JP2003039735A - Apparatus for driving optical write head, and method for driving optical write head using the apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for driving an optical write head and a method for driving an optical write head using the apparatus by which the optical write head is efficiently manufactured, the manufacturing yield is improved and printing images having a printing position deviation eliminated can be obtained in relation to an optical write head-driving apparatus for optically writing to a photosensitive material or the like and a method for driving an optical write head using the apparatus. SOLUTION: The optical write head-driving apparatus is constituted of a shift register 60, a latch circuit 62, a delay circuit 68, an AND gate 66, a buffer 67 and an LED array chip 31. Set values set to delay circuits 68-1 to 68-56 are values in conformity with deviation amounts from reference positions of corresponding LED array chips. When LED elements in each LED array chip 31 are driven, a strobe signal is delayed by corresponding delay circuits 68-1 to 68-56 and outputted to the LED elements. Images without the printing deviation in a vertical scanning direction are provided accordingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus for performing a printing process using an electrophotographic system, and more particularly to an optical writing head driving apparatus for optically writing on a photosensitive material or the like, and an optical writing apparatus using the apparatus. The present invention relates to a write head driving method.

[0002]

2. Description of the Related Art Recently, as an optical writing head, a tandem type color electrophotographic recording apparatus has been adopted which uses, for example, LED elements in an array and uses an image forming unit for each color. In such a color electrophotographic recording apparatus, an image forming unit using, for example, yellow (Y), magenta (M), cyan (C), and black (BK) toners is arranged, and each image forming unit is charged,
Exposure, development and transfer processing are performed to form an image on recording paper.

FIG. 20 shows an example of a drive circuit used in a color electrophotographic recording apparatus having such a structure. Also, FIG.
FIG. 1 is a diagram for explaining the drive timing. Bit map data is supplied to the shift register 100 from an interface circuit (not shown) in synchronization with a clock signal (CLK), and data for one line is supplied to the shift register 100.
Input to the latch circuit 101 in synchronization with the latch signal.
The data for one line is latched in parallel. Then, the data latched by the latch circuit 101 is output to the AND gate 102, and all the corresponding LED elements 10 are output according to the strobe signal output at the same timing.
3 is output. Each LED element 103 is controlled to emit light or not to emit light according to the data, and the light emitted from the LED element exposes the peripheral surface of the photosensitive drum.

In the above example, LE is used as an optical writing element.
Although the case of the D element has been described, the present invention is not limited to the optical writing head using the LED element.

[0005]

However, the conventional device has the following problems. (A) First, in the above-mentioned apparatus, yellow (Y), magenta (M), cyan (C), and black (BK) toners are sequentially transferred onto a sheet to form a color image, so that image formation of each color is performed. The placement accuracy of the unit is important. That is, if the arrangement accuracy of the image forming units for each color is poor,
The formed image is misaligned, resulting in an image with poor print quality.

In particular, the linear accuracy in the sub-scanning direction is based on the LED head structure, that is, if the size of the LED element is 300 dpi, the LED element of 84.7 μm square is aligned in a straight line with the paper width (for A3 paper, about 300 mm. Width) of about 3500 pieces should be arranged in a straight line, and the linearity of the light spot of the LED element imaged on the photoconductor through the SELFOC lens is not affected by visual observation. An accuracy within about 80 μm is required in order to fit within mm.

However, with the above-mentioned accuracy, a predetermined number of LEs are
It is difficult to accurately arrange the array chip having the D element formed therein. Therefore, in order to improve the assembling accuracy, it takes time to form the optical writing head, and the manufacturing yield is low. For example, when the positional displacement shown in FIG. 22 (a) occurs in the arrangement of the LED array chips, the character "A" shown in FIG. 22 (b) is printed, so that the drive circuit shown in FIG. When processing is performed,
The print result is shown in FIG. That is, FIG.
When the 1st, 4th and 8th LED array chips from the left shown in (a) are used as a reference, the 2nd LED array chip is advanced by "1" with respect to the reference LED array chip (reference The third LED array chip is advanced by "2" and the fifth LED array chip is delayed by "1" (reference LED is the reference LED). The delay direction is indicated by + (plus) with respect to the array chip), the sixth LED array chip is delayed by "2", and the seventh LED array chip is delayed by "1". Therefore, if the printing process is performed according to the conventional printing control in this state, an image with poor printing quality will be obtained as shown in FIG. (B) On the other hand, the above-mentioned tandem type image forming apparatus has the following problems.

That is, in the case where the LED heads of the respective colors are displaced from each other in the sub-scanning direction (Y direction), the right and left ends of the head have different amounts of deviation in the sub-scanning direction. This is the case of so-called θ direction deviation. In addition, when uneven rotation of the photosensitive drum drive system or uneven rotation due to eccentricity of the drum occurs,
This is a case where uneven rotation occurs in a transport drive system such as a transport belt.

In such a case, in the conventional print control, a print position shift occurs, resulting in an image with poor print quality. In view of the above conventional circumstances, an object of the present invention is to efficiently manufacture an optical writing head, improve manufacturing yield, and use an optical writing head drive device that can obtain a printed image without printing position deviation, and an apparatus using the same. A method for driving an optical writing head is provided.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a plurality of optical writing heads for recording a reference image and a non-reference image in the sub-scanning direction. In an optical writing head drive device of an image forming apparatus, which is arranged and compositely records an image formed on a recording medium by the plurality of optical writing heads, a mutual image formed by the plurality of optical writing heads. Measuring means for measuring the amount of positional deviation with respect to the sub-scanning direction, and an optical writing element for recording a non-reference image required to match the non-reference image with the reference image on the recording medium based on the measurement result of the measuring means. Calculation means for calculating the drive timing correction data, write means for writing the drive timing correction data in the storage means, and drive time written in the storage means It can be achieved by providing an optical writing head driving device having a drive timing control means for controlling the driving timing of the optical writing device according to the correction data.

According to the present invention, a plurality of optical writing heads each composed of an array of optical writing elements for recording a reference image and a non-reference image are arranged in the sub-scanning direction, and the plurality of optical writing heads are formed on a recording medium. The present invention relates to an optical writing head driving device used in a recording device for composite recording of recorded images on a recording medium, for example, a tandem type image forming device, and a reference image and a non-reference image formed by a plurality of optical writing heads by a measuring unit. The amount of positional deviation between the images is measured, and the correction data for matching the non-reference image with the reference image on the recording medium is calculated from the measurement result, and the correction data is stored in the storage means. The drive timing of the optical writing element is controlled based on the correction data stored in the means.

With this configuration, for example, in the tandem type image forming apparatus, it is possible to correct the print position deviation in the sub-scanning direction which occurs between the image forming units. The second aspect of the invention embodies the invention of the optical writing head drive device of the first aspect, and, for example, each of the individual images in the synthetic image synthesized on the recording medium formed by the plurality of optical writing heads. The positional deviation of the image with respect to the sub-scanning direction results from the relative deviation of the optical writing heads with respect to the moving direction of the recording medium.

That is, this embodiment is a tandem type image forming apparatus showing a specific example in the case of correcting the print position deviation in the sub-scanning direction which occurs between the image forming units. The so-called Y direction correction in between is embodied. The third aspect of the invention also embodies the invention of the optical writing head driving device of the first aspect. For example, each of the individual images in the synthetic image synthesized on the recording medium formed by the plurality of optical writing heads. The positional deviation of the image with respect to the sub-scanning direction is caused by the degree of imbalance between the optical writing heads.

That is, this embodiment also has a configuration showing a specific example in the case of correcting the print position deviation in the sub-scanning direction which occurs between the image forming units in the tandem type image forming apparatus. The so-called θ correction in between is embodied. The description of claim 4 is also the above-mentioned claim 1.
Of the optical writing head driving device of the present invention, for example, the positional deviation of individual images in the sub-scanning direction in the composite image composed on the recording medium formed by the plurality of optical writing heads is It is caused by the difference in relative movement speed with respect to the recording medium for each optical writing head.

