JP2010048853A - Method of measurement, optical scanner, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the shift amount of write starting timing in a plurality of scanning lines in real time and with high precision. <P>SOLUTION: A write control circuit 219 includes: a synchronous lighting control circuit 219c which selects a front end synchronous light emission part and a rear end synchronous light emission part, and generates a plurality of synchronous lighting signals for lighting the selected light emission parts; a measurement circuit 219d for two points, which measures the time interval of rising time of a front end synchronous detection signal and the rising time of a rear end synchronous detection signal; and a correction data generation circuit 219e which individually generates correction data in the respective light emission parts on the basis of the measured results or the like at the measurement circuit 219d for two points. Thus, the shift amount of the beginning times of write of the light emission parts ch2 to ch16 with respect to the light emission part ch1 are individually obtained in real time and with higher accuracy than the conventional art as the correction data with a "phase difference corresponding time" as a unit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a measurement method, an optical scanning apparatus, and an image forming apparatus. More specifically, the present invention relates to a measurement method for measuring a deviation amount of writing start timing in a plurality of scanning lines, an optical scanning apparatus having a plurality of light emitting units, and the The present invention relates to an image forming apparatus including an optical scanning device.

  In image forming apparatuses such as laser printers and digital copiers, there is an increasing demand for improvement in image formation speed (high speed) and improvement in writing density (high image quality). As one of the methods for achieving these demands, A method of scanning a surface to be scanned with a plurality of light beams using a multi-beam light source capable of emitting a plurality of light beams has been considered.

  By the way, in a multi-beam light source having a plurality of light emitting units, in order to narrow the scanning line interval, the light emitting units are arranged so as to be shifted from each other in the direction corresponding to the main scanning direction. In this case, it is necessary to control the lighting timing of each light emitting unit in order to align the writing start positions in a plurality of scanning lines.

  For example, in Patent Document 1, the lighting timing of at least one light emitting unit of the light source unit is determined based on the image clock generated in synchronization with the detection signal of the synchronization detecting unit, and the lighting timing of the other light emitting units. An image forming apparatus including a control unit that controls the lighting of a plurality of light emitting units of a light source unit by determining the value by changing the count value of the image clock.

JP 2003-276234 A

  By the way, in the image forming apparatus, the optical characteristics of the optical components may change or the positional relationship between the optical components may change due to temperature change or aging change after shipment. As a result, the light spot position on the surface to be scanned may deviate from the desired position. For example, this causes a shift in the writing position of the image data in the main scanning direction. However, in the image forming apparatus disclosed in Patent Document 1, it is difficult to accurately correct the deviation in the writing position in real time.

  The present invention has been made under such circumstances, and a first object of the invention is to provide a measurement method capable of measuring in real time with high accuracy a deviation amount of write start timing in a plurality of scanning lines. is there.

  A second object of the present invention is to provide an optical scanning device capable of performing high-density optical scanning with high accuracy.

  A third object of the present invention is to provide an image forming apparatus capable of forming a high quality image at high speed.

  From the first viewpoint, the present invention scans a plurality of light beams from a plurality of light emitting units arranged at least in positions corresponding to the direction corresponding to the scanning line direction along the plurality of scanning lines, In the optical scanning device for writing image information on the surface to be scanned, a measuring method for measuring a deviation amount of writing start timing in the plurality of scanning lines, wherein light from the first light emitting unit among the plurality of light emitting units is received. The time from when light is received by the first light receiving element that outputs the synchronization detection signal before the start of writing until it is received by the second light receiving element that outputs the synchronization detection signal after the end of writing is defined as the first time. A step of acquiring; light from the second light emitting part among the plurality of light emitting parts received by the second light receiving element after light from the first light emitting part is received by the first light receiving element; Time until Obtaining as a second time; obtaining a shift amount of the second light emitting part with respect to the first light emitting part from a difference between the second time and the first time. This is a measurement method.

  According to this, it is possible to measure the deviation amount of the writing start timing in a plurality of scanning lines in real time with high accuracy.

  From a second viewpoint, the present invention is an optical scanning device that scans a surface to be scanned in a main scanning direction along a plurality of scanning lines with a plurality of light beams, and at least relates to a direction corresponding to the direction of the scanning lines. A light source having a plurality of light emitting portions arranged at different positions; condensing a plurality of light beams from the light source on the surface to be scanned, and a plurality of light spots on the surface to be scanned An optical system that moves in the main scanning direction along the scanning line; a first light receiving element on which light before writing starts; a second light receiving element on which light after writing ends; and the plurality of light emitting elements And the time from when the light from the first light-emitting part is received by the first light-receiving element to when the light from the first light-emitting part is received by the second light-receiving element, and the light from the first light-emitting part is The plurality of light emission after being received by one light receiving element Control for obtaining the shift amount of the second light emitting unit with respect to the first light emitting unit from the difference from the time until the light from the second light emitting unit is received by the second light receiving element. And an optical scanning device.

  According to this, high-density optical scanning can be performed with high accuracy.

  According to a third aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the present invention that scans the at least one image carrier with a light beam modulated according to image information. And an image forming apparatus.

  According to this, since the optical scanning device of the present invention is provided, as a result, a high-quality image can be formed at high speed.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a laser printer 1000 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a charge eliminating unit 1034, a cleaning unit 1035, a toner cartridge 1036, a paper feeding roller 1037, a paper feeding tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, a communication control device 1050, a printer control device 1060 that comprehensively controls the above-described units, and the like are provided. These are housed in predetermined positions in the printer housing 1044.

  The communication control device 1050 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 rotates in the direction of the arrow in FIG.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning unit 1035 are each disposed in the vicinity of the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning unit 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 irradiates the surface of the photosensitive drum 1030 charged by the charging charger 1031 with a light beam modulated based on image information from the host device. As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 1030. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  The toner cartridge 1036 stores toner, and the toner is supplied to the developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038, and the paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning unit 1035 removes the toner remaining on the surface of the photosensitive drum 1030 (residual toner). The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position facing the charging charger 1031 again.

  Next, the configuration of the optical scanning device 1010 will be described.

