JP2003182142A - Method for driving optical write head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a shift in a y axis direction of a light point array on an optical drum in an optical write head where light emitting element array chips are mounted in a staggered arrangement. <P>SOLUTION: An interval of center lines of light emitting point arrays of self scanning type light emitting element array chips 29 is made an integral multiple of a distance on a photosensitive drum which moves in the y axis direction in one line time. Image data corresponding to odd-number or even- number self scanning type light emitting element array chips are shifted together by a value of (integral multiple value)×(number of light emitting elements transferred in one line time) and arranged on a memory prepared for image data. Each self scanning type light emitting element array chip 29 is driven by sequentially reading out image data on the memory in a physical arrangement older of the memory. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an optical writing head used in an optical printer, and more particularly to a method for driving an optical writing head in which light emitting element array chips are mounted in a staggered arrangement.

[0002]

2. Description of the Related Art A writing head (optical writing head) of an optical printer is a light source for exposing light to a photosensitive drum and has a light emitting point array composed of a light emitting element array. A principle diagram of an optical printer having an optical writing head is shown in FIG. On the surface of the cylindrical photosensitive drum 2, a photoconductive material (photoconductor) such as amorphous Si is formed. This drum is rotating at print speed. The photoconductor surface of the rotating drum is uniformly charged by the charger 4. Then, the optical writing head 6 irradiates the photosensitive member with the light of the dot image to be printed, and neutralizes the charging where the light hits. Subsequently, the developing device 8 applies toner onto the photoconductor according to the charged state of the photoconductor. Then, the transfer device 10 transfers the toner onto the sheet 14 sent from the cassette 12. The sheet of paper is heated and fixed by the fixing device 16 and is fixed to the stacker 18. On the other hand, in the drum after the transfer, the erase lamp 20 neutralizes the charge over the entire surface, and the cleaning device 22 removes the remaining toner.

The structure of the optical writing head 6 is shown in FIG.
The optical writing head 6 is composed of a light emitting element array 24 and a rod lens array 26, and the focal point of the lens is located on the photosensitive drum 2. The rod lens array is
For example, it is configured by stacking rod lenses in a bag.

On the other hand, the present inventors have paid attention to a three-terminal light emitting thyristor having a pnpn structure as a constituent element of a light emitting element array, and have already filed a patent application (Japanese Patent Laid-Open No. 1-238962, which discloses that self-scanning of a light emitting point can be realized). Japanese Patent Laid-Open No. 2-14
No. 584, No. 2-92650, No. 2
No. 92651), it has been shown that it is easy to mount as a light source for an optical writing head, the light emitting element pitch can be made fine, and a compact light emitting element array can be manufactured.

Furthermore, the present inventors have proposed a self-scanning light emitting element array having a structure in which a transfer element array composed of a light emitting thyristor having a pnpn structure is used as a shift register and is separated from the light emitting element array (JP-A-2- 26366
No. 8).

FIG. 3 shows the self-scanning light emitting element array.
Equivalent circuit diagram of (2-phase drive 1 point lighting common cathode type)
Show. This light emitting element array includes switch elements T (1) to
From T (4), the writing light emitting elements L (1) to L (4)
Become. Use a diode connection for the switch element configuration.
I am V_GKIs a power supply (usually 5V) and a load resistance R
_L Through the gate electrode G of each switch element₁ ~ G₃ Connected to
Has been done. Also, the gate electrode G of the switch element₁ ~ G
₃ Is also connected to the gate electrode of the writing light-emitting element.
It The gate electrode of the switch element T (1) has a start pattern.
Ruth φ_S Is added to the anode electrode of the switch element.
Of the transfer clock pulses φ1 and φ2 are alternately applied.
Write on the anode electrode of the light emitting element for writing.
Signal φ_I Has been added.

The operation will be briefly described. First, the transfer clock
When the voltage of pulse pulse φ1 is high level, the switching element T
It is assumed that (2) is on. At this time, the gate electrode
G₂ Potential is V_GKFrom 5 V to almost zero V.
The effect of this potential drop is diode D₂ By gated
Pole G₃ To about 1 V (diode D
₂ Forward voltage (equal to the diffusion potential) of
It However, the diode D₁ Is in reverse bias
Gate electrode G₁ No potential is connected to the gate
Pole G₁ The potential remains at 5V. Light-emitting thyristor
The gate potential is the gate electrode potential + the diffusion potential of the pn junction (about 1
V), the next transfer clock pulse φ2
H level voltage is about 2V (switch element T (3) is turned on
Is higher than the required voltage) and about 4V (switch
Switch element T (5) to turn on)
If set to, only the switch element T (3) is turned on,
Other switch elements can be left off
It Therefore, the on state changes with two transfer clock pulses.
Will be sent.

