JP4261079B2 - Scanning beam measurement evaluation apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scanning beam measurement evaluation apparatus and an image forming apparatus.
[0002]
[Prior art]
The writing scanning optical unit used in electrophotographic image forming apparatuses such as laser beam printers, copiers, and facsimiles has a scanning optical system mainly composed of a laser light source, collimating lenses, various lenses / mirrors, polygon mirrors, etc. Have. In general, in such an image forming apparatus, a laser beam generated from a laser light source is converted into parallel light by a collimator lens, irradiated to a polygon mirror, and deflected by its rotation. The light beam reflected by the polygon mirror forms an image on the photosensitive member by an imaging lens and a mirror system.
[0003]
The point image on the photosensitive member is scanned in the main scanning direction by the rotation of the polygon mirror, and is scanned in the sub-scanning direction by the rotation of the photosensitive drum to form an electrostatic latent image. A toner image is formed by attaching a toner to the surface of the photosensitive drum on which the electrostatic latent image is formed, and forming the toner image. The toner image is transferred to a transfer paper and fixed, and the toner image is transferred to the transfer paper. It is known to form an image.
[0004]
By the way, when there are abnormalities such as surface accuracy (waviness), surface defects, internal defects, etc. in the optical elements constituting the scanning optical system, the scanning position deviation in the main scanning direction of the scanning beam scanned onto the photosensitive member The focus position shift in the depth direction of the beam causes a decrease in the peak light amount of the beam and an influence on the beam diameter, which causes a defect in image formation.
[0005]
Conventionally, the evaluation of the scanning beam of a scanning optical system is based on the beam diameter in a stationary state measured by a light receiving element after a pinhole or slit is provided at a position corresponding to the surface of the photoreceptor. It is known that this is done depending on whether or not there is a point that changes rapidly.
[0006]
[Problems to be solved by the invention]
However, in the conventional beam diameter measuring method, when the measurement is performed over the entire scanning range, for example, every 1 mm, the measurement time becomes enormous. In addition, since the beam is measured in a stationary state, there is a problem that the beam characteristics in the scanning state cannot be measured.
[0007]
As a method of measuring the scanning beam of the scanning optical system, it is configured to detect the dot position in the entire scanning system by combining the position measurement by the position detection unit of the moving means and the dot position at that position. Is also possible.
[0008]
In such a measuring apparatus, in consideration of measurement time, vibration, and the like, the beam position is adjusted while moving the two-dimensional sensor, which is a measuring means, in the main scanning direction instead of repeatedly moving and stopping at each measurement. It seems that there are many cases of measurement, but when the position is stored when the scanning reference signal is generated and the beam position in the entire scanning area is detected, an error in the measurement time as described below occurs. Since this cannot be ignored with respect to the position measurement error, it becomes a problem when performing position measurement with high accuracy.
[0009]
Below, the speed fluctuation of the moving mechanism and the effect on the position accuracy of the observation time will be described. That is, if the moving speed V (mm / sec) of the moving mechanism, the moving speed fluctuation δV (mm / sec), and the scanning frequency F (1 / sec) of one laser line, the moving amount of the moving mechanism in one line scanning time L (mm) is “L = (V + δV) / F”, and the movement amount error δL when the speed variation of the moving stage is about ± 10% is “δL = ± 0.1 · V / F”. When V = 100 and F = 2000, “δL = ± 5 * 10E-3 (mm) = ± 5 μm”.
[0010]
As a response to the deviation from the reference position, it can be considered that the trigger PD is attached to the front stage of the detection system, but adding the trigger PD not only complicates the apparatus configuration, There is a problem that the control configuration becomes complicated, for example, it is necessary to perform lighting control so that the scanning beam enters the trigger PD reliably.
[0011]
Also, in the above moving stage, if there is a fluctuation in the time interval from the position detection synchronization signal to the actual position detection, it also leads to an error in the beam position, and if there is a detection time fluctuation of 1 msec in the above setting In terms of position, it contains an error of 10 μm. Since the beam diameter of the scanning system is smaller than 100 μm, there is a problem that the measurement accuracy is remarkably lowered.
[0012]
Furthermore, in order to reduce this variation in detection time, it is necessary to configure the system with detection-dedicated hardware or a real-time OS that guarantees real-time performance in the μSec order, and is controlled by a general-purpose PC. Compared to the case, the cost of the apparatus increases.
