JP2007003549A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately scan an object to be scanned with a plurality of light beams emitted from a light source unit. <P>SOLUTION: When a photoreceptor drum is scanned with the plurality of light beams including image information emitted from the light source unit having a plurality of light sources including a main light source (B1), a sublight source (B2) and a spare light source (A1), a driving signal for the plurality of light sources is generated by a processing circuit on the basis of the positional information of pixels which is formed in the scanning process. In this case, when a positional deviation in the subscanning direction smaller than one pixel exists at the position of light from the main light source, at least one driving signal of the sublight source is generated for correcting the positional deviation. Further, when a positional deviation in the subscanning direction equal to or larger than one pixel exists at the position of light from the main light source, at least one driving signal of the spare light source is generated for correcting the positional deviation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning device and an image forming apparatus, and more particularly to an optical scanning device that scans light from a light source with respect to an object to be scanned and an image forming apparatus including the optical scanning device.

  In an image forming apparatus such as a laser printer or a digital copying machine, light from a light source modulated according to image information is condensed on a photoconductor via a polygon mirror, a scanning lens, and the like, and on the photoconductor. And a latent image (electrostatic latent image) is formed on the photosensitive member. Then, the image information is visualized by attaching toner to the latent image.

  In recent years, we have responded to the demand for higher printing speed by increasing the rotation speed of the polygon mirror or increasing the frequency of the clock signal used when modulating the light from the light source. These methods have limitations, and a so-called multi-beam method using a plurality of light sources has been devised in order to cope with further increase in speed. (For example, see Patent Documents 1 to 3)

  Recently, the number of pixels of digital cameras has increased dramatically, and the demand for higher print quality has also increased. However, in the devices disclosed in Patent Documents 1 to 3, it is difficult to satisfy the user's requirements sufficiently because no consideration is given to pixel misalignment particularly in the sub-scanning direction. .

JP 2001-272615 A JP 2001-350111 A JP 2003-72135 A

  The present invention has been made under such circumstances, and a first object thereof is to provide an optical scanning device capable of scanning a scanning object with a plurality of lights from a light source unit with high accuracy. It is in.

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

  The invention according to claim 1 is an optical scanning device that scans light including image information with respect to a scanning object and forms an image on the scanning object, in a first direction corresponding to the sub-scanning direction. And a second direction that is different from the first direction and is inclined with respect to a direction corresponding to the main scanning direction, and a light source unit having a plurality of light sources arranged two-dimensionally along the second direction. And generating a control signal of a plurality of main light sources included in the plurality of light sources forming a main pixel on the scanning object based on the image information, and at least one pixel in the sub-scanning direction of the main pixel And a signal generation circuit that generates a control signal of at least one auxiliary light source included in the plurality of light sources so that the positional deviation is corrected based on the positional deviation information of the magnitude.

  According to this, when scanning the scanning object with light including image information from a light source unit having a plurality of light sources, a main pixel is formed on the scanning object by the signal generation circuit based on the image information. Control signals of a plurality of main light sources are generated, and at least one auxiliary light source is corrected so that the position shift is corrected based on position shift information having a size of one pixel or more in the sub-scanning direction of the main pixel. A control signal is generated. Thereby, when the light from a plurality of light sources is scanned with respect to the scanning object, the positional deviation in the sub-scanning direction can be corrected. Therefore, it becomes possible to scan the scanning object with a plurality of lights from the light source unit with high accuracy.

  In this case, as in the optical scanning device according to claim 2, the signal generation circuit further detects the positional shift based on positional shift information having a size of less than one pixel in the sub-scanning direction of the main pixel. A control signal for at least one sub-light source included in the plurality of light sources may be generated so as to be corrected.

  The invention according to claim 3 is an optical scanning device that scans a scanning object with light including image information and forms an image on the scanning object, and the scanning object corresponds to the image information. A plurality of main light sources used when forming main pixels, and at least one auxiliary light source used for correcting a positional shift of one or more pixels in the sub-scanning direction of the main pixels in the scanning object A light source unit having a plurality of light sources including: a signal for generating a control signal for the auxiliary light source for correcting a positional shift of the size of one pixel or more based on positional shift information of the main pixel in the sub-scanning direction And a generation circuit.

  According to this, when scanning the scanning object with the light including the image information from the light source unit having a plurality of light sources, the signal generation circuit, based on the positional deviation information regarding the sub-scanning direction of the main pixel, A control signal for at least one auxiliary light source is generated so that a positional shift of one pixel or more in the sub-scanning direction of the main pixel is corrected. Thereby, when the light from a plurality of light sources is scanned with respect to the scanning object, the positional deviation in the sub-scanning direction can be corrected. Therefore, it becomes possible to scan the scanning object with a plurality of lights from the light source unit with high accuracy.

  In this case, as in the optical scanning device according to claim 4, the plurality of light sources of the light source unit correct a positional shift of less than one pixel in the scanning target with respect to the sub-scanning direction of the main pixel. The signal generation circuit further includes at least one sub-light source used for correction, and the signal generation circuit corrects a positional shift of less than one pixel based on positional shift information of the main pixel in the sub-scanning direction. One sub-light source control signal may be further generated.

  In this case, as in the optical scanning device according to claim 5, the plurality of light sources have a first direction corresponding to the sub-scanning direction and a direction different from the first direction, and the main scanning direction. , And a second direction inclined with respect to the direction corresponding to.

  In each of the optical scanning devices according to Claims 2 and 5, as in the optical scanning device according to Claim 6, the plurality of light sources may be in any of the first direction and the second direction. They can be arranged at equal intervals.

  In this case, as in the optical scanning device according to claim 7, each of the plurality of main light sources is either the sub light source or the auxiliary light source with respect to any of the first direction and the second direction. Can be adjacent.

  In this case, as in the optical scanning device according to claim 8, at least one sub-light source is disposed between two main light sources adjacent to each other with respect to the position in the first direction. can do.

  In this case, as in the optical scanning device according to claim 9, the number of the sub light sources arranged between the two main light sources is one, two, or three. Can be.

