JPS62299359A - Image exposure device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive image exposure device capable of producing high-quality images, by arranging a multiplicity of minute image exposure elements in an array form, dividing the elements into a plurality of blocks along the array direction, and controlling the light exposure of the exposure elements in each of the blocks at random. CONSTITUTION:Random control signals b1, b1...bM are inputted from a driving circuit 110 to control terminals of common drives 1051, 1052...105M of blocks B1, B1...BM on a line basis. When the control signal is at an H level, the common driver becomes active (conductive state), and when the control signal is at an L level, the common driver becomes disabled (cut-off state). The active period t' of each of the common drivers in a period (t) is varied at random on a line basis by the signals B1, B2...BM from the driving circuit 110. The light emission periods of LED elements 104, 104... in the blocks B1, B2...BM are thus varied, whereby an image for which exposure is performed is prevented from being affected by variations in the light exposure of the LED elements 104, 104....

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Use) The present invention relates to an image exposure apparatus used in an electrophotographic printer or the like.

(Prior Art) Recently, as the above-mentioned printer, a device using a solid-state optical scanner as an image exposure device has been attracting attention due to its accuracy, high speed, miniaturization, reliability, etc. Among them, L that uses an LED array as an image exposure device is attracting attention.
It is an ED printer.

A printer using this LED array can be made smaller than a laser printer, and has improved reliability because it has no mechanically moving parts. Also, compared to other solid state scanners, e.g. liquid crystal shutter arrays.

Since the element itself emits light, it does not require a light source and can be easily miniaturized, and a sufficient amount of light can be obtained, making it compatible with high-speed printers.

(Problems to be Solved by the Invention) However, such prior art has the following problems. In other words, in an LED array in which several thousand LED elements are arranged, there is variation in the amount of light emitted from each element.
This variation in the amount of light emitted appears as a result of shading in the image. Moreover, since the shading of this image appears in a streak-like manner in a direction perpendicular to the direction in which the elements are arranged, it becomes very noticeable, especially when a graphic image is output, and there is a problem in that a good image cannot be obtained.

Therefore, in order to solve the above-mentioned problems, it has been considered to measure the amount of light emitted from all the LED elements in advance and correct the amount of light emitted to a constant value by controlling the driving voltage of each element. However, in this case, the extremely troublesome work of measuring the amount of light emitted from all the LED elements in advance is required, and the amount of light emitted from all the elements must be controlled, making the configuration extremely complicated. There is a problem. Also, LEDs with the same amount of light emission
Although it is possible to configure an LED array by selecting elements, in this case, there is a problem that the cost of the LED array itself becomes extremely high.

The present invention has been made in order to solve the problems of the prior art described above, and its purpose is to eliminate the sliver-like unevenness in light amount with a simple configuration, and to produce high-quality images at low cost. The purpose of the present invention is to provide an exposure device.

(Means for Solving the Problems) In order to achieve the above object, the present invention arranges a large number of thin image exposure elements in an array, and arranges the image exposure elements along the arrangement direction. Divide into multiple blocks,
It is configured to provide a control means for randomly controlling the exposure amount of the image exposure element of each blow 2.

(Function) In the present invention, by randomly controlling the exposure amount of the image exposure elements of each block, the variation in the exposure amount of each image exposure element does not appear in the exposed image. Make sure not to.

(Example) The present invention will be explained below based on illustrated embodiments.

FIG. 9 shows an image forming apparatus to which the image exposure apparatus according to the present invention is applied. In FIG. 6, 1 is an image exposure apparatus, and the image exposure apparatus 1 includes an LED array 100 and a small-diameter imaging element array. It consists of 3. 4 is a photoreceptor drum 4 rotating in the direction of arrow A, and the photoreceptor drum 4 is
After the surface is uniformly charged by the Wf′\L device 5,
A light signal from the LED array 100 forms an electrostatic latent image on its surface in accordance with an image signal. This latent image is developed by a developing device 6 in a normal electrophotographic process, and the developed image is transferred by a transfer charger 7 onto a transfer sheet P that is transported in the direction of arrow B. The transferred image is finally fixed onto the transfer paper P by the fixing device 9, forming an image. In FIG. 6, 8 indicates a cleaner.

