JP5096789B2 - Image forming apparatus and image writing timing setting method - Google Patents

Description

  The present invention belongs to the technical field of image forming apparatuses, and particularly relates to a laser irradiation technique for performing exposure by irradiating a surface of a photosensitive drum with a laser.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, 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, and electrostatically adhere to the surface of the photosensitive drum. What forms a latent image is widely known. In addition, in this type of apparatus, a technology is also known in which a BD (Beam Detect) sensor that receives laser light at a predetermined position is installed, and the light scanning start timing (start position) is set using an output signal of the BD sensor. It has been.

  Further, for example, there are the following Patent Documents 1 to 3 as documents related to this type of technical field. Patent Document 1 below discloses a multi-beam light source that can emit two light beams simultaneously, and if the shift amount Δx in the main scanning direction on the synchronous detection sensor of the two light beams is larger than 0, It is described that two beams can be detected by the same synchronous detection sensor. In Patent Document 2 below, in an image forming apparatus in which writing to a plurality of scanning lines is performed in one scan by a laser array device having a plurality of light emitting elements, the light receiving timing of the first passing laser beam and the optical system A technique for adjusting the drawing start timing of another laser beam based on a delay value determined by the magnification of λ, the interval between light emitting elements and the resolution is disclosed.

Further, in Patent Document 3 below, two optical sensors that are arranged at an angle and detect the passage of two light beams that scan the surface of the photosensitive member, and the passage time of the beams in these optical sensors are measured. Disclosed is a technique for calculating a pitch in the sub-scanning direction based on a measuring means, a phase detecting means for detecting the phase of each light beam, and a transit time measured by the measuring means and a phase detected by the phase detecting means. Has been.
JP 2002-139690 A JP 2003-305886 A JP-A-11-216905

  In an image forming apparatus in which a plurality of light sources are installed at different positions in the main scanning direction and each light source scans a plurality of light beams on a plurality of lines in one scan, each light beam is BD at different timings when scanning is performed. In order to enter the sensor, it is necessary to set the image writing timing of each light beam based on each incident timing.

  However, when the positional deviation amount of each light source in the main scanning direction is 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.

  Therefore, 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. However, such a technique causes an increase in cost and a decrease in detection accuracy of laser light.

  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. An object is to provide a forming apparatus.

  According to the first aspect of the present invention, a light source unit in which four or more light sources are installed at different positions at least in the main scanning direction, and each light beam output from the light source unit is in a predetermined fixed region. A scanning unit for repeatedly scanning in the main scanning direction, a light receiving unit that performs a photoelectric conversion operation installed in the fixed region, and a surface of a photoconductor that includes a part of the fixed region. A light source control unit that causes the light source unit to perform an image writing operation based on image data, and an image writing timing setting that sets a start timing of the image writing operation for each scanning line based on a signal output from the light receiving unit. And the image writing timing setting unit causes the light source control unit to turn on at least three light sources and less than all of the light sources to be turned on. Both of the two light sources are turned on using the output timing of the light receiving signal output from the light receiving unit when scanning by the scanning unit is performed in a manner of being separated from each other via at least one non-lighted light source. The scanning line image writing timing by the non-lighting light source is set, and the scanning line image writing timing by the non-lighting light source is set to the scanning line image writing timing by the two light sources adjacent to the non-lighting light source. The light source control unit controls the light emission operation of each light source according to the image writing timing set by the image writing timing setting unit, and sets the image for each scanning line on the surface of the photosensitive member. Performs writing operation.

