JP5708206B2 - Image forming apparatus, optical scanning unit, and optical scanning unit manufacturing method - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, an optical scanning unit including a rotary drive source and a rotary polygon mirror used in the image forming apparatus, and a method for manufacturing the optical scanning unit.

  As an image forming apparatus, image formation of one line in the main scanning direction is performed with a light beam according to image data, and image formation of the light beam for each line in the main scanning direction is repeated in the sub-scanning direction for one page. One that performs image formation is known.

  As an example, in an electrophotographic image forming apparatus, a main scanning is performed with a laser beam emitted according to image data using an optical scanning unit comprising a rotary drive source (polygon motor) and a rotary polygon mirror (polygon mirror). In parallel with this, an image is formed by the laser beam on an image carrier (photosensitive drum) that rotates in the sub-scanning direction. In this case, a laser beam is emitted according to image data with reference to a clock signal (write clock) called a dot clock.

  In order to achieve high image quality with such an image forming apparatus, the main scanning direction start position and the main scanning direction end position of the laser beam are aligned, that is, the main scanning length is unified between the laser beams, and the main scanning is performed. It is important to eliminate the direction deviation.

  Such a deviation in the main scanning direction occurs due to uneven rotation with a period of one rotation or half rotation of the motor, or a difference in flatness of each surface of the polygon mirror. Even if the deviation in the main scanning direction is slight, it is visually recognized as a horizontal streak or as a vertical line fluctuation, which causes deterioration in image quality.

  In addition, when a six-sided polygon mirror is used, the main scanning direction is shifted as shown in FIGS. The horizontal direction in FIG. 14 is the main scanning direction, and the right side is the main scanning direction end. In this case, it becomes easy to observe the fluctuation of the vertical line at the end in the main scanning direction (the rightmost dot in FIGS. 14A to 14F).

  In the case of a color image forming apparatus in which images of a plurality of colors are superimposed, if the deviation in the main scanning direction has different characteristics for each color, in FIGS. 15 (a) to 15 (f), particularly FIGS. 15 (a) and 15 (c). As described above, since dots of the same pixel appear densely and densely at the end portion in the main scanning direction, there is a problem that it is easily recognized as a color shift.

  In addition, as a technique capable of solving such a problem, for example, various solutions are described in Patent Document 1 below.

  In this technique, the main scanning length is made constant by adjusting the dot clock using the SOS (Start Of Scan) signal on the start position side in the main scanning direction and the EOS (End Of Scan) signal on the end position side in the main scanning direction. You are in control.

Japanese Patent Laid-Open No. 2002-267961

  As a result of investigations by the inventors of the present application, it has been found that there is a problem as described below even if adjustment is made to eliminate the deviation in the main scanning direction by the method described in the above patent documents.

  As a first problem, in addition to an existing SOS sensor for obtaining an SOS (Start Of Scan) signal on the start position side in the main scanning direction, an EOS (End Of Scan) signal is obtained on the end position side in the main scanning direction. It is necessary to add a new EOS sensor.

  Further, it is necessary to add a frequency modulation circuit or the like for frequency-modulating the dot clock based on the measurement results of the SOS sensor and the EOS sensor to align the main scanning length. For this reason, the number of parts of the image forming apparatus is increased, such as addition of sensors and processing circuits, and further, processing functions are added in the processing program, leading to an increase in cost.

  Further, as a second problem, even if the main scanning lengths from the start end to the end can be made uniform by the SOS sensor and the EOS sensor, the main scanning direction is changed due to the variation in the flatness of the polygon mirror and the variation in the polygon motor characteristics. The above-described dot coarse / dense color misalignment may occur in the intermediate portion. Such color misregistration at the intermediate portion cannot be eliminated by the SOS sensor and the EOS sensor.

  In addition, since the above-mentioned color deviation of the dot density is generated in one rotation cycle of the polygon mirror, there is a problem that it is easily recognized as deterioration in image quality.

  The present invention has been made to solve the above-described problems, and an image forming apparatus and an optical scanning capable of eliminating color misregistration when a color image is formed using an optical scanning unit including a polygon motor and a polygon mirror. It is an object to realize the means and the optical scanning means manufacturing method.

  That is, the present invention as means for solving the problems is as described below.

  (1) The invention according to claim 1 is rotationally driven by an image carrier on which an image is formed by exposure of a light beam, a light source that generates the light beam that emits light according to image data, and a rotational drive source. Optical scanning means for scanning the light beam in the main scanning direction on the image carrier by a plurality of reflecting surfaces of the rotating polygon mirror, a reflecting surface identifying unit for identifying each reflecting surface of the rotating polygon mirror, and the main scanning direction And a sub-scanning direction driving means for relatively moving the image carrier and the light beam in a sub-scanning direction orthogonal to the plurality of colors, and performing the exposure with a plurality of colors, thereby providing a plurality of color images. A plurality of reference marks that can be identified by the reflecting surface identifying unit based on a characteristic of a main scanning length for each reflecting surface of the rotary polygon mirror and a predetermined common application condition. Attached to each of the rotating polygon mirrors of color And a controller for controlling the rotating polygon mirror to rotate in a state where the surface phases of the reference marks are aligned in the optical scanning means of a plurality of colors based on the identification result of the reflecting surface identifying unit. An image forming apparatus.