  As shown in FIG. 2, the optical scanning device 1010 includes a light source 14, a coupling lens 15, an aperture plate 16, a cylindrical lens 17, a polygon mirror 13, an fθ lens 11a, a toroidal lens 11b, two light detection sensors (18a). 18b) includes two light detection mirrors (19a, 19b), a scanning control device 22 (not shown in FIG. 2, see FIG. 5), and the like. These are assembled at predetermined positions in the housing 21.

  In this specification, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of the photosensitive drum 1030 is defined as the Y-axis direction, and the direction along the optical axis of the fθ lens 11a and the toroidal lens 11b is defined as the X-axis direction. To do. In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  As shown in FIG. 3 as an example, the light source 14 includes a two-dimensional array 100 in which 16 light emitting units (ch1 to ch16) are two-dimensionally arranged and formed on one substrate. Note that the M direction in FIG. 3 is the main scanning corresponding direction, and the S direction is the sub scanning corresponding direction.

  The light emitting units ch1, ch5, ch9, and ch13 are the first row light emitting units, the light emitting units ch2, ch6, ch10, and ch14 are the second row light emitting units, and the light emitting units ch3, ch7, ch11, and ch15 are the third row light emitting units. The parts ch4, ch8, ch12, and ch16 are also referred to as a fourth row light emitting part. Here, with respect to the M direction, the intervals between the columns are equal, for example, 30 μm.

  Further, the two-dimensional array 100 is arranged such that the intervals between adjacent light emitting units are equal when all the light emitting units are orthogonally projected onto a virtual line extending in the S direction. In the present specification, the “interval between the light emitting portions” refers to the distance between the centers of the two light emitting portions. Therefore, it is possible to scan the surface of the photosensitive drum 1030 with 16 light beams at the same time.

  Each light emitting unit is a vertical cavity surface emitting laser (VCSEL) having an oscillation wavelength of 780 nm band. That is, the two-dimensional array 100 is a so-called surface emitting laser array.

  Returning to FIG. 2, the coupling lens 15 converts the light beam emitted from the light source 14 into substantially parallel light.

  The aperture plate 16 has an aperture and defines the beam diameter of the light beam through the coupling lens 15.

  The cylindrical lens 17 forms an image of the light beam that has passed through the opening of the aperture plate 16 in the vicinity of the deflection reflection surface of the polygon mirror 13 in the Z-axis direction.

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system. In the present embodiment, the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, and a cylindrical lens 17.

  The polygon mirror 13 has a four-sided mirror, and each mirror serves as a deflection reflection surface. The polygon mirror 13 rotates at a constant speed around an axis parallel to the Z-axis direction, and deflects the light beam from the cylindrical lens 17.

  The fθ lens 11 a is disposed on the optical path of the light beam deflected by the polygon mirror 13.

  The toroidal lens 11b is disposed on the optical path of the light beam through the fθ lens 11a. Then, a light beam through the toroidal lens 11b is irradiated on the surface of the photosensitive drum 1030, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 13 rotates. That is, the surface of the photosensitive drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”. The rotation direction of the photosensitive drum 1030 is the “sub-scanning direction”.

  The optical system arranged on the optical path between the polygon mirror 13 and the photosensitive drum 1030 is also called a scanning optical system. In the present embodiment, the scanning optical system includes an fθ lens 11a and a toroidal lens 11b. Note that at least one folding mirror may be disposed on at least one of the optical path between the fθ lens 11a and the toroidal lens 11b and the optical path between the toroidal lens 11b and the photosensitive drum 1030.

  In the present embodiment, when the 16 light emitting units (ch1 to ch16) are turned on simultaneously, as shown in FIG. 4, the light spot sp1 from the light from the light emitting unit ch1 and the light from the light emitting unit ch2 are used. A light spot sp2, a light spot sp3 due to light from the light emitting portion ch3,..., A light spot sp16 due to light from the light emitting portion ch16 is formed on the surface of the photosensitive drum 1030.

  The light spots sp1, sp5, sp9, sp13 are the first row spot, the light spots sp2, sp6, sp10, sp14 are the second row spot, the light spots sp3, sp7, sp11, sp15 are the third row spot, the light spot sp4, sp8, sp12, and sp16 are also referred to as fourth row spots.

  Returning to FIG. 2, a part of the light beam before the start of writing in one scan out of the light beam that is deflected by the polygon mirror 13 and passes through the scanning optical system enters the light detection sensor 18a via the light detection mirror 19a. To do. The light detection sensor 18a is “high level” when the amount of received light is below a predetermined level, and changes to “low level” when the amount of received light exceeds a predetermined level (hereinafter referred to as “tip synchronization detection signal”). Are generated and output to the scanning control device 22.

  Further, a part of the light beam after completion of writing in one scan out of the light beam that is deflected by the polygon mirror 13 and passes through the scanning optical system enters the light detection sensor 18b through the light detection mirror 19b. The light detection sensor 18b is “high level” when the amount of received light is below a predetermined level, and changes to “low level” when the amount of received light exceeds a predetermined level (hereinafter referred to as “rear end synchronization detection signal”). Is generated and output to the scanning control device 22.

  As shown in FIG. 5 as an example, the scanning control device 22 includes a high frequency clock generation circuit 213, a pixel clock generation circuit 215, an image data creation circuit 216, a write control circuit 219, a light source drive circuit 221 and the like. . Note that the arrows in FIG. 5 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.

The high frequency clock generation circuit 213 generates a plurality of high frequency clock signals having different phases. Here, as an example, as shown in FIG. 6, it is assumed that two high-frequency clock signals (VCLK ₁ , VCLK ₂ ) whose phases are different by 180 degrees are generated. Therefore, the time corresponding to the phase difference between the high frequency clock signal VCLK ₁ and the high frequency clock signal VCLK ₂ is ½ period of the high frequency clock signal. Each high-frequency clock signal generated here is supplied to the pixel clock generation circuit 215 and the write control circuit 219. When there is no need to distinguish between the two high-frequency clock signals, they are collectively referred to as a high-frequency clock signal VCLK. Hereinafter, for convenience, the time corresponding to the phase difference between the high frequency clock signal VCLK ₁ and the high frequency clock signal VCLK ₂ is also referred to as “phase difference corresponding time” for short.

