JP2017090738A - Optical scanning device - Google Patents

Abstract

A phase of a plurality of reflecting surfaces of a rotating polygon mirror is specified based on a detection result of a voltage applied to a motor for rotating the rotating polygon mirror.
An optical scanning device includes a light source that emits a light beam and a plurality of reflecting surfaces that deflect the light beam so that the light beam emitted from the light source scans the surface of the photosensitive member in the main scanning direction. A rotating polygon mirror 15a, a motor 15 for rotating the rotating polygon mirror, a rotation position detection means 16 for detecting a change in magnetic flux generated by the rotation of the motor and generating a rotation position detection signal 22, and a motor applied to the motor. The voltage detection means 33 which detects a voltage and produces | generates a permission signal, and the specific means 31 which pinpoints the phase of several reflective surfaces of a rotary polygon mirror based on a rotation position detection signal and a permission signal are provided.
[Selection] Figure 4

Description

  The present invention relates to an optical scanning device having a rotating polygon mirror.

  Conventionally, an electrophotographic image forming apparatus has an optical scanning device. The optical scanning device deflects a light beam emitted from a light source by a rotating polygon mirror. The deflected light beam scans the surface of the photosensitive drum through the fθ lens to form an electrostatic latent image.

  On the other hand, the light beam emitted from the semiconductor laser needs to be accurately exposed at a predetermined position on the photosensitive drum. However, the tilting of the reflecting surface of the rotary polygon mirror causes variations in the scanning line interval in the sub-scanning direction on the photosensitive drum, and causes uneven density of the image called banding.

  Patent Document 1 proposes a technique for reducing density unevenness due to variations in scanning line intervals in the sub-scanning direction by correcting image data. In order to correct the image data, it is necessary to identify the reflecting surface of the rotary polygon mirror and associate the surface tilt amount stored in advance with the identified reflecting surface. In order to specify the reflecting surface of the rotating polygon mirror, a reference position mark provided on the upper surface of the rotating polygon mirror is detected by a reference position sensor. Based on the detection signal of the reference position sensor, the reflection surface is specified by specifying the rotation angle of the motor of the rotary polygon mirror.

  In Patent Document 2, a light beam deflected by a reflecting surface of a rotary polygon mirror is detected by a beam detector, and reflected by a pattern match between a periodic interval of a beam detection signal from the beam detector and a periodic interval stored in advance. It proposes a method for identifying faces.

JP 2001-260413 A JP 2011-148142 A

  However, Patent Document 1 has a problem that an additional mark or sensor is required, resulting in an increase in cost. In Patent Document 2, the light beam emission timing for obtaining the beam detection signal is determined in the speed control of the rotary polygon mirror, and then the reflection surface is changed after the rotation of the rotary polygon mirror is stabilized in the phase control by the beam detection signal. Identify. For this reason, it is difficult to shorten the time from when an image formation start instruction is received until image formation is started. In addition, since an error of the order of several nanoseconds (ns) occurs in the periodic interval of the beam detection signal, a high-frequency count clock is required, which may increase the circuit scale.

  Therefore, the present invention provides an optical scanning device that can specify the phases of a plurality of reflecting surfaces of a rotating polygon mirror based on a detection result of a voltage applied to a motor that rotates the rotating polygon mirror.

In order to solve the above problems, an optical scanning device according to an embodiment of the present invention includes:
A light source that emits a light beam;
A rotating polygon mirror having a plurality of reflecting surfaces for deflecting the light beam so that the light beam emitted from the light source scans the surface of the photosensitive member in the main scanning direction;
A motor for rotating the rotary polygon mirror;
Rotational position detection means for detecting a change in magnetic flux generated by rotation of the motor and generating a rotational position detection signal;
Voltage detection means for detecting a voltage applied to the motor and generating a permission signal;
Identification means for identifying phases of the plurality of reflecting surfaces of the rotary polygon mirror based on the rotational position detection signal and the permission signal;
It is characterized by providing.

  ADVANTAGE OF THE INVENTION According to this invention, the phase of the several reflective surface of a rotary polygon mirror can be specified based on the detection result of the voltage applied to the motor which rotates a rotary polygon mirror. Therefore, the phases of the plurality of reflecting surfaces of the rotary polygon mirror can be accurately identified without using the reference mark detector or the BD sensor.

1 is a cross-sectional view of an image forming apparatus according to a first embodiment. Explanatory drawing of the optical scanning apparatus of 1st Example. Explanatory drawing of the motor of 1st Example. The block diagram of the surface specific | specification part and image control part of 1st Example. The timing chart which shows operation | movement of the surface specific part of 1st Example. The figure which shows the voltage of the FG period ratio and power supply at the time of starting of a motor. The block diagram of the structure which produces | generates reference | standard period ratio data and phase data. The timing chart which shows the operation | movement of a FG-BD phase measurement part. The figure which shows reference | standard period ratio data. The flowchart which shows the production | generation control operation | movement of the reference | standard period ratio data and phase data which are performed with a tool. The figure which shows FG cycle ratio and deviation with respect to FG cycle data. Explanatory drawing of the voltage detection part of 1st Example. The block diagram of the surface specific part and phase angle specific part of 2nd Example. The timing chart which shows the operation | movement of the phase angle specific | specification part of 2nd Example. The block diagram of the surface specific part and phase angle specific part of 3rd Example. The timing chart which shows operation | movement of the phase angle specific | specification part of 3rd Example. It is explanatory drawing of the voltage detection part of 3rd Example.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

(Image forming device)
An electrophotographic image forming apparatus 1 in this embodiment will be described. FIG. 1 is a cross-sectional view of an image forming apparatus 1 according to the first embodiment. The image forming apparatus 1 includes an optical scanning device 2 (2Y, 2M, 2C, 2K), an image control unit 5, an image reading unit 500, an image forming unit 503 including a photosensitive drum (photosensitive member) 25, a fixing unit 504, and a paper feed. / Conveyance unit 505. The image reading unit 500 illuminates a document placed on a document table, optically reads the image of the document, and converts the read image into image data (electrical signal). The image control unit 5 receives the image data from the image reading unit 500 and converts the received image data into an image signal. The image control unit 5 transmits an image signal to the optical scanning device 2 and controls light emission of the optical scanning device 2.

  The image forming unit 503 includes four image forming stations P (PY, PM, PC, PK). The four image forming stations P include yellow (Y), magenta (M), cyan (C) and black (C) along the rotation direction indicated by an arrow R2 of an endless intermediate transfer belt (hereinafter referred to as an intermediate transfer member) 511. K). Each of the image forming stations P includes a photosensitive drum 25 (25Y, 25M, 25C, 25K) as an image carrier that rotates in a direction indicated by an arrow R1. Around the photosensitive drum 25, along the rotation direction R1, a charger (charging means) 3, an optical scanning device 2, a developing device (developing means) 4, a primary transfer member 6 (6Y, 6M, 6C, 6K) and Cleaning devices 7 (7Y, 7M, 7C, 7K) are arranged.

