JP2013123879A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a capacitor from being uselessly mounted, a semiconductor laser from being uselessly lighted, and the density unevenness of an image from being generated, in an image forming apparatus including an APC (Automatic Power Control) means controlling a drive current of the semiconductor laser, based on a voltage of the capacitor charged and discharged according to comparison results between a detection value of a light quantity of the semiconductor laser and a light quantity control reference value.SOLUTION: Charge and discharge characteristics of a capacitor are measured before a print job is started, to set an APC execution interval based on the results. When the drive of a semiconductor laser based on image data is not continuously performed with respect to a plurality of surfaces of a rotary polygon mirror, APC is executed at the interval.

Description

  The present invention relates to an image forming apparatus having an APC (Automatic Power Control) function for keeping a light quantity of a semiconductor laser, which is a light source for exposing a photosensitive member, constant.

  Since a general current-light output characteristic of a semiconductor laser is temperature-dependent, even if it is driven at a constant current, the light output fluctuates due to ambient temperature change or self-heating. Therefore, a photodiode generally called a monitor diode is incorporated in the package of the semiconductor laser, thereby detecting the optical output of the semiconductor laser and controlling the drive current so as to keep the light quantity (optical output) constant. An APC circuit for performing feedback control is provided.

  Further, in an image forming apparatus including a laser driving circuit that turns on / off a semiconductor laser in accordance with image data, APC is performed during a period in which an image is not formed (hereinafter referred to as a non-image forming period). It is known to prevent the body from being irradiated with unnecessary light, to obtain a predetermined amount of light by this APC, and to prevent uneven density of the image during the image formation period (hereinafter referred to as the image formation period). Yes. Here, the sample / hold capacitor is charged / discharged according to the difference between the output of the monitor diode and the reference voltage, and the drive control signal of the laser drive circuit is generated based on the voltage of the sample / hold capacitor. It has been.

  However, in APC using a sample / hold capacitor, if the APC interval is longer than a certain period, the voltage in the hold state of the sample / hold capacitor (hold voltage) falls below the reference voltage due to leakage current, and the sample / hold The charging period and the APC period corresponding to the capacity of the capacitor are not appropriate. As a result, there is a problem that the amount of light of the semiconductor laser does not increase to a predetermined amount of light within the APC period, and density unevenness occurs in the image.

  As an image forming apparatus that addresses such a problem, there is an image forming apparatus described in Patent Document 1. In this image forming apparatus, for the purpose of optimizing the charging period of the sample / hold capacitor with respect to the APC period, the rise time of the potential of the sampling period of the sample / hold capacitor (APC sampling period) and / or the discharge characteristics in the hold state are set. It is possible to select a sample / hold capacitor having a different capacitance based on the detection result. It is also possible to select a sampling period according to the capacity of the selected sample / hold capacitor.

However, in this image forming apparatus, capacitors having different capacities are required. Therefore, capacitors that are not always selected may be generated depending on the discharge characteristics, and there is a possibility of wasteful mounting.
In addition, since APC is performed for each surface of the rotary polygon mirror regardless of “image forming surface” and “image non-image forming surface”, it is not necessary to consider a reduction in the amount of light that originally causes image density unevenness. There is a problem that the semiconductor laser is wasted lightly by performing APC on the “surface not to be formed”, and as a result, the semiconductor laser is rapidly deteriorated. With respect to this problem, if APC is performed only immediately before the “image forming surface”, it is possible to prevent unnecessary lighting of the semiconductor laser and to reduce deterioration of the semiconductor laser. However, when the “surface where image formation is not performed” continues, the voltage decreases due to leakage current in the hold state of the sample / hold capacitor. Therefore, in the APC control immediately before “surface where image formation is performed”, the voltage of the sample / hold capacitor is reduced. There is a possibility that image density unevenness may occur because the voltage cannot be raised to the target voltage within the sampling period.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a sample / hold that is charged / discharged in accordance with a comparison result between a light amount detection value of a semiconductor laser and a light amount control reference value. In an image forming apparatus having an APC means for controlling the amount of light of the semiconductor laser by controlling the drive current of the semiconductor laser based on the voltage of the capacitor, wasteful mounting of the sample / hold capacitor, wasteful of the semiconductor laser It is to prevent lighting and occurrence of density unevenness of the image.

