JP2009023162A - Image forming device and image writing timing setting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device enabling to set an image writing timing for each scanning line without increasing cost and reducing the detecting accuracy of a laser beam. <P>SOLUTION: Two BD sensors 496, 497 are arranged side by side at a certain space in a main scanning direction, and a reference laser beam L1 is only scanned in the main scanning direction and received by each of the two BD sensors 496, 497. A combination of each of other laser beam sources LD2-LD4 and reference laser beam source LD1 is set, and laser beams from the pair of laser beam sources belonging to the combination are scanned and the laser beams from the two laser beam sources belonging to the combination are received by the different BD sensors. A displacement between the emission positions of the reference laser beam and the other laser beam in the main scanning direction is detected as a time difference between the beam receiving timings of the BD sensors 496, 497. The time difference is utilized to set the image writing timing of each of the laser beam sources LD2-LD4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to the technical field of image forming apparatuses, and particularly relates to a laser unit that performs exposure by irradiating a surface of a photosensitive drum with a laser.

Conventionally, an electrophotographic method in which laser light emitted from a laser irradiation unit is reflected by each reflecting surface of a rotary polygon mirror to expose the surface of the photosensitive drum to form an electrostatic latent image on the surface of the photosensitive drum. Image forming apparatuses are widely known. Also, in this type of image forming apparatus, a BD (Beam Detect) sensor that receives laser light at a predetermined position is installed, and an image writing timing (photosensitive member) in the main scanning direction of the light beam using an output signal of the BD sensor. A technique for setting a light beam irradiation start position on the drum is also known (see, for example, Patent Document 1 below). Furthermore, for the purpose of shortening the time required for image formation, a technique for scanning a plurality of light beams on a plurality of lines in one scan has been proposed.
JP-A-8-72309

  In an image forming apparatus that scans a plurality of light beams on a plurality of lines in one scan, each light beam is configured to irradiate a position shifted from each other by a predetermined shift amount in the main scanning direction for a desired purpose. There may be. In this case, since each light beam enters the BD sensor at a different timing when scanning is performed, it is necessary to set an image writing timing for each light beam based on each incident timing.

  However, when the amount of deviation of the irradiation position of each light beam in the main scanning direction is very small, a state occurs in which the next light beam enters the BD sensor before the previous light beam passes through the BD sensor. In this case, since all the light beams are always incident on the BD sensor until all the light beams have passed through the BD sensor, a constant signal is output from the BD sensor. It is impossible to detect the passage timing of the light beam.

  For this reason, conventionally, further techniques such as changing the frequency and power of each laser beam and causing a voltage difference in the output of the BD sensor to separate the BD signal by each laser beam have been required. The technology increases the cost and decreases the detection accuracy of the laser beam.

  The present invention has been made to solve the above-described problems, and can set the image writing timing to each scanning line without incurring an increase in cost and a decrease in detection accuracy of laser light. It is an object to provide a forming apparatus and an image writing timing setting method.

  According to the first aspect of the present invention, a light source unit that outputs a plurality of light beams at least from different positions in the main scanning direction, and the light beams output from the light source unit in the main scanning direction within a predetermined region. A first scanning unit for repeatedly scanning the first and second light receiving units that are installed in the fixed region at a predetermined interval in the main scanning direction and perform a photoelectric conversion operation; and the fixed region A light source control unit that causes the light source unit to perform an image writing operation based on image data with respect to the surface of the photoconductor that is installed, and a signal output from the first and second light receiving units, An image writing timing setting unit for setting a start timing of the image writing operation for each scanning line, and the image writing timing setting unit scans one of the plurality of light beams with the main scanning. And detecting the output timing difference of each detection signal obtained from each of the light receiving units as a first output timing difference by scanning in the direction and receiving the light by the first and second light receiving units. A combination of each of the other light beams and the first light beam is set and scanning is performed for each combination, and in each scan, the light receiving objects of the first and second light receiving units are different from each other in the scanning. Detecting an output timing difference of each light reception signal obtained from each of the light receiving units by causing the first and second light receiving units to receive light beams belonging to a corresponding combination as a second output timing difference for each of the combinations; A difference between each of the second output timing differences detected for each combination and the first output timing difference is calculated, and each of the other light rays is written out with the light rays. The start timing of the image writing operation for the scanning line that performs the operation is set to a timing that is shifted from the start timing of the image writing operation for the scanning line that performs the writing operation by the one light beam by a time based on the difference corresponding to the light beam. The light source control unit controls the light emission operation of the light source unit according to the image writing timing set by the image writing timing setting unit, and performs image writing operation for each scanning line on the surface of the photoconductor. Device.

