JP2004174720A - Exposure device, image forming apparatus employing it and method of regulating color matching - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device in which positional deviation among color images can be corrected with a continuous correction amount when the color images are transferred while being superposed and the correction amount can be varied in one line, and to provide an image forming apparatus employing it and a method of regulating color matching. <P>SOLUTION: The exposure device is provided with an optical unit 40 and an fθ lens 41. The optical unit 40 is provided with an LD 5, and a polygon mirror 3 for deflecting/reflecting a laser beam irradiated from the LD 5 toward a photosensitive drum 22 and scanning the photosensitive drum 22. On an optical path formed by the polygon mirror 3, a liquid crystal cell 1 for deflecting a laser beam irradiated from the polygon mirror 3 toward the photosensitive drum 22 is disposed. The liquid crystal cell 1 is connected with a circuit 2 for controlling deflection of the laser beam based on the positional shift between electrostatic latent images. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure apparatus for exposing a photoreceptor with a light beam from a light source to form an electrostatic latent image on the surface of the photoreceptor, an image forming apparatus using the same, and a color matching adjustment method in electrophotographic image formation. It is about.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus such as a digital color copying machine decomposes input data into respective color components, performs image processing, and then superimposes images for each color component to form a multicolor image.
[0003]
In forming such a multi-color image, if the images of the respective color components are not accurately superimposed, a shift (position shift) occurs in the position of the formed multi-color image, which may cause deterioration in image quality. In particular, in an image forming apparatus provided with an image forming unit for each color component in order to improve the formation speed of a multicolor image, an image of each color component is formed in each image forming unit, and the image of each color component is sequentially formed. A multicolor image is formed by superimposition.
[0004]
In such an image forming apparatus, the transfer position of the image of each color component is easily shifted, and the position shift (color shift) of the multicolor image is a serious problem.
[0005]
The causes of such a positional shift include, for example, a shift in the mounting position of the photoconductor and a peripheral speed, a shift in the exposure position with respect to the photoconductor, a shift in the linear speed of the transfer belt, and expansion and contraction of each part of the apparatus due to a temperature change. There is something.
[0006]
Therefore, the image forming apparatus performs color matching adjustment for correcting misregistration of a multi-color image (between color images) in order to accurately overlay images of the respective color components.
[0007]
In the color matching adjustment, first, a shift of an image forming position of another color component from an image forming position of a reference color component is detected using an optical detector. Then, a correction amount is determined based on the detection result, and adjustment is performed according to the correction amount so that the transfer positions of the images of the respective color components match. In order to determine the correction amount, generally, the image of each color component is transferred at the same timing, and the distance between the transfer positions of each color component is detected, or the density of the multicolor image in which each color component is superimposed is determined. Measuring.
[0008]
There is a color image forming apparatus that adjusts the timing (writing timing) of forming an image of each color component so that the transfer position of the image of each color component matches in accordance with the correction amount (for example, see Patent Document 1).
[0009]
This color image forming apparatus detects the temperature of the writing unit and corrects the image forming timing, thereby preventing a color image of each color from being displaced due to the temperature. A polygon scanner is used as an exposure device that exposes the photoreceptor to form an electrostatic latent image, and the image forming timing is corrected using the rotation of the polygon scanner.
[0010]
There is also an optical scanning device that corrects scanning line interval unevenness in the sub-scanning direction (for example, see Patent Document 2). This optical scanning device detects the rotation speed of the photosensitive drum, and a polarization element provided in the optical path of the laser beam (between the collimator lens and the polygon mirror) by an electro-optic effect. Correct the positional deviation in the paper feed direction.
[0011]
Further, there is an exposure device that corrects rotation unevenness of the photosensitive drum in the sub-scanning direction (for example, see Patent Document 3). This exposure device detects the rotation speed of the photosensitive drum and arranges a liquid crystal cell in the optical path of the laser beam (between the collimator lens and the polygon mirror). Thereby, the laser beam can be deflected, and the positional deviation in the paper feeding direction on the photosensitive drum due to the speed fluctuation of the photosensitive drum is corrected.
[0012]
[Patent Document 1]
JP-A-3-293679 (published on December 25, 1991)
[0013]
[Patent Document 2]
JP-A-5-40398 (published February 19, 1993)
[0014]
[Patent Document 3]
JP 2001-328294 A (published November 27, 2001)
[0015]
[Problems to be solved by the invention]
However, in the configuration described in Patent Literature 1, since the writing timing is used for correcting the positional deviation, the resolution of the polygon scanner having the polygon mirror becomes the line pitch, and only discrete correction can be performed.
[0016]
That is, by correcting the positional deviation by the writing timing due to the rotation of the polygon mirror, the same correction amount is obtained for the positional deviation in a predetermined range. For this reason, highly accurate correction cannot be performed.
[0017]
In the configurations described in Patent Literature 2 and Patent Literature 3, a control system is established by detecting the speed fluctuation of the photosensitive drum in real time and feeding it back. Here, the cause of the uneven rotation of the photosensitive drum is a dynamic component of (several / 10) Hz or more in the speed fluctuation.
[0018]
By the way, in the case of a tandem type image forming apparatus in which a plurality of photoconductor drums are provided and the color image formed on each photoconductor drum is transferred to a recording medium as one image, mechanical or optical in the photoconductor drum or the exposure device is used. The combined form of these, such as the actual positional deviation and the speed deviation of the driving system or the transport system, may appear as a color deviation (position deviation) in the image quality as a result, and the main factor is the difference between the colors on the image. Is a stationary position deviation of
[0019]
In such a case, what is needed is a control system that detects and feeds back a steady-state deviation, and it is difficult to cope with a real-time control system that uses only speed fluctuation feedback that is used to suppress banding. In a normal image forming apparatus, such a steady deviation contributes very little to uneven rotation of the photosensitive drum.
[0020]
That is, the configurations described in Patent Literature 2 and Patent Literature 3 include a deflecting unit (deflection element, liquid crystal cell), and thus can continuously correct the positional shift. This is a correction of a positional shift in one photosensitive drum, and does not disclose a correction of a positional shift of a color image when a plurality of color images are transferred in an overlapping manner.
[0021]
Further, in this configuration, since the deflection means is provided between the collimator lens and the polygon mirror, the correction amount cannot be changed in one line. Therefore, when there is a skew in one line, it cannot be corrected.
[0022]
The present invention has been made in view of the above-described problems, and an object of the present invention is to perform position correction between color images with a continuous correction amount when color images are transferred in an overlapping manner. Another object of the present invention is to provide an exposure apparatus capable of changing a correction amount in one line, an image forming apparatus using the same, and a color matching adjustment method.
[0023]
[Means for Solving the Problems]
An exposure apparatus according to the present invention includes a light source, and an optical scanning system that deflects and reflects a light beam emitted from the light source toward a member to be exposed and scans the member to be exposed, in order to solve the above problem. In an exposure apparatus for exposing a plurality of exposed members on the surface of which an electrostatic latent image is formed by exposure, the exposure device is disposed on an optical path formed by the optical scanning system, and is irradiated onto the exposed member from the optical scanning system. A deflecting member for deflecting the light beam, and a control unit connected to the deflecting member for controlling the deflection of the light beam by the deflecting member. It is characterized in that the amount of displacement between the electrostatic latent images when formed is detected, and the deflection of the light beam by the deflecting member is controlled based on the amount of displacement.
[0024]
According to the above configuration, the exposure position of the member to be exposed can be moved by the deflection member. For example, when the exposure apparatus is used in a color image forming apparatus, it is possible to perform the correction of the positional shift between the color images to be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0025]
Further, the control unit can detect and hold (memory) the position shift amount, and correct the irradiation position of the light beam based on the held (memory) position shift amount information. For example, it is possible to detect the amount of displacement using a test patch, sample and hold, or memorize, and control based on the sample / hold value or the memory value.
[0026]
Therefore, it is possible to correct a mechanical or optical displacement of the member to be exposed or the optical scanning system, and a displacement of the electrostatic latent image due to a speed deviation of the driving system or the transport system.