The pixel clock generation circuit 215 generates a pixel clock signal PCLK serving as an output reference of pixel (dot) data based on the high frequency clock signal VCLK ₁ from the high frequency clock generation circuit 213. Here, as an example, as shown in FIG. 7, the pixel clock signal PCLK is a clock signal equivalent to the frequency divided by 8 of the high-frequency clock signal VCLK ₁ . The pixel clock generation circuit 215 also generates a line clear signal LCLR. The pixel clock signal PCLK and the line clear signal LCLR generated here are supplied to the image data creation circuit 216 and the write control circuit 219 in synchronization with the leading edge synchronization detection signal.

Specifically, as shown in FIG. 7, the rising timing of the high frequency clock signal VCLK ₁ immediately after the leading edge synchronization detection signal changes from “high level” to “low level” is used as a base point (first clock), and the high frequency The pixel clock signal PCLK is output in synchronization with the rising timing of the 10th clock of the clock signal VCLK ₁ . Further, the line clear signal LCLR is changed from “low level” to “high level” at the first rising timing of the synchronized pixel clock signal PCLK, and the line clear signal LCLR is changed to “high” at the next rising timing of the pixel clock signal PCLK. “Level” is changed to “Low level”.

Returning to FIG. 5, the image data creation circuit 216 raster-develops image information received from the host device via the printer control device 1060, performs predetermined halftone processing, and the like, and then uses the pixel clock signal PCLK as a reference. Image data representing the gradation of each pixel is generated for each light emitting unit. Then, as shown in FIG. 8 as an example, the image data generation circuit 216 detects the change of the line clear signal LCLR from “low level” to “high level”, and synchronizes with the rising timing of the pixel clock signal PCLK. Thus, the image data (S216 _{1 to} S216 ₁₆ ) are output to the write control circuit 219 in order from the first pixel data (ID1). Here, it is assumed that one pixel data is 4-bit data. Further, the image data S216 ₁ is image data corresponding to the light emitting unit ch1, the image data S216 ₂ is image data corresponding to the light emitting unit ch2,..., And the image data S216 ₁₆ corresponds to the light emitting unit ch16. Image data.

  As shown in FIG. 9 as an example, the write control circuit 219 includes a modulation data generation circuit 219a, a PWM data generation circuit 219b, a synchronous lighting control circuit 219c, a two-point measurement circuit 219d, and a correction data generation circuit 219e. ing.

  The two-point measuring circuit 219d has two counters (first counter and second counter), and measures the time interval between the leading edge synchronization detection signal rising timing and the trailing edge synchronization detection signal rising timing, The measurement data Dint is output to the correction data creation circuit 219e. The two-point measurement circuit 219d outputs a measurement end signal Dfin for notifying the end of measurement to the synchronous lighting control circuit 219c and the correction data creation circuit 219e.

  The operation of the two-point measuring circuit 219d will be described with reference to the timing charts of FIGS. FIG. 11 is a detailed timing chart in the vicinity of the timing when the rear end synchronization detection signal changes from “high level” to “low level”.

(1-1) When the line clear signal LCLR changes from “low level” to “high level”, the value of the first counter and the value of the second counter are set to “0” at the next rising timing of the pixel clock signal PCLK. Reset to. The value of the first counter is counted up in synchronization with the rising timing of the pixel clock signal PCLK. On the other hand, the value of the second counter is counted up in synchronization with the rising timing of the high frequency clock signal VCLK ₁ and the high frequency clock signal VCLK ₂ (see FIG. 11).

(1-2) When the rear end synchronization detection signal changes from “high level” to “low level”, the value of the first counter and the value of the second counter at that time are obtained. In FIG. 11, the value of the first counter is “X”, and the value of the second counter is “10”.

(1-3) The value of the first counter and the value of the second counter are output as measurement data Dint to the correction data creation circuit 219e. At the same time as the measurement data Dint is output, the measurement end signal Dfin is changed from “low level” to “high level”. In the following description, the contents of the measurement data Dint are expressed in the form of (the value of the first counter, the value of the second counter).

(1-4) In synchronization with the next rising timing of the pixel clock signal PCLK, the measurement end signal Dfin is changed from “high level” to “low level”.

  Returning to FIG. 9, the synchronous lighting control circuit 219 c is detected by a light emitting unit that emits light detected by the light detection sensor 18 a (hereinafter, also referred to as “tip synchronized light emitting unit” for convenience) and the light detection sensor 18 b. A light emitting unit that emits light (hereinafter, also referred to as “rear end synchronized light emitting unit” for convenience) is selected, and a plurality of synchronized lighting signals (ch1 synchronized lighting signal to ch16 synchronized) for lighting the selected light emitting unit are selected. Lighting signal). The plurality of synchronous lighting signals generated here are output to the PWM data generation circuit 219b. The ch1 synchronized lighting signal corresponds to the light emitting unit ch1, the ch2 synchronized lighting signal corresponds to the light emitting unit ch2, and the ch16 synchronized lighting signal corresponds to the light emitting unit ch16.

  Further, the synchronous lighting control circuit 219c notifies the correction data creation circuit 219e of the front end ch information Dfch for specifying the front end synchronized light emitting unit and the rear end ch information Dech for specifying the rear end synchronized light emitting unit.

  The operation of the synchronous lighting control circuit 219c will be described with reference to the timing chart of FIG. Here, as an example, both the front-end synchronized light emitting unit and the rear-end synchronized light emitting unit are assumed to be the light emitting unit ch1.

(2-1) When the line clear signal LCLR changes from “low level” to “high level”, the value of the internal counter is reset to “0” in synchronization with the next rising timing of the pixel clock signal PCLK. The counter value is counted up in synchronization with the rising timing of the pixel clock signal PCLK.

