JP4738002B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic method such as a digital copying machine, a laser printer, a facsimile, or a composite machine thereof, and more particularly, after forming a plurality of latent images by scanning a plurality of laser beams. The present invention relates to an image forming apparatus for forming a color image.

  Conventionally, in an image forming apparatus such as a digital color copying machine or a laser color printer, a tandem type in which a plurality of image carriers (photosensitive drums) are arranged in parallel in order to prevent color misregistration and achieve high resolution. Is often used.

  Specifically, the laser beams respectively emitted from a plurality of light sources are deflected by a polygon mirror (light deflector), and then passed through respective optical paths by an imaging optical system, onto a plurality of image carriers (photosensitive drums). Focused. Further, the light spot of the laser beam condensed on each image carrier is scanned in the main scanning direction, and each image carrier is rotated in the sub-scanning direction (a direction perpendicular to the main scanning direction). Thus, a desired electrostatic latent image is formed on each image carrier.

  Thereafter, the latent image formed on each image carrier is developed at a position facing the developing unit, and a toner image of each color is formed on each image carrier. The toner images respectively formed on the plurality of image carriers are transferred onto the transfer target (an intermediate transfer belt, a recording medium, etc.) facing the plurality of image carriers. Thus, a color toner image is formed on the transfer target.

On the other hand, in Patent Document 1 or the like, the potential of a latent image pattern is detected by a potential sensor, or the image density of a toner pattern is set for the purpose of detecting unevenness in the scanning line pitch of laser light emitted from a plurality of light sources. A technique for detecting with an optical sensor is disclosed.
Further, in Patent Document 2, etc., for the purpose of optimizing the beam diameter and beam pitch of the laser beam, the laser beam irradiated on the photosensitive drum is detected and the beam diameters in the main scanning direction and the sub-scanning direction are detected. Techniques for measuring are disclosed.

Japanese Patent Laid-Open No. 10-58746 JP 2001-281572 A

  In the conventional image forming apparatus described above, the positional deviation of the laser beam is not sufficiently adjusted, and the image quality of the output image may be insufficient.

Details are as follows.
In recent color image forming apparatuses, in order to achieve miniaturization, high image quality, and high speed, intervals between laser beams emitted from a plurality of light sources are narrow. For this reason, the pitch interval and the scanning line width of the laser beams are reduced, and it is difficult to position the scanning lines in the plurality of laser beams.

In addition, a laser beam position shift (scanning state change) may occur due to a change (disturbance) in the apparatus installation environment such as a temperature change or a humidity change, and a defect such as a color shift may occur on the output image.
Furthermore, when the apparatus is operated for a long time and heat is generated in the polygon mirror and the fixing unit, temperature fluctuations between optical elements constituting the scanning imaging optical system and temperature distribution in the optical elements are caused, There may be a problem such as color misregistration on the output image due to laser beam misregistration.

  The degree of such laser beam misregistration is often different for each laser beam emitted from a plurality of light sources. That is, since the laser beams emitted from a plurality of light sources pass through independent optical paths (separate optical elements or different reflection positions or transmission positions in a common optical element) and reach each image carrier, disturbances are caused respectively. And the degree of heat effects are not equal. For this reason, when a plurality of toner images obtained by developing the latent images formed on the respective image carriers are transferred on the transfer target body, color misregistration occurs.

On the other hand, the above-described technologies such as Patent Document 1 and Patent Document 2 detect only the toner pattern or only the laser beam and correct the scanning state of the laser beam based on the detection result. There was a high possibility that the positional deviation of the was not adjusted sufficiently.
For example, when correcting the scanning state of laser light based on the detection result of only the toner pattern, even if the scanning position of the laser light corresponding to each scanning line is moved by the correction width, The passing position before correction of the laser beam cannot be grasped, and the laser beam cannot be appropriately moved to the target position.

  Further, by correcting one of the inclination of the laser beam in the scanning line direction, the registration shift (pitch interval shift) and the magnification error in the sub-scanning direction, another positional shift may newly occur.

In the case of a tandem type color image forming apparatus (or revolver type color image forming apparatus), a plurality of latent images are formed on a plurality (or a single number) of image carriers. Even if the scanning state of the laser beam was corrected based on the detection result, a sufficient effect could not be obtained. In other words, positional displacement may occur during the transfer process from the image carrier to the transfer target after the latent image process.
In addition, there are a plurality of causes of misalignment due to superposition, such as uneven pitch in the sub-scanning direction between a plurality of scan lines (position misalignment between a plurality of superposed scan lines) and magnification error between scan lines. In some cases, variations in individual scanning states for each scanning line are also included. Therefore, since they cannot be detected at the same time, it is not possible to achieve highly accurate scanning line superposition.

  The present invention has been made in order to solve the above-described problems, and it is an object of the present invention to provide an image forming apparatus in which the positional deviation of laser light is reliably adjusted and image quality defects such as color deviation do not occur.