[0027]
In the above exposure apparatus, it is preferable that the deflecting member has a liquid crystal layer made of liquid crystal and a pair of electrodes for applying a voltage to the liquid crystal layer and changing the refractive index of the liquid crystal layer.
[0028]
According to the above configuration, by using the liquid crystal, the voltage required for driving the deflecting member can be lower than when using an electro-optical element such as LPZT. Therefore, power consumption can be reduced. Further, the light beam can be deflected to a greater extent than the electro-optical element.
[0029]
In the above exposure apparatus, it is preferable that different voltages are applied to one of the pair of electrodes of the deflection member from near both ends of the one electrode.
[0030]
According to the above configuration, an inclination of the potential occurs in a portion corresponding to one line in the deflection member. Therefore, for example, even if a skew occurs in a color image due to an assembly error at the time of assembling the image forming apparatus or a processing error of a part of the image forming apparatus, it is possible to correct the skew.
[0031]
In the above exposure apparatus, it is preferable that the deflection member is disposed between the optical scanning system and the member to be exposed.
[0032]
Normally, when the deflecting member is disposed between the light source and the optical scanning system, that is, when the light beam input position on the deflecting member is fixed, the deflection voltage is changed within one line scan when correcting the skew. It is necessary to deflect the preliminary beam each time it is performed, and the deflecting member is required to have a high-speed responsiveness that can follow this.
[0033]
However, according to the above configuration, since the deflecting member is arranged between the member to be exposed and the optical scanning system, the light beam on the deflecting member is changed according to the optical scanning system (for example, rotation of the polygon mirror). The input position moves (scans).
[0034]
Therefore, for example, by using a deflecting member to which a different voltage is applied from near both ends of the one electrode to one of the pair of electrodes, that is, by using a deflecting member that changes to a predetermined amount of deflection depending on the beam input position, The skew can be corrected without changing the deflection voltage according to the scan position, and the deflection member does not require high-speed response.
[0035]
Accordingly, even when a skew occurs due to an assembly error at the time of assembling the image forming apparatus or a processing error of a part of the image forming apparatus, it is possible to correct the skew.
[0036]
In order to solve the above-described problems, an image forming apparatus according to the present invention includes an image carrier having a photoreceptor on a surface thereof, and exposing the image carrier based on image data to form an electrostatic latent image on the surface of the image carrier. A plurality of image forming means for forming a color image including an exposure device for forming an image and a developing device for developing a portion exposed by the exposure device are arranged in parallel, and are conveyed in the direction in which the image forming means are arranged. An image forming apparatus that forms one image of multiple colors by transferring the color image onto a conveying unit, wherein the exposing device includes a light source and a light beam emitted from the light source on an image carrier. An optical scanning system for deflecting and reflecting light and scanning the image carrier, and disposed on an optical path formed by the optical scanning system to deflect a light beam emitted from the optical scanning system to the image carrier. A deflection member connected to the deflection member; Control means for controlling the deflection of the light beam by the deflecting member, wherein the control means detects a positional shift amount between the electrostatic latent images when the electrostatic latent images are formed on different image carriers. The deflection of the light beam by the deflecting member is controlled based on the displacement amount.
[0037]
According to the above configuration, the exposure position on the image carrier can be moved. That is, it is possible to perform the correction of the positional deviation between the color images that should be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0038]
Further, it is possible to correct a mechanical or optical displacement of the image carrier or the optical scanning system, and a displacement of the electrostatic latent image due to a speed deviation of the driving system or the transport system.
[0039]
In the above image forming apparatus, it is preferable that the deflecting member has a liquid crystal layer made of liquid crystal, and a pair of electrodes for applying a voltage to the liquid crystal layer to change the refractive index of the liquid crystal layer.
[0040]
According to the above configuration, by using the liquid crystal, the voltage required for driving the deflecting member can be lower than when using an electro-optical element such as LPZT. For example, a driving voltage of LPZT requires a driving voltage of several hundreds to several kilometers (V), but a deflecting member using liquid crystal may have a driving voltage of several (V). Therefore, power consumption can be reduced. Further, a deflecting member using liquid crystal is less expensive than an electro-optical element, and can deflect a light beam largely.
[0041]
In the above image forming apparatus, it is preferable that the pair of electrodes of the deflecting member be disposed so as to face each other with the liquid crystal layer interposed therebetween.
[0042]
According to the above configuration, by arranging the deflecting member at a predetermined angle with respect to the optical axis of the incident light beam, the deflecting member can function as a prism.
[0043]
Therefore, the deflecting member can translate the incident light beam in the sub-scanning direction. As a result, the exposure position of the image carrier can be moved, and the positional shift between the color images can be corrected.
[0044]
In the above-described image forming apparatus, it is preferable that the pair of electrodes of the deflecting member be formed separately on one of the pair of substrates sandwiching the liquid crystal layer.
[0045]
According to the above configuration, the deflecting member can have a lens function by forming the lines of electric force. Therefore, the deflecting member can translate the incident light beam in the sub-scanning direction. As a result, the exposure position of the image carrier can be moved, and the positional shift between the color images can be corrected.
[0046]
In the above-described image forming apparatus, it is preferable that different voltages are applied to one of the pair of electrodes of the deflection member from near both ends of the one electrode.
[0047]
Conventionally, when a skew occurs in a color image due to an assembling error at the time of assembling the image forming apparatus or a processing error of parts of the image forming apparatus, mechanical adjustment has been performed using a folding mirror or the like.
[0048]
However, according to the above configuration, a potential gradient occurs in a portion corresponding to one line in the deflection member. Therefore, even if a skew occurs in the color image, it can be corrected. That is, even when skew occurs, electrical automatic correction becomes possible.
[0049]
The image forming apparatus includes a position shift detecting unit that detects a position shift between the color images of the respective colors transferred onto the conveying unit, and the deflecting member is detected by the position shift detecting unit when the image forming apparatus is initially set. It is preferable to correct the misalignment.
[0050]
According to the above configuration, at the time of initial setting of the image forming apparatus, it is possible to detect a positional shift of a color image using a pattern image (patch image). Accordingly, it is possible to correct a positional error and a skew of a color image caused by an assembling error at the time of assembling the image forming apparatus, a processing error of parts of the image forming apparatus, and the like from the time of initial setting (to the start of image forming). it can.
[0051]
It is preferable that the image forming apparatus includes a temperature detecting unit that detects a temperature inside the image forming apparatus, and the deflecting member deflects the light beam based on the detected temperature.
[0052]
According to the above configuration, it is possible to correct a positional shift due to expansion and contraction of each part of the device due to a temperature change.
[0053]
The image forming apparatus includes a timing correction unit that corrects a positional shift between the color images of the respective colors transferred on the conveyance unit by shifting a writing timing on the image carrier by the optical scanning system, and a deflecting member. It is preferable to provide a switching means for switching between analog correction for correcting positional deviation by irradiating the image carrier with a light beam from the optical scanning system.
[0054]
According to the above configuration, therefore, by using the analog correction and the timing correction together, the timing correction is performed when the displacement amount is large, and the correction is performed to some extent using the small displacement amount or the timing correction. When the row length is reduced (the deviation amount is close to the target value), analog correction can be performed.
[0055]
As a result, when the deviation amount is near the target value, high-precision correction can be performed by analog correction, and by using timing correction together, a wide range of position deviation can be corrected without imposing a load on the deflection member. It becomes.
[0056]
In the above image forming apparatus, it is preferable that the deflection member is disposed between the optical scanning system and the image carrier.
[0057]
According to the above configuration, since the deflecting member is provided between the optical scanning system and the image carrier, the moving amount (correction amount) of the light beam applied to the image carrier changes in one line. Can be done.
[0058]
Accordingly, even when a skew occurs due to an assembly error at the time of assembling the image forming apparatus or a processing error of a part of the image forming apparatus, it is possible to correct the skew.
