JP2000347471A - Image forming method and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where the change of image density with time is efficiently corrected. SOLUTION: In the image forming device where an electrostatic latent image corresponding to image information is formed on an image carrier B provided with a photoreceptor by a writing unit A and a visual image is obtained by developing the electrostatic latent image, an image patch of a specified pixel density is formed on the photoreceptor by varying the output of a laser beam by the writing unit A, this image patch is developed, the density of the developed image patch is detected by a density sensor C, and the output of the laser beam where the density of the image patch of the specified pixel density reaches a specified density is derived using the detected density information and an image is formed by the derived output of the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming method and an image forming apparatus, and more particularly to an electrophotographic image forming method and an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, there has been provided an electrophotographic image forming apparatus which forms a latent image on a photoreceptor by a laser beam or the like and forms the image by developing the latent image.

In order to obtain an image in such an image forming apparatus, the image is determined by adjusting the power of the laser beam and the exposure time. As a method of adjusting the exposure time of the laser beam, PWM (pulse width modulation) for adjusting the time for turning on the laser by a pulse width is known.

A multi-valued image obtained by a laser writing system has been subjected to γ curve correction by laser power and laser pulse width to obtain a constant gradation. In addition, a binary image (on, of based on 0, 1 data) by 1-bit dots
The density of the “f image” is defined by a halftone dot pattern, and if the diameter (area) of each dot forming the halftone dot changes, the halftone density as an image changes. FIG.
FIG. 3 is a schematic diagram showing that a character image formed by dots of the same pattern also becomes a crushed character or a thin character when the dot diameter changes, and the image quality changes. Also, as can be seen from the figure, even if the image is a binary image, the change in the dot diameter changes the amount of toner used per character, and if it changes, the amount of toner consumed per image also changes. Resulting in.

[0005] The dot diameter of a 1-bit image changes due to fluctuation factors such as deterioration of the photoreceptor and deterioration of sensitivity, contamination of the optical system, and deterioration of the developer. For this reason, it is necessary to stabilize the halftone density and the toner consumption in a 1-bit image by controlling the dot diameter to be constant.

[0006] As a conventional example in such a situation,
There are the following.

A first conventional example is an invention disclosed in Japanese Patent No. 2746942. This first conventional example compares the ratio of the main scanning line visible pattern with the difference from a preset reference value. Is calculated, and one line width of the laser diode power is corrected according to the calculation result.

A second conventional example is an invention disclosed in Japanese Patent Application Laid-Open No. 7-25063. In the second conventional example, a plurality of lasers are independently driven to form a specified image density. , Density detection and comparison to adjust the output level of the laser diode.

A third conventional example is disclosed in Japanese Patent Application Laid-Open No. 61-189575.
The third conventional example is an invention disclosed in
Means for creating a halftone image and visualizing the image, detecting the image with a sensor, and controlling the light emission intensity in accordance with the detected density.

[0010]

However, the above-described first method
In the case of detecting and correcting in the main scanning line as in the related art, there is a problem that the line width in the sub-scanning direction can be detected but cannot be detected in the main scanning direction.

Further, in the above-mentioned second conventional example, even though each of the images formed by each of the plurality of lasers can be made to have the same density, it is not possible to correct the temporal change of the image density. .

In the third conventional example described above, each dot of the generated halftone image is formed by pulse width modulation.
The concentration is adjusted by adjusting the power of the laser diode. In this case, if the density curve (so-called γ curve) when the pulse width is changed is constant, the density of the highest density portion can be adjusted by adjusting the density of the halftone, but γ correction is performed. The γ curve varies to the extent that it must be performed, and in density optimization in a halftone image created by a pulse width, the density of the highest density portion (near the maximum pulse width) used in a 1-bit image is not always constant. . FIG. 8 is a schematic diagram showing the variation of the highest density portion due to the variation of the γ curve. For example, even if the density is optimized with the PWM value m in FIG. 8, the image density changes significantly in the highest density portion (PWM value X) used in the above 1-bit image due to the variation in the γ curve.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus capable of efficiently correcting a temporal change in image density.