  The charger 3 (3Y, 3M, 3C, 3K) uniformly charges the surface of the rotating photosensitive drum 25 (25Y, 25M, 25C, 25K). The optical scanning device 2 (2Y, 2M, 2C, 2K) emits a light beam modulated according to an image signal, and forms an electrostatic latent image on the surface of the photosensitive drum 25 (25Y, 25M, 25C, 25K). To do. The developing device 4 (4Y, 4M, 4C, 4K) develops the electrostatic latent image formed on the photosensitive drum 25 (25Y, 25M, 25C, 25K) into a toner image with each color toner (developer). To do. The primary transfer members 6 (6Y, 6M, 6C, and 6K) sequentially transfer the toner images on the photosensitive drums 25 (25Y, 25M, 25C, and 25K) sequentially onto the intermediate transfer member 511 and superimpose them. The cleaning device 7 (7Y, 7M, 7C, 7K) collects the toner remaining on the photosensitive drum 25 (25Y, 25M, 25C, 25K) after the primary transfer.

  A recording medium (hereinafter referred to as a sheet) S is conveyed from the paper feed cassette 508 or the manual feed tray 509 of the paper feed / conveyance unit 505 to the secondary transfer roller 510. The secondary transfer roller 510 secondary-transfers the toner images on the intermediate transfer member 511 onto the sheet S at once. The sheet S on which the toner image is transferred is conveyed to the fixing unit 504. The fixing unit 504 heats and pressurizes the sheet S, melts the toner, and fixes the toner image on the sheet S. As a result, a full color image is formed on the sheet S. The sheet S on which the image is formed is discharged to a discharge tray 512.

  The optical scanning device 2 (2Y, 2M, 2C, 2K) sequentially starts emitting light beams of magenta, cyan, and black images respectively from the emission start timing of the light beam of the yellow image. By controlling the emission start timing of the optical scanning device 2 in the sub-scanning direction, a full color toner image without color misregistration is transferred onto the intermediate transfer member 511.

(Optical scanning device)
FIG. 2 is an explanatory diagram of the optical scanning device 2 in the first embodiment. The optical scanning device 2 includes a laser control unit 11, a semiconductor laser (light source) 12, a collimator lens 13, a cylindrical lens 14, a motor 15, an fθ lens 17, a reflection mirror 18, a condenser lens (hereinafter referred to as a BD lens) 19, and the like. It has a beam detector (hereinafter referred to as BD) 20. The motor 15 has a rotor 15b. The rotary polygon mirror 15a rotates integrally with the rotor 15b. In the present embodiment, the image control unit 5 is provided in the main body of the image forming apparatus 1 outside the optical scanning device 2. The image control unit 5 and the optical scanning device 2 are electrically connected. The image control unit 5 may be provided in the optical scanning device 2. Laser light (hereinafter referred to as a light beam) L emitted from the semiconductor laser 12 passes through the collimating lens 13 and the cylindrical lens 14 and reaches the rotary polygon mirror 15a. The light beam L1 deflected by the rotary polygon mirror 15a enters the BD 20 via the fθ lens 17 and the BD lens 19 in the non-image region. When the BD 20 receives the light beam L1, the BD 20 outputs a beam detection signal (hereinafter referred to as a BD signal) 21 for making the image writing position in the main scanning direction indicated by the arrow X constant. The light beam L2 emitted from the semiconductor laser 12 based on the BD signal 21 scans the photosensitive drum 25 in the main scanning direction X via the fθ lens 17 and the reflection mirror 18 in the image region, and thereby the electrostatic latent image. Form. The semiconductor laser 12 may emit a plurality of light beams.

  The surface specifying unit (specifying unit) 31 is provided in the laser control unit 11. The surface specifying unit 31 outputs a reference surface signal 41 based on a rotation detection signal (hereinafter referred to as an FG signal) 22 output from a hall element (FG sensor) 16 provided in the motor 15.

(motor)
FIG. 3 is an explanatory diagram of the motor 15 according to the first embodiment. FIG. 3A is a cross-sectional view of the motor 15. The motor (deflecting means) 15 is a 3-phase 6-pole brushless DC motor. The number of phases and the number of poles of the motor 15 are not limited to these. The rotary polygon mirror 15a has four reflecting surfaces (deflection surfaces). The number of reflecting surfaces of the rotary polygon mirror 15a is not limited to four, and may be three, five, six, or the like.

  The rotary polygon mirror 15a and the rotor 15b are integrally fixed by a motor shaft 81. These are collectively referred to as the rotor portion. A magnet (permanent magnet) 15d in which six sets of magnetic poles are arranged is mounted on the inner peripheral surface of the rotor 15b shown by a broken line in FIG. For convenience of explanation, in FIG. 3A, the position of the rotor 15b with respect to the motor control board 15e is drawn at a position higher than the actual position. The motor bearing 80 rotatably supports the motor shaft 81 fixed to the rotor 15b. The winding 15c is formed by connecting three slots (coils). The three slots (coils) are arranged on the motor control board 15e so as to drive a three-phase current. Only one Hall element 16 is shown in FIG. However, in practice, as shown in FIG. 3B, the same number of Hall elements 16a, 16b and 16c as the number of slots (3) of the winding 15c are arranged.

  FIG. 3B is a diagram showing the winding 15c, the magnet 15d, and the Hall element (rotational position detecting means) 16 (16a, 16b, 16c). FIG. 3C is a time chart showing the magnet 15d, the output of the Hall element 16a, and the FG signal 22 when the rotor 15b rotates clockwise. The hall element (rotational position detecting means) 16a converts a magnetic flux change generated with the rotation of the rotor 15b into an electrical signal, and generates a (+) output indicated by a solid line and a (−) output indicated by a broken line. An FG signal (rotational position detection signal) 22 shown in FIG. 3C is obtained from the differential output of the Hall element 16a. The FG signal 22 is generated from the output of any one of the plurality of Hall elements 16a, 16b, and 16c. Therefore, in the following description, any one of the plurality of Hall elements 16a, 16b and 16c will be described as the Hall element 16. In the present embodiment, the Hall element 16 is used as the rotational position detecting means. However, instead of the Hall element 16, the FG signal 22 may be generated using a magnetic pattern or a rectangular detection pattern for detecting a change in magnetic flux generated as the rotor 15b rotates.

(Surface identification part)
FIG. 4 is a block diagram of the surface specifying unit 31 and the image control unit 5 of the first embodiment. When the motor driver 45 receives the motor activation signal 43 output from the motor control unit 44 provided in the image control unit 5, the motor driver 45 rotates the motor 15. When the motor 15 rotates, the Hall element 16 outputs an FG signal 22. The voltage detection unit (voltage detection means) 33 detects the voltage Vcc of the power supply 46 for supplying the drive current Id to the motor 15 via the motor driver 45. The voltage detector 33 may detect the drive current Id output from the motor driver 45 to the motor 15 and obtain the voltage Vcc applied to the motor 15. The voltage detection unit 33 includes a threshold voltage generation unit 54 (FIG. 12A) that outputs a preset threshold voltage Vth. The voltage detector 33 outputs a permission signal (voltage detection signal) 34 as a detection result of the voltage Vcc. The voltage detector 33 outputs a permission signal 34 when the voltage Vcc is larger than a preset threshold voltage Vth. That is, the voltage detector 33 outputs the permission signal 34 when the amount of change in the voltage Vcc is within a preset range.