That is, this embodiment also shows a specific example in the case of correcting the print position deviation in the sub-scanning direction which occurs between the image forming units in the tandem type image forming apparatus. It is intended to correct a printing position shift caused by uneven rotation of the photosensitive drum or the like.

The fifth aspect of the invention also embodies the invention of the optical writing head driving device of the first aspect, for example, a composite image synthesized on a recording medium formed by the plurality of optical writing heads. The positional deviation of each image in the sub-scanning direction occurs due to fluctuations in the moving speed of the recording medium conveying unit.

That is, this embodiment also has a configuration showing a specific example in the case of correcting the print position deviation in the sub-scanning direction which occurs between the image forming units in the tandem type image forming apparatus, and for example, conveys a recording medium. It is intended to correct a print position deviation caused by uneven rotation of the conveyor belt.

In order to solve the above-mentioned problems, a sixth aspect of the present invention comprises a plurality of optical writing heads for recording a reference image and a non-reference image, the optical writing heads being arranged in the sub-scanning direction. A method for driving an optical writing head of an image forming apparatus for synthesizing and recording an image formed on a recording medium by the optical writing head of 1 above, in a sub-scanning direction of mutual images formed by the plurality of optical writing heads. Measurement process for measuring the amount, and calculation for calculating drive timing correction data of the optical writing element for recording the non-reference image required to match the non-reference image with the reference image on the recording medium from the measurement result Processing and
Provided is an optical writing head driving method for performing a writing process of writing the drive timing correction data in a storage unit and a drive timing control process of controlling a drive timing of the optical writing element according to the drive timing correction data written in the storage unit. Can be achieved by

While this example relates to the optical writing head driving device described in claims 1 to 5, the present example relates to an optical writing head driving method. Further, the present example relates to a tandem type optical writing head driving method, for example. As described above, by the method of driving the optical writing head, for example, in the tandem type image forming apparatus, it is possible to correct the print position deviation in the sub-scanning direction which occurs between the image forming units.

Further, the claims 7 to 10 are the same as the claim 6.
Claims 2 to 5, which embody the invention described above.
Corresponds to the description.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. << First Embodiment Example >> FIG. 2 is a diagram showing an example in which an optical writing head driving device for explaining a first embodiment example of the present invention is applied to a color electrophotographic recording apparatus. The color electrophotographic recording apparatus used in the description of this example is a so-called tandem type color printer.

In FIG. 1, the color printer 1 comprises a paper supply / conveyance mechanism 2, an image forming section 3 and a fixing section 4. The paper supply / conveyance mechanism 2 is composed of a paper feed cassette 5 in which papers P are stacked and stored, and a paper conveyance system 6. Further, the paper transport system 6 supplies a paper feed roller 8 for carrying out the paper P from the paper feed cassette 5, a paper transport path 7 for carrying the paper P carried out by the paper feed roller 8, and a paper position in conformity with the toner image. Standby roll 9 for feeding paper by feeding
It is composed of drive rolls 10 and 11 for driving the sheet 2, transport guide plates 14, transport rolls 15 and 16, a paper discharge guide 17, and a paper discharge roll 18.

By rotating the paper feed roller 8, the paper feed cassette 5
The paper P carried out from the paper is sent to the standby roll 9 through the paper carrying path 7 and carried out on the carrying belt 12 at the same timing as the toner image formed on the photosensitive drum described later. While the paper P moves on the conveyor belt 12, the toner images are transferred to the paper P on the conveyor belt 12 by the image forming units 21, 22, 23, and 24, and the transfer process to the paper P is performed. . After that, a heat fixing process is performed by the fixing unit 4, the paper is sent to the paper discharge guide 17 by the transport rolls 15 and 16, and is discharged from the paper discharge roll 18 to the outside of the machine.

The fixing section 4 is composed of a heat roll 4a and a pressure contact roll 4b. While the paper P is nipped and conveyed between the heat roll 4a and the pressure contact roll 4b, a plurality of colors transferred to the paper P are transferred. The toner image is melted and fixed on the paper P. On the other hand, the image forming unit 3 is composed of four image forming units 21 to 24 of yellow (Y), magenta (M), cyan (C), and black (BK), which are arranged in this order. In addition, the three image forming units 21 to 23
Is a unit that transfers toner of each color of yellow (Y), magenta (M), and cyan (C) onto the paper P, and performs color printing based on subtractive color mixture. The black (BK) image forming unit 24 is a monochrome unit. This is the unit used for printing. The reason why the black (BK) image forming unit 24 is provided is that it takes time to process a monochrome image with yellow (Y), magenta (M), and cyan (C) toners. This is because an exclusive image forming unit is used to reproduce an accurate color of black (BK).

The image forming units 21 to 24 have the same structure except for the developer (color) stored in the developing container, and a charging device, an LED head, and an LED head are provided near the peripheral surface of the photosensitive drum.
This is a configuration in which a developing device and a transfer roll are sequentially arranged. Here, as an example of the four image forming units 21 to 24, the configuration of the unit will be described by taking an example of the cyan image forming unit 23. The peripheral surface of the photosensitive drum 25 is made of, for example, an organic photoconductive material, and a charger 26, an LED head 27, a developing device 28, and a transfer roll 29 are sequentially arranged near the peripheral surface of the photosensitive drum 25. Has been done. The photoconductor drum 25 rotates in the direction of the arrow, and firstly, the peripheral surface of the photoconductor drum 25 is uniformly charged by the charge applied from the charger 26. next,
By the exposure from the LED head 27, the photosensitive drum 25
An electrostatic latent image is formed on the peripheral surface of, and a toner image is formed by the development processing by the developing device 28. At this time, the photosensitive drum 25
The toner image formed on the peripheral surface of the toner is cyan (C) color toner stored in the developing container 28. The toner image thus formed on the peripheral surface of the photoconductor drum 25 reaches the position of the transfer roll 29 as the photoconductor drum 25 rotates in the direction of the arrow, and is transported by the transfer roll 29 on the transport belt 12. It is transferred to the paper P to be printed.

The toner image transferred onto the upper surface of the paper P is conveyed in the direction of the arrow along with the movement of the conveyor belt 12, and is formed on the paper P by the other image forming units 21 and 22 having the same structure as described above. The yellow (Y) toner and the magenta (M) toner are heat-fixed by the fixing unit 4,
Color printing based on subtractive color mixing is performed. For example, if the print image is blue, the magenta (M) toner is transferred from the image forming unit 22 to the paper P based on the subtractive color mixture, and then the cyan (C) toner is transferred from the image forming unit 23 to the paper P. Realize a blue image. Also, for example,
If the printed image is red, after transferring the yellow (Y) toner from the image forming unit 21 to the paper P, the magenta (M) toner is transferred from the image forming unit 22 to the paper P to realize a red image. .

FIG. 3 shows the image forming units 21 to 2 described above.
LED head (optical writing head) 27 arranged in 4
FIG. The LED head 27 is configured by disposing a plurality of LED array chips 31 on an LED array substrate 30, and a drive IC 31 for LED drive is provided in an adjacent portion.
a and 31b are provided. Each LED light emitting part (LED array chip 31) is a drive IC 31a, 3
A drive signal is sent from 1b via the bonding wires 32a and 32b, and light is emitted according to the drive signal. still,
Reference numeral 33 in the figure denotes a SELFOC lens for forming an image of the light emitted from the LED light emitting portion on the photosensitive drum 25 described above, and is supported by the lens supporting portion 34.

The LED array substrate 30 is attached to a substrate support portion 35 integrally formed with the lens support portion 34, and the substrate support portion 35 (lens support portion 34) is attached to a casing 36 of the image forming unit. There is. FIG. 4 shows a control circuit of the color printer 1 having the above-mentioned mechanical structure. The control circuit of the color printer 1 includes an interface controller (hereinafter referred to as an I / F controller) 40 and an I / F controller 40.
A printer controller 41 connected to the I / F controller 40. A host computer 42 is connected to the I / F controller 40.
Each mechanical unit in the color printer 1 is connected to.