The image forming apparatus according to the first aspect of the present invention forms a plurality of latent images on a plurality or a single image carrier that scans a laser beam in the main scanning direction and travels in the sub-scanning direction. An image forming apparatus for transferring a plurality of toner images formed by developing the plurality of latent images formed on the image carrier in a superimposed manner on the transfer target body, outside of both ends of the scanning region of the laser beam A plurality of light receiving elements respectively disposed on the plurality of light receiving elements, and detecting the laser light incident on the plurality of light receiving elements to detect an inclination of a scanning line in the laser light, a registration shift in a main scanning direction, and a sub scanning direction. First detection means for detecting at least one of the registration error and magnification error in the main scanning direction, and second detection means for detecting an overlay error of the plurality of toner images transferred onto the transfer target body; Inject the laser beam Variably controlling a deflection angle in a deflecting element disposed in an optical path of the laser light from the light source to the image carrier, and controlling a pulse of image data input to the light source to Adjusting means for adjusting the inclination of the scanning line, the registration deviation in the main scanning direction, the registration deviation in the sub-scanning direction, and the magnification error in the main scanning direction, respectively, and the adjustment means uses the detection result of the second detection means. Based on the inclination of the scanning line in the laser beam, the registration deviation in the main scanning direction, the registration deviation in the sub-scanning direction, and the magnification error in the main scanning direction, the detection result does not match the target value and needs to be adjusted. after adjusting based on the optimal adjustment values obtained against the control table so as to approach the target value, the slope based on the detection result of the first detecting means of the scanning lines in the laser beam, Registration deviation in the scanning direction, registration deviation in the sub-scanning direction, and magnification error in the main scanning direction that do not match the target value and need to be adjusted until the difference from the target value falls within a predetermined range To be adjusted.

The image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the adjusting means is configured such that the first detecting means causes the scanning line inclination and the magnification in the main scanning direction in the laser light to be adjusted. When an error is detected, the magnification error in the main scanning direction is adjusted after adjusting the inclination of the scanning line of the laser beam.

The image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect , wherein the adjusting unit is configured to detect the inclination of the scanning line in the laser beam and the resist in the sub-scanning direction by the first detecting unit. When a deviation is detected, the registration deviation in the sub-scanning direction is adjusted after adjusting the inclination of the scanning line of the laser beam.

The image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect , wherein the adjustment unit is configured such that the first detection unit causes the magnification error in the main scanning direction in the laser light and the sub-scanning direction. When the registration error is detected, the registration error in the sub-scanning direction is adjusted after adjusting the magnification error of the laser beam in the main scanning direction.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the adjustment unit is prepared in advance with the detection result of the second detection unit. By collating with the control table, the inclination of the scanning line in the laser beam, the registration deviation in the main scanning direction, the registration deviation in the sub-scanning direction, and the magnification error in the main scanning direction are adjusted.

According to a sixth aspect of the present invention, in the image forming apparatus according to any of the first to fifth aspects of the present invention, the first detection unit is configured to provide each laser beam corresponding to the plurality of latent images. A plurality of them are arranged.

The image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, wherein the adjusting means is configured to adjust the inclination of the scanning line in the laser light by the feedback control. It adjusts the registration error in the scanning direction, the registration error in the sub-scanning direction, and the magnification error in the main scanning direction.

An image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to any one of the first to seventh aspects, further comprising third detection means for detecting temperature or / and humidity in the apparatus. The adjusting means adjusts the scanning line inclination, registration deviation in the main scanning direction, registration deviation in the sub-scanning direction, and magnification error in the main scanning direction by feedforward control based on the detection result of the third detection means. Is to adjust.

An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to any one of the first to eighth aspects, wherein the adjusting means is configured to emit a plurality of laser beams corresponding to the plurality of latent images. By adjusting the inclination of the scanning line in one laser beam, the registration deviation in the main scanning direction, the registration deviation in the sub-scanning direction, and the magnification error in the main scanning direction, scanning with the other laser light with the one laser beam as a reference. This adjusts the inclination of the line, the registration error in the main scanning direction, the registration error in the sub-scanning direction, and the magnification error in the main scanning direction.

An image forming apparatus according to a tenth aspect of the present invention is the image forming apparatus according to any one of the first to ninth aspects, wherein the plurality of latent images are respectively emitted from a plurality of light sources. It is formed on each of the plurality of image carriers.

  According to the present invention, the positional deviation of the laser beam is adjusted based on the detection result of the positional deviation of the laser beam and the detection result of the positional deviation of the plurality of toner images transferred onto the transfer target. As a result, it is possible to provide an image forming apparatus in which the positional deviation of the laser light is reliably adjusted, and image quality defects such as color deviation do not occur.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a main body of a tandem type color copier as an image forming apparatus, 2 is an optical scanning device (writing unit) that emits laser light based on input image information, and 3 is an original D to an original reading unit 4. A document conveying unit for conveying, 4 is a document reading unit (scanner) for reading image information of document D, and 21Y, 21M, 21C, and 21BK are image carriers on which toner images of respective colors (yellow, magenta, cyan, and black) are formed. As the photosensitive drum, 22 is a charging unit for charging each of the photosensitive drums 21Y, 21M, 21C, and 21BK, and 23 is for developing an electrostatic latent image formed on each of the photosensitive drums 21Y, 21M, 21C, and 21BK. A developing unit 24, a transfer bias roller for transferring the toner images formed on the photosensitive drums 21Y, 21M, 21C, and 21BK to the intermediate transfer belt 27; Body drum 21Y, 21M, 21C, a cleaning unit for collecting the untransferred toner on 21BK shown.