[0013]
An object of the present invention is to measure all scanning system positions in the main scanning direction with high accuracy for a scanning optical apparatus.
[0014]
An object of the present invention is to reduce the influence of positional deviation in the sub-scanning direction caused by backlash and vibration of the mechanism in the sub-scanning direction, and to measure all scanning system positions in the main scanning direction with high accuracy.
[0015]
An object of the present invention is to improve the convenience of the high-precision measurement by comparing the measurement evaluation pattern and the detection system position.
[0016]
An object of the present invention is to improve the convenience of the high-precision measurement.
[0017]
An object of the present invention is to reduce manufacturing costs.
[0018]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a reference position detecting means for detecting a reference position for starting scanning of a scanning beam output from a scanning optical device that performs exposure scanning of an electrostatic latent image, and an evaluation target pixel for scanning beam evaluation. An evaluation pattern generating means for generating a pattern, a light emitting element control means for controlling a light emitting element for irradiating light to a polygon mirror of the scanning optical device based on the pattern, and a light quantity distribution of the scanning beam received by the light receiving element. Light detecting means for detecting, moving means for moving the light receiving element in the main scanning direction, position detecting means for detecting the position of the light receiving element, and moving the light receiving element in the beam main scanning direction by the moving means The light detection means detects the scanning beam, stores the position of the light receiving element detected by the position detection means in synchronization with the scanning beam evaluation pattern, and stores the light. A measurement evaluation means by said light receiving element position detected by the scanning beam position detected by means output a position detection means for evaluating measuring the position of the scanning beam, which is to have the scanning beam measurement evaluation apparatus comprising a.
[0019]
Therefore, by acquiring the position information of the moving system in synchronization with the detection evaluation pattern, the positions of all the scanning systems in the main scanning direction can be measured with high accuracy.
[0022]
According to a second aspect of the invention, in the scanning beam measurement evaluation apparatus according to claim 1, measurement evaluation means is for storing the position of the light receiving element in synchronization with the scanning beam evaluation pattern generation section.
[0023]
Therefore, by acquiring the position information of the moving system in synchronization with the detection evaluation pattern, the positions of all the scanning systems in the main scanning direction can be measured with high accuracy.
[0024]
According to a third aspect of the present invention, in the scanning beam measurement / evaluation apparatus according to the first or second aspect , the measurement / evaluation means detects the scanning beam evaluation pattern and the position of the light receiving element which are set independently. In relation to the trigger position, the position of the light receiving element is stored in synchronization with a detection trigger signal generated at the trigger position when an actual scanning pattern is generated.
[0025]
Therefore, by acquiring the position information of the moving system in synchronization with the detection evaluation pattern, the positions of all the scanning systems in the main scanning direction can be measured with high accuracy.
[0026]
According to a fourth aspect of the present invention, in the scanning beam measurement evaluation apparatus according to any one of the first to third aspects, the measurement evaluation unit is determined by a pixel counter integrated value integrated from a reference position signal. The beam position is compared with the position of the light receiving element obtained from the position detecting means, and the position of the light receiving element is stored in synchronization with a predetermined condition.
[0027]
Therefore, the convenience of high-precision measurement can be improved by comparing the measurement evaluation pattern and the detection system position.
[0028]
According to a fifth aspect of the present invention, in the scanning beam measurement / evaluation apparatus according to the fourth aspect , the measurement evaluation unit includes a beam position determined from a pixel counter integrated value as a condition for storing the position of the light receiving element. The position of the light receiving element is stored in synchronization with the first pixel clock signal after the position of the scanning beam passes the position of the position detecting means from the position information of the position detecting means.
[0029]
Therefore, the convenience of high-precision measurement can be improved by comparing the measurement evaluation pattern and the detection system position.
[0030]
According to a sixth aspect of the present invention, the measurement evaluation unit stores in advance a beam position determined from a pixel counter integrated value corresponding to the position information of the position detection unit as a condition for storing the position of the light receiving element. The position of the light receiving element is stored in synchronization with the first pixel clock signal after the scanning beam passes through the corresponding position of the position detecting means.
[0031]
Therefore, the convenience of high-precision measurement can be improved by comparing the measurement evaluation pattern and the detection system position.
