JP2013045009A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly correct the amount of light of a laser beam that is different depending on a scanning position even when a storage area is small.SOLUTION: An image forming apparatus comprises: a photoreceptor; a light source unit which emits a laser beam; a scanning lens which makes the laser beam scan on a peripheral surface of the photoreceptor; a correction value storage unit which divides a scanning position into a predetermined number of correction blocks aligned in a main scanning direction and stores correction values predetermined in association with a plurality of selective correction blocks discretely selected for each preset number, respectively; a correction value interpolation unit which calculates a correction value corresponding to a correction block held between two selective correction blocks adjacent to each other by interpolating between two correction values stored in association with the two selective correction blocks; and a light amount correction unit which corrects the amount of light of the laser beam by using a correction value of a correction block corresponding to a scanning position on the basis of the correction value stored in the correction value storage unit and the correction value calculated by the correction value interpolation unit.

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for correcting a light amount at the time of exposure in the image forming apparatus.

  Conventionally, in an exposure apparatus provided in an image forming apparatus, a latent image is formed on the peripheral surface of the photoconductor by scanning the peripheral surface of the photoconductor with a laser beam through a condenser lens or a mirror at a constant speed. The forming technique is known. At this time, due to the characteristics of the optical element, such as the incident angle of the laser beam to the condenser lens that passes through until reaching the peripheral surface of the photosensitive member, and the thickness of the condenser lens, the light amount of the laser beam is It is known that it varies depending on the scanning position on the surface.

  Therefore, in order to uniformly correct the light amount of the laser beam at such a scanning position, for example, in Patent Document 1 below, a light source unit that generates a light beam, a deflection unit that deflects and scans the light beam from the light source unit, In the beam scanning type image forming apparatus having the scanning imaging optical means for condensing the light beam from this deflecting means as a light spot on the surface to be scanned, the scanning position of the light spot is detected and detected. A technique for controlling the light amount of the light source corresponding to the scanning position of the light spot based on the light amount correction data given in advance corresponding to the scanning position is described. The light amount correction data is stored in the storage unit for each portion obtained by dividing the entire scanning position of the light spot into a predetermined number, and is stored in the storage unit for each portion corresponding to the light amount correction data. It describes that light amount correction is performed using light amount correction data.

JP 2000-71510 A

  However, in order to apply the above-described conventional technology, it is necessary to store light amount correction data in advance according to the number of divisions of the peripheral surface of the photoconductor, so a storage area for storing the light amount correction data is provided. When only a small amount could be secured, the number of divisions on the peripheral surface of the photoreceptor had to be reduced. If the number of divisions of the peripheral surface of the photosensitive member is reduced, the size of each divided portion increases, so that a large difference occurs between the light amount correction data given in advance corresponding to the respective portions. There is a possibility that the correction amount of the light amount of the laser light is greatly different between the parts. As a result, in the image formed using the latent image formed on the peripheral surface of the photoconductor by the scanning of the laser beam, there is a possibility that a density change that can be visually recognized by the user at regular intervals may occur.

  The present invention has been made in view of such circumstances, and provides an image forming apparatus that can uniformly correct the amount of laser light that varies depending on the scanning position even if the storage area is small. Objective.

  An image forming apparatus according to the present invention includes a photosensitive member having a peripheral surface on which a latent image is formed, a light source unit that emits laser light, a scanning lens that scans the peripheral surface of the photosensitive member, and a scanning lens. The scanning position of the laser beam on the peripheral surface of the photosensitive member is divided into a predetermined number of correction blocks arranged in the main scanning direction, which is the direction in which the laser beam is scanned, A plurality of correction value storage units each storing a predetermined correction value in association with a plurality of selected correction blocks which are a plurality of correction blocks discretely selected for each set number set in advance in the scanning direction; A correction value corresponding to a correction block located at a position between two selection correction blocks adjacent to each other among the selected correction blocks is associated with the two selection correction blocks and the correction value A correction value interpolation unit that is calculated by interpolating between two correction values stored in the memory unit, a correction value of a correction block that is stored in the correction value storage unit, and a correction value interpolation unit A light amount correction unit that corrects the light amount when the laser light is scanned on the peripheral surface of the photosensitive member based on the correction value of the correction block using the correction value of the correction block corresponding to the scanning position of the laser light; .

