JP2013029667A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the possibility of non-uniform density in a line of latent image in a main scanning direction, which is formed on a photoreceptor.SOLUTION: An image forming apparatus comprises: a light receiving position detecting part fixed in a position separate from the photoreceptor and configured to detect a laser beam receiving position; a light emitting part fixed to part of a photoreceptor support member and configured to emit a laser beam toward the light receiving position detecting part; and an exposure part configured to scan the photoreceptor with a quantity of laser beam corresponding to a density value of each pixel of image data and form a latent image for each line. A light receiving position when the light emitting part is caused to emit a laser beam when scanning is not carried out is used as a reference position, and displacement from the reference position of the light receiving position is constantly monitored when the light emitting part is caused to continuously emit a laser beam during scanning. The quantity of laser beam to be scanned is adjusted such that in a case where the direction of displacement satisfies a condition for reducing the density of a latent image, the density of the latent image is increased by an amount corresponding to the displacement and in a case where the direction of displacement satisfies a condition for increasing the density of the latent image, the density of the latent image is decreased by an amount corresponding to the displacement.

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for reducing the possibility of density unevenness occurring in a latent image formed on a photoreceptor.

  Conventionally, in an image forming apparatus using a semiconductor laser that emits a plurality of laser beams, such as a copying machine, a printer, and a fax machine, a latent image is formed (exposed) by scanning the peripheral surface of the photoreceptor with the laser beams. In this case, the latent image writing position may be deviated from the assumed position due to the vibration of the photosensitive member or the vibration of the exposure unit that emits laser light, and this may cause density unevenness in the formed latent image. .

  Therefore, for example, Patent Document 1 below includes a sub-scanning position detection sensor that detects the irradiation position of the laser beam in the sub-scanning direction on the surface of the photosensitive drum (photosensitive member), and scans the photosensitive member with laser light. In the laser exposure apparatus (exposure unit), a technique is described in which the amount of laser light is set for each scanning line based on the irradiation position in the sub-scanning direction detected by the sub-scanning position detection sensor.

JP 2007-145041 A

  However, in the technique described in Patent Document 1, there is a control for adjusting density of laser light and suppressing density unevenness for each scanning line based on the irradiation position in the sub-scanning direction detected by the sub-scanning position detection sensor. As a result, the density unevenness that occurs when the photosensitive member or the exposure unit is displaced from the assumed position due to vibration or the like during the formation of the latent image for one line in the main scanning direction cannot be suppressed. .

  Accordingly, the present invention has been made in view of such circumstances, and an image forming apparatus capable of reducing the possibility of density unevenness occurring in a latent image for one line in the main scanning direction formed on a photoconductor. The purpose is to provide.

  An image forming apparatus according to the present invention includes a photosensitive member having a circumferential surface that is rotationally driven, a photosensitive member supporting member that rotatably supports the photosensitive member, a position spaced apart from the photosensitive member, and a laser beam. A light receiving position detecting unit that detects a light receiving position of the laser beam on the light receiving surface, and a laser beam that is fixed to a part of the photosensitive member support member and directed toward the light receiving position detecting unit. By scanning the emitted light emitting unit and laser light of a light amount corresponding to the density value of each pixel of the image data from one end of the photoconductor to the other end, the peripheral surface of the photoconductor is lined by one line in the main scanning direction. An exposure unit that forms a latent image, and the laser detected by the light receiving position detection unit by causing the light emitting unit to emit laser light when laser light is not scanned by the exposure unit. A reference position determining unit that determines a light receiving position as a reference position, and a laser beam that is detected by the light receiving unit by continuously emitting laser light to the light emitting unit while the exposure unit scans the laser beam. When the light receiving position monitoring unit that constantly monitors the deviation of the light receiving position of the laser light from the reference position, and the direction of the deviation being monitored by the light receiving position monitoring unit satisfies the condition for thinning the latent image, If the amount of laser light scanned by the exposure unit is adjusted so that the latent image is darkened by an amount corresponding to the magnitude of the shift, and the condition of the shift satisfies the condition for darkening the latent image, A feedback control unit that adjusts the amount of laser light scanned by the exposure unit so that the latent image is thinned by an amount corresponding to the magnitude of the shift.

  According to this configuration, the deviation of the light receiving position of the laser beam emitted from the light emitting unit fixed to a part of the photosensitive member supporting member from the reference position is constantly monitored by the light receiving position monitoring unit. In other words, the degree to which the photosensitive member supporting member is deviated from the reference position is constantly monitored, in other words, the degree of deviation of the photosensitive member supported by the photosensitive member supporting member from the reference position. Is constantly monitored.

  When the direction of deviation being monitored satisfies the condition for thinning the latent image formed on the photoconductor by the feedback control unit, the exposure unit is configured to darken the latent image by an amount corresponding to the magnitude of the deviation. If the amount of laser light to be scanned is adjusted and the direction of deviation satisfies the condition for darkening the latent image, the laser light that scans the exposure unit to make the latent image thinner by the amount of deviation The amount of light is adjusted.

  Therefore, while the laser beam is scanned from one end to the other end of the peripheral surface of the photoconductor, the photoconductor is displaced due to vibration or the like, so that one main scanning line formed on the photoconductor is generated. This can reduce the possibility of density unevenness in the latent image.

  In addition, when the shift direction monitored by the light receiving position monitoring unit is a main scanning direction, the feedback control unit determines the amount of laser light to be scanned by the exposure unit from each pixel of image data. Is adjusted to the amount of light corresponding to the density value of the pixel formed earlier or later by an amount corresponding to the magnitude of the deviation, and the direction of the deviation being monitored by the light receiving position monitoring unit is the sub-scanning direction. In this case, it is preferable to adjust the light amount of the laser light scanned by the exposure unit to a light amount corresponding to a density value obtained by increasing or decreasing the density value of each pixel of the image data by an amount corresponding to the magnitude of the deviation. .

  According to this configuration, when the photoconductor is displaced in the main scanning direction while the laser beam is scanned from one end to the other end of the peripheral surface of the photoconductor, the light amount of the laser light scanned by the exposure unit is The amount of light corresponding to the density value of the pixel formed earlier or later is adjusted by an amount corresponding to the magnitude of the deviation from each pixel of the image data.

  For this reason, the photoconductor is displaced in the main scanning direction while the laser beam is scanned, so that even when the intervals between the pixels which are equal are sparse, the photoconductor is formed on the photoconductor. Each pixel of the latent image is formed at an appropriate position according to the magnitude of the shift. This can reduce the occurrence of density unevenness in the main scanning direction of the latent image.

  Further, according to this configuration, when the photosensitive member is shifted in the sub-scanning direction while the laser beam is scanned from one end to the other end of the peripheral surface of the photosensitive member, the amount of laser light to be scanned by the exposure unit However, the light amount corresponding to the density value obtained by increasing or decreasing the density value of each pixel of the image data by an amount corresponding to the magnitude of the deviation is adjusted.

  For this reason, even when the uniform line spacing becomes sparse due to the photoconductor shifting in the sub-scanning direction while the laser beam is scanned, the latent image formed on the photoconductor The density is appropriately adjusted according to the density of the line interval. This can reduce the occurrence of density unevenness in the sub-scanning direction of the latent image.

  As described above, in the latent image for one main scanning line formed on the photosensitive member due to the positional deviation of the photosensitive member in both the main scanning direction and the sub scanning direction, both the main scanning direction and the sub scanning direction are used. This can reduce the possibility of uneven density.

