JP2011189613A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for correcting shading occurring in an exposure surface, including a factor caused by a temperature change, which is a simple means suitable for incorporation into an image forming apparatus. <P>SOLUTION: A shading correction part 30p selects correction data adapted to a detected lighting start threshold current value Ith from a data base where a stored lighting start threshold current value Ith and the correction data for shading are associated with each other, on the basis of the lighting start threshold current value Ith of an LD1e detected by an Ith detection part 17. An image writing control part 30 light-controls the LD1e by image data to be written, corrects the light emission amount of the LD1e by the correction data for shading selected by the shading correction part 30p, and instructs an LD control part 15 on control conditions for controlling the light emission amount on the basis of data after correction. The LD control part 15 receives the instruction from the image writing control part 30, to control a laser drive part and emit the LD1e. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus (for example, a laser printer) having means for scanning an exposure surface (image surface) of a photosensitive member with a light beam from a light emitting element whose lighting is controlled by input image data. The present invention relates to an image forming apparatus and an image forming method in which the light emission amount of a light emitting element is controlled in order to make the light amount of an exposure surface uniform.

In an image forming apparatus called an electrophotographic printer, a so-called digital copying machine, or a multifunction peripheral, a laser (LD: Laser Diode) is used as a light-emitting element whose lighting is controlled by image data, and a laser that emits light is used as a beam. The beam periodically scans the exposed surface (image surface) of the photoconductor to generate an electrostatic latent image on the exposed surface of the photoconductor (this operation is also referred to as “image writing” or simply “writing”). The method is conventionally employed.
When the light emission amount of the LD element used in such a laser beam writing method varies, the image density varies. For this reason, a technique for adjusting the light emission amount by performing APC (Automatic Power Control) lighting outside the image area for each main scan and monitoring the back beam inside the LD is already known.

However, in APC that monitors the back beam inside the LD, if the divergence angle characteristic of the LD changes, the coupling efficiency at the aperture (see FIG. 1 to be described later) changes. Will occur. Further, if the LD monitor current itself has temperature characteristics, the APC light quantity itself varies. Further, when the deflection angle characteristic of the LD fluctuates, the shading characteristic (the nature of the light quantity fluctuation on the image plane) changes.
As a method that can avoid the problem of shading caused by fluctuations in the divergence angle characteristics, monitor current characteristics, deflection angle characteristics, etc. of the LD due to temperature fluctuations, which cannot be solved by the method of monitoring the back beam inside the LD, Patent Literature Proposals shown in 1 and 2 have been made.
In Patent Document 1, a single light receiving sensor in which a light amount monitor for synchronous detection and light amount adjustment of a scanned laser beam is provided in a beam scanning path is used. Further, Patent Document 2 provides sensors for detecting non-uniform density by providing sensors for detecting beam power at a plurality of positions in the main scanning direction of a light beam for exposing a photosensitive member.

However, Patent Document 1 cannot detect fluctuations in the amount of light in the main scanning direction of a light beam that causes shading.
Japanese Patent Laid-Open No. 2004-26883 can detect fluctuations in the amount of light on the exposure surface (image surface), but requires a plurality of detection means for detecting the beam power including the sensor, and corrects based on the detection result of the sensor. In order to carry out the processing for generating the data in real time, a high-performance processing means is required, resulting in a problem that the cost is increased.
An object of the present invention is made in view of the above-described problems of the prior art in which shading caused by fluctuations in LD divergence angle characteristics, monitor current characteristics, deflection angle characteristics, etc. due to temperature fluctuations is corrected by controlling the light emission amount of the light emitting element. Therefore, it is possible to correct the non-uniformity in the amount of light generated on the exposure surface, including factors due to temperature fluctuations, and to realize a simple means for making the amount of light uniform by means suitable for incorporation into an image forming apparatus. With the goal.

The present invention includes a light emitting element capable of controlling the light emission amount, a light emission control unit for controlling the light emission amount of the light emitting element according to the setting, and controlling lighting based on input image data, and a beam of output light from the light emitting element. An image forming apparatus having optical scanning means for periodically scanning the exposure surface of the photosensitive member with the beam, the threshold current detection means for detecting a lighting start threshold current value of the light emitting element, and the threshold current detection Based on the lighting start threshold current value detected by the means, it comprises a set value determining means for determining a set value of the light emission amount for uniformizing the amount of light on the exposure surface at the beam scanning position, the lighting control means, The light emission amount is controlled in accordance with the set value determined by the set value determining means.
In the present invention, lighting of a light emitting element whose light emission amount can be controlled is controlled by input image data, output light from the light emitting element is used as a beam, and an exposure surface of a photosensitive member is periodically scanned by the beam. An image forming method for forming an image by the threshold current detection step of detecting the lighting start threshold current value of the light emitting element, and based on the lighting start threshold current value detected in the threshold current detection step, A setting value determining step for determining a setting value of the light emission amount that equalizes the light amount on the exposure surface at the beam scanning position; and a lighting control step for controlling the light emission amount according to the setting value determined in the setting value determination step; It is characterized by having.