  According to a third aspect of the present invention, a light source unit that outputs a plurality of light beams from at least different positions in the main scanning direction, and the light beams output from the light source unit in the main scanning direction within a predetermined region. A first scanning unit for repeatedly scanning the first and second light receiving units that are installed in the fixed region at a predetermined interval in the main scanning direction and perform a photoelectric conversion operation; and the fixed region A light source control unit that causes the light source unit to perform an image writing operation based on image data with respect to the surface of the photoconductor that is installed, and a signal output from the first and second light receiving units, An image writing timing setting method in an image forming apparatus, comprising: an image writing timing setting unit that sets a start timing of the image writing operation for each scanning line, wherein The output timing of each detection signal obtained from each light receiving unit when the imming setting unit scans one of the plurality of light beams in the main scanning direction and receives the light by the first and second light receiving units. The step of detecting the difference as a first output timing difference, and the image writing timing setting unit sets a combination of each of the other light beams other than the first light beam and the first light beam, and scans each combination. And the first and second light receiving units receive the light beams belonging to the combination corresponding to the scanning as the light receiving objects of the first and second light receiving units different from each other in each scan. Detecting an output timing difference of each light reception signal obtained from each light receiving unit for each combination as a second output timing difference; and setting the image writing timing Calculates a difference between each of the second output timing differences detected for each of the combinations and the first output timing difference, and for each of the other light beams, the scanning line that performs the writing operation with the light beams Setting the start timing of the image writing operation to a timing shifted from the start timing of the image writing operation for the scanning line that performs the writing operation by the one light beam by a time based on the difference corresponding to the light beam; and the light source control An image writing step including a step of controlling an emission operation of the light source unit according to an image writing timing set by the image writing timing setting unit and performing an image writing operation for each scanning line on the surface of the photosensitive member. This is a timing setting method.

  According to the first and third aspects of the present invention, the first and second light receiving portions are installed through the predetermined interval, so that the first light beam is scanned in the main scanning direction. Then, by receiving light by the first and second light receiving units, a difference in output timing of each light receiving signal obtained by the light receiving operation of each light receiving unit appears. Further, a combination of each of the other light beams other than the first light beam and the first light beam is set and scanning is performed for each combination, and the light receiving target of the first and second light receiving units in each scan By making the first and second light receiving parts receive light beams belonging to the combination corresponding to the scanning as different light beams, the other light beams and the first light beam are output from different positions in the main scanning direction. And the fact that the first and second light-receiving units are installed at the predetermined interval are the outputs of the respective light-receiving signals obtained by the light-receiving operation of the first and second light-receiving units. Appears as a timing difference. Therefore, by calculating the difference between these output timing differences, a time difference caused by the output of the other light beam and the first light beam from different positions in the main scanning direction is calculated.

  According to the present invention, the time difference is derived by performing the above operation, and the start timing of the image writing operation for the scanning line that performs the writing operation with the other light beam is set to the scanning line that performs the writing operation with the one light beam. Since it is set to the timing shifted by the time based on the difference corresponding to the light beam from the start timing of the image writing operation, the cost increases and the detection accuracy of the laser beam is not reduced as in the conventional case, It is possible to reliably set the start timing of the image writing operation for the scanning line that performs the writing operation with another light beam.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the light source unit is configured to be capable of outputting four light beams, and the image writing timing setting unit includes the light source unit. When scanning is performed by the scanning unit in a state where all light beams are output, the first light beam incident on the light receiving unit is the first light beam and the second to fourth light beams are incident on the light receiving unit. As the other light rays, the start timing of the image writing operation for the scanning line that performs the writing operation with the second to fourth incident light rays, and the start of the image writing operation for the scanning line that performs the writing operation with the first light beam. It is set based on the timing.

  According to the present invention, when the light source unit is configured to be able to output four light beams, the second to fourth incident light beams are used to determine the image writing timing of the first incident light beam. And can be calculated by calculation.

  According to the present invention, it is possible to set the start timing of the image writing operation for the scanning line corresponding to each light beam without causing an increase in cost and a decrease in the detection accuracy of laser light as in the prior art.

  Embodiments according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a side view schematically showing an internal configuration of a multifunction peripheral as an example of an image forming apparatus according to an embodiment of the present disclosure. The multifunction device 1 has functions such as a copy function, a printer function, a scanner function, and a facsimile function. The multifunction device 1 has a main body 2, a stack tray 3 disposed on the left side of the main body 2, and a main body 2. The document reading unit 5 is disposed above the document reading unit 5 and the document feeding unit 6 is disposed above the document reading unit 5.

  An operation unit 47 is provided at the front part of the multifunction machine 1. The operation unit 47 displays a start key 471 for the user to input a print execution instruction, a numeric keypad 472 for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. A display unit 473 formed of a liquid crystal display or the like having a touch panel function, a reset key 474 for resetting setting contents set in the display unit 473, and a stop key 475 for stopping a printing (image forming) operation being executed. And a function switching key 477 for switching between a copy function, a printer function, a scanner function, and a facsimile function.

  The document reading unit 5 includes a scanner unit 51 including a CCD (Charge Coupled Device) sensor and an exposure lamp, and a document table 52 and a document reading slit 53 made of a transparent member such as glass. The scanner unit 51 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 52, the scanner unit 51 is moved along the document surface at a position facing the document table 52, and the document image is scanned. Image data acquired while scanning is output to an unillustrated image processing unit. Further, when reading a document fed by the document feeding unit 6, the document is moved to a position facing the document reading slit 53 and synchronized with the document feeding operation by the document feeding unit 6 via the document reading slit 53. The image of the original is acquired and the image data is output to the image processing unit.

  The document feeding unit 6 includes a document placing unit 61 for placing a document, a document discharge unit 62 for discharging a document whose image has been read, and a document placed on the document placing unit 61. A document transport mechanism 63 including a paper feed roller (not shown), a transport roller (not shown) and the like for feeding the paper one by one to a position facing the document reading slit 53 and discharging it to the document discharge section 62 is provided. The document conveyance mechanism 63 further includes a sheet reversing mechanism (not shown) that reverses the document and reversely conveys the document to a position facing the document reading slit 53, and scans the images on both sides of the document via the document reading slit 53. The data can be read from the unit 51.