The I / F controller 40 prints on the paper P according to the print information output from the host computer 42.
Bit map data corresponding to each other is created. Incidentally, I
A display unit 44 is connected to the / F controller 40 and performs various displays. Further, the printer controller 41 uses the CP
The U45, the ROM 46, the EEPROM 47, the LED head controller 48, the driver 49, and the buffer 50. The CPU 45 controls printing according to a program stored in the ROM 46, and, for example, the I / F controller 40
The LED head controller 4 uses the bitmap data created in
Output to 8. Further, correction data based on the amount of displacement of the LED elements is written in the EEPROM 47.
In this example, this correction data is data of delay time corresponding to the amount of deviation of the LED array chip 31 in the sub-scanning direction.

The LED head controller 48 is provided with a photoreceptor corresponding to yellow (Y), magenta (M), cyan (C), and black (BK) color toners arranged in the image forming units 21 to 24. LED heads 27Y, 27M, 27C, and 27BK for transferring to the drum are connected. Here, the LED head 27Y is a print head disposed in the yellow (Y) image forming unit 21,
The LED head 27M is a print head provided in the magenta (M) image forming unit 22, and similarly, the LED heads 27C and 27BK are provided in the cyan (C) color and black (BK) image forming units 23 and 24, respectively. The print head is arranged.

On the other hand, the driver 49 is provided with the above-mentioned thermo roll 4
a, a high-voltage power supply unit 51, a DC motor 52, a pulse motor 53, a developing clutch 54, a belt up / down motor 55,
The standby clutch 56 and the fixing clutch 57 are connected. The heat roll 4a is disposed in the heat fixing unit 4 as described above, and is heated to a predetermined temperature according to the control signal output from the driver 49. The high-voltage power supply unit 51 is a circuit that applies a predetermined high voltage to the charger 26 and the transfer roll 29 described above, and is driven by a control signal output from the driver 49. The DC motor 52 and the pulse motor 53 are motors for rotating the photosensitive drum 25 and various rolls, and are driven by a drive signal output from the driver 49. The belt up / down motor 55 is a motor that is driven when switching between monochrome printing and color printing.

Further, the developing clutch 54 is provided on the developing roll 28 ′ provided in the developing device 28 and has the above-mentioned DC motor 52.
Of the pulse motor 53 to the standby roll 9, and the fixing clutch 57 to the fixing roll 29 of the DC motor 52.
It is a clutch that transmits the rotational force of. Further, the drive signal for the above-described paper feed roller 8 is also output from the driver 49, and the drive signal and the control signal are output to various other loads.

On the other hand, each sensor 58 is connected to the CPU 45 via a buffer 50. Each sensor 58 includes a position detection sensor for the paper P, a temperature detection sensor for the LED head 27, and the like. FIG. 1 shows the LED head 2 described above.
It is a figure explaining the circuit structure in 7Y-27BK. still,
The four LED heads 27Y to 27BK have the same configuration, and FIG. 1 is a circuit diagram corresponding to any of the LED heads 27Y to 27BK. In addition, the LED head 27Y of this example
Each of ~ 27BK is composed of 3584 LED elements, and one LED array chip is formed with 64 LED elements. Therefore, the LED elements 1 to 64 shown in FIG. 1 are the first LED array chip “1”.
The LED elements from 65 to 128 are mounted on the second LED array chip “2”, ..., 35
The LED elements 21 to 584 are mounted on the last (56th) LED array chip "56".

The circuit of FIG. 1 will be specifically described below. Shift registers 60, 61, latch circuits 62, 63, frequency divider 64, delay circuit 68, AND gate 66, buffer 6
7 and 56 LED array chips 31 described above. The shift register 60 is a serial-in / parallel-out register and has a clock signal (CLK).
The bit map data (DATA) is input in synchronization with. The shift register 60 has an area for storing "3584" data, and when data is input to all areas, the "3584" data stored in the shift register 60 is latched in synchronization with the latch signal. Latched to 62. The previous data latched by the latch circuit 62 is output to the AND gate 66.

The AND gate 66 is also composed of "3584" gate circuits, and the data supplied to the AND gate 66 is output to the corresponding LED element via the buffer 67, and the corresponding LED element is supplied to the corresponding LED element in accordance with the supplied data. It emits light. Here, the strobe signal is supplied to the AND gate 66, and the bitmap data is output to the LED element according to the supply timing of the strobe signal. This strobe signal is output from the delay circuit 68.

The delay circuit 68 is specifically composed of 56 delay circuits 68-1 to 68-56. The output timing of the strobe signal output from each of the delay circuits 68-1 to 68-56 is It depends on the set value described later.
The set value is a value in which the correction data stored in the EEPROM 47 is preset in the delay circuits 68-1 to 68-56 by the shift register 61 and the latch circuit 63. That is, the set value described above is a value according to the correction value due to the installation position error of each LED array chip 31, etc., and the set values set in the individual delay circuits 68-1 to 68-56 are different, and therefore each delay circuit Circuit 68-1 to 68
The output timing of the strobe signal output via -56 is different.

FIG. 7 shows the delay circuits 68-1 to 68-5 described above.
6 is a specific circuit diagram of FIG. Incidentally, 56 delay circuits 68
-1 to 68-56 have the same circuit configuration. In the figure, the correction circuit 68-1 (to 68-56) is composed of two subtraction counters 70 and 71 and an inverter 72. The subtraction counters 70 and 71 have shift registers 61.
A set signal is input (to the SET terminal) via the latch circuit 63, and the set values (correction values) are set in advance in the subtraction counters 70 and 71. Also, the subtraction counter 7
0 and 71 are respectively START terminal, RST terminal,
A CLK terminal and an OUT terminal are provided.

The set value (correction value) set in the subtraction counter 70 starts counting when the strobe signal (STB) input to the START terminal is input, and is input to the clock signal (CLK) supplied to the CLK terminal. When the clock signal (CLK) counts the set value to zero "0" in synchronization with the countdown process, the output of the strobe signal (STBn) from the OUT terminal is started. Therefore, the set value set in the subtraction counter 70 has a function of delaying the output start timing of the strobe signal (STBn).

On the other hand, the strobe signal (STB) is supplied to the START terminal of the subtraction counter 71 via the inverter 72.
Therefore, contrary to the case of the subtraction counter 70 described above, the set value set in the subtraction counter 71 starts counting when the output of the strobe signal (STB) is stopped and the clock signal (CLK). When the clock signal (CLK) counts the set value to zero "0" in synchronization with the input, the OUT terminal outputs a reset signal to the RST terminal of the subtraction counter 70. Therefore, the output of the strobe signal output from the subtraction counter 70 is stopped. Therefore, the set value set in the subtraction counter 71 has a function of delaying the output stop timing of the strobe signal (STBn).

Therefore, the delay circuit 68-1 shown in FIG.
68 to 56 are configurations in which the output of the strobe signal (STB) is delayed by the time according to the set value. Next, the processing operation of the above-described first embodiment will be described. First, setting of a set value (correction value) set in the delay circuits 68-1 to 68-56 will be described. This set value (correction value)
Is a value obtained by calculating an arrangement error for each LED array chip 31. This calculation uses the LED array chip 31 as L
The drive I is installed at a predetermined position on the ED array substrate 30.
Bonding wires 32a and 32b to C31a and 31b
After manufacturing the LED head by connecting via LED, each LED element is made to emit light by driving signal, and the light is detected by an image pickup element such as a CCD sensor to detect the displacement of the arrangement position. is there. Hereinafter, this process will be described with reference to FIG.

Assuming that the process speed (= paper transport speed) is
When set to 50 mm / s, the frequency of the clock signal (CLK)
When the frequency is set to 10MHz and the frequency is divided by 1/100 by the frequency divider 64, the output of the frequency divider 64 becomes 0.1MHz (10μs / clock),
The process movement distance in one clock is 0.5 μm / clock. In addition, the subtraction counter 7 that constitutes the delay circuit 68
If 0 is an 8-bit binary subtraction count, the maximum is 25.
With 6 clocks, 128μm position control is possible. Hereinafter, specific numerical values will be described.