  According to a fourth aspect of the present invention, there is provided a light source unit in which four or more light sources are installed at different positions at least in the main scanning direction, and each light beam output from the light source unit is within a predetermined fixed region. A scanning unit for repeatedly scanning in the main scanning direction, a light receiving unit that performs a photoelectric conversion operation installed in the fixed region, and a surface of a photoconductor that includes a part of the fixed region. A light source control unit that causes the light source unit to perform an image writing operation based on image data, and an image writing timing setting that sets a start timing of the image writing operation for each scanning line based on a signal output from the light receiving unit. An image writing timing setting method in an image forming apparatus, wherein the image writing timing setting unit includes all three or more of the image writing timing setting units by the light source control unit. When the scanning unit scans in such a manner that at least two of the light sources to be turned on and at least two of the light sources to be turned on are separated from each other via at least one non-lighted light source, the light is output from the light receiving unit. A step of setting an image writing timing of a scanning line by a light source that is turned on using an output timing of a light reception signal, and a step of setting the image writing timing of the scanning line by the non-lighting light source by the image writing timing setting unit. A step of setting using the image writing timing of each scanning line by two light sources adjacent to the non-lighting light source among the light sources that have been turned on, and the image writing set by the light source control unit by the image writing timing setting unit The light emitting operation of each light source is controlled according to the timing to In which and a step of performing an image writing operation for each scanning line on the surface of the.

  According to these inventions, the light source control unit turns on three or more light sources less than the total number, and at least two of the light sources to be turned on are separated from each other via at least one non-lighted light source. Using the output timing of the light receiving signal output from the light receiving section when scanning by the scanning section is performed, the image writing timing of the scanning line by the light source that is lit is set.

  The scanning line image writing timing by the non-lighted light source is set by using the scanning line image writing timing by two light sources adjacent to the non-lighting light source among the lighted light sources.

  Thus, as in the prior art, each light beam is received by the light receiving unit without changing the frequency and power of each laser beam and separating the BD signal from each laser beam by giving a voltage difference to the output of the BD sensor. The timing of passing through the surface can be calculated relatively easily.

  Here, when two light sources adjacent to the non-lighting light source exist at substantially the same distance from the non-lighting light source as in the invention described in claim 2, scanning by the non-lighting light source is performed. The image writing timing of the line may be set to an intermediate timing between the image writing timings of the scanning lines by the respective light sources existing at substantially the same distance from the non-lighting light source.

  When two light sources adjacent to the non-lighting light source are present at different distances from the non-lighting light source as in the third aspect of the invention, an image of the scanning line by the non-lighting light source The writing timing may be set to a timing for proportionally distributing the period between the image writing timings of the scanning lines by the respective light sources that are lit on both sides of the non-lighting light source.

  According to the second and third aspects of the present invention, each image writing of the scanning line by the non-lighting light source is performed according to the positional relationship between the non-lighting light source and two light sources adjacent to the non-lighting light source. Timing is set appropriately.

  According to the present invention, as compared with the conventional method in which the frequency and power of each laser beam is changed and a voltage difference is given to the output of the BD sensor to separate the BD signal by each laser beam, the light is not turned on. Since the image writing timing of the light source can be calculated by a relatively simple calculation, the image writing timing can be set without causing an increase in cost and a decrease in the detection accuracy of the laser beam.

  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”). 496).

  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 at a predetermined interval on the front end surface Y, and the laser light sources LD4 and 4 are located on the inner side of the normal to the front end surface Y. It is configured to be rotatable in the direction of arrow A with a normal G passing through the intermediate position of LD5 as a rotation axis.

  When the optical scanning device 49 turns on all the laser light sources LD1 to LD8 and irradiates the surface of the photosensitive drum 43 with the laser beams L1 to L8, the arrangement direction of the irradiation positions (imaging positions) is: The laser irradiation unit 491 is set in a rotated state so as to have an inclination angle with respect to each of the main scanning direction and the sub-scanning direction (a direction perpendicular to the main scanning direction when the surface of the photosensitive drum 43 is developed). Thus, the image can be written to the plurality of scanning lines by one scanning, 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.

  The BD (Beam Detect) sensor 496 is configured using a photodiode. The laser beams LD1 to LD8 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 sensor 496 includes the photosensitive drum 43 within the scanning range. It is installed at a position for receiving the laser beam before the laser beam is incident on it.

  When receiving the laser beam, the BD sensor 496 outputs a received light signal to the BD signal converter 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 LD8 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 496 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, the polygons are turned on with all the laser light sources LD1 to LD8 turned on. When scanning with the mirror 494 is performed, each laser beam passes through the light receiving surface of the BD sensor 496 with a certain time difference.