  The document feeding unit 6 is provided so as to be rotatable with respect to the main body unit 2 so that the front side thereof can move upward. By moving the front side of the document feeder 6 upward to open the upper surface of the document table 52, the operator can place a read document, for example, a book in a spread state, on the upper surface of the document table 52. It has become.

  The main body 2 includes a plurality of paper feed cassettes 461, a paper feed roller 462 that feeds the recording paper from the paper feed cassette 461 one by one and transports it to the recording unit 40, and a recording paper transported from the paper feed cassette 461. And a recording unit 40 for forming an image.

  The recording unit 40 outputs a laser or the like based on the image data acquired by the scanner unit 51 or the like and exposes the photosensitive drum 43, and a developing unit 44 that forms a toner image on the photosensitive drum 43. A transfer unit 41 that transfers the toner image on the photosensitive drum 43 to the recording paper, a fixing unit 45 that heats the recording paper to which the toner image has been transferred and fixes the toner image on the recording paper, and a recording unit 40. And transport rollers 463, 464, etc. for transporting the recording paper to the stack tray 3 or the discharge tray 48.

  When forming images on both sides of the recording paper, the recording unit 40 forms an image on one side of the recording paper, and then the recording paper is nipped by the conveyance roller 463 on the discharge tray 48 side. In this state, the conveyance roller 463 is reversed to switch back the recording paper, and the recording paper is sent to the paper conveyance path L and conveyed again to the upstream area of the recording unit 40, and an image is formed on the other surface by the recording unit 40. Thereafter, the recording paper is discharged to the stack tray 3 or the discharge tray 48.

  FIG. 2 is a configuration diagram of the optical scanning device 49. As shown in FIG. 2, the optical scanning device 49 according to the present invention includes a laser irradiation unit 491, a collimator lens 492, a prism 493, a polygon mirror (rotating polygonal mirror) 494, an f-θ lens 495, and a beam detector sensor (hereinafter referred to as “beam detector”). , BD sensor).

  As shown in FIG. 3, the laser irradiation unit 491 emits light according to image data to the surface of the photosensitive drum 43 having a cylindrical surface that is configured to be rotatable while being supported by the support shaft 43a. Irradiation. The direction in which the support shaft 43a extends is called the main scanning direction. The laser irradiation unit 491 is formed by unitizing a plurality of laser light sources (LD1 to LD4) arranged in a line on the front end surface Y at regular intervals, and is located on the inner side of the normal to the front end surface Y. It is configured to be rotatable in the direction of an arrow A with a normal G passing through an intermediate position between LD2 and LD3 as a rotation axis.

  In the optical scanning device 49, the arrangement directions of the irradiation positions (imaging positions) of the laser beams L1 to L4 output from the laser light sources LD1 to LD4 on the surface of the photosensitive drum 43 are the main scanning direction and the sub scanning direction. By setting the laser irradiation unit 491 in a rotated state so as to have an inclination angle with respect to each of (the direction perpendicular to the main scanning direction when the surface of the photosensitive drum 43 is developed), a plurality of scanning lines are set. The image can be written in one scan, and the resolution in the sub-scanning direction can be adjusted by adjusting the tilt angle.

  The collimator lens 492 is for condensing the laser light output from each laser light source. The prism 493 converts the light transmitted through the collimator lens 492 into parallel light, and emits it toward the polygon mirror 494. The polygon mirror 494 has a plurality of reflecting surfaces that reflect incident light toward the photosensitive drum 43. For example, the polygon mirror 494 rotates at a constant speed in the direction of the arrow in FIG. The photosensitive drum 43 is scanned in the rotation axis direction (main scanning direction) while being reflected by the drum 43. The f-θ lens 495 forms an image of the laser beam reflected by the polygon mirror 494 in a spot shape having a predetermined diameter on the surface of the photosensitive drum 43.

  With the above configuration, the laser beam is repeatedly scanned on the surface of the photosensitive drum 43 at a constant speed in the main scanning direction. When the surface of the charged photoconductive drum 43 is irradiated with laser light, the charge of the irradiated portion is removed. The multi function device 1 irradiates the surface of the photosensitive drum 43 with laser light in accordance with the image data, and selectively attenuates the potential of the surface of the photosensitive drum 43 to form an electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 43 is developed with toner, and the toner image is transferred to a recording sheet.

  BD (Beam Detect) sensors 496 and 497 have substantially the same configuration, and are configured using photodiodes. The laser beams LD1 to LD4 are scanned within a scanning range that is a predetermined amount longer than the length of the photosensitive drum 43 in the main scanning direction, and the BD sensors 496 and 497 are photosensitive members within the scanning range. Before the laser beam enters the drum 43, the drum 43 is installed at a position to receive the laser beam.

  When receiving the laser beam, the BD sensors 496 and 497 output a light reception signal to the BD signal conversion unit 9. Based on this light reception signal, the optical scanning device 49 sets a timing for starting writing of an image based on the image data (charge removal operation by laser light irradiation) on the photosensitive drum 43.

  As shown in FIG. 4, the laser light sources LD1 to LD4 are arranged as described above, and the irradiation positions of the laser beams on the surface of the photosensitive drum 43 and the light receiving surface of the BD sensor 497 are as follows. Since each of the main scanning direction and the sub-scanning direction is arranged with a certain interval in one direction inclined at a certain inclination angle, each laser beam is reflected on the light receiving surface of the BD sensor 497. Each passes through a certain time difference.