  According to the present invention, the light quantity on the exposure surface is corrected by correcting the non-uniformity in the light quantity on the exposure surface (image surface) caused by temperature fluctuation by means having a simple configuration and suitable for incorporation into the image forming apparatus. Can be made uniform, and as a result, cost increases can be suppressed.

1 is a diagram illustrating a schematic configuration of an optical writing optical system of an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows the processing system in the optical writing control which concerns on embodiment of this invention with the flow of data and a signal. It is a diagram explaining the correction | amendment operation | movement of a shading. It is a diagram explaining the situation of the correction operation when the shading characteristic varies due to temperature. It is a diagram which shows the light emission characteristic of LD which fluctuates with temperature with lighting start threshold current (Ith). It is a diagram explaining the correction | amendment operation | movement of the shading which fluctuates with temperature. It is the schematic which shows the principal part structure of the image writing control system provided with the correction function of the shading which makes the light quantity of an exposure surface uniform. It is a figure which shows the control flow of the light quantity correction | amendment operation | movement of the image writing control system shown in FIG.

Embodiments of the present invention will be described with reference to the accompanying drawings.
In the following embodiments, an image forming apparatus such as a laser printer, a digital copying machine equipped with a laser printer engine, or a multifunction machine is used as an example of the present invention. These image forming apparatuses create image data for print output based on PDL (page description language) data or image data input through scanner reading, and control the lighting of the laser based on this image data. And an image writing unit that periodically scans the exposure surface of the photosensitive member with the beam, and forms an image by an electrophotographic method.

The present invention is characterized by means for correcting non-uniformity in the amount of light of the laser beam that scans the exposure surface (hereinafter referred to as “shading correction”) and making the amount of light uniform, and this feature configuration will be described in detail later. Before the description, an outline of a presumed image writing unit will be described.
It should be noted that processing such as development with toner, transfer of a toner image onto a recording sheet, and fixing, which are normally performed in an electrophotographic image forming apparatus after image writing, can be performed by applying existing technology. Is omitted.

[Optical writing optical system]
FIG. 1 is a diagram illustrating a schematic configuration of an optical writing optical system of an image forming apparatus according to an embodiment of the present invention.
In the optical writing optical system shown in FIG. 1, since the optical path of the output beam from the LD (laser diode) 1 is shown, the components of the optical writing optical system and their functions will be described in the order of the optical paths.
The beam emitted from the LD 1 passes through the aperture 2 and becomes parallel light, and enters the rotating polygon mirror 3. The magnification of the beam scanned by the polygon mirror 3 is corrected by the fθ lens 4 so that the speed in the main scanning direction (indicated by the broken arrow in FIG. 1) is constant.
The beam passing through the fθ lens 4 is reflected by the three folding mirrors 5, 6, and 7 and then irradiates the exposure surface (image surface) of the photosensitive member 9.
The beam scanned in the main scanning direction irradiates the synchronization detection sensor 8 placed on the scanning optical path outside the photoconductor 9. The synchronization detection sensor 8 detects the incidence of a beam and generates a synchronization detection signal. An image writing control unit (see FIG. 2) described later controls the start of image writing based on the timing of the synchronization detection signal.

[Optical writing control system]
FIG. 2 is a block diagram showing a processing system in the optical writing control according to the embodiment of the present invention together with the flow of data and signals.
The processing system in the image writing control unit 30 in FIG. 2 performs a process for controlling the lighting of the LD 1 and a process for controlling the rotation of the polygon motor 3m.
The process for controlling the lighting of the LD 1 is an LD lighting generated based on the input of image data and an image area signal from an image processing ASIC (Application Specific Integrated Circuit) or the image processing controller 10. Although not explicitly shown in FIG. 2 and FIG. 2, this is a process of outputting to the laser drive unit 41 a control signal of the light emission amount of the LD that performs light amount correction described later.

