JP2014119733A - Image forming apparatus and detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure necessary detection accuracy without the need to provide a diaphragm mechanism to an optical sensor used for color shift correction control and density correction control.SOLUTION: An image forming apparatus includes: light receiving means for receiving light radiated from irradiation means and reflected on an image carrier, and outputting detection signals according to the amount of received light; forming means for forming detection images that are developer images on the image carrier; and detection means for detecting position information or density information on the detection images on the basis of the detection signals output from the light receiving means in a period during which the detection images formed on the image carrier pass through an area irradiated with light by the 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 the detection signals corresponding to the amount of received light including regular reflection light components from a first position of the detection images and on the surface of the image carrier, and the average of the respective values of the detection signals corresponding to the amount of received light including regular reflection light components from a second position located on the downstream side in a direction of movement of the detection images with respect to the first position and from a third position located on the upstream side in the direction of movement of the detection images with respect to the first position.

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.

  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, which is a developer image, on the image carrier, and the light receiving means while the detection image formed on the image carrier passes through an irradiation region by the irradiation means. Detecting means for detecting position information or density information of the detection image based on the detection signal output from the detection means, the detection means from the first position on the surface of the detection image and the image carrier. The value of the detection signal corresponding to the amount of received light including the regular reflection light component, and the second position and the first position on the downstream side in the moving direction of the detection image with respect to the first position The upstream of the detected image in the moving direction The signal corresponding to the difference between the average value of the detection signal each value corresponding to the light receiving amount containing the specular reflection light component from the third position and detecting position information or density information of the detected image.

  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 scattered reflected light removal 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. The figure which shows the detection image containing the line of several intermediate density by one Embodiment. Explanatory drawing of the scattered reflected light removal in the detection image containing the line of a some intermediate density. Explanatory drawing of the process with respect to the detection image containing the line of the some intermediate | middle density by one Embodiment. Explanatory drawing of the difference between 3rd embodiment and other embodiment. 1 is a schematic configuration diagram of a detection system according to an embodiment. FIG. Explanatory drawing of the relationship between the detection image and light receiving element by one 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. 16 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.

  Note that, as shown in FIG. 4B, the waveform of the scattered image is slightly distorted at the end of the detection image 40 with much scattered reflection because the scattered reflected light component is not uniform. If this waveform distortion can be suppressed to a smaller level, the detection accuracy of the signal amplitude can be improved. Below, in order to improve this detection accuracy, the method of arrange | positioning two areas on the both sides before and behind the area 1, and taking a difference is demonstrated.

  FIG. 7A shows a waveform of the scattered reflected light component indicated by a dotted line in FIG. As the detection image 40 moves into the detection range of the optical sensor 27, the scattered reflected light gradually increases. Further, as the detection image 40 moves outside the detection range of the optical sensor 27, the scattered reflected light gradually becomes weak. Therefore, as shown in FIG. 7A, the temporal change of the scattered reflected light component to be received has a waveform with an inclination at both ends thereof.

  In the present embodiment, as shown in FIG. 7A, the section 2 is provided at a position earlier in time than the section 1, and the section 3 is provided at a position later in time than the section 1. Then, the difference between section 1 and sections 2 and 3 is taken. Note that the concept of setting the time interval between the interval 1 and the interval 2 and the time interval between the interval 1 and the interval 3 is the same as in the case of the two intervals, and can be set to the same time interval. FIG. 7B shows a waveform corresponding to the difference between the moving average values of the two sections 1 and 2 shown in FIG. Since the scattered reflected light component increases or decreases at the end of the detection image 40, the scattered reflected light component is not canceled out by the difference between the two sections, and thus the scattered light component remains even if differential processing is performed. In FIG. 7B, the remaining scattered light components are exaggerated for the sake of explanation.

