JPH05294006A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent change in image density caused by aged deterioration of a line head. CONSTITUTION:An electrostatic latent image is formed on a photosensitive body 9 by light emitted from an end face of an end face emit type EL element of a line head 8. Light having a high light