JP2018205382A - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: A dedicated sensor for specifying a reflection surface of a polygon mirror is required, and the configuration is complicated. An irradiation means for irradiating a laser beam, a rotary polygon mirror having a plurality of reflecting surfaces for reflecting light emitted from the irradiation means, a drive means for driving the rotary polygon mirror, and the rotation Light detecting means for detecting the laser light reflected by the polygon mirror and outputting a signal corresponding to the laser light, generating means for generating a signal corresponding to the rotational speed of the driving means, and a signal corresponding to the rotational speed Based on the speed detection means for detecting the rotational speed fluctuation of the driving means during one rotation of the rotary polygon mirror, the detection result by the light detection means, and the rotational speed fluctuation by the speed detection means, Control means for specifying the reflecting surface of the rotary polygon mirror. [Selection] Figure 3

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus that scan a surface to be scanned by deflecting laser light with a rotating polygon mirror.

  Conventionally, an image that forms an electrostatic latent image on a photosensitive drum by deflecting laser light emitted from a light source with an optical deflector such as a rotary polygon mirror (hereinafter also referred to as a polygon mirror) and scanning the photosensitive drum. Forming devices are known. Each reflective surface of the polygon mirror as an optical deflector may have a variation in accuracy for each surface such as surface tilt or mismatch of surface lengths due to the accuracy of cutting processing and the accuracy of attachment during manufacturing. As a result, there is a possibility that density unevenness, color unevenness, moire, etc. may occur in the image to be formed, and the image quality may be deteriorated.

  In order to suppress the deterioration in image quality caused by such variations, there is a technique for specifying the surface of the polygon mirror that is being scanned and electrically correcting the influence of the accuracy variation of the specified surface. There are several methods for specifying the surface of the polygon mirror. For example, in Patent Document 1, a dedicated index pulse is output for each pulse of the polygon mirror. A method is disclosed in which a polygon mirror surface is specified from a correspondence relationship between a predetermined polygon mirror surface and an index pulse.

JP-A-10-82963

  However, in the conventional method, a dedicated sensor for specifying the reflection surface of the polygon mirror is required, and the configuration is complicated.

  The invention according to the present application has been made in view of the situation as described above, and an object thereof is to specify a reflection surface of a polygon mirror even with a simple configuration.

  In order to achieve the above object, an irradiating means for irradiating laser light, a rotating polygon mirror having a plurality of reflecting surfaces for reflecting light emitted from the irradiating means, and a driving means for driving the rotating polygon mirror Detecting means for detecting the laser beam reflected by the rotary polygon mirror and outputting a signal corresponding to the laser beam; generating means for generating a signal corresponding to the rotational speed of the driving means; and the rotational speed On the basis of a signal corresponding to the speed, a speed detecting means for detecting a rotational speed fluctuation of the driving means during one rotation of the rotary polygon mirror, a detection result by the light detecting means, and the rotational speed fluctuation by the speed detecting means. And a control means for specifying the reflecting surface of the rotary polygon mirror.

  According to the configuration of the present invention, the reflection surface of the polygon motor can be specified even with a simple configuration.

1 is a schematic configuration diagram of an image forming apparatus. The schematic diagram which shows the state which irradiated the laser beam LB to the reflective surface of a polygon mirror. FIG. 3 is a control block diagram of the optical scanning device 101. The block diagram which shows the reflective surface specific means 311. FIG. 6 is a timing chart showing the specification of the reflecting surface 304. The flowchart which shows the specific operation | movement of the reflective surface 304. FIG. FIG. 3 is a control block diagram of the optical scanning device 101. The figure which shows the relationship between a phase voltage waveform and a rotational speed signal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the invention according to the scope of claims, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention.

(First embodiment)
[Image forming apparatus]
FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 includes an optical scanning device 101 as an optical scanning unit. The optical scanning device 101 scans the laser beam LB toward the photosensitive drum 103 as a photosensitive member charged by the charging roller. Thereby, an electrostatic latent image is formed on the photosensitive drum 103. The electrostatic latent image formed on the photosensitive drum 103 is visualized as a toner image (image) by the developing roller. An integrated process cartridge 105 including a charging roller, a photosensitive drum 103, a developing roller, a developer container for storing toner, and the like can be obtained. The process cartridge 105 is not limited to this configuration. For example, the cartridge including the photosensitive drum 103 and the cartridge including the developer container may be separated.