  In this case, as in the optical scanning device according to claim 10, the number of the sub light sources arranged between the two main light sources is one, and the plurality of light sources are in the second direction. It can be assumed that the number of light sources in each column is an odd number.

  In the optical scanning device according to claim 9, the number of the sub light sources arranged between the two main light sources is two as in the optical scanning device according to claim 11, and the plurality of sub light sources The light sources may be arranged so that the number of light sources in each column in the second direction is a number excluding multiples of 3.

  The optical scanning device according to claim 9 is the optical scanning device according to claim 12, wherein the number of sub-light sources arranged between the two main light sources is three, and the plurality of sub-light sources The light sources may be arranged so that the number of light sources in each column in the second direction is a multiple of three.

  The optical scanning device according to claim 9 is the optical scanning device according to claim 13, wherein the number of the sub light sources arranged between the two main light sources is three, and the signal generation is performed. The circuit may generate a control signal for forming a main pixel using a central sub-light source among the three sub-light sources when the size of the one pixel is changed to ½. .

  In each of the optical scanning devices according to the first to thirteenth aspects, as in the optical scanning device according to the fourteenth aspect, the number of the preliminary light sources is an amount of positional deviation of light from the main light source in the sub-scanning direction. Can be determined accordingly.

  15. Each optical scanning device according to claim 1, wherein the light source unit has a surface emitting laser in which the plurality of light sources are formed on the same chip as in the optical scanning device according to claim 15. It can be.

  According to a sixteenth aspect of the present invention, at least one scanning object; and at least one scanning object according to the first to fifteenth aspects, wherein light is scanned with respect to the at least one scanning object and an image is formed on the scanning object. An image forming apparatus comprising: the optical scanning device according to claim 1; and a transfer device that transfers an image formed on the scanning object to the transfer object.

  According to this, the optical scanning apparatus as described in any one of Claims 1-15 which can make a scanning target object scan the some light from a light source unit with a sufficient precision is provided. Therefore, a high-quality image can be formed at high speed.

  In this case, when a color image is transferred to the transfer object as in the image forming apparatus according to claim 17, a plurality of the scan objects correspond to a plurality of colors constituting the color image. It is possible to provide the optical scanning devices individually corresponding to the plurality of scanning objects. For example, a tandem color machine.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a laser printer 100 as an image forming apparatus according to an embodiment of the present invention.

  A laser printer 100 shown in FIG. 1 includes an optical scanning device 900, a photosensitive drum 901 as a scanning object, a charging brush 902, a developing roller 903, a toner cartridge 904, a cleaning blade 905, a paper feed tray 906, and a paper feed roller 907. A registration roller pair 908, a transfer roller 911, a fixing roller 909, a paper discharge roller 912, a paper discharge tray 910, a pixel formation position detector 915, and the like.

  The charging brush 902, the developing roller 903, the transfer roller 911, and the cleaning blade 905 are arranged in the vicinity of the surface of the photosensitive drum 901, respectively. Then, with respect to the rotation direction of the photosensitive drum 901, the charging brush 902, the developing roller 903, the transfer roller 911, and the cleaning blade 905 are arranged in this order.

  A photosensitive layer is formed on the surface of the photosensitive drum 901. Here, the photosensitive drum 901 rotates in the clockwise direction (arrow direction) in the plane in FIG. The charging brush 902 charges the surface of the photosensitive drum 901.

  The optical scanning device 900 irradiates the surface of the photosensitive drum 901 charged by the charging brush 902 with light modulated based on image information from a host device (for example, a personal computer). As a result, on the surface of the photosensitive drum 901, the charge is lost only in the portion irradiated with light, and a latent image corresponding to the image information is formed on the surface of the photosensitive drum 901. The latent image formed here moves in the direction of the developing roller 903 as the photosensitive drum 901 rotates. The longitudinal direction (direction along the rotation axis) of the photosensitive drum 901 is referred to as “main scanning direction”, and the rotational direction of the photosensitive drum 901 is referred to as “sub-scanning direction”. Hereinafter, for convenience, the length of the pixel in the main scanning direction in the latent image formed on the surface of the photosensitive drum 901 is also referred to as “pixel width”. The configuration of the optical scanning device 900 will be described later.

  The toner cartridge 904 stores toner, and the toner is supplied to the developing roller 903. The amount of toner in the toner cartridge 904 is checked when the power is turned on or when printing is completed. When the remaining amount is low, a message prompting replacement is displayed on a display unit (not shown).

  As the developing roller 903 rotates, the toner supplied from the toner cartridge 904 is charged and thinly and uniformly attached to the surface thereof. Further, the developing roller 903 has an electric field in the opposite direction between a charged portion (a portion not irradiated with light) and an uncharged portion (a portion irradiated with light) in the photosensitive drum 901. A voltage is generated to generate. By this voltage, the toner adhering to the surface of the developing roller 903 adheres only to the portion irradiated with light on the surface of the photosensitive drum 901. That is, the developing roller 903 causes the toner to adhere to the latent image formed on the surface of the photosensitive drum 901 and visualizes the image information. Here, the latent image to which the toner is attached moves in the direction of the transfer roller 911 as the photosensitive drum 901 rotates.

  The paper feed tray 906 stores recording paper 913 as a transfer object. The paper feed roller 907 is disposed in the vicinity of the paper feed tray 906, and the paper feed roller 907 takes out the recording paper 913 one by one from the paper feed tray 906 and conveys it to the registration roller pair 908. The registration roller pair 908 is disposed in the vicinity of the transfer roller 911, temporarily holds the recording paper 913 taken out by the paper feed roller 907, and the recording paper 913 is synchronized with the rotation of the photosensitive drum 901. It is sent out toward the gap between the drum 901 and the transfer roller 911.

  A voltage having a polarity opposite to that of the toner is applied to the transfer roller 911 in order to electrically attract the toner on the surface of the photosensitive drum 901 to the recording paper 913. With this voltage, the latent image on the surface of the photosensitive drum 901 is transferred to the recording paper 913. The recording sheet 913 transferred here is sent to the fixing roller 909.