[0014]

According to the present invention, in order to achieve the above object, an electrostatic latent image corresponding to image information is formed on a photoreceptor by a laser beam generated from a laser,
In the image forming method of developing the electrostatic latent image to obtain a visible image, changing the output of the laser beam to create an image patch of a specified pixel density on the photoconductor, and developing the image patch, The density of the developed image patch is detected, and based on the detected density detection information, the output of the laser beam at which the image patch of the specified pixel density has the specified density is obtained.
An image is formed with the output of the obtained laser beam.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a schematic mechanism of an embodiment of an image forming apparatus according to the present invention.

In FIG. 1, the image carrier B is 280 mm
/ Sec] or 125 [mm / sec], and has a diameter of 80 formed of a (-) charged coating type OPC that rotates in the direction of the arrow.
[Mm] drum-shaped photosensitive member, and an encoder 15 for detecting a phase is provided on the rotation axis of the image carrier B. The encoder 15 controls a phase signal indicating the phase of the image carrier B to be described later. It is sent to means 1.

A writing unit A, a charging device 20, a developing unit 30, a separating device 44, a transfer device 43, and a cleaning unit 50, which will be described later, are provided on the periphery of the image carrier B. A paper feed system including a belt and the like is provided.

The writing unit A causes the semiconductor laser to emit light based on, for example, a recording signal read from a page memory or a patch recording signal for recording an image patch to be described later. A line image is formed by line scanning, and a so-called exposure process is performed.

The charging device 20 is, for example, a scorotron charger, and performs fog prevention or the like by uniformly charging the image carrier B to a predetermined voltage and adjusting gradation reproducibility before the latent image forming process. .

The developing unit 30 has an average particle size of about 8.5.
[Μm] A toner composed of a polyester-based material and a ferrite-based coating carrier having an average particle size of about 60 [μm] are stirred at a toner concentration of 4 to 6%. After rotating by stirring at about 400 [rpm] or 180 [rpm] outside the magnet roller 32.
A magnetic brush is formed on the outer circumference of the developing sleeve 31 which rotates by applying a predetermined bias voltage to the developing sleeve 31 to visualize the latent image in the developing area facing the image carrier B into a toner image. It is.

The developing unit 30 has a rotating shaft of a magnet roller 32 covered with a sleeve 31 having a diameter of 40 [mm] near an opening of the housing 300 facing the image carrier B.
0, and the diameter is 16 [mm] behind it.
The drive shafts of the stirring screws 33A, 33B, 33C are fitted into the side walls of the housing 300, and these sleeves 31,
The drive shafts of the stirring screws 33A, 33B, and 33C are connected to a drive system (not shown) via gears, for example, so that the number of rotations can be changed. This control operation is performed by the control means 1. By utilizing this function, for example, the rotational speed of the sleeve 33 is set to 200 [rpm], 250 [rpm], 300 [r], for example.
pm] so that the maximum image density is fixed.

As is well known, the transfer device 43 superimposes the transfer paper P on a toner image electrostatically carried on the image carrier B, and discharges electric charges from the back side of the transfer paper P, thereby transferring the transfer paper P
It is a device for transferring toner thereon, and is preferably a scorotron discharger, but is not limited thereto, and may be a transfer paper P such as a corotron charger or a charging roller.
Any material may be used as long as it can transfer a toner image electrostatically.

As is well known, the separating device 44 includes an image carrier B
By removing electricity from the transfer paper P electrostatically attracted to the
The transfer paper P is separated, and a scorotron charger,
A corotron charger, a charging roller, or the like is used.

The cleaning unit 50 contacts the surface of the image carrier B with a blade or the like to scrape off toner and dust adhering to the surface of the image carrier B and capture it in a waste toner box. The density sensor C is a density sensor that detects the density of an image patch visualized on the image carrier B.

The fixing device 60 is a device for permanently fixing the toner image on the transfer paper P by applying heat or heat and pressure to the transfer paper P carrying the toner image, as is well known. 62 has a thickness of 70 [μm]
FA (which is an abbreviation of a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer) coated with a rubber hardness of 30 °, for example, LTV (which is an abbreviation of Roten Para Vulcanizing), and 200 [W]
The upper roller 61 has a diameter of 50 [mm] and a total length of 324 [mm], for example, A50.
It is made of a core material of 56TD (aluminum), and its surface is coated with PFA, and includes an electric heater (not shown) of 1100 [W].

FIG. 2 is a block diagram showing a main configuration of an embodiment of the image forming apparatus according to the present invention.