The start pulse φ _S is a pulse for starting such a transfer operation, and the start pulse φ S
At the same time when _{S is set} to the L level (about 0 V), the transfer clock pulse φ2 is set to the H level (about 2 to about 4 V), and the switch element T (1) is turned on. Immediately after that, the start pulse φ _S is returned to the H level.

Now, assuming that the switch element T (2) is in the ON state, the potential of the gate electrode G ₂ becomes lower than V _GK and becomes almost 0V. Therefore, if the voltage of the write signal φ _I is the diffusion potential of the pn junction (about 1 V) or more,
The light emitting element L (2) can be in a light emitting state.

On the other hand, the gate electrode G ₁ is about 5V and the gate electrode G ₃ is about 1V. Therefore, the writing voltage of the light emitting element L (1) is about 6 V,
The write voltage of (3) is about 2V. From this, the voltage of the write signal φ _I which can be written only to the light emitting element L (2) is in the range of 1 to 2V. Light-emitting element L (2) is on,
That is, when entering the light emitting state, the light emission intensity is the write signal φ.
It is determined by the amount of current flowing through _I , and it is possible to write images at any intensity. In order to transfer the light emitting state to the next light emitting element, the voltage of the write signal φ _I line is once set to 0.
It is necessary to turn off the light emitting element which is emitting light to V.

Such a self-scanning light emitting device array is
It has a feature that the number of bonding pads may be smaller than that of a normal light emitting element array. This feature has the advantage that the chip area can be reduced. By disposing the bonding pads on both ends of the rectangular chip, the chip width can be reduced to a width almost required by the bonding pad itself. However, when it is applied to an optical print head or the like, if a plurality of chips are arranged in one direction, it is not possible to make the intervals of the light emitting point arrays constant at the chip ends. In order to avoid this, there is a so-called zigzag arrangement method in which a part of the chips are arranged in an overlapping manner (Japanese Patent Laid-Open No. 8-2.
16448 gazette).

FIG. 4 is a diagram showing this zigzag arrangement method. For convenience of explanation, the xy coordinate axes are defined as shown in the figure. That is, the x-axis direction is the chip arrangement direction (main scanning direction), and the y-axis direction is the direction orthogonal to the chip arrangement direction (sub-scanning direction). The self-scanning light emitting element array chip 28 has bonding pads 3 on both ends.
0 is provided, and the light emitting element 32 is provided linearly between them.

Such a light emitting element array chip 28 is
Both ends of the chips are overlapped with each other by shifting in the axial direction, arranged in a zigzag pattern in the x-axis direction, and fixed on the substrate with an adhesive. With such an arrangement, the intervals of the light emitting elements in the x-axis direction can be made constant throughout the plurality of chips.

[0014]

However, when an optical writing head in which light emitting element array chips are arranged in a zigzag pattern is used and a light spot array is projected on a photosensitive drum, the array chips are arrayed while being shifted in the y-axis direction. The light spots on the photosensitive drum are displaced (stepped) in the y-axis direction.
The output image also has a step corresponding to the displacement width of the array chip.

When outputting an image, the optical writing head synchronizes the image data in the memory with a desired timing and transfers it to the corresponding light emitting element on the array chip to cause the light emitting element to emit light. At this time, the time for transferring one line is also the time for sequentially turning on the light emitting elements for the number of one line and projecting the light emitting elements on the photosensitive drum, and the photosensitive drum also rotates during this time.

In the staggered array of light-emitting element array chips, if the reference array chip is an odd-numbered array chip, in order to light the even-numbered array chip, an odd-numbered array chip is placed at a distance corresponding to the time when the photosensitive drum rotates. It must be turned on when the array of light spots projected by the array chip arrives. This shift in lighting time is realized by adjusting the timing of transferring image data to each light emitting element array chip.