  An image forming apparatus according to the present invention includes a photoconductor, a semiconductor laser, a drive circuit that supplies a drive current to the semiconductor laser, a modulation circuit that turns on / off the drive current based on image data, and the semiconductor laser. Based on the result of comparing the rotary polygon mirror that deflects the emitted light beam and scans the photosensitive member, the light receiving element that detects the light amount of the semiconductor laser, and the output value of the light receiving element and the light amount control reference value APC means for performing sampling which is charging / discharging of the sample / hold capacitor and controlling the drive current based on the voltage of the sample / hold capacitor, and for controlling the light quantity of the semiconductor laser; When the drive current based on the image data continues to be turned off for a plurality of surfaces, the charge characteristics and discharge of the sample / hold capacitor An APC interval setting unit that sets an operation interval of the APC unit so that the sampling is performed before the hold voltage of the sample / hold capacitor drops to a predetermined value based on the characteristics. is there.

  According to the present invention, the driving current of the semiconductor laser is controlled based on the voltage of the sample / hold capacitor charged / discharged according to the comparison result between the detected value of the light amount of the semiconductor laser and the light amount control reference value. Thus, in the image forming apparatus provided with the APC means for controlling the light quantity of the semiconductor laser, it is possible to prevent wasteful mounting of the sample / hold capacitor, wasteful lighting of the semiconductor laser, and occurrence of uneven density of the image.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of an optical scanning device in an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a control unit of an optical scanning device in an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a diagram for explaining the configuration and basic operation of an APC circuit in a laser diode unit in an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the time-dependent change of the light quantity of the laser diode in general APC, and the voltage of a sample / hold capacitor | condenser. It is a figure which shows the time-dependent change of the light quantity of a laser diode and the voltage of a sample / hold capacitor | condenser at the time of performing APC once for the several surface of a polygon mirror. It is a flowchart which shows the procedure for calculating the space | interval of the APC sampling period in APC of embodiment of this invention. It is a figure which shows the time-dependent change of the light quantity of the laser diode in APC of embodiment of this invention, and the voltage of a sample / hold capacitor | condenser.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<Configuration of image forming apparatus>
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.
This image forming apparatus is a tandem color image forming apparatus, and includes four photosensitive drums 10a to 10d, four charging units 11a to 11d, four toner cartridges 12a to 12d as developing units, and four Transfer rollers 13a to 13d, four cleaners (not shown) for removing toner on the respective photosensitive drums, an intermediate transfer roller 14, an intermediate transfer belt 15, an intermediate transfer belt cleaning device 16, a transfer device 17, and a resist The configuration includes an adjustment roller 18, a fixing device 19, a paper discharge device 20, and an optical scanning device 21.

  When the start button (not shown) of the color image forming apparatus is pressed or a print job start signal from a printer host (not shown) is validated, the optical scanning device 21 controls the timing-controlled light beam. Is irradiated onto each of the photosensitive drums 10a to 10d to expose the photosensitive drums 10a to 10d, thereby forming an electrostatic latent image.

  As will be described later, in this optical scanning device 21, a polygon mirror, which is a multi-surface reflecting mirror, is rotated by a polygon motor to deflect a light beam from a laser diode, which is a light source, to be scanned surface of each of the photosensitive drums 10a to 10d. Are scanned and exposed to form an electrostatic latent image. The formed electrostatic latent images are developed with the toner supplied from the toner cartridges 12a to 12d, and single color images are formed on the photosensitive drums 10a to 10d.

  Here, first, black (K) toner is adhered to the photosensitive drum 10a, and a black image is formed, and is transferred onto the intermediate transfer belt 15 by the transfer roller 13a. Next, cyan (C) toner is deposited on the photosensitive drum 10b, a cyan image is formed, and is transferred onto the intermediate transfer belt 15 by the transfer roller 13b. At this time, since a black image has already been transferred onto the intermediate transfer belt 15, a cyan image is transferred thereon. Next, yellow (Y) toner is adhered on the photosensitive drum 10c, a yellow image is formed, and is transferred onto the intermediate transfer belt 15 by the transfer roller 13c. At this time, since the black image and the cyan image have already been transferred onto the intermediate transfer belt 15, the yellow image is transferred onto them. Finally, magenta (M) toner is adhered on the photosensitive drum 10d and transferred onto the intermediate transfer belt 15 by the transfer roller 13d. At this time, a black image, a cyan image, and a yellow image have already been transferred onto the intermediate transfer belt 15, and a magenta image is transferred thereon.

