JP2001092195A - Light quantity controller, image position detector and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embody the rapid optimization of the light quantity of the light emitted in a light emitting part of a pattern detecting means with simple constitution. SOLUTION: Patterns 130 for light quantity control consisting of a single color (C in Figure) having a size of a prescribed value or above along a sub- scanning direction are formed separately from pattern 132 for image position detection for detecting and regulating the positions of respective color toner images are formed on an intermediate transfer belt 30 formed with the toner images of respective colors Y, M, C, and Bk by plural image forming sections The light quantity of the IR light emitted from LEDs and reflected by the patterns 130 for light quantity control is detected by photodiodes and the LED drive current value for regulating the light quantity of the light emitted by the LEDs when detecting the patterns 132 for image position detection to an optimum value is determined in each of image detecting sections 90A, 90B and 90C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount control device, an image position detecting device, and an image forming apparatus, and more particularly to a result of detecting a light amount emitted from a light emitting section and reflected by a light amount control pattern formed on a medium. Light amount control device that controls the amount of light emitted from the light emitting unit based on the image, an image forming device that forms each image on the transfer body by the plurality of image forming units, and an image that is formed on the transfer body by the plurality of image forming units The present invention relates to an image position detection device that detects a position detection pattern.

[0002]

2. Description of the Related Art Heretofore, a photosensitive drum, a charger for charging the photosensitive drum, an optical scanning device for forming an electrostatic latent image by scanning a light beam on the photosensitive drum, and developing the electrostatic latent image have been developed. A plurality of image forming units provided with a developing device for forming a toner image along the moving direction of the endless transfer belt,
The toner images of different colors formed on each photoconductor drum by each image forming unit are sequentially transferred on a transfer belt,
2. Description of the Related Art A so-called tandem type color image forming apparatus that forms a color image on a recording material by collectively transferring a color toner image formed on a transfer belt to the recording material is known.

A tandem type color image forming apparatus can efficiently form a color image because an image forming section is provided for each color. However, the transfer positions of the toner images of each color on a transfer belt are accurately matched. However, there is a problem in that fine color misregistration often occurs and good image quality cannot be obtained. Causes of the color misregistration include errors inherent in the apparatus, such as errors in the rotation speed of each photoconductor drum, errors in the moving speed of the transfer belt, meandering, and errors in image writing timing of each image forming unit. In addition, a minute change in the relative position of each image forming unit, a deformation of the image forming unit itself, a change in each control timing, and the like due to a change over time and an environmental change also cause a color shift.

[0004] The color misregistration caused by an error inherent to the apparatus can be suppressed to within an allowable range by performing various adjustments at the time of shipping the apparatus. However, since the adjustment requires time and labor, the apparatus requires time and labor. This leads to a significant rise in costs. Also,
Since color shift due to aging or environmental change can occur every day after the device is shipped, it is difficult to stably obtain good image quality without color shift. For this reason, the position of the pattern image for image position detection formed on the transfer belt by each image forming unit is detected by the image position detecting unit, and the shift amount of the formation position of the pattern image of each color is calculated. 2. Description of the Related Art It has conventionally been proposed to periodically perform color misregistration correction for controlling an image forming position on a transfer belt by an image forming unit to move by the calculated amount of misalignment.

However, in order to obtain an image of good image quality by the above-described color misregistration correction, the detection accuracy of the pattern image by the image position detector becomes extremely important. In general,
The allowable amount of color shift in a high-quality color image is at most about 0.15 mm. On the other hand, considering that dimensional errors of various components and errors in the calculation of the correction amount also affect the accuracy of the color shift correction, the image position detection unit needs to be installed in order to suppress the color shift amount to an allowable value or less. It is required to detect the position of the pattern image with a detection accuracy of μm to several tens μm or less.

On the other hand, the image position detecting section includes a light emitting section (light source) and a detecting section for detecting the light emitted from the light emitting section and reflected by the transfer belt. Although a configuration for detecting an image (reflection type) is often employed, the detection accuracy is reduced due to variations in the amount of light emitted from the light-emitting unit and fluctuations in the distance from the belt due to vibration of the transfer belt. It is difficult to perform detection stably and accurately. In addition, the output of the image position detecting unit also changes due to dirt attached to the transfer belt, toner and dust attached to the light emitting unit, and the like, as the use period after the apparatus is installed becomes longer.

Further, in order to solve the above-mentioned problems, Japanese Patent Application Laid-Open Nos. 64-86175 and 6-3885 disclose a pattern image for detecting an image position formed by each image forming section. There has been proposed a method of optimizing the light amount of a light emitting unit when detecting with a detecting unit, thereby always enabling stable and accurate pattern detection. That is,
Japanese Patent Application Laid-Open No. 64-86175 discloses a technique for adjusting the amount of light based on the level of an output signal of a light receiving unit when an area outside an image forming area of a transfer belt is detected. The gazette discloses a technique in which an image pattern for image position correction is formed on a recording medium, and the amount of illumination of an illumination unit is adjusted based on a correction amount obtained by reading the image pattern.

For reference, see Japanese Patent Application Laid-Open No. 6-106779.
JP-A-6-127039 and JP-A-8-27039
Japanese Patent No. 44134 discloses an image forming apparatus provided with a transmission-type image position detection unit (a structure for detecting a pattern for image position detection by a light source and a light-receiving element which are arranged opposite to each other with a light-transmissive transfer belt therebetween). The light amount control in the device is described.

The above-mentioned JP-A-64-86175, JP-A-6-3885, and JP-A-8-69146.
The technology described in Japanese Patent Application Laid-Open No. 6-3885 discloses an image position detecting pattern image composed of fine lines (for example, "+").
Publication), “−”, “| −” (JP-A-6-10677)
No. 9) is used to optimize the amount of light emitted from the light emitting unit. However, in order to accurately detect the amount of light reflected at a thin line portion on the transfer belt that is moved at a constant speed, the amount of light reflected on the transfer belt must be adjusted. Since it is necessary to repeatedly sample the detection value in a short cycle so that the detection interval at is smaller than the thin line width,
High-speed control by a circuit having a high-speed sample and hold function and software is essential.

In order to suppress a change in the detected value when the output of the light receiving element fluctuates instantaneously due to noise or the like, a circuit configuration for minimizing the influence of noise or the like or a sample hold function is provided. It is also necessary to provide a noise determination circuit and the like separately from the circuit. As described above, when the light amount control is performed using the pattern image for detecting the image position, a special control system is required to stably and accurately perform the light amount control. There has been a problem that a large increase is caused.

In Japanese Patent Application Laid-Open No. 8-69146, patches for density detection are formed on a transfer belt for each color (Y / M / C / Bk) separately from a pattern image for image position correction. It is disclosed that the amount of light emitted from the light emitting unit and the developing bias voltage are controlled based on the density data of each color obtained by reading the patch. However, when executing the above control, it is necessary to detect patches formed for each color (Y / M / C / Bk). Therefore, it takes time until the control is completed, and the image position is corrected after the control is completed. Considering that, it takes a long time from when instructing the start of image formation on the recording material to when the recording material on which the image is formed is actually output, causing a decrease in the actual processing capacity of the image forming apparatus, There was a problem.

In the technique described in the above publication, an expensive C is used as a sensor for detecting a pattern image and a patch.
Using a CD, calculate integrated data of main scanning and sub-scanning,
Since the density data is obtained by performing a complicated process of calculating the density data of each color pattern based on the integrated data, there is also a problem that the configuration of the apparatus becomes complicated and the cost is greatly increased.

[0013]

As described above, when light amount control is performed using a pattern image for detecting an image position composed of fine lines, a special light amount is required to stably and accurately perform light amount control. Since a control system is required, there is a problem that the configuration of the device becomes complicated and the cost increases significantly.
When the light amount control is performed based on the density data of each color obtained by reading the density detection patches formed for each color, there is a problem that the actual processing capability of the image forming apparatus is reduced. .

In each of the light quantity control described in each of the above publications, detecting the amount of received light (or density) while changing the amount of light emitted from the light emitting portion in a stepwise manner is performed until the detected value falls within a predetermined range. Since this is repeated, there is also a problem that it takes time until the detected value converges within a predetermined range and the light amount control is completed.

The present invention has been made in view of the above-mentioned facts, and has as its object to provide a light amount control device which can realize optimization of the light emission amount of the light emitting section with a simple configuration.

Another object of the present invention is to provide an image position detecting apparatus and an image forming apparatus which can realize the optimization of the amount of light emitted from the light emitting section of the pattern detecting means in a short time with a simple configuration.

[0017]

According to a first aspect of the present invention, there is provided a light quantity control device which moves in a predetermined direction and emits light to a medium on which a light quantity control pattern is formed. A detecting unit that detects a light amount emitted from the light emitting unit and reflected by the light amount control pattern on the medium; and a light amount control unit that controls a light emitting amount of the light emitting unit based on a detection result of the detecting unit. Wherein the size of the light amount control pattern in the moving direction of the transfer body is equal to or greater than a value corresponding to a product of a moving speed of the medium and a time required for light amount control by the light amount control means. It is characterized by:

The light quantity control means according to the first aspect of the present invention controls the light quantity of the light emitting section based on the detection result of the light quantity emitted from the light emitting section and reflected by the light quantity control pattern formed on the medium. Therefore, the amount of light emitted from the light emitting unit is optimized. The size of the light amount control pattern along the moving direction of the medium is determined by the moving speed of the medium and the time required for the light amount control by the light amount control unit (that is, the light emitting unit after the light amount control unit starts the light amount control). (The time until the light emission amount of the light-emitting portion reaches the optimum value) is equal to or more than the product of the light-emission amount of the light-emitting portion by the light-amount control means. As described above, there is no need to repeatedly sample the detection value in a short cycle.

This eliminates the need to provide a circuit having a high-speed sample and hold function or to perform high-speed control by software, and simplifies the device configuration. Optimizing the amount of light emitted from the light emitting unit can be realized with a simple device configuration.

According to a second aspect of the present invention, in the first aspect of the invention, the light amount control means detects the amount of reflected light detected by the detecting unit in a plurality of states where the drive values of the light emitting units are different from each other. Based on the value, the relationship between the drive value and the detected value of the reflected light amount is calculated, and based on the calculated relationship,
It is characterized in that a drive value when the light amount detection value by the detection unit reaches a target value is obtained.

