JP2019082538A - Image forming apparatus and image formation control program - Google Patents

Abstract

To eliminate a change in image quality generated due to positional deviation of light beams in image formation by simultaneous exposure of a plurality of lines.SOLUTION: When driving an image carrier scanned in a first direction by a plurality of light beams in a second direction to form an image on the image carrier through the scanning by the light beams, an image forming apparatus determines a first direction scan time and second direction beam positions from a result of detection performed by a detection unit that can detect the time of scanning in the first direction performed by the light beams and the positions in the second direction of the light beams, determines an edge in the second direction from the distribution of pixels in image data, calculates a deviation of the edge in the second direction as a second direction edge deviation from the first direction scan time and second direction beam positions, and controls light emission drive of a light emission driving unit, so as to correct the quantity of light corresponding to the edge to eliminate the second direction edge deviation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and an image forming control program, and in particular, an image carrier such as a photosensitive member (recording Medium) and a control program thereof.

An image forming apparatus that forms an image of one line in the main scanning direction according to image data and repeatedly forms an image of one line in the main scanning direction in the subscanning direction to form an image of one page Are known.
As an example, in an electrophotographic image forming apparatus, a light beam modulated according to image data is scanned in the main scanning direction of the image carrier, and in parallel with this, the image carrier rotates in the sub scanning direction ( An image is formed on the image carrier by the light beam. In this case, the light beam is modulated with the image data based on a clock signal (pixel clock) called a dot clock.

  In addition, in order to perform image formation at high speed or high resolution, an increase in the number of revolutions of the polygon mirror or an increase in the modulation frequency of the light beam causes an increase in the size of the apparatus and an increase in cost. Therefore, in order to form an image at high speed or high resolution, a light source such as a laser diode (LD) having two or more light emitting parts is provided, and a plurality of light beams from the plural light emitting parts are used to form an image. It is known that image formation for one page is repeated by repeating image formation for each of a plurality of lines in the main scanning direction corresponding to data in the sub scanning direction.

By the way, in this type of image forming apparatus, the phenomenon that the sub scanning direction interval of the light beam becomes narrower or wider than the predetermined value may occur for some reason, and the image quality may be deteriorated. Hereinafter, this phenomenon will be described.
Here, in FIG. 20 to FIG. 22, a scan n is performed on an image forming apparatus that executes image formation for every four lines in one scan by simultaneously using four beams of light emission of LD # 1 to LD # 4 as a plurality of light emitting units. And a scan n + 1 shows an example of exposure by two adjacent scans.

  In this case, a plurality of light emitting portions are reflected by the reflecting surface of the rotating polygon mirror by four beams emitted by the light sources LD # 1 to LD # 4 and scanned on the image carrier in the main scanning direction. The four beams generated by the light emission of # 4 are reflected by the next reflecting surface of the rotating polygon mirror and scanned on the image carrier in the main scanning direction. Since the image carrier rotates in the sub-scanning direction, exposure of four beams in the main scanning direction is repeatedly performed in the sub-scanning direction to form a two-dimensional image.

  In FIGS. 20 to 22, in the scanning n, the lower 2 light emitting portions of the 4 light emitting portions are made to emit light to form the lower 2 dots on the image carrier, and in the next scanning n + 1, of the 4 light emitting portions An example is shown in which the upper two light emitting portions emit light to form upper two dots on the image carrier, and four dots adjacent in the sub-scanning direction are formed on the image carrier by a total of two scans.

FIG. 20A shows an exposure state formed by scanning n and scanning n + 1 on the image carrier at a certain timing. Hatching indicates that exposure has been made. In addition, since the periphery of the exposure is spread in practice, the toner on the image carrier is painted out as shown in FIG. 20 (b).
Here, since the interval between the scan n and the scan n + 1 is narrowed for some reason, the hatched area in FIG. 20D is smaller than the hatched area in FIG. . This means that as the toner area on the image carrier, the hatched area in FIG. 20 (d) is smaller than the hatched area in FIG. 20 (b). That is, the toner concentration in the hatching in FIG. 20 (d) due to the exposure in FIG. 20 (c) is perceived to be lower than the appropriate toner concentration in the hatching in FIG. 20 (b) due to the exposure in FIG. Be done. Therefore, the decrease in scanning interval results in the decrease in density.

  Similarly, in FIG. 21C, since the interval between the scan n and the scan n + 1 is expanded for some reason, the hatched area in FIG. 21D is the hatched area in FIG. It is getting bigger. In addition, since toner around the exposure spreads, the part where the interval spreads is also painted out as shown in FIG. 21 (d). This means that as the toner area on the image carrier, the hatched area in FIG. 21 (d) is larger than the hatched area in FIG. 21 (b). That is, the toner concentration in the hatching in FIG. 21 (d) due to the exposure in FIG. 21 (c) is visually recognized to be higher than the appropriate toner concentration in the hatching in FIG. 21 (b) due to the exposure in FIG. Be done. Therefore, a change in density occurs due to a change in scanning interval for each beam. An increase in the scanning interval will result in an increase in concentration.

  FIG. 22 (a) is a proper exposure state formed by scanning n and scanning n + 1 on the image carrier at a certain timing, and FIG. 22 (b) is formed by scanning n and scan n + 1 on the image carrier Shows the appearance of the proper toner. FIG. 22C shows an exposure state formed by scanning n and scanning n + 1 on the image carrier at a certain timing, and FIG. 22D shows toner formed by scanning n and scanning n + 1 on the image carrier. Show the situation. In FIGS. 22 (c) and 22 (d), exposure is performed at a position lower than the appropriate position between scan n and scan n + 1. In the cases of FIG. 22C and FIG. 22D, the toner area is the same as in the appropriate state, and no change occurs in the density. However, since the position of exposure is different, a defect such as moiré may occur in relation to other exposures not shown.

  In the above FIGS. 20 to 22, the scanning interval may change due to the difference in the inclination of the reflecting surface of the polygon mirror. Similarly, in FIGS. 20 to 22 described above, the scanning interval may change due to the difference in the scanning speed of the light beam. For example, if the scanning speed of the light beam is high, the position of the light beam is shifted above the predetermined value, and if the scanning speed of the light beam is slow, the position of the light beam is shifted below the predetermined value. The situation will be described below.

  FIG. 23A shows a proper state when the light beam from the light source 151 is scanned by the rotating polygon mirror 154 and irradiated to the image carrier 161. The main scanning of the light beam is realized in the direction perpendicular to the paper surface of FIG. 23, and the sub-scanning is realized in the vertical direction of the paper surface of FIG. 23 by the rotation of the image carrier 161. In FIG. 23 (b), when the light beam from the light source 151 is scanned by the rotating polygon mirror 154 and irradiated to the image carrier 161, the light beam is in an appropriate state due to the inclination (involvement) of the reflecting surface of the polygon mirror. It shows a state in which it is directed downward in the sub scanning direction. In FIG. 23C, when the light beam from the light source 151 is scanned by the rotating polygon mirror 154 and irradiated to the image carrier 161, the light beam is in an appropriate state due to the inclination (trouble) of the reflecting surface of the polygon mirror. It shows a state in which it is directed upward in the sub scanning direction. That is, due to the difference in inclination (inconvenient) of each reflecting surface of the polygon mirror, it may change as shown in FIGS. 23 (a) to (c), and the difference in scanning interval as shown in FIGS. As a result, density differences and dot position differences may occur.

  FIG. 24 is an explanatory view showing a problem due to the difference in the planarity of the reflecting surfaces 154R1 to 154R6 of the polygon mirror 154. FIG. FIG. 24 (a) shows how the light beam is reflected by the substantially flat reflecting surface 154R1, and FIG. 24 (b) shows how the light beam is reflected by the reflecting surface 154R2 having a weak convex surface. (C) shows how the light beam is reflected by the reflecting surface 154R5 having a weak concave surface.

  Here, it is assumed that the light beam is reflected by the reflecting surface 154R1 shown in FIG. Here, when the light beam is reflected by the reflecting surface 154R2 having a weak convex surface as shown in FIG. 24B, the main scanning speed is increased and the main scanning time is shortened. Therefore, since the main scan is performed earlier than the predetermined timing, the dot formed by the light beam on the surface of the image carrier approaches the dot of the previous scan (the scan interval is narrowed). Become.

  On the other hand, when the light beam is reflected by the reflecting surface 154R5 having a weak concave surface as shown in FIG. 24C, the main scanning speed decreases and the main scanning time becomes long. Therefore, since the main scan is performed later than the predetermined timing, the dot formed by the light beam on the image carrier surface is separated from the dot of the previous scan (in a state where the scan interval is extended). Become. That is, due to the difference in the planarity of each reflecting surface of the polygon mirror, the difference in scanning interval as shown in FIG.

JP, 2009-29115, A JP 2000-238329 A

  In the above-mentioned Patent Document 1, the sub-scanning deviation amount measured at the time of assembly etc. is stored in the EEPROM. The polygon jitter is calculated from the period difference of the SOS sensor. In addition, the light quantity correction is performed on the density unevenness of a few line cycle determined from the visual characteristic curve. Here, since the amount of sub-scanning deviation is a value stored in the EEPROM, if the amount of sub-scanning deviation changes with time, it is necessary to re-measure and rewrite the EEPROM. In addition, it corresponds to only a few line cycles determined from the visual characteristic curve. Furthermore, since the determination is not made based on the image edge, the uneven density may be remarkable depending on the conditions.

  In the above-mentioned patent document 2, the deviation of the scanning position in the sub-scanning direction due to bow or skew is measured using a sensor and the light amount is corrected. A measurement mode is provided, and measurement is performed at three points: SOI, COI, and EOI. It is not measured except in the measurement mode. Also, sensors are provided on the back of the triangular aperture. Also, the correction pixels are only edge pixels. Further, the light amount correction is calculated from the shift amount of the scanning position. Here, since the detection of the shift amount of the scanning position is only in the measurement mode, there is a possibility that correction can not always be performed with the optimum value. In addition, although the light amount correction needs to include different correction amounts at the upper edge and the lower edge of the image, the line space in the sub scanning direction is narrowed so that the line space does not open between the areas in which the line space in the sub scanning direction is wide. Since the light amount correction is performed so that the line spacing does not overlap between the areas, uneven density may occur depending on the conditions.