  A plurality of the light emitting units are provided, and a first light emitting unit which is one of the plurality of light emitting units is fixed to a portion of the photoconductor support member that supports one end of the photoconductor, A second light emitting portion different from the first light emitting portion is fixed to a portion of the photosensitive member supporting member that supports the other end of the photosensitive member, and a plurality of light receiving position detecting portions are provided. And a first light receiving position detector, which is one of the plurality of light receiving position detectors, is provided at a position facing the first light emitter, and is emitted from the first light emitter. A second light receiving position detector that receives light and is different from the first light receiving position detector of the plurality of light receiving position detectors is provided at a position facing the second light emitter, Receiving the laser light emitted from the second light emitting unit, The position determining unit emits laser light from the first light emitting unit and the second light emitting unit when the exposure unit is not scanning with laser light, and is detected by the first light receiving position detecting unit. The light receiving position of the laser light is determined as a first reference position, the light receiving position of the laser light detected by the second light receiving position detection unit is determined as a second reference position, the light receiving position monitoring unit, While the laser beam is scanned by the exposure unit, the laser beam is detected by the first light receiving position detection unit by continuously emitting laser light to the first light emitting unit and the second light emitting unit. The deviation of the laser light receiving position from the first reference position is constantly monitored as a first deviation, and the laser light receiving position detected by the second light receiving position detection unit is detected. The deviation from the two reference positions is constantly monitored as a second deviation, and the feedback control unit is constantly monitored by the light receiving position monitoring unit, and one of the first deviation and the second deviation is monitored. When the deviation is a reference deviation and the direction of the reference deviation satisfies the condition for making the latent image thinner, the exposure unit is scanned so that the latent image is darkened by an amount corresponding to the magnitude of the reference deviation. When the amount of laser light is adjusted and the direction of the reference deviation satisfies the condition for thickening the latent image, the exposure unit is adjusted so as to make the latent image thinner by an amount corresponding to the magnitude of the reference deviation. When a reference deviation adjustment process for adjusting the amount of laser light to be scanned is performed and a difference in deviation is seen between the first deviation and the second deviation, after the execution of the reference deviation adjustment process, Before detecting the reference deviation A position from which the light emitting unit corresponding to the light receiving position detection unit is fixed as a reference light emitting position, and a distance from the reference light emitting position to a position where the photosensitive member is irradiated with laser light; Based on the distance between one light-emitting part and the second light-emitting part, after correcting the difference in deviation between the first deviation and the second deviation, the difference in deviation after the correction If the direction satisfies the condition for thinning the latent image, the amount of laser light to be scanned by the exposure unit is adjusted so that the latent image is darkened by an amount corresponding to the magnitude of the difference in deviation after correction. When the adjustment and the direction of the difference in the deviation after the correction satisfy the condition for darkening the latent image, the latent image is thinned by an amount corresponding to the magnitude of the difference in the deviation after the correction. It is possible to adjust the amount of laser light scanned by the exposure unit Masui.

  In this configuration, the light receiving position monitoring unit causes the first shift, which is a shift from the first reference position of the light receiving position of the laser light emitted from the first light emitting unit, and the laser emitted from the second light emitting unit. A second shift, which is a shift of the light receiving position from the second reference position, is constantly monitored. Then, the feedback control unit sets one of the first shift and the second shift as a reference shift, and determines the amount of laser light to be scanned by the exposure unit based on the direction and magnitude of the reference shift. A reference deviation adjustment process to be adjusted is performed.

  If there is a difference in deviation between the first deviation and the second deviation, that is, if the photoconductor is in a twisted state, after the reference deviation adjustment process is performed, the feedback control unit further The position from which the light emitting unit corresponding to the light receiving position detecting unit that has detected the reference deviation is fixed is set as the reference light emitting position, and the distance from the reference light emitting position to the position where the photosensitive member is irradiated with the laser beam, Based on the distance between the first light emitting part and the second light emitting part, the difference in deviation between the first deviation and the second deviation is corrected. Then, based on the magnitude and direction indicated by the difference in deviation after the correction, that is, on the basis of the magnitude and direction of the twist of the photoconductor, the amount of laser light scanned by the exposure unit is adjusted.

  This reduces the risk of density unevenness occurring in both the main scanning direction and the sub-scanning direction in the latent image for one main scanning line formed on the photosensitive member by twisting the photosensitive member. Can do.

  According to the present invention, it is possible to provide an image forming apparatus capable of reducing the possibility of density unevenness occurring in a latent image for one line in the main scanning direction formed on a photoconductor.

1 is a cross-sectional view illustrating an example of a configuration of a printer as an image forming apparatus according to the present invention. The top view which shows an example of a structure of a laser scanner unit. The AB sectional view taken on the line which shows an example of a structure of a drum support member. Explanatory drawing which shows an example of the time-sequential change of the light quantity of the laser beam radiate | emitted from a semiconductor laser. FIG. 2 is a block diagram illustrating an electrical configuration of the printer. The flowchart which shows an example of adjustment control of the light quantity of a laser beam. Explanatory drawing which shows an example of the shift | offset | difference of the main scanning direction from the reference position in the light-receiving surface of a light-receiving position detection part. FIG. 8 is an explanatory diagram illustrating an example in which pixels of a latent image formed on a photoconductor are shifted in a main scanning direction due to the shift described in FIG. 7. (A) is explanatory drawing which shows an example which changes the light quantity of a laser beam into the light quantity which shows the density value of the pixel formed after each pixel of image data, (b) is the light quantity of a laser beam. FIG. 5 is an explanatory diagram showing an example of changing to a light amount indicating a density value of a pixel formed before each pixel of image data. Explanatory drawing which shows an example of the shift | offset | difference of the subscanning direction from the reference position in the light-receiving surface of a light-receiving position detection part. Explanatory drawing which shows an example which a shift | offset | difference arises in the position of the subscanning direction where a laser beam is irradiated in a photoreceptor by the shift | offset | difference of FIG. (A) is explanatory drawing which shows an example which changes the light quantity of a laser beam into the light quantity which shows the density value of each pixel after increasing the density value of each pixel of image data, (b) is laser It is explanatory drawing which shows an example which changes the light quantity of light into the light quantity which shows the density value of each pixel after reducing the density value of each pixel of image data. Explanatory drawing which shows an example of the shift | offset | difference of both the main scanning direction and the subscanning direction from the reference position in the light-receiving surface of a light-receiving position detection part. The flowchart which shows an example different from FIG. 6 of adjustment control of the light quantity of a laser beam. The flowchart which shows the control following FIG. 14 of adjustment control of the light quantity of a laser beam. (A) is explanatory drawing which shows an example of the shift | offset | difference (1st shift | offset | difference) from the 1st reference position in the light-receiving surface of a 1st light reception position detection part, (b) is a 2nd light reception position detection part. It is explanatory drawing which shows an example of the shift | offset | difference (2nd shift | offset | difference) from the 2nd reference position in the light-receiving surface, (c) is the 1st shift | deviation as described in (a), and the 2nd as described in (b). It is explanatory drawing which shows an example of the difference of the shift | offset | difference between. It is explanatory drawing which shows an example by which the magnitude | size of the difference of the shift | offset | difference between a 1st shift | offset | difference and a 2nd shift | offset | difference is correct | amended based on the distance from the position detection laser as a reference | standard.

[First embodiment]
Hereinafter, a printer as an example of an image forming apparatus according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the printer 1 includes a photosensitive drum 10, a charger 11, a laser scanner unit 12, a developing device 13, a transfer roller 15, and a fixing device 16.

  The photosensitive drum 10 (an example of the photosensitive member according to the present invention) is a cylindrical member having a long main scanning direction (the front and back direction in FIG. 1), and receives a driving force from a motor (not shown). , Rotated in the clockwise direction in FIG.

  The charger 11 is a cylindrical member having a long main scanning direction (the front and back direction in FIG. 1). The charger 11 is in contact with the photosensitive drum 10 and rotated counterclockwise in FIG. The surface of the drum 10 is charged substantially uniformly.

  The laser scanner unit 12 (an example of an exposure unit according to the present invention) includes a light source such as a laser diode, and supports image data with respect to the circumferential surface of the photosensitive drum 10 that is substantially uniformly charged by the charger 11. By irradiating an optical signal, an electrostatic latent image of image data is formed. Here, the image data is data received by the printer 1 that is transmitted from a personal computer or the like connected to the printer 1 via a network.

  Details of the photosensitive drum 10 and the laser scanner unit 12 will be described later.