A change in the amount of light emitted from the light emitting unit with respect to a change in the drive value (eg, a drive current value or a drive voltage value) of the light emitting unit,
The change in the amount of light detected by the detection unit with respect to the change in the amount of received light depends on the characteristics of the elements constituting the light emitting unit and the light receiving unit, and the characteristics of the elements themselves also vary from one element to another. Therefore, in order to control the light quantity detection value by the detection unit to be the target value, it is necessary to detect the drive value when the light quantity detection value becomes the target value.

The driving value when the detected light amount reaches the target value is generally detected by monitoring the change in the detected light amount while changing the driving value by a fixed amount. According to the invention, the relationship between the drive value and the detected value of the reflected light amount is calculated based on the detected value of the reflected light amount detected by the detecting unit in a plurality of states in which the drive values of the light emitting units are different from each other. Based on the relationship, it is possible to easily obtain the drive value when the light amount detection value by the detection unit becomes the target value.

Therefore, according to the second aspect of the present invention, it is necessary to monitor the change in the light amount detection value while changing the drive value by a fixed amount in order to detect the drive value when the light amount detection value reaches the target value. However, the drive value when the light amount detection value becomes the target value can be obtained in a short time.

The calculation of the relationship between the drive value and the detected value of the amount of reflected light in the second aspect of the invention can be performed by applying, for example, a least squares method. Thus, based on the detected value of the reflected light amount when the light emitting unit is driven by the first drive value and the detected value of the reflected light amount when the light emitting unit is driven by the second drive value different from the first drive value It is preferable to obtain a linear expression representing the relationship as a relationship between the drive value and the detection value of the reflected light amount.

According to the third aspect of the present invention, a linear expression representing the relationship between the drive value and the detected value of the reflected light amount is obtained from the detected value of the reflected light amount when the light emitting section is driven with two types of drive values. Acquisition of the detected value of the reflected light amount for obtaining the relationship between the drive value and the detected value of the reflected light amount, and calculation of the relationship can be performed in a short time.

In consideration of the possibility that noise may be superimposed on the detected value of the amount of reflected light for some reason, the driving value of the light emitting section of the pattern detecting means is set to a predetermined value. A value obtained by detecting the amount of reflected light a plurality of times by the detection unit of the pattern detection unit while maintaining the value, and averaging a plurality of detection values obtained by the plurality of detections as a detection value when the drive value is a predetermined value. It is preferable to use (for example, an average value, a median value of a plurality of detection values, an average value after excluding a maximum value and a minimum value from a plurality of detection values, and the like).
This can reduce the influence of noise or the like when detecting the light amount control pattern.

Further, when a pattern having a constant density such as a light quantity control pattern is formed on a medium, the density of a pattern actually formed on the medium may slightly fluctuate near the outer edge. In consideration of this, as described in claim 5, the section of the light quantity control pattern from the end of the light quantity control pattern along the moving direction of the medium until the distance reaches a predetermined value (for example, about 1 mm) is defined. It is preferable to control the amount of emitted light based on a detection value when the removed portion corresponds to the detection range of the detection unit.

Thus, the amount of light emitted from the light emitting unit is controlled using only the detected value when the portion where the density is stable in the light amount controlling pattern corresponds to the detection range of the detecting unit. In other words, it is possible to eliminate the influence of the density fluctuation in the section near the outer edge of the light amount control pattern, and to optimize the light emission amount of the light emitting unit with higher accuracy.

According to a sixth aspect of the present invention, there is provided an image position detecting apparatus which emits light to a transfer member which is moved in a predetermined direction and on which images of different colors are formed by a plurality of image forming units. And a detection unit for detecting light emitted from the light emitting unit and reflected by the transfer body, for detecting an image position detection pattern formed on the transfer body by the plurality of image forming units. A pattern detection unit, based on a light amount of light emitted from a light emitting unit of the pattern detection unit, reflected on a portion of the transfer body where a light amount control pattern is formed, and detected by a detection unit; Light amount control means for controlling the amount of light emitted from the light emitting unit when detecting the image position detection pattern; and a size along the moving direction of the transfer body, the moving speed of the transfer body and the light amount A single image forming unit corresponding to the specific single color so that a light amount control pattern consisting of a specific single color is formed with a value equal to or more than a value corresponding to a product of a time required for the light amount control by the control unit. And pattern formation control means for controlling the pattern formation.

According to a sixth aspect of the present invention, there is provided a light quantity control means for detecting the light emitted from the light emitting part of the pattern detection means, reflected on a portion of the transfer member where the light quantity control pattern is formed, and detected by the detection part. Based on the amount of light, the amount of light emitted from the light emitting unit when the pattern detection unit detects the pattern for detecting the image position is controlled. Optimized.

Further, the pattern formation control means controls the light amount of the transfer member so that the size along the moving direction is equal to or more than the value corresponding to the product of the moving speed of the transfer member and the time required for the light amount control by the light amount control means. Since the control is performed so that the light amount control pattern is formed, the light amount control pattern is detected by the pattern detecting means in the same manner as in the first aspect of the invention. There is no need to repeatedly sample in a short cycle. Therefore, there is no need to provide a circuit with a high-speed sample and hold function or perform high-speed control by software.
The device configuration can be simplified.

According to a sixth aspect of the present invention, there is provided a pattern forming control unit, comprising: a single image forming unit corresponding to a specific single color such that a light amount control pattern of a specific single color is formed on a transfer body; The light quantity control pattern is completed in a short time, and the light quantity of the light emitted from the light emitting part of the pattern detection means and reflected by the portion of the transfer body where the light quantity control pattern is formed is controlled. The detection by the detection unit of the pattern detection means (hereinafter, simply referred to as “detection of the light amount control pattern by the pattern detection means”) can be performed in a short time. Therefore, according to the invention described in claim 6, it is possible to realize the optimization of the light emission amount of the light emitting unit of the pattern detection means in a short time with a simple device configuration.

When a color image is formed by superimposing a plurality of images of different colors formed by a plurality of image forming units on a transfer member, the plurality of colors may be, for example, Y (yellow) or M (magenta). , C (cyan),
In many cases, four colors of Bk (black) are used, and the image position detection pattern formed on the transfer body also includes a portion of each color of the plurality of colors, except for Bk. The three colors have a very high reflectance for light having a wavelength in the infrared region and exhibit substantially the same reflectance value. Therefore, the amount of light emitted from the light emitting unit when the pattern detecting unit detects the image position detecting pattern is a specific single color (for example, any one of C, M, and Y) emitted from the light emitting unit and on the transfer body. Optimization can be performed based on the amount of light having a wavelength in the infrared region that is reflected by the portion where the pattern is formed and detected by the detection unit.

For this reason, the invention according to claim 7 is the invention according to claim 6, wherein the detecting section of the pattern detecting means comprises:
It is characterized by detecting light having a wavelength in the infrared region emitted from the light emitting section and reflected by the transfer member. Accordingly, the color of the light amount control pattern (for example, any one of C, M, and Y)
Regardless, the amount of light emitted from the light emitting unit when the pattern detection unit detects the image position detection pattern can be optimized with high accuracy.

When the area of the light amount control pattern occupying the detection range on the transfer body by the detection unit changes upon detection of the light amount control pattern by the pattern detection means, the light amount by the detection unit is changed according to the change in the area. The detection value also changes. On the other hand, in the pattern forming control means according to the present invention, the size of the light amount control pattern formed on the transfer body is larger than the size of the detection range on the transfer body by the detection unit. The formation of the light quantity control pattern is controlled as described above, so that when the pattern detection section detects the light quantity control pattern, the light quantity control pattern always occupies the entire range of the detection range of the detection section. (The detection of the reflected light amount at the portion where the light amount control pattern is formed) can be accurately performed.

When the pattern detecting section detects the light amount control pattern, the light amount control pattern always occupies the entire range of the detection range of the detecting section.
As in the technique described in Japanese Patent Application Laid-Open No. 69146, an expensive CCD is used as a detection unit to divide the detection range into a large number of parts for detection, and integrated data of main scanning and sub-scanning are calculated and the density is calculated based on the integrated data. Calculate the data (extract the data of the part corresponding to the light amount control pattern in the detection range)
It is not necessary to perform complicated processing such as the above, and the apparatus configuration can be simplified.

Further, the light amount detection value by the detection unit when the pattern detecting means detects the light amount control pattern varies depending on the density of the light amount control pattern. On the other hand, the pattern control means according to the ninth aspect controls the single image forming section so that the density of the light quantity control pattern formed on the transfer body becomes a predetermined value. Fluctuation of the light amount detection value due to the fluctuation of the density of the light pattern can be suppressed, and the detection of the light amount control pattern (detection of the reflected light amount at the portion where the light amount control pattern is formed) by the pattern detection unit can be accurately performed. be able to.

According to a tenth aspect of the present invention, in the sixth aspect of the present invention, the light amount control means includes a detection value of a reflected light amount at a portion where the predetermined image position detecting pattern is formed and a light amount control pattern. The target value of the light amount detection value by the detection unit of the pattern detection unit is determined based on the correlation with the detection value of the reflected light amount of the part where the is formed, so that the light amount detection value by the detection unit matches the target value. It is characterized by controlling the amount of light emitted from the light emitting section.

When the light amount control pattern is formed separately from the image position detection pattern as in the present invention, since the two patterns are different, the light amount detection value by the detection unit when the light amount control pattern is detected is Even when the light emission amount of the light emitting unit is constant, it differs from the light amount detection value by the detection unit when the pattern detection unit detects the pattern for image position detection.

On the other hand, the light amount control means according to the present invention is characterized in that the detected value of the reflected light amount of the portion where the image position detecting pattern is formed and the reflected light amount of the portion where the light amount control pattern is formed. Since the target value of the light amount detection value by the detection unit of the pattern detection means is determined based on the correlation with the light amount detection value, the light amount detection value for detecting the image position detection pattern is used as the target value of the light amount detection value. Can be set to a value corresponding to a light amount detection value when a light amount control pattern is detected in a state where the light emission amount of the light emitting unit is controlled so that the light emission amount is optimized.