That is, there has been no technique for correcting the deterioration of the image quality caused by the difference in scanning interval shown in FIGS.
The present invention has been made to solve the above-mentioned problems, and in the case of image formation by simultaneous exposure of a plurality of lines, the positional deviation of the light beam due to the trouble of the polygon mirror and the flatness of the reflection surface of the polygon mirror. The image quality change caused by the beam interval difference in the sub-scanning direction due to the positional deviation of the light beam due to the change in main scanning time is well resolved, not only under specific conditions, but also with aging. It is an object of the present invention to realize an image forming apparatus and an image forming control program that can

That is, the present invention as means for solving the problems is described below.
(1) One aspect of an image forming apparatus in which one aspect of the present invention is reflected includes a light source capable of generating a plurality n of light beams from a plurality n of light emitting units, and a plurality n of light emitting units according to image data. The plurality of n light beams are scanned in a first direction orthogonal to the alignment direction of the plurality n of light emitting units by the light emission drive unit that drives light emission and each reflection surface of the polygon mirror that rotates with the plurality m of reflection surfaces And an image carrier on which a plurality of the light beams are scanned in a first direction by driving the image carrier in a second direction orthogonal to the first direction and scanning the light beam produces the image carrier. An image forming unit for converting a latent image into a visible image and transferring it onto a sheet; a detection unit capable of detecting a first direction scanning time of the light beam and a second direction beam position of the light beam; The first direction scanning time and the second direction beam position from the detection result of The edge in the second direction is obtained from the pixel distribution of the image data, and the second direction shift of the edge is calculated as the second direction edge shift from the first direction scanning time and the second direction beam position. A control unit configured to control the light emission drive of the light emission drive unit so as to correct the light amount corresponding to the edge and eliminate the second direction edge shift.

  Further, one aspect of the image formation control program in which one aspect of the present invention is reflected includes light sources capable of generating plural n light beams from plural n light emitters and plural n light emitters corresponding to image data. Light that scans the plurality n of light beams in a first direction orthogonal to the alignment direction of the plurality n of light emitting units by the light emission drive unit to be driven and the respective reflection surfaces of the rotating polygon mirror having the plurality m of reflection surfaces A scanning unit, an image carrier on which the plurality of n light beams are scanned in a first direction is driven in a second direction orthogonal to the first direction to scan a latent image formed on the image carrier by the scanning of the light beams; An image forming unit for converting into a visible image and transferring it onto a sheet, a detection unit capable of detecting a first direction scanning time of the light beam and a second direction beam position of the light beam, the detection result of the detection unit First direction scan time and second direction beam position The edge in the second direction is obtained from the pixel distribution of the image data, and the second direction shift of the edge is calculated as the second direction edge shift from the first direction scanning time and the second direction beam position. The computer of the image forming apparatus may function as a control unit that controls light emission driving of the light emission drive unit so as to correct the light amount corresponding to the edge and eliminate the second direction edge shift.

  (2) In the above (1), the detection unit is disposed at a position which is parallel to the first detection region, the first detection region having the second direction as the longitudinal direction, and different in the first direction. A second detection area, and a third detection area which is sandwiched between the first detection area and the second detection area and includes components of both the first direction and the second direction; The control unit determines a detection time difference of the light beam in the first detection area and the second detection area as the first direction scanning time, and the light beam in the first detection area and the third detection area The beam position in the second direction is determined from the detection time difference.

  (3) In the above (1) to (2), in the case where the first direction scanning time is shorter than a predetermined time for the component of the second direction edge shift caused by the first direction scanning time, the control unit It is characterized in that calculation is performed as occurring in the second direction upstream side, and calculation is made as occurring in the second direction downstream side when the first direction scanning time is longer than the predetermined time.

  (4) In the above (2), the control unit controls the light beam in the first detection area and the third detection area with respect to the component of the second direction edge shift caused by the second direction beam position. When the first direction scanning time, which is the detection time difference between the first and second detection areas, is greater than the predetermined time, it is calculated that the distance between the first detection area and the third detection area is increasing. When the first direction scan time, which is the detection time difference of the light beam between the area and the third detection area, is smaller than the predetermined time, the interval between the first detection area and the third detection area moves in the closing direction. It is characterized that it is calculated as having occurred.

  (5) In the above (1) to (4), the control unit reduces the light amount of the second direction upstream edge when the second direction edge shift occurs toward the second direction upstream side At the same time, the light amount of the second direction downstream side edge is increased, and the light amount of the second direction upstream side edge is increased when the second direction edge deviation occurs toward the second direction downstream side, the second direction The light emission drive of the light emission drive unit is controlled so as to reduce the light amount of the downstream edge and eliminate the second direction edge shift.

  (6) In the above (5), the detection unit is disposed at a position different from the first detection region in the first direction, the first detection region having the second direction as the longitudinal direction, and the first detection region. A second detection area, and a third detection area which is sandwiched between the first detection area and the second detection area and includes components of both the first direction and the second direction. The control unit may set the predetermined value of the detection time difference of the light beam in the first detection area and the third detection area to a, and the detection time difference of the light beam in the first detection area and the third detection area. The measured value of the light beam a ', the predetermined value of the detection time difference of the light beam in the first detection area and the second detection area b, and the detection of the light beam in the first detection area and the second detection area The measured value of the time difference is b ', the second direction down due to the first direction scanning time The second direction edge shift toward the side and detected in the second detection region is c, and the second direction edge shift toward the second direction downstream side due to the first direction scanning time; 3 c ′ detected in the detection region, d in the second direction edge deviation toward the second direction upstream due to the first direction scanning time and detected in the second detection region d, The second direction edge shift toward the second direction upstream side due to the first direction scanning time, which is detected in the third detection area, is d ', and the second direction downstream due to the second direction beam position The second direction edge shift toward the side C, the second direction edge shift toward the second direction upstream due to the second direction beam position D, the first detection due to the second direction beam position In the direction in which the distance between the area and the third detection area increases Let C be the second direction edge shift toward the second direction, and D be the second direction edge shift toward the direction in which the distance between the first detection region and the third detection region resulting from the second direction beam position is closed. In the case of a ′ = a + c ′ = a + (a / b) c, b ′ = b + c, for the measured values a ′ and b ′, the second direction edge shift c is eliminated. , A '= a-d' = a- (a / b) d, b '= bd, a' = a + C, b '= so as to eliminate the second direction edge shift d. When it is b, so as to eliminate the second direction edge deviation C, when a ′ = aD, b ′ = b, so as to eliminate the second direction edge deviation D. When a + c ') + C = (a + (a / b) c) + Cb' = b + c, a '= (a + c) so as to eliminate the second direction edge shift C and c. c ')-D = (a + (a / b) c)-D, b' = b + c, so as to eliminate the second direction edge shift D and c, a '= (a- d ′) + C = (a− (a / b) d) + C, b ′ = bd, the second direction edge deviations C and d are In order to erase, when a '= (a-d')-D = (a- (a / b) d) -D, b '= bd, the second direction edge deviations D and d are eliminated As described above, it is characterized in that the light amount corresponding to the edge is corrected to be fitted to any corresponding pattern, and control is made to eliminate the second direction edge deviation.

  (7) In the above (1) to (6), when the light beam is scanned in the first direction by the image carrier, the detection unit is a region in the first direction close to the image carrier. The light scanning unit is disposed outside, and the light scanning unit scans a plurality n of the light beams in a first direction with respect to the image carrier and the detection unit.

  (8) In the above (1) to (7), the detection unit is disposed at a position scanned with the light beam prior to the image carrier, and the control unit detects the detection result of the detection unit. The light emission drive of the light emission drive unit is controlled so as to eliminate the second direction edge shift corresponding to the reflection surface of the polygon mirror from which the detection result is obtained.

  (9) In the above (1) to (8), the light scanning unit includes a surface identification unit that generates reflection surface identification information that identifies each reflection surface of the polygon mirror, and the control unit is The correction information for correcting the light amount corresponding to the edge is stored corresponding to each reflection surface of the polygon mirror with reference to the reflection surface identification information at the time of acquisition of the correction information, and the reflection at the time of image formation The stored correction information is assigned corresponding to each reflecting surface of the polygon mirror with reference to the surface identification information, and the light emission drive of the light emission drive unit is controlled to eliminate the second direction edge deviation. , It is characterized.

  (10) In the above (9), the detection unit is disposed at a position different from the first detection region in the first direction, the first detection region having the second direction as the longitudinal direction, and the first detection region. A second detection area, and a third detection area which is sandwiched between the first detection area and the second detection area and includes components of both the first direction and the second direction; The first detection area and the third detection area are disposed at positions scanned with the light beam prior to the image carrier, and the second detection area is scanned with the light beam after the image carrier. Are placed at the following positions.

  (11) In the above (1) to (10), the control unit is provided with a notification unit for notifying various information to the outside, and the control unit is configured to calculate the second direction edge deviation calculated if it exceeds a predetermined threshold. And controlling the notification unit to notify an error related to the scanning of the light beam.

According to one aspect of the image forming apparatus and the image formation control program in which one aspect of the present invention is reflected, the following effects can be obtained.
(1) In one aspect of an image forming apparatus and an image formation control program in which one aspect of the present invention is reflected, an image carrier in which a plurality of light beams are scanned in a first direction is driven in a second direction to When an image is formed on the image carrier by the scanning of the first direction, the first direction scanning time and the first direction scanning time are detected from the detection result of the detection unit capable of detecting the first direction scanning time of the light beam and the second direction beam position of the light beam. Two-directional beam position is determined, the edge in the second direction is determined from the pixel distribution of image data, and the second-direction deviation of the edge is calculated as the second-direction edge deviation from the first-direction scanning time and the second direction beam position. The light emission drive of the light emission drive unit is controlled so as to correct the light amount corresponding to the edge and eliminate the second direction edge shift.