  According to this configuration, the correction value corresponding to the correction block located at a position sandwiched between two selection correction blocks adjacent to each other by the correction value interpolation unit is stored in the correction value in association with the two selection correction blocks. It is calculated by interpolating between two correction values stored in the unit. Then, when the laser light is scanned on the peripheral surface of the photoreceptor based on the correction value of the correction block stored in the correction value storage unit and the correction value of the correction block calculated by the correction value interpolation unit by the light amount correction unit. Is corrected using the correction value of the correction block corresponding to the scanning position.

  In other words, since the storage area of the correction value storage unit is small, the number of correction values that can be stored in association with a plurality of correction blocks is limited, and there is a large difference between the correction values. However, the correction value of the correction block located at a position sandwiched between two selection correction blocks adjacent to each other is calculated by interpolating between the correction values corresponding to the two selection correction blocks. For this reason, only the correction value of the selected correction block, which is a part of all the correction blocks, is stored, and the correction blocks adjacent to each other are used for each correction block using the stored small amount of correction values. It can be avoided that the corresponding correction values differ greatly. This makes it possible to uniformly correct the amount of light when the laser beam is scanned on the peripheral surface of the photoreceptor.

  The correction value interpolation unit corresponds to the correction value corresponding to the correction block located at a position sandwiched between two selection correction blocks adjacent to each other among the plurality of selection correction blocks. In addition, it is preferable to calculate by linearly interpolating between two correction values stored in the correction value storage unit.

  According to this configuration, the correction value of the correction block located at a position sandwiched between two selection correction blocks adjacent to each other is calculated by linearly interpolating between the correction values corresponding to the two selection correction blocks. Therefore, the amount of light when the two selected correction blocks are scanned with the laser beam can be gradually increased or decreased, and the correction values corresponding to the respective correction blocks are greatly different between the adjacent correction blocks. You can avoid that. This makes it possible to uniformly correct the amount of light when the laser beam is scanned on the peripheral surface of the photoreceptor.

  Further, the preset set number is 2, and the correction value interpolating unit is arranged in one correction block located at a position sandwiched between two selection correction blocks adjacent to each other among the plurality of selection correction blocks. It is preferable that the corresponding correction value is an average value of the two correction values stored in the correction value storage unit in association with the two selected correction blocks.

  According to this configuration, the average value of the two correction values stored in the correction value storage unit in association with the two selected correction blocks is used, for example, by using a circuit element capable of bit calculation such as a shift register or an adder. It is easy to simplify the configuration of the correction value interpolation unit by being configured to calculate.

  According to the present invention, it is possible to provide an image forming apparatus that can uniformly correct the amount of laser light that varies depending on the scanning position even if the storage area is small.

1 is a schematic structural diagram of a copying machine as an example of an image forming apparatus according to the present invention. 1 is a block diagram illustrating an example of an electrical configuration of a copying machine. An explanatory view for explaining an example of a configuration of an optical scanning device. Explanatory drawing which shows an example of the relationship between the correction value memorize | stored in the correction value memory | storage part, and the correction value calculated in a correction value interpolation part. 6 is a flowchart showing an example of control for correcting the amount of laser light for exposing a photosensitive drum. Explanatory drawing which shows another example of the relationship between the correction value memorize | stored in the correction value memory | storage part, and the correction value calculated in a correction value interpolation part from FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic structural diagram of a copying machine as an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an example of the electrical configuration of the copying machine 1 shown in FIG.

  As shown in FIG. 1, the copying machine 1 includes a main unit 8, a stack tray 3 disposed on the left side of the main unit 8, a document reading unit 5 disposed on the top of the main unit 8, and a document A document feeding unit 6 disposed above the reading unit 5 and a control unit 10 disposed inside the main body unit 8 are provided.

  An operation panel unit 47 is provided at the front part of the copying machine 1. The operation panel unit 47 includes a display unit 473 and an operation key unit 476. The display unit 473 is configured by, for example, a liquid crystal display having a touch panel function. The operation key unit 476 includes various key switches such as a start key for the user to input a print execution instruction and a numeric keypad for inputting the number of copies to be printed.

  The document reading unit 5 includes a scanner unit 51 including an exposure lamp 511 and a CCD (Charge Coupled Device) 512 (FIG. 2), a document table 52 and a document reading slit 53 made of a transparent member such as glass.

