JP2009012258A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of setting an image writing timing to each scanning line without increasing the cost nor decreasing detection accuracy of laser light. <P>SOLUTION: Light sources LD4 to LD10 are allowed to scan by each preset group in a condition that the light sources LD4 to LD10 are lightened together with a reference light source LD1. Light beam pass-through timings T4 to T10 of the light sources LD4 to LD10 on the basis of a light beam pass-through timing T1 of the light source LD1 are detected. Light beam pass-through timings T5', T6' of the light sources LD5, LD6 on the basis of light beam pass-through timings T2', T3' of light sources LD2, LD3 which are obtained by allowing the light sources LD2, LD3 to respectively scan, are detected in a condition that the light sources LD3, LD6 are lightened. Light beam pass-through timings T2, T3 of the light sources LD2, LD3 on the basis of the light beam pass-through timing T1 are detected based on the timings T5, T6, T5', T6'. The above detecting operations are carried out before forming an image. The detecting timings are utilized in the forming of an image. <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 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, as a document related to this type of technical field, for example, there is Patent Document 1 below. 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.
JP 2002-139690 A

  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 three or more light sources are installed at different positions in the main scanning direction and the sub-scanning direction, and each light beam output from the light source unit is determined in advance. A scanning unit for repeatedly scanning in the main scanning direction within a certain region and a light receiving unit for performing a photoelectric conversion operation are installed in the certain region, and a BD signal is generated based on an output signal of the light receiving unit. 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 photosensitive member that includes a part of the certain area, and the light beam receives the light. A light beam passage timing passing through the light source is acquired from a BD signal of the BD signal generation unit, and is a start timing of the image writing operation to each scanning line by the light source based on the light beam passage timing. An image writing timing setting unit for setting the image writing timing, and when the scanning unit performs scanning with all the light sources turned on, the output period of the BD signal by the light beam output from each light source is The image writing timing setting unit turns on a predetermined light source among the light sources, partially overlapping with an output period of a BD signal by light beams output from one or more light sources existing next to the light source By comparing a light reception signal obtained from the light receiving unit by scanning performed in a state of being made with a predetermined reference, a light source that outputs a light beam that cannot detect the light beam passage timing is detected, and the detected light source and A light source other than a predetermined light source is set as an extinguished light source, and a light source other than the extinguished light source is set as an illuminating light source. The image writing timing by the lighting light source is set based on the light receiving signal obtained from the light receiving unit when the light beam scanned, and the image writing timing by the unlit light source is set by using the image writing timing by the lighting light source. The light emission control unit controls the light emission operation of each light source according to the image write timing set by the image write timing setting unit, and performs image write operation for each scanning line on the surface of the photosensitive member. Device.

  According to the present invention, the image writing timing setting unit compares a light reception signal obtained by scanning performed in a state where a predetermined light source among the light sources is turned on with a predetermined reference, and the light beam A light source that outputs a light beam whose passage timing cannot be detected is detected, and a light source other than the detected light source and the predetermined light source is set as an unlit light source, and a light source other than the unlit light source is set as a lit light source. .

  Accordingly, it is possible to realize a configuration in which the extinguishing light source and the lighting light source are automatically set.

  Then, an image writing timing by the lighting light source is set based on a light receiving signal obtained from the light receiving unit when a light beam output from the lighting light source is scanned, and an image writing timing by the unlit light source is It is set using the image writing timing by the light source.

  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.

  In the form in which the output periods of the BD signal partially overlap, the rising timing (falling timing) of a certain BD signal and the falling timing (rising timing) of the next BD signal are the same timing, Or the case where it has a minute time difference is also included.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the predetermined reference includes a reference value for the number of the received light signals, and the image writing timing setting unit is The number of light receiving signals obtained from the light receiving unit by scanning the light beam of a predetermined light source is compared with the reference value for the number of light receiving signals, and when the two do not match, the predetermined light source It is determined that there is a light source that outputs a light beam that cannot detect the light beam passage timing.

  According to this invention, it is possible to reliably detect the presence or absence of a light source that outputs a light beam that cannot detect the light beam passage timing among predetermined light sources.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the image writing timing setting unit is obtained from the light receiving unit when individually scanning the light beams of the predetermined light source. The output timing of each light reception signal when each waveform of the light reception signal is represented on the same time axis is stored in advance, and the light reception signal obtained from the light receiving unit is scanned by scanning the light beam of the predetermined light source. When the number and the reference value for the number of the received light signals do not match, the predetermined timing is determined by comparing the output timing of the received light signal obtained from the light receiving unit with the output timing stored in advance. Among these light sources, a light source that outputs a light beam that cannot detect the light beam passage timing is detected.