  In the fixing roller 909, heat and pressure are applied to the recording paper 913, whereby the toner is fixed on the recording paper 913. The recording paper 913 fixed here is sent to the paper discharge tray 910 via the paper discharge roller 912 and sequentially stacked on the paper discharge tray 910.

  The cleaning blade 905 removes toner remaining on the surface of the photosensitive drum 901 (residual toner). The removed residual toner is used again. The surface of the photosensitive drum 901 from which the residual toner has been removed returns to the position of the charging brush 902 again.

  The pixel formation position detector 915 is disposed in the vicinity of the photosensitive drum 901, detects the position of the pixel formed on the photosensitive drum 901, and outputs a signal including positional deviation information in the sub-scanning direction.

  Next, the configuration of the optical scanning device 900 will be described with reference to FIGS.

  The optical scanning device 900 includes a light source unit 801, a collimating lens CL, a cylinder lens 805, a polygon mirror 808, a polygon motor (not shown) that rotates the polygon mirror 808, an fθ lens 806, a folding mirror 807, a toroidal lens 812, two It includes a light receiving element (813, 814), two printed circuit boards (802, 809), a processing circuit 815, and the like. In the following, from the collimating lens CL, the cylinder lens 805, the polygon mirror 808, the fθ lens 806, the folding mirror 807, the toroidal lens 812, and the like disposed on the light path from the light source unit 801 to the photosensitive drum 901. This optical system is also referred to as a “scanning optical system”.

  The light source unit 801 includes a semiconductor laser LD that emits laser light modulated in accordance with image information toward a polygon mirror 808. As an example, this semiconductor laser LD is a so-called surface emitting laser having 48 light emitting portions each having substantially the same light emission characteristics as shown in FIG.

  The 48 light emitting units have a direction corresponding to the sub-scanning direction (hereinafter also referred to as “dir_sub direction” for convenience) and a direction different from the dir_sub direction and corresponding to the main scanning direction (hereinafter referred to as convenience). , Also referred to as “dir_main direction”), and two-dimensionally arranged along a direction (hereinafter also referred to as “α direction” for convenience) inclined by an angle θ (0 degree <θ <90 degrees). ing. Here, as an example, the number of light emitting unit rows arranged in the α direction is eight (referred to as “A column to H column” in order from the top to the bottom in FIG. 4), and the number of light emitting unit rows arranged in the dir_sub direction. Are six columns (referred to as “first to sixth columns” in order from the left to the right in FIG. 4). Therefore, in the following, for example, the light emitting unit in the third row in the B row is referred to as a B3 light emitting unit, and the light emitting unit in the sixth column in the F row is referred to as an F6 light emitting unit. For the dir_sub direction, the direction from the upper side to the lower side in FIG. 4 is referred to as the + direction, and for the α direction, the direction from the left side to the right side in FIG. In addition, the 48 light emitting units are arranged at equal intervals in both the dir_main direction and the dir_sub direction. Here, the interval in the dir_main direction is ΔXa1, and the interval in the dir_sub direction is ΔYa1. Accordingly, the light emitting units are also arranged at equal intervals in the α direction.

  In the present embodiment, when the B1 light emitting unit, the B5 light emitting unit, the C3 light emitting unit, the D1 light emitting unit, the D5 light emitting unit, the E3 light emitting unit, the F1 light emitting unit, the F5 light emitting unit, and the G3 light emitting unit form the main pixel. The main light source used. In addition, the A1 light emitting unit, the A2 light emitting unit, the A3 light emitting unit, and the H1 light emitting unit to the H6 light emitting unit are spare light sources used when correcting a positional deviation of one or more main pixels in the sub-scanning direction. is there. The remaining light emitting units are sub-light sources that are used when correcting a positional shift of less than one pixel of the main pixel in the sub-scanning direction. That is, the light source unit 801 has a plurality of light sources including nine main light sources, thirty sub-light sources, and nine auxiliary light sources.

  The misregistration means the misregistration of the latent image formed on the surface of the photoconductor drum 901. Scanning unevenness caused by the characteristics of the fθ lens 806, so-called surface tilt of the deflecting reflection surface of the polygon mirror 808, and deflection. This is caused by variations in the distance from the rotation axis of the reflection surface, rotation unevenness of the polygon mirror 808, wavelength fluctuation of the laser light emitted from the semiconductor laser LD, and the like. In the following, for the sake of convenience, the positional deviation in the main scanning direction is also referred to as “main scanning direction deviation”, and the positional deviation in the sub scanning direction is also referred to as “sub scanning direction deviation”.

  In addition, each main light source is adjacent to either the auxiliary light source or the auxiliary light source in both the dir_sub direction and the α direction. Three sub light sources are arranged between two main light sources adjacent to each other with respect to the position in the dir_sub direction. Therefore, the distance (referred to as ΔYa1) in the dir_sub direction between two main light sources adjacent to each other with respect to the position in the dir_sub direction is ΔYa2 × 4. That is, the size of one pixel in the dir_sub direction is ΔYa1 (= ΔYa2 × 4).

  Therefore, for example, as shown in FIG. 5, if the amount of positional deviation (denoted as devB5) in the sub-scanning direction of the main pixel formed by the B5 light emitting unit is ΔYa2 or less, the sub-light source for correcting the deviation. B4 light emitting part or B6 light emitting part is used. If ΔYa2 <devB5 ≦ ΔYa2 × 2, the B3 light emission unit or the C1 light emission unit is used as a sub-light source for correcting the deviation. If ΔYa2 × 2 <devB5 ≦ ΔYa2 × 3, a B2 light emitting unit or a C2 light emitting unit is used as a sub-light source for correcting the deviation.

