JPS62258559A - Controller of plot head for electrophotograph - Google Patents

Abstract

PURPOSE:To suppress the deterioration in the picture quality basedon the sot whose intensity is deficient by controlling the sum of outputs of a spot whose intensity is deficient and an adjacent spot so as to be equal to the sum of the outputs of other spots. CONSTITUTION:A picture signal outputted from a memory 20 is latched by a latch circuit 22. A control section 23 outputs an enable signal VE having a duty ratio in response to the luminous intensity of the light spot 26 of a light emitting diode array to an AND circuit 24, its AND output turns on/off a transistor 25 to drive each spot 26. The duty ratio of the enable signal is brought into 100% to the spot with deficient rating, the sum of outputs of adjacent spots is made equal to the sum of outputs of other spots. As a result, the deterioration in the picture quality by the spot with deficient rating is suppressed.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention aims to reduce the decrease in the print density of a print spot where the print density does not reach the standard value even if the duty ratio of the drive time is set to 100% by reducing the print density of the adjacent print spot. The present invention relates to a control device for an electrophotographic plot head which is adapted to compensate by harmonizing.

[Conventional technology]

Some electrophotographic plot heads are constructed from, for example, a light emitting diode array. FIG. 4 shows an electrophotographic device that employs this light emitting diode array.
, light emitting diode array 3 and rod lens array 4
An exposure means 5, a developer a6, a transfer means 7, a static eliminator 8, and a cleaning device 9 are provided, and a fixing device 10 is provided downstream of the transfer means 7.

In the above configuration, after uniformly charging the photoreceptor drum 1 with the charger 2, when the light emitting diode array 3 is driven according to an image signal, output light passes through the rod lens array 4 and exposes the photoreceptor drum 1. to form an electrostatic latent image on its surface. This electrostatic latent image is developed as a toner image by a developing device 6, and the toner image is transferred onto recording paper by a transfer means 7. The toner image transferred to the recording paper is fixed by the fixing device 10, and recording is completed. On the other hand, the photoreceptor drum 1
After the static electricity is removed by the cleaning device 9, the cleaning device 9 cleans it.

In driving the light emitting diode array 3 described above, if there is variation in the luminous intensity of the luminous spots, the duty ratio of the driving time of the luminous spots is controlled depending on the luminous intensity, or
Alternatively, as shown in Japanese Patent Laid-Open No. 59-110267, a photosensitive material for shading correction is arranged to control light transmittance, thereby keeping the scene constant and suppressing deterioration in image quality.

[Problem that the invention seeks to solve]

However, according to the conventional electrophotographic apparatus, as shown in FIG.
(As shown in C1, the light-emitting diode array has a spot 7 whose luminous intensity is about 1/4 of the standard value).
1)), even if the driving duty ratio of that spot is set to 100% (Fig. 5 (b)), the light intensity reaches only about 1/2 of the standard value (Fig. 5 (C)), and other 50 spots
Since the amount of light reaches the standard value at a duty ratio of %, there is an inconvenience that the depth of the spot portion where the amount of light is insufficient is reduced when an image is formed by, for example, reversal development.

On the other hand, if the duty ratios of other spots are lowered to make the light intensity equal to the light intensity of the specific spot S (1/2 of the standard value), the plotting speed will decrease, and it will also prevent the existence of spots with insufficient light intensity. If a light emitting diode array is manufactured using the same method, the yield will be reduced and the cost will be increased.

The above has described the control of the light amount of the light emitting diode array, but the same can be said of the control of the amount of heat generated by the thermal head array or the amount of charge of the stylus head.

[Means for solving problems]

The present invention has been made in view of the above, and in order to suppress the deterioration of image quality due to the decrease in the output amount due to the under-rated spot of a specific spot without causing a decrease in plotting speed or an increase in cost, the present invention has been made to reduce the output amount of the under-rated spot. The present invention relates to a control device for an electrophotographic plot head in which the sum of the output amounts of adjacent standard rated spots is made equal to the sum of the output amounts of other standard rated spots.

Hereinafter, a control device for an electrophotographic plotting head according to the present invention will be explained.

〔Example〕

FIG. 1 shows an embodiment of the present invention, which includes a memory 20 that stores an image signal, a shift register 21 that inputs the image signal from the memory 20 as a serial signal 11, and outputs it as a parallel signal I, and a shift register. A launch circuit 22 that latches parallel signals of 21 and a launch circuit 2
The AND circuit 24 outputs under the AND condition of the output of 2 and the enable signal ■ of the control unit 23;
Switching transistor 2 is turned on by the output of
5, and a light emitting spot 26 that is driven by turning on a switching transistor 25.

The control unit 23 stores the luminous intensity information of the spot 26 of the light emitting diode array, outputs an enable signal with a duty ratio based on the luminous intensity, and controls the operation of other circuits.