(2-2) When the value of the counter reaches a value (M) corresponding to a preset lighting timing for rear end synchronization detection, the ch1 synchronous lighting signal is changed from “low level” to “high level”. Change to As a result, the light emitting unit ch1 is turned on. At the same time, “1” is notified as the rear end channel information Dech. Note that the ch2 synchronized lighting signal to the ch16 synchronized lighting signal all remain at “low level”.

(2-3) When the measurement end signal Dfin from the two-point measuring circuit 219d changes from “low level” to “high level”, the ch1 synchronous lighting signal is set to “high level” at the next rising timing of the pixel clock signal PCLK. To "low level". Thereby, the light emitting unit ch1 is turned off.

(2-4) When the value of the counter reaches a value (N) corresponding to a preset lighting timing for tip synchronization detection, the ch1 synchronous lighting signal is changed from “low level” to “high level”. change. As a result, the light emitting unit ch1 is turned on. At the same time, “1” is notified as the tip ch information Dfch. Note that the ch2 synchronized lighting signal to the ch16 synchronized lighting signal all remain at “low level”.

(2-5) When the line clear signal LCLR changes from “low level” to “high level”, the counter value is reset to “0” in synchronization with the next rising timing of the pixel clock signal PCLK, and ch1 Change the synchronized lighting signal from “high level” to “low level”. Thereby, the light emitting unit ch1 is turned off.

  Note that the front-end synchronized light emitting section and the rear-end synchronized light emitting section may be different light emitting sections. For example, FIG. 13 shows a timing chart in the case where the light emitting unit ch1 is the front end synchronized light emitting unit and the light emitting unit ch2 is the rear end synchronized light emitting unit. In this case, in the above (2-2) and (2-3), the signal level of the ch2 synchronous lighting signal is changed instead of the ch1 synchronous lighting signal.

  Returning to FIG. 9, the correction data creation circuit 219e individually creates correction data for each light emitting unit based on the measurement data Dint, the measurement end signal Dfin, the front ch information Dfch, and the rear ch information Dech.

Here, as shown in FIG. 14, the correction data creation circuit 219e includes a measurement data determination circuit 219e ₁ , a memory 219e ₂ , and a correction data calculation circuit 219e ₃ .

When the measurement data discriminating circuit 219e ₁ detects the end of measurement from the measurement end signal Dfin, it is determined whether or not the light emitting unit specified from the front ch information Dfch and the light emitting unit specified from the rear ch information Dech are the same light emitting unit. Judging. If the light emitting unit specified from the front ch information Dfch and the light emitting unit specified from the rear ch information Dech are the same light emitting unit, the input measurement data Dint is stored in the memory 219e ₂ as “reference data”. . Note that the tip ch information Dfch at this time is also stored in the memory 219e ₂ as “reference light emitting unit data”. On the other hand, if the light emitting part specified from the front ch information Dfch and the light emitting part specified from the rear ch information Dech are different light emitting parts, the light emitting part specified from the front ch information Dfch and the memory 219e ₂ are held. It is determined whether or not the light emitting parts specified from the “reference light emitting part data” are the same light emitting part. If the light emitting unit specified from the tip ch information Dfch and the light emitting unit specified from the “reference light emitting unit data” are the same light emitting unit, the correction data calculation circuit 219e ₃ is instructed to calculate correction data. On the other hand, if the light emitting unit specified from the tip ch information Dfch and the light emitting unit specified from the “reference light emitting unit data” are different light emitting units, the measurement data determination circuit 219e ₁ does nothing.

The correction data calculation circuit 219e ₃ calculates the difference between the “reference data” held in the memory 219e ₂ and the measurement data Dint at that time from the rear end ch information Dech based on the instruction of the measurement data determination circuit 219e _1. The correction data Dmod in the specified light emitting unit is obtained. For example, if the reference data stored in the memory 219e ₂ is (X1, Y1) and the measurement data Dint at that time is (X2, Y2), the correction data Dmod is obtained from the following equation (1). . Note that “16” in equation (1) indicates that one period of the pixel clock signal (hereinafter also referred to as “one pixel clock”) is ½ period of the high-frequency clock signal (hereinafter “1/2 high-frequency clock”). This is because it corresponds to 16).

Dmod = (X1 × 16 + Y1) − (X2 × 16 + Y2) (1)

  Therefore, for example, when the correction data Dmod obtained from the above equation (1) is represented by an 11-bit binary number, the lower 4 bits (bit 3 to bit 0) are values in units of 1/2 high-frequency clock. The upper 7 bits (bit 10 to bit 4) are values in units of one pixel clock.

  A specific operation of the correction data generation circuit 219e will be described with reference to the timing chart of FIG. Here, the front end synchronized light emitting unit is the light emitting unit ch1 in any of the first to 16th scans, and the rear end synchronized light emitting unit is the light emitting unit ch1 for the first scan and the light emitting unit ch2 for the second scan. It is assumed that the third scan is the light emitting unit ch3,..., And the 16th scan is the light emitting unit ch16. In FIG. 15, up to the third scan is shown due to space limitations.

(3-1) When the measurement end is detected from the measurement end signal Dfin in the first scan, the light emitting unit specified from the front end ch information Dfch is compared with the light emitting unit specified from the rear end ch information Dech. Here, since the light emitting part specified from the front ch information Dfch and the light emitting part specified from the rear ch information Dech are both light emitting parts ch1, input measurement data (here, (X1, Y1)) Are stored as “reference data”.

(3-2) In the second scan, when the measurement end is detected from the measurement end signal Dfin, the light emitting unit specified from the front end ch information Dfch is compared with the light emitting unit specified from the rear end ch information Dech. Here, since the light emitting unit specified from the front end ch information Dfch is the light emitting unit ch1, and the light emitting unit specified from the rear end ch information Dech is the light emitting unit ch2, “reference data” (X1, Y1) is input. The difference from the measured data (here, (X2, Y2)) is obtained and output as the correction data Dmod2 of the light emitting unit ch2.

