JP2019082500A - Optical scanner and determination method for light beam for synchronous detection - Google Patents

Abstract

To prevent a scanning position of a light beam for synchronous detection from being displaced in a sub-scanning direction, and from being deviated from a detection surface of a light detection sensor due to an assembly error of a rotary polygon mirror or a light source in an optical scanner.SOLUTION: An optical scanner comprises: a sub-scanning position calculation part for calculating a time from a light detection time by a first light detection sensor 41 to a light detection time by a second light detection sensor 42 for each of a plurality of light beams, and for calculating a sub-scanning position of each light beam with respect to a central position P0 in a sub-scanning direction of a detection surface 41a of the first light detection sensor 41 on the basis of the calculated time; and a determination part for specifying the light beam having the minimum distance from the central position P0 from among the plurality of light beams on the basis of a calculation result by the sub-scanning position calculation part, and for determining the specified light beam as the light beam for synchronous detection.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an optical scanning device and a method of determining a light beam for synchronous detection.

  Conventionally, a light source for emitting a plurality of light beams having different positions in the sub-scanning direction, a rotary polygon mirror for deflecting and scanning a plurality of light beams emitted from the light source, and a light beam deflected for scanning by the rotary polygon mirror There is known a multi-beam type optical scanning device provided with an imaging lens for forming an image on a surface to be scanned.

  This type of optical scanning device is provided with a light detection sensor in order to synchronize writing timing of image data by a plurality of light beams (see, for example, Patent Document 1). On the downstream side of the optical path of the rotary polygon mirror, a reflection mirror that reflects a plurality of light beams deflected by the rotary polygon mirror and guides the light beams to a light detection sensor is provided. The light detection sensor detects a plurality of light beams reflected by the reflection mirror and outputs respective detection signals to the control unit. Then, the control unit receives, as a synchronization signal, a detection signal corresponding to the light beam for synchronization detection among the plurality of light beams. Then, the control unit controls the writing timing of the image data by each light beam on the basis of the reception time of the synchronization signal.

JP 2008-279632 A

  In the conventional multi-beam type optical scanning device shown in the above-mentioned Patent Document 1, there is a possibility that the distance and the light diameter of the respective light beams on the surface to be scanned may vary due to the assembling error of the optical element such as the rotating polygon mirror. is there.

  Therefore, when assembling the light scanning device, the position of the light source may be adjusted so that the distance between the light beams on the surface to be scanned and the light diameter become design values.

  However, in this case, the sub-scanning position of the light beam incident on the light detection sensor changes depending on the adjustment position of the light source. As a result, there is a problem that the light beam for synchronous detection deviates from the detection surface of the light detection sensor and synchronous detection becomes impossible.

  The present invention has been made in view of such a point, and the purpose thereof is that the scanning position of the light beam for synchronous detection is in the sub-scanning direction due to the assembling error of the rotary polygon mirror or the light source. It is to prevent displacement and detachment from the detection surface of the light detection sensor.

