JP2008089761A - Optical sensor, pattern detecting device, multicolor image forming apparatus, pattern detecting method, program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the position or the density of a pattern even if the edge of the pattern becomes rough, a transfer belt is scratched or local density distribution still remains on the pattern. <P>SOLUTION: The optical sensor has a light source to emit light to a predetermined object, and a photodetecting means to detect the light from the object. The optical sensor is equipped with an intensity distribution converting means to change the intensity distribution of the light from the light source and/or a light branching means to branch the light from the light source into a plurality of light beams. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical sensor, a pattern detection apparatus, a multicolor image forming apparatus, a pattern detection method, a program, and a recording medium.

  In recent years, color image forming apparatuses are so-called tandems in which four photoconductors (image carriers) corresponding to toners of four colors (black, cyan, magenta, and yellow) are arranged in parallel to meet the demand for higher speed. The method has become mainstream. While the tandem method can increase the speed, color misalignment and color change are likely to occur in the paper feeding direction (sub-scanning direction), so the pattern formed with toner is detected and corrected by the optical sensor. There are many. In recent years, the required quality for color images has been increasing, and for this purpose, it is necessary to reduce color shift and color variation in color images more than ever. For this purpose, it is necessary to improve the detection accuracy of the toner pattern.

  For example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5 disclose a line image of each color on a transfer belt as a conventional example in which a toner pattern is detected by an optical sensor and color misregistration is corrected. A technique for detecting and correcting color misregistration by detecting the passage timing of the line image with an optical sensor is disclosed, but this has the following problems. That is, when detecting the passage timing of the toner pattern by the optical sensor, the factors that degrade the detection accuracy are that the toner is scattered at the edge portion of the toner pattern and the edge becomes rough, scratches on the surface of the transfer belt, etc. The surface shape characteristics of Since the toner is particles, it is scattered at the edge portion, and a clean edge cannot be formed by any means. Also, scratches on the transfer belt surface inevitably occur due to changes over time. If such a toner pattern is detected by an optical sensor, problems such as deterioration in detection accuracy and erroneous detection occur, a color misregistration correction error occurs, and an image with color misregistration is output.

  Also, for example, Patent Document 3 and Patent Document 4 disclose a technique for detecting and correcting toner density by detecting a toner pattern using an optical sensor, but this has the following problems. . That is, when detecting a toner pattern using an optical sensor, a factor that degrades the detection accuracy is that density variation locally remains in one toner pattern. If such a pattern is detected by the optical sensor, the detection accuracy is deteriorated and erroneous detection occurs, a toner density correction error occurs, and an image with uneven color is output.

In the above optical sensor, an LED is generally used as a light source, and the intensity distribution of light from the LED has a Gaussian distribution. The Gaussian distribution is a distribution in which the intensity at the center is the strongest and the intensity becomes weaker toward the periphery. When the position or density of the toner pattern is detected using light having such a Gaussian distribution, the intensity is biased toward a part of the area. Therefore, information on the part of the toner pattern is strongly detected. Will end up. This increases the problems of deterioration in detection accuracy and false detection described above.
Japanese Patent Publication No.7-19084 JP 2004-101567 A JP 2006-91472 A Japanese Patent No. 3644923 Japanese Patent No. 3648786

  The present invention can detect the position or density of a pattern with high accuracy even if the edge of the pattern is rough, the transfer belt is scratched, or the local density distribution remains in the pattern. It is an object of the present invention to provide a photosensor, a pattern detection apparatus, a multicolor image forming apparatus, a pattern detection method, a program, and a recording medium.

  In order to achieve the above object, the invention described in claim 1 is an optical sensor having a light source that emits light to a predetermined object, and a light detection means that detects light from the object, The optical sensor further includes an intensity distribution conversion unit that changes an intensity distribution of light from the light source and / or a light branching unit that branches light from the light source into a plurality of lights.

  According to a second aspect of the present invention, in the optical sensor according to the first aspect, the intensity distribution converting means and / or the light branching means are two-dimensionally controlled diffractive optical elements that control the phase of light from the light source. The light intensity distribution from the light source is changed and / or the light from the light source is branched into a plurality of lights.

  According to a third aspect of the present invention, in the optical sensor according to the first or second aspect, the intensity distribution converting means flattens a central portion of the intensity distribution of light from the light source. .

  According to a fourth aspect of the present invention, in the optical sensor according to any one of the first to third aspects, a coupling lens for coupling light from the light source is further provided. Yes.

  According to a fifth aspect of the present invention, at least one of the optical sensor according to any one of the first to fourth aspects, a predetermined pattern, light in the optical sensor, and the predetermined pattern is moved. A pattern detecting apparatus comprising: a moving means for detecting the predetermined pattern based on a light detection signal from the light detecting means of the light sensor;

  According to a sixth aspect of the present invention, in the pattern detection device according to the fifth aspect, the light intensity distribution is at least flattened in a direction perpendicular to the moving direction of the predetermined pattern as viewed from the optical sensor. It is characterized by that.

  According to a seventh aspect of the present invention, in the pattern detection device according to the fifth or sixth aspect, the two-dimensional shape of the light intensity distribution in the optical sensor is a quadrangle.

  According to an eighth aspect of the present invention, in the pattern detection apparatus according to any one of the fifth to seventh aspects, the two-dimensional shape of the light intensity distribution in the optical sensor is viewed from the optical sensor. The light width in the direction perpendicular to the moving direction of the predetermined pattern is longer than the light width in the moving direction of the predetermined pattern.

  The invention according to claim 9 is the pattern detection apparatus according to any one of claims 5 to 8, wherein the detection means detects the edge of the predetermined pattern to thereby detect the optical sensor. The time during which the predetermined pattern passes through the light at is detected.

  The pattern detection device according to any one of claims 5 to 8 is characterized in that the detection means detects the peak position of the light detection signal to detect the predetermined value. It is characterized in that the center of gravity position of the pattern is detected.

The invention described in claim 11 is the pattern detection device according to claim 10, wherein the light width (1 / e ^{2 of the} maximum intensity) of the light sensor in the moving direction of the predetermined pattern as viewed from the light sensor. The width of the predetermined pattern is substantially equal to the width of the predetermined pattern.

  A twelfth aspect of the invention is a multicolor image forming apparatus that includes an optical scanning device and forms a color image, and includes the pattern detection device according to any one of the fifth to eleventh aspects, A predetermined pattern is formed by toner, and the predetermined pattern is detected based on a light detection signal from the optical sensor while moving the predetermined pattern.