  According to the present invention, when there is a light source that outputs a light beam whose light passage timing cannot be detected among predetermined light sources, the light source can be reliably identified.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second aspect, the image writing timing setting unit is configured to receive a light reception signal obtained from the light receiving unit when scanning with a light beam of the predetermined light source. The total output time is stored in advance for each overlap mode, and the number of received light signals obtained from the light receiving unit by scanning the light beam of the predetermined light source and the reference value for the number of received light signals Is calculated, the total output time of each received light signal is calculated, the overlap mode corresponding to the calculated total output time is derived from the stored content, and the light beam is generated based on the derived overlap mode. A light source that outputs a light beam whose passage timing cannot be detected is detected.

  According to the present invention, when there is a light source that outputs a light beam whose light passage timing cannot be detected among predetermined light sources, the light source can be specified.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the image writing timing setting unit sets each image writing timing by each lighting light source located on both sides of the extinguishing light source. The timing for proportionally allocating the period to be the start point and the end point by the ratio of the distance from the unlit light source to each of the unlit light sources is set as the image writing timing by the unlit light source.

  According to the present invention, the image writing timing by the extinguished light source can be accurately calculated by a relatively simple calculation in accordance with the positional relationship between the extinguished light source and each lit light source located on both sides of the extinguished light source. .

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the image writing timing setting unit sets each of light beams of two lighting light sources that are predetermined among the lighting light sources. A reference value for the length of the period with the light beam passing timing as the start point and end point, and a period with the output timing of each received light signal obtained from the light receiving unit by scanning the light beams of the two lighting light sources as the start point and end point The ratio of the length is calculated, and the image writing timing by the extinguished light source positioned between the two lit light sources is determined in advance for the light beam passing timing predetermined for the light beam of the extinguished light source and the light beam of the two lit light sources. It is calculated based on a value obtained by multiplying the time difference from the light beam passing timing by the ratio.

  According to the present invention, due to environmental changes (for example, temperature change or humidity change) of the image forming apparatus, the positional relationship of the irradiation position on the light receiving unit by the light of each light source changes, and the light beam passing timing changes. Even if it occurs, the light beam passage timing can be accurately calculated by a relatively simple calculation.

  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.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. 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 476 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 LD8 arranged in a line at a constant interval on the front end surface Y, and the laser light sources LD4 and LD4 located inside the normal line to the front end surface Y are arranged. 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.

  Returning to FIG. 2, 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.

  Since the laser light sources LD1 to LD8 are arranged as described above, 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 as shown in FIG. Are arranged in a direction inclined at a certain inclination angle in each direction of the main scanning direction and the sub-scanning direction with a constant interval. Therefore, when scanning by the polygon mirror 494 is performed with all the laser light sources LD1 to LD8 turned on, the laser beams L1 to L8 pass through the light receiving surface of the BD sensor 496 with a certain time difference. Will be.

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. For example, as shown in FIG. 10, the BD signal converter 9 includes a photodiode 91, an amplifier 92, and a Schmitt trigger 93. In the BD signal conversion unit 9, when the light beam is irradiated to the photodiode 91, the light reception signal is output from the photodiode 91 to the amplifier 92, and the amplification signal is amplified after the amplifier 92 amplifies the light reception signal. Is input to the inverting input terminal of the Schmitt trigger 93. Further, the Schmitt trigger 93 has two threshold values V _SHL and V _SHH that are different with respect to the voltage value of the amplified signal. The voltage value of the amplified signal input to the inverting input terminal and the threshold value input to the non-inverting input terminal. Output signals corresponding to the magnitudes of V _SHL and V _SHH are output.

That is, when the positional relationship (interval) between the irradiation positions of the respective light rays is as shown in FIG. 11A, for example, the light reception signal output from the photodiode 91 is indicated by the arrow P1 in FIG. The waveform shown in FIG. At this time, when the voltage value of the amplified signal increases and becomes larger than the threshold value V _SHH , the output signal of the Schmitt trigger 93 becomes L (low), and from this state, the voltage value of the amplified signal decreases and the threshold value V SH _When it becomes smaller than _SHL, the output signal of the Schmitt trigger 93 becomes H (high). In the following description, the L (low) output signal of the L (low) output signal and the H (high) output signal output from the Schmitt trigger 93 is referred to as a BD signal.