  On the other hand, FIG. 7C shows the difference between the moving average value of section 1 and the moving average values of section 2 and section 3 as shown in FIG. In addition, the moving average value of the section 2 and the section 3 is an average value of the moving average value of the section 2 and the moving average value of the section 3. As shown in FIG. 7C, by providing two sections 2 and 3 before and after section 1, the scattered reflected light components in the moving average values of sections 2 and 3 are within the moving average value of section 1. Accordingly, the remaining scattered reflected light component can be largely suppressed. 7A to 7C show only the scattered light component, FIG. 8 shows a light detection signal corresponding to the total amount of received light. The waveforms in FIGS. 8A and 8B are the same as those in FIGS. 4A and 4B. On the other hand, FIG. 8C shows a scattered light removal signal obtained by performing differential processing in the three sections shown in FIG. Compared with the form in which differential processing is performed in two sections shown in FIG. 8B, the scattered reflected light component is also present at the end of the detected image 40 where there is much scattered reflection in the waveform shown in FIG. It can be seen that it is greatly suppressed. Thereby, waveform distortion is suppressed, and the detection accuracy of the signal amplitude is improved. As a result, it is possible to detect the density of each color toner using the amplitude value information with higher accuracy.

  Note that the amplitude value (density value) can be detected by the same signal processing as shown in FIG. That is, it is possible to detect the density information of the detection image 40 of each color by the same processing even in the case where the toner scattering reflection is uneven or the toner scattering reflection is not uniform.

  Further, if the distortion of the signal waveform is suppressed, it is effective even when detecting the position information of the detected image 40, that is, the arrival timing. FIG. 9A shows a waveform corresponding to FIG. 5A, FIG. 9B shows a waveform corresponding to FIG. 5B, and section 1 and section 2 shown in FIG. The scattered light removal signal by the differential processing is shown. In FIG. 9B, the distortion of the waveform due to the residual scattered light component at the end of the detected image 40 is highlighted and displayed from FIG. 5B. As shown in FIG. 9B, the threshold value for detecting the position of the detected image 40 must be set so as to avoid waveform distortion. That is, if the waveform distortion increases, the threshold setting range becomes constrained.

  On the other hand, FIG. 9C shows the signal waveform of the difference obtained by obtaining the moving average values of the section 1, the section 2 and the section 3 shown in FIG. By obtaining the moving average values of the sections 2 and 3 provided before and after the section 1, the scattered reflected light component is greatly suppressed, and the distortion of the signal waveform is significantly suppressed. When the waveform distortion is suppressed, the setting range of the threshold value is widened. As a result, the possibility of erroneous detection due to irregularly generated noise or the like can be reduced when the position information of the detected image 40 is acquired.

  As described above, with respect to the light detection signal, the first section (section 1), the second section (section 2), and the third section in the first section in the earlier position and the later position in time. A section (section 3) is provided. Then, by obtaining the difference between the moving average value of the first section and the moving average value of the second section and the third section, it is possible to suppress the remaining scattered reflected light regardless of the amount of scattered reflected light. It becomes. As a result, the density of the detection image 40 of each color can be detected with higher accuracy. Furthermore, the position of the detected image can be detected with higher accuracy. In the detection image 40 including one line, the shorter the line width, the smaller the waveform distortion of the scattered light removal signal. Furthermore, the greater the distance between the intermediate transfer belt 8 and the optical sensor 27, the smaller the waveform distortion of the scattered light removal signal. 6, in the detection system of FIG. 6, in the detection system of FIG. 6, the moving average processing unit 32 obtains the moving average value of the section 1, and the moving average processing unit 33 calculates the moving average values of the section 2 and the section 3. It can be configured as desired.

