JP2014119731A - Image forming apparatus and detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately performing color shift correction control or density correction control without providing a diaphragm mechanism to an optical sensor.SOLUTION: An image forming apparatus includes: forming means for forming, on an image carrier, detection images including one or more lines formed with developer extending in a direction different from a direction of movement of the image carrier; and detection means for detecting position information or density information on the detection images on the basis of detection signals output from light receiving means in a period during which the detection images formed on the image carrier pass through an area irradiated with light by irradiation means. The detection means detects the position information or the density information on the detection images on the basis of signals according to a difference between the values of detection signals corresponding to the amount of received light including regular reflection light components from a first area of the detection images and on the surface of the image carrier, and values of the detection signals corresponding to the amount of received light including regular reflection light components from a second area of the detection images and on the surface of the image carrier, in which the respective lengths in the direction of movement of the first area and the second area are shorter than the length in the direction of movement of the lines.

Description

  The present invention relates to a color misregistration and density detection technique in an image forming apparatus such as a color laser printer, a color copying machine, and a color facsimile mainly employing an electrophotographic process.

  In recent years, an electrophotographic image forming apparatus is mainly a tandem type in which a photoconductor is provided for each color in order to increase the printing speed. In a tandem type image forming apparatus, for example, a detection image, which is a developer image for color misregistration or density detection, is formed on an intermediate transfer belt, and reflected light from the detection image is detected by an optical sensor, whereby color misregistration or Density correction is executed.

  Patent Document 1 includes two optical sensors that detect specularly reflected light (also referred to as specularly reflected light) and scattered reflected light from a toner image, and controls image density according to the output difference between the two optical sensors. Disclosure. Patent Document 2 discloses an optical sensor that detects both regular reflection light and scattered reflection light using a prism. In these methods, only the reflected light component is detected by detecting only the scattered reflected light component with one of the light receiving elements and subtracting it from the sum of the specular reflected light and scattered reflected light detected with the other light receiving element. Take out. The method of detecting the density from the extracted regular reflection light component mainly detects the regular reflection light from the ground, not the scattered reflection light from the toner. Accordingly, it is possible to detect the density regardless of the color of the developer having a difference in the amount of scattered reflected light, and to detect a highlight area sensitive to human visual characteristics. However, in the case of the system as in Patent Document 1, the error in the correction process for extracting only the specularly reflected light component is said to be large. For this reason, Patent Document 3 discloses that the accuracy is improved by reducing the ratio of the scattered reflected light component by reducing the effective spot diameter of the regular reflected light.

  Further, it is required to reduce the consumption of the developer by the detected image for detecting color misregistration and density as much as possible. That is, it is preferable to make the detected image as small as possible. A sensor with high spatial resolution is required in order to accurately detect a density even with a small detection image, and Patent Document 4 discloses a sensor with a small irradiation area on the light emission side.

JP-A-3-209281 JP 2003-76129 A JP-A-2005-300918 JP 2005-241933 A

  When the spot diameter of specular reflection light is reduced in a conventional optical sensor, the manufacturing yield and detection accuracy are greatly affected by variations in the position of LED chips in the optical sensor and mechanical variations in the aperture mechanism. There was a problem. For example, to increase the spatial resolution of the optical sensor, it is necessary to reduce the aperture mechanism. However, according to Patent Document 4, the spot diameter of specularly reflected light is limited to about 1 mm in consideration of manufacturing variations and the like. Further, the higher the spatial resolution of the optical sensor, the greater the noise generated by the fine irregularities on the surface of the intermediate transfer belt, and as a result, the S / N ratio is lowered, and the density detection accuracy is particularly affected. .

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a sensor with a simple configuration and to increase detection resolution.

  According to one aspect of the present invention, an image carrier, an irradiation unit that irradiates light toward the image carrier, a reflected light of the light emitted by the irradiation unit, and a detection signal corresponding to the amount of received light A light receiving means for outputting; a forming means for forming a detection image on the image carrier including a line of one or more developers in a direction different from a moving direction of the image carrier; and the formed on the image carrier. Detecting means for detecting position information or density information of the detection image based on the detection signal output by the light receiving means while the detection image passes through an irradiation region by the irradiation means, and the detection means A value of the detection signal corresponding to a received light amount including a specularly reflected light component from a first region of the detection image and the surface of the image carrier, and a second value of the detection image and the surface of the image carrier. Receiving including specularly reflected light component from the area The position information or the density information of the detected image is detected by a signal corresponding to the difference from the value of the detection signal corresponding to the amount, and the lengths in the moving direction of the first area and the second area are respectively The line is shorter than the length in the moving direction.

  It is possible to increase the detection resolution by using a sensor with a simple configuration.

The figure which shows the detection image containing the optical sensor and one line by one Embodiment. The figure which shows the detection image containing the optical sensor and several line by one Embodiment. The figure which shows the time change of the light reception amount when detecting the detection image containing the some line by one Embodiment. Explanatory drawing of the process with respect to the detection image containing the some line by one Embodiment. Explanatory drawing of the process with respect to the detection image containing one line by one Embodiment. 1 is a schematic configuration diagram of a detection system according to an embodiment. FIG. Explanatory drawing of the relationship between an area and a scattered light removal signal. Explanatory drawing of the relationship between section length reduction amount and S / N ratio. Explanatory drawing of the relationship between noise and a threshold setting possible range. 1 is a schematic configuration diagram of a detection system according to an embodiment. FIG. Explanatory drawing of the difference between 1st embodiment and 2nd embodiment. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings. In the following drawings, the same reference numerals are used for the same components.

<First embodiment>
First, the image forming unit 101 of the image forming apparatus according to the present embodiment will be described with reference to FIG. Note that Y, M, C, and Bk at the end of the reference numerals in FIG. 12 indicate that the colors of the toners that are the developers targeted by the corresponding members are yellow, magenta, cyan, and black, respectively. Yes. In the following description, when it is not necessary to distinguish between colors, reference numerals without Y, M, C, and Bk at the end are used. The charging unit 2 uniformly charges the photosensitive member 1 that is an image bearing member that is rotationally driven in the direction of the arrow in the figure, and the exposure unit 7 irradiates the photosensitive member 1 with laser light to irradiate the photosensitive member 1. An electrostatic latent image is formed on the surface. The developing unit 3 supplies a developer to the electrostatic latent image by applying a developing bias, so that the electrostatic latent image is a visible toner image (developer image). The primary transfer roller 6 transfers the toner image on the photoreceptor 1 to the intermediate transfer belt 8 by the primary transfer bias. The intermediate transfer belt 8 is rotationally driven in the direction of the arrow 81. Each photoconductor 1 transfers the toner image on the intermediate transfer belt 8 so as to form a color image. The cleaning blade 4 removes the toner that is not transferred to the intermediate transfer belt 8 and remains on the photoreceptor 1.