  The invention according to claim 13 is the multicolor image forming apparatus according to claim 12, further comprising image forming position correcting means in the sub-scanning direction, wherein the image forming position correcting means Based on this, the position of the image in the sub-scanning direction is corrected.

  According to a fourteenth aspect of the present invention, in the multicolor image forming apparatus according to the thirteenth aspect, the image forming position correcting means changes the angle of the emitted light from the optical scanning apparatus in the sub-scanning direction. Alternatively, it is configured as a position changing means for changing the position in the sub-scanning direction of the emitted light from the optical scanning device.

  According to a fifteenth aspect of the present invention, in the multicolor image forming apparatus according to the fourteenth aspect, the angle changing means or the position changing means is a means for rotating or moving a mirror provided in the optical scanning device. It is characterized by being composed.

  According to a sixteenth aspect of the present invention, in the multicolor image forming apparatus according to the fourteenth aspect, the angle changing means is configured as means for controlling a voltage applied to a liquid crystal deflecting element provided in an optical scanning device. It is characterized by being.

  According to a seventeenth aspect of the present invention, in the multicolor image forming apparatus according to the thirteenth aspect, the image forming position correcting means controls the light emission timing of the light source inside the optical scanning device to thereby adjust the image sub-scanning direction. Is formed as means for shifting in the sub-scanning direction in units of one line corresponding to the image resolution.

  According to an eighteenth aspect of the present invention, in the multicolor image forming apparatus according to the twelfth aspect, the pattern detection device detects the density of the predetermined pattern and uses the detection result of the density of the predetermined pattern. The toner image forming conditions are controlled.

  According to a nineteenth aspect of the present invention, at least one of the light and the predetermined pattern in the optical sensor according to any one of the first to fourth aspects is moved, and a light detection signal from the optical sensor is used. The pattern detection method includes detecting the predetermined pattern.

  According to a twentieth aspect of the present invention, at least one of the light and the predetermined pattern in the optical sensor according to any one of the first to fourth aspects is moved, and a light detection signal from the optical sensor is used. A program for causing a computer to implement a detection process for detecting the predetermined pattern.

  According to a twenty-first aspect of the present invention, at least one of the light and the predetermined pattern in the optical sensor according to any one of the first to fourth aspects is moved, and a light detection signal from the optical sensor is used. A computer-readable recording medium recording a program for causing a computer to execute a detection process for detecting the predetermined pattern.

  According to invention of Claim 1 thru | or Claim 11, Claim 19 thru | or 21, It has a light source which radiate | emits the light to a predetermined target object, and the light detection means which detects the light from the said target object The optical sensor further includes an intensity distribution conversion unit that changes an intensity distribution of light from the light source and / or an optical branching unit that branches the light from the light source into a plurality of lights. By using this optical sensor, even when a pattern with rough edges is detected or there is a scratch on the ground on which the pattern is formed, the detection accuracy of the position or density of the pattern is improved and false detection is prevented. Can be achieved.

  Particularly, in the invention described in claim 2, in the optical sensor described in claim 1, the intensity distribution conversion means and / or the light branching means is a diffractive optical element that two-dimensionally controls the phase of light from the light source. The intensity distribution of the light from the light source is changed by using and / or the light from the light source is branched into a plurality of lights, so that the intensity distribution conversion means while suppressing the increase in the difficulty of production as much as possible , Optical branching means can be obtained.

  According to a fourth aspect of the present invention, the optical sensor according to any one of the first to third aspects further includes a coupling lens for coupling light from the light source. A light spot with a flattened intensity distribution can be obtained without increasing the difficulty of device fabrication.

  In the invention according to claim 6, since the light intensity distribution is at least flattened in a direction perpendicular to the moving direction of the predetermined pattern as viewed from the photosensor, the photodetection signal from the photosensor is When detecting a pattern (predetermined pattern), it is possible to average the influence of rough edges in the pattern and the effect of scratches on the background of the pattern, improving the detection accuracy and error of the pattern position or density. Detection can be prevented.

  According to a seventh aspect of the present invention, in the pattern detection device according to the fifth or sixth aspect, since the two-dimensional shape of the light intensity distribution in the optical sensor is a quadrangle, the light that crosses the edge of the pattern The cross section of the spot can always have substantially the same shape regardless of the positional relationship between the pattern and the light spot, and the detection accuracy of the position or density of the pattern can be improved and erroneous detection can be prevented.

  According to an eighth aspect of the present invention, in the pattern detection apparatus according to any one of the fifth to seventh aspects, the two-dimensional shape of the light intensity distribution in the optical sensor is viewed from the optical sensor. Further, since the width of light in the direction perpendicular to the moving direction of the predetermined pattern is longer than the width of light in the moving direction of the predetermined pattern, it is detected by the light detection means (for example, a photodiode) of the light sensor. The rise (or fall) of the optical signal becomes steep, and the effects of edge roughness in the pattern and scratches on the pattern ground can be more averaged, improving the detection accuracy and false detection of the pattern position or density. Can be prevented.

  According to the ninth aspect of the present invention, it is possible to detect the time required for the predetermined pattern to pass through the light spot in the optical sensor.

  In the inventions according to claims 10 and 11, the center of gravity position of the predetermined pattern can be detected.

  According to a twelfth to eighteenth aspect of the present invention, in the multicolor image forming apparatus that includes the optical scanning device and forms a color image, the pattern detection according to any one of the fifth to eleventh aspects. The apparatus includes a device that forms a predetermined pattern with toner and detects the predetermined pattern based on a light detection signal from the optical sensor while moving the predetermined pattern. Even when a pattern is detected, or when there is a scratch on the ground on which the pattern is formed, the detection accuracy of the position or density of the pattern can be improved and false detection can be reduced, and color misregistration can be corrected well. Color images can be obtained.

  In particular, in the inventions according to claims 13 to 17, in the multicolor image forming apparatus according to claim 12, the image forming position correcting means in the sub-scanning direction includes the predetermined pattern. Based on the detection result, the position of the image in the sub-scanning direction is corrected. Thus, for example, the position-shift detection result of each color pattern with respect to the reference color is used to correct the sub-scanning position deviation of each color image. can do.

The invention according to claim 18 is the multicolor image forming apparatus according to claim 12, wherein the pattern detection device detects the density of the predetermined pattern and uses the detection result of the density of the predetermined pattern. Thus, the toner image forming conditions are controlled, so that, for example, the toner density in the image can be maintained appropriately, and a color image in which a change in color is suppressed can be obtained.