  In FIGS. 7 to 9, differential processing is performed between one first section, one second section, and one third section, but one set of these three sections is used. It is also possible to adopt a configuration in which a plurality of sets are provided. At this time, the second section and the third section can be shared with other groups. For example, the second interval of the first set can be used as the third interval of the second set that is earlier in time than the first set. Further, since the average value for each section is used, the widths of the first section to the third section need not be the same. For example, the second section and the third section can be half of the first section. This makes it easy to set each section to belong to one set when three sections are set as one set and a plurality of sets are provided. Furthermore, it is the structure which calculates | requires the difference of the 1st time position and the average value of a 2nd time position and a 3rd time position, moving these three time positions instead of the moving average value of an area. Also good. Note that the second time position is earlier than the first time position, and the third time position is later than the first time position. At this time, the time interval between the first time position and the second time position and the time interval between the first time position and the third time position can be made equal.

<Second embodiment>
In the present embodiment, a detection image 40 (hereinafter referred to as a gradation detection image) in which the density of each line is changed in stages is used.

  FIG. 10 shows a gradation detection image formed on the intermediate transfer belt 8. The line 81a of the gradation detection image in FIG. 10 has a density of 10%, the line 81b has a density of 20%, the line 81c has a density of 30%, and similarly, the density is increased in increments of 10%. The densities of the lines 81d, 81e, and 81f are 80%, 90%, and 100%, respectively. Note that the 10% increment is an example, and a line in which the density increases or decreases at an arbitrary increment can be used.

  FIG. 11A is a waveform showing the scattered reflected light component when the optical sensor 27 detects the gradation detection image shown in FIG. The scattered reflected light component gradually increases as the density of the gradation detection image increases. Since the increase amount increases as the density increases, the slope gradually increases. When the gradation detection image goes out of the detection range of the optical sensor 27, the scattered reflected light decreases with an inclination.

  FIG. 11B shows a waveform when a moving average value is obtained by setting two sections, as in the first embodiment. For the same reason as described in the first embodiment, waveform distortion due to the remaining reflected light component occurs at the rear end in the moving direction of the gradation detection image whose density changes greatly. On the other hand, on the front side in the moving direction of the gradation detection image, the density is low, and therefore there is little scattered reflected light, so that waveform distortion due to the remaining scattered reflected light hardly occurs. However, the remaining scattered reflected light component gradually increases as the concentration increases. That is, in the waveform shown in FIG. 11B, the amplitude gradually increases toward the position where the waveform distortion occurs at the rear end of the gradation detection image. As described above, when the gradation detection image is used, if differential processing is performed in two sections, a relatively large waveform distortion occurs at the end portion on the high density side, and the entire detection image also has a high density from the low density side. Waveform distortion occurs toward the side.

  FIG. 11C shows a waveform obtained by performing a differential process between the moving average value of section 1 and the moving average values of section 2 and section 3 shown in FIG. By performing the differential processing between the section 1 and the sections 2 and 3 provided before and after the section 1, the scattered reflected light component can be effectively suppressed even at the high density side end of the gradation detection image.

  FIGS. 11A to 11C show only the scattered reflected light component, but the light detection signal output from the optical sensor 27 and the scattered light removal signal obtained by differentially processing the light detection signal are shown in FIG. Shown in (A) to (C). FIG. 12A shows a light detection signal when a gradation detection image is detected. FIG. 12B shows a scattered light removal signal when differential processing is performed using only two sections. FIG. 11C shows sections 1 and 2 in FIG. It is a scattered light removal signal at the time of performing differential processing with section 3. In the waveform shown in FIG. 11B, the scattered reflected light component cannot be completely cancelled, a relatively large waveform distortion occurs at the end portion on the high density side of the detected image, and the waveform distortion also occurs in the entire detected image. . On the other hand, in the signal waveform shown in FIG. 12C, the inclined state of the scattered reflected light is canceled, and the distortion of the signal waveform is greatly suppressed. Therefore, the detection accuracy of the signal amplitude is improved.

<Third embodiment>
In the first embodiment, reflected light when irradiated with a divergent light beam from a point light source is detected using a 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.

