JP2012073558A - Device and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the timing of emission of a plurality of laser beams without providing a mechanism for discriminating between deflection faces.SOLUTION: In a device and a method for forming an image, a reference laser beam, one of a plurality of laser beams, is emitted at first predetermined emission timing, deflected on a reference deflection face, one of a plurality of deflection faces, and output time of the detection signal of the reference laser beam is reference output time. First lapse time is lapse time from the reference output time to after-rotation output time for outputting the detection signal of the reference laser beam deflected again on the reference deflection face by the rotation of a rotary polyhedron after the reference output time. A second laser beam of the plurality of laser beams other than the reference laser beam is emitted at second predetermined emission timing, deflected on the reference deflection face by the rotation of the rotary polyhedron after the after-rotation output time. Second lapse time is from the reference output time to second beam reference output time for outputting the detection signal of the second laser beam. The second predetermined emission timing corresponding to the second laser beam is to be adjusted based on the difference of time between the first and second lapse times.

Description

  The present invention relates to an image forming apparatus and an image forming method using a semiconductor laser.

  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, the laser beam emitted from the semiconductor laser is deflected by each deflection surface of a rotary polygon mirror, and a photoconductor When an electrostatic latent image is formed (exposed) by scanning the surface, the output timing of each laser beam is shifted due to the different emission timing of each laser beam. There was a problem.

  Therefore, for example, Patent Document 1 below includes a rotary polygon mirror that deflects light beams emitted from a plurality of light emitting units, and when the light beam emitted from a light emitting unit is deflected by the first deflecting surface in the detection unit. The light emitted from a plurality of light emitting units is obtained by using a signal obtained and a signal obtained when a light beam emitted from another light emitting unit is deflected by a second deflection surface adjacent to the first deflection surface. A technique for adjusting timing is described.

JP 2007-112061 A

  However, in Patent Document 1, a signal obtained when a light beam emitted from a certain light emitting unit is deflected by the first deflection surface, and a light beam emitted from another light emitting unit is the first deflection surface. Any one of the deflection surfaces provided in the rotary polygon mirror is the first deflection surface or the second deflection surface in order to distinguish the signal obtained when deflected by the second deflection surface adjacent to Therefore, it is necessary to provide a mechanism for outputting a signal including identification information for identifying whether or not. That is, there is room for avoiding complication in configuring such an image forming apparatus.

  Therefore, the present invention has been made in view of such circumstances, and image formation capable of adjusting the emission timings of a plurality of laser beams without providing a mechanism for identifying each deflection surface of the rotary polygon mirror. An object is to provide an apparatus and an image forming method.

The invention according to claim 1 is a photoconductor on which a latent image is formed;
A light source unit that emits a plurality of laser beams;
A plurality of deflection surfaces for reflecting light are provided on the peripheral surface, and the plurality of laser beams emitted from the light source unit are reflected by the same deflection surface while being driven to rotate, and the plurality of laser beams are reflected on the photosensitive member. A rotating polyhedron that deflects toward
A synchronous sensor that receives the plurality of laser beams deflected by the deflection surface and outputs a detection signal indicating the received light;
A light source drive control unit that causes the light source unit to emit the plurality of laser beams according to the latent image to be formed at a predetermined emission timing corresponding to each laser beam;
Any one of the plurality of laser beams as a reference laser beam,
The reference laser beam is emitted at the predetermined emission timing corresponding to the reference laser beam, and the reference laser beam deflected by any one of the deflection surfaces is a reference deflection surface. From the reference output time that is the output time of the detection signal when received by the synchronous sensor,
Rotation at which the detection signal is output from the synchronization sensor when the reference laser beam deflected by the reference deflection surface again by the rotation of the rotating polyhedron after the reference output timing is received by the synchronization sensor. Until after output time,
The elapsed time of
From the reference output time,
Of the plurality of laser beams, another laser beam different from the reference laser beam is emitted at the predetermined emission timing corresponding to the other laser beam, and is rotated by the rotation polyhedron after the output timing after the rotation. Until the other light reference output time, which is the time when the detection signal is output from the synchronization sensor when the other laser light deflected by the reference deflection surface is received by the synchronization sensor,
The elapsed time of
An emission timing adjustment unit that adjusts the predetermined emission timing corresponding to the other laser beam based on the time difference of
An image forming apparatus.