  The BD signal conversion unit 9 shapes the detection signal output from the BD sensor 496 into a rectangular wave BD signal, and outputs the BD signal 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.

  By the way, as described above, the light beams output from the laser light sources pass through the light receiving surface of the BD sensor 496 and the surface of the photosensitive drum 43 with a certain time difference. When attention is paid to spot light that reaches the top, when the distance between adjacent laser light sources is relatively large and the pitch between adjacent spot lights in the main scanning direction is designed to be large, FIG. ), The light reception signals corresponding to the laser beams L1 to L8 are individually obtained from the BD sensor 496, and the timings T1 to T8 at which the laser beams have passed through the BD sensor 496 can be detected.

  However, if the pitch between adjacent spot lights in the main scanning direction is designed to be small, the next light beam passes through the light receiving surface before the light beam passing through the light receiving surface at the previous timing has finished passing through the light receiving surface. It passes through and some laser light always enters the BD sensor 496. Therefore, the light reception signal output from the BD sensor 496 is a constant signal until all the light beams have passed through the light receiving surface of the BD sensor 496, as shown in FIG.

  As a result, it is possible to detect the timing of the first laser beam passing through the light receiving surface and the timing of the last laser beam passing through the light receiving surface, but detect the other laser beam passing timings. As a result, the image writing timing of the scanning line corresponding to each laser beam cannot be set.

  Therefore, in the present embodiment, scanning is performed in a state where only four laser light sources (for example, laser light sources LD1, LD3, LD5, and LD7) that are not adjacent to each other are lit, and the image writing timing by the lit laser light sources is An image writing timing in which the laser light output from the laser light source is set based on the timing at which the BD sensor 496 receives light, and the image writing timing by the remaining laser light sources (laser light sources that are not turned on) is set for the lighted laser light sources. Is calculated and set by calculation.

  At this time, a light reception signal is individually output from the BD sensor 496 by the laser beams L1, L3, L5, and L7. That is, as shown in FIG. 5C, a light reception signal (indicated by an arrow A1) is obtained from the BD sensor 496 by the laser light L1 of the first laser light source LD1, and then the laser light L3 of the third laser light source LD3. A light reception signal (indicated by arrow A2) is obtained, and then a light reception signal (indicated by arrow A3) is obtained by the laser light L5 of the fifth laser light source LD5, and then a light reception signal by the laser light L7 of the seventh laser light source LD7. (Indicated by arrow A4) is obtained.

  The image writing timing setting unit 101 sets the image writing timing of each of the laser light sources LD1, LD3, LD5, and LD7 based on the output timing of the received light signal thus obtained. That is, the image writing timing setting unit 101 sets the image writing timing of the laser light source LD1 based on, for example, the falling timing T1 of each received light signal, and performs the image writing operation after a predetermined reference clock count from the timing T1. An image writing signal for giving an instruction to start is output to the drawing unit 103. Similarly, the image writing timing setting unit 101 sets the image writing timing of the laser light source LD3 based on the falling timing T3 of the received light signal, and draws the image writing signal after a predetermined reference clock count from the timing T3. 103, sets the image writing timing of the laser light source LD5 based on the falling timing T5 of the received light signal, outputs the image writing signal to the drawing unit 103 after a predetermined reference clock count from the timing T5, and receives the light The image writing timing of the laser light source LD7 is set based on the signal falling timing T7, and the image writing signal is output to the drawing unit 103 after a predetermined reference clock count from the timing T7.

  Next, the image writing timings of the remaining laser light sources LD2, LD4, LD6, and LD8 are set using the image writing timings of the laser light sources LD1, LD3, LD5, and LD7. In the present embodiment, for the remaining laser light sources LD2, LD4, LD6, and LD8, each image writing timing of the laser light source adjacent to the laser light source is set.