  FIGS. 13A, 13 </ b> B, and 13 </ b> C are explanatory views of scattered light removal of the first embodiment using a single light receiving element 277. 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. In FIGS. 13A to 13F, the solid line indicates specularly reflected light, and the broken line indicates scattered reflected light. FIG. 13A 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. Scattered reflected light from the detection image 40 arranged in the region B2 is also received. Thereafter, 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 hardly receives specularly reflected light and receives scattered reflected light from a line arranged in the region B2. FIG. 13C 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. 13A to 13C, but the regular reflected light is not received in the state of FIG. 13B. Therefore, as described in the first embodiment, the scattered light component is accurately suppressed by subtracting the received light amount in the states (A) and (C) from the received light amount in the state of FIG. 13 (B). Can do.

  Subsequently, the present embodiment using the light receiving element array 280 including the light receiving elements 281, 282, and 283 will be described. In FIG. 13D, the light receiving element 281 receives the regular reflection light from the region B3 of the intermediate transfer belt 8, and the light reception element 283 receives the regular reflection light from the region B5. On the other hand, the light receiving element 282 receives almost no regular reflection light because there is a line of the detection image at the reflection position of the regular reflection light. FIG. 13E shows a state in which the intermediate transfer belt 8 has moved from FIG. 13D, and the light receiving element 282 receives regular reflection light from the region B3 of the intermediate transfer belt 8. On the other hand, since there is a line of the detection image at the reflection position of the regular reflection light to the light receiving element 281 and the light receiving element 283, these hardly receive the regular reflection light. In FIG. 13F, the intermediate transfer belt 8 further moves, and the light receiving elements 281 and 283 receive specularly reflected light, but the light receiving element 282 receives little specularly reflected light. .

  In addition, about the scattered reflected light from the detection image 40, the light receiving element 281, the light receiving element 282, and the light receiving element 283 are light-receiving in each state of FIG.13 (D)-(F). As the surface of the intermediate transfer belt 8 moves in this way, the amount of light received by each light receiving element sequentially changes according to the line of the detected image 40. In the present embodiment, the photodetection signal output from the light receiving element 282 and the photodetection signals of the light receiving elements 281 and 283 disposed on both sides of the light receiving element 282 in the moving direction of the detection image 40 are differential at the same time position. Process. With this configuration, it is possible to generate a signal that effectively removes scattered reflected light even at the end of the detected image 40.

  FIG. 14 is a schematic configuration diagram of the detection system according to the present embodiment. As shown in FIG. 14, 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, 282 and 283. Currents corresponding to the amounts of light received by the light receiving elements 281 to 283 are converted into light detection signals by the detection circuits 273, 274, and 279 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 has been removed by differential processing between the light detection signal from the detection circuit 274 and the light detection signals from the detection circuits 273 and 279. In this embodiment, the light receiving elements 281 to 283 are arranged in the order of the light receiving elements 281, 282, and 283 along the moving direction of the surface of the intermediate transfer belt 8, that is, the sub-scanning direction. In this embodiment, only one set of the light receiving elements 281 to 283 is provided, but a plurality of sets may be provided in the sub-scanning direction. In this case, the scattered light removal signal is the sum of signals obtained by performing differential processing for each set. In the first embodiment, this corresponds to a configuration for obtaining a difference between the moving average of the plurality of first sections and the moving average of the plurality of second sections and the plurality of third sections. Further, as described in the first embodiment, when a plurality of sets are provided, the light receiving elements 281 and 283 may belong to both adjacent sets. In the present embodiment, the distance between the light receiving element 281 and the light receiving element 282 corresponds to the time interval between the first section and the second section in the first embodiment. Similarly, the distance between the light receiving element 282 and the light receiving element 283 corresponds to the time interval between the first section and the third section in the first embodiment.

  Hereinafter, as in the first embodiment, the signal processing unit 28 detects density information and position 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.