  The conveyance rollers 14, 15 and 16 convey the recording material in the cassette 13 to the secondary transfer roller 11 along the conveyance path 9. The secondary transfer roller 11 transfers the toner image on the intermediate transfer belt 8 to the recording material by a secondary transfer bias. The toner that is not transferred to the recording material and remains on the intermediate transfer belt 8 is removed by the cleaning blade 21 and collected in a waste toner collecting container 22. The recording material onto which the toner image has been transferred is heated and pressurized in the fixing unit 17 to fix the toner image, and is discharged out of the apparatus by the transport roller 20. The engine control unit 25 includes a microcontroller 26, and performs sequence control of various drive sources (not shown) of the image forming apparatus, various controls using sensors, and the like. An optical sensor 27 is provided at a position facing the intermediate transfer belt 8.

  For example, in a tandem type image forming apparatus, the mechanical dimension is deviated from the design value due to assembly error, part tolerance, thermal expansion of the part, etc. at the time of manufacturing the apparatus, thereby causing a positional deviation for each color. For this reason, a detection image for detecting color misregistration of each color is formed on the intermediate transfer belt 8 or the like, and the reflected light from the formed detection image is detected by the optical sensor 27. Then, based on the detection result, color misregistration is corrected by adjusting the writing position in the main scanning and sub-scanning directions and the image clock for each color. Further, in the image forming apparatus, the color or density of an image output by time-dependent change or continuous printing can change. In order to correct this variation, density control is performed. In density control, a detection image for detecting the density of each color is formed on the intermediate transfer belt 8 and the like, and reflected light from the formed detection image is detected by the optical sensor 27. Then, the maximum density of each color and the halftone gradation characteristics are corrected by feeding back the detection result to process formation conditions such as each voltage condition and laser beam power. The density detection by the optical sensor 27 is generally performed by irradiating a detection image with a light source and detecting the intensity of reflected light with a light receiving element. A signal corresponding to the intensity of the reflected light is processed by the microcontroller 26 and fed back to the process formation conditions. The purpose of the control of the maximum density is to keep the color balance of each color constant, and to prevent the overlaid color image from being overloaded and the fixing failure. On the other hand, halftone gradation control is intended to prevent the output density from deviating from the input image signal due to nonlinear input / output characteristics to prevent a natural image from being formed.

  Hereinafter, details of the optical sensor 27 of the present embodiment will be described with reference to FIG. FIG. 1A is a perspective view showing the relationship between the optical sensor 27 and the detected image 40. A detection image 40 shown in FIG. 1A is a toner image including one line of toner in a direction orthogonal to the moving direction of the intermediate transfer belt 8. In the following embodiments, one line is described as a solid line, but a broken line such as a dotted line or a broken line may be used. Further, in FIG. 1A, the intermediate transfer belt 8 itself is omitted for easy understanding of the drawing. The optical sensor 27 according to the present embodiment includes a light emitting element 272, a light receiving element 277, a processing circuit 275, and a light shielding wall 276 disposed on the package substrate 271. A normal light emitting element used for color shift and density detection is provided with a reflector in the element in order to collect light diffused from the light emitting element into the flare. In the case of a bullet-type light emitting element, a condensing lens is also configured. On the other hand, in the optical sensor 27 of the present embodiment, only the LED chip is disposed without providing a reflector or a condenser lens, so that the intermediate transfer belt 8 is irradiated with a divergent light beam of a point light source. Also on the light receiving side, a condensing lens or the like is not used, and for example, a photodiode that outputs a current corresponding to the amount of received light is used. That is, the reflected light from the intermediate transfer belt 8 is converted into a signal corresponding to the amount of light received by the light receiving element without passing through an optical member for narrowing or condensing the light. The processing circuit 275 controls the light emitting element 272 and processes the signal detected by the light receiving element 277, and outputs the processed signal to the microcontroller 26. The optical sensor 27 is packaged with resin and glass. The light shielding wall 276 is provided in order to prevent light emitted from the light emitting element 272 from directly entering the light receiving element 277 as stray light, or light reflected by the interface of the package from entering the light receiving element 277.

  The image forming apparatus irradiates the intermediate transfer belt 8 and the detection image 40 formed on the intermediate transfer belt 8 with light from the light emitting element 272 and receives reflected light from the light receiving element 277 to cause color misregistration. Or detect the concentration. Basically, the amount of color misregistration is obtained by detecting the relative passage timing of the detection image 40 of each color, and the density is determined by detecting the average amount of light from the detection image 40 formed in a halftone. The color misregistration and density are detected by monitoring the specularly reflected light component from the intermediate transfer belt 8. The image forming apparatus of this embodiment uses four colors of toner, but the light absorption / reflection characteristics differ depending on the color of the toner. For example, in the case of infrared light, black toner substantially absorbs light, and other color toners scatter and reflect light. In the case of red light, black and cyan toners almost absorb light, and other color toners scatter and reflect light.

  That is, it is necessary to perform a process of removing the scattered light component from the detected image 40 in a state where a toner having a large amount of scattered reflection and a toner having a small amount of scattered reflection or a toner that hardly generates a scattering reflection are mixed. For this reason, in conventional color misregistration and density control, an optical sensor is provided with a diaphragm mechanism, and a light receiving element for detecting only the scattered reflected light component is separately provided. However, the optical sensor 27 of the present embodiment removes the scattered reflected light component from the detected image 40 without providing a diaphragm mechanism. Since no diaphragm mechanism is provided, the optical sensor 27 of the present embodiment can be downsized to a fraction of the size of the conventional sensor.

  Hereinafter, the state of reflected light from the intermediate transfer belt 8 and the detection image 40 on the intermediate transfer belt will be described in detail with reference to FIGS. 1B and 1C. FIG. 1B is a view as seen from the X-axis direction of FIG. 1A, and the intermediate transfer belt 8 advances from the rear side to the front side. FIG. 1C is a view as seen from the Y-axis direction of FIG. 1A, and the intermediate transfer belt 8 advances in the direction of the white arrow in the drawing. On the surface of the intermediate transfer belt 8, the light emitted from the light emitting element 272 is mainly specularly reflected and detected by the light receiving element 277. This regular reflection light is indicated by a solid arrow. As shown in FIG. 1B, the width of the reflected light incident on the light receiving element 277 is such that the light emitting element 272 is a point light source, and the optical path length of the incident light and the reflected light on the intermediate transfer belt 8. Is the same arrangement relationship, the length of the intermediate transfer belt is twice as long. On the other hand, the light emitted from the light emitting element 272 is mainly scattered and reflected by the toner line of the detection image 40 formed on the intermediate transfer belt 8 and is detected by the light receiving element 277. This scattered reflected light is indicated by a broken line arrow. Note that, with respect to the scattered reflected light, since the drawing becomes complicated, the irradiation light from the light emitting element 272 to the intermediate transfer belt 8 is omitted, and the broken line arrow is also briefly described for the reflected light.