  The scanner unit 51 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 52, the scanner unit 51 is moved along the document surface at a position facing the document table 52, and the document image is scanned. The image data acquired while scanning is output to the control unit 10. Further, when reading a document fed by the document feeding unit 6, the document is moved to a position facing the document reading slit 53 and synchronized with the document feeding operation by the document feeding unit 6 via the document reading slit 53. The image of the original is acquired and the image data is output to the control unit 10.

  The document feeding unit 6 includes a document placing unit 61 for placing a document, a document discharge unit 62 for discharging a document whose image has been read, and a document placed on the document placing unit 61. A document transport mechanism 63 is provided that feeds the sheets one by one to transport them to a position facing the document reading slit 53 and discharges them to the document discharge section 62.

  The main body 8 includes a plurality of paper feed cassettes 461, a paper feed roller 412 that feeds the paper from the paper feed cassette 461 one by one and transports it to the image forming unit 40, and an image on the paper that has been carried out of the paper feed cassette 461 An image forming unit 40, a discharge tray 48 on which a sheet on which an image is formed is discharged, and a control unit 10 that controls operation of the entire apparatus.

  The image forming unit 40 includes a paper transport unit 41, an optical scanning device 42, a photosensitive drum (photosensitive member) 43, a developing unit 44, a transfer unit 45, and a fixing unit 46.

  The paper transport unit 41 is provided in the paper transport path in the image forming unit 40, and transports the paper transported by the paper feed roller 412 to the photosensitive drum 43 and transports the paper to the stack tray 3. A transport roller 414 for transporting the paper to the discharge tray 48, and the like.

  The optical scanning device 42 outputs a laser beam based on the image data output from the control unit 10 and exposes the photosensitive drum 43 with the laser beam, thereby forming an electrostatic latent image on the photosensitive drum 43. To do.

  The developing unit 44 forms a toner image by attaching toner to the electrostatic latent image on the photosensitive drum 43. The transfer unit 45 transfers the toner image on the photosensitive drum 43 to a sheet. The fixing unit 46 heats the sheet on which the toner image is transferred to fix the toner image on the sheet.

  The control unit 10 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, a RAM (Random Access Memory) that temporarily stores data, ASIC (Application Specific Integrated Circuits), which is dedicated hardware configured to be capable of high-speed processing of predetermined processing such as image processing, and peripheral circuits thereof are provided.

  As shown in FIG. 2, the document reading unit 5, the image forming unit 40, and the operation panel unit 47 are connected to the control unit 10. The control unit 10 executes the control program stored in the ROM or the like by the CPU, thereby controlling the operation of each unit in the apparatus and executing copying of the document image.

  Specifically, the control unit 10 converts the image data read from the document by the document reading unit 5 into a drive signal S1 of the laser light source and transmits it to the optical scanning device 42, and a latent image on the photosensitive drum 43. Then, an image is formed on the sheet using the developing unit 44, the transfer unit 45, the fixing unit 46, and the sheet conveying unit 41.

  Below, control which correct | amends the light quantity of the laser beam which exposes the photosensitive drum 43 among the control performed by the control part 10 is demonstrated. In relation to the control for correcting the light amount of the laser light, the control unit 10 particularly functions as a correction value storage unit 11, a correction value interpolation unit 12, and a light amount correction unit 13. Details of the correction value storage unit 11, the correction value interpolation unit 12, and the light amount correction unit 13 will be described later.

  FIG. 3 is an explanatory diagram for explaining an example of the configuration of the optical scanning device 42. As shown in FIG. 3, the optical scanning device 42 includes an exposure unit 29, an optical sensor 21, and a DA (digital analog) converter 23.

  The exposure unit 29 includes a laser light source (light source unit) 91, a collimator lens 92, a prism 93, a polygon mirror 94, an f-θ lens (scanning lens) 95, and a drive signal output unit 96.

  The laser light source 91 outputs a laser beam having a light amount corresponding to the signal level of the drive signal S3 output from the drive signal output unit 96.

  The collimator lens 92 condenses the laser light output from the laser light source 91. The prism 93 converts the light transmitted through the collimator lens 92 into parallel light and emits it toward the polygon mirror 94.

  The polygon mirror 94 has a plurality of reflecting surfaces that reflect incident light toward the photosensitive drum 43, and rotates at a constant speed in the direction of an arrow in FIG. 3, for example, by a driving force of a driving motor (not shown).