  Here, the intermediate transfer belt 15 conveys the transferred toner image of each color in a predetermined direction by rotating with the intermediate transfer roller 14 as a driving roller. In this manner, the toner images of the respective colors are superimposed on the intermediate transfer belt 15 to form a composite color image. Here, the images are formed in the order of black, cyan, yellow, and magenta, but the order of colors to be formed is not limited to this.

  On the other hand, when the print job start signal is validated, this color image forming apparatus separates the transfer sheets SH one by one from the sheet feeding apparatus, feeds and conveys them, and transfers the transfer sheets by a registration sensor (not shown). When SH is detected, the paper feeding is temporarily stopped. The registration roller 18 is rotated in synchronization with the conveyance of the composite color image on the intermediate transfer belt 15, and the transfer paper is sent between the intermediate transfer belt 15 and the transfer device 17.

  The transfer device 17 transfers the composite color image to the transfer paper SH, and the fixing device 19 fixes the transfer paper SH onto which the composite color image has been transferred by applying heat and pressure. After fixing, the transfer sheet SH is discharged by a paper discharge roller attached to the paper discharge device 20 and stacked on a paper discharge tray (not shown).

<Configuration of optical scanning device>
FIG. 2 is a diagram showing a configuration of the optical scanning device 21 in FIG.
The optical scanning device 21 includes a laser diode (hereinafter referred to as LD) unit 31 including a laser light source, a first mirror lens group, a rotary polygon mirror 37, a second mirror lens group, and a synchronization detection unit.

  The LD unit 31 includes an LD and a collimating lens that converts a divergent laser beam emitted from the LD into a parallel laser beam, as well as a photodiode (hereinafter referred to as PD) for the purpose of detecting the light amount of the LD output. And a sample / hold capacitor (hereinafter referred to as S / H capacitor), and an APC circuit for performing APC.

  The first mirror lens group includes a first cylindrical lens 32, a first mirror 33, and an imaging lens 34. The first cylindrical lens 32 has a refractive index determined in the sub-scanning direction, and condenses the parallel laser beam emitted from the LD unit 31 in the sub-scanning direction. The imaging lens 34 converts the parallel laser beam reflected by the first mirror 33 into a convergent laser beam and makes it incident on the rotating polygon mirror 37.

  The rotary polygon mirror 37 is an optical deflector composed of a polygon motor 35 and a polygon mirror 36 capable of high-speed rotation in the direction of arrow A in the figure. A laser beam from the imaging lens 34 is formed on each surface 38 of the polygon mirror 36. As the polygon motor 35 rotates, the reflected and deflected laser beam is incident on the second mirror lens group.

  The second mirror lens group includes a second mirror 39 and a second cylindrical lens 40. The second mirror 39 reflects the laser beam reflected and polarized by the polygon mirror 37 toward the photosensitive drum 10, and the second cylindrical lens 40 forms an image of the reflected light on the photosensitive drum 10. Here, the photosensitive drum 10 is one of the photosensitive drums 10a to 10d in FIG.

  The synchronization detection unit includes a third mirror 41, a condenser lens 42, and a synchronization detection sensor 43. The third mirror 41 is installed at a position where the laser beam reflected and deflected by the polygon mirror 36 deviates from the scanning area on the photosensitive drum 10, and reflects the incident laser beam toward the synchronization detection sensor 43. The laser beam reflected by the third mirror 41 is condensed by a condenser lens 42 and detected by a synchronization detection sensor 43 configured by a light receiving element such as a PD.