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

  FIG. 1 is a diagram (perspective view) illustrating a configuration example of an optical scanning device applied to a full-color image forming apparatus.

  In the example of FIG. 1, scanning is performed for two stations in a direction facing the polygon mirror 213. In FIG. 1, for simplification of explanation, scanning for only one station is shown. FIG. 2 is a cross-sectional view of FIG.

  Referring to FIGS. 1 and 2, four photosensitive drums 1Y, 1M, 1C, and 1K are arranged along the moving direction of the transfer belt 105, and a color image is formed by sequentially transferring toner images of different colors. In the image forming apparatus, each optical scanning device is integrally formed, and all light beams are scanned by a single polygon mirror 213.

  In the example of FIGS. 1 and 2, a pair of semiconductor lasers are provided for each photoconductor, and scanning is performed by shifting one line pitch in the sub-scanning direction according to the recording density, thereby scanning two lines at a time. Like to do.

  In the optical scanning device (image forming apparatus) shown in FIGS. 1 and 2, the light beam emitted from the semiconductor laser is converted into a parallel beam by a coupling lens (201), and then shaped by an aperture (not shown). The laser beam is focused only in the sub-scanning direction by the cylindrical lens 209, and is formed as a line image long in the main scanning direction at the deflection reflection surface position of the polygon mirror 213.

  A light beam is scanned by a single polygon mirror 213, and is provided by a photodiode (PD) (not shown) provided in the region that does not contribute to image formation from the polygon mirror 213 toward the photoconductor and on the light scanning start side. After a certain period of time after the light is detected, the light source is modulated based on the image signal, and image formation is started.

  The fθ lenses 2181, 2182, 2183, and 2184, together with the toroidal lenses 2201, 2202, 2203, and 2204, form a scanning optical system corresponding to each color. Note that 2181 and 2182 (2183 and 2184) are held in an overlapping manner in the sub-scanning direction.

  The fθ lens 2182 has a non-arc surface shape in which power is given so that the beam moves at a constant speed on each photoconductor surface in accordance with the rotation of the polygon mirror in the main scanning direction. It has a surface tilt correction function. After passing through the fθ lens 2182, the light is reflected by the folding mirror 224, is incident on the toroidal lens 2202, is further reflected by the folding mirror 227, and forms a spot image on the photosensitive drum. The An image (for example, a yellow image) can be formed on the photosensitive drum by scanning the photosensitive drum with a light spot by the polygon mirror and rotating the photosensitive drum. In the example of FIGS. 1 and 2, four photoconductor drums 1Y, 1M, 1C, and 1K can be simultaneously scanned to form images of four colors at the same time.

  FIG. 3 is a diagram showing a basic configuration of the multicolor image forming apparatus.

In FIG. 3, Y: yellow, M: magenta, C: cyan, K: black,
1Y, 1M, 1C, 1K: photoconductor,
2Y, 2M, 2C, 2K: charger,
20: optical scanning device,
4Y, 4M, 4C, 4K: developing unit,
5Y, 5M, 5C, 5K: cleaning means,
6Y, 6M, 6C, 6K: charging means for transfer,
105: transfer belt,
30: Fixing means.

  In FIG. 3, an optical scanning device 20 is the optical scanning device described with reference to FIGS. In FIG. 3, photoconductors 1Y, 1M, 1C, and 1K rotate in the direction of the arrow, and charging members 2Y, 2M, 2C, and 2K, developing members 4Y, 4M, 4C, and 4K, transfer charging means in the order of the rotation direction. 6Y, 6M, 6C, 6K and cleaning means 5Y, 5M, 5C, 5K are provided.

  The charging members 2Y, 2M, 2C, and 2K are charging members that constitute a charging device for uniformly charging the surface of the photoreceptor. The surface of the photosensitive member between the charging member and the developing members 4Y, 4M, 4C, and 4K is irradiated with a light beam by a writing unit so that an electrostatic latent image is formed on the photosensitive member. Then, based on the electrostatic latent image, a toner image is formed on the photoreceptor surface by the developing member. Further, the respective transfer toner images are sequentially transferred onto the recording paper by the transfer charging means 6Y, 6M, 6C, 6K, and finally the image is fixed on the recording paper by the fixing means 30.

  Next, a color misregistration detection mechanism by detecting a toner pattern with an optical sensor will be described. A plurality of toner patterns of each color are formed at a predetermined pitch in the rotation direction of the transfer belt at three points on both ends and the center in the main scanning direction on the transfer belt 105 in FIG. 1, and main scanning is performed according to the movement of the transfer belt 105. By sequentially reading with optical sensors respectively provided at both ends and the center of the direction, and detecting the positional deviation of the toner pattern in the main scanning direction and the sub-scanning direction with respect to the reference color of each color (for example, set to black) The color misregistration correction in the main scanning direction and the sub-scanning direction is performed.

  FIG. 4 is a diagram for explaining how to detect a misregistration measurement pattern formed by toner of each color on a transfer belt using an optical sensor. A method for detecting a positional deviation of each color toner pattern with respect to the reference color (black) will be described with reference to FIG. In FIG. 4, toner patterns of K (black), C (cyan), M (magenta), and Y (yellow) are formed on the transfer belt 105 along the traveling direction of the transfer belt 105. Two types of toner patterns are formed: a pattern perpendicular to the traveling direction of the transfer belt 105 (a pattern perpendicular to the sub-scanning direction) and a pattern inclined by 45 ° with respect to the traveling direction of the transfer belt 105.

  In this case, the edge of the pattern and the position of the center of gravity can be detected by the light detection signal from the optical sensor by moving the toner pattern. In other words, in FIG. 4, the toner pattern position shift in the C sub-scanning direction with respect to K can be detected by the difference between the detection time difference tkc between the K toner pattern and the C toner pattern and the theoretical value t0. Further, the toner pattern position deviation in the main scanning direction of C with respect to K can be detected by the difference between the detection time differences tk and tc. This toner pattern misregistration corresponds to the beam spot misregistration (color misregistration) of each color, so that the color misregistration of each color with respect to black is known. Therefore, the main scanning and sub-scanning color misregistration can be corrected using this detection result.

  FIG. 5 is a diagram showing a toner pattern for density detection. A toner pattern for density detection is formed for each color, and in FIG. 5, a pattern in which the toner density is changed in C (cyan) (the toner density increases from C1 to C5) is used using an optical sensor. Are detected sequentially. At this time, the pattern in which the toner density is changed is detected under the condition that the light from the optical sensor does not reach the edge of the pattern. Using this detection result, the optical power of the semiconductor laser in the optical scanning device is corrected, the developing bias in the developing unit is corrected, or the charging bias in the charging unit is corrected, so that the desired toner density is obtained. In addition, the image forming conditions can be reset.