The light quantity control means controls the light quantity of the light emitting section so that the detected light quantity by the detection section coincides with the target value. Therefore, the light quantity control pattern is different from the image position detection pattern by using the light quantity control pattern. The amount of emitted light can be controlled so that the amount of emitted light from the light emitting unit when detecting the detection pattern is optimized.

According to the sixth aspect of the present invention, the light amount control means adjusts the reflected light amount detected value detected by the detecting section in a plurality of states where the driving values of the light emitting section of the pattern detecting section are different from each other. It is preferable that a relationship between the drive value and the detected value of the reflected light amount is calculated based on the calculated value, and a drive value when the light amount detected value by the detector reaches the target value is calculated based on the calculated relationship. This eliminates the need to monitor the change in the light amount detection value while changing the drive value by a fixed amount in order to detect the drive value when the light amount detection value reaches the target value, as in the second aspect of the invention. In addition, the drive value when the light amount detection value reaches the target value can be obtained in a short time.

The above calculation of the relationship between the drive value and the detected value of the reflected light amount can be performed by applying, for example, the least-squares method, but the light-emitting portion of the pattern detection means is driven by the first drive. The detected value of the amount of reflected light when driven by the value, and the second driving value different from the first driving value for the light emitting portion of the pattern detecting means.
Based on the detected value of the amount of reflected light when driven with the drive value of
It is preferable to obtain a linear expression representing the relationship as the relationship between the drive value and the detected value of the reflected light amount. As a result, similarly to the third aspect of the invention, it is possible to obtain the detected value of the reflected light amount for obtaining the relationship between the drive value and the detected value of the reflected light amount, and to calculate the relationship in a short time.

Further, in the invention according to claim 6, the amount of reflected light is detected a plurality of times by the detecting section of the pattern detecting means while the driving value of the light emitting section of the pattern detecting means is maintained at a predetermined value. As a detection value at a predetermined value,
A value obtained by averaging a plurality of detection values obtained by a plurality of detections (for example, an average value of a plurality of detection values, a median value, an average value after excluding a maximum value and a minimum value from a plurality of detection values, and the like). Preferably, it is used. This makes it possible to reduce the influence of noise or the like when detecting the light amount control pattern, as in the fourth aspect of the present invention.

In the invention according to claim 6, the section of the light quantity control pattern from the end of the light quantity control pattern along the moving direction of the transfer member until the distance reaches a predetermined value (for example, about 1 mm). It is preferable to control the amount of emitted light based on a detection value when the removed portion corresponds to the detection range of the detection unit. Thus, similarly to the invention according to claim 5, it is possible to eliminate the influence of the fluctuation of the density in the section near the outer edge of the light amount control pattern, and to optimize the light emission amount of the light emitting unit with higher accuracy. Can be

In the invention according to claim 6, the control of the amount of emitted light by the light amount control means is performed under a predetermined condition (for example, when the temperature inside the image forming apparatus to which the image position detecting device according to the present invention is attached is lower than a predetermined value). (E.g., when the power is turned on in this state, when a unit or part of a predetermined portion of the image forming apparatus is replaced, when execution of control of the light emission amount is instructed, etc.) is satisfied.

According to an eleventh aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of image forming units; and a transfer member which is moved in a predetermined direction and on which images of different colors are formed by the plurality of image forming units. A light emitting unit for irradiating the transfer body with light, and a detection unit for detecting light emitted from the light emitting unit and reflected by the transfer body, and images formed on the transfer body by the plurality of image forming units, respectively. A pattern detection unit for detecting a position detection pattern, and a light beam emitted from a light emitting unit of the pattern detection unit, reflected on a portion of the transfer body where the light amount control pattern is formed, and detected by the detection unit. Based on the amount of light, the amount of light emitted from the light emitting unit when the pattern detection unit detects the image position detection pattern is controlled by the light amount control unit. In order to form a light amount control pattern consisting of a specific single color with a value equal to or greater than a product of the moving speed of the object and the time required for the light amount control by the light amount control means, the specific single color And a pattern forming control unit for controlling a corresponding single image forming unit.

According to the eleventh aspect, the size of the transfer body in the moving direction is equal to or more than a value corresponding to the product of the moving speed of the transfer body and the time required for the light amount control by the light amount control means and specified. The control is performed so that the light quantity control pattern composed of a single color is formed on the transfer body, and the light is emitted from the light emitting unit, reflected at the portion where the light quantity control pattern is formed on the transfer body, and detected by the detection unit. The amount of light emitted from the light emitting unit when the pattern detecting means detects the image position detection pattern is controlled based on the amount of light emitted from the light emitting unit. Optimization of the light amount in a short time can be realized with a simple configuration.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In the following, description will be made using numerical values that do not hinder the present invention, but the present invention is not limited to the numerical values described below.

FIG. 2 shows a color image forming apparatus 10 according to this embodiment. The color image forming apparatus 10 corresponds to the image forming apparatus according to the present invention, and exposes and scans a document 16 placed at a predetermined position on a platen glass 14, reads the document 16 with a CCD sensor 13, and converts it into an image signal. Based on the original reading device 12 and an image signal obtained by reading by the original reading device 12,
And an image forming apparatus 18 for forming a color image thereon.

The image forming apparatus 18 converts the image signals obtained by reading by the CCD sensor 13 into Y, M, C,
The color image forming apparatus 10 includes an image storage unit 82 that converts digital image data of each color of Bk and stores the digital image data, and a control unit 80 that includes a CPU, a ROM, a RAM, and the like, and controls overall processing in the color image forming apparatus 10. On the upper surface of the color image forming apparatus 10, a display 84A for displaying a message or the like is provided.
And an operation unit 84 including a keyboard 84B for the operator to input various commands and the like. The operation unit 84 is connected to the control unit 80 (not shown).

The image forming apparatus 18 includes the driving roller 3
An endless intermediate transfer belt 30 is wound around 2, 34, 36, and 38. The intermediate transfer belt 30 is a dielectric material whose volume resistance is adjusted by carbon to electrostatically transfer the toner image, and includes a driving roller 32, 34, 36,
The paper is conveyed around in a predetermined direction (in a direction indicated by an arrow B between the drive rollers 32 and 38). The intermediate transfer belt 30 is
As an example, the circumference may be 2111 mm, and the transport speed (process speed) may be 264 mm / sec. In this case, the intermediate transfer belt 30 rotates in 8 seconds. The medium according to claim 1, wherein the intermediate transfer belt 30 is a medium according to claim 1.
Corresponds to the transcript described in (1).

Above the intermediate transfer belt 30, an image forming unit 20 for forming a Y color toner image on the intermediate transfer belt 30 along an arrow B direction, and an M color toner image on the intermediate transfer belt 30. An image forming unit 22 for forming; an image forming unit 24 for forming a C color toner image on the intermediate transfer belt 30; an image forming unit 26 for forming a Bk color toner image on the intermediate transfer belt 30; (Details will be described later) are provided in order.

The image forming section 20 includes a photosensitive member 20C which is substantially cylindrical, is rotatable about an axis in the direction of arrow A, and is arranged so that the outer peripheral surface thereof is in contact with the intermediate transfer belt 30. A charger 20D for charging the outer peripheral surface of the photoconductor 20C to a predetermined potential is provided on the outer periphery of the photoconductor 20C. A scanning exposure unit 20A is provided near the charger 20D. The scanning exposure unit 20A modulates the laser light according to the Y image data, and scans the modulated laser light on the outer peripheral surface of the photoconductor 20C via the mirror 20H, thereby charging the outer peripheral surface of the photoconductor 20C. An electrostatic latent image corresponding to the Y color component of the image is formed on the portion where the image is formed.

The developing device 20 is located downstream of the laser beam irradiation position on the outer peripheral surface of the photosensitive member 20C in the direction of arrow A.
B, a transfer device 20F and a cleaning device 20E are sequentially provided. The developing device 20B includes the toner supply unit 20
The Y color toner is supplied from G, and the electrostatic latent image formed by the scanning exposure unit 20A is developed with the Y color toner.
A color toner image is formed. The transfer device 20F is disposed so as to face the outer peripheral surface of the photoconductor 20C with the intermediate transfer belt 30 interposed therebetween, and transfers the Y toner image formed on the outer peripheral surface of the photoconductor 20C to the intermediate transfer belt 30. Transfer to the outer peripheral surface. Further, the toner remaining on the outer peripheral surface of the photoconductor 20C after the transfer of the toner image is removed by the cleaning device 20E.

As apparent from FIG. 2, the configuration of the image forming units 22, 24, and 26 is the same as the configuration of the image forming unit 20 (however, the colors of the toner images to be formed are different from each other). Omitted. Image forming units 20, 22, 2
Reference numerals 4 and 26 transfer the toner images such that the toner images of the respective colors formed on each other overlap on the outer peripheral surface of the intermediate transfer belt 30. Thus, a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 30. The image forming units 20, 22, 24, and 26 correspond to a plurality of image forming units according to the present invention.

Further, along the peripheral circuit of the intermediate transfer belt 30, the intermediate transfer belt 30 is provided on the upstream side in the rotation direction of the intermediate transfer belt 30 with respect to the intermediate transfer belt 30 in order to improve the toner adsorption property of the intermediate transfer belt 30. A suction roller 40 for maintaining the surface potential of the transfer belt 30 at a predetermined potential, a cleaning device 42 for removing toner from the intermediate transfer belt 30, a predetermined reference position on the intermediate transfer belt 30 (for example, a seal having a high light reflectance, etc. ) Are provided in order.

On the other hand, below the position where the intermediate transfer belt 30 is provided, a tray 5 for storing a large number of sheets 50 in a stacked state is provided.
4 are provided. The paper 50 stored in the tray 54 is pulled out of the tray 54 with the rotation of the pull-out roller 52, and the transfer position (the driving roller 36 and the transfer roller 60 is disposed by the pair of transport rollers 55, 56, 58). Position). The transfer roller 60 is disposed so as to face the drive roller 36 with the intermediate transfer belt 30 interposed therebetween. The sheet 50 conveyed to the transfer position is sandwiched between the transfer roller 60 and the intermediate transfer belt 30, The full-color toner image formed on the outer peripheral surface of the intermediate transfer belt 30 is transferred. The sheet 50 on which the toner image has been transferred is conveyed to a fixing device 46 by a pair of conveying rollers 62 and is subjected to a fixing process by the fixing device 46.
The paper is discharged to the paper tray 64.