That is, in the staggered arrangement of the light emitting element array chips, the displacement in the y-axis direction inevitably occurs, and the correction of the displacement in the y-axis direction is performed by calling the image data from the image memory for each array chip and array. This is done by adjusting the timing of transferring the image data to the corresponding light emitting element on the chip.

Therefore, in the conventional optical writing head, it is necessary to incorporate a circuit for adjusting the timing for each array chip, and since the timing is adjusted for each array chip, the timing of each array chip can be adjusted. It is necessary to store the set value, and it is also necessary to synchronize the generation timing of the start pulse supplied to the start pulse line with the set value, which complicates the circuit configuration.

The present invention has been made by paying attention to such a conventional problem, and an object thereof is to call image data from an image memory for each array chip and to send the image data to a corresponding light emitting element on the array chip. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of driving an optical writing head that can correct a shift of a light spot array on a photosensitive drum in the y-axis direction without requiring a circuit for adjusting the timing of transferring the data.

[0020]

According to the present invention, a plurality of light emitting element array chips in which a plurality of light emitting elements are arranged in a row are arranged in a staggered pattern, and a direction orthogonal to the arrangement direction of the light emitting element array chips is provided. In the method of driving the optical writing head, in which each light emitting element array chip is mounted by setting the interval between the center lines of the light emitting point arrays of each light emitting element array chip to be an integral multiple of the distance on the photosensitive drum that moves in one line time, Image data corresponding to the even-numbered light emitting element array chips by the value of (the integer multiple) × (the number of light emitting elements transferred in one line time) On the other hand, the light-emitting elements are arranged by shifting them collectively on a memory prepared for image data and arranging them in the memory, and sequentially reading out the image data on the memory in the physical memory arrangement order. And drives the Reichippu.

Further, according to the present invention, a plurality of light emitting element array chips in which a plurality of light emitting elements are arranged in a row are arranged in a staggered pattern, and each light emitting element in a direction orthogonal to the arrangement direction of the light emitting element array chips. In a method of driving an optical writing head in which each light emitting element array chip is mounted by setting the interval between the center lines of the light emitting point arrays of the array chip to be an integral multiple of the distance on the photosensitive drum that moves in one line time, Value) ×
Only the value of (the number of light emitting elements transferred in one line time),
The image data corresponding to the odd-numbered light emitting element array chips are arranged in the memory by collectively shifting the image data corresponding to the even-numbered light emitting element array chips on the memory prepared for the image data, It is characterized in that the image data in the memory is sequentially read out in order of physical arrangement of the memory to drive each light emitting element array chip.

When collectively shifting and arranging in the memory prepared on the memory prepared for the image, it is desirable to write data indicating no image writing to the address where the image data was not written by the shift. The process of shifting the data and arranging the data in the memory is preferably performed by software when the image data is expanded on the memory.

Further, it is desirable that the light emitting element array chip is a self-scanning light emitting element array chip, and the timing for sequentially reading the image data on the memory is the clock signal for shifting the self scanning light emitting element array. Is preferred.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 5 is a diagram showing a state in which the self-scanning light emitting element array chips according to the present invention are arranged in a staggered pattern on the head. In FIG. 5, the x-axis direction is the chip arrangement direction (main scanning direction), and the y-axis direction is the direction orthogonal to the chip arrangement direction (sub-scanning direction).

Self-scanning light emitting element array chip (c1,
Each of the c2, c3, c4) 29 is provided with a bonding pad 31 at both ends thereof, and a light emitting element 33 is linearly provided between them. In the self-scanning light emitting element array chip 29, the distance d between the center lines of the light emitting point arrays is an integer multiple n of the distance on the photosensitive drum that moves in the y-axis direction for one line time.
The two ends of the array chips are overlapped with each other so as to be arranged in a zigzag manner, arranged in a zigzag pattern in the x-axis direction, and fixed on the substrate with an adhesive. With such an arrangement, the intervals of the light emitting elements 33 in the x-axis direction are constant throughout the plurality of self-scanning light emitting element array chips.

In this embodiment, as described above, when the self-scanning type light emitting element array chips are mounted on the head in a staggered arrangement, the distance between the center lines of the light emitting point arrays of the self scanning type light emitting element array chips is large. d is an integral multiple n of the distance on the photosensitive drum that moves in the y-axis direction for one line time.