  The f-θ lens 95 forms an image of the laser beam reflected by the polygon mirror 94 in a spot shape having a predetermined diameter on the peripheral surface of the photosensitive drum 43, and the peripheral surface of the photosensitive drum 43 is formed on the photosensitive drum. 43 is scanned at a constant speed in the main scanning direction, which is the direction in which the support shaft 43a that rotatably supports the shaft 43 extends.

  The amount of laser light when scanning the circumferential surface of the photosensitive drum 43 depends on the scanning position due to optical characteristics such as the incident angle with respect to the f-θ lens 95 and the thickness of the f-θ lens 95. It is known that the amount of light differs.

  Therefore, the drive signal output unit 96 corrects the signal level of the drive signal S1 output from the control unit 10 in accordance with the signal level of a correction signal S2 described later output from the DA converter 23, whereby the laser light source 91 is corrected. The drive signal S3 is generated.

  The optical sensor 21 is provided in the vicinity of the end of the photosensitive drum 43 on the start side of the image scanning line. When receiving the laser beam, the optical sensor 21 outputs a detection signal BD indicating that the laser beam has been received to the control unit 10.

  The DA converter 23 converts the digital signal indicating the light amount correction value input from the control unit 10 into an analog signal, and outputs the analog signal to the drive signal output unit 96 as the correction signal S2.

  Hereinafter, the control for correcting the light amount of the laser light that exposes the photosensitive drum 43 by the correction value storage unit 11, the correction value interpolation unit 12, and the light amount correction unit 13 will be described in detail.

  The correction value storage unit 11 is configured using a non-volatile storage element such as an EEPROM (Electrically Erasable and Programmable Read Only Memory).

  In the correction value storage unit 11, for example, as shown in FIG. 4, a predetermined number (15 in FIG. 4) of scanning positions of laser light on the peripheral surface of the photosensitive drum 43 is arranged in the main scanning direction. The correction blocks B [0] to B [14] are divided into a plurality of correction blocks B [0] to B [14] for each set number preset in the main scanning direction (in FIG. A plurality of selected correction blocks B [0], B [2], B [4], B [6], B [8], B [10] which are a plurality of correction blocks discretely selected. ], B [12], B [14], and predetermined correction values D [0], D [2], D [4], D [6] for correcting the amount of laser light. , D [8], D [10], D [12], D [14] are stored.

  Here, the numbers in parentheses described as subscripts of the correction block B indicate the order in which the correction blocks are arranged in the main scanning direction. That is, when n is an integer, the correction block B [n] and the correction block B [n + 1] indicate that they are adjacent to each other in the main scanning direction, and the laser beam is at a position corresponding to the correction block B [n]. After scanning, the position corresponding to the correction block B [n + 1] is scanned. A correction value D [n] indicates a correction value corresponding to the correction block B [n].

  The predetermined correction value associated with the selected correction block is determined based on an actual measurement value of the optical characteristic of the f-θ lens 95, for example, by a test operation before the product of the copying machine 1 is shipped.

  The correction value interpolation unit 12 associates a correction value corresponding to a correction block located at a position sandwiched between two selection correction blocks adjacent to each other among the plurality of selection correction blocks with the two selection correction blocks. Calculation is performed by interpolating between two correction values stored in the correction value storage unit 11.

  For example, as shown in FIG. 4, the correction value interpolation unit 12 corresponds to a correction block B [1] located at a position sandwiched between two selection correction blocks B [0] and B [2] adjacent to each other. The two correction values D [0] and D [2] stored in the correction value storage unit 11 in association with the two selected correction blocks B [0] and B [2]. Calculated as the average value of.

  Similarly, the correction value interpolation unit 12 corrects the correction value D corresponding to the correction block B [3] located at a position sandwiched between two adjacent selection correction blocks B [2] and B [4]. [3] is an average value of two correction values D [2] and D [4] stored in the correction value storage unit 11 in association with the two selected correction blocks B [2] and B [4]. Calculate as

  Similarly, the correction value interpolation unit 12 calculates the correction value D [5] corresponding to the correction block B [5] as an average value of the two correction values D [4] and D [6], and corrects the correction block. The correction value D [7] corresponding to B [7] is calculated as the average value of the two correction values D [6] and D [8], and the correction value D [9] corresponding to the correction block B [9] is calculated. The correction value D [11] corresponding to the correction block B [11] is calculated as an average value of the two correction values D [8] and D [10], and the two correction values D [10] and D [12]. The correction value D [13] corresponding to the correction block B [13] is calculated as the average value of the two correction values D [12] and D [14].