  The developing device 13 includes a toner container that stores toner, and supplies toner to the surface of the photosensitive drum 10 on which the electrostatic latent image is formed to form a toner image. The toner image formed on the photosensitive drum 10 is transferred to a recording paper or a transfer belt (not shown) conveyed on the conveyance path P by a transfer roller 15 described later.

  The transfer roller 15 is disposed at a position facing the photosensitive drum 10. The transfer roller 15 is made of a conductive rubber material or the like, and transfers the toner image formed on the photosensitive drum 10 onto a recording sheet or transfer belt that is transported through the transport path P.

  The fixing device 16 includes a fixing roller 160 including a heater and the like, and a pressure roller 161 provided at a position facing the fixing roller 160, and heats and conveys the recording paper on which the toner image is formed. The formed toner image is fixed.

  Next, an image forming operation of the printer 1 will be briefly described. First, the surface of the photosensitive drum 10 is charged substantially uniformly by the charger 11. Then, the surface of the charged photosensitive drum 10 is exposed by the laser scanner unit 12, and an electrostatic latent image of an image formed on the recording paper is formed on the surface of the photosensitive drum 10. The electrostatic latent image is visualized by attaching toner to the surface of the photosensitive drum 10 by the developing device 13, and the toner image on the surface of the photosensitive drum 10 is transferred to the recording paper by the transfer roller 15. After this operation is performed, the toner image transferred onto the recording paper by the fixing device 16 is fixed.

  Details of the photosensitive drum 10 and the laser scanner unit 12 will be described below with reference to FIGS.

  As shown in FIGS. 2 and 3, the photosensitive drum 10 is integrally formed with a drum shaft 102 that is rotationally driven by a motor (not shown), and a drum support member 101 (an example of a photosensitive member support member according to the present invention). ) Is rotatably supported.

  The drum support member 101 (an example of a photoconductor support member according to the present invention) is a member for supporting the photoconductor drum 10 and is disposed at both ends of the photoconductor drum 10. The drum support member 101 is provided with holes for inserting the drum shaft 102 and the rotating shaft of the charger 11. That is, the drum support member 101 rotatably supports the photosensitive drum 10 and the charger 11 through the hole.

  Further, at least one drum support member 101 is provided with a position detection laser (an example of a light emitting unit according to the present invention) 2 a that emits laser light having a predetermined wavelength toward the laser scanner unit 12.

  The laser scanner unit 12 includes a dust-proof glass 3, a semiconductor laser 4, a polygon mirror 5, a scanning lens 6, a BD (Beam Detect) sensor 9, a reflection mirror 8, and a position detection sensor 7a.

  The dustproof glass 3 is a transparent glass member that constitutes one side surface of the laser scanner unit 12. The dust-proof glass 3 prevents dust from entering the laser scanner unit 12 and emits the laser light emitted from the position detection laser 2a, or the semiconductor laser 4 via a polygon mirror 5 or the like as will be described later. The transmitted laser beam is transmitted.

  The semiconductor laser 4 adjusts the density value of each pixel continuous in the main scanning direction in the image data of the latent image formed on the peripheral surface of the photosensitive drum 10 under the control of the light source drive control unit 21 (FIG. 5) described later. A laser beam having a corresponding intensity (light quantity) is emitted. It should be noted that the density value of each pixel (each pixel value) indicates that the density of the image increases as it increases, and the density of the image decreases as it decreases. However, the purpose is not limited to this.

  For example, as shown in FIG. 4, the amount of laser light emitted from the semiconductor laser 4 is adjusted by the voltage value of the laser light, and is formed on the peripheral surface of the photosensitive drum 10 every time a predetermined period ΔT elapses. In the image data of the latent image to be changed, it changes so as to indicate a voltage value corresponding to each pixel value continuous in the main scanning direction.

  Specifically, the semiconductor laser 4 emits laser light having a voltage Vj corresponding to the density value of the jth pixel from the top in the main scanning direction in the image data of the latent image formed on the peripheral surface of the photosensitive drum 10. The laser beam is emitted after the elapse of time (j × ΔT) from the start of emission. In addition, the light quantity of a laser beam may be adjusted with an electric current value not only the voltage value of a laser beam.

  The polygon mirror 5 includes mirrors P1 to P6 that reflect light on its peripheral surface, and is configured to be driven to rotate at a constant speed in the direction of an arrow in the drawing by a driving force supplied by a polygon motor (not shown). Laser light emitted from the semiconductor laser 4 is incident on each of the mirrors P1 to P6. In each of the mirrors P <b> 1 to P <b> 6, the incident laser light becomes a deflected beam that continuously changes its angle as it rotates, and is reflected toward the photosensitive drum 10.

  The scanning lens 6 condenses the laser beam that has become a deflected beam reflected by the polygon mirror 5, transmits the laser light through the dust-proof glass 3, and moves the peripheral surface of the photosensitive drum 10 in the main scanning direction (X direction in the figure). Are horizontally scanned at a constant speed.

  The reflection mirror 8 is a mirror that reflects light, and is arranged to reflect the laser light toward the BD sensor 9 when the laser light reflected by the polygon mirror 5 is incident.

  The BD sensor 9 is used to synchronize the emission timing of the laser light from the semiconductor laser 4 and the rotation of the polygon mirror 5, which is the timing for starting horizontal scanning with respect to the photosensitive drum 10 by the laser light.

  Specifically, the BD sensor 9 receives the laser light reflected by the polygon mirror 5 and the reflection mirror 8 and outputs a detection signal indicating that the light has been received. The detection signal output by the BD sensor 9 is used to synchronize rotation of the polygon mirror 5 and image data writing timing, that is, writing in the X direction in FIG.

  In this way, by rotating the polygon mirror 5, horizontal scanning (exposure) for one line in the main scanning direction of the image data (one-dot chain line extending in the X direction in FIG. 2) is performed on the photosensitive drum 10. Will be. Then, the photosensitive drum 10 is rotated by a predetermined line interval in the sub-scanning direction (Y direction in FIG. 2), and exposure for one line in the main scanning direction of the next image data is performed.

  The position detection sensor 7 a (an example of a light receiving position detection unit according to the present invention) is disposed at a position facing the position detection laser 2 a provided in the drum support member 101. The position detection sensor 7a has a light receiving surface on which a plurality of light receiving elements are two-dimensionally arranged so as to extend in both the main scanning direction and the sub-scanning direction. When the position detection sensor 7a receives the laser beam emitted from the position detection laser 2a on the light receiving surface, the position of the light receiving element that receives the laser light (for example, relative coordinates with the upper left end of the light receiving surface as a reference point). A detection signal indicating is output.

  Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 5, the printer 1 includes a control unit 20 that controls the entire printer 1.

  The control unit 20 includes a CPU, a ROM that stores an operation program for the entire apparatus, such as a control program for controlling an image forming operation, a RAM that temporarily stores image data and the like, and functions as a work area, and various control parameters. A non-volatile memory for storing the set value and a memory such as a hard disk (HDD). The operation program stored in the ROM is executed by the CPU, whereby the entire apparatus is controlled. In the following, adjustment control of the amount of laser light emitted from the semiconductor laser 4, which is the gist of the present invention, of the control performed by the control unit 20 will be described.

  The control unit 20 includes a position detection laser 2a, a position detection sensor 7a, a BD sensor 9, a semiconductor laser 4, a polygon motor 32 that is a drive source of the polygon mirror 5, and a drum motor 33 that is a drive source of the photosensitive drum 10. Are connected, and a detection signal output from the position detection sensor 7a and the BD sensor 9 and a control signal for controlling driving of the position detection laser 2a, the semiconductor laser 4, the polygon motor 32, and the drum motor 33 are not illustrated. Interface circuit.

  Further, the control unit 20 functions as a light source drive control unit 21, a reference position determination unit 22, a light receiving position monitoring unit 23, and a feedback control unit 24.