On the memory prepared for the image data,
When the image data corresponding to the odd-numbered array chip is used as a reference, the image data corresponding to the even-numbered array chip is (integer multiple value n) × (the number P of light emitting elements transferred in one line time) Value, that is, n × P pixels are collectively shifted and arranged in the memory. Where 1
The line time is the time for which the light emitting elements for one line are sequentially turned on and projected onto the photosensitive drum.

When the self-scanning light emitting element array chip is driven, the data on the memory is sequentially read in the physical memory arrangement order to drive the light emitting element array chip.

With such a configuration, the start timing can be made the same for all array chips and made common by merely arranging the image data on software only when the image data is expanded on the memory. That is, a special circuit for adjusting the timing of calling the image data from the image memory and transferring the image data to the corresponding light emitting element on the array chip becomes unnecessary.

In this embodiment, by adjusting the timing of calling the image data from the image memory and transferring the image data to the corresponding light emitting element on the array chip, the light spot array on the photosensitive drum in the y-axis direction is adjusted. Instead of eliminating the deviation, the arrangement of the image data in the memory is arranged according to the distance between the array chips to eliminate the deviation in the y-axis direction.

[0032]

EXAMPLES Next, examples of the present invention will be described.

1200 dpi (120 per inch
The light emitting elements are arranged at a density of 0 element), and the self-scanning light emitting element array chip
Consider a case where a hard copy of dpi × 1200 dpi in the sub-scanning direction is obtained.

Since the sub-scanning direction is 1200 dpi,
The distance on the photosensitive drum that moves in one line time is 21.
It becomes 16 μm. The interval between the center lines of the light emitting point arrays of the staggered array chips is an integer multiple n of 21.16 μm, and the interval between the center lines of the light emitting point arrays is 63.48 μm when n = 3. And when n = 4, 84.6
It becomes 4 μm.

Here, a case will be described in which the interval between the center lines of the light emitting point rows of the staggered array chips is three times 21.16 μm (n = 3). In FIG. 5, the center lines of the light emitting point arrays of the array chips c2 and c4 are arranged 63.48 μm apart from the center lines of the light emitting point arrays of the array chips c1 and c3 in the y-axis direction.

On the memory for storing the image data to be transferred to the array chips c1, c2, c3, c4, the image data of the array chips c2, c4 has 25 pixels in one line.
In the case of 6 pixels, 256 × 3 = 768 pixels are shifted and arranged in the memory. The process of shifting the image data and arranging it in the memory is performed by software when the image data is expanded on the memory.

FIG. 6 is an image diagram of the memory when the image data is stored in the memory without being shifted. One line is composed of 256 pixel data. c1-1 indicates image data on the memory of the first line corresponding to the array chip c1.

FIG. 7 is an image diagram of the memory when the image data is stored in the memory in a shifted state. If the data of the address where the image data has not been written due to the memory shift is left undefined, an unintended image is output and the image quality is degraded. Therefore, data indicating that no image has been written is written to the address where the image data has not been written due to the memory shift. The same effect may be obtained by initializing the memory before writing the image data. The image data corresponding to the array chips c2 and c4 is 256 × 3 = from the position shown in FIG. 6 on the memory.
They are arranged by being shifted by 768 pixels.

When the array chips c1, c2, c3 and c4 are driven, image data is sequentially called from the memory in the physical memory arrangement order shown in FIG.
1, c2, c3, c4 are transferred and driven. At this time, the read timing uses a clock signal of the shift unit of the self-scanning light emitting element or a signal generated from this clock signal.

FIG. 8 is a diagram showing an image output when the image data is not shifted on the memory and an image output when the image data is shifted. When the array chips c1, c2, c3, and c4 are driven to output an image without shifting the image data of the array chips c2 and c4 on the memory, as shown in FIG. Of the array chips c2, c2, c3, c4 by shifting the image data of the array chips c2, c4 on the memory.
When is driven to output an image, as shown in FIG. 8B, a step is not generated in the image, and the originally desired image is output.

When the head mounting direction is opposite to that of the above-described embodiment or the image output direction is opposite, and the distance between the light emitting elements in the staggered arrangement is n = 2, FIG.
Although a step as shown in FIG. 9B occurs in the image,
As shown in (a), it is possible to prevent the occurrence of a step by shifting the memory arrangement of the image data corresponding to the array chips c1 and c3.