  FIG. 15 is an explanatory diagram of the relationship between the line of the detected image 40 and the light receiving element array. Note that the lines in FIGS. 15A to 15C indicate shadows generated at the positions where the light receiving element arrays are arranged by the lines of the detection image 40. That is, the lines in FIGS. 15A to 15C are dark portions due to the lines of the detected image 40, and the areas between the lines in FIGS. 15A to 15C are bright portions due to the spaces in the detected image 40. Show. For example, assuming that the optical path length from the light emitting element to the detection image 40 is equal to the optical path length from the detection image 40 to the light receiving element array, the actual line width and space width of the detection image 40 are dark and bright as shown in FIG. Half the width of the part. In FIG. 15A, the light and dark widths of the detected image 40 and the lengths of the light receiving regions of the light receiving elements 281, 282 and 283 in the moving direction of the intermediate transfer belt 8 are the same. The three light receiving elements are respectively provided with a light receiving element 281 and a light receiving element 283 on both the front and rear sides in the sub-scanning direction with the light receiving element 282 as the center.

  In FIG. 15B, the size of the light receiving region of each light receiving element is the same as that in FIG. 15A, and the distance between the light receiving elements is set apart. 15A and 15B, the total light receiving area of the light receiving element 281 and the light receiving element 283 is twice the light receiving area of the light receiving element 281. When the length of each light receiving element in the main scanning direction is shorter than the length of the light and dark main scanning direction generated by the detection image 40, the total width of the light receiving regions of the light receiving element 281 and the light receiving element 283 in the sub scanning direction. The value is twice that of the light receiving element 281. In order to cancel the scattered reflected light component, the total amount of light received by the light receiving element 281 and the light receiving element 283 is divided by 2 to obtain an average value, and a differential operation is performed with the amount of light received by the light receiving element 282. That is, the signal for differential calculation is obtained from the same width of the light receiving element in the sub-scanning direction.

  15C, the line width and the space width are made larger than those in FIG. 15A, the width of the light receiving region of the light receiving element 282 in the sub scanning direction, and the sub scanning of the light receiving regions of the light receiving elements 281 and 283. The sum of the widths in the direction is made equal. In FIG. 15C, the widths of the light receiving regions of the light receiving elements 281 and 283 in the sub-scanning direction are each half the width of the light receiving region of the light receiving element 282 in the sub scanning direction. If the differential operation is performed after correcting the signal corresponding to the same width in the sub-scanning direction between the light receiving element arranged in the center and the two light receiving elements arranged on both sides of the light receiving element, the scattered reflected light component is canceled. It can be removed. As a result, it is possible to suppress the waveform distortion of the differential operation signal generated at the edge of the detected image and the like, and to generate a signal from which scattered reflected light is removed with higher accuracy.

  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 average value of the second time position earlier than the first time position and the third time position later than the first time position. Shall be performed. In addition, the position on the detection image 40 which is the reflection position of the regular reflection light to the light receiving element 277 in the first time to the third time is defined as the first position to the third position. In this case, the distance between the first position and the second position downstream of the first position is 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. Is equal to The same applies to the distance between the first position and the third position upstream of the first position. Therefore, performing the differential processing of the first time position and the second and third time positions means that the total received light amount when the regular reflection light is received from the first position, and the second and second time positions. This corresponds to performing differential processing with the average value of the total amount of light received when the regular reflection light is received from the position 3. 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.