(2) In the invention according to claim 2, in the above (1), the reference mark has a maximum error on the plus side or a maximum on the minus side with respect to the main scanning length for each reflecting surface of the rotary polygon mirror. It is attached based on the predetermined common grant conditions based on either one.

  (3) The invention according to claim 3 is rotationally driven by an image carrier on which an image is formed by exposure of the light beam, a light source that generates the light beam that emits light according to image data, and a rotational drive source. Optical scanning means for scanning the light beam in the main scanning direction on the image carrier by a plurality of reflecting surfaces of the rotating polygon mirror, a reflecting surface identifying unit for identifying each reflecting surface of the rotating polygon mirror, and the main scanning direction Sub-scanning direction driving means for relatively moving the image carrier and the light beam in a sub-scanning direction orthogonal to the plurality of colors, and a plurality of colors based on the identification result of the reflecting surface identification unit Used in an image forming apparatus that forms images of a plurality of colors by performing the exposure in a plurality of colors while controlling the rotating polygon mirror to rotate in a state where the surface phases of the reference marks are aligned in the optical scanning unit. Said The rotation means, wherein the reference mark that can be identified by the reflecting surface identifying unit based on a characteristic of the main scanning length for each reflecting surface of the rotating polygon mirror and a predetermined common application condition is a plurality of colors. An optical scanning unit is provided on each of the polygon mirrors.

(4) In the invention according to claim 4, in the above (3), the reference mark has a plus-side maximum or minus-side maximum error with respect to a main scanning length for each reflecting surface of the rotary polygon mirror. It is attached based on the predetermined common grant conditions based on either one.

(5) According to the invention described in claim 5, the light beam emitted according to the image data is scanned in the main scanning direction of the image carrier by the plurality of reflecting surfaces of the rotary polygon mirror driven to rotate by the rotation driving source. The reference mark attached to the rotary polygon mirror is exposed to the image carrier surface by driving the image carrier and the light beam to move relative to each other in the sub-scanning direction orthogonal to the main scanning direction. An image forming apparatus that controls to rotate the rotary polygon mirror in a state in which the surface phases of the optical polygons are aligned with each other. Receiving a light beam from the light source that is scanned by the rotating polygon mirror on the extension line of the surface that coincides with the surface of the image carrier and a manufacturing apparatus light source that generates a light beam that emits light at a position corresponding to the end of the direction Run A main scanning length measuring unit for measuring a length, a mark applying unit for attaching a temporary reference mark or a reference mark to identify any reflecting surface of the rotating polygon mirror, and each reflecting surface of the rotating polygon mirror is connected to the temporary reflecting mirror. And a manufacturing apparatus reflecting surface identification unit identified by a reference mark, and a temporary reference mark is attached by the mark applying unit in order to identify any reflecting surface of the rotary polygon mirror by the manufacturing apparatus reflecting surface identification unit. Then, the characteristic of the main scanning length for each reflecting surface of the rotary polygon mirror is obtained by the main scanning length measuring unit with reference to the temporary reference mark by the reflecting surface identifying unit of the manufacturing apparatus , A reference mark that can be identified by the reflecting surface identification unit based on the application condition is attached by the mark application unit.

(6) In the invention described in claim 6, in the above (5), the reference mark has a maximum plus-side error or a minus-side maximum error with respect to a main scanning length for each reflecting surface of the rotary polygon mirror. It is attached based on the predetermined common grant conditions based on either one.

  According to the present invention described above, the following effects can be obtained.

  An image carrier on which an image is formed by light beam exposure, a light source that generates a light beam that emits light according to image data, and a plurality of reflecting surfaces of a rotary polygon mirror that is driven to rotate by a rotational drive source. The optical scanning means for scanning the light beam in the main scanning direction, the reflecting surface identifying unit for identifying each reflecting surface of the rotary polygon mirror, and the image carrier and the light beam in the sub scanning direction orthogonal to the main scanning direction. Main scanning length for each reflecting surface of the rotary polygon mirror in an image forming apparatus that forms a multi-color image by performing exposure in a plurality of colors. A reference mark that can be identified by the reflecting surface identifying unit based on the characteristics of the lens and a predetermined common application condition is attached to each of the rotary polygon mirrors of the plurality of colors, and a plurality of marks are determined based on the identification result of the reflecting surface identifying unit. In the color optical scanning means, the reference marker By controlling the rotating polygon mirror to rotate while the surface phases are aligned, the dot positions of the corresponding pixels of multiple colors are aligned, and the same pixel can be obtained without correcting the main scanning length. Since the density of the dots does not occur, color misregistration does not occur.