  As a result, when forming an image by simultaneous exposure of a plurality of lines, it is caused by the positional deviation of the light beam due to the polygon mirror and the positional deviation of the light beam due to the change of the main scanning time due to the planarity of the reflecting surface of the polygon mirror. The change in the image quality caused by the beam interval difference in the second direction (sub scanning direction) can be favorably resolved while dealing with not only specific conditions but also aging.

  (2) In the above (1), the detection unit is disposed at a position different from the first detection area having the second direction as the longitudinal direction and the first detection area in a direction different from the first detection area. The first detection area and the second detection area include: a second detection area; and a third detection area that is sandwiched between the first detection area and the second detection area and includes components in both the first direction and the second direction. The detection time difference of the light beam in the area is determined as the first direction scanning time, and the second direction beam position is determined from the detection time difference of the light beam in the first detection area and the third detection area.

  As a result, the first direction scanning time and the second direction beam position can be appropriately determined for each actual scan, and when an image is formed by the multiple line simultaneous exposure, the light beam due to the trouble of the polygon mirror can be obtained. A change in image quality caused by a difference in beam spacing in the second direction (sub-scanning direction) due to a positional shift of the light beam due to a positional shift or a positional shift of the light beam due to a change in main scanning time It is possible to resolve well while responding not only to the lower side but also to the change over time.

  (3) In the above (1) to (2), regarding the component of the second direction edge shift due to the first direction scanning time, if the first direction scanning time is smaller than the predetermined time, the second direction upstream side It is calculated as occurring toward the second direction, and when the first direction scanning time is longer than the predetermined time, it is calculated as occurring toward the downstream side in the second direction.

  As a result, the first direction scan time can be properly obtained for each actual scan, and when an image is formed by simultaneous exposure of a plurality of lines, displacement of the light beam due to the trouble of the polygon mirror or polygon mirror reflection can be obtained. The change in image quality caused by the difference in beam spacing in the second direction (sub-scanning direction) due to the positional deviation of the light beam due to the change in main scanning time due to the planarity of the surface, not only under specific conditions It is possible to resolve well while responding to

  (4) In the above (2), with respect to the component of the second direction edge shift caused by the second direction beam position, the first direction scanning time which is the detection time difference of the light beam in the first detection area and the third detection area Is larger than the predetermined time, it is calculated that the distance between the first detection area and the third detection area is increasing, and the detection time difference of the light beam in the first detection area and the third detection area If the first direction scanning time, which is the first direction scanning time, is smaller than the predetermined time, it is calculated that the space between the first detection area and the third detection area is generated in the closing direction.

  As a result, it is possible to appropriately determine the second direction edge shift for each actual scan, and at the time of image formation by multiple line simultaneous exposure, displacement of the light beam due to the trouble of the polygon mirror or polygon mirror reflection The change in image quality caused by the difference in beam spacing in the second direction (sub-scanning direction) due to the positional deviation of the light beam due to the change in main scanning time due to the planarity of the surface, not only under specific conditions It is possible to resolve well while responding to

  (5) In the above (1) to (4), when the second direction edge shift occurs toward the second direction upstream side, the light amount of the second direction upstream edge is reduced and the second direction The light amount of the downstream edge is increased, and the light amount of the second direction upstream edge is increased when the second direction edge deviation occurs toward the second direction downstream side, and the light amount of the second direction downstream edge is increased. To control the light emission drive of the light emission drive unit so as to eliminate the second direction edge shift.

  As a result, the light quantity of the edge can be appropriately adjusted based on the second direction edge shift, and when an image is formed by the simultaneous exposure of a plurality of lines, displacement of the light beam due to the trouble of the polygon mirror, polygon The change in image quality caused by the difference in beam spacing in the second direction (sub-scanning direction) due to the displacement of the light beam due to the change in main scanning time due to the planarity of the mirror reflection surface is not only under specific conditions, It is possible to achieve good resolution while coping with changes over time.

(6) In the above (5), the measured value is compared with the default value to predict in advance the pattern of the deviation,
The measurement value is fitted to the corresponding pattern, and the light amount corresponding to the edge is corrected to control to cancel the second direction edge deviation.

  As a result, the light quantity of the edge can be appropriately adjusted based on the second direction edge shift, and when an image is formed by the simultaneous exposure of a plurality of lines, displacement of the light beam due to the trouble of the polygon mirror, polygon The change in image quality caused by the difference in beam spacing in the second direction (sub-scanning direction) due to the positional deviation of the light beam due to the change in main scanning time due to the planarity of the mirror reflection surface is not limited to It is possible to achieve good resolution while coping with changes over time.

(7) In the above (1) to (6), when the light beam is scanned in the first direction by the image carrier, the detection unit is disposed outside the region in the first direction close to the image carrier. The light scanning unit scans a plurality n of light beams in the first direction with respect to the image carrier and the detection unit.
As a result, it is possible to appropriately determine the second direction edge shift for each actual scan, and at the time of image formation by multiple line simultaneous exposure, displacement of the light beam due to the trouble of the polygon mirror or polygon mirror reflection The change in image quality caused by the difference in beam spacing in the second direction (sub-scanning direction) due to the positional deviation of the light beam due to the change in main scanning time due to the planarity of the surface, not only under specific conditions It is possible to resolve well while responding to

(8) In the above (1) to (7), the detection unit is disposed at a position where it is scanned with the light beam before the image carrier, and the detection result is obtained corresponding to the reflection surface of the polygon mirror The light emission drive of the light emission drive unit is controlled so as to eliminate the two-direction edge shift.
As a result, the light amount of the edge can be appropriately adjusted in real time based on the second direction edge shift, and the position shift of the light beam due to the troublesomeness of the polygon mirror can be obtained at the time of image formation by multiple line simultaneous exposure. The change in image quality caused by the beam direction difference in the second direction (sub-scanning direction) due to the positional deviation of the light beam due to the change in the main scanning time due to the planarity of the polygon mirror reflection surface under specific conditions only. It is possible to resolve the problem well while coping with changes over time.

  (9) In the above (1) to (8), correction information for correcting the light quantity corresponding to the edge is stored corresponding to each reflection surface of the polygon mirror, and the correction information stored at the time of image formation is stored in the polygon mirror The light emission drive of the light emission drive unit is controlled so as to correspond to each of the reflection surfaces and to eliminate the second direction edge shift.

  As a result, correction information of each surface of the polygon mirror is stored, and the stored light information can be used to appropriately adjust the light amount of the edge based on the second direction edge shift, and a plurality of lines are simultaneously exposed. At the time of image formation, the second direction (sub-scanning direction) due to the positional deviation of the light beam due to the polygon mirror and the positional deviation of the light beam due to the change of the main scanning time due to the planarity of the reflecting surface of the polygon mirror ) It becomes possible to well resolve the change in image quality caused by the beam interval difference, not only under specific conditions, but also with aging.

  (10) In the above (9), the detection unit is disposed at a position different from the first detection region having the second direction as the longitudinal direction and the first detection region in a direction different from the first detection region. And a third detection area including components of both the first direction and the second direction sandwiched between the first detection area and the second detection area, The third detection area is disposed at a position scanned with the light beam prior to the image carrier, and the second detection area is disposed at a position scanned by the light beam later than the image carrier.

  As a result, the distance between the first detection area and the second detection area is increased, so that highly accurate correction information is stored, and the stored light information is used to calculate the light quantity of the edge based on the second direction edge shift. It becomes possible to adjust appropriately, and in the case of image formation by multiple line simultaneous exposure, it is due to the displacement of the light beam due to the troublesomeness of the polygon mirror and the change of the main scanning time due to the flatness of the polygon mirror reflection surface. It is possible to satisfactorily resolve the change in image quality caused by the beam interval difference in the second direction (sub-scanning direction) due to the positional deviation of the light beam, not only under specific conditions, but also with aging. become.

  (11) In the above (1) to (10), when the calculated second direction edge deviation exceeds a predetermined threshold value, an error regarding the scanning of the light beam is notified. Thereby, it is possible to prevent the operation in the abnormal state.

FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is an explanatory view showing a configuration of an image forming apparatus according to an embodiment of the present invention. It is a flowchart which shows operation | movement of the image formation of one Embodiment of this invention. It is a flowchart which shows operation | movement of the image formation of one Embodiment of this invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing the operation state of one embodiment of the present invention. It is an explanatory view showing other composition of an embodiment of the present invention. It is an explanatory view showing other composition of an embodiment of the present invention. It is an explanatory view showing a conventional situation. It is an explanatory view showing a conventional situation. It is an explanatory view showing a conventional situation. It is an explanatory view showing a conventional situation. It is an explanatory view showing a conventional situation.

Hereinafter, the best mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. In the following description of the embodiment, the main scanning direction of image formation is referred to as a first direction, and the sub-scanning direction of image formation is referred to as a second direction.
〔Constitution〕
The image forming apparatus to which the present embodiment is applied scans a plurality of n light beams from a light source having a plurality of light emitting portions in the main scanning direction of the image carrier, and performs exposure of a plurality n lines in parallel. It is a multi-beam type image forming apparatus to perform. Hereinafter, the configuration of the first embodiment of the multi-beam type image forming apparatus 100 of the present embodiment will be described in detail based on FIG. In this embodiment, basic configuration requirements of the image forming apparatus 100 using a plurality of light beams for exposure will be mainly described without degrading the image quality. Therefore, components that are generally used as an image forming apparatus and are well known are omitted.

  In FIG. 1, a control unit 101 is constituted by a CPU, a processor, etc. to control each part of the image forming apparatus 100, controls the light emission of the laser according to image data and predetermined command data, Control of deviation correction. The operation display unit 103 receives an operation input and notifies the control unit 101, and displays or notifies information instructed by the control unit 101. The storage unit 105 stores data of uneven density measured in advance, data necessary for various corrections, and the like. The image input unit 110 receives image data from an external device, a scanner, or the like (not shown). The image processing unit 120 executes predetermined image processing in accordance with the image data. The light emission drive unit 130 drives a light source having a plurality of light emission units based on the control of the control unit 101.