  In this way, the preset set number is 2, and the correction value interpolating unit 12 calculates the correction value corresponding to one correction block located at a position sandwiched between two adjacent selection correction blocks. When calculating as an average value of two correction values stored in the correction value storage unit 11 in association with the two selected correction blocks, the correction value storage unit 11 stores them in association with the two selection correction blocks. For example, the average value of the two correction values can be calculated by using a circuit element capable of bit calculation such as a shift register or an adder, so that the configuration of the correction value interpolation unit 12 is simplified. It becomes easy.

  When the light amount correction unit 13 receives the detection signal BD output from the optical sensor 21, the light amount correction unit 13 reads out from the correction value storage unit 11 or synchronizes with the scanning position of the laser beam by the exposure unit 29 or by the correction value interpolation unit 12. A digital signal indicating the calculated correction value of the correction block corresponding to the scanning position is output to the DA converter 23.

  The light amount correction unit 13 measures an elapsed time from the time when the detection signal BD signal is received by a timer or the like built in the control unit 10, and on the circumferential surface of the photosensitive drum 43 based on the measured time. The scanning position of the laser beam moving at a constant speed is grasped. Thus, the light amount correction unit 13 can output a digital signal indicating a correction value to the DA converter 23 while synchronizing with the scanning position of the laser beam.

  Hereinafter, the flow of control for correcting the amount of laser light for exposing the photosensitive drum 43 will be described with reference to FIG.

  When the user inputs a copy function execution instruction by operating the operation panel unit 47 or the like, and the control unit 10 starts the image forming operation by the image forming unit 40 in accordance with the image data output from the document reading unit 5 ( S1), the control unit 10 outputs a drive signal S1 having a predetermined signal level to the drive signal output unit 96 (S2).

  The drive signal output unit 96 generates the drive signal S3 of the laser light source 91 without correcting the signal level of the drive signal S1 output from the control unit 10, and the predetermined signal level from the laser light source 91 is generated. The laser beam is output (S3).

  When the light amount correction unit 13 receives the detection signal BD output from the optical sensor 21 (S4; YES), the correction value of the correction block corresponding to the position where the laser beam is subsequently scanned is read from the correction value storage unit 11. Read and acquire (S5). Here, the light amount correction unit 13 can read out and acquire the correction value of the correction block corresponding to the position where the laser beam is subsequently scanned from the correction value storage unit 11 (S5; YES), that is, If the correction block corresponds to the selected correction block, the control unit 10 causes step S7 described later to be executed.

  On the other hand, when the light amount correction unit 13 cannot read out and acquire the correction value of the correction block corresponding to the position where the laser beam is subsequently scanned from the correction value storage unit 11, that is, the correction block is the selected correction block. If this is not the case (S5; NO), the correction value interpolation unit 12 is caused to calculate the correction value of the correction block (S6).

  For example, as shown in FIG. 4, when the correction block corresponding to the position where the laser beam is subsequently scanned is correction block B [1] in step S6, the correction value interpolation unit 12 corrects the correction value storage unit 11. Correction values D [0] and D [2] associated with two selection correction blocks B [0] and B [2] sandwiching the correction block B [1] are stored. The average value of the two correction values D [0] and D [2] is calculated and used as the correction value of the correction block B [1].

  Returning to FIG. 5, when the correction value of the correction block corresponding to the scanning position of the laser beam is read out and acquired from the correction value storage unit 11 (S5; YES), or the correction value of the correction block is the correction value interpolation unit. 12 (S6), the control unit 10 in the image data output from the document reading unit 5 forms an image of a latent image formed at a position corresponding to the correction block on the peripheral surface of the photosensitive drum 43. The drive signal S1 having a signal level corresponding to the data is output to the drive signal output unit 96 (S7).

  Then, the light amount correction unit 13 directs the digital signal indicating the correction value of the correction block acquired in step S5 or calculated in step S6 to the DA converter 23 while synchronizing with the scanning position of the laser beam. The correction signal S2 obtained as a result of converting the digital signal into an analog signal is output to the drive signal output unit 96 (S8).