(3-3) When the measurement end is detected from the measurement end signal Dfin in the third scan, the light emitting unit specified from the front end ch information Dfch and the light emitting unit specified from the rear end ch information Dech are compared. Here, since the light emitting unit specified from the front end ch information Dfch is the light emitting unit ch1, and the light emitting unit specified from the rear end ch information Dech is the light emitting unit ch3, “reference data” (X1, Y1) is input. The difference from the measured data (here, (X3, Y3)) is obtained and output as correction data Dmod3 of the light emitting unit ch3.

  Hereinafter, when the measurement end is detected from the measurement end signal Dfin in the 4th to 16th scans, similarly, correction data (Dmod4 to Dmod16) of the light emitting units ch4 to ch16 are output.

  The correction data is acquired before the actual writing, and the subsequent writing is performed using the correction data acquired there. In addition, correction data can be arbitrarily acquired.

Returning to FIG. 9, the modulation data creation circuit 219a converts the image data (S216 _{1 to} S216 ₁₆ ) from the image data creation circuit 216 into modulation data (Sa _{1 to} Sa ₁₆ ). Further, the output timing of the modulation data (Sa _{1 to} Sa ₁₆ ) is corrected based on the input correction data (Dmod _{1 to} Dmod ₁₆ ). As a result, the light spots (sp1 to sp16) at the start of writing by the light emitting units are aligned at the same position on the photosensitive drum 1030 in the main scanning direction as shown in FIG.

As shown in FIG. 17, the modulation data creation circuit 219a includes a ch1 data creation / correction circuit 219a ₁ , a ch2 data creation / correction circuit 219a ₂ , a ch3 data creation / correction circuit 219a ₃ ,. - has a data creating and correcting circuit 219a ₁₆ for ch16.

  Each data creation / correction circuit has the same configuration, converts the corresponding image data into modulation data, and corrects the output timing of the modulation data based on the corresponding correction data.

  Here, as shown in FIG. 18, each data creation / correction circuit includes a delay circuit a2-1, an FF circuit a2-2, a first data conversion circuit a2-3, a second data conversion circuit a2-4, and a modulation. It has a data selection circuit a2-5.

  The delay circuit a2-1 delays the input image data by the value of the upper 7 bits (bit 10 to bit 4) of the input correction data in units of one pixel clock, and outputs the delayed image data A.

  The FF circuit a2-2 further delays the delayed image data A by one pixel clock and outputs it as delayed image data B.

  The first data conversion circuit a2-3 modulates the input delayed image data A based on the conversion table shown in FIG.

  The second data conversion circuit a2-4 modulates the input delayed image data B based on the conversion table shown in FIG.

  Here, one pixel data in the modulation data A and the modulation data B is 16-bit data, and is output to the modulation data selection circuit a2-5 as parallel data.

  The modulation data selection circuit a2-5 refers to the selection table shown in FIG. 20, and 16 bits from the modulation data A and the modulation data B according to the value of the lower 4 bits (bit3 to bit0) of the input correction data. And output as parallel modulation data.

  For example, if the lower 4 bits of the correction data are “0000”, bits 15 to 0 of the modulation data A are selected. If the lower 4 bits of the correction data are “0001”, bits 14 to of the modulation data A are selected. Bit 0 and bit 15 of modulation data B are selected. If the lower 4 bits of the correction data are “0010”, bits 13 to 0 of the modulation data A and bits 15 and 14 of the modulation data B are selected, and the lower 4 bits of the correction data are “0011”. For example, bits 12 to 0 of modulation data A and bits 15 to 13 of modulation data B are selected.

  The operation of each data creation / correction circuit will be described with reference to FIG. Here, as an example, the correction data is assumed to be “0000101101100” in binary. That is, the upper 7 bits of the correction data are “6” in decimal, and the lower 4 bits are “1100” in binary.

  When the image data is input, since the upper 7 bits of the correction data are “6”, the delayed image data A is data delayed by 6 pixel clocks with respect to the image data. For example, the image data (IDn) input at the timing of T1 becomes the data of the delayed image data A at the timing of T2, which is T1 + 6 pixel clock. Since the delayed image data B is data obtained by delaying the delayed image data A by one pixel clock, the image data immediately preceding the image data IDn (IDn-1) is the delayed image data at the timing T2. B data.

  At the timing of T3 which is a T2 + 1 pixel clock, the modulation data A is data (MDn) obtained by modulating the image data IDn, and the modulation data B is data (MDn-1) obtained by modulating the image data IDn-1. ).

  At this time, since the lower 4 bits of the correction data are “1100” in binary, the modulation data selection circuit a2-5 selects bits 3 to 0 of modulation data A and bits 15 to 4 of modulation data B. Is done. That is, MDn [3: 0] and MDn-1 [15: 4] are output as modulation data.

  In the present embodiment, since the light emission timing of the light emitting unit ch1 is used as a reference, the correction data Dmod1 of the light emitting unit ch1 is “00000000000000”.

Returning to FIG. 9, the PWM data creation circuit 219b converts the modulation data (Sa _{1 to} Sa ₁₆ ) from the modulation data creation circuit 219a into serial PWM data (Sb _{1 to} Sb ₁₆ ).

The PWM data creating circuit 219b, as shown in FIG. 22, for ch2 which converts the modulated data Sa ₁ ch1 data creating circuit for converting the PWM data Sb ₁ to 219b _1, the modulation data Sa ₂ to the PWM data Sb ₂ data creating circuit 219b _2, modulated data Sa ₃ the PWM data Sb ₃ data generating circuit for ch3 converted to 219b _3, · · · · ·, data preparation ch16 converts the modulated data _{Sa 16} to the PWM data _{Sb 16} circuit 219b ₁₆ .

Each data creation circuit has the same configuration, and converts the corresponding modulation data into serial PWM data. Here, as shown in FIG. 23 and FIG. 24 as an example, 16-bit modulation data is generated from the lower side at the rising timing of the high-frequency clock signal VCLK ₁ and the high-frequency clock signal VCLK ₂ , that is, every 1/2 high-frequency clock. One bit is output at a time.

  FIG. 23 shows a case where the modulation data is composed of bits 15 to 0 of modulation data A, and FIG. 24 shows bits 3 to 0 of modulation data A and bits 15 to 4 of modulation data B. The case where it consists of is shown. In FIG. 24, the timing at which MDn [0] is output is delayed by 12 by 1/2 high frequency clock unit as compared with FIG. In this way, it is possible to delay the writing start timing of each light emitting unit with an accuracy of 1/2 high frequency clock.

