JPH10297017A - Electrophotographic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform image by making constant the emission quantity of a self-scanning type emission device(SLED). SOLUTION: A quantity of light control section 109 inputs an ICONT corresponding to an unevenness correction data to an LED array drive circuit 11 to control the driving current of a transfer thyristor through voltage variation of the ICONT. Since current consumption in an LED array control section 102 is varied when the current of the transfer thyristor is varied, the voltage drops due to the wiring resistance from a power supply and the potential between the power supply and the GND is varied in the LED array control section 102. Consequently, the current of an emission thyristor is varied to cause variation in the quantity of light. According to the arrangement, the quantity of light is controlled to a constant level and a uniform image can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrophotographic apparatus using a light emitting element array as an exposure source.

[0002]

2. Description of the Related Art Conventionally, a self-scanning light emitting device (SLED:
As the light amount unevenness correction in the self-scanning light emitting diode, for example, there is a method of controlling the light emission duty of the light emitting thyristor.

[0003]

However, the method of controlling the light emission duty is complicated and the circuit configuration is also complicated.

Accordingly, an object of the present invention is to provide an electrophotographic apparatus which has solved the above problems.

[0005]

According to the first aspect of the present invention, an image is formed on a photoreceptor using a light emitting element array in which a plurality of self-scanning light emitting elements are arranged in an array as an exposure source. An electrophotographic apparatus to be formed, wherein driving means for driving the self-scanning light emitting element based on image data,
By controlling the current supplied from the driving unit to the transfer unit of the self-scanning light emitting element in response to the correction data of the light amount unevenness in the self-scanning light emitting element,
Light quantity control means for controlling the light emission output of the self-scanning light emitting element.

According to a second aspect of the present invention, in the first aspect, the light quantity control means changes a voltage between a power supply and a ground of the light control means in accordance with a change in a current supplied to the transfer means. It is characterized by the following.

Further, according to a third aspect of the present invention, in the first aspect, the light quantity control means controls a light emission output in synchronization with a lighting timing of the self-scanning light emitting element.

According to a fourth aspect of the present invention, in the first aspect, the light quantity control means converts the correction data into data of a predetermined number of bits in response to a signal from the driving means, and further converts the correction data into an analog voltage. It is characterized by having means for converting.

Further, the invention of claim 5 is characterized in that, in claim 4, the light quantity control means has means for offsetting the analog voltage.

Further, the invention of claim 6 is characterized in that, in claim 1, the self-scanning light emitting element has a light emitting thyristor and a transfer thyristor.

Further, according to a seventh aspect of the present invention, in the sixth aspect, the light quantity control means controls a gate voltage of a switching enhancement type FET of the transfer thyristor in response to the correction data. I do.

Further, the invention of claim 8 is characterized in that, in claim 2, there is provided means for adjusting a wiring resistance from the power supply to the light quantity control means.

Further, the invention of claim 9 is characterized in that, in claim 1, the correction data is obtained based on light emission unevenness of the self-scanning light emitting element measured in advance.

Further, the invention of claim 10 is characterized in that, in claim 1, a distributed refractive index lens is attached to the self-scanning light emitting element. [Detailed description of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of the present embodiment.
An ED array 102, an LED array control unit 103, an image data output unit 103, a photoconductor (drum) 105, a charging device 106, and a printer control unit 107 for centrally controlling the operation of the printer.

The LED array 101 is provided with a self-fox (distributed refractive index) lens array 108, and forms an image on a photoconductor 105. LED array controller 102
A light amount control unit 109 is incorporated therein, and an image is read from the image data output unit 103 to the LED array control unit 102 according to an image forming timing signal from the printer control unit 107.
An LED array drive signal is generated in the ED array drive circuit, and the LED array 101 emits light. Light intensity control unit 10
9, when the light amount unevenness correction data of the light emitting element set from the printer control unit 107 is input, the transfer current is synchronized with the LED array drive signal generated in the LED array drive circuit in the LED array control unit 102. Is controlled so that the light emission amount of the LED array is not uneven. The printer control unit 107 also includes the photoconductor 10
5 and the charging device 106 are also controlled.