Next, the configuration of the image detecting section 28 will be described. As shown in FIG. 3, the image detection unit 28 includes three image detection units 90A, 90B, and 90C. These image detection units 90A to 90C
0 along the center and both sides (intermediate transfer belt 30
(Positions corresponding to the center and both ends of the image area along the width direction of the image area). Note that FIG.
3 shows a state in which an image position detection pattern (described in detail later) is formed on the outer peripheral surface of the intermediate transfer belt 30. Each of the image detection units 90A to 90C corresponds to a pattern detection unit according to the present invention. Since the image detection units 90A to 90C have the same configuration, the configuration will be described below with reference to FIGS. 4 and 5 taking the image detection unit 90A as an example.

As shown in FIG. 4, the image detecting unit 90
A includes a pair of reflected light amount detection units 92A and 92B. In FIG. 4, “D1” is displayed in the reflected light amount detection unit 92A,
The reflected light amount detection unit 92B is denoted by “D2” to distinguish them. The reflected light amount detecting unit 92A includes a single LED 94 corresponding to the light emitting unit of the present invention and two photodiodes 96A and 96B corresponding to the detecting unit (specifically, the detecting unit according to claim 7) of the present invention. Similarly, the reflected light amount detection unit 92B also includes a single LED 98 and two photodiodes 100A and 100B. In the present embodiment, the LEDs 94 and 98 are in the infrared region (for example, 900 n).
LEDs that emit light of a wavelength range of m to 1200 nm) are used.

FIG. 6A shows the light reflectance characteristics (spectral reflectance characteristics) of the Y toner in the visible region, and FIG. 7A shows the light reflectance characteristics of the Y toner in the infrared region. Have been. As is clear from these figures, the Y color toner has a light reflectance largely different depending on the wavelength in the visible region, but the infrared region (for example, 900 nm to 1200 nm).
It can be understood that a high light reflectance of as much as 95% or more is exhibited in the wavelength range of).

FIGS. 6B and 7B show the light reflectance characteristics of the M color toner in each wavelength range, and FIG. 6C shows the light reflectance characteristics of the C color toner in each wavelength range. As is clear from FIG. 7 and FIG. 7C, the M color toner and the C color toner also have 95% in the infrared region similarly to the Y color toner.
The above shows a high light reflectance.

On the other hand, in the density detection by the image detecting section 28, the light reflectance of the intermediate transfer belt 30, which is the base of the light amount control pattern and the image position detecting pattern to be detected, is about 10 to 20%. In the outer region, the difference in light reflectance between the intermediate transfer belt 30 as the base and the toner image of each color is very large. Therefore, the light emitting unit (LED 9) of the image detecting unit 28
By using an LED that emits light having a wavelength in the infrared region as (4, 98), it is possible to accurately detect the density of each color toner image.

As shown in FIG. 5A, the LEDs 94 and 98 of the reflected light amount detectors 92A and 92B are located at positions slightly shifted on the outer peripheral surface of the intermediate transfer belt 30 along the width direction of the intermediate transfer belt 30. The direction is adjusted so as to irradiate light (for example, in FIG. 1, the trajectories of the irradiation positions of the LEDs 94 and 98 on the outer peripheral surface of the intermediate transfer belt 30 when the intermediate transfer belt 30 is conveyed at a constant speed. Are shown by two imaginary lines for each image detection unit).

On the other hand, as shown in FIG. 5B, a total of four photodiodes 96 of the reflected light amount detection units 92A and 92B are provided.
The light receiving surfaces of A, 96B, 100A, and 100B are each a flat parallelogram. Photodiode 96
The light-receiving surfaces of A and 96B form a single parallelogram-shaped light-receiving surface region by their long sides being in contact with each other. Similarly, the light-receiving surfaces of photodiodes 100A and 100B also have their long sides in contact with each other. Thus, a single parallelogram-shaped light receiving surface region is formed, and the light receiving surface regions of the photodiodes 96A and 96B and the light receiving surface regions of the photodiodes 100A and 100B are formed into a single substantially L-shaped (substantially mountain-shaped). The short sides of each other are in contact with each other so as to form the light receiving surface region of (1).

Photodiodes 96A, 96B, 100
The detection range on the outer peripheral surface of the intermediate transfer belt 30 by A and 100B is substantially mountain-shaped (substantially L-shaped) corresponding to the shape of the light receiving surface region (see FIG. 1). A figure showing a detection range on the outer peripheral surface of the intermediate transfer belt 30 is shown in the block).
A, 96B, 100A, and 100B correspond to the intermediate transfer belt 30 according to the shape of an image position detection pattern described later.
The positions corresponding to the substantially mountain-shaped tops of the detection range on the outer peripheral surface are located on the most upstream side along the moving direction of the intermediate transfer belt 30.

Thus, the photodiode 96 of the reflected light amount detection unit 92A on the outer peripheral surface of the intermediate transfer belt 30
The detection range of A, 96B is the LE of the reflected light amount detection unit 92A.
D94 traverses the trajectory of the irradiation position, and is located at a position shifted from each other along the moving direction of the intermediate transfer belt 30.
The light of the wavelength in the infrared region reflected by the outer peripheral surface (or the image formed on the outer peripheral surface) of the photodiode 96
A and 96B respectively receive light.

Similarly, the photodiodes 100A and 100A of the reflected light amount detection unit 92B on the outer peripheral surface of the intermediate transfer belt 30
The detection range of 100B is the LED of the reflected light amount detection unit 92B.
98, and are located at positions deviated from each other along the moving direction of the intermediate transfer belt 30 and emitted from the LED 98.
The light of the wavelength in the infrared region reflected by the outer peripheral surface (or the image formed on the outer peripheral surface) of
A and 100B receive light (light quantity detection).

Instead of emitting light of an infrared wavelength from an LED as a light emitting unit and detecting the amount of reflected light with a photodiode as a detecting unit, the light emitting unit emits light of a predetermined wavelength including an infrared wavelength. Light in the wavelength range (which may include the visible range) may be emitted, and the detection unit may detect only the amount of light in the infrared range of the reflected light.

As shown in FIG.
The output terminal of A is a current-voltage converter 102, an amplifier 104,
The photodiode 9 is connected to the microcomputer 108 of the control unit 80 via the A / D converter 106.
A current having a magnitude corresponding to the amount of received light output from 6A is converted into digital data representing an output voltage of photodiode 96A and input to microcomputer 108. The microcomputer 108 is an LED driver 11
0 is connected to the LED 94.

At the time of LED light quantity control processing described later (when the image detecting section 28 detects a light quantity control pattern), the microcomputer 108 detects the photodiode 96A represented by the data input through the A / D converter 106. Of the LED 9 via the LED driver 110 based on the output voltage of
4 is controlled. Note that FIG. 1 shows an approximate change in the output voltage of the photodiode 96A when the image detection unit 28 detects the light amount control pattern, in association with the light amount control pattern 130.

The output terminal of the photodiode 96 B is connected to a differential input amplifier 114 via a current-voltage converter 112.
, And the other of the two input terminals is connected to the output terminal of the current-voltage converter 102. The differential input amplifier 114 is connected to the current-voltage converter 11
Amplify the difference between the signals input from 2 and 102 (corresponding to the difference in the amount of light received by photodiodes 96A and 96B) and output. FIG. 1 shows an approximate change in the output voltage of the differential input amplifier 114 when the image detection unit 28 detects the image position detection pattern, in association with the image position detection pattern 132.

The output terminal of the differential input amplifier 114 is connected to a microcomputer 108 via a comparator 116, a buffer 118, and a counter 120. The comparator 116 compares the level of the signal input from the differential input amplifier 114 with a preset threshold value, and when the signal level is equal to or higher than the threshold value, sets the output signal to a high level (referred to as “ON” for convenience), Is lower than the threshold value, the output signal is switched to a low level (referred to as “OFF” for convenience). The output signal from the comparator 116 is input to the counter 120 via the buffer 118.

The counter 120 starts counting when the level of the input signal is switched from “OFF” to “ON”, and is switched from “OFF” to “OFF” again after the signal level is switched from “ON” to “OFF”. When it is switched to "ON", the count value up to that point is
8 and resetting the count value, and then repeatedly counting the time until the signal level switches from “OFF” to “ON”.

At the time of image position correction described later (when the image detecting section 28 detects the image position detecting pattern), the microcomputer 108 performs image (image position detecting pattern) based on the count result input from the counter 120. ) Is detected, and the image forming units 20, 22, 24, and 2 are detected.
6. The image forming position according to Step 6 is corrected.

Since the photodiodes 100A and 100B of the reflected light amount detection unit 92B are also connected to a circuit having the same configuration as that of the reflected light amount detection unit 92A, the same reference numerals are given to the respective parts of the connected circuit (FIG. FIG. 4), the description is omitted.

Next, as an operation of the present embodiment, the control unit 80
The LED light amount control process executed by the microcomputer 108 will be described with reference to the flowchart of FIG. Note that this LED light quantity control processing can be executed, for example, when the following conditions are satisfied.

(1) When the power is turned on while the temperature inside the color image forming apparatus 10 is low (for example, the fixing device 4
(6) When the power is turned on while the temperature of the fixing roller is 70 ° C. or less (2) Replacement of the photoconductor, the intermediate transfer belt 30, or a part related to development of the image forming units 20, 22, 24, and 26 (3) When the user instructs execution of the LED light amount control process via the keyboard 84B due to a change in the installation environment of the color image forming apparatus 10, etc. Only when the above condition is satisfied, LED described below
By executing the light amount control process, for example, by frequently executing the LED light amount control process, the average time required for image formation of the color image forming apparatus 10 becomes longer,
It is possible to avoid giving the user uncomfortable feeling by waiting the user at the time of the D light quantity control.

A temperature sensor and a humidity sensor are provided,
When it is detected that the installation environment of the color image forming apparatus 10 has changed (for example, it has been detected that the temperature has changed by 3 degrees or more or the humidity has changed by 20% or more since the previous execution of the LED light amount control processing). , Etc.), the LED light amount control processing may be performed.