In the above configuration, when the serial image signal I5 is input from the memory 20 to the shift register 21, it is manually transmitted from the shift register 21 to the launch circuit 2.2 as parallel image signals II and p, where it is notched. . The control unit 23 outputs an enable signal Vt (FIG. 2(a)) based on the clock (FIG. 2(a)). The enable signal ■ is the light emitting spot 26 of the light emitting diode array.
It has a duty ratio according to the luminous intensity. The enable signal VtS corresponding to the 174 spots S with the standard luminous intensity has a duty ratio of 100%, and the duty ratio for the adjacent spots is 75%. 25% at the same time as the enable signal VES with a duty ratio of 75%,
An enable signal (2) with a duty ratio of 75%, 25%, etc. is output (FIG. 2(b)). This enable signal ■. , VE-, the AND circuit 24 becomes "1" according to the time limit based on the duty ratio and the latch state of the launch circuit 22, thereby turning on the switching transistor 25, and this turning on drives the light emitting spot 26. . Figure 2 (bl indicates the duty ratio of the lighting time of the light-emitting spot 26; the light-emitting spot S with insufficient brightness is lit with a duty ratio of 100%, and the other spots are lit with a duty ratio of 75% and 25%. With this lighting, the light intensity of spot S with insufficient luminous intensity becomes the standard value of 172, and the light intensity of the other spots becomes 3 of the standard value by lighting with a duty ratio of 75%.
72, and by lighting with a duty ratio of 25%, the standard value becomes 172 (FIG. 2(C)).

As is clear from Fig. 2(e), the sum of the light amounts of two adjacent spots becomes (2/3 + 1/2) X standard value, and the influence of the spot S with insufficient light intensity is removed, resulting in a decrease in image quality. can be suppressed.

Figures 3+a) to (C1) show other embodiments of the present invention, and parts common to Figures 2(al to (C)) are designated by the same reference numerals, so redundant explanations will be omitted. In order to prevent the influence of the insufficient spot S from reaching distant spots as much as possible, the lighting duty ratios of other spots located on both sides (in the main scanning direction) of the insufficient luminous intensity spot S are changed from 75% and 25%. It was controlled to approximate 50% (Fig. 3 (al and (b)).

Through this control, the light intensity of the spot S with insufficient luminous intensity becomes the standard value of 172, and the spots located on both sides (in the main scanning direction) with the standard value of 273 light intensity and the standard value of 172 light intensity become the standard value of transfer. It approximates the amount of light.

Although each of the above embodiments describes a light emitting diode array, the amount of heat generated by a thermal hand array having a heat generating element,
The present invention can be similarly applied to controlling the amount of charge etc. by a stylus head having a discharge gap.

〔Effect of the invention〕

As described above, according to the control device for an electrophotographic plotting head of the present invention, the sum of the output amount of the seven under-rated subpots and the output amount of the adjacent standard-rated spot can be compared to other standard-rated spots. By making the output amount equal to the sum of the output amounts, it is possible to suppress the deterioration in image quality due to a decrease in the output amount due to an insufficient rating of a specific spot without causing a decrease in plotting speed or an increase in cost.

4. Brief explanation of drawings 1
FIG. 1 is a circuit diagram showing an embodiment of the present invention.

Figure 2 +a), (bl, (C) is an explanatory diagram showing the waveform diagram of the control signal, the duty ratio of the lighting time, and the amount of light in one embodiment of the present invention. Figure 3 (a), Tb), ( C1 is a waveform diagram of a control signal, an explanatory diagram showing a duty ratio of lighting time, and an explanatory diagram of light amount in another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an electrophotographic apparatus. Figure 5 fa), (
b) and (C) are explanatory diagrams showing the luminous intensity, lighting time duty ratio, and light amount of a light emitting diode array of a conventional electrophotographic device.

Explanation of symbols 20--Memory 21--Shift register≧2--Latch circuit 23--
. . . Control unit 24 --- AND circuit 25 --- Switching transistor 26 ---
・−・・Light-emitting switch (light-emitting diode array) Applicant Fuji Xerox Co., Ltd. Agent Patent attorney
Hei 1) Tadao Figure 2 tσ no 2nd place 1 Figure 3 tσノ (b noyo); Toy Ll

Claims (1)

[Claims] In an electrophotographic plot head having an array of printing spots driven in accordance with an image signal, even if the duty ratio of the driving time is set to 100% during the printing spots, standard output is not achieved. When there is a spot with insufficient output that does not reach the capacity, a control means is provided for controlling the sum of the output amounts of the spot with insufficient output and the adjacent spots to be equal to the sum of the output amounts of the other spots. A control device for a plot head for electrophotography.