JP2010211118A - Image detecting device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately detect a speed of a moving medium for forming an image and to detect and correct the position shift and image density of respective colors of the formed image. <P>SOLUTION: Laser light is obliquely applied from a first light source 51 to the moving medium 53 through a collimating lens 52 and a speckle pattern of the reflected light is picked up by a first area sensor 56. A speed change is detected by the speckle pattern. Further, an image pattern is formed from reflected light 5 obtained by illumination from a second light source 61 to the moving medium 53 on a second area sensor 66 through a second imaging lens 64. Each color image pattern of a rectangular shape on the moving medium 53, which is formed on the second area sensor 66, is photoelectrically converted as an optical image, edge positions of both major sides of the image pattern are detected while setting a threshold and the center of the edge positions is set as a forming position. Based on a forming position of a leading color, time up to a forming position of each color toner is measured to obtain a position shift. Simultaneously, a reflection factor of the image pattern is detected while setting a threshold to obtain image density. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for handling multicolor images such as digital copying machines, printers, facsimiles, and the like by writing by laser scanning or writing by an ink jet method, and in particular, by detecting the speed of an intermediate transfer belt and a conveyance belt and forming the formed image. The present invention relates to an image detection apparatus that also detects pattern displacement or image density, and an intermediate transfer type or direct transfer type image forming apparatus including the image detection apparatus.

  In recent color image forming apparatuses, four photoconductors (image carriers) corresponding to toners of four colors (black, cyan, magenta, yellow) are arranged in parallel to meet the demand for higher speed. Tandem systems are becoming mainstream. In such a tandem system, each color toner image developed on each photoconductor needs to be finally superimposed on a recording medium such as paper (standard paper, postcard, cardboard, continuous paper, OHP sheet, etc.). There are two methods of superimposing: direct transfer method that directly superimposes on the recording medium and intermediate image that uses the intermediate transfer belt to superimpose the color toner images on the intermediate transfer belt and transfer them to the recording medium all at once. There are two transfer belt methods. If the conveyance belt for feeding a recording medium such as paper is not driven in the direct transfer method and the intermediate transfer belt is driven with high accuracy in the intermediate transfer belt method, color misregistration occurs.

  In response to such problems, in order to drive the intermediate transfer belt with high accuracy, for example, as disclosed in Patent Document 1, a mark is directly formed on the belt, and the belt speed fluctuation is detected by reading the mark. A method for realizing high-precision driving by feeding it back to a drive motor is known. Patent Document 2 discloses an embodiment in which high-precision paper conveyance is performed by detecting speckles of laser light from an observation object with a two-dimensional image sensor and performing drive control.

  On the other hand, an image formed by such an image forming apparatus is a “toner image”. As is well known, in order to obtain a good image, toner supplied to the development of an electrostatic latent image is used. The amount must be appropriate. The amount of toner supplied to the developing unit where the electrostatic latent image is developed is referred to as “toner density”. When the toner density is too low, a sufficient amount of toner is not supplied to the electrostatic latent image, and the resulting toner image is an image with insufficient image density. On the other hand, when the toner density is too high, the image density distribution of the toner image is biased toward “high density side”, and the toner image is also difficult to see. Thus, in order to form an appropriate toner image, the toner density must be in an appropriate range.

  Correspondingly, in order to control the toner density within an appropriate range, a method for detecting a change in reflected light by forming a toner pattern for detecting a toner density and irradiating it with detection light has been widely used. ing. An optical device that irradiates a toner pattern with detection light and receives reflected light is called a “reflective optical sensor”. Various reflective optical sensors have been proposed for a long time. (Refer to Patent Documents 3 to 6) These conventionally known reflection-type optical sensors include 1 to 3 light emitting units (LEDs) and 1 to 2 light receiving units (photodiodes or light receiving units) for receiving reflected light. Phototransistor).

  In order to perform the above-described high-precision paper conveyance drive control, for example, in the conventional technique described in Patent Document 1, since it takes a lot of time to directly form a mark on the intermediate transfer belt, mass productivity is poor. It became a factor of big cost increase. Apart from this, in order to detect the toner density, the difference between the reflection characteristic of the toner support and the reflection characteristic of the toner pattern is performed by a plurality of light emitting arrays and light receiving arrays. As described above, there is no disclosure of a method for simultaneously detecting the conveyance speed variation and the image density detection related to image formation.

  The present invention detects a change in speed of a moving medium (an intermediate transfer belt, a conveyance belt, or a recording medium such as paper) in an image forming apparatus with high accuracy and also detects an image density so that each color of a formed image is detected. An object of the present invention is to provide an image detection apparatus and an image forming apparatus capable of correcting the positional deviation of the image and correcting the gradation of the image.

  In order to achieve the above object, an image detection apparatus according to claim 1 of the present invention includes a first light source that emits coherent light, a second light source that emits non-interfering light, and a moving medium on which an image pattern is formed. And a light-receiving element array having a one-dimensional or two-dimensional light-receiving surface, and an imaging unit that forms an image of reflected light from the moving medium on the light-receiving element array. Are reflected on the first light receiving element array via the first imaging means, and a plurality of image signals that are different in time are acquired along with the movement of the moving medium. First detection means for detecting a moving speed of a moving medium by performing a cross-correlation calculation between two different image signals and obtaining a shift of a position where a correlation peak of the cross-correlation calculation occurs, and a second light source irradiates Reflected light from the moving medium An image pattern is formed from the image pattern of the image signal obtained by irradiation with the second light source by forming an image on the second light receiving element array via the image means, acquiring temporally different image signals as the moving medium moves. And a second detection means for detecting the image density, and the processing of the first detection means and the processing of the second detection means are performed in different time regions.

  With this configuration, it is possible to easily and accurately detect the speed fluctuation of the moving medium, and it is also possible to detect the positional deviation of each color image pattern formed on the moving medium and the image density of the image pattern.

  According to a second aspect of the present invention, there is provided an image detection apparatus including a first light source that emits coherent light, a second light source that emits non-interfering light, a moving medium on which an image pattern is formed, and a one-dimensional or two-dimensional light receiving surface. And an imaging means for forming an image of the reflected light from the moving medium on the light receiving element array, the reflected light from the moving medium by the irradiation of the first light source, and the second light source Processing of the first detection means for forming an image on the light receiving element array via the imaging means in which one set of each of the reflected light from the moving medium due to irradiation is arranged, and detecting the moving speed of the moving medium; The processing of the second detecting means for detecting the positional deviation of the image pattern and / or the image density is performed in different time regions.

  With this configuration, in addition to the above effects, the image detection apparatus can be further simplified, reduced in size, and reduced in cost.

  According to a third aspect of the present invention, in the image detection apparatus according to the first or second aspect, the time that the first light source used for processing of the first detecting means irradiates and the second light source used for processing of the second detecting means. The irradiation time of the first light source and the second light source is synchronized with the frame reading time of the light receiving element array and is shorter than the frame reading time interval for reading one frame. .