According to a sixth aspect of the present invention, the photosensitive member on which a latent image is formed, a light source unit that emits a plurality of laser beams, and a plurality of deflection surfaces that reflect the light are provided on a peripheral surface, A rotating polyhedron that reflects the plurality of laser beams emitted from the light source unit on the same deflection surface and deflects the plurality of laser beams toward the photoconductor, and the plurality of the beams deflected on the deflection surface A synchronization sensor that receives a laser beam and outputs a detection signal indicating the received light, and an image forming method in an image forming apparatus,
A light source drive control step of emitting the plurality of laser beams corresponding to the latent image to be formed to the light source unit at a predetermined emission timing corresponding to each laser beam;
Any one of the plurality of laser beams as a reference laser beam,
The reference laser beam is emitted at the predetermined emission timing corresponding to the reference laser beam, and the reference laser beam deflected by any one of the deflection surfaces is a reference deflection surface. From the reference output time that is the output time of the detection signal when received by the synchronous sensor,
Rotation at which the detection signal is output from the synchronization sensor when the reference laser beam deflected by the reference deflection surface again by the rotation of the rotating polyhedron after the reference output timing is received by the synchronization sensor. Until after output time,
The elapsed time of
From the reference output time,
Of the plurality of laser beams, another laser beam different from the reference laser beam is emitted at the predetermined emission timing corresponding to the other laser beam, and is rotated by the rotation polyhedron after the output timing after the rotation. Until the other light reference output time, which is the time when the detection signal is output from the synchronization sensor when the other laser light deflected by the reference deflection surface is received by the synchronization sensor,
The elapsed time of
An emission timing adjustment step for adjusting the predetermined emission timing corresponding to the other laser beam based on the time difference of
Is an image forming method.

  In these inventions, only one reference deflection surface of the plurality of deflection surfaces of the rotating polyhedron is used without identifying each surface of the plurality of deflection surfaces of the rotating polyhedron, The output time after rotation and the other light reference output time are derived, and other lasers are based on the time difference between the elapsed time from the reference output time to the output time after rotation and the elapsed time from the reference output time to the other light reference output time. The light emission timing is adjusted.

  That is, without identifying each surface of the plurality of deflection surfaces of the rotating polyhedron, only one reference deflection surface of the plurality of deflection surfaces of the rotating polyhedron is used, and the emission timing of the other laser light Can be adjusted.

The invention according to claim 2 is the image forming apparatus according to claim 1, wherein the emission timing adjusting unit is
The reference laser light deflected by the plurality of deflecting surfaces by the rotation of the rotating polyhedron after the reference output time is received by the synchronization sensor, and the deflecting surfaces provided in the rotating polyhedron counted from the reference output time The number of detection signals corresponding to a first predetermined number of times the number of
Calculating a reference rotation time that is a result of dividing an elapsed time from the reference output time to the post-rotation output time by the first predetermined number;
After the output time after rotation, the emission of the reference laser light is stopped and the other laser light is emitted at the predetermined emission timing corresponding to the other laser light, and the rotation is performed after the output time after the rotation. The reference laser beam and the other laser beam deflected by the plurality of deflection surfaces by the rotation of the polyhedron are received by the synchronous sensor, and counted from the output timing after the rotation of the deflection surfaces provided in the rotation polyhedron. The timing at which the number of the detection signals corresponding to the second predetermined number of times is output from the synchronization sensor as the other light reference output timing,
The amount of laser misalignment, which is the result of subtracting the result obtained by multiplying the reference rotation time by the sum of the first predetermined number and the second predetermined number, from the elapsed time from the reference output time to the other light reference output time. Based on this, the predetermined emission timing corresponding to the other laser beam is adjusted.

  In this invention, the time when the rotating polyhedron is rotated by the first predetermined number of times from the reference output time is set as the output time after rotation, and the reference deflection is performed when the rotating polyhedron finishes the second predetermined number of rotations after the output time after the rotation. The output timing of the detection signal output by receiving another laser beam deflected on the surface by the synchronous sensor is measured as the other light reference output timing. And, as a result of multiplying the reference rotation time by the sum of the first predetermined number and the second predetermined number from the elapsed time from the reference output time to the other light reference output time, in other words, the first predetermined number and the second predetermined number The time required for the rotating polyhedron to rotate by the sum is subtracted.

  That is, the reference laser beam is converted into the reference deflection surface by using only one reference deflection surface of the plurality of deflection surfaces of the rotating polyhedron without identifying each surface of the plurality of deflection surfaces of the rotating polyhedron. The amount of misalignment between lasers that can be considered as a difference between the timing at which the laser beam is emitted and the timing at which other laser beams are emitted with respect to the reference deflection surface can be calculated as the above subtraction result. A predetermined emission timing corresponding to another laser beam can be adjusted.