Note that the reference mark is based on a predetermined common application condition in which the error of the main scanning length for each reflecting surface of the rotary polygon mirror and the design reference value is based on either the plus side maximum or the minus side maximum. By attaching the optical scanning means, it is possible to easily realize an optical scanning means in which the characteristics of the main scanning length are uniform.

1 is a block diagram illustrating a configuration of an image forming apparatus using an optical scanning unit according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus using an optical scanning unit according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus using an optical scanning unit according to an embodiment of the present invention. It is a block diagram which shows the structure of the manufacturing apparatus used for the manufacturing method of the optical scanning means of one Embodiment of this invention. It is explanatory drawing which shows the mode at the time of manufacture of the optical scanning means of one Embodiment of this invention. It is explanatory drawing which shows the mode at the time of manufacture of the optical scanning means of one Embodiment of this invention. It is a flowchart which shows the procedure at the time of manufacturing the optical scanning means of one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of manufacturing the optical scanning means of one Embodiment of this invention. It is explanatory drawing which shows the characteristic (at the time of a single color) of the optical scanning means of one Embodiment of this invention. It is explanatory drawing which shows the characteristic (at the time of multiple colors) of the optical scanning means of one Embodiment of this invention. 6 is a time chart illustrating an operation of the image forming apparatus according to the embodiment of the present invention. It is explanatory drawing which shows the characteristic (at the time of multiple colors) of the optical scanning means of one Embodiment of this invention. It is explanatory drawing which shows the characteristic (at the time of multiple colors) of the optical scanning means of one Embodiment of this invention. It is explanatory drawing which shows the mode of the main scanning direction shift | offset | difference (at the time of a single color). It is explanatory drawing which shows the mode of the main scanning direction shift | offset | difference (at the time of multiple colors).

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings.

  The image forming apparatus to which the present embodiment is applied scans a light beam emitted according to image data in the main scanning direction of the image carrier, and in the sub scanning direction orthogonal to the main scanning direction. The image forming apparatus forms an image by exposing the surface of the image carrier by driving to move the beam relatively. The optical scanning unit to which the present embodiment is applied is an optical scanning unit composed of a rotary drive source (polygon motor) and a rotary polygon mirror (polygon mirror), and is used for scanning a light beam in the image forming apparatus. Is.

[Image forming apparatus using optical scanning means]
Hereinafter, an outline of an image forming apparatus using an optical scanning unit will be described.

  The electrical configuration of the first embodiment of the image forming apparatus 100 of this embodiment will be described in detail with reference to FIG. Here, the image forming apparatus 100 will be described in the state of monochromatic image formation in a state related to the manufacturing apparatus 200 described later.

  In the present embodiment, description will be made focusing on the configuration requirements necessary for describing the embodiment. Therefore, it is common for an image forming apparatus, and well-known constituent elements are omitted.

  The control unit 101 includes a CPU, a control program, and the like for controlling each unit of the image forming apparatus 100. In addition to a normal image forming operation, the optical scanning unit 120 is used to form a plurality of colors. The polygon mirror 121 is controlled to rotate in a state in which the surface phases of the reference marks assigned to are aligned.

  The laser diode (LD) 110 is a light source that generates a laser beam (light beam) that performs exposure while scanning on the photosensitive member. The laser beam from the laser diode 110 may be a single beam or a plurality of beams.

  The optical scanning unit 120 includes a polygon mirror 121 as a rotary polygon mirror and a polygon motor 122 as a rotation drive source. Here, the polygon mirror 121 is a rotating polygon mirror that scans a laser beam in the main scanning direction on the surface of the photosensitive member by a plurality of rotating reflecting surfaces. The polygon motor 122 is a rotational drive source that receives the polygon drive signal and rotates the polygon mirror 121 at a predetermined rotational speed.

  The surface detection sensor 125 detects the reference mark 120d attached to the polygon mirror 121, generates a surface detection signal for identifying the reflection surface, and transmits the surface detection signal to the reflection surface identification unit 103.

  The optical system 130 includes a cylindrical lens 130a and an f− for performing an optical process so that the laser beam irradiated from the laser diode 110 and reflected by the polygon mirror 121 has a predetermined main scanning speed on the surface of the photoreceptor. These are various optical members such as the θ lens 130b.

  The light detector 145 on the start end side is an SOS sensor for detecting a light beam and obtaining an SOS (Start Of Scan) signal on the main scan start end side on the extended line of the main scan position on the photoconductor 160, and is detected. The result is transmitted to the optical scanning drive control unit 101 b and the reflection surface identification unit 103 in the control unit 101. Here, the light detection unit 145 is detected using the mirror 141 on the main scanning start end side, but the mirror 141 is not necessarily used.

  The exposure unit 150 includes a laser diode 110, a light scanning unit 120, an optical system 130, a light detection unit 145, and the like, and scans the photosensitive member with a laser beam. Correspondingly provided.