  FIG. 6 is a diagram illustrating an optical sensor for toner pattern detection. In the optical sensor of FIG. 6, a light is emitted from an LED as a light source, and a spot is formed on the transfer belt (on the toner pattern) by a lens. Then, the specularly reflected light and diffused light from the toner pattern are detected by the specularly reflected light PD (photodiode) and the diffused light PD (photodiode) through the lens, respectively. At this time, both the regular reflection light PD and the diffused light PD may be provided, or one of them may be provided.

  By the way, the optical sensor of the present invention includes intensity distribution conversion means for changing the intensity distribution of light from the light source and / or light branching means for branching light from the light source into a plurality of parts.

  FIG. 17 shows an example in which light is branched using light branching means to detect a toner pattern. That is, in FIGS. 17 (a), (b) and (c), in addition to the light when there is no light branching means, the pattern is detected by a total of three lights of two lights branched by the light branching means. FIG. 17A shows an example in which light is branched in the moving direction of the toner pattern. FIG. 17B shows an example in which light is branched in an oblique direction with respect to the moving direction of the toner pattern. 17C shows an example in which light is branched in a direction perpendicular to the moving direction of the toner pattern.

  In the example of FIG. 17A, a single pattern can be detected three times, and the position of the toner pattern is determined using the three detection results (for example, the three detection results are averaged). Therefore, it is possible to improve the detection accuracy of the position of the toner pattern and prevent erroneous detection. Further, in the example of FIG. 17B, detection can be performed at a plurality of locations (three locations in the example of FIG. 17B) in a single pattern, so that the position of the toner pattern is determined using the detection result three times. (For example, by averaging three detection results), the influence of variations due to the location of the toner pattern (direction perpendicular to the moving direction of the toner pattern) can be reduced, and the detection accuracy and error of the toner pattern can be improved. Prevention of detection can be realized. In the example of FIG. 17C, the signal is detected only once, but since the signal includes information on a plurality of locations in a single pattern, the location of the toner pattern (direction perpendicular to the moving direction of the toner pattern). The effect of variation due to the toner can be reduced, the detection accuracy of the toner pattern position can be improved, and erroneous detection can be prevented.

  In the three examples of FIGS. 17A, 17B, and 17C, signals are detected three times in FIGS. 17A and 17B, so that later signal processing is slightly complicated. In the present invention, FIG. 17 (c), the simplest signal processing, is desirable.

  In the present invention, it is also possible to improve the detection accuracy of the position of the toner pattern and also the density and prevent erroneous detection by using the intensity distribution conversion means. Hereinafter, this will be described below. In the following description, it is assumed that the central portion of the light intensity distribution is flattened by the intensity distribution conversion means.

  Further, by using the intensity distribution conversion means and the light branching means together, it is possible to further improve the detection accuracy of the position of the toner pattern and also the density and to prevent erroneous detection.

  When detecting the position of a toner mark using an optical sensor, the factors that degrade accuracy include the scattering of toner at the edge of the toner pattern and rough edges, and surface shape characteristics such as scratches on the transfer belt surface. Can be mentioned. In general, in an optical sensor used to detect a toner mark, an LED is used as a light source. The intensity distribution of light from the LED has a Gaussian distribution, and the intensity distribution of the spot also has a Gaussian distribution. The light intensity at the center is strong, and the intensity decreases as the distance from the center increases. When a toner mark is detected using light having such an intensity distribution, the intensity distribution of the light spot is biased toward the center, so that the detection sensitivity at the center is increased and the detection sensitivity is decreased at the periphery. This corresponds to a strong detection of part of the information on the toner mark (or transfer belt). As a result, there is a problem that it becomes susceptible to local roughness of the edge portion of the toner pattern, local scratches on the transfer belt, and the like, resulting in deterioration of detection accuracy and erroneous detection.

  Therefore, in the present invention, when the intensity distribution conversion unit is used, the central portion of the light intensity distribution is flattened by the intensity distribution conversion unit, or a plurality of peaks exist in the light intensity distribution. And disperse the strong part.

  FIG. 7A shows an example of the intensity distribution of light from a conventional LED, and FIG. 7B shows that the intensity distribution in the center portion is flattened with respect to the intensity distribution of light in FIG. FIG. 7C shows an example in which a plurality of peaks are present with respect to the light intensity distribution of FIG. 7A. By making the light intensity distribution as shown in FIG. 7B or FIG. 7C, the aforementioned intensity deviation is reduced, and a relatively wide area of the toner pattern is detected with uniform (or close) intensity. Therefore, it is possible to reduce the influence of roughness at the edge portion and scratches on the transfer belt. In other words, an edge portion averaged over a relatively wide area can be detected, and even if the transfer belt is damaged, it can be detected by averaging over a wide area. By doing so, it is possible to improve the detection accuracy of the position of the toner pattern and reduce false detection, and provide a color image with small color misregistration.

  When detecting the toner concentration using an optical sensor, it is preferable to use a light spot with a flattened intensity distribution. Detecting density using a Gaussian-distributed light spot makes it more susceptible to local variations in toner density, but it uses a light spot with a flattened intensity distribution at the center. When the density is detected, the toner density in a wider range can be averaged and detected, so that it is less affected by local variations in the toner density, and the toner density detection accuracy can be improved.

  Here, in the present invention, “flattening” of the central portion of the light intensity distribution means that the central portion is flattened as compared to the Gaussian distribution, and includes that a plurality of peaks exist. Shall be.

  In the above description, an example has been shown in which the central portion of the light intensity distribution is flattened to improve the detection accuracy of the optical sensor and prevent erroneous detection. In accordance with the surface characteristics of the belt), it is possible to obtain an optimal light intensity distribution other than flattening.

  Next, a method of flattening the central portion of the light intensity distribution (how to control the light intensity distribution) will be described.

  Flattening of the central portion of the light intensity distribution can be performed using a diffractive optical element. Here, the diffractive optical element is an element that can two-dimensionally control the phase distribution of light, and specifically, an element in which a two-dimensional height distribution is provided on a transparent substrate (FIG. 8). See). In the example of FIG. 8, a plane wave having a Gaussian distribution intensity distribution is incident on the diffractive optical element to give a desired phase distribution and obtain an intensity distribution with a flat central portion as a far-field diffraction pattern. It is shown that. By appropriately controlling the height distribution (phase distribution) of the diffractive optical element, it is possible to obtain an arbitrary intensity distribution as well as an intensity distribution in which the central portion is flattened, and it is divided into a plurality of beams. It is also possible. That is, the light branching means can also be realized by the diffractive optical element. Further, not only the far field pattern but also a near field pattern can be used.

  The diffractive optical element preferably has a pixel structure from the viewpoint of ease of design and ease of manufacture.

  FIG. 9 shows an example of an optical sensor using a diffractive optical element. In the example of FIG. 9, in the optical sensor of FIG. 6, the light from the LED is collected by the lens and then passed through the diffractive optical element, so that on the toner pattern (on the transfer belt), ) A toner pattern can be detected using a light spot having a flattened intensity distribution at the center. In FIG. 9, the diffractive optical element can also be provided on the LED side of the lens. Furthermore, since the diffractive optical element can provide a lens function in addition to the function of flattening the intensity distribution, the lens between the LED and the toner pattern in FIG. 9 can be removed. Cost reduction can be realized.

  In the above-described example, the LED is used as the light source of the optical sensor. However, an LD (laser diode; semiconductor laser) may be used instead of the LED. However, since the light from the LD is coherent, when the intensity distribution is flattened using a diffractive optical element, speckles (a phenomenon in which a locally strong and weak part occurs) occur in the flat part. It becomes easy. On the other hand, since speckle is not generated in partial coherent light such as an LED, partial coherent light such as an LED is more preferable in the present invention.

  Further, as another method for flattening the intensity distribution of the Gaussian distribution, an aspheric lens can be used instead of the diffractive optical element. However, since the surface shape of such an aspheric lens is very complicated and difficult to manufacture, and it is also susceptible to manufacturing errors, it is desirable to use a diffractive optical element.

  If only the function of flattening the intensity distribution of light is possible, it can be realized with a diffractive optical element configured with a height distribution of two steps or a small number of steps. In this case, the height of the multi-stage (eight or more stages) is required, which makes it difficult to manufacture the diffractive optical element. Therefore, as shown in FIG. 9, it is desirable to provide a lens (for example, a coupling lens for coupling light from the light source) between the LED and the toner pattern. That is, in the optical sensor of the present invention, when a coupling lens that couples light from a light source is further provided, light with a flattened intensity distribution without increasing the difficulty of manufacturing a diffractive optical element. You can get a spot.

  The pattern detection apparatus of the present invention includes the above-described optical sensor of the present invention, a predetermined pattern, a moving unit that moves at least one of the light in the optical sensor and the predetermined pattern, and the optical sensor. And detecting means for detecting the predetermined pattern based on a light detection signal from the light detecting means.

  In such a pattern detection device, it is preferable that the light intensity distribution is at least flattened in a direction perpendicular to the moving direction of the predetermined pattern as viewed from the optical sensor. That is, as shown in FIG. 10, the light intensity distribution should be flattened at least in the direction perpendicular to the moving direction of the toner pattern. In other words, in order to reduce the influence of edge roughness and the transfer belt, it is effective to average the influence in the direction perpendicular to the moving direction of the toner pattern. It is possible to improve the position detection accuracy and prevent false detection.

  Further, when used for toner density detection, it is desirable to flatten the light intensity distribution in both the horizontal direction and the vertical direction of the toner pattern. This is because when detecting the toner density, light is not applied to the edge.

  In the pattern detection apparatus of the present invention, the two-dimensional shape of the light intensity distribution in the optical sensor may be a quadrangle. In other words, as shown in FIG. 11, it is more desirable that the light spot shape is a quadrangle as shown in FIG. By making the light spot shape square, it is possible to further improve the detection accuracy of the position of the toner pattern and also the density, and to reduce false detection. Such a spot shape can be created using the diffractive optical element described above. Strictly speaking, a rectangular spot generated using a diffractive optical element does not become a perfect square, the boundary of the edge portion is blurred, and the corners of the four corners of the square are rounded. Such a spot shape is also referred to as a square. By making the spot shape square, the cross section of the spot that crosses the edge of the toner pattern is always almost the same shape regardless of the positional relationship between the spot and the toner pattern, so that the edge can be detected stably, It becomes possible to further improve the detection accuracy of the position and density of the toner pattern and to prevent erroneous detection.

Here, the shape of the light spot is a shape obtained by joining places having the same intensity in the intensity distribution. In the present invention, the place having the intensity of 1 / e ² of the maximum intensity is joined. Shape.

  In the pattern detection apparatus of the present invention, the two-dimensional shape of the light intensity distribution in the optical sensor is perpendicular to the movement direction of the predetermined pattern rather than the light width in the movement direction of the predetermined pattern as viewed from the optical sensor. The width of the light in any direction should be longer. That is, as shown in FIG. 12, it is preferable to form the light spot so that the width in the direction perpendicular to the moving direction is longer than the width in the moving direction of the toner pattern. This is because the detection accuracy can be improved when the width of the light spot in the moving direction of the toner pattern is narrow, and the detection accuracy can be improved when the width of the light spot in the direction perpendicular to the moving direction of the toner pattern is wide. . In the direction of movement of the toner pattern, the narrower the light spot, the sharper the rise (or fall) of the optical signal detected by the PD (photodiode) as the light detection means. Detection accuracy is improved. In addition, when the width of the light spot in the direction perpendicular to the moving direction of the toner pattern is wider, the influence of rough edges and the effect of scratches on the transfer belt can be averaged, and the detection accuracy of the position of the toner pattern can be improved.

  In FIG. 12, spots on an ellipse are shown. In FIG. 12, the spot shape is changed to a quadrangular shape (in FIG. 12, a horizontally long square shape) (by combining with the example of FIG. 11), the toner. It is possible to further improve the detection accuracy of the position of the pattern and the density and prevent erroneous detection.

  When it is used for toner density detection, it is desirable to use as shown in FIG. 12, and by doing so, the width of the toner pattern in the moving direction of the toner pattern can be narrowed, the toner consumption is reduced, and the environmental load is reduced. Can contribute to reduction.

  FIG. 13 shows a signal from a regular reflection light PD (photodiode) when the toner pattern is moved and the toner pattern is detected by a light spot. The output signal from the PD is sampled and detected, and the time when the toner pattern passes the photosensor is determined from the time when the preset threshold value is crossed from the bottom to the top and the time when the threshold value is crossed from the top to the bottom. The time when the toner pattern passes through the optical sensor may be determined only by the time that crosses the threshold value from the bottom to the top or only the time that crosses the threshold value from the top to the bottom, but the circuit can be simplified, but the detection accuracy is possible. Falls a little.

  Thus, in the pattern detection apparatus of the present invention, the detection means can detect the time for which the predetermined pattern passes the light in the optical sensor by detecting the edge of the predetermined pattern.

  In addition, a peak occurs in the light detection signal due to the relationship between the pattern size and the light size. Therefore, in the pattern detection apparatus of the present invention, the detection means can also detect the barycentric position of the predetermined pattern by detecting the peak position of the light detection signal. That is, in the output signal from the PD (photodiode) in FIG. 13, the peak position can be detected using the peak hold circuit. This corresponds to detecting the position of the center of gravity of the toner pattern.

At this time, in the moving direction of the predetermined pattern viewed from the optical sensor, the width of light in the optical sensor (defined by the intensity width that is 1 / e ^{2 of the} maximum intensity) and the width of the predetermined pattern are substantially equal. (That is, the width in the moving direction of the toner pattern and the width of the light spot (the width of the light spot in the moving direction of the toner pattern) (defined at 1 / e ^{2 of the} maximum intensity)). Thus, there is a peak in the output signal from the PD.

  In the above description, the toner pattern formed on the transfer belt has been described as an example of the predetermined pattern. However, the present invention is not limited to this, for example, directly on the moving medium (for example, belt). It can also be used when detecting a pattern. Even when the pattern is directly formed on the belt, the edge of the pattern is considered to be rough. The pattern detection apparatus of the present invention has at least an optical sensor and a predetermined pattern, and detects a time during which the predetermined pattern passes through the optical sensor while moving at least one of the optical sensor or the predetermined pattern. It can be used for

  In addition, an optical scanning device, a plurality of image carriers, and an optical scanner scans the image carrier with a beam spot to form an electrostatic image, and the formed electrostatic image is visualized with each color toner. A multi-color image forming apparatus for forming a color image, and a photosensor according to the present invention, and a developing unit that transfers the image visualized on the image carrier to a medium such as paper. A pattern detection apparatus can be applied.

  In the multicolor image forming apparatus as described above, when detecting the toner pattern formed on the transfer belt, the optical sensor of the present invention has one optical sensor near the center of the optical scanning range, as shown in FIG. It is preferable to provide a total of three, one near each end. That is, in this case, the optical sensor in the vicinity of the center can detect a deviation in the sub-scanning direction (image writing position deviation) of each color (cyan, yellow, magenta) with respect to the reference color (for example, black), and the vicinity of both ends. With this optical sensor, it is possible to detect an inclination deviation of each color image, an image writing position deviation in the main scanning direction, and an image width deviation in the main scanning direction. These misregistration amounts can be corrected by using a correcting unit described later, and a color image in which the color misregistration is favorably corrected can be obtained.

  As a method of correcting the image writing position deviation in the sub-scanning direction, the angle or position of the light emitted from the optical scanning device in the sub-scanning direction may be changed. Further, when the optical scanning devices corresponding to the respective colors are not integrated as shown in FIG. 1 but are independent for each color, it is also possible to move the optical scanning devices for the respective colors.

  The means for changing the angle or position of the light emitted from the optical scanning device in the sub-scanning direction can be realized by rotating or moving an optical path bending mirror provided in the optical scanning device. Also, the tilt of the image can be corrected by rotating or moving the mirror.

  Further, as another means for changing the angle of the light emitted from the optical scanning device in the sub-scanning direction, a liquid crystal deflecting element as shown in FIG. 14 is provided between the polygon mirror and the light source in the optical scanning device. It is also possible.

Here, the liquid crystal deflecting element is an element that deflects light by utilizing a change in refractive index with respect to light having a certain polarization direction when a voltage is applied. The liquid crystal deflecting element is not limited to liquid crystal, but may be LiNbO ₃ or the like. It can also be realized using other electro-optic materials. Hereinafter, a liquid crystal is taken as an example of the electro-optic material, and description is made with reference to FIG. The liquid crystal deflecting element is used by being installed between the light source and the deflecting means, as in the wedge prism described later.

  FIG. 14A shows the outer shape of the liquid crystal element 43. FIG. 14C shows a schematic diagram of the configuration of the liquid crystal deflecting means. That is, (i) in FIG. 14C shows the cross-sectional structure of the liquid crystal element 43 and the alignment state of the liquid crystal molecules.

  In (i) of FIG. 14C, a liquid crystal layer 54 having a thickness of about several to several tens [μm] is provided with two glass substrates 51 via transparent electrodes 52-1 and 52-2 and an alignment film 53. -1 and 51-2. In this figure, the transparent electrodes 52-1 on the lower side (laser beam incident surface side) are striped electrode patterns 56 (56-1, 56-) arranged at equal intervals as shown in FIG. 2, ..., 56-n), and the transparent electrode 52-2 on the upper side (laser beam emitting surface side) has a uniform electrode pattern on the entire surface.

  Here, FIG. 14B is a view of the transparent electrode 52-1 in the effective area where the optical path can be deflected as viewed from the incident side. In the transparent electrode 52-1, striped transparent electrode patterns 56 that are long in the vertical direction of the drawing are arranged at equal intervals (in the left-right direction), and the striped transparent electrodes 56-1, 56-2,. , 56-n are electrically connected by a pair of resistance members 55. Note that the horizontal direction in the drawing is the direction in which the light beam (laser beam) is deflected in the optical path, and corresponds to the sub-scanning direction when correcting the scanning line interval of a plurality of beams.

  Two terminals (terminal 1 and terminal 2) are provided at the left and right ends (56-1 and 56-n) of the striped electrode pattern, and a drive signal can be applied to these two terminals. By applying different voltages to the terminal 1 and the terminal 2, as shown in (ii) of FIG. 14C, a linear potential distribution (constant constant) in which the resistance value R of the resistor 55 is a proportional constant in the liquid crystal layer. Gradient) can be generated. According to this potential distribution, the tilt angle φ of the liquid crystal molecules in the liquid crystal layer 54 can be changed. When a light beam polarized in the major axis direction of the liquid crystal (when no voltage is applied) is incident on the liquid crystal molecules thus aligned, the light beam is polarized as shown in (iii) of FIG. Feel the gradient of refractive index in the same direction. Therefore, this liquid crystal element works like a prism and can deflect the light beam. When the voltage applied to the terminals 1 and 2 is changed, the gradient of the refractive index can be changed, so that the deflection angle of the light beam can be controlled.

  As another means for changing the angle of the light emitted from the optical scanning device in the sub-scanning direction, a wedge-shaped prism can be used as shown in FIG. That is, in FIG. 15, the angle in the sub-scanning direction of the beam emitted from the wedge prism can be changed by rotating the wedge prism about the x axis. The wedge-shaped prism is a prism-like member having a non-parallel entrance surface and exit surface, and is preferably installed between the light source and the deflecting means. By rotating around the x-axis shown in FIG. 15, the angle of the beam emitted from the wedge prism in the sub-scanning direction changes, and the sub-scanning position of the beam on the surface to be scanned can be corrected. .

  Further, the formation start position in the sub-scanning direction of the image can be corrected by electrical means, and can be corrected in units of one line corresponding to the image resolution. This will be described with reference to FIGS. 16 (a) and 16 (b).

  First, the start of image formation will be described. After the optical scanning control unit operation start signal (STOUT signal) for starting the operation of the optical scanning control unit is detected, the optical scanning start signal (SOS signal) is counted and reaches a preset count number (Cs). Then, image formation is started ((1) in FIGS. 16A and 16B). The SOS signal is detected once per scan by light detection means such as a PD.

  In order to adjust the image formation start position in the sub-scanning direction in units of one line according to the image resolution, the value of Cs may be changed. If the value of Cs is decreased by 1 ((2) in FIGS. 16A and 16B), image formation in the sub-scanning direction is accelerated by one line, and if the value of Cs is increased by 1 (FIG. 16A). , (B) (3)), image formation in the sub-scanning direction is delayed by one line.

  As described above, by changing the count value of the SOS signal, it is possible to correct the formation start position of the image in the sub-scanning direction. If 600 dpi, the correction is performed in units of 42.3 μm, and 1200 dpi in units of 21.2 μm. can do. That is, the sub-scanning position can be corrected by adjusting the formation start position of the image in the sub-scanning direction.

  Also, for example, the same as above can be achieved by providing a blank line at the head of the image data and changing the number of blank lines.

  The example of correcting the formation start position of several images in the sub-scanning direction has been described above. However, the method of correcting the formation start position of the image in the sub-scanning direction in units of one line is the simplest and suitable for the present invention. It is. However, since the minimum correction unit is one line unit of image resolution, a method using rotation or movement of a mirror, a method using a wedge prism, or a method using a liquid crystal deflecting element is used for more accurate correction. It is necessary to use this, and an analog correction can be made with one line or less.

  If a pattern as shown in FIG. 4 is formed in the vicinity of both ends of the scanning area, it is possible to further detect an image writing position deviation in the main scanning direction and a full width deviation of the image. As described above, the image writing position deviation in the main scanning direction is the time from when the signal is detected by the PD (photo detector) provided on the optical scanning start side and in the area not contributing to the image formation until the image formation is started. The time can be corrected by advancing or delaying (accurately, the number of clocks counted from when a signal is detected by the PD to when image formation is started is increased or decreased). Further, the full width deviation of the image in the main scanning direction can be corrected by changing the clock frequency for driving the light source.

  Also, the conditions for forming a desired toner concentration may change over time. Therefore, in the multicolor image forming apparatus of the present invention, the pattern detection device is configured to detect the density of a predetermined pattern and control the toner image forming conditions using the detection result of the density of the predetermined pattern. Can do. Specifically, using the above-described optical sensor, a toner density detection pattern is detected, and the detection result is used to correct the optical power of the laser in the optical scanning device, or to correct the developing bias in the developing unit, The image forming conditions are reset so as to correct the charging bias in the charging unit or to obtain a desired toner density. By doing so, it is possible to obtain a color image in which the color change is suppressed.

  As described above, when the detection accuracy of the toner pattern is improved and the false detection is reduced, the correction frequency can be reduced and the frequency of forming the toner pattern can be reduced. Thereby, resource saving can be achieved by reducing toner consumption.

  FIG. 18 is a diagram illustrating a hardware configuration example of the pattern detection apparatus of the present invention. In this pattern detection apparatus, a CPU 501, ROM 502, RAM 503, HDD (hard disk drive) 504, HD (hard disk) 505, FDD (flexible disk drive) 506, and optical sensor (optical sensor of the present invention) 511 are connected by a bus 500. Configured.

  A CPU 501 controls the entire apparatus. A basic input / output program is stored in the ROM 502. The RAM 503 is used as a work area for the CPU 501. The HDD 504 controls data read / write with respect to the HD 505 according to the control of the CPU 501. The HD 505 stores data written according to the control of the HDD 504. The FDD 506 controls data read / write with respect to the FD (flexible disk) 507 in accordance with the control of the CPU 501.

  In the pattern detection apparatus of the present invention, a detection process of moving at least one of the light and the predetermined pattern in the optical sensor of the present invention and detecting the predetermined pattern by a light detection signal from the optical sensor is performed by the CPU 501. It can be realized by control.

  Then, the processing in the pattern detection apparatus described in the above-described best mode for carrying out the present invention (specifically, at least one of the light and the predetermined pattern in the optical sensor of the present invention is moved, and the optical sensor The detection process for detecting the predetermined pattern by the light detection signal from can be provided in the form of a program realized by a computer (for example, CPU 501).

  Further, the processing in the pattern detection apparatus described in the above-described best mode for carrying out the present invention (specifically, at least one of the light and the predetermined pattern in the optical sensor of the present invention is moved, and the optical sensor A program for causing a computer to execute a detection process for detecting the predetermined pattern using a light detection signal from a computer is a hard disk (505), a floppy (registered trademark) disk 507, a computer such as a CD-ROM, MO, or DVD. Are recorded on a readable recording medium, and are executed by being read from the recording medium by a computer. The program can be distributed via the recording medium and a network such as the Internet.

The present invention can be used for digital copying machines, laser printers, laser facsimiles, and the like.

1 is a diagram (perspective view) illustrating a configuration example of an optical scanning device applied to a full-color image forming apparatus. It is sectional drawing of FIG. 1 is a diagram illustrating a basic configuration of a multicolor image forming apparatus. FIG. 6 is a diagram for explaining how to detect a positional deviation measurement pattern formed by toner of each color on a transfer belt using an optical sensor. FIG. 6 is a diagram illustrating a toner pattern for density detection. It is a figure which shows the optical sensor for a toner pattern detection. It is a figure which shows intensity distribution of light. It is a figure for demonstrating a diffractive optical grating. It is a figure which shows the example of the optical sensor using a diffractive optical element. . FIG. 10 is a diagram illustrating flattening of the light intensity distribution in a direction perpendicular to the moving direction of the toner pattern. It is a figure which shows the case where the spot shape of light is made into the rectangle. FIG. 6 is a diagram illustrating a case where a light spot is formed so that a width in a direction perpendicular to a moving direction is longer than a width in a moving direction of a toner pattern. It is a figure which shows the signal from PD for regular reflection light (photodiode) when a toner pattern is moved and a toner pattern is detected with a light spot. It is a figure for demonstrating a liquid-crystal deflection | deviation element. It is a figure which shows a wedge-shaped prism. FIG. 5 is a diagram for explaining a method of correcting a formation start position in the sub-scanning direction of an image. It is a figure which shows the example which branches a light using a light branching means, and detects a toner pattern. It is a figure which shows the hardware structural example of the pattern detection apparatus of this invention.

Explanation of symbols

105 Transfer Belt 213 Polygon Mirror 209 Cylindrical Lens 4fθ Lens 2181, 2182, 2183, 2184
Toroidal lenses 2201, 2202, 2203, 2204
227 Folding mirror 1Y, 1M, 1C, 1K photoconductor,
2Y, 2M, 2C, 2K charger,
20 optical scanning device,
4Y, 4M, 4C, 4K developer,
5Y, 5M, 5C, 5K cleaning means,
6Y, 6M, 6C, 6K charging means for transfer,
105 transfer belt,
30 Fixing means 500 Bus 501 CPU
502 ROM
503 RAM
504 HDD
505 HD
506 FDD
507 FD
511 Optical sensor

Claims (21)

An optical sensor having a light source that emits light to a predetermined object and a light detection unit that detects light from the object, wherein the optical sensor further changes an intensity distribution of light from the light source. An optical sensor comprising: an intensity distribution conversion unit that performs the above and / or a light branching unit that branches light from the light source into a plurality of lights. 2. The optical sensor according to claim 1, wherein the intensity distribution conversion means and / or the light branching means uses a diffractive optical element that two-dimensionally controls the phase of light from the light source, An optical sensor characterized by changing distribution and / or branching light from a light source into a plurality of lights. 3. The optical sensor according to claim 1, wherein the intensity distribution conversion unit flattens a central portion of the intensity distribution of light from the light source. The optical sensor according to any one of claims 1 to 3, further comprising a coupling lens for coupling light from the light source. 5. The optical sensor according to claim 1, a predetermined pattern, a moving unit that moves at least one of light in the optical sensor and the predetermined pattern, and the optical sensor. A pattern detection apparatus comprising: detection means for detecting the predetermined pattern based on a light detection signal from a light detection means. 6. The pattern detection apparatus according to claim 5, wherein an intensity distribution of light is at least flattened in a direction perpendicular to a moving direction of the predetermined pattern as viewed from the optical sensor. 7. The pattern detection apparatus according to claim 5, wherein the two-dimensional shape of the light intensity distribution in the optical sensor is a quadrangle. 8. The pattern detection device according to claim 5, wherein the two-dimensional shape of the light intensity distribution in the optical sensor is light in a moving direction of the predetermined pattern as viewed from the optical sensor. The pattern detection apparatus is characterized in that the width of light in the direction perpendicular to the moving direction of the predetermined pattern is longer than the width of the predetermined pattern. 9. The pattern detection apparatus according to claim 5, wherein the detection unit detects the edge of the predetermined pattern, so that the predetermined pattern passes through the light in the optical sensor. 10. A pattern detection apparatus for detecting time. 9. The pattern detection apparatus according to claim 5, wherein the detection unit detects a barycentric position of the predetermined pattern by detecting a peak position of the light detection signal. A characteristic pattern detection apparatus. The pattern detection apparatus according to claim 10, wherein in the moving direction of the predetermined pattern viewed from the optical sensor, the width of light in the optical sensor (defined by the intensity width that is 1 / e ^{2 of the} maximum intensity) and the A pattern detection apparatus characterized in that the width of the predetermined pattern is substantially equal. A multi-color image forming apparatus having an optical scanning device and forming a color image, comprising the pattern detection device according to any one of claims 5 to 11, forming a predetermined pattern with toner, The multicolor image forming apparatus, wherein the predetermined pattern is detected based on a light detection signal from the photosensor while moving the predetermined pattern. 13. The multicolor image forming apparatus according to claim 12, further comprising an image forming position correcting unit in the sub-scanning direction, wherein the image forming position correcting unit determines a position of the image in the sub-scanning direction based on the detection result of the predetermined pattern. A multicolor image forming apparatus, wherein correction is performed. 14. The multicolor image forming apparatus according to claim 13, wherein the image forming position correcting means is an angle changing means for changing an angle in a sub-scanning direction of light emitted from the optical scanning device, or an output from the optical scanning device. A multi-color image forming apparatus configured as position changing means for changing the position of incident light in the sub-scanning direction. 15. The multicolor image forming apparatus according to claim 14, wherein the angle changing means or the position changing means is configured as means for rotating or moving a mirror provided in an optical scanning device. Color image forming apparatus. 15. The multicolor image forming apparatus according to claim 14, wherein the angle changing means is configured as means for controlling a voltage applied to a liquid crystal deflecting element provided in an optical scanning device. Image forming apparatus. 14. The multi-color image forming apparatus according to claim 13, wherein the image forming position correcting unit controls the light emission timing of the light source inside the optical scanning device, thereby determining the formation start position of the image in the sub-scanning direction according to the image resolution. A multi-color image forming apparatus configured as means for shifting in the sub-scanning direction in units of one line. 13. The multicolor image forming apparatus according to claim 12, wherein the pattern detection device detects the density of the predetermined pattern, and controls a toner image forming condition using a detection result of the density of the predetermined pattern. A multicolor image forming apparatus. The light of the optical sensor according to any one of claims 1 to 4 is moved and at least one of the predetermined pattern is moved, and the predetermined pattern is detected by a light detection signal from the optical sensor. Characteristic pattern detection method. 5. A detection process in which at least one of the light and the predetermined pattern in the optical sensor according to claim 1 is moved, and the predetermined pattern is detected by a light detection signal from the optical sensor. A program to make a computer realize. 5. A detection process in which at least one of the light and the predetermined pattern in the optical sensor according to claim 1 is moved, and the predetermined pattern is detected by a light detection signal from the optical sensor. The computer-readable recording medium which recorded the program for making a computer perform.

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