JP2013052650A - Exposure device, image forming apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure device capable of controlling variation in light quantity between light emitting elements, an image forming apparatus, and a program.SOLUTION: The exposure device includes: an EEPROM 112 that memorizes a light-amount non-uniformity correction value after shipment to correct the light quantity of each of LEDs with corrected variation in the light quantity between them under a specific use condition of emitting light so that the variation in the light quantity between LEDs remains within a prescribed range when they emit light under a different use condition; and a correction value operation part 112 that corrects the light quantity of the LED, if a use condition different from the specific use condition is satisfied, which is regarded as a luminescence object according to the light-amount non-uniformity correction value after shipment memorized in the EEPROM.

Description

  The present invention relates to an exposure apparatus, an image forming apparatus, and a program.

  Patent Document 1 discloses a light emitting array in which a plurality of light emitting elements are arranged, lighting signal generating means for generating lighting signals for the plurality of light emitting elements in the light emitting array according to input image data, and a plurality of light emitting arrays in the light emitting array. A sequential lighting means for sequentially lighting the light emitting elements, and the lighting signal generating means takes into account the conditions for the recovery of the power supply voltage to the state of the light emitting element that is turned on Nth (N is an integer of 1 or more). Thus, there is disclosed a light-emitting device that generates a lighting signal for lighting a light-emitting element N + 1th.

  In Patent Document 2, a plurality of light emitting element array members in which a plurality of light emitting elements are arranged in a row, and a signal for sequentially lighting each of the plurality of light emitting elements arranged in each of the plurality of light emitting element array members are arranged. An exposure apparatus comprising: a driving unit that transfers a signal in a direction at a predetermined transfer cycle, wherein the driving unit is configured to change a transfer cycle when transferring a signal.

JP 2005-53145 A JP 2008-93896 A

  An object of the present invention is to provide an exposure apparatus, an image forming apparatus, and a program that suppress variation in the amount of light between light emitting elements.

  In order to achieve the above object, the exposure apparatus according to claim 1 includes a plurality of light emitting elements that are corrected so that a difference in light amount between them when the light is emitted under a specific use condition is within a predetermined range. The light quantity of each of the plurality of light emitting elements is such that the difference in light quantity between the light emitting elements when the plurality of light emitting elements emit light under use conditions other than the specific use conditions except for the type Storage means storing correction information for correcting the light source, and when the use conditions corresponding to the different use conditions are satisfied, among the plurality of light emitting elements according to the correction information stored in the storage means And a correction unit that corrects the light amount of the light emitting element that is the light emission target.

  The exposure apparatus according to claim 1, as in the invention according to claim 2, the light quantity obtained by causing the different use conditions to emit light at the temperature at a predetermined time at the use destination. It is also possible to include at least one of a preset light quantity and a light emission interval of the light emitting element.

  According to a second aspect of the present invention, in the exposure apparatus according to the third aspect, the number specifying information for specifying the number of light emitting elements that are actually light-emitting among the plurality of light emitting elements, as in the invention according to the third aspect. May be further included.

  In the exposure apparatus according to claim 1, as in the invention according to claim 4, the different use conditions may be the number of light emitting elements that actually emit light among the plurality of light emitting elements. .

  In order to achieve the above object, the exposure apparatus according to claim 5 includes a plurality of light emitting elements that are corrected so that a difference in light amount between them when the light is emitted under a specific use condition is within a predetermined range. The plurality of light emitting elements so that the difference in light quantity between the light emitting elements when the plurality of light emitting elements emit light under each of a plurality of use conditions different from the specific use conditions except for the type is within a predetermined range. When the storage means for storing the correction information for correcting the light quantity of each of the elements corresponding to each of the plurality of use conditions and the use condition corresponding to any of the plurality of use conditions are satisfied, Of the correction information stored in the storage means, the light emitting element of the plurality of light emitting elements to be emitted according to the correction information corresponding to the use condition corresponding to the use condition satisfied at the present time. Correction means for correcting the amount of light; Was constructed comprise.

  In the exposure apparatus according to claim 5, as in the invention according to claim 6, each of the plurality of use conditions causes the light emitting element to emit light at a temperature at a predetermined time at the use destination. The obtained light quantity may include at least one of a preset light quantity and a light emission interval of the light emitting element.

  In the exposure apparatus according to claim 6, as in the invention according to claim 7, each of the plurality of use conditions specifies the number of light emitting elements that actually emit light among the plurality of light emitting elements. The number specifying information may be further included.

  In the exposure apparatus according to claim 5, as in the invention according to claim 8, each of the plurality of use conditions is the number of light emitting elements that actually emit light among the plurality of light emitting elements. It is also good.

  In the exposure apparatus according to any one of claims 1 to 8, as in the invention according to claim 9, each of the plurality of light emitting elements is arranged in a predetermined direction and extends along the predetermined direction. The plurality of light emitting element groups disposed in series may be included, and the plurality of light emitting elements may sequentially emit light from one end to the other end in the predetermined direction.

  In order to achieve the above object, the image forming apparatus according to claim 10 emits light from the exposure apparatus according to any one of claims 1 to 9 and the plurality of light emitting elements of the exposure apparatus. The electrostatic latent image formed on the surface of the photoconductor is irradiated with the irradiated light to develop the developed image as a developed image with a developer, and the developed image is transferred to a recording medium. And image forming means for forming an image.

  In order to achieve the above object, a plurality of light emitting elements corrected so that a light amount difference between them when a program according to claim 11 emits light under a specific use condition is within a predetermined range, and Except for the type, the light quantity of each of the plurality of light emitting elements is adjusted so that the light quantity difference between the light emitting elements when the plurality of light emitting elements are caused to emit light under use conditions different from the specific use conditions. When a computer that controls an exposure apparatus including a storage unit that stores correction information for correction satisfies a use condition corresponding to the different use condition, the computer stores the correction unit according to the correction information stored in the storage unit. It is intended to function as a correction unit that corrects the light amount of the light emitting element that is a light emitting target among the plurality of light emitting elements.

  In order to achieve the above object, a plurality of light emitting elements corrected so that a light amount difference between them when a program according to claim 12 is made to emit light under a specific use condition is within a predetermined range, and The plurality of light emitting elements so that the difference in light quantity between the light emitting elements when the plurality of light emitting elements emit light under each of a plurality of use conditions different from the specific use conditions except for the type is within a predetermined range. A computer that controls an exposure apparatus including a storage unit that stores correction information for correcting the amount of light corresponding to each of the plurality of use conditions, and uses the computer corresponding to any of the plurality of use conditions When the condition is satisfied, the light emission of the plurality of light emitting elements according to the correction information corresponding to the use condition corresponding to the use condition currently satisfied among the correction information stored in the storage unit Subject and The light amount of the light-emitting element was assumed to function as correcting means for correcting.

  According to the inventions according to claims 1, 5, and 10 to 12, when the use conditions other than the type satisfy the use conditions different from the specific use conditions, they are stored in the storage means. Compared to the case where the light amount of the light emitting element is not corrected according to the correction information, the effect that the variation in the light amount between the light emitting elements is suppressed can be obtained.

  According to the invention according to claim 2 and claim 6, the use condition different from the specific use condition is the temperature measured at a predetermined time at the use destination, and the amount of light obtained by causing the light emitting element to emit light. As compared with the case where the light amount set in advance and the condition including at least one of the light emission intervals of the light emitting element are not used, the effect that the variation in the light amount between the light emitting elements is easily and highly accurately suppressed can be obtained.

  According to the inventions according to claim 3, claim 4, claim 7, and claim 8, light emission that is actually emitted from a plurality of light emitting elements under use conditions different from the specific use conditions except for the type. Compared to the case where the number of elements is not used, there is an effect that the variation in the amount of light between the light emitting elements is easily and highly accurately suppressed.

  According to the ninth aspect of the present invention, each of the plurality of light emitting elements includes a plurality of light emitting element groups arranged in a predetermined direction and arranged in series along the predetermined direction. Compared to the case where there is no configuration in which light is emitted in order from one end to the other in the direction, there is an effect that the variation in the amount of light between the light emitting elements is easily and highly accurately suppressed.