An optical scanning device according to one aspect of the present invention comprises: a light source having a plurality of light emitting units for emitting a light beam; a rotary polygon mirror for reflecting a plurality of light beams emitted from the light source and scanning in a main scanning direction; A first light detection sensor having a detection surface capable of detecting a plurality of light beams reflected by the rotary polygon mirror and outputting a detection signal when each light beam is detected, and output from the first light detection sensor And a control unit that receives, as a synchronization signal, a detection signal corresponding to the light beam for detecting synchronization among the plurality of detection signals.
And it has a detection surface which can detect the plurality of light beams, and the distance between the detection surface of the light beam in the scanning direction and the detection surface of the first light detection sensor may differ depending on the position in the sub scanning direction. The time from the time of light detection by the first light detection sensor to the time of light detection by the second light detection sensor is calculated for each of the second light detection sensor configured as described above and the plurality of light beams A sub-scanning position calculation unit that calculates a sub-scanning position of each light beam with respect to the center position of the detection surface of the first light detection sensor in the sub-scanning direction based on time; And a determination unit that identifies the light beam with the smallest distance from the center position among the plurality of light beams, and determines the identified light beam as the light beam for synchronous detection.
According to another aspect of the present invention, there is provided a determination method comprising: a light source having a plurality of light emitting units for emitting a light beam; a rotary polygon mirror for reflecting a plurality of light beams emitted from the light source and scanning in a main scanning direction; A first light detection sensor having a detection surface capable of detecting a plurality of light beams reflected by the rotating polygon mirror and outputting a detection signal when each light beam is detected, and an output from the first light detection sensor An optical scanning device comprising: a control unit that receives as a synchronization signal a detection signal corresponding to a light beam for detecting synchronization among the plurality of detection signals; It is a method of determining as a light beam for synchronous detection.
The light emitting step of emitting a light beam from one of the light emitting portions provided in the light source and the light beam detection on the rotary polygon mirror side of the first light detecting sensor, and A sensor preparation step of preparing a movable light detection sensor movable in the sub scanning direction, and linearly moving the prepared movable light detection sensor from the state where the detection surface is located out of the light path of the light beam into the light path Based on the position of the moving light detecting sensor when the moving light detecting sensor first receives the light beam in the sensor moving step and the sensor moving step, the central position in the sub-scanning direction on the detecting surface of the first light detecting sensor Calculating the sub-scanning position of the one light beam with respect to the light beam, and the sub-scanning direction of the plurality of light emitting units that are known in advance, Based on the interval, the calculation step of calculating the sub-scanning position of the other light beam with respect to the center position and the light beam having the smallest distance from the center position is specified based on the calculation result in the calculation step. And determining the specified light beam as a light beam for synchronous detection.

  According to the present invention, it is possible to prevent the scanning position of the light beam for synchronous detection from being displaced in the sub-scanning direction and coming off from the detection surface of the light detection sensor due to an assembly error of the rotary polygon mirror or the light source. Can.

FIG. 1 is a schematic view showing an entire configuration of an image forming apparatus provided with a light scanning device in the embodiment. FIG. 2 is a plan view showing the internal structure of the light scanning device in the present embodiment. FIG. 3 is a view of the light source as viewed from the tip side. FIG. 4 is a view on arrow IV in FIG. FIG. 5 is a block diagram showing a part of a control system of the optical scanning device. FIG. 6 is a flowchart showing a process of determining a light beam for detecting synchronization performed by the control unit. FIG. 7 is a view corresponding to FIG. 2 showing the second embodiment. FIG. 8 is an explanatory view for explaining a method of determining a light beam for detecting synchronization, and is a view corresponding to a view on arrow VIII of FIG.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The present invention is not limited to the following embodiments.

Embodiment 1
FIG. 1 is a cross-sectional view showing a schematic configuration of a laser printer 1 provided with an optical scanning device 30 in the present embodiment.

  As shown in FIG. 1, the laser printer 1 includes a box-like printer main body 2, a manual paper feed unit 6, a cassette paper feed unit 7, an image forming unit 8, a fixing unit 9, and a paper discharge unit 10. Is equipped. Then, the laser printer 1 is configured to form an image on a sheet based on image data transmitted from a terminal (not shown) or the like while conveying the sheet along the conveyance path L in the printer main body 2 ing.

  The manual feed unit 6 includes a manual feed tray 4 provided on the side of one side of the printer main body 2 so as to be openable and closable, and a manual feed paper feed roller 5 rotatably provided inside the printer main body 2. ing.

  The cassette sheet feeding unit 7 is provided at the bottom of the printer body 2. The cassette feeding unit 7 separates the fed sheets one by one from a sheet feeding cassette 11 for storing a plurality of sheets stacked one another, a pick roller 12 for taking out sheets in the sheet feeding cassette 11 one by one, and A feed roller 13 and a retard roller 14 for feeding the sheet to the conveyance path L are provided.

  The image forming unit 8 is provided above the cassette feeding unit 7 in the printer body 2. The image forming unit 8 includes a photosensitive drum 16 as an image carrier rotatably provided in the printer main body 2, a charger 17 disposed around the photosensitive drum 16, a developing unit 18, and a transfer roller. The image forming apparatus further includes a cleaning unit 20, a light scanning device 30 disposed above the photosensitive drum 16, and a toner hopper 21. Then, the image forming unit 8 forms an image on the sheet supplied from the manual sheet feeding unit 6 or the cassette sheet feeding unit 7.