  Returning to FIG. 2, the BD signal conversion unit 9 shapes the light reception signals output from the BD sensors 496 and 497 into rectangular wave BD signals, and outputs the BD signals to the image writing timing setting unit 101. . The image memory 8 temporarily stores image data obtained by the reading operation of the document reading unit 5 and outputs the image data to the control unit 10 as image data of an image to be written on the photosensitive drum 43.

  The control unit 10 includes a ROM that stores each control program, a RAM that temporarily stores data, a central processing unit that reads and executes the control program from the ROM, and the like. A drawing unit 102 and an LD driving unit 103 are provided.

  The image writing timing setting unit 101 starts writing an image (irradiation of the laser beam on the surface of the photosensitive drum 43 based on the image data) based on the BD signal input from the BD signal conversion unit 9 (hereinafter referred to as an image). Is set), and information indicating the image writing timing is output to the drawing unit 102. This case is characterized by this image writing timing setting method, which will be described below.

  First, as shown in FIG. 5A, the image writing timing setting unit 101 sets the laser light L1 output from the laser light source LD1 as a reference laser light, turns on only the laser light source LD1, and then turns on the laser light L1. Are scanned in the main scanning direction (hereinafter, this operation is referred to as a first operation). As a result, the BD sensors 496 and 497 output light reception signals when receiving the laser light L1. As shown in FIG. 6A, the output time difference between these light reception signals corresponds to the time Ta required for the irradiation position of the laser light L1 to move from the BD sensor 496 to the BD sensor 497. The image writing timing setting unit 101 performs this first operation in advance during a period other than the time of image formation.

  Next, the image writing timing setting unit 101 combines each of the other laser light sources LD2 to LD4 with the reference laser light source LD1, that is, a combination of the laser light source LD1 and the laser light source LD2, and the laser light source LD1 and the laser light source LD3. And a combination of the laser light source LD1 and the laser light source LD4, respectively, and in a period other than the scanning period for image formation, each of the pair of laser light sources belonging to each combination is scanned with laser light, Laser beams of two laser light sources belonging to the combination are received by different BD sensors.

  More specifically, as shown in FIG. 5B, the image writing timing setting unit 101 is configured so that the laser beam L1 is received by the BD sensor 496 and the laser beam L2 is received by the BD sensor 497. The polygon mirror 494 is scanned while the light sources LD1 and LD2 are turned on and off. Further, as shown in FIG. 5C, the image writing timing setting unit 101 causes the laser light sources LD1 and LD3 to receive the laser light L1 by the BD sensor 496 and the laser light L3 by the BD sensor 497. The polygon mirror 494 is caused to scan while performing the on / off operation. Further, as shown in FIG. 5D, the image writing timing setting unit 101 causes the laser light sources LD1 and LD4 to receive the laser light L1 by the BD sensor 496 and the laser light L4 by the BD sensor 497. The polygon mirror 494 is caused to scan while performing the on / off operation.

  By performing the operation shown in FIG. 5B, as shown in FIG. 6B, the timing t1 when the laser beam L1 passes through the BD sensor 496, and the timing t2 when the laser beam L2 passes through the BD sensor 497. Is obtained. A time difference (t2−t1) between these passage timings is a positional deviation W1 (see FIG. 4) of the BD sensors 496 and 497 and a positional deviation r2 in the main scanning direction of the irradiation positions of the laser beams L1 and L2 (see FIG. 4). This is caused by

  Further, by performing the operation shown in FIG. 5C, as shown in FIG. 6C, the timing t3 when the laser beam L1 passes through the BD sensor 496 and the timing when the laser beam L3 passes through the BD sensor 497. t4 is obtained. The time difference (t4−t3) between these passage timings is the positional deviation W1 (see FIG. 4) of the BD sensors 496 and 497 and the positional deviation r3 in the main scanning direction of the irradiation positions of the laser beams L1 and L3 (see FIG. 4). This is caused by

  Further, by performing the operation shown in FIG. 5D, as shown in FIG. 6D, the timing t5 when the laser beam L1 passes through the BD sensor 496 and the timing when the laser beam L4 passes through the BD sensor 497. t6 is obtained. The time difference (t6-t5) between these passage timings is the positional deviation W1 (see FIG. 4) of the BD sensors 496 and 497 and the positional deviation r3 in the main scanning direction of the irradiation positions of the laser beams L1 and L4 (see FIG. 4). This is caused by

  Here, the time difference caused by the positional deviation W1 of the BD sensors 496 and 497 is obtained in advance as the time Ta as described above. Therefore, the image writing timing setting unit 101 shifts the time ΔT1 (= t2−t1−Ta) obtained by subtracting the time Ta from the time difference (t2−t1) to the positional deviation in the main scanning direction of the irradiation positions of the laser beams L1 and L2. Calculated as the time difference caused by the amount r1. Similarly, the image writing timing setting unit 101 performs main scanning of the irradiation positions of the laser beams L1 and L3 by using a time ΔT2 (= t4−t3−Ta) obtained by subtracting the time Ta from the time difference (t4−t3). Time ΔT3 (= t6−t5−Ta) obtained by subtracting the time Ta from the time difference (t6−t5) is calculated as the time difference caused by the positional deviation amount r2 in the direction, and is the irradiation position of the laser beams L1 and L4. This is calculated as a time difference caused by the positional deviation amount r3 in the main scanning direction.