[0059]
In order to solve the above-described problems, the color matching adjustment method of the present invention scans the image carrier while deflecting and reflecting a light beam toward the image carrier, and scanning the image carrier. An optical scanning system is provided, and an image forming unit that forms a color image by including an exposure device that exposes and scans the image carrier based on image data and a developing device that develops a portion exposed by the exposure device is provided. A plurality of the color images are transferred onto the conveying means conveyed in the direction of juxtaposition of the image forming means, and are transferred onto the conveying means in an image forming apparatus for forming one image composed of multiple colors. A color matching adjustment method for correcting a positional shift between color images of respective colors, wherein a light beam emitted from the optical scanning system to the image carrier is arranged on an optical path formed by the optical scanning system. Above by deflection member By deflecting the sub-scanning direction of the academic scanning system is characterized in that to correct the positional deviation between the color images of the respective colors transferred onto the conveying means.
[0060]
According to the above method, the exposure position on the image carrier can be moved. That is, it is possible to perform the correction of the positional deviation between the color images that should be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0061]
Further, it is possible to correct a mechanical or optical displacement of the image carrier or the optical scanning system, and a displacement of the electrostatic latent image due to a speed deviation of the driving system or the transport system.
[0062]
The color matching adjustment method described above includes a timing correction for correcting a positional shift between the color images of the respective colors transferred on the transporting means by shifting a writing timing on the image carrier by the optical scanning system, and a method of adjusting the timing via the deflection member. By irradiating the image carrier with a light beam from the optical scanning system, it is preferable to switch between analog correction for correcting positional deviation.
[0063]
According to the above-described method, when the displacement amount is large, the timing correction is performed, and when the displacement amount is small, the correction is performed to some extent using the timing correction, and the correction amount is reduced to some extent (the deviation amount is close to the target value). ), Analog correction can be performed.
[0064]
As a result, when the deviation amount is near the target value, high-precision correction can be performed by analog correction, and by using timing correction together, a wide range of position deviation can be corrected without imposing a load on the deflection member. It becomes.
[0065]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
One embodiment of the present invention will be described below with reference to FIGS. 1 to 4, 6, 7, 9, and 10.
[0066]
FIG. 1 shows a configuration of a main part of an exposure apparatus according to the present embodiment. As shown in the figure, this exposure apparatus is an LSU (laser beam scanner unit), and includes an optical unit 40, an fθ lens 41, and mirrors 42 and 43 (see FIG. 10) described later. Note that the mirrors 42 and 43 are omitted here for simplicity of description.
[0067]
The optical unit 40 includes a liquid crystal cell (liquid crystal deflecting element, deflecting member) 1, a control circuit 2, a polygon mirror (optical scanning system) 3, a collimator lens 4, and an LD (laser diode, light source) 5. .
[0068]
The optical unit 40 irradiates a photosensitive drum (image carrier, light exposure member) 22 with a laser beam (light beam) via an fθ lens 41. The laser beam from the optical unit 40 travels on the photosensitive drum 22 in the main scanning direction indicated by an arrow B (the direction of the central axis of the photosensitive drum 22, which is perpendicular to the sheet conveyance direction described later on the photosensitive drum 22). Direction).
[0069]
lens 41 performs f-θ correction on the laser beam.
[0070]
The LD 5 is a modulatable light source composed of a semiconductor laser. The laser beam emitted from the LD 5 is converted into a parallel beam by the collimator lens 4.
[0071]
The polygon mirror 3 is connected to a motor (not shown), and is rotated in the direction of arrow C by this motor. The polygon mirror 3 has a substantially regular polygonal prism shape.
[0072]
The laser beam that has entered the polygon mirror 3 from the collimator lens 4 is deflected and reflected on the side surface of the polygon mirror 3 and irradiates the photosensitive drum 22 via the liquid crystal cell 1 and the fθ lens 41.
[0073]
The liquid crystal cell 1 includes substrates 61 and 62, electrodes 63 and 64, and a liquid crystal layer 65, as shown in FIG.
[0074]
The substrates 61 and 62 are transparent flat plates, and are made of, for example, glass. The electrodes 63 and 64 are transparent and connected to the control circuit 2 (see FIGS. 1 and 3) to which a voltage is applied.
[0075]
The liquid crystal layer 65 is made of liquid crystal and has a thickness of about several μm (eg, 5 μm). As the liquid crystal, those having a large change in refractive index Δn are preferable. For example, an azoxy-based liquid crystal (Δn = 0.28) which is a nematic liquid crystal having positive dielectric anisotropy, and a cyanobiphenyl-based liquid crystal (Δn = 0. 2), biphenyl-based liquid crystal (Δn = 0.22) and the like.
[0076]
In this liquid crystal cell 1, first, the electrodes 63 and 64 are formed on the substrates 61 and 62 by depositing the materials of the electrodes 63 and 64 on the back surfaces of the substrates 61 and 62 in a thin film shape by vapor deposition or sputtering. I do. Subsequently, the substrate 61 and the substrate 62 are arranged to face each other with a predetermined gap so that the surfaces on which the electrodes are formed (back surfaces) face each other. Then, the liquid crystal is sealed between the electrodes 63 and 64, whereby the liquid crystal cell 1 can be manufactured.
[0077]
Next, the prism function in the liquid crystal cell 1 will be described with reference to FIGS.
[0078]
As shown in FIG. 1, the liquid crystal cell 1 is disposed between the polygon mirror 3 and the fθ lens 41. At this time, the liquid crystal cell 1 is arranged so as to have a predetermined angle with respect to the optical axis of the laser beam emitted from the polygon mirror 3.
[0079]
The control circuit 2 connected to the liquid crystal cell 1 includes a transformer (not shown) and an ON / OFF switch.
[0080]
When the control circuit 2 is turned on and a voltage is applied to the electrodes 63 and 64, an electric field is formed in the thickness direction of the liquid crystal layer 65. At this time, the liquid crystal molecules are arranged in a vertical direction at a predetermined angle with respect to the direction of the electric field, whereby the distribution of the refractive index in the liquid crystal becomes uniform and the effect of the prism is generated.
[0081]
Therefore, as shown in FIG. ₁ And the laser beam incident from the substrate 61 side has an angle θ ₂ And is emitted from the substrate 62. Here, FIG. 3 is a diagram schematically showing that the substrates 61 and 62, the liquid crystal layer 65, and the electrodes 63 and 64 have the same refractive index.
[0082]
Angle (refraction angle) θ ₂ That is, the refractive index is determined by the arrangement direction of the liquid crystal molecules in the liquid crystal layer 65. That is, the angle θ ₂ Varies with the magnitude of the voltage applied from the control circuit 2. The magnitude of the voltage applied by the control circuit 2 can be adjusted by the transformer of the control circuit 2.
[0083]
Accordingly, by changing the voltage applied to the liquid crystal cell 1 by the control circuit 2, the laser beam incident from the substrate 61 is translated in the D direction by an arbitrary distance (Δy) (see FIG. 1), and Can be emitted toward the fθ lens 41.
[0084]
The displacement can be corrected by associating the amount of parallel movement (Δy) with the displacement described below.
[0085]
Hereinafter, the positional deviation and the correction of the positional deviation will be described with reference to FIGS.
[0086]
First, the displacement will be described.
[0087]
In a color image forming apparatus, photoconductors (photoconductor drums) corresponding to a plurality of different colors are arranged side by side, and an electrostatic latent image is formed on each photoconductor by an exposure device. Then, each electrostatic latent image is developed with a developer (toner) of a corresponding color to form a toner image (color image), and a toner image (color image) is sequentially transferred to form a multicolor image on paper. . The configuration of such a color image forming apparatus will be described later in detail.
[0088]
For example, assuming that the toner images of the respective colors are sequentially transferred (here, in the order of Y, M, C, and K) on the conveyed paper, as shown in FIG. The toner image is transferred so as to overlap the toner image.