  The conveyance path L is provided with a pair of registration rollers 15 which supply the sheet having been fed out to the image forming section 8 at a predetermined timing after temporarily making the sheet stand by.

  The fixing unit 9 is disposed to the side of the image forming unit 8. The fixing unit 9 includes a fixing roller 22 and a pressure roller 23 which are pressed against each other and rotate. Then, the fixing unit 9 is configured to fix the toner image transferred onto the sheet by the image forming unit 8 to the sheet.

  The paper discharge unit 10 is provided above the fixing unit 9. The paper discharge unit 10 includes a paper discharge tray 3, a paper discharge roller pair 24 for conveying the paper to the paper discharge tray 3, and a plurality of conveyance guide ribs 25 for guiding the paper to the paper discharge roller pair 24. . The discharge tray 3 is formed in a concave shape in the upper portion of the printer body 2.

  When the laser printer 1 receives the image data, the photosensitive drum 16 is rotationally driven in the image forming unit 8 and the charger 17 charges the surface of the photosensitive drum 16.

  Then, a laser beam is emitted from the light scanning device 30 to the photosensitive drum 16 based on the image data. An electrostatic latent image is formed on the surface of the photosensitive drum 16 by being irradiated with a laser beam. The electrostatic latent image formed on the photosensitive drum 16 is developed by the developing unit 18 to be a visible image as a toner image.

  Thereafter, the sheet is pressed against the surface of the photosensitive drum 16 by the transfer roller 19. As a result, the toner image on the photosensitive drum 16 is transferred to the sheet. The sheet on which the toner image has been transferred is heated and pressed by the fixing roller 22 and the pressure roller 23 in the fixing unit 9. As a result, the toner image is fixed to the sheet.

  Next, the details of the optical scanning device 30 will be described with reference to FIG. The light scanning device 30 has a sealed housing 31. The housing 31 has a bottomed box-like housing main body 31a opened on the ceiling side, and a lid (not shown) closing the ceiling side of the housing main body 31a. A multi-beam type light source 32 is attached to the side wall of the housing body 31a. The light source 32 is a multi-beam type light source having four light emitting units 32a to 32d (see FIG. 3), and emits four light beams D1 to D4. In FIG. 2, the four light beams D1 to D4 are simplified and shown by a single two-dot chain line.

  In the housing 31, a polygon mirror 33 for deflecting and scanning the light beams D1 to D4 emitted from the light source 32 is accommodated. The polygon mirror 33 is a polygonal mirror having a plurality of reflecting surfaces on the circumferential surface. The polygon mirror 33 is supported on the bottom wall of the housing body 31a via a polygon motor. A collimator lens 35 and a cylindrical lens 36 are disposed between the polygon mirror 33 and the light source 32. An imaging lens 37 is provided on the side of the polygon mirror 33 in the bottom wall portion of the housing body 31a. The imaging lens 37 is constituted by, for example, an fθ lens.

  The light beams D1 to D4 emitted from the light source 32 are collimated by the collimator lens 35 and then condensed on the reflection surface of the polygon mirror 33 by the cylindrical lens 36. The condensed light beams D1 to D4 are converted to equal angular velocity light by the polygon mirror 33, and then converted to equal velocity scanning light by an imaging lens (fθ lens) 37. Then, the light beams D1 to D4 having passed through the imaging lens 37 are reflected by a return mirror (not shown) and irradiated on the surface of the photosensitive drum 16.

  In the housing 31, a synchronization detection mirror 40, a first light detection sensor 41, and a second light detection sensor 42 are further provided. The synchronization detection mirror 40 is provided outside the scanning start side end of the effective scanning range of the light beams D1 to D4 (a range in which the image data is actually written). The first light detection sensor 41 and the second light detection sensor 42 are provided upright on the bottom wall portion of the housing body 31a outside the scanning end side end of the effective scanning range.