  In each data generation circuit, when the input synchronous lighting signal is “high level”, the PWM data is forcibly set to “high level”.

Returning to FIG. 9, the light source drive circuit 221 has a plurality of drive units (ch1 drive unit to ch16 drive unit) corresponding to the plurality of light emitting units (ch1 to ch16). The corresponding PWM data from the PWM data creation circuit 219b is input to each drive unit. The output signal of each driving unit is supplied to the corresponding light emitting unit. That is, the light emitting unit ch1 is driven by the ch1 drive unit based on the PWM data Sb _1, the light emitting unit ch2 is driven by the ch2 driver based on the PWM data Sb _2, · · · · · ·, the light emitting unit ch16 is PWM It is driven by ch16 drive unit based on the data _{Sb 16.}

  As is clear from the above description, in the optical scanning device 1010 according to the present embodiment, the scanning control device 22 performs the measurement method.

As described above, according to the scanning control device 22 according to the present embodiment, the high-frequency clock generation circuit 213 that generates _two high-frequency clock signals (VCLK ₁ , VCLK ₂ ) having different phases from each other, and a plurality of high-frequency clock generation circuits 213 according to image information. An image data creation circuit 216 for creating a plurality of image data (data for writing) corresponding to a plurality of light emitting units, a plurality of modulation data corresponding to a plurality of light emitting units from a plurality of image data, and a plurality of modulations Write control circuit 219 that individually adjusts data output timing in units of “phase difference corresponding time”, and light source drive that drives a plurality of light emitting units based on a plurality of PWM data output from write control circuit 219 Circuit 221.

  Then, the writing control circuit 219 selects the front end synchronized light emitting unit and the rear end synchronized light emitting unit, and generates a plurality of synchronized lighting signals for lighting the selected light emitting unit, Based on the measurement results of the two-point measurement circuit 219d that measures the time interval between the leading edge synchronization detection signal rising timing and the trailing edge synchronization detection signal rising timing, and the correction result in each light emitting unit A correction data creation circuit 219e that individually creates data is provided. Thereby, the deviation amount of the writing start timing of the light emitting units ch2 to ch16 with respect to the light emitting unit ch1 can be individually acquired in real time with higher accuracy than before as correction data in units of “phase difference corresponding time”. . Therefore, it is possible to control the lighting timing of the plurality of light emitting units in real time with higher accuracy than in the past.

  In addition, since the write control circuit 219 includes the modulation data creation circuit 219a, the output timings of the plurality of modulation data are set based on the correction data so that the write start timings in the plurality of light emitting units coincide with each other. It can be individually adjusted in units of “phase difference corresponding time”.

  Further, the modulation data generation circuit 219a delays the input signal by the value of the upper 7 bits (first correction data) of the correction data in units of one pixel clock, and the delay circuit. The FF circuit a2-2 delays the output signal of a2-1 by one pixel clock, and is obtained from the output signal of the delay circuit a2-1 according to the value of the lower 4 bits (second correction data) of the correction data. Since it has a modulation data selection circuit a2-5 for selecting a plurality of data from the parallel data and the parallel data obtained from the output signal of the FF circuit a2-2, the output timing of the modulation data with a simple circuit configuration Adjustments can be made.

  Further, according to the optical scanning device 1010 according to the present embodiment, since the scanning control device 22 is included, high-density optical scanning can be performed with high accuracy.

  Further, even if the optical characteristics of the optical components change due to temperature changes or changes over time, or the positional relationship between the optical components changes, the scanning control device 22 obtains appropriate correction data according to the changes in almost real time. Therefore, it is possible to stably align the writing positions on a plurality of scanning lines.

  In addition, the laser printer 1000 according to the present embodiment includes the optical scanning device 1010 that can accurately perform high-density optical scanning, and as a result, a high-quality image can be formed at high speed. It becomes.

  In the above embodiment, the delay circuit a2-1 of each data creation / correction circuit in the modulation data creation circuit 219a may be constituted by a shift register and a selector circuit. In this case, the number of stages of the shift register is determined according to the distance in the M direction between the reference light emitting unit and another light emitting unit. Thereby, the circuit can be configured more efficiently, and the circuit size can be reduced. In FIG. 25, as an example, when the resolution is 1200 dpi (21 μm / dot), all of the cases where the magnification of the optical system is expected to change within a range of 4 to 6 times due to temperature change or secular change. The position of the second row spot, the third row spot position, and the third row spot position from the first row spot on the surface of the photosensitive drum (scanned surface) when the light emitting unit is turned on simultaneously is the number of pixels. Is shown as a unit.

  In this case, with reference to the first row light emitting section, as shown in FIG. 26, the delay circuit corresponding to the second row light emitting section requires a nine-stage shift register and corresponds to the third row light emitting section. This delay circuit requires an 18-stage shift register, and the delay circuit corresponding to the fourth row light emitting section requires a 26-stage shift register.

  Then, in the delay circuit corresponding to the second row light emitting section, as shown in FIG. 27, the output signals of the fifth to ninth shift registers are input to the selector circuit. The selector circuit also receives the upper 7 bits of the correction data, and selects one of the output signals of the fifth to ninth shift registers according to the value of the upper 7 bits of the correction data. Output as delayed image data A. Specifically, when the value of the upper 7 bits of the correction data is “5”, the output signal of the fifth-stage shift register is selected, and when the value of the upper 7 bits of the correction data is “6”, When the output signal of the 6th stage shift register is selected and the value of the upper 7 bits of the correction data is “7”, the output signal of the 7th stage shift register is selected and the value of the upper 7 bits of the correction data Is “8”, the output signal of the eighth-stage shift register is selected, and when the value of the upper 7 bits of the correction data is “9”, the output signal of the ninth-stage shift register is selected. .