  With this configuration, in addition to the effects described above, highly accurate speed fluctuations and image pattern misregistration can be detected.

  According to a fourth aspect of the present invention, in the image detection apparatus according to any one of the first to third aspects, the displacement of the image pattern formed on the moving medium in the second detecting unit is detected by the first detecting unit. , And the imaging position of the image pattern on the light receiving element array on which the reflected light of the moving medium is imaged by irradiation of the second light source.

  With this configuration, it is possible to detect the displacement amount of the image pattern with high accuracy reflecting the real-time speed fluctuation of the moving medium.

  According to a fifth aspect of the present invention, an image forming apparatus includes a plurality of image carriers, a light scanning device that scans a light beam on the plurality of image carriers to form an electrostatic latent image, and a plurality of light scanning devices. Development means for visualizing the electrostatic latent image formed on the image carrier with each color toner, a movable intermediate transfer belt disposed opposite to the plurality of image carriers, and the image formed on the image carrier. A first transfer means for transferring the respective color toner images to the intermediate transfer belt, a second transfer means for further transferring the respective color toner images transferred on the intermediate transfer belt onto the sheet-like recording medium, and a recording medium 5. An image forming apparatus for forming a multicolor or color image, the image detecting apparatus according to any one of claims 1 to 4 being provided, and an intermediate transfer belt. Detecting moving speed and intermediate transfer belt And detecting the positional deviation, and / or image density of each color toner image.

  With this configuration, it is possible to provide an image forming apparatus capable of detecting the speed fluctuation of the intermediate transfer belt, the positional deviation of the toner image pattern on the intermediate transfer belt, and the image density.

  The image forming apparatus described in claim 6 includes a plurality of image carriers, a light scanning device that scans a light beam on the plurality of image carriers to form an electrostatic latent image, and a plurality of light scanning devices. A developing unit that visualizes the electrostatic latent image formed on the image carrier with each color toner, a conveyance transfer belt that conveys a sheet-like recording medium disposed opposite to the plurality of image carriers, and a conveyance transfer belt. The image forming apparatus includes a transfer unit that superimposes and directly transfers each color toner image visualized on a recording medium to be conveyed, and a fixing unit that fixes each color toner image transferred to the recording medium, thereby forming a multicolor or color image. 5. An image forming apparatus according to claim 1, wherein the image detecting device according to any one of claims 1 to 4 is provided to detect a moving speed of the transport transfer belt and to shift a position of each color toner image on a recording medium transported by the transport transfer belt. And / or image density And detecting.

  With this configuration, it is possible to provide an image forming apparatus capable of detecting the speed fluctuation of the transport transfer belt that transports a moving medium such as paper, the positional deviation of the toner image pattern formed on the moving medium, and the image density.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, a writing start position correcting means for correcting a writing start position by the light beam of the optical scanning device, and an intermediate transfer belt or a transfer transfer belt One or both of belt speed correction means for correcting the speed of the feed driving is provided, and correction is performed based on detection by the image detection apparatus.

  With this configuration, using the result detected by the image detection device, in addition to correcting the speed fluctuation of the moving medium, the positional deviation of each formed color image is detected and corrected, and a high-quality image with greatly reduced color deviation is obtained. Obtainable.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the fifth to seventh aspects, a means for correcting the image density for image formation is further provided, and correction is performed based on detection by the image detection apparatus. To do.

  With this configuration, it is possible to obtain a high-quality image in which the image gradation is appropriately corrected by correcting the image density using the result detected by the image detection device.

  According to the present invention, the speed of the moving medium is detected by detecting the speed fluctuation of the moving medium easily and with high accuracy, and further detecting the positional deviation of each color image pattern formed on the moving medium and the image density of the image pattern. In addition to correction of fluctuations, it is possible to detect and correct misregistration of each formed color image, further correct the image density, and obtain a high-quality image in which the color misregistration is greatly reduced and the image gradation is also corrected appropriately. There is an effect that can be done.

1 is a diagram illustrating a schematic configuration of an intermediate transfer type image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of a direct transfer type image forming apparatus according to an exemplary embodiment. Schematic configuration diagram showing an example of an optical scanning device developed in the image forming apparatus according to the present embodiment The figure which shows the structural example of the image detection apparatus of Example 1 in this embodiment. FIG. 6 is a diagram illustrating an example of the shape of a toner pattern for detecting a positional deviation of the toner image pattern according to the first exemplary embodiment. (A) formed on the area sensor of the first embodiment is a toner pattern image, and (b) is an image signal of the A pixel row. Detecting the image density of the toner pattern of the first embodiment (a) is a toner gradation pattern, (b) is an image reflectance plotted in the x direction, and (c) is a schematic diagram showing the image density. The figure which shows the structural example of the image detection apparatus of Example 2 in this embodiment. The figure which shows the structural example of the image detection apparatus of Example 3 in this embodiment. Timing chart of detection operation of image detection apparatus of embodiment 3 (A) formed on the area sensor of the third embodiment is a toner pattern image, and (b) is an image signal of an A pixel row. Timing chart of another detection operation of the image detection apparatus according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an intermediate transfer type image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a schematic configuration of a direct transfer type image forming apparatus.

  As shown in FIG. 1, an intermediate transfer type image forming apparatus is a tandem color machine that supports a color image and includes a plurality of photosensitive drums. The tandem color machine is a photosensitive drum for black (K). K1, charging unit K2, developing unit K4, cleaning unit K5, transfer charging unit K6, cyan (C) photosensitive drum C1, charging unit C2, developing unit C4, cleaning unit C5, and transfer charging unit C6, photosensitive drum M1 for magenta (M), charger M2, developing device M4, cleaning means M5, charging means M6 for transfer, photosensitive drum Y1 for yellow (Y), charger Y2, development Y4, cleaning means Y5, transfer charging means Y6, optical scanning device 20, intermediate transfer belt 105, fixing means 30, transfer roller 40, transport belt 41 It has a etc..

  The optical scanning device 20 includes a light emitting unit for black, a light emitting unit for cyan, a light emitting unit for magenta, and a light emitting unit for yellow. The light from the black light emitting unit is irradiated to the photosensitive drum K1 via the black scanning optical system, and the light from the cyan light emitting unit is irradiated to the photosensitive drum C1 through the cyan scanning optical system. The light from the light emitting unit for magenta is irradiated to the photosensitive drum M1 through the scanning optical system for magenta, and the light from the light emitting unit for yellow is irradiated to the photosensitive member through the scanning optical system for yellow. The drum Y1 is irradiated. An optical scanning device 20 may be provided for each color.

  Each photosensitive drum 1 rotates in the direction of the arrow in FIG. 1, and a charger 2, a developing device 4, a transfer charger 6, and a cleaning unit 5 are arranged in the order of rotation. Each charger 2 uniformly charges the surface of the corresponding photosensitive drum 1. The surface of the photosensitive drum 1 charged by the charger 2 is irradiated with light by the optical scanning device 20 so that an electrostatic latent image is formed on the photosensitive drum 1. Then, the corresponding developing device 4 forms a toner image of each color on the surface of the photosensitive drum 1. Further, the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 105 by the corresponding transfer charger 6, and finally transferred onto the paper medium from the intermediate transfer belt 105 by the transfer roller 40, and then on the transport belt 41. Then, the image is fixed on the paper medium by the fixing unit 30.