[0034]
Invention according to claim 7, in the scanning beam measurement evaluation apparatus according to any one of claims 1 to 6, wherein the position detecting means, and outputs a pulse train signal, the evaluation pattern generating means The counter means for counting the number of pulses of the pulse train signal is provided.
[0035]
Therefore, the manufacturing cost can be reduced by providing the evaluation pattern generating means with a position storage function of the detection system.
[0036]
The invention according to claim 8 is provided with the scanning beam measurement evaluation apparatus according to any one of claims 1 to 7 , and the position of the scanning beam of the scanning optical apparatus that performs exposure scanning of the electrostatic latent image by the apparatus. This is an electrophotographic image forming apparatus for measuring and evaluating the above.
[0037]
Therefore, the same operation and effect as the invention according to any one of claims 1 to 9 can be achieved.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
[0039]
FIG. 1 is a block diagram illustrating a schematic configuration of a scanning beam measurement evaluation apparatus 1 which is an apparatus for measuring and evaluating a scanning beam of a scanning optical system in an electrophotographic image forming apparatus according to an embodiment of the present invention. It is.
[0040]
This scanning beam measurement / evaluation apparatus 1 is set in the scanning optical unit 50 for measurement. A light receiving sensor for detecting the scanning start position of the scanning beam is used as the reference position detecting means, and the reference position signal from this sensor is hereinafter referred to as a synchronization signal.
[0041]
The scanning optical unit 50 performs scanning beam measurement evaluation on a laser diode (hereinafter referred to as LD) 12 that is a laser light source and a photodiode (hereinafter referred to as PD) 13 that is a light receiving sensor that detects a scanning start position of the scanning beam. A connector can be connected so that input / output can be performed with the apparatus 1. Further, a signal input / output to / from the rotary polygon mirror 14 can be connected to the connector.
[0042]
Accordingly, the scanning beam measurement / evaluation apparatus 1 irradiates the light beam from the LD 12 toward the reflection surface of the rotary polygon mirror 14, reflects the light beam, and causes the scanning optical unit 50 to scan. First, the light beam is irradiated onto the PD 13 to obtain a synchronization signal 16 that is a scanning start position of the scanning beam. Next, the light beam is scanned by a configuration such as an fθ lens 15 and focused on the photoreceptor image position R to form an image on a straight line.
[0043]
In the scanning beam measurement / evaluation apparatus 1, a CCD two-dimensional area sensor 20 is disposed as a detection means at the photoconductor image position R. Further, the CCD two-dimensional area sensor 20 can enlarge and detect a spot image of a scanning beam by an objective lens 21 that is a detachable magnifying optical element. Further, a slight positional deviation in the optical axis direction that occurs when the objective lens 21 is attached or detached can be finely adjusted by a moving stage (not shown) in the optical axis direction.
[0044]
The scanning beam measurement / evaluation apparatus 1 uses the lighting control unit 17 of the LD 12 based on the synchronization signal 16 obtained by the PD 13 to take the timing of light emission of the scanning beam and to trigger the capture of the CCD two-dimensional area sensor 20. Then, the camera trigger shutter 22 is opened to receive light. Here, the synchronization signal 16 is counted according to the number of surfaces of the rotary polygon mirror 14 (six surfaces in this example), so that the surface can be selected, and the light emission to the lighting control unit 17 of the LD 12 is performed only on a specific surface. It can also be used at the timing.
[0045]
After imaging by the CCD two-dimensional area sensor 20, the acquired image data is transferred to the data storage unit 32 via the controller box 40 in accordance with a command from the measurement unit CPU 41. At the same time, the position detection unit 25 transfers the position information of the imaging position acquired based on the trigger from the position detection PD 27 from the storage unit 34 to the measurement unit CPU 41.
[0046]
At this time, the position detection PD 27 detects the scanning beam so that the position information acquisition trigger is activated in accordance with the timing at which the scanning beam enters the detection system.