  A period indicated by an arrow W in FIG. 11B is a period in which each light beam is received by the photodiode 91 (a period in which each light beam passes through the photodiode 91). In this manner, strictly speaking, the period in which each light beam passes through the photodiode 91 and the output period of the BD signal corresponding to each light beam are slightly shifted, but the following description will be made assuming that the two periods coincide with each other. And FIG. 11A shows the positional relationship between the BD sensor 496 and the irradiation position of each light beam at the time indicated by the arrow Tx in FIG.

  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.

  As described above, the light beams output from the laser light sources LD1 to LD8 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 the irradiation position of each light beam on the light receiving surface 496, the distance between adjacent laser light sources is relatively large, and the pitch in the main scanning direction between the irradiation positions of each light beam to the BD sensor 496 is designed to be large. Since the light receiving signals corresponding to the laser beams L1 to L8 are individually obtained from the BD sensor 496, the timings T1 to T8 when the laser beams L1 to L8 have passed through the BD sensor 496 are used as the light receiving signals. Can be detected individually using.

  However, when the pitch in the main scanning direction between the irradiation positions on the BD sensor 496 by each light beam is small, the next light beam passes through the light receiving surface at the previous timing before the light beam passes through the light receiving surface. A situation occurs that the light passes through the light receiving surface, so that a laser beam is always incident on the BD sensor 496. That is, when each light beam is scanned with all the laser light sources LD1 to LD8 turned on, the light beams L1 to L8 output from the respective laser light sources LD1 to LD8 are output from the laser light source existing next to the laser light source. And the irradiation period to the BD sensor 496 partially overlap. 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 reception surface of the BD sensor 496.

  As a result, the passage timing of the laser light that first passes through the light receiving surface and the passage timing of the laser light that passes through the end can be detected from the light reception signal itself, but the passage timing of the other laser light is as follows. It cannot be detected from the light reception signal itself, and as a result, the image writing timing of the scanning line corresponding to each of the laser light sources LD1 to LD8 cannot be set. Therefore, in this embodiment, the image writing timing by each of the laser light sources LD1 to LD8 is set by the method described below.

  The image writing timing setting unit 101 scans each light beam in a state in which a predetermined laser light source among the laser light sources LD1 to LD8 is turned on, and the number of laser light sources turned on in the scanning is a BD sensor. It is determined whether a BD signal is obtained from 496. The part of the laser light sources determined in advance as the laser light source to be turned on is determined by, for example, a factory combination, and is a combination of laser light sources selected so that the irradiation periods of the light beams of the laser light sources do not overlap at the factory shipment. is there.

  FIG. 5A shows that when all the laser light sources LD1 to LD8 are turned on, the irradiation period in which each of the light beams L1 to L8 irradiates the BD sensor 496 is output from the laser light source next to the laser light source. It is the figure which represented on the same time axis the waveform of the BD signal each obtained when each light beam of each laser light source LD1-LD8 was scanned individually in the aspect which overlaps with the irradiation period of the light beam to be performed. FIG. 5B shows a waveform of a BD signal actually obtained when scanning is performed in a state where all the laser light sources LD1 to LD8 are turned on in the overlap mode shown in FIG. FIG. 5C shows that only some of the laser light sources LD1 to LD8 (here, the first, third, fifth, and seventh laser light sources LD1, LD3, LD5, and LD7) are turned on. The waveform of the BD signal obtained from the BD sensor 496 when scanning is performed in the above state is shown.

  In FIG. 6A, when all the laser light sources LD1 to LD8 are turned on, the irradiation period in which each of the light beams L1 to L8 irradiates the BD sensor 496 is output from the laser light source next to the laser light source. It is the figure which represented on the same time axis the waveform of the BD signal each obtained when each light beam of each laser light source LD1-LD8 was scanned individually in the aspect which overlaps with the irradiation period of the light beam to be performed. FIG. 6B shows the waveform of the BD signal actually obtained when scanning is performed in a state where all the laser light sources LD1 to LD8 are turned on in the overlap mode shown in FIG. FIG. 6C shows scanning in a state where only some of the laser light sources LD1 to LD8 (here, the first, fourth, and seventh laser light sources LD1, LD4, and LD7) are turned on. The waveform of the BD signal obtained from the BD sensor 496 when performed is shown. Hereinafter, the laser light source to be turned on is referred to as a light source, and the laser light source to be turned off is referred to as a light source that is turned off.