  The photosensitive member 160 responds to image data by exposure of a laser beam scanned in the main scanning direction by the rotation of the polygon mirror 121 and relative movement of the light beam in the sub-scanning direction perpendicular to the main scanning direction. The photosensitive member is an image carrier on which an electrostatic latent image is formed on the surface, and the electrostatic latent image is developed to form a toner image. The charging for forming the electrostatic latent image, the toner image formation by developing the electrostatic latent image, the transfer of the toner image onto the recording paper, and the fixing of the toner image on the recording paper are generally used as an image forming apparatus. Therefore, the description is omitted.

  The control unit 101 includes a light emission drive control unit 101a, an optical scanning drive control unit 101b, an image processing unit 102, a reflection surface identification unit 103, and a photoconductor drive unit 105.

  Here, the light emission drive control unit 101a is a drive source that generates a light emission drive signal for driving the laser diode 110 to emit light and supplies the light emission drive signal to the laser diode 110. The light emission drive signal corresponding to the image data is supplied to the laser diode 110. Supply.

  The optical scanning drive control unit 101 b is a drive signal generation unit that generates a polygon drive signal for rotating the polygon mirror 121 at a predetermined rotation number and supplies the polygon drive signal to the polygon motor 122. Note that the optical scanning drive control unit 101b controls the polygon mirror 121 to rotate in a state where the surface phases of the reference marks provided to the optical scanning units 120 are aligned when image formation of a plurality of colors is performed.

  The image processing unit 102 is an image processing unit that performs various kinds of image processing necessary for image formation on the image data, and outputs necessary data to the light emission drive control unit 101a in synchronization with a write clock.

  The reflection surface identification unit 103 identifies the reflection surface of the polygon mirror 121 in response to the surface detection signal from the surface detection sensor 125 and the detection result from the light detection unit 145, and on what surface from the reference mark 120d. The reflection surface identification result, such as whether or not there is, is transmitted to the optical scanning drive control unit 101b.

  The photoconductor driving unit 105 is photoconductor rotation driving means that rotates the photoconductor 160 in the sub-scanning direction at a predetermined rotation speed. The photosensitive member driving unit 105 drives the photosensitive member 160 so that the number of rotations of the photosensitive member corresponds to the image forming speed determined by the optical scanning drive control unit 101b.

  In the case where the image forming apparatus 100 is a color image forming apparatus that forms a color image by superimposing a plurality of color images, as shown in FIGS. 2 and 3, exposure units 150Y to 150K and photoconductors 160Y to 160K. Thus, a plurality of units are arranged according to a plurality of colors, and the control unit 101 is configured in common. 2 and 3 exemplify a case where image formation is performed with four colors of yellow Y, magenta M, cyan C, and black K. FIG. Here, the electrostatic latent images formed on the photoconductors 160Y to 160K by the exposure units 150Y to 150K are converted into YMCK toner images by the developing units 170Y to 170K, and the respective color toner images are formed on the intermediate transfer member 180. Superimposed. The toner image on the intermediate transfer member 180 is transferred to the recording paper from the paper feed tray T in the transfer unit 185, and the toner image on the recording paper is thermally fixed in the fixing unit 190 to form a stable color image. The In such an image forming apparatus 100, each of the exposure units 150Y to 150K is provided with the optical scanning unit 120 in a state where the characteristics of the main scanning length are aligned as will be described later.

[Manufacturing apparatus for optical scanning means]
Hereinafter, a manufacturing apparatus 200 for manufacturing the optical scanning unit 120 will be described with reference to FIG. Here, basic steps such as shaping and polishing of the polygon mirror 121, manufacture of the coil and stator of the polygon motor 122, and coupling of the polygon mirror 121 and the polygon motor 122 are omitted, and a procedure for attaching a reference mark to the polygon mirror 121 is omitted. Will be described in detail.

  In the following embodiment, it is called a manufacturing procedure by the manufacturing apparatus 200, but the reference mark may be attached by an adjusting device different from the manufacturing apparatus.

  Further, the manufacturing apparatus 200 is configured to have characteristics that are mechanically or optically similar to those of the image forming apparatus 100 in which the optical scanning unit 120 is used. In addition, the optical scanning unit 120 is set in the manufacturing apparatus 200 configured to have characteristics that are mechanically or optically approximate to those of the image forming apparatus 100 as described above.

The control unit 201 is configured by a CPU, a control program, and the like to control each unit of the manufacturing apparatus 200, and attaches a temporary reference mark to any reflective surface of the polygon mirror 121, and refers to the temporary reference mark. Control is performed so that the characteristic of the length in the main scanning direction for each reflection surface of the polygon mirror 121 is obtained, and a reference mark that can be identified by the image forming apparatus 100 is attached based on the obtained characteristic and a predetermined common application condition.