  That is, the laser light sources LD1 to LD8 are arranged in a line at regular intervals, that is, the laser light source LD2 is located at an intermediate position between the laser light sources LD1 and LD3, and the laser light source LD4 is connected to the laser light sources LD3 and LD3. It is assumed that the laser light source LD6 is located at an intermediate position between the light source LD5 and the laser light source LD6 is located at an intermediate position between the laser light source LD5 and the laser light source LD7.

  Based on this, the image writing timing setting unit 101 passes the BD sensor 496 through the BD sensor 496 at a timing intermediate between the timing at which the laser beam 1 passes through the BD sensor 496 and the timing at which the laser beam 3 passes through the BD sensor 496. The image writing timing of the laser light source LD2 is set based on the intermediate timing T2 between the falling timings T1 and T3, and the image writing signal is sent to the drawing unit 103 after a predetermined reference clock count from the timing T2. Output.

  Similarly, the image writing timing setting unit 101 passes the BD sensor 496 at a timing intermediate between the timing at which the laser beam 3 has passed through the BD sensor 496 and the timing at which the laser beam 5 has passed through the BD sensor 496. The image writing timing of the laser light source LD4 is set based on the intermediate timing T4 between the falling timings T3 and T5, and the image writing signal is sent to the drawing unit 103 after a predetermined reference clock count from the timing T4. The laser beam L6 is regarded as having passed through the BD sensor 496 at a timing intermediate between the timing at which the laser beam 5 has passed through the BD sensor 496 and the timing at which the laser beam 7 has passed through the BD sensor 496. Based on the intermediate timing T6 between T5 and T7, Set the image writing timing of the laser light source LD6, and outputs a write signal of the image from the timing T6 after a predetermined reference clock count to the drawing portion 103.

  For the laser light source L8, the laser light source LD7 is the only adjacent laser light source, and the image writing timing cannot be set by the calculation method as described above. Therefore, for example, the timing T7 is equal to the timing difference between the timing T6 and the timing T7. The timing T8 delayed from is calculated, and the image writing timing of the laser light source LD8 is set based on the timing T8.

  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.

  FIG. 6 is a flowchart showing image write timing adjustment processing by the control unit 10. In this case as well, the laser irradiation unit 491 is assumed to have eight laser light sources LD1 to LD8 as shown in FIGS. 3 to 5, and the description will be made with reference to FIG.

  As shown in FIG. 6, the controller 10 scans the laser beams L1, L3, L5, and L7 with the laser light sources LD1, LD3, LD5, and LD7 turned on (step # 1), and the BD sensor. A BD signal is generated based on the light reception signal output from 496, and the falling timings T1, T3, T5, and T7 of each BD signal are detected (step # 2).

  Next, the control unit 10 uses the fall timings T1, T3, T5, and T7 detected in step # 2, and laser light sources LD1, LD3 when scanning the laser beams L1, L3, L5, and L7 in step # 1. , LD5, LD7 and laser light sources LD2, LD4, LD6, LD8 are assumed to be turned on, and the falling timing of the BD signal obtained by passing the laser beams L2, L4, L6, L8 through the BD sensor 496 T2, T4, T6 and T8 are calculated (step # 3). That is, the controller 10 sets the falling timing T2 to (T1 + T3) / 2, sets the falling timing T4 to (T5 + T3) / 2, sets the falling timing T6 to (T7 + T5) / 2, and sets the falling timing. Let T8 be T7 + (T7-T5) / 2.

  Then, the control unit 10 sets the image writing timing of each of the laser light sources LD1 to LD8 based on the timings T1 to T8 obtained in steps # 2 and # 3 (step # 4).

  As described above, every other laser light source (in this case, LD1, LD3, LD5, and LD7) to be turned on is set, and each of the laser light when these laser light sources are turned on is scanned in the main scanning direction to obtain a BD signal. And setting the image writing timing of the scanning line corresponding to the lit laser light source based on the passing timing of the laser beams L1, L3, L5, and L7 that can be detected from each BD signal itself. Using this image writing timing, the image writing timing of the scanning light source corresponding to the laser light source (in this case, LD2, LD4, LD6, LD8) that was not turned on by the scanning is used. Since it is calculated by the calculation used, it corresponds to the laser light source that was not turned on by the scanning. It can be relatively easily derive image write timing 査 line. Therefore, as compared with the conventional method in which the frequency and power of each laser beam is changed and a voltage difference is given to the output of the BD sensor 496 to separate the BD signal by each beam, the cost is increased and the detection of the laser beam is performed. The image writing timing for each scanning line can be set while suppressing a decrease in accuracy.