  When BD signals are obtained by the number of laser light sources, the laser light output from the lighting light source has the irradiation time of the laser light output from the lighting light source existing next to the lighting light source and the BD sensor 496. A BD signal is obtained corresponding to each laser beam output from the lighting light source without overlapping, and the timing at which the laser beam of each lighting light source passes through the BD sensor 496 is detected from these BD signals. be able to. Accordingly, when the BD signal is obtained by the number of laser light sources, the image writing timing setting unit 101 sets the lighting light source as a lighting light source in the next or subsequent scan, and the light source of the lighting light source is a BD sensor. Based on the timing of passing 496, the image writing timing by the lighting light source is set.

  On the other hand, when the number of BD signals as many as the number of laser light sources is not obtained, the image writing timing setting unit 101 selects a combination of laser light sources that outputs light beams whose irradiation positions on the BD sensor 496 are further separated in the main scanning direction. Then, scanning is performed with the selected laser light source turned on. Note that as a factor that the BD signals cannot be obtained as many as the number of laser light sources, the distance between the irradiation positions of the respective light beams is further reduced due to the environmental temperature, the environmental humidity, and the like of the multi-function device 1, for example as shown in FIG. From the overlap mode, for example, as in the overlap mode shown in FIG. 6A, it is considered that the overlap period of the irradiation period of each light beam output from each laser light source has further increased.

  The image writing timing setting unit 101 changes the laser light source to be turned on when BD signals are not obtained in the number of laser light sources. At that time, each laser light source selected is a combination of laser light sources in which the distance between the irradiation positions is larger in the main scanning direction than that of the laser light source before the change. For example, as shown in FIG. 5, when scanning was performed with the first, third, fifth, and seventh laser light sources LD1, LD4, and LD7 turned on, BD signals were not obtained for the number of laser light sources. At this time, as shown in FIG. 6, the first, fourth, and seventh laser light sources LD1, LD4, and LD7 are selected as the lighting light sources.

  The image writing timing setting unit 101 performs scanning with the first, fourth, and seventh laser light sources LD1, LD4, and LD7 turned on, and the number of BD signals obtained by the scanning and the number of lighting light sources. Are matched, and if they do not match, the laser light source is changed in the same manner as described above, and scanning is performed again with the changed laser light source turned on.

  Then, the image writing timing setting unit 101 repeatedly executes the process of changing the laser light source until the number of laser light sources that output the scanned light beam matches the number of BD signals obtained by the scanning. If they match, the laser light source that was turned on in the most recent scan is set as the lighting light source, and the other light sources are set as the extinguishing light sources. Is actually set based on the BD signal from the BD sensor 496.

  As described above, the image writing timing by the lit light source can be directly obtained from the BD signal, but the image writing timing by the unlit light source cannot be obtained. Therefore, the calculation is set by using the image writing timing by the lighting light source. To do.

  That is, the distance from the extinguished light source to each lit light source located on both sides is a period starting from the timing when each light beam output from the lit light source located on both sides of the extinguished light source passes through the BD sensor 496. Is set as the timing at which the light from the extinguishing light source passes through the light receiving surface of the BD sensor 497.

  For example, in the overlap mode shown in FIG. 5, the image writing timing setting unit 101 sets the timing T2 at which the light beam of the second laser light source LD2 that is one of the extinguishing light sources passes through the BD sensor 496, to the second laser light source LD2. The distance from the second laser light source LD2 to the lighting light sources LD1 and LD3 is a period starting from the timings T1 and T3 when the light beams output from the lighting light sources LD1 and LD3 located on both sides of the laser beam pass through the BD sensor 496. Is calculated as “T1 + {(T3−T1) / (1 + 1)}”. Similarly, the image writing timing setting unit 101 calculates the timing T4 at which the fourth laser light source LD4 starts to pass through the BD sensor 496 as “T1 + {(T5−T3) / (1 + 1)}”.