  Next, the amount of light received by the optical sensor 27 when the striped detection image 40 including a plurality of lines is used, that is, the light detection signal output from the optical sensor 27 will be described with reference to FIGS. Although each line is described as a solid line, it may be a broken line such as a broken line or a dotted line. FIG. 2 is a perspective view showing the detection image 40 including a plurality of toner lines in a direction orthogonal to the moving direction of the intermediate transfer belt 8 and the optical sensor 27. Also in FIG. 2, the intermediate transfer belt 8 itself is omitted for easy understanding of the drawing. FIG. 3 is a diagram illustrating a temporal change in the amount of light received by the light receiving element 277 when the detection image 40 including a plurality of lines passes through the irradiation region of the light emitting element 272. Note that the width of the detection image 40 in the sub-scanning direction, that is, the movement direction of the intermediate transfer belt 8 is about 100 mm, and FIGS. , Called a space) is a temporal change in the amount of received light when the widths are different from each other. Specifically, the line width and the space width in FIG. 3A are the narrowest, and the line width and the space width are increased in the order of FIG. 3B, FIG. 3C, and FIG. In FIG. 3, toner lines and spaces are shown at the bottom of the waveform for reference. Here, the horizontal direction in the figure corresponds to the sub-scanning direction. Further, FIG. 3 shows the amount of scattered reflected light in addition to the total amount of light received by the light receiving element 277.

  The scattered reflected light in the line of the detected image 40 interferes with each other, and the reflection state of the scattered reflected light in the entire detected image 40 is determined by the degree of this interference. When the line pitch is large and the space width is wide, even if the scattered reflected light interferes with each other, it does not become a uniform state but vibrates or fluctuates. Here, the line pitch is the distance between the centers of adjacent lines, and is equal to the sum of the line width and the space width. For example, when the line pitch is larger than the state of FIG. 3C, the vibration of the scattered reflected light is very large. In the state of FIG. 3D, the scattered reflected light in each line almost interferes. Not. On the contrary, in FIG. 3B, the vibration of the scattered reflected light becomes very small, and in the state of FIG. 3A, the vibration is not generated and is almost uniform. The vibration of the scattered reflected light component varies depending not only on the line pitch but also on the distance between the optical sensor 27 and the intermediate transfer belt 8. On the other hand, since the amount of specular reflection from the space portion of the detection image 40 vibrates according to the line pitch, the total amount of received light repeats the vibration in a form superimposed on the waveform of the scattered reflected light indicated by the broken line. .

  Note that the lines shown in FIG. 3 are formed in a state where the concentration is almost 100%. When the density is detected, this line is formed with a halftone density. In this case, although the scattered reflected light component vibrates at the cycle of the line pitch, the vibration amplitude value becomes smaller than that at the density of 100%. For example, if the density is 0%, the vibration amplitude of the scattered reflected light component is 0. If the density is 100%, the vibration amplitude is as shown in FIG. That is, if a plurality of lines are formed under the condition that the scattered reflected light component is substantially constant when the density is 100%, the scattered reflected light component is substantially constant even when the density is halftone.

  Next, a method of extracting the specular reflection component by removing the scattered reflected light component from the toner from the total received light amount detected by the optical sensor 27 will be described with reference to FIGS.

  FIG. 4 is an explanatory diagram of processing for the light detection signal output from the optical sensor 27, and can be used mainly for concentration detection. FIG. 4 shows each signal (left side in the figure) for the detection image 40 formed with toner having a color with much scattered reflected light and each signal for the detection image 40 formed with toner having a color with little scattered reflected light (shown in the figure). Both right) are shown. The space width of the detected image 40, the distance between the optical sensor 27 and the intermediate transfer belt 8, and the like are adjusted so that the vibration of the scattered reflected light amount is within a predetermined amount.

  FIG. 4A shows a light detection signal output from the optical sensor 27. In the detection image 40 of a color having a lot of scattered reflections, the entire waveform is lifted by the influence of the scattered reflected light as in FIG. In the detection image 40 having a color with little scattered reflection, the irradiation light is absorbed by the toner, and therefore, the waveform vibrates with little waveform lifting.

  For example, FIG. 4B shows a case where two sections are set, the moving average values of the two sections are obtained, and the differential processing of the moving average values is performed. The interval between the two sections is set to a predetermined period in which the phase of the light detection signal is different. For example, the period is set to be approximately half of the vibration period of the light detection signal. As described above, since the detection image 40 is formed so that the vibration of the scattered light removal signal falls within a predetermined range, the vibration of the light detection signal shown in FIG. It is. Therefore, by performing the differential processing of the two sections, the scattered reflection component is removed or suppressed to a predetermined amount or less. That is, the signal shown in FIG. 4B is a scattered light removal signal obtained by removing the scattered light component from the total received light amount. The amplitude of the scattered light removal signal indicates the detected image line and space, that is, the contrast of the reflected light from the surface portion of the intermediate transfer belt 8, that is, the toner density information. For example, when the line density of the detection image 40 is lowered, the amplitude of the waveform shown in FIG.

  FIG. 4C shows an amplitude value extracted from the scattered light removal signal shown in FIG. 4B, and can be used as density information. In addition, since the scattered reflected light component is not uniform in the vicinity of the detection start and end of the detection image 40, the waveform is slightly distorted as shown in FIG. If an amplitude value is extracted from a portion where the waveform is distorted, an error is caused. Therefore, the length of the detected image 40 in the sub-scanning direction is increased to some extent, and a state where the amount of scattered reflected light is uniform is ensured. If the scattered reflected light component is uniform, the amplitude value can be extracted from that portion with high accuracy. That is, it is possible to detect highly accurate density information.

  FIG. 5 is an explanatory diagram of a photodetection signal and its processing when a detection image 40 including one line is used unlike FIG. Here, the detection image 40 including one line can be used, for example, for color misregistration detection. As in FIG. 4, FIG. 5 shows the case where the detection image 40 is formed with a toner with a lot of scattered reflected light (left side in the figure) and the detection image 40 is formed with a toner with a little scattered reflected light. Both cases (right side of the figure) are shown. As shown in FIG. 5A, the detection image 40 including one line has a waveform in which the amount of received light is attenuated when the line comes to a position where the light receiving element 277 receives specularly reflected light. As shown in FIG. 5A, when the amount of scattered reflected light is large, the amount of received light increases before and after regular reflected light falls due to the influence of scattered reflected light.