The exposure unit 150 scans with a plurality of n light beams. The exposure unit 150 is composed of various optical components described later. The image carrier 161 is a photosensitive drum or the like included in the process unit.
In FIG. 1, an exposure unit 150 includes a light source 151 such as a semiconductor laser having a plurality of light emitting portions for generating a plurality of light beams, a collimator lens 152 and a cylindrical lens 153 for optically correcting the light beams variously, A polygon mirror 154 that scans in the first direction (main scanning direction), an fθ lens 155 that optically corrects a scanning angle, a cylindrical lens 156 that optically corrects, a detection that is scanned with a light beam together with an image carrier 161 The unit 158 is configured.

  The portion shown as the light source 151 in FIG. 1 may be configured by one element to generate a plurality of n light beams, or may be configured by a plurality of elements to generate a plurality n of light beams in total. But it is good. Although FIG. 1 shows a state in which light beams of four lines are generated due to the space of the paper, specific examples of light amount correction to be described later show specific examples of light beams of eight lines. The plural n is not limited to 4 or 8.

  Then, a plurality of light beams scanned as described above are scanned on the image carrier 161, and the rotation of the image carrier 161 is regarded as scanning in the second direction (sub scanning direction) on the surface of the image carrier 161. A latent image is formed according to the light beam. In the case of a color image forming apparatus, the exposure units 150 shown here are arranged by the number of colors.

  In the above configuration, the image processing unit 120 is an image processing unit that performs various types of image processing necessary for image formation. In this embodiment, a plurality of light sources 151 having a plurality of light emitting units perform simultaneous exposure. The light source 151 has a function of outputting image data of each line in parallel, corresponding to the light source 151 having the light emitting unit. Alternatively, the image processing unit 120 outputs image data for each line, and the light emission drive unit 130 stores the image data for a plurality of lines, and drives the light source 151 in parallel for a plurality of lines. May be

  Further, in the above configuration, the control unit 101 determines the correction value of the light quantity for the light beam of the plurality n lines, and based on each correction value, the light quantity of the light source 151 having the plurality n of light emitting units by the light emission drive unit 130 It is supposed to correct the When the control unit 101 instructs the light emission drive unit 130 to make correction values for each light beam, D− between the control output of the control unit 101 and the control input of the light emission drive unit 130 as necessary. An A converter may be arranged.

  The detection unit 158 can also detect the first direction scanning time of the light beam and the second direction beam position of the light beam. The detection unit 158 will be described below with reference to FIG. Here, the detection unit 158 includes a first detection area 158s1 whose longitudinal direction is the second direction, and a second detection area 158s2 parallel to the first detection area and disposed at a different position in the first direction. And a third detection area 158s3 sandwiched between the first detection area 158s1 and the second detection area 158s2 and including components of both the first direction and the second direction. Then, the control unit 101 obtains the detection time difference of the light beam in the first detection area 158s1 and the second detection area 158s2 as the first direction scanning time. Further, the control unit 101 obtains the beam position in the second direction from the detection time difference of the light beam in the first detection area 158s1 and the third detection area 158s3.

In addition, when the light beam is scanned in the first direction by the image carrier, the detection unit 158 is disposed outside the region in the first direction close to the image carrier 161, and the exposure unit 150 A plurality n of light beams are scanned in the first direction with respect to the detection unit 158.
Further, the detection unit 158 is disposed at a position where the light beam is scanned prior to the image carrier, and the control unit 101 uses the detection result of the detection unit 158 to obtain the detection result of the polygon mirror from which the detection result is obtained. Correspondingly, the light emission drive of the light emission drive unit is controlled so as to eliminate the second direction edge shift.

  The detection unit 158 also includes a first detection area 158s1 whose longitudinal direction is the second direction, and a second detection area 158s2 parallel to the first detection area 158s1 and disposed at a different position in the first direction. And a third detection area 158s3 sandwiched between the first detection area 158s1 and the second detection area 158s2 and including components of both the first direction and the second direction. Here, the first detection area 158s1, the second detection area 158s2, and the third detection area 158s3 are disposed at positions scanned with the light beam prior to the image carrier. The first detection area 158s1 and the third detection area 158s3 are disposed at positions scanned with the light beam prior to the image carrier, and the second detection areas 158s2 are positioned at the position scanned with the light beam after the image carrier. It may be arranged.

  In this embodiment, a light source 151 capable of generating a plurality n of light beams from a plurality n of light emitting units, a light emission driving unit 130 for emitting light to drive each of a plurality n of light emitting units according to image data, An exposure unit 150 for scanning a plurality of n light beams in a first direction orthogonal to the alignment direction of the plurality n of light emitting units by each of the reflective surfaces of the polygon mirror 154 having a reflective surface and rotating; Drives an image carrier scanned in a first direction in a second direction orthogonal to the first direction to convert a latent image formed on the image carrier 161 by the scanning of a light beam into a visible image and form the sheet Based on the detection results of the image forming unit to be transferred, the detection unit 158 capable of detecting the first direction scanning time of the light beam and the second direction beam position of the light beam, the first direction scanning time and the second direction Beam position and image data The edge in the second direction is determined from the pixel distribution of the second direction, the second direction shift of the edge is calculated as the second direction edge shift by the first direction scanning time and the second direction beam position, and the light amount corresponding to the edge is corrected And a control unit 101 that controls the light emission drive of the light emission drive unit 130 so as to eliminate the second direction edge shift.

  Further, the control unit 101 calculates the component of the second direction edge shift caused by the first direction scanning time as being generated toward the second direction upstream side when the first direction scanning time is smaller than the predetermined time. If the first direction scanning time is longer than the predetermined time, it is calculated as occurring toward the second direction downstream side.

  Further, the control unit 101 causes the first direction scanning time, which is the detection time difference of the light beam between the first detection area 158s1 and the third detection area 158s3, for the component of the second direction edge shift caused by the second direction beam position. If the time is longer than the predetermined time, it is calculated that the distance between the first detection area 158s1 and the third detection area 158s3 is increasing, and the light beam in the first detection area 158s1 and the third detection area 158s3 If the first direction scanning time, which is the detection time difference between the two, is smaller than the predetermined time, it is calculated that the interval between the first detection area 158s1 and the third detection area 158s3 occurs in the closing direction.

  The control unit 101 reduces the light amount of the second direction upstream edge and increases the light amount of the second direction downstream edge when the second direction edge displacement occurs toward the second direction upstream side. When the second direction edge shift is generated toward the second direction downstream side, the light amount of the second direction upstream edge is increased, and the light amount of the second direction downstream edge is reduced, the second direction The light emission drive of the light emission drive unit is controlled so as to eliminate the edge shift.

  In addition, when the exposure unit 150 includes a surface identification unit that generates reflection surface identification information that identifies each reflection surface of the polygon mirror 154, the control unit 101 corrects the correction information for correcting the light amount corresponding to the edge. The stored correction information is stored in correspondence with each reflecting surface of the polygon mirror 154 with reference to the reflecting surface identification information at the time of information acquisition, and with reference to the reflecting surface identification information at the time of image formation. The light emission drive of the light emission drive unit is controlled so as to correspond to each of the reflection surfaces and to eliminate the second direction edge shift.

Further, when the calculated second direction edge deviation exceeds a predetermined threshold value, the control unit 101 controls the operation display unit 103 to notify an error related to the scanning of the light beam.
[Operation Summary (1)]
Here, the outline of the operation of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG. The operation of this embodiment is performed by the control of the control unit 101, that is, the execution of the image formation control program in the control unit 101.

  First, the control unit 101 causes the image processing unit 120 to perform image processing on image data that is input from the image input unit 110 and is to form an image (step S101 in FIG. 3). The image data is subjected to edge discrimination for obtaining an edge in the second direction based on the pixel distribution of the image data as described later by the control unit 101 (step S102 in FIG. 3).

  Here, the image processing unit 120 outputs image data of a plurality n lines in parallel to the light emission drive unit 130 in order to perform simultaneous exposure with the light source 151 on image data subjected to image processing. The light emission drive unit 130 drives light emission of each of the plurality of light emission units according to the image data of the plurality of n lines. Thus, the light source 151 generates a plurality n of light beams from the plurality n of light emitting units. Then, the plurality of n light beams are scanned in the first direction orthogonal to the alignment direction of the plurality n of light emitting units by each of the reflection surfaces of the polygon mirror 154 which has the plurality m of reflection surfaces and is rotated (FIG. 3 Step S103). The plurality n of light beams scan the detection unit 158 and the surface of the image carrier 161 in the first direction (main scanning direction). At the same time, the image carrier 161 is rotationally driven in the second direction (sub scanning direction).

Then, the plurality n of light beams are detected by the detection unit 158 immediately before scanning the image carrier 161 (step S104 in FIG. 3). The detection unit 158 notifies the control unit 101 of the detection result.
The control unit 101 having received the detection result of the detection unit 158 obtains the first direction scanning time and the second direction beam position from the detection result of the detection unit 158. Then, the control unit 101 calculates the deviation in the second direction of the edge as the second direction edge deviation based on the first direction scanning time and the second direction beam position (step S105 in FIG. 3), and corrects the deviation. The correction amount at that time is calculated (step S106 in FIG. 3). The method of calculating this deviation will be described in detail later.

  Then, if an edge is present when forming an image (YES in step S107 in FIG. 3), the control unit 101 controls the light emission drive unit 130 to apply the light amount correction to the edge portion (see FIG. Step S108 in 3). If no edge is present when forming an image (NO in step S107 in FIG. 3), the control unit 101 does not perform control for light amount correction.

Then, as described above, the control unit 101 performs the light amount correction as needed, and a plurality n of light beams scan the image carrier 161, and the surface of the image carrier 161 responds to the light beam. Each part is controlled to form an electrostatic latent image (step S109 in FIG. 3).
The control unit 101 controls each unit so that the detection by the detection unit 158 as described above, deviation calculation, correction amount calculation, light beam correction of light beam and exposure are repeated over the entire surface of the sheet (step in FIG. 3). S110).