  In the direct transfer type image forming apparatus shown in FIG. 2, the surface of the photosensitive drum 1 is uniformly charged by each charger 2 by substantially the same processing, and the surface of the photosensitive drum 1 is applied to the surface of the photosensitive drum 1 from the optical scanning device 20. An electrostatic latent image is formed by the light irradiation. Then, the corresponding developing device 4 forms a toner image of each color on the surface of the photosensitive drum 1. Further, the corresponding transfer charger 6 sequentially transfers the toner images of the respective colors onto the paper medium conveyed on the conveyance transfer belt 106, and finally the image is fixed on the paper medium by the fixing unit 30.

  Here, in the image forming apparatus having the configuration shown in FIGS. 1 and 2, the intermediate transfer belt 105 is not driven with high accuracy in the case of the intermediate transfer method, and the conveyance transfer belt 106 is not driven with high accuracy in the case of the direct transfer method. Deviation occurs. In order to drive the belt with high accuracy, a method of making all the components with high accuracy is conceivable, but there are many components and it is difficult to realize from the viewpoint of cost.

  In view of this, it is conceivable to provide a detecting means for detecting the belt speed fluctuation and feed back the detection result to the belt driving motor. As a detecting means for detecting the speed fluctuation of the belt, in the above-mentioned Patent Document 1, a method of directly forming a mark on the belt is performed. However, it is difficult to directly process such a belt, Since it takes time to process, mass productivity is poor, which is also a factor of significant cost increase.

  The present invention is an image in which a speed change of a moving medium such as a belt can be easily detected without directly processing the belt, and a positional deviation and an image density of a toner image pattern formed on the belt can be simultaneously detected. A detection device is provided.

  FIG. 3 is a schematic configuration diagram illustrating an example of an optical scanning device developed in the image forming apparatus. The optical scanning device 20 will be described with reference to FIG. As shown in FIG. 3, four photosensitive drums 301, 302, 303, and 304 (corresponding to the photosensitive members 1 (K, C, M, and Y) in FIG. 1 or 2) are transferred to a transfer belt 400 (in FIG. 1). In the image forming apparatus for forming a color image by sequentially transferring toner images of different colors, the optical scanning devices are arranged along the moving direction of the intermediate transfer belt 105 or the transfer transfer belt 106 in FIG. Are integrally formed, and all light beams are scanned by a single optical deflector (for example, a polygon mirror) 1050. The polygon mirror 1050 has six surfaces and a two-stage structure.

  More specifically, the optical scanning device 20 includes a light source unit 1001, a single polygon mirror 1050 that deflects and scans a light beam from the light source unit 1001, and a light beam scanned by the polygon mirror 1050 as a photosensitive member. A scanning lens 1061 that forms an image on the surface to be scanned of the drum 302 is included, and here, scanning is performed for two stations in a direction facing the polygon mirror 1050. In FIG. 3, for simplification of explanation, three light source units for scanning the other photosensitive drums 301, 303, and 304 and the optical system after the scanning lens are omitted, and only one station is illustrated. ing.

  The light source unit 1001 includes a light source (for example, a semiconductor laser (LD), an LD array, etc.), a coupling lens, and an aperture. A light beam emitted from a light source (not shown) of the light source unit 1001 is converted into a substantially parallel light, a substantially divergent light beam, or a substantially convergent light beam by a coupling lens (not shown), and then cut into a desired light beam width by an aperture (not shown). A line image forming lens (for example, a cylindrical lens) 1041 is once condensed in the sub-scanning direction in the vicinity of the polygon mirror 1050, and a beam spot is formed on the image plane (scanned surface) 2001 by the scanning optical system including the scanning lens 1061. .

  As described above, the normal optical scanning apparatus employs a surface tilt correction optical system that once collects light in the sub-scanning direction in the vicinity of the polygon mirror in order to reduce deterioration of optical characteristics due to surface tilt between the mirrors of the polygon mirror 1050. ing. The scanning lens is made of resin, and one or more diffraction gratings may be formed on the optical surface. Normally, folding mirrors 1111 and 1121 are inserted between the light deflection means and the image plane, and the optical path is folded. Moreover, although the scanning optical system has been shown as an example constituted by a single scanning lens, two or more scanning lenses may be used. Here, writing start position correcting means (for example, a liquid crystal deflecting element) for correcting the writing start position by the optical scanning device is preferably provided between the coupling lens of the light source unit 1001 and the cylindrical lens (line image forming lens 1041). .

  FIG. 4 is a diagram illustrating a basic configuration example of the image detection apparatus according to the first embodiment of the present embodiment. The image detection apparatus has a function of detecting the moving speed of the moving medium as the first detecting means, and detecting the formation position deviation of the toner image pattern formed on the moving medium and the image density as the second detecting means in parallel therewith. have.

  As shown in FIG. 4, with respect to speed detection, the speed and speed fluctuation of a moving medium 53 (endless belt-like member such as an intermediate transfer belt or a conveyance transfer belt, or a drum-like member, or a recording medium such as paper) 53 are detected. A first light source 51 that emits laser light that is coherent light, a collimator lens 52 that makes the laser light emitted from the first light source 51 substantially parallel, and a one-dimensional or two-dimensional image can be acquired. A first area sensor 56 composed of a light receiving element array, a first imaging lens 54 and an aperture stop 55 provided between the moving medium 53 and the first area sensor 56 are provided.

  Then, the laser beam emitted from the first light source 51 and made substantially parallel light by the collimator lens 52 is irradiated obliquely onto the moving medium 53, and is one-dimensional or two-dimensional from the direction perpendicular to the moving plane of the moving medium 53. The first area sensor 56 takes an image. The moving medium 53 is a member having light diffusibility on the surface or inside thereof, and when irradiated with laser light, reflects the diffuse reflected light 57 having the distribution shown in FIG.

  In the image detection apparatus according to the first embodiment, another second light source 61 that emits non-interference light such as a light emitting diode (LED) as a light source, and a second light receiving element array that can acquire a one-dimensional or two-dimensional image. An area sensor 66 and a second imaging lens 64 provided between the moving medium 53 and the second area sensor 66 are provided.

  When a part of the diffusely reflected light 57 is taken into the first imaging lens 54 and imaged on the first area sensor 56, a random image pattern called a speckle pattern by the diffused laser light is obtained.