  The light source drive control unit 21 rotates the polygon mirror 5 at a predetermined rotation speed by rotating the polygon motor 32 at a predetermined rotation speed. When the detection signal output from the BD sensor 9 is used to detect that the predetermined emission timing is synchronized with the rotation of the polygon mirror 5, the main scanning direction 1 formed on the peripheral surface of the photosensitive drum 10 is detected. A signal indicating each pixel value of the image data of the latent image for the line in time series is generated, and laser light (see FIG. 4) whose light amount changes in time series according to the signal is emitted to the semiconductor laser 4.

  The light source drive control unit 21 scans the laser beam in the main scanning direction of the photosensitive drum 10 by the rotation of the polygon mirror 5 and forms a latent image for one line in the main scanning direction on the photosensitive drum 10. 33 is rotated by a predetermined rotation angle, that is, the photosensitive drum 10 is rotated by a predetermined line interval in the sub-scanning direction.

  The light source drive control unit 21 adjusts the amount of laser light emitted to the semiconductor laser 4 under the control of a feedback control unit 24 described later.

  When the laser beam is not emitted from the semiconductor laser 4, the reference position determination unit 22 emits the laser beam to the position detection laser 2a, and the emitted laser beam is received by the light receiving surface of the position detection sensor 7a. The position of the light receiving element that receives the laser beam indicated by the detection signal output from the position detection sensor 7a (for example, relative coordinates with the upper left end of the light receiving surface as a reference point) is stored in the memory as a reference position. To do.

  The light receiving position monitoring unit 23 continues to cause the position detecting laser 2a to emit laser light while the laser light is emitted from the semiconductor laser 4 and the photosensitive drum 10 is irradiated with the laser light. The light receiving position monitoring unit 23 compares the position of the light receiving element that has received the laser light indicated by the detection signal output from the position detection sensor 7a with the reference position stored in the memory by the reference position determining unit 22. Thus, the deviation of the position of the light receiving element that has received the laser light from the reference position is constantly monitored, and a detection signal indicating the deviation is output.

  When the direction of the deviation indicated by the detection signal output from the light receiving position monitoring unit 23 satisfies the condition for darkening the latent image formed on the photosensitive drum 10, the feedback control unit 24 responds to the magnitude of the deviation. A control signal indicating an instruction to adjust the amount of laser light applied to the peripheral surface of the photoconductive drum 10 is output to the light source drive control unit 21 so that the latent image is thinned by that amount.

  Further, when the direction of the deviation satisfies the condition for thinning the latent image formed on the photosensitive drum 10, the feedback control unit 24 increases the latent image by an amount corresponding to the magnitude of the deviation. A control signal indicating an instruction to adjust the amount of laser light to be irradiated onto the peripheral surface of the photosensitive drum 10 is output to the light source drive control unit 21.

  Below, the flow of the adjustment control of the light quantity of the laser beam radiate | emitted from the semiconductor laser 4 is explained in full detail.

  As shown in FIG. 6, the reference position determination unit 22 causes the position detection laser 2a to emit laser light when laser light is not emitted from the semiconductor laser 4 (S1). Then, as shown in FIG. 7, for example, the reference position determination unit 22 receives the laser light indicated by the detection signal output when the emitted laser light is received by the light receiving surface of the position detection sensor 7a. The position P0 of the received light receiving element is stored in the memory as a reference position, and emission of laser light from the position detecting laser 2a is stopped (S2). Note that the reference position determination unit 22 may be configured to continuously emit laser light from the position detection laser 2a even after the reference position is stored in the memory in step S2.

  Here, for convenience of explanation, FIG. 7 shows a view seen through the light receiving surface from the back of the light receiving surface of the position detection sensor 7a in the directions of arrows C to D in FIG. The Y direction corresponds to the X direction (main scanning direction) and the Y direction (sub scanning direction) in FIG.

  Returning to FIG. 6, exposure of the received image data to the photosensitive drum 10 is started by the control unit 20, for example, by receiving image data from a personal computer connected to the printer 1 via the network. Then (S3; YES), the light receiving position monitoring unit 23 causes the position detection laser 2a to emit laser light (S4). The light receiving position monitoring unit 23 compares the position of the light receiving element that has received the laser beam indicated by the detection signal output from the position detection sensor 7a with the reference position stored in the memory in step S2, and A detection signal indicating the deviation of the position of the light receiving element that has received the laser beam from the reference position is output (S5).

  If the direction of the shift indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 indicates a shift in the main scanning direction (S6; YES), the feedback control unit 24 further shifts in the main scanning direction. It is determined whether or not the direction satisfies the condition for increasing or decreasing the latent image formed on the photosensitive drum 10 (S7). On the other hand, when the shift direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 does not indicate a shift in the main scanning direction (S6; NO), the process proceeds to step S10 described later.

  In step S7, when the direction of deviation of the main scanning direction satisfies the condition for thinning the latent image formed on the photosensitive drum 10 (S7; YES), the feedback control unit 24 sets the laser light voltage to Instead of the voltage corresponding to the density value of each pixel of the original image data, the voltage corresponding to the density value of the pixel formed after an amount corresponding to the magnitude of the shift from each pixel of the original image data A control signal indicating an instruction for adjustment is output to the light source drive control unit 21 (S8).

  On the other hand, when the direction of deviation in the main scanning direction satisfies the condition for darkening the latent image formed on the photosensitive drum 10 (S7; NO), the feedback control unit 24 changes the laser light voltage to the original level. Instead of the voltage corresponding to the density value of each pixel of the image data, the voltage corresponding to the density value of the pixel formed earlier than each pixel of the original image data by an amount corresponding to the magnitude of the deviation. As shown, a control signal indicating an instruction to adjust is output to the light source drive control unit 21 (S9).

  Specifically, for example, as shown in FIG. 7, the light receiving position monitoring unit 23 receives the laser beam indicated by the detection signal output from the position detection sensor 7 a in step S <b> 5 (light receiving position). P1 is compared with the reference position P0 stored in the memory in Step 2, and light is received by the size D1 in the direction opposite to the direction in which the scanning of the laser light proceeds in the main scanning direction (the −X direction in the figure). A detection signal indicating that the position P1 is deviated from the reference position P0 is output.

  In this case, as shown in FIG. 8A, the photosensitive drum 10 has a size D1 larger than that when the reference position P0 is determined in step S2 (as shown in FIG. 8B). In the scanning direction, the laser beam is shifted in the direction opposite to the direction in which scanning proceeds (S6; YES).

  Therefore, when the photosensitive drum 10 is at the reference position (in the case of FIG. 8B), the position indicated by the oval portion in the drawing of the photosensitive drum 10 is irradiated, for example, main scanning of image data. Laser light having a voltage value V5 corresponding to the density value of the pixel formed fifth in the direction is irradiated with laser light having a voltage value V6 corresponding to the density value of the pixel formed sixth. The position will be irradiated. In other words, since each pixel of the image data is formed at a position later than the original, the distance from the previously formed pixel tends to be widened, and thereby the density of the formed latent image is considered to be reduced. It is done.

  Therefore, in step S7, the feedback control unit 24 detects that the deviation in the main scanning direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 is opposite to the direction in which the scanning of the laser light proceeds in the main scanning direction. When it indicates that the direction is shifted, it is determined that the condition for thinning the latent image formed on the photosensitive drum 10 is satisfied (S7; YES).

  In this case, in step S8, the feedback control unit 24 converts the laser light voltage to the voltage corresponding to the density value of each pixel of the original image data (see FIG. 9 (FIG. 9 (a)). In place of the solid line portion in a), a light source driving control is performed using a control signal indicating an instruction to adjust the voltage corresponding to the density value of the pixel formed one pixel after the original pixel of the image data, for example. To the unit 21. As a result, the amount of laser light is adjusted so that each pixel of the image data has a narrow interval from the previously formed pixel, that is, the density of the formed latent image is increased.

  It should be noted that how much later the voltage of the laser light corresponds to the density value of the pixel formed after each pixel of the original image data is a deviation indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5. It is adjusted according to the size.