  Reference numeral 27 denotes an intermediate transfer belt as a transfer medium onto which toner images of a plurality of colors are transferred, and 28 denotes a second transfer for further transferring the toner image transferred on the intermediate transfer belt 27 to the recording medium P. Bias roller 29 is an intermediate transfer belt cleaning unit that collects untransferred toner on the intermediate transfer belt 27, 30 is a conveyance belt that conveys a recording medium P onto which a four-color toner image has been transferred, and 61 is transfer paper or the like A paper feeding unit 66 for storing the recording medium P, and a fixing unit 66 for fixing an unfixed image on the recording medium P are shown.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, an image processing unit (not shown) performs color conversion processing, color correction processing, spatial frequency correction processing, and the like on the basis of RGB color separation image signals, so that yellow, magenta, cyan, and black are processed. Get color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the optical scanning device 2. The optical scanning device 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 21Y, 21M, 21C, and 21BK.

On the other hand, the four photosensitive drums 21Y, 21M, 21C, and 21BK rotate in the clockwise direction in FIG. First, the surfaces of the photosensitive drums 21Y, 21M, 21C, and 21BK are uniformly charged at a position facing the charging unit 22 (a charging process). Thus, a charging potential is formed on the photoconductive drums 21Y, 21M, 21C, and 21BK. Thereafter, the charged surfaces of the photosensitive drums 21Y, 21M, 21C, and 21BK reach the irradiation positions of the respective laser beams.
In the optical scanning device 2, laser light corresponding to the image signal is emitted from four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process). The configuration and operation of the optical scanning device 2 will be described in detail later.

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 21Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotational axis direction (main scanning direction) of the photosensitive drum 21Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 21Y after being charged by the charging unit 22.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 21M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 21C from the left side of the drawing, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 21BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photosensitive drums 21Y, 21M, 21C, and 21BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 23, respectively. Then, each color toner is supplied from the developing devices 23 onto the photosensitive drums 21Y, 21M, 21C, and 21BK, and the latent images on the photosensitive drums 21Y, 21M, 21C, and 21BK are developed (development process). .)
Thereafter, the surfaces of the photosensitive drums 21Y, 21M, 21C, and 21BK after the development process reach positions facing the intermediate transfer belt 27 (transfer body), respectively. Here, the transfer bias roller 24 is installed at each facing position so as to contact the inner peripheral surface of the intermediate transfer belt 27. Then, the toner images of the respective colors formed on the photosensitive drums 21Y, 21M, 21C, and 21BK are sequentially superimposed and transferred onto the intermediate transfer belt 27 at the position of the transfer bias roller 24 (in the first transfer step). is there.).

Then, the surfaces of the photosensitive drums 21Y, 21M, 21C, and 21BK after the first transfer process reach positions facing the cleaning unit 25, respectively. Then, the untransferred toner remaining on the photosensitive drums 21Y, 21M, 21C, and 21BK is collected by the cleaning unit 25 (this is a cleaning process).
Thereafter, the surfaces of the photoconductor drums 21Y, 21M, 21C, and 21BK pass through a charge removal unit (not shown), and a series of image forming processes on the photoconductor drums 21Y, 21M, 21C, and 21BK is completed.

On the other hand, the surface of the intermediate transfer belt 27 on which the toner images of the respective colors on the photosensitive drums 21Y, 21M, 21C, and 21BK are transferred in an overlapping manner travels in the direction of the arrow in the figure, and reaches the position of the second transfer bias roller 28. Reach. Then, the full-color toner image on the intermediate transfer belt 27 is secondarily transferred onto the recording medium P at the position of the second transfer bias roller 28 (this is the second transfer step).
Thereafter, the surface of the intermediate transfer belt 27 reaches the position of the intermediate transfer belt cleaning unit 29. Then, the untransferred toner on the intermediate transfer belt 27 is collected by the intermediate transfer belt cleaning unit 29, and a series of transfer processes on the intermediate transfer belt 27 is completed.

Here, the recording medium P at the position of the second transfer bias roller 28 is transported from the paper feeding unit 61 via the transport guide 63, the registration roller 64, and the like.
Specifically, the transfer paper P fed by the paper feed roller 62 from the paper feed unit 61 that stores the recording medium P passes through the conveyance guide 63 and is guided to the registration roller 64. The recording medium P that has reached the registration roller 64 is conveyed toward the position of the second transfer bias roller 28 in synchronization with the toner image on the intermediate transfer belt 27.

Thereafter, the recording medium P on which the full-color image is transferred is guided to the fixing unit 66 by the conveyance belt 30. In the fixing unit 66, the color image is fixed on the recording medium P at the nip between the heating roller 67 and the pressure roller 68.
Then, the recording medium P after the fixing process is discharged as an output image by the paper discharge roller 69 to the outside of the apparatus main body 1, and a series of image forming processes is completed.

Hereinafter, the optical scanning device 2 will be described in detail.
FIG. 2 is a perspective view showing a part of the optical scanning device 2 and the vicinity thereof. FIG. 3 is a cross-sectional view showing an optical path for black in the optical scanning device 2.
2 and 3, the first laser beam L1 (light beam) emitted from the first light source 40BK (semiconductor laser) sequentially passes through a coupling lens, an aperture, and a cylindrical lens (not shown). Then, the light enters the first deflection unit 45a of the polygon mirror 45 (light deflection unit). Then, the laser beam L1 reflected by the first deflection unit 45a is sequentially transmitted through the fθ lens 46D made of a resin material, a glass material, etc., and the liquid crystal deflection element 51BK as the adjusting means, and then reflected by the mirror 47h. Then, the light enters the half mirror 50D. Then, a part of the laser light L1 incident on the half mirror 50D is transmitted through the half mirror 50D and irradiated onto the surface to be scanned of the black photosensitive drum 21BK.