  This speckle pattern is a pattern corresponding to a fine random uneven shape on the surface or inside of the moving medium 53, and is formed by random interference of laser light. Therefore, when the moving medium 53 moves, the speckle pattern also moves. As a characteristic of the speckle pattern, the speckle pattern is not lost even when the imaging position is moved back and forth in the optical axis direction of the lens. Therefore, the image pattern corresponding to the uneven shape on the surface or inside of the moving medium 53 is very stable. Can be obtained. Therefore, a lens between the first area sensor 56 and the moving medium 53 is usually not necessary. However, when the moving medium 53 is tilted with respect to the moving plane due to some disturbance, the speckle pattern changes on the first area sensor 56 and is detected when a speed change described later is detected. An error will occur.

  Therefore, in order to avoid the above problem, the first imaging lens 54 is disposed between the first area sensor 56 and the moving medium 53 so that the moving medium 53 and the first area sensor 56 have a conjugate relationship of imaging. It is desirable to set so that As a result, even if the moving medium 53 is tilted with respect to the moving plane, the change in the speckle pattern on the first area sensor 56 can be reduced, and the speed detection error can be reduced. .

  The first imaging lens 54 is preferably set so that the moving medium 53 and the first area sensor 56 have an imaging conjugate relationship, but the first imaging lens 54 is not necessarily limited to this and is shifted from the imaging conjugate relationship. However, there is an effect of reducing the change amount of the speckle pattern due to the inclination of the moving medium 53. Therefore, if the inclination generated in the moving medium 53 is not so large, even if it is shifted from the conjugate relationship, it can be suppressed to a practically sufficient speed detection error.

  Further, it is desirable that the first imaging lens 54 is used at an imaging magnification for reducing and imaging the moving medium 53 on the first area sensor 56. By doing so, a wide range on the moving medium 53 can be reduced on the first area sensor 56, and the first area sensor 56 can be reduced in size. Further, by using the reduction optical system, the moving speed of the speckle pattern on the first area sensor 56 can be reduced even when the moving speed of the moving medium 53 is high. If the moving speed on the first area sensor 56 is low, the time interval for acquiring the speckle pattern can be lengthened. As a result, it is possible to increase the time for calculation processing and cope with high-speed movement of the moving medium 53. In addition, the processing speed of the electronic circuit can be reduced, and low power consumption and low cost can be realized.

  In the first embodiment, the collimating lens 52 illuminates the moving medium 53 with the laser light being substantially parallel light. However, the present invention is not limited to this, and the laser light is focused or diverged depending on the arrangement of the collimating lens. The moving medium 53 may be illuminated.

  The aperture stop 55 shown in FIG. 4 greatly affects the size of the minimum diameter of the speckle pattern on the first area sensor 56. At the time of detecting the speckle pattern, it is desirable that the minimum diameter of the speckle pattern on the first area sensor 56 is an appropriate size with respect to the size of one pixel of the first area sensor 56. The minimum diameter of the speckle pattern on the first area sensor 56 is directly proportional to the light source wavelength and inversely proportional to the angle at which the pupil diameter of the first imaging lens 54 is expected. The pupil diameter of the first imaging lens 54 is optimized by the aperture stop 55, and the minimum diameter of the speckle pattern is optimized with the size of one pixel of the first area sensor 56.

  In order to detect the velocity of the moving medium 53 from the one-dimensional or two-dimensional image acquired by the first area sensor 56, the cross-correlation function between the two speckle images acquired at the time interval τ is calculated and the mutual correlation function is calculated. A speckle pattern positional deviation amount Δ at a time interval τ is obtained from a position where a correlation peak occurs.

  From the above time interval τ and the peak position deviation amount Δ, the moving speed v of the moving medium 53 is obtained as (Equation 1).

ここで、Ｋは比例定数であり、レーザ光源やレンズの位置等の光学配置から決まり、このＫは予め求めておく必要がある。

Here, K is a proportional constant, which is determined from the optical arrangement such as the position of the laser light source and the lens, and this K needs to be obtained in advance.

  The calculation of the cross-correlation function between the two speckle images is performed according to (Equation 2).

ここで、２つのスペックル画像をｆ１、ｆ２とする。またフーリエ変換をＦ［ ］、逆フーリエ変換をＦ^−１［ ］、記号★は相互相関演算を表し、＊は位相共役を表す。

Here, let two speckle images be f1 and f2. The Fourier transform is F [], the inverse Fourier transform is F ^-1 [], the symbol ★ indicates a cross-correlation operation, and * indicates a phase conjugate.

f1 * f2 ^* is image data after the cross-correlation calculation, and is two-dimensional if f1 and f2 are two-dimensional images, and one-dimensional data if f1 and f2 are one-dimensional images. In the image data of f1 * f2 ^* , the position of the steepest peak (correlation peak) intensity represents the amount of displacement between the two speckle images. Therefore, the amount of movement between two speckle images can be calculated by searching for the steepest peak.

  Since the above-described cross-correlation calculation method can use fast Fourier transform, the amount of positional deviation Δ between speckle patterns can be detected with a relatively small amount of calculation and with high accuracy. Therefore, since the positional deviation amount Δ and the time difference τ between the two speckle images are known, the moving speed v of the moving medium 53 can be calculated.

  In addition, a method for detecting the formation position shift of the image pattern formed on the moving medium 53 by non-interfering light and the image density will be described. The light emitted from the second light source 61 that emits non-interfering light illuminates the moving medium 53, and the diffusely reflected light 57 diffusely reflected by the moving medium 53 is converted into a one-dimensional or two-dimensional second area sensor by the second imaging lens 64. 66 is imaged. At this time, the moving medium 53 and the second area sensor 66 have a conjugate relationship of image formation. As a result, the image pattern formed on the moving medium 53 is photoelectrically converted as an optical image by the one-dimensional or two-dimensional second area sensor 66.

  In FIG. 4, the movement of the moving medium 53 is shown in the direction indicated by the moving direction 58, that is, the direction perpendicular to the paper surface. However, the present invention is not limited to this, and can be similarly applied to the case where the moving medium 53 moves in any direction in the plane.

  FIG. 5 shows an example of the shape of a toner pattern for detecting a deviation in the formation position of the toner image pattern formed on the moving medium. Four color toner pattern groups are formed on a moving medium that moves in the x direction. 5, the main scanning direction of the image forming apparatus corresponds to the y direction and the sub scanning direction corresponds to the x direction. The four-color toner patterns are cyan (C), magenta (M), yellow (Y), and black (K) toner patterns, respectively.

  The toner pattern A group in FIG. 5 is a rectangular pattern having long sides formed in parallel to the y-axis, and is a pattern group for detecting a toner formation position shift in the sub-scanning direction. The toner pattern B group is a rectangular pattern whose long sides are formed in a 45 ° direction with respect to the y-axis, and is a pattern group for detecting a toner formation position shift in the main scanning direction.

  To detect the toner formation position deviation in the sub-scanning and main-scanning directions using the above toner patterns A and B, the following is performed. These toner pattern groups are illuminated with the LED light of the second light source 61 that emits non-interfering light. This is the elliptical light distribution shown in FIG. Although the LED light to illuminate is fixed, as the moving medium 53 moves, the LED light sequentially scans the positional deviation detection pattern. The toner pattern image formed on the one-dimensional or two-dimensional second area sensor 66 is photoelectrically converted, and the edge positions on both long sides of each color rectangular toner pattern are detected by setting a threshold value from the photoelectric conversion signal. Then, the center of each side edge position is defined as the toner formation position.