  On the other hand, for example, as shown in FIG. 7, the light receiving position monitoring unit 23 receives the position (light receiving position) P2 of the light receiving element that has received the laser beam indicated by the detection signal output from the position detection sensor 7a in step S5. 2 is compared with the reference position P0 stored in the memory, and the light receiving position P2 is deviated from the reference position P0 by the size D2 in the direction in which the scanning of the laser beam proceeds in the main scanning direction (the + X direction in the figure). It is assumed that a detection signal indicating that the

  In this case, as shown in FIG. 8 (c), the photosensitive drum 10 is larger by the size D2 than when the reference position P0 is determined in step S2 (as shown in FIG. 8 (b)). That is, the laser beam is shifted in the scanning direction in the scanning direction (S6; YES).

  Therefore, when the photosensitive drum 10 is at the reference position (in the case of FIG. 8B), the position indicated by the oval portion in the drawing of the photosensitive drum 10 is irradiated, for example, main scanning of image data. Laser light having a voltage value V5 corresponding to the density value of the pixel formed fifth in the direction is irradiated with laser light having a voltage value V4 corresponding to the density value of the pixel formed fourth. The position will be irradiated. In other words, since each pixel of the image data is formed at a position ahead of the original, the distance from the previously formed pixel tends to be narrowed, and thus the density of the formed latent image is considered to be high. It is done.

  Therefore, in step S7, the feedback control unit 24 shifts the deviation in the main scanning direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 in the direction in which the scanning of the laser light proceeds in the main scanning direction. If it is determined that the latent image formed on the photosensitive drum 10 is satisfied, it is determined that the condition for thickening the latent image is satisfied (S7; NO).

  In this case, in step S9, the feedback control unit 24 changes the voltage of the laser light to a voltage corresponding to the density value of each pixel of the original image data (see FIG. 9 (FIG. 9 (b)). In place of the solid line portion b), a control signal indicating an instruction to adjust the voltage corresponding to the density value of the pixel formed one pixel ahead of each pixel of the original image data is driven by the light source. Output to the control unit 21. As a result, the amount of laser light is adjusted so that each pixel of the image data is spaced from the previously formed pixel, that is, the density of the formed latent image is reduced.

  The detection signal output from the light receiving position monitoring unit 23 in step S5 indicates how much the voltage of the laser light corresponds to the density value of the pixel formed earlier than each pixel of the original image data. It is adjusted according to the magnitude of the deviation.

  Thus, even when the photosensitive drum 10 is displaced in the main scanning direction due to vibration or the like while the laser beam is scanned from one end to the other end of the peripheral surface of the photosensitive drum 10, the photosensitive drum The light amount of the laser light irradiated on the peripheral surface 10 is adjusted to a light amount corresponding to the density value of the pixel formed earlier or later by an amount corresponding to the magnitude of deviation from each pixel value of the image data.

  For this reason, even when the intervals between the pixels, which are uniform, become dense due to the photosensitive drum 10 being displaced in the main scanning direction while the laser beam is scanned, the photosensitive drum 10. Each pixel of the latent image formed is formed at an appropriate position according to the amount of deviation. This can reduce the occurrence of density unevenness in the main scanning direction of the latent image.

  Returning to FIG. 6, when the shift direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S <b> 5 indicates the shift in the sub-scanning direction (S <b> 10; YES), the feedback control unit 24 further performs the sub-scanning. It is determined whether the direction of the direction deviation satisfies a condition for thinning the latent image formed on the photosensitive drum 10 (S11). On the other hand, when the shift direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 does not indicate a shift in the sub-scanning direction (S10; NO), the process proceeds to step S14 described later.

  In step S11, when the direction of deviation in the sub-scanning direction satisfies the condition for thinning the latent image formed on the photosensitive drum 10 (S11; YES), the feedback control unit 24 sets the laser light voltage to A control signal indicating an instruction to adjust the density value of each pixel of the original image data so as to indicate the voltage corresponding to the density value increased by the magnitude of the deviation is output to the light source drive control unit 21. (S12).

  On the other hand, when the direction of deviation in the sub-scanning direction satisfies the condition for darkening the latent image formed on the photosensitive drum 10 (S11; NO), the feedback control unit 24 changes the laser light voltage to the original level. A control signal indicating an instruction to adjust the density value of each pixel of the image data so as to indicate the voltage corresponding to the density value that is decreased by the magnitude of the shift is output to the light source drive control unit 21 ( S13).

  Specifically, for example, as shown in FIG. 10, the light receiving position monitoring unit 23 receives the laser beam indicated by the detection signal output from the position detection sensor 7a (light receiving position) in step S5. P3 and the reference position P0 stored in the memory in step 2 are compared, and in the sub-scanning direction, the direction of the line horizontally scanned first in the main scanning direction (the + Y direction in the figure, hereinafter referred to as “upstream side”). ), A detection signal indicating that the light receiving position P3 is shifted from the reference position P0 by the size D3 is output.

  Here, for convenience of explanation, FIG. 10 shows a diagram seen through the light receiving surface from the back surface of the light receiving surface of the position detection sensor 7a in the directions of arrows C to D in FIG. The Y direction corresponds to the X direction (main scanning direction) and the Y direction (sub scanning direction) in FIG.

  In this case, as shown by the solid line rectangle in FIG. 11A, the photosensitive drum 10 has a size D3 that is larger than when the reference position P0 is determined in step S2 (as shown in FIG. 11B). Therefore, it is shifted to the upstream side in the sub-scanning direction (S10; YES).

  Therefore, when the photosensitive drum 10 is at the reference position (in the case of FIG. 11B), the laser light applied to the line indicated by the shaded rectangular portion in the drawing of the photosensitive drum 10 is As indicated by the broken-line rectangle shown in FIG. 11A, the downstream line is irradiated in the sub-scanning direction. As a result, the interval between the lines in the sub-scanning direction of the latent image formed on the photosensitive drum 10 tends to be widened, that is, the density of the formed latent image is considered to be thin.

  Therefore, when the feedback control unit 24 indicates in step S11 that the shift in the sub-scanning direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 is shifted upstream in the sub-scanning direction. Then, it is determined that the condition for thinning the latent image formed on the photosensitive drum 10 is satisfied (S11; YES).

  In this case, in step S12, the feedback control unit 24 originally sets the voltage of the laser beam and the density value of each pixel of the image data (solid line in FIG. 12A), as indicated by the broken line portion in FIG. A control signal indicating an instruction to adjust so as to indicate a voltage corresponding to the density value increased more than that of the light source drive control unit 21. As a result, the amount of laser light is adjusted so as to increase the density of the formed latent image. Note that the amount by which the density value of each pixel is increased is adjusted according to the amount of deviation indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5.

  On the other hand, for example, as shown in FIG. 10, the light receiving position monitoring unit 23 performs the step (light receiving position) P4 of the light receiving element that has received the laser beam indicated by the detection signal output from the position detection sensor 7a in step S5. 2 is compared with the reference position P0 stored in the memory, and in the sub-scanning direction, the direction of the line to be horizontally scanned later in the main scanning direction (−Y direction in the figure, hereinafter referred to as “downstream side”) A detection signal indicating that the light receiving position P4 is displaced from the reference position P0 by the size D4 is output.

  In this case, as shown by the solid line rectangle in FIG. 11C, the photosensitive drum 10 has a size D4 that is larger than that when the reference position P0 is determined in step S2 (as shown in FIG. 11B). Therefore, it is shifted to the downstream side in the sub-scanning direction (S10; YES).

  Therefore, when the photosensitive drum 10 is at the reference position (in the case of FIG. 11B), the laser light applied to the line indicated by the shaded rectangular portion in the drawing of the photosensitive drum 10 is As indicated by the broken-line rectangle shown in 11 (c), the line on the upstream side in the sub-scanning direction is irradiated. As a result, the interval between the lines in the sub-scanning direction of the latent image formed on the photosensitive drum 10 tends to be narrowed, that is, the density of the formed latent image is considered to be high.