In step 200, the driving of the intermediate transfer belt 30 is started, and the intermediate transfer belt 30 is moved at a constant speed. In step 202, it is determined whether or not the reference position detection sensor 44 has detected the reference position on the intermediate transfer belt 30, and the process waits until the determination is affirmed. When the reference position on the intermediate transfer belt 30 is detected, the process proceeds to step 204, where the image forming unit 24 that forms a C-color image is
It instructs formation of an LED light amount control pattern and execution of transfer to the intermediate transfer belt 30. This step 2
Reference numeral 04 corresponds to the pattern formation control means (and the pattern formation means of the first aspect) of the present invention.

In this embodiment, as shown in FIG. 1, a light amount control pattern 130 having a rectangular shape and a single C color is used as the light amount control pattern, the longitudinal direction of which is the moving direction of the intermediate transfer belt 30. . By forming the light quantity control pattern 130 into a simple shape as described above, the light quantity control pattern 130 can be easily formed by the image forming unit 24. In the present embodiment, the image detecting unit 2
8 in consideration of a detection cycle at the time of detecting the light amount control pattern 130 and the stability of a signal output from the photodiode of the image detection unit 28.
The size is determined.

That is, when a pattern having a small dimension along the moving direction of the intermediate transfer belt 30 such as a pattern made of fine lines is used as the light amount control pattern, the detection cycle needs to be extremely short, so It is necessary to provide a circuit having a simple sample-and-hold function or to perform high-speed control by software. Further, it is necessary to adopt a circuit configuration for minimizing the influence of noise or the like, or to provide a noise determination circuit or the like separately from the circuit having the sample and hold function. In order to solve this, the size of the light amount control pattern 130 along the moving direction (sub-scanning direction) of the intermediate transfer belt 30 is increased to some extent (the moving speed of the intermediate transfer belt 30 and the LED light amount A required time (a time from the start of the LED light amount control process to the time when the light amount of the LED 94 reaches the target value) or more is required.

FIG. 9A shows the intermediate transfer belt 30.
(Direction corresponding to the scanning direction of the laser beam by the scanning exposure unit: hereinafter referred to as the main scanning direction)
5 shows a change in the output voltage of the photodiode when the image detecting unit 28 detects the light amount control pattern with respect to the change in the size of the light amount control pattern along the line. The size of the light amount control pattern along the moving direction of the intermediate transfer belt 30 (hereinafter referred to as the sub-scanning direction) is determined by the size of the image detection unit 90 on the outer peripheral surface of the intermediate transfer belt 30. Photodiodes 96A, 96
B, 100A, and 100B (hereinafter, these are collectively referred to as “detectors”) are larger than the size along the sub-scanning direction of the detection range.

As apparent from FIG. 9A, when the size of the light amount control pattern along the main scanning direction is smaller than the size of the detection range of the detector along the main scanning direction, the detection is performed. Value detected by the detector (output voltage of the photodiode)
The light amount control pattern changes in accordance with the change in size along the main scanning direction, and the accuracy of the formation size when the light amount control pattern is formed on the outer peripheral surface of the intermediate transfer belt 30 is determined by the detector. Affects the accuracy of detecting the amount of reflected light.

On the other hand, when the size of the light quantity control pattern in the main scanning direction is larger than the size of the detection range of the detector in the main scanning direction, the light quantity control pattern in the main scanning direction Is substantially constant (saturated) regardless of the change in size along the line. Therefore, it is desirable that the size of the light amount control pattern along the main scanning direction is larger than the size of the detection range of the detector along the main scanning direction.

Based on the above description, in the present embodiment, taking into account the fact that fetching of detection values is performed a plurality of times and averaging processing of a plurality of detection values (details will be described later), the light amount control pattern along the main scanning direction is taken into consideration. The size of 130 is 20 mm, and the size of the light amount control pattern along the sub-scanning direction is 70 mm.

As described above, by increasing the size of the light quantity control pattern 130 along the sub-scanning direction, detection is performed at a long period that can be detected within the dimension of the light quantity control pattern 130 along the sub-scanning direction. be able to. As an example, in the present embodiment, the detection of the light amount control pattern 130 is performed at a cycle of 2 ms under the condition that the transport speed is 264 mm / sec and the rotation time of the intermediate transfer belt 30 is 8 seconds. As a result, there is no need to provide a circuit having a high-speed sample and hold function or to perform high-speed control by software. In addition, by performing the averaging process, the influence of noise can be reduced without providing a special circuit.

In addition, by making the size of the light quantity control pattern 130 along the main scanning direction larger than the size of the detection range of the detection unit along the main scanning direction, the formation size of the light quantity control pattern is increased. It is possible to accurately detect the amount of reflected light without being affected by the accuracy of The control to form the light-amount control pattern 130 having the above-described size as the light-amount control pattern corresponds to the pattern formation control unit according to the eighth aspect.

As described above, Y, M, C
Since the toner of each color has a light reflectance of 95% or more in the infrared region, the light amount control pattern is formed using only the C color toner in the present embodiment. The light amount control pattern may be formed using M or Y color toner.

The intermediate transfer belt 3 according to the present embodiment
0 is a dielectric material whose volume resistance is adjusted by carbon to electrostatically transfer a toner image, and therefore has a light reflectance of about 10 to 20% for light having a wavelength in the infrared region (wavelength in the visible region). It also has the property of absorbing most of the incident light. On the other hand, the C color toner used for forming the light amount control pattern reflects about 95% of light having a wavelength in the infrared region, and thus has characteristics opposite to those of the intermediate transfer belt 30. For this reason, the output voltage when the light amount control pattern formed on the outer peripheral surface of the intermediate transfer belt 30 is detected by the detector depends on the density of the light amount control pattern in FIG.
It changes as shown in FIG.

That is, the density of the light amount control pattern at this time corresponds to the amount of toner per unit area.
0) does not appear (or the area ratio of the portion where the base appears) is small, so that the ratio of incident light reflected by the toner increases, and the amount of reflected light increases, so that the amount of light received by the detector (output voltage) Will be higher. On the other hand, in a low-density portion, since the toner is sparsely present, the area ratio of the portion where the base appears is large, so that the ratio of the incident light absorbed by the intermediate transfer belt 30 increases, and the amount of reflected light decreases. Therefore, the amount of received light (output voltage) of the detector decreases.

As described above, when the density of the light quantity control pattern fluctuates, the output voltage of the detector fluctuates, thereby lowering the detection accuracy of the reflected light quantity. Therefore, in the present embodiment, when forming the light quantity control pattern 130, control is performed so that the density of the light quantity control pattern 130 becomes a predetermined constant value. Thereby, the light amount control pattern 130
Can be prevented from deteriorating the detection accuracy of the reflected light amount due to the fluctuation of the density of the reflected light. Controlling the density of the light quantity control pattern 130 as described above corresponds to the pattern formation control means according to the ninth aspect.

When the above-described light amount control pattern 130 is formed on the intermediate transfer belt 30 by the image forming section 24, the processing after step 206 is performed. The processing after step 206 corresponds to the light amount control means of the present invention. Hereinafter, the processing will be described with a single LED 94 as a control target. However, the image detection unit 28 is provided with two LEDs per single image detection unit 90, that is, a total of six LEDs.
The processing described below is actually executed in parallel on six LEDs.

In the next step 206, the LED driver 1
LED drive current supplied from 10 to the LED 94 is 0 m
A (in this case, the LED 94 is turned off).
Then, data (detection value) representing the output voltage of the photodiode 96A is repeatedly taken in at a predetermined cycle (2 ms in this embodiment), and based on a change in the detection value, a light amount control pattern on the outer peripheral surface of the intermediate transfer belt 30 is detected. When it is detected that the part where the is formed has reached the detection range of the detector, in the next step 208, the A / D converter 106
The detection value (light amount detection value at 0 mA) fetched through is stored in a memory or the like as offset data.

As shown in FIG. 11, for example, the output voltage of the detector when detecting the light quantity control pattern is such that the vicinity of the leading end of the light quantity control pattern is within the detection range of the detector. It has been confirmed that when the light amount control pattern is located near the rear end side end thereof within the detection range of the detector, the pattern is not stable, and a phenomenon of changing at a certain inclination occurs. This is because the boundary between the area where the toner is attached and the area where the toner is not attached is not exactly a straight line but fluctuates within a certain fluctuation range near the end of the light amount control pattern. are doing. It should be noted that the occurrence of the above phenomenon occurs in the color image forming apparatus 10 according to the present embodiment.
The present invention is not limited to this, and occurs in various types of image forming apparatuses.

For this reason, in this embodiment, “4 m
s ", the captured detection value is stored as data after a lapse of 4 ms after the detection value starts to change due to the leading end of the light amount control pattern covering the detection range of the detector ( The previous step 208) is started. Also, as shown as a “detection value acquisition period” in FIG. 11, at least 4 ms before the detection value starts to change due to at least the rear end of the light amount control pattern covering the detection range of the detector. An LED light amount control process is performed so that storing the detected value as data (step 238 described later) is completed.

Thus, it is possible to prevent the accuracy of the light quantity control from being lowered by storing the detection values taken as data during the period in which the detection values fluctuate.
As described above, storing a detection value taken during a period in which the detection value does not fluctuate as data and using the data for light amount control corresponds to the light amount control means according to claim 5.

In the next step 210, it is determined whether or not the captured detection value has been stored K times (for example, 5 times). If the determination is negative, the process returns to step 208, where the detection value is fetched again, and the fetched detection value is stored as offset data in a memory or the like K times. If the determination in step 210 is affirmative, the process proceeds to step 212,
An averaging process is performed on the K offset data stored in the memory or the like.

In this averaging process, for example, the average value of K pieces of offset data, and the K-value obtained by excluding the data showing the maximum value and the data showing the minimum value among the K pieces of offset data.
Either the average value of the two offset data or the weighted average value of the K offset data can be calculated. As a result, it is possible to obtain the averaged offset data OFFSET_DATA in which the influence of noise or the like is reduced. As described above, storing the K pieces of offset data and performing averaging processing to obtain the averaged offset data OFFSET_DATA corresponds to the light amount control means according to the fourth aspect.