Further, the process for controlling the rotation of the polygon motor 3m, that is, the process for controlling the rotation of the polygon mirror 3, is performed based on a command from a CPU (Central Processing Unit) 20 of the main control unit. This is a process of outputting a control clock or the like.
It should be noted that the lighting operation of the LD 1 and the rotation of the polygon mirror 3 are controlled at a predetermined timing, and the image writing by the LD 1 is a synchronous detection sensor 8 that detects a beam scanned by the rotation of the polygon mirror 3 (FIG. 1). Therefore, these operation timings are centrally managed by the image area control and various timing control units 38 according to the commands of the CPU 20 of the main control unit.

Hereinafter, the configuration of the image writing control unit 30 that performs the above processing will be described in more detail.
The image writing control unit 30 includes a speed conversion line memory 31, various pattern generation units 32, a writing γ conversion unit 33, LD modulation and various clock generation units 34, a continuous lighting detection unit 35, and an LUT (lookup table) 36. , A bias and lighting current generation unit 37, an image area control and various timing control unit 38, various setting registers, and a polygon motor control unit 39.
The image writing control unit 30 also receives an external data or signal input by an image data input I / F 11, a command I / F 21, an LD modulation I / F 42, a synchronization detection I / F 46, and a polygon motor I / F 44. Outputs data or signals to

The image data input I / F 11 inputs image data and an image area signal from the image processing ASIC or the image processing controller 10 into the image writing control unit 30.
The LD modulation I / F 42 outputs an LD lighting signal, an APC signal, and the like generated in the image writing control unit 30 as a control signal to the laser driving unit 41 that drives the LD 1.
The synchronization detection I / F 46 inputs the synchronization detection signal detected by the synchronization detection sensor 8 into the image writing control unit 30.
The command I / F 21 inputs a command such as synchronous serial from the CPU 20 of the main control unit into the image writing control unit 30.
The polygon motor I / F 44 outputs a control clock and the like generated in the image writing control unit 30 as a control signal to the polygon motor driver 43 that drives the polygon motor 3m.

The image writing control unit 30 composed of such components stores the image data input through the image data input I / F 11 in the speed conversion line memory 31, and the lines acquired via the continuous lighting detection unit 35. Each LD lighting time is read into the LUT 36. The bias and lighting current generator 37 reads the bias current and lighting current corresponding to the LD lighting time stored in the LUT 36 as set values, and based on the obtained setting value, the bias current and lighting current corresponding to the LD lighting time. To turn on LD1. At this time, the set value of the lighting current read from the LUT 36 is further corrected to perform shading correction described later.
The bias current is output from the LD modulation and various clock generation unit 34 to the laser drive unit 41 based on the synchronization detection signal from the synchronization detection sensor 8. The output from the LD modulation and various clock generation unit 34 is input to the laser drive unit 41 via the LD modulation I / F 42.

The image area control and various timing control unit 38 is configured to output an image area control signal and an image area control signal based on the image area signal output from the image processing ASIC or the image processing controller 10 and signals input from the various setting registers and the polygon motor control unit 39. A timing control signal is generated.
The various setting registers and the polygon motor control unit 39 receive a synchronous serial signal or the like from the CPU 20 of the main control unit, and output a drive signal to the polygon motor driver 43 to the polygon motor 3m. The polygon motor 3m rotates the polygon mirror 3 (see FIG. 1) and causes the modulated laser beam emitted from the LD 1 to move in the main scanning direction of the photosensitive member, for example, the surface of the drum type photosensitive member 9 shown in FIG. Is exposed and scanned in the main scanning direction indicated by an arrow in FIG. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum.

[Shading correction]
Shading refers to uneven density caused by unevenness in the amount of light of a laser beam that scans the exposure surface (image surface). In order to eliminate shading, the LD is caused to emit light so that the amount of light is uniform on the exposure surface. This operation is called shading correction.
FIG. 3 is a diagram for explaining a shading correction operation. Fig (A) ~ (C) are each takes the horizontal axis in the main scanning direction of the beam, (A) the shading in the change of the beam power P ₁ of the LD in the image plane, (B) each position of the image plane Correction data C ₁ and (C) indicate the light quantity L ₁ at each position on the image plane after correction.