  The recording materials P stacked on the stacking plate 106 in the sheet feeding cassette are separated and fed one by one by the sheet feeding roller 107 and the separation pad 108. After the recording material P is fed, the recording material P is conveyed by the intermediate roller 109 and the conveying roller 110 to a transfer unit including the photosensitive drum 103 and the transfer roller 111. The toner image formed on the photosensitive drum 103 is transferred by the transfer roller 111 to the recording material P conveyed to the transfer unit. The recording material P to which the toner image has been transferred is conveyed to the fixing device 112 and is heated and fixed by the fixing device 112 so that the toner image is fixed to the recording material P. The recording material P on which the toner image is fixed is discharged to a discharge tray by a discharge roller 113.

[Optical scanning device]
The irradiation control of the laser beam LB by the optical scanning device 101 will be described with reference to FIGS. FIG. 2 is a schematic diagram showing a state in which the reflection surface (mirror surface) 304 of the polygon mirror 303 is irradiated with the laser beam LB. FIG. 3 is a control block diagram of the optical scanning device 101. For simplification of description, optical components such as a collimator lens and an fθ lens are not shown in FIGS.

  The laser beam generation unit 301 includes a light source 302 as an irradiation unit that irradiates the laser beam LB, a drive circuit (not shown) that drives the light source 302, and the like. As the light source 302, for example, a semiconductor laser is used. A polygon mirror 303 as a rotating polygon mirror reflects and deflects the laser beam LB emitted from the light source 302. The polygon mirror 303 rotates in the direction of the arrow R1 about the rotation shaft 315 by driving the polygon motor 308. The polygon mirror 303 has a plurality of (n-plane) reflection surfaces 304 that reflect the laser beam LB. For example, in this embodiment, it has four reflective surfaces.

  As shown in FIG. 2, the laser beam LB deflected by the reflecting surface 304 is repeatedly scanned in the main scanning direction in a scanning range longer than the length D1 of the photosensitive drum 103 in the main scanning direction. That is, the scanning line SL is scanned with the laser beam LB. The light receiving sensor 306 serving as a light detecting means is installed at a position where the laser beam LB is received before the laser beam LB scans on the photosensitive drum 103 in the scanning range, that is, upstream of the photosensitive drum 103 in the main scanning direction. ing. That is, the light receiving sensor 306 can also be called a BD sensor or a synchronization sensor. When the laser beam LB is received by the light receiving sensor 306, a BD (BEAM DETECT) signal is generated as a detection result. The generation of a BD signal that is a horizontal synchronization signal will be described later.

  The BD signal generation unit 305 includes a light receiving sensor 306 and a signal conversion unit 307. When receiving the laser beam LB, the light receiving sensor 306 outputs a light receiving signal to the signal conversion unit 307. The signal conversion unit 307 converts the received light signal into a rectangular wave BD signal and outputs the BD signal to the control unit 300. The BD signal output to the control unit 300 is used as a reference signal for the motor control unit 310, the reflection surface specifying unit 311, and the optical scanning control unit 313. In the present embodiment, the number of reflecting surfaces of the polygon mirror 303 is four, so that when the polygon mirror 303 makes one rotation, a BD signal is output four times.

  The polygon motor 308 is an outer rotor type brushless motor in which the polygon mirror 303 is integrally attached to the rotor. The polygon mirror 303 is rotationally driven based on a control signal generated by a motor control unit 310 in the control unit 300 described later. The polygon motor 308 is equipped with an FG signal generation means 309 and generates a pulse signal proportional to the rotational speed of the polygon motor 308. In the present embodiment, a configuration is used in which a change in the magnetic pole of the rotor magnet is detected by a Hall element, and a rectangular wave FG (FREQENCY GENERATOR) signal is output. The number of poles of the rotor magnet is 12. When the polygon motor 308 makes one revolution, the FG signal is output six times.