Note that the averaged offset data OFFSET # DAT
If the value of A is significantly different from the normal value, there is a possibility that the intermediate transfer belt 30 is damaged or an abnormality such as the LED 94 is not turned off has occurred. May be reported.

In the next step 214, the LED drive current supplied from the LED driver 110 to the LED 94 is set to the maximum value MAX_POWER (for example, 100 mA). In step 216, the detected value (the reflected light amount detection value of the light amount control pattern when the light emission amount of the LED 94 is the maximum) captured via the A / D converter 106 is stored in a memory or the like as the light amount detection value data at the maximum light amount. Remember. In step 218,
It is determined whether or not step 216 has been repeated K times. If the determination is negative, the process returns to step 216.

Step 216 is repeated K times, and when the K light amount detection value data at the time of the maximum light amount is stored in the memory or the like, the determination in step 218 is affirmed and step 220 is performed.
Then, the averaging process similar to that in step 212 is performed on the K light amount detection value data at the time of the maximum light amount stored in the memory or the like. This makes it possible to obtain averaged maximum light amount value data MAX_DATA in which the influence of noise or the like is reduced. As described above, it is also possible to store the K light amount detection value data at the maximum light amount and perform an averaging process to obtain the averaged maximum light amount value data MAX_DATA, which corresponds to the light amount control means according to claim 4. are doing.

Subsequently, at step 222, the LED drive current supplied from the LED driver 110 to the LED 94 is set to the minimum value MIN # POWER (for example, 10 mA). In step 224, the detected value (the reflected light amount detection value of the light amount control pattern when the light emission amount of the LED 94 is minimum) taken in via the A / D converter 106 is stored in a memory or the like as the light amount detection value data when the light amount is minimum. Remember. In step 226,
It is determined whether or not step 224 has been repeated K times. If the determination is negative, the process returns to step 224.

Step 224 is repeated K times, and when the K light amount detection value data at the minimum light amount is stored in a memory or the like, the determination in step 226 is affirmed and step 228 is performed.
Then, the same averaging processing as in the previous steps 212 and 220 is performed on the K light amount detection value data at the time of the minimum light amount stored in the memory or the like. As a result, it is possible to obtain the averaged minimum light amount value data MIN # DATA in which the influence of noise or the like is reduced. As described above, it is also possible to store the K light amount detection value data at the time of the minimum light amount and perform averaging processing to obtain the averaged minimum light amount value data MIN # DATA. are doing.

In the next step 230, the LED drive current is calculated based on the averaged maximum light amount value data MAX_DATA, the averaged minimum light amount value data MIN # DATA and the averaged offset data OFFSET # DATA obtained by the above-described processing. And a linear function representing the relationship between the detected light amount and the detected light amount. That is, first, the following equation (1) is used to calculate the slope of the linear function (the slope of the change in the detected value output voltage with respect to the change in the LED drive current:
(Corresponding to the gradient of the change of the bold line shown in FIG. 2). α = (MAX # DATA−MIN # DATA) / (MAX # POWER−MIN # POWER) (1)

Then, by substituting the obtained inclination α and the averaged offset data OFFSET # DATA into the following equation (2),
A linear function for calculating a target value TARGET_POWER of the LED drive current for making the light amount detection value coincide with the target value TARGET_DATA of the light amount detection value is calculated. TARGET # POWER = (TARGET # DATA-OFFSET # DATA) / α (2)

In step 232, the target value TARGET # DATA of the light amount detection value at the time of detecting the light amount control pattern for controlling the light emission amount of the LED when the image detecting section 28 detects the image position detection pattern to the optimum value. Take in. In order for the image detection unit 28 to accurately detect the image position detection pattern, the amount of LED light emission when the image detection unit 28 detects the image position detection pattern is controlled to an optimum value (more specifically, the light amount detection Set the value to the optimal value (for example, 4 [V])
Is preferably controlled.

On the other hand, in the present embodiment, the light amount control pattern 130 is different from the image position detection pattern as is clear from FIG. 1, and as is clear from FIG. A signal processing circuit (current-voltage converter 102, amplifier 104, A
/ D converter 106) and a signal processing circuit (current-voltage converter 1) used for detecting an image position detection pattern.
12, 102, differential input amplifier 114, comparator 1
16, buffer 118, counter 120). Therefore, even if the light emission amount (drive current) of the LED 94 is controlled so that the light amount detection value becomes the optimum value when the image detection unit 28 is detecting the light amount control pattern, the image position detection pattern is detected. The detected light amount does not coincide with the target value.

For this reason, in the present embodiment, the image detecting unit 2
An experiment is performed to find the correlation between the light amount detection value when the light amount control pattern 8 detects the light amount control pattern and the light amount detection value when the image detection unit 28 detects the image position detection pattern. Target value of light intensity detection value when detecting control pattern
TARGET # DATA is required in advance.

More specifically, first, while the image detecting section 28 is detecting the pattern for detecting the image position, the LED drive current is adjusted so that the detected light amount becomes an optimum value. next,
The light amount control pattern is detected by the image detection unit 28 without changing the LED drive current. The light amount detection value at this time is a target value TARGET # of the light amount detection value at the time of detecting the light amount control pattern for controlling the LED light emission amount at the time when the image detection unit 28 detects the image position detection pattern. D
Becomes ATA.

The determination of the target value TARGET_DATA of the light amount detection value at the time of detecting the light amount control pattern as described above corresponds to the light amount control means according to the tenth aspect. It should be noted that various methods other than the above can be used for obtaining the correlation, and the method is not limited to the above method. Further, as the density of the light quantity control pattern 130, a value within a range where the above correlation is not broken is used.

In the next step 234, step 232 is executed.
The target value TARGET # DATA of the light amount detection value captured in step (2)
L when substituting into the equation and detecting the image position detection pattern
Calculate the target value TARGET # POWER of the ED drive current (FIG. 12)
See also). As a result, the light amount detection value becomes the target value TARGET # DAT
LED to detect LED drive current when it becomes A
It is not necessary to monitor the change in the light amount detection value while changing the drive current by a constant amount. Even when the relationship between the LED drive current and the light amount detection value changes due to, for example, dust adhering to the LED, the light amount The LED drive current (= target value TARGET_POWER) when the detected value reaches the target value TARGET_DATA can be obtained in a short time from equation (2).

As described above, the averaged maximum light amount data MA
LED for obtaining X # DATA, averaged minimum light value data MIN # DATA and averaged offset data OFFSET # DATA, and matching the light amount detection value to the target value TARGET # DATA of the light amount detection value
A linear function (formula (2)) for calculating the target value TARGET # POWER of the drive current is calculated, and the target value TARGET # DAT of the light amount detection value is calculated.
L when detecting the image position detection pattern by substituting A
Calculating the target value TARGET # POWER of the ED drive current is as follows.
This corresponds to the light amount control means according to the second aspect.

The LED drive current (maximum value MAX_POWER) for obtaining the averaged maximum light amount value data MAX_DATA is the first drive value and the averaged minimum light amount value data described in claim 3.
LED drive current when calculating MIN # DATA (minimum value MIN # PO
(WER) respectively corresponds to the second drive value according to the third aspect, and equation (2) corresponds to the linear equation according to the third aspect.

In step 236, the LED drive current supplied to the LED 94 is set to the target value TARGET # POWER of the LED drive current when detecting the image position detecting pattern.
In step 238, the detected value fetched via the A / D converter 106 is stored in a memory or the like as light amount detected value data. In step 240, it is determined whether or not step 238 has been repeated K times. If the determination is negative, the process returns to step 238.

Step 238 is repeated K times, and when K pieces of light quantity detection value data are stored in the memory or the like, the determination in step 240 is affirmed, and the process shifts to step 242 to store the K pieces of light quantity stored in the memory or the like. An averaging process is performed on the detection value data. This makes it possible to obtain averaged light amount detection value data in which the influence of noise or the like is reduced. As described above, the K light quantity detection value data is stored and subjected to an averaging process to obtain the averaged light quantity detection value data, which also corresponds to the light quantity control means.

In step 244, the averaged light amount detection value data is compared with the target value TARGET # DATA of the light amount detection value, and the deviation is calculated. At step 246, it is determined whether the deviation is within the target range. If the determination is affirmative, the LED light amount control process ends, but if the determination is negative, the process proceeds to step 248, where the target value of the LED drive current TARGET # POW
It is determined whether the ER has been corrected a predetermined number of times (for example, five times) or more.

If this determination is also negative, step 2
The process proceeds to 50, where the target value TARGET_POWER of the LED drive current is corrected based on the deviation obtained in step 244. When this correction is performed, the process returns to step 236, and the processes after step 236 are performed again based on the new target value TARGET_POWER after the correction. As a result, even when it is determined in the previous step 246 that the deviation is out of the target range, the target value TARGET_POWER of the LED drive current is corrected, so that the deviation during the predetermined correction is performed. Will fall within the target range.

The size of the light amount control pattern 130 along the sub-scanning direction is equal to the target value TARGET of the LED drive current.
Even if the #POWER correction has been performed a predetermined number of times, the captured value must be detected 4 ms or more before the detection value starts to change due to the rear end of the light amount control pattern covering the detection range of the detector. It is determined that storing the value as the light amount detection value data (step 238) is completed.

On the other hand, the target value of the LED drive current TARGET # POW
If the deviation does not fall within the target range even after performing the ER correction a predetermined number of times (if the determination in step 248 is affirmative),
Since there is a high possibility that some abnormality has occurred, an error message is displayed on the display 84B to notify the occurrence of the abnormality, and the LED light amount control process ends. in this case,
No image position detection pattern is detected.

Next, an image position detection pattern formed on the outer peripheral surface of the intermediate transfer belt 30 subsequent to the light amount control pattern, and the image position detection pattern formed following the LED light amount control process described above. The detection will be described.

In this embodiment, the light amount control pattern 1 is formed on the outer peripheral surface of the intermediate transfer belt 30 by the image forming unit 24.
When the LED 30 is formed, the image position detection pattern 132 as shown in FIG. 1 is formed on the outer peripheral surface of the intermediate transfer belt 30 in parallel with the execution of the LED light amount control processing described above. The image forming units 20, 22, 24, and 26 are controlled so as to be formed at a slight interval.