[0089]
However, for example, as shown in FIG. 7, due to a shift in the mounting position or peripheral speed of the photoconductor, expansion or contraction of each unit due to a temperature change, a shift in the exposure position with respect to the photoconductor, or a shift in the linear speed of the transfer belt. In addition, the transfer position of the toner image may not match. For example, the formation position of the K toner image and the formation position of the Y toner image may be displaced from each other and have a distance between them (a deviation amount ΔY in displacement).
[0090]
In such a case, color misregistration occurs between colors having misregistration, resulting in degradation of image quality.
[0091]
By the way, such a displacement occurs in the paper transport direction, that is, in the sub-scanning direction. Therefore, in order to correct such a displacement, the optical axis of the laser beam irradiated on the photosensitive drum 22 must be moved in the direction of the double arrow D (see FIG. 1).
[0092]
Next, correction of the position shift (timing correction) when the liquid crystal cell 1 is OFF (the liquid crystal cell 1 is not used) will be described.
[0093]
In such a case, the displacement can be corrected by the rotation timing of the polygon mirror 3.
[0094]
Here, the laser beam emitted from the LD 5 is formed on the polygon mirror 3 in accordance with the image data (YDATA, MDATA, CDATA, KDATA) of each color input from an LD driver (not shown).
[0095]
As described above, the polygon mirror 3 is rotated by a motor (not shown), and scans the laser beam with polarized light. The laser beam reaches the photosensitive drum 22 via the fθ lens 41 (see FIG. 1) and the mirrors 42 and 43 (see FIG. 10). Here, the rotation speed of the polygon mirror 3 is controlled to be constant by control means (not shown).
[0096]
Therefore, when a position shift (exposure position) of a toner image of a certain color is changed to correct the position shift between the toner images, control is performed so as to shift the irradiation timing of the laser beam to the polygon mirror 3. Just fine. That is, the position shift is corrected (hereinafter, referred to as timing correction) by controlling the timing of writing to the photosensitive drum 22.
[0097]
In the case of this timing correction, by performing the correction based on the write timing due to the rotation of the polygon mirror 3, the same amount of correction is obtained for the positional deviation within a predetermined range (see the timing correction area in FIG. 9).
[0098]
Next, a description will be given of the correction (analog correction) of the positional shift when the liquid crystal cell 1 is turned on (using the liquid crystal cell 1).
[0099]
In this case, as described above, by changing the voltage applied to the liquid crystal cell 1 by the control circuit 2, the laser beam to the photosensitive drum 22 is moved a desired distance in the sub-scanning direction (the direction of the double arrow D in FIG. 1). The beam can be moved. That is, the amount of displacement and the amount of correction can be made to correspond one-to-one (see the analog correction region in FIG. 9).
[0100]
Thus, the exposure position can be moved by a desired amount, and the formation position of the formed toner image can be changed. Therefore, it is possible to correct the positional deviation between the toner images (hereinafter, referred to as analog correction). In addition, high-precision correction can be performed as compared with the timing correction.
[0101]
Note that a switching unit (for example, a CPU (control unit) in the image forming apparatus) that switches between the timing correction and the analog correction according to the amount of displacement may be provided.
[0102]
That is, as described above, the analog correction enables fine correction. On the other hand, since the change in the refractive index of the liquid crystal is used, the correction amount is compared with the timing correction using the rotation timing of the polygon mirror 3. Then you can't take that much.
[0103]
Therefore, when the analog correction and the timing correction are used together, as shown in FIG. 7, the timing correction is performed when the displacement amount is large, and the correction is performed to some extent using the small displacement amount or the timing correction. It is preferable to perform the analog correction when the row amount is reduced (the deviation amount becomes close to 0 (target position)).
[0104]
Note that the configuration of the liquid crystal cell 1 is not particularly limited as long as the optical path of the laser beam can be moved and the displacement can be corrected. For example, as shown in FIG. It does not matter.
[0105]
That is, instead of the electrodes 63 and 64 shown in FIG. 2, electrodes 73 and 74 may be provided as shown in FIG. The electrodes 73 and 74 are both disposed on the laser beam incident side of the liquid crystal layer 65 in the liquid crystal cell 1.
[0106]
For example, first, the liquid crystal cell is provided with electrodes 73 and 74 above and below (near the upstream and downstream ends in the sub-scanning direction) the back surface (one surface) of the substrate 61 which is the substrate on the laser beam incident side. The electrodes 73 and 74 are formed on the substrate 61 by depositing the above material in a thin film shape by vapor deposition or sputtering. Subsequently, the substrate 61 and the substrate 62 are arranged facing each other with a predetermined gap so that the surfaces on which the electrodes are formed face each other. Then, liquid crystal is sealed between the substrates 61 and 62, whereby a liquid crystal cell can be manufactured. In FIG. 4, the substrates 61 and 62 are omitted.
[0107]
Here, the electrode 73 and the electrode 74 are separated. Thus, when a voltage is applied to the liquid crystal cell by the control circuit 2, electric lines of force are formed between the electrodes 73 and 74, and act as a convex lens. Hereinafter, such a liquid crystal cell acting as a convex lens will be described as a liquid crystal lens.
[0108]
Therefore, by changing the voltage applied from the control circuit 2 to the liquid crystal lens, the swelling of the lines of electric force changes, and the focal length of the liquid crystal lens changes. As a result, as shown in FIG. 4, the optical path of the laser beam is shifted by Δy in the sub-scanning direction. _d Can be moved. That is, when the focal length is increased (from L2 to L1), the exposure position on the photosensitive drum 22 is shifted upward by Δy. _d Can be moved, and the color image transfer position is also Δy _d Can be moved. In this manner, the displacement of the toner image can be corrected.
[0109]
In this case, in order to translate the optical path of the laser beam in parallel, it is necessary to enter the laser beam while being shifted from the optical axis of the liquid crystal lens.
[0110]
Hereinafter, a configuration of a digital color copying machine (hereinafter, referred to as a copying machine) using the optical unit 40 including the liquid crystal cell shown in FIG. 2 will be described with reference to FIG.
[0111]
As shown in FIG. 10, a document table 111 and an operation panel (not shown) are provided on the upper surface of the main body of the copying machine (image forming apparatus), and an image reading unit 52 and an image forming unit 53 are provided inside the main body of the copying machine. Configuration.
[0112]
A two-sided automatic document feeder (RADF; Reversing Automatic Document Feeder) 51 is supported on the upper surface of the document table 111 so as to be openable and closable with respect to the document table 111 and has a predetermined positional relationship with respect to the surface of the document table 111. It is installed.
[0113]
Further, the double-sided automatic document feeder 51 conveys the document such that one side of the document faces the image reading unit 52 at a predetermined position on the document table 111, and after the image reading on one side is completed, the other side. The document is inverted and transported toward the document table 111 such that the surface of the document faces the image reading unit 52 at a predetermined position on the document table 111.
[0114]
Then, after the two-sided image reading for one document has been completed, the double-sided automatic document feeder 51 discharges this document and executes a double-sided conveyance operation for the next document. The above-described document conveyance and reverse operation are controlled in relation to the operation of the entire copying machine.
[0115]
The image reading unit 52 is arranged below the document table 111 for reading an image of the document conveyed onto the document table 111 by the automatic duplex document feeder 51. The image reading section 52 has document scanning bodies 113 and 114 that reciprocate in parallel along the lower surface of the document table 111, an optical lens 115, and a CCD (Charge Coupled Device) line sensor 116 that is a photoelectric conversion element. ing.
[0116]
The original scanning bodies 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 113 has an exposure lamp for exposing the surface of the original image, and a first mirror for deflecting the reflected light image from the original in a predetermined direction. It reciprocates in parallel at a predetermined scanning speed while maintaining the distance.
[0117]
The second scanning unit 114 has second and third mirrors for further deflecting the reflected light image from the document deflected by the first mirror of the first scanning unit 113 in a predetermined direction. It reciprocates in parallel with one scanning unit 113 while maintaining a constant speed relationship.
[0118]
The optical lens 115 reduces the reflected light image from the document deflected by the third mirror of the second scanning unit 114 and forms the reduced light image at a predetermined position on the CCD line sensor 116. .