  As in the case of the detection image 40 including a plurality of lines, two sections are provided, moving average values of the two sections are obtained, and a signal waveform obtained by differentially processing the moving average values is shown in FIG. It is. In the signal waveform of FIG. 5 (B), the scattered reflected light is almost eliminated, and it is corrected to the same waveform regardless of the magnitude of the scattered / reflected toner. In the case of the detection image 40 including one line, the amount of scattered reflected light when the detection image 40 passes through the detection region of the optical sensor 27 is not constant, and therefore the scattered light removal signal shown in FIG. Scattered light components remain. However, in the case of detecting the amount of color misregistration, since the purpose is to detect the passage timing of the detected image 40, this does not hinder. However, in order to prevent the remaining component of the scattered reflected light from becoming a hindrance, the time width during which the detection image 40 passes through the detection region of the optical sensor 27 is sufficiently smaller than the time width for detecting the scattered reflected light. can do. By generating timing data by comparing the signal in FIG. 5B with a predetermined threshold value, it is possible to detect the arrival timing of the detected image 40, that is, position information. In the present embodiment, it is possible to detect the density information and position information of the detection image 40 of each color by the same processing regardless of whether the toner is scattered or reflected. Note that even when the detection image 40 includes a plurality of lines shown in FIG. 4, the arrival timing can be detected by comparing the signal shown in FIG. 4B with a predetermined threshold.

  Next, an exemplary detection system that performs the processing described in FIGS. 4 and 5 is shown in FIG. The optical sensor 27 detects the reflected light from the intermediate transfer belt 8 and the detection image 40 on the intermediate transfer belt 8, and converts the current corresponding to the amount of light received from the light receiving element 277 into a voltage to detect light. And a processing circuit 275 that outputs a signal. The signal processing unit 28 includes a scattered light removal unit 30 that is provided in the engine control unit 25 of FIG. 1 and generates a scattered light removal signal obtained by removing the scattered reflected light component from the light detection signal. Further, the signal processing unit 28 includes an amplitude data generation unit 50 that extracts amplitude data of the scattered light removal signal, and a timing data generation unit 60 that extracts arrival timing data of the scattered light removal signal.

  The sampling unit 31 of the scattered light removing unit 30 samples the light detection signal, and the moving average processing units 32 and 33 calculate a moving average value of each section of the sampled light detection signal. Specifically, the moving average processing unit 32 calculates the moving average value of the section 1 in FIGS. 4A and 5A, and the moving average processing unit 33 calculates the moving average processing unit 33 in FIGS. The moving average value of section 2 in A) is calculated. The differential processing unit 34 performs a differential operation on the moving average values calculated by the moving average processing units 32 and 33, thereby generating a scattered light removal signal that cancels or cancels the scattered reflected light components from each other. To do. Note that the interval between the sections in which the moving average processing units 32 and 33 calculate the moving average value is set to a value corresponding to the line pitch of the detected image 40 including a plurality of lines. For example, it can be a section including a position where the amplitude of the light detection signal is different. For example, while the moving average processing unit 32 obtains the moving average of the section including the maximum value of the light detection signal in FIG. 4A, the moving average processing unit 33 detects the light detection signal in FIG. The interval between the two sections can be set so as to obtain the moving average of the section including the local minimum value.

  In addition, although the form which calculates | requires the difference of the moving average of two areas is demonstrated, the structure which calculates | requires the difference of the total of the moving average of several 1st area, and the total of the moving average of several 2nd area, You can also For example, while each of the three first sections obtains a moving average of sections including different maximum values of the photodetection signal in FIG. 4A, each of the three second sections includes the photodetection signal. A total of six intervals can be set so as to obtain a moving average of intervals including different local minimum values. That is, each section can be set so that the phases of the light detection signals in the plurality of first sections are in phase, and the phases of the light detection signals in the plurality of second sections are in phase. The number of sections, the length of each section, and the interval between sections can be set to various values other than those described above, but basically the detection image 40 formed on the intermediate transfer belt 8 can be set. It is set to a state where contrast due to presence / absence and density difference can be detected. In the present embodiment, the case of two sections having the simplest configuration is illustrated, but other numbers may be used.

  The scattered light removal signal output from the scattered light removal unit 30 is input to the amplitude data generation unit 50 and the timing data generation unit 60. The amplitude detector 51 of the amplitude data generator 50 detects the amplitude value of the scattered light removal signal. The detected amplitude value of the scattered light removal signal is stored by the amplitude data management unit 52 and managed as data corresponding to the intensity of the reflected light amount from the detected image 40, for example, density information. In addition, the timing detection unit 61 of the timing data generation unit 60 detects the timing at which the scattered light removal signal exceeds the threshold value. The detected timing data is position information corresponding to the formation position of the detected image 40, and can be handled as color misregistration information by managing the relative relationship of the timing data with respect to the detected image 40 of each color.

  For example, the maximum density and halftone gradation characteristics of each color are corrected by feeding back density information to process formation conditions such as the voltage conditions of each bias and the power of laser light. Further, based on the color misregistration information, the color misregistration is corrected by adjusting the writing position in the main scanning and sub scanning directions and the image clock for each color. As described above, the line includes not only a solid line but also a broken line such as a broken line or a dotted line. In the above-described embodiment, the line of the detection image 40 is a direction orthogonal to the moving direction of the intermediate transfer belt 8. For example, even if the line is obliquely drawn with respect to the orthogonal direction, good. That is, the detected image 40 may be an image in which the toner amount (developer amount) regularly changes in the moving direction of the intermediate transfer belt 8 and includes a line in a direction different from the moving direction of the detected image 40. be able to.

  In addition, since the optical sensor 27 of the present embodiment has a configuration without a light aperture mechanism, it can be downsized to a fraction of the conventional size, and the scattered light component from the detection image 40 can be reduced. It is possible to generate a signal removed with high accuracy. Furthermore, since there is no diaphragm mechanism, it is possible to increase the detection resolution without causing problems due to manufacturing variations. Furthermore, since the detection resolution is high, it is possible to reduce the size of an image used for color shift and density detection.

  The signal waveforms shown in FIGS. 4 and 5 are obtained when the intermediate transfer belt 8 having a very smooth surface is used. However, many surfaces of the intermediate transfer belt 8 have irregularities. This unevenness causes a shake (hereinafter referred to as belt surface noise) in the light detection signal. In the optical sensor 27 exemplified in the present embodiment, the light emitting area of the light emitting element 272 and the light receiving area of the light receiving element 277 are set to several tens μm to several hundreds μm, and therefore several tens μm to several hundreds μm on the surface of the intermediate transfer belt 8. If there is unevenness, a relatively large belt surface noise is generated. When this belt surface noise is superimposed on the light detection signal, the detection accuracy may be lowered. Therefore, in the case of a density where detection accuracy is important, it is sufficient to reduce the error due to the influence of the belt surface noise as much as possible.