  Similarly, for example, as shown in FIG. 6A, the main pixel formed by the B1 light emitting portion is displaced in the + side in the sub-scanning direction, and the displacement amount in the sub-scanning direction (devB1). ) Is equal to or less than ΔYa2, the A6 light emitting unit is used as a sub-light source for correcting the deviation. If ΔYa2 <devB1 ≦ ΔYa2 × 2, A5 is used as a sub-light source for correcting the deviation. If ΔYa2 × 2 <devB1 ≦ ΔYa2 × 3, an A4 light emitting unit is used as a sub-light source for correcting the deviation. If ΔYa2 × 3 <devB1 ≦ ΔYa2 × 4, an A3 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 4 <devB1 ≦ ΔYa2 × 5, the A2 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 5 <devB1 ≦ ΔYa2 × 6, the A1 light emitting unit is used as a preliminary light source for correcting the deviation.

  Further, for example, as shown in FIG. 6B, the main pixel formed by the G3 light emitting unit is displaced in the minus direction in the sub-scanning direction, and the displacement amount in the sub-scanning direction (denoted as devG3). However, if ΔYa2 or less, the G4 light emitting unit is used as a sub-light source for correcting the deviation. If ΔYa2 <devG3 ≦ ΔYa2 × 2, G5 is used as a sub-light source for correcting the deviation. If ΔYa2 × 2 <devG3 ≦ ΔYa2 × 3, the G6 light emitting unit is used as a sub-light source for correcting the deviation. If ΔYa2 × 3 <devG3 ≦ ΔYa2 × 4, the H1 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 4 <devG3 ≦ ΔYa2 × 5, the H2 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 5 <devG3 ≦ ΔYa2 × 6, an H3 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 6 <devG3 ≦ ΔYa2 × 7, an H4 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 7 <devG3 ≦ ΔYa2 × 8, the H5 light emitting unit is used as a preliminary light source for correcting the deviation. If ΔYa2 × 8 <devG3 ≦ ΔYa2 × 9, an H6 light emitting unit is used as a preliminary light source for correcting the deviation.

  Returning to FIG. 2, the light source unit 801 is in contact with the wall surface of the optical housing 804 by a spring with the printed circuit board 802 mounted on the back surface thereof. Note that the posture of the contact with the wall surface can be adjusted by an adjusting screw 803. Thereby, the emission direction of light from the light source unit 801 can be adjusted. The adjustment screw 803 is screwed into a protrusion formed on the wall surface of the optical housing 804. Inside the optical housing 804, as shown in FIG. 3, the collimating lens CL, cylinder lens 805, polygon mirror 808, polygon motor (not shown), fθ lens 806, folding mirror 807, toroidal lens 812, and 2 Two light receiving elements (813, 814) are respectively positioned and supported at predetermined positions. Further, the printed circuit board 809 is attached to the wall surface of the optical housing 804 from the outside in the same manner as the light source unit 801. The upper portion of the optical housing 804 is sealed with a cover 811 and is fixed to the frame member of the laser printer 100 with screws by a plurality of mounting portions 810 protruding from the wall surface.

  The collimating lens CL makes light from the light source unit 801 substantially parallel light. The cylinder lens 805 shapes the light from the collimating lens CL.

  The operation of the scanning optical system will be briefly described. The light from the light source unit 801 is once imaged near the deflection surface of the polygon mirror 808 via the collimator lens CL and the cylinder lens 805. The polygon mirror 808 is rotated in the direction of arrow B in FIG. 3 at a constant speed by a polygon motor (not shown), and the light imaged in the vicinity of the deflecting surface is deflected at a constant angular velocity with the rotation. The The light deflected by the polygon mirror 808 enters the folding mirror 807 through the fθ lens 806, is reflected by the folding mirror 807, and scans the surface of the photosensitive drum 901 through the toroidal lens 812. In the following, in the scanning in the main scanning direction, one scanning from the scanning start position to the scanning end position is also referred to as “one-line scanning”.

  The two light receiving elements (813 and 814) for detecting the start and end of one line scanning are provided at both ends of the folding mirror 807 in the main scanning direction. Here, the light deflected by the polygon mirror 808 is arranged so as to enter the light receiving element 813 before scanning the surface of the photosensitive drum 901 by one line and to enter the light receiving element 814 after scanning one line. Yes. Each light receiving element outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  As shown in FIG. 7, two I / V amplifiers (60, 61), two binarization circuits (62, 63), two inverters (64, 65) and the like are mounted on the printed circuit board 809. Has been.

  The I / V amplifier 60 converts the photoelectric conversion signal from the light receiving element 813 into a voltage signal and amplifies it with a predetermined gain. The I / V amplifier 61 converts the photoelectric conversion signal from the light receiving element 814 into a voltage signal and amplifies it with a predetermined gain.

  The binarization circuit 62 binarizes the output signal of the I / V amplifier 60. The binarization circuit 63 binarizes the output signal of the I / V amplifier 61.

  The inverter 64 inverts the output signal of the binarization circuit 62 and outputs it as the first horizontal synchronization signal Hsync1. The inverter 65 inverts the output signal of the binarization circuit 63 and outputs it as the second horizontal synchronization signal Hsync2. Therefore, when light is incident on the light receiving element 813, the first horizontal synchronization signal Hsync1 changes from “H (high level)” to “L (low level)”. When light is incident on the light receiving element 814, the second horizontal synchronization signal Hsync2 changes from “H” to “L”.

  As shown in FIG. 7, a laser driving circuit 50 and the like are mounted on the printed circuit board 802. The laser driving circuit 50 generates a driving signal for the semiconductor laser LD based on a pulse train signal (control signal) described later from the processing circuit 815 and outputs the driving signal to the light source unit 801. The light source unit 801 supplies the drive signal to the semiconductor laser LD.

  As shown in FIG. 7, the processing circuit 815 includes a positional deviation information acquisition circuit 10, a pixel clock generation circuit 20, a pulse train generation circuit 30, an image data generation circuit 40, a memory 15, and the like.

  A positional deviation information acquisition circuit 10 acquires main scanning direction deviation information based on the first horizontal synchronization signal Hsync1 and the second horizontal synchronization signal Hsync2, and a sub-position based on the output signal of the pixel formation position detector 915. Scan direction deviation information is acquired.