[0119]
The CCD line sensor 116 photoelectrically converts the formed light image in order and outputs it as an electric signal. The CCD line sensor 116 is a three-line color CCD capable of reading a black-and-white image or a color image and outputting line data separated into R (red), G (green), and B (blue) color components. . The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit and subjected to predetermined image data processing.
[0120]
Next, the configuration of the image forming unit 53 and the configuration of each unit related to the image forming unit 53 will be described.
[0121]
Below the image forming unit 53, a paper feed mechanism 54 is provided, which separates sheets (recording media) P stacked and accommodated in the sheet tray one by one and supplies the separated sheets P toward the image forming unit 53. Then, the sheets P separated and supplied one by one are conveyed to the image forming unit 53 at a controlled timing by a pair of registration rollers 12 disposed in front of the image forming unit 53. Further, the sheet P on which an image is formed on one side is re-supplied and conveyed to the image forming unit 53 in synchronization with the image formation of the image forming unit 53.
[0122]
In the image forming section 53, the transfer and conveyance belt mechanism 13 is disposed. The transfer / transport belt mechanism 13 includes transfer dischargers 25a to 25d, a transfer / transport belt 16, a transfer belt cleaning unit 11, a drive roller 14, a driven roller 15, and a tension roller 31. Hereinafter, the four transfer dischargers 25a to 25d corresponding to each color are collectively referred to as a transfer discharger 25.
[0123]
The transfer discharger 25 is rotatably supported by a frame inside the transfer and transport belt mechanism 13, and stretches the transfer and transport belt 16 together with the drive roller 14, the tension roller 31, and the driven roller 15. Here, the transfer conveyance belt 16 is stretched between the driving roller 14 and the driven roller 15 so as to extend substantially in parallel.
[0124]
The transfer discharger 25 is based on a metal shaft having a diameter of 8 to 10 mm, and its surface is covered with a conductive elastic material such as EPDM or urethane foam. The transfer discharger 25 can uniformly apply a high voltage having a polarity opposite to the charge polarity of the toner to the paper by the conductive elastic material, and is formed on the photosensitive drums 22a to 22d. The toner image is transferred onto the transfer / transport belt 16 or a sheet that is adsorbed on the transfer / transport belt 16 and conveyed.
[0125]
A pattern image detection sensor (position shift detection unit) 32 is provided near the lower side of the transfer conveyance belt 16. The pattern image detection sensor 32 is for detecting the amount of misregistration (registration) or the amount of skew based on the patch image created on the transfer / conveyance belt 16.
[0126]
In the case of registration detection, patch images of different colors are formed one by one, and in the case of skew detection, patch images of a certain color are placed at both ends of the image area (in the image area in a direction perpendicular to the paper transport direction). One piece (two in total) is formed near each end. Therefore, one pattern image detection sensor 32 is arranged at each end near the both ends of the image area (both ends in the direction perpendicular to the sheet conveying direction in the image area) when detecting skew. I have.
[0127]
A temperature and humidity sensor (not shown) detects the temperature and humidity in the copying machine, and is installed in the vicinity of the process section where there is no rapid temperature change or humidity change.
[0128]
Therefore, the liquid crystal cell 1 can deflect the laser beam based on the detected temperature. Thereby, it is possible to correct a positional shift due to expansion and contraction of each part of the device due to a temperature change.
[0129]
In this case, the detected temperature and a correction amount based on the detected temperature are stored as a table in the copying machine in association with each other. When the temperature is detected, the correction amount is determined using this table, and a voltage corresponding to the correction amount is applied to the liquid crystal cell 1 from the control circuit 2.
[0130]
Further, a fixing device 17 for fixing the toner image transferred and formed on the paper P to the paper P is disposed downstream of the transfer and transport belt mechanism 13 in the paper transport path. The paper P that has passed through the nip between the pair of fixing rollers of the fixing device 17 passes through a conveyance direction switching gate 18 and is discharged by discharge rollers 19 onto a discharge tray 20 attached to the outer wall of the copying machine main body. .
[0131]
The switching gate 18 selectively switches the conveyance path of the sheet P after fixing between a path for discharging the sheet P to the copying machine main body and a path for re-supplying the sheet P toward the image forming unit 53. It is. The sheet P whose transport direction has been switched again toward the image forming unit 53 by the switching gate 18 is turned upside down via the switchback transport path 21, and is again supplied to the image forming unit 53.
[0132]
In the image forming section 53, a first image forming station Pa, a second image forming station Pb, and a third image forming station Pc are provided above the transfer conveyance belt 16 and close to the transfer conveyance belt 16. And a fourth image forming station Pd are arranged side by side in order from the upstream side of the sheet transport path.
[0133]
The transfer conveyance belt 16 is frictionally driven by the drive roller 14 in the direction indicated by the arrow Z in FIG. 1 and carries the sheet P fed through the sheet feeding mechanism 54 as described above. Conveyed sequentially to Pd.
[0134]
The image forming stations Pa to Pd form four types of latent images according to each color in order to form a multicolor image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Exposure units 27a, 27b, 27c, 27d, developing devices 24a, 24b, 24c, 24d, photosensitive drums 22a, 22b, 22c, 22d, cleaner units 26a, 26b, 26c, 26d, charger 23a 23b, 23c, and 23d, each of which is provided with four. Each of the image stations Pa to Pd has substantially the same configuration. Here, a, b, c, and d are black (K), cyan (C), and magenta (M), respectively. , Yellow (Y).
[0135]
Note that, in the following, members provided for each color are collectively referred to as an exposure unit 27 except for a case where a member corresponding to a specific color is designated among the four members provided for each color. , A developing device 24, a photosensitive drum 22, a cleaner unit 26, a charger 23, and a transfer discharger 25.
[0136]
The photoreceptor drum 22 is arranged at the center of the copying machine main body, and forms an electrostatic latent image or a toner image on the surface according to input image data. Around the photoconductor drum 22, a charger 23, an exposure unit 27, a developing device 24, a transfer discharger 25 for transferring the developed toner image on the photoconductor drum 22d to the sheet P, A cleaner unit 26 for removing the toner remaining on the drum 22 is sequentially arranged along the rotation direction of the photosensitive drum 22 (the direction of arrow F).
[0137]
The charger 23 uniformly charges the surface of the photosensitive drum 22 to a predetermined potential. As the charger 23, a roller type or a brush type that does not contact the photoconductor drum 22 or the like, in addition to a roller type or a brush type that contacts the photoconductor drum 22, is used.
[0138]
The exposure unit 27 is disposed above the photosensitive drum 22, and connects the above-described optical unit 40 for polarizing a laser beam in the main scanning direction to the laser beam polarized by the optical unit 40 on the surface of the photosensitive drum 22. It comprises an fθ lens 41 for imaging and mirrors 42 and 43. The exposure unit 27 forms an electrostatic latent image on the photosensitive drum 22 according to the image data by exposing according to the input image data.
[0139]
The developing device 24 visualizes (develops) the electrostatic latent image formed on the photoconductor drum 22 with toner (developer) of each color.
[0140]
The cleaner unit 26 develops and transfers the electrostatic latent image formed on the surface of the photoconductor drum 22, and then removes and collects the toner remaining on the photoconductor drum 22.
[0141]
The exposure unit 27a receives a pixel signal corresponding to the black component image of the color original image, the exposure unit 27b receives a pixel signal corresponding to the cyan component image of the color original image, and the exposure unit 27c outputs a color original image. The pixel signal corresponding to the magenta color component image is input to the exposure unit 27d, and the pixel signal corresponding to the yellow color component image of the color original image is input to the exposure unit 27d.
[0142]
As a result, an electrostatic latent image corresponding to the color-converted document image information is formed on each of the photosensitive drums 22a to 22d. The developing device 24a contains a black toner, the developing device 24b contains a cyan toner, the developing device 24c contains a magenta toner, and the developing device 24d contains a yellow toner. The electrostatic latent images on the photosensitive drums 22a to 22d are developed with the toners of these colors. In this way, the document image information color-converted by the image forming unit 53 is reproduced as a toner image of each color.