  This point will be described in detail. In the image detection apparatus of FIG. 4, the moving medium 53 is imaged on the second area sensor 66 by the second imaging lens 64. Therefore, when a toner pattern is formed on the moving medium 53, the pattern is imaged on the second area sensor 66 by the second imaging lens 64.

  FIG. 6A shows a toner pattern image formed on the second area sensor 66. An area corresponding to the LED light illumination area on the moving medium 53 is imaged on the second area sensor 66 of the two-dimensional light receiving surface in which pixels are arranged in a square shape, and formed on the moving medium 53 in the area. There is a toner pattern image. Among the output signals of the second area sensor 66, the image signal of the A pixel row is shown in FIG. This is an intensity distribution waveform of the toner pattern image. From the image signal of the toner pattern image, the front edge and rear edge positions 72 and 73 are detected based on the appropriately set edge detection threshold value 71, and the toner pattern center position 74 is specified from the edge positions. Thus, the formation position of the toner pattern can be specified. As a result, the position of the toner image for detecting the toner pattern position shift shown in FIG. 5 can be detected.

  In FIG. 6, the toner pattern image is extracted based on the image signal of the A pixel row, but the present invention is not limited to this. The toner pattern image is extracted by adding the image signals of a plurality of rows in the column direction. You may do it.

  In addition, in FIG. 5, the deviation of the formation position of each color toner pattern in the sub-scanning direction is obtained by measuring the time to the formation position of each color toner with reference to the leading cyan toner formation position. The time t1 for the magenta toner, the time t2 for the yellow toner, and the time t3 for the black toner are the formation positions for the cyan toner. If each time is equal, there is no color shift, but if it is not equal, it is a formation position shift.

  On the other hand, the formation position deviation in the main scanning direction is detected by the time difference between the same colors of the toner patterns A and B. That is, time t4 for cyan toner, time t5 for magenta toner, time t6 for yellow toner, and time t7 for black toner. If t4 to t7 are the same, there is no displacement in the formation position in the main scanning direction for each color, but if this is not equal, it can be detected that there is a displacement in the main scanning direction for each color.

  By the above method, it is possible to detect the deviation of the formation position of the toner pattern formed on the moving medium.

  FIG. 7 is a diagram showing a case where the image density of the toner pattern on the moving medium is also detected in addition to the above. In FIG. 7A, a toner gradation pattern is formed on a moving medium, for example, a belt substrate. The LED illumination light of the image detection apparatus of FIG. 4 is incident on the belt substrate, and the LED illumination light traces the toner gradation pattern as the belt substrate moves in the x direction. FIG. 7B is a schematic diagram in which the photoelectric conversion signal is plotted with respect to the x direction of the belt substrate when the LED illumination light traces the toner gradation pattern.

  In FIG. 7B, photoelectric conversion signals are plotted as being proportional to the reflectance of the toner pattern with gradation. Since the absolute value of the reflectance of the belt substrate without the toner pattern is known, the absolute value on the vertical axis in FIG. 7B can be specified as the reflectance R. From the reflectance R, the image density D of the toner pattern can be calculated by the definition formula “D = −logR”.

  FIG. 7C is a schematic diagram when the reflectance distribution of FIG. 7B is converted into an image density distribution by a definition formula. From FIG. 7C, it is possible to provide an image detection apparatus that also detects the image density of the toner pattern on the moving medium by illumination of LED light that is non-interference light and imaging.

  However, when the detection surface to be detected is the same region as in the first embodiment, the speed detection of the moving medium using the speckle pattern by coherent light and the image pattern formed on the moving medium by non-interfering light It is not preferable to simultaneously detect the formation position shift and the image density detection because they affect each other as noise. In order to avoid this, the speed detection of the moving medium using the speckle pattern by coherent light, the misalignment of the image pattern formed on the moving medium by non-interfering light, and the image density detection are overlapped in time. Do this in an independent time domain. The first light source that emits coherent light and the second light source that emits non-interfering light are individually turned on exclusively so that the coherent light and non-interfering light are not simultaneously irradiated onto the detected surface.

  FIG. 8 shows an image detection apparatus according to the second embodiment of the present embodiment, in which one imaging lens is arranged in common with respect to the first area sensor 56 and the second area sensor 66 shown in FIG. It is composed. In order to form an image with the common imaging lens 44 for the two area sensors, the detection position of the detection surface on the moving medium 53 is point a for the first area sensor 56, and the second area sensor. For point 66, point b is imaged on each sensor and detected. Diffuse reflected light 57-1 is generated from the point a, and diffuse reflected light 57-2 is generated from the point b. These are captured by the entrance pupil diameter of the common imaging lens 44 and imaged on the respective area sensors. . In this case, even if the detection position on the moving medium 53 is different, there is no particular problem for the purpose of the present invention as long as the position is known in advance. The operation of the image detection apparatus for this other example is the same as that shown in FIG.

  FIG. 9 is a diagram illustrating an image detection apparatus according to Example 3 of the present embodiment. In the third embodiment, separate first and second area sensors 56 and 66 corresponding to the first light source 51 for coherent light and the second light source 61 for non-interfering light in each of the embodiments shown in FIGS. A single one-dimensional or two-dimensional area sensor 46 is used in common. The first light source 51 that emits coherent light and the second light source 61 that emits non-interfering light are used in the same manner as in the first and second embodiments in FIGS. 4 and 8, but the illumination light from both light sources is a moving medium. The reflected light diffusely reflected by 53 is imaged on a common area sensor 46 by a common imaging lens 44 and an aperture stop 45. With this configuration, the overall size of the image detection apparatus can be reduced, and simplification and cost reduction can be achieved by reducing the number of parts.

  However, even when the imaging system and the area sensor are shared in this way, the speed detection of the moving medium 53 using the speckle pattern by coherent light and the image pattern formed on the moving medium 53 by non-interfering light are used. It is difficult to simultaneously detect the formation position deviation and the image density detection. In order to make this possible, time detection of the speed of the moving medium 53 using the speckle pattern by coherent light, displacement of the formation position of the image pattern formed on the moving medium 53 by non-interfering light, and image density detection are timed. In independent time domains that do not overlap. The first light source 51 that emits coherent light and the second light source 61 that emits non-interfering light are independently turned on independently, and the speckle pattern by coherent light and the image pattern by non-interfering light are the same area. It is necessary to avoid redundant photoelectric conversion by sensors.

  In the image detection apparatus of each embodiment described above, the first light source 51 that emits coherent light and the second light source 61 that emits non-interfering light are turned on intermittently, but the lighting timing is one-dimensional or two-dimensional. The area sensor 46 is lit in time synchronization with the drive timing of the image reading frame. In particular, it is desirable to perform lighting once per frame. This is due to the movement of the moving medium 53, and the image formation pattern on the area sensor moves from moment to moment, and lighting multiple times per frame results in information on multiple moving positions being mixed in one frame, resulting in high accuracy. This is because it is difficult to detect correctly.