The invention according to claim 3 is the image forming apparatus according to claim 2, wherein the emission timing adjustment unit is
By dividing the reference rotation time by the number of the deflection surfaces provided in the rotary polyhedron, the average value of the time for deflecting the plurality of laser beams by each surface of the deflection surface and scanning the surface of the photoreceptor is obtained. Calculate a reference scan time,
From the reference output time,
Each output of the detection signal when the reference laser beam deflected by all the deflection surfaces different from the reference deflection surface by rotation of the rotating polyhedron immediately after the reference output time is received by the synchronization sensor. Each elapsed time to time,
The respective deflections from the reference deflection surface to the deflection surface that deflects the reference laser beam received by the synchronization sensor at the respective output timings, counting in the direction opposite to the rotation direction of the rotating polyhedron. Each multiplication result obtained by multiplying the number of faces by the reference scanning time;
The predetermined emission timing corresponding to each of the plurality of laser beams is based on the average amount of deviation between mirrors, which is the result of dividing the sum of the respective time differences by the number of deflection surfaces provided in the rotating polyhedron. adjust.

  In the present invention, a plurality of rotation polyhedrons that use only one reference deflection surface among the plurality of deflection surfaces of the rotation polyhedron without identifying each surface of the plurality of deflection surfaces of the rotation polyhedron. Deviation of the start position of writing of the latent image when the reference laser beam is deflected by each deflection surface and scans the surface of the photosensitive member, for example, due to a deviation in angle or length between the respective deflection surfaces. It is possible to calculate an average deviation amount between mirrors that can be considered as an average value of the two, and it is possible to adjust a predetermined emission timing corresponding to each of a plurality of laser beams based on the average deviation amount between mirrors.

  According to a fourth aspect of the invention, there is provided the image forming apparatus according to the second aspect, wherein the emission timing adjustment unit uses the predetermined emission timing corresponding to the reference laser beam as a reference emission timing. The emission timing obtained by correcting the emission timing by the amount of deviation between the lasers is set as the predetermined emission timing corresponding to the other laser beam.

  In the present invention, a reference laser beam is corrected by relatively correcting a predetermined emission timing corresponding to another laser beam based on a predetermined emission timing corresponding to any one of the plurality of laser beams. It is possible to correct a deviation amount between the timing at which the light is emitted with respect to the reference deflection surface and the timing at which the other laser light is emitted with respect to the reference deflection surface.

  The invention according to claim 5 is the image forming apparatus according to claim 3, wherein the emission timing adjustment unit rotates the rotation at the predetermined emission timing corresponding to each of the plurality of laser beams. The respective emission timings for all the deflecting surfaces provided in the polyhedron are corrected by the average amount of deviation between the mirrors.

  In the present invention, the timing at which a plurality of laser beams are emitted to each deflection surface is corrected by the amount of average deviation between the mirrors, and each laser beam is deflected by each deflection surface to scan the surface of the photoreceptor. It is possible to correct the shift amount when the start position of writing the latent image is deviated between the deflected surfaces to be deflected.

  According to the present invention, it is possible to provide an image forming apparatus and an image forming method capable of adjusting the emission timings of a plurality of laser beams without providing a mechanism for identifying each deflection surface of the rotary polygon mirror. .

1 is a cross-sectional view illustrating an example of a mechanical configuration of a printer as an image forming apparatus according to an embodiment of the present invention. The block diagram which shows an example of the mechanical structure of a laser scanner. FIG. 3 is a block diagram illustrating an electrical configuration of the printer. The flowchart which shows an example of an emission timing adjustment step. The timing chart which shows an example of the output time of the detection signal from the synchronous sensor which received the some laser beam.

  Hereinafter, an embodiment 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 laser scanner 11, a developing device 12, a charger 13, a photosensitive drum 14, a transfer roller 15, and a fixing device 16.

  A photosensitive drum 14 as a photosensitive member according to the present invention is a cylindrical member, and is rotated in a clockwise direction in FIG. 1 in response to a driving force from a motor (not shown). The charger 13 charges the surface of the photosensitive drum 14 substantially uniformly. The laser scanner 11 includes a light source such as a laser diode, and irradiates the surface of the photosensitive drum 14 that is substantially uniformly charged by the charger 13 with an optical signal corresponding to the image data, thereby statically reducing the image data. An electrostatic latent image is formed.

  The image data is data received by the printer 1 that is transmitted by a PC (personal computer) or the like connected to the printer 1. Details of the laser scanner 11 will be described later with reference to FIG.

  The developing device 12 includes a toner container that stores toner, and supplies toner to the surface of the photosensitive drum 14 on which the electrostatic latent image is formed to form a toner image. A toner image formed on the photosensitive drum 14 is transferred onto a recording sheet or a transfer belt (not shown) conveyed on the conveyance path P by a transfer roller 15 described later.