[0047]
The CCD two-dimensional area sensor 20 can be moved in the X-axis direction, which is the main scanning direction, by an X-axis moving stage 23. Thereby, the CCD two-dimensional area sensor 20 can detect the scanning beam at an arbitrary position in the scanning region. At this time, the X-axis movement stage 23 is driven by the mechanism control unit 24 from the measurement unit CPU 41 via the controller box 40. Further, the amount of movement of the X-axis moving stage 23 is measured by the position detection unit 25 using a linear scale 26 that is a position detection sensor (in addition, an optical side lengther, a laser microsensor, or the like can also be used). Thereby, the data acquisition position of the CCD two-dimensional area sensor 20 can be measured accurately and at high speed.
[0048]
The CCD two-dimensional area sensor 20 repeats the routine of acquiring the image data and transferring it to the data storage unit 32 over the entire scanning area while moving in the X-axis direction which is the main scanning direction. Get the data. Thereafter, the measurement evaluation of the linearity and the scanning line bending amount in the entire scanning area of the scanning optical system is completed by analyzing the light amount distribution data imaged by the signal processing unit 33.
[0049]
The measurement result is calculated by the measurement unit CPU 41, and based on the image data of the scanning beam, the linearity in the entire scanning area of the scanning optical system in the scanning line and the display of the scanning line bending amount are displayed on the display unit 42. Can be done.
[0050]
FIG. 2 shows a basic timing chart in the scanning beam lighting control unit 17. In FIG. 2, (a) is an LD basic signal. In order to obtain the synchronization signal 16 which is the scanning start position of the scanning beam, the PD 13 which is the light receiving sensor receives a certain amount of time in order to receive light reliably. The LD 12 emits light. (B) is a light reception trigger of the PD 13, which is a synchronization signal 16. At the falling timing of (b), the clock phase shift caused by the rotation unevenness of the polygon mirror 14 is adjusted, and the basic clock signal (pixel CLOCK) 19 of the optical writing system shown in (c) is generated. The signal (d) is a counter value (pixel counter) driven by this basic clock signal, and the counter is reset to 0 by the synchronization signal. Using this counter value, the actual LD 12 write timing (that is, the counter value) Position).
[0051]
The signal (e) is a signal for actually driving the LD 12 (Ld drive signal) based on a predetermined program in the measurement unit CPU 41, and a pattern can be output in comparison with the count value of (d). For example, in FIG. 2, Tp is set as a quaternary counter. Thus, the time interval of Tp can be set arbitrarily, and can be set as the time interval for causing the dots to emit light. Here, since the timing of the clock signal (c) is exactly the same as that of the synchronizing signal 16, the reproducibility of the position where the light emitting dot is struck is greatly improved by the LD drive signal (e). Can do.
[0052]
Next, the timing relating to the detection of the position of the mobile system is shown as a signal (g) according to the synchronization signal (b) (position detection trigger). Since the detection system moves, the detection system position changes every moment as in the signal (f), and the difference between the reference position and the actual evaluation pattern position becomes an error in the detection system position. If the delay time from the position detection trigger signal (g) until the position is actually stored as a system is Td, the moving system moves within this delay time. This leads to detection error of position information.
[0053]
In the case of a writing type having a resolution of 600 dpi for an A4 horizontal width of about 300 mm, at least the number of dots in the main scanning direction is “7000≈300 (mm) /25.4 (mm / inch) * 600 (dpi = dot / inch) ", the movement of the scanning time detection system and the jitter of the clock also lead to a decrease in measurement accuracy.
[0054]
As described above, when this influence is reduced by separately providing a position detection trigger PD and performing timing control or the like, the trigger PD and its measurement circuit are required, and the beam is surely entered into the trigger PD. It is necessary to control the light emission timing of the beam, which complicates the apparatus configuration.
[0055]
In contrast, the operation of the scanning beam measurement evaluation apparatus 1 will be described with reference to an example of a position detection trigger signal by the scanning beam measurement evaluation apparatus 1 shown in FIG. The trigger for storing the signal (g1) (position detection trigger) is synchronized with the rising edge of the pattern generation section signal of (e1), thereby performing stable position measurement of the detection system regardless of the position of the scanning system. The pattern generation section signal is for generating a scanning beam evaluation pattern for the evaluation target pixel.
[0056]
Further, the trigger for storing the signal (g2) is generated at the set value of the pixel counter signal (here, when the count value 101 rises). Thereby, stable position measurement of the detection system is possible regardless of the position of the scanning system, and when a delay time (the above Td) is actually written from the position detection trigger signal to the data storage unit 32, etc. There is an effect that it can be corrected.