  The FG cycle measuring unit 32 measures the cycles PT1 to PT6 of the FG signal 22 and outputs FG cycle data 35. In this embodiment, six FG signals 22 are output by one rotation of the motor 15. That is, there are six periods PT1 to PT6 per one rotation of the motor 15. However, the number of cycles of the FG signal 22 during one rotation of the motor 15 is not limited to 6, and may be 5 or 7 depending on the number of magnetic pole pairs of the magnet 15d. . The phase angle specifying unit 36 obtains cycle ratio data 49 from the FG cycle data 35 of the FG cycle measuring unit 32. When the phase angle specifying unit 36 receives the permission signal 34 from the voltage detection unit 33, the pattern of the FG cycle ratio data (detection data) 49 and the reference cycle ratio data (reference data) 38 of the data storage unit (storage unit) 37. Matching (hereinafter referred to as collation) is performed. The phase angle specifying unit 36 outputs a phase angle signal 39 at the timing when the cycle ratio data 49 matches the reference cycle ratio data 38. The reference surface signal generation unit 40 generates a reference surface signal 41 based on the phase angle signal 39 output from the phase angle specifying unit 36 and the phase data 48 stored in the data storage unit 37.

  The data storage unit 37 is composed of, for example, one EEPROM. The data storage unit 37 is connected to the phase angle specifying unit 36 and the reference plane signal generation unit 40 through a single serial interface. The EEPROM stores in advance the cycle data (reference cycle ratio data 38) of the FG signal 22 for one rotation of the motor 15 and the phase difference data (phase data 48) between the phase angle signal 39 and the BD signal 21. The reference cycle ratio data 38 and the phase data 48 are measured in advance at a factory or the like. A method for generating the reference period ratio data 38 and the phase data 48 will be described later.

  The surface tilt correction unit 42 provided in the image control unit 5 controls the exposure amount for each reflection surface of the rotary polygon mirror 15a based on the reference surface signal 41 output from the reference surface signal generation unit 40, thereby causing the surface tilt. Make corrections. The reflecting surface of the rotating polygon mirror 15a has a different surface tilt amount for each reflecting surface due to the inclination of the reflecting surface and the eccentricity or inclination of the rotation axis of the rotating polygon mirror 15a. Therefore, the reflecting surface of the rotary polygon mirror 15a is specified, the image data is corrected for each reflecting surface, and the surface tilt amount is corrected.

  FIG. 5 is a timing chart showing the operation of the surface specifying unit 31 of the first embodiment. The motor 15 starts to rotate in response to the motor activation signal 43 from the motor control unit 44. When the motor 15 rotates, the Hall element 16 outputs an FG signal 22. The FG cycle measuring unit 32 sequentially measures the cycles PT1, PT2, PT3, PT4, PT5, and PT6 of the FG signal 22, and sequentially outputs FG cycle data 35 as shown in FIG. The permission signal 34 is generated by the voltage detection unit 33 based on the voltage Vcc of the power supply 46. The phase angle signal 39 is output from the phase angle specifying unit 36 at the timing when the cycle ratio data 49 obtained from the FG cycle data 35 and the reference cycle ratio data 38 coincide. The reference cycle ratio data 38 indicates the ratio of the cycles PTu1, PTu2, PTu3, PTu4, PTu5, and PTu6 of the FG signal 22 with respect to one rotation cycle PT0 of the motor 15. In FIG. 5, PT5 to PT4 of the FG cycle data 35 coincide with the reference cycle ratio data 38, and the phase angle signal 39 is output. A verification method in the phase angle specifying unit 36 will be described later.

  The reference plane signal generation unit 40 outputs the reference plane signal 41 based on the phase data 48 stored in the data storage unit 37 with the rising edge of the phase angle signal 39 as a starting point. The phase data 48 is a value obtained by using the phase angle signal 39, the BD signal 21, and the phase difference as time.

  Actually, in the rotational direction of the motor 15, the magnetizing strength or magnetizing position of the magnet 15d arranged on the inner peripheral surface of the rotor 15b varies, and therefore the period PT1 to PT6 of the FG signal 22 is about 1%. Variation occurs. In addition, due to the assembly error of the motor 15, the distance between the magnet 15d and the Hall element 16 varies, and therefore the periods PT1 to PT6 of the FG signal 22 vary. As a result, the periods of the plurality of FG signals 22 generated in one rotation period PT0 of the motor 15 are not constant. Therefore, using the variation of the periods PT1 to PT6 of the FG signal 22, light is generated based on the relative positional relationship between the plurality of sets of magnetic poles (S pole and N pole) of the magnet 15d and the plurality of reflecting surfaces of the rotary polygon mirror 15a. The reflecting surface on which the beam L2 is incident is specified.

  However, since the periods PT1 to PT6 of the FG signal 22 are time data, they change according to the rotation speed of the motor 15. Therefore, it is necessary to measure the periods PT1 to PT6 of the FG signal 22 in a state where the motor 15 is stably rotating at the target rotation speed. In general, after the motor 15 is raised to the target rotational speed by the FG signal 22, the rotary polygon mirror 15a is stably rotated at the target rotational speed by the BD signal 21. When measurement of the periods PT1 to PT6 of the FG signal 22 is started after determining that the motor 15 is stably rotating at the target rotation speed based on the FG signal 22, the rotation of the rotary polygon mirror 15a starts from the start of rotation of the motor 15. The time until the reflecting surface is specified becomes longer. Therefore, in this embodiment, the reflecting surface of the rotary polygon mirror 15a is specified based on the ratio of the periods PT1 to PT6 of the FG signal 22 to the one rotation period PT0 of the motor 15 (hereinafter referred to as FG period ratio). The FG cycle ratio is theoretically constant regardless of the rotation speed of the motor 15. Therefore, by using the FG cycle ratio, the specific control operation of the reflecting surface of the rotary polygon mirror 15a can be started immediately before the rotation speed of the motor 15 reaches the target rotation speed. Therefore, it is possible to shorten the time from the start of the rotation of the motor 15 until the reflection surface of the rotary polygon mirror 15a is specified.

  However, there is a possibility that a measurement error of the FG signal 22 may occur due to noise flowing into the Hall element 16 that generates the FG signal 22 when the motor 15 is started. FIG. 6 is a diagram showing the FG cycle ratio and the voltage Vcc of the power supply 46 when the motor 15 is started. FIG. 6A is a diagram illustrating the behavior of the FG cycle ratio when the motor 15 is started. Since six sets of magnets (permanent magnets) 15d of magnetic poles (S pole and N pole) are arranged on the inner peripheral surface of the rotor 15b, six FG signals 22 are output during one rotation of the motor 15. Six FG periods PT1 to PT6 are generated per one rotation of the motor 15. The rotary polygon mirror 15a has four reflecting surfaces. In FIG. 6A, FG cycle ratios RP1, RP2, RP3, RP4, RP5, and RP6 represent ratios of FG cycles PT1 to PT6 with respect to one rotation cycle PT0 of the motor 15. That is, RP1 = PT1 / PT0, RP2 = PT2 / PT0, RP3 = PT3 / PT0, RP4 = PT4 / PT0, RP5 = PT5 / PT0 and RP6 = PT6 / PT0. FG cycle ratios RP1, RP2, RP3, RP4, RP5 and RP6 are ideally 1/6 (= 0.166...). However, in practice, the ratios RP1 to RP6 of the FG cycle differ due to variations in the magnetization intensity or magnetization position of the magnet 15d. In this embodiment, the reflecting surface of the rotary polygon mirror 15a is specified based on the difference in the ratios RP1 to RP6 of the FG cycle. However, as shown in FIG. 6A, it can be seen that the fluctuation of the FG cycle ratio is large in the section indicated by the arrow A from the start of the motor 15 to about 0.600 seconds.