  Then, the synchronization detection mirror 40 reflects the light beams D1 to D4 deflected by the polygon mirror 33 and traveling along the optical path out of the effective scanning range and causes the light beams D1 to D4 to be incident on the first light detection sensor 41 and the second light detection sensor 42. The first light detection sensor 41 and the second light detection sensor 42 are configured by, for example, a photodiode, a phototransistor, a photo IC or the like. The first light detection sensor 41 and the second light detection sensor 42 are both fixed to the bottom wall of the housing body 31a.

  The first light detection sensor 41 detects the four light beams D1 to D4 reflected by the synchronization detection mirror 40, and outputs the detection signal to the control unit 100 (see FIG. 5). The control unit 100 detects a detection signal corresponding to the light beam for synchronization detection among the four light beams D1 to D4 as a synchronization signal. Then, the control unit 100 controls the write start timing of the image data by the other three light beams based on the time when the synchronization signal is received.

  The second light detection sensor 42 is a sensor used when the control unit 100 determines a light beam for detecting synchronization from the four light beams D1 to D4.

  As shown in FIG. 4, each of the first light detection sensor 41 and the second light detection sensor 42 has detection surfaces 41 a and 42 a in the form of an elongated slit. The detection surfaces 41a and 42a intersect at different angles with respect to the scanning direction (main scanning direction) of the light beam. The first light detection sensor 41 is disposed such that the detection surface 41 a extends in the sub-scanning direction (a direction perpendicular to the main scanning direction and in the vertical direction of 4). The second light detection sensor 42 is disposed such that the detection surface 42 a is inclined by a predetermined angle θ with respect to the sub scanning direction. Here, θ may be any angle as long as it is an angle larger than 0 and smaller than π / 2, and is set to, for example, π / 4 in this embodiment. According to this configuration, the distance between the detection surface 41a of the first light detection sensor 41 and the detection surface 42a of the second light detection sensor 42 in the scanning direction of the light beam differs depending on the position in the sub-scanning direction.

  Therefore, the time from detection of the light beam by the first light detection sensor 41 to detection of the light beam by the second light detection sensor 42 (hereinafter referred to as detection time difference) t differs depending on the sub-scanning position of the light beam. That is, the detection time difference t0 when the light beam passes through the central position P0 in the sub-scanning direction on the detection surface 41a of the first light detection sensor 41 is above the central position P0 (the ceiling side of the housing body 31a And the detection time difference t2 when the light beam passes the predetermined position P2 below the central position P0 (bottom side of the housing 31).

  The control unit 100 measures the detection time difference t for each of the four light beams D1 to D4, and calculates the difference value between the measured detection time difference t and the detection time difference t0 when the light beam passes the central position P0. The sub-scanning position of the light beam with respect to the central position P0 is calculated based on the calculated difference value. Then, the control unit 100 determines the light beam with which the distance from the central position P0 is minimized as the light beam for synchronous detection.

  FIG. 6 is a flowchart showing determination processing of a light beam for detecting synchronization in the control unit 100.

  In step S1, the light beams D1 to D4 are sequentially emitted from the light emitting units 32a to 32d of the light source 32 with a time difference therebetween, and the polygon mirror 33 is rotated at a predetermined speed by the polygon motor.

  In step S2, for each of the four light beams D1 to D4, the time (detection time difference t) from the time of light detection by the first light detection sensor 41 to the time of light detection by the second light detection sensor 42 is calculated. The detection time difference t is preferably a sampling average per rotation of the polygon mirror 33.

  In step S3, based on the calculation result in step S2, the sub-scanning position with respect to the central position P0 in the sub-scanning direction on the detection surface 41a of the first light detection sensor 41 is calculated for each of the four light beams D1 to D4.

  In step S4, the light beam closest to the central position P0 is specified based on the sub-scanning position of each of the light beams D1 to D4 calculated in step S3.

  In step S5, it is determined whether or not there are a plurality of specified light beams. If the determination is NO, the process proceeds to step S7, and if YES, the process proceeds to step S6.