  Then, the image writing timing setting unit 101 sets the image writing timing by the laser light sources LD2 to LD4 based on the respective times ΔT1 to ΔT3. FIG. 5E is a time chart showing signals LSYNC1 to LSYNC4 in which the image writing timing setting unit 101 instructs the drawing unit 102 to write the images of the laser light sources LD1 to LD4.

  As shown in FIG. 5E, the image writing timing setting unit 101 sets the image writing timing by the laser light source LD1 based on the timing at which the laser light L1 is received by the BD sensor 496 or 497 during scanning for image formation. And a signal LSYNC1 instructing the image writing timing is output to the drawing unit 102. The image writing timing setting unit 101 outputs a signal LSYNC2 instructing the image writing timing of the laser light source LD2 to the drawing unit 102 after the time ΔT1 has elapsed from the output timing, and after the time ΔT2 has elapsed from the output timing. A signal LSYNC3 instructing the image writing timing of the laser light source LD3 is output to the drawing unit 102. After the time ΔT2 has elapsed from the output timing, a signal LSYNC4 instructing the image writing timing of the laser light source LD4 is output to the drawing unit 102.

  As described above, the two BD sensors (BD sensors 496 and 497) are arranged in parallel in the main scanning direction at a constant interval, and only the reference laser beam (laser beam L1) is scanned in the main scanning direction. Each of the two BD sensors 496 and 497 receives light, and sets a combination of each of the other laser light sources LD2 to LD4 and the reference laser light source LD1, and scans the laser light of a pair of laser light sources belonging to each combination. Since each is performed and the laser beams of the two laser light sources belonging to the combination are received by different BD sensors, the positional deviation amount in the main scanning direction of the irradiation position of the reference laser beam and the other laser beam is It can be detected as a time difference between light reception timings by the BD sensors 496 and 497. Therefore, by using this time difference to set the image writing timing of each of the laser light sources LD2 to LD4, the image writing timing to each scanning line can be reliably ensured without causing an increase in cost and a decrease in laser beam detection accuracy. Can be set to

  Here, the laser beam L1 is used as a reference laser beam, and a combination of other laser light sources LD2 to LD4 and a reference laser light source LD1 (a combination of a laser light source LD1 and a laser light source LD2, a laser light source LD1 and a laser light source LD3). And a combination of the laser light source LD1 and the laser light source LD4), and each pair of laser beams belonging to each combination is scanned. However, the present invention is not limited to this. These laser beams are set as a reference laser beam, a combination of this reference laser beam and another laser light source is set, and a pair of laser beams belonging to each combination is shown in FIGS. An operation corresponding to may be performed.

(Second Embodiment)
The present embodiment is different from the first embodiment only in the method of setting the image writing timing, and the other points are substantially the same, so only the differences from the first embodiment will be described. And The same members as those in the first embodiment will be described with the same numbers.

  The image writing timing setting unit 101 of the present embodiment performs the first operation in advance as shown in FIG. 5A, and each BD sensor 496, 497 receives each of the BD sensors 496 and 497 as shown in FIG. The point that the time Ta required for the irradiation position of the laser beam L1 of the laser light source LD1 to move from the BD sensor 496 to the BD sensor 497 is calculated from the output timing difference of the received light signal is the same as in the first embodiment.

  This embodiment is different from the first embodiment in the method of setting the image writing timing by the other laser beams L2 to L4. Hereinafter, this setting method will be described.

  First, as described above, the image writing timing setting unit 101 sets the laser light L1 output from the laser light source LD1 as a reference laser light, turns on only the laser light source LD1, and sets the laser light L1 in the main scanning direction. A first operation for scanning is performed. As a result, the BD sensors 496 and 497 output light reception signals when receiving the laser light L1. The difference in output time of these light reception signals corresponds to the time Ta required for the irradiation position of the laser light L1 to move from the BD sensor 496 to the BD sensor 497. The image writing timing setting unit 101 performs this first operation in advance to prepare for scanning for image formation.

  Next, the image writing timing setting unit 101 performs the following second operation for each scan for image formation. That is, the image writing timing setting unit 101 receives only the laser beams L1 and L3 in the BD sensor 496 as shown in FIGS. 7A and 7B within one scanning period. As shown in (d), the polygon mirror 494 is scanned in the main scanning direction while the laser light sources LD1 to LD4 are turned on / off so that only the laser beams L2 and L4 are received by the BD sensor 497. Make it.

  By this second operation, as shown in FIG. 8A, after the light reception signal of the laser light L1 is output from the BD sensor 496 (indicated as “BD1” in FIG. 8), the light reception signal of the laser light L3 is output. Is output. Thereafter, as shown in FIG. 8B, after the light reception signal of the laser light L2 is output from the BD sensor 497 (indicated as “BD2” in FIG. 8), the light reception signal of the laser light L4 is output.

  Here, focusing on the timing at which the laser beams L1 to L4 pass through the BD sensor 496 or the BD sensor 497 in the second operation, as shown in FIG. 9, the timing t11 at which the laser beam L1 passes through the BD sensor 496, Each time difference generated at timing t12 to t14 when the laser beams L2 to L4 pass through the BD sensor 496 or the BD sensor 497 is different from a time difference generated by a positional deviation W1 (see FIG. 4) in the main scanning direction of the BD sensors 496 and 497. This includes at least one of the time differences caused by the positional deviations r1 to r3 (see FIG. 4) of the laser beams L1 and L2 to L4 in the main scanning direction.