  Based on the detection signal output from the synchronization detection sensor 43, a synchronization detection signal (XDETP) for maintaining a constant starting position in the main scanning direction for writing an image on the photosensitive drum 10 is obtained. The laser beam modulated based on the image signal is repeatedly turned on / off (on / off) from the LD unit 31 using this synchronization detection signal as a reference. The output laser beam is repeatedly scanned in the main scanning direction as the polygon mirror 36 rotates, and the photosensitive drum 10 rotates in the sub-scanning direction, whereby an electrostatic latent image is formed on the photosensitive drum 10. The

<Configuration of control unit of optical scanning device>
FIG. 3 is a diagram illustrating the configuration of the control unit of the optical scanning device 21. As shown in the figure, the control unit of the optical scanning device 21 includes an image processing control unit 51 that performs image processing, and a write control unit that performs control to convert image data sent from the image processing control unit 51 into an LD modulation signal. 52 and a CPU 53 for performing these controls.

  The write control unit 52 includes a RAM 52a, generates an LD lighting signal and a sample / hold signal (hereinafter referred to as an S / H signal) as a control signal when APC is executed, and supplies the LD lighting signal to the LD unit 31. .

<Configuration and basic operation of APC circuit>
FIG. 4 is a diagram for explaining the configuration and basic operation of the APC circuit in the LD unit 31. This APC circuit constitutes the APC means of the present invention.
The LD lighting circuit 103 is turned on by inputting the LD lighting signal to the LD modulation circuit 103, and the switch SW is turned on by setting the S / H signal to the sample state. When the switch SW is turned on, a current control signal based on the voltage value of the S / H capacitor 107 is input to the LD modulation circuit 103, and a current based on the current control signal is input to the LD 101, whereby the LD 101 emits light. To do.

  A current in accordance with the light amount level output from the LD 101 is output from the PD 102, and the output current of the PD 102 flows into the I / V conversion circuit 104 and is converted into a voltage corresponding to the current value. The comparator 106 compares the converted voltage with the reference voltage generated by the light quantity reference voltage generation circuit 105, and the S / H capacitor 107 is charged or discharged based on the comparison result.

  The drive current of the LD modulation circuit 103 is controlled by changing the voltage value of the S / H capacitor 107 by charging or discharging of the S / H capacitor 107, and the light amount of the LD 101 is kept at a constant value corresponding to the light amount reference voltage. It is.

  In the LD modulation circuit 103, the current control signal output based on the voltage of the S / H capacitor 107 is used to control the current value supplied to the LD 101 when the LD 101 is turned on, and the LD lighting signal input from the write control unit 52 is controlled. By inputting two signals converted into positive logic / negative logic, current supply to the LD 101 is controlled to perform LD modulation.

  In the image forming period after the light quantity of the LD 101 becomes constant in the above APC, the S / H signal is in the hold state and the switch SW is turned off. When the switch SW is turned off, the current control signal output from the S / H capacitor 107 is fixed to a constant value (hold voltage), and as a result, the current input to the LD 101 is kept constant.

  In the image forming period, LD modulation is performed by the LD modulation circuit 103 in the LD unit 31 in accordance with the LD lighting signal output based on the image data from the writing control unit 52, and the laser beam is applied to the rotary polygon mirror 37. Is emitted.

<Operation of APC circuit>
Hereinafter, the operation of the APC circuit will be described. In order to facilitate understanding of the APC operation of the present embodiment, a general APC operation and an APC operation in which APC is performed once on a plurality of surfaces of a polygon mirror have been described. The APC operation of this embodiment will be described later.

<< General APC operation >>
FIG. 5 is a diagram showing temporal changes in the light amount of the LD 101 and the voltage of the S / H capacitor 107 in a general APC.

  In the conventional general APC, in order to prevent the hold voltage of the S / H capacitor 107 from dropping below the light amount reference voltage, the APC is executed regardless of the “image forming surface” and “image forming surface”. Yes. In this figure, the maximum light quantity in each period of APC lighting, BD (beam detection: synchronous detection) lighting, and image data lighting is APC lighting> BD lighting> image data lighting. However, the light amount level in each lighting period is an example, and these relationships vary depending on the configuration of the image forming apparatus.

  The light quantity of the LD 101 during the APC lighting period falls to the reference light quantity level determined by the APC before starting the BD lighting, after reaching the prescribed light quantity level for APC lighting for the light quantity detection by the PD 102. When the specified light amount level for BD lighting is reached during the BD lighting period, a synchronization detection signal generated based on the detection signal of the synchronization detection sensor 43 is output from the synchronization detection unit to the writing control unit 52.