[0057]
As described above, it is possible to reduce the difference between the pattern generation interval signal and the position detection time of the detection system and reduce the detection error, but in actual use as an apparatus, It is necessary to ensure that the light distribution part is captured by the detection system.
[0058]
The beam position scanned from the pixel counter value and the detection system position are measured from the detection system position detection means, respectively, and this correspondence corresponds to the change in the position of the detection system position detection means as shown in the graph of FIG. On the other hand, the pixel counter crosses many times (the Y axis is normalized so that the scanning width is 1). This corresponds to the scanning beam entering the detection system at the cross portion. In addition, the beam positions 1-8 shown in FIG. 4 show the beam position currently scanned for every time.
[0059]
In this way, by generating a position detection trigger signal based on the correlation between the beam position scanned from the pixel counter value and the detection system position, the light distribution part of the generated evaluation pattern is captured by the detection system. Can be guaranteed.
[0060]
As with the normalized detection system position Ps, a position detection trigger signal is generated at the first rising edge of the pixel that satisfies Pb> Ps at the normalized beam spot position Pb.
[0061]
Alternatively, if the linearity of the moving system and scanning beam is not sufficient, measure the correspondence between Pb and Ps in advance and save the correspondence in memory such as LUT, and Pb> LUT (Ps) (LUT supports The position detection trigger signal is generated at the first pixel rising edge that satisfies (Table).
[0062]
By these means, it is possible to automatically detect the moving system detection position with high accuracy without changing the evaluation dot row pattern over the entire system. The generation of the trigger for storing the signals (g1) and (g2) shown in FIG. 3 and the generation of the position detection trigger signal based on the correlation between the beam position being scanned and the detection system position are both predetermined. Since it occurs at the rise of the pixel counter value, it can be performed simultaneously. For example, if the rising edge of the first pixel that satisfies Pb > Ps and the rising edge of a predetermined pixel counter value for generating a trigger for storing the signals (g1) and (g2) shown in FIG. Good.
[0063]
In addition, the relationship between Pb and Ps described above is used when projecting a short pattern for evaluation of a limited spot (one, five, or six dot rows) instead of continuous dot row evaluation. Therefore, by automatically changing the pattern generation interval for the location where the current measurement system exists, and storing the pattern generation start position and the movement system detection position at that time together, There is no need to perform control from outside.
[0064]
Since the generation unit for the position detection trigger signal 28 synchronized with the pattern and the data storage unit 32 for storing the position of the PD 27 are provided, the trigger from the position detection PD 27 in the figure is not necessary.
[0065]
Further, by directly connecting the position detector 25 for detecting the position of the PD 27 and the means for outputting the pattern generation section signal, it is possible to reduce the influence of the delay time Td from the trigger signal until the position is stored. It becomes possible.
[0066]
Furthermore, the pulse train is directly connected to the inside of the means for outputting the pattern generation section signal to the position detection unit 25 that outputs pulses in the AB phase such as a linear sensor, a magnescale, an encoder, etc. By providing a counter function, it is possible to reduce the cost of the entire apparatus.
[0067]
With the configuration as described above, position detection timing control enables position measurement at the timing of actual sensor input, so it is possible to measure even minute positional deviations in the sub-operation direction caused by vibration, mechanism play, etc. Therefore, it is possible to measure the scanning beam position with high accuracy.
[0068]
【The invention's effect】
According to the first aspect of the present invention, the position information of the entire scanning system in the main scanning direction can be measured with high accuracy by acquiring the position information of the moving system in synchronization with the detection evaluation pattern.
[0070]
According to a second aspect of the invention, in the scanning beam measurement evaluation apparatus according to claim 1, by acquiring the position information of the synchronous moving system to the detection evaluation pattern, with high accuracy in the main scanning direction of the entire scanning system The position can be measured.
[0071]
According to a third aspect of the present invention, in the scanning beam measurement / evaluation apparatus according to the first or second aspect of the present invention, the position information of the moving system is acquired in synchronization with the detection evaluation pattern, so that all scanning in the main scanning direction can be performed with high accuracy. The position of the system can be measured.