  On the other hand, FIG. 6B is a diagram showing a change in the voltage Vcc of the power supply 46 when the motor 15 is started. The fv output is a voltage value obtained by converting the frequency of the FG signal 22 into a voltage. That is, the fv output increases as the rotation speed of the motor 15 increases. As can be seen from the fv output in FIG. 6B, the voltage Vcc applied from the power source 46 to the motor 15 is reduced from when the motor 15 is started until the rotational speed of the motor 15 is stabilized. The voltage Vcc of the power source 46 decreases in the section indicated by the arrow A from the start of the motor 15 to about 0.600 seconds. From this, it can be seen that the fluctuation of the FG cycle ratio is large in the section A where the voltage Vcc of the power supply 46 is reduced.

  Therefore, in this embodiment, when the voltage Vcc recovers after the section A in which the voltage Vcc of the power supply 46 is decreasing, the FG cycle data 35 of the FG cycle measuring unit 32 and the reference cycle ratio of the data storage unit 37 are recovered. Collation with the data 38 is started. Thereby, the time from the start of the motor 15 to the specification of the reflecting surface of the rotary polygon mirror 15a can be shortened.

(Generation method of reference period ratio data and phase data)
FIG. 7 is a block diagram of a configuration for generating the reference period ratio data 38 and the phase data 48. The reference cycle ratio data 38 and the phase data 48 are generated in advance at a factory or the like and stored in the data storage unit 37. A portion surrounded by a broken line is a tool 100 that generates the reference period ratio data 38 and the phase data 48 when the optical scanning device 2 is assembled. The tool 100 includes a tool control unit 101, an FG-BD phase measurement unit 103, and a tool FG measurement unit (rotational position signal measurement unit) 104. The tool 100 is arranged with respect to the optical scanning device 2 when generating the reference period ratio data 38 and the phase data 48 in a factory or the like before shipping the image forming apparatus 1. The tool 100 is removed from the optical scanning device 2 after generating the reference period ratio data 38 and the phase data 48. In this way, the optical scanning device 2 can be manufactured.

  In order to generate the reference cycle ratio data 38 and the phase data 48, the tool control unit 101 outputs a motor activation signal 43 from the motor control unit 44 to rotate the motor 15. When the motor 15 rotates, the Hall element 16 outputs an FG signal 22. The FG signal 22 is input to the FG-BD phase measurement unit 103 and the tool FG measurement unit 104. The tool control unit 101 controls the laser control unit 11 provided in the optical scanning device 2 to emit the light beam L from the semiconductor laser 12. The light beam L emitted from the semiconductor laser 12 is deflected by the rotary polygon mirror 15a. The light beam L1 deflected by the rotating polygon mirror 15a in the non-image area is incident on the BD 20 via the BD lens 19. When receiving the light beam L1, the BD 20 outputs a BD signal 21. The BD signal 21 is input to the FG-BD phase measurement unit 103. The FG-BD phase measurement unit 103 generates a phase detection signal 105 based on the FG signal 22 and the BD signal 21. The phase detection signal 105 is input to the tool FG measurement unit 104. The tool FG measurement unit 104 measures the FG cycle in order from the FG signal 22 synchronized with the phase detection signal 105.

  A method for generating the phase detection signal 105 by the FG-BD phase measurement unit 103 will be described with reference to FIG. FIG. 8 is a timing chart showing the operation of the FG-BD phase measurement unit 103. In this embodiment, six FG signals 22 are output in one rotation period PT0 of the motor 15. In the present embodiment, since the rotary polygon mirror 15a has four reflecting surfaces, four BD signals 21 are output in one rotation period PT0 of the motor 15. The FG-BD phase measurement unit 103 generates a phase difference between the FG signal 22 and the BD signal 21. As shown in FIG. 8, a plurality of phase differences Pd1, Pd2, Pd3, Pd4, Pd5, and Pd6 are obtained as the phase differences between the FG signal 22 and the BD signal 21. If the phase time corresponding to the phase difference is too short, the phase relationship may be reversed due to the jitter of the FG signal 22, which is not appropriate as a reference phase difference. In addition, if the phase time corresponding to the phase difference is too long, the data length of the data storage unit 37 becomes long, so that it is not appropriate as a reference phase difference. Therefore, in this embodiment, the FG-BD phase measurement unit 103 sets the phase time ΔFG-BD within a predetermined range among the phase times corresponding to the plurality of phase differences Pd1, Pd2, Pd3, Pd4, Pd5, and Pd6. The corresponding phase difference Pd1 is determined as the reference phase difference. The FG-BD phase measurement unit 103 generates a phase detection signal 105 based on the reference phase difference Pd1. The FG-BD phase measurement unit 103 outputs a phase detection signal 105 to the tool FG measurement unit 104. Further, the FG-BD phase measurement unit 103 outputs the phase time ΔFG-BD to the tool control unit 101. The tool control unit 101 generates phase data 48 based on the phase time ΔFG-BD. The tool control unit 101 stores the phase data 48 in the data storage unit 37.

  The tool FG measurement unit 104 measures the periods PTu1, PTu2, PTu3, PTu4, PTu5, and PTu6 of the FG signal 22 in one rotation period PT0 of the motor 15 in order from the FG signal 22 synchronized with the phase detection signal 105. The tool FG measurement unit 104 outputs the cycles PTu1, PTu2, PTu3, PTu4, PTu5, and PTu6 of the FG signal 22 to the tool control unit 101 as reference FG cycle data. The tool control unit 101 generates reference cycle ratio data 38 from the cycles PTu1, PTu2, PTu3, PTu4, PTu5, and PTu6 as reference FG cycle data. The reference cycle ratio data 38 is a ratio of the cycles PTu1, PTu2, PTu3, PTu4, PTu5 and PTu6 of the FG signal 22 with respect to one rotation cycle PT0 of the motor 15. The reference cycle ratio data 38 includes reference FG cycle ratios RPu1, RPu2, RPu3, RPu4, RPu5, and RPu6. One rotation period PT0 is the sum of periods PTu1, PTu2, PTu3, PTu4, PTu5, and PTu6. That is, PT0 = PTu1 + PTu2 + PTu3 + PTu4 + PTu5 + PTu6. The reference FG cycle ratio is obtained from RPu1 = PTu1 / PT0, RPu2 = PTu2 / PT0, RPu3 = PTu3 / PT0, RPu4 = PTu4 / PT0, RPu5 = PTu5 / PT0 and RPu6 = PTu6 / PT0. The tool control unit 101 stores the reference cycle ratio data 38 in the data storage unit 37.