  In the third embodiment, a plurality of, for example, three light receiving elements are used, and differential processing is performed at the same time position of signals indicating temporal changes in the amount of received light detected by the respective light receiving elements. Since the arrangement positions of the light receiving elements cannot be the same and are different, this is the difference between the reflected light amount including the specularly reflected light components from the different positions of the detected image 40 and the front and back surfaces of the intermediate transfer belt 8. It is what you take. For example, in the third embodiment, the second light receiving unit and the third light receiving unit are arranged on both sides of the first light receiving unit in the sub-scanning direction, and the first light receiving unit outputs the first detection signal, It is assumed that the second light receiving unit outputs a second detection signal and the third light receiving unit outputs a third detection signal. It is assumed that the length of the light receiving area of each light receiving portion is the same in the sub-scanning direction. In addition, the reflection position of the regular reflection light to the second light reception unit and the third light reception unit in the first time when the first light reception unit receives the regular reflection light from the first position of the detection image 40. The detected image 40 or the position on the surface of the intermediate transfer belt 8 is defined as the second position and the third 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 the optical path length from the light emitting element to the detection image 40 is equal to the optical path length from the detection image 40 to the light receiving unit, the distance between the first position and the second position is the first light receiving unit and the second light receiving unit. It is half the distance to the light receiving part. The same applies to the first position and the third position. In this case, the differential processing of the average value of the first detection signal and the second and third detection signals is performed by the amount of received light when the regular reflection light is received from the first position, This corresponds to performing differential processing with the average value of the amounts of received light when the regular reflected light is received from the second and third positions. That is, in both the first embodiment and the third embodiment, the difference in the amount of reflected light including the specularly reflected light components from different positions on the surface of the intermediate transfer belt 8 before and after the detected image 40 is obtained.

  The light receiving area of the light receiving element is not a line in the main scanning direction but has a certain width in the sub scanning direction. 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 differential processing is performed. However, the width of the section in the first embodiment is the length in the sub-scanning direction of the light receiving region of the light receiving element in the third embodiment. It corresponds to. In the third embodiment, the interval of the interval for performing the differential processing in the first embodiment corresponds to the arrangement interval of the light receiving elements in the sub-scanning direction.

  Furthermore, it can be said that both the first embodiment and the third embodiment perform differential processing by shifting the phase of the light detection signal. Specifically, in the first embodiment, one photodetection signal is branched into three, for example, the first photodetection signal has no delay, and the second photodetection signal has a first amount of delay. This is equivalent to performing the differential processing by giving the third light detection signal a delay twice as large as the first amount. Here, the first amount is equal to the section interval in the first embodiment. Of course, it is also possible to perform differential processing by performing moving average processing rather than simply performing differential processing by shifting the phase. And in 3rd embodiment, although the differential process of the light detection signal of each of several light-receiving parts is carried out, since the arrangement position of several light-receiving parts differs, the light detection signal of each of several light-receiving parts is They are out of phase with each other. The phase difference in this case corresponds to the distance between the arrangement positions of the light receiving units.

<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 (20)