  At this time, the first laser beam L1 is scanned in the main scanning direction of the photosensitive drum 21BK (in the direction of the broken line arrow in FIG. 2) as the polygon mirror 45a rotates. Further, a desired latent image for black is formed on the photosensitive drum 21BK by rotation (running) of the photosensitive drum 21BK in the sub-scanning direction.

On the other hand, the remainder of the laser beam L1 incident on the half mirror 50D is reflected by the half mirror 50D, and a part of the laser beam L1 is incident on the laser beam detector 53BK as the first detection means.
Here, referring to FIG. 4, the laser light detector 53BK includes a plurality of light receiving elements 54A, 54B, 55 such as phototransistors arranged outside both ends of the scanning region A. Specifically, the laser beam detector 53BK is a pair of laser beams L1 arranged in parallel at both ends of the scanning area A of the laser beam L1 (corresponding to the latent image forming area on the photosensitive drum 21BK). The light receiving elements 54 </ b> A and 54 </ b> B and one light receiving element 55 disposed obliquely at one end of the scanning region A are configured. The laser beam detector 53BK detects the laser beam L1 before the start of writing and the laser beam L1 after the end of writing in the scanning region A. The positional deviation adjustment of the laser beam L1 using the laser beam detector 53BK will be described in detail later.

  Similarly, referring to FIG. 2, the second laser light L2 emitted from the second light source (not shown) sequentially passes through a coupling lens, an aperture, and a cylindrical lens (not shown), The light enters the second deflection unit 45 b of the polygon mirror 45. Then, the laser beam L2 reflected by the second deflecting unit 45b sequentially passes through the fθ lens 46C and the liquid crystal deflecting element 51, is then reflected by the mirrors 47g, 47e, and 47f, and enters the half mirror 50C. Then, a part of the laser beam L2 incident on the half mirror 50C is transmitted through the half mirror 50C and irradiated onto the scanned surface of the cyan photosensitive drum 21C. On the other hand, the remainder of the laser light L2 that has entered the half mirror 50C is reflected by the half mirror 50C, and a part of the laser light L2 enters a laser light detector (not shown) as first detection means.

  The third laser light L3 emitted from a third light source (not shown) sequentially passes through a coupling lens, an aperture, and a cylindrical lens (not shown), and reaches the first deflection unit 45a of the polygon mirror 45. Incident. Then, the laser beam L3 reflected by the first deflecting unit 45a sequentially passes through the fθ lens 46A and the liquid crystal deflecting element 51, is then reflected by the mirrors 47a and 47b, and enters the half mirror 50A. A part of the laser beam L3 incident on the half mirror 50A is transmitted through the half mirror 50A and irradiated onto the surface to be scanned of the photosensitive drum 21Y for yellow. On the other hand, the remainder of the laser beam L3 incident on the half mirror 50A is reflected by the half mirror 50A, and a part of the laser beam L3 is incident on a laser beam detector (not shown) as the first detection means.

  A fourth laser beam L4 emitted from a fourth light source (not shown) sequentially passes through a coupling lens, an aperture, and a cylindrical lens (not shown) to reach the second deflection unit 45b of the polygon mirror 45. Incident. Then, the laser beam L4 reflected by the second deflecting unit 45b sequentially passes through the fθ lens 46B and the liquid crystal deflecting element 51, then is reflected by the mirrors 47c and 47d, and enters the half mirror 50B. A part of the laser beam L4 incident on the half mirror 50B is transmitted through the half mirror 50B and irradiated onto the surface to be scanned of the magenta photosensitive drum 21M. On the other hand, the remainder of the laser light L4 incident on the half mirror 50B is reflected by the half mirror 50B, and a part of the light is incident on a laser light detector (not shown) as the first detecting means.

2 and 3, on the downstream side of the intermediate transfer belt 27 (the position after the toner images on the four photosensitive drums 21Y, 21M, 21C, and 21BK are transferred in an overlapping manner). Photosensors 52 </ b> A to 52 </ b> C serving as second detection means are disposed at both ends and the center in the scanning direction. Each of the photosensors 52A to 52C includes a light emitting element such as a light emitting diode and a light receiving element such as a phototransistor, and a predetermined toner pattern (each photosensitive drum 21Y, 21M) formed on the intermediate transfer belt 27. , 21C, 21BK, a plurality of toner images transferred in an overlapping manner).
Referring to FIG. 3, a temperature / humidity sensor 58 as third detection means for detecting temperature and humidity is installed in the apparatus main body 1.

  In the image forming apparatus configured as described above, laser light is generated based on the detection results of the laser light detectors 53BK, 53Y, 53M, and 53C (first detection means) and the detection results of the photosensors 52A to 52C. The positional deviation (scanning state) of L1 to L4 is adjusted.