Beam power P ₁ of the LD in the image plane, as shown in FIG. 3 (A), varies depending on the position in the main scanning direction, i.e., typically, becomes smaller toward the larger end at the center of the image plane, it is sufficient to multiply the correction for emitting LD in amount to counteract this change in light amount, and drives the LD current amount of the correction data C ₁ of reversed as in FIG. 3 (B), causes the emission (Note that the drive The current and the light emission amount are generally proportional as shown in FIG.
By doing so, as shown in FIG. 3 (C), the light amount L ₁ of the image plane after correction becomes uniform over the main scanning direction can be corrected shading.

However, the non-uniformity (shading characteristics) in the amount of light that occurs in the main scanning direction on the image plane is affected by the deflection angle characteristics of the LD, and when the LD deflection angle characteristics are temperature dependent, Shading characteristics change. In this case, if the correction data is not changed, the non-uniformity occurs again in the image plane light quantity.
FIG. 4 is a diagram for explaining the shading correction operation in this situation. Fig (A) ~ (C) is taken on the horizontal axis in the main scanning direction of the beam, respectively, (A) the shading in the change of the beam power P ₂ of the LD in the image plane, (B) each position of the image plane Correction data C ₂ and (C) indicate the light quantity L ₂ at each position of the corrected image plane.

In the operation example shown in FIG. 4, beam power P ₂ of the LD in the image plane is affected by changes in environmental temperature, from the state shown in FIG. 3 (A), varies as shown in FIG. 4 (A), That is, the power does not decrease from the center of the image plane toward the end in the main scanning direction, and the power is substantially constant. In this situation, as shown in FIG. 4B, the shading correction is performed in the same manner as shown in FIG. In such a case, as shown in FIG. 4 (C), the light amount L ₂ of the image plane after correction without being uniformly toward the end portion on the side toward the main scanning direction from the center of the image plane, The shading is not corrected.
In order to completely correct the shading in such a situation, a correction operation in consideration of the environmental temperature condition is required.

[Shading correction method]
The above-described correction of shading affected by the environmental temperature is realized by a conventional technique (see Patent Document 2) in which shading correction is performed using a sensor that detects the amount of light at each point in the main scanning direction of the image plane in real time. Is possible. However, a plurality of beam power detection sensors are required, and high-performance processing means are required to perform processing for generating correction data in real time based on the detection results of the sensors.
Based on this awareness of the problem, the present invention corrects non-uniformity (shading) of the amount of light generated on the exposure surface, including factors due to temperature fluctuations, as described in [Problems to be Solved by the Invention] above. It is an object of the present invention to realize the above means by means suitable for incorporation into an image forming apparatus that is simple and does not have such high processing performance.

As a means for solving this problem, in this embodiment, an assumed environmental temperature condition is set, and correction data is obtained based on the light quantity actually detected by the light quantity detection sensor in advance in an actual machine under the condition. A database in which the corrected data is associated with the environmental temperature is created.
The created database is stored in the image forming apparatus, and at the time of image formation, correction data suitable for the environmental temperature at that time is acquired from the database, and shading correction is performed. By adopting such a method, a means for correcting shading generated on the exposure surface, including factors due to temperature fluctuations, can be mounted on an image forming apparatus that is simple and does not have so high processing performance. .

<Detection of environmental temperature (lighting start threshold current value Ith)>
A means for capturing the environmental temperature of the image forming apparatus, which is an element necessary for realizing the correction operation, will be described.
The environmental temperature of the image forming apparatus that is an element for solving the problem is a temperature that is captured for the purpose of forming an image with high performance without causing shading in the image forming operation by the beam exposure of the LD, In this embodiment, attention is paid to the lighting start threshold current value in the LD.
FIG. 5 is a diagram showing the light emission characteristics of an LD that varies with temperature. The figure shows the amount of light emission (vertical axis) with respect to the drive current (horizontal axis), the characteristic line La at low temperatures, and the characteristic line Lb at high temperatures. It shows that it differs depending on the temperature.

As shown by the characteristic line in FIG. 5, when the drive current is increased, the LD emits light suddenly with a certain value as a boundary, and thereafter the light quantity increases almost in proportion to the drive current value. This current value that is a threshold value at which light emission starts suddenly is referred to as a lighting start threshold current value Ith. The lighting start threshold current value Ith takes a unique value depending on the individual LD, and changes depending on the environmental temperature.
In general, as the temperature increases, the lighting start threshold current value Ith increases and takes a different value corresponding to the temperature. By utilizing such characteristics, in the image forming apparatus, when forming an image, the lighting start threshold current value Ith is set in advance in order to determine the set value of the LD drive current control used in the image forming operation to be performed. The operation to detect is performed.