  Therefore, when the feedback control unit 24 indicates in step S11 that the shift in the sub scanning direction indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5 is shifted downstream in the sub scanning direction. Then, it is determined that the condition for deepening the latent image formed on the photosensitive drum 10 is satisfied (S11; NO).

  In this case, in step S13, the feedback control unit 24 originally sets the voltage of the laser beam and the density value of each pixel of the image data (solid line in FIG. 12B), as indicated by the broken line portion in FIG. A control signal indicating an instruction to adjust so as to indicate a voltage corresponding to the density value that is reduced more than that of the light source drive control unit 21. As a result, the amount of laser light is adjusted so as to reduce the density of the formed latent image. The amount by which the density value of each pixel is reduced is adjusted according to the magnitude of the deviation indicated by the detection signal output from the light receiving position monitoring unit 23 in step S5.

  Thus, even when the photosensitive drum 10 is displaced in the sub-scanning direction due to vibration or the like while the laser beam is scanned from one end to the other end of the peripheral surface of the photosensitive drum 10, the photosensitive drum The light amount of the laser light irradiated on the peripheral surface 10 is adjusted to a light amount corresponding to a density value obtained by increasing or decreasing the density value of each pixel of the image data by an amount corresponding to the magnitude of the deviation.

  For this reason, the photosensitive drum 10 is formed on the photosensitive drum 10 even when the uniform line spacing becomes sparse by shifting the photosensitive drum 10 in the sub-scanning direction while the laser beam is scanned. The density of the latent image is appropriately adjusted according to the density of the line interval. This can reduce the occurrence of density unevenness in the sub-scanning direction of the latent image.

  As another example, as shown in FIG. 13, when the light reception position monitoring unit 23 receives a detection signal indicating the light reception position P5 output from the position detection sensor 7a in step S5, the laser beam is emitted in the main scanning direction. The detection signal indicating that the light receiving position P5 is deviated from the reference position P0 by the size D5x in the opposite direction (−X direction in the figure) to the direction in which the scanning proceeds, and upstream in the sub-scanning direction ( And a detection signal indicating that the light receiving position P5 is deviated from the reference position P0 by the size D5y.

  Here, for convenience of explanation, FIG. 13 shows a view seen through the light receiving surface from the back of the light receiving surface of the position detection sensor 7a in the directions of arrows C to D in FIG. The Y direction corresponds to the X direction (main scanning direction) and the Y direction (sub scanning direction) in FIG.

  In this case, the feedback control unit 24 indicates that the shift is shifted in the main scanning direction in a direction opposite to the direction in which the laser beam scan proceeds. It is determined that the condition for thinning the image is satisfied (S6; YES, S7; YES), and the voltage of the laser light is formed after each pixel of the original image data by an amount corresponding to the shift size D5x. A control signal indicating an instruction to adjust the voltage corresponding to the density value of the pixel is output to the light source drive control unit 21 (S8).

  In addition, the feedback control unit 24 indicates that the shift is shifted upstream in the sub-scanning direction, and therefore determines that the condition for thinning the latent image formed on the photosensitive drum 10 is satisfied ( S10; YES, S11; YES), so that the voltage of the laser beam indicates a voltage corresponding to a density value obtained by increasing the density value of each pixel of the image data by an amount corresponding to the deviation D5y. A control signal indicating an instruction for adjustment is output to the light source drive controller 21 (S12).

  As described above, the control unit 20 repeatedly executes the adjustment of the light amount of the laser light in steps S5 to S13 while the exposure of the image data to the photosensitive drum 10 is not completed (S14; NO). When the exposure to the photosensitive drum 10 is completed (S14; YES), the control of the adjustment of the laser light quantity is terminated. Thus, even when the photosensitive drum 10 is displaced in the main scanning direction and the sub-scanning direction due to vibration or the like while the laser beam is scanned from one end to the other end of the peripheral surface of the photosensitive drum 10, It is possible to reduce the possibility of uneven density in the latent image for one main scanning line formed on the photosensitive drum 10 due to the shift.

  The feedback control unit 24 is configured to be simplified so as to perform Step S11 to Step S13 without performing Step S7 to Step S9, whereby the sub-scanning is performed on the latent image formed on the photosensitive drum 10. You may reduce only a possibility that the density unevenness of a direction will arise. Further, the feedback control unit 24 is configured to be simplified so as to perform Steps S7 to S9 without performing Steps S11 to S13, whereby main scanning is performed on the latent image formed on the photosensitive drum 10. You may reduce only a possibility that the density unevenness of a direction will arise.

[Second Embodiment]
In the following description of the second embodiment, only portions different from the first embodiment will be described in detail, and description of the same portions as the first embodiment will be omitted.

  In the configuration of the second embodiment, as shown in FIG. 2, position detection lasers 2 a and 2 b are provided on the drum support members 101 at both ends of the photosensitive drum 10, respectively. Correspondingly, the laser scanner unit 12 is provided with position detection sensors 7a and 7b at positions facing the position detection lasers 2a and 2b, respectively. Further, as shown in FIG. 5, the control unit 20 is connected to position detection lasers 2a and 2b and position detection sensors 7a and 7b, and detection signals output from the position detection sensors 7a and 7b, and position detection An interface circuit (not shown) for inputting and outputting control signals for controlling the driving of the lasers 2a and 2b is provided.

  As shown in FIG. 14, the reference position determination unit 22 causes the position detection lasers 2a and 2b to emit laser light when no laser light is emitted from the semiconductor laser 4 (S21).

  Then, as shown in FIG. 16A, for example, the reference position determination unit 22 detects when the laser beam emitted to the position detection laser 2a is received by the light receiving surface of the position detection sensor 7a. The position P0_1 of the light receiving element that has received the laser light indicated by the signal is stored in the memory as a first reference position, and emission of the laser light from the position detection laser 2a is stopped. Further, for example, as shown in FIG. 16B, the reference position determination unit 22 detects when the laser beam emitted to the position detection laser 2b is received by the light receiving surface of the position detection sensor 7b. The position P0_2 of the light receiving element that has received the laser beam indicated by the signal is stored in the memory as the second reference position, and the emission of the laser beam from the position detecting laser 2b is stopped (S22). The reference position determination unit 22 may be configured to continuously emit laser light from the position detection lasers 2a and 2b after the reference position is stored in the memory in step S22.

  Here, FIG. 16A and FIG. 16B are transmitted through each light receiving surface from the back of the light receiving surface of the position detection sensors 7a and 7b in the direction of arrows C to D in FIG. The X direction and the Y direction in the figure correspond to the X direction (main scanning direction) and the Y direction (sub scanning direction) in FIG. 2, respectively.

  When exposure of image data to the photosensitive drum 10 is started (S3; YES), the light receiving position monitoring unit 23 causes the position detection lasers 2a and 2b to emit laser light (S23).

  Then, the light receiving position monitoring unit 23 compares the position of the light receiving element that has received the laser light indicated by the detection signal output from the position detection sensor 7a with the first reference position stored in the memory in step S22. A detection signal indicating a first shift that is a shift from the first reference position of the position of the light receiving element that has received the laser light is output. The light receiving position monitoring unit 23 compares the position of the light receiving element that has received the laser light indicated by the detection signal output from the position detection sensor 7b with the second reference position stored in the memory in step S22. Then, a detection signal indicating a second shift that is a shift from the second reference position of the position of the light receiving element that has received the laser beam is output (S24).

  Next, the feedback control unit 24 determines one of the first deviation and the second deviation indicated by the detection signal output from the light receiving position monitoring unit 23 in step S24 as a reference deviation (S25). ).

  Specifically, in step S24, when the light reception position monitoring unit 23 receives a detection signal indicating the light reception position P6 output from the position detection sensor 7a as shown in FIG. 16A, for example, in the main scanning direction. A detection signal indicating that the light receiving position P6 is deviated from the first reference position P0_1 by the size D6x in the direction opposite to the direction in which the scanning of the laser light proceeds (−X direction in the figure), and the sub scanning direction , The detection signal indicating that the light receiving position P6 is shifted from the first reference position P0_1 by the size D6y is output as a detection signal indicating the first shift upstream (in the + Y direction in the figure).