  Here, as an example, the positional deviation information acquisition circuit 10 takes a time required for one-line scanning calculated from the first horizontal synchronization signal Hsync1 and the second horizontal synchronization signal Hsync2 (hereinafter also referred to as “scanning time” for convenience). And the reference time (hereinafter also referred to as “scanning reference time”) set in advance (hereinafter also referred to as “scanning time difference”), main-scanning direction deviation information is acquired and stored in the memory 15. The phase data Sphase is generated with reference to the main scanning direction deviation correction information table. The phase data Sphase generated here is output to the pixel clock generation circuit 20.

  In the present embodiment, for a plurality of scanning time differences, the main scanning direction deviation of each pixel is measured for each scanning time difference, and the phase is changed in accordance with the scanning time difference based on the measurement result. A map is created for the change amount, and a map for each scanning time difference is stored in the memory 15 as the main scanning direction deviation correction information table.

  Further, the positional deviation information acquisition circuit 10 acquires the sub-scanning direction deviation from the output signal of the pixel formation position detector 915 for the scanning result of the trial scan performed in advance, and stores it in the memory 15 as a sub-scanning direction deviation information table. Store. Then, with reference to the sub-scanning direction deviation information table during actual scanning, a correction signal Sdev for correcting the sub-scanning direction deviation is output to the pulse train generation circuit 30. Specifically, a correction signal Sdev is generated for shifting the light from the light source unit 801 in the direction opposite to the direction of the sub-scanning direction deviation by the same amount as the magnitude of the sub-scanning direction deviation with respect to the dir_sub direction.

  Here, the correction signal Sdev will be described with reference to FIGS. 8 (A) to 10 (F). Here, as an example, the positional deviation amount devB5 in the sub-scanning direction of the main pixel formed by the B5 light emitting unit is ΔYa2 or less, and the B4 light emitting unit or the B6 light emitting unit is used as a sub light source for correcting the deviation. The case will be described. As an example, as shown in FIGS. 8A and 8B, 11 types (M1 to M11) of driving modes are used.

  The drive mode M1 is applied to a pixel whose sub-scanning direction deviation is 0, and only the B5 light emitting unit is driven with a normal pulse width (referred to as “Ts”). The center of gravity of the light at this time substantially coincides with the light emitting point of the B5 light emitting portion, as indicated by reference numeral Ga in FIG. That is, the shift amount is zero.

  The driving mode M2 is applied to a pixel having a sub-scanning direction shift of −d 1/5, the B5 light emitting unit is driven with a pulse width of 4 / 5Ts, and the B6 light emitting unit is driven with a pulse width of 1 / 5Ts. The center of gravity of the light at this time becomes + in the dir_sub direction by d1 / 5 from Ga, as indicated by reference numeral Gb in FIG. That is, the shift amount is + d1 / 5. Note that d1 = ΔYa2.

  The driving mode M3 is applied to a pixel having a sub-scanning direction deviation of −2 × d 1/5, the B5 light emitting unit is driven with a pulse width of 3 / 5Ts, and the B6 light emitting unit is driven with a pulse width of 2 / 5Ts. . At this time, the center of gravity of the light becomes + in the dir_sub direction by 2 × d 1/5 from Ga, as indicated by reference numeral Gc in FIG. 9C. That is, the shift amount is + 2 × d1 / 5.

  The drive mode M4 is applied to a pixel having a sub-scanning direction deviation of −3 × d 1/5, the B5 light emitting unit is driven with a pulse width of 2 / 5Ts, and the B6 light emitting unit is driven with a pulse width of 3 / 5Ts. . At this time, the center of gravity of the light becomes + in the dir_sub direction by 3 × d 1/5 from Ga, as indicated by a symbol Gd in FIG. 9D. That is, the shift amount is + 3 × d1 / 5.

  The driving mode M5 is applied to a pixel having a sub-scanning direction deviation of −4 × d 1/5, the B5 light emitting unit is driven with a pulse width of 1/5 Ts, and the B6 light emitting unit is driven with a pulse width of 4/5 Ts. . The center of gravity of the light at this time becomes + in the dir_sub direction by 4 × d 1/5 from Ga, as indicated by reference numeral Ge in FIG. That is, the shift amount is + 4 × d1 / 5.

  The drive mode M6 is applied to a pixel whose sub-scanning direction deviation is −d1, and only the B6 light emitting unit is driven with a pulse width of Ts. The center of gravity of the light at this time substantially coincides with the light emitting point of the B6 light emitting portion as indicated by the symbol Gf in FIG. 9F, and becomes + in the dir_sub direction by d1 from Ga. That is, the shift amount is + d1.

  The drive mode M7 is applied to a pixel whose sub-scanning direction deviation is + d1 / 5, the B5 light emitting unit is driven with a pulse width of 4 / 5Ts, and the B4 light emitting unit is driven with a pulse width of 1 / 5Ts. At this time, the center of gravity of the light becomes − in the dir_sub direction by d 1/5 from Ga, as indicated by a symbol Gg in FIG. That is, the shift amount is -d1 / 5.

  The driving mode M8 is applied to a pixel with a sub-scanning direction shift of + 2 × d1 / 5, the B5 light emitting unit is driven with a pulse width of 3 / 5Ts, and the B4 light emitting unit is driven with a pulse width of 2 / 5Ts. At this time, the center of gravity of the light is − in the dir_sub direction by 2 × d 1/5 from Ga, as indicated by a symbol Gh in FIG. That is, the shift amount is -2 * d1 / 5.

  The drive mode M9 is applied to a pixel with a sub-scanning direction shift of + 3 × d 1/5, the B5 light emitting unit is driven with a pulse width of 2 / 5Ts, and the B4 light emitting unit is driven with a pulse width of 3 / 5Ts. At this time, the center of gravity of the light is − in the dir_sub direction by 3 × d 1/5 from Ga, as indicated by a symbol Gi in FIG. That is, the shift amount is −3 × d 1/5.