  The control means 300 is constituted by, for example, a CPU, a ROM that stores various programs and data necessary for the execution thereof, a microcomputer that is a RAM serving as a working memory, a peripheral circuit thereof, and the like. The control unit 300 includes a motor control unit 310, a reflection surface specifying unit 311, a reflection surface information storage unit 312, an optical scanning control unit 313, and a storage unit 314.

  The motor control unit 310 controls the rotational drive of the polygon motor 308. The motor control means 310 detects the period indicating the rotation speed by the rotation speed detection means 317 based on the BD signal when scanning with the laser light and based on the FG signal when not scanning the laser light. . The motor control unit 310 compares the cycle indicating the rotation speed detected by the rotation speed detection unit 317 with the commanded rotation speed in the motor control unit 310. Then, a control signal is output to control the rotational speed of the polygon motor 308 so as to follow the commanded rotational speed. For example, as a method for controlling the rotational speed, a voltage value applied to the polygon motor 308 is calculated using general PI (proportional integration) control, and is output as a control signal using pulse width modulation or the like.

  The reflecting surface specifying unit 311 specifies the reflecting surface 304 that reflects the laser beam LB based on the FG signal and the BD signal, which are information indicating the rotational speed of the polygon motor 308. In addition, each surface of the reflective surface 304 is shown as 1 surface-4 surfaces below. The reflecting surface specifying unit 311 includes a rotation phase detecting unit 316, and specifies the phase of the rotation cycle variation of the polygon motor 308 based on the FG signal. Then, the reflection surface 304 is specified by associating the phase of the rotation cycle fluctuation with the BD signal. Using the BD signal used as a reference of the laser beam LB and the FG signal that is a signal for detecting the speed of the polygon motor 308, the reflecting surface 304 can be specified using an existing configuration. That is, since the reflective surface 304 can be specified without adding a dedicated sensor for specifying the reflective surface and making the configuration complicated, an increase in cost can be suppressed. A detailed method for specifying the reflecting surface 304 of the polygon mirror 303 will be described later.

  The reflecting surface information storage unit 312 stores correction information for correcting variations in surface accuracy such as flatness and surface tilt of each reflecting surface 304 in association with the number of the reflecting surface. For example, before shipping the optical scanning device 101 to the factory, the laser beam LB is scanned while the polygon motor 308 is rotationally driven, and the reflection surface 304 is specified. Then, the surface accuracy is measured for each identified reflection surface number and stored as correction information. As an example of the correction information, information for correcting the shift amount between the scanning line length and the ideal length in the main scanning direction for each reflecting surface 304 and density unevenness due to the influence of surface tilt are corrected. Information etc. That is, the influence of the tilting is suppressed by correcting the irradiation position of the laser beam or correcting the light amount of the laser beam in accordance with such information.

  The light scanning control means 313 is a laser light generation means based on the reflection surface number specified by the reflection surface specification means 311, correction information stored in the reflection surface information storage means 312, and image data stored in the storage means 314. The laser beam LB scanned by 301 is controlled. For example, in order to correct the surface tilt amount for each reflecting surface 304, the light amount of the laser beam LB is corrected using the correction value stored in the reflecting surface information storage unit 312 and the density in the sub-scanning direction due to the effect of the surface tilting. Reduce unevenness. Note that a detailed description of a specific method of correcting the surface accuracy variation of the reflecting surface 304 is omitted in this embodiment.

[Specifying Method of Reflecting Surface 304]
A method for specifying the reflecting surface 304 will be described with reference to FIGS. FIG. 4 is a block diagram showing the reflecting surface specifying means 311. FIG. 5 is a timing chart showing the specification of the reflective surface 304. FIG. 6 is a flowchart showing the specific operation of the reflecting surface 304.

  In FIG. 4, 401 is an FG signal cycle detection unit, 402 is an FG signal phase number storage unit, 403 is an FG signal cycle storage unit, 404 is a rotation cycle variation specifying unit, and 405 is a reflecting surface information output unit. As described above, in this embodiment, the FG signal is input six times for one rotation of the polygon motor 308. In addition, the BD signal is input four times for one rotation of the polygon mirror 303. When the sequence for specifying the reflecting surface of the polygon mirror 303 starts, the FG signal cycle detection means 401 detects the cycle between the falling edges of the FG signal, that is, detects the rotational speed information of the polygon motor 308, and the FG signal cycle count. Output as a value. The FG signal cycle count value is, for example, a value obtained by counting a reference clock used for operating the control means 300 with a counter (not shown).