  A laser diode (LD) 210 is a light source that generates a laser beam (light beam) in the same manner as the laser diode 110 of the image forming apparatus. In order to obtain characteristics of the main scanning length on each surface of the polygon mirror 121, the main scanning is performed. The controller 201 controls to emit light at the end of the direction. The laser diode 210 is a manufacturing apparatus light source in the claims.

  As shown in the perspective view of FIG. 5, the mark applying unit 223 applies the temporary reference mark and the reference mark 120 d to the polygon mirror 121 by, for example, ink ejection or sticking a sticker, according to the control unit 201. Since the temporary reference mark is used only at the time of manufacturing, it can be removed after manufacturing, the surface detection sensor 125 of the image forming apparatus 100 cannot be detected, or the surface detection of the image forming apparatus 100 is detected. It is desirable that the sensor 125 be a mark of color, shape, and size that can be distinguished from the reference mark. The reference mark 120d is a mark of a color, shape, and size that can be detected by the surface detection sensor 125 of the image forming apparatus 100 because it is given at the time of manufacture and used in the image forming apparatus 100.

  As shown in the perspective view of FIG. 6, the surface detection sensor 225 detects the temporary reference mark or the reference mark 120d attached to the polygon mirror 121, generates a surface detection signal for identifying the reflection surface, and generates a reflection surface. This is transmitted to the identification unit 203.

  The optical system 230 performs various optical processes such as a cylindrical lens 230a and an f-θ lens 230b for performing the same optical processing as the optical system 130 on the laser beam irradiated from the laser diode 210 and reflected by the polygon mirror 121. It is a member.

  The light detection unit 245S on the start end side detects a light beam at a position optically equivalent to the main scan start end side on the extension line of the main scan position of the photoconductor 160 in the image forming apparatus 100 to detect SOS (Start Of Scan). This is an SOS sensor for obtaining a signal, and is disposed at a position optically equivalent to the light detection unit 145 of the image forming apparatus 100, and the detection result is transmitted to the reflection surface identification unit 203 in the control unit 201.

  The light detector 245E on the end side detects a light beam at an optically equivalent position to the main scanning end side on the extension line of the main scanning position of the photoconductor 160 in the image forming apparatus 100 to detect EOS (End Of Scan). This is an EOS sensor for obtaining a signal, and the detection result is transmitted to the scanning length measurement unit 204 in the control unit 201. The light detection unit 245E is configured by either a line sensor of a plurality of light receiving elements or a sensor of a single light receiving element whose position is variable such as a microstage in order to measure the main scanning length on the main scanning end side. .

  The control unit 201 includes a light emission drive control unit 201a, an optical scanning drive control unit 201b, a reflection surface identification unit 203, and a scanning length measurement unit 204.

  Here, the light emission drive control unit 201 a is a drive source that generates a light emission drive signal for driving the laser diode 210 to emit light and supplies the light emission drive signal to the laser diode 210, and the characteristics of the main scanning length on each surface of the polygon mirror 121. Therefore, a light emission drive signal that emits light at the end in the main scanning direction is supplied to the laser diode 210.

  The optical scanning drive control unit 201b generates a polygon drive signal for rotating the polygon mirror 121 at a predetermined rotational speed equivalent to that of the image forming apparatus 100 and supplies the polygon drive signal to the polygon motor 122. This is a drive signal generation unit that gives an instruction to apply the mark and the reference mark 120d to the mark applying unit 223.

  The reflective surface identifying unit 203 is a manufacturing device reflective surface identifying unit in the claims, and identifies the reflective surface of the polygon mirror 121 in response to the surface detection signal from the surface detection sensor 225 and the detection result from the light detection unit 245S. Then, the reflection surface identification result such as the temporary reference mark or the number of the surface from the reference mark 120d is transmitted to the optical scanning drive control unit 201b.

  The scanning length measurement unit 204 refers to the detection result by the light detection unit 245E on the main scanning end side, measures the main scanning length by the laser beam on each surface of the polygon mirror 121, and uses the measurement result as the optical scanning drive control unit 201b. Notify

[Production procedure]
Hereinafter, a procedure (manufacturing operation) for manufacturing the optical scanning unit 120 will be described with reference to a flowchart of FIG.

  First, the optical scanning unit 120 is mounted on the manufacturing apparatus 200 so as to be in the same position as the optical scanning unit 120 in the image forming apparatus 100 (step S101 in FIG. 7). In addition, this installation means performing predetermined installation and connection mechanically and electrically. In addition, when the optical scanning unit 120 is attached to the manufacturing apparatus 200, the alignment or the like is completed in advance on the manufacturing apparatus 200 side so that each of the light detection units 245S and 245E comes to a predetermined end position in the main scanning direction. It is desirable that

  Then, with the optical scanning unit 120 mounted on the manufacturing apparatus 200 as described above, the mark applying unit 223 applies a temporary reference mark to a position indicating any surface of the polygon mirror 121 based on an instruction from the control unit 201. (Step S102 in FIG. 7).