The distance d between the center lines of the light emitting point arrays of the light emitting element array chip may be an integral multiple n of the distance on the photosensitive drum that moves in one line time, and n = 1, 2, 3,
4, 5, 6, 7, and 8 are desirable.

[0043]

As described above, according to the present invention, the image data is called from the image memory for each array chip by simply shifting the image data on the memory based on the mounting state of the light emitting element array chip, Without adding a special circuit for adjusting the timing of transferring image data to the corresponding light emitting element on the array chip,
It is possible to correct the shift of the light spot sequence on the optical drum in the y-axis direction.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of an optical printer including an optical writing head.

FIG. 2 is a diagram showing a structure of an optical writing head.

FIG. 3 is a self-scanning light-emitting element array chip (2-phase drive 1
It is an equivalent circuit diagram of a basic structure of a point lighting type cathode common type).

FIG. 4 is a diagram showing a method of staggered arrangement.

FIG. 5 is a diagram showing a state in which light emitting element array chips according to the present invention are arranged in a staggered pattern on a head.

FIG. 6 is an image diagram of a memory when image data is stored in the memory without being shifted.

FIG. 7 is an image diagram of a memory when image data is stored in the memory in a shifted state.

FIG. 8 is a diagram showing an image output when the image data is not shifted on the memory and an image output when the image data is shifted.

FIG. 9 is a diagram showing another embodiment of the present invention and a state in which a step is generated in an image.

[Explanation of symbols]

2 photosensitive drum 4 charger 6 Optical writing head 8 developer 10 Transfer device 12 cassettes 14 sheets 16 Fixing device 18 Stacker 20 Erase lamp 22 Cleaner 24 Light emitting element array 26 Rod lens array 28,29 Self-scanning light emitting element array chip 30,31 Bonding pad 32, 33 light emitting element

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukisa Kusunoda             4-7 28 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Within Nippon Sheet Glass Co., Ltd. F-term (reference) 2C162 AE28 AE47 AF07 AF14 AF59                       FA04 FA17

Claims (6)

[Claims] 1. A plurality of light emitting element array chips in which a plurality of light emitting elements are arranged in a row are arranged in a staggered pattern, and light emission of each light emitting element array chip in a direction orthogonal to the arrangement direction of the light emitting element array chips. In the method of driving the optical writing head in which each light emitting element array chip is mounted by setting the interval between the center lines of the dot rows to be an integral multiple of the distance on the photosensitive drum that moves in one line time, (the value of the integral multiple) × ( The image data corresponding to the even-numbered light-emitting element array chips are converted into image data corresponding to the value of (the number of light-emitting elements transferred in one line time) for the image data corresponding to the odd-numbered light-emitting element array chips. All the light-emitting element array chips are driven by shifting them in the prepared memory and arranging them in the memory, reading the image data in the memory sequentially in the physical memory arrangement order. A method for driving an optical writing head, comprising: 2. A plurality of light emitting element array chips in which a plurality of light emitting elements are arranged in a row are arranged in a staggered pattern, and light emission of each light emitting element array chip in a direction orthogonal to the arrangement direction of the light emitting element array chips. In the method of driving the optical writing head in which each light emitting element array chip is mounted by setting the interval between the center lines of the dot rows to be an integral multiple of the distance on the photosensitive drum that moves in one line time, (the value of the integral multiple) × ( The image data corresponding to the odd-numbered light-emitting element array chips are converted into image data corresponding to the value of (the number of light-emitting elements transferred in one line time) for the image data corresponding to the even-numbered light-emitting element array chips. All the light-emitting element array chips are driven by shifting them in the prepared memory and arranging them in the memory, reading the image data in the memory sequentially in the physical memory arrangement order. A method for driving an optical writing head, comprising: 3. When data is collectively shifted on a memory prepared for the image and arranged in the memory, data indicating that no image is written is written at an address where the image data was not written by the shift. Claim 1
Alternatively, the method of driving the optical writing head according to the item 2. 4. The light according to claim 1, wherein the process of shifting the image data and arranging the image data in the memory is performed by software when the image data is expanded on the memory. How to drive the write head. 5. The light emitting element array chip is a self-scanning light emitting element array chip.
5. The method for driving the optical writing head according to any one of 4 to 4. 6. A shift clock signal of a self-scanning light emitting element array is used as a timing for sequentially reading image data on the memory.
6. The method for driving the optical writing head according to any one of 5 above.