  The FG signal phase number storage unit 402 counts up the phase number each time a falling edge of the FG signal is detected, and assigns a phase number for the rotor position to the FG signal. Since FG signals are generated 6 times per rotation of the polygon motor 308, phase numbers 1 to 6 are repeatedly assigned. That is, by checking the FG signal phase number stored in the FG signal phase number storage unit 402, it is possible to determine in which phase the polygon motor 308 is rotationally driven.

  The FG signal cycle storage unit 403 stores the FG signal cycle count value output from the FG signal cycle detection unit 401 and the FG signal phase number output from the FG signal phase number storage unit 402 in association with each other. In this embodiment, since the polygon motor 308 generates FG signals 6 times per revolution, it holds six data for one revolution of the polygon motor 308. In addition, it is not restricted to hold | maintaining data of 1 rotation, It is good also as a structure which hold | maintains the FG signal period count value for several rotations, and takes an average value for every FG signal phase number.

  The rotation cycle variation specifying unit 404 detects the rotation cycle variation of the polygon motor 308 based on the data stored in the FG signal cycle storage unit 403 and specifies the rotation phase of the polygon motor 308. The polygon motor 308 is rotated once during one rotation of the polygon motor 308 due to the eccentric component of the stator and rotor shapes due to the influence of the processing accuracy of the manufacturing apparatus during manufacturing and the eccentric component of the magnetized state of the rotor magnet. Rotational speed fluctuation occurs. At the stage where the production of the polygon motor 308 is completed, the phase at which the rotation speed is increased and the phase at which the rotation speed is decreased are fixed. Therefore, when the polygon motor 308 is driven to rotate, fluctuations in rotational speed occur at the same phase. Rotational speed fluctuation that occurs in one cycle while the polygon motor 308 makes one rotation can be detected by performing comparison processing or arithmetic processing such as a filter on the FG signal cycle count value. In the present embodiment, as an example, by setting the FG signal phase number having the smallest FG signal cycle count value, that is, the fastest rotation speed of the polygon motor 308 as a phase that can be uniquely specified, the polygon motor 308 is rotated once. Rotational speed fluctuation that occurs in one cycle is detected. It should be noted that the FG signal cycle count value is not limited to the smallest value as long as the rotation cycle fluctuation that occurs in one cycle during one rotation of the polygon motor 308 can be detected uniquely.

  The reflecting surface information output unit 405 compares the phase number stored in the FG signal phase number storage unit 402 with the phase number specified by the rotation period variation specifying unit 404. When the falling edge of the BD signal is detected after determining that the phase numbers are the same, the surface number of the reflecting surface 304 is determined as one surface (reference surface), and the surface number of the reflecting surface 304 is output. Further, each time the polygon mirror 303 is driven to rotate and a falling edge of the BD signal is detected, the surface numbers of 1 surface → 2 surface → 3 surface → 4 surface → 1 surface and the reflective surface 304 are repeatedly output.

  Next, a method for specifying the reflecting surface will be described with reference to the timing chart of FIG. FIGS. 5A to 5E show the FG signal, the FG signal phase number, the FG signal cycle count value, the BD signal, and the surface number of the reflecting surface, respectively.

  FIG. 5A shows the FG signal. As described above, the FG signal is output six times during one rotation of the polygon motor 308. The phase from the falling edge to the falling edge of the FG signal is defined as one FG signal phase. In addition, the FG signal cycle count value in each phase is described as a numerical value. FIG. 5B shows the FG signal phase number. When the specific sequence of the reflective surface 304 is started at the timing of the black triangle mark S, the FG signal phase number storage unit 402 operates and assigns an FG signal phase number. In the present embodiment, since the FG signal is output six times during one rotation of the polygon motor 308, six phase numbers are assigned to the FG signal.