  In step S24, when the light reception position monitoring unit 23 receives a detection signal indicating the light reception position P7 output from the position detection sensor 7b, for example, as shown in FIG. A detection signal indicating that the light receiving position P7 is deviated from the second reference position P0_2 by the size D7x in a direction opposite to the direction in which the scanning proceeds (−X direction in the figure), and upstream in the sub-scanning direction In the (Y direction in the figure), a detection signal indicating that the light receiving position P7 is shifted from the second reference position P0 by the size D7y is output as a detection signal indicating the second shift.

  Next, in step S25, the feedback control unit 24 uses, for example, the detection signal output from the light receiving position monitoring unit 23 in step S24, and the size D6x of the first deviation in the main scanning direction and the sub scanning direction. From the magnitude D6y, the first deviation magnitude D6 (FIG. 16A) is calculated, and the second deviation is calculated from the magnitude D7x in the main scanning direction and the magnitude D7y in the sub-scanning direction of the second deviation. The size D7 (FIG. 16B) is calculated. Then, the feedback control unit 24 determines, for example, the first deviation that is the smaller one of the calculated deviations as the reference deviation.

  The feedback control unit 24 determines which of the first deviation and the second deviation as the reference deviation in step S25 is not limited to this. For example, the magnitude of the deviation is large. May be determined as a reference deviation.

  Returning to FIG. 14, when the reference deviation is determined in step S25, when the reference deviation includes a deviation in the main scanning direction (S26; YES), the feedback control unit 24 executes step S7 to execute the reference deviation. Is determined to satisfy the condition for thinning the latent image formed on the photosensitive drum 10 (S7; YES), step S8 is executed, and the direction of the reference deviation is the latent image formed on the photosensitive drum 10. If it is determined that the condition for thickening is satisfied (S7; NO), step S9 is executed.

  In the case of the above specific example, the feedback control unit 24 indicates that the reference deviation is shifted by the size D6x in the direction opposite to the direction in which the scanning of the laser light proceeds in the main scanning direction. It is determined that the condition for thinning the latent image formed on the drum 10 is satisfied (S7; YES), and the magnitude of the deviation in the main scanning direction in the reference deviation of the voltage of the laser beam is set from each pixel of the original image data. A control signal indicating an instruction to adjust the voltage corresponding to the density value of the pixel formed later by the amount corresponding to D6x is output to the light source drive control unit 21 (S8).

  Further, when the reference deviation includes a sub-scanning direction deviation (S27; YES), the feedback control unit 24 executes step S11, and the latent image in which the reference deviation direction is formed on the photosensitive drum 10 is executed. If it is determined that the condition for thinning the image is reduced (S11; YES), Step S12 is executed, and if it is determined that the direction of the reference deviation satisfies the condition for increasing the latent image formed on the photosensitive drum 10 (S11; NO) ), Step S13 is executed.

  In the case of the above specific example, the feedback control unit 24 thins the latent image formed on the photosensitive drum 10 in order to indicate that the reference shift is shifted by the size D6y upstream in the sub-scanning direction. (S11; YES), and corresponds to a density value obtained by increasing the voltage of the laser beam by an amount corresponding to the magnitude D6y of the deviation from the density value of each pixel of the original image data. A control signal indicating an instruction to adjust the voltage is output to the light source drive control unit 21 (S12).

  Next, as shown in FIG. 15, the feedback control unit 24 compares the first deviation and the second deviation indicated by the detection signal output from the light receiving position monitoring unit 23 in step S <b> 24. It is determined whether or not there is (S28).

  Specifically, based on the specific example using FIG. 16A and FIG. 16B described above, the feedback control unit 24, in step S28, the first reference position P0_1 and the second reference position P0_2. If the light receiving position P6 and the light receiving position P7 are not at the same position, it is determined that there is a difference in deviation.

  In this specific example, as shown in FIG. 16 (c), assuming that the first reference position P0_1 and the second reference position P0_2 are at the same position, the scanning direction of the laser light in the main scanning direction is In the reverse direction (−X direction in the figure), the light receiving position P7 is shifted from the light receiving position P6 by the size D67x, and by the size D67y upstream in the sub-scanning direction (+ Y direction in the figure). The light receiving position P7 is shifted from the light receiving position P6.

  For this reason, the feedback control unit 24 has a difference in size D67x in the direction opposite to the direction in which the laser beam scan proceeds in the main scanning direction (the −X direction in the figure), and is upstream in the sub-scanning direction. It is determined that there is a difference in the deviation of the size D67y (in the + Y direction in the figure).

  Returning to FIG. 15, when the feedback control unit 24 determines that there is a difference in deviation between the first deviation and the second deviation in step S <b> 28 (S <b> 28; YES), the position detection sensor that detects the reference deviation. The position where the position detecting laser corresponding to is fixed is determined as the reference light emitting position (S29). Then, the feedback control unit 24 calculates the distance from the reference light emission position determined in step S29 to the position (scanning position) where the photosensitive drum 10 is irradiated with laser light (S30).

  Then, the feedback control unit 24 indicates the first signal indicated by the detection signal output from the light receiving position monitoring unit 23 in step S24 based on the distance calculated in step S30 and the distance between the position detection lasers 2a and 2b. The difference in deviation between the deviation and the second deviation is corrected (S31).

  Specifically, based on the specific example using FIG. 16A, FIG. 16B, and FIG. 16C described above, the feedback control unit 24 is determined in step S25 in step S29. The position at which the position detection laser 2a corresponding to the position detection sensor 7a that has detected the first deviation (see FIG. 16A), which is the reference deviation, is fixed is determined as the reference light emission position.

  In step S30, the feedback control unit 24 calculates the distance from the position where the position detection laser 2a, which is the determined reference light emission position, is fixed to the scanning position. In the following, the distance calculated in step S30 is denoted as α.

  Next, in step S31, the feedback control unit 24 uses the distance α calculated in step S30 and the distance L between the position detection lasers 2a and 2b, for example, as shown in FIG. By changing the difference D67x in the main scanning direction to D67x × (L−α) / L and changing the difference D67y in the sub-scanning direction in the difference in difference to D67y × (L−α) / L, Correct the difference in deviation.

  Returning to FIG. 15, when the feedback control unit 24 corrects the difference in shift between the first shift and the second shift in step S <b> 31, the corrected shift difference indicates a shift in the main scanning direction. In this case (S32; YES), if step S7 is executed and it is determined that the direction of the difference in deviation after the correction satisfies the condition for thinning the latent image formed on the photosensitive drum 10 (S7; YES), If step S8 is executed and it is determined that the direction of the difference in the corrected deviation satisfies the condition for increasing the latent image formed on the photosensitive drum 10 (S7; NO), step S9 is executed.

  In the case of the above specific example, the difference in deviation after the correction is shifted by a size D67x × (L−α) / L in the direction opposite to the direction in which the laser beam scan proceeds in the main scanning direction. Therefore, the feedback control unit 24 determines that the condition for thinning the latent image formed on the photosensitive drum 10 is satisfied (S7; YES), and sets the voltage of the laser light from each pixel of the original image data. Also, a control signal indicating an instruction to adjust to a voltage corresponding to the density value of a pixel to be formed later by an amount corresponding to the size D67x × (L−α) / L in the main scanning direction in the difference of the corrected deviation. Is output to the light source drive controller 21 (S8).

  When the difference in deviation after correction indicates a deviation in the sub-scanning direction in step S31 (S33; YES), the feedback control unit 24 executes step S11 to determine the direction of the difference in deviation after correction. If it is determined that the condition for thinning the latent image formed on the photoconductive drum 10 is satisfied (S11; YES), step S12 is executed, and the direction of the difference in the corrected deviation is the latent image formed on the photoconductive drum 10. If it is determined that the condition for darkening the image is satisfied (S11; NO), step S13 is executed.