  The drive mode M10 is applied to a pixel having a sub-scanning direction shift of + 4 × d1 / 5, the B5 light emitting unit is driven with a pulse width of 1 / 5Ts, and the B4 light emitting unit is driven with a pulse width of 4 / 5Ts. At this time, the center of gravity of the light is − in the dir_sub direction by 4 × d 1/5 from Ga, as indicated by a symbol Gj in FIG. That is, the shift amount is −4 × d 1/5.

  The drive mode M11 is applied to a pixel whose sub-scanning direction deviation is + d1, and only the B4 light emitting unit is driven with a pulse width of Ts. The center of gravity of the light at this time substantially coincides with the light emitting point of the B4 light emitting portion as indicated by the symbol Gk in FIG. 10F, and becomes d in the dir_sub direction by d1 from Ga. That is, the shift amount is -d1.

  As long as the correction signal can be recognized by the pulse train generation circuit 30, the correction signal may be the drive mode itself or the pulse width information of each light source. Thereby, the gravity center of the light from the light source unit 801 can be shifted in the dir_sub direction while keeping the light amount of the light from the light source unit 801 constant.

  For example, when the straight line image information from the host device as shown in FIG. 11A becomes a non-straight line as shown in FIG. 11B in the test scan, it is shown in FIG. As shown in FIG. 11D, the driving mode as shown is selected, and each pixel can be formed at the optimum position in the sub-scanning direction in the latent image.

  Returning to FIG. 7, the pixel clock generation circuit 20 generates a pixel clock signal PCLK having partially different phases based on the phase data Sphase. The pixel clock signal PCLK is supplied to the positional deviation information acquisition circuit 10 and the pulse train generation circuit 30.

  The image data generation circuit 40 generates image data based on image information from the host device. The image data generated here is output to the pulse train generation circuit 30.

  The pulse train generation circuit 30 generates a pulse train signal based on the image data, the correction signal Sdev, and the pixel clock signal PCLK. Note that if the amount of deviation in the sub-scanning direction deviation is within a preset allowable range, as shown in FIG. 12A as an example, the pixel is formed at the optimum position only by the main pixel. There is no need to form sub-pixels. As an example, as shown in FIG. 12B, the pulse train signal of the B5 light emitting unit is generated, but the pulse train signal of the B4 light emitting unit and the pulse train signal of the B6 light emitting unit are Is not generated. That is, usually only the main light source is used. On the other hand, the sub-light source and the auxiliary light source are used only when the amount of deviation in the sub-scanning direction exceeds the allowable range and correction of the sub-scanning direction deviation is necessary.

  As is clear from the above description, in the optical scanning device 900 according to the present embodiment, a signal generation circuit is configured by the processing circuit 815.

  In the laser printer 100 as the image forming apparatus according to the present embodiment, the charging brush 902, the developing roller 903, the toner cartridge 904, and the transfer roller 911 constitute a transfer device.

  As described above, according to the optical scanning device 900 according to this embodiment, light including image information from the light source unit 801 having a plurality of light sources including the main light source, the sub light source, and the auxiliary light source is supplied to the photosensitive drum 901. When scanning is performed, the processing circuit 815 generates driving signals for a plurality of light sources based on the position information of the pixels formed in the scanning. In this case, if the position of the light from the main light source in the sub-scanning direction has a position shift exceeding an allowable range, and the position shift is less than one pixel, at least one position is corrected to correct the position shift. If the sub-light source drive signal is generated and the positional deviation is one pixel or more, at least one auxiliary light source drive signal is generated to correct the positional deviation. This makes it possible to correct the sub-scanning direction deviation when scanning the photosensitive drum 901 with light from a plurality of light sources. Therefore, it becomes possible to scan the scanning object with a plurality of lights from the light source unit with high accuracy.

  Further, according to the present embodiment, the distance between two main light sources adjacent to each other with respect to the position in the dir_sub direction can be made longer than before, and so-called crosstalk can be reduced.

  In addition, the laser printer 100 according to the present embodiment includes the optical scanning device 900 capable of scanning a plurality of lights with high accuracy, so that a high-quality image can be formed at high speed.

  In the above embodiment, the case where there are eleven types of drive modes has been described, but the present invention is not limited to this.

  In the above-described embodiment, the case where the number of drive modes is the same when the sub-scanning direction deviation is positive and when it is negative has been described. However, the present invention is not limited to this, and the sub-scanning direction deviation is not limited. The number of drive modes may be different between positive and negative.

  Moreover, although the said embodiment demonstrated the case where the said semiconductor laser LD was a surface emitting laser, it is not limited to this. In short, the plurality of light emitting units may be two-dimensionally arranged along the dir_sub direction and the α direction, respectively.

  For example, instead of the semiconductor laser LD in the above embodiment, a semiconductor laser LDa shown in FIG. 13 may be used. This semiconductor laser LDa is obtained by adding a preliminary light source to the semiconductor laser LD. That is, this semiconductor laser LDa is preferably used when there is a large sub-scanning direction deviation that cannot be corrected by the preliminary light source in the above embodiment. Even in this case, the same effect as that of the above embodiment can be obtained.

  Further, instead of the semiconductor laser LD in the above embodiment, a semiconductor laser LDb shown in FIG. 14 may be used. In the semiconductor laser LDb, two sub light sources are arranged between two main light sources adjacent to each other with respect to the position in the dir_sub direction. Further, in the semiconductor laser LDb, the number of light emitting unit rows arranged in the α direction is six (A column to F column), and the number of light emitting unit columns arranged in the dir_sub direction is four columns (first column to fourth column). Yes. Even in this case, the same effect as that of the above embodiment can be obtained. Here, if the resolution of the pixel formed by the main light source is 1200 dpi, 1200 dpi can be divided into three by the sub light source, and therefore, the sub-scanning direction deviation can be corrected with an accuracy equivalent to 3600 dpi.