  Further, it is desirable that the lighting time for one lighting per frame is shorter than the reading time for one frame. In a numerical example, the moving speed of the moving medium 53 is 300 mm / sec. This is reduced and imaged by an imaging lens at an imaging magnification of 0.5. At this time, the image moving speed on the area sensor is 150 mm / sec. When the frame frequency of the area sensor is 1 KHz, the image moving distance in one frame is 150 μm / sec.

  For example, if the size of one pixel of the area sensor is 10 μm, when the light source is lit for one frame time of the area sensor, the image on the area sensor moves 150 μm during the lighting time, which is 15 pixels worth. Corresponds to the movement of In such a situation, the position resolution for speed detection and displacement detection is about 150 μm, and high-precision speed detection and displacement detection cannot be performed. Therefore, for example, if the lighting time of the light source is 0.1 ms that is 1/10 of the reading time of one frame, the image movement amount during lighting is 15 μm, and only 1.5 pixels move during the lighting time. High-precision speed detection and position shift detection with a position resolution of about 15 μm are possible.

  As described above, emitting light at a light source lighting time shorter than the time interval of one frame is not only for detecting a speed by a speckle pattern using coherent light but also for detecting a positional deviation of an image pattern using non-interfering light. Also applies. A method of emitting light at a time interval shorter than the time interval of one frame is a light emitting diode (LED) when a semiconductor laser is used as a first light source that emits coherent light and a second light source that emits non-interfering light. ) In both cases, the light emission is shortened, so that it is possible to emit light with a higher output than continuous light emission. In addition, when the light emission power is the same, the light source life can be extended.

  As another method, the first and second light sources are intermittently turned on for each frame time, and the exposure accumulation time of the area sensor that photoelectrically converts the imaging light from each light source is set to 1. There is also a method in which the area sensor is read and driven so that the time interval is shorter than the frame time interval.

  FIG. 10 is a timing chart of the detection operation of the image detection apparatus according to the third embodiment shown in FIG. In FIG. 10, the horizontal axis is the time axis, and (a) shows the operation timing of the area sensor 46, which is a continuous imaging operation by repeating one frame time TF0. One frame time TF0 is composed of the exposure accumulation time TS of the speckle pattern exposure accumulation operation S accompanying the light reception of the area sensor 46 and the readout time TR of the signal readout operation R. In the third embodiment, the moving speed of the moving medium 53 is detected by the first light source 51 that emits coherent light, and the position of the image pattern formed on the moving medium 53 is shifted by the second light source 61 that emits non-interfering light. The image density detection is alternately performed for each frame in synchronization with each frame of the area sensor 46.

  FIG. 10B is a light emission timing chart of the first light source 51 that emits coherent light in FIG. 9 and emits light for a light emission time TC indicated by a light emission pulse C every other frame. At this time, TC <TF0, and the light emission time TC of the first light source 51 is set to be shorter than one frame time TF0. Further, the light emission time TC of the first light source 51 is set to be shorter than the exposure accumulation time TS, and TC <TS.

  FIG. 10C shows a timing chart of the cross correlation process. After reading the speckle pattern accompanying the light emission of the first light source 51, the image signal is delivered at the timing indicated by the dashed arrow 1, and the two frames stored in the frame memory by the correlation calculation process indicated by the operation region MC. A cross-correlation calculation is performed with the previous speckle pattern image signal. By this correlation calculation, the amount of shift of the correlation peak position is detected, the amount of movement of the moving medium 53 between the previous frame and the current frame can be detected, and the moving speed during this period can be calculated from the result.

  FIG. 10 (d) shows the light emission timing of the second light source 61 that emits non-interfering light in FIG. 9, and FIG. 10 (b) emits light for a light emission time TI indicated by the light emission pulse I every other frame. At this time, TI <TF0 and the light emission time of the second light source 61 is set to be smaller than one frame time TF0. Further, the light emission time TI of the second light source 61 is set to be shorter than the exposure accumulation time TS, and TI <TS.

  FIG. 10E shows a detection timing chart of the displacement of the image pattern formation position on the moving medium 53 by the second light source 61. After reading out the formed image pattern accompanying the light emission of the second light source 61, the image signal is delivered at the timing indicated by the broken line arrow 3, and the speed information of the moving medium 53 detected by the correlation calculation process is also indicated by the broken line arrow 2. The position deviation of the image pattern formed on the moving medium 53 is detected by the position deviation detection process indicated by the operation region MP, which is delivered at the timing shown and combined with these signals.

  In this detection process, the image forming position detected by the light emission of the second light source 61 two frames before, the moving speed of the moving medium 53 detected by the light emission of the first light source 51, and the second light source 61 in the current frame. The detection processing is performed from the three pieces of information of the image forming position detected by the light emission. FIG. 11 shows how the image detection position is detected by the light emission of the second light source 61. FIG. 11A shows an LED light illumination area by the second light source 61 on the moving medium 53 imaged on the two-dimensional light receiving surface of the area sensor 46, and a toner pattern for detecting displacement in the LED light illumination area. Show the image.

  The toner pattern image on the moving medium 53 in the image detection apparatus of FIG. 9 is imaged on the area sensor 46 via the imaging lens 44. Among the output signals from the area sensor 46 of the toner pattern image formed on the moving medium 53, the image signal of the A pixel row is shown in FIG. The toner pattern has an intensity distribution waveform. From the image signal of the toner pattern image, the front edge position 72 and the rear edge position 73 are detected based on an appropriately set edge detection threshold value 71, and the central position of the toner pattern is detected from these edge positions. 74 is calculated to specify the toner pattern formation position.

  As shown in FIG. 11B, the digitization of the toner pattern image formation position is performed by setting a pixel X0 that is the origin of the column of the area sensor 46, and the distance X2 from X0 to the toner pattern center position 74 is the formation position. Become. Since the pixels are arranged in the area sensor 46 with high accuracy, the formation position can be calculated with high accuracy using the pixel interval as a scale.

  In FIG. 11A, the toner pattern image is extracted based on the image signal of one row of the A pixels. However, the present invention is not limited to this, and the toner pattern image is obtained by adding the image signals of a plurality of rows in the column direction. May be extracted.

  The optical image on the area sensor 46 is not necessarily a similar pattern on the moving medium 53 due to the distortion of the imaging lens 44, but the distortion aberration of the imaging lens 44 is numerically reverse-corrected. Thus, the influence of aberration can be avoided.

  When detecting the formation position deviation of the toner pattern image by the above method, if the entire toner pattern group for detecting the position deviation shown in FIG. Although the position shift can be detected, but when the whole cannot be captured by one imaging, the second light source 61 of non-interfering light is irradiated so that it is captured once every two frames as shown in the timing chart of FIG. The formation position deviation is obtained from two adjacent images of the image signal.