  FIG. 9 is a diagram showing the reference cycle ratio data 38. The horizontal axis represents the reference FG cycle data. In the reference FG cycle data, the cycles PTu1, PTu2, PTu3, PTu4, PTu5 and PTu6 of the FG signal 22 are arranged in order starting from the phase detection signal 105 shown in FIG. The vertical axis represents the reference FG cycle ratio (reference value). The reference FG cycle ratios RPu1, RPu2, RPu3, RPu4, RPu5, and RPu6 are ideally 1/6 (= 0.166...). However, in practice, in the rotation direction of the motor 15, the magnetizing strength or the magnetizing position of the magnet 15d arranged on the inner peripheral surface of the rotor 15b varies, so that the cycle of the FG signal 22 varies. In addition, since the distance between the magnet 15d and the Hall element 16 varies due to the assembly error of the motor 15, the period of the FG signal 22 varies. As a result, a plurality of FG signals 22 generated in one rotation period PT0 of the motor 15 are not constant. Therefore, the reference FG cycle ratios RPu1, RPu2, RPu3, RPu4, RPu5, and RPu6 vary from 1/6 (= 0.166...) Of the ideal value.

  In the present embodiment, the light beam L2 is based on the relative positions of the plurality of sets of magnetic poles (S pole and N pole) of the magnet 15d and the plurality of reflecting surfaces of the rotary polygon mirror 15a using the variation of the reference FG cycle ratio. Specifies the reflective surface on which the light enters. The surface tilt correction unit 42 of the image control unit 5 includes a first reflection surface, a second reflection surface, a third reflection surface, and a fourth reflection surface of the rotary polygon mirror 15a that are sequentially arranged in the direction opposite to the rotation direction of the rotary polygon mirror 15a. Each surface has a surface tilt correction value corresponding to the surface. The reference period ratio data 38 and the phase data 48 are set so that the surface tilt correction unit 42 can identify the first reflecting surface of the rotary polygon mirror 15a.

  FIG. 10 is a flowchart showing the generation control operation of the reference period ratio data 38 and the phase data 48 executed by the tool 100. The tool 100 executes a generation control operation of the reference cycle ratio data 38 and the phase data 48 according to a program stored in the ROM 106 provided in the tool 100. When the generation control operation of the reference cycle ratio data 38 and the phase data 48 is started, the tool control unit 101 outputs a motor start signal 43 from the motor control unit 44 and rotates the motor 15 at the target rotation speed (S101). . When the motor 15 rotates, the Hall element 16 outputs the FG signal 22 (S102). The tool control unit 101 controls the laser control unit 11 to start emission of the light beam L from the semiconductor laser 12 (S103). When receiving the light beam L1, the BD 20 outputs a BD signal 21 (S104). The FG signal 22 and the BD signal 21 are input to the FG-BD phase measurement unit 103. The FG-BD phase measurement unit 103 generates the phase detection signal 105 from the phase relationship between the FG signal 22 and the BD signal 21, and measures the phase time ΔFG-BD between the FG signal 22 and the BD signal 21 (S105). The phase time ΔFG-BD is input to the tool control unit 101. The phase detection signal 105 is input to the tool FG measurement unit 104. The tool FG measurement unit 104 measures PTu2, PTu3, PTu4, PTu5, and PTu6 in order from the period PTu1 of the FG signal 22 at the timing of receiving the phase detection signal 105 (S106). Periods PTu1, PTu2, PTu3, PTu4, PTu5 and PTu6 in one rotation period PT0 of the motor 15 are input to the tool control unit 101 as reference FG period data. The tool control unit 101 generates reference cycle ratio data 38 and phase data 48 based on the reference FG cycle data of the tool FG measurement unit 104 and the phase time ΔFG-BD of the FG-BD phase measurement unit 103 (S107). The tool control unit 101 stores the reference cycle ratio data 38 and the phase data 48 in the data storage unit 37 (S108). The tool control unit 101 controls the motor control unit 44 and the laser control unit 11 to stop the rotation of the motor 15 and stop the emission of the light beam L from the semiconductor laser 12 (S109). The tool 100 ends the generation control operation of the reference cycle ratio data 38 and the phase data 48.

(Verification method by phase angle identification part)
Next, the collation method by the phase angle specific | specification part 36 is demonstrated using FIG. FIG. 11 is a diagram showing the FG cycle ratio and deviation with respect to the FG cycle data 35. FIG. 11A is a diagram showing the FG cycle ratio and deviation when the FG cycle data 35 is PT1 to PT6. FIG. 11B is a diagram showing the FG cycle ratio and deviation when the FG cycle data 35 is PT2 to PT1. FIG. 11C is a diagram showing the FG cycle ratio and deviation when the FG cycle data 35 is PT3 to PT2. FIG. 11D is a diagram showing the FG cycle ratio and deviation when the FG cycle data 35 is PT4 to PT3. FIG. 11E is a diagram showing the FG cycle ratio and deviation when the FG cycle data 35 is PT5 to PT1. FIG. 11F is a diagram showing the FG cycle ratio and deviation when the FG cycle data 35 is PT6 to PT5. As shown in FIG. 11, the head of the FG cycle data 35 changes in the order of the FG cycles PT1, PT2, PT3, PT4, PT5, and PT6.

  A broken line in FIG. 11 indicates the reference cycle ratio data 38 stored in the data storage unit 37. A solid line in FIG. 11 indicates period ratio data 49 obtained from the FG period data 35. The period ratio data 49 is a ratio of the periods PT1, PT2, PT3, PT4, PT5, and PT6 of the FG signal 22 with respect to one rotation period PT0 of the motor 15. The cycle ratio data 49 includes FG cycle ratios RP1, RP2, RP3, RP4, RP5 and RP6. One rotation period PT0 is the sum of periods PT1, PT2, PT3, PT4, PT5, and PT6. That is, PT0 = PT1 + PT2 + PT3 + PT4 + PT5 + PT6. The FG cycle ratio is obtained from RP1 = PT1 / PT0, RP2 = PT2 / PT0, RP3 = PT3 / PT0, RP4 = PT4 / PT0, RP5 = PT5 / PT0 and RP6 = PT6 / PT0. The deviation represents the ratio of the period ratio data 49 to the reference period ratio data 38. Therefore, when the deviation is 1, the cycle ratio data 49 is the same as the reference cycle ratio data 38. A one-dot chain line in FIG. 11 indicates a threshold value for determining whether or not the period ratio data 49 matches the reference period ratio data 38. The threshold is set to ± 0.5%. The deviation of the period ratio data 49 from the reference period ratio data 38 is indicated by *.

  The phase angle specifying unit 36 collates the period ratio data 49 sequentially obtained from the FG period data 35 with the reference period ratio data 38 as shown in FIGS. 11 (a) to 11 (f). As shown in FIG. 11E, the deviation of the period ratio data 49 obtained from the FG period data 35 starting from the period PT5 is within the threshold range. Therefore, it is determined that the cycle ratio data 49 obtained from the FG cycle data 35 starting from the cycle PT5 matches the reference cycle ratio data 38. Therefore, the phase angle specifying unit 36 outputs the phase angle signal 39 corresponding to the period PT5.

(Operation of voltage detector)
FIG. 12 is an explanatory diagram of the voltage detection unit 33 of the first embodiment. FIG. 12A is a block diagram of the voltage detection unit 33. The voltage detection unit 33 includes a level shifter (level shift circuit) 51, a low-pass filter (hereinafter referred to as LPF) 52, a comparator 53, and a threshold voltage generation unit 54. The voltage Vcc of the power supply 46 of the motor 15 is input to the level shifter 51. The level shifter 51 functions as an amplifier that converts the voltage Vcc into a signal 55 that swings between the ground GND and a predetermined DC voltage. The LPF 52 decreases the frequency component higher than a predetermined cutoff frequency in the signal 55 in order to remove the noise component of the voltage Vcc, and outputs a signal 56. When the voltage detection unit 33 detects the drive current Id output from the motor driver 45 to the motor 15, for example, a predetermined value of the LPF 52 is removed so as to remove the ripple of the drive current Id when the motor 15 is chopper-controlled. The cutoff frequency is set. The threshold voltage generator 54 outputs a preset threshold voltage Vth. The comparator 53 compares the signal 56 output from the LPF 52 with the threshold voltage Vth output from the threshold voltage generation unit 54, and outputs a permission signal 34.