  FIG. 5C is a plot of the FG signal cycle count values shown at the bottom of FIG. In this embodiment, the speed control of the polygon motor 308 is performed so that the FG signal cycle count value becomes 100 as an example. Therefore, the FG signal cycle count value is plotted with the count value 100 as the center. As described above, the rotation speed fluctuates in one cycle while the polygon motor 308 rotates once. Therefore, also in FIG. 5C, it can be confirmed that the FG signal cycle count value fluctuates in one cycle while the polygon motor 308 rotates once. In the present embodiment, as an example, the rotation cycle variation specifying unit 404 finds the phase number corresponding to the FG signal having the smallest FG signal cycle count value surrounded by a dotted line while the polygon motor 308 makes one rotation. One cycle fluctuation is detected. Then, the phase number corresponding to the FG signal having the smallest FG signal cycle count value is output to the reflecting surface information output means 405. Note that finding the smallest value as the count value is an example. If the fluctuation that occurs in one cycle during one rotation of the polygon motor 308 can be detected, for example, the largest value is detected. It may be. In addition, the phase of one cycle fluctuation that occurs during one rotation of the polygon motor 308 differs for each individual polygon motor 308. Therefore, it is necessary to set the detection reference by measuring the FG signal for each individual polygon motor 308.

  FIG. 5D shows the BD signal. In this embodiment, since the four-surface polygon mirror 303 is used, four BD signals are generated while the polygon motor 308 makes one rotation. FIG. 5E shows the surface number of the reflection surface specified by the reflection surface information output means 405. At the timing of the black triangle mark T, the rotation cycle variation specifying means 404 specifies the phase number corresponding to the FG signal having the smallest FG signal cycle count value. Thereafter, the reflection surface information output means 405 identifies the reflection surface. The reflecting surface information output unit 405 compares the phase number stored in the FG signal phase number storage unit 402 with the phase number specified by the rotation period variation specifying unit 404. When the falling edge of the BD signal is detected after determining that the phase numbers are the same, the surface number of the reflecting surface 304 is specified as one surface. Further, each time the polygon mirror 303 is driven to rotate and a falling edge of the BD signal is detected, the surface numbers of 1 surface → 2 surface → 3 surface → 4 surface → 1 surface and the reflective surface 304 are repeatedly output.

  FIG. 6 is a flowchart showing a method for specifying the reflection surface of the polygon mirror 303. In S <b> 1, the control unit 300 drives the polygon motor 308 by the motor control unit 310. Then, it is determined whether or not the rotation speed of the polygon mirror 303 is stable. If the rotational speed is not stable, the polygon motor 308 is accelerated / decelerated to stabilize the rotational speed. If the rotational drive is stable, the process proceeds to S2.

  In S <b> 2, the control unit 300 starts a specific sequence of the reflecting surface of the polygon mirror 303. First, the falling edge of the FG signal generated by the rotation of the polygon motor 308 is detected. When the falling edge of the FG signal is detected, in S3, the control means 300 obtains the FG signal cycle count value between the falling edges. In S <b> 4, the control means 300 counts up the FG signal phase number each time it detects a falling edge of the FG signal and stores it in the FG signal phase number storage means 402. In S5, the control means 300 associates the FG signal cycle count value obtained in S3 with the FG signal phase number obtained in S4, and stores it in the FG signal cycle storage means 403. In S6, the control unit 300 determines whether the FG signal for one rotation of the polygon mirror 303 has been detected, that is, whether the FG signal cycle count values from the phase number 1 to the phase number 6 are stored in the FG signal cycle storage unit 403. To do. S2 to S6 are repeated until the FG signal cycle count value for one rotation is stored.

  When the FG signal cycle count value for one rotation of the polygon mirror 303 is stored, in S7, the control unit 300 causes the rotation cycle variation specifying unit 404 to store the FG signal of each FG signal phase number stored in the FG signal cycle storage unit 403. Compare the cycle count values. Then, the phase number corresponding to the FG signal having the smallest FG signal cycle count value is specified. In S8, the reflecting surface information output unit 405 compares the phase number stored in the FG signal phase number storage unit 402 with the phase number specified in S7. When the falling edge of the BD signal is detected after determining that the phase numbers are the same, the surface number of the reflecting surface 304 is specified as one surface. In S9, whenever the reflecting surface information output means 405 detects the falling edge of the BD signal, it repeatedly outputs the surface numbers of 1 surface → 2 surfaces → 3 surfaces → 4 surfaces → 1 surface and the reflecting surface 304. As a result, the relationship between the FG signal and the reflecting surface of the polygon mirror 303 can be specified.