As shown in FIG. 4, the LED array 100 includes minute LED elements 104, 104, . . . as image exposure elements.
It has a large number of LEDs arranged in an array.
A plurality of elements 104, 104, . . . are M blocks Bl along the arrangement direction.

B2... Divided into BM. The above LED element 10
4.104... is block B as shown in FIG.
l, B2. ...driver 1031 for each BM. 10
32, . . . 103M, and the drivers 1031 . 103. ,...103° is latch 10
21, 1022, . . . Serial-to-parallel converter 1a11 . . . consisting of a shift register via bow 02M. 10
12,...101. are connected to each. Thus, the serial image data 106 is converted into parallel data by the serial-to-parallel converters 1011, 1022, .
2,...102M, and the latch 1
02. , 1022.

...Driver 1031゜1 for the signal within 102M
LED element 104゜1 via 032, . . . 103M
04... is turned on and off. In addition, LED element 1
04, 104... and drivers 1031, 1032,
Since there is a limit to the size of the ICs constituting the 103M etc., they are usually arranged in rows as shown in the figure. The size of this IC is unified into one, which is usually the size of one LED array chip, and is composed of M pieces as shown in the figure.

The common side of the LED elements 104, 104, . . . is connected to a common driver 105 consisting of a switching element such as a transistor. ．． 1052, . . . 105N, blocks Bl, B2 . ... are connected for each BM, and the common driver 105. , 1052, . . . 105M are connected to a drive circuit 110 as a control means.

FIG. 2 is a block diagram showing the drive circuit. This drive circuit 110 sends a random number signal to a random number signal generator 120,
A control section 110 comprising a pulse width correction circuit 121 that generates a pulse signal with a width according to the random number signal. ．． 1102
, . . , 110M as many as the clocks.

FIG. 3 is a circuit diagram showing the control section, and in FIG.
122 is a pseudo random number generator, which generates 1 bit “H” or “L” when triggered by the edge or level of the input clock 126.
This is a circuit that randomly generates a signal ".This random number signal 128 and the AND output of the trigger enable signal TRIGEN within l line period by the AND circuit 124 and the OR output of the latch signal 108 by the OR circuit 125 are the retriggerable one. It is input to the shot circuit 123.

The retriggerable one-shot circuit 123 outputs a pulse signal having a width determined by the time constant of an external resistor R and a capacitor C, depending on the rise or fall of an input signal. Since the random number signal is input to the retriggerable one-shot circuit 123 when the trigger enable signal TRIG EX is at "H" level, the retriggerable one-shot circuit 123
The output circuit 123 is triggered again, and the width of the pulse signal output becomes longer by the delay time, producing a common driver control signal bn as shown in FIG. By this signal bn.

The lighting time of the LED elements 104, 104, . . . in each block is controlled.

Further, in the above embodiment, each block is provided with one control section, but as shown in FIG. 7, each block may be further wired in a matrix to reduce the number of control sections.
In this case, the configuration of the drive circuit 110 is simplified and costs can be reduced.

In the above configuration, in this embodiment, the light emission of the LED array is controlled as shown in FIG. That is, 10
6 is serial image data, which is sequentially shifted by serial-parallel converters 1011, 1012, . .1022, ... Store data in 102M. Therefore, the LED element 104°104...
・is the driver 1031 . 1032.

. . , when the enable signal EN of 103M is at "H" level, the latches 1021 . 1022, . . . are turned on or off according to the data of 102M. Furthermore, when this enable signal EN is at the "L" level, the LED element 104
, 104 . . . and the driver 1031 . 1032,・
...103M is nearly cut out, LED element 1
04, 104, and 104 maintain the OFF state.