FIG. 2 shows an LED array controller 1 according to this embodiment.
FIG. 2 is a diagram showing input and output of 02, 103 is an image data output unit such as a scanner or a computer, and 107 is a printer control unit which outputs image forming timing and unevenness correction data. The image data output unit 103 receives image formation timing from the printer control unit 107.
Supply READCLOCK for image reading to
Further, an LED array drive signal (φI, φS, φ1, φ2) necessary for sequentially turning on the LED array 101 is generated, and the light emission pulse φI and the input pixel data are ANDed.
To create image data φD for LED array emission,
An LED array drive circuit for outputting to the LED array 101,
Reference numeral 109 denotes a signal (φI,
φS) and the unevenness correction data from the printer control unit 107, and outputs an ICONT for controlling the amount of emitted light.
And an LED array control unit 102 having a light quantity control unit 109 and a power supply, a GND, and a circuit pattern of a conductive substance of a signal line are arranged on a base on which an output signal from the LED array drive circuit 11 sequentially outputs. Multiple LEs that emit light
A latent image is formed on the surface of the photoconductor whose potential changes by light using an LED head in which the chips of the D array 101 are arranged in rows. The light emitting pulse φI is a signal for setting a light emitting time (Duty) of one bit of each chip of the LED array. The light emitting pulse φI is composed of image data input to a light emitting thyristor capable of sequentially emitting light by the transfer pulses φ1 and φ2 and the light emitting pulse φI. A
By taking ND, this is an LED ON pulse for turning on the light emitting thyristor in the light emitting enabled state, and φS is a synchronization pulse.

First, after the printer control unit 107 receives a print ON signal from the outside, it outputs a timing signal for forming a latent image on the photoreceptor to the LED array control unit 102, and the clock in the LED array drive circuit 11 The image reading clock generated by the image data output unit 103
To receive the image data. The received image data is input to the LED array driving circuit 11 as LED array lighting pixel data. The LED array driving circuit 1
The image data inputted to the LED array driving circuit 11 is
The image data φD for LED array light emission is generated by ANDing the light emission pulse φI of the LED array drive signals (φI, φS, φ1, φ2) necessary for sequentially turning on the LED arrays formed in the LED array, LED array drive signal (φ
S, φ1, φ2) are output to the LED array.

FIG. 3 is a diagram showing input / output to the light quantity control unit 109 and an internal circuit of the light quantity control unit 109. When a non-uniformity correction data read clock output in synchronization with φS generated by the LED array drive circuit 11 is input to the printer control unit 107, the non-uniformity of the light emission amount measured in advance for each LED head is converted into an A / D signal. Converted (Figure 4),
The unevenness correction data input to the printer control unit 107 and stored in the memory of the printer control unit 107 is input to the light amount control unit 109. FIG. 5 shows the light amount control unit 10.
9 and the light quantity control unit 109
The φS and φI generated by the array drive circuit 11 are input, and φ
In S, the arithmetic unit 110 is reset, and φI latches the input unevenness correction data and converts it into 8-bit data in the arithmetic unit 110. The converted 8-bit data is D / A
D / A conversion is performed by the converter 11 and the voltage is further divided. The voltage waveform obtained here is converted to an offset voltage, passes through the amplifier 112, is output as ICONT, and is input to the LED array drive circuit 11. ICONT is connected to the gate of the enhancement-type FET that switches the transfer thyristor of the LED array drive circuit 11, and utilizes the fact that it can be used as a variable resistor that can be controlled by the gate-source voltage in the unsaturated region of this FET.
The transfer current of the transfer thyristor is controlled by the voltage change of ICONT (FIG. 6). By changing the current of the transfer thyristor, a voltage drop occurs due to the wiring resistance from the power supply as the current consumption in the LED array control unit 102 changes.
The potential between ND changes. It should be noted that the wiring of the LED array controller 10 is controlled during wiring so that the wiring resistance from the power supply is always constant.
Adjusted by a variable resistor at 2.

When the potential between the power supply and GND changes, the current of the light emitting thyristor changes, and the light quantity changes. Thus, the light amount is controlled to be constant, and a uniform image is formed.

FIG. 7 is an equivalent circuit of a light-emitting integrated device using a PNPN thyristor structure used in the LED array of the present embodiment, which is a self-scanning light-emitting device (a self-scanning light-emitting device capable of performing a light emitting point cyst register function). SLED). This is described in the literature: JP-A-1-238896.
No. 2, Japanese Unexamined Patent Application Publication No. 2-208067, Japanese Unexamined Patent Application Publication No.
No. 70, JP-A-3-20457, JP-A-3-1949
No. 78, JP-A-4-5872, JP-A-4-23367
JP-A-4-296579, JP-A-5-84771
No. and Japan Hard Copy '91 (A-17) Proposal of a light-emitting element array for an optical printer integrated with a driving circuit, IEICE ('90 .3.5) Self-scanning light-emitting element using a PNPN thyristor structure ( (SLED).