  FIG. 7A is an enlarged view of the waveform of FIG. The detection image 40 was formed so that the line width and the space width were each 0.55 mm. The light receiving region of the light receiving element 277 has a width (length) in the sub-scanning direction. Therefore, the light receiving element 277 simultaneously receives regular reflection light from the region on the intermediate transfer belt 8 according to the width of the light receiving region in the sub-scanning direction. For this reason, the change in the amount of light received by the light receiving element at the boundary between the line and the space of the detected image 40 is averaged by the width of the light receiving region in the sub-scanning direction. Therefore, even if the reflection characteristic changes greatly at the boundary between the space and the line of the detected image 40, the light detection signal does not change abruptly, and the inclination becomes dull by averaging. That is, the inclination of the light detection signal becomes smaller as the width of the light receiving region in the sub-scanning direction becomes larger. In this example, the width of the light receiving region in the sub-scanning direction is 160 μm. At this time, the light receiving element 277 simultaneously receives regularly reflected light in the range of a length of 80 μm in the sub-scanning direction of the surface of the intermediate transfer belt 8.

  In FIG. 7B, the interval between the two intervals shown in FIG. 5A is set to 0.55 mm which is half the pitch of the line, and the length of the interval, that is, the length of the period for obtaining the average value is set. It is a signal waveform when it is changed. Specifically, a broken line wa in FIG. 7B is a scattered light removal signal when the lengths of the two sections are set to 0.55 mm, which is the same as the line width. Similarly, the solid line wb is a waveform when the length of the two sections is set to 0.45 mm which is 0.1 mm smaller than the line width. Further, the dotted line wc is a waveform when the length of the two sections is set to 0.05 mm which is 0.5 mm smaller than the line width.

  The amplitude value of the scattered light removal signal becomes larger as the section length is shortened as indicated by the solid line wb and the dotted line wc, as compared with the broken line wa having a wider section length. However, in the waveform of the dotted line wc narrowed to the section length of 0.05 mm, it can be seen that although the amplitude value is increased, a relatively large belt surface noise is superimposed at the amplitude peak. That is, if the section length is narrowed while maintaining the same section interval, the signal amplitude increases, but the belt surface noise also increases. Hereinafter, the condition of the section length where the S / N ratio is optimum will be described by defining the signal-to-noise ratio (S / N ratio) = (signal amplitude / belt surface noise).

  In the following description, the line width = space width is a reference section length, and the difference between the line width / space width and the line length / space width is the section length reduction amount. FIG. 8A shows the relationship between the section length reduction amount and the signal amplitude value that is the amplitude in one cycle of the scattered light removal signal. FIG. 8A shows that the signal amplitude value is minimum when the section length reduction amount is 0 mm, and increases when the section length reduction amount is increased. However, it is not a proportional relationship. First, when the section length reduction amount is increased from 0 mm, the signal amplitude increases sharply. This is because the time length of averaging at the rising and falling portions of the signal in FIG. As shown in FIG. 8A, when the amplitude increases to some extent, the increase amount of the amplitude value becomes dull even if the interval length decrease amount is increased thereafter. If the section length reduction amount is further increased, the amplitude value again increases sharply due to the influence of the belt surface noise superimposed on the signal waveform.

  Next, the relationship between the section length reduction amount and the belt surface noise will be described. FIG. 8B shows the relationship between the section length reduction amount and the noise amplitude value in one cycle of the scattered light removal signal. When the section length reduction amount is 0.35 mm or more, that is, the section length is 0.2 mm or less, the amplitude value of the belt surface noise increases sharply. This is due to the uneven shape of the surface of the intermediate transfer belt 8 used for this measurement. As a result of the verification, the noise period due to the unevenness on the surface of the intermediate transfer belt is formed around 0.2 mm. Therefore, if the section length is made smaller than 0.2 mm, the belt surface noise cannot be averaged, and the noise is reduced. The level has risen sharply.

  FIG. 8C shows the relationship between the S / N ratio and the section length reduction amount determined from the signal amplitude value of FIG. 8A and the noise amplitude value shown in FIG. 8B. In this example, the S / N ratio becomes maximum when the section length reduction amount is 0.1 mm, that is, when the section length is 0.45 mm.

  Further, the line width and space width other than the line width and space width in FIG. 7A were also measured, but the results were the same. The amount of decrease in the section length that maximizes the S / N ratio is almost constant regardless of the line width and section interval. This is because the rising and falling slopes of the signal waveform hardly change even when the line width is changed. It is. Therefore, in the above-described example, a high S / N ratio can be ensured by setting the section length to be 0.1 mm smaller than the line width of the detected image 40.

  However, the noise cycle of the intermediate transfer belt 8 that affects the S / N ratio varies depending on the material and type of the intermediate transfer belt 8. Therefore, the numerical value of the section reduction amount of 0.1 mm is an example, and the optimal section length reduction amount varies depending on the material and surface state of the intermediate transfer belt 8, the size of the light receiving element 277, and the like.

  Note that the intermediate transfer belt 8 mounted on the image forming apparatus has unevenness of several hundred μm or more that causes disturbance of the image that can be recognized by humans, even if there are unevenness of the belt surface that is below the level that cannot be recognized by humans due to its use. There is hardly any. Here, the noise increases sharply when the section length becomes less than or equal to the level of the unevenness. On the other hand, the signal amplitude value in FIG. 8A does not depend on the surface shape of the intermediate transfer belt 8 but depends on the slope of the signal waveform. Therefore, regardless of the material of the intermediate transfer belt 8 and the surface state, the highest S / N ratio can be obtained by setting the section length slightly smaller than the line width. If a high S / N ratio can be obtained, the accuracy of detecting the concentration can be increased.

  Further, if a high S / N ratio is obtained, it is effective even when the position of the detected image 40 is detected. FIGS. 9A and 9B show light detection when a detection image 40 including one line is measured using the intermediate transfer belt 8 having unevenness of several tens μm to several hundreds μm on the surface. The signal and the scattered light removal signal are shown. As in FIG. 5, waveforms are shown for the case of a color with a lot of scattered reflected light (left side in the figure) and the color with a small amount (right side in the figure). The position of the detected image 40 can be detected by comparing the scattered light removal signal shown in FIG. 9B with a threshold value. FIG. 9B shows a settable range of the threshold in consideration of the belt surface noise. If the belt surface noise is small, the settable range of the threshold is widened. In other words, the higher the S / N ratio, the wider the threshold setting range, and the greater the resistance to erroneous detection against irregularly generated noise or the like.