  After the writing control unit 52 detects the synchronization detection signal, the light amount of the LD 101 is reduced to the above-described reference light amount level as in the APC lighting period. When image formation is performed after BD lighting, LD output proportional to image data (DATA) is performed from the reference light amount level, and a light amount corresponding to the output is obtained.

  When the S / H capacitor 107 is charged / discharged as necessary in the APC sample state (APC sampling period), the S / H capacitor 107 enters a hold state. Although charging / discharging is not performed in the hold state, the voltage (hold voltage) gradually decreases with time due to the leakage current of the S / H capacitor 107.

  In the conventional general APC, proper APC can always be performed by executing APC before the voltage of the S / H capacitor 107 falls below the reference voltage and charging the S / H capacitor 107.

<< APC to be executed once on multiple surfaces of polygon mirror >>
FIG. 6 is a diagram showing temporal changes in the light quantity of the LD 101 and the voltage of the S / H capacitor 107 when APC is executed once for a plurality of surfaces (here, three surfaces) of the polygon mirror 36.

  When APC is executed once for a plurality of surfaces of the polygon mirror 36, the lighting time of the LD 101 is reduced, so that deterioration of the LD 101 can be reduced. However, since the APC execution interval is too long, the voltage of the S / H capacitor 107 falls below the reference voltage before the next APC sampling is performed (a broken line in the figure).

  If the voltage of the S / H capacitor 107 is lower than the reference voltage, the voltage of the S / H capacitor 107 cannot be raised to the target voltage within the APC sampling period, so that a low voltage is detected.

  As a result, since the reference light amount level after detection is lower than before the APC sampling, the light amount level at the time of BD lighting and image data lighting after APC sampling is lower than the original light amount indicated by the broken line. , “Synchronization detection is not performed”, “Image density is low”, etc. occur. Since the decrease in the reference light amount level occurs every time APC sampling is performed, the above problem becomes more prominent.

<< APC operation of this embodiment >>
As described with reference to FIG. 6, if APC is performed once on a plurality of surfaces of the polygon mirror 36, the APC sampling interval is too long, so that the voltage of the S / H capacitor 107 becomes the next APC sampling. May fall below the reference voltage before executing.

  Therefore, in the present embodiment, the charge characteristic and discharge characteristic of the S / H capacitor 107 are measured before the start of the print job, and the APC sampling execution interval, that is, the APC sampling period interval is set based on the result.

  FIG. 7 is a flowchart showing a procedure for calculating the interval of the APC sampling period. This procedure is executed by the CPU 53 of the control unit (FIG. 3) of the optical scanning device, and corresponds to the APC interval setting means, the capacitor characteristic measuring means, the measurement number setting means and the like in the present invention.

  Before the start of measurement, the number of measurements is set to N (N is an integer equal to or greater than 1) (step S1), and after waiting for the start of the APC period (step S2), the measurement is executed. Simultaneously with the start of measurement, the counter 1 that is a counter for measuring the charging characteristics of the S / H capacitor 107 is started (steps S3 and S4). Here, it is assumed that the cycle of the counter 1 depends on the operating frequency of the CPU 53.

  The comparison is repeated until the voltage of the S / H capacitor 107 reaches the APC reference voltage, and when the reference voltage is reached (step S5: YES), the counter 1 stops counting (step S6). Next, after the end of the APC period (step S7), the counter 2 which is a counter for measuring the discharge characteristics of the S / H capacitor 107 starts counting (step S8). Similarly to the counter 1, the counter 2 depends on the operating frequency of the CPU 53.

  The comparison is repeated until the voltage of the S / H capacitor 107 falls below a reference voltage that is a voltage that can be charged by APC (step S9). When the voltage falls below (step S9: YES), the counter 2 stops counting (step S10). . Next, the measurement results of the counters 1 and 2 are stored in the RAM 52a (step S11), and one measurement is completed (step S12).

  This series of measurement operations is repeated until the number of measurements set in step S1 is reached (step S13: YES). After reaching the number of times of measurement, each measurement result is stored in the RAM 52 a in the write control unit 52.

  Based on the results stored in the RAM 52a, the time required for charging the S / H capacitor 107 to a certain voltage and the time required for discharging are calculated (step S14). Based on these times calculated before the start of the print job, it is possible to calculate the interval of the APC sampling period in which proper APC is possible.