[0143]
Further, a paper suction charger 28 is provided between the first image forming station Pa and the paper feeding mechanism 54. The attraction charger 28 charges the surface of the transfer / transport belt 16, and the sheet P supplied from the sheet feeding mechanism 53 is transferred from the first image forming station Pa while being securely attracted onto the transfer / transport belt 16. The fourth image forming station Pd is transported without shifting.
[0144]
On the other hand, a static eliminator 29 is provided almost directly above the drive roller 14 between the fourth image station Pd and the fixing device 17. An alternating current for separating the paper P electrostatically attracted to the transfer and transport belt 16 from the transfer and transport belt 16 is applied to the neutralizer 29.
[0145]
In the copying machine having the above configuration, cut sheet-shaped paper is used as the paper P. When the sheet P is sent out from the sheet cassette and supplied to the guide of the sheet feeding path of the sheet feeding mechanism 54, the leading end of the sheet P is detected by a sensor (not shown) and output from the sensor. Is temporarily stopped by the pair of registration rollers 12 based on the detection signal.
[0146]
Then, the paper P is sent onto the transfer / conveying belt 16 rotating in the direction of arrow Z in FIG. 1 at the timing of each of the image stations Pa to Pd. At this time, as described above, the transfer conveyance belt 16 is given a predetermined charge by the attraction charger 28, so that the paper P is stably conveyed and supplied while passing through the image stations Pa to Pd. You.
[0147]
In each of the image stations Pa to Pd, a toner image of each color is formed, and is superposed on the support surface of the paper P conveyed by being electrostatically attracted and conveyed by the transfer conveyance belt 16. When the transfer of the image by the fourth image station Pd is completed, the sheet P is sequentially separated from the transfer conveyance belt 16 by the discharging device from the leading end thereof, and is guided to the fixing device 17. Finally, the paper P on which the toner image has been fixed is discharged onto a paper discharge tray 20 from a paper discharge port (not shown).
[0148]
In the above description, optical writing to the photoconductor is performed by scanning and exposing a laser beam using an exposure unit including an LSU, but the present invention is not limited to this. For example, a writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used instead of the LSU.
[0149]
This LED head is smaller in size than the LSU, and has no moving parts and is silent. Therefore, it can be suitably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.
[0150]
As described above, the copying machine (image forming apparatus) includes the photosensitive drum 22 having the photosensitive member on the surface, the exposure device 27 that exposes the photosensitive drum 22 based on the image data, and the exposure device 27 that performs the exposure. A plurality of image forming units (image forming stations Pa to Pd and a transfer discharger 25) for forming a color image (toner image) including a developing device 24 for developing the formed portion. One image of multiple colors is formed by transferring the above color image onto a conveying means (transfer conveying belt 16 or paper) conveyed in the setting direction.
[0151]
The exposure device 27 includes an LD 5, a polygon mirror 3 that deflects and reflects the laser beam emitted from the LD 5 toward the photosensitive drum 22 and scans the photosensitive drum 22, and on an optical path formed by the polygon mirror 3 ( For example, a liquid crystal cell 1 disposed between the polygon mirror 3 and the photosensitive drum 22 for deflecting a laser beam emitted from the polygon mirror 3 to the photosensitive drum 22, and a liquid crystal cell 1 connected to the liquid crystal cell 1. And a control circuit 2 for controlling the deflection of the laser beam by the laser beam.
[0152]
The control circuit 2 detects the amount of displacement between the electrostatic latent images when the exposure device 27 forms the electrostatic latent images on different photosensitive drums 22, and controls the liquid crystal cell 1 based on the amount of displacement. Controls the deflection of the laser beam.
[0153]
Thereby, the exposure position on the photosensitive drum 22 can be moved. That is, it is possible to perform the correction of the positional deviation between the color images that should be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0154]
Further, it is possible to correct a mechanical or optical displacement of the photosensitive drum 22 or the polygon mirror 3 and a displacement of an electrostatic latent image due to a speed deviation of a driving system or a transport system.
[0155]
The exposure device 27 includes an LD 5, a polygon mirror 3 that deflects and reflects the laser beam emitted from the LD 5 toward the photoconductor drum 22 and scans the photoconductor drum 22, and the polygon mirror 3 and the photoconductor drum 22. A liquid crystal cell 1 arranged between the polygon mirror 3 and deflecting a laser beam emitted from the polygon mirror 3 to the photosensitive drum 22.
[0156]
Thereby, the exposure position on the photosensitive drum 22 can be moved. That is, it is possible to perform the correction of the positional deviation between the color images that should be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0157]
Further, the liquid crystal cell 1 has a liquid crystal layer 65 made of liquid crystal, and a pair of electrodes 63 and 64 (73 and 74) for applying a voltage to the liquid crystal layer 65 and changing the refractive index of the liquid crystal layer 65. Is preferred.
[0158]
As a result, by using liquid crystal, the voltage required for driving the liquid crystal cell 1 can be lower than when using an electro-optical element such as LPZT. For example, a driving voltage of LPZT requires a driving voltage of several hundreds to several kilometers (V), but a liquid crystal cell 1 using liquid crystal may have a driving voltage of several (V). Therefore, power consumption can be reduced. Further, the liquid crystal cell 1 (81) using liquid crystal is less expensive than the electro-optical element, and can largely deflect the light beam.
[0159]
Further, the copying machine is provided with a misregistration detecting means for detecting misregistration between the color images of the respective colors transferred on the conveying means, and the liquid crystal cell 1 is detected by the misregistration detecting means at the time of initial setting of the copying machine. It is preferable to correct the misalignment.
[0160]
Thus, at the time of initial setting of the image forming apparatus, it is possible to detect the displacement of the color image using the pattern image (patch image). Accordingly, it is possible to correct a positional error and a skew of a color image caused by an assembling error at the time of assembling the image forming apparatus, a processing error of parts of the image forming apparatus, and the like from the time of initial setting (to the start of image forming). it can.
[0161]
In the present embodiment, the liquid crystal cell 1 has been described as being disposed between the polygon mirror 3 and the F-θ lens 41. However, if the liquid crystal cell 1 is disposed on the optical path of a laser beam, this configuration is adopted. The present invention is not limited to this. For example, it may be arranged between the collimator lens 4 and the polygon mirror 3 or on the optical path downstream of the F-θ lens 41.
[0162]
[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. 1, 4, 5 and 8. Note that, in the present embodiment, components having the same functions as the components in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0163]
As shown in FIG. 5A, the liquid crystal cell 81 of the exposure apparatus according to the present embodiment is different from the control circuit 2 in place of the electrodes 63 and 64 or the electrodes 73 and 74 and the control circuit 2 of the liquid crystal cell 1 in the first embodiment. , Electrodes 83 and 84, and a control circuit 85.
[0164]
As shown in FIG. 5B, the electrode 83 has a voltage (E _y1 , E _y2 ) Is applied. The electrode 84 is grounded. The electrodes 83 and 84 are formed of resistor electrodes having higher resistance than metal.
[0165]
By the way, a skew as shown in FIG. 8 may occur due to an assembly error at the time of assembling the image forming apparatus, a processing error of parts of the image forming apparatus, or the like. The skew means that a certain color image has an inclination (a shift of the distance ΔS in the transport direction) in one line.
[0166]
Where E _y1 And E _y2 Is different, the moving amount (correction amount) of the laser beam applied to the photosensitive drum 22 can be changed in one line.
[0167]
Therefore, by providing the liquid crystal cell 81 between the polygon mirror 3 and the photosensitive drum 22, even if there is a skew in one line, the skew is corrected together with the above-described positional deviation correction (see Embodiment 1). Can be corrected.