  Further, even when the positional relationship of spot light (such as the pitch between adjacent spot lights) by each laser light source changes in accordance with the environment of the multifunction device 1 (environment temperature, environmental humidity, etc.) The laser beam passage start timing can be easily calculated.

  In addition, this case includes the following forms instead of or in addition to the above embodiments.

  (1) In the embodiment, the laser light sources to be turned on are set to the laser light sources LD1, LD3, LD5, and LD7. However, the laser light sources to be turned on are set to the laser light sources LD2, LD4, LD6, and LD8. Based on the falling timings T2, T4, T6, and T8 of the BD signal obtained by scanning with the laser beams L2, L4, L6, and L8, the image writing timing of the scanning lines corresponding to the laser light sources LD1, LD3, LD5, and LD7 is determined. You may make it set.

  In the above-described embodiment, the laser light sources LD1, LD3, LD5, and LD7 are set to be turned on. However, the laser light source LD8 may be turned on instead of the laser light source LD7. In this case, among the laser light sources LD2, LD4, LD6, and LD7 that are not turned on, the method for calculating the image writing timing of the laser light sources LD2 and LD4 is substantially the same as in the first embodiment. Regarding the image writing timing of the laser light sources LD6, LD7 that are not lit, the laser light sources LD5, LD5, LD5, LD7, LD7 that are not lit, and the laser light sources LD5, LD5, LD5, LD5, LD5, LD5, LD8 that are closest to each side of the light sources LD6, LD7 that are not lit. It can be calculated by calculation using the image writing timing of the LD8. That is, it is assumed that the laser light sources LD5 to LD8 are arranged as an example at regular intervals, and the image writing timing setting unit 101 determines the falling timings T6 and T7 of the BD signal by the laser beams L6 and L7 as the laser beams L5 and L7. The BD signal fall timings T5 and T8 by L8 are set to timings (T8-T5) / 3, {(T8-T5) × 2} / 3, respectively, and the laser light source is set based on this timing. The image writing timing of scanning lines corresponding to LD6 and LD7 is set.

  Furthermore, the combination of the laser light sources LD1, LD3, LD5, and LD7 and the combination of the laser light sources LD1, LD3, LD5, and LD8 may be switched for each scan. When the combination of the laser light sources to be turned on is not switched between the two combinations, an error is included in the falling timing of the BD signal by the laser light L8 calculated in the former combination. If the error is included in the case, or the error is included in the falling timing of the BD signal by the laser beam L8 calculated by the latter combination, the error appears as a relatively remarkable pattern, and the user feels uncomfortable in the image. However, by switching the combinations, it is difficult for the user to recognize the patterns generated due to the errors, and it is possible to make it difficult for the user to feel uncomfortable with the image.

  (2) The number of laser light sources to be lit is not limited to four. Further, the separation distance between the laser light sources to be lit does not have to be constant, such as a combination of laser light sources LD1, LD3, and LD7 and a combination of LD2, LD5, and LD8. In this case, the image writing timing of each laser light source may be set as follows. Hereinafter, a description will be given with reference to FIG. 5 as a laser light source for turning on the laser light sources LD1, LD3, and LD7.

  First, the image writing timing of the laser light sources LD1, LD3, and LD7 is set by the same method as in the first embodiment. The image writing timing of the laser light source LD2 may be set to an intermediate timing between the image writing timing of the laser light source LD1 and the image writing timing of the laser light source LD3.