  For example, in the overlap mode shown in FIG. 6, the image writing timing setting unit 101 positions the timing T2 at which the second laser light source LD2 starts to pass through the BD sensor 496 on both sides of the second laser light source LD2. The period from the timing T1, T4 at which the light beams output from the lighting light sources LD1, LD4 passing through the BD sensor 496 start and end points is proportional to the ratio of the distance from the second laser light source LD2 to the lighting light sources LD1, LD4. The distribution timing “T1 + {(T4−T1) / (2 + 1)}” is calculated. Similarly, the image writing timing setting unit 101 calculates the timing T3 at which the third laser light source LD3 starts to pass through the BD sensor 496 as T3 = T1 + 2 × {(T4−T1) / (2 + 1)}. . Note that the above processing is performed on the assumption that the pitch in the main scanning direction between the irradiation positions of the respective light beams is constant. In this embodiment, the timing at which each light beam starts to pass through the light receiving surface of the BD sensor 497 is regarded as the timing at which each light beam passes through the light receiving surface of the BD sensor 497.

  The image writing timing setting unit 101 sets the image writing timing to the scanning line by each of the laser light sources LD1 to LD8 based on the light beam passing timing calculated in this way, and outputs it to the drawing unit 103. That is, the image writing timing setting unit 101 outputs an image writing signal to the drawing unit 103 after a predetermined reference clock count from the calculated light beam passage timing. The predetermined reference clock count number is determined for each machine at the time of adjustment at the time of machine manufacture.

  The drawing unit 103 starts driving of the LD driving unit 101 based on the image signal of the image to be written output from the image memory 9 by the image writing signal. The LD driving unit 101 drives and controls the laser irradiation unit 491 based on an instruction from the drawing unit 103. The BD signal conversion unit 102 outputs the BD signal output from the BD sensor 496 to the image writing timing setting unit 101.

  FIG. 7 is a flowchart showing the laser light source on / off setting process by the control unit 10. Here again, it is assumed that the laser irradiation unit 491 has eight laser light sources LD1 to LD8.

  As shown in FIG. 7, the control unit 10 scans each light beam with a predetermined laser light source (for example, LD1, LD3, LD5, LD7) turned on, and outputs each BD signal from the BD sensor 497. Is acquired (step # 1). Next, the control unit 10 determines whether or not the number of acquired BD signals matches the number of laser light sources that are turned on in the scan performed in step # 1 (step # 2), and does not match. In this case (NO in step # 2), scanning is performed after changing the laser light source to be turned on, and each BD signal is acquired from the BD sensor 497 (step # 3). The control unit 10 repeatedly executes the processes of steps # 2 and # 3 until the number of acquired BD signals matches the number of laser light sources that are turned on in the scanning performed at step # 1, and if they match (step # 2). YES), the laser light source turned on in the current scanning is set as a lighting light source, and the other light sources are set as extinguishing light sources (step # 4).

  FIG. 8 is a flowchart showing image writing timing setting processing by the control unit 10.

  As shown in FIG. 8, the control unit 10 scans the light beam of the lighting light source set at step # 4 (step # 11), and sets the image writing timing by the lighting light source based on the obtained BD signal (step # 11). Step # 12). Further, the control unit 10 calculates the image writing timing by the extinguished light source by calculation using the image writing timings for the lighting light sources located on both sides of the extinguished light source (step # 13). Then, the controller 10 executes an image writing operation (lighting control of each laser light source) in accordance with the image writing timing set in step # 12 or # 13 (step # 14).

  As described above, the lighting light source and the non-lighting light source are set so that the irradiation positions of the light beams do not overlap on the light receiving surface of the BD sensor 496, and the light beams of the lighting light source are scanned, and the scanning is obtained. Since the image writing timing by the lighting light source is set from the BD signal, and the image writing timing by the unlit light source is calculated by calculation using the image writing timing, the image writing timing by the unlit light source can be derived relatively easily. can do.

  Therefore, as compared with the conventional method in which the frequency and power of each laser beam is changed and the output of the BD sensor 497 is given a voltage difference to separate the BD signal by each beam, the cost is increased and the laser beam is detected. The image writing timing for each scanning line can be set while suppressing a decrease in accuracy.

  In particular, in this embodiment, the number of BD signals obtained from the BD sensor 496 and the number of laser light sources that are turned on are scanned until the number of laser light sources that are turned on matches, and the number of BD signals is turned on. When the number of laser light sources matches, the laser light source that was turned on in that scan is set as the laser light source that is turned on in the next or subsequent scans. A configuration to be determined can be realized.