  Specifically, X1 of the pattern formation position of the reference toner pattern image in the first image of two adjacent images is calculated based on the origin pixel X0, and similarly, the target pattern in the image after two frames is calculated. The pattern forming position X2 is calculated using the origin pixel X0 as a base point. Further, the moving distance L1 of the moving medium between the two frames is calculated from (Expression 3) from the moving medium velocity v1 detected by the correlation calculation process delivered at the timing indicated by the broken line arrow 2 shown in FIG. it can.

ここで、ｔｆはフレーム繰返し時間である。
以上より、基準パターンに対する注目パターンの形成位置Ｘは（数４）より算出できる。

Here, tf is a frame repetition time.
From the above, the formation position X of the target pattern with respect to the reference pattern can be calculated from (Equation 4).

  As described above, the formation position of the formed toner pattern can be detected with high accuracy using the moving speed v1 of the moving medium detected by the image detection apparatus.

  FIG. 12 is a timing chart of another detection operation of the image detection apparatus according to the third embodiment shown in FIG. In FIG. 12, the horizontal axis is the time axis, and (a) shows the operation timing of the area sensor 46, which is a continuous imaging operation by repeating one frame time TF0. The one frame time TF0 here is the one frame time TF0 shown in FIG. Similarly in FIG. 12, the moving speed detection of the moving medium 53 by the first light source 51 that emits coherent light, the formation position shift of the image pattern formed on the moving medium 53 by the second light source 61 that emits non-interfering light, and Image density detection is alternately performed for each frame in synchronization with each frame of the area sensor 46.

  FIG. 12B is a light emission timing chart of the first light source 51 that emits coherent light in FIG. 9 and emits light for a light emission time TC indicated by a light emission pulse C every other frame. At this time, the exposure accumulation time TS of the speckle pattern exposure accumulation operation S accompanying the light reception of the area sensor 46 shown in FIG. 12A is set to TS <TF0, and the exposure accumulation time TS is set to be smaller than one frame time. ing. Here, the light emission time TC of the first light source 51 is set to be longer than the exposure accumulation time TS, and TC> TS.

  FIG. 12C shows a timing chart of the cross correlation process. After reading the speckle pattern accompanying the light emission of the first light source 51, the image signal is delivered at the timing indicated by the dashed arrow 1, and the two frames stored in the frame memory by the correlation calculation process indicated by the operation region MC. A cross-correlation calculation is performed with the previous speckle pattern image signal. By this correlation calculation, the amount of shift of the correlation peak position is detected, the amount of movement of the moving medium 53 between the previous frame and the current frame can be detected, and the moving speed during this period can be calculated from the result.

  FIG. 12D shows the light emission timing of the second light source 61 that emits non-interfering light in FIG. 9, and FIG. 12B emits light with a light emission time TI indicated by the light emission pulse I every other frame. At this time, TS <TF0 and TS <TI are set.

  FIG. 12E shows a detection timing chart of the displacement of the image pattern formation position on the moving medium 53 by the second light source 61. After reading out the formed image pattern accompanying the light emission of the second light source 61, the image signal is delivered at the timing indicated by the broken line arrow 3, and the speed information of the moving medium 53 detected by the correlation calculation process is also indicated by the broken line arrow 2. These signals are delivered at the timing shown, and the formation displacement of the image pattern formed on the moving medium 53 is detected by the displacement detection processing indicated by the operation region MP. Subsequent toner pattern formation positions can be calculated by the method described with reference to FIG.

  The image forming apparatus of Example 4 in the embodiment of the present invention is obtained by applying the image detecting apparatus of Examples 1 to 3 described above to the intermediate transfer type image forming apparatus shown in FIG. The image detection apparatus according to the fourth exemplary embodiment is disposed downstream of the position of the final photosensitive drum K1 of the intermediate transfer belt 105 illustrated in FIG. 1, and always detects the feed speed of the intermediate transfer belt 105 itself. In parallel to this, among the toner image patterns transferred from the respective photosensitive drums to the intermediate transfer belt 105, a toner pattern as shown in FIG. 5 can be detected to detect a deviation in the formation position of the toner image pattern.

  Further, it is possible to detect the toner gradation pattern as shown in FIG. 7 and detect the image density of the toner image pattern. As described above, one image detection apparatus can detect three of the speed fluctuation of the intermediate transfer belt 105, the toner image pattern formation position shift, and the image density.

  In Example 5 of the present embodiment, the image detection apparatus is applied to the direct transfer type image forming apparatus shown in FIG. 2 as in Example 4 described above. This image detection apparatus is disposed downstream of the position of the final photosensitive drum K1 of the transport transfer belt 106 that transports a recording medium such as paper, and always detects the feed speed of the transport transfer belt 106 itself. In parallel with this, a toner image pattern transferred to a recording medium such as paper conveyed on the conveyance transfer belt 106 is also detected. Of the toner image patterns transferred from the respective photosensitive drums onto the paper transported on the transport transfer belt 106, a toner pattern as shown in FIG. 5 can be detected to detect a deviation in the formation position of the toner image pattern. . Further, it is possible to detect the toner gradation pattern as shown in FIG. 7 and detect the image density of the toner image pattern. As described above, one image detection apparatus can detect three of the speed variation of the transfer transfer belt 106, the toner image pattern formation position shift, and the image density.

  Further, in the image forming apparatuses according to the fourth and fifth embodiments described above, a means (belt) for controlling the motor driving of the transfer belt feed by feedback in order to control the belt feed speed constant according to the detection signal of the mounted image detection apparatus. Speed correction means).

  Specifically, when applied to the above-described image forming apparatus of FIG. 1, the belt is fed back to the motor drive control of the transfer belt feeding means based on the speed fluctuation of the intermediate transfer belt 105 detected by the image detection apparatus, Keep the feed speed constant. Alternatively, when applied to the image forming apparatus of FIG. 2, the belt feed speed is made constant by feeding back to the motor drive control of the transfer belt feed means based on the speed fluctuation of the transfer transfer belt 106 detected by the image detection apparatus. To do.

  Further, based on the toner image pattern formation position deviation result detected by the image detection device, a means for correcting the writing start position (writing start position correcting means) is provided for the position deviation in the sub-scanning direction. Both the image forming apparatuses in FIGS. 1 and 2 change the selection of the image writing scanning line in accordance with the positional deviation to reduce the toner image positional deviation in the sub-scanning direction. Further, for correction of a deviation equal to or smaller than the interval between the sub-scan lines, a method of correcting the write light beam in the sub-scan direction by using a variable light deflection element formed of liquid crystal or the like in the scanning optical system. and so on.

  Further, a positional deviation in the main scanning direction of the toner image pattern detected by the image detection device is corrected by providing means for shifting the main scanning writing position of each main scanning.

  The image forming apparatus includes a writing start position correcting unit that corrects a writing start position by the optical scanning device, a belt speed correcting unit that corrects a feeding speed of the intermediate transfer belt or the conveyance transfer belt, or both units. Although it may be configured, at least one of them may be provided.