FIG. 6 shows the measurement results of the deviation amount of the light spot position when 56 LED array chips 31 are mounted on the LED array substrate 30 and the positions thereof are measured by a CCD image pickup device (not shown). As shown in the figure, when the first LED array chip “1” is set to zero (0), the 14th LED array chip has a shift amount of −4.
The 28th LED array chip is −0 μm off
The LED array chip is shifted by 10 μm, the 42nd LED array chip is shifted by +40 μm, and the 56th LED array chip is shifted by +10 μm. Incidentally, other LED array chips not shown in the figure also have respective deviation amounts.

Here, the correction process of this example is-(minus)
The position where the amount of deviation in the direction is maximum is set as the correction distance 0, and the correction distances of other LED array chips are set with this position as a reference. In this example, the position of −40 μm is the position where the amount of deviation in the − (minus) direction is the maximum. Therefore,
For example, the correction distance of the first LED array chip is +40
The correction distance of the 28th LED array chip is +30 μm, the correction distance of the 42nd LED array chip is +80 μm, and the correction distance of the 56th LED array chip is +50 μm.

Next, the correction time [tn] in the above example.
Is calculated by the following calculation formula. That is, tn [μ
s] = (1 / process speed [mm / s]) × 1n [μ
m] × 1000 calculation formula, and the correction time [tn] of each LED array chip 31 calculated by this calculation formula is the correction time t1 = 800 (μs) of the first LED array chip 14th LED array Correction time of chip t14 = 0 (μs) Correction time of 28th LED array chip t28 = 600 (μs) Correction time of 42nd LED array chip t42 = 1600 (μs) 56th LED array chip The correction time t56 = 1000 (μs).

Further, the correction value (Cn) of each LED array chip is set from the above correction time. The relational expression in this case is Cn [count] = tn [μs] × 0.1 [MHz], and the correction value [Cn] of each LED array chip 31 is the correction value Cn = 80 (count of the first LED array chip. ) Correction value Cn = 0 (count) of the 14th LED array chip Correction value Cn = 60 (count) of the 28th LED array chip Correction value Cn = 160 (count) of the 42nd LED array chip The correction value Cn of the 56th LED array chip is 100 (count).

The above-mentioned correction value Cn is the above-mentioned EEPROM4.
7 and the correction data is stored in the corresponding delay circuit 68.
-1 to 68-56 (subtraction counters 70 and 71) are set. For example, the correction value 68 (Cn = 80 (count)) of the above-mentioned first LED array chip is set in the correction circuit 68-1. Further, for example, the above-mentioned correction value 0 (Cn = 0 (count)) is set in the fourteenth correction circuit 68-14. Furthermore, the 28th correction circuit 6
The above-mentioned correction value 60 (Cn = 60 (count)) is set in 8-28, the correction value 160 (Cn = 160 (count)) is set in the 42nd correction circuit 68-42, and the 56th A correction value of 100 is applied to the th correction circuit 68-56.
Set (Cn = 100 (count)). Incidentally, similarly calculated correction values are set in advance also for other correction circuits 68 not shown.

Next, the correction circuit 68-
After setting a set value (correction value) to 1 to 68-56 in advance, the printing process is started. First, the host computer 4
The print data output from No. 2 is converted into bitmap data by the interface controller 40, and L
LED heads 27Y to 2Y via the ED head controller 48
It is output to 7BK.

For example, here, the data is the LED head 27.
If it is output to Y, the LED head 27Y has the circuit configuration shown in FIG. 1 as described above, and the above-mentioned bitmap data is sequentially supplied to the shift register 60 in synchronization with the clock signal (CLK). Then, as described above, it is latched by the latch circuit 62 according to the latch signal and output to the AND gate 66.

On the other hand, each delay circuit 68-1 to 68-56 is set with a correction value based on the arrangement error of the corresponding LED array chip as described above, and each delay circuit 68 is input by the strobe signal. The subtraction counters 70 and 71 in -1 to 68-56 perform subtraction processing on the set value that has been set, and output a strobe signal (STBn) delayed in accordance with the set value to the corresponding AND gate 66. Therefore, the strobe signal (STBn) delayed according to the arrangement error of the LED array chip is output to the AND gate 66, and the corresponding LED array chip emits light.

FIG. 8 is a time chart for explaining this. The output timing of the strobe signal is delayed by the time t corresponding to the set value with respect to the original output timing of the strobe signal (STB), and the output of the strobe signal is started at time t. Only delays the strobe signal output stop. For example, in the case of the delay circuit 68-1, since the set value is 80, the corresponding time is 800 μ.
A strobe signal delayed by s is output, and printing can be performed at a position without deviation. In addition, the delay circuit 68-28
, The set value is 60, so the corresponding time 600
A strobe signal delayed by μs is output, and printing can be performed at a position without deviation.

The same applies to the case of the other delay circuits. Since the set value is 160 in the delay circuit 68-42, a strobe signal delayed by a corresponding time of 1600 μs is output, and the set value is 100 in the delay circuit 68-56. Therefore, it is possible to output a strobe signal delayed by a corresponding time of 1000 μs and perform printing at a position without deviation.

The same applies to the other LED array chips 31, and an image can be printed at a position without deviation by outputting a strobe signal delayed by a time corresponding to the deviation amount. FIG. 9 is a time chart explaining the above processing. As shown in the figure, first, a set value is set in each of the delay circuits 68-1 to 68-56. This process is executed at the timing indicated by I in FIG. The latch signal (latch 2) used at this time is for latching the data output from the shift register 61 in the latch circuit 63.

On the other hand, the shift register 60 described above has LE
When the bitmap data is supplied from the D head controller 48 in synchronization with the clock signal (CLK) and the bitmap data for one line is stored in the shift register 60,
The latch circuit 62 is synchronized with the latch signal (latch 1 signal).
Bit map data for one line is latched. The bit map data latched by the latch circuit 62 is output to the AND gate 66, and the corresponding LED is output according to the strobe signal output at each timing described above.
The LED elements in the array chip 31 are driven.

For example, assuming that the original (basic) strobe signal is (STB), the strobe signal (STB1) delayed by the time t1 from the delay circuit 68-1 is the first LED.
It is output to the array chip "1". This delay time t1 is the time for the photosensitive drum 25 to move from the reference position by 40 μm, and the electrostatic latent image formed on the photosensitive drum 25 according to the output of the strobe signal (STB1) has no displacement. Therefore, when this electrostatic latent image is developed and printed on the paper P, it becomes a printed image in which the arrangement error of the LED array chip 31 is corrected.

Similarly, for example, the strobe signal (STB28) delayed by the time t28 from the correction circuit 68-28 is LE which constitutes the 28th LED array chip "28".
The delay time t28 supplied to the D element corresponds to the distance that the photosensitive drum 25 moves by 30 μm, and the image corrected according to the strobe signal (STB28) is printed on the paper P at an accurate position. Furthermore, the same applies to the strobe signals (STB42, 56) output from the correction circuits 68-42 and 68-56, and the strobe signals are supplied to the corresponding LED array chips "42" and "56", and L
Printing is performed at a position where the arrangement error of the ED array chip 31 is corrected.

As described above, according to this example, it is possible to correct the arrangement error of the LED array chip 31 and perform printing on the accurate position of the paper P. Further, according to this example, since the printing position can be easily corrected by the delayed strobe signal, it is possible to simplify the mechanism assembly of the optical writing head, efficiently manufacture the optical writing head, and improve the manufacturing yield.

According to the present example, the LED array chip 31
The correction circuits 68-1 to 68-56 are provided for each of them, and the correction value based on the arrangement error of the LED array chip 31 is performed by delaying the output time of the strobe signal. The strobe signal delay time may be set for each LED element. In such a case, the positional error in the sub-scanning direction is corrected for each individual LED element, and printing can be performed at an accurate position on the paper P.

Further, according to the above-described embodiment, the drive device of the optical writing head of this example has been described, but a means for executing each means, for example, a storage means constituted by the EEPROM 47, a CPU 45 and an LED element. The drive means configured and the drive timing control means configured by the delay circuits 68-1 to 68-56 are not limited to these specific circuits.

Further, these means can also be realized by program processing. For example, instead of the above means, storage processing,
It may be a method of driving the optical writing head in which the driving process and the driving timing control process are sequentially performed. << Second Embodiment >> Next, a second embodiment of the present invention will be described.

The above-described embodiment is an application example for dealing with the dislocation of the LED (chip), but the technique using the strobe signal of the present invention is not limited to this example, and LE
It is shown that all of them can be applied to the position adjustment of the image formed by the D element in the sub-scanning direction.

In other words, in the tandem type image forming apparatus, when the LED heads of respective colors are arranged with respect to the sub-scanning direction (Y direction), the right and left ends of the head are in the sub-scanning direction. In the case of a so-called θ-direction deviation with a different deviation amount, the image forming position is corrected to face uneven rotation in the drive system of the photosensitive drum or uneven rotation due to eccentricity of the drum, and the transfer drive system such as the transfer belt It can be used to correct the image forming position in the sub-scanning direction, such as correcting the image forming position to face uneven rotation.

In these cases, the test charts are used to actually show the amount of deviation in the Y direction, the amount of deviation in the θ direction, the amount of uneven rotation of the photosensitive drum, and the amount of uneven rotation of the conveyor belt, depending on the purpose of each correction described above. Form an image, measure the adjustment amount,
This can be achieved by storing the correction data corresponding to this in the EEPROM and controlling the driving of the LED.

A detailed description will be given below. Also in this example, the drawings used in the above-described embodiment are partially used, and the tandem color printer 1 shown in FIG. 2 and FIG.
The system diagram shown in FIG. 1 and the drawings such as FIG. 1 showing the circuit configuration in the LED head are used. <Position Correction in Sub-scanning Direction (Y Direction)> FIG. 10 is a test chart for detecting the amount of deviation of the non-reference image from the reference image. FIG. 10A is a dotted line showing a reference image, and in this example, an image created by the print head 27BK of the monochrome (BK) image forming unit 24 is used as the reference image. Then, the dotted line of C shown in FIG. 7B is a non-reference image created by the print head 27C of the cyan (C) image forming unit 23, for example. Therefore, in this case, the shift amount of cyan (C) (non-reference image) in the sub-scanning direction with respect to the black (BK) reference image is measured, the result is written in the EEPROM 47, and the delay circuit 68- The set value may be set to 1 to 68-56.

Specifically, LEs from "1" to "56"
Correction data for the reference image is created for each D array chip and set as a set value in the delay circuits 68-1 to 68-56 shown in FIG. By configuring in this way,
For example, the corrected non-reference image is printed from the cyan (C) optical writing head, and black (BK) L is printed.
The print position shift of the cyan (C) LED head 27C with respect to the ED head 27BK can be corrected.

The same applies to the other image forming units 21 and 22, and the deviation amount of yellow (Y) (non-reference image) from the reference image of black (BK) is measured by the test chart shown in FIG. Further, the deviation amount of magenta (M) (non-reference image) with respect to the black (BK) reference image is measured, and the result is written in the EEPROM 47. Then, the delay value 68-1 in the LED heads 22Y and 22M corresponding to the set value based on this data
It is possible to create an image having no print position deviation by setting the value to 68-56. <Position Correction in θ Direction> FIG. 11 is a test chart showing position correction in the θ direction with respect to the reference image. As before,
FIG. 6A is a dotted line showing a reference image, and in this example, the black (BK) image forming unit 2 for monochrome is also used.
4 is a reference image created by the print head 27BK of FIG. Then, the dotted line of C shown in FIG. 7B is a non-reference image created by the print head 27C of the cyan (C) image forming unit 23, for example. In this case, black (B
The non-reference image of cyan (C) has a deviation of the angle θ with respect to the reference image of K).

Therefore, this result is stored in the EEPROM 47.
To the delay circuit 68 based on this data.
The set value may be set to -1 to 68-56. The specific processing is the same as the above Y direction correction, and the delay circuit 6
According to the set value set to 8-1 to 68-56, for example, the cyan (C) optical writing head outputs the corrected print data, and there is no print position deviation with respect to the black (BK) reference image. Make a correction. Also, in the other image forming units 21 and 22, the yellow (Y) and magenta (M) corrections that do not cause the print position deviation with respect to the black (BK) reference image are performed according to the test chart shown in FIG. <Displacement correction for uneven rotation of drum and uneven rotation of belt> Also in this case, the amount of positional deviation with respect to the reference image is measured using the test chart, and the correction amount based on the result is used as a set value for the delay circuits 68-1 to 68-68. Write to -56. Although the print result of the test chart is not particularly shown, non-reference images of yellow (Y), cyan (C), and magenta (M) for black (BK) are printed, and correction is performed for each color.

With this configuration, it is possible to accurately correct the printing deviation of each color with respect to the black (BK) reference image. Further, according to this example, since the printing position can be easily corrected by the delayed strobe signal, it is possible to simplify the mechanism assembly of the optical writing head, efficiently manufacture the optical writing head, and improve the manufacturing yield.

In the above example, the printing position deviation of each LED array chip 31 due to the uneven rotation of the photosensitive drum 25 and the uneven rotation of the conveyor belt 12 is corrected, but it is based on the uneven rotation of other drive systems. The same method can be applied to so-called wow and flutter. Further, although the optical writing head driving device has been described in this example, it is configured by means for executing individual means, for example, calculation means and writing means configured by the CPU 45 or the like, storage means configured by the EEPROM 47, and delay circuit 68. The drive timing control means to be performed is not limited to these specific circuits.

These means can also be realized by program processing. For example, instead of the above means, calculation processing,
It may be a method of driving the optical writing head that sequentially performs the writing process and the drive timing control process. << Third Embodiment Example >> Next, a third embodiment example of the present invention will be described.

In the above-mentioned two embodiments, the decrease in the light emission output of the LED element is dealt with by the process of delaying the output time of the strobe signal (STB). However, this example corresponds to the address control when reading the image data. The configuration of this example uses the system configuration diagram of FIG. 4 described in the above two embodiments, and further includes a correction circuit shown in FIG. That is, the interface controller 40 and the printer controller 41 have the same configurations as those shown in FIG. 4, and the image data output from the host computer 42 is converted into bitmap data and stored in, for example, a frame memory (not shown). In FIG. 12, the interface controller 4
0 and the printer controller 41 are collectively shown in one block.

The bitmap data stored in the interface controller 41 corresponds to the corresponding LED head 2
It is output to 7Y to 27BK. In this example, the interface controller 40 (printer controller 4
1) and the correction circuit 8 between each LED head 27Y to 27BK
This is a configuration in which 0Y to 80BK are arranged. This correction circuit 8
0Y to 80BK are used to specify a read address and correct a print position deviation amount when outputting bitmap data of a corresponding color to a corresponding optical writing head.

FIG. 13 shows the above-mentioned correction circuits 80Y-80B.
It is a figure which illustrates the structure of K concretely. Note that all the four correction circuits 80Y to 80BK have the same configuration, and a representative example of the correction circuit 80Y will be described. The correction circuit 80Y includes an input control unit 81, a data buffer 82, an output control unit 83,
The address control unit 84, each LED array chip displacement amount storage memory (hereinafter, simply referred to as displacement amount storage memory) 85, an adder 86, and a multiplexer 87. The input control unit 81 outputs the image data output from the interface controller 40 (printer controller 41) to a data buffer 82 serving as a second storage unit, and stores, for example, bitmap data for 20 lines in the data buffer 82.

Here, the bitmap data stored in the data buffer 82 is written to the address designated by the write address (write address) output from the address control unit 84. The write address (write address) has an address in the main scanning direction and an address in the sub scanning direction, and is output to the data buffer 82 via the multiplexer 87.

The bit map data (image data) stored in the data buffer 82 is read by the main scanning direction read address and the sub scanning direction read address output from the address control unit 84 as the read control means. Further, the shift amount storage memory 8 as the first storage means
5 stores the displacement amount of the LED array chip 31 formed in the optical writing head. Then, the correction data stored in the shift amount storage memory 85 is output to the adder 86, the correction data is added to the sub-scanning direction read address, and the result is output to the data buffer 82 via the multiplexer 87.

The data buffer 82 reads the bitmap data from the address area designated by the read address in the main scanning direction and the read address in the sub scanning direction,
The data is output to the corresponding LED head 22 via the output control unit 83. FIG. 14 illustrates an example of the correction data stored in the shift amount storage memory 85, and further, the data buffer 82.
The address coordinates of the data to be stored in are described. First, FIG. 7A shows an example of the correction data stored in the shift amount storage memory 85. This correction data is the above-mentioned first data.
It is created by the method described in the embodiment example. That is, 56 LEDs are arranged on the LED array substrate 30 shown in FIG.
This is data obtained as a result of measurement of the shift amount of the light spot position when the array chip 31 is attached and the position is measured by a CCD image pickup device (not shown). Correction data is calculated from the measurement result thus obtained, and the calculation result is stored in the shift amount storage memory 85 as correction data. The correction data obtained from the measurement result may be temporarily stored in the EEPROM 47 and then stored in the shift amount storage memory 85.

The optical writing head of this example has 56 lines per line.
Although one LED array chip is used, the correction data corresponding to the first to eighth LED array chips will be described for the sake of explanation. That is, as shown in FIG. 14A, when the first, fourth, and eighth LED array chips are used as reference positions, the second LED array chip is- 1 (the direction of advance with respect to the reference LED array chip is − (indicated by a minus is the same as in the case of FIG. 16 described above)) and the third L
The ED array chip is -2, the fifth LED array chip is +1 (the delay direction is indicated by + (plus) with respect to the reference LED array chip, as shown in FIG.
The same), the sixth LED array chip is +2,
The seventh LED array chip is +1. Therefore, this correction data is stored in the shift amount storage memory 85 of each of the correction circuits 80Y to 80BK.

Next, the processing operation of the third embodiment will be described. First, the print data output from the host computer 42 is converted into bitmap data by the interface controller 40 and output to the corresponding correction circuit. Here, for example, in the case of the correction circuit 80Y, yellow (Y) bitmap data is supplied from the interface controller 40 (printer controller 41) to the correction circuit 80Y.

At this time, the image data written in the data buffer 82 is supplied line by line, and 56 L
Corresponding to the ED array chip, the data corresponding to the first LED array chip “1” is sequentially arranged to the second LE.
Data is written in the order of D array chip "2", third LED array chip "3", .... The addressing at this time is executed according to the write address in the main scanning direction and the sub-scanning direction, and this addressing is sequentially performed from the uppermost storage area to the lowermost storage area of the data buffer 82 in a bit map of 20 lines. Data is written as in normal processing.

The image data stored in the data buffer 82 as described above is read by the read address output from the address controller 84. This data reading process is executed according to the read addresses in the main scanning direction and the sub scanning direction output from the address control unit 84,
At this time, the correction data stored in the shift amount storage memory 85 is added to the read address in the sub-scanning direction and output to the data buffer 82.

Hereinafter, description will be made according to the example shown in FIG.
First, the address control unit 84 sequentially reads the bit map data of the line designated according to the read address in the sub-scanning direction. For example, when the line is the address 12 lines before the line indicated by the dotted arrow in FIG. 14B (however, the reference line in this case is the lowest line in FIG. 14B), the read in the main scanning direction is performed. The 64-bit bitmap data corresponding to the first LED array chip is addressed in the order of second, third, ... In accordance with the address. At this time, the storage area of 64-bit bitmap data (indicated by a in FIG. 6B) corresponding to the third LED array chip is the address area 12 lines before. 64-bit data is read to the LED head 27Y according to this addressing. Therefore, the 64-bit data read by the LED head 27Y at this time is the LED located 12th before the third LED.
The data is 64-bit data of the array chip "3" and is output two lines earlier than the original data.

Next, the scan line (12
The read process of the (th line) is continued, and when the 56th LED array chip “56” (not shown) is reached, the read process of the next line (the 11th line) is performed. In this line, the 64-bit bitmap data of the second LED array chip is addressed (FIG. 15).
B) of (b). Therefore, the 64-bit data is output one line earlier than the original data.

Further, the read processing of the next line (10th line) is performed, and the 1st, 4th, 8th, ... 64-bit data having no print deviation is output to the LED head 27Y. . Similarly, for the 9th line, 64-bit data corresponding to the 5th, 7th, etc. LED array chips is output to the LED head 27Y, and for the 8th line, the 6th, etc. LED array chips are output. 64-bit data corresponding to the chip LED head 2
Output to 7Y.

When the printing process up to the reference line is completed by controlling as described above, the data buffer 8
The data stored in No. 2 is output to the LED head 27Y, and the data of one line in a stepped shape with unevenness shown by the solid line in FIG.
5 is optically written. Although not shown, the same applies to other lines, and since the LED array chips are displaced in the same direction for the same optical writing head, the print position can be corrected by shifting the same line.

FIG. 15 is a diagram for explaining this.
That is, when the LED array chip shown in FIG. 10A is displaced, the data buffer 82 outputs the bitmap data at the timing shown in FIG. As shown in FIG. 15C, the image (electrostatic latent image) formed on the photoconductor drum 25 by the exposure from the LED head 27Y is data according to the read address in the sub-scanning direction based on the correction data.
An accurate printed image as shown in is obtained.

As described above, according to this example, the arrangement error of the LED array chip 31 can be corrected, and printing can be performed at the correct position on the paper P without misalignment. Further, according to this example, since the printing position can be easily corrected by the address control, the mechanical assembly of the optical writing head can be simplified, the optical writing head can be efficiently manufactured, and the manufacturing yield can be improved.

The LED array chip 3 is also used in this example.
The deviation amount in the sub-scanning direction for each LED element formed in 1 is stored in the deviation amount storage memory 85 as correction data,
Addressing may be performed based on the placement error for each individual LED element. << Fourth Embodiment >> Next, a fourth embodiment of the present invention will be described.

In this example, the arrangement error of the LED array chip is
This is an invention in which an error is measured with respect to a chip sampled from a large number of LED array chips and a deviation in the Y direction of all the LED array chips is corrected. Also in this example,
The system configuration diagram of FIG. 4 described in the above-described three embodiments is used, and the correction circuit shown in FIG. 16 is further added. That is, the interface controller 40
The printer controller 41 has the same configuration as that shown in FIG. 4, and the image data output from the host computer 42 is converted into bitmap data and expanded in a frame memory (not shown) of the interface controller 40.

The bitmap data stored in the interface controller 40 corresponds to the corresponding LED head 2
It is output to 7Y to 27BK. Also in this example, the correction circuit 90 is provided between the interface controller 40 (printer controller 41) and each of the LED heads 27Y to 27BK. The correction circuit 90
It is composed of four correction circuits 90Y to 90BK corresponding to each color. In addition, these correction circuits 90Y to 90B
K is for correcting the print position deviation in the Y direction when outputting the bitmap data of the corresponding color to the corresponding optical writing head.

As shown in FIG. 16, each correction circuit 90Y-9
0BK is composed of a control circuit and an EEPROM.
That is, the correction circuit 90Y includes the control circuit 90Y-1 and the EE.
The correction circuit 90M includes a control circuit 90M-1 and an EEPROM 90M-2.
The correction circuit 90C includes a control circuit 90C-1 and an EEPROM 9
0C-2, the correction circuit 90BK is a control circuit 90
It is composed of BK-1 and EEPROM 90BK-2.

The correction circuits 90Y to 90BK for the respective colors have the same configuration, and FIG. 17 shows the configuration. still,
Although FIG. 17 is basically the same as FIG. 13 described above, the memory for storing the displacement amount of the array chip is composed of an EEPROM, and the displacement amount is written in the EEPROM and then mounted in the apparatus. In this example, the EEP
Circuits other than ROM are used as control circuits. Hereinafter, the configuration of the correction circuit 90Y will be described on behalf of the correction circuits 90Y to 90BK.

The correction circuit 90Y has the control circuit 9 as described above.
0Y-1 and an EEPROM 90Y-2, the control circuit 90Y-1 includes an input control unit 91 and a data buffer 9
2, output control unit 93, address control unit 94, adder 9
5 and a multiplexer 96. On the other hand, EE
The PROM 90Y-2 is configured to be attachable to and detachable from the correction circuit 90Y (with respect to the device), and stores the amount of deviation of the LED array chip.

The input control unit 91 outputs the image data output from the interface controller 40 (printer controller 41) to the data buffer 92, and the data buffer 92 stores, for example, a bitmap for 20 lines, as in the above-described embodiment. Store the data. Here, the bitmap data stored in the data buffer 92 is written to the address designated by the write address output from the address control unit 94. Further, this write address is sent to the data buffer 9 via the multiplexer 96.
2 is output.

The bit map data (image data) stored in the data buffer 92 is read by the read address output from the address control unit 94. on the other hand,
The EEPROM 90Y-2 stores the displacement amount of the LED array chip formed in the optical writing head. Then, the correction data stored in the EEPROM 90Y-2 is output to the adder 95, the correction data is added to the read address in the sub-scanning direction, and output to the data buffer 92 via the multiplexer 96.

The process of creating the correction data stored in the above-mentioned EEPROM 90Y-2 will be described below. 18 (a) and 18 (b) are diagrams for explaining generation of correction data. The horizontal axes shown in FIGS.
The number of D array chips is shown. In this example, 56 L
The ED array chips are arranged in a line.

First, in FIG. 9A, even if the LED array chips are arranged in a line, there is a mounting error in each array chip as described above, and there is a gap between the LED array chip and the photoconductor. Twist or the like also occurs in the SLA (selfoc lens array) arranged, and the LED array chips are arranged so as to be displaced from each other. Here, in this example, the LED array chip whose displacement is to be measured is specified. For example, 5 LEs should be evenly spaced.
D array chip "1", "14", "28", "4"
2 "and" 56 "are selected. Then, the deviation amount of these LED array chips is measured.

The amount of deviation is measured by, for example, mounting 56 LED array chips on the LED array substrate,
It is obtained by measuring its position with a CCD image pickup device (not shown). The five black dots a1 to a5 shown in FIG. 18B are plots of the shift amounts obtained as a result of the above measurement.

From the above-obtained measurement results, the deviation amounts of all LED array chips are calculated and used as correction data. In this example, the shift amount of another LED array chip is calculated using an approximate expression. Specifically, the following calculation formula is used. Chips 2 to 14: Δy _n = -l _1-n / l _1-13 xy ₁₄ Chips 15 to 28: Δy _n = -y ₁₄ -{(l _14-n / l
_14-28 ) × (y ₂₈ −y ₁₄ )} Chips 29 to 42: Δy _n = −y ₂₈ − {(l _{28 −n} / l
_28-42 ) × (y ₄₂ −y ₂₈ )} chips 43 to 56: Δy _n = −y ₄₂ − {(l _{42 −n} / l
_42-56 ) × (y ₅₆ −y ₄₂ )} (Δy _n = approximate value of deviation amount of each LED chip, y _x = deviation amount of sampled chip, l = dimension between chips (dimension between chips is constant) ) That is, for the correction values Δyn of the LED array chips “1” to “14”, the LED array chips “1” to “14”
Any array chip n in between has a slope L1-n / L1-13, and the result of multiplying this slope by the above-mentioned measurement error value y14 is the error value of any array chip n. The reason why − (minus) is added is to calculate the correction value for correcting the error.

In addition, the LED array chips "14" to "2"
For the correction value Δyn of “8”, the LED array chip “1
An arbitrary array chip n between 4 "and" 28 "has a slope L14-n / L14-28 as described above, and the result obtained by multiplying this slope by a value obtained by subtracting y14 from the above measurement error value y28 Is the error value of an arbitrary array chip n. The reason why − (minus) is added is the same as above, and the reason why the measurement error value y14 is further subtracted is that the results obtained above are cumulative from the previous correction values, and y14 is obtained from the above results. Subtract and obtain the correction value (Δyn).

Next, LED array chips "28" to "4"
For the correction value Δyn of “2”, the LED array chip “2
An arbitrary array chip n between "8" and "42" has a slope L28-n / L28-42 as described above, and the result obtained by multiplying this slope by a value obtained by subtracting y28 from the above measurement error value y42 Is an error value of an arbitrary array chip n, and y28 is subtracted from the above result to obtain a correction value (Δyn) in the same manner as described above.

Furthermore, the LED array chip "42"-
The same applies to the correction value Δyn of "56", and the arbitrary array chip n between the LED array chips "42" to "56" has the inclination L42-n / L42-56 as described above. The result of multiplying the slope by the value obtained by subtracting y42 from the above measurement error value y56 is the error value of an arbitrary array chip n,
Y42 is subtracted from the above result to obtain a correction value (Δyn).

From the above calculation results, the correction value of each LED array chip for the approximation error shown by the dotted line in FIG. 18B can be calculated, and this correction value is stored in the above-mentioned EEPROM 90Y-.
Write to 2. FIG. 19 shows the above-mentioned EEPROM 90Y-2.
It is a figure explaining the writing process of the correction value to. In the figure, a personal computer (PC) 97 performs an editing process when writing correction data, and the correction data supplied to the personal computer 97 is controlled by the personal computer 97 to an EEPROM writer 98.
Is output to. The EEPROM writer 98 is a CPU 99
And the EEPROM 90Y-2 described above, and the CPU 9
Reference numeral 9 controls writing when the supplied correction data is written in the EEPROM 90Y-2.

The EEPROM 90Y-2 in which the correction data is written in this way is attached to the apparatus (control board) and functions as the EEPROM 90Y-2 shown in FIG. That is, the correction data is read by the read signals in the main scanning direction and the sub-scanning direction, added to the image data in the same manner as in the third embodiment described above, and output to the data buffer 92. In this way, the data output to the data buffer 92 is data in which an error such as the arrangement with respect to the LED array chip is corrected, is output to the print head 27Y via the output control unit 93, and is output from the corresponding LED array chip. The light is emitted to the correct position.

In the above example, the processing for yellow (Y) was mainly described, but other magenta (M), cyan (C), and black (BK) can be processed in the same manner. Although the processing for the LED array chip has been described in the description of this example, the same processing can be performed for array chips of other optical writing elements.

[0104]

As described above, according to the present invention, the following effects occur. According to one aspect of the invention, the light emission timing of the optical writing element is controlled based on the correction data stored in the storage means, and the printing position of each optical writing element shifted in the sub-scanning direction can be corrected.

Further, according to this embodiment, it is possible to correct the displacement of the arrangement between the array chips on which a predetermined number of optical writing elements are formed, and to accurately correct the printing position of the array chips displaced in the sub-scanning direction. . Further, according to the above-mentioned invention, the mechanical assembly of the optical writing head can be facilitated, the optical writing head can be efficiently manufactured, and the manufacturing yield can be improved.

According to one aspect of the present invention, by applying the optical writing head driving device or the optical writing head driving method of the present invention to a tandem type image forming apparatus, an image having no print position deviation in the sub-scanning direction is formed. can do.
Further, according to this embodiment, it is possible to correct the deviation of the printing position in the sub-scanning direction due to the deviation in the Y direction, the deviation in the θ direction, the uneven rotation of the photosensitive drum, and the like.

According to one aspect of the invention, for example, the print position of each optical writing element deviated in the sub-scanning direction can be corrected by controlling the read address of the image data stored in the buffer. Further, according to this aspect, it is possible to correct the displacement of the arrangement between the array chips on which a predetermined number of optical writing elements are formed, and to accurately correct the printing position of the array chips displaced in the sub-scanning direction.

According to one aspect of the invention, the arrangement deviation of the array chips can be corrected by measuring the arrangement deviation of a small number of array chips among the large number of array chips on which the optical writing element is formed. The time and labor can be reduced as compared with the case of measuring the displacement of all array chips.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an optical writing head according to a first embodiment.

FIG. 2 is an overall configuration diagram of a color printer illustrating an example of the first embodiment.

FIG. 3 is a sectional view of an LED head (optical writing recording head) arranged in each image forming unit.

FIG. 4 is a circuit diagram of an optical writing head according to an exemplary embodiment.

FIG. 5 is a specific circuit diagram of a delay circuit.

FIG. 6 is an example showing an average value of deviation amounts.

FIG. 7 is a time chart illustrating a process of calculating correction data.

FIG. 8 is a time chart of a delay circuit.

FIG. 9 is a time chart illustrating output control of a strobe signal.

FIG. 10 is a test chart for detecting a Y-direction displacement amount of a non-reference image with respect to a reference image. FIG. 10A is a dotted line showing the reference image, and C is a dotted line shown in FIG. , A non-reference image created by a cyan (C) print head, for example.

FIG. 11 is a test chart for detecting a deviation amount of a non-reference image with respect to a reference image in the θ direction. FIG. 11A is a dotted line showing the reference image, and C is a dotted line shown in FIG. , A non-reference image created by a cyan (C) print head, for example.

FIG. 12 is a system configuration diagram of a second embodiment example.

FIG. 13 is a circuit configuration of a correction circuit.

FIG. 14A is a diagram for explaining the positional displacement of the LED array chip, and FIG. 14B is a diagram for explaining the order of addressing when reading the image data from the data buffer.

FIG. 15A is a diagram showing a state in which the LED array chip is displaced, and FIG. 15B is a diagram for explaining a data read state according to a read address in the sub-scanning direction based on correction data. FIG. 7C is a diagram showing an accurate printed image obtained as a result of the correction process.

FIG. 16 is a system configuration diagram including a correction circuit according to a fourth embodiment.

FIG. 17 is a specific example of the correction circuit according to the fourth embodiment.

18 (a) and 18 (b) are diagrams for explaining generation of correction data.

FIG. 19 is a diagram illustrating a process of writing a correction value in an EEPROM.

FIG. 20 is a circuit diagram of a conventional optical writing head.

FIG. 21 is a diagram illustrating the operation timing of the conventional optical writing head.

FIG. 22 is a diagram illustrating a state in which print misalignment occurs when there is misalignment in the sub-scanning direction.

[Explanation of symbols]

1 color printer 2 Paper supply / transport mechanism 3 Image forming unit 4 fixing section 4a heat roll 4b Pressure contact roll 5 paper cassettes 6 Paper transport system 8 paper feed rollers 9 Standby roll 10, 11 drive roll 12 Conveyor belt 14 Transport guide plate 15, 16 Conveyor roll 17 Paper ejection guide 18 Paper ejection roll 21, 22, 23, 24 Image forming unit 25 photoconductor drum 26 Charger 27 LED head 27Y, 27M, 27C, 27BK LED head 28 Developer 28 'developing roll 29 Transfer Roll 30 LED array substrate 31 LED array chip 31a, 31b drive IC 32a, 32b Bonding wire 33 Selfoc lens 34 Lens support 35 substrate support 36 housing 40 interface controller 41 Printer controller 42 Host computer 44 Display 45 CPU 46 ROM 47 EEPROM 48 LED head controller 49 driver 50 buffers 51 High-voltage power supply 52 DC motor 53 pulse motor 54 Development clutch 55 Belt up / down motor 56 Standby clutch 57 Fixing clutch 58 each sensor 60, 61 shift register 62, 63 latch circuit 64 frequency divider 66 AND GATE 67 buffer 68, 68-1 to 68-56 Delay circuit 70, 71 Subtraction counter 72 Inverter 80Y-80BK, 90Y-90BK, correction circuit 81, 91 Input control unit 82, 92 data buffer 83, 93 Output control unit 84, 94 address control unit 86,95 adder 87, 96 multiplexer 97 personal computer 98 EEPROM writer 99 CPU

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Takano             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. (72) Inventor Kazutaka Otsuka             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. (72) Inventor Yutaka Ichimura             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. (72) Inventor Yukio Akita             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. (72) Inventor Yoshiyuki Matsuoka             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. (72) Inventor Kozo Sato             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. (72) Inventor Tsutomu Kobayashi             2-229 Sakuragaoka, Higashiyamato-shi, Tokyo             Casio Electronics Co., Ltd. F-term (reference) 2C162 AE12 AE28 AE47 AF13 AF22                       AF54 AF62 AF76 AF82 FA04                       FA17                 5C051 AA02 CA08 DA03 DB02 DB04                       DB08 DB22 DB29 DC01 DC07                       DD03 DE02 EA01

Claims (10)

[Claims] 1. A plurality of optical writing heads each comprising an array of optical writing elements for recording a reference image and a non-reference image are arranged in the sub-scanning direction and are formed on a recording medium by the plurality of optical writing heads. In an optical writing head driving device of an image forming apparatus for compositely recording an image on a recording medium, a measuring unit for measuring a positional deviation amount of a mutual image formed by the plurality of optical writing heads in a sub-scanning direction, and a measuring unit of the measuring unit. Calculating means for calculating the drive timing correction data of the optical writing element for recording the non-reference image necessary to match the non-reference image with the reference image on the recording medium from the measurement result; and the drive timing in the storage means. Write means for writing correction data, and a drive timing of the optical writing element according to the drive timing correction data written in the storage means. Optical writing head driving device characterized in that it comprises a Gosuru drive timing control means. 2. The positional deviation of individual images in the composite image formed on the recording medium formed by the plurality of optical writing heads with respect to the sub-scanning direction is relative to the moving direction of the recording medium with respect to each other. The optical writing head drive device according to claim 1, wherein the optical writing head drive device is caused by a relative shift. 3. The positional deviation of the individual images in the sub-scanning direction in the composite image composed on the recording medium formed by the plurality of optical writing heads is caused by the degree of imbalance between the optical writing heads. The optical writing head driving device according to claim 1, wherein 4. The positional shift of each image in the sub-scanning direction in the composite image composed on the recording medium formed by the plurality of optical writing heads is the relative movement speed with respect to the recording medium of each of the optical writing heads. 2. The optical writing head drive device according to claim 1, wherein the optical writing head drive device is generated by the difference between 5. The positional deviation of individual images in a combined image formed on the recording medium formed by the plurality of optical writing heads with respect to the sub-scanning direction is caused by fluctuations in the moving speed of the conveying unit of the recording medium. The optical writing head drive device according to claim 1, wherein: 6. A plurality of optical writing heads each comprising an array of optical writing elements for recording a reference image and a non-reference image are arranged in the sub-scanning direction, and are formed on a recording medium by the plurality of optical writing heads. In a method for driving an optical writing head of an image forming apparatus for compositely recording an image on a recording medium, a measuring process for measuring a positional deviation amount of a mutual image formed by the plurality of optical writing heads in a sub-scanning direction, On the recording medium, a calculation process for calculating drive timing correction data of an optical writing element that records a non-reference image necessary to match the non-reference image with the reference image; Write processing for writing, and drive for controlling the drive timing of the optical writing element according to the drive timing correction data written in the storage means Optical writing head driving method and performing a timing control process, the. 7. The positional deviation of the individual images in the sub-scanning direction in the composite image composed on the recording medium formed by the plurality of optical writing heads with respect to the moving direction of the optical recording heads with respect to each other. 7. The optical writing head driving method according to claim 6, wherein the optical writing head is caused by a relative shift. 8. The misalignment of the individual images in the sub-scanning direction in the composite image composed on the recording medium formed by the plurality of optical writing heads is caused by the degree of imbalance between the optical writing heads. 7. The optical writing head driving method according to claim 6, which is characterized in that. 9. The positional deviation of each image in the sub-scanning direction in the composite image composed on the recording medium formed by the plurality of optical writing heads is the relative movement speed of each optical writing head with respect to the recording medium. 7. The optical writing head driving method according to claim 6, which is caused by the difference between 10. The positional deviation of individual images in a combined image formed on the recording medium formed by the plurality of optical writing heads with respect to the sub-scanning direction is caused by fluctuations in the moving speed of the conveying unit of the recording medium. 7. The optical writing head driving method according to claim 6, wherein.