The image forming apparatus of this embodiment employs an electrophotographic system in which an exposure process is performed by a semiconductor laser. For example, a gradation image is expressed by the number of dots drawn by a laser within a certain area. Things.

As shown in FIG. 1, the image forming apparatus according to the present embodiment includes a dot diameter correcting means 2 for correcting the diameter of a dot drawn by a laser, a maximum density correcting means 3 for correcting the highest image density, The image processing apparatus includes a gradation correction unit 4 for correcting the gradation of an image, and a control unit 1 for controlling operations of the dot diameter correction unit 2, the maximum density correction unit 3, and the gradation correction unit 4.

FIG. 3 is a block diagram showing the structure of the dot diameter correcting means 2 shown in FIG.

As shown in FIG. 3, the dot diameter correcting means 2
Are image patch creating means 5 for creating an image patch on the image carrier B, image patch detecting means 6 for detecting the density of the image patch on the image carrier B, and parameters such as a power value for emitting a semiconductor laser. And a laser power adjusting unit 8 for emitting a semiconductor laser using the power value stored in the storage unit 7.

Since the maximum density correction means 3 and the gradation correction means 4 shown in FIG. 2 are conventionally provided, detailed description will be omitted. The maximum density correction means 3 is a means for adjusting the developability by changing Vs / Vp, which is the ratio between the rotation speed Vs of the sleeve 31 and the rotation speed Vp of the image carrier B, and determining the maximum density. Further, the gradation correcting means 4 is a means for adjusting the gradation by changing the pulse width of the laser by PWM and correcting the γ curve.

Next, the operation of this embodiment will be described.

The control means 1 first includes a dot diameter correction means 2
And corrects the diameter of the dot exposed by the laser and visualized by the developing device. In the dot diameter correcting means 2, first, an image patch is generated by the image patch generating means 5.

The image patch creating means 5 has the writing unit A shown in FIG. 1, and forms a latent image image patch on the image carrier B by the writing unit A. Thereafter, the image carrier B rotates, and the image patch is developed by the developing unit 30 with the developer.

When an image patch is created, the laser pulse width per dot is fixed at a predetermined value, for example, near the highest density portion (near the PWM value X). It is preferable that a plurality of image patches are prepared by changing the laser power. In the embodiment, six image patches are prepared by changing the laser power. The laser power for creating individual image patches may be varied at regular intervals within the range of the laser power variable width, or may be changed before and after the power currently used for image formation. Good.

This image patch may be formed as a 1-bit dot image (dot image pattern) in which dots are drawn at a fixed density in a fixed area. The pattern of the point image is
It is formed by an appropriate method such as error diffusion, a screen method, or another unique point array. It is desirable that the pattern of the image patch to be created is a point where each dot is isolated from each other. An intermediate image as a binary image is formed by the isolated dot pattern. The image patch, which is a group of dots, is measured with a macro reflection density.
The halftone is desirably about 0.2 to 0.6, and is preferably a density that can be detected with high sensitivity by a density sensor that detects a change in the size of each dot as a difference in reflection density. In the embodiment, the reflection density is 0.3
As a considerable dot array. In addition, the size of the patch image can be measured by a density sensor with a high precision of 20 [mm].
A size of about 30 [mm] is preferable.

Next, the dot diameter correction means 2 uses the image patch detection means 6 to change the size of each dot by changing the laser power and changing the size of each dot. The reflection density sensor C detects a macro image density change. FIG. 5 is a schematic diagram of detecting a patch density by an image density sensor and detecting a change in dot diameter as a change in output of the density sensor.

The density sensor C does not need to measure the diameter or area of each dot in an image patch, but only needs to detect the average density of the entire patch. For example, a sensor using diffused light is preferable.