  This temporary reference mark is used only at the time of manufacture, and may be any reflective surface position of the polygon mirror 121. Further, since this temporary reference mark is used only at the time of manufacture, it is removed after manufacture, or has a color, shape and size that are not detected by the surface detection sensor 125 of the image forming apparatus 100 during image formation. Mark it. A temporary reference mark using a paint that disappears under specific conditions such as light irradiation and time passage may be provided.

  Then, the light emission drive control unit 201a causes the laser diode 210 to emit light at the start and end positions on the first surface of the polygon mirror 121 based on the temporary reference mark, based on the light emission drive signal as shown in FIG. In this case, only the first surface is repeatedly emitted several times, and the other surfaces are not light-emitted, so that the scanning length measurement unit 204 detects the first surface of the polygon mirror 121 from the detection result of the light detection unit 245E. The main scanning length is measured (step S103 in FIG. 7). In this case, if the light detection unit 245E is a line sensor, the scanning length measurement unit 204 measures the main scanning length from the detection result of the light detection unit 245E. If the light detection unit 245E is accompanied by movement by the macro stage, the scanning length measurement unit 204 measures the main scanning length from the movement amount of the micro stage.

  Similarly, the measurement of the main scanning length is repeated for the second surface, the third surface, the fourth surface, the fifth surface, and the sixth surface of the polygon mirror 121.

  Thereby, the optical scanning drive control unit 201b obtains the characteristic of the length in the main scanning direction for each reflecting surface of the polygon mirror 121 based on the temporary reference mark. In FIG. 9, the main scanning length for each reflecting surface of the polygon mirror 121 is shown as an error characteristic from the design reference value. The optical scanning drive control unit 201b may temporarily store this characteristic in the storage unit.

Then, the optical scanning drive control unit 201b, the main scanning length of the measurement results, according to a common grant conditions defined in advance for standards marks, gives instructions to the marking unit 223, the surface detection of the image forming apparatus 100 A reference mark 120d that can be identified by the sensor 125 and the reflecting surface identifying unit 103 is attached to the polygon mirror 121 (step S104 in FIG. 7). The temporary reference mark is removed from the polygon mirror 121 as necessary.

Here, the predetermined common application condition regarding the reference mark corresponds to either the maximum on the positive side or the maximum on the negative side with respect to the main scanning length for each reflection surface of the polygon mirror 121 with respect to the design reference value. This is a reference in which the reflecting surface is a predetermined surface (for example, the first surface).

Assuming that there are multiple values on the positive side maximum value or the negative side maximum value on multiple surfaces, the positive side maximum and negative side maximum are matched by pattern matching, and then the positive side maximum is reflected. Predetermined common application conditions such that the surface is a predetermined surface (for example, the first surface) may be determined.

For example, based on the temporary reference mark, the polygon mirror 121 showing the main scanning length characteristic shown in FIG. 9 gives the reference mark 120d having a predetermined common application condition that sets the error plus side maximum value on the first surface. The fifth surface of the temporary reference mark is the first surface of the reference mark 120d, and the main scanning length characteristic is as shown in FIG.

  Then, the optical scanning unit 120 provided with the reference mark 120d is removed from the manufacturing apparatus 200 (step S105 in FIG. 7).

  If there is another optical scanning means 120 to which the reference mark 120d is to be added (NO in step S106 in FIG. 7), the optical scanning means 120 is installed in the manufacturing apparatus 200 by the same procedure, and the reference mark 120d. (Steps S101 to S105 in FIG. 7).

  On the other hand, if there is no other optical scanning means 120 to which the reference mark 120d is to be provided (YES in step S106 in FIG. 7), the manufacturing operation is terminated (end in FIG. 7).

As described above, the main scanning length for each reflecting surface of the polygon mirror 121 is based on a predetermined common application condition in which an error from the design reference value is based on either the plus side maximum or the minus side maximum. By attaching the reference mark 120d, it is possible to easily manufacture the optical scanning means 120 in a state where the main scanning length characteristics are uniform.

That is, for the image forming apparatus 100 that forms a color image by superimposing a plurality of color images, the optical scanning unit 120 provided with the reference mark according to the common application condition determined in advance as described above is used as the exposure unit for each color. 150 each manufactured. Then, the optical scanning means 120 for each color manufactured by applying the reference mark according to the same application condition (predetermined common application condition) as described above is installed in the image forming apparatus 100 that performs color image formation. . The operation of the image forming apparatus 100 will be described in detail below.

[Normal operation of image forming apparatus]
Hereinafter, the normal operation of the image forming apparatus 100 of the present embodiment will be described. Here, the image forming apparatus 100 that forms a color image by superimposing a plurality of color images will be described as a specific example. Here, it is assumed that the light scanning means 120 manufactured by applying the reference mark according to the same application condition (predetermined common application condition) as described above is provided in each exposure unit 150 of each color.

