is scanned by a polygon mirror and an image is written on one photosensitive member has been described. The forming apparatus may be a counter scanning optical system. FIG. 9 is a block diagram illustrating a main configuration of an image forming apparatus 2 according to another example. The image forming apparatus 2 includes four LDs 102a to 102d corresponding to four colors.

LDs 102a-10 on LD (laser diode) driver boards 109a-109d
A laser beam corresponding to each color is irradiated from 2d. The laser beam is incident on the polygon mirror 105 via optical members such as the cylindrical lenses 103a to 103d and the mirrors 104a and 104b. The laser beam is further deflected and scanned by the polygon mirror 105, passes through optical members such as the fθ lenses 106a and 106b and the folding mirrors 107a to 107d, and is written on the photoreceptors 108a to 108d. In the image forming apparatus 2, four stations corresponding to the four photoconductors 108 a to 108 d are scanned by one polygon mirror 105.

  Further, a horizontal synchronization sensor 110 is provided at a predetermined station, and the image forming apparatus 2 specifies a polygon plane based on a detection result by the horizontal synchronization sensor 110. Specifically, the image forming apparatus 2 includes main scanning registration control units 125a to 125d corresponding to the four LDs 102a to 102d. The main scanning registration control units 125a to 125d are specified by the algorithm specifying unit 123. The reference plane is specified from a plurality of time differences obtained by the scanning period measurement unit 121 using the algorithm thus determined. Furthermore, the main scanning registration control units 125a to 125d refer to the main scanning offset value storage unit 124 at the time of image formation, and identify and specify the main scanning offset value corresponding to each surface based on the identified reference surface. The main scanning offset value is output to the LD driver 101.

  In addition, as another example of the image forming apparatus, a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function may be used. As another example, a copier, a printer, and the like may be used. It may be a scanner device, a facsimile device, or the like.

1, 2 Image forming apparatus 101 LD driver 102 LD
DESCRIPTION OF SYMBOLS 108 Photoconductor 110 Horizontal synchronization sensor 120 Writing position control part 121 Scan period measurement part 122 Algorithm memory | storage part 123 Algorithm specification part 124 Main scanning offset value memory | storage part 125 Main scanning registration control part

JP 2006-187868 A

Claims (4)

A light source that emits laser light;
A rotating polyhedron having a plurality of surfaces and deflecting and scanning the laser light by the plurality of surfaces;
A light receiving portion for receiving the laser light deflected by each surface of the rotating polyhedron;
A scanning period measuring unit for measuring a time difference between timings at which the light receiving unit receives the laser beam from two adjacent surfaces which are two adjacent surfaces of the rotating polyhedron;
A first storage unit that associates and stores an algorithm that specifies a preset reference surface from the plurality of surfaces of the rotating polyhedron based on the time difference obtained from the rotating polyhedron, and a feature indicated by the time difference; ,
In the first storage unit, an algorithm specifying unit that specifies the algorithm associated with the feature indicated by the plurality of time differences obtained from each of the plurality of adjacent two surfaces of the rotating polyhedron by the scanning cycle measuring unit;
A reference surface specifying unit for specifying the reference surface based on the algorithm specified by the algorithm specifying unit and the time difference obtained from the rotating polyhedron by the scanning period measuring unit;
A second storage unit that stores each surface of the rotating polyhedron in association with an adjustment amount of a writing position written by a laser beam deflected by each surface;
Based on the reference surface specified by the reference surface specifying unit, a surface specifying unit for specifying each surface of the rotating polyhedron,
The second storage unit includes a control unit that controls irradiation of the laser light to be irradiated to each surface based on the adjustment amount associated with each surface specified by the surface specifying unit. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the rotating polyhedron has a prime number of faces. A plurality of the light sources;
The light receiving unit receives the laser light emitted from a predetermined light source among the plurality of light sources,
The image forming apparatus according to claim 1, wherein the control unit controls irradiation of the laser light emitted from each of a plurality of light sources based on the adjustment amount. An image forming method executed by an image forming apparatus,
The image forming apparatus includes:
A light source that emits laser light;
A rotating polyhedron having a plurality of surfaces and deflecting and scanning the laser light by the plurality of surfaces;
A light receiving portion for receiving the laser light deflected by each surface of the rotating polyhedron;
A first storage unit that associates and stores an algorithm that specifies a preset reference surface from the plurality of surfaces of the rotating polyhedron based on the time difference obtained from the rotating polyhedron, and a feature indicated by the time difference; ,
A second storage unit that stores each surface of the rotating polyhedron in association with an adjustment amount of a writing position written by a laser beam deflected by each surface;
A scanning cycle measuring step for measuring the time difference between the timings at which the light receiving unit receives the laser light from each of the two adjacent surfaces of the rotating polyhedron;
A feature specifying step for specifying a plurality of features indicated by the plurality of time differences obtained from each of the plurality of adjacent two surfaces of the rotating polyhedron in the scanning cycle measuring step from the plurality of features stored in the first storage unit;
In the first storage unit, an algorithm specifying step for specifying the algorithm associated with the characteristics indicated by the plurality of time differences obtained from each of the plurality of adjacent two surfaces of the rotating polyhedron in the scanning cycle measuring step;
A reference surface specifying step for specifying the reference surface based on the algorithm specified in the algorithm specifying step and the time difference obtained from the rotating polyhedron by the scanning period measuring unit;
A surface identifying step for identifying each surface of the rotating polyhedron based on the reference surface identified in the reference surface identifying step;
And a control step of controlling irradiation of the laser light to be irradiated on each surface based on the adjustment amount associated with each surface specified in the surface specifying step in the second storage unit. An image forming method.

Images