  In step S6, among the plurality of light beams identified in step S5, the light beam close to the ceiling side of the housing body 31a is determined as the light beam for synchronous detection, and then the process returns.

  In step S7, which proceeds when the determination in step S5 is NO, the light beam specified in step S5 is determined as a light beam for synchronous detection, and then the process returns.

  As described above, the control unit 100 calculates, for each of the four light beams D1 to D4, the time difference from the time of light detection by the first light detection sensor 41 to the time of light detection by the second light detection sensor 42. Based on this time difference, the sub-scanning position of each of the light beams D1 to D4 with respect to the center position P0 in the sub-scanning direction of the detection surface 41a of the first light detection sensor 41 is calculated. Among the beams D1 to D4, the light beam closest to the central position P0 is specified, and the specified light beam is determined as a light beam for synchronous detection.

  Therefore, when the light beam for synchronous detection is displaced in the sub-scanning direction due to the assembly error of the polygon mirror 33 and the light source 32, the light beam passage position should be avoided as much as possible from the detection surface 41a. Can.

  Further, when the control unit 100 determines that there are a plurality of light beams with which the distance from the center position P0 of the detection surface 41a of the first light detection sensor 41 is minimized, the light beam closer to the ceiling side of the housing body 31a As a light beam for synchronous detection.

  According to this configuration, when the sub-scanning positions of the four light beams D1 to D4 are entirely displaced to the lower side (the bottom side of the housing main body 31a) due to the thermal deformation of the housing main body 31a during the operation of the light scanning device 30 In addition, the light beam for detecting synchronization can be avoided as much as possible from coming off the detection surface 41 a of the first light detection sensor 41.

<< Embodiment 2 >>
7 and 8 show the second embodiment. In this embodiment, an example of a determination method (determination method of the present invention) for determining a light beam for synchronous detection from among a plurality of light beams D1 to D4 will be described.

  The determination method includes a light emission process, a sensor preparation process, a sensor movement process, a calculation process, and a determination process. This determination method is used in the assembly process of the light scanning device 30.

  In the light emitting process, a light beam is emitted from one of the plurality of light emitting units 32 a to 32 d provided in the light source 32.

  In the sensor preparation step, a moving light detection sensor 43 capable of detecting a light beam on the side of the polygon mirror 33 relative to the first light detection sensor 41 and movable in the sub scanning direction is prepared. The moving light detection sensor 43 is fixed to a manual or motorized linear movement stage (linear movement mechanism) 44.

  In the movement step, the moving light detection sensor 43 is moved by the linear movement stage 44 from the state where the detection surface 43a is located outside the optical path of the light beam to the position where it enters the optical path (see FIG. 8).

  In the calculation step, based on the position of the sensor 43 when the moving light detection sensor 43 first detects the light beam in the movement step, the light beam with respect to the central position P0 of the detection surface 41a of the first light detection sensor 41 Calculate the sub-scanning position. Then, based on the calculated sub-scanning position of the light beam and the distance d in the sub-scanning direction between the plurality of light emitting units 32a to 32d which are known in advance, the sub-scanning of the other three light beams with respect to the central position P0 Calculate the position.

  In the determination step, based on the calculation result in the calculation step, the light beam with the smallest distance from the central position P0 is specified. Then, when there is one specified light beam, the light beam is determined as a light beam for synchronous detection, and when there are two specified light beams, it is located on the ceiling side of the housing body 31a. The closer light beam is determined as the light beam for synchronous detection.

  As described above, in the present embodiment, as in the first embodiment, the light beam with which the distance from the center position P0 in the sub-scanning direction on the detection surface 41a of the first light detection sensor 41 is minimized is used for synchronous detection. It is determined as a light beam. Therefore, the same effects as those of Embodiment 1 can be obtained.

  Further, the moving light detection sensor 43 is used only in the assembly process of the light scanning device 30, and is not mounted on the light scanning device 30 which is a finished product. Therefore, the number of light detection sensors mounted on the light scanning device 30 can be reduced compared to the first embodiment, and the product cost can be suppressed.

  As described above, the present invention is useful for an optical scanning device and a method of determining a light beam for detecting synchronization.