[Operation Summary (2)]
Here, a second outline of the operation of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG. 4.
In the second operation outline, the first detection area 158s1 and the third detection area 158s3 of the detection unit 158 are disposed at positions scanned with the light beam before the image carrier 161, and the second detection area 158s2 Is arranged at a position scanned with the light beam after the image carrier 161.

In the second operation outline, although not shown in FIG. 1, the exposure unit 150 is provided with a surface identification unit for generating reflection surface identification information for identifying each reflection surface of the polygon mirror 154, and the reflection surface The identification information is notified to the control unit 101.
First, the control unit 101 causes the image processing unit 120 to perform image processing on image data that is input from the image input unit 110 and is to form an image (step S201 in FIG. 4). Note that edge determination is performed on the image data to obtain an edge in the second direction based on the pixel distribution of the image data as described later by the control unit 101 (step S202 in FIG. 4).

  Here, the image processing unit 120 outputs image data of a plurality n lines in parallel to the light emission drive unit 130 in order to perform simultaneous exposure with the light source 151 on image data subjected to image processing. The light emission drive unit 130 drives light emission of each of the plurality of light emission units according to the image data of the plurality of n lines. Thus, the light source 151 generates a plurality n of light beams from the plurality n of light emitting units. Then, the plurality of n light beams are scanned in the first direction orthogonal to the alignment direction of the plurality n of light emitting units by each of the reflection surfaces of the rotating polygon mirror having the plurality of m reflection surfaces (FIG. 4 Step S203). The plurality n of light beams scan the detection unit 158 and the surface of the image carrier 161 in the first direction (main scanning direction). At the same time, the image carrier 161 is rotationally driven in the second direction (sub scanning direction).

Then, the plurality n of light beams are detected by the first detection area 158s1 and the third detection area 158s3 of the detection unit 158 immediately before scanning the image carrier 161 (step S204 in FIG. 4). The detection unit 158 notifies the control unit 101 of the detection result.
Then, if an edge is present when forming an image (YES in step S205 in FIG. 4), the control unit 101 stores the stored correction information with reference to the reflective surface identification information at the time of image formation. 4 (step S206 in FIG. 4), the correction information is allocated corresponding to each reflection surface of the polygon mirror 154, and the light emission drive unit 130 is controlled to apply the light amount correction to the edge portion (FIG. 4). Step S207 in). If no edge is present when forming an image (NO in step S205 in FIG. 4), the control unit 101 does not perform control on light amount correction.

Then, as described above, the control unit 101 performs the light amount correction as needed, and a plurality n of light beams scan the image carrier 161, and the surface of the image carrier 161 responds to the light beam. Each part is controlled to form an electrostatic latent image (step S208 in FIG. 4).
Then, the plurality n of light beams obtained by scanning the image carrier 161 are detected by the second detection area 158 s 2 of the detection unit 158 immediately after scanning the image carrier 161 (step S 209 in FIG. 4). The detection unit 158 notifies the control unit 101 of the detection result.

  Then, the control unit 101 which receives the detection result of the detection unit 158 in two times before and after the scanning of the image carrier 161 obtains the first direction scanning time and the second direction beam position from the detection result of the detection unit 158 . Then, the control unit 101 calculates the deviation in the second direction of the edge as the second direction edge deviation based on the first direction scanning time and the second direction beam position (step S210 in FIG. 4), and corrects the deviation. The correction amount at that time is calculated (step S211 in FIG. 4). The method of calculating this deviation will be described in detail later. Then, the control unit 101 causes the storage unit to store the calculated deviation together with the reflective surface identification information (step S212 in FIG. 4).

The control unit 101 controls each unit so that the detection by the detection unit 158 as described above, the correction application, the light amount correction and exposure of the light beam, the deviation calculation, the correction amount calculation, and the correction amount storage are repeated over the entire sheet. (Step S213 in FIG. 4).
Further, in the case of this second operation outline, as shown in FIGS. 18 and 19 described later, the first detection area 158s1 and the third detection area 158s3 are provided immediately before the scanning of the image carrier 161, and the second detection area 158s2 is provided. Since the detection lengths of the first detection area 158 s 1 to the second detection area 158 s 2 can be made longer by providing them immediately after the scanning of the image carrier 161, there is an advantage that the accuracy is enhanced. In addition, since the calculation of the deviation and the correction amount can be performed in a state other than real time, the calculation time can be spared, and highly accurate calculation can be performed.

[Principle of correction]
・ Edge discrimination:
The present embodiment is to prevent the image quality deterioration due to the beam interval difference in the second direction (sub scanning direction) due to the positional deviation of the light beam, and the edge misalignment causing the beam interval difference in the second direction (sub scanning direction) It is necessary to eliminate it. For this purpose, it is necessary to determine the presence of edges distributed in the image.

The edge determination will be described below with reference to FIG.
In FIG. 5, the case of five pixels in the sub scanning direction is exemplified from px1 to px5 (FIG. 5 (a)).
First, when edge determination is performed with the pixel px2 with dots (black) as the target pixel, the pixel px1 adjacent on the upstream side in the sub scanning direction and the pixel px3 adjacent on the downstream side in the sub scanning direction are extracted (see FIG. b) Check dot present (black) / dot absent (white).

  When the pixel px2 has dots (black) and the pixel px1 has no dots (white), it is determined that the pixel px2 is [upstream-side edge] (FIG. 5 (b)). When the pixel px2 is in the dot state (black) and the pixel px3 is in the dot state (black), it is determined that the edge of the pixel px3 is [no edge] (FIG. 5B).

  Further, when the edge determination is performed with the pixel px3 with dots (black) as the target pixel, the pixel px2 adjacent on the upstream side in the sub scanning direction and the pixel px4 adjacent on the downstream side in the sub scanning direction are extracted (FIG. c) Check dot present (black) / dot absent (white). When the pixel px2 is dot present (black) and the pixel px4 is dot present (black), it is determined that there is no edge on both sides (FIG. 5C).

  In addition, when performing edge determination with the pixel px4 with dots (black) as the pixel of interest, the pixel px3 adjacent on the upstream side in the sub scanning direction and the pixel px5 adjacent on the downstream side in the sub scanning direction are extracted (see FIG. d) Check dot present (black) / dot absent (white). When the pixel px4 has dots (black) and the pixel px5 has no dots (white), it is determined that the pixel px4 is [downstream-side edge] (FIG. 5 (d)). When the pixel px4 is in the dot state (black) and the pixel px3 is in the dot state (black), it is determined that the side of the pixel px3 is [no edge] (FIG. 5 (d)).

That is, the edge determination is performed by the control unit 101 based on the following algorithm.
Upstream edge = dots exist only on the downstream side.
No edge = Dots exist on both upstream and downstream sides.
Downstream edge = dots exist only on the upstream side.

Then, in the present embodiment, the light amount of the light emitting unit corresponding to the edge portion of the control unit 101 is based on the above-described edge determination result in the second direction and the second direction beam position detected by the detecting unit 158 described later. Correct the
・ Edge position correction:
The present embodiment is to prevent the image quality deterioration due to the beam interval difference in the second direction (sub scanning direction) due to the positional deviation of the light beam, and the edge misalignment causing the beam interval difference in the second direction (sub scanning direction) It is necessary to eliminate it. For this purpose, correction corresponding to the positional deviation of the light beam is performed on the determined edge in the second direction. The outline of the correction is shown below.

Hereinafter, the manner in which the control unit 101 corrects the light quantity of each light emitting unit based on the edge determination result and the light emitting position in the plurality of light emitting units will be described in principle using FIGS. 6 and 7.
FIG. 6A exemplifies four pixels in the case where four light beams in one scanning exist at a proper second direction position. FIG. 6B exemplifies four pixels in the case where four light beams in one scan are present on the upstream side in the second direction than the appropriate second direction position. Here, when the four pixels shown here correspond to the upstream edge, the control unit 101 controls the light emission drive unit 130 to reduce the light amount of each pixel (FIG. 6C). Thus, the upstream end of each pixel shown in FIG. 6 (c) matches the upstream end of the pixel when the light beam is in the proper second direction position (FIG. 6 (a)). Do. On the other hand, when the four pixels shown here correspond to the downstream edge, the control unit 101 controls the light emission drive unit 130 to increase the light amount of each pixel (FIG. 6 (d)). Thus, the downstream end of each pixel shown in FIG. 6 (d) coincides with the upstream end of the pixel when the light beam is in the appropriate second direction position (FIG. 6 (a)). Do. Note that such correction is performed for pixels corresponding to the upstream edge and the downstream edge as described above, and such correction is not necessary for pixels that are not edges.

  FIG. 7A exemplifies four pixels in the case where four light beams in one scanning exist at a proper second direction position. FIG. 7B exemplifies four pixels in the case where four light beams in one scanning exist on the downstream side in the second direction with respect to the appropriate second direction position. Here, when the four pixels shown here correspond to the upstream edge, the control unit 101 controls the light emission drive unit 130 to increase the light amount of each pixel (FIG. 7C). Thus, the upstream end of each pixel shown in FIG. 7C matches the upstream end of the pixel when the light beam is in the proper second direction position (FIG. 7A). Do. On the other hand, when the four pixels shown here correspond to the downstream edge, the control unit 101 controls the light emission drive unit 130 to reduce the light amount of each pixel (FIG. 7 (d)). Thus, the downstream end of each pixel shown in FIG. 7 (d) matches the downstream end of the pixel when the light beam is in the proper second direction position (FIG. 7 (a)). Do. Note that such correction is performed for pixels corresponding to the upstream edge and the downstream edge as described above, and such correction is not necessary for pixels that are not edges.

Detection of misalignment of light beam:
The present embodiment is to prevent the image quality deterioration due to the beam interval difference in the second direction (sub scanning direction) caused by the positional deviation of the light beam on the image carrier 161. First, the positional deviation of the light beam is accurately detected. There is a need to.

  Hereinafter, the outline of position detection of a light beam is shown using FIGS. 8-12. In FIGS. 8 to 12, (a) shows the detection unit 158, (b) to (d) are detection results at the appropriate time, and (e) to (j) are the detection results at the incorrect time Is shown. Further, the third detection area 158s3 of the detection unit 158 is configured to open toward the downstream side in the second (sub scanning) direction as a specific example.