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

  (1) In the embodiment, until the number of BD signals obtained from the BD sensor 496 matches the number of laser light sources that have been turned on, scanning is performed by changing the laser light source to be turned on, and the number of BD signals is turned on. When the number of laser light sources coincides, the laser light source that is turned on by the scanning is set as the laser light source that is turned on at the next time or the next and subsequent scans.

  That is, when the image writing timing setting unit 101 scans each light beam with all the laser light sources LD1 to LD8 turned on, the timing at which each light beam is predicted to pass through the BD sensor 496 (the BD signal from the BD sensor 496). Is obtained from the BD sensor 497 by storing T1 to T8 in advance as reference timings T1 to T8 and scanning each light beam with a predetermined laser light source turned on. If the number of the BD signals that are lit does not match the number of the laser light sources that are turned on, the output timing of the BD signals is compared with the reference output timings T1 to T8, and the output that could not be detected by the scanning Extract timing. Then, the image writing timing setting unit 101 determines that the BD signal corresponding to the extracted output timing overlaps with the other BD signal, and sets the laser light source corresponding to the BD signal as the extinguishing light source. Other laser light sources may be set as lighting light sources.

  In addition to this form, the extinguishing light source may be determined using the total output time of the BD signal.

  The total output time of the BD signal obtained when scanning with a certain combination of laser light sources turned on is the overlap mode, that is, the light beam output from the laser light source next to the laser light source. Depending on whether it is a mode that partially overlaps the irradiation period or a mode that partially overlaps the irradiation period of the light beam output from the laser light source next to the laser light source. Each aspect has a unique range for the total output time of the obtained BD signal.

  That is, in the overlap mode as shown in FIG. 5A, the first, third, fifth, and seventh laser light sources LD1, LD3, LD5, and LD7 are turned on as shown in FIG. 5C. The total output time of the BD signal obtained when scanning is performed is (L1 + L2 + L3 + L4), and this total time belongs to a certain range of the total corresponding to the overlap mode. In the overlap mode as shown in FIG. 6A, as shown in FIG. 6C, when scanning is performed with the first, fourth, and seventh laser light sources LD1, LD4, and LD7 turned on. The total output time of the obtained BD signal is (L5 + L6 + L7), and this total time belongs to a certain range of the total corresponding to the overlap mode.

  Therefore, the image writing timing setting unit 101 stores the correspondence between the total output time of the BD signal and the extinguishing light source, and determines a predetermined laser light source (here, first, third, fifth, The number of BD signals obtained from the BD sensor 497 and the number of the laser light sources that are turned on by scanning each light beam while the seventh laser light sources LD1, LD3, LD5, and LD7 are turned on) If they do not match, the image writing timing setting unit 101 calculates the total output time of the BD signals.

  If the total output time of each BD signal obtained by the scan is, for example, (L5 + L6 + L7), the total time (L5 + L6 + L7) is within the total time range corresponding to the overlap mode shown in FIG. Therefore, the image writing timing setting unit 101 determines that the actual overlap mode of each light beam is the mode shown in FIG. 6, and derives the extinguished light source corresponding to the total time (L5 + L6 + L7) from the stored contents. It is preferable to set a laser light source other than the extinguished light source as a laser light source to be turned on in the next scanning.

  In consideration of an error included in the total output time of the BD signal, if a certain margin is provided in the range of the total time, the light amount of the laser light source, the change of the power supply voltage, etc. Even when the total time fluctuates, the extinguishing light source and the lighting light source can be appropriately set.

  (2) In the above embodiment, the timing at which each laser beam begins to pass through the light receiving surface of the BD sensor 497, the timing at which each laser beam passes through the light receiving surface of the BD sensor 497, and the BD signal from the BD sensor 497 are output. The timing at which each laser beam has passed through the light receiving surface of the BD sensor 497, the timing at which each laser beam has passed through the light receiving surface of the BD sensor 497, and the timing at which the BD signal is output from the BD sensor 497 are regarded as timing. Alternatively, each laser beam has passed through the light receiving surface of the BD sensor 497 at an intermediate timing in a period from the timing at which each laser beam starts to pass through the light receiving surface of the BD sensor 497 to the timing at which it finishes passing. As a timing and timing when the BD signal is output from the BD sensor 497 And it may be.