  In this way, the rotational speed fluctuation that occurs in one cycle while the polygon motor 308 makes one rotation is detected based on the FG signal. Thereby, the FG signal and the BD signal can be associated with each other, and the reflection surface of the polygon mirror 303 can be specified from the FG signal and the BD signal without using a dedicated sensor for specifying the reflection surface. In addition, since the reflecting surface of the polygon mirror 303 can be specified, it is possible to correct the surface accuracy variation according to the correction information for correcting the surface accuracy variation for each reflecting surface 304.

(Second Embodiment)
In the first embodiment, the method for detecting the FG signal has been described. In the present embodiment, a description will be given of a method for specifying the reflecting surface 304 when the polygon motor 308 is driven to rotate using the sensorless control method without mounting the FG signal generation unit 309 for detecting the FG signal. In addition, detailed description here is abbreviate | omitted about the structure similar to previous 1st Embodiment.

  FIG. 7 is a control block diagram of the optical scanning apparatus 101 in the present embodiment. Note that the laser beam generation unit 301, the BD signal generation unit 305, the reflection surface specifying unit 311, the reflection surface information storage unit 312, the optical scanning control unit 313, and the storage unit 314 in FIG. 7 are the same as those in the first embodiment. Since it is a structure, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The polygon motor 701 is the same as that of the first embodiment in that it is an outer rotor type brushless motor in which the polygon mirror 303 is integrally attached to the rotor. However, a magnetic pole position detection sensor such as a Hall element and a control circuit such as a driver as in the first embodiment are not mounted on the polygon motor 701. Instead, a function for detecting the position of the rotor is mounted on the control means 700. In the present embodiment, in order to control the rotational speed of the polygon motor 701, the position speed estimation means 704 is added to the control means 700 instead of the magnetic pole position detection sensor as the FG signal generation means 309 used in the first embodiment. Is provided. A driver 703 is also mounted on the control means 700. Therefore, the interface between the control means 700 and the polygon motor 701 is connected by phase winding (U phase, V phase, W phase).

  The control unit 700 includes a speed control unit 702, a driver 703, and a position / speed estimation unit 704 for controlling the rotation of the polygon motor 701. The speed control means 702 is based on the BD signal when scanning with laser light, and based on the rotational speed signal obtained from the position speed estimation means 704 when not scanning with laser light. The period indicating the rotation speed is detected by. The speed control unit 702 compares the cycle indicating the rotation speed detected by the rotation speed detection unit 317 with the commanded rotation speed in the speed control unit 702. Then, the voltage value to be applied to the polygon motor 701 is calculated using PI control or the like so as to follow the commanded rotation speed, and is used as a control signal using pulse width modulation or the like. Output.

  Furthermore, it is necessary to switch the energized phase to which the voltage is applied according to the rotor position of the polygon motor 701. In the case of the first embodiment, based on the output signal from the magnetic pole position detection sensor, the rotor position is detected and the energized phase is switched. On the other hand, in the present embodiment, since the magnetic pole position detection sensor is not mounted, on the basis of the rotation speed signal obtained from the position speed estimation means 704, energization switching control is performed in a general 120-degree rectangular wave energization control, A drive signal is output to the driver 703. As the driver 703, for example, a MOS-FET is used.