  A transfer roller 15 is disposed at a position facing the photosensitive drum 14. The transfer roller 15 is made of a conductive rubber material or the like, and transfers the toner image formed on the photosensitive drum 14 onto a recording paper 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 14 is charged almost uniformly by the charger 13. Then, the surface of the charged photosensitive drum 14 is exposed by the laser scanner 11, and an electrostatic latent image of an image formed on the recording paper is formed on the surface of the photosensitive drum 14. The electrostatic latent image is visualized by attaching toner to the surface of the photosensitive drum 14 by the developing device 12, and the toner image on the surface of the photosensitive drum 14 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.

  As shown in FIG. 2, a laser scanner 11 includes a semiconductor laser 101 as a light source unit according to the present invention, a collimator lens 102, a diaphragm 103, a rotating polygon mirror 104 as a rotating polyhedron according to the present invention, a lens group 105, and the present invention. It comprises the BD (Beam Detect) sensor 106 as a synchronous sensor which concerns on this.

  A plurality of (for example, two) semiconductor lasers 101 are provided in the front and back direction in FIG. 2, and each semiconductor laser 101 emits laser light having a predetermined wavelength. Each semiconductor laser 101 is provided with a photodiode (not shown) for detecting a part of the laser beam, and a light source drive control unit (to be described later) controls the light emission amount of the laser diode using the detection signal of the photodiode ( Automatic Power Control control (hereinafter referred to as APC control) is performed.

  The collimator lens 102 and the aperture 103 collimate the laser beam generated from the semiconductor laser 101 into a substantially parallel beam and enter the rotary polygon mirror 104 with a predetermined beam diameter.

  The rotary polygon mirror 104 includes mirrors P1 to P6 that reflect light as deflection surfaces according to the present invention on the peripheral surface, and is driven to rotate at a constant speed in the direction of the arrow in the figure by a driving force supplied by a polygon motor described later. Is configured to do. 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 14.

  The lens group 105 condenses the laser beam, which is a deflected beam reflected by the rotary polygon mirror 104, and horizontally scans the photosensitive drum 14 at a constant speed in the main scanning direction (A direction in the figure). .

  The BD sensor 106 is used to synchronize the emission timing of the laser beam from the semiconductor laser 101 and the rotation of the rotary polygon mirror 104, which is the timing for starting horizontal scanning of the photosensitive drum 14 by the laser beam. Specifically, the BD sensor 106 receives the laser light reflected by the rotary polygon mirror 104 and outputs a detection signal indicating that the light has been received. The detection signal output by the BD sensor 106 is used to synchronize the rotation of the rotary polygon mirror 104 and the writing start timing of the image data, that is, the writing in the arrow A direction.

  As described above, by rotating the rotary polygon mirror 104, lines corresponding to the number of the semiconductor lasers 101 in the main scanning direction (A direction in the figure) of the image data (for example, one-dot chain line and dotted line in the figure). Minute horizontal scanning (exposure) is performed on the photosensitive drum 14. Then, the photosensitive drum 14 is rotated by the number of lines corresponding to the number of semiconductor lasers 101 in the sub-scanning direction (direction B in the drawing), and the line corresponding to the number of semiconductor lasers 101 in the main scanning direction of the next image data. Minute exposure.

  Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 3, 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. And a memory such as a hard disk (HDD). The operation program stored in the ROM is executed by the CPU, thereby controlling the entire apparatus.

  In the following, laser light emission control (exposure control) from the semiconductor laser 101, which is the gist of the present invention, of the control performed by the control unit 20 will be described.

  Connected to the control unit 20 are a BD sensor 106, a semiconductor laser 101, a polygon motor 32 that is a driving source of the rotary polygon mirror 104, and a drum motor 33 that is a driving source of the photosensitive drum 14, and is output from the BD sensor 106. And an interface circuit (not shown) for inputting and outputting control signals for controlling the driving of the semiconductor laser 101, the polygon motor 32, and the drum motor 33. Further, the control unit 20 functions as a light source drive control unit 21 and an emission timing adjustment unit 22.

  The light source drive control unit 21 causes each semiconductor laser 101 to emit a plurality of laser beams corresponding to the image data of the latent image formed on the surface of the photosensitive drum 14 at a predetermined emission timing corresponding to each laser beam (light source drive). In addition to the control step, the APC control is performed using a detection signal of a photodiode provided in the semiconductor laser 101.

  The predetermined emission timing corresponding to each laser beam is associated with the rotation angle of the rotary polygon mirror 104, and the emission timing at which each laser beam is emitted to each mirror provided in the rotary polygon mirror 104. It is defined and determined in advance based on an experimental value obtained by a test operation before product shipment and stored in a memory such as a ROM or a nonvolatile memory.