  The image writing timing of the laser light sources LD4 to LD6 is set as follows. The image writing timing setting unit 101 sets the period between the falling timing t3 of the BD signal by the laser beam L3 and the falling timing t7 of the BD signal by the laser beam L7 between the laser light source LD3 and the laser light source LD7. Timings t4, t5, and t6 for dividing the period when the number of light sources is added to 1, that is, equal to 4 in this case, are obtained. The image writing timing setting unit 101 sets the image writing timing of the scanning lines corresponding to the laser light sources LD4 to LD6 based on the timings t4, t5, and t6.

  In addition, the image writing timing setting unit 101, for example, for the image writing timing of the scanning line corresponding to the laser light source LD8, is a BD signal falling timing t6 by the laser beam L6 and a BD signal falling timing t7 by the laser beam L7. Is set based on the timing delayed from the timing t7.

  Furthermore, the number of laser light sources is not limited to eight, and can be arbitrarily set as long as it is four or more, and the number of laser light sources to be lit is not limited to three or four and can be arbitrarily set.

  (3) When the laser light source to be turned on is set to a laser light source that is spaced apart at regular intervals (for example, every other) as in the above-described embodiment, the following method may be used in addition to the method of the first embodiment. The timing at which the light beam of each light source passes on the light receiving surface of the BD sensor 496 can also be calculated by the method. In the following description, similarly to the first embodiment, a case where the number of laser light sources is eight (laser light sources LD1 to LD8) will be described.

  First, the positional relationship of the irradiation positions of the laser beams L1 to L8 in a state where all the laser light sources LD1 to LD8 are turned on is measured in advance by a measuring device (not shown), and the laser beams L1 to L1 are measured from the measured values. The timing at which L8 passes through the BD sensor 496 is calculated, and this timing is stored as a reference timing in a storage unit (not shown) provided in the control unit 10.

  Referring to FIG. 7, for example, when scanning is performed in the main scanning direction with only the laser light sources LD1, LD5, and LD8 turned on, the image writing timing adjustment unit 104 is the same as in the first embodiment. , The falling timings T1 ′, T5 ′, T8 ′ of the BD signals by the laser beams L1, L5, L8 are detected based on the received light signals output from the BD sensor 496, and these timings T1 ′, T5 ′, T8 are detected. Based on ', the image writing timing of the scanning line corresponding to the laser light sources LD1, LD5, LD8 is set.

  Next, in the image writing timing setting unit 101, the time difference between the falling timing T1 ′ of the BD signal by the laser beam L1 and the falling timing T5 ′ of the BD signal by the laser beam L5 is stored in the control unit 10. When the time difference between the downstream timings T1 and T5 (hereinafter referred to as a reference time difference) is changed by D times, the laser light on the assumption that the falling timing T1 and the laser light sources LD2 to LD4 are also turned on. It is considered that the time difference from the falling timing of the BD signal by L2 to L4 also changes D times.

  Based on this, when the image writing timing adjusting unit 104 detects the falling timings T1 ′ and T5 ′, it uses the falling timings T1 ′ and T5 ′ to set the ratio D to (T5′−T1 ′) / ( T5−T1), and using this ratio D, the falling timings T2 ′ to T4 ′ of the BD signals by the laser beams L2 to L4 are calculated.

  That is, the image writing timing adjustment unit 104 calculates the falling timing T2 ′ of the BD signal by the laser light L2 by T2 ′ = T1 ′ + {(T5−T1) / 4} × D, and the BD by the laser light L3. The signal falling timing T3 ′ is calculated by T3 ′ = T1 ′ + {(T5−T1) × 2/4} × D, and the falling timing T4 ′ of the BD signal by the laser light L4 is T4 ′ = T1. '+ {(T5−T1) × 3/4} × D.

  The BD signal falling timings T6 ′ and T7 ′ by the laser beams L6 and L7 are also calculated by the same calculation method as described above using the BD signal falling timings T5 ′ and T8 ′ by the laser beams L5 and L8. can do.

  Then, the image writing timing adjustment unit 104 sets the image writing timing of the scanning lines corresponding to the laser light sources LD1 to LD8 based on the timings T1 'to T8' thus calculated.