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, which is a developer image, on 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 the value of the detection signal corresponding to an amount of received light including a specularly reflected light component from the detection image and a first position of the surface of the image carrier and the first position. Corresponding to the received light amount including the specularly reflected light component from the second position on the downstream side in the moving direction of the image and the third position on the upstream side in the moving direction of the detected image with respect to the first position. An image forming apparatus, wherein position information or density information of the detected image is detected by a signal corresponding to a difference between an average value of each value of the detection signals.   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.   4. The image formation according to claim 1, wherein a distance between the first position and the second position is equal to a distance between the first position and the third position. 5. apparatus. In the detected image, the developer amount changes in the moving direction of the detected image,
The distance between the image carrier and the light receiving means and the development of the detection image so that the vibration of the amount of scattered reflected light from the detection image received by the light receiving means is less than or equal to a predetermined amount due to the movement of the detection image. The image forming apparatus according to claim 1, wherein a change in the amount of the agent is set. The detected image includes a plurality of lines in a direction different from the moving direction of the detected image,
The image forming apparatus according to claim 1, wherein the plurality of lines of the detected image have different densities.   5. The image forming apparatus according to claim 1, wherein the detected image includes one line in a direction different from a moving direction of the detected image. 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, which is a developer image, on 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 first time position of the detection signal, a value of a second time position earlier than the first time position of the detection signal, and a time later than the first time position of the detection signal. An image forming apparatus, wherein position information or density information of the detected image is detected by a signal corresponding to a difference from an average value of third time position values.   9. The image forming apparatus according to claim 8, wherein a time interval between the first time position and the second time position is equal to a time interval between the first time position and the third time position. .   The value of the first time position is an average value of the first section of the detection signal, and the value of the second time position is an average value of a second section earlier than the first section. The image forming apparatus according to claim 8, wherein the value of the third time position is an average value of a third section that is later than the first section. The detected image includes a plurality of lines in a direction different from the moving direction of the detected image,
11. The interval between the plurality of lines is an interval in 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 falls within a predetermined amount. The image forming apparatus according to any one of the above. An image carrier;
Irradiating means for irradiating light toward the image carrier;
A 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;
A 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;
A third light receiving means for receiving reflected light of the light emitted by the irradiating means and outputting a third detection signal corresponding to the amount of received light;
Forming means for forming a detection image, which is a developer image, on the image carrier;
Each of the first light receiving means, the second light receiving means, and the third light receiving means outputs while the detection image formed on the image carrier passes through the irradiation region of the irradiation means. Detecting means for detecting position information or density information of the detected image based on the detection signal, the second detection signal, and the third detection signal;
With
The detection means detects position information or density information of the detected image by a signal according to a difference between the first detection signal and the second detection signal and the third detection signal,
The image forming apparatus, wherein the second light receiving unit and the third light receiving unit are arranged on both sides of the first light receiving unit in the moving direction of the detected image.   The image forming apparatus according to claim 12, wherein a distance between the first light receiving unit and the second light receiving unit is equal to a distance between the first light receiving unit and the third light receiving unit.   In the moving direction of the detected image, the total length of the light receiving areas of the second light receiving means and the third light receiving means is equal to the length of the light receiving area of the first light receiving means. The image forming apparatus according to claim 12 or 13. In the moving direction of the detection image, the length of the light receiving area of the second light receiving means and the third light receiving means is equal to the length of the light receiving area of the first light receiving means,
The detection means detects position information or density information of the detection image by differentially processing the first detection signal and an average value of the second detection signal and the third detection signal. The image forming apparatus according to claim 12, wherein the image forming apparatus is an image forming apparatus. The detected image includes a plurality of lines in a direction different from the moving direction of the detected image,
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 according to any one of the above.   17. 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;
Position information or density information of the detected image is detected based on the detection signal output by the light receiving unit while a detection image, which is a developer image formed on the image carrier, passes through an irradiation region by the irradiation unit. Detection means;
With
The detection means detects the value of the detection signal corresponding to an amount of received light including a specularly reflected light component from the detection image and a first position of the surface of the image carrier and the first position. Corresponding to the received light amount including the specularly reflected light component from the second position on the downstream side in the moving direction of the image and the third position on the upstream side in the moving direction of the detected image with respect to the first position. A detection apparatus that detects position information or density information of the detected image based on a signal corresponding to a difference between an average value of each value of the detection signals. 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;
Position information or density information of the detected image is detected based on the detection signal output by the light receiving unit while a detection image, which is a developer image formed on the image carrier, passes through an irradiation region by the irradiation unit. Detection means;
With
The detection means includes a value of the first time position of the detection signal, a value of a second time position earlier than the first time position of the detection signal, and a time later than the first time position of the detection signal. A detection apparatus that detects position information or density information of the detected image based on a signal corresponding to a difference from an average value of third time position values. Irradiating means for irradiating light toward the image carrier;
A 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;
A 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;
A third light receiving means for receiving reflected light of the light emitted by the irradiating means and outputting a third detection signal corresponding to the amount of received light;
Each of the first light receiving means, the second light receiving means, and the third light receiving means is detected while a detection image that is a developer image formed on the image carrier passes through an irradiation region by the irradiation means. Detecting means for detecting position information or density information of the detected image based on the first detection signal, the second detection signal, and the third detection signal to be output;
With
The detection means detects position information or density information of the detected image by a signal according to a difference between the first detection signal and the second detection signal and the third detection signal,
The detection apparatus, wherein the second light receiving means and the third light receiving means are arranged on both sides of the first light receiving means in the moving direction of the detection image.

Images