  For example, paying attention to the laser beams L1 and L3, as shown in FIG. 9A, the time difference (t12−t11) between the timings t11 and t12 when the laser beams L1 and L3 pass through the BD sensor 496, respectively, is the laser beam L1. , L3 is caused by the displacement r2 of the irradiation position in the main scanning direction.

  As shown in FIG. 9B, the time difference (t13−t11) between the timing t11 when the laser beam L1 passes through the BD sensor 496 and the timing t13 when the laser beam L2 passes through the BD sensor 497 is the BD sensor. This occurs due to the positional deviation W1 (see FIG. 4) of the main scanning direction of 496 and 497 and the positional deviation r1 (see FIG. 4) of the laser beams L1 and L2 in the main scanning direction.

  Further, as shown in FIG. 9C, the time difference (t14−t11) between the timing t11 when the laser beam L1 passes through the BD sensor 496 and the timing t14 when the laser beam L4 of the laser light source LD4 passes through the BD sensor 497. Is caused by the positional deviation W1 (see FIG. 4) of the BD sensors 496 and 497 in the main scanning direction and the positional deviation r3 of the irradiation position in the main scanning direction of the laser beams L1 and L2 (see FIG. 4). It is.

  The image writing timing setting unit 101 sets the image writing timing of the laser light source LD1 to the timing t11 (timing when the laser beam L1 passes through the BD sensor 496) obtained by the operation shown in FIG. When the image writing timing of the laser light source LD1 is determined based on the above, it is determined how much the image writing timing of the other laser light sources LD2 to LD4 is delayed with respect to the image writing timing of the laser light source LD1.

  This delay amount corresponds to a time difference caused by the displacement amounts r1 to r3 of the irradiation position in the main scanning direction between the reference laser beam L1 and the other laser beams L2 to L4. This time difference can be obtained from each time difference obtained by the operations shown in FIGS.

  That is, the time difference caused by the displacement r2 of the irradiation position in the main scanning direction of the laser beams L1 and L3 is the time difference (t12−t11) obtained by the operation shown in FIG. Accordingly, the image writing timing setting unit 101 sets the image writing timing by the laser light source LD3 to a timing delayed by the time ΔT11 (t12−t11) from the image writing timing by the laser light L1.

  Also, the time differences (t13-t11) and (t14-t11) obtained by the operations shown in FIGS. 9B and 9C are the positional deviations W1 of the BD sensors 496 and 497 in the main scanning direction (FIG. 4) and the positional deviation r1 (see FIG. 4) of the laser beams L1 and L2 in the main scanning direction, and the time difference caused by the positional deviation W1 of the BD sensors 496 and 497 is As described above, the time Ta is obtained in advance.

  Accordingly, the time difference caused by the positional deviation amount r2 of the laser beams L1 and L2 in the main scanning direction is a time ΔT12 (= t13−t11−Ta) obtained by subtracting the time Ta from the time difference (t13−t11). The time difference caused by the positional deviation r3 in the main scanning direction of the laser beams L1 and L4 is a time ΔT13 (= t14−t11−Ta) obtained by subtracting the time Ta from the time difference (t14−t11).

  Therefore, the image writing timing setting unit 101 sets the image writing timing by the laser light source LD2 to a timing delayed by the time ΔT12 (= t13−t11−Ta) from the image writing timing by the laser light source LD1, and the laser light source LD4. Is set to a timing delayed by a time ΔT13 (= t14−t11−Ta) from the image writing timing by the laser light source LD1.

  FIGS. 8C to 8F are time charts showing signals LSYNC1 to LSYNC4 in which the image writing timing setting unit 101 instructs the drawing unit 102 to write images of the laser light sources LD1 to LD4. As shown in FIGS. 8C to 8F, when the image writing timing setting unit 101 outputs the signal LSYNC1 instructing the image writing timing of the laser light source LD1 to the drawing unit 102, the time ΔT12 has elapsed from the output timing. Later, a signal LSYNC2 instructing the image writing timing of the laser light source LD2 is output to the drawing unit 102, and after the time ΔT11 has elapsed from the output timing, a signal LSYNC3 instructing the image writing timing of the laser light source LD3 is output to the drawing unit 102. Then, after the time ΔT13 has elapsed from the output timing, a signal LSYNC4 for instructing the image writing timing of the laser light source LD4 is output to the drawing unit 102.

  The drawing unit 102 starts driving of the LD driving unit 103 at the image writing timing instructed by the image writing timing setting unit 101 based on the image data of the writing target image output from the image memory 8. . The LD driving unit 103 controls driving of the laser irradiation unit 491 based on an instruction from the drawing unit 102.