  The drive signal output unit 96 corrects the signal level of the drive signal S1 output from the control unit 10 according to the signal level of the correction signal S2 output from the DA converter 23, thereby driving the drive signal of the laser light source 91. S3 is generated, and the laser light having the corrected signal level is output from the laser light source 91 (S9).

  When the time required to scan the laser beam for one correction block has elapsed, that is, when exposure for one correction block on the peripheral surface of the photosensitive drum 43 is completed (S10; YES), the control unit 10 determines whether the exposure for one line is completed (S11).

  When it is determined in step S11 that the exposure for one line has not been completed (S11; NO), the control unit 10 scans the position corresponding to the next correction block arranged in the main scanning direction by the laser beam. Accordingly, the light amount correction unit 13 is caused to execute step S5.

  On the other hand, when it is determined in step S11 that the exposure for one line is completed (S11; YES), the control unit 10 determines whether the exposure for all lines is completed (S12).

  When it is determined in step S12 that the exposure for all the lines has not been completed (S12; NO), the control unit 10 rotates the photosensitive drum 43 at a predetermined rotation angle so as to perform the exposure for the next line. Only the rotation is performed, and the process proceeds to step S2.

  On the other hand, when it is determined in step S12 that the exposure for all the lines has been completed (S12; YES), the control unit 10 ends the exposure of the photosensitive drum 43 by the exposure unit 29 and also the photosensitive drum 43. This completes the control of the correction of the light amount of the laser light for exposing the light.

  As a specific example different from FIG. 4, as shown in FIG. 6, the correction value storage unit 11 has predetermined laser beam scanning positions on the peripheral surface of the photosensitive drum 43 arranged in the main scanning direction. 17 correction blocks B [0] to B [16], which are a predetermined number, and among the correction blocks B [0] to B [16], the preset number 4 is set in the main scanning direction. In correspondence with each of a plurality of selected correction blocks B [0], B [4], B [8], B [12], B [16], which are a plurality of correction blocks discretely selected, It is assumed that predetermined correction values D [0], D [4], D [8], D [12], and D [16] for correcting the amount of laser light are stored.

  In this case, the correction value interpolating unit 12 determines that the correction block corresponding to the scanning position of the laser beam is one of the correction blocks B [1], B [2], and B [3] in step S6. Is a correction value D [0] associated with two adjacent selection correction blocks B [0] and B [4] that sandwich the correction block among the correction values stored in the correction value storage unit 11. , D [4], and linearly interpolate between the two correction values D [0], D [4] to calculate the correction value of the correction block.

Specifically, if the correction block corresponding to the laser beam scanning position is the correction block B [1] in step S6, the correction value interpolation unit 12 sets the correction value D [1] of the correction block B [1]. The linear interpolation is performed between the two correction values D0 and D4 by calculating the following equation (1).
D [1] = D [0] + 1 × (D [4] −D [0]) / 4 (1)

Further, when the correction block corresponding to the laser light scanning position is the correction block B [2] in step S6, the correction value interpolation unit 12 sets the correction value D [2] of the correction block B [2] as follows. (2) is linearly interpolated between the two correction values D [0] and D [4].
D [2] = D [0] + 2 × (D [4] −D [0]) / 4 (2)

Further, when the correction block corresponding to the laser light scanning position is the correction block B [3] in step S6, the correction value interpolation unit 12 sets the correction value D [3] of the correction block B [3] as follows. (2) is linearly interpolated between the two correction values D [0] and D [4].
D [3] = D [0] + 3 × (D [4] −D [0]) / 4 (3)

That is, the preset set number is denoted by m, the number indicating the order in which the correction blocks are arranged in the main scanning direction, and the selection correction block that is scanned earlier of two adjacent selection correction blocks When the number indicating the order of the correction blocks is indicated by q and the number indicating the order of the correction blocks counted from the selected correction block which is the q-th correction block is indicated by r, the correction value interpolating unit 12 is adjacent to the two. By calculating the correction value D [q + r] of the correction block B [q + r] located at a position between the selected correction blocks B [q] and B [q + m] by the following equation (4), Linear interpolation is performed between correction values D [q] and D [q + m] of matching selection correction blocks B [q] and B [q + m].
D [q + r] = D [q] + r × (D [q + m] −D [q]) / m (4)

  As described above, when the correction value of the correction block located at a position between two selection correction blocks adjacent to each other is calculated by linear interpolation between the correction values corresponding to the two selection correction blocks The amount of light at the time of scanning between the two selected correction blocks can be gradually increased or decreased, and the correction value corresponding to each correction block is greatly different between adjacent correction blocks. It can be avoided. As a result, the amount of light when the laser beam is scanned on the peripheral surface of the photosensitive drum 43 can be corrected uniformly.