As shown in FIG. 1, the image position detecting pattern 132 according to the present embodiment has a substantially mountain shape (substantially L-shape) substantially in the same manner as the shape of the light receiving surface of the detecting section (see FIG. 5B). )so,
A pattern formed so that a position corresponding to the top of the mountain shape is located on the most upstream side along the sub-scanning direction (hereinafter, referred to as a “mountain pattern” for convenience) is a basic pattern.
A large number of pattern groups each including a plurality of mountain-shaped patterns formed at regular intervals are formed along the sub-scanning direction.

Each chevron pattern includes at least one of the three colors Y, M, and C by being formed by at least one of the toners of the colors Y, M, and C, and is the same. The three mountain-shaped patterns included in the pattern group are formed in colors at least partially different from each other.

FIG. 9B shows the change in the size of the chevron pattern (the size along the main scanning direction and the size along the sub-scanning direction). 2
8 shows a change in the output voltage of the photodiode when the detection is performed. As is clear from FIG. 9B, when the size of the mountain-shaped pattern is smaller than the size of the detection range of the detector, the detection value (output voltage of the photodiode) of the detector becomes And that the accuracy of the formation size when forming the chevron pattern on the outer peripheral surface of the intermediate transfer belt 30 affects the detection accuracy of the amount of reflected light by the detector. become.

On the other hand, when the size of the chevron pattern is larger than the size of the detection range of the detector, the detection value by the detector is substantially constant regardless of the change in the size of the chevron pattern. Has become (saturated). Therefore, in the present embodiment, the size of each chevron pattern is made larger than the size of the detection range by the detector.

The Bk color toner is partially used as the base of the mountain pattern. That is, Bk
The light reflectance characteristics of the color toners are shown in FIGS. 6D and 7D.
As is clear, the light reflectance is 10% or less in a wavelength range of 350 nm to 1200 nm (visible range and infrared range),
Since the difference in light reflectance between the intermediate transfer belt 30 and the Bk toner is small, it is difficult to accurately detect a pattern formed by the Bk toner using the intermediate transfer belt 30 as a base.

For this reason, in the present embodiment, as shown in FIG. 1, a part of the pattern group (the third pattern group viewed from the light amount control pattern 130 side in FIG. 1) constitutes the pattern group. B in the gap between the mountain-shaped patterns
The base region 132A is formed by k-color toner.
As a result, the base region 132A and the mountain pattern adjacent to the base region 132A and formed of any one of the Y, M, and C toners (in FIG. 1, as an example, the mountain pattern formed of the Y toner or the C toner). Since the difference in light reflectance between the image forming unit 26 and the image forming unit 26 increases, the position of the base region 132A formed by the image forming unit 26,
It is possible to accurately detect the formation position of the color toner image.

The image position detecting pattern 132 is formed on the intermediate transfer belt 30, and the L
When the ED light amount control process is completed, the image detection unit 28 detects the image position detection pattern 132. When detecting the image position detection pattern 132, the LED 9
4 is controlled to the target value TARGET_POWER finally obtained by the LED light amount control processing.

Since the detection range of the photodiodes 96A and 96B on the outer peripheral surface of the intermediate transfer belt 30 is shifted in the sub-scanning direction, the image position detection pattern 1
32, a waveform corresponding to the difference between the signals input from the current-voltage converters 112 and 102 (the difference in the amount of light received by the photodiodes 96A and 96B) from the differential input amplifier 114, that is, the “pattern” in FIG. As shown by a “detection waveform”, each time a single mountain pattern crosses the detection range of the photodiodes 96A and 96B on the outer peripheral surface of the intermediate transfer belt 30, the level of the output signal is pulsed in the negative and positive directions. A signal having a waveform that changes in the form is output.

The output signal of the differential input amplifier 114 is input to a comparator 116, which compares the level of the output signal with a preset threshold value (for example, 2.67 [V]). Comparator 116
When the level of the input signal is equal to or higher than the threshold, the level of the output signal is set to “ON”, and when the level of the input signal is lower than the threshold, the level of the output signal is set to “OFF” (see “Final output shown in FIG. 13”). "reference). Comparator 11
The signal output from 6 is input to the counter 120 via the buffer 118, and the time interval at which the signal level switches from “OFF” to “ON” is sequentially counted.
The count value of the counter 120 is input to the microcomputer 108.

The microcomputer 108 receives count values from two (six in total) counters 120 per single image detection unit 90. In the signal output from the comparator 116, the level is “ON”
Is the period during which the detector is detecting the mountain pattern, and the period during which the level is “OFF” is the period during which the detector is not detecting the mountain pattern (for the mountain pattern). (A period during which a gap is detected). Therefore, the count value input from the counter 120 indicates the interval between the mountain-shaped patterns formed in the image position detection pattern 132.

The microcomputer 108 detects the interval at which the mountain-shaped pattern is formed at each part in the image position detection pattern 132 based on the count value input from each counter 120. Then, the microcomputer 108 compares the two count values input from the single image detection unit 90 to thereby obtain each color formed at the position corresponding to the image detection unit 90 in the image position detection pattern 132. The amount of deviation of the pattern forming interval (main scanning direction and sub-scanning direction) is detected for each of the image detection units 90A, 90B, and 90C.

Thus, each position along the main scanning direction (near SOS (Start Of Scan), COS (Center Of Scan)
The color shift amount along the main scanning direction and the color shift amount along the sub-scanning direction near (n) and near EOS (End Of Scan) are respectively detected. Then, for example, according to the amount of color misregistration along the main scanning direction, the image forming units 20 and 2
1 of the laser beam by each of the scanning exposure units 2, 24 and 26
The image forming units 20 and 2 change the modulation period in scanning relatively, or change the color shift amount along the sub-scanning direction.
The color misregistration can be eliminated by relatively changing the image forming start timing of each of 2, 2, and 26.

As described above, the interval between the mountain-shaped patterns can be detected based on the count value input from the counter 120. Therefore, in order to detect the interval between the patterns, Japanese Patent Application Laid-Open No. 8-69146 has been disclosed. As in the publication, an expensive CCD is used as a detection unit, and there is no need to perform complicated processing such as extracting a portion corresponding to a mountain-shaped pattern from an image obtained by imaging by the CCD, and the peripheral circuit is inexpensive. Can also use a simple photodiode as the detection unit.

By the way, the “pattern detection waveform” shown in FIG.
The output signal of the differential input amplifier 114 in a state where the light emission amount of the LED at the time of detecting 32 is controlled to the optimum value (the light amount detection value is controlled to the optimum value (for example, 4 [V])) However, if the light emission amount of the LED when detecting the image position detection pattern is lower than the optimum value by a predetermined value or more, as shown in FIG. The amplitude of the output signal of the amplifier 114 becomes small (in FIG. 14, an example is shown in the case of a light emission amount where the light amount detection value becomes 2 [V]), and the image position detection pattern 1
It is difficult to accurately detect 32.

That is, the image position detecting pattern 132
In the case where the amount of light emitted from the LED is detected to be an optimum value when detecting the pattern, the “pattern detection waveform” has a large amplitude and a large slope of change as shown by a solid line in FIG. As described above, when the inclination of the change of the “pattern detection waveform” is large, the timing at which the comparison result by the comparator 116 switches when the same image position detection pattern is repeatedly detected (“OFF” → “ON” or “ON”)
→ The timing of switching to “OFF” is always constant, as in “final output” shown by the solid line in FIG.

On the other hand, when the light emission amount of the LED when detecting the image position detection pattern 132 is lower than the optimum value by a predetermined value or more, the “pattern detection waveform” has the amplitude and change as shown by the broken line in FIG. Has a small slope. When the inclination of the change of the “pattern detection waveform” is small, the timing at which the comparison result is switched by the comparator 116 is “final output” indicated by a broken line in FIG. 15, even if the same image position detection pattern is repeatedly detected. And the count value output from the counter 120 varies, which leads to a decrease in the detection accuracy of the image position detection pattern 132.

As described above, in the image position detecting pattern 132 according to the present embodiment, the light emission amount of the LED at the time of pattern detection has a great influence on the pattern detection accuracy. On the other hand, in the present embodiment, the image position detection pattern 132
Since the LED light amount control process described above is performed before detecting the image position, the light emission amount of the LED when the image position detection pattern 132 is detected is controlled to an optimum value. The detection can be performed with high accuracy, and the color shift of the full-color image formed by the color image forming apparatus 10 can be corrected with high accuracy.

In the above description, the rectangular light amount control pattern 130 is used as the light amount control pattern according to the present invention. However, the shape of the light amount control pattern is not limited to this, but may be any shape. The following pattern can be adopted. Also, the image position detection pattern is not limited to the image position detection pattern 132 described in the above embodiment, and it goes without saying that various known patterns can be adopted.

In the above description, the relationship between the drive value of the light-emitting portion of the pattern detection means and the detected value of the reflected light amount is determined based on the target value TARGET # DATA of the detected light amount and the target value TAR of the LED drive current.
Although a linear function (formula (2)) for obtaining GET_POWER was calculated, the present invention is not limited to this.
An n-th order function (n ≧ g) representing the above relationship by applying the least squares method or the like
2) may be obtained.

[0142]

As described above, according to the first aspect of the present invention, the amount of light emitted from the light emitting unit is determined based on the result of detection of the amount of light emitted from the light emitting unit and reflected by the light amount control pattern formed on the medium. In addition to the control, the size of the light amount control pattern along the moving direction of the medium is set to a value equal to or more than the product of the moving speed of the medium and the time required for the light amount control by the light amount control means. There is an excellent effect that the light emission amount can be optimized with a simple configuration.

According to a second aspect of the present invention, in the first aspect of the present invention, based on the detected values of the reflected light amounts respectively detected by the detecting section in a plurality of states in which the driving values of the light emitting section are different from each other. The relationship between the drive value and the detection value of the reflected light amount is calculated, and the drive value when the light amount detection value by the detection unit reaches the target value is obtained based on the calculated relationship. This has the effect that the drive value when reaching the target value can be obtained in a short time.