FIG. 8 shows pulses applied to the SLED. Transfer clocks φ1 and φ2 are applied to the cathode for the transfer operation. At the start of transfer, start pulse φS
Is applied. Now, assuming that S3 'is turned on by the low level voltage of φ1, the gate potential (zero volt) in the on state affects the thyristor on the right through diode C. Only the element on the right is selectively turned on by the low level voltage of the next φ2 clock, so that light emission can be transferred to the right.

FIG. 7 shows an example in which the shift register function and the light emitting function of the light emitting thyristor described above are used, and
An SLED for an electrophotographic printer combining a light emitting thyristor and a transfer (shift) thyristor for driving the thyristor
Is an equivalent circuit. In FIG. 7, S1 ', S2', S
Are thyristors S1, S2, S3,... For light emission, and 128 thyristors are formed on one light-emitting integrated device. Pulses φS, φ shown in FIG.
1, φ2 is applied, the N-bit parallel image data is converted into serial data, and φD produced by taking AND with φI is applied at a LOW level to turn on the light emitting thyristor corresponding to the image data.

[0025]

As described above, according to the present invention, S
By controlling the current of the transfer means of the LED, the emission current can be controlled, and the unevenness of the light amount of the SLED can be corrected, and a clear image without unevenness can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a basic configuration of an LED array control unit including a light amount control unit according to the embodiment.

FIG. 3 is a diagram illustrating an example of a basic equivalent circuit of a light control unit according to the embodiment.

FIG. 4 is a diagram illustrating an example of A / D conversion for obtaining unevenness correction data from uneven light intensity.

FIG. 5 is a diagram illustrating an example of an input signal to a light amount control unit according to the embodiment.

FIG. 6 is a diagram illustrating waveforms of a change in an ICONT voltage and a change in a φI (light emission) current by a light amount control unit according to the embodiment.

FIG. 7 is a diagram illustrating an example of an equivalent circuit of an SLED.

FIG. 8 is a diagram illustrating an example of a pulse applied to the SLED in FIG. 7;

[Explanation of symbols]

 Reference Signs List 11 LED array drive circuit 101 LED array 102 LED array control unit 103 Image data output unit 107 Printer control unit 109 Light intensity control unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Tanioka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (10)

[Claims] 1. An electrophotographic apparatus for forming an image on a photosensitive member using a light emitting element array in which a plurality of self-scanning light emitting elements are arranged in an array as an exposure source, wherein the self-scanning is performed based on image data. A driving unit for driving the self-scanning light-emitting element, and a current supplied from the driving unit to the transfer unit of the self-scanning light-emitting element, which is controlled in response to correction data of light amount unevenness in the self-scanning light-emitting element. ,
An electrophotographic apparatus comprising: a light amount control unit that controls a light emission output of the self-scanning light emitting element. 2. The electrophotographic apparatus according to claim 1, wherein the light quantity control means changes a voltage between a power supply and a ground of the light control means in accordance with a change in a current supplied to the transfer means. apparatus. 3. The electrophotographic apparatus according to claim 1, wherein the light quantity control means controls a light emission output in synchronization with a lighting timing of the self-scanning light emitting element. 4. The apparatus according to claim 1, wherein the light quantity control means has means for converting the correction data into data of a predetermined number of bits in response to a signal from the driving means, and further converting the data into an analog voltage. An electrophotographic apparatus characterized by the following. 5. The electrophotographic apparatus according to claim 4, wherein said light quantity control means has means for offsetting said analog voltage. 6. The electrophotographic apparatus according to claim 1, wherein the self-scanning light emitting element has a light emitting thyristor and a transfer thyristor. 7. The electrophotographic apparatus according to claim 6, wherein the light quantity control means controls a gate voltage of a switching enhancement type FET of the transfer thyristor in response to the correction data. 8. The electrophotographic apparatus according to claim 2, further comprising: means for adjusting a wiring resistance from the power supply to the light quantity control means. 9. The electrophotographic apparatus according to claim 1, wherein the correction data is obtained based on light emission unevenness of the self-scanning light emitting element measured in advance. 10. The electrophotographic apparatus according to claim 1, wherein a distributed index lens is attached to the self-scanning light emitting element.