  FIG. 12B is a timing chart showing the operation of the voltage detection unit 33. The level shifter 51 converts the voltage Vcc of the power supply 46 into a signal 55 that swings between the ground GND indicated by a broken line and a predetermined DC voltage. The LPF 52 removes the harmonic AC component of the signal 55 from the level shifter 51 and outputs a signal 56. The comparator 53 compares the signal 56 of the LPF 52 with the threshold voltage Vth and outputs a permission signal 34. The H (High) level of the permission signal 34 indicates a permission section in which collation of the period ratio data 49 and the reference period ratio data 38 by the phase angle specifying unit 36 is permitted. The L (Low) level of the permission signal 34 indicates a non-permission period in which the phase angle specifying unit 36 does not collate the period ratio data 49 with the reference period ratio data 38. Since the voltage detection unit 33 generates the permission signal 34 that permits the collation of the phase angle specifying unit 36, the surface specifying accuracy of the rotary polygon mirror 15a can be improved. In addition, by starting the comparison between the period ratio data 49 and the reference period ratio data 38 by the phase angle specifying unit 36 in response to the permission signal 34 of the voltage detection unit 33, the timing of the comparison can be advanced. Therefore, according to the present embodiment, in the rotation control of the motor 15 based on the FG signal, after the rotational speed of the motor 15 is stabilized, the surface of the rotary polygon mirror 15a is earlier than when the surface of the rotary polygon mirror 15a is specified. Surface identification can be performed. The voltage detection unit 33 detects the voltage Vcc applied to the motor driver 45 by the power supply 46, but the voltage detection unit 33 obtains the voltage Vcc based on the drive current Id of the motor driver 45 or other signals. Also good.

  According to the present embodiment, the reflecting surface of the rotary polygon mirror 15a can be accurately identified without using the reference mark detector or the BD 20. According to the present embodiment, the surface of the rotary polygon mirror 15a can be specified in a section where the fluctuation of the cycle of the FG signal 22 is small based on the change in the voltage Vcc of the motor 15 detected by the voltage detector 33. Therefore, the surface of the rotary polygon mirror 15a can be accurately identified at an earlier time.

  Next, a second embodiment will be described. In the second embodiment, the same structure as that of the first embodiment is denoted by the same reference numeral, and the description thereof is omitted. Since the image forming apparatus 1, the optical scanning device 2, and the motor 15 of the second embodiment are the same as those of the first embodiment, description thereof is omitted. The surface specifying unit (specifying means) 131 of the second embodiment is different from the surface specifying unit 31 of the first embodiment. Hereinafter, the surface specifying part 131 of the second embodiment will be described.

(Surface identification part)
FIG. 13 is a block diagram of the surface specifying unit 131 and the phase angle specifying unit 136 of the second embodiment. FIG. 13A shows the surface specifying unit 131 and the image control unit 5. When the motor driver 45 receives the motor activation signal 43 output from the motor control unit 44 provided in the image control unit 5, the motor driver 45 rotates the motor 15. When the motor 15 rotates, the Hall element 16 outputs an FG signal 22. The voltage detector 33 outputs a permission signal (voltage detection signal) 34 as a detection result of the voltage Vcc. The voltage detector 33 outputs a permission signal 34 when the voltage Vcc of the power supply 46 for supplying the drive current Id to the motor 15 via the motor driver 45 is larger than a preset threshold voltage Vth. That is, the voltage detector 33 outputs the permission signal 34 when the amount of change in the voltage Vcc is within a preset range. The voltage detector 33 may detect the drive current Id output from the motor driver 45 to the motor 15 and obtain the voltage Vcc applied to the motor 15. The time measuring unit 71 measures the time during which the permission signal 34 is output. The time measurement unit 71 outputs a time measurement signal 72 when the measured time is equal to or greater than a preset time (time set value).

  The FG cycle measuring unit 32 measures the cycles PT1 to PT6 of the FG signal 22 and outputs FG cycle data 35. The phase angle specifying unit 136 outputs a phase angle signal 39 based on the FG signal 22, the FG cycle data 35, the reference cycle ratio data 38, the time measurement signal 72 and the permission signal 34. The operation of the phase angle specifying unit 136 will be described later. The reference plane signal generation unit 40 generates a reference plane signal 41 based on the phase angle signal 39 output from the phase angle specifying unit 136 and the phase data 48 stored in the data storage unit 37. Note that the method for generating the reference period ratio data 38 and the phase data 48 is the same as that in the first embodiment, and a description thereof will be omitted. The surface tilt correction unit 42 performs surface tilt correction by controlling the exposure amount for each reflecting surface of the rotary polygon mirror 15 a based on the reference surface signal 41.

(Phase angle identification part)
Hereinafter, the phase angle specifying unit 136 will be described with reference to FIG. FIG. 13B is a block diagram of the phase angle specifying unit 136 and the time measuring unit 71 of the second embodiment. The phase angle specifying unit 136 includes a period verification unit 61, a period variation detection unit 63, an auxiliary signal generation unit 65, and a changeover switch 67. The period checking unit 61 obtains the period ratio data 49 from the FG period data 35 of the FG period measuring unit 32. The period collating unit 61 collates the period ratio data 49 with the reference period ratio data 38 in the data storage unit 37. The period matching unit 61 outputs a matching signal 62 at a timing when the period ratio data 49 matches the reference period ratio data 38. The verification signal 62 is output as the phase angle signal 39 from the phase angle specifying unit 136 via the changeover switch 67.

  The time measuring unit 71 has a preset time set value T0. The time measuring unit 71 starts measuring time T when the permission signal 34 becomes L level. The time T indicates the time of the non-permitted section where the permission signal 34 is not output. In the non-permission section, the phase angle specifying unit 36 does not collate the period ratio data 49 with the reference period ratio data 38. The time measurement unit 71 outputs a time measurement signal 72 when the measured time T is greater than the time set value T0. The time measurement signal 72 is input to the period variation detector 63.

  The period variation detector 63 generates an auxiliary operation signal 64 based on the time measurement signal 72 and the collation signal 62. The auxiliary operation signal 64 is input to the auxiliary signal generation unit 65. The output timing of the auxiliary operation signal 64 is in phase with the output timing of the verification signal 62. The auxiliary signal generation unit 65 generates an auxiliary signal 66 having the same phase as that of the verification signal 62 based on the FG signal 22 in a section where the auxiliary operation signal 64 is output. The auxiliary signal 66 is input to the changeover switch 67. In addition, the period variation detector 63 generates a variation detection signal 68 based on the permission signal 34 and the verification signal 62. The fluctuation detection signal 68 is input to the changeover switch 67. The changeover switch 67 switches between the collation signal 62 and the auxiliary signal 66 in accordance with the fluctuation detection signal 68. That is, the changeover switch 67 outputs the collation signal 62 or the auxiliary signal 66 as the phase angle signal 39 according to the fluctuation detection signal 68.