  The first direction scanning time is generated due to the difference in the first direction scanning speed of the light beam as described with reference to FIG. That is, if the first direction scanning speed of the light beam is higher than the predetermined value, the first direction scanning time is smaller than the predetermined value. On the other hand, if the first direction scanning speed of the light beam is slower than the predetermined value, the first direction scanning time will be larger than the predetermined value.

  In FIG. 8, the measurement values obtained between the first detection area 158s1 and the third detection area 158s3 when the first direction scanning speed of the light beam and the second direction position of the light beam due to trouble are in an appropriate ideal state. Is a (Fig. 8 (b), (c)) and the measured value obtained between the first detection area 158s 1 and the second detection area 158 s 2 is b (Fig. 8 (b), (d)). . The control unit 101 stores the a and b in advance as a predetermined time.

  Further, in FIG. 8, when the second direction position of the light beam due to the trouble of the reflecting surface of the polygon mirror 154 or the like is an ideal state, but the first direction scanning speed of the light beam is slower than the predetermined speed, Measurement values a 'obtained between the first detection area 158s1 and the third detection area 158s3 are obtained between the first detection area 158s1 and the second detection area 158s2 a1 (FIGS. 8E and 8F). The measured value b ′ is notified to the control unit 101 as b1 (FIG. 8 (e), (g)). Here, since the first direction scanning speed is lower than the predetermined speed, a1> a, b1> b.

  Further, in FIG. 8, when the position of the light beam in the second direction due to the trouble of the reflecting surface of the polygon mirror 154 is an appropriate ideal state, but the scanning speed of the light beam in the first direction is higher than the predetermined speed. The measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is obtained between a2 (FIG. 8 (h) and (i)) and between the first detection area 158s1 and the second detection area 158s2. The measured value b ′ is notified to the control unit 101 as b2 (FIG. 8 (h), (j)). Here, since the first direction scanning speed is higher than the predetermined speed, a2 <a, b2 <b.

  In FIG. 9, the measured values obtained between the first detection area 158s1 and the third detection area 158s3 when the first direction scanning speed of the light beam and the second direction position of the light beam due to the trouble are in the appropriate ideal state. Is a (Fig. 9 (b), (c)), and the measured value obtained between the first detection area 158s 1 and the second detection area 158 s 2 is b (Fig. 9 (b), (d)). . The control unit 101 stores the a and b in advance as a predetermined time.

  Further, in FIG. 9, the first direction scanning velocity of the light beam is the same as the predetermined velocity, but the second directional position of the light beam is in the direction of increasing the distance between the first detection region 158s1 and the third detection region 158s3. If it occurs, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a3 (FIGS. 9E and 9F), and the first detection area 158s1 and the second detection The measured value b ′ obtained between the regions 158s2 is notified to the control unit 101 as b3 (FIGS. 9E and 9G). Here, since the second direction position of the light beam is shifted to the downstream side, a3> a, b3 = b.

  Further, in FIG. 9, the first direction scanning speed of the light beam is the same as the predetermined speed, but the second direction position of the light beam is in the direction in which the distance between the first detection area 158s1 and the third detection area 158s3 closes. If it occurs, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a4 (FIG. 9 (h), (i)), and the first detection area 158s1 and the second detection The measured value b ′ obtained between the regions 158s2 is notified to the control unit 101 as b4 (FIGS. 9H and 9J). Here, since the second direction position of the light beam is shifted to the upstream side, a4 <a, b4 = b.

  In FIG. 10, the first direction scanning speed of the light beam is the same as the predetermined speed, but the second direction position of the light beam is generated in the direction of increasing the distance between the first detection area 158s1 and the third detection area 158s3. In the case where the first detection area 158s1 and the third detection area 158s3 are present, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a5 (FIGS. 10 (b) and 10 (c)). The measurement value b ′ obtained between the two is notified to the control unit 101 as b5 (FIG. 10 (b), (d)). Here, since the second direction position of the light beam is shifted to the downstream side, a5 = a3> a, b5 = b.

  Further, in FIG. 10, the first direction scanning speed of the light beam is slower than the predetermined speed, and the second direction position of the light beam is generated in the direction in which the distance between the first detection area 158s1 and the third detection area 158s3 increases. In the case where the first detection area 158s1 and the third detection area 158s3 are measured, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a6 (FIG. 10 (e), (f)). The measured value b ′ obtained during 158 s 2 is notified to the control unit 101 as b 6 ((e) and (g) in FIG. 10). Here, since the first direction scanning speed is low and the second direction position of the light beam is shifted to the downstream side, a6> a, b6> b.

  Further, in FIG. 10, the first direction scanning speed of the light beam is higher than the predetermined speed, and the second direction position of the light beam is generated in the direction in which the distance between the first detection area 158s1 and the third detection area 158s3 increases. In the case where the first detection area 158s1 and the third detection area 158s3 are measured, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a7 (FIG. 10 (h), (i)). The measured value b ′ obtained during 158 s 2 is notified to the control unit 101 as b 7 ((h) and (j) in FIG. 10). Here, since the first direction scanning speed is high and the second direction position of the light beam is shifted to the downstream side, a7 ≠ a, b7 <b.

  In FIG. 11, the first direction scanning speed of the light beam is the same as the predetermined speed, but the second direction position of the light beam occurs in the direction in which the distance between the first detection area 158s1 and the third detection area 158s3 closes. In the case where the first detection area 158s1 and the third detection area 158s3 are present, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a8 (FIGS. 11B and 11C), and the first detection area 158s1 and the second detection area 158s2 The measurement value b ′ obtained between the two is notified to the control unit 101 as b8 (FIGS. 11B and 11D). Here, since the second direction position of the light beam is shifted to the upstream side, a8 = a4 <a, b8 = b.

  Further, in FIG. 11, the first direction scanning speed of the light beam is slower than the predetermined speed, and the second direction position of the light beam occurs in the direction in which the distance between the first detection area 158s1 and the third detection area 158s3 closes. In the case where the first detection area 158s1 and the third detection area 158s3 are measured, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a9 (FIGS. 11 (e) and (f)). The measured value b ′ obtained during 158 s 2 is notified to the control unit 101 as b 9 (FIG. 11 (e), (g)). Here, since the first direction scanning speed is low and the second direction position of the light beam is shifted to the upstream side, a9 ≠ a, b9> b.

  Further, in FIG. 11, the first direction scanning speed of the light beam is higher than the predetermined speed, and the second direction position of the light beam is generated in the direction in which the distance between the first detection area 158s1 and the third detection area 158s3 closes. In the case where the first detection area 158s1 and the third detection area 158s3 are measured, the measured value a ′ obtained between the first detection area 158s1 and the third detection area 158s3 is a10 (FIGS. 11 (h) and 11 (i)). The measured value b ′ obtained during 158 s 2 is notified to the control unit 101 as b 10 ((h) and (j) in FIG. 11). Here, a10 <a, b10 <b, because the first direction scanning speed is high and the second direction position of the light beam is shifted to the upstream side.

here,
A second direction edge shift toward the second direction downstream side due to the first direction scanning time, which is detected in the second detection area, c,
C ′ which is a second direction edge shift toward the second direction downstream side due to the first direction scanning time and which is detected in the third detection region, c ′,
A second direction edge shift toward the second direction upstream side due to the first direction scanning time, which is detected in the second detection area, d,
A second direction edge shift toward the second direction upstream side due to the first direction scanning time, which is detected in the third detection region, d ′,
The second direction edge shift toward the direction in which the distance between the first detection region and the third detection region is increased due to the second direction beam position C,
A second direction edge shift toward a direction in which the distance between the first detection region and the third detection region is closed due to the second direction beam position D,
It is written as

Then, the measured value a ′ and the measured value b ′ in FIGS. 8, 9, 10, and 11 described above can be expressed by the following mathematical expressions.
In this case, in FIG. 8 (e) (f) (g), for the measured values a ′ and b ′
a '= a + c' = a + (a / b) c,
b '= b + c,
It can be expressed as. For this reason, the control unit 101 controls the light emission drive unit 130 so as to eliminate the second direction edge shift toward the second direction downstream due to the first direction scanning time at the pixels of the determined edge portion. .

Also, in FIG. 8 (h) (i) (j), for the measured values a ′ and b ′
a '= a-d' = a- (a / b) d,
b '= bd,
It can be expressed as. For this reason, the control unit 101 controls the light emission drive unit 130 so as to eliminate the second direction edge shift toward the second direction upstream due to the first direction scanning time at the pixels of the determined edge portion. .

Also, in FIGS. 9 (e) (f) (g) and FIGS. 10 (b) (d) (d), for the measured values a ′ and b ′,
a '= a + C,
b '= b,
It can be expressed as. For this reason, the control unit 101 eliminates the second direction edge shift in the direction in which the distance between the first detection region and the third detection region increases due to the second direction beam position in the pixels of the determined edge portion. Thus, the light emission drive unit 130 is controlled.

Also, in FIGS. 9 (h) (i) (j) and FIGS. 11 (b) (d) (d), for the measured values a ′ and b ′,
a '= aD,
b '= b,
It can be expressed as. For this reason, the control unit 101 cancels the second direction edge shift in the direction in which the distance between the first detection region and the third detection region resulting from the second direction beam position is closed in the pixels of the determined edge portion. Thus, the light emission drive unit 130 is controlled.

Also, in FIGS. 10 (e) (f) (g), the measured values a 'and b'
a '= (a + c') + C = (a + (a / b) c) + C
b '= b + c,
It can be expressed as. For this reason, the control unit 101 causes a second direction edge shift toward a direction in which the distance between the first detection region and the third detection region increases due to the beam position in the second direction at the pixels of the determined edge portion;
The light emission drive unit 130 is controlled to eliminate the second direction edge shift toward the second direction downstream due to the first direction scan time.