  (3) After determining the laser light source to be turned on, the image writing timing for the laser light source to be turned off can also be calculated by the following method.

  First, the positional relationship of the irradiation positions on the BD sensor 496 of the light beams output from the respective laser light sources is measured in advance by a measuring device (not shown), and the passage timing of the respective light beams calculated from the measured values on the light receiving surface. Is stored in a storage unit (not shown) provided in the control unit 10 as a reference timing. Then, the image writing timing setting unit 101 performs scanning in a state where a predetermined laser light source is turned on, and based on the BD signal output from the BD sensor 496, the light beam of the laser light source causes the BD sensor 96 to be scanned. Detect the passing timing.

  Here, as shown in FIG. 9, the image writing timing setting unit 101 pays attention to two laser light sources, for example, the laser light sources LD1 and LD3, among the lighted laser light sources, and the light beam passage timing T1 ′ of the laser light source LD1. And a time difference (hereinafter referred to as a detection time difference) between the light passage timing T3 ′ of the laser light source LD3 and a time difference (hereinafter referred to as a reference time difference) between the passage timings T1 and T3 recorded in the storage unit. When the image writing timing setting unit 101 detects that the detection time difference is changed D times with respect to the reference time difference, the laser light source (for example, the laser light source LD2) that has been turned off in the scanning is temporarily turned on. In this case, it is considered that the time difference between the light beam passage timing of the laser light source and the passage timing T1 also changes D times. Here, the ratio D is (T3'-T1 ') / (T3-T1).

  Based on this, when the image writing timing setting unit 101 detects the passage timings T1 and T3 ′, the ratio D is calculated using the passage timings T1 ′ and T3 ′ and the passage timings T1 and T3 stored in advance. It is assumed that the laser light source LD2 positioned between the laser light sources LD1 and LD3 is lit by the scan using the previously stored passage timing T2 of the laser light source LD2 and the ratio D. In this case, a timing T2 ′ at which the light beam of the laser light source LD2 passes through the BD sensor 496 is calculated. For example, when the overlap mode of each light beam is as shown in FIG. 5, the image writing timing setting unit 101 sets the light beam passage timing T2 ′ of the laser light source LD2 as T2 ′ = T1 + (T2−T1) × D. Calculated by

  Thereby, even when the irradiation position on the BD sensor 496 of the light beam output from each laser light source changes, the light beam passage timing of each extinguishing light source can be easily calculated according to the change.

  (4) 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.

  (5) In the first embodiment, since the irradiation positions of the light beams overlap in the main scanning direction, the light reception signal output from the BD sensor 496 causes all the light beams to travel on the light receiving surface of the BD sensor 496. It has been described that the signal becomes a constant signal until it passes, and the timing at which each light beam passes through the light receiving surface cannot be detected from this signal. However, due to the configuration of the BD signal converter 9, the irradiation of each light beam is performed. Even if the positions do not overlap in the main scanning direction, a constant signal is generated until all the light beams have passed through the light receiving surface of the BD sensor 496, and the timing at which each light beam has passed through the light receiving surface is detected. It may not be possible.

  FIG. 12 is a diagram illustrating an example of a case where the irradiation position of each light beam does not overlap in the main scanning direction, but a BD signal cannot be obtained for each light beam.

As shown in FIG. 12A, even when the irradiation positions of the respective light beams do not overlap in the main scanning direction, as shown by the arrow Q in FIG. Before the output value of the light reception signal of the photodiode 91 falls below the threshold value V _SHL , it rises by the next light beam, and as a result, it remains constant at L (low) until all the light beams have passed on the light receiving surface of the BD sensor 496. A signal is output from the BD signal converter 9. FIG. 12A shows the positional relationship between the BD sensor 496 and the irradiation position of each light beam at the time indicated by the arrow Tx in FIG.

As described above, a BD signal cannot be obtained for each light beam due to the time difference between the rising period and the falling period of the output signal of the photodiode 91 and the hysteresis voltage that is the difference between the threshold values V _SHL and V _SHH. In some cases, the present invention can be applied in the same manner.

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 a main scanning direction and a subscanning direction on the surface of a photoreceptor 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 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 on / off setting process of a laser light source by a control part. It is a flowchart which shows the image writing timing setting process by a control part. It is explanatory drawing of the deformation | transformation form of the image writing timing setting process by a control part. It is a figure which shows the electrical structure of a BD signal conversion part. It is a figure which shows the positional relationship of the irradiation position of each light beam, and the light reception signal obtained from a photodiode in the case of this positional relationship, and the BD signal obtained from a Schmitt trigger. It is a figure which shows the deformation | transformation form which concerns on the positional relationship of the irradiation position of each light ray, and the BD signal obtained from the light reception signal and Schmidt trigger obtained from a photodiode in the case of this positional relationship.

Explanation of symbols

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

Claims (6)

A light source unit in which three or more light sources are installed at different positions in the main scanning direction and the sub-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 area;
A light receiving unit that performs a photoelectric conversion operation is installed in the fixed region, and generates a BD signal based on an output signal of the light receiving unit;
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 which is a start timing of the image writing operation to each scanning line by the light source based on the light beam passage timing obtained from the BD signal of the BD signal generation unit. An image export timing setting unit for setting the export timing,
When scanning by the scanning unit is performed with all the light sources turned on, the output period of the BD signal by the light beam output from each light source is output from one or a plurality of light sources adjacent to the light source. It partially overlaps with the output period of the BD signal by the light beam,
The image writing timing setting unit
By comparing a light reception signal obtained from the light receiving unit with a predetermined reference by scanning performed with a predetermined light source among the light sources turned on, a light beam that cannot detect the light beam passage timing is detected. When an output light source is detected, a light source other than the detected light source and the predetermined light source is set as a turn-off light source, and a light source other than the turn-off light source is set as a turn-on light source, and a light beam output from the turn-on light source is scanned Setting the image writing timing by the lighting light source based on the light reception signal obtained from the light receiving unit, and setting the image writing timing by the extinguishing light source using the image writing timing by the lighting light source,
The light emission control unit
An image forming apparatus that controls the light emission operation of each light source in accordance with the image writing timing set by the image writing timing setting unit and performs the image writing operation for each scanning line on the surface of the photosensitive member. The predetermined reference includes a reference value for the number of the received light signals,
The image writing timing setting unit
The number of received light signals obtained from the light receiving unit by scanning the light beam of the predetermined light source is compared with the reference value for the number of the received light signals. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that there is a light source that outputs a light beam that cannot detect the light beam passage timing. The image writing timing setting unit
Preliminarily storing the output timing of each light reception signal when each waveform of the light reception signal obtained from the light receiving unit is represented on the same time axis when individually scanning the light beam of the predetermined light source,
When the number of received light signals obtained from the light receiving unit by scanning the light beam of the predetermined light source and the reference value for the number of received light signals do not match, the received light signal obtained from the light receiving unit 3. The image formation according to claim 2, wherein a light source that outputs a light beam that cannot detect the light beam passage timing among the predetermined light sources is detected by comparing the output timing of the light source and the output timing stored in advance. apparatus. The image writing timing setting unit
The total output time of the received light signal obtained from the light receiving unit when scanning the light beam of the predetermined light source is stored in advance for each overlap mode,
When the number of received light signals obtained from the light receiving unit by scanning the light beam of the predetermined light source does not match the reference value for the number of received light signals, the total output time of each received light signal is 3. An overlap mode corresponding to the calculated total output time is derived from the stored contents, and a light source that outputs a light beam whose light passage timing cannot be detected is detected based on the derived overlap mode. The image forming apparatus described in 1.   The image writing timing setting unit proportionally distributes a period in which each image writing timing by each lighting light source located on both sides of the extinguishing light source is a start point and an ending point by a ratio of a distance from the extinguishing light source to each lighting light source. The image forming apparatus according to claim 1, wherein the timing is set as an image writing timing by the extinguishing light source.   The image writing timing setting unit includes a reference value for a length of a period having respective light beam passage timings as a start point and an end point for light beams of two lighting light sources of the lighting light sources, and the two lighting light sources. The ratio of the output timing of each light reception signal obtained from the light receiving unit obtained by scanning the light beam to the length of the period from the start point to the end point is calculated, and the image writing timing by the extinguishing light source located between the two lighting light sources is calculated. The calculation is based on a value obtained by multiplying a time difference between a predetermined light beam passing timing for the light beam of the extinguished light source and a predetermined light beam passing timing for the light beams of the two lighting light sources by the ratio. The image forming apparatus according to claim 5.

Images