1 is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to a first embodiment. It is a schematic block diagram which shows an example of a structure of the LED print head (LPH) which concerns on 1st Embodiment. It is a schematic block diagram which shows an example of a structure of the LED circuit board which concerns on 1st Embodiment. It is a schematic block diagram which shows an example of the circuit structure of SLED which concerns on 1st Embodiment. 1 is a block diagram illustrating an example of a configuration of a signal generation circuit according to a first embodiment. It is a block diagram which shows an example of a structure of the reference clock generation part which concerns on 1st Embodiment. It is a block diagram which shows an example of a structure of the lighting time control and drive part which concerns on 1st Embodiment. It is a schematic block diagram which shows an example of the wiring between the signal generation circuit formed on the LED circuit board which concerns on 1st Embodiment, and SLED. It is a schematic block diagram which shows an example of a structure of the LED chip which concerns on 1st Embodiment. It is a wave form diagram which shows an example of the displacement of the magnitude | size of the voltage applied to LED contained in the edge part of SLED which concerns on 1st Embodiment. The displacement of the magnitude of the voltage applied to the LED included in the end of the SLED according to the first embodiment, the magnitude of the voltage when the printing speed is 175 mm / sec and 225 mm / sec. It is a wave form diagram which shows an example of a displacement. It is a wave form diagram which shows an example of the light quantity displacement of LED included in the edge part of SLED which concerns on 1st Embodiment, Comprising: When the printing speed is 121 mm / sec and 225 mm / sec. It is a wave form diagram which shows an example of the difference (light quantity difference) of two waveforms shown in FIG. It is a wave form diagram which shows an example of the light quantity displacement when it is the light quantity displacement of LED contained in the edge part of SLED which concerns on 1st Embodiment, and a setting light quantity is 0.6 mJ and 1.8 mJ. It is a wave form diagram which shows an example of the difference (light quantity difference) of two waveforms shown in FIG. Difference in light amount displacement (light amount difference) of LEDs included in the end portion of the SLED according to the first embodiment, which is a difference between the light amount displacement when the measurement temperature is 14 ° C. and the light amount displacement when the measurement temperature is 46 ° C. It is a wave form diagram which shows an example. It is a schematic diagram which shows an example of the light quantity nonuniformity correction database which concerns on 1st Embodiment. The displacement of the magnitude of the voltage applied to the LED included in the end of the SLED according to the first embodiment, the magnitude of the voltage when the printing speed is 175 mm / sec and 225 mm / sec. It is a wave form diagram which shows an example of the displacement for 1 period. FIG. 19 is a waveform diagram showing an example of a waveform obtained by converting a difference between two waveforms shown in FIG. 18 into a light amount variation rate. It is a flowchart which shows an example of the flow of a process of the 1st correction value calculation processing program which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of a process of the 2nd correction value calculation processing program which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of a process of the 3rd correction value calculation processing program which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of a process of the 4th correction value calculation processing program which concerns on 1st Embodiment. 4 is a time chart illustrating an example of a drive signal output from a signal generation circuit and a level shift circuit according to the first embodiment. An example of the timing at which the lighting signal ΦI, transfer signal CK1, and transfer signal CK2 are output for each line in the sub-scanning direction when the printing speed is 100 mm / sec, and the change in voltage supplied from the three-terminal regulator at that time It is a time chart which showed an example, respectively. An example of the timing at which the lighting signal ΦI, the transfer signal CK1, and the transfer signal CK2 are output for each line in the sub-scanning direction when the printing speed is 150 mm / sec, and the change in the voltage supplied from the three-terminal regulator at that time It is a time chart which showed an example, respectively. It is a schematic diagram which shows an example of the light quantity nonuniformity correction database which concerns on 2nd Embodiment. It is a flowchart which shows an example of the flow of a process of the correction value calculation processing program which concerns on 2nd Embodiment.

  Hereinafter, an example of an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus using a print head which is an example of an exposure apparatus according to the first embodiment. The image forming apparatus shown in FIG. 1 is a so-called tandem digital color printer, and an image forming process unit 10 serving as an image forming unit that forms an image corresponding to image data of each color, and the operation state of the image forming apparatus. And a control unit 30 that acquires various types of information and controls the operation of the image forming apparatus. The image forming apparatus shown in FIG. 1 is connected to an external device such as a personal computer (PC) 2 or an image reading device 3, for example, and an image processing unit 40 that performs predetermined image processing on image data received from these devices. It has.

  The image forming process unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (hereinafter collectively referred to simply as “image forming unit 11”) that are arranged in parallel at a predetermined interval. Yes. Each image forming unit 11 includes a photosensitive drum 12 as an image holding member that forms an electrostatic latent image and holds a toner image, a charger 13 that uniformly charges the surface of the photosensitive drum 12 with a predetermined potential, and a charger 13. An LED print head (LPH) 14 as an example of an exposure device that exposes the photosensitive drum 12 charged by the image based on image data, a developing device 15 that develops an electrostatic latent image formed on the photosensitive drum 12, And a cleaner 16 for cleaning the surface of the photosensitive drum 12 after transfer. Each image forming unit 11 forms a toner image that is an example of a developed image with toner that is an example of a developer of yellow (Y), magenta (M), cyan (C), and black (K). . Furthermore, each image forming unit 11 includes a temperature sensor 17 that measures the temperature of each specific area (for example, an area within a predetermined distance from the LPH 14), and the temperature measured by the temperature sensor 17 is acquired by the control unit 30. Is done.

  The image forming process unit 10 includes an intermediate transfer belt 21 onto which the toner images of the respective colors formed on the photosensitive drums 12 of the image forming units 11 are transferred, and the color toner images of the image forming units 11 to the intermediate transfer belt 21. A primary transfer roll 22 that sequentially transfers (primary transfer) to the paper, and a secondary transfer roll 23 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the intermediate transfer belt 21 onto a sheet P that is a recording material (recording paper). , And a fixing device 25 for fixing the second-transferred image on the paper P.

  In the image forming apparatus according to the first embodiment, the image forming process unit 10 performs an image forming operation based on a control signal such as a synchronization signal supplied from the control unit 30. At that time, the image data input from the PC 2 or the image reading device 3 is subjected to image processing by the image processing unit 40 and supplied to each image forming unit 11 via the interface. In the yellow image forming unit 11Y, for example, the surface of the photosensitive drum 12 uniformly charged at a predetermined potential by the charger 13 is exposed by the LPH 14 that emits light based on the image data obtained from the image processing unit 40. Then, an electrostatic latent image is formed on the photosensitive drum 12. The electrostatic latent image formed on the photosensitive drum 12 is developed by the developing device 15, and a yellow (Y) toner image is formed on the photosensitive drum 12. Similarly, magenta (M), cyan (C), and black (K) toner images are also formed in the image forming units 11M, 11C, and 11K.

  Each color toner image formed by each image forming unit 11 is sequentially electrostatically attracted by the primary transfer roll 22 onto the intermediate transfer belt 21 rotating in the direction of the arrow in FIG. A toner image (superimposed toner image) is formed. The superimposed toner image is conveyed to a region (secondary transfer portion) where the secondary transfer roll 23 is disposed as the intermediate transfer belt 21 moves. When the superimposed toner image is conveyed to the secondary transfer unit, the paper P is supplied to the secondary transfer unit in accordance with the timing at which the superimposed toner image is conveyed to the secondary transfer unit. Then, the superimposed toner images are collectively electrostatically transferred onto the conveyed paper P by the transfer electric field formed by the secondary transfer roll 23 in the secondary transfer portion.

  Thereafter, the sheet P on which the superimposed toner image has been electrostatically transferred is peeled off from the intermediate transfer belt 21 and conveyed to the fixing device 25 by the conveying belt 24. The unfixed toner image on the paper P conveyed to the fixing device 25 is fixed on the paper P by being subjected to fixing processing by heat and pressure by the fixing device 25. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge placement portion (not shown) provided in the discharge portion of the image forming apparatus.

  FIG. 2 is a diagram showing the configuration of an LED print head (LPH) 14 that is an exposure apparatus. As shown in FIG. 2, the LPH 14 includes a housing 61 as a support, an LED circuit board 62 on which a self-scanning LED array (SLED) 63 and a signal generation circuit 100 (see FIG. 3) for driving the SLED 63 are mounted. A rod lens array 64 that is an optical member that forms an image of light from the SLED 63 on the surface of the photosensitive drum 12, a holder 65 that supports the rod lens array 64 and shields the SLED 63 from the outside, and a housing 61 that is a rod lens. And a leaf spring 66 that pressurizes in the direction of the array 64.

  The housing 61 is formed of a block or sheet metal such as aluminum or SUS, and supports the LED circuit board 62. The holder 65 supports the housing 61 and the rod lens array 64, and is set so that the light emitting point of the SLED 63 and the focal point of the rod lens array 64 coincide. Furthermore, the holder 65 is configured to seal the SLED 63. This prevents dust from adhering to the SLED 63 from the outside. On the other hand, the leaf spring 66 presses the LED circuit board 62 in the direction of the rod lens array 64 through the housing 61 so as to maintain the positional relationship between the SLED 63 and the rod lens array 64.

  The LPH 14 configured in this manner is configured to be movable in the optical axis direction of the rod lens array 64 by an adjustment screw (not shown), and the imaging position (focal plane) of the rod lens array 64 is the surface of the photosensitive drum 12. It is adjusted so that it is located above.

  As shown in FIG. 3 (a plan view of the LED circuit board 62), the LED circuit board 62 includes SLED chips (CHIP1 to CHIP58) as examples of 58 light emitting element array members. Are arranged in a straight line with high accuracy so as to be parallel to the axial direction of the photosensitive drum 12. In this case, each LED array is continuous at the connecting portion between the SLED chips at the end boundary of the array (LED array) of the light emitting elements (LEDs) arranged along the axial direction on each SLED chip (CHIP1 to CHIP58). The SLED chips are alternately arranged in a staggered pattern so that they are arranged in series and arranged in series.

  The LED circuit board 62 includes a signal generation circuit 100 and a level shift circuit 104 that generate a signal (lighting signal) for driving the SLED 63, a three-terminal regulator 101 that outputs a predetermined voltage, a light amount unevenness correction value of the SLED 63, and the like. And a harness 103 that transmits / receives signals to / from the control unit 30 and the image processing unit 40.

  Next, the SLED 63 provided on the LED circuit board 62 will be described. FIG. 4 is a diagram for explaining an example of the circuit configuration of the SLED 63. The SLED 63 shown in FIG. 4 shows an SLED chip for resolution (light emitting element arrangement density) 600 dpi (dot per inch) as an example, and 256 light emitting points (LEDs) are arranged per SLED chip.

  The SLED 63 according to the first embodiment is connected to the signal generation circuit 100 via the level shift circuit 104. The level shift circuit 104 has a configuration in which a resistor R1B and a capacitor C1, and a resistor R2B and a capacitor C2 are arranged in parallel, one end of which is connected to the input terminal of the SLED 63, and the other end of the signal generation circuit 100. Connected to the output terminal. Based on the transfer signals CK1R and CK1C and the transfer signals CK2R and CK2C output from the signal generation circuit 100, the transfer signal CK1 and the transfer signal CK2 are output to the SLED 63.

  In the SLED 63 of the first embodiment, 58 SLED chips are arranged in series, but FIG. 4 shows only one SLED chip and a signal line connected thereto.

  The SLED chip according to the first embodiment shown in FIG. 4 includes 128 thyristors S1 to S128 as switching elements, 128 LEDs L1 to L128 as light emitting elements, and 128 diodes D1 to D128, 128. A pair of units each having transfer current limiting resistors R1A and R2A for preventing excessive current from flowing through the resistors R1 to R128 and the signal lines Φ1 and Φ2 are along the longitudinal direction of the chip frame (the axial direction). Are arranged in a straight line (see FIG. 9). Hereinafter, in order to avoid complications, one unit of the pair of units included in the SLED chip will be described.

  In the SLED chip shown in FIG. 4, the anode terminals (input terminals) A <b> 1 to A <b> 128 of the thyristors S <b> 1 to S <b> 128 are connected to the power supply line 105. The power supply line 105 is supplied with the output voltage VDD (VDD = + 3.5 V) of the three-terminal regulator 101.

  .., S127 are supplied with the transfer signal CK1 from the signal generation circuit 100 and the level shift circuit 104 via the transfer current limiting resistor R1A. The cathode terminals (output terminals) K1, K3,... K127 of the odd-numbered thyristors S1, S3,. Sent.

  In addition, the transfer signal CK2 from the signal generation circuit 100 and the level shift circuit 104 is transferred to the transfer current limiting resistor R2A at the cathode terminals (output terminals) K2, K4,... K128 of the even-numbered thyristors S2, S4,. Sent through.

  On the other hand, gate terminals (control terminals) G1 to G128 of the thyristors S1 to S128 are respectively connected to the power supply line 106 via resistors R1 to R128 provided corresponding to the thyristors S1 to S128. The power supply line 106 is grounded (GND).

The gate terminals G1 to G128 of the thyristors S1 to S128 are connected to the gate terminals of the LEDs L1 to L128 provided corresponding to the thyristors S1 to S128, respectively.

  Furthermore, the cathode terminals of the diodes D1 to D128 are connected to the gate terminals G1 to G128 of the thyristors S1 to S128. The gate terminals G1 to G127 of the thyristors S1 to S127 are connected to the anode terminals of the next-stage diodes D2 to D128, respectively. That is, the diodes D1 to D128 are connected in series with the gate terminals G1 to G127 interposed therebetween.

  The anode terminal of the diode D1 is connected to the signal generation circuit 100 via the transfer current limiting resistor R2A and the level shift circuit 104, and the transfer signal CK2 is transmitted. Further, the cathode terminals of the LEDs L1 to L128 are connected to the signal generation circuit 100, and the lighting signal ΦI is transmitted.

  Further, a light shielding mask 50 is disposed on the SLED 63 so as to cover the thyristors S1 to S128 and the diodes D1 to D128. This is because during the image forming operation, light emission from the thyristors S1 to S128 in the on state and current is flowing, and from the diodes D1 to D128 in the current flow state is blocked, and unnecessary light is removed from the photoconductor. It is provided to suppress exposure of the drum 12.

  Next, the signal generation circuit 100 provided on the LED circuit board 62 will be described. FIG. 5 is a block diagram illustrating an example of the configuration of the signal generation circuit 100. The signal generation circuit 100 includes an image data development unit 110, a correction value calculation unit 112, a timing signal generation unit 114, a reference clock generation unit 116, and a lighting time control / drive unit 118 (118-1 to 118-58). It is configured.

  Image data expansion unit 110 is serially supplied with image data from image processing unit 40. The image data development unit 110 transmits the supplied image data for each SLED chip (CHIP1 to CHIP58) such as the 1st to 128th dots, the 129th to 256th dots,. Processes such as dividing into data. The divided image data is output to the lighting time control / drive units 118-1 to 118-58.

  The correction value calculation unit 112 is serially supplied with image data from the image processing unit 40. The correction value calculation unit 112 calculates a light amount unevenness correction value used for correcting variations in the amount of emitted light for each LED in the SLED 63 based on the supplied image data. In synchronization with the data read signal from the signal generator 114, the correction value is output to the lighting time control / drive units 118-1 to 118-58. The light amount unevenness correction value is, for example, data in a profile format set for each LED of 2 dots. Note that the present invention is not limited to this, and data in a profile format set for each LED for one dot may be used. In this case, for example, data is formed as 8 bits (0 to 255).

In the EEPROM 102, the image forming apparatus is actually started before shipping so that the unevenness in the amount of light between the LEDs included in the LPH 14 is within a predetermined error (for example, 1% error), and the unevenness in the amount of light between the LEDs is corrected. This is a light amount unevenness correction value calculated in advance assuming use conditions (pre-shipment use conditions) at the time of image processing, and is applied when actually correcting the light amount unevenness between LEDs by actually starting the image forming apparatus before shipping. The stored light amount unevenness correction value (pre-shipment light amount unevenness correction value) is stored. The pre-shipment light amount unevenness correction value is stored in a profile format in units of SLED chips. Further, the EEPROM 102 is calculated in advance so that the non-uniformity in the amount of light between the LEDs in the LPH 14 for each of a plurality of use conditions that are different from the pre-shipment use conditions except for each type is within a predetermined error (for example, 1% error). The light amount unevenness correction value applied when the image forming apparatus is actually started up at the installation destination of each image forming apparatus after shipping to correct the light amount unevenness between LEDs (light amount unevenness after shipment). A light amount unevenness correction database including a correction value is stored. Further, a post-shipment light amount unevenness correction value is also stored in a profile format in units of SLED chips.
In the first embodiment, printing speed, temperature, light quantity, and LED emission interval (printing speed as an example) are applied as types of use conditions. The size of the usage conditions is the same before and after shipment, with the above types unchanged. That is, in the first embodiment, the change in usage conditions before and after shipment means that the printing speed, temperature, light quantity, and LED emission interval change.

  The correction value calculation unit 112 acquires a pre-shipment light amount unevenness correction value from the EEPROM 102 when the machine power is turned on before shipment, and the acquired pre-shipment light amount unevenness correction value is turned on for the lighting time control / drive units 118-1 to 118-. 58. Further, when the machine power is turned on after shipment, a light amount unevenness correction database is acquired from the EEPROM 102, and a correction value is obtained based on at least the light amount unevenness database among the acquired light amount unevenness correction database and the image data supplied from the image processing unit 40. The derived correction value is output to the lighting time control / drive units 118-1 to 118-58.

  The reference clock generation unit 116 is connected to the control unit 30, the timing signal generation unit 114, and the lighting time control / drive units 118-1 to 118-58.

  As shown in FIG. 6 (a block diagram illustrating the configuration of the reference clock generation unit 116), the reference clock generation unit 116 includes a crystal oscillator 140, a frequency divider 1 / M142, a frequency divider 1 / N144, and a phase comparator. 146 and a PLL circuit 134 having a voltage controlled oscillator 148, and a lookup table (LUT) 132. The LUT 132 stores a table for determining the frequency division ratios M and N based on the light amount adjustment data from the control unit 30. The crystal oscillator 140 is connected to the frequency divider 1 / N144, oscillates at a predetermined frequency, and outputs the oscillated signal to the frequency divider 1 / N144. The frequency divider 1 / N 144 is connected to the LUT 132 and the phase comparator 146, and divides the signal oscillated by the crystal oscillator 140 based on the frequency division ratio N determined by the light amount adjustment data from the LUT 132. The phase comparator 146 is connected to the frequency divider 1 / M142, the frequency divider 1 / N144, and the voltage controlled oscillator 148, and the output signal from the frequency divider 1 / M142 and the frequency divider 1 / N144. Is compared with the output signal. The control voltage supplied to the voltage controlled oscillator 148 is controlled according to the comparison result (phase difference) by the phase comparator 146. The voltage controlled oscillator 148 outputs a clock signal at a frequency based on the control voltage. In the first embodiment, a control voltage corresponding to a frequency that divides the lighting-enabled period into 256 is supplied, a clock signal (reference clock signal) having this frequency is generated, and the timing signal generator 114 and all the Output to lighting time control / drive units 118-1 to 118-58. The voltage controlled oscillator 148 is also connected to the frequency divider 1 / M142, and the clock signal output from the voltage controlled oscillator 148 is also branched and input to the frequency divider 1 / M142. The frequency divider 1 / M 142 divides the clock signal fed back from the voltage controlled oscillator 148 based on the frequency division ratio M determined by the light amount adjustment data from the LUT 132.

  The timing signal generation unit 114 is connected to the control unit 30 and the reference clock generation unit 116, and is synchronized with the horizontal synchronization signal (Lsync) from the control unit 30 based on the reference clock signal from the reference clock generation unit 116. Thus, transfer signals CK1R and CK1C and transfer signals CK2R and CK2C are generated. The transfer signals CK1R and CK1C and the transfer signals CK2R and CK2C are transferred to the SLED 63 as the transfer signal CK1 and the transfer signal CK2 through the level shift circuit 104. In FIG. 5, the timing signal generation unit 114 is described so as to output one set of transfer signals CK1R and CK1C and transfer signals CK2R and CK2C, but actually, a plurality of sets (for example, six sets) are output. Transfer signals CK1R and CK1C and transfer signals CK2R and CK2C are output.

  The timing signal generation unit 114 is connected to the correction value calculation unit 112 and the image data development unit 110 and is synchronized with the Lsync signal from the control unit 30 based on the reference clock signal from the reference clock generation unit 116. Thus, a data read signal for reading image data corresponding to each pixel from the image data development unit 110, and a data read signal for reading a light amount unevenness correction value corresponding to each pixel (each LED) from the correction value calculation unit 112 Are output for each. Further, the timing signal generation unit 114 is also connected to the lighting time control / drive units 118-1 to 118-58, and based on the reference clock signal from the reference clock generation unit 116, the trigger signal TRG for starting the lighting of the SLED 63. Is output.

  The lighting time control / drive units 118-1 to 118-58 correct the lighting time of each pixel (each LED) based on the light amount unevenness correction value supplied from the correction value calculation unit 112 and light each pixel of the SLED 63. A lighting signal ΦI (ΦI1 to ΦI58) is generated. Specifically, the lighting time control / drive units 118-1 to 118-58 are presettable digital one-shot multi, as shown in FIG. 7 (block diagram for explaining the configuration of the lighting time control / drive unit 118). A vibrator (PDOMV) 160, a linearity correction unit 162, and an AND circuit 170 are included. The AND circuit 170 is connected to the image data development unit 110 and the timing signal generation unit 114. When the image data from the image data development unit 110 is 1 (ON), the AND signal 170 receives the trigger signal TRG from the timing signal generation unit 114. When the image data is output to the PDOMV 160 and the image data is 0 (OFF), the trigger signal is set not to be output. The PDOMV 160 is connected to the AND circuit 170, the OR circuit 168, the correction value calculation unit 112, and the reference clock generation unit 116, and the number of clock pulses corresponding to the image data is synchronized with the trigger signal from the AND circuit 170. Is generated.

  The linearity correction unit 162 corrects and outputs the lighting pulse signal from the PDOMV 160 in order to correct the variation in the light emission start time of each LED in the SLED 63. Specifically, the linearity correction unit 162 includes a plurality of delay circuits 164 (eight of 164-0 to 164-7 in the first embodiment), a delay signal selection unit 165, a delay selection register 166, The circuit includes an AND circuit 167, an OR circuit 168, and a lighting signal selection unit 169. The delay circuits 164-0 to 164-7 are connected to the PDOMV 160, and different times for delaying the lighting pulse signal from the PDOMV 160 are set. The delay selection register 166 is connected to the delay signal selection unit 165 and the lighting signal selection unit 169, and the delay selection register 166 stores the delay selection data for each LED in the SLED 63 and the lighting signal selection data. . The delay selection data and lighting signal selection data for each LED are measured in advance and stored in the EEPROM 102. The delay selection data and lighting signal selection data stored in the EEPROM 102 are downloaded to the delay selection register 166 when the machine power is turned on. Note that a flash ROM can also be used as the storage means, and in that case, the flash ROM itself can function as the delay selection register 166.

  The delay signal selection unit 165 is connected to the AND circuit 167 and the OR circuit 168, and is one of outputs from the delay circuits 164-0 to 164-7 based on the delay selection data stored in the delay selection register 166. Select one. The AND circuit 167 lights up the logical product of the lighting pulse signal from the PDOMV 160 and the delayed lighting pulse signal selected by the delay signal selection unit 165, that is, both the lighting pulse signal before the delay and the lighting pulse signal after the delay are turned on. If it is in a state, a lighting pulse is output. The OR circuit 168 lights up the logical sum of the lighting pulse signal from the PDOMV 160 and the delayed lighting pulse signal selected by the delay signal selection unit 165, that is, at least one of the lighting pulse signal before the delay and the lighting pulse signal after the delay is turned on. If it is in a state, a lighting pulse is output.

  The lighting signal selection unit 169 selects one of the outputs from the AND circuit 167 or the OR circuit 168 based on the lighting selection data stored in the delay selection register 166. Then, the selected lighting pulse is output as the lighting signal ΦI to the SLED 63 via the MOSFET 172.

  Further, as shown in FIG. 5, a three-terminal regulator 101 is connected to the SLED 63, and an output voltage VDD = + 3.5 V from the three-terminal regulator 101 is supplied to drive the SLED 63.

  The signal generation circuit 100 configured in this way is connected to the SLED 63 via the level shift circuit 104 by wiring formed on the LED circuit board 62. Then, signals (drive signals) for driving the SLED 63 such as the generated lighting signals ΦI (ΦI1 to ΦI58), transfer signals CK1R and CK1C, transfer signals CK2R and CK2C, and transfer signals CK1 and CK2 are output.

  FIG. 8 is a diagram showing wiring between the signal generation circuit 100 formed on the LED circuit board 62 and the SLED 63. As shown in FIG. 8, on the LED circuit board 62, the power supply line 105 that supplies the output voltage from the three-terminal regulator 101 to each SLED chip, the grounded (GND) power supply line 106, and the signal generation circuit 100. A signal line 107 (107_1 to 107_58) that transmits a lighting signal ΦI (ΦI1 to ΦI58) to each SLED chip, and a signal line that transmits a transfer signal CK1 (CK1_1 to 1_6) from the level shift circuit 104 to each SLED chip. 108 (108_1 to 108_6) and a signal line 109 (109_1 to 109_6) for transmitting the transfer signal CK2 (CK2_1 to 2_6) are wired. At that time, six sets of transfer signals CK1 (CK1_1 to CK1_6) and CK2 (CK2_1 to CK2_6) are connected to 9 to 10 SLED chips for each set of transfer signals CK1 and CK2.

  By the way, in the image forming apparatus according to the first embodiment, before the shipment, the variation in the light amount between the LEDs in the individual SLED chips included in the SLED 63 is corrected using the pre-shipment light amount unevenness correction value. . Accordingly, if the use condition after shipment is, for example, the use condition corresponding to the use condition at the time of correction before shipment, by using the pre-shipment light amount unevenness correction value, the variation in the light amount of the SLED chip even after shipment (light amount difference between LEDs) ) Fall within a predetermined error.

  However, if the use conditions after shipment of the image forming apparatus are significantly different from the use conditions at the time of correction before shipment, the amount of light between LEDs in the SLED chip can be corrected even if correction is performed using the pre-shipment light amount unevenness correction value. Variation is not within a predetermined error.

  Each SLED chip is configured by arranging a pair of units so that the light emission order is symmetric in the longitudinal direction (the axial direction) as shown in FIG. 9 as an example. That is, the LED is sequentially emitted one dot at a time from both ends of the SLED chip toward the center. Therefore, in one LED included in the end portion of the SLED chip (here, as an example, the first dot LED located at the tip of a plurality of LEDs arranged linearly included in one unit of the SLED chip) As an example, as shown in FIG. 10, when a voltage related to the first scan is applied, the voltage value rises to 3.446V (to the voltage value of “first dot light emission” shown in FIG. 10), and light emission starts. Along with this, a phenomenon (voltage drop) of dropping to 3.423V occurs. After the voltage drop, the voltage value is restored to 3.428V by feedback control, and the magnitude is maintained until the 128th LED emits light (until "128 dot emission" shown in FIG. 10). Next, since a voltage is applied in a pause period for the second scan, the voltage value rises to 3.446 V, and a voltage drop occurs with the start of light emission related to the second scan.

  Through experiments, the present inventors have found that the magnitude of the voltage drop that occurs in each scan of the LED included in the end of the SLED chip is caused by the light emission speed of the LED, particularly the printing speed. FIG. 11 shows an example of fluctuations in the voltage value of the LED included in the end of the SLED chip when the printing speed is 175 mm / sec and when the printing speed is 225 mm / sec. In the example shown in FIG. 11, the vertical axis indicates the voltage magnitude, and the horizontal axis indicates time. Further, the voltage value profile when the printing speed is 175 mm / sec is indicated by a solid line, and the voltage value profile when the printing speed is 225 mm / sec is indicated by a broken line. As shown in FIG. 11, the LED included in the end portion of the SLED chip (here, as an example, the first dot LED located at the tip of the linearly arranged LEDs included in one unit of the SLED chip) The voltage applied to the LED as the voltage required for light emission (applied voltage) is larger when the printing speed is 225 mm / sec than when the printing speed is 175 mm / sec. The size is larger when the printing speed is 225 mm / sec than when the printing speed is 175 mm / sec. As described above, the difference in the magnitude of the applied voltage and the magnitude of the voltage drop depending on the printing speed naturally appears as a difference in the amount of light between the LEDs.

  FIG. 12 shows an example of the light amount profile of the SLED chip when the printing speed is 121 mm / sec and when the printing speed is 225 mm / sec. In the example shown in FIG. 12, the light amount profile indicated by the solid line indicates the change in light amount when the printing speed is 121 mm / sec, and the light amount profile indicated by the broken line is the case when the printing speed is 225 mm / sec. It shows the change in the amount of light. In the example shown in FIG. 12, the vertical axis indicates the amount of light, and the horizontal axis indicates the position of the LED in the SLED chip. The SLED according to the first embodiment has a length in the scanning direction of 5.4 mm as shown in FIG. As shown in FIG. 12, the influence of the variation in the magnitude of the voltage applied to the LED included in the end of the SLED chip is the case where the printing speed is 121 mm / sec even when the printing speed is 225 mm / sec. Is reflected in the magnitude of the light quantity of the corresponding LED included in the end portion of the SLED chip, and the degree of the influence is larger than the degree of influence on the light quantity of the LED included in the central part of the SLED chip. Further, in the LED included in the end portion of the SLED chip, the degree of decrease in the amount of light is larger when the printing speed is 121 mm / sec than when the printing speed is 225 mm / sec.

  FIG. 13 shows a graph showing the difference between the light quantity profile when the printing speed shown in FIG. 12 is 121 mm / sec and the light quantity profile when the printing speed is 225 mm / sec. As shown in FIG. 13, it can be seen that the light amount difference of the LEDs included in the end portions of the SLED chip is larger than the light amount difference of the LEDs included other than the end portions of the SLED chip. Therefore, when the pre-shipment light amount unevenness correction value is calculated under the usage conditions assuming a printing speed of 225 mm / sec, the print speed is high even if the light amount unevenness correction is performed using the pre-shipment light amount unevenness correction value. The light amount in the case of 121 mm / sec is not corrected and appears as periodic uneven light amount. On the contrary, when the pre-shipment light amount unevenness correction value is calculated under the use condition assuming a printing speed of 121 mm / sec, the light amount is calculated using the pre-shipment light amount unevenness correction value under the use condition where the print speed is 225 mm / sec. When the unevenness correction is performed, the correction value is too large, and thus the light amount when the printing speed is 225 mm / sec is not corrected correctly, and the light amount unevenness appears periodically.

  As a cause for causing such periodic unevenness in light quantity, there is a light quantity set directly for each image forming apparatus in addition to a printing speed individually set for each image forming apparatus. As an example of the setting of the light amount in this case, there is an example in which the light amount is set according to the sensitivity of the photosensitive drum 12, the developing method, the use environment, and the like.

  FIG. 14 shows an example of the light amount profile of the SLED chip when the light amount (set light amount) set in the image forming apparatus is 0.6 mJ and when the set light amount is 1.8 mJ. In the example shown in FIG. 14, the light amount profile indicated by the solid line indicates a change in the light amount when the set light amount is 0.6 mJ, and the light amount profile indicated by the broken line indicates the case where the set light amount is 1.8 mJ. It shows the change in the amount of light. In the example shown in FIG. 14, the vertical axis indicates the amount of light, and the horizontal axis indicates the position of the LED in the SLED chip. The SLED according to the first embodiment has a length in the scanning direction of 5.4 mm as shown in FIG. As shown in FIG. 14, regardless of whether the set light amount is 0.6 mJ or 1.8 mJ, the magnitude of the voltage applied to the LED included in the end of the SLED chip is as follows. This affects the magnitude of the light quantity of the LED included in the end of the LED, and the degree of the influence is larger than the degree of influence on the light quantity of the LED included in the central part of the SLED chip. Further, in the LED included in the end portion of the SLED chip, the degree of decrease in the light amount is larger when the set light amount is 0.6 mJ than when the set light amount is 1.8 mJ.

  FIG. 15 is a graph showing the difference between the light amount profile when the set light amount shown in FIG. 14 is 0.6 mJ and the light amount profile when the set light amount is 1.8 mJ. As shown in FIG. 15, the light amount difference of the LEDs included in the end portions of the SLED chip is larger than the light amount difference of the LEDs included other than the end portions of the SLED chip. For this reason, if the pre-shipment light amount unevenness correction value is calculated under the usage conditions assuming a set light amount of 1.8 mJ, the set light amount is not changed even if the pre-shipment light amount unevenness correction value is corrected. The amount of light in the case of 0.6 mJ is not corrected and appears as a periodic uneven amount of light. Conversely, if the pre-shipment light amount unevenness correction value is calculated under the usage conditions assuming a set light amount of 0.6 mJ, the light amount is calculated using the pre-shipment light amount unevenness correction value under the use conditions where the set light amount is 1.8 mJ. When the unevenness correction is performed, the correction value is too large, and thus the light amount in the case of 1.8 mJ is not corrected correctly, and appears as periodic uneven light amount.

  In addition to the printing speed and the set light amount, other causes that cause periodic light amount unevenness include temperature, humidity, and deterioration over time. FIG. 16 is a graph showing the difference between the light intensity profile of the SLED chip when the temperature (measurement temperature) measured by the temperature sensor 17 is 46 ° C. and the light intensity profile of the SLED chip when the measurement temperature is 14 ° C. It is shown. As shown in FIG. 16, it can be seen that the light amount difference of the LEDs included in the end portion of the SLED chip is larger than the light amount difference of the LEDs included other than the end portion of the SLED chip (for example, the central portion of the SLED chip). Therefore, when the pre-shipment light amount unevenness correction value is calculated under the usage conditions assuming a measurement temperature of 46 ° C., the measurement temperature is 14 even if the light amount unevenness correction is performed using the pre-shipment light amount unevenness correction value. The amount of light in the case of ° C. is not corrected and appears as a periodic uneven amount of light. On the contrary, when the pre-shipment light amount unevenness correction value is calculated under the use condition assuming the measurement temperature of 14 ° C., the light amount unevenness correction is performed using the pre-shipment light amount unevenness correction value under the use condition where the measurement temperature is 46 ° C. Even when the light is applied, the light amount is not corrected correctly and appears as periodic uneven light amount.

  Furthermore, other causes that cause periodic light amount unevenness include image data acquired from the image processing unit 40 in addition to the above-described printing speed, set light amount, temperature, humidity, and temporal change. This is because the image data uniquely determines the number of LEDs that emit light, and the magnitude of the applied voltage and the magnitude of the voltage drop vary depending on the number of LEDs.

In order to suppress the occurrence of periodic light amount unevenness as described above, in the image forming apparatus according to the first embodiment, a light amount unevenness correction database is constructed in the EEPROM 102. FIG. 17 shows a correction database 190 which is an example of a light amount unevenness correction database. As shown in FIG. 17, the light amount unevenness correction database 190 includes a printing speed correction table 190A, a set light amount correction table 190B, an image data correction table 190C, and a temperature correction table 190D. In the printing speed correction table 190A, different post-shipment light amount unevenness correction values for different printing speeds are assigned in a profile format in units of SLED chips. In the example shown in FIG. 17, the post-shipment light amount unevenness correction values C _{P1 to} C _P4 are assigned one-to-one to the printing speeds P _{1 to} P ₄ . Further, in the set light quantity correction table 190B, different post-shipment light quantity unevenness correction values are assigned to different set light quantities. In the example shown in FIG. 17, post-shipment light amount unevenness correction values C _{E1 to} C _E4 are assigned on a one-to-one basis to the set light amounts E _{1 to} E ₄ . In addition, in the image data correction table 190C, different post-shipment light amount unevenness correction values are assigned to different numbers of light emitting LEDs (simultaneous lighting number). In the example illustrated in FIG. 17, the post-shipment light amount unevenness correction values C _{N1 to} C _N4 are assigned on a one-to-one basis with respect to the simultaneous lighting numbers N _{1 to} N ₄ . Further, in the temperature correction table 190D, different post-shipment light amount unevenness correction values are assigned for different measurement temperatures. In the example shown in FIG. 17, the post-shipment light amount unevenness correction values C _{T1 to} C _T4 are assigned on a one-to-one basis to the temperatures T _{1 to} T ₄ .

Each of the post-shipment light amount unevenness correction values is a value obtained by actually using the image forming apparatus under different use conditions before shipment. As a calculation method of the post-shipment light amount unevenness correction value included in the printing speed correction table 190A, for example, the set light amount, the number of simultaneous lighting, the temperature, the humidity, and the degree of deterioration over time are used within predetermined errors. in the lower, end of the SLED chips when a printing speed _{P 1} as shown in FIG. 18 the case of 225 mm / sec and the printing speed _{P 2} is caused to emit light all the LED included in the SLED chip in the case of 175mm / sec Based on a profile (light quantity fluctuation rate profile) obtained by converting the difference in voltage change amount for one cycle for all LEDs included in the LED into a light quantity fluctuation rate as shown in FIG. There is a method of calculating a correction value. Specifically, a correction profile configured to set the light amount fluctuation rate of the light amount fluctuation rate profile to 0% within a predetermined error is created for each SLED chip. Preferably, for example, the light quantity fluctuation rate for each LED in the light quantity fluctuation rate profile shown in FIG. 18 is set to 0% (for example, a value symmetrical to the light quantity fluctuation rate (for example, the current light quantity fluctuation for one LED). If the rate is “−0.2”, a correction profile having a value symmetric to this value is “0.2”)) may be created.

  Hereinafter, the operation of the main part of the image forming apparatus according to the first embodiment will be described. First, the first correction calculation process executed by the correction value calculation unit 112 will be described with reference to FIG. FIG. 20 shows an example of the processing flow of the first correction value calculation processing program executed by the correction value calculation unit 112 when a printing speed different from that at the time of correction of the light amount unevenness before shipment is set. It is a flowchart. Here, a case will be described in which the set light amount, the measured temperature, and the number of simultaneous lighting are not considered in order to avoid complications.

In step 200 in the figure, after the print speed correction table 190A is acquired from the EEPROM 102, the process proceeds to step 202, and from the print speed correction table 190A acquired in the process of step 200, the currently set print speed is set. A light amount unevenness correction value corresponding to the speed is acquired. For example, the printing speed set at present is the light amount unevenness correction value C _P1 is obtained by the process of step 202 in the case of P _1.

  In the next step 204, the process waits until image data is supplied from the image processing unit 40. In this step 204, when image data is supplied from the image processing unit 40, an affirmative determination is made and the routine proceeds to step 206, where the light amount unevenness correction value obtained in the processing of step 202 is used as the lighting time control / drive unit 118-. After output to 1-118-58, the first correction value calculation processing program is terminated.

  Next, the second correction calculation process executed by the correction value calculation unit 112 will be described with reference to FIG. FIG. 21 is a flowchart showing an example of the processing flow of the second correction value calculation processing program executed by the correction value calculation unit 112 when the set light amount is different from that at the time of correcting the light amount unevenness before shipment. It is. Here, a case will be described in which printing speed, measurement temperature, and number of simultaneous lighting are not considered in order to avoid complications.

In step 250 of the figure, after the set light amount correction table 190B is acquired from the EEPROM 102, the process proceeds to step 252, and the setting currently applied from the set light amount correction table 190B acquired in the processing of step 250 above. A light amount unevenness correction value corresponding to the light amount is acquired. For example, if the set light amount currently applied is E ₁ , the light amount unevenness correction value C _E1 is acquired by the processing of step 252.

  In the next step 254, the process waits until image data is supplied from the image processing unit 40. In this step 254, when image data is supplied from the image processing unit 40, an affirmative determination is made, and the process proceeds to step 256. The light amount unevenness correction value acquired in the processing of step 252 is used as the lighting time control / drive unit 118-. After outputting to 1-118-58, the second correction value calculation processing program is terminated.

  Next, the third correction calculation process executed by the correction value calculation unit 112 will be described with reference to FIG. Note that FIG. 22 shows the flow of processing of the second correction value calculation processing program executed by the correction value calculation unit 112 when the temperature sensor 17 measures a temperature different from that at the time of correction of the light amount unevenness before shipment. It is a flowchart which shows an example. Here, a case where the printing speed, the set light amount, and the simultaneous lighting number are not considered in order to avoid complications will be described.

In step 300 of the figure, after obtaining the temperature correction table 190D from the EEPROM 102, the process proceeds to step 302, where the temperature correction table 190D obtained in the processing of step 300 is obtained from the temperature sensor 17 at the present time. The light intensity unevenness correction value corresponding to the measured temperature is acquired. For example, if the current measured temperature is T ₁ , the light amount unevenness correction value C _T1 is acquired by the processing of step 302.

  In the next step 304, the process waits until image data is supplied from the image processing unit 40. In this step 304, when image data is supplied from the image processing unit 40, an affirmative determination is made and the process proceeds to step 306, where the light amount unevenness correction value acquired in the processing of step 302 is used as the lighting time control / drive unit 118-. After outputting to 1-118-58, the third correction value calculation processing program is terminated.

  Next, a fourth correction calculation process executed by the correction value calculation unit 112 will be described with reference to FIG. FIG. 23 is a flowchart illustrating an example of a process flow of a fourth correction value calculation processing program executed by the correction value calculation unit 112 when the power of the image forming apparatus is turned on. Here, a case where the printing speed, the set light amount, and the measurement temperature are not considered in order to avoid complications will be described.

  In step 350 in the figure, after the image data correction table 190C is acquired from the EEPROM 102, the process proceeds to step 352 and waits until image data is supplied from the image processing unit 40. In this step 352, when image data is supplied from the image processing unit 40, an affirmative determination is made and the process proceeds to step 354. After calculating the number of simultaneous lighting based on the image data acquired in the process of step 352, Control goes to step 356.

  In step 356, the light intensity unevenness correction value corresponding to the number of simultaneous lighting calculated in the process of step 354 is acquired from the image data correction table 190C acquired in the process of step 350, and then the process proceeds to step 358. After the light amount unevenness correction value acquired in the process of step 356 is output to the lighting time control / drive units 118-1 to 118-58, the fourth correction value calculation processing program is terminated.

  FIG. 24 is a timing chart illustrating the output timings of the drive signals output from the signal generation circuit 100 and the level shift circuit 104. In the timing chart shown in FIG. 24, the case where all LEDs perform optical writing (lights up) is described.

  (1) First, when a reset signal is input from the control unit 30 to the signal generation circuit 100, the transfer signal CK1C is at a high level (hereinafter referred to as “H”) in the timing signal generation unit 114 of the signal generation circuit 100. The transfer signal CK1R is set to “H”, and the transfer signal CK1 is set to “H”. Further, the transfer signal CK2C is set to a low level (hereinafter referred to as “L”), the transfer signal CK2R is set to “L”, and the transfer signal CK2 is set to “L”. Thereby, all the thyristors S1 to S128 of the SLED 63 are set to an off state (FIG. 4A).

  (2) Following the reset signal, the horizontal synchronization signal Lsync output from the control unit 30 becomes “H” (FIG. 24A), and the operation of the SLED 63 is started. Then, in synchronization with the horizontal synchronization signal Lsync, the transfer signal CK2C and the transfer signal CK2R are set to “H” and the transfer signal CK2 is set to “H” as shown in FIGS. (FIG. 24B).

  (3) Next, as shown in FIG. 24C, the transfer signal CK1R is set to “L” (FIG. 24C).

  (4) Subsequently, as shown in FIG. 24B, the transfer signal CK1C is set to “L” (FIG. 24D). In this state, the gate current of the thyristor S1 starts to flow. At that time, the tri-state buffer B1R of the signal generation circuit 100 is set to high impedance (Hiz) to prevent current backflow. Thereafter, the thyristor S1 starts to be turned on by the gate current of the thyristor S1, and the gate current gradually increases. At the same time, when a current flows into the capacitor C1 of the level shift circuit 104, the potential of the transfer signal CK1 also gradually increases.

  (5) After the elapse of a predetermined time (the time when the transfer signal CK1 potential becomes close to GND), the tristate buffer B1R of the signal generation circuit 100 is set to “L” (FIG. 24E). Then, as the gate G1 potential rises, the signal line Φ1 potential rises and the transfer signal CK1 potential rises, and accordingly, current starts to flow to the resistor R1B side of the level shift circuit 104. On the other hand, the current flowing into the capacitor C1 of the level shift circuit 104 gradually decreases as the potential of the transfer signal CK1 increases. When the thyristor S1 is completely turned on and becomes a steady state, a current for maintaining the on state of the thyristor S1 flows to the resistor R1B of the level shift circuit 104, but does not flow to the capacitor C1. At this time, as shown in FIG. 24B, the tri-state buffer B1C of the signal generation circuit 100 is set to high impedance (Hiz) (FIG. 24E).

  (6) With the thyristor S1 completely turned on, the lighting signal ΦI is set to “L” as shown in FIG. 24H (FIG. 24F). At this time, since the potential of the gate G1> the potential of the gate G2, the LED L1 having a thyristor structure is turned on earlier and lights up. As the LED L1 is turned on, the potential of the signal line ΦI increases, so that the LEDs after the LED L2 are not turned on. That is, for the LEDs L1, L2, L3, L4,..., Only the LED L1 having the highest gate voltage is turned on (lighted).

  (7) Next, as shown in FIG. 24 (F), when the transfer signal CK2R is set to “L” (FIG. 24 (g)), a current flows as in the case of FIG. A voltage is generated across the capacitor C2 104.

  (8) As shown in FIG. 24E, when the transfer signal CK2C is set to “L” in this state (FIG. 24H), the thyristor S2 is turned on.

  (9) Then, as shown in FIGS. 24B and 24C, when the transfer signals CK1C and CK1R are simultaneously set to “H” (FIG. 24I), the thyristor S1 is turned off and passes through the resistor R1. As a result of the discharge, the potential of the gate G1 gradually decreases. At that time, the thyristor S2 is completely turned on. Then, the lighting signal ΦI is “L” / “H” in synchronization with the thyristor S2 being turned on, whereby the LED L2 can be turned on / off. In this case, since the potential of the gate G1 is already lower than the potential of the gate G2, the LED L1 is not turned on.

  (10) The operation as described above is sequentially performed to sequentially turn on the LEDs L1 to L128.

  As described above, in the signal generation circuit 100 according to the first embodiment, the timing signal generation unit 114 outputs the transfer signals CK1C and CK1R and the transfer signals CK2C and CK2R from “H” to “L” at predetermined timings, respectively. , “L” to “H”. Accordingly, the odd-numbered thyristors S1, S3,..., S127 are sequentially turned off by repeatedly setting the potential of the transfer signal CK1 from the level shift circuit 104 from “H” to “L” and from “L” to “H”. → Operate from on to off. Further, by alternately setting the potential of the transfer signal CK2 from the level shift circuit 104 from “H” to “L” and from “L” to “H” alternately with the transfer signal CK1, the even-numbered thyristor S2, S4,..., S128 are sequentially operated from OFF to ON to OFF. As a result, the thyristors S1 to S128 are sequentially turned off, on, and off in the order of S1, S2,..., S127, and S128, and are synchronized with the lighting time control / drive units 118-1 to 118-. By outputting lighting signals ΦI1 to ΦI58 from 58, the LEDs L1 to L128 are sequentially lit.

  In the LPH 14 of the first embodiment, since the SLED 63 is driven by three drive signals of the lighting signal ΦI, the transfer signal CK1, and the transfer signal CK2, the wiring is simplified as shown in FIG. The LPH 14 can be downsized. Furthermore, the image forming apparatus equipped with the LPH 14 can be downsized.

  25 and 26, the lighting signal ΦI (FIG. 24 (H)), the transfer signal CK1 (FIG. 24 (D)), and the transfer signal CK2 (FIG. 24 (G)) in FIG. 24 are in the sub-scanning direction. FIG. 6 is a diagram illustrating a timing of output for each line and a change in voltage (supply voltage) supplied from the three-terminal regulator 101 at that time. FIG. 25 shows a case where the printing speed of the image forming apparatus is 100 mm / sec, for example, and FIG. 26 shows a case where the printing speed is 150 mm / sec, for example.

  In FIG. 25, the horizontal synchronizing signal Lsync for setting the output timing for each line in the sub-scanning direction is slower than the case where the printing speed (100 mm / sec in this case) is 150 mm / sec, so the output cycle is 150 mm / sec. It is set longer than the case of sec. Therefore, in the timing signal generation unit 114 of the signal generation circuit 100, the cycle in which the thyristors S1 to S128 are alternately turned on / off (hereinafter referred to as “thyristor transfer cycle”), that is, the thyristors S1 to S128 shown in FIG. Long on time can be set. In addition, a period from when the 127th lighting signal Φ128 of the Nth line in the sub-scanning direction is output to when the 0th lighting signal Φ1 of the next N + 1th line in the subscanning direction is output (hereinafter referred to as “pause”). The period can be set longer.

  On the other hand, in FIG. 26, since the horizontal synchronization signal Lsync is faster than the case where the printing speed (150 mm / sec in this case) is 100 mm / sec, the output cycle is set shorter than that in the case of 100 mm / sec. . Therefore, in the timing signal generation unit 114 of the signal generation circuit 100, the thyristor transfer cycle is set shorter than the case where the printing speed is 100 mm / sec. The pause period is also set shorter than when the printing speed is 100 mm / sec.

  By the way, the 3-terminal regulator 101 tries to output a predetermined voltage VDD (3.5 V in the first embodiment) to the SLED 63, but the voltage actually supplied to the SLED 63 is the 3-terminal regulator. When the predetermined voltage VDD (3.5 V) by 101 is a specified voltage V0, the SLED 63 is turned on due to the current consumption in the SLED 63 due to the lighting of the LED, although there is a difference in degree due to the difference in the lighting rate in each SLED chip. During this period (this is called “lighting / transfer period”), a phenomenon occurs in which the supply voltage falls below the specified voltage V0.

  The supply voltage lowered during the lighting / transfer period gradually recovers during the pause period and approaches the specified voltage V0, but the recovery level varies depending on the length of the pause period. For example, when the printing speed is 100 mm / sec shown in FIG. 25, the recovery period is large because the pause period is relatively long, and the voltage difference Vg between the specified voltage V0 and the supply voltage (Vg = V0−supply voltage) is compared. Small. On the other hand, in the case of the printing speed of 150 mm / sec shown in FIG. 26, since the pause period is shorter than in the case of the printing speed of 100 mm / sec, the recovery amount is small and the voltage difference Vg is relatively large.

  As described above, when the image forming apparatus is configured to be operable at a plurality of different printing speeds, for example, when the image formation shifts from the Nth line in the sub-scanning direction to the N + 1th line in the next sub-scanning direction, Depending on the length, the supply voltage to the SLED 63 differs.

  As described above, the correction value calculation unit 112 of the signal generation circuit 100 calculates a light amount unevenness correction value, and outputs the calculated light amount unevenness correction value to the lighting time control / drive units 118-1 to 118-58. Is done. Since this uneven light intensity correction value is uniquely determined according to the current use conditions of the image forming apparatus, even if the use conditions differ from those at the time of correcting the uneven light quantities before shipment, the uneven light quantity between the LEDs is highly accurate. It is corrected. Further, since the SLED 63 is configured to include a plurality of SLED chips arranged in a predetermined arrangement direction (in a straight line as an example), conventionally, the amount of light caused by the voltage drop of the LED included in the end portion of the SLED chip. Although the decrease appeared as periodic light amount unevenness between the SLED chips, in the image forming apparatus according to the first embodiment, the light amount unevenness of each SLED chip is corrected as described above. Uneven light intensity is less likely to occur.

[Second Embodiment]
In the first embodiment, the description has been given by taking the form example in the case where the light amount unevenness correction value is associated with each of the printing speed, the set light amount, the measured temperature, and the simultaneous lighting number. However, the second embodiment is described. Now, a case where the light amount unevenness correction value is associated on a one-to-one basis for each combination of the printing speed and the set light amount will be described. In the following description, parts different from those of the first embodiment will be described, and constituent members corresponding to the constituent members of the first embodiment will be attached to the constituent members of the first embodiment. The reference numerals corresponding to the reference numerals are attached and the description thereof is omitted.

In the image forming apparatus according to the second embodiment, an EEPROM 102 stores a correction table. FIG. 27 shows a correction table 390 which is an example of a correction table. The process speed shown in FIG. 27 corresponds to the printing speed described in the first embodiment. As shown in FIG. 27, in the correction table 390, a post-shipment light amount unevenness correction value is assigned in a profile format in SLED chip units for each different set light amount for each of different printing speeds. In the example shown in FIG. 27, for each of the printing speeds P _{1 to} P ₄ , post-shipment light amount unevenness correction values C _{11 to} C ₁₄ are associated with the set light amount E ₁ . For each of the printing speeds P _{1 to} P ₄ , post-shipment light amount unevenness correction values C _{21 to} C ₂₄ are associated with the set light amount E ₂ . For each of the printing speeds P _{1 to} P ₄ , post-shipment light amount unevenness correction values C _{31 to} C ₃₄ are associated with the set light amount E ₃ . Further, for each of the printing speeds P _{1 to} P ₄ , post-shipment light amount unevenness correction values C _{41 to} C ₄₄ are associated with the set light amount E ₄ .

  Next, the correction calculation processing according to the second embodiment executed by the correction value calculation unit 112 will be described with reference to FIG. FIG. 28 shows an example of the processing flow of the correction value calculation processing program executed by the correction value calculation unit 112 when a printing speed and set light amount different from those at the time of correcting the light amount unevenness before shipment are set. It is a flowchart. Here, a case where the measured temperature and the number of simultaneous lighting are not considered in order to avoid complications will be described.

In step 400 of the figure, after the correction table 390 is acquired from the EEPROM 102, the process proceeds to step 402, and from the correction table 390 acquired in the processing of step 400, the print currently applied to the image forming apparatus. A light amount unevenness correction value corresponding to the speed and the set light amount is acquired. For example, if the currently set printing speed is P ₁ and the set light amount is E ₁ , the light amount unevenness correction value C ₁₁ is acquired by the processing of this step 402.

  In the next step 404, the process waits until image data is supplied from the image processing unit 40. In this step 404, when image data is supplied from the image processing unit 40, an affirmative determination is made and the process proceeds to step 406, where the light amount unevenness correction value acquired in the processing of step 402 is used as the lighting time control / drive unit 118-. After output to 1-118-58, the correction value calculation processing program is terminated.

  In the second embodiment, an example of determining the light amount unevenness correction value according to the combination of the printing speed and the set light amount has been described. However, the present invention is not limited to this, and the print speed, the set light amount, A correction table in which a light amount unevenness correction value is associated with at least one of the measured temperature and the number of simultaneous lighting is created, and a light amount unevenness correction value corresponding to the current use condition is acquired from the correction table to obtain the light amount. Unevenness correction may be performed. For example, a correction table configured by associating unevenness correction values for each combination of printing speed, set light amount, measurement temperature, and number of simultaneous lightings is created in advance, and the printing speed and setting included in this correction table are set. When the image forming device is used with a combination of the printing speed, set light quantity, measurement temperature, and the number of simultaneous lightings, which corresponds to the combination of the light quantity, the measurement temperature, and the number of simultaneous lightings, the light quantity unevenness correction value corresponding to this combination is corrected An example of obtaining from a table is given. When the number of simultaneous lighting is included, when image data is acquired at a predetermined acquisition time (for example, every time image data of one image unit is supplied), it is calculated based on the image data. A light amount unevenness correction value corresponding to the number of simultaneous lighting is acquired from the correction table.

  In each of the above embodiments, the temperature sensor 17 measures the temperature in a region within a predetermined distance from the LPH 14. However, the measurement location is not limited to this, and the temperature of a specific portion of the LPH 14 is described. May be measured directly. As an example of this specific part, any LED contained in LPH14 is mentioned. Thus, the closer the measurement location is to the LED, the more accurately the unevenness in the amount of light is corrected.

  Moreover, in each said embodiment, although the software form which implement | achieves each step of the flowchart shown to FIGS. 20-23 and FIG. 28 by executing the program by the correction value calculating part 112 was illustrated, Not limited to this, a hardware form configured by connecting various circuits (for example, an ASIC (Application Specific Integrated Circuit)), or a combination of a software form and a hardware form can be exemplified.

  In each of the above embodiments, the program is stored in advance in the EEPROM 102. However, the present invention is not limited to this, and various processing programs can be read by a computer such as a CD-ROM, DVD-ROM, or USB (Universal Serial Bus) memory. A form provided in a state of being stored in a storage medium may be applied, or a form distributed via wired or wireless communication means may be applied.

11 Image forming unit 12 Photosensitive drum 14 LED print head 17 Temperature sensor 30 Control unit 63 SLED
102 EEPROM
112 Correction value calculator

Claims (12)

A plurality of light emitting elements that have been corrected so that the difference in the amount of light between them when emitting light under specific use conditions is within a predetermined range;
Except for the type, the light quantity of each of the plurality of light emitting elements is adjusted so that the light quantity difference between the light emitting elements when the plurality of light emitting elements are caused to emit light under use conditions different from the specific use conditions. Storage means for storing correction information for correction;
Correcting means for correcting the light quantity of the light emitting element to be emitted among the plurality of light emitting elements according to the correction information stored in the storage means when the use conditions corresponding to the different use conditions are satisfied When,
Exposure apparatus.   The different use conditions include at least one of a temperature at a predetermined time at a use destination, a light amount set in advance as a light amount obtained by causing the light emitting element to emit light, and a light emission interval of the light emitting element. Item 4. The exposure apparatus according to Item 1.   The exposure apparatus according to claim 2, wherein the different use conditions further include number specifying information for specifying the number of light emitting elements that actually emit light among the plurality of light emitting elements.   2. The exposure apparatus according to claim 1, wherein the different use condition is the number of light emitting elements that actually emit light among the plurality of light emitting elements. A plurality of light emitting elements that have been corrected so that the difference in the amount of light between them when emitting light under specific use conditions is within a predetermined range;
The plurality of light emitting elements so that the difference in light quantity between the light emitting elements when the plurality of light emitting elements emit light under each of a plurality of use conditions different from the specific use conditions except for the type is within a predetermined range. Storage means for storing correction information for correcting each light quantity in correspondence with each of the plurality of use conditions;
When the use condition corresponding to any of the plurality of use conditions is satisfied, the correction corresponding to the use condition corresponding to the use condition currently satisfied among the correction information stored in the storage unit Correction means for correcting the light quantity of the light emitting element that is the light emitting target of the plurality of light emitting elements according to the information for
Exposure apparatus.   Each of the plurality of use conditions includes at least one of a temperature at a predetermined time at a use destination, a light amount set in advance as a light amount obtained by causing the light emitting element to emit light, and a light emission interval of the light emitting element. The exposure apparatus according to claim 5, comprising:   The exposure apparatus according to claim 6, wherein each of the plurality of use conditions further includes number specifying information for specifying the number of light emitting elements that actually emit light among the plurality of light emitting elements.   6. The exposure apparatus according to claim 5, wherein each of the plurality of use conditions is the number of light emitting elements that actually emit light among the plurality of light emitting elements. Each of the plurality of light emitting elements includes a plurality of light emitting element groups arranged in a predetermined direction and arranged in series along the predetermined direction,
The exposure apparatus according to any one of claims 1 to 8, wherein the plurality of light emitting elements are caused to emit light sequentially from one end to the other end in the predetermined direction. An exposure apparatus according to any one of claims 1 to 9,
The electrostatic latent image formed on the surface of the photosensitive member by irradiating the surface of the photosensitive member with light emitted from the plurality of light emitting elements of the exposure apparatus is developed as a developed image with a developer and developed. Image forming means for forming an image by transferring the developed image to a recording medium;
An image forming apparatus including: A plurality of light emitting elements that are corrected so that a difference in light quantity between them when emitting light under a specific use condition is within a predetermined range, and the plurality of light emitting elements other than the specific use condition except for the plurality of light emitting elements An exposure apparatus including a storage unit that stores correction information for correcting the amount of light of each of the plurality of light emitting elements so that the difference in amount of light between the light emitting elements when the light emitting elements emit light is within a predetermined range. The computer to control,
Correcting means for correcting the light quantity of the light emitting element to be emitted among the plurality of light emitting elements according to the correction information stored in the storage means when the use conditions corresponding to the different use conditions are satisfied Program to function as. Each of a plurality of light emitting elements that are corrected so that a difference in light quantity between them when emitting light under a specific use condition is within a predetermined range, and a plurality of use conditions that are different from the specific use condition except for the type The correction information for correcting the light amount of each of the plurality of light emitting elements so that the difference in light amount between the light emitting elements when the plurality of light emitting elements emit light within a predetermined range is used A computer for controlling the exposure apparatus including the storage means stored corresponding to each of the conditions;
When the use condition corresponding to any of the plurality of use conditions is satisfied, the correction corresponding to the use condition corresponding to the use condition currently satisfied among the correction information stored in the storage unit The program for functioning as a correction means which corrects the light quantity of the light emitting element made into light emission object among the said several light emitting elements according to use information.

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