  Further, the image density value of the toner gradation pattern detected by the above-described image detection apparatus is fed back to the development bias of the developing device and controlled so that each color has an image density having an appropriate gradation, or photosensitive. Control is performed by feeding back the voltage of the charger of the body drum or adjusting the exposure amount by adjusting the laser writing power of the optical scanning device so that each color has an image density having an appropriate gradation.

  In each of the embodiments described above, an example in which the image detection apparatus of the present invention is applied to an image forming apparatus using an electrophotographic process has been described. However, the image detection apparatus of the present invention is not limited to this. In addition, the present invention can be similarly applied to detection of movement speed fluctuation of a recording sheet in a multi-color image forming apparatus by an inkjet process or the like, positional deviation of each color ink image pattern on the recording sheet, and detection of image density.

  The image detection apparatus and the image forming apparatus according to the present invention detect the speed fluctuation of the moving medium easily and with high accuracy, and further detect the positional deviation of each color image pattern formed on the moving medium and the image density of the image pattern. In addition to correcting the speed fluctuation of the moving medium, it detects and corrects the position shift of each color image formed, further corrects the image density, greatly reduces the color shift, and corrects the image gradation appropriately. Such as a digital copying machine, a printer, and a facsimile, and is useful as an apparatus that handles multicolor images.

1,301 to 304 Photoconductor drum 2 Charger 4 Developer 5 Cleaning means 6 Transfer charger 20 Optical scanning device 30 Fixing means 40 Transfer roller 41 Conveying belt 44 Imaging lens 45, 55 Aperture stop 46 Area sensor 47 Two-dimensional Light-receiving surface 51 First light source 52 Collimator lens 53 Moving medium 54 First imaging lens 56 First area sensors 57, 57-1, 57-2 Diffuse reflected light 58 Moving direction 61 Second light source 64 Second imaging lens 66 First Two-area sensor 71 Edge detection threshold 72 Front edge position 73 Rear edge position 74 Toner pattern center position 105 Intermediate transfer belt 106 Conveyance transfer belt 400 Transfer belt 1001 Light source unit 1041 Line image forming lens 1050 Polygon mirrors 1061 to 1064 Scanning lenses 1111 and 1121 Folding mirror

JP 2008-65743 A Japanese Patent Laid-Open No. 2003-2666828 JP-A 64-35466 JP 2004-309292 A JP 2004-21164 A JP 2002-72612 A

Claims (8)

A first light source that emits coherent light, a second light source that emits non-interfering light, a moving medium on which an image pattern is formed, a light receiving element array having a one-dimensional or two-dimensional light receiving surface, and reflection from the moving medium In an image detection apparatus having an imaging means for imaging light on the light receiving element array,
The reflected light from the moving medium irradiated by the first light source forms an image on the first light receiving element array via the first imaging means, and a plurality of images that are temporally different as the moving medium moves. The movement of the moving medium is performed by obtaining a signal, performing a cross-correlation operation between two time-different image signals of the plurality of image signals, and obtaining a shift in a position where a correlation peak of the cross-correlation operation occurs. First detecting means for detecting a speed;
The reflected light from the moving medium irradiated by the second light source is imaged on the second light receiving element array via the second imaging means, and image signals that are temporally different as the moving medium moves. A second detecting means for detecting a positional deviation and / or image density of the image pattern from an image pattern of an image signal acquired and irradiated by irradiation of the second light source;
The image detection apparatus according to claim 1, wherein the process of the first detection unit and the process of the second detection unit are performed in different time regions. A first light source that emits coherent light, a second light source that emits non-interfering light, a moving medium on which an image pattern is formed, a light receiving element array having a one-dimensional or two-dimensional light receiving surface, and reflection from the moving medium In an image detection apparatus having an imaging means for imaging light on the light receiving element array,
The reflected light from the moving medium due to the irradiation of the first light source and the reflected light from the moving medium due to the irradiation of the second light source are connected to the light receiving element array via an imaging unit in which one set is commonly arranged. The processing of the first detecting means for detecting the moving speed of the moving medium and the processing of the second detecting means for detecting the displacement of the image pattern of the moving medium and / or the image density are performed in different time regions. An image detection apparatus characterized by that.   The time of irradiation of the first light source used for the processing of the first detection means and the time of irradiation of the second light source used for the processing of the second detection means are synchronized with the frame reading time of the light receiving element array, 3. The image detection apparatus according to claim 1, wherein the irradiation time of the first light source and the second light source is shorter than the interval of the frame reading time for reading one frame.   The positional deviation of the image pattern formed on the moving medium in the second detecting means is the value of the moving speed of the moving medium detected by the first detecting means and the reflected light of the moving medium due to the irradiation of the second light source. The image detection apparatus according to claim 1, wherein the detection is performed based on an image formation position of an image pattern on the light receiving element array on which the light is imaged. A plurality of image carriers, an optical scanning device that scans a light beam on the plurality of image carriers to form an electrostatic latent image, and an electrostatic that the optical scanning device forms on the plurality of image carriers. Developing means for visualizing each latent image with toner of each color, a movable intermediate transfer belt disposed opposite to the plurality of image carriers, and each color toner image visualized on the image carrier for the intermediate transfer A first transfer means for transferring to the belt; a second transfer means for further transferring each color toner image transferred on the intermediate transfer belt onto the sheet-like recording medium; and each color toner transferred to the recording medium. In an image forming apparatus that includes a fixing unit that fixes an image and forms a multicolor or color image,
5. The image detection apparatus according to claim 1, wherein the moving speed of the intermediate transfer belt is detected, the positional deviation of each color toner image on the intermediate transfer belt, and / or the image density is detected. An image forming apparatus. A plurality of image carriers, an optical scanning device that scans a light beam on the plurality of image carriers to form an electrostatic latent image, and an electrostatic that the optical scanning device forms on the plurality of image carriers. A developing unit that visualizes the latent image with toner of each color, a conveyance transfer belt that conveys a sheet-like recording medium disposed opposite to the plurality of image carriers, and a recording medium that is conveyed by the conveyance transfer belt. In an image forming apparatus for forming a multicolor or color image, the image forming apparatus includes a transfer unit that directly transfers the imaged color toner images in a superimposed manner and a fixing unit that fixes the color toner images transferred to the recording medium.
5. The image detection apparatus according to claim 1, wherein the transfer speed of the conveyance transfer belt is detected, the position of each color toner image on the recording medium conveyed by the conveyance transfer belt, and / or An image forming apparatus for detecting an image density.   One or both of a writing start position correcting unit that corrects a writing start position by a light beam of the optical scanning device and a belt speed correcting unit that corrects a feed driving speed of the intermediate transfer belt or the conveyance transfer belt. The image forming apparatus according to claim 5, wherein correction is provided based on detection by the image detection apparatus.   8. The image forming apparatus according to claim 5, further comprising means for correcting an image density for image formation, and performing correction based on detection by the image detection apparatus.

Images