  The emission timing adjustment unit 22 uses any one of the plurality of laser beams as the reference laser beam, emits the reference laser beam at a predetermined emission timing corresponding to the reference laser beam, and outputs the reference laser beam from the plurality of mirrors P1 to P6. From the reference output timing which is the output timing of the detection signal when the reference laser beam deflected by the reference mirror as the reference deflection surface according to the present invention which is any one of the mirrors is received by the BD sensor 106, the reference After the output timing, until the output timing after rotation, which is the timing when the detection signal is output from the BD sensor 106 when the reference laser light deflected by the reference mirror again by the rotation of the rotary polygon mirror 104 is received by the BD sensor 106, From the elapsed time and the reference output time, another laser beam different from the reference laser beam among the plurality of laser beams is determined corresponding to the other laser beam. Timing at which a detection signal is output from the BD sensor 106 when another laser beam that is emitted at the emission timing and is deflected by the reference mirror by the rotation of the rotary polygon mirror 104 after the output timing after rotation is received by the BD sensor 106 The predetermined emission timing corresponding to the other laser light is adjusted based on the time difference from the elapsed time until the other light reference output time.

  Specifically, the emission timing adjustment unit 22 receives the reference laser light deflected by the plurality of mirrors P1 to P6 by the rotation of the rotary polygon mirror 104 after the reference output time, and receives it from the reference output time. Thus, the output after rotation from the reference output time is defined as the above-mentioned output time after rotation, which is the time when the number of detection signals corresponding to the first predetermined number times the number of mirrors provided in the rotary polygon mirror 104 is output from the BD sensor 106. The reference rotation time, which is the result of dividing the elapsed time until the time by the first predetermined number, is calculated, and after the output time after rotation, the emission of the reference laser light is stopped and the other laser light is changed to the other laser light. A reference laser beam and other laser beams that are emitted at a corresponding predetermined emission timing and deflected by the plurality of mirrors P1 to P6 by the rotation of the rotary polygon mirror 104 after the output timing after the rotation are BD center. The time when the detection signals corresponding to the second predetermined number of times of the number of mirrors received at 106 and output from the post-rotation output timing and corresponding to the number of mirrors provided in the rotary polygon mirror 104 are output from the BD sensor 106 is the other light reference output. As a timing, a laser obtained by subtracting the result obtained by multiplying the reference rotation time by the sum of the first predetermined number and the second predetermined number from the elapsed time from the reference output time to the other light reference output time. Based on the amount of misalignment, a predetermined emission timing corresponding to another laser beam is adjusted.

  Further, the emission timing adjustment unit 22 divides the reference rotation time by the number of mirrors provided in the rotary polygon mirror 104, thereby deflecting a plurality of laser beams by each surface of the mirror, thereby causing the surface of the photosensitive drum 14 to be deflected. A reference scanning time that is an average value of the scanning time is calculated, and the reference laser light deflected by all mirrors different from the reference mirror by the rotation of the rotary polygon mirror 104 from the reference output time immediately after the reference output time is BD. The elapsed time until each output timing of the detection signal when received by the sensor 106 is counted in the direction opposite to the rotation direction of the rotary polygon mirror 104, and the BD sensor 106 is output from the reference mirror at each output timing. The result of multiplying the reference scanning time by the number of each mirror up to the mirror that deflects the reference laser beam received by The sum of the time difference, respectively, based on the average amount of deviation between the mirrors is a result of dividing the number of mirrors provided in the rotary polygon mirror 104 to adjust the predetermined emission timing corresponding to each of the plurality of laser beams.

  Hereinafter, as shown in FIG. 2, assuming that the rotary polygon mirror 104 has six mirrors P <b> 1 to P <b> 6, a timing adjustment process (a process for adjusting a predetermined emission timing of a plurality of laser beams by the emission timing adjustment unit 22 ( The emission timing adjustment step) will be described in detail.

  As shown in FIGS. 4 and 5, the emission timing adjustment unit 22 starts the timing adjustment process at a predetermined time such as when power is supplied to the printer 1 or after a predetermined number of image forming processes have been completed. Then, first, emission of laser light (reference laser light) is started at a predetermined emission timing only from any one of the plurality of semiconductor lasers 101 (S1).

  Subsequently, when the reflected light from the mirror is received by the BD sensor 106, the emission timing adjustment unit 22 uses any one of the mirrors provided in the rotary polygon mirror 104 as the reference mirror. The output timing of the detection signal is stored in the RAM as the reference output timing t10 (S2).

  Here, the measurement of the output time is measured by a timer such as a CPU timer, for example, but the measurement method is not limited to this. In the following description, it is assumed that the reference mirror is the mirror P1, but the present invention is not limited to this.

  Subsequently, the emission timing adjustment unit 22 is provided as six first predetermined multiples of the number of mirrors P1 to P6 provided in the rotary polygon mirror 104 by the rotation of the rotary polygon mirror 104 after the reference output timing t10. Until the detection signal is output from the BD sensor 106 (S3), the output timing of each detection signal is measured, and the measured output timing is stored in the RAM as output timings t11 to t16, respectively (S4). In this case, the first predetermined number is set to 1. However, the present invention is not limited to this, and other positive integer values may be set.