In this embodiment, the lighting start threshold current value Ith is detected by means for performing APC lighting outside the image area for each main scan. Therefore, when the APC lighting is performed using the APC lighting operation. This can be implemented by adding a means for measuring the drive current when lighting is started.
Since the environmental temperature can be known from the lighting start threshold current value Ith thus detected, shading correction data adapted to this environmental temperature is obtained from the above-mentioned database, and this main scanning line is obtained according to the obtained correction data. The amount of light emission is controlled by adjusting the LD drive current on the image plane (see [Shading correction function for writing control] described later for this shading correction means).

FIG. 6 is a diagram for explaining a shading correction operation that varies with temperature.
Fig (A) ~ (C) is taken on the horizontal axis in the main scanning direction of the beam, respectively, (A) the shading in the change of the beam power P _a of the LD in the image plane, (B) each position of the image plane Correction data C _a and (C) indicate the light quantity L at each position on the image plane after correction.
In addition, the LD beam power on the image plane of FIG. 6A and the correction data of FIG. 5B indicate that the LD beam power is in the range of P _a → P _{b as} the temperature changes. Each value fluctuates in the range of C _a → C _b .

In the present embodiment, as described above, a method of acquiring correction data adapted to the environmental temperature at that time from the database based on the lighting start threshold current value Ith representing the environmental temperature is used.
Therefore, FIG. 6 (A) shows the actual detection at each position on the image plane by the light quantity detection sensor in advance in the actual machine at the setting of each environmental temperature (corresponding to the lighting start threshold current value Ith) in the process of creating the database. _6B shows the beam power (light amount) P _{a to} P _b of the LD, and FIG. 6B corrects shading by causing the LD to emit light with a light amount that cancels the light amount change of the LD shown in FIG. The correction data C _{a to} C _b for this are shown.
That is, the created database is associated with the environmental temperature represented by the lighting start threshold current value Ith and shading correction data (FIG. 6B) adapted to the temperature. Accordingly, shading correction data adapted to this current value is obtained from the lighting start threshold current value Ith from the database, and the light emission amount of the LD is controlled according to the obtained correction data, as shown in FIG. 6C. The light quantity L of the image plane after correction becomes uniform in the main scanning direction, and shading can be corrected.

[Image writing control system with shading correction function]
The configuration and operation of an image writing control system having a function of controlling the light emission amount of the LD based on the LD lighting start threshold current value Ith and correcting shading will be described.
FIG. 7 is a schematic diagram showing a main part configuration of an image writing control system having a shading correction function for making the light amount of the exposure surface uniform.
As shown in FIG. 7, the image writing control system having a shading correction function includes an image writing control unit 30 (corresponding to the image writing control unit 30 in FIG. 2), and an LD 1 (in FIGS. 1 and 2). The elements are an LD control unit 15 (corresponding to a control unit that generates an LD lighting signal, an APC signal, and the like inside the image writing control unit 30 in FIG. 2), and an Ith detection unit 17.
In addition to the LD 1e as the light emitting element, the LD 1 has a diode 1m on a branch line connected to the Ith detection unit 17 in order to detect the drive current of the LD 1e.
Further, a laser driving unit (not shown) whose operation is controlled by the LD control unit 15 is provided between the LD control unit 15 and the LD 1e.

The image writing control unit 30 includes a shading correction unit 30p. The shading correction unit 30p associates the lighting start threshold current value Ith with the shading correction data adapted to the temperature, for example, a LUT format database, and stores this.
As described with reference to FIG. 6B, the database used for the shading correction corresponds to the assumed environmental temperature (lighting start threshold current value Ith) as data inherent to the image forming apparatus in advance. Is used to set the lighting current at the time of image formation, and in this respect, the lighting current corresponds to the LD lighting time in units of scanning lines. It is handled in the same manner as the above-described LUT 36 prepared for setting.

<Shading correction operation of control system in FIG. 7>
FIG. 8 is a diagram showing a control flow of the shading correction operation of the control system shown in FIG.
Since the control flow in FIG. 8 makes it possible to use APC lighting performed outside the image area for each main scan, this control flow is activated in synchronization with the APC operation.
The control flow is started, and first, the lighting start threshold current value Ith is detected (step S101). The detection of Ith is by driving the LD 1e and measuring the drive current when the lighting is started by the Ith detector 17. The start of lighting can be known from, for example, a backlight detection signal used for the APC operation, and the measured value of the Ith detector 17 at this time is detected and held as the lighting start threshold current value Ith.