At this time, the common drivers 1051 . Random control signals bl, b2 . . . bM as shown in FIG. 5 are input from the drive circuit 110 to the control terminals 1052, . . . 105M for every l line. This control signal bl.

b2...When bM is at "H" level, common driver 1
051. 1052,...105M are active (
0 time (1), which is disabled (interrupted state 8) when it is at "L" level, indicates the l line write cycle, and within this time (1), each common driver 1051
．． 1052,...105M active time (t'
), the signals bl, b2...bM from the drive circuit 110
As shown in FIG. 5, by randomly changing each line, each block Bl, B2...
The light emission time of the LED elements 104, 104, . . . of the BM is changed.

In this way, each block Bl, B2 . ...BM's LE
By randomly changing the light emitting time of the DJ elements 104, 104... each line, each LED element 104
, 104, . . . even if there is variation in the amount of light emitted by the light emitting devices, the effect thereof does not appear on the exposed image, and it is possible to form an apparently uniform high quality image.

In the illustrated embodiment, a case has been described in which the light emission time of the LED element is controlled using the drivers 1051, 1052, . . . 105M on the common side of the LED element, but the invention is not limited to this. , as shown in FIG. 8, the driver 130. enable signals ENI, E
N2... may be controlled, that is, the transistors 1311 to 13 connected to the driver 130
The common control signal shown in the above embodiment may be applied as an enable signal to the base of 1M. In this case, the pulse width of the applied enable signal changes randomly.

Further, in the above embodiment, a case was explained in which a pulse width modulation method was adopted as the control means, but the invention is not limited to this, and the voltage level or the amount of current may be controlled. Although it varies depending on the configuration of the driver IC at the final stage of the array, for example, depending on the voltage level or current amount of the enable signal, the LE of each block
Controls the current value of the D element. In this case, the same implementation can be achieved by replacing the pulse width correction circuit of the above embodiment with a voltage level correction circuit or a current level correction circuit.

Further, in the above embodiment, a case was explained in which an LED element was used as a single image exposure element, but the invention is not limited to this, and the light from a light source is turned on as an image exposure element.
, a liquid crystal shutter array with OFF control may be used. In this case, the influence of uneven light distribution of the light source can be ignored to some extent, there is no need to use a highly accurate light source, and cost reduction is possible. be.

(Effects of the Invention) The present invention has the above-described configuration and operation, and provides an inexpensive image exposure device that can correct variations in the exposure amount of the image exposure element with a simple configuration and can obtain high-quality images. Can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an image exposure apparatus according to the present invention, FIG. 2 is a block diagram showing a drive circuit, FIG. 3 is a circuit diagram showing a control section of the drive circuit in FIG. Figure 4 is L
5 is a timing chart showing the operation of the circuit in FIG. 1, FIG. 6 is a timing chart showing the operation of the circuit in FIG. 3, and FIG. 7 is a diagram showing the operation of the circuit in FIG. 3. FIG. 8 is a block diagram showing another embodiment of the present invention, and FIG. 9 is a schematic configuration diagram showing an image forming apparatus to which the present invention is applied. Explanation of symbols 100...LED array 104...LED element 110...Drive circuit agent Patent attorney Back 1) Rules 2 Figure 2 Figure 3 Figure 6 Figure 7 Figure 1n Figure 9 A

Claims (2)

[Claims] (1) A control means that arranges a large number of fine image exposure elements in an array, divides the image exposure elements into a plurality of blocks along the arrangement direction, and randomly controls the exposure amount of the image exposure elements of each block. An image exposure device characterized by being provided with. (2) A patent characterized in that the control means has a random number generator, and controls at least one of the exposure time, drive voltage, or current of the image exposure element using a random number signal from the random number generator. An image exposure apparatus according to claim 1.