  The influence on the inclination of the light detection signal waveform has been described using an example in which the light receiving element 277 having a light receiving region width of 160 μm in the sub-scanning direction is used. Here, when the light receiving element 277 whose width of the light receiving region in the sub-scanning direction is smaller than 160 μm is used, the inclination of the light detection signal becomes steeper than that shown in FIG. growing. As a result, the section length reduction amount that maximizes the S / N ratio is smaller than when the length of the light receiving region in the sub-scanning direction is 160 μm. Thus, the slope of the signal waveform can change depending on the length of the light receiving element 277 in the sub-scanning direction.

  However, the slope of the signal waveform does not depend only on the length of the light receiving area of the light receiving element 277 in the sub-scanning direction, but can be changed by subsequent processing, for example, averaging light detection signals or removing noise with a low-pass filter. it can. Therefore, even when a light receiving element having a shorter light receiving area length is used, it is possible to generate a signal having the same slope by the subsequent processing and obtain a signal having the maximum S / N ratio with the same section length reduction amount. It is. That is, the maximum S / N ratio can be obtained by optimally setting the interval reduction amount according to the slope of the signal waveform before differential processing.

<Second embodiment>
In the first embodiment, the reflected light when the intermediate transfer belt 8 is irradiated with the divergent light beam of the point light source is detected using the single light receiving element 277. In the present embodiment, it will be described that even if a light receiving element array including a plurality of light receiving elements is used, the influence of scattered reflected light can be reduced as in the first embodiment. In the following description, differences from the first embodiment will be mainly described, and description of parts similar to those of the first embodiment will be omitted.

  11A, 11B, and 11C are explanatory views of scattered light removal of the first embodiment using a single light receiving element 277. FIG. In addition, although irradiation light uses the divergent light beam of a point light source, since the figure becomes complicated, the description is abbreviate | omitted. FIG. 11A shows a state in which the light receiving element 277 receives specularly reflected light from the region indicated by B3 of the intermediate transfer belt 8. FIG. The scattered reflected light from the line of the detection image 40 arranged in the region B2 is also received. After that, the intermediate transfer belt 8 is rotationally driven, and the state where the line of the detection image 40 reaches the reflection position of the regular reflection light to the light receiving element 277 is shown in FIG. The light receiving element 277 receives almost no specularly reflected light but receives scattered reflected light from the line arranged in the region B2. FIG. 11C shows a state in which the intermediate transfer belt 8 is further driven to rotate and receives regular reflection light from the region B1. Even in this state, the scattered reflected light from the line in the region B2 is received. That is, the scattered reflected light is received in any of the states of FIGS. 11A to 11C, but the specularly reflected light is hardly received in the state of FIG. 11B. Therefore, as described in the first embodiment, the striped detection image 40 is formed so that the scattered reflected light is in a uniform state, and the moving average value of each section is differentially calculated, thereby scattering. A signal from which reflected light is removed can be generated.

  11D and 11E are explanatory views of scattered light removal using the light receiving element array 280 according to the present embodiment. In the present embodiment, for the sake of convenience of explanation, the simplest case of two light receiving elements will be described. However, the number of light receiving elements may be three or more. Note that the divergent light beam of the point light source is used for the irradiation light, but the illustration is partially omitted because the figure becomes complicated. In FIG. 11D, the light receiving element 282 receives the specularly reflected light from the region indicated by B3 of the intermediate transfer belt 8, and the other light receiving element 281 receives the specularly reflected light due to the presence of the line of the detection image 40. It is in a state of hardly receiving light. Thereafter, the surface of the intermediate transfer belt 8 moves, and the state where the line of the detection image 40 reaches the reflection position of the regular reflection light to the light receiving element 282 is shown in FIG. Therefore, the light receiving element 282 hardly receives regular reflection light. However, in the state of FIG. 11E, the light receiving element 281 receives regular reflection light. In addition, about the scattered reflected light in the line of the detection image 40, both the light receiving element 281 and the light receiving element 282 are light-receiving in both the state of FIG.11 (D) and FIG.11 (E). Therefore, a signal obtained by removing the scattered reflected light from the detected image 40 is generated by differentially processing the light detection signal corresponding to the amount of light received detected simultaneously by the light receiving elements 281 and 282. It becomes possible to do.

  FIG. 10 is a schematic configuration diagram of a light detection system according to this embodiment. As shown in FIG. 10, the optical sensor 27 in the present embodiment includes a light receiving element array 280, and the light receiving element array 280 includes light receiving elements 281 and 282. Currents corresponding to the amounts of light received by the light receiving elements 281 and 282 are converted into light detection signals by the detection circuit 273 and the detection circuit 274 of the processing circuit 275, respectively, and output to the differential processing unit 290. The differential processing unit 290 generates a signal from which the scattered reflected light component is removed by performing differential processing on the input light detection signal. In the present embodiment, each of the light receiving element 281 and the light receiving element 282 is a single light receiving element. However, a configuration in which a plurality of light receiving elements 281 and a plurality of light receiving elements 282 are alternately arranged in the sub-scanning direction to perform differential processing of the total light receiving amount of the plurality of light receiving elements 281 and the total light receiving amount of the plurality of light receiving elements 282. It can also be. In the first embodiment, this corresponds to a configuration for obtaining a difference between the sum of moving averages of a plurality of first sections and the sum of moving averages of a plurality of second sections. In the present embodiment, the arrangement distance between the light receiving element 281 and the light receiving element 282 corresponds to the section interval in the first embodiment.

  Hereinafter, as in the first embodiment, the signal processing unit 28 detects density information and color misregistration information for each color by using amplitude value information and timing information of a signal from which scattered reflected light has been removed. The present embodiment is a method for detecting regularly reflected light at different sub-scanning positions of the intermediate transfer belt 8 using a plurality of light receiving elements at the same time timing. Therefore, there is an advantage that a simple configuration can be obtained for signal processing and the like. Further, there is an advantage that a signal obtained by removing the scattered reflected light from the detected image 40 can be monitored in real time.

  Further, as in the first embodiment, the light in the sub-scanning direction of the light receiving region of the light receiving element is determined by the width at the position of the light receiving element of the light regularly reflected with a width equal to the line width of the detection image 40 on the intermediate transfer belt 8. By reducing the width, the S / N ratio can be increased. This corresponds to setting the section length of the first embodiment shorter than the line width.