  FIG. 14 is a timing chart showing the operation of the phase angle specifying unit 136 of the second embodiment. The time measurement signal 72 is output from the time measurement unit 71 when the time T of the non-permission section where the permission signal 34 is not output is larger than the time set value T0. As shown in the part surrounded by the dotted line in FIG. 14, when the time T of the non-permission section where the permission signal 34 is not output is smaller than the time set value T0, the time measurement signal 72 is not output. The verification signal 62 is output from the cycle verification unit 61 at a timing when the cycle ratio data 49 obtained from the FG cycle data 35 of the FG cycle measurement unit 32 coincides with the reference cycle ratio data 38. The output timing of the verification signal 62 is the timing when the magnetic pole position is determined. On the other hand, when fluctuation occurs in the cycle of the FG signal 22, since the cycle ratio data 49 does not match the reference cycle ratio data 38, the verification signal 62 is not output as shown by the portion surrounded by the dotted line in FIG. .

  The auxiliary operation signal 64 is a signal that permits the operation of the auxiliary signal generation unit 65. The output of the auxiliary operation signal 64 is stopped when the time measurement signal 72 is output. When the verification signal 62 is output, the auxiliary operation signal 64 is output. The auxiliary signal 66 generated in the same phase as the verification signal 62 based on the auxiliary operation signal 64 and the FG signal 22 is output in a section in which the auxiliary operation signal 64 is output.

  The fluctuation detection signal 68 is output when the time T during which the permission signal 34 is not output is smaller than the time set value T0. The output of the fluctuation detection signal 68 is stopped when the collation signal 62 is output. The changeover switch 67 outputs the collation signal 62 as the phase angle signal 39 when the fluctuation detection signal 68 is not received. The changeover switch 67 outputs the auxiliary signal 66 as the phase angle signal 39 when receiving the fluctuation detection signal 68. That is, in the phase angle signal 39, the changeover switch 67 selects the auxiliary signal 66 in the interval in which the fluctuation detection signal 68 is output, and the changeover switch 67 selects the verification signal 62 in the interval in which the fluctuation detection signal 68 is not output. Is output.

  According to this embodiment, when the fluctuation of the cycle of the FG signal 22 due to the fluctuation of the rotation speed of the motor 15 is small, the output of the phase angle signal 39 generated before the fluctuation of the cycle of the FG signal 22 is held. Can do. Therefore, since it is not necessary to generate a new phase angle signal 39 based on the FG cycle data 35 again in a section where the fluctuation of the cycle of the FG signal 22 is small, the time required for specifying the surface of the rotary polygon mirror 15a is shortened. Can do.

  Next, a third embodiment will be described. In the third embodiment, the same structure as that of the first embodiment is denoted by the same reference numeral, and the description thereof is omitted. Since the image forming apparatus 1, the optical scanning device 2, and the motor 15 of the third embodiment are the same as those of the first embodiment, description thereof is omitted. The surface specifying unit (specifying means) 231 of the third embodiment is different from the surface specifying unit 31 of the first embodiment. Hereinafter, the surface specifying part 231 of the third embodiment will be described.

(Surface identification part)
FIG. 15 is a block diagram of the surface specifying unit 231 and the phase angle specifying unit 236 of the third embodiment. FIG. 15A shows the surface specifying unit 231 and the image control unit 5. When the motor driver 45 receives the motor activation signal 43 output from the motor control unit 44 provided in the image control unit 5, the motor driver 45 rotates the motor 15. When the motor 15 rotates, the Hall element 16 outputs an FG signal 22. The voltage detection unit (voltage detection unit) 233 functions as a fluctuation amount detection unit that detects the fluctuation amount of the voltage Vcc of the power supply 46 for supplying the drive current Id to the motor 15 via the motor driver 45. The voltage detector 233 detects the amount of fluctuation of the voltage Vcc by comparing the voltage Vcc with a plurality of preset threshold voltages. The voltage detection unit 233 outputs a first detection signal (voltage detection signal) 82 as a detection result of the voltage Vcc. Specifically, the voltage detection unit 233 outputs the H level of the first detection signal 82 when the voltage Vcc is greater than the first threshold voltage Vth1. The voltage detection unit 233 outputs the L level of the second detection signal 83 when the voltage Vcc is smaller than the second threshold voltage Vth2. The first detection signal 82 and the second detection signal 83 are input to the phase angle specifying unit 236. The voltage detector 33 may detect the drive current Id output from the motor driver 45 to the motor 15 and obtain the voltage Vcc applied to the motor 15. The operation of the voltage detection unit 233 will be described later.

  The FG cycle measuring unit 32 measures the cycles PT1 to PT6 of the FG signal 22 and outputs FG cycle data 35. The phase angle specifying unit 236 outputs a phase angle signal 39 based on the FG signal 22, the FG cycle data 35, the reference cycle ratio data 38, and a plurality of detection signals (first detection signal 82, second detection signal 83). The operation of the phase angle specifying unit 236 will be described later. The reference plane signal generation unit 40 generates a reference plane signal 41 based on the phase angle signal 39 output from the phase angle specifying unit 236 and the phase data 48 stored in the data storage unit 37. Note that the method for generating the reference period ratio data 38 and the phase data 48 is the same as that in the first embodiment, and a description thereof will be omitted. The surface tilt correction unit 42 performs surface tilt correction by controlling the exposure amount for each reflecting surface of the rotary polygon mirror 15 a based on the reference surface signal 41.

(Phase angle identification part)
Hereinafter, the phase angle specifying unit 236 will be described with reference to FIG. FIG. 15B is a block diagram of the phase angle specifying unit 236 and the voltage detection unit 233 according to the third embodiment. The phase angle specifying unit 236 of the third embodiment is the same as the phase angle specifying unit 136 of the second embodiment. Hereinafter, only different points will be described, and description of similar points will be omitted.

  FIG. 16 is a timing chart showing the operation of the phase angle specifying unit 236 of the third embodiment. The first detection signal 82 is output from the voltage detection unit 233 when the voltage Vcc is smaller than the first threshold voltage Vth1. The first detection signal 82 corresponds to the permission signal 34 of the second embodiment. The L level of the first detection signal 82 indicates a non-permitted section in which the phase angle specifying unit 36 does not collate the period ratio data 49 with the reference period ratio data 38. The second detection signal 83 is output from the voltage detection unit 233 when the voltage Vcc is smaller than the second threshold voltage Vth2. The second detection signal 83 corresponds to the time measurement signal 72 of the second embodiment. The output of the auxiliary operation signal 64 is stopped when the second detection signal 83 is output. When the verification signal 62 is output, the auxiliary operation signal 64 is output.