  As described above, the two BD sensors (BD sensors 496 and 497) are arranged in parallel in the main scanning direction at a constant interval, and only the reference laser beam (laser beam L1) is scanned in the main scanning direction. On / off operation of each of the laser light sources LD1 to LD4 so that the two BD sensors 496 and 497 receive light respectively, and two laser beams whose irradiation positions are adjacent in the main scanning direction are received by different BD sensors in one scanning period. Since the polygon mirror 494 performs scanning while controlling the position, the amount of positional deviation in the main scanning direction of the irradiation position of the reference laser beam and the other laser beam is determined based on the light reception timing by the BD sensors 495 and 497. It can be detected as a time difference. Therefore, by using this time difference to set the image writing timing of each of the laser light sources LD2 to LD4, the image writing timing to each scanning line can be reliably ensured without causing an increase in cost and a decrease in laser beam detection accuracy. Can be set to

  In the first embodiment, the laser beam LD1 is set as the reference laser beam, but another laser beam is set as the reference laser beam, and the image writing timing of the scanning line corresponding to the laser beam is set. As a reference, the image writing timing of the scanning line corresponding to another laser beam may be set.

(Third embodiment)
The present embodiment is different from the first and second embodiments only in the method of setting the image writing timing, and the other points are substantially the same, and therefore only the differences from the second embodiment. I will explain. The same members as those in the first embodiment will be described with the same numbers.

  The image writing timing setting unit 101 according to the present embodiment performs the first operation in advance, and the laser light L1 of the laser light source LD1 is output from the BD sensor 496 to the BD sensor based on the output time difference between the light reception signals from the BD sensors 496 and 497. The point of calculating the time Ta required to move to 497 is the same as in the first and second embodiments.

  Further, in the second operation, the laser beams L1 and L2 are operated in the same manner as the operations in FIGS. 7A and 7C, and as shown in FIG. The time difference ΔT12 caused by the positional deviation amount r2 in the main scanning direction is calculated, and the image writing timing by the laser light source LD2 is set to a timing delayed by the time ΔT2 from the image writing timing by the laser light source LD1. This is the same as in the second embodiment.

  This embodiment is different from the first embodiment in the method of setting the image writing timing by the other remaining laser beams (here, the laser beams L3 and L4). Hereinafter, this setting method will be described.

  In the present embodiment, it is assumed that the spot diameters of the laser beams L1 to L4 are all the same diameter and are arranged at regular intervals in the main scanning direction, and the image writing timing is set by the laser light sources LD3 and LD4. It is what you do. That is, when the separation distance between the irradiation position of the laser beam L1 and the irradiation position of the laser beam L2 is r1, the irradiation position of the laser beam L3 is separated from the irradiation position of the laser beam L2 by the positional deviation amount r1, and It is estimated that the irradiation position of the laser beam L4 is separated from the irradiation position of the laser beam L3 by the positional deviation amount r1.

  Since the image writing timing setting unit 101 has the same scanning speed of each of the laser beams L1 to L4, if the distance between the irradiation positions of the laser beams having adjacent irradiation positions is the same as described above. Since the laser beams L1 to L4 are considered to enter the BD sensors 496 and 497 in this order with the same time difference, the image writing timing by the laser light source LD2 is delayed by ΔT12 with respect to the image writing timing by the laser light source LD1. In this case, based on the estimation, the image writing timing by the laser light source LD3 is set to a timing delayed by the time ΔT12 from the image writing timing by the laser light source LD2, and the image writing timing by the laser light source LD4 is set as the laser light source. Is the image writing timing by LD3? Is set to a timing delayed by time ΔT12.

  Even with such a process, it is possible to reliably set the image writing timing to each scanning line without incurring an increase in cost or a decrease in the detection accuracy of the laser beam.

  Here, the laser beam L1 is used as a reference laser beam, and the time difference ΔT12 caused by the positional shift amount r2 of the laser beams L1 and L2 in the main scanning direction in the second operation is calculated to obtain the laser beam L2. Is set based on the time difference ΔT12, and then the scan line image write timing corresponding to the laser beams L3 and L4 is calculated by calculation as described above. When there is sufficient time from when the lights L1 to L4 are incident on the BD sensors 496 and 497 until the leading laser light L1 is incident on the photosensitive drum 43, the reference laser light or the second operation causes the reference laser light L1 to enter the photosensitive drum 43. The laser beam scanned together with the laser beam can be set as appropriate.

  For example, when the laser beam LD2 is set as the reference laser beam, the image writing timing setting unit 101 causes the laser beam LD2 to perform the first operation. In this first operation, the time difference between the timing when the laser beam L2 passes through the BD sensor 496 and the timing when it passes through the BD sensor 497 is the time difference ΔTa.

  In addition, when the laser beam scanned with the laser beam L2 in the second operation is set to, for example, the laser beam 3 in the image writing timing setting unit 101, only the laser beams L2 and L3 are shown in FIGS. The same operation as that shown in FIG. Based on the time difference ΔTa between the output timing of the light reception signal of the BD sensor 496 that has received the laser light 3 and the output timing of the light reception signal of the BD sensor 497 that has received the laser light 2, the image writing timing setting unit 101 A time difference caused by the positional deviation amount x in the main scanning direction of the lights L2 and L3 is calculated.

  Based on this time difference, the image writing timing by the laser light source LD2 is set as a reference, and the image writing timing by the laser light source LD3 is set to a timing delayed by the time difference ΔTa from the image writing timing by the laser light source LD2.

  Further, the image writing timing setting unit 101 irradiates the laser beam 1 on the assumption that the spot diameters of the laser beams L1 to L4 are all the same diameter and are arranged at a constant interval in the main scanning direction. It is assumed that the position is separated from the irradiation position of the laser beam 2 by the displacement amount x, and the irradiation position of the laser beam 4 is separated from the irradiation position of the laser beam 3 by the displacement amount x. The image writing timing by the laser light source LD1 is set to a timing earlier by the time difference ΔTa than the image writing timing by the laser light source LD2, and the image writing timing by the laser light source LD4 is delayed by the time difference ΔTa from the image writing timing by the laser light source LD3. Set the timing.