  Further, instead of the semiconductor laser LD in the above embodiment, a semiconductor laser LDc shown in FIG. 15 may be used. In the semiconductor laser LDc, two sub light sources are arranged between two main light sources adjacent to each other with respect to the position in the dir_sub direction. Further, in the semiconductor laser LDc, the number of light emitting unit rows arranged in the α direction is six (A column to F column), and the number of light emitting unit columns arranged in the dir_sub direction is five (first column to fifth column). Yes. Even in this case, the same effect as that of the above embodiment can be obtained. Here, if the resolution of the pixel formed by the main light source is 1200 dpi, 1200 dpi can be divided into three by the sub light source, and therefore, the sub-scanning direction deviation can be corrected with an accuracy equivalent to 3600 dpi.

  Further, instead of the semiconductor laser LD in the above embodiment, a semiconductor laser LDd shown in FIG. 16 may be used. In this semiconductor laser LDd, one sub light source is arranged between two main light sources adjacent to each other with respect to the position in the dir_sub direction. Further, in the semiconductor laser LDd, the number of the light emitting unit rows arranged in the α direction is 7 (A column to G column), and the number of the light emitting unit rows arranged in the dir_sub direction is 5 columns (the first column to the fifth column). Yes. Even in this case, the same effect as that of the above embodiment can be obtained. Here, if the resolution of the pixel formed by the main light source is 1200 dpi, the sub-light source can divide 1200 dpi into two, so that the sub-scanning direction deviation can be corrected with an accuracy equivalent to 2400 dpi.

  Further, instead of the semiconductor laser LD in the above embodiment, a semiconductor laser LDe shown in FIG. 17 may be used. In the semiconductor laser LDe, one sub light source is disposed between two main light sources adjacent to each other with respect to the position in the dir_sub direction. Further, in the semiconductor laser LDe, the number of light emitting unit rows arranged in the α direction is 10 rows (A column to J column), and the number of light emitting unit rows arranged in the dir_sub direction is 3 rows (first column to third column). Yes. Even in this case, the same effect as that of the above embodiment can be obtained. Here, if the resolution of the pixel formed by the main light source is 1200 dpi, the sub-light source can divide 1200 dpi into two, so that the sub-scanning direction deviation can be corrected with an accuracy equivalent to 2400 dpi.

  Further, instead of the semiconductor laser LD in the above embodiment, a semiconductor laser LDf shown in FIG. 18 may be used. In the semiconductor laser LDf, three sub light sources are arranged between two main light sources adjacent to each other with respect to the position in the dir_sub direction. Further, in the semiconductor laser LDf, the number of the light emitting unit rows arranged in the α direction is 7 (A column to G column), and the number of the light emitting unit rows arranged in the dir_sub direction is 5 columns (the first column to the fifth column). Yes. Even in this case, the same effect as that of the above embodiment can be obtained. When the size of one pixel is halved, as shown in FIG. 19, it is possible to easily cope with the problem by changing the central sub-light source among the three sub-light sources to the main light source. For example, if the resolution shown in FIG. 18 is 600 dpi in the sub-scanning direction, the resolution shown in FIG. 19 can be 1200 dpi. In this manner, an optical scanning device capable of switching the resolution can be realized by switching the function of the light source. The function switching of the light source is performed by the processing circuit 815.

  Further, even an image forming apparatus that forms a color image can form a high-quality image by using an optical scanning device corresponding to the color image. In this case, for example, the image information includes image information relating to yellow (hereinafter referred to as “Y image information”), image information relating to magenta (hereinafter referred to as “M image information”), and image information relating to cyan (hereinafter referred to as “C image information”). ) And image information relating to black (hereinafter referred to as “K image information”), the sub-scanning direction deviation information table may be prepared for each image information. Only the sub-scanning direction deviation information table for a specific color (for example, yellow) set in advance may be prepared. In this case, when obtaining misregistration information for a color other than a specific color, the misregistration information obtained by referring to the subscanning direction misregistration information table for the specific color may be used as it is or set in advance. Each shift information converted by a conversion method (conversion formula, conversion table, etc.) may be used. Thereby, for example, as shown in FIGS. 19A and 19B, the tendency of the sub-scanning direction shift in each image information can be made substantially equal, and the color shift can be suppressed. In addition, it is possible to reduce the recording capacity of the memory storing the sub-scanning direction deviation information table. In this case, a light source group including a main light source, a sub light source, and a spare light source may be provided for each image information (here, four light source groups).

  The image forming apparatus may be a tandem color machine that corresponds to a color image and includes a photosensitive drum for each piece of image information. As an example, the tandem color machine shown in FIG. 20 includes an optical scanning device 900a that forms a latent image of Y image information on a photosensitive drum 901a for Y image information, and M image information on a photosensitive drum 901b for M image information. An optical scanning device 900b that forms a latent image, an optical scanning device 900c that forms a latent image of C image information on a photosensitive drum 901c for C image information, and a latent image of K image information on a photosensitive drum 901d for K image information An optical scanning device 900d for forming In this case, since the sub-scanning direction shift in each photosensitive drum is corrected in the same manner as in the above-described embodiment, it is possible to form a high-quality image at high speed.

  In the above embodiment, at least a part of the circuit constituting the processing circuit 815 may be mounted on the printed circuit board 802.

  In the above-described embodiment, the case where the image forming apparatus is the laser printer 100 has been described. However, the image forming apparatus is not limited to this. For example, a digital copying machine, a scanner, a facsimile, and a so-called multifunction machine including the optical scanning device 900 Also good. In short, an image forming apparatus including the optical scanning device 900 can form a high-quality image at high speed.

  As described above, the optical scanning device of the present invention is suitable for scanning a plurality of lights from the light source unit with high accuracy with respect to the scanning object. The image forming apparatus of the present invention is suitable for forming a high-quality image at high speed.