[0072]
According to a fourth aspect of the present invention, in the scanning beam measurement evaluation apparatus according to any one of the first to third aspects, the convenience of high-precision measurement is improved by comparing the measurement evaluation pattern with the position of the detection system. Can do.
[0073]
According to the fifth aspect of the present invention, in the scanning beam measurement evaluation apparatus according to the fourth aspect , the convenience of high-precision measurement can be improved by comparing the measurement evaluation pattern and the detection system position.
[0074]
The invention described in claim 6 can improve the convenience of high-precision measurement in the scanning beam measurement evaluation apparatus according to claim 4 by comparing the measurement evaluation pattern with the position of the detection system.
[0076]
Invention according to claim 7, in the scanning beam measurement evaluation apparatus according to any one of claims 1 to 6, by the evaluation pattern generating means, provided the position storage function of the detection system, it reduces manufacturing costs can do.
[0077]
The invention according to claim 8 can achieve the same operations and effects as the invention according to any one of claims 1 to 7 .
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of a scanning beam measurement evaluation apparatus according to an embodiment of the present invention.
FIG. 2 is a timing chart for explaining the operation of the scanning beam measurement evaluation apparatus.
FIG. 3 is a timing chart of the same.
FIG. 4 is an explanatory diagram of the same.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Scanning beam measurement evaluation apparatus 12 Light emitting element 13 Light receiving element 50 Scanning optical unit

Claims (8)

A reference position detecting means for detecting a reference position for starting scanning of a scanning beam output from a scanning optical device that performs exposure scanning of the electrostatic latent image;
Evaluation pattern generating means for generating a scanning beam evaluation pattern on the evaluation target pixel;
A light emitting element control means for controlling a light emitting element for irradiating light to the polygon mirror of the scanning optical device based on the pattern;
A light detection means for receiving and detecting a light amount distribution of the scanning beam by a light receiving element;
Moving means for moving the light receiving element in the main scanning direction;
Position detecting means for detecting the position of the light receiving element;
The light detecting means detects the scanning beam while moving the light receiving element in the beam main scanning direction by the moving means, and the position of the light receiving element detected by the position detecting means is synchronized with the scanning beam evaluation pattern. Measurement and evaluation means for measuring and evaluating the position of the scanning beam by the scanning beam position detected by the light detection means and the light receiving element position detected by the position detection means,
A scanning beam measurement evaluation apparatus comprising: 2. The scanning beam measurement evaluation apparatus according to claim 1 , wherein the measurement evaluation means stores the position of the light receiving element in synchronization with a generation period of the scanning beam evaluation pattern. The measurement evaluation means synchronizes with a detection trigger signal generated at the trigger position when an actual scanning pattern is generated, with respect to the scanning beam evaluation pattern set independently and the detection trigger position of the position of the light receiving element. scanning beam measurement evaluation apparatus according to claim 1 or 2 position is for storing said light-receiving element. The measurement evaluation unit compares a beam position determined by a pixel counter integrated value integrated from a reference position signal with a position of a light receiving element obtained from the position detection unit, and synchronizes with a predetermined condition. The scanning beam measurement evaluation apparatus according to any one of claims 1 to 3 , which stores a position of a light receiving element. As a condition for storing the position of the light receiving element, the measurement evaluation means passes the position of the position detection means from the beam position determined from the integrated value of the pixel counter and the position information of the position detection means. 5. The scanning beam measurement and evaluation apparatus according to claim 4 , wherein the position of the light receiving element is stored in synchronization with a subsequent first pixel clock signal. The measurement evaluation unit stores in advance a beam position determined from a pixel counter integrated value corresponding to the position information of the position detection unit as a condition for storing the position of the light receiving element. 5. The scanning beam measurement and evaluation apparatus according to claim 4 , wherein the position of the light receiving element is stored in synchronization with the first pixel clock signal after the scanning beam passes through the position. The position detection means outputs a pulse train signal,
The scanning beam measurement evaluation apparatus according to claim 1 , wherein the evaluation pattern generation unit includes a counter unit that counts the number of pulses of the pulse train signal. An electrophotographic apparatus comprising the scanning beam measurement evaluation apparatus according to any one of claims 1 to 7 , wherein the scanning beam position of a scanning optical apparatus that performs exposure scanning of an electrostatic latent image is measured and evaluated by the apparatus. Type image forming apparatus.

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