1: Laser printer (image forming apparatus)
30: Optical scanning device 31a: Housing body (housing)
32: light source 32a: light emitting unit 32b: light emitting unit 32c: light emitting unit 32d: light emitting unit 33: polygon mirror (rotation polygon mirror)
40: synchronization detection mirror 41: first light detection sensor 41a: detection surface 42: second light detection sensor 42a: detection surface 43: moving light detection sensor 43a: detection surface 100: control unit (sub scanning position calculation unit, determination unit )
D1: light beam D2: light beam D3: light beam D4: light beam P0: central position t: detection time difference

Claims (4)

A light source having a plurality of light emitting units for emitting a light beam, a rotary polygon mirror for reflecting a plurality of light beams emitted from the light source and scanning in a main scanning direction, and a plurality of light beams reflected by the rotary polygon mirror A first light detection sensor that has a detection surface that can detect the light beam and outputs a detection signal when each light beam is detected, and for detecting synchronization among a plurality of detection signals output from the first light detection sensor A control unit that receives a detection signal corresponding to a light beam as a synchronization signal, the optical scanning device comprising:
A detection surface capable of detecting the plurality of light beams is provided, and the distance between the detection surface of the light beam and the detection surface of the first light detection sensor is different depending on the position in the sub-scanning direction. A second light detection sensor,
The time from light detection by the first light detection sensor to light detection by the second light detection sensor is calculated for each of the plurality of light beams, and the first light detection sensor is calculated based on the calculated time. A sub-scanning position calculation unit that calculates the sub-scanning position of each light beam with respect to the center position of the detection surface in the sub-scanning direction;
Among the plurality of light beams, the light beam with the smallest distance from the central position is specified based on the calculation result by the sub-scanning position calculation unit, and the specified light beam is used as the light beam for synchronous detection. An optical scanning device comprising: a determining unit to determine. In the optical scanning device according to claim 1,
And a housing main body having a bottomed box shape and accommodating the rotary polygon mirror,
The first and second light detection sensors are provided upright on the bottom wall of the housing body,
In the determination unit, when there are two light beams having a minimum distance from the central position among the plurality of light beams, the light of the two light beams closer to the ceiling side of the housing main body is present A light scanning device that identifies the beam as a light beam for synchronous detection. A light source having a plurality of light emitting units for emitting a light beam, a rotary polygon mirror for reflecting a plurality of light beams emitted from the light source and scanning in a main scanning direction, and a plurality of light beams reflected by the rotary polygon mirror A first light detection sensor that has a detection surface that can detect the light beam and outputs a detection signal when each light beam is detected, and for detecting synchronization among a plurality of detection signals output from the first light detection sensor A light scanning apparatus comprising: a control unit for receiving a detection signal corresponding to a light beam as a synchronization signal, wherein a light beam of the plurality of light beams is determined as the light beam for the synchronization detection. There,
A light emitting step of emitting a light beam from one of a plurality of light emitting units provided in the light source;
A sensor preparation step of preparing a moving light detection sensor capable of detecting a light beam on the rotary polygon mirror side of the first light detection sensor and movable in the sub scanning direction;
A sensor moving step of linearly moving the prepared moving light detection sensor from the state where the detection surface is located out of the light path of the light beam into the light path;
Based on the position of the moving light detecting sensor when the moving light detecting sensor first receives a light beam in the sensor moving step, the one light relative to the center position in the sub scanning direction on the detecting surface of the first light detecting sensor The sub-scanning position of the beam is calculated, and based on the calculated sub-scanning position of the light beam and the distance between the plurality of light emitting units known in advance in the sub-scanning direction, A calculation step of calculating the sub-scanning position;
Determining the light beam having the smallest distance from the central position based on the calculation result in the calculation step, and determining the specified light beam as a light beam for synchronous detection . In the determination method according to claim 3,
In the determination step, when there are two light beams having a minimum distance from the central position, one of the two light beams that is closer to the ceiling side of the housing main body housing the rotary polygon mirror. The determination method which determines a light beam as a light beam for synchronous detection.

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