  The position speed estimation means 704 uses a general position sensorless control method at the time of energization control of a 120-degree rectangular wave of a three-phase brushless motor. By detecting the induced voltage of the non-energized phase, the rotor position is estimated and output to the speed control means 702 and the reflecting surface specifying means 311 as a rotational speed signal. FIG. 8 is a diagram showing the relationship between the phase voltage waveform and the rotation speed signal. FIG. 8A shows a phase voltage waveform for one phase during 120-degree rectangular wave energization control. FIG. 8B shows a rotation speed signal for one phase generated by the position / speed estimation means 704. From the induced voltage waveform in the non-energized section shown in FIG. 8A, the rectangular wave-shaped rotation speed signal shown in FIG. 8B is generated. This rotational speed signal is a signal in which 1 and 0 are repeated every 180 degrees of electrical angle by detecting the timings U and V by comparing the induced voltage with a voltage approximately half of the power supply voltage by a comparator. As the rotation speed signal, a signal for one phase in FIG. 8B may be used. Alternatively, a configuration may be adopted in which signals for the other two phases whose phases are shifted by 120 degrees in electrical angle are synthesized, and six rectangular wave rotational speed signals are generated per electrical angle of 360 degrees and output.

  In this manner, by outputting the rotation speed signal to the reflecting surface specifying unit 311 instead of the FG signal in the first embodiment, a sequence for specifying the reflecting surface can be performed as in the first embodiment. In the present embodiment, the reflection surface 304 of the polygon mirror 303 can be specified even in a configuration in which the rotation speed detection unit 317 is not provided.

DESCRIPTION OF SYMBOLS 101 Optical scanning device 300 Control means 301 Laser light generation means 303 Polygon mirror 306 Light reception sensor 309 FG signal generation means 311 Reflection surface specification means

Claims (11)

Irradiating means for irradiating laser light;
A rotating polygon mirror having a plurality of reflecting surfaces for reflecting the light emitted from the irradiating means;
Driving means for driving the rotary polygon mirror;
Light detecting means for detecting the laser light reflected by the rotary polygon mirror and outputting a signal corresponding to the laser light;
Generating means for generating a signal corresponding to the rotational speed of the driving means;
Based on a signal corresponding to the rotational speed, speed detecting means for detecting a rotational speed fluctuation of the driving means during one rotation of the rotary polygon mirror;
An optical scanning apparatus comprising: a control unit that identifies a detection result by the light detection unit and a reflection surface of the rotary polygon mirror according to the rotation speed fluctuation by the speed detection unit.   Period detection means is provided for detecting a period during one rotation of the rotary polygon mirror, with one period from the falling edge of the signal to the next falling edge of the signals corresponding to the rotation speed of the driving means. The optical scanning device according to claim 1. Comprising a counting means for counting clocks in a plurality of periods detected by the period detecting means;
The speed detecting means detects a period that can be uniquely specified by a count value counted by the counting means among a plurality of periods detected by the period detecting means as a rotational speed fluctuation of the driving means. The optical scanning device according to claim 2.   4. The control unit according to claim 1, wherein the control unit determines that one of the signals corresponding to the laser beam is from one signal fall to the next fall as one reflection surface. The optical scanning device according to 1.   The control unit associates a period that can be uniquely specified among the plurality of periods detected by the period detection unit with a reflection surface of the rotary polygon mirror according to the specified period, so that the rotation polygon mirror 5. The optical scanning device according to claim 3, wherein a reflecting surface is specified.   The control means reflects at a timing at which a uniquely identifiable period among the plurality of periods detected by the period detection means is detected with reference to a reflection surface reflecting the laser light among the plurality of reflection surfaces. The optical scanning device according to claim 3, wherein a surface is specified.   The optical scanning device according to claim 1, wherein the control unit corrects the irradiation position of the laser light in accordance with the identified reflecting surface of the rotary polygon mirror.   8. The optical scanning device according to claim 1, wherein the control unit corrects the light amount of the laser light in accordance with the identified reflection surface of the rotary polygon mirror. 9.   9. The optical scanning device according to claim 1, wherein the signal corresponding to the rotation speed is an FG signal generated in accordance with driving of the driving unit.   9. The optical scanning apparatus according to claim 1, wherein the signal corresponding to the rotation speed is a signal obtained by detecting an induced voltage of the driving unit. An optical scanning device according to any one of claims 1 to 10,
A photoreceptor on which an electrostatic latent image is formed by light scanned by the optical scanning device;
An image forming apparatus comprising: a developing unit that develops the electrostatic latent image formed on the photosensitive member.

Images