Next, the control means 1 obtains the relationship between the laser power and the density of the image patch from the density of the image patch detected by the image patch detection means 6, as shown in FIG. In the case of linear approximation, the calculation may use the least square method or the like. If the created image patch is formed with an appropriate dot diameter, it will have a constant density output as a macro reflection density. In the embodiment, a density patch equivalent to 0.3 is used, and the output of the reflection density sensor is 2.95.
A patch [V] was created. Conversely, with the laser power at which the output of the reflection density sensor becomes 2.95 [V],
A patch has been created with an appropriate dot diameter. In this way, a laser power output value that is an appropriate density sensor output value is selected and stored in the storage unit 7. That is, the stored value is obtained when the pulse width of the predetermined PWM value is X and the image density is Do (for example,
0.3 equivalent). If the relationship between the laser power and the output of the image patch (for example, a correction table and a calculation formula are prepared) is known in advance, only one image patch needs to be created by the image patch creating means 5. By detecting this one patch density by the image patch density detecting means 6 and performing correction processing on the detected patch density, an appropriate laser power output can be obtained.

The laser power adjusting means 8 shown in FIG. 3 operates to perform the subsequent image formation using the laser power value stored in the storage means 7.

In the case of an image forming apparatus provided with two or more lasers and performing image formation using a plurality of laser beams, separate image patches are created for each of the plurality of laser beams, and a dot is formed for each laser. The correction by the diameter correcting means 2 may be performed, or one image patch is created by a plurality of laser beams (at this time, each dot in the image patch having a fixed area is substantially formed by each of the plurality of laser beams). It is preferable that the dot numbers are corrected by the dot diameter correcting means 2 for a plurality of lasers at the same time.

As described above, the maximum density correction means 3 shown in FIG.
Is a means for adjusting the developing property by changing the ratio Vs / Vp to the rotation speed Vp of the lens, and for determining the maximum density. The gradation correcting means 4 changes the pulse width of the laser by PWM. This is a means for adjusting the gradation and correcting the γ curve. The maximum density correction means 3 and the gradation correction means 4 are also similar to the dot diameter correction means 2,
A correction image patch is formed on the image carrier B, the density of the image patch is detected by a density sensor, and the Vs / Vp and the PWM pulse width are adjusted so as to have a desired density. The adjustment by the maximum density correction means 3 and the gradation correction means 4 is performed under the laser power value stored in the storage means 7.

FIG. 4 is a diagram showing each density sensor when the image carrier B shown in FIG. 1 is viewed from the side.

The density sensor 9 is a density sensor used in the maximum density correction means 3, and is a density sensor whose sensitivity is increased at a high density. On the other hand, the density sensor 10 is a density sensor used in the gradation correction means 4, and is a density sensor whose sensitivity is increased at an intermediate density. The density sensors 9 and 10 are conventionally provided. This density sensor has little sensitivity to the photosensitive layer of the photoreceptor, for example, 95
The patch surface is turned on using a 0 nm LED, and the amount of reflected light is converted into a current using, for example, a photodiode transistor, and is used by I / V conversion.

In this embodiment, the density sensor C used in the dot diameter correction means 2 detects the density of the halftone portion, and is used as the density sensor 10 for the gradation correction means 4 shown in FIG. Can also be used. At this time, the image patch for the dot diameter correction unit 2 may be created on the image carrier B in the same phase as the image patch for the gradation correction unit 4.

When the correction by the dot diameter correction means 2 is completed, the control means 1 performs the correction by the maximum density correction means 3 and the correction by the gradation correction means 4. As described above, the order of image adjustment is such that the laser power is adjusted, the dot diameter is corrected by the dot diameter correction unit 2, and then the correction by the maximum density correction unit 3 and the correction by the gradation correction unit 4 are performed. After the correction by the maximum density correction unit 3 and the correction by the gradation correction unit 4, the correction by the dot diameter correction unit 2 is not always necessary, but
After the correction by the dot diameter correcting means 2, it is desirable to perform the correction by the maximum density correcting means 3 and the correction by the gradation correcting means 4.

The correction by the dot diameter correction means 2 is performed as follows.
It is desirable to perform this periodically, for example, every fixed number of prints or every certain time (for example, an integrated value of the rotation time of the image carrier B, the charging ON time, the development rotation time, the polygon rotation time, etc.). In addition, in order not to disturb the collection sequence, it is preferable to carry out the process in addition to the last print sequence. Conversely, when the charge amount of the developer is unstable, for example, immediately after the power of the image forming apparatus is turned on at the beginning of the day, it is not preferable to perform the correction by the dot diameter correction unit 2.