  In the case of the above specific example, the feedback control unit 24 indicates that the difference in deviation after the correction is shifted by an amount of D67y × (L−α) / L upstream in the sub-scanning direction. Then, it is determined that the condition for thinning the latent image formed on the photosensitive drum 10 is satisfied (S11; YES), and the corrected laser beam voltage is shifted from the density value of each pixel of the original image data after the correction. A control signal indicating an instruction to adjust to a voltage corresponding to the density value increased by an amount corresponding to the size D67y × (L−α) / L in the sub-scanning direction in the difference between the two is output to the light source drive control unit 21. (S12).

  Then, the control unit 20 repeatedly executes the processes after step S24 until the exposure of the image data to the photosensitive drum 10 is completed (S14; YES).

  That is, an example of the reference deviation adjustment processing according to the present invention is configured by the processing from step S7 to step S9 and the processing from step S11 to step S12 performed between step S26 and step S28.

  As described above, in the configuration of the second embodiment, one of the first shift and the second shift is set as a reference shift, and the photosensitive drum 10 is moved based on the direction and magnitude of the reference shift. The amount of laser light to be scanned is adjusted.

  After the light amount of the laser beam that scans the photosensitive drum 10 is adjusted based on the direction and magnitude of the reference deviation, when a difference in deviation is seen between the first deviation and the second deviation, that is, When the photosensitive drum 10 is in a twisted state, the laser from the reference light emission position is further set with the position where the position detection laser corresponding to the position detection sensor detecting the reference deviation is fixed as the reference light emission position. Based on the distance to the position where the light is irradiated and the distance between the position detection lasers 2a and 2b, the difference in deviation between the first deviation and the second deviation is corrected. Then, based on the magnitude and direction indicated by the difference in deviation after the correction, that is, based on the magnitude and direction of the twist of the photosensitive drum 10, the amount of laser light that scans the photosensitive drum 10 is adjusted. The

  For this reason, when the photosensitive drum 10 is twisted, in the latent image for one main scanning line formed on the photosensitive drum 10, there is a possibility that density unevenness occurs in both the main scanning direction and the sub-scanning direction. Can be reduced.

  Note that, similarly to the configuration of the first embodiment, in the configuration of the second embodiment, the feedback control unit 24 may be simplified to perform step S9 without performing step S7. Further, the feedback control unit 24 may be simplified and configured to perform step S7 without performing step S9.

  Further, the present invention is not limited to the configuration of the above embodiment, and various modifications can be made. The configuration and processing shown in FIGS. 1 to 17 are merely examples of the embodiment according to the present invention, and are not intended to limit the present invention to the above embodiment.

1 Printer (image forming device)
10 Photosensitive drum (photosensitive member)
101 Drum support member (photoreceptor support member)
12 Laser scanner unit (exposure section)
20 control unit 21 light source drive control unit 22 reference position determination unit 23 light receiving position monitoring unit 24 feedback control unit 2a, 2b position detection laser (light emitting unit)
7a, 7b Position detection sensor (light receiving position detector)
P0 reference position P0_1 first reference position P0_2 second reference position

Claims (3)

A photoreceptor having a circumferential surface to be rotated;
A photoconductor support member for rotatably supporting the photoconductor;
A light receiving position detection unit that is fixed at a position away from the photosensitive member, includes a light receiving surface that receives laser light, and detects a light receiving position of the laser light on the light receiving surface;
A light emitting unit fixed to a part of the photosensitive member supporting member and emitting a laser beam toward the light receiving position detecting unit;
Exposure that forms a latent image for each line in the main scanning direction on the peripheral surface of the photosensitive member by scanning a laser beam having a light amount corresponding to the density value of each pixel of the image data from one end to the other end of the photosensitive member. And
Reference position determination for determining the light receiving position of the laser light detected by the light receiving position detecting section as a reference position by emitting the laser light to the light emitting section when the exposure section is not scanning the laser light. And
While the laser beam is scanned by the exposure unit, the laser beam is continuously emitted from the light emitting unit, so that the deviation of the laser beam receiving position detected by the light receiving position detection unit from the reference position is always detected. A light receiving position monitoring unit for monitoring,
When the direction of the deviation being monitored by the light receiving position monitoring unit satisfies the condition for thinning the latent image, the exposure unit is scanned so that the latent image is darkened by an amount corresponding to the magnitude of the deviation. When the amount of laser light to be adjusted is adjusted and the direction of the deviation satisfies the condition for thickening the latent image, the exposure unit is scanned so that the latent image is thinned by an amount corresponding to the magnitude of the deviation. A feedback control unit for adjusting the amount of laser light to be
An image forming apparatus comprising:   When the shift direction monitored by the light receiving position monitoring unit is a main scanning direction, the feedback control unit sets the amount of laser light to be scanned by the exposure unit rather than each pixel of image data. When the light amount corresponding to the density value of the pixel formed earlier or later is adjusted according to the magnitude of the deviation, and the direction of the deviation being monitored by the light receiving position monitoring unit is the sub-scanning direction The light amount of the laser beam scanned by the exposure unit is adjusted to a light amount corresponding to a density value obtained by increasing or decreasing the density value of each pixel of the image data by an amount corresponding to the magnitude of the shift. Image forming apparatus. A plurality of the light emitting units are provided, and a first light emitting unit, which is one of the plurality of light emitting units, is fixed to a portion of the photoconductor supporting member that supports one end of the photoconductor, and the plurality of light emitting units. A second light emitting portion different from the first light emitting portion is fixed to a portion of the photosensitive member supporting member that supports the other end of the photosensitive member,
A plurality of the light receiving position detection units are provided, and a first light receiving position detection unit, which is one of the plurality of light receiving position detection units, is provided at a position facing the first light emitting unit, A second light receiving position detector different from the first light receiving position detector among the plurality of light receiving position detectors is connected to the second light emitter. Provided at the opposite position, receiving the laser light emitted from the second light emitting unit,
The reference position determining unit emits laser light from the first light emitting unit and the second light emitting unit when the exposure unit does not scan the laser beam, and the first light receiving position detecting unit The detected light receiving position of the laser light is determined as a first reference position, the received light position of the laser light detected by the second received light position detection unit is determined as a second reference position,
The light receiving position monitoring unit detects the first light receiving position by continuously emitting laser light to the first light emitting unit and the second light emitting unit while the exposure unit scans the laser light. The laser light receiving position that is detected by the second light receiving position detecting unit is constantly monitored as a first deviation of the laser light receiving position from the first reference position, and detected by the second light receiving position detecting unit. Constantly monitoring the deviation from the second reference position as the second deviation,
The feedback control unit uses either one of the first deviation and the second deviation, which is constantly monitored by the light receiving position monitoring unit, as a reference deviation, and the direction of the reference deviation indicates the latent image. When the condition for thinning is satisfied, the amount of laser light scanned by the exposure unit is adjusted so that the latent image is darkened by an amount corresponding to the size of the reference deviation, and the direction of the reference deviation is set to the latent deviation. If the condition for darkening the image is satisfied, a reference deviation adjustment process is performed to adjust the amount of laser light scanned by the exposure unit so that the latent image is thinned by an amount corresponding to the magnitude of the reference deviation. ,
When a difference in deviation is found between the first deviation and the second deviation, the light emitting unit corresponding to the light receiving position detecting unit that has detected the reference deviation after the execution of the reference deviation adjustment process. The reference light emission position is a position where the light is fixed, and the distance from the reference light emission position to the position where the photosensitive member is irradiated with laser light from the exposure part, the first light emission part and the second light emission part Based on the distance between the first deviation and the second deviation, after correcting the difference in deviation, the direction of the difference in deviation after the correction is such that the latent image is thinned. When satisfying, the amount of laser light scanned by the exposure unit is adjusted so that the latent image is darkened by an amount corresponding to the magnitude of the deviation after the correction, and the deviation difference after the correction is adjusted. When the direction satisfies the condition for darkening the latent image, Only so thinning the latent image amount corresponding to the magnitude of the difference in the positive post of the deviation, the image forming apparatus according to claim 1 or 2 for adjusting the light quantity of the laser beam is scanned in the exposure unit.

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