[0168]
That is, E _y2 = E _y1 In the case of + ΔE, if ΔE = 0, the liquid crystal cell 81 shown in FIG. 5 has the same configuration as the liquid crystal cell shown in FIG. 4 of the first embodiment, and corrects the displacement of the toner image between different colors. be able to.
[0169]
Also, E _y2 > E _y1 , E _y2 <E _y1 In this case, skew in one line can be corrected by ΔE.
[0170]
Further, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims, and the technical means disclosed in the different embodiments may be appropriately combined. The obtained embodiments are also included in the technical scope of the present invention.
[0171]
【The invention's effect】
As described above, the exposure apparatus of the present invention is disposed on the optical path formed by the optical scanning system, and is connected to the deflecting member that deflects the light beam emitted from the optical scanning system to the member to be exposed, and the deflecting member. Control means for controlling the deflection of the light beam by the deflecting member, the control means detects the amount of positional deviation between the electrostatic latent images when an electrostatic latent image is formed on a different exposed member, The configuration is such that the deflection of the light beam by the deflection member is controlled based on the displacement amount.
[0172]
Thereby, the exposure position of the member to be exposed can be moved. For example, when the exposure apparatus is used in a color image forming apparatus, it is possible to perform the correction of the positional shift between the color images to be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0173]
Therefore, there is an effect that it is possible to correct a mechanical or optical displacement of the member to be exposed or the optical scanning system and a displacement of the electrostatic latent image due to a speed deviation of the driving system or the transport system.
[0174]
The exposure apparatus of the present invention has a configuration in which the deflection member includes a liquid crystal layer made of liquid crystal, and a pair of electrodes that apply a voltage to the liquid crystal layer and change the refractive index of the liquid crystal layer.
[0175]
As a result, the voltage required to drive the deflecting member can be lower than when an electro-optical element such as LPZT is used. Therefore, power consumption can be reduced. In addition, there is an effect that the light beam can be largely deflected as compared with the electro-optical element.
[0176]
The exposure apparatus of the present invention has a configuration in which different voltages are applied to one of a pair of electrodes of a deflection member from near both ends of the one electrode.
[0177]
As a result, a potential gradient occurs in a portion corresponding to one line in the deflection member. Therefore, for example, even when a skew occurs in a color image due to an assembly error at the time of assembling the image forming apparatus or a processing error of a part of the image forming apparatus, it is possible to correct the skew.
[0178]
The exposure apparatus according to the present invention has a configuration in which the deflection member is disposed between the optical scanning system and the member to be exposed.
[0179]
Accordingly, even when skew occurs due to an assembling error at the time of assembling the image forming apparatus or a processing error of parts of the image forming apparatus, it is possible to correct the skew.
[0180]
As described above, the image forming apparatus of the present invention forms an image carrier having a photoreceptor on its surface, and forms an electrostatic latent image on the surface of the image carrier by exposing the image carrier based on image data. A plurality of image forming means for forming a color image including an exposing device and a developing device for developing a portion exposed by the exposing device are arranged in parallel, and on a conveying means which is conveyed in the juxtaposition direction of the image forming means. An image forming apparatus for forming one image of multiple colors by transferring the color image, wherein the exposure device deflects a light source and a light beam emitted from the light source toward an image carrier. And an optical scanning system for scanning the image carrier, and a deflecting member disposed on an optical path formed by the optical scanning system and deflecting a light beam emitted from the optical scanning system to the image carrier, The deflection member is connected to the deflection member, Control means for controlling the deflection of the light beam by detecting the position shift amount between the electrostatic latent images when the electrostatic latent images are formed on different image carriers, and In this configuration, the deflection of the light beam by the deflection member is controlled based on the shift amount.
[0181]
According to the above configuration, the exposure position on the image carrier can be moved. That is, it is possible to perform the correction of the positional deviation between the color images that should be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0182]
Further, there is an effect that it is possible to correct a mechanical or optical displacement of the image carrier or the optical scanning system, and a displacement of the electrostatic latent image due to a speed deviation of the driving system or the transport system.
[0183]
The image forming apparatus of the present invention has a configuration in which the deflecting member includes a liquid crystal layer made of liquid crystal, and a pair of electrodes that apply a voltage to the liquid crystal layer and change the refractive index of the liquid crystal layer.
[0184]
As a result, the voltage required to drive the deflecting member can be lower than when an electro-optical element such as LPZT is used. Therefore, power consumption can be reduced. In addition, the deflecting member using the liquid crystal is more inexpensive than the electro-optical element, and has an effect that the light beam can be largely deflected.
[0185]
The image forming apparatus of the present invention has a configuration in which a pair of electrodes of a deflecting member are arranged to face each other with a liquid crystal layer interposed therebetween.
[0186]
Thus, the deflecting member can function as a prism. Therefore, the deflecting member can translate the incident light beam in the sub-scanning direction. As a result, there is an effect that the exposure position of the image carrier can be moved, and the positional deviation between the color images can be corrected.
[0187]
The image forming apparatus according to the present invention has a configuration in which a pair of electrodes of a deflecting member are formed on one of a pair of substrates sandwiching a liquid crystal layer and are spaced apart from each other.
[0188]
Thereby, the deflecting member can have a lens function by forming the lines of electric force. Therefore, the deflecting member can translate the incident light beam in the sub-scanning direction. As a result, there is an effect that the exposure position of the image carrier can be moved, and the positional deviation between the color images can be corrected.
[0189]
The image forming apparatus of the present invention has a configuration in which different voltages are applied to one of the pair of electrodes of the deflection member from near both ends of the one electrode.
[0190]
As a result, a potential gradient occurs in a portion corresponding to one line in the deflection member. Therefore, even if a skew occurs in the color image, it can be corrected. That is, even when skew occurs, there is an effect that electrical automatic correction becomes possible.
[0191]
The image forming apparatus of the present invention includes a misregistration detecting unit that detects misregistration between the color images of the respective colors transferred onto the conveying unit, and the deflecting member is moved by the misalignment detecting unit when the image forming apparatus is initially set. This is a configuration for correcting the detected positional deviation.
[0192]
Thus, at the time of initial setting of the image forming apparatus, it is possible to detect the displacement of the color image using the pattern image (patch image). Accordingly, it is possible to correct a positional error and a skew of a color image caused by an assembling error at the time of assembling the image forming apparatus, a processing error of parts of the image forming apparatus, and the like from the time of initial setting (to the start of image forming). It has the effect of being able to.
[0193]
The image forming apparatus of the present invention includes temperature detecting means for detecting the temperature inside the image forming apparatus, and the deflecting member deflects the light beam based on the detected temperature.
[0194]
As a result, it is possible to correct the displacement caused by the expansion and contraction of each part of the device due to the temperature change.
[0195]
The image forming apparatus according to the present invention includes a timing correction for correcting a positional shift between the color images of the respective colors transferred onto the conveying means by shifting a writing timing of the optical scanning system to the image carrier, and a deflecting member. And a switching unit that switches between analog correction for correcting positional deviation by irradiating a light beam from the optical scanning system to the image carrier via the optical scanning system.
[0196]
Thus, when the displacement amount of the displacement is large, the timing correction is performed, and when the displacement amount is small, or the correction is performed to some extent by using the timing correction, the displacement amount is reduced (the displacement amount becomes close to the target value). In this case, analog correction can be performed.
[0197]
Therefore, when the deviation amount is near the target value, high-precision correction can be performed by analog correction, and by using timing correction together, a wide range of position deviation can be corrected without burdening the deflection member. It has the effect of becoming.
[0198]
The image forming apparatus according to the present invention has a configuration in which the deflection member is disposed between the optical scanning system and the image carrier.
[0199]
Accordingly, since the deflection member is provided between the optical scanning system and the image carrier, the moving amount (correction amount) of the light beam applied to the image carrier can be changed in one line. .
[0200]
Therefore, even when a skew occurs due to an assembly error at the time of assembling the image forming apparatus or a processing error of a part of the image forming apparatus, it is possible to correct the skew.