1 is a side view schematically showing an internal configuration of a multifunction peripheral as an example of an image forming apparatus according to an embodiment of the present disclosure. It is a block diagram of an optical scanning device. It is a figure which shows the structure of a laser irradiation part. It is a figure which shows the state in which each light beam output from each said laser light source is imaged in a position which is each different in a main scanning direction and a subscanning direction on the surface of a photoreceptor drum, or the light-receiving surface of a BD sensor. 5 is a time chart regarding a light reception signal output from a BD sensor and a signal for instructing image writing timing in the first embodiment. It is explanatory drawing of the setting method of image writing timing. It is explanatory drawing of the setting method of the image writing timing which concerns on 2nd Embodiment. 10 is a time chart relating to a light reception signal output from a BD sensor and a signal indicating image writing timing in the second embodiment. It is explanatory drawing of the setting method of image writing timing. It is explanatory drawing of the setting method of the image writing timing which concerns on 3rd Embodiment.

Explanation of symbols

49 Optical Scanning Device 101 Image Writing Timing Adjustment Unit 102 Drawing Unit 103 LD Drive Units 496 and 497 BD Sensor

Claims (3)

A light source unit that outputs a plurality of light beams at least from different positions in the main scanning direction;
A scanning unit for repeatedly scanning each light beam output from the light source unit in the main scanning direction within a predetermined region;
A first and a second light receiving unit that are installed in the fixed region at a predetermined interval in the main scanning direction and perform a photoelectric conversion operation;
A light source control unit that causes the light source unit to perform an image writing operation based on image data on the surface of the photoconductor installed to include the certain area;
An image writing timing setting unit that sets a start timing of the image writing operation for each scanning line based on signals output from the first and second light receiving units;
The image writing timing setting unit
By scanning one of the plurality of light beams in the main scanning direction and receiving the light by the first and second light receiving units, an output timing difference of each detection signal obtained from each of the light receiving units is set to a first value. Detect as output timing difference,
A combination of each of the other light beams other than the first light beam and the first light beam is set and scanning is performed for each combination, and the light receiving targets of the first and second light receiving units are set to each other in each scan. As the second output timing difference, the output timing difference of each received light signal obtained from each of the light receiving units by causing the first and second light receiving units to receive the light beams belonging to the combination corresponding to the scanning as different light beams. Detect for each combination,
A difference between each of the second output timing differences detected for each of the combinations and the first output timing difference is calculated, and image writing is performed on the scanning line that performs the writing operation for each of the other light beams. The operation start timing is set to a timing that is shifted by a time based on the difference corresponding to the light beam from the image writing operation start timing for the scanning line that performs the writing operation with the one light beam,
The light source controller is
An image forming apparatus that controls an emission operation of the light source unit according to an image writing timing set by the image writing timing setting unit and performs an image writing operation for each scanning line on the surface of the photosensitive member. The light source unit is configured to be capable of outputting four light beams,
The image writing timing setting unit sets the first light beam incident on the light receiving unit as the first light beam when the scanning unit performs scanning with the light source unit outputting all light beams, and the first light beam. With the first light beam, the start timing of the image writing operation with respect to the scanning line that performs the writing operation with the second to fourth light beams as the second light beam to the fourth light beam is set as the other light beam. The image forming apparatus according to claim 1, wherein the image forming apparatus is set based on a start timing of an image writing operation for a scanning line that performs the writing operation. A light source unit that outputs a plurality of light beams at least from different positions in the main scanning direction; and a scanning unit that repeatedly scans each light beam output from the light source unit in the main scanning direction within a predetermined area. The first and second light receiving units that are installed in the fixed region at a predetermined interval in the main scanning direction and perform a photoelectric conversion operation, and a photosensitive member that includes the fixed region. A light source control unit that causes the light source unit to perform an image writing operation based on image data on the surface, and the image writing operation for each scanning line based on signals output from the first and second light receiving units. An image writing timing setting method in an image forming apparatus comprising an image writing timing setting unit for setting a start timing,
Each detection signal obtained from each of the light receiving units when the image writing timing setting unit scans one of the plurality of light beams in the main scanning direction and receives the light by the first and second light receiving units. Detecting an output timing difference as a first output timing difference;
The image writing timing setting unit sets a combination of each light beam other than the first light beam and the first light beam to perform scanning for each combination, and the first and second scans are performed in each scan. The light receiving target of the light receiving unit is different from each other, and the first and second light receiving units receive the light beams belonging to the combination corresponding to the scanning, and thereby the output timing difference of each light receiving signal obtained from each of the light receiving units is determined. Detecting for each combination as a second output timing difference;
The image writing timing setting unit calculates a difference between each of the second output timing differences detected for each of the combinations and the first output timing difference, and writes each of the other light beams with the light beam. The start timing of the image writing operation for the scanning line that performs the operation is set to a timing that is shifted from the start timing of the image writing operation for the scanning line that performs the writing operation by the one light beam by the time based on the difference corresponding to the light beam. Steps,
The light source control unit controlling the light emission operation of the light source unit according to the image writing timing set by the image writing timing setting unit, and performing the image writing operation for each scanning line on the surface of the photoconductor. Image writing timing setting method provided.

Images