According to a third aspect of the present invention, in the second aspect of the present invention, the detected value of the amount of reflected light when the light emitting section is driven at the first drive value and the light emitting section having the second drive value different from the first drive value. Since a linear expression representing the relationship between the drive value and the detected value of the reflected light amount is obtained based on the detected value of the reflected light amount when driven with the drive value of 2, the drive value and the detected value of the reflected light amount are obtained in addition to the above effects. And the calculation of the relationship can be performed in a short time.

According to a fourth aspect of the present invention, in the first aspect of the present invention, while the drive value of the light emitting section is maintained at a predetermined value, the reflected light amount is detected a plurality of times by the detection section, and the drive value is set to the predetermined value. Since a value obtained by averaging a plurality of detection values obtained by a plurality of detections is used as the detection value at the time of, in addition to the above-described effects, it is possible to reduce the influence of noise or the like when detecting the light amount control pattern. Has the effect of

According to a fifth aspect of the present invention, in the first aspect of the present invention, a section of the light quantity control pattern from the end of the light quantity control pattern along the moving direction of the medium until the distance reaches a predetermined value. Since the amount of emitted light is controlled based on the detected value when the removed portion corresponds to the detection range of the detecting unit, in addition to the above effects, the amount of emitted light of the light emitting unit can be optimized with higher accuracy. It has the effect of.

According to a sixth aspect of the present invention, the size of the transfer body in the moving direction is a value corresponding to the product of the moving speed of the transfer body and the time required for the light quantity control by the light quantity control means. As described above, the light amount control pattern composed of a specific single color is controlled so as to be formed on the transfer body, and is detected by being emitted from the light emitting portion and reflected at the portion of the transfer body where the light amount control pattern is formed. The amount of light emitted from the light emitting unit when the pattern detection unit detects the image position detection pattern is controlled based on the amount of light detected by the unit. There is an excellent effect that optimization with time can be realized with a simple configuration.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, light having a wavelength in the infrared region emitted from the light emitting section and reflected by the transfer member is detected by the detecting section. In addition, regardless of the color of the light amount control pattern, there is an effect that the light emission amount of the light emitting unit when the pattern detection unit detects the image position detection pattern can be optimized with high accuracy.

According to an eighth aspect of the present invention, in the sixth aspect of the present invention, the size of the light amount control pattern formed on the transfer member is larger than the size of the detection range on the transfer member by the detecting section. Since the formation of the light quantity control pattern is controlled as described above, in addition to the above-described effects, there is an effect that the light quantity control pattern can be accurately detected by the pattern detection unit.

According to a ninth aspect of the present invention, in the sixth aspect of the present invention, the density of the light amount control pattern formed on the transfer body is controlled to be a predetermined value. This has the effect that the light amount control pattern can be accurately detected by the unit.

According to a tenth aspect of the present invention, in the sixth aspect of the present invention, the detection value of the reflected light amount of the portion where the image position detecting pattern is formed and the reflected light amount of the portion where the light amount controlling pattern is formed. Since the target value of the light amount detection value by the detection unit of the pattern detection unit is determined based on the correlation with the detection value of the pattern detection unit, the light emission amount of the light emitting unit is controlled so that the light amount detection value by the detection unit matches the target value. In addition to the above effects, the amount of emitted light can be controlled by using a light amount control pattern different from the image position detection pattern so that the amount of light emitted from the light emitting unit when detecting the image position detection pattern is optimized. Has the effect of

[Brief description of the drawings]

FIG. 1 is a plan view illustrating an example of a light amount control pattern and an image position detection pattern formed on an outer peripheral surface of an intermediate transfer belt.

FIG. 2 is a schematic configuration diagram of a color image forming apparatus according to the embodiment.

FIG. 3 is a perspective view illustrating an arrangement of each image detection unit of the image detection unit.

FIG. 4 is a block diagram illustrating a schematic configuration of an image detection unit.

FIG. 5A is a perspective view showing an arrangement of an LED and a photodiode of the image detection unit, and FIG. 5B is a plan view showing a shape of a light receiving portion of the photodiode.

FIG. 6 (A) is Y, (B) is M, (C) is C,
(D) is a diagram showing an example of a light reflectance characteristic of a toner of each color of Bk in a visible region.

(A) is Y, (B) is M, (C) is C,
(D) is a diagram showing an example of a light reflectance characteristic in the infrared region of each color Bk toner.

FIG. 8 is a flowchart showing the contents of an LED light amount control process.

FIG. 9A is a light amount control pattern, and FIG.
(B) is an explanatory diagram for explaining the relationship between the pattern size and the photodiode output voltage when detecting the image position detection pattern.

FIG. 10 is a diagram illustrating an example of a change in detector output voltage with respect to a change in the density of the light amount control pattern.

FIG. 11 is a diagram illustrating an example of a change (transition) of a detector output voltage with the passage of time when a light amount control pattern is detected.

FIG. 12 is a diagram illustrating an example of a relationship between an LED drive current and a detector output voltage.

FIG. 13 is a timing chart showing an example of a detection waveform when the image detection unit detects an image position detection pattern in a state where the light emission amount of the LED is controlled to an optimum value.

FIG. 14 is a timing chart showing an example of a detection waveform when the image detection unit detects an image position detection pattern in a state where the light emission amount of the LED is lower than the optimum value.

FIG. 15 is a diagram showing changes in outputs of the differential input amplifier and the comparator when the amount of light emitted from the LED changes.

[Explanation of symbols]

 Reference Signs List 10 color image forming device 24 image forming unit 28 image detecting unit 80 control unit 90 image detecting unit 94 LED 96 photodiode 98 LED 100 photodiode 108 microcomputer 130 light intensity control pattern 132 image position detecting pattern

Claims (11)

[Claims] 1. A light emitting unit that moves in a predetermined direction and irradiates a medium on which a light amount control pattern is formed, and detects a light amount emitted from the light emitting unit and reflected by the light amount control pattern on the medium. And a light amount control unit that controls the light emission amount of the light emitting unit based on the detection result of the detection unit, wherein the size of the light amount control pattern along the moving direction of the transfer body is: A light amount control device, wherein the light amount control device is at least a value corresponding to a product of a moving speed of the medium and a time required for light amount control by the light amount control means. 2. The light amount control unit according to claim 1, wherein the drive value and the reflected light amount are detected based on the reflected light amount detected by the detection unit in a plurality of states where the drive values of the light emitting unit are different from each other. 2. The light amount control device according to claim 1, wherein a relationship with the detected value is calculated, and a drive value when the light amount detected value by the detection unit becomes a target value is obtained based on the calculated relationship. 3. The light amount control means includes:
The drive value and the reflection value are determined based on the detected value of the amount of reflected light when driven by the drive value of the above, and the detected value of the amount of reflected light when the light emitting unit is driven by the second drive value different from the first drive value. 3. The light quantity control device according to claim 2, wherein a linear expression representing the relation is obtained as a relation with the detected light quantity value. 4. The light amount control means causes the detection unit to detect the reflected light amount a plurality of times while maintaining the drive value of the light emitting unit at a predetermined value, and detects a detected value when the drive value is the predetermined value. The light amount control device according to claim 1, wherein a value obtained by averaging a plurality of detection values obtained by the plurality of detections is used. 5. The light quantity control means includes a light quantity control pattern which is a part of the light quantity control pattern excluding a section until a distance reaches a predetermined value from an end of the light quantity control pattern along a moving direction of the medium. The light amount control device according to claim 1, wherein the light amount control unit controls the light emission amount based on a detection value corresponding to a detection range. 6. A light-emitting portion for irradiating light to a transfer member which is moved in a predetermined direction and in which images of different colors are formed by a plurality of image forming portions, respectively, and is emitted from the light-emitting portion and reflected by the transfer member. A pattern detection unit for detecting an image position detection pattern formed on the transfer body by the plurality of image forming units; and a light emitting unit of the pattern detection unit. The light emitting unit when the pattern detection unit detects the image position detection pattern based on the light amount of light reflected by a portion on the transfer body where the light amount control pattern is formed and detected by the detection unit. And a size along the moving direction of the transfer body corresponds to a product of a moving speed of the transfer body and a time required for the light quantity control by the light quantity control means. A pattern formation control unit that controls a single image forming unit corresponding to the specific single color so that a light amount control pattern having a value equal to or more than a specific single color is formed. . 7. The image position detecting device according to claim 6, wherein the detecting unit of the pattern detecting unit detects light having a wavelength in an infrared region emitted from the light emitting unit and reflected by the transfer member. 8. The pattern formation control unit, wherein the size of the light amount control pattern formed on the transfer body is larger than the size of the detection range on the transfer body by the detection unit of the pattern detection unit. 7. The image position detecting device according to claim 6, wherein formation of the light amount control pattern by the image forming device is controlled. 9. The single image forming unit controls the single image forming unit such that the density of a light amount control pattern formed on the transfer body has a predetermined value. 7. The image position detecting device according to 6. 10. The light amount control means detects a reflection light amount detection value of a portion where the image position detection pattern is formed and a reflection light amount of a portion where the light amount control pattern is formed. A target value of the light amount detection value by the detection unit of the pattern detection unit is determined based on the correlation with the value, and the light emission amount of the light emitting unit is controlled such that the light amount detection value by the detection unit matches the target value. The image position detecting device according to claim 6, wherein: 11. A plurality of image forming units, a transfer member that is moved in a predetermined direction, and forms images of different colors from each other by the plurality of image forming units, and a light emitting unit that irradiates the transfer member with light. And a detection unit for detecting light emitted from the light emitting unit and reflected by the transfer body, and a pattern detection unit for detecting an image position detection pattern formed on the transfer body by the plurality of image forming units. Means for detecting the image based on the amount of light emitted from the light emitting portion of the pattern detecting means, reflected on the portion of the transfer member where the light amount controlling pattern is formed, and detected by the detecting portion. A light amount control unit that controls a light emission amount of the light emitting unit when detecting a position detection pattern; and a size along a moving direction of the transfer body is determined by a movement speed of the transfer body and the light amount control unit. A single image forming unit corresponding to the specific single color is controlled so that a light amount control pattern composed of a specific single color having a value equal to or more than a product of the time required for the light amount control is formed. And an image forming apparatus comprising: