JP2004216709A - Image writing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image writing unit in which an unevenness in quantity of light is prevented from occurring at the joint positions of a plurality of light emitting element array units arranged in zigzag. <P>SOLUTION: When a line of image data is transferred from an LED write control circuit 51 to three LED heads 25a, 25b and 25c arranged in zigzag in the axial direction of a photosensitive body while being divided, a digital copy machine 1 transfers a line of image data a plurality of times to each LED head 25a, 25b, 25c during one main scanning line. Furthermore, the digital copy machine 1 controls the image data being transferred to an LED element at any one or both joint positions of overlapping LED heads 25a, 25b and 25c in order to control the number of lighting times of the LED element at the joint position thus increasing the gray level of binary image data at the joint position and preventing an unevenness in quantity of light. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image writing apparatus, and in particular, transfers image data to a plurality of light emitting element array units arranged in a staggered manner a plurality of times during one main scanning line, and connects the light emitting element array units. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image writing apparatus that controls image data to a light-emitting element at an eye position to prevent light amount unevenness at a joint position and to improve image quality.
[0002]
[Prior art]
[Patent Document 1]
JP-A-10-86438
2. Description of the Related Art In an image forming apparatus such as a copier, a printer, and a facsimile apparatus using an electrophotographic method, a uniformly charged photoconductor is irradiated with writing light modulated by image data in an optical writing unit. Then, an electrostatic latent image is formed on the photoconductor, and toner is supplied to the photoconductor on which the electrostatic latent image is formed by a developing unit to develop the photoconductor. The image forming apparatus transfers the toner image on the photoreceptor to recording paper at a transfer unit, and then heats and presses the toner image transferred onto the recording paper at a fixing unit to form an image.
[0003]
As an optical writing unit of such an image forming apparatus, an LD scanning method using a laser beam scanning optical system including an LD (Laser Diode) for emitting a laser as a light source and a polygon mirror rotated and driven by a polygon motor; As a light source, a light emitting element array system in which light emitting elements such as LEDs (Light Emitting Diodes) are arranged in an array is generally used.
[0004]
The light emitting element array method has no moving parts like the polygon mirror of the LD scanning method, has high reliability, and has a main scanning in the case of a wide-area machine that requires large-format print output such as A0 width. Optical space for scanning the light beam in the direction is unnecessary, and it can be dealt with by arranging an LED head (light emitting element array unit) in which an optical element such as an LED array and a selfoc lens is integrated, Since the whole apparatus can be miniaturized, the LD scanning method has been replaced.
[0005]
On the other hand, in the light emitting element array system, it is necessary to use a light emitting element array unit having a length longer than the image writing width as a light emitting element array unit. In order to maintain the accuracy of the write beam arrangement, the number of LED element driver ICs used in accordance with the long light emitting element array unit increases and the production yield decreases. It is necessary to use components with high accuracy, and the unit cost of the components is extremely high as compared with a light emitting element array unit of a small printer or copying machine. In addition, if even one dot in the long light emitting element array unit fails, the entire light emitting element array unit must be replaced, which is expensive from this viewpoint.
[0006]
Therefore, the present applicant firstly configured the exposing means by a plurality of solid linear writing devices arranged along the axial direction of the photoconductor, and set a plurality of maximum photoconductor widths in the axial direction of the photoconductor. (Japanese Patent Application Laid-Open No. H11-163873) proposes an image forming apparatus capable of performing divided exposure using a solid line writing device.
[0007]
That is, in this prior art, a plurality of (two or three) LED heads are arranged along the axis of the photoreceptor and divided exposure is performed. By arranging three LED heads in a staggered manner in the seed scanning direction to form an A0 width as a whole and performing divided exposure, an inexpensive writing unit is formed even in a large machine.
[0008]
[Problems to be solved by the invention]
However, in the above-mentioned conventional technology, as a solid line writing device, for example, a plurality of LED heads are arranged along the axial direction of the photoconductor by a maximum photosensitive width in the axial direction of the photoconductor, and each LED head is arranged. Due to the divisional exposure, there is a problem that the image quality at the joint between the LED heads deteriorates.
[0009]
That is, for example, when three LED array units 1001, 1002, and 1003 are arranged in a zigzag pattern as shown in FIG. 8, for example, the light emitting element array unit 1001 and the light emitting element array unit 102 overlap. If the joint dot Da is binary data “1”, the distance between the dot Da and the dot Db of the light emitting element array unit 1001 as shown in FIG. However, there is a problem that the light amount increases due to interference with the dots Dc of the light emitting element array unit 1001 and black stripes are generated. In this case, as shown in FIG. 9, when the dot Da is set to the binary data “0”, the amount of light is reduced, white stripes are generated, and the image quality is also deteriorated.
[0010]
However, if the gradation of the one-dot image data is multi-valued, it is possible to easily correct the light amount unevenness of the white streak and the black streak by controlling the light amount at the joint portion. In the case of binary (“0” or “1”), even if the light amount is corrected by controlling the image data of the joint portion to “0” or “1”, as described above, the joint portion Cannot be corrected, and the image quality deteriorates.
[0011]
Therefore, according to the first aspect of the present invention, a plurality of light emitting element array units each having a light emitting element array in which a plurality of light emitting elements are arranged in one direction are arranged in a sub-scanning direction with the axial direction of the photoconductor as a main scanning direction. It is arranged in a staggered manner with a predetermined amount of displacement in the main scanning direction with a certain amount of displacement, and one line of image data is divided for each light emitting element array unit and transferred to each light emitting element array unit, When driving each light emitting element and performing main scanning, one line of image data is transferred to each light emitting element array unit a plurality of times during one main scanning line, and each light emitting element is driven. It is an object of the present invention to provide an image writing device that increases the gradation of image data, prevents light amount unevenness at joint positions, and improves image quality.
[0012]
According to a second aspect of the present invention, among the light emitting elements at the joint positions between the light emitting element array units at the overlapping portion of the light emitting element array units, the joint of one or both of the overlapping light emitting element array units is provided. By controlling the image data to be transferred to the light emitting element at the position and controlling the number of times of lighting of the light emitting element at the joint position, the gradation of the binary image data at the joint position is further increased, and It is an object of the present invention to provide an image writing device that further prevents unevenness in the amount of light at a position and further improves image quality.
[0013]
The invention according to claim 3, wherein the image data to be transferred to the light emitting element at the joint position is based on the distance between the light emitting elements between the overlapping light emitting element array units at the joint position, and the light emitting element at the joint position. By controlling the image data to be transferred to the light emitting element and controlling the number of times the light emitting element is turned on, the gradation of the binary image data at the joint position is further increased, and the uneven light amount at the joint position is further reduced. It is an object of the present invention to provide an image writing apparatus which prevents the image writing and further improves the image quality.
[0014]
[Means for Solving the Problems]
The image writing apparatus according to the first aspect of the present invention includes a light emitting element array in which a plurality of light emitting elements are arranged in one direction, and a plurality of image forming means for forming light emitted from the light emitting element array on a photosensitive member. The light emitting element array units are arranged in a zigzag manner so as to be shifted by a predetermined amount in the sub-scanning direction with the axial direction of the photosensitive member being the main scanning direction and overlap by a predetermined amount in the main scanning direction. In an image writing apparatus for dividing the image data for a line for each light emitting element array unit, transferring the divided data to each light emitting element array unit, and driving each light emitting element of the light emitting element array unit to perform main scanning, The data transfer control means transfers one line of image data to each of the light emitting element array units a plurality of times during one main scanning line, and drives each of the light emitting elements. It has achieved.
[0015]
According to the above configuration, the plurality of light emitting element array units having the light emitting element array in which the plurality of light emitting elements are arranged in one direction are shifted by a predetermined amount in the sub-scanning direction with the axial direction of the photoconductor as the main scanning direction, Arranged in a staggered manner with a predetermined amount of overlap in the main scanning direction, image data for one line is divided for each light emitting element array unit and transferred to each light emitting element array unit, and each light emitting element of the light emitting element array unit is transferred. When driving the main scanning, the image data for one line is transferred to each light emitting element array unit a plurality of times during one main scanning line to drive each light emitting element. By increasing the gradation, unevenness in the amount of light at the joint position can be prevented, and the image quality can be improved.
[0016]
In this case, for example, as described in claim 2, the image data transfer control means, among the light emitting elements at the joint position between the light emitting element array units in the overlapping portion of each light emitting element array unit, Image data to be transferred to one or both of the overlapping light emitting element array units to the light emitting element at the joint position may be controlled to control the number of times the light emitting element at the joint position is turned on.
[0017]
According to the above configuration, among the light emitting elements at the joint positions between the light emitting element array units in the overlapping portion of the respective light emitting element array units, one of the overlapping light emitting element array units or both of the overlapping light emitting element array units have the joint position. Since the number of times of lighting of the light emitting element at the joint position is controlled by controlling the image data transferred to the light emitting element, the gradation of the binary image data at the joint position is further increased, and the joint position is increased. Can be further prevented, and the image quality can be further improved.
[0018]
Further, for example, as described in claim 3, the image data transfer control means transmits the image data to be transferred to the light emitting element at the joint position between the overlapping light emitting element array units at the joint position. The number of lighting of the light emitting element may be controlled by controlling image data to be transferred to the light emitting element at the joint position based on the element interval.
[0019]
According to the configuration, the image data to be transferred to the light emitting element at the joint position is transferred to the light emitting element at the joint position based on the distance between the light emitting elements between the overlapping light emitting element array units at the joint position. Image data to be controlled to control the number of times the light emitting element is turned on, so that the gradation of the binary image data at the joint position is further increased, and the uneven light amount at the joint position is further prevented. Image quality can be further improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferred limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.
[0021]
FIGS. 1 to 7 are diagrams showing an embodiment of the image writing apparatus of the present invention. FIG. 1 is a schematic diagram of a digital copying apparatus 1 to which an embodiment of the image writing apparatus of the present invention is applied. It is a block diagram.
[0022]
In the digital copying apparatus 1, a paper feeding unit 3, a transporting unit 4, an image forming unit 5, a fixing unit 6, a paper discharging unit 7, an image reading unit 8, and the like are housed in a main body housing 2. A tray 10, a document table 11, a separation charger 12, a transport tank 13, a paper discharge tray 14, and the like are provided, and an operation unit 15 (see FIG. 2) is provided.
[0023]
A plurality of transfer papers 21 are set in the paper supply unit 3, and the transport unit 4 includes a registration roller 22 and the like. It is transported to the forming section 5. The transfer unit 4 also transfers the transfer paper 21 set on the manual feed tray 10 to the image forming unit 5 after adjusting the timing with the registration rollers 22.
[0024]
The image forming unit 5 includes a charging unit 24, an optical writing unit 25, a developing unit 26, a transfer unit 27, a cleaning unit 28, and the like, with the photosensitive member 23 driven to rotate counterclockwise in FIG. The charging unit 24 uses, for example, a scorotron charger with a grid, and charges the photoconductor 23 uniformly (for example, to −1200 V). The image forming unit 5 irradiates the photoconductor 23 uniformly charged by the charging unit 24 with light whose lighting is controlled based on image data of a document read by the image reading unit 8 by the optical writing unit 25. Then, the charge on the surface of the photoreceptor 23 in the portion irradiated with light is caused to flow to the ground by a photoconductive phenomenon to be extinguished to form an electrostatic latent image, and is developed on the photoreceptor 23 on which the electrostatic latent image is formed. The unit 26 applies toner to form a toner image. That is, the toner in the developing unit 26 is negatively charged by stirring, the bias is applied to −700 V, and the toner adheres only to the light irradiation part. The image forming unit 5 transfers the toner image formed on the photoreceptor 23 to the transfer paper 21 conveyed from the paper supply unit 3 by the transfer unit 27, and separates the transfer paper 21 on which the transfer is completed by the separation charger 12. Then, the sheet is transported to the fixing unit 6 in the transport tank 13. Further, the image forming unit 5 cleans the residual toner on the photoconductor 23 to which the transfer has been completed by the cleaning unit 28, removes the electricity of the cleaned photoconductor 23 by the charge removing unit (not shown), and then removes the charged toner by the charging unit 24. In the same manner as above, and the image is formed again.
[0025]
As shown in FIG. 2, for example, when the photoconductor 23 has a writing width of A0 width, the optical writing unit 25 includes three LED heads (light emitting element array units) 25a of A3 width. , 25b, 25c, an LED writing control circuit 51, and imaging means such as a SAL (Selfoc lens array) (not shown), etc., and the LED heads 25a to 25c are arranged in an array in the axial direction of the photoconductor 23. The photoconductors 23 are arranged in a staggered manner while being displaced in the rotation direction of the photoconductor 23. As shown in FIG. 3, the LED heads 25a to 25c have 40 LED arrays (light emitting element arrays) 25b_LA1 to 25b_LA40 arranged in a row at equal intervals, and each LED array 25b_LA1 25b_LA40, 192 LED elements LE1 to LE192,..., LE7489 to LE7680 are arranged in a row, and 7680 (192 × 40 = 7680) LED elements are arranged in total. To each of the LED elements LE1 to LE7680, a driver 25b_Dr1 to 25b_Dr40 is connected to each of the LED arrays 25b_LA1 to 25b_LA40, and an LED writing control circuit 51 is connected to each of the drivers 25b_Dr1 to 25b_Dr40.
[0026]
The LED write control circuit (image data transfer control means) 51 causes each of the drivers 25b_Dr1 to 25b_Dr40 to turn on the LED element LE1 to LE7680 for that time, the strobe signal STB, the clock CLK for data transfer, and the start of data transfer. Is output to each of the drivers 25b_Dr1 to 25b_Dr40.
[0027]
In the LED head 25b, a chip thermistor 25b_TH is provided on a heat sink or a printed circuit board, and is connected to each of the drivers 25b_Dr1 to 25b_Dr40. The chip thermistor 25b_TH detects the temperature and detects the temperature of each of the LED elements LE1 to LE7680. Control the emission current. The detection voltage of the chip thermistor 25b_TH is also input to the LED write control circuit 51, which can monitor the temperature based on the temperature detection result from the chip thermistor 25b_TH. The correction can be performed by the Vref signal from the read control circuit 51. Then, the LED write control circuit 51 transfers the image data DATA0 to DATA3 to the respective drivers 25b_Dr1 to 25b_Dr40 simultaneously for four pixels, and the respective drivers 25b_Dr1 to 25b_Dr40 latch the internally transferred image data DATA0 to DATA3, respectively. Then, the LED elements LE1 to LE7680 are turned on and off.
[0028]
The driver 25b_Dr1 to 25b_Dr40 includes a pulse clock 101, a data bus 102, a data latch 103, a current driver 104, and a chip correction data latch 105 for the driver 25b_Dr1, as shown in FIG. A data select signal, a load signal LOAD, image data (light amount correction data) DATA0 to DATA3, a clock CLK, and a set signal RESET are input to the bus clock 101. The load signal LOAD is a switching signal for switching between the LED light quantity correction data transfer mode when the power is on and the normal image data transfer mode. When the power is turned on, the driver 25b_Dr1 latches the light amount correction data of each of the LED elements LE1 to LE7680 and the driver chip correction image data DATA0 to DATA3 to the driver 25b_Dr1 via a data line, and stores the data in the chip correction data latch 105. The driver 25b_Dr1 transfers the image data DATA0 to DATA3 from the bus clock 101 to the data bus 102, latches the data from the data bus 102 by a data latch, and transfers the image data to the constant current driver 104. The driver 25b_Dr1 uses the constant current driver 104 to perform correction based on temperature, correction based on a signal from Vref, and correction of light amount correction data, and causes each of the LED elements LE1 to LE192 to emit light by the strobe signal STB.
[0029]
Referring again to FIG. 1, the fixing unit 6 includes a heating roller heated to a predetermined fixing temperature and a pressure roller pressed against the heating roller, and forms a toner image conveyed from the image forming unit 5. The toner image is fixed on the transfer paper 21 by heating and pressurizing while transferring the transfer paper 21 which is present, and the transfer paper 21 on which the fixing is completed is discharged to the paper discharge unit 7.
[0030]
The paper discharge unit 7 discharges the transfer paper 21 on which the fixing has been completed onto the paper discharge tray 14.
[0031]
The image reading unit 8 includes a roller 31, a contact sensor 32, a white roller 33 and a roller 34 disposed at positions opposed to the contact sensor 32, and the like. It is transported between the contact sensor 32 and the white roller 33. The image reading unit 8 performs main scanning and sub-scanning of the document by the contact sensor 32 while conveying the document conveyed between the contact sensor 32 and the white roller 33 by the roller 31 with the white roller 33, the roller 31, and the roller 34. To read the image of the original. That is, the contact sensor 32 irradiates the original with reading light from the light source (eg, LED), photoelectrically converts reflected light including image information reflected by the original, and outputs an analog image signal. The image reading section 8 discharges the read original to the original discharge tray 16 by the rollers 34. The white roller 33 is used for shading correction for correcting variations due to illumination unevenness, sensitivity unevenness of each pixel of the contact sensor 32, and the like. Shading correction is performed using data output from the sensor 32 as shading data (white reference data).
[0032]
The digital copying apparatus 1 has a circuit block configuration as shown in FIG. 2, and includes the image reading unit 8, the image forming unit 5, the operation unit 15, and the like, and also includes an image information storage unit 41 and the like. ing.
[0033]
The image reading section 8 includes the close contact sensor 32, and further includes an image amplification circuit 81, an A / D conversion circuit 82, a shading correction circuit 83, an image processing circuit 84, a synchronization control circuit 85, a reading control circuit 86, and a scanner drive. An analog image signal of the document read by the contact sensor 32 is input to the image amplification circuit 81. The image amplification circuit 81 amplifies the analog image signal input from the contact sensor 32 and outputs the amplified image signal to the A / D conversion circuit 82. The A / D conversion circuit 83 converts the analog image signal amplified by the image amplification circuit 81. The data is converted into multi-value digital image data for each pixel and output to the shading correction circuit 83. The shading correction circuit 83 takes in the multi-valued digital image data converted by the A / D conversion circuit 82 in synchronization with the clock input from the synchronization control circuit 85, and causes unevenness in light amount, dirt on the contact glass, sensitivity of the contact sensor 32. The distortion due to unevenness or the like is corrected and output to the image processing circuit 84. The image processing circuit 84 converts the multi-valued digital image data shading-corrected by the shading correction circuit 83 into digital recording image data, and stores image information. The data is output to the image memory unit 61 of the unit 41.
[0034]
The image information storage unit 41 includes an image memory unit 61, a system control unit 62, a drive control circuit 63, and the like. The image forming unit 5 includes the LED heads 25a, 25b, 25c and the LED write control circuit 51. And a printer drive unit 52.
[0035]
The digital recording image data from the image processing circuit 84 of the image reading unit 8 is written in the image memory unit 61 of the image information storage unit 41, and the image data written in the image memory unit 61 is processed by the synchronization signal clock. The data is transferred to the LED writing control circuit 51 of the forming unit 5.
[0036]
The system control unit 62 controls the entire digital copying apparatus 1, controls the transfer of image data in the read control circuit 86, the image memory unit 61, and the LED write control circuit 51, and controls the drive control circuit 63. The scanner driving unit 87 and the printer driving unit 52 are controlled via the control unit to drive a motor and the like, so that the conveyance of the original and the conveyance of the transfer paper 21 are smoothly controlled.
[0037]
The image forming unit 5 transfers the digitally recorded image data from the image memory unit 61 to the LED writing control circuit 51 with a synchronization signal clock, and the LED writing control circuit 51 converts the transferred digitally recorded image data into one. Bit conversion is performed on a pixel-by-pixel basis and output to the LED elements LE1 to LE7680 of the LED heads 25a, 25b, and 25c to control the light emission of the LED elements LE1 to LE7680.
[0038]
The flow of digitally recorded image data from the image memory unit 61 to the LED write control circuit 51 is as follows: binary image data of even (E) and odd (O) is converted from the image memory unit 61 to a 2-line parallel 16 MHz To the LED write control circuit 51. The digitally stored image data sent to the LED writing control circuit 51 in two lines is once combined into one line in the LED writing control circuit 51 and then transferred to each of the LED heads 25a, 25b, 25c. You.
[0039]
The operation unit 15 includes an operation panel 71 for performing various operations for causing the digital copier 1 to operate, and an operation control circuit 72. The operation control circuit 72 stores the operation contents of the operation panel 71 in the image information storage unit 41. And outputs the information from the system control unit 62 to the display unit of the operation panel 71.
[0040]
The LED write control circuit 51 is specifically configured as shown in FIG. 5, and includes an image data input unit 90, a first IC 91, a second IC 92, image data RAM units 93A_1 to 93A_3, 93B_1 to 93B_3, It includes image data delay units 94A to 94C, a light amount correction RAM unit 95, an image data output unit 96, a double copy RAM unit 97, a download unit 98, a reset circuit unit 99, and the like.
[0041]
The image data input unit 90 receives a binary image signal even (PKDE), an odd (PKDO), and a timing signal from the image memory unit 61, and these signals are input to the low-voltage operation signal element LVDS of the image data memory unit 61. It has been converted from parallel to serial using a driver. Therefore, the image data input unit 90 converts the serial signal into a parallel signal using an LVDS receiver, and inputs the two signals to the first IC 91 as two image signals PKDE, PKDO, a clock CLKA, and timing signals LSYNC_N, LGATE_N, and FGATEIPU_N. .
[0042]
The first IC 91 synchronizes the timing signals LSYNC_N and FGATEIPU_N with the internal clock of the first IC 91, delays them by the image signal processing time, and outputs them to the second IC 92 as RLSYNC and RFGATE.
[0043]
The first IC 91 internally latches and delays the input image signal to form a 4-bit SRAMDI (3.0.) Together with the SRAM address signals ADRA (10..0) and ADRB (10.0.0). The image data is transferred to the three A group SRAMs 93A_1 to 93A_3 of the RAM units 93A_1 to 93B_3 and the B group SRAMs 93B_1 to 93B_3 at 8 MHz. The SRAM 93A_1 is assigned to the LED head 25a, the SRAM 93A_2 is assigned to the LED head 25b, and the SRAM 93A_3 is assigned to the LED head 25c. The image data RAM units 93A_1 to 93B_3 sequentially store the image signals at 8 MHz in the A group SRAMs 93A_1 to 93A_3, and when one line is completed, read the image signals from the three A group SRAMs 93A_1 to 93A_3 at the same time and transfer them to the first IC 91. I do.
[0044]
The first IC 91 latches the image signal read from the A-group SRAMs 93A_1 to 93A_3 by an internal circuit, and sets the image data for the LED head 25a in the second IC 92 to the LED head 25b and the LED head 25c in 8-bit units. Image data is transferred to image data delay units 94A to 94C, which are FM (field memories), and a read operation from group A SRAMs 93A_1 to 93A_3 is performed several times during one main scanning line. Transfer in the same way.
[0045]
Further, the image data RAM units 93A_1 to 93B_3 store the next line image signal in the B group SRAMs 93B_1 to 93B_3 in the same manner as the A group SRAMs 93A_1 to 93A_3 while reading the A group SRAMs 93A_1 to 93A_3. The image data RAM units 93A_1 to 93B_3 connect the lines by performing the read operation and the write operation by toggling the A group SRAMs 93A_1 to 93A_3 and the B group SRAMs 93B_1 to 93B_3.
[0046]
As described above, the optical writing unit 25 arranges the LED heads 25a, 25b, and 25c having the A3 width in a staggered manner, so that the LED head 25b is positioned on the mechanical layout with respect to the LED head 25a. , 17 mm apart from each other in the sub-scanning direction.
[0047]
Therefore, when the image signals output from the A-group SRAMs 93A_1 to 93A_3 and the B-group SRAMs 93B_1 to 93B_3 are simultaneously processed and transferred to the LED head 25b, the LED head 25b is 17 mm (17 mm) in the sub-scanning direction with respect to the LED head 25a. /42.3 μm (1 dot at 600 dpi) = about 400 lines).
[0048]
Therefore, the LED write control circuit 51 converts the 8-bit image signal of the LED head 25b transferred from the first IC 91 into the field memory 94A of the image data delay units 94A to 94C in order to correct such a maker-like shift. Are transferred in line order, and data is written for 200 lines (fixed). Next, the LED write control circuit 51 reads out the image signal from the field memory 94A in which the image signal has been written, and at the same time, writes 200 lines (variably) in the cascade-connected field memory 94B. The image signal is read out from 94B and input to the second IC 92 as L2DFMO (7.0). Therefore, the image signal to the LED head 25b is delayed by 400 lines (17 mm). Since the number of lines to be delayed differs individually depending on the component accuracy of the LED head 25b, assembling variation, and the like, the number of lines to be delayed can be controlled in units of one line (42.3 μm).
[0049]
Also, as described above, since the optical writing unit 25 has the A3 width LED heads 25a, 25b, and 25c arranged in a staggered manner, the LED heads 25c are arranged in a mechanical layout based on the LED heads 25a. , Are shifted by 1 mm in the sub-scanning direction.
[0050]
Therefore, when the image signals output from the A group SRAMs 93A_1 to 93A_3 and the B group SRAMs 93B_1 to 93B_3 are simultaneously processed and transferred to the LED head 25c, the LED head 25c is 1 mm (1 mm) in the sub-scanning direction with respect to the LED head 25a. /42.3 μm (1 dot at 600 dpi) = approximately 23 lines).
[0051]
Therefore, the LED write control circuit 51 converts the 8-bit image signal of the LED head 25c transferred from the first IC 91 into the field memory 94C of the image data delay units 94A to 94C in order to correct such a manufacturer-like shift. Are transferred in line order, and are written for 23 lines (variable). Next, the LED write control circuit 51 reads the image signal from the field memory 94C in which the image signal has been written, and inputs the image signal to the second IC 92 as L3DFMO (7.0). Therefore, the image signal to the LED head 25c is delayed by 23 lines (1 mm). Since the number of lines to be delayed differs depending on the component accuracy and the assembly variation of the LED head 25c, it can be controlled in units of one line (42.3 μm).
[0052]
The LED heads 25a, 25b, and 25c are provided with 6-bit correction data for each of the LED elements LE1 to LE7680 and an LED array every 192 of the LED elements LE1 to LE7680 in order to correct the light amount variation among the LED elements LE1 to LE7680. A light amount correction ROM (not shown) containing chip correction data is mounted, and when the power is turned on, the digital copying apparatus 1 transmits the light amount variation correction data of the light amount correction ROM to each of the LED heads 25a, 25b, and 25c. Transfer to
[0053]
That is, when the power is turned on and after the LED write control circuit 51 is reset, the LED write control circuit 51 first passes through the second IC 92 from the light amount correction ROM (EEPROM) mounted in the LED head 25a via the second IC 92. Serial / parallel conversion is performed by an internal circuit, and stored in the light quantity correction data RAM unit 95 in order from 0000H by an address signal HOSEIAD (12.0). An SRAM is used as the light amount correction data RAM unit 95. When the data for the dots of the LED heads 25a, 25b, and 25c are stored in the light amount correction data RAM unit 95, the LED write control circuit 51 next reads the data from the light amount correction data RAM unit 95 to perform the light amount correction. The data HOSEID (7.0) is again input to the second IC 92, and the internal circuit of the second IC 92 converts the data in 4-bit units, transfers the data from the L1DT (3.0) to the LED head 25a, The light amount of the LED head 25a is corrected.
[0054]
When the LED write control circuit 51 transfers the light amount correction data to the LED head 25a in this way, similarly to the LED head 25a, it sequentially performs the light amount correction on the LED heads 25b and 25c in the same manner.
[0055]
Then, the light quantity correction data transferred in this manner is held inside the LED heads 25a, 25b, 25c unless the power of the LED heads 25a, 25b, 25c is turned off.
[0056]
Further, the digital copying apparatus 1 has a double copy function of printing and copying the same image up to 420 mm (A2 vertical size) in the main scanning direction twice on a sheet of maximum 841 mm (A0 vertical size). I have.
[0057]
At the time of this double copy, the digital copier 1 transfers the binary image signal (PKDE, PKDO) from the image memory unit 61 to the LED write control circuit 51 at a half or less of LSYNC_N. The dubbing operation of the image signal is performed in one LSYNC_N. That is, the LED write control circuit 51 converts the image signals (PKDE, PKDO) transmitted at 16 MHz from the image memory unit 61 into the double copy RAM unit 97 as WDE and WDO from the first IC 91 as address signals WADR (13. 0), and the image data is stored in the double copy RAM unit 97 and, at the same time, stored in the three A group SRAMs 93A_1 to 93A_3 of the image data RAM units 93A_1 to 93A_3 and 93B_1 to 93B_3. Simultaneously with the end of storing the image signal from the image memory unit 61, the image data stored in the double copy RAM unit 97 is read out and taken into the first IC 91, and the LED write control circuit 51 reads the image data sent from the image memory unit 61. Similarly to the data, the group A SRAMs 93A_1 to 93A_3 are additionally read. Therefore, the main-scan 1-line portion of the double-copy image is stored in the A-group SRAMs 93A_1 to 93A_3. The LED write control circuit 51 performs this operation by toggling the group A SRAMs 93A_1 to 93A_3 and the group B SRAMs 93B_1 to 93B_3 to connect the lines.
[0058]
Then, when the digitally recorded image data in units of 8 dots is input as described above, the second IC 92 formats the data in units of 4 dots inside the second IC 92 and sends the data to the image data output unit 96 together with the data transfer clock CLK and the lighting timing signal. Output. When image data formatted in units of 4 dots is input from the second IC 92 together with the data transfer clock CLK and the lighting timing signal, the image data output unit 96 transfers the image data to the LED heads 25a, 25b, and 25c.
[0059]
The LED write control circuit 51 includes a download section 98 for storing a write control program, and the download section 9 is configured by, for example, an EPROM (Erasable and Programmable ROM). The first IC 91 and the second IC 92 are SRAM (Static RAM) type CPLDs having the download unit 98 in this manner, and when the power is turned off, the write control program in the first IC 92 and the second IC 92 is provided. Is erased, and when the power is turned on, it is necessary to download (configure) the write control program every time. That is, when the power is turned on, the LED write control circuit 51 transfers the program as DOWNLOAD_CPLD1 from the download unit 98 to the first IC 91 as serial data, and performs the download. The LED write control circuit 51 transfers the program as DOWNLOAD_CPLD2 from the download unit 98 to the second IC 92 as serial data at the same time that the program download to the first IC 91 is completed, and downloads the program.
[0060]
Further, the LED write control circuit 51 includes a reset circuit 99, and performs initialization of the system. That is, when the power is turned on and when the voltage drop of the power supply of the LED write control circuit 51 occurs, the reset circuit 99 outputs the system reset signal RESET_CPLD1 and the system reset signal RESET_CPLD2. The system reset signal RESET_CPLD1 is input to the first IC 91, and the system reset signal RESET_CPLD2 is input to the second IC 92. The first IC 91 and the second IC 92 reset the internal counter based on the system reset signal RESET_CPLD1 and the system reset signal RESET_CPLD2, respectively, and initialize the system.
[0061]
Then, the system control unit 62 inputs the control signal input data bus LDATA (7.0.), The address bus LADR (5.0.0), the latch signal VDBCS, and the image transfer signal SGATE_N to the first IC 91 and the second IC 92. Thus, the setting and control of the writing conditions (whether double copy is performed, the size of the writing paper, etc.) to the LED writing control circuit 51 are performed.
[0062]
Next, the operation of the present embodiment will be described. The digital copying apparatus 1 of the present embodiment transfers the image data to the LED heads 25a, 25b, and 25c several times during one main scanning line to emit light, and also transfers the image data to the joint dots (LED elements). By controlling the data, the gradation of the binarized hand is increased, and the unevenness in the light amount at the joints between the LED heads 25a, 25b, and 25c, which are binary LED heads, is eliminated.
[0063]
That is, the optical writing unit 25 is arranged such that the three LED heads 25a, 25b, and 25c are arranged in a staggered manner in the axial direction of the photoconductor 23, and the dot positions of the LED heads 25a and 25c are not overlapped. Is controlled so that the joint portion with the LED head 25b is overlapped by less than one dot, and in each of the LED heads 25a, 25b, and 25c, the binary image data is transferred only once as in the related art. When turned on, as shown in FIGS. 9 and 10, black streaks and white streaks are generated at the joints between the LED heads 25a, 25b, and 25c.
[0064]
Therefore, the digital copying apparatus 1 of the present embodiment performs dot data correction control of the joint between the LED heads 25a, 25b, and 25c by giving the binary data a gradation.
[0065]
That is, as shown in FIG. 6, a one-line lighting image (one-dot interval lighting) of the LED heads 25 a, 25 b, and 25 c, a joint dot (LED) from the image effective widths L1 to L3 of the LED heads 25 a, 25 b, and 25 c. The element) a1 and the joint dot (LED element) a2 overlap by less than one dot between the LED heads 25a, 25b, and 25c. In FIG. 6, the dot a1 is simplified as a dot a, and the dot a2 is simplified as a dot b.
[0066]
Then, as shown in the timing chart of FIG. 6, the digital copying apparatus 1 simultaneously connects three LED heads 25a, 25b, and 25c to one LED scanning line in one main scanning line L. The dots to 7680 dots are repeatedly turned on three times.
[0067]
Further, when performing the three scans, the digital copying apparatus 1 applies one dot between the main scanning one line to the joint dots a1 and a2 of the LED head 25b as shown in the timing chart of FIG. In the first scan, “1” (lighting: black data) is printed. In the second scanning, the seam dot a1 is “0” (light off: white data), and the seam dot a2 is “1”. (Lighting: black data) is printed, and in the third scan, “0” (light off: white data) is printed for both the joint dot a1 and the joint dot a2.
[0068]
In other words, the LED heads 25a, 25b, and 25c are simply scanned three times in one main scanning line L to turn on or off the joint dots a1 and a2 as shown by the light amount waveform in FIG. 7A. As shown by the light amount waveform in FIG. 7B, when the image data of the joint dots a1 and a2 is controlled to be turned on and off as compared with the case where the light amount waveform is shown in FIG. Tones can be provided, and the density of the joints can be made even more uniform, thereby preventing the occurrence of black streaks and white streaks due to uneven light quantity at the joints.
[0069]
Further, the digital copying apparatus 1 performs the above three scans, when controlling the image data of the joint dots a1 and a2, based on the interval between the dots a1 and a2 of the joint. The image data may be controlled.
[0070]
In this case, the gradation of data in the beech determining section can be further increased, and the unevenness in the light amount at the joint can be further prevented, and the image quality can be further improved.
[0071]
In the above description, the image data is controlled for the joint dots (LED elements) 1a and 2a of the LED head 25b. However, the control of the image data is performed for the joint dots (LED elements) of the LED heads 25a and 25c. Alternatively, the control of the image data may be performed, or the control of the image data may be performed only for the joint dots of the LED heads 25a and 25c.
[0072]
As described above, in the digital copying apparatus 1 of the present embodiment, the plurality of LED heads 25a, 25b, and 25c each having the LED array in which the plurality of LED elements are arranged in one direction are mainly arranged in the axial direction of the photoconductor 23. The scanning direction is shifted by a predetermined amount in the sub-scanning direction, and is arranged in a staggered manner so as to overlap by a predetermined amount in the main scanning direction. One line of image data is divided into LED heads 25a, 25b, and 25c, and each LED head 25a is divided. , 25b, and 25c to drive the LED elements of the LED heads 25a, 25b, and 25c to perform main scanning, so that one line of image data is written to each of the LED heads 25a, 25b during one main scanning line. , 25c to drive each LED element.
[0073]
Accordingly, it is possible to increase the gradation of the binary image data, prevent the light amount unevenness at the joint position, and improve the image quality.
[0074]
In the digital copying apparatus 1 of the present embodiment, the LED elements (dots) at the joint positions (joint portions) between the LED heads 25a, 25b, and 25c at the overlapping portions of the LED heads 25a, 25b, and 25c. Controlling the image data to be transferred to one or both of the overlapping LED heads 25a, 25b, and 25c to the LED element at the joint position, and controlling the number of lighting of the LED element at the joint position. I have.
[0075]
Therefore, it is possible to further increase the gradation of the binary image data at the joint position, to further prevent the light amount unevenness at the joint position, and to further improve the image quality.
[0076]
Further, the digital copying apparatus 1 according to the present embodiment transfers the image data to be transferred to the LED element at the joint position based on the distance between the LED elements between the overlapping LED heads 25a, 25b, and 25c at the joint position. The image data to be transferred to the LED element at the joint position is controlled to control the number of times the LED element is turned on.
[0077]
Therefore, it is possible to further increase the gradation of the binary image data at the joint position, to further prevent the light amount unevenness at the joint position, and to further improve the image quality.
[0078]
As described above, the invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and can be variously modified without departing from the gist thereof. Needless to say.
[0079]
【The invention's effect】
According to the image writing apparatus of the first aspect, the plurality of light emitting element array units each having the light emitting element array in which the plurality of light emitting elements are arranged in one direction are arranged such that the axial direction of the photoconductor is the main scanning direction. It is arranged in a staggered manner with a predetermined amount of displacement in the sub-scanning direction and a predetermined amount of overlap in the main scanning direction, and the image data for one line is divided for each light emitting element array unit and transferred to each light emitting element array unit. When each light emitting element of the light emitting element array unit is driven to perform main scanning, one line of image data is transferred to each light emitting element array unit a plurality of times during one main scanning line to drive each light emitting element. Therefore, it is possible to increase the gradation of the binary image data, prevent the light amount unevenness at the joint position, and improve the image quality.
[0080]
According to the image writing apparatus of the present invention, any one of the overlapping light emitting element array units among the light emitting elements at the joint position between the light emitting element array units at the overlapping portion of the light emitting element array units. Since the image data to be transferred to one or both of the light emitting elements at the joint position is controlled to control the number of times of lighting of the light emitting element at the joint position, the gradation of the binary image data at the joint position is controlled. Can be further increased, and the uneven light amount at the joint position can be further prevented, and the image quality can be further improved.
[0081]
According to the image writing device of the third aspect of the present invention, the image data to be transferred to the light emitting element at the joint position is determined based on the distance between the light emitting elements between the overlapping light emitting element array units at the joint position. Since the image data to be transferred to the light emitting element at the joint position is controlled to control the number of times the light emitting element is turned on, the gradation of the binary image data at the joint position is further increased, and The unevenness in the light amount at the eye position can be further prevented, and the image quality can be further improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a digital copying apparatus to which an embodiment of an image writing apparatus according to the present invention is applied.
FIG. 2 is a block diagram of a main part circuit of the digital copying apparatus of FIG. 1;
FIG. 3 is a circuit configuration diagram of the LED head of FIG. 2;
FIG. 4 is a detailed circuit diagram of a driver of the LED head of FIG. 3;
FIG. 5 is a detailed circuit diagram of the LED write control circuit of FIG. 2;
FIG. 6 is an explanatory diagram of scanning control of the LED head by the LED writing control circuit of FIG. 5;
7A and 7B are explanatory diagrams of scanning control of an LED head and waveforms of light amounts of LED elements before (a) and after performing image data control of joint dots by the LED writing control circuit of FIG. 5; .
FIG. 8 is an explanatory diagram of a conventional LED head and its joint dot.
FIG. 9 is an explanatory diagram in a case where a black streak occurs at a joint portion in the LED head of FIG. 8;
FIG. 10 is an explanatory diagram of a case where white streaks occur at a joint portion in the LED head of FIG. 8;
[Explanation of symbols]
1 Digital copier
2 Body case
3 Paper feed unit
4 Transport unit
5 Image forming unit
6 Fixing section
7 Paper output unit
8 Image reading unit
10 Bypass tray
11 Platen
12 Separate charger
13 Transfer tank
14 Output tray
15 Operation unit
16 Document output tray
21 Transfer paper
22 Registration roller
23 Photoconductor
24 Charging part
25 Optical writing unit
25a, 25b, 25c LED head
26 Developing section
27 Transfer unit
28 Cleaning unit
31 rollers
32 Adhesion sensor
33 white roller
34 rollers
41 Image information storage unit
51 LED write control circuit
52 Printer driver
61 Image memory section
62 System control unit
63 Drive control circuit
71 Operation panel
72 Operation control circuit
81 Image amplification circuit
82 A / D conversion circuit
83 Shading correction circuit
84 Image processing circuit
85 Synchronous control circuit
86 reading control circuit
87 Scanner driver
90 Image data input section
91 1st IC
92 2nd IC
93A_1 to 93A_3, 93B_1 to 93B_3 Image data RAM unit
94A-94C Image data delay unit
95 Light intensity correction RAM section
96 Image data output unit
97 Double copy RAM
98 Download Department
99 Reset circuit
101 pulse clock
102 Data bus
103 Data latch
104 current driver
105 Chip correction data latch

Claims (3)

A plurality of light emitting element array units each including a light emitting element array in which a plurality of light emitting elements are arranged in one direction and an image forming means for forming light emitted from the light emitting element array on a photosensitive member are arranged in an axial direction of the photosensitive member. Are shifted in the sub-scanning direction by a predetermined amount with respect to the main scanning direction, and are arranged in a staggered manner so as to overlap by a predetermined amount in the main scanning direction. In an image writing apparatus which divides and transfers to each light emitting element array unit and drives each light emitting element of the light emitting element array unit to perform main scanning, the image data transfer control means is provided between one main scanning line. An image writing apparatus, wherein one line of image data is transferred to each of the light emitting element array units a plurality of times to drive each of the light emitting elements. The image data transfer control unit may include, among the light emitting elements at the seam position between the light emitting element array units at the overlapping portion of the light emitting element array units, the light emitting element array unit of one or both of the overlapping light emitting element array units. 2. The image writing device according to claim 1, wherein the image data transferred to the light emitting element at the joint position is controlled to control the number of times the light emitting element at the joint position is turned on. The image data transfer control means transmits the image data to be transferred to the light emitting element at the joint position, based on the distance between the light emitting elements between the overlapping light emitting element array units at the joint position, the light emission at the joint position. 3. The image writing apparatus according to claim 2, wherein the number of times of lighting of the light emitting element is controlled by controlling image data transferred to the element.

Images