  FIG. 8 is a diagram showing temporal changes in the light quantity of the LD 101 and the voltage of the S / H capacitor 107 in the APC according to the embodiment of the present invention. The interval of the APC sampling period in this figure is calculated by the procedure shown in FIG.

  In the figure, it is assumed that there is an interval of three surfaces of the polygon mirror 36 from the completion of the previous image formation to the next image formation. In this case, the voltage of the S / H capacitor 107 does not fall below the reference voltage by performing APC not only immediately before the image forming surface but also the immediately preceding surface (dashed line in the figure). As can be seen from FIG.

  Although an example in which image formation is performed on the three surfaces of the polygon mirror 36 at a single interval has been described here, an appropriate APC can be obtained by performing APC at a calculated interval even when the image formation surface interval is three or more. Will continue to be implemented.

  Here, the condition that the interval between the image forming surfaces exceeds one surface, that is, the “surface that does not form an image” continuously occurs is that a white line that is continuous in the sub-scanning direction of image data for one page is included. There are margins after image data formation. In addition, by thinning out the image writing in the main / sub-scanning direction based on the synchronization detection signal from the synchronization detection unit, the surface of the polygon mirror 36 is thinned out without changing the number of rotations of the polygon motor 35. The same condition occurs in the control for outputting the resolution image. Under these conditions, the APC is performed at the above-described interval in the present embodiment, so that unnecessary APC can be eliminated.

  Further, in the measurement accompanying the calculation of the interval of the APC sampling period, if the number of times of measurement is a large value if the number of times of measurement is fixed, the measurement may not be completed before the start of the print job. Furthermore, the possibility of not being able to store all measurement results due to the limitation of the information storage area of the RAM 52a and the processing load on the CPU 53 due to measurement execution cannot be ignored. In this embodiment, the number of measurements can be set arbitrarily, so that these problems can be prevented.

  As described above, according to the image forming apparatus of the present embodiment, an appropriate APC sampling period interval is calculated before the start of a print job, APC is performed based on the calculation result, and unnecessary APC is suppressed. Can be reduced, and the occurrence of uneven image density with respect to the image data can be prevented.

  DESCRIPTION OF SYMBOLS 10,10a-10d ... Photosensitive drum, 101 ... LD, 102 ... PD, 103 ... LD modulation circuit, 104 ... I / V conversion circuit, 105 ... Light quantity reference voltage generation circuit, 106 ... Comparator, 107 ... S / H capacitor .

JP 2002-211032 A

Claims (5)

A photoreceptor,
A semiconductor laser;
A drive circuit for supplying a drive current to the semiconductor laser;
A modulation circuit for turning on and off the drive current based on image data;
A rotating polygon mirror that deflects a light beam emitted from the semiconductor laser and scans the photosensitive member;
A light receiving element for detecting the light quantity of the semiconductor laser;
Sampling, which is charging / discharging of the sample / hold capacitor, is performed based on the comparison result between the output value of the light receiving element and the light amount control reference value, and the drive current is controlled based on the voltage of the sample / hold capacitor. APC means for controlling the light quantity of the semiconductor laser by:
When the drive current based on the image data continues to be turned off for a plurality of surfaces of the rotary polygon mirror, the hold voltage of the sample / hold capacitor reaches a predetermined value based on the charge characteristics and discharge characteristics of the sample / hold capacitor. APC interval setting means for setting an operation interval of the APC means so that the sampling is performed before being lowered;
An image forming apparatus. The image forming apparatus according to claim 1,
Capacitor characteristic measuring means for measuring the charge characteristic and discharge characteristic of the sample / hold capacitor, and the APC interval setting means sets the operation interval of the APC means based on the measurement result of the capacitor characteristic measuring means apparatus. The image forming apparatus according to claim 2,
The APC means is an image forming apparatus that operates during a non-image forming period in which the light beam does not scan the photoconductor. The image forming apparatus according to claim 2,
An image forming apparatus having a measurement number setting means for setting the measurement number of the capacitor characteristic measurement means to an arbitrary number of one or more. The image forming apparatus according to claim 2,
The capacitor characteristic measuring unit is an image forming apparatus that performs measurement before starting a print job.

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