  According to the above configuration, since the storage area of the correction value storage unit 11 is small, the number of correction values that can be stored is limited, and a large difference occurs between the correction values stored in the correction value storage unit 11. Even if the photosensitive drum 43 is divided into a large number of correction blocks, the correction values of the correction blocks located between the two adjacent selection correction blocks are the values of the two selection correction blocks. Calculated by interpolating between correction values.

  For this reason, only the correction value of the selected correction block, which is a part of all the correction blocks, is stored, and the correction blocks adjacent to each other are used for each correction block using the stored small amount of correction values. It can be avoided that the corresponding correction values differ greatly. As a result, the amount of light when the laser beam is scanned on the peripheral surface of the photosensitive drum 43 can be corrected uniformly.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above-described embodiment, an example in which the image forming apparatus according to the present invention is applied to the copying machine 1 has been described. However, the present invention is not limited thereto, and the image forming apparatus according to the present invention is not limited to a color printer for color image formation, The present invention may be applied to a scanner device, a facsimile device, a printer device, and a copy device.

  In the above embodiment, the configurations and settings shown in FIGS. 1 to 6 are merely examples, and the present invention is not limited to the embodiment.

  For example, the number of laser beam scanning positions on the circumferential surface of the photosensitive drum 43 divided into correction blocks arranged in the main scanning direction (predetermined number) is 15 as shown in FIG. 4 or as shown in FIG. It is not intended to limit the number to 17.

  Further, the preset number is not limited to the two shown in FIG. 4 or the four shown in FIG. 6, but according to the capacity of the storage area available as the correction value storage unit 11. That is, you may change according to the capacity | capacitance of the memory area for memorize | storing the correction value of a selection correction block. For example, when only a small storage area that can be used as the correction value storage unit 11 can be secured, only a small amount of correction values for the selected correction block can be stored. .

DESCRIPTION OF SYMBOLS 10 Control part 11 Correction value memory | storage part 12 Correction value interpolation part 13 Light quantity correction | amendment part 21 Optical sensor 23 DA converter 29 Exposure part 42 Optical scanning device 43 Photosensitive drum (photosensitive body)
91 Laser light source (light source)
94 Polygon mirror 95 f-θ lens (scanning lens)
96 Drive signal output part B Correction block D Correction value

Claims (3)

A photoreceptor having a peripheral surface on which a latent image is formed;
A light source that emits laser light;
A scanning lens that scans the laser beam on the circumferential surface of the photoreceptor;
The scanning position of the laser beam on the peripheral surface of the photosensitive member is divided into a predetermined number of correction blocks arranged in the main scanning direction, which is the direction in which the laser beam is scanned, A correction value storage unit that stores a predetermined correction value in association with a plurality of selected correction blocks that are a plurality of correction blocks discretely selected for each set number preset in the scanning direction;
A correction value corresponding to a correction block located at a position between two selection correction blocks adjacent to each other among the plurality of selection correction blocks is stored in the correction value storage unit in association with the two selection correction blocks. A correction value interpolation unit that calculates by interpolating between two correction values that are
Based on the correction value of the correction block stored in the correction value storage unit and the correction value of the correction block calculated by the correction value interpolation unit, the amount of light when the laser beam is scanned on the peripheral surface of the photoconductor is determined. A light amount correction unit that corrects using the correction value of the correction block corresponding to the scanning position of the laser beam;
An image forming apparatus comprising:   The correction value interpolating unit associates a correction value corresponding to a correction block located at a position between two adjacent selection correction blocks among the plurality of selection correction blocks with the two selection correction blocks. The image forming apparatus according to claim 1, wherein calculation is performed by linear interpolation between two correction values stored in the correction value storage unit. The preset number is 2,
The correction value interpolation unit corresponds to a correction value corresponding to one correction block located at a position sandwiched between two selection correction blocks adjacent to each other among the plurality of selection correction blocks. The image forming apparatus according to claim 1, wherein an average value of two correction values stored in the correction value storage unit is added.

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