  Here, the positional deviations of the laser beams L1 to L4 are caused by disturbances such as temperature and humidity fluctuations in the apparatus main body 1, and there are various modes as shown in FIGS. The first mode is called scanning line inclination (scanning line inclination). As shown in FIG. 5A, the actual latent image S1 (or toner image) is compared to the actual latent image S1 (or toner image). Toner image) is inclined. The second mode is called registration shift in the main scanning direction. As shown in FIG. 5B, the actual latent image S1 (or toner image) is compared to the ideal latent image S0 (or toner image). Is shifted in the main scanning direction. The third mode is called registration shift in the sub-scanning direction. As shown in FIG. 5C, the actual latent image S1 (or toner image) is compared to the ideal latent image S0 (or toner image). Is shifted in the sub-scanning direction. The fourth aspect is called a magnification error in the main scanning direction. As shown in FIG. 5D, the actual latent image S1 (or toner image) is compared to the ideal latent image S0 (or toner image). However, the magnification increases or decreases in the main scanning direction.

  With reference to FIG. 3, in the first embodiment, first, the photosensors 52 </ b> A to 52 </ b> C detect the positional deviation (overlapping deviation) of the toner pattern formed on the intermediate transfer belt 27, and the detection result is obtained. After transmitting to the control unit 57, the positional deviation of the laser beam is roughly adjusted. Then, the positional deviation after the coarse adjustment is detected by the laser light detectors 53BK, 53Y, 53M, and 53C, and the detection result is transmitted to the control unit 57, and then the positional deviation of the laser light is finely adjusted.

The coarse adjustment and fine adjustment of the positional deviation of the laser beam are performed by controlling the liquid crystal deflecting element 51 and the light source 40.
Specifically, the scanning line is adjusted by the liquid crystal deflection element 51 when the laser beam pitch shifts in the sub-scanning direction and the scanning line interval is shifted. The liquid crystal deflection element 51 is an element that can arbitrarily deflect the emission direction of the laser light by electrical control. The deflection angle can be arbitrarily changed by the peak value of the driving voltage waveform or the pulse width duty.
In addition, when a scanning state variation such as a magnification error of each scanning line, a positional deviation between start and end points, a scanning line bending or a tilt occurs, scanning is performed by controlling a pulse of image data input to the light source 40. The state is adjusted.

  As described above, after the coarse adjustment of the laser beam based on the toner pattern overlay error information on the intermediate transfer belt 27, the fine adjustment of the laser beam is performed based on the detection results of the laser beam detectors 53BK, 53Y, 53M, and 53C. By performing the adjustment, the absolute coordinate data on the photosensitive drums 21BK, 21Y, 21M, and 21C of the laser beams L1 to L4 are specified, and the laser beams L1 to L4 are based on the absolute coordinate data. The scanning state can be optimized with high accuracy. That is, after roughly adjusting the positional deviation by detecting the positional deviation of the toner pattern, fine adjustment is performed using the positional deviation detection of the laser light detector, thereby effectively and reliably suppressing the positional deviation of the laser beam. Can do.

  After roughly adjusting the positional deviation by the photo sensors 52A to 52C, the scanning states (start / end point positional deviation, magnification error) on the photosensitive drums 21Y, 21M, 21C, and 21BK are changed to laser light detectors 53Y, 53M, Detected by 53C and 53BK. At the same time, the laser beam detectors 53Y, 53M, 53C, and 53BK detect the coordinates of the laser beams L1 to L4 in the sub-scanning direction on the photosensitive drum, and determine the origin in the scanning direction of each scanning line before adjustment. .

  The scanning state for each color is detected by the respective laser light detectors 53Y, 53M, 53C, 53BK, and the position of the laser light is set as the origin. The start point / end point position shift and magnification error are individually adjusted for each color, and the sub-scanning direction pitch unevenness and scan position shift are calculated from the amount of overlap by the photosensors 52A to 52C. And adjust.

  The laser light detectors 53Y, 53M, 53C, and 53BK are set so that the detection time difference between the light receiving portions 54A and 54B is constant even when the scanning position of the laser light moves in the sub-scanning direction. Thereby, the movement amount and absolute coordinates of the laser beam in the sub-scanning direction can be detected. Further, the position coordinates in the sub-scanning direction can be detected from the time during which the laser light passes through the light receiving parts 54A and 54B and the time difference between the light receiving parts 54A and 54B.

  In the first embodiment, fine adjustment of the laser light is performed based on the detection results of the laser light detectors 53BK, 53Y, 53M, and 53C after coarse adjustment of the laser light is performed based on the detection results of the photosensors 52A to 52C. After the adjustment, the laser light is roughly adjusted based on the detection results of the laser light detectors 53BK, 53Y, 53M, and 53C, and then the laser light is finely adjusted based on the detection results of the photosensors 52A to 52C. You can also

  In the first embodiment, when the inclination of the scanning line and the magnification error in the main scanning direction occur (the state in FIG. 6A), first, the inclination of the scanning line is adjusted (FIG. 6). (B) state.) Thereafter, the magnification error state is detected from the laser beam detectors 53BK, 53Y, 53M, and 53C, and the magnification error in the main scanning direction is adjusted (the state shown in FIG. 6C). By such a procedure, even when a new magnification error in the main scanning direction occurs due to the adjustment of the scanning line inclination, the positional deviation of the laser beam can be adjusted efficiently and reliably.