Also, in FIGS. 11 (e) (f) (g), for the measured values a ′ and b ′
a '= (a + c')-D = (a + (a / b) c) -D,
b '= b + c,
It can be expressed as. For this reason, the control unit 101 causes the second direction edge deviation in which the distance between the first detection region and the third detection region resulting from the second direction beam position in the pixels of the determined edge portion is decreased, The light emission drive unit 130 is controlled so as to eliminate the second direction edge shift toward the second direction downstream side due to the one direction scanning time.

Also, in FIG. 10 (h) (i) (j), regarding the measured values a ′ and b ′,
a ′ = (a−d ′) + C = (a− (a / b) d) + C,
b '= bd,
It can be expressed as. For this reason, the control unit 101 causes a second direction edge shift toward a direction in which the distance between the first detection region and the third detection region increases due to the beam position in the second direction at the pixels of the determined edge portion;
The light emission drive unit 130 is controlled so as to eliminate the second direction edge shift toward the second direction upstream due to the first direction scanning time.

Also, in FIG. 11 (h) (i) (j), for the measured values a ′ and b ′
a '= (a-d')-D = (a- (a / b) d) -D,
b '= bd,
It can be expressed as. For this reason, the control unit 101 causes the second direction edge deviation in which the distance between the first detection region and the third detection region resulting from the second direction beam position in the pixels of the determined edge portion is decreased, The light emission drive unit 130 is controlled to eliminate the second direction edge shift toward the second direction upstream due to the one direction scanning time.

  Each of the above states can be summarized in FIG. 12 and FIG. In the second direction position of the light beam due to the polygon mirror, the direction in which the distance between the first detection area and the third detection area is larger is +, and the closing direction is-. In addition, the case where the first direction scanning speed is slower than the predetermined speed and the detection time is longer is +, and the case where the detection time is faster and the time is smaller is −.

  Then, the control unit 101 applies the above-mentioned corresponding pattern to correct the light amount corresponding to the determined edge to control to eliminate the second direction edge deviation. In the case of the displacement of the light beam by the above, the same positional displacement is maintained until the end of the scan in the first direction on the image carrier 161. On the other hand, in the case of the deviation of the light beam due to the first direction scanning time, the error is accumulated as the scanning position in the first direction on the image carrier 161 comes to the end. Therefore, the control unit 101 corrects the second direction edge shift in consideration of the above conditions.

  As a result, when forming an image by simultaneous exposure of a plurality of lines, it is caused by the positional deviation of the light beam due to the polygon mirror and the positional deviation of the light beam due to the change of the main scanning time due to the planarity of the reflecting surface of the polygon mirror. Therefore, it is possible to satisfactorily eliminate the change in image quality caused by the beam interval difference in the second direction (sub scanning direction).

And, in the present embodiment, since the light beam is detected by the detection unit 158 in accordance with the scanning of the light beam, it is possible to resolve well while dealing with not only a specific condition but also temporal change. become.
[Specific example of correction]
Here, in FIG. 14 to FIG. 17, a scan n is performed on an image forming apparatus that executes image formation for every four lines in one scan by simultaneously using four beams of light emission of LD # 1 to LD # 4 as a plurality of light emitting units. And a specific example of the correction of this embodiment in the exposure by two adjacent scans of scan n + 1.

  In this case, a plurality of light emitting portions are reflected by the reflecting surface of the rotating polygon mirror by four beams emitted by the light sources LD # 1 to LD # 4 and scanned on the image carrier in the main scanning direction. The four beams generated by the light emission of # 4 are reflected by the next reflecting surface of the rotating polygon mirror and scanned on the image carrier in the main scanning direction. Since the image carrier rotates in the sub-scanning direction, exposure of four beams in the main scanning direction is repeatedly performed in the sub-scanning direction to form a two-dimensional image. In FIGS. 14 to 17, the lower 2 light emitting portions of the 4 light emitting portions are made to emit light in scan n to form the lower 2 dots on the image carrier, and in the next scan n + 1, of the 4 light emitting portions An example is shown in which the upper two light emitting portions emit light to form upper two dots on the image carrier, and four dots adjacent in the sub-scanning direction are formed on the image carrier by a total of two scans.

  FIG. 14A shows an exposure state in an ideal state formed by scanning n and scanning n + 1 on the image carrier at a certain timing. Hatching indicates that exposure has been made. In addition, since the periphery of the exposure actually spreads, the toner on the image carrier is painted out as shown in FIG. 14 (b). Here, as described above, at least one of the second direction edge shift due to the first direction scan time or the second direction edge shift due to the second direction beam position occurs in the scan n + 1, as shown in FIG. The interval between scan n and scan n + 1 is narrower than in the predetermined state. For this reason, the area of hatching in FIG. 14D is smaller than the area of hatching in FIG. 14B which is the appropriate state, and is recognized as a decrease in density.

  Note that this state is calculated by the control unit 101 with reference to the detection result of the detection unit 158 as the second direction edge shift. Also, in parallel with this, the control unit 101 determines that the second pixel px2 from the top in the scan n + 1 in FIG. 14C is the downstream edge. Thereby, the control unit 101 corrects the light amount of the pixel corresponding to the downstream side edge to eliminate the second direction edge shift, the downstream side of the pixel (px2 ′) corresponding to the downstream side edge in FIG. The light emission drive of the light emission drive unit 130 is controlled so as to increase the light amount so that the side end matches the predetermined position. As a result, as shown in FIG. 14 (f), the toner area on the image carrier is not reduced and the state is the same as the ideal exposure state (FIG. 14 (b)).

  FIG. 15A shows an exposure state in an ideal state formed by scanning n and scanning n + 1 on the image carrier at a certain timing. Hatching indicates that exposure has been made. In addition, since the periphery of exposure is spread in practice, the toner on the image carrier is painted out as shown in FIG. Here, as described above, at least one of the second direction edge shift due to the first direction scan time or the second direction edge shift due to the second direction beam position occurs in the scan n + 1, as shown in FIG. The interval between the scan n and the scan n + 1 is wider than in the predetermined state. For this reason, the area of hatching in FIG. 15D is larger than the area of hatching in FIG. 15B which is the appropriate state, and is visually recognized as an increase in density.

  Note that this state is calculated by the control unit 101 with reference to the detection result of the detection unit 158 as the second direction edge shift. Also, in parallel with this, the control unit 101 determines that the second pixel px2 from the top in the scan n + 1 in FIG. 15C is the downstream edge. Thereby, the control unit 101 corrects the light amount of the pixel corresponding to the downstream side edge to eliminate the second direction edge shift, the downstream side of the pixel (px2 ′) corresponding to the downstream side edge in FIG. The light emission drive of the light emission drive unit 130 is controlled so as to reduce the light amount so that the side end matches the predetermined position. As a result, in the toner on the image carrier, as shown in FIG. 15F, the enlargement of the toner area is eliminated, and the state is the same as the ideal exposure state (FIG. 15B).

  FIG. 16A shows an exposure state in an ideal state formed by scanning n and scanning n + 1 on the image carrier at a certain timing. Hatching indicates that exposure has been made. In addition, since the periphery of exposure is spread in practice, the toner on the image carrier is painted out as shown in FIG. Here, as described above, the second direction edge shift due to the first direction scan time or the second direction edge shift toward the upstream of the second direction due to the second direction beam position is the scan n and It is equally generated in scan n + 1. Since the second direction deviation occurs equally, the interval between the scan n and the scan n + 1 is the same as the predetermined state. Therefore, although the hatching area in FIG. 16D is in the proper state and the density is proper, the exposure position in the second direction is not proper.

  This state is calculated by the control unit 101 with reference to the detection result of the detection unit 158 as the second direction edge shift in the scan n and the scan n + 1. In addition, parallel to this, the third pixel from the top in scan n in FIG. 16C is the upstream edge, and the second pixel from the top in scan n + 1 is the downstream edge. It is determined by the part 101. Thus, the control unit 101 corrects the light amount of the pixel corresponding to the upstream side edge and the light amount of the pixel corresponding to the downstream side edge to eliminate the second direction edge deviation, as shown in FIG. The light amount is reduced so that the upstream end of the pixel (px3′_0) corresponding to the edge coincides with the predetermined position, and the downstream end of the pixel (px2′_0) corresponding to the downstream edge is the predetermined position The light emission drive of the light emission drive unit 130 is controlled to increase the light amount so as to coincide with the above. As a result, as shown in FIG. 16 (f), the toner on the image carrier is free from positional deviation of the toner, and is in the same state as the ideal exposure state (FIG. 16 (b)).

  FIG. 17A shows an exposure state in an ideal state formed by scanning n and scanning n + 1 on the image carrier at a certain timing. Hatching indicates that exposure has been made. In addition, since the periphery of the exposure spreads in practice, the toner on the image carrier is painted out as shown in FIG. 17 (b). Here, as described above, the second direction edge shift due to the first direction scan time or the second direction edge shift toward the second direction downstream due to the second direction beam position is the scan n and It is equally generated in scan n + 1. Since the second direction deviation occurs equally, the interval between the scan n and the scan n + 1 is the same as the predetermined state. Therefore, although the hatching area in FIG. 17D is in the proper state and the density is appropriate, the exposure position in the second direction is not appropriate.

  This state is calculated by the control unit 101 with reference to the detection result of the detection unit 158 as the second direction edge shift in the scan n and the scan n + 1. Further, in parallel with this, the control is performed assuming that the third pixel px3_0 from the top in scan n in FIG. 17C is the upstream edge and the second pixel px2_1 from the top in scan n + 1 is the downstream edge. It is determined by the part 101. Thus, the control unit 101 corrects the light amount of the pixel corresponding to the upstream edge and the light amount of the pixel corresponding to the downstream edge to eliminate the second direction edge deviation, as shown in FIG. The light amount is increased so that the upstream end of the pixel (px3′_0) corresponding to the edge matches the predetermined position, and the downstream end of the pixel (px2′_0) corresponding to the downstream edge is the predetermined position The light emission drive of the light emission drive unit 130 is controlled so as to reduce the light amount so as to coincide with the above. As a result, as shown in FIG. 17F, the toner displacement on the image carrier is eliminated, and the toner is in the same state as the ideal exposure state (FIG. 17B).