  Thereby, also in this embodiment, even when the positional relationship of the spot light (pitch between adjacent spot lights) by each laser light source changes according to the environment (environment temperature, environmental humidity, etc.) of the multifunction machine 1, The passage timing of each ray can be easily calculated according to the change.

  (4) In each of the above embodiments, the image writing timing of each of the laser light sources LD1 to LD8 is set based on the falling timing of each BD signal. It may be set on the basis of the timing, or may be set based on an intermediate timing between the falling timing and the rising timing.

  (5) This case is not limited to the number of laser light sources provided in the laser irradiation unit 491 being eight, and includes, for example, those having four or sixteen laser light sources.

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 arrangement | sequence state of a laser light source. 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 the main scanning direction and a subscanning direction on the surface of a photoconductive drum, or the light-receiving surface of a BD sensor. It is a figure for demonstrating the method to calculate the timing which the light ray of each laser light source passes the light-receiving surface of a BD sensor. It is a flowchart which shows the image writing timing adjustment process by a control part. It is explanatory drawing of a deformation | transformation form.

Explanation of symbols

49 Optical Scanning Device 101 LD Drive Unit 103 Drawing Unit 104 Image Writing Timing Adjustment Unit 105 Abnormality Detection Processing Unit 496 BD Sensor

Claims (2)

A light source unit in which four or more light sources are installed at different positions in at least the main scanning direction;
A scanning unit for scanning repeatedly in the main scanning direction of each light beam that is output a predetermined constant region from the light source unit,
A light receiving unit that performs a photoelectric conversion operation installed in the predetermined 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 of a photoconductor including a part of the certain region;
An image writing timing setting unit that sets a start timing of the image writing operation for each scanning line based on a signal output from the light receiving unit;
The image writing timing setting unit
The light source control unit turns on three or more light sources less than the total number, and at least two of the light sources to be turned on are scanned by the scanning unit in a manner of being separated from each other via at least one non-lighting light source. Sometimes, using the output timing of the received light signal output from the light receiving unit, set the image writing timing of the scanning line by the light source turned on,
The scanning line image writing timing by the non-lighting light source is set by using the scanning line image writing timings by two light sources adjacent to the non-lighting light source among the lit light sources,
The light source controller is
There line the image writing operation for each scanning line on the surface of the photosensitive member by controlling the light emitting operation of the light sources in accordance with the image write timing set by the image write timing setting unit,
When two light sources adjacent to the non-lighting light source are present at different distances from the non-lighting light source, the scanning line image writing timing by the non-lighting light source is set on both sides of the non-lighting light source. An image forming apparatus that sets a period between image writing timings of scanning lines by light sources that are turned on at a timing that is proportionally distributed by the ratio of the distances . A light source section 4 or more light sources, which are placed at different positions at least in the main scanning direction, for scanning repeatedly in the main scanning direction at a predetermined constant region of each ray that is output from the light source unit An image writing operation based on image data with respect to the surface of a photoconductor installed including a part of the fixed region, a light receiving unit that performs a photoelectric conversion operation installed in the fixed region, An image in an image forming apparatus comprising: a light source control unit to be performed by a light source unit; and an image writing timing setting unit that sets a start timing of the image writing operation for each scanning line based on a signal output from the light receiving unit. An export timing setting method,
The image writing timing setting unit causes the light source control unit to turn on at least three light sources and less than all light sources, and at least two light sources to be turned on are separated from each other via at least one non-lighting light source. Using the output timing of the light receiving signal output from the light receiving section when scanning by the scanning section, setting the image writing timing of the scanning line by the lit light source;
The image writing timing setting unit uses the image writing timing of the scanning line by the non-lighted light source as the image writing timing of the scanning line by two light sources adjacent to the non-lighting light source among the lit light sources. And when the two light sources adjacent to the non-lighting light source are present at different distances from the non-lighting light source, the scanning line image writing timing by the non-lighting light source is set to the non-lighting time. Setting a period between each image writing timing of the scanning line by each light source that is lit on both sides of the light source to a timing that is proportionally distributed by the ratio of the distance ;
The light source control unit controlling the light emission operation of each light source 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