Next, correction data for shading is selected based on the detected lighting start threshold current value Ith (step S102). In this operation, the lighting start detected and held by the Ith detection unit 17 in step S101 from the database that stores the lighting start threshold current value Ith and the shading correction data stored in the shading correction unit 30p in advance. This is an operation for selecting correction data adapted to the threshold current value Ith.
That is, the shading correction unit 30p uses correction data adapted to the current environmental temperature in the current LD 1e to be used for correction of shading that may occur on the image plane due to LD light emission used for writing to be executed later. Select from a database (for example, LUT) prepared in advance.

Next, shading correction is executed (step S103). This operation is based on the shading correction data selected by the shading correction unit 30p, and the amount of laser light when the image writing is actually performed on the exposure surface (image surface) of the photosensitive member by the laser beam modulated by the image data. This is a correction operation.
In other words, the image writing control unit 30 controls the lighting of the LD 1e based on the image data to be written, and corrects the light emission amount of the LD 1e based on the shading correction data selected by the shading correction unit 30p. A control condition for controlling the light emission amount is instructed to the LD control unit 15 on the basis. The light emission amount control condition is set corresponding to the beam position in the main scanning direction, as shown in the shading correction data in FIG. In response to the above instruction from the image writing control unit 30, the LD control unit 15 controls a laser driving unit (not shown) to cause the LD 1e to emit light.
By performing the above control, the light emission amount of the LD 1e is controlled so as to cancel the shading, so that a high-quality image can be formed without shading on the exposure surface (image surface) of the photoreceptor. it can.

  1 .... LD, 3 .... polygon mirror, 8 .... synchronous detection sensor, 9 .... photosensitive member, 10 .... image processing ASIC or image processing controller, 15 .... LD controller, 17 .... Ith detector, 20 ... CPU, 30... Image writing control section, 30p... Shading correction section, 34 .. LD modulation and various clock generation sections, 36... LUT, 37.

Japanese Patent Laid-Open No. 9-230259 JP 2005-219386 A

Claims (5)

A light emitting device capable of controlling the amount of light emission;
A lighting control means for controlling the light emission amount of the light emitting element according to the setting, and for controlling the lighting by the input image data,
An image forming apparatus having an optical scanning unit configured to periodically scan an exposure surface of a photosensitive member with a beam using an output light from a light emitting element as a beam,
Threshold current detection means for detecting a lighting start threshold current value of the light emitting element;
Based on the lighting start threshold current value detected by the threshold current detection means, comprising a set value determining means for determining a set value of the light emission amount for uniformizing the amount of light on the exposure surface at the beam scanning position,
The image forming apparatus, wherein the lighting control unit controls a light emission amount according to a set value determined by the set value determining unit. The image forming apparatus according to claim 1,
A database in which the lighting start threshold current value of the light emitting element and the setting value of the light emission amount for equalizing the light amount at the beam scanning position are associated as data unique to the image forming apparatus;
The set value determining means acquires a set value of the light emission amount at the time of lighting corresponding to the lighting start threshold current value detected by the threshold current detecting means from the database, and determines the obtained value as the set value. An image forming apparatus. The image forming apparatus according to claim 1,
A set value storage means for storing a set value of a light emission amount at the beam scanning position obtained in advance as data unique to the image forming apparatus at each of a predetermined low temperature and a high temperature;
The set value determining means emits a set value of a light emission amount adapted to the lighting start threshold current value detected by the threshold current detecting means to emit light at each of a predetermined low temperature and high temperature stored in the set value storage means. An image forming apparatus that calculates based on a set value of an amount and determines the calculated value as a set value. The image forming apparatus according to any one of claims 1 to 3,
The photoreceptor generates an electrostatic latent image on an exposure surface by scanning a beam with the optical scanning unit;
An image forming apparatus comprising: means for developing the electrostatic latent image generated on the exposure surface of the photosensitive member with toner. The lighting of a light emitting element whose light emission amount can be controlled is controlled according to the input image data, and the output light from the light emitting element is used as a beam, and an image is obtained by periodically scanning the exposure surface of the photosensitive member with the beam. An image forming method for forming,
A threshold current detection step of detecting a lighting start threshold current value of the light emitting element;
A setting value determining step for determining a setting value of the light emission amount for equalizing the amount of light on the exposure surface at the scanning position of the beam, based on the lighting start threshold current value detected in the threshold current detection step;
And a lighting control step of controlling the light emission amount according to the set value determined in the set value determining step.

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