  In the first embodiment, differential processing is performed at different time positions of signals indicating temporal changes in the amount of received light detected using one light receiving element. This is to take the difference in the amount of reflected light including the specularly reflected light components from different positions on the surface of the detection image 40 and the surrounding intermediate transfer belt 8 when the detection image 40 passes through the irradiation region of the light emitting element 272. . For example, in the first embodiment, the differential processing between the first time position of the detection signal and the second time position after the first time position is performed. Note that the position on the detection image 40 that is the reflection position of the regular reflection light to the light receiving element 277 in the first time is the first position, and the reflection position of the regular reflection light to the light reception element 277 in the second time. The position of a certain detected image 40 or the surface of the intermediate transfer belt 8 is defined as a second position. In this case, the distance between the first position and the second position is equal to a value obtained by multiplying the moving speed of the surface of the intermediate transfer belt 8 by the difference between the first time and the second time. Therefore, performing the differential processing between the first time position and the second time position means that the total amount of light received when the light receiving element 277 receives specularly reflected light from the first position and the light receiving element 277 This corresponds to performing differential processing with the total amount of light received when regular reflection light is received from the second position. Here, the amount of reflected light including the specularly reflected light component is not only the space where the detection image 40 is received or the state of receiving strong specularly reflected light from the surface of the intermediate transfer belt 8, but is also scattered and reflected by the line. It is assumed that the specular reflection light component includes zero or a very small state. Furthermore, in the first embodiment, the values of the first time position and the second time position are set as the average value of the section, and this section is made shorter than the time during which the intermediate transfer belt 8 moves by the line width of the detected image 40. It was. This is equivalent to taking an average value while receiving regular reflection light from the region of the intermediate transfer belt 8 shorter than the line width of the detection image 40. In other words, in the above-described embodiment, the total amount of received light while the regular reflection light from the first area of the detection image 40 is received, and the second area on the surface of the detection image 40 and the surrounding intermediate transfer belt 8 are detected. This is equivalent to taking the difference in the total amount of received light while receiving the regular reflection light.

  In the second embodiment, a plurality of, for example, two light receiving units each including one light receiving element are used, and a differential signal at the same time position of a signal indicating a temporal change in the amount of received light detected by each light receiving unit. It was what was to be processed. Since the arrangement positions of the light receiving portions cannot be the same and are different, this is the difference in the amount of reflected light including the specularly reflected light components from different positions on the detected image 40 and the front and back surfaces of the intermediate transfer belt 8. Is. For example, in the second embodiment, the two light receiving units, the first light receiving unit and the second light receiving unit, are arranged in the sub-scanning direction, the first light receiving unit outputs the first detection signal, and the second light receiving unit. Assume that the unit outputs the second detection signal. In the first time when the first light receiving unit receives specularly reflected light from the first position of the detection image 40, the detection image 40 or the intermediate transfer that becomes the reflection position of the specularly reflected light to the second light receiving unit A position on the surface of the belt 8 is defined as a second position. In this case, the distance between the first position and the second position is a distance corresponding to the distance between the first light receiving unit and the second light receiving unit. For example, when two light receiving parts are arranged as shown in FIG. 11D, the distance between the first position and the second position is half of the distance between the first light receiving part and the second light receiving part. . In this case, performing the differential processing of the first time position value of the first detection signal and the second detection signal means that the first light receiving unit receives the specularly reflected light from the first position, This corresponds to performing differential processing of each received light amount when the two light receiving portions receive regular reflection light from the second position. That is, in both the first embodiment and the second embodiment, the difference in the amount of reflected light including the specularly reflected light components from different positions on the detected image 40 and the front and back surfaces of the intermediate transfer belt 8 is obtained.

  Since the light receiving area of the light receiving unit is not a line in the main scanning direction but has a certain width in the sub scanning direction, the light receiving unit is regularly reflected from a certain width in the sub scanning direction of the detection image 40 and the intermediate transfer belt 8. Receive light simultaneously. This corresponds to obtaining the average value of the amount of received light in the sub-scanning direction. That is, in the first embodiment, the average value of the section is obtained and the differential processing is performed. However, the length of the section in the first embodiment is the length of the light receiving region of the light receiving unit in the sub scanning direction in the second embodiment. It corresponds to. Therefore, if the length of the section in the first embodiment is made shorter than the time required to move the line width of the detection image 40, the length in the sub-scanning direction of the light receiving region of the light receiving unit is reflected by the entire line width. This corresponds to making the reflected light shorter than the length in the sub-scanning direction at the position of the light receiving portion. In the second embodiment, the interval between the two intervals for performing the differential processing in the first embodiment corresponds to the arrangement interval in the sub-scanning direction of the two light receiving elements. It should be noted that one light receiving section may not be a form including one light receiving element, but one light receiving section may include a plurality of light receiving elements.

  Furthermore, it can be said that both the first embodiment and the second embodiment perform differential processing by shifting the phase of the light detection signal. Specifically, in the first embodiment, this is equivalent to performing a differential process by branching one photodetection signal into two and delaying one photodetection signal by a predetermined amount. Here, the predetermined amount to be delayed is equal to the section interval in the first embodiment. Of course, instead of simply shifting the phase, it is also possible to perform differential processing by moving average processing. In the second embodiment, the first light receiving unit and the second light receiving unit perform differential processing of the respective light detection signals. The first light receiving unit and the second light receiving unit are arranged at their positions. Therefore, the light detection signals of the first light receiving unit and the second light receiving unit are out of phase with each other. The phase difference in this case corresponds to the distance between the arrangement positions of the first light receiving unit and the second light receiving unit.

<Other embodiments>
Although the present invention has been described by taking the image forming apparatus as an example, it can also be mounted as a detection apparatus that can be mounted on the image forming apparatus or the like. The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (15)