If the result of the correction by the dot diameter correcting means 2 is that the laser power value is corrected so as to be significantly different from the previous value, the laser power value previously used without correction is used. It is desirable to use the value as it is. The reason is that the deterioration of the developer and the contamination of the writing optical system, which are corrected by the dot diameter correcting means 2, are considered to change temporarily, and when a value significantly different from the previous value is obtained. Is likely to be an error.

In the above-described embodiment, the correction is performed by developing the image patch and detecting the density with the density sensor C. However, the present invention is not limited to this. A potential sensor for detecting the potential of the image patch of the latent image written by A may be provided, and the correction may be performed based on the output of the potential sensor. However, in this case, the deterioration of the developer cannot be corrected, and the writing optical system is corrected.

[0051]

As described above, according to the present invention, the writing optical system can be corrected by the laser power, and there is an effect that dots of a fixed size can always be formed.

Further, if the correction is performed by developing the image patch and detecting the density with a density sensor, the change in the dot diameter due to the change in the developing property can be corrected.
There is an effect that dots of a fixed size can always be formed.

Further, according to the present invention, since the size of the dot is always kept constant, the toner consumption can be kept at a constant rate.

Further, according to the present invention, the change in the maximum density due to the contamination of the writing optical system and the change in the developing property can be obtained.
The laser power can be adjusted, and a margin for the adjustment width of Vs / Vp can be gained when Vs / Vp is adjusted by the maximum density correction means.

Further, according to the present invention, the size of the dot system is corrected by adjusting the laser power, and the gradation correction is performed by PWM modulation. Correction with a small influence can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic mechanism of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram illustrating a main configuration of an embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of a dot diameter correction unit illustrated in FIG. 2;

FIG. 4 is a diagram showing each density sensor when the image carrier shown in FIG. 1 is viewed from the side.

FIG. 5 is a schematic diagram for detecting a change in dot diameter as a change in output of a density sensor.

FIG. 6 is a diagram showing a relationship between laser power and image patch density.

FIG. 7 is a schematic diagram illustrating a change in image quality depending on a dot diameter.

FIG. 8 is a schematic diagram of a change in a highest density portion due to a variation in a γ curve.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 control means 2 dot diameter correcting means 3 maximum density correcting means 4 gradation correcting means 5 image patch creating means 6 image patch detecting means 7 storage means 8 laser power adjusting means 9, 10 density sensor A writing unit B image carrier C density Sensor 15 Encoder 20 Charging device 30 Developing unit 31 Developing sleeve 32 Magnet roller 33A, 33B, 33C Stirring screw 300 Housing 42 Registration roller 43 Transfer device 44 Separation device 50 Cleaning unit 60 Fixing device 61 Upper roller 62 Lower roller

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H04N 1/23 103 (72) Inventor Koichi Gunji 2970 Ishikawacho, Hachioji City, Tokyo Inside Konica Corporation

Claims (16)