1 is a diagram for explaining a schematic configuration of a laser printer as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic perspective view (No. 1) illustrating the optical scanning device in FIG. 1. FIG. 3 is a schematic perspective view (No. 2) illustrating the optical scanning device in FIG. 1. It is a figure for demonstrating the semiconductor laser in FIG. It is FIG. (1) for demonstrating the selection criteria of a sublight source. FIGS. 6A and 6B are diagrams (No. 2) for explaining selection criteria for the spare light source, respectively. It is a figure for demonstrating the various circuits and processing circuit which are mounted in the printed circuit board in FIG. FIG. 8A and FIG. 8B are diagrams for explaining the types of drive modes when correcting the sub-scanning direction deviation, respectively. FIG. 9A to FIG. 9F are diagrams (part 1) for describing each drive mode. FIGS. 10A to 10F are diagrams (part 2) for describing the drive mode. FIGS. 11A to 11D are diagrams for explaining correction of displacement in the sub-scanning direction. FIG. 12A and FIG. 12B are diagrams for explaining a case where the sub-scanning direction deviation is within an allowable range. It is a figure for demonstrating the modification 1 of the semiconductor laser in FIG. It is a figure for demonstrating the modification 2 of the semiconductor laser in FIG. It is a figure for demonstrating the modification 3 of the semiconductor laser in FIG. It is a figure for demonstrating the modification 4 of the semiconductor laser in FIG. It is a figure for demonstrating the modification 5 of the semiconductor laser in FIG. It is a figure for demonstrating the modification 6 of the semiconductor laser in FIG. It is a figure for demonstrating the example which changed a part of sublight source in the semiconductor laser of FIG. 18 into the main light source. 20A and 20B are diagrams for explaining correction of displacement in the sub-scanning direction when corresponding to a color image. It is the schematic for demonstrating a tandem color machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Laser printer (image forming apparatus), 801 ... Light source unit, 815 ... Processing circuit (signal generation circuit), 900 ... Optical scanning device, 901 ... Photosensitive drum (scanning object), 902 ... Charging brush (transfer device) 903... Development roller (part of transfer device) 904... Toner cartridge (part of transfer device) 909. Fixing roller (part of transfer device) 913.

Claims (17)

An optical scanning device that scans light including image information on a scanning object and forms an image on the scanning object,
Two-dimensionally along a first direction corresponding to the sub-scanning direction and a second direction that is different from the first direction and is inclined with respect to the direction corresponding to the main scanning direction. A light source unit having a plurality of light sources arranged;
Based on the image information, a control signal for a plurality of main light sources included in the plurality of light sources forming a main pixel on the scanning object is generated, and the size of the main pixel is one pixel or more in the sub-scanning direction. And a signal generation circuit that generates a control signal for at least one auxiliary light source included in the plurality of light sources so that the positional deviation is corrected based on the positional deviation information.   The signal generation circuit further includes at least one sub-light included in the plurality of light sources so that the position shift is corrected based on position shift information having a size of less than one pixel in the sub-scanning direction of the main pixel. The optical scanning device according to claim 1, wherein a light source control signal is generated. An optical scanning device that scans light including image information on a scanning object and forms an image on the scanning object,
A plurality of main light sources used when forming main pixels corresponding to image information on the scanning object and a positional deviation of one or more pixels in the sub-scanning direction of the main pixels in the scanning object are corrected. A light source unit having a plurality of light sources, including at least one auxiliary light source used in the process;
A signal generation circuit that generates a control signal for the auxiliary light source that corrects a positional shift of one or more pixels based on positional shift information in the sub-scanning direction of the main pixel. The plurality of light sources of the light source unit further includes at least one sub light source used for correcting a positional shift of less than one pixel in the sub scanning direction of the main pixel in the scanning object,
The signal generation circuit further generates a control signal for the at least one sub-light source that corrects a position shift of a size less than one pixel based on position shift information of the main pixel in the sub-scanning direction. The optical scanning device according to claim 3.   The plurality of light sources includes a first direction corresponding to the sub-scanning direction and a second direction that is different from the first direction and is inclined with respect to the direction corresponding to the main scanning direction. The optical scanning device according to claim 4, wherein the optical scanning device is two-dimensionally arranged along each.   6. The optical scanning device according to claim 2, wherein the plurality of light sources are arranged at equal intervals in any of the first direction and the second direction. 7.   7. Each of the plurality of main light sources is adjacent to either the auxiliary light source or the auxiliary light source in any of the first direction and the second direction. Optical scanning device.   8. The optical scanning device according to claim 7, wherein at least one sub-light source is disposed between two main light sources adjacent to each other with respect to the position in the first direction.   The optical scanning device according to claim 8, wherein the number of the sub-light sources arranged between the two main light sources is one, two, or three. The number of the sub-light sources arranged between the two main light sources is one,
The optical scanning device according to claim 9, wherein the plurality of light sources are arranged such that the number of light sources in each column in the second direction is an odd number. The number of the sub light sources arranged between the two main light sources is two,
The optical scanning device according to claim 9, wherein the plurality of light sources are arranged such that the number of light sources in each column in the second direction is a number excluding a multiple of three. The number of the sub light sources arranged between the two main light sources is three,
The optical scanning device according to claim 9, wherein the plurality of light sources are arranged such that the number of light sources in each column in the second direction is a multiple of three. The number of the sub light sources arranged between the two main light sources is three,
The signal generation circuit generates a control signal for forming a main pixel by using a central sub-light source among the three sub-light sources when the size of the one pixel is changed to ½. The optical scanning device according to claim 9.   The optical scanning device according to claim 1, wherein the number of the preliminary light sources is determined in accordance with a positional deviation amount of light from the main light source in the sub-scanning direction.   The optical scanning device according to claim 1, wherein the light source unit includes a surface emitting laser in which the plurality of light sources are formed on the same chip. At least one scan object;
The at least one optical scanning apparatus according to any one of claims 1 to 15, wherein the optical scanning device scans light with respect to the at least one scanning object and forms an image on the scanning object;
An image forming apparatus comprising: a transfer device that transfers an image formed on the scan target to the transfer target. A color image is transferred to the transfer object,
A plurality of the scanning objects are provided corresponding to a plurality of colors constituting the color image,
The image forming apparatus according to claim 16, wherein the optical scanning devices are individually provided corresponding to the plurality of scanning objects.

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