[0201]
As described above, the color matching adjustment method of the present invention includes an image carrier having a photoreceptor on its surface, and an optical scanning system that scans the image carrier while deflecting and reflecting a light beam toward the image carrier. A plurality of image forming means for forming a color image, comprising: an exposure device for exposing and scanning the image carrier based on image data; and a developing device for developing a portion exposed by the exposure device. A color image of each color transferred on the conveying means in an image forming apparatus for forming one image of multiple colors by transferring the color image on a conveying means conveyed in the direction in which the image forming means are arranged side by side A color matching adjustment method for correcting a positional deviation between the optical scanning system, wherein a light beam emitted from the optical scanning system to the image carrier is deflected by a deflecting member arranged on an optical path formed by the optical scanning system. Sub of optical scanning system By deflecting the 査 direction, a configuration for correcting a positional deviation between the color images of the respective colors transferred onto the conveying means.
[0202]
According to the above method, the exposure position on the image carrier can be moved. That is, it is possible to perform the correction of the positional deviation between the color images that should be transferred in a superimposed manner by a continuous correction amount (analog correction).
[0203]
Further, there is an effect that it is possible to correct a mechanical or optical displacement of the image carrier or the optical scanning system, and a displacement of the electrostatic latent image due to a speed deviation of the driving system or the transport system.
[0204]
The color matching adjustment method according to the present invention includes a timing correction for correcting a positional shift between color images of respective colors transferred onto a conveying unit by shifting a writing timing on an image carrier by an optical scanning system, and a deflecting member. By irradiating a light beam from the optical scanning system to the image carrier via the optical scanning system, switching is made between analog correction for correcting positional deviation.
[0205]
Thus, when the displacement amount of the displacement is large, the timing correction is performed, and when the displacement amount is small, or the correction is performed to some extent by using the timing correction, the displacement amount is reduced (the displacement amount becomes close to the target value). In this case, analog correction can be performed.
[0206]
Therefore, when the deviation amount is near the target value, high-precision correction can be performed by analog correction, and by using timing correction together, a wide range of position deviation can be corrected without burdening the deflection member. It has the effect of becoming.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a main part of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a configuration of a liquid crystal cell.
FIG. 3 is a diagram illustrating a prism function of a liquid crystal cell.
FIG. 4 is a diagram showing a configuration of a liquid crystal cell having a lens function.
5A and 5B are diagrams showing a configuration of a main part of a liquid crystal cell in an exposure apparatus according to another embodiment of the present invention, wherein FIG. 5A is a side view thereof, and FIG. FIG.
FIG. 6 is a diagram illustrating a configuration of a toner image when toner images of each color are sequentially transferred to a sheet in a color image forming apparatus.
FIG. 7 is a diagram showing a displacement.
FIG. 8 is a diagram showing a skew.
FIG. 9 is a graph showing the relationship between the amount of displacement and the amount of correction.
FIG. 10 is a diagram showing a configuration of a digital color copying machine using the optical unit shown in FIG.
[Explanation of symbols]
1 Liquid crystal cell (deflection member)
2 control circuit (control means)
3 Polygon mirror (optical scanning system)
5 LD (laser diode, light source)
22 Photoreceptor drum (exposed member, image carrier)
27 Exposure unit (exposure device)
40 Optical unit
61, 62 substrate
63, 64 electrodes
65 liquid crystal layer
73,74 electrode
81 liquid crystal cell
83,84 electrodes

Claims (15)

A light source; and an optical scanning system that deflects and reflects the light beam emitted from the light source toward the member to be exposed and scans the member to be exposed. In an exposure apparatus that exposes an exposure member,
A deflecting member arranged on an optical path formed by the optical scanning system and deflecting a light beam emitted from the optical scanning system to the exposed member;
Control means connected to the deflecting member and controlling deflection of the light beam by the deflecting member,
The control means detects a displacement amount between the electrostatic latent images when an electrostatic latent image is formed on a different exposed member, and controls the deflection of the light beam by the deflecting member based on the displacement amount. An exposure apparatus, comprising: 2. The exposure apparatus according to claim 1, wherein the deflecting member has a liquid crystal layer made of liquid crystal, and a pair of electrodes for applying a voltage to the liquid crystal layer to change a refractive index of the liquid crystal layer. The exposure apparatus according to claim 2, wherein different voltages are applied to one of the pair of electrodes from near both ends of the one electrode. 2. The exposure apparatus according to claim 1, wherein the deflection member is disposed between the optical scanning system and the exposed member. An image carrier having a photoreceptor on the surface, an exposure device for exposing the image carrier based on image data to form an electrostatic latent image on the surface of the image carrier, and a portion exposed by the exposure device. A plurality of image forming means for forming a color image including a developing device for developing, and a multicolor image forming apparatus which transfers the color image onto a conveying means which is conveyed in the direction in which the image forming means are arranged. An image forming apparatus for forming one image,
The exposure apparatus includes: a light source; an optical scanning system that deflects and reflects a light beam emitted from the light source toward the image carrier and scans the image carrier; and an optical path formed by the optical scanning system. A deflecting member that deflects a light beam emitted from the optical scanning system to the image carrier, and a control unit that is connected to the deflecting member and controls deflection of the light beam by the deflecting member. ,
The control means detects a displacement amount between the electrostatic latent images when the electrostatic latent images are formed on different image carriers, and controls the deflection of the light beam by the deflecting member based on the displacement amount. An image forming apparatus, comprising: 6. The image forming apparatus according to claim 5, wherein the deflecting member includes a liquid crystal layer made of liquid crystal, and a pair of electrodes for applying a voltage to the liquid crystal layer to change a refractive index of the liquid crystal layer. . The image forming apparatus according to claim 6, wherein the pair of electrodes are arranged to face each other with the liquid crystal layer interposed therebetween. The image forming apparatus according to claim 6, wherein the pair of electrodes are formed separately on one of the pair of substrates sandwiching the liquid crystal layer. 9. The image forming apparatus according to claim 8, wherein different voltages are applied to one of the pair of electrodes from near both ends of the one electrode. A position shift detecting unit that detects a position shift between the color images of each color transferred on the transport unit as a position shift of the electrostatic latent image,
The image forming apparatus according to claim 5, wherein the deflection member corrects the position shift detected by the position shift detecting unit at the time of initial setting of the image forming apparatus. A temperature detecting unit for detecting a temperature inside the image forming apparatus;
The image forming apparatus according to claim 5, wherein the deflecting member deflects the light beam based on the detected temperature. By shifting the writing timing on the image carrier by the optical scanning system, a timing correction for correcting a positional shift between the color images of the respective colors transferred on the conveying means, and the optical scanning via the deflecting member The image forming apparatus according to claim 5, further comprising a switching unit configured to irradiate the image carrier with a light beam from a system to switch between the analog correction for correcting the positional deviation. The image forming apparatus according to claim 5, wherein the deflection member is disposed between the optical scanning system and the image carrier. An image carrier having a photoreceptor on its surface, and an optical scanning system for deflecting and reflecting a light beam toward the image carrier and scanning the image carrier are provided, and the image carrier is exposed based on image data. A plurality of image forming units that form a color image, each including an exposure device that scans and a developing device that develops a portion exposed by the exposure device, and a conveying unit that is conveyed in a direction in which the image forming units are arranged. A color matching adjustment method for correcting a positional shift between color images of each color transferred on the transporting means in an image forming apparatus that forms one image of multiple colors by transferring the color image onto the image forming apparatus. ,
The light beam emitted from the optical scanning system to the image carrier is deflected in a sub-scanning direction of the optical scanning system by a deflecting member disposed on an optical path formed by the optical scanning system, thereby conveying the image carrier. A color misregistration method for correcting misregistration between color images of respective colors transferred on the means. By shifting the writing timing on the image carrier by the optical scanning system, a timing correction for correcting a positional shift between the color images of each color transferred on the transporting means, and the optical scanning via the deflecting member 15. The color matching adjustment method according to claim 14, wherein the system is switched from an analog correction for correcting the positional deviation by irradiating the image carrier with a light beam from a system.

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