  FIG. 11 is a time chart when the image forming apparatus 100 forms an image. Here, FIG. 11A shows the SOS signal obtained by the light detection unit 145 in the exposure unit 150Y, and shows the timing of the main scanning start end when the laser beam from the laser diode 110 is scanned by the polygon mirror 121. Yes. FIG. 11B shows a surface detection signal obtained by the surface detection sensor 125 detecting the reference mark 120d attached to the polygon mirror 121 in the exposure unit 150Y. Further, FIG. 11C shows a reflection surface based on the reference mark 120d of the polygon mirror 121 identified by the reflection surface identification unit 103 based on the SOS signal and the surface detection signal in the exposure unit 150Y.

  11D shows an SOS signal obtained by the light detection unit 145 in the exposure unit 150M. FIG. 11E shows a surface detection signal obtained by the surface detection sensor 125 in the exposure unit 150M. f) is a reflection surface of the polygon mirror 121 identified by the reflection surface identification unit 103 in the exposure unit 150M. FIG. 11G shows an SOS signal obtained by the light detection unit 145 in the exposure unit 150C, and FIG. 11H shows a surface detection signal obtained by the surface detection sensor 125 in the exposure unit 150C. i) is a reflection surface of the polygon mirror 121 identified by the reflection surface identification unit 103 in the exposure unit 150C. FIG. 11 (j) shows the SOS signal obtained by the light detection unit 145 in the exposure unit 150K, and FIG. 11 (k) shows the surface detection signal obtained by the surface detection sensor 125 in the exposure unit 150K. l) is a reflection surface of the polygon mirror 121 identified by the reflection surface identification unit 103 in the exposure unit 150K.

  As shown in FIGS. 11B, 11E, 11H, and 11K, the optical scanning drive control unit 101b performs the identification results of the reflection surface identification units 103Y to 103K for the exposure units 150Y to 150K of the respective colors. Based on the above, the polygon mirror 121 is controlled to rotate in a state where the surface phases of the reference marks are aligned in the optical scanning means 120 of a plurality of colors.

  Here, when the characteristics of the main scanning length by the polygon mirror 121 of the optical scanning unit 120 are not uniform, the color image forming apparatus in FIG. 12 uses the error between the design reference value and the actual value for the main scanning length. As shown in FIG. 4, dot position deviations that vary among the colors occur. In this case, periodic density is generated between the color dots of the same pixel as described with reference to FIG. 15, and deterioration of image quality due to color misregistration is easily visible.

  On the other hand, as in this embodiment, a reference mark is attached to each of the rotary polygon mirrors of a plurality of colors based on the characteristics of the main scanning length for each reflecting surface of the polygon mirror 121 and a predetermined common application condition. When image formation is performed in a state where the surface phases are aligned on the basis of the reference mark 120d by the polygon mirror 121 of a plurality of colors, as shown in FIG. 13, the tendency of an error between the design reference value and the actual value for the main scanning length Are aligned between multiple colors. As a result, the color dots of the same pixel are evenly spaced, and color misregistration due to periodic density does not occur or becomes extremely small.

  Conventionally, there has been a case where color misalignment of dots in the middle portion in the main scanning direction has occurred due to variations in the flatness of the polygon mirror, etc., but in this embodiment, the design reference value and the actual value for the main scanning length are different. Since the error tendency is uniform among a plurality of colors and the color dots of the same pixel are evenly spaced, color misregistration at the intermediate portion in the main scanning direction can also be eliminated.

  Further, according to the present embodiment, the terminal-side photodetector for generating the EOS signal is not required on the image forming apparatus 100 side, and control for adjusting the dot clock for each reflection surface of the polygon mirror 121 is also possible. While not necessary, an effect of preventing image quality deterioration due to color misalignment can be obtained.

  In the specific example shown in the time chart of FIG. 11, in the image forming apparatus using four colors, the surface phases of the polygon mirror 121 are aligned by the light scanning means 120 of all four colors, but the present invention is not limited to this. It is not a thing. That is, an operation is possible in which the surface phase of the polygon mirror 121 is made uniform between two colors, magenta M and cyan C, where color misalignment is noticeable, and the surface phases of yellow Y and black K are not made uniform. In this case, since the number of colors for aligning the surface phase is small, there is an advantage that the control can be simplified.

<Other embodiment (1)>
In the above embodiment, an electrophotographic image forming apparatus using laser beam scanning has been described. However, the present invention is not limited to this. For example, each embodiment of the present invention can be applied to various image forming apparatuses such as a laser imager that exposes photographic paper using laser beam scanning, and good results can be obtained. .