  In addition, when the inclination of the scanning line and the registration deviation (pitch deviation) in the sub-scanning direction are generated (the state shown in FIG. 7A), first, the inclination of the scanning line is adjusted (FIG. 7 ( B).) Thereafter, the status of registration deviation is detected from the laser beam detectors 53BK, 53Y, 53M, and 53C, and the registration deviation in the sub-scanning direction is adjusted (the state in FIG. 7C). By such a procedure, even when a new registration deviation in the sub-scanning direction occurs due to the adjustment of the scanning line inclination, the positional deviation of the laser beam can be adjusted efficiently and reliably.

  Although not shown, when a magnification error in the main scanning direction and a registration error in the sub-scanning direction occur, first, the magnification error in the main scanning direction is adjusted. Thereafter, the registration deviation in the sub-scanning direction is adjusted based on the detection results of the laser beam detectors 53BK, 53Y, 53M, and 53C. By such a procedure, even when a new registration error in the sub-scanning direction occurs due to the adjustment of the magnification error in the main scanning direction, the positional deviation of the laser beam can be adjusted efficiently and reliably.

  Note that a control table (adjustment rule table) for collating with the detection results detected by the photosensors 52A to 52C is stored in advance in the calculation unit of the control unit 57. And the adjustment means 40 and 51 are controlled based on the optimal adjustment value obtained by collating the detection results detected by the photosensors 52A to 52C with the control table. Thereby, it is possible to adjust the positional deviation of the laser light quickly and appropriately.

  In the first embodiment, the scanning states of the laser beams L1 to L4 emitted from a plurality of light sources and irradiated onto the plurality of photosensitive drums 21Y, 21M, 21C, and 21BK are varied in a varying manner. However, it is possible to adjust the sub-scanning beam pitch unevenness and the inter-scanning positional deviation in the plurality of photosensitive drums 21Y, 21M, 21C, and 21BK. Since the tandem type image forming apparatus can simultaneously form latent images on the plurality of photosensitive drums 21Y, 21M, 21C, and 21BK, high-speed image output is achieved. In the first embodiment, since the scanning line position adjustment can be performed in parallel with the high-speed image output, an increase in the image output time due to the scanning line adjustment process hardly occurs. Thereby, an increase in the heating time of the heater of the fixing unit 66 and the driving time of the polygon mirror 45 accompanying the image output is also suppressed, and an increase in power consumption is prevented.

  In the first embodiment, laser light detectors 53BK, 53Y, 53M, and 53C are provided for each of the laser beams L1 to L4 emitted from a plurality of light sources, and the positional deviations of the laser beams L1 to L4 are shifted. Adjustment is performed while grasping the scanning state between the laser beams. Thereby, the adjustment of the laser beams L1 to L4 balanced as a whole is accurately performed.

  In the first embodiment, when the positional deviation of the laser beams L1 to L4 is adjusted based on the detection results of the laser beam detectors 53BK, 53Y, 53M, and 53C, the deviation of the positional deviation is within a predetermined range. It is possible to control so that the adjustment is finished at the time. As a result, it is possible to prevent the occurrence of a problem (infinite loop) in which the positional deviation adjustment control is continued indefinitely until it matches the target value, and the laser beam positional deviation can be maintained within a certain range.

  In the first embodiment, the laser light emitted from a specific light source (for example, the black light source 40BK) among the laser lights L1 to L4 emitted from a plurality of light sources is used as a reference laser light. The adjustment process can also be performed. In this case, first, after adjusting the positional deviation of the reference laser beam, the positional deviation of the other laser beam is adjusted by adjusting the beam pitch of the other laser beam in the sub-scanning direction. As a result, an adjustment that takes into account a new misalignment that occurs due to the adjustment of one laser beam is possible, and a quick and reliable misalignment adjustment is performed as a whole.

  In the first embodiment, after adjusting the pitch in the sub-scanning direction of the laser beams L1 to L4 emitted from a plurality of light sources, the positional deviations of the laser beams L1 to L4 can be adjusted. Thereby, the adjustment of the laser beams L1 to L4 balanced as a whole is accurately performed.

  In the first embodiment, the order of scanning the laser beams L1 to L4 emitted from a plurality of light sources can be made constant. By specifying the scanning order of the laser beams L1 to L4 for forming the toner pattern on the intermediate transfer belt 27, the writing environment in a fixed state is maintained, and a stable output image can be formed.

In the first embodiment, as shown in FIG. 8, it is possible to adjust the positional deviation of the laser beam by feedback control.
Referring to FIG. 8, first, a toner pattern is formed on intermediate transfer belt 27 (step S1), and scanning line pitch deviation is detected by photosensors 52A to 52C (second detection means) (steps S2 to S2). S3). Using this as an initial value, an adjustment value is calculated by the calculation unit of the control unit based on this initial value, and a positional deviation adjustment signal is transmitted to the adjustment means (steps S4 to S5).

Thereafter, the adjustment of the laser light is performed by the adjusting means (step S6). On the other hand, the temperature and humidity in the apparatus main body 1 is detected by the temperature and humidity sensor 58 as the third detection means (step S8), and the scanning state of the laser beam is corrected based on the detection result (step S7). .
Then, the laser beam is irradiated to the photosensitive drum line by line (step S9), and the beam position in the sub-scanning direction is detected by the laser beam detectors 53BK, 53Y, 53M, and 53C (first detection means). (Steps S10 to S11). This detected value is fed back and compared with the initial value detected in step S3 (step S4), and the flow after step S5 is repeated.

  As described above, the position deviation data obtained by the second detection means is used as an initial value, the calculation value is calculated by the adjustment means corresponding to the toner pattern position deviation by the calculation unit, and the adjustment light is adjusted and controlled by the adjustment value. By detecting the scanning state and performing feedback control so that the difference from the target value is within a predetermined range, the positional deviation and the shape variation of each scanning line are reduced, and the pitch interval between the scanning lines, The misalignment can be adjusted. Further, since the absolute coordinates of the laser light on each photosensitive drum are detected by the first detection means, the number of feedback control loops necessary for adjusting the positional deviation can be reduced, The time required for adjustment and the time required for image output can be shortened.

  As described above, in the first embodiment, the detection result of the positional deviation of the laser beams L1 to L4 and the detection result of the positional deviation of the plurality of toner images transferred and superimposed on the intermediate transfer belt 27 are included. Based on this, the positional deviation of the laser beams L1 to L4 is adjusted. Thereby, the positional deviation of the laser beams L1 to L4 is reliably adjusted, and the occurrence of image quality defects such as color deviation can be suppressed.

  In the first embodiment, the polygon mirror 45 is provided with the first deflection unit 45a and the second deflection unit 45b, and the first laser beam L1 and the third laser beam L3 are supplied to the first deflection unit 45a. The second laser beam L2 and the fourth laser beam L4 are incident on the second deflecting unit 45b. On the other hand, the polygon mirror 45 may be provided with four deflecting units so that the laser beams L1 to L4 are incident on the deflecting units. Even in such a case, the same effect as in the first embodiment can be obtained.

  In the first embodiment, the present invention is applied to a tandem type color image forming apparatus in which a plurality of photosensitive drums 21BK, 21Y, 21M, and 21C are arranged in parallel. On the other hand, a revolver type in which an image forming process of each color is sequentially performed on a single photosensitive drum, and toner images of each color sequentially formed on the photosensitive drum are sequentially transferred onto the transfer target. Of course, the present invention can be applied to a color image forming apparatus. Even in such a case, the positional deviation of the laser beam is adjusted based on the detection result of the positional deviation of the laser beam of each color and the detection result of the positional deviation of the plurality of toner images transferred onto the transfer target. Thus, the same effect as in the first embodiment can be obtained.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a flowchart showing a procedure for adjusting the positional deviation of the laser beam performed in the image forming apparatus in the second embodiment, and corresponds to FIG. 8 in the first embodiment. The second embodiment is different from the first embodiment in that the feedforward control is performed based on the detection result of the temperature / humidity sensor 58 as the third detecting means.

  Referring to FIG. 9, first, a toner pattern is formed on intermediate transfer belt 27 (step S1), and scanning line pitch deviation is detected by photosensors 52A to 52C (second detection means) (steps S2 to S2). S3). Using this as an initial value, an adjustment value is calculated by the calculation unit (PID control unit) based on the initial value (steps S4 and S15). At this time, the temperature / humidity in the apparatus main body 1 is detected by the temperature / humidity sensor 58 as the third detection means (step S18), and an adjustment value is calculated as a scanning amount that cancels the disturbance based on the detection result. Then, the laser light is adjusted by feedforward control based on the detection result of the temperature / humidity sensor 58 (step S16).

  Then, after adjusting the laser beam by the adjusting unit, the laser beam is irradiated to the photosensitive drum line by line (steps S17 and S9), and the laser beam detectors 53BK, 53Y, 53M, and 53C (first detecting unit). ) To detect the beam position and the like in the sub-scanning direction (steps S10 to S11). This detected value is fed back and compared with the initial value detected in step S3 (step S4), and the flow after step S15 is repeated.

  As described above, in the second embodiment, the variation in the scanning state of each of the laser beams L1 to L4 and the displacement of the toner pattern due to disturbances such as temperature and humidity fluctuations in the apparatus main body 1 and the inclination of the apparatus main body 1 are preliminarily taught. It is fixed as data (data relating to the adjustment amount of the adjusting means 40, 51). As a result, the influence of disturbance can be minimized, and the variation in misalignment can be minimized. In other words, image deterioration due to temperature fluctuations can be adjusted in a relatively short time by smoothly adjusting the target value of the appropriate positional deviation deviation while detecting the state of the positional deviation amount after adjustment.

  As described above, also in the second embodiment, as in the first embodiment, the detection result of the positional deviation of the laser beams L1 to L4 and the plurality of toner images transferred on the intermediate transfer belt 27 are transferred. The positional deviation of the laser beams L1 to L4 is adjusted based on the detection result of the positional deviation. Thereby, the positional deviation of the laser beams L1 to L4 is reliably adjusted, and the occurrence of image quality defects such as color deviation can be suppressed.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing an optical scanning device in the image forming apparatus of FIG. 1. It is sectional drawing which shows an optical scanning device. It is a figure which shows arrangement | positioning of the scanning direction of the 1st detection means in an optical scanning device. It is a figure which shows the mode of the position shift of a laser beam. It is a figure which shows the procedure of the positional offset adjustment of a laser beam. It is a figure which shows another procedure of position shift adjustment of a laser beam. It is a flowchart which shows the procedure of the position shift adjustment of a laser beam. It is a flowchart which shows the procedure of the positional offset adjustment of the laser beam performed with the image forming apparatus in Embodiment 2 of this invention.

Explanation of symbols

1 image forming apparatus main body (apparatus main body), 2 optical scanning device,
21BK, 21Y, 21M, 21C photosensitive drum (image carrier),
27 Intermediate transfer belt (transfer object),
40BK light source, 45 polygon mirror (light deflector),
45a first deflection unit, 45b second deflection unit,
46A to 46D fθ lens (imaging optical system), 47a to 47h mirror,
50A-50D half mirror,
51, 51BK liquid crystal deflection element (adjustment means),
52, 52A to 52C Photosensor (second detection means),
53BK, 53Y, 53M, 53C Laser light detector (first detection means),
54A, 54B, 55 light receiving element,
57 control part (adjustment means), 58 temperature / humidity sensor (third detection means),
L1 to L4 Laser light (light beam), A scanning region.

Claims (10)

A plurality of latent images are formed on a plurality or a single image carrier that scans laser light in the main scanning direction and travels in the sub-scanning direction, and the plurality of latent images formed on the image carrier are developed. An image forming apparatus for transferring a plurality of toner images formed on a transfer target,
A plurality of light receiving elements respectively disposed outside both ends of the scanning region of the laser light, and detecting the laser light incident on the plurality of light receiving elements to detect an inclination of a scanning line in the laser light; First detection means for detecting at least one of registration deviation in the main scanning direction, registration deviation in the sub-scanning direction, and magnification error in the main scanning direction;
Second detection means for detecting an overlay error of the plurality of toner images transferred onto the transfer target;
While variably controlling the deflection angle in the deflection element disposed in the optical path of the laser beam from the light source emitting the laser beam to the image carrier, the pulse of image data input to the light source is controlled. Adjusting means for adjusting the inclination of the scanning line in the laser beam, the registration deviation in the main scanning direction, the registration deviation in the sub-scanning direction, and the magnification error in the main scanning direction, respectively.
With
The adjustment means detects a detection result among the inclination of the scanning line in the laser beam, registration deviation in the main scanning direction, registration deviation in the sub-scanning direction, and magnification error in the main scanning direction based on the detection result of the second detection means. After adjusting based on the optimum adjustment value obtained by collating the control value with the control table so that it does not coincide with the target value and needs to be adjusted, based on the detection result of the first detection means Among the laser beam inclination, main scanning direction registration deviation, sub-scanning direction registration deviation, and main scanning direction magnification error, the detection result does not match the target value and needs to be adjusted. The image forming apparatus is characterized in that the adjustment is performed until the difference between the two is within a predetermined range.   The adjusting means adjusts the inclination of the scanning line of the laser light after adjusting the inclination of the scanning line of the laser light when the first detecting means detects the inclination of the scanning line in the laser light and the magnification error in the main scanning direction. The image forming apparatus according to claim 1, wherein a magnification error is adjusted.   The adjusting means adjusts the inclination of the scanning line of the laser light after adjusting the inclination of the scanning line of the laser light when the first detecting means detects the inclination of the scanning line in the laser light and the registration deviation in the sub-scanning direction. The image forming apparatus according to claim 1, wherein the registration deviation is adjusted.   The adjustment unit adjusts the magnification error of the laser beam in the main scanning direction when the first detection unit detects a magnification error in the main scanning direction and a registration error in the sub-scanning direction of the laser beam. The image forming apparatus according to claim 1, wherein a registration shift in the sub-scanning direction is adjusted.   The adjustment unit collates the detection result of the second detection unit with a control table prepared in advance, and scan line inclination, registration deviation in the main scanning direction, registration deviation in the sub-scanning direction, main scanning direction in the laser light The image forming apparatus according to claim 1, wherein the magnification error is adjusted.   The image forming apparatus according to claim 1, wherein a plurality of the first detection units are provided for each laser beam corresponding to the plurality of latent images.   The adjustment means adjusts a scanning line inclination, a registration deviation in the main scanning direction, a registration deviation in the sub-scanning direction, and a magnification error in the main scanning direction by feedback control. Item 7. The image forming apparatus according to Item 6. A third detection means for detecting temperature or / and humidity in the apparatus;
The adjusting unit is configured to reduce the scanning line inclination, the registration error in the main scanning direction, the registration error in the sub-scanning direction, and the magnification error in the main scanning direction by feedforward control based on the detection result of the third detection unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is adjusted.   The adjusting unit is configured to detect a scanning line inclination, a registration deviation in the main scanning direction, a registration deviation in the sub-scanning direction, and a magnification error in the main scanning direction in one laser beam among the plurality of laser lights corresponding to the plurality of latent images. By adjusting, the inclination of the scanning line, the registration deviation in the main scanning direction, the registration deviation in the sub-scanning direction, and the magnification error in the main scanning direction are adjusted with respect to the one laser beam as a reference. The image forming apparatus according to claim 1.   The image formation according to claim 1, wherein the plurality of latent images are formed on the plurality of image carriers by laser beams respectively emitted from a plurality of light sources. apparatus.

Images