  Also, in the delay circuit corresponding to the third row light emitting section, the output signals of the 11th to 18th shift registers are input to the selector circuit, and one of them is selected according to the value of the upper 7 bits of the correction data. Is done. Further, in the delay circuit corresponding to the fourth row light emitting unit, the output signals of the 17th to 26th shift registers are input to the selector circuit, and one of them is selected according to the value of the upper 7 bits of the correction data. Is done.

  In the above-described embodiment, the case where two high-frequency clock signals having phases different from each other by 180 degrees are used as the plurality of high-frequency clock signals has been described. However, the present invention is not limited to this. For example, by using a plurality of high-frequency clock signals having a smaller phase difference, it is possible to align the writing positions on the plurality of scanning lines with finer time accuracy.

As an example, FIG. 28 shows a case where the high-frequency clock generation circuit 213 generates four high-frequency clock signals (VCLK ₁ , VCLK ₂ , VCLK ₃ , VCLK ₄ ) having different phases. In this case, the time corresponding to the phase difference between the plurality of high frequency clock signals is ¼ period of the high frequency clock signal. As shown in FIG. 29, the second counter of the two-point measuring circuit 219d is counted up every quarter cycle of the high-frequency clock signal. Therefore, the correction data Dmod is obtained from the following equation (2).

Dmod = (X1 × 32 + Y1) − (X2 × 32 + Y2) (2)

  For example, when the correction data Dmod obtained from the above equation (2) is represented by a 12-bit (bit 11 to bit 0) binary number, the lower 5 bits (bit 4 to bit 0) represent a 1/4 high frequency clock. The unit value and the upper 7 bits (bits 11 to 5) are values in units of one pixel clock.

  In this case, the upper 7 bits of the correction data Dmod are input to the delay circuit a2-1. In the first data conversion circuit a2-3 and the second data conversion circuit a2-4, one pixel data is converted into 32-bit data (see FIG. 30). Then, the modulation data selection circuit a2-5 selects 32 bits from the modulation data A and the modulation data B according to the value of the lower 5 bits of the input correction data, and outputs it as parallel modulation data (FIG. 31). reference).

  Moreover, although the said embodiment demonstrated the case where one measurement data was calculated | required by one scan, it is not limited to this. For example, as shown in FIG. 32, three measurement data may be obtained by one scan.

  In the above embodiment, the case where the writing position by the light emitting unit ch1 is used as a reference has been described, but the present invention is not limited to this.

  Further, in the above embodiment, when there is almost no difference in the writing position of the light emitting units (for example, the light emitting units ch1, ch5, ch9, ch13) in the same row, instead of the tip ch information Dfch, Tip row information that can identify the row may be used. Similarly, instead of the rear end ch information Dech, rear end column information that can specify a column may be used. In this case, correction data is created for each column.

  Moreover, although the said embodiment demonstrated the case where the 1st row light emission part, the 2nd row light emission part, the 3rd row light emission part, and the 4th row light emission part were equidistant about M direction, it is limited to this. is not.

  Moreover, although the said embodiment demonstrated the case where the two-dimensional array 100 had 16 light emission parts, it is not limited to this.

  In the above embodiment, the case of the laser printer 1000 as the image forming apparatus has been described. However, the present invention is not limited to this. In short, an image forming apparatus including the optical scanning device 1010 can form a high-quality image at high speed as a result.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  As an example, as shown in FIG. 33, a color printer 2000 including a plurality of photosensitive drums may be used.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow). The black “photosensitive drum K1, charging device K2, "Developing device K4, cleaning unit K5, and transfer device K6", cyan "photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6", and magenta "photosensitive drum" M1, charging device M2, developing device M4, cleaning unit M5, and transfer device M6 ”,“ photosensitive drum Y1, charging device Y2, developing device Y4, cleaning unit Y5, and transfer device Y6 ”for yellow, and light A scanning device 2010, a transfer belt 2080, a fixing unit 2030, and the like are provided.

  Each photosensitive drum rotates in the direction of the arrow in FIG. 33, and a charging device, a developing device, a transfer device, and a cleaning unit are arranged around each photosensitive drum along the rotation direction. Each charging device uniformly charges the surface of the corresponding photosensitive drum. The surface of each photoconductive drum charged by the charging device is irradiated with light by the optical scanning device 2010, and an electrostatic latent image is formed on each photoconductive drum. Then, a toner image is formed on the surface of each photosensitive drum by a corresponding developing device. Further, the toner image of each color is transferred onto the recording paper by the corresponding transfer device, and finally the image is fixed on the recording paper by the fixing unit 2030.

  The optical scanning device 2010 has a light source similar to the light source 14 and a scanning control device similar to the scanning control device 22 for each color. Accordingly, the optical scanning device 2010 can have the same effect as the optical scanning device 1010. The color printer 2000 can have the same effect as the laser printer 1000.

  In this color printer 2000, instead of the optical scanning device 2010, the optical scanning device 1010 may be used for each color.