(Operation of voltage detector)
FIG. 17 is an explanatory diagram of the voltage detector 233 of the third embodiment. FIG. 17A is a block diagram of the voltage detection unit 233. The voltage detection unit 233 includes a level shifter 51, a first LPF 152, a first threshold voltage generation unit 154, a first comparator 153, a second LPF 252, a second threshold voltage generation unit 254, and a second comparator 253. The level shifter 51, the first LPF 152, the first threshold voltage generation unit 154, and the first comparator 153 are the same as the level shifter 51, the LPF 52, the threshold voltage generation unit 54, and the comparator 53 of the voltage detection unit 33 of the first embodiment. . The second LPF 252 has a cutoff frequency different from that of the first LPF 152. The voltage Vcc of the power supply 46 of the motor 15 is input to the level shifter 51. The level shifter 51 converts the voltage Vcc into a signal 55 that swings between the ground GND and a predetermined DC voltage. The first LPF 152 decreases the component of the signal 55 having a frequency higher than a predetermined cutoff frequency in order to remove the noise component of the voltage Vcc, and outputs a signal 156. The first threshold voltage generator 154 outputs a preset first threshold voltage Vth1. The first comparator 153 compares the signal 156 output from the first LPF 152 with the first threshold voltage Vth1 output from the first threshold voltage generator 154, and outputs a first detection signal 82. The second LPF 252 decreases the frequency component higher than the cutoff frequency different from the predetermined cutoff frequency of the first LPF 152 and outputs a signal 256. The second threshold voltage generation unit 254 outputs a second threshold voltage Vth2 that is different from the first threshold voltage Vth1. The second comparator 253 compares the signal 256 output from the second LPF 252 with the second threshold voltage Vth2 output from the second threshold voltage generator 254, and outputs a second detection signal 83.

  FIG. 17B is a time chart for explaining the operation of the voltage detection unit 233. Hereinafter, with reference to FIG. 17B, two voltage changes having different fluctuation amounts (amplitude amounts) of the voltage Vcc of the power supply 46 will be described as an example. The signal 55 of the level shifter 51 is input to the first LPF 152 and the second LPF 252. The frequency band of the first LPF 152 is set higher than the frequency band of the second LPF 252. The first threshold voltage Vth1 is set higher than the second threshold voltage Vth2. Therefore, the first detection signal 82 is output even when the fluctuation amount of the voltage Vcc of the power supply 46 is small, but the second detection signal 83 is not output when the fluctuation amount of the voltage Vcc is small. Thereby, the magnitude of the fluctuation amount of the voltage Vcc of the power supply 46 can be distinguished. For example, when the fluctuation amount of the voltage Vcc is large, it corresponds to the case where the motor 15 is started. A case where the amount of change in the voltage Vcc is small corresponds to a case where the rotational speed of the motor 15 is changed when the number of printed sheets is changed during the job.

  The phase angle specifying unit 236 performs the second implementation based on the first detection signal 82 corresponding to the permission signal 34 of the second embodiment and the second detection signal 83 corresponding to the time measurement signal 72 of the second embodiment. The same operation as in the example is performed, and the phase angle signal 39 is output.

  According to this embodiment, the voltage detector 233 can detect the fluctuation amount of the rotation speed of the motor 15, so that a high-speed clock for measuring the fluctuation time of the cycle of the FG signal 22 becomes unnecessary. Therefore, the circuit configuration for driving the motor 15 can be simplified.

  According to this embodiment, when the fluctuation of the cycle of the FG signal 22 due to the fluctuation of the rotation speed of the motor 15 is small, the output of the phase angle signal 39 generated before the fluctuation of the cycle of the FG signal 22 is held. Can do. Therefore, since it is not necessary to generate a new phase angle signal 39 based on the FG cycle data 35 again in a section where the fluctuation of the cycle of the FG signal 22 is small, the time required for specifying the surface of the rotary polygon mirror 15a is shortened. Can do.

  According to the present embodiment, it is possible to specify the phases of the plurality of reflecting surfaces of the rotating polygon mirror based on the detection result of the voltage applied to the motor that rotates the rotating polygon mirror. Therefore, the phases of the plurality of reflecting surfaces of the rotary polygon mirror can be accurately identified without using the reference mark detector or the BD sensor.

2 ... Optical scanning device 12 ... Semiconductor laser (light source)
15 ... Motor 15a ... Rotating polygon mirror 16 ... Hall element (rotating position detecting means)
22 ... FG signal (rotation position detection signal)
31, 131, 231... Surface identification part (identification means)
33, 233 ... Voltage detection unit (voltage detection means)
34 ... permission signal 82 ... first detection signal (permission signal)

Claims (9)

An optical scanning device,
A light source that emits a light beam;
A rotating polygon mirror having a plurality of reflecting surfaces for deflecting the light beam so that the light beam emitted from the light source scans the surface of the photosensitive member in the main scanning direction;
A motor for rotating the rotary polygon mirror;
Rotational position detection means for detecting a change in magnetic flux generated by rotation of the motor and generating a rotational position detection signal;
Voltage detection means for detecting a voltage applied to the motor and generating a permission signal;
Identification means for identifying phases of the plurality of reflecting surfaces of the rotary polygon mirror based on the rotational position detection signal and the permission signal;
An optical scanning device comprising:   The optical scanning device according to claim 1, wherein the specifying unit starts specifying the phases of the plurality of reflecting surfaces when receiving the permission signal.   The optical scanning device according to claim 1, wherein the voltage detection unit outputs the permission signal when the voltage applied to the motor is greater than a predetermined threshold voltage.   The identifying unit collates detection data generated based on the rotational position detection signal with reference data stored in a storage unit, and outputs a collation signal for identifying phases of the plurality of reflecting surfaces. The optical scanning device according to claim 1.   The optical scanning device according to claim 4, wherein when the time during which the permission signal is not output is smaller than a predetermined setting value, the specifying unit generates an auxiliary signal having the same phase as the verification signal. The voltage detection means outputs the permission signal when the voltage applied to the motor is greater than a first threshold voltage,
The identification means collates detection data generated based on the rotational position detection signal with reference data stored in a storage unit, and outputs a collation signal for identifying phases of the plurality of reflecting surfaces. ,
The said specific | specification means produces | generates the auxiliary signal of the same phase as the said collation signal, when the said voltage applied to the said motor is smaller than the 2nd threshold voltage smaller than the said 1st threshold voltage. 2. The optical scanning device according to 2. A photoreceptor,
Charging means for charging the photoreceptor;
The optical scanning device according to claim 1, which emits a light beam to form an electrostatic latent image on the surface of the photoreceptor.
Developing means for developing on the surface of the photoreceptor a toner image to be developed and transferred to the recording medium by developing the electrostatic latent image;
An image forming apparatus comprising: A light source that emits a light beam; and a rotary polygon mirror having a plurality of reflecting surfaces that deflect the light beam so that the light beam emitted from the light source scans on the surface of a photoreceptor in a main scanning direction; A motor for rotating the rotary polygon mirror; rotational position detecting means for detecting a change in magnetic flux generated by the rotation of the motor to generate a rotational position detection signal; and writing of the light beam to the photoconductor in the main scanning direction. A method of manufacturing an optical scanning device including a beam detector that outputs a beam detection signal for determining an emission start timing of the light beam from the light source based on the rotational position detection signal in order to make the position constant. ,
Arranging a tool having a phase measurement unit, a rotational position signal measurement unit and a control unit with respect to the optical scanning device;
Generating the rotational position detection signal by rotating the motor;
Generating reference data based on a plurality of cycles of the rotational position detection signal during one rotation of the motor;
Generating phase data representing a phase difference between the rotational position detection signal and the beam detection signal;
Storing the reference data and phase data in a storage unit;
Removing the tool from the optical scanning device;
A method comprising:   The method according to claim 8, wherein the reference data is a ratio of the plurality of cycles of the rotational position detection signal to one rotation cycle of the motor.

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