  Further, the emission timing adjusting unit 22 outputs an output timing t16 when detection signals corresponding to a first predetermined number of times the number of mirrors P1 to P6 provided in the rotary polygon mirror 104 are output from the BD sensor 106 after the reference output timing t10. Is set as the output time after rotation.

  When the output timing t22 stores the output timings t11 to t16 in the RAM, the emission timing adjustment unit 22 divides the elapsed time from the reference output timing t10 to the post-rotation output timing t16 by 1 which is the first predetermined number, so that the rotating polygon mirror 104 is A reference rotation time t16-t10 required for one round is calculated. Then, the emission timing adjustment unit 22 deflects the laser beam by each mirror surface and divides the calculated reference rotation time t16-t10 by the number of mirrors (t16-t10) / 6 to make the surface of the photosensitive drum 14 The reference scanning time Tb, which is the average value of the scanning time, is stored in the RAM (S5).

  The emission timing adjustment unit 22 receives the reference laser light deflected by all the mirrors P2 to P6 different from the reference mirror P1 stored in the RAM from the reference output timing t10 stored in the RAM. The respective elapsed times from the output timings t11 to t15 of the detection signals at the time and the rotation direction of the rotary polygon mirror 104 are counted in the opposite direction from the reference mirror P1 to the respective output timings t11 to t15. Respective multiplication results Tb × 1, Tb × 2,... Obtained by multiplying the reference scanning time Tb by the number of mirrors 1 to 5 of the mirrors P2 to P6 deflected by the reference laser beam received by the sensor 106. , Tb × 5 and time differences Δt12 to Δt16 are calculated.

  Further, the emission timing adjustment unit 22 divides the total of the calculated time differences Δt12 to Δt16 by the number of mirrors provided in the rotary polygon mirror 104, and calculates the division result (Δt12 +... + Δt16) / 6 to the rotary polygon. Deviation of the latent image writing start position when the reference laser beam is deflected by each mirror and scans the surface of the photosensitive drum 14 due to a deviation in angle or length between the mirrors of the mirror 104 Is stored in the non-volatile memory as an average amount (an average deviation amount between mirrors) (S6).

  Subsequently, the emission timing adjustment unit 22 stops emission of the reference laser light from the semiconductor laser 101 that has emitted the reference laser light after the output time t16 after rotation (S7), and emits the reference laser light. The laser light (other laser light) starts to be emitted at a predetermined emission timing from only one of the semiconductor lasers 101 different from the semiconductor laser 101 (S8).

  The emission timing adjustment unit 22 outputs the six detection signals from the BD sensor 106 as the second predetermined number times the number of mirrors provided in the rotary polygon mirror 104 after the post-rotation output timing t16. Wait (S9). In this case, 1 is set as the second predetermined number. However, the present invention is not limited to this, and other positive integer values may be set.

  Then, after the output timing t16 after the rotation, the emission timing adjustment unit 22 receives the reference laser light and other laser lights deflected by the mirrors P1 to P6 by the rotation of the rotary polygon mirror 104 by the BD sensor 106, and after the rotation When it is determined that six detection signals corresponding to the second predetermined multiple of the number of mirrors provided in the rotary polygon mirror 104 from the output time t16 are output from the BD sensor 106 (S9; YES) The detection signal output timing t2 is stored in the RAM as the other light output timing (S10), and the emission of the other laser light from the semiconductor laser 101 that has emitted the other laser light is stopped (S11).

  Then, the emission timing adjustment unit 22 multiplies the reference rotation time t16-t10 by the sum of the first predetermined number and the second predetermined number from the elapsed time t2-t10 from the reference output timing t10 to the other light output timing t2. In other words, the elapsed time from the reference output timing t10 until the rotary polygon mirror 104 makes two rounds is subtracted, and the result of the subtraction is calculated based on the timing at which the reference laser beam is emitted to the reference mirror and the other laser beams. Is stored in the non-volatile memory as a deviation of the timing of emission (laser deviation amount) (S12).

  Subsequently, the emission timing adjusting unit 22 determines the predetermined emission timing corresponding to the reference laser beam and other laser beams stored in the ROM or the nonvolatile memory, and the interval between the lasers stored in the nonvolatile memory in step S12. The deviation amount is read, and a predetermined emission timing corresponding to the read reference laser beam is set as a reference emission timing, and a predetermined emission timing corresponding to the other read laser beam is read from the read reference emission timing. Correction is made to the emission timing corrected by the amount of deviation between the lasers, and the predetermined emission timing corresponding to the other laser light stored in the ROM or nonvolatile memory is updated at the corrected emission timing (S13).