<Other embodiment (3)>
In the above embodiment, the photosensitive drum is used as a specific example as the photosensitive member 160, but the photosensitive member 160 is not limited to the drum type, and may be a belt. In addition, the laser beam and the photoconductor 160 are applied not only to the rotation of the photoconductor 160 in the sub-scanning direction but also to various sub-scanning methods for relatively moving the photoconductor 160 and the laser beam in the sub-scanning direction. can do.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Control part 101a Light emission drive control part 101b Optical scanning drive control part 103 Reflective surface identification part 110 Laser diode 120 Optical scanning means 121 Polygon mirror 122 Polygon motor 125 Surface detection sensor 130 Optical system 145 Optical detection part (SOS sensor) )
150 Exposure Unit 160 Photoconductor

Claims (6)

An image carrier on which an image is formed by light beam exposure;
A light source that generates the light beam that emits light according to image data;
Optical scanning means for scanning the light beam in the main scanning direction on the image carrier by a plurality of reflecting surfaces of a rotary polygon mirror that is rotationally driven by a rotational drive source;
A reflecting surface identifying unit for identifying each reflecting surface of the rotary polygon mirror;
Sub-scanning direction driving means for relatively moving the image carrier and the light beam in a sub-scanning direction orthogonal to the main scanning direction;
For each of a plurality of colors, and forming an image of a plurality of colors by performing the exposure in a plurality of colors,
A reference mark that can be identified by the reflecting surface identification unit based on a characteristic of the main scanning length for each reflecting surface of the rotating polygon mirror and a predetermined common application condition is attached to each of the rotating polygon mirrors of a plurality of colors. ,
A control unit configured to control the rotating polygon mirror to rotate in a state where the surface phases of the reference marks are aligned in the optical scanning unit of a plurality of colors based on the identification result of the reflecting surface identifying unit;
An image forming apparatus. The fiducial mark is based on the predetermined common application condition with respect to the main scanning length for each reflecting surface of the rotary polygon mirror, which is based on whether the error from the design reference value is the plus side maximum or the minus side maximum. Attached,
The image forming apparatus according to claim 1. The image is formed by an image carrier on which an image is formed by exposure of a light beam, a light source that generates the light beam that emits light according to image data, and a plurality of reflecting surfaces of a rotary polygon mirror that is driven to rotate by a rotational drive source. Optical scanning means for scanning the light beam in the main scanning direction on the carrier, a reflection surface identification unit for identifying each reflection surface of the rotary polygon mirror, and the image carrier in the sub-scanning direction orthogonal to the main scanning direction And a sub-scanning direction driving unit that relatively moves the light beam for each of a plurality of colors, and a surface phase by the reference mark in the plurality of colors of the optical scanning unit based on the identification result of the reflection surface identification unit The optical scanning unit used in an image forming apparatus that forms an image of a plurality of colors by performing the exposure in a plurality of colors while controlling to rotate the rotary polygon mirror in a state where
A reference mark that can be identified by the reflecting surface identification unit based on a characteristic of the main scanning length for each reflecting surface of the rotating polygon mirror and a predetermined common application condition is attached to each of the rotating polygon mirrors of a plurality of colors. Optical scanning means characterized by the above. The fiducial mark is based on the predetermined common application condition with respect to the main scanning length for each reflecting surface of the rotary polygon mirror, which is based on whether the error from the design reference value is the plus side maximum or the minus side maximum. Attached,
The optical scanning means according to claim 3. The light beam emitted according to the image data is scanned in the main scanning direction of the image carrier by the plurality of reflecting surfaces of the rotary polygon mirror that is rotationally driven by the rotational driving source, and the sub scanning direction is orthogonal to the main scanning direction. The image bearing member and the light beam are driven to move relative to each other to expose the surface of the image bearing member, and the rotating polygon mirror is in a state where the surface phases are aligned by the reference marks attached to the rotating polygon mirror. A method of manufacturing the optical scanning unit including the rotation driving source and the rotary polygon mirror used in an image forming apparatus that controls the rotation of the image forming apparatus.
A manufacturing apparatus light source that generates a light beam that emits light at a position corresponding to the end in the main scanning direction, and a light beam from the light source that is scanned by the rotary polygon mirror on an extended line that coincides with the surface of the image carrier. A main scanning length measuring unit for measuring a main scanning length, a mark providing unit for attaching a temporary reference mark or a reference mark to identify any reflecting surface of the rotating polygon mirror, and each reflecting surface of the rotating polygon mirror Using a manufacturing apparatus reflecting surface identifying unit that identifies the temporary reference mark,
In order to identify any reflective surface of the rotary polygon mirror by the manufacturing apparatus reflective surface identification unit, a temporary reference mark is attached by the mark applying unit,
The provisional reference mark is referred to by the manufacturing apparatus reflecting surface identification unit, and the main scanning length characteristic for each reflecting surface of the rotary polygon mirror is determined by the main scanning length measuring unit,
A reference mark that can be identified by the reflecting surface identification unit based on the characteristic and a predetermined common application condition is attached by the mark application unit.
An optical scanning means manufacturing method characterized by the above. The fiducial mark is based on the predetermined common application condition with respect to the main scanning length for each reflecting surface of the rotary polygon mirror, which is based on whether the error from the design reference value is the plus side maximum or the minus side maximum. Attached,
6. The method of manufacturing an optical scanning means according to claim 5, wherein: