JP2005254739A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation device capable of reducing a physical installation errors generated at the time of arranging two or more LED arrays in a main scanning direction. <P>SOLUTION: The sum of the amounts of luminescence of LEDs corresponding to the duplication section of each LED array is so set as to be equal to that of luminescence of the LED other than that of the duplication section. In details, the amount of luminescence of the LED corresponding to the duplication section is so set as to be equal to one half of the amount of luminescence other than the one of the duplication section, then the luminescence of each LED is controlled. Thereby, since the dot by LED of one LED array and the dot by LED of other LED array are composed in the duplication section and then the dot corresponding to the duplication section serves at the center position of two LEDs, the pitch between the dots corresponding to both ends of the duplication section gets equal to P+a/2, and the installation errors between the LED arrays is enabled to be equally dispersed to both ends of the duplication section. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image using a printer head in which a plurality of light emitting elements such as LEDs are arranged.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, an electrostatic latent image is formed by exposing a photoconductor according to an image, and the electrostatic latent image is formed on a photoconductor by developing toner. The toner image is transferred onto a recording sheet (hereinafter referred to as “sheet”) to form an image.

  As a light source for forming an electrostatic latent image on a photoreceptor, an LD (Laser Diode) has been conventionally used. In recent years, a laser printer that prints a large amount at a high speed uses an LED ( A light emitting element array in which light emitting elements such as light emitting diodes (LEDs) are arranged in a line corresponding to each pixel is used as an effective element. For example, an optical print head including the light emitting element array and an imaging element lens array such as a Selfoc lens array in which an imaging lens is arranged so as to image light output from each light emitting element on the surface of the photoreceptor. Is used.

  In such an image forming apparatus using the optical print head, each LED element of the optical print head is driven based on the image data to output light based on the image data, and the light output by the imaging lens is used as the photosensitive member. The photosensitive member is exposed based on the image data by forming an image on the surface, and the exposure position is moved by moving the photosensitive member and the optical print head relative to each other (this moving direction is referred to as “sub-scanning direction”). An image is formed on the photoreceptor.

  By the way, in the optical print head as described above, variations in performance for each light emitting chip equipped with a plurality of light emitting elements, variations in each light emitting element, variations in refractive index distribution of the Selfoc lens array, lens arrangement disorder, Output unevenness (variation in output energy) occurs due to an assembly error between the light emitting element array and the Selfoc lens array. This output unevenness appears as density unevenness when an image is formed by the image forming apparatus and causes deterioration in image quality. Therefore, the optical print head needs to perform light amount correction so as to reduce output unevenness.

As a technique for reducing output unevenness, Patent Document 1 proposes a circuit that changes the luminance of each dot in order to suppress exposure variation, and this circuit corrects variation in light quantity for each dot. It has been proposed.
JP-A-11-221939

  However, as the printing paper becomes wider, the LED array needs to have the same width, and its manufacturing facilities are becoming larger. For this reason, as shown in FIG. 7, it is possible to deal with a wide range of paper by arranging a plurality of conventional LED arrays in the main scanning direction, but a physical mounting error a occurs when arranging a plurality of LED arrays. There is a problem.

  The present invention has been made to solve the above-described problem, and an object thereof is to provide an image forming apparatus capable of reducing a physical attachment error that occurs when a plurality of LED arrays are arranged in the main scanning direction. And

  In order to achieve the above object, according to the first aspect of the present invention, a plurality of light emitting element arrays in which a plurality of light emitting elements are arranged in the recording paper width direction are shifted adjacent to each other in a direction perpendicular to the arrangement of the light emitting elements. The light sources arranged in the width direction of the recording paper so as to overlap each other, and the light emitting elements in the light emitting elements corresponding to the overlapping portions of the adjacent portions of the light emitting element array, while controlling the light emission of each light emitting element of the light source Control means for controlling the light emission of the light emitting elements corresponding to the overlapping portions so that the sum of the light emission intensities of the light emitting elements arranged in a direction orthogonal to the light emitting intensity of the light emitting elements other than the overlapping portions is provided. It is characterized by that.

  According to the first aspect of the present invention, the light source is shifted in the direction perpendicular to the light emitting element array so that adjacent portions of the light emitting element array in which the plurality of light emitting elements are arranged overlap, and the width direction of the recording paper It is arranged and arranged. For example, LEDs can be used as the light emitting elements, and the light sources can be staggered so that adjacent portions of the light emitting element arrays overlap.

  The control means controls the light emission of each light emitting element, and the sum of the light emission intensities of the light emitting elements arranged in the direction orthogonal to the light emitting element array in the light emitting element corresponding to the overlapping part of the light emitting element array is the light emitting element other than the overlapping part. The emission intensity is controlled to be. That is, in adjacent portions of the light emitting element array, one dot is formed by a plurality of overlapping light emitting elements. For example, when the light emitting element array is arranged in a staggered arrangement, the light emission control is performed so that the light emission amount of the light emitting element corresponding to the overlapping portion becomes half the light emission amount of the light emitting elements other than the overlapping portion. Thereby, in the overlapping portion, one dot is obtained by the sum of the light emitting elements of the respective light emitting element arrays.

  Further, by controlling the light emission of the light emitting elements in the overlapping portion of the light emitting element array as described above, the mounting error between the light emitting element arrays can be dispersed in the overlapping portion.

  For example, when the light emitting element array is arranged in a staggered arrangement and the light emission amount of the light emitting element corresponding to the overlapping portion of the light emitting element array is half the light emission amount of the light emitting elements other than the overlapping portion, light is emitted to both end portions of the overlapping portion. It is possible to disperse the error of attaching the element array by 1/2.

  Note that, as in the invention described in claim 2, the control means includes the overlapping portion so that the light emission intensity gradually decreases toward the end portion of the light emitting element array in the overlapping portion of the adjacent portions of the light emitting element array. The light emission of the light emitting element corresponding to the above may be further controlled.

  For example, as in the invention described in claim 3, when the number of light emitting elements in the overlapping portion of adjacent portions of the light emitting element array is n (n is a natural number of 3 or more), By controlling the light emission of the light emitting elements corresponding to the overlapping portions so that the light emission intensity decreases by 1 / (n + 1) toward the end portion, the mounting error of the light emitting element arrays at the overlapping portions between the light emitting element arrays. Can be error-dispersed by 1 / (n + 1).

  As described above, according to the present invention, there is an effect that it is possible to reduce a physical attachment error that occurs when a plurality of LED arrays are arranged in the main scanning direction.

Hereinafter, an example of an embodiment of 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 according to the first embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 12 that rotates at a constant speed in the direction of arrow A in FIG. The rotation direction of the photosensitive drum 12 (the direction of arrow A in FIG. 1) corresponds to the sub-scanning direction.

  Around the photosensitive drum 12, along the rotational direction of the photosensitive drum 12, there are a charger 14, a print head 16, a developing unit 18, a transfer roller 20, a cleaner (not shown), and an erase lamp (not shown). The ranking is arranged.

  That is, the surface of the photosensitive drum 12 is uniformly charged by the charger 14 and then irradiated with a light beam by the print head 16 to form a latent image on the photosensitive drum 12. The print head 16 is connected to a control device 46 (see FIG. 4), and is controlled by the control device 46 to output a light beam based on the image data.

  The latent image formed on the photosensitive drum 12 is developed by supplying toner by the developing unit 18, and a toner image is formed on the photosensitive drum 12. The toner images on the photosensitive drum 12 are taken out from the paper tray 22 one by one by the transfer roller 20 and transferred to the paper P conveyed by the paper conveying belt 24. The toner remaining on the photosensitive drum 12 after the transfer is removed by a cleaner (not shown), neutralized by an erase lamp (not shown), charged by the charger 14 again, and the above operation is repeated.

  On the other hand, the sheet P on which the toner image is transferred is conveyed to a fixing device 26 including a pressure roller 26A and a heating roller 26B, and subjected to a fixing process. As a result, the toner image is fixed and a desired image is formed on the paper P. The paper P on which the image is formed is discharged out of the apparatus.

  Next, the print head 16 will be described in detail. FIG. 2 is a cross-sectional view of the print head 16. As shown in FIG. 2, the print head 16 includes an LED array 30, a printed circuit board 32 that supports the LED array 30, and on which a circuit for supplying various signals for controlling the driving of the LED array 30 is formed, And an imaging element array 34 for imaging the light emitted from the LED array 30 onto the photosensitive drum 12.

  The LED array 30 is composed of a plurality of LED chips in which a plurality of LEDs 28 are arranged in a row (see FIG. 3), and the print head 16 has a plurality of LED arrays 30 arranged as shown in FIG. The total number of LEDs 28 provided in the print head 16 is provided by the number of pixels (dots) corresponding to the resolution.

  As shown in FIG. 3, the print head 16 makes the main scanning direction by alternately shifting the positions of the adjacent LED arrays 30 in the sub-scanning direction by matching the arrangement direction of the LEDs 28 of each LED array 30 to the main scanning direction. They are arranged in a direction (staggered arrangement) and attached to the printed circuit board 32.

  In addition, each LED array 30 of the print head 16 is arranged so that the LEDs 28 of the LED arrays 30 adjacent to each other between the LED arrays 30 adjacent to each other in the main scanning direction have overlapping portions 34 that overlap in the sub-scanning direction. In the present embodiment, each LED array 30 is arranged so that there are five LEDs 28 in the overlapping portion 34, but the present invention is not limited to this.

  The imaging element array 34 is configured by arranging, as an imaging lens, a refractive index distribution type plastic rod lens or the like corresponding to each pixel (dot) corresponding to the resolution, and from each LED array 30. Dots are formed by forming an image of the emitted light beam on the photosensitive drum 12.

  The printed circuit board 32 is disposed in the housing 36 with the mounting surface of the LED array 30 facing the photosensitive drum 12. In addition to the LED array 30, the printed circuit board 32 includes a shift register 38 for storing image data for one line, a latch circuit 40, and each LED 28 for driving each LED 28 of the LED array 30 as shown in FIG. A driver 42 provided for the LED 28 and a ROM 44 are provided. The shift register 38, the latch circuit 40, and the driver 42 are connected to the control device 46, and each operation is controlled by the control device 46.

  Specifically, the control device 46 outputs the image data for one line to the shift register 38 in synchronization with the transfer clock (transfer CLK), and when the output of the image data for one line to the shift register 38 is completed, The signal is output to the latch circuit 40. As a result, the image data for one line stored in the shift register 38 is latched by the latch circuit 40.

  When the control device 46 outputs an enable signal to the driver 42, each driver 42 supplies a current having a current value corresponding to the corresponding pixel data to the LED 28. Thereby, each LED 28 emits light according to the current value output from the driver 42.

  Each driver 42 is provided with a register (not shown) for adjusting the current value of the LED 28 corresponding to the overlapping portion 34 described above, and the amount of light emitted from the LED 28 corresponding to the overlapping portion 34 is stored in this register. The overlapping portion data for adjustment is written, and the current value based on the image data is adjusted by the overlapping data, and then the current is output to the LED 28.

  This duplication data consists of data for dispersing mounting errors between the LED arrays 30, and is stored in the ROM 44 when the print head 16 is manufactured, and at a predetermined timing such as when the image forming apparatus 10 is turned on. The data is written from the ROM 44 to the register of each driver 42.

  In the present embodiment, the overlapping portion data 44 </ b> A stored in the ROM 44 indicates that the light emission amount of the LED 28 corresponding to the overlapping portion 34 of the LED array 30 is half (1/2) the light emission amount of the LEDs 28 other than the overlapping portion 34. It sets so that it may become and it may become the light-emission amount of LED28 other than the duplication part 34, when each overlaps. In other words, one dot is formed by the two LEDs 28 in the overlapping portion 34, and the sum of the light emission amounts of both LEDs 28 is the same as the light emission amount of the LEDs 28 other than the overlapping portion 34.

  As the driver 42, for example, a lighting circuit of an LED print head disclosed in Japanese Patent Application Laid-Open No. 11-221939 can be applied, and thereby the light emission amount of the LED 28 of the overlapping portion 34 can be adjusted. .

  Next, a description will be given of how to reduce the mounting error between the LED arrays 30 in the print head 16 of the image forming apparatus 10 configured as described above.

  In the print head 16 configured as described above, an installation error occurs between the LED arrays 30, and the pitch of the LEDs 28 between the LED arrays 30 becomes discontinuous.

  Therefore, in this embodiment, the light emission amount of the LEDs 28 of the overlapping portion 34 between the LED arrays 30 is controlled to disperse the mounting error between the LED arrays 30.

  Specifically, error dispersion is performed by controlling the light emission amount of the LED 28 corresponding to the overlapping portion 34 using the overlapping portion data 44 </ b> A stored in the ROM 44.

  In the present embodiment, the overlapping portion data 44 </ b> A stored in the ROM 44 is such that the sum of the light emission amounts of the LEDs 28 corresponding to the overlapping portions 34 of each LED array 30 is the light emission amount of the LEDs 28 other than the overlapping portion 34. As described above, the light emission amount of the LED 28 corresponding to the overlapping portion 34 is set to be ½ of the light emission amount of the LEDs 28 other than the overlapping portion 34.

  That is, as shown in FIG. 5, when the pitch between the LEDs 28 is P and the mounting error between the LED arrays 30 is a, the inter-dot pitch corresponding to the LEDs 28 other than the overlapping portion 34 remains P. In the portion 34, the dot by the LED 28 of one LED array 30 and the dot by the LED 28 of the other LED array 30 are combined, and the dot corresponding to the overlap portion 34 becomes the center position of the two LEDs 28. The inter-dot pitch corresponding to both ends is P + a / 2, and the mounting error between the LED arrays 30 is evenly distributed to both ends of the overlapping portion 34.

  In the present embodiment, since the light emission amount of the LED 28 of the overlap portion 34 is set to ½ of the light emission amount of the LED 28 other than the overlap portion 34, the mounting error a is a / 2 at the LED 28 pitch of the overlap portion 34. Dispersed, the pitch of the LEDs 28 at both ends of the overlapping portion 34 becomes P + a / 2.

  In this way, by controlling the light emission amount of the LEDs 28 corresponding to the overlapping portions 34 of the plurality of LED arrays 34 of the print head 16, it is possible to disperse the mounting error of the LED array 30. It is possible to reduce a physical attachment error that occurs when arranging in the main scanning direction.

In the first embodiment, the number of LEDs 28 in the overlapping portion 34 is five, but the number is not limited to this, and may be five or less or five or more.
[Second Embodiment]
Next, an image forming apparatus according to the second embodiment of the present invention will be described. In the first embodiment, the light emission is controlled so that the light emission amount of the LED 28 corresponding to the overlapping portion 34 of the LED array 30 is ½ of the light emission amount of the LED 28 other than the overlapping portion 34. Second Embodiment Then, the light emission of the LEDs 28 in the overlap portion 34 is controlled so that the sum of the light emission amounts of the LEDs 28 corresponding to the dots in the overlap portion 34 becomes the light emission amount of the LEDs 28 other than the overlap portion 34, and toward the end of the LED array 30. Thus, the light emission amount is controlled to gradually decrease. Note that the configuration itself of the image forming apparatus is the same as that of the first embodiment, and thus detailed description thereof is omitted.

  In the second embodiment, as shown in FIG. 6, in the print head, LED arrays 30 are arranged so that three LEDs 28 overlap each other. That is, the LED arrays 30 are arranged so that there are three LEDs 28 corresponding to the overlapping portion 34.

  In addition, the ROM 44 controls the light emission so that the sum of the light emission amounts of the LEDs 28 corresponding to the respective dots becomes the light emission amount of the LEDs 28 other than the overlap portion 34 in the LED 28 of the overlap portion 34, and at the end of the LED array 30. The overlapping portion data for controlling the light emission so that the light emission amount gradually decreases toward the light source is stored.

  Specifically, the light emission amount of the LED 28 in the overlapping portion 34 gradually becomes 3/4, 1/2, and 1/4 toward the end of the LED array 30 with respect to the light emission amount of the LED 28 other than the overlapping portion 34. The data for overlapping parts is reduced. That is, when the light emission amount other than the overlap portion 34 is 1, in the overlap portion, the light emission amount of one LED array 30 is 3/4 dots and the light emission amount of the other LED array 30 is 1/4 dots. Overlap. In addition, the dots of which the light emission amount of each LED array 30 is ½ overlap, and similarly, the light emission amount of one LED array 30 is 1/4 and the light emission amount of the other LED array 30 is 3/4. The dots overlap. That is, the sum of the light emission amounts of the respective dots becomes the light emission amount of the LEDs 28 other than the overlapping portion 34.

  Next, a description will be given of how to reduce the mounting error between the LED arrays 30 in the print head 16 of the image forming apparatus configured as described above.

  In this embodiment, if the pitch between the LEDs 28 is P and the mounting error between the LED arrays 30 is a, the inter-dot pitch corresponding to the LEDs 28 other than the overlapping portion 34 remains P, but in the overlapping portion 34, In order from the left in FIG. 6, a dot with a light emission amount of 3/4 overlaps with a light emission amount with a light emission amount of 1/4 with respect to the light emission amount other than the overlapping portion 34, and the dot position is on the right side of FIG. Therefore, the inter-dot pitch becomes P + a / 4 with reference to the upper LED array 30 in FIG. Similarly, with respect to the dot at the center of the overlapping portion 34, the dots whose emission amounts are ½ overlap each other, and the dot position is shifted by a / 2 with respect to the LED array 30 on the upper side of FIG. As a result, the inter-dot pitch becomes P + a / 4 as described above. Moreover, about the dot of the right end of FIG. 6 of the duplication part 34, the dot of 1/4 light emission amount and the dot of 3/4 light emission amount overlap, and a dot position shifts to the right of 3a / 4, but LED of FIG. Assuming the array 30 as a reference, the above-mentioned amount is shifted to the right by a / 2, so that the dot pitch is P + a / 4.

  Therefore, the mounting error is evenly distributed by a / 4 at the overlapping portion 34 of the LED array 30, and the physical mounting error that occurs when arranging the plurality of LED arrays 30 in the main scanning direction can be reduced.

  By the way, in 2nd Embodiment, it was set as the structure which arrange | positions the LED array 30 so that three LED28 may overlap, However, When the number of LED28 of the duplication part 34 is set to n (3 or more natural number), the edge of LEDarray 30 By controlling the light emission so that the light emission amount decreases by 1 / (n + 1) toward the portion, the mounting error a of the LED array 30 is equalized by a / (n + 1) at the overlapping portion 34 as in the second embodiment. Can be dispersed.

  For example, when the number of LEDs 28 in the overlapping portion 34 is 5, light emission control is performed so that the light emission amount decreases by 1/6 toward the end of the LED array 30. That is, the light emission is controlled so that the light emission amount of the LED 28 of the overlapping portion 34 of each LED array 30 becomes 5/6, 4/6, 3/6, 2/6, and 1/6 toward the end. In other words, the amount of light emitted from the overlapping portion 34 of one LED array 30 becomes 5/6, 4/6, 3/6, 2/6, and 1/6 toward the end, and the other LED array 30 The LED emission amount of the overlapping portion 34 is 1/6, 2/6, 3/6, 4/6, and 5/6 from the end of the LED array 30 toward the center. Thus, by controlling the light emission of the LED 28 corresponding to the overlapping portion 34, the inter-dot pitch can be dispersed by 1/6 in the overlapping portion 34.

  In the above-described embodiment, the LED array 30 is a staggered array. However, the present invention is not limited to this, and any array may be used as long as the LED array 30 is arranged so that the overlapping portion 34 is formed.

  In the above embodiment, the case where the LED 28 is applied as the light emitting element of the present invention has been described. However, the present invention is not limited to the LED 28, and other light emitting elements may be applied.

1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view of a print head. It is a figure which shows the arrangement | sequence of a LED array. FIG. 2 is a block diagram illustrating a configuration of an electrical system of a print head. In the image forming apparatus according to the first embodiment, it is a diagram for explaining the mounting error variance of the LED array. It is a figure for demonstrating attachment error dispersion | distribution of an LED array in the image forming apparatus concerning 2nd Embodiment. It is a figure which shows the example which arranged the conventional LED array in multiple numbers in the main scanning direction.

Explanation of symbols

10 Image forming apparatus 16 Print head 28 LED
30 LED array 32 Printed circuit board 34 Overlapping part 38 Shift register 40 Latch circuit 42 Driver 44 ROM
44A Duplicate data 46 Controller

Claims (3)

A plurality of light emitting element arrays in which a plurality of light emitting elements are arranged in the recording paper width direction, a light source arranged in the width direction of the recording paper so that adjacent portions overlap each other by shifting in a direction orthogonal to the arrangement of the light emitting elements,
While controlling the light emission of each light emitting element of the light source, the sum of the light emission intensities of the light emitting elements arranged in the direction orthogonal to the arrangement of the light emitting elements in the light emitting elements corresponding to the overlapping portions of the adjacent portions of the light emitting element array is Control means for controlling the light emission of the light emitting elements corresponding to the overlapping portions, respectively, so as to be the light emission intensity of the light emitting elements other than the overlapping portions;
Image forming apparatus provided with   The control means further emits light from the light emitting element corresponding to the overlapping portion so that the light emission intensity gradually decreases toward the end of the light emitting element array in the overlapping portion of adjacent portions of the light emitting element array. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled.   When the number of light emitting elements in an overlapping portion of adjacent portions of the light emitting element array is n (n is a natural number of 3 or more), the control means 1 / (n + 1) toward the end of the light emitting element array. The image forming apparatus according to claim 2, wherein the light emission of the light emitting element corresponding to the overlapping portion is controlled so that the light emission intensity decreases.

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