  Further, the emission timing adjustment unit 22 reads out each predetermined emission timing corresponding to all the laser beams stored in the ROM or the nonvolatile memory and the average deviation amount between the mirrors stored in the nonvolatile memory in step S6. Thus, the respective emission timings for all the mirrors P1 to P6 provided in the rotary polygon mirror 104 at each of the read predetermined emission timings are corrected by the amount of average deviation between the mirrors, respectively. Each predetermined emission timing stored in the ROM or the nonvolatile memory is updated at a predetermined emission timing (S14).

  As described above, according to the present configuration, only any one reference mirror of the plurality of mirrors included in the rotating polygon mirror 104 is identified without identifying each surface of the plurality of mirrors included in the rotating polygon mirror 104. As a difference between the timing at which any one of the plurality of laser beams is emitted to the reference mirror and the timing at which another laser beam different from the reference laser beam is emitted to the reference mirror A possible laser shift amount can be calculated.

  Then, by correcting the predetermined emission timing corresponding to the other laser light by an amount corresponding to the difference between the lasers with reference to the predetermined emission timing corresponding to the reference laser light, the reference laser light becomes the reference mirror. On the other hand, it is possible to correct the amount of deviation between the timing of emission and the timing of emission of other laser beams with respect to the reference mirror.

  Further, without identifying each surface of the plurality of mirrors included in the rotating polygon mirror 104, only one of the plurality of mirrors included in the rotating polygon mirror 104 is used, and the rotating polygon mirror 104 is used. Starting writing of a latent image when scanning the surface of the photosensitive drum 14 with the reference laser beam deflected by each mirror, for example, caused by a deviation in angle or length between the mirrors of the plurality of mirrors It is possible to calculate an average deviation amount between mirrors that can be considered as an average value of positional deviations.

  Then, by correcting the timing at which the plurality of laser beams are emitted to the respective mirrors by the amount of average deviation between the mirrors, the latent beam when scanning the surface of the photosensitive drum 14 by deflecting the laser beams by the respective mirrors is corrected. It is possible to correct the shift amount when the image writing start position is shifted between the deflected mirrors.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above embodiment, the monochrome image forming printer 1 is shown as an example of the image forming apparatus according to the present invention. However, the image forming apparatus according to the present invention is not limited to this, and a color printer for forming a color image, It may be a multi-function machine having a scanner function, a facsimile function, a printer function, a copy function, and the like.

  In addition, the emission timing adjustment unit 22 is configured not to perform the processes of steps S5, S6, and S14 described above, that is, only a deviation in emission timing between laser beams emitted from the plurality of semiconductor lasers 101. It may be configured to be simplified so as to adjust.

  In the above embodiment, the configurations and settings shown in FIGS. 1 to 5 are merely examples, and the present invention is not limited to the embodiment.

1 Printer (image forming device)
14 Photosensitive drum (photosensitive member)
20 control unit 21 light source drive control unit 22 emission timing adjustment unit 101 semiconductor laser (light source unit)
104 Rotating polygon mirror (Rotating polyhedron)
106 BD sensor (synchronous sensor)
t10 Reference output time t16 Output time after rotation t2 Other light reference output time

Claims (6)