An image carrier;
Irradiating means for irradiating light toward the image carrier;
A light receiving unit that receives reflected light of the light irradiated by the irradiation unit and outputs a detection signal according to the amount of received light;
Forming means for forming a detection image on the image carrier including a line formed by one or more developers in a direction different from a moving direction of the image carrier;
Detection means for detecting position information or density information of the detection image based on the detection signal output by the light receiving means while the detection image formed on the image carrier passes through an irradiation region by the irradiation means;
With
The detection means includes a value of the detection signal corresponding to a received light amount including a specularly reflected light component from the detection image and a first region of the surface of the image carrier, and the detection image and the surface of the image carrier. Detecting position information or density information of the detected image by a signal corresponding to a difference in value of the detection signal corresponding to the amount of received light including the specularly reflected light component from the second region of
The length in the moving direction of each of the first area and the second area is shorter than the length of the line in the moving direction.   The image forming apparatus according to claim 1, wherein the irradiation unit irradiates the image carrier with a divergent light beam.   The reflected light from the image carrier is received by the light receiving means and converted into the detection signal without passing through an optical member for focusing or condensing the light. The image forming apparatus according to 2. The detected image includes a plurality of lines in a direction orthogonal to the moving direction,
The interval between the plurality of lines is an interval at which the vibration of the amount of scattered reflected light from the detection image received by the light receiving means due to the movement of the detection image becomes a predetermined amount or less. The image forming apparatus according to any one of the above.   4. The image forming apparatus according to claim 1, wherein the detected image includes one line in a direction orthogonal to the moving direction. 5. An image carrier;
Irradiating means for irradiating light toward the image carrier;
A light receiving unit that receives reflected light of the light irradiated by the irradiation unit and outputs a detection signal according to the amount of received light;
Forming means for forming a detection image on the image carrier including a line formed by one or more developers in a direction different from a moving direction of the image carrier;
Detection means for detecting position information or density information of the detection image based on the detection signal output by the light receiving means while the detection image formed on the image carrier passes through an irradiation region by the irradiation means;
With
The detection means detects position information or density information of the detected image based on a signal according to a difference between an average value of a first section of the detection signal and an average value of a second section of the detection signal,
The image forming apparatus, wherein the first section and the second section are shorter than a time required for the image carrier to move by a length of the line in the moving direction. The detected image includes a plurality of lines in a direction orthogonal to the moving direction,
The interval between the first section of the detection signal and the second section of the detection signal is different from the period of vibration generated in the detection signal as the plurality of lines of the detection image move. The image forming apparatus according to claim 6. The detected image includes a plurality of lines in a direction orthogonal to the moving direction,
The interval between the plurality of lines is an interval at which the vibration of the amount of scattered reflected light from the detection image received by the light receiving unit due to the movement of the detection image becomes a predetermined amount or less. The image forming apparatus described in 1. An image carrier;
Irradiating means for irradiating light toward the image carrier;
One or more first light receiving means for receiving reflected light of the light emitted by the irradiating means and outputting a first detection signal corresponding to the amount of received light;
One or more second light receiving means for receiving reflected light of the light emitted by the irradiating means and outputting a second detection signal corresponding to the amount of received light;
Forming means for forming, on the image carrier, a detection image including a line of one or more developers in a direction orthogonal to the moving direction of the image carrier;
The first detection signal and the one or more second light output by the one or more first light receiving means while the detection image formed on the image carrier passes through the irradiation region by the irradiation means. Detecting means for detecting position information or density information of the detected image based on the second detection signal output by the light receiving means;
With
The detecting means detects position information or density information of the detected image by a signal corresponding to a difference between a sum of the first detection signals and a sum of the second detection signals;
The length in the moving direction of the light receiving area of each of the one or more first light receiving means is the length of the light regularly reflected at the position of the image carrier separated by the length in the moving direction of the detection image line. Shorter than the length in the moving direction at the position where the one or more first light receiving means are disposed,
The length of the light receiving area of each of the one or more second light receiving means is the length of the light regularly reflected at the position of the image carrier separated by the length of the moving direction of the line of the detection image. An image forming apparatus having a length shorter than a length in the moving direction at a position where the one or more second light receiving units are arranged. The detected image includes a plurality of lines in a direction orthogonal to the moving direction,
In the first detection signal and the second detection signal, vibration occurs due to movement of the plurality of lines of the detection image,
The image according to claim 9, wherein the first light receiving unit and the second light receiving unit are arranged so that phases of the first detection signal and the second detection signal are different from each other. Forming equipment. The detected image includes a plurality of lines in a direction orthogonal to the moving direction,
The interval between the plurality of lines is an interval at which the vibration of the amount of scattered reflected light from the detection image received by the first light receiving unit and the second light receiving unit is not more than a predetermined amount due to the movement of the detection image. The image forming apparatus according to claim 9, wherein the image forming apparatus is an image forming apparatus.   The position of an image to be formed is corrected using the position information, or the density of an image to be formed is corrected using the density information. Image forming apparatus. Irradiating means for irradiating light toward the image carrier;
A light receiving unit that receives reflected light of the light irradiated by the irradiation unit and outputs a detection signal according to the amount of received light;
The detection unit outputs the detection image formed on the image carrier including a line of one or more developers in a direction different from the moving direction of the image carrier through the irradiation region by the irradiation unit. Detecting means for detecting position information or density information of the detected image based on the detection signal;
With
The detection means includes a value of the detection signal corresponding to a received light amount including a specularly reflected light component from the detection image and a first region of the surface of the image carrier, and the detection image and the surface of the image carrier. Detecting position information or density information of the detected image by a signal corresponding to a difference in value of the detection signal corresponding to the amount of received light including the specularly reflected light component from the second region of
The length of the moving direction of each of the first region and the second region is shorter than the length of the line in the moving direction. Irradiating means for irradiating light toward the image carrier;
A light receiving unit that receives reflected light of the light irradiated by the irradiation unit and outputs a detection signal according to the amount of received light;
The detection unit outputs the detection image formed on the image carrier including a line of one or more developers in a direction different from the moving direction of the image carrier through the irradiation region by the irradiation unit. Detecting means for detecting position information or density information of the detected image based on the detection signal;
With
The detection means detects position information or density information of the detected image based on a signal according to a difference between an average value of a first section of the detection signal and an average value of a second section of the detection signal,
The detection apparatus according to claim 1, wherein the first section and the second section are shorter than a time required for the image carrier to move by a length of the line in the moving direction. Irradiating means for irradiating light toward the image carrier;
One or more first light receiving means for receiving reflected light of the light emitted by the irradiating means and outputting a first detection signal corresponding to the amount of received light;
One or more second light receiving means for receiving reflected light of the light emitted by the irradiating means and outputting a second detection signal corresponding to the amount of received light;
While the detection image including a line formed by one or more developers in a direction different from the moving direction of the image carrier formed on the image carrier passes through the irradiation region by the irradiation unit, the one or more one or more Detection means for detecting position information or density information of the detected image based on the first detection signal output from the first light receiving means and the second detection signal output from the one or more second light receiving means. When,
With
The detecting means detects position information or density information of the detected image by a signal corresponding to a difference between a sum of the first detection signals and a sum of the second detection signals;
The length in the moving direction of the light receiving area of each of the one or more first light receiving means is the length of the light regularly reflected at the position of the image carrier separated by the length in the moving direction of the detection image line. Shorter than the length in the moving direction at the position where the one or more first light receiving means are disposed,
The length of the light receiving area of each of the one or more second light receiving means is the length of the light regularly reflected at the position of the image carrier separated by the length of the moving direction of the line of the detection image. The detection apparatus, wherein the length is shorter than a length in the moving direction at a position where the one or more second light receiving means are arranged.

Images