[Other configuration example]
FIG. 18 and FIG. 19 are explanatory diagrams showing an example of the configuration described as the operation outline (2) of this embodiment. Here, a detection unit 158-1 including a first detection area 158s1 and a third detection area 158s3 as the detection unit 158 and disposed at a position scanned with the light beam earlier than the image carrier 161, and a second detection It is possible to divide into two, a detection unit 158-2 provided with a region 158s2 and disposed at a position scanned with the light beam after the image carrier 161.

  As a result, the distance between the first detection area 158s1 provided in the detection unit 158-1 and the second detection area 158s2 provided in the detection unit 158-2 is increased, so that the first detection area 158s1 and the second detection area are generated. It becomes possible to generate accurate correction information between 158s2. However, since the correction information is obtained after the light beam scans the image carrier 161, the control unit 101 refers to the reflection surface identification information generated by the surface identification unit 159 for identifying each reflection surface of the polygon mirror 154, The correction information is stored corresponding to each reflection surface of the polygon mirror 154. Then, the control unit 101 refers to the reflection surface identification information, assigns the stored correction information in correspondence with each reflection surface of the polygon mirror 154, and eliminates the light emission drive unit 130 so as to eliminate the second direction edge deviation. Control the light emission drive of the

Other Embodiments
In the above description of the embodiment, the light emission of each light emitting portion and the dots formed by the light emission are shown as being approximated by a circle, but the actual shape is not limited to the illustrated circular shape, any of which Even if it is the shape of, good results can be obtained by applying the embodiment described above.

  In the above embodiments, an electrophotographic image forming apparatus using a light beam has been described, but 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 a printing paper using a light beam, and good results can be obtained.

  Moreover, it is possible to apply even when it is a case where other light sources other than a semiconductor laser (LD) are used as a light source.

100 image forming apparatus 101 overall control unit 120 image processing unit 130 light emission drive unit 140 print engine 150 exposure unit 160 process unit

Claims (12)

A light source capable of generating plural n light beams from plural n light emitting parts;
A light emission drive unit configured to drive light emission of each of the plurality of light emitting units according to the image data;
A light scanning unit configured to scan the plurality of n light beams in a first direction orthogonal to the alignment direction of the plurality n of light emitting units by each reflecting surface of the rotating polygon mirror having a plurality m of reflecting surfaces;
A latent image formed on the image carrier by scanning the light beam is driven by driving the image carrier in which the plurality of n light beams are scanned in the first direction in a second direction orthogonal to the first direction. An image forming unit that converts image data into
A detection unit capable of detecting a first direction scanning time of the light beam and a second direction beam position of the light beam;
The first direction scan time and the second direction beam position are determined from the detection result of the detection unit, and the edge in the second direction is determined from the pixel distribution of the image data, and the first direction scan time and the second direction beam position And the second direction shift of the edge is calculated as the second direction edge shift, and the light emission drive unit is driven so as to correct the light amount corresponding to the edge and eliminate the second direction edge shift. A control unit to control
An image forming apparatus comprising: The detection unit includes a first detection area having a second direction as a longitudinal direction, a second detection area parallel to the first detection area and disposed at a different position in the first direction, and the first detection area. And a third detection area including components of both the first direction and the second direction sandwiched between the detection area and the second detection area.
The control unit determines a detection time difference of the light beam in the first detection area and the second detection area as the first direction scanning time, and the light beam in the first detection area and the third detection area Determining the beam position in the second direction from the detection time difference of
The image forming apparatus according to claim 1, The control unit
Regarding the component of the second direction edge shift resulting from the first direction scanning time,
If the first direction scanning time is smaller than the predetermined time, it is calculated as occurring in the second direction upstream side,
If the first direction scanning time is longer than the predetermined time, it is calculated as occurring toward the second direction downstream side.
The image forming apparatus according to claim 1 or 2, wherein The control unit
Regarding the component of the second direction edge deviation resulting from the second direction beam position,
When the first direction scanning time, which is the detection time difference of the light beam between the first detection area and the third detection area, is longer than the predetermined time, the interval between the first detection area and the third detection area is Calculated as occurring in the opening direction,
When the first direction scanning time which is the detection time difference of the light beam in the first detection area and the third detection area is smaller than the predetermined time, the interval between the first detection area and the third detection area is Calculate as occurring towards the closing direction,
The image forming apparatus according to claim 2, The control unit
When the second direction edge shift occurs toward the second direction upstream side, the light amount of the second direction upstream edge is reduced, and the light amount of the second direction downstream edge is increased,
When the second direction edge shift occurs toward the second direction downstream side, the light amount of the second direction upstream edge is increased, and the light amount of the second direction downstream edge is reduced,
Controlling the light emission drive of the light emission drive unit so as to eliminate the second direction edge shift;
The image forming apparatus according to any one of claims 1 to 4, characterized in that: The detection unit includes a first detection area having a second direction as a longitudinal direction, a second detection area parallel to the first detection area and disposed at a different position in the first direction, and the first detection area. And a third detection area including components of both the first direction and the second direction, which are sandwiched between the detection area and the second detection area.
The control unit
The predetermined value of the detection time difference of the light beam in the first detection area and the third detection area is a,
The measurement value of the detection time difference of the light beam in the first detection area and the third detection area is a ′,
The predetermined value of the detection time difference of the light beam in the first detection area and the second detection area is b,
The measurement value of the detection time difference of the light beam in the first detection area and the second detection area is b ′,
The second direction edge shift toward the second direction downstream side due to the first direction scanning time, which is detected in the second detection area, c,
The second direction edge shift toward the second direction downstream side due to the first direction scanning time, which is detected in the third detection area, c ′,
The second direction edge shift toward the second direction upstream side due to the first direction scanning time, which is detected in the second detection area, d,
The second direction edge shift toward the second direction upstream side due to the first direction scanning time, which is detected in the third detection area, is d ′,
The second direction edge shift toward the direction in which the distance between the first detection area and the third detection area is increased due to the second direction beam position C,
The second direction edge shift toward the direction in which the space between the first detection area and the third detection area is closed due to the second direction beam position is D,
If you
For the measured values a 'and b'
a '= a + c' = a + (a / b) c,
b '= b + c,
To eliminate the second direction edge shift c,
a '= a-d' = a- (a / b) d,
b '= bd,
To eliminate the second direction edge shift d,
a '= a + C,
b '= b,
To eliminate the second direction edge shift C,
a '= aD,
b '= b,
To eliminate the second direction edge deviation D,
a '= (a + c') + C = (a + (a / b) c) + C
b '= b + c,
To eliminate the second direction edge deviations C and c,
a '= (a + c')-D = (a + (a / b) c) -D,
b '= b + c,
To eliminate the second direction edge deviation D and c,
a ′ = (a−d ′) + C = (a− (a / b) d) + C,
b '= bd,
To eliminate the edge deviations C and d in the second direction,
a '= (a-d')-D = (a- (a / b) d) -D,
b '= bd,
To eliminate the edge deviations D and d in the second direction,
Fitting to any corresponding pattern to correct the light amount corresponding to the edge and to control to cancel the second direction edge deviation;
The image forming apparatus according to claim 5, When the light beam is scanned in the first direction by the image carrier, the detection unit is disposed outside a region in the first direction close to the image carrier.
The light scanning unit scans a plurality n of the light beams in a first direction with respect to the image carrier and the detection unit.
The image forming apparatus according to any one of claims 1 to 6, characterized in that: The detection unit is disposed at a position where the light beam is scanned prior to the image carrier.
The control unit controls the light emission of the light emission drive unit so as to eliminate the second direction edge shift corresponding to the reflection surface of the polygon mirror which has obtained the detection result using the detection result of the detection unit. Control,
The image forming apparatus according to any one of claims 1 to 7, characterized in that: The light scanning unit includes a surface identification unit that generates reflection surface identification information that identifies each reflection surface of the polygon mirror,
The control unit
The correction information for correcting the light amount corresponding to the edge is stored corresponding to each reflection surface of the polygon mirror with reference to the reflection surface identification information at the time of acquisition of the correction information,
The light emission drive unit is configured to assign the correction information stored corresponding to each reflection surface of the polygon mirror with reference to the reflection surface identification information at the time of image formation, and eliminate the second direction edge deviation. Control the light emission drive of the
An image forming apparatus according to any one of claims 1 to 8, characterized in that. The detection unit includes a first detection area having a second direction as a longitudinal direction, a second detection area parallel to the first detection area and disposed at a different position in the first direction, and the first detection area. And a third detection area including components of both the first direction and the second direction sandwiched between the detection area and the second detection area.
The first detection area and the third detection area are disposed at positions scanned with the light beam prior to the image carrier, and the second detection area is scanned with the light beam after the image carrier. Placed in the
The image forming apparatus according to claim 9, It has a notification unit that notifies various information to the outside,
If the calculated second direction edge deviation exceeds a predetermined threshold value, the control unit may
Controlling the notification unit to notify an error related to the scanning of the light beam;
The image forming apparatus according to any one of claims 1 to 10, wherein A light source capable of generating a plurality n of light beams from a plurality n of light emitting units,
A light emission drive unit that drives light emission of each of a plurality of n light emission units according to image data
A light scanning unit configured to scan the plurality of n light beams in a first direction orthogonal to the alignment direction of the plurality n of light emitting units by each reflecting surface of the rotating polygon mirror having the plurality m of reflecting surfaces;
A latent image formed on the image carrier by scanning the light beam is driven by driving the image carrier in which the plurality of n light beams are scanned in the first direction in a second direction orthogonal to the first direction. Image forming unit that converts image data to
A detection unit capable of detecting a first direction scanning time of the light beam and a second direction beam position of the light beam;
The first direction scan time and the second direction beam position are determined from the detection result of the detection unit, and the edge in the second direction is determined from the pixel distribution of the image data, and the first direction scan time and the second direction beam position And the second direction shift of the edge is calculated as the second direction edge shift, and the light emission drive unit is driven so as to correct the light amount corresponding to the edge and eliminate the second direction edge shift. Control unit to control,
An image forming control program that causes a computer of an image forming apparatus to function.

Images