  As described above, according to the measuring method of the present invention, it is suitable for measuring the deviation amount of the writing start timing in a plurality of scanning lines in real time with high accuracy. The optical scanning device of the present invention is suitable for performing high-density optical scanning with high accuracy. The image forming apparatus of the present invention is suitable for forming a high quality image at high speed.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. It is a figure for demonstrating the surface emitting laser array contained in the light source in FIG. It is a figure for demonstrating the light spot formed on the surface of a photoconductor drum. It is a block diagram for demonstrating the structure of a scanning control apparatus. It is a wave form diagram for demonstrating two high frequency clock signals from which a phase mutually differs. 6 is a timing chart for explaining the operation of the pixel clock generation circuit in FIG. 5. 6 is a timing chart for explaining the operation of the image data creation circuit in FIG. 5. FIG. 6 is a diagram for illustrating a configuration of a write control circuit in FIG. 5. FIG. 10 is a timing chart (part 1) for explaining the operation of the two-point measuring circuit in FIG. 9; FIG. FIG. 10 is a timing chart (No. 2) for explaining the operation of the two-point measuring circuit in FIG. 9. FIG. 10 is a timing chart (part 1) for explaining the operation of the synchronous lighting control circuit in FIG. 9; FIG. 10 is a timing chart (No. 2) for explaining the operation of the synchronous lighting control circuit in FIG. 9. FIG. It is a figure for demonstrating the structure of the correction data creation circuit in FIG. It is a timing chart for demonstrating operation | movement of a correction data creation circuit. It is a figure for demonstrating each light spot position formed on the surface of a photoconductor drum at the time of a writing start. It is a figure for demonstrating the structure of the modulation data creation and correction circuit in FIG. It is a figure for demonstrating the structure of the data preparation and correction circuit in FIG. It is a figure for demonstrating the relationship between image data and modulation data. It is a figure for demonstrating the relationship between the lower 4 bits of correction data, and the modulation data output from a modulation data selection circuit. It is a timing chart for demonstrating operation | movement of a data preparation and correction circuit. It is a figure for demonstrating the structure of the PWM data creation circuit in FIG. FIG. 23 is a timing chart (No. 1) for explaining the operation of the data creation circuit in FIG. 22; FIG. FIG. 23 is a timing chart (No. 2) for explaining the operation of the data creation circuit in FIG. 22; FIG. FIG. 6 is a diagram (part 1) for describing a modification of the delay circuit; FIG. 9 is a second diagram illustrating a modification of the delay circuit. FIG. 10 is a third diagram illustrating a modification of the delay circuit. It is a figure for demonstrating four high frequency clock signals from which a phase mutually differs. It is a timing chart for demonstrating operation | movement of the measuring circuit between two points corresponding to FIG. It is a figure for demonstrating the relationship between the image data corresponding to FIG. 28, and modulation | alteration data. It is a figure for demonstrating the relationship between the low-order 5 bits of the correction data corresponding to FIG. 28, and the modulation data output from a modulation data selection circuit. It is a timing chart for demonstrating the modification of operation | movement of a synchronous lighting control circuit. 1 is a diagram illustrating a schematic configuration of a color printer.

Explanation of symbols

  11a ... fθ lens (part of optical system), 11b ... toroidal lens (part of optical system), 13 ... polygon mirror (part of optical system), 14 ... light source, 15 ... coupling lens (one part of optical system) Part), 17 ... cylindrical lens (part of optical system), 18a ... light detection sensor (first light receiving element), 18b ... light detection sensor (second light receiving element), 22 ... scanning control device (control device) , 100 ... Two-dimensional array (surface emitting laser array), 213 ... High frequency clock generation circuit, 215 ... Pixel clock generation circuit, 219c ... Synchronous lighting control circuit (part of control device), 219d ... Two-point measurement circuit (control) Part of apparatus), 219e ... Correction data generation circuit (part of controller), 1000 ... Laser printer (image forming apparatus), 1010 ... Optical scanning apparatus, 1030 ... Photosensitive drum (image carrier) , 2000 ... color printer (image forming apparatus), 2010 ... optical scanning device, CH1 to CH16 ... light-emitting section, K1, C1, M1, Y1 ... photosensitive drum (image bearing member).

Claims (9)

An optical scanning device that scans a plurality of light beams from a plurality of light emitting sections arranged at different positions in a direction corresponding to at least a scanning line direction along a plurality of scanning lines, and writes image information on a surface to be scanned In the measurement method, the amount of deviation of the writing start timing in the plurality of scanning lines is measured,
A second light output from the first light-emitting unit among the plurality of light-emitting units is received by a first light-receiving element that outputs a synchronization detection signal before the start of writing, and then outputs a synchronization detection signal after the end of writing. Obtaining the time until light is received by the light receiving element as a first time;
Time from when the light from the first light emitting unit is received by the first light receiving element to when the light from the second light emitting unit among the plurality of light emitting units is received by the second light receiving element. Obtaining as a second time;
A step of determining the amount of shift of the second light emitting unit with respect to the first light emitting unit from the difference between the second time and the first time. An optical scanning device that scans a scanned surface in a main scanning direction along a plurality of scanning lines with a plurality of light beams,
A light source having a plurality of light emitting portions arranged at least in positions corresponding to the direction corresponding to the direction of the scanning line;
An optical system for condensing a plurality of light beams from the light source on the surface to be scanned and moving a plurality of light spots on the surface to be scanned in the main scanning direction along the plurality of scanning lines;
A first light receiving element on which light before writing starts is incident;
A second light receiving element on which light after writing is incident;
Of the plurality of light emitting units, the time from when the light from the first light emitting unit is received by the first light receiving element to when the light is received by the second light receiving element, and from the first light emitting unit From the difference between the time from when light is received by the first light receiving element to the time when light from the second light emitting part is received by the second light receiving element among the plurality of light emitting parts, the first light receiving element is used. And a control device that acquires the amount of deviation of the second light emitting unit with respect to the light emitting unit. The control device includes a high-frequency clock generation circuit that generates a plurality of high-frequency clock signals having different phases from each other,
The optical scanning device according to claim 2, wherein the control device acquires the shift amount in units of time corresponding to the phase differences of the plurality of high-frequency clock signals. The control device includes a high-frequency clock generation circuit that generates a plurality of high-frequency clock signals having different phases, and a pixel clock generation circuit that generates a pixel clock signal from one high-frequency clock signal generated by the high-frequency clock generation circuit. And
The control device divides the shift amount into a first shift amount that is an integral multiple of the period of the pixel clock signal and a second shift amount that is less than one period of the remaining pixel clock signal, and The first shift amount is acquired in units of a cycle of the pixel clock signal, and the second shift amount is acquired in units of time corresponding to phase differences of the plurality of high frequency clock signals. 2. The optical scanning device according to 2.   5. The optical scanning device according to claim 2, wherein the control device acquires the shift amount of one light emitting unit in one scan.   5. The optical scanning device according to claim 2, wherein the control device individually acquires the shift amounts of a plurality of light emitting units in one scan.   The optical scanning device according to claim 2, wherein the light source includes a surface emitting laser array. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to any one of claims 2 to 7 that scans the at least one image carrier with a light beam modulated according to image information.   The image forming apparatus according to claim 8, wherein the image information is multicolor color image information.

Images