A photoreceptor on which a latent image is formed;
A light source unit that emits a plurality of laser beams;
A plurality of deflection surfaces for reflecting light are provided on the peripheral surface, and the plurality of laser beams emitted from the light source unit are reflected by the same deflection surface while being driven to rotate, and the plurality of laser beams are reflected on the photosensitive member. A rotating polyhedron that deflects toward
A synchronous sensor that receives the plurality of laser beams deflected by the deflection surface and outputs a detection signal indicating the received light;
A light source drive control unit that causes the light source unit to emit the plurality of laser beams according to the latent image to be formed at a predetermined emission timing corresponding to each laser beam;
Any one of the plurality of laser beams as a reference laser beam,
The reference laser beam is emitted at the predetermined emission timing corresponding to the reference laser beam, and the reference laser beam deflected by any one of the deflection surfaces is a reference deflection surface. From the reference output time that is the output time of the detection signal when received by the synchronous sensor,
Rotation at which the detection signal is output from the synchronization sensor when the reference laser beam deflected by the reference deflection surface again by the rotation of the rotating polyhedron after the reference output timing is received by the synchronization sensor. Until after output time,
The elapsed time of
From the reference output time,
Of the plurality of laser beams, another laser beam different from the reference laser beam is emitted at the predetermined emission timing corresponding to the other laser beam, and is rotated by the rotation polyhedron after the output timing after the rotation. Until the other light reference output time, which is the time when the detection signal is output from the synchronization sensor when the other laser light deflected by the reference deflection surface is received by the synchronization sensor,
The elapsed time of
An emission timing adjustment unit that adjusts the predetermined emission timing corresponding to the other laser beam based on the time difference of
An image forming apparatus comprising: The emission timing adjustment unit is
The reference laser light deflected by the plurality of deflecting surfaces by the rotation of the rotating polyhedron after the reference output time is received by the synchronization sensor, and the deflecting surfaces provided in the rotating polyhedron counted from the reference output time The number of detection signals corresponding to a first predetermined number of times the number of
Calculating a reference rotation time that is a result of dividing an elapsed time from the reference output time to the post-rotation output time by the first predetermined number;
After the output time after rotation, the emission of the reference laser light is stopped and the other laser light is emitted at the predetermined emission timing corresponding to the other laser light, and the rotation is performed after the output time after the rotation. The reference laser beam and the other laser beam deflected by the plurality of deflection surfaces by the rotation of the polyhedron are received by the synchronous sensor, and counted from the output timing after the rotation of the deflection surfaces provided in the rotation polyhedron. The timing at which the number of the detection signals corresponding to the second predetermined number of times is output from the synchronization sensor as the other light reference output timing,
The amount of laser misalignment, which is the result of subtracting the result obtained by multiplying the reference rotation time by the sum of the first predetermined number and the second predetermined number, from the elapsed time from the reference output time to the other light reference output time. The image forming apparatus according to claim 1, wherein the predetermined emission timing corresponding to the other laser beam is adjusted based on. The emission timing adjustment unit is
By dividing the reference rotation time by the number of the deflection surfaces provided in the rotary polyhedron, the average value of the time for deflecting the plurality of laser beams by each surface of the deflection surface and scanning the surface of the photoreceptor is obtained. Calculate a reference scan time,
From the reference output time,
Each output of the detection signal when the reference laser beam deflected by all the deflection surfaces different from the reference deflection surface by rotation of the rotating polyhedron immediately after the reference output time is received by the synchronization sensor. Each elapsed time to time,
The respective deflections from the reference deflection surface to the deflection surface that deflects the reference laser beam received by the synchronization sensor at the respective output timings, counting in the direction opposite to the rotation direction of the rotating polyhedron. Each multiplication result obtained by multiplying the number of faces by the reference scanning time;
The predetermined emission timing corresponding to each of the plurality of laser beams is based on the average amount of deviation between mirrors, which is the result of dividing the sum of the respective time differences by the number of deflection surfaces provided in the rotating polyhedron. The image forming apparatus according to claim 2, which is adjusted.   The emission timing adjustment unit uses a predetermined emission timing corresponding to the reference laser beam as a reference emission timing, and an emission timing obtained by correcting the reference emission timing by the amount of deviation between the lasers corresponds to the other laser beam. The image forming apparatus according to claim 2, wherein a predetermined emission timing is set.   The emission timing adjustment unit is configured to calculate each emission timing for all the deflection surfaces provided in the rotating polyhedron for the average deviation amount between the mirrors at the predetermined emission timing corresponding to each of the plurality of laser beams. The image forming apparatus according to claim 3, wherein only the correction is performed. The photosensitive member on which a latent image is formed, a light source unit that emits a plurality of laser beams, and a plurality of deflection surfaces that reflect the light are provided on the peripheral surface, and the plurality of laser beams that are emitted from the light source unit while being driven to rotate. A rotating polyhedron for reflecting the plurality of laser beams toward the photoconductor and receiving the plurality of laser beams deflected by the deflection surface to indicate the received light. An image forming method in an image forming apparatus comprising: a synchronization sensor that outputs a detection signal;
A light source drive control step of emitting the plurality of laser beams corresponding to the latent image to be formed to the light source unit at a predetermined emission timing corresponding to each laser beam;
Any one of the plurality of laser beams as a reference laser beam,
The reference laser beam is emitted at the predetermined emission timing corresponding to the reference laser beam, and the reference laser beam deflected by any one of the deflection surfaces is a reference deflection surface. From the reference output time that is the output time of the detection signal when received by the synchronous sensor,
Rotation at which the detection signal is output from the synchronization sensor when the reference laser beam deflected by the reference deflection surface again by the rotation of the rotating polyhedron after the reference output timing is received by the synchronization sensor. Until after output time,
The elapsed time of
From the reference output time,
Of the plurality of laser beams, another laser beam different from the reference laser beam is emitted at the predetermined emission timing corresponding to the other laser beam, and is rotated by the rotation polyhedron after the output timing after the rotation. Until the other light reference output time, which is the time when the detection signal is output from the synchronization sensor when the other laser light deflected by the reference deflection surface is received by the synchronization sensor,
The elapsed time of
An emission timing adjustment step for adjusting the predetermined emission timing corresponding to the other laser beam based on the time difference of
An image forming method comprising:

Images