[Claims] An electrostatic latent image corresponding to image information is formed on a photosensitive member by a laser beam generated from a laser,
In the image forming method of developing the electrostatic latent image to obtain a visible image, changing the output of the laser beam to form an image patch of a specified pixel density on the photoconductor, and developing the image patch; The density of the developed image patch is detected, and based on the detected density detection information, the output of the laser beam at which the image patch of the specified pixel density has the specified density is obtained, and an image is formed with the output of the obtained laser beam. An image forming method comprising: 2. The image forming method according to claim 1, wherein the image patch having the specified pixel density has a halftone density. 3. When detecting the density of the image patch,
3. The image forming method according to claim 1, wherein an average density of the image patch is detected. 4. An image forming method in which an electrostatic latent image corresponding to image information is formed on a photoreceptor by laser beams generated from a plurality of lasers, and the electrostatic latent image is developed to obtain a visible image. 4. The image forming apparatus according to claim 1, wherein the number of pixels in an image patch having a specified pixel density created by changing the output of the laser beam is substantially the same for each laser beam. Method. 5. An image forming method for forming an electrostatic latent image corresponding to image information on a photoreceptor by using laser beams generated from a plurality of lasers and developing the electrostatic latent image to obtain a visible image, An image patch having a specified pixel density is created for each laser beam, the density of the image patch is detected for each laser beam, and an image patch having a specified pixel density is specified based on the detected density detection information. 4. The image forming method according to claim 1, wherein an output of a laser beam that becomes a density is obtained, and an image is formed by the obtained output of the laser beam. 6. The method according to claim 1, wherein after obtaining an output of a laser beam at which the image patch of the specified pixel density has a specified density, tone correction is performed by adjusting a pulse width of the laser beam by PWM control. Item 2. The image forming method according to Item 1. 7. The method according to claim 1, wherein after obtaining an output of a laser beam at which the image patch having the specified pixel density has a specified density, the developability is adjusted to perform a maximum density correction.
Or the image forming method according to 6. 8. An electrostatic latent image corresponding to image information is formed on a photosensitive member by a laser beam generated from a laser,
In the image forming method of developing the electrostatic latent image to obtain a visible image, changing the output of the laser beam to create an image patch of a specified pixel density on the photoconductor, Detecting an electric potential, based on the detected electric potential detection information, obtaining an output of a laser beam at which an image patch having a specified pixel density has a specified electric potential, and forming an image with the obtained output of the laser beam. Image forming method. 9. The method according to claim 1, wherein after obtaining an output of a laser beam at which the image patch of the specified pixel density has a specified potential, tone correction is performed by adjusting a pulse width of the laser beam by PWM control. Item 10. The image forming method according to Item 8. 10. The method according to claim 8, wherein the maximum density correction is performed by adjusting the developability after obtaining the output of the laser beam at which the image patch of the specified pixel density has a specified potential. Image forming method. 11. An image forming method in which an electrostatic latent image corresponding to image information is formed on a photoreceptor by a laser beam generated from a laser, and the electrostatic latent image is developed to obtain a visible image. Every or every fixed time, in the image forming last sequence, by changing the output of the laser beam to create an image patch of a specified pixel density on the photoconductor, develop the image patch, and develop the image patch Detecting the density, based on the detected density detection information, obtaining an output of a laser beam at which an image patch of a specified pixel density has a specified density, and forming an image with the obtained output of the laser beam. Image forming method. 12. An image forming method in which an electrostatic latent image corresponding to image information is formed on a photoreceptor by a laser beam generated from a laser, and the electrostatic latent image is developed to obtain a visible image. Every or every fixed time, in the image forming last sequence, by changing the output of the laser beam to create an image patch of a specified pixel density on the photoconductor, to detect the potential of the image patch on the photoconductor, An image forming method comprising: obtaining an output of a laser beam at which an image patch having a specified pixel density has a specified potential based on the detected potential detection information; and forming an image with the obtained output of the laser beam. 13. An image forming apparatus for forming an electrostatic latent image corresponding to image information on a photoconductor by a laser beam generated from a laser, and developing the electrostatic latent image to obtain a visible image, wherein the laser beam Image patch creating means for creating an image patch of a specified pixel density on the photoreceptor by changing the output of the image patch, developing means for developing the image patch, and density detecting means for detecting the density of the developed image patch Control means for obtaining an output of a laser beam at which an image patch having a specified pixel density has a specified density based on density detection information from the density detection means, and forming an image with the obtained laser beam output. An image forming apparatus comprising: 14. A tone detecting density detecting means for detecting the density of an image patch created and developed on the photoconductor,
A tone correction unit for adjusting the pulse width of the laser beam by PWM control based on the density information detected by the tone correction density detection unit to perform tone correction; 14. The image forming apparatus according to claim 13, wherein the image forming apparatus is also used as the tone correction density detecting unit. 15. A maximum density correction density detecting means for detecting the density of an image patch created and developed on the photoreceptor, and a developing property based on density information detected by the maximum density correction density detecting means. 15. The apparatus according to claim 13, further comprising a maximum density correction unit that adjusts and performs a maximum density correction, wherein the density detection unit is provided separately from the maximum density correction density detection unit. Image forming apparatus. 16. An image forming apparatus for forming an electrostatic latent image corresponding to image information on a photoreceptor by a laser beam generated from a laser and developing the electrostatic latent image to obtain a visible image, wherein the laser beam Image patch creating means for creating an image patch of a specified pixel density on the photoreceptor by changing the output of the image sensor; and potential detecting means for detecting the potential of the image patch. Potential detection from the potential detecting means An image forming apparatus comprising: a control unit that obtains an output of a laser beam at which an image patch having a specified pixel density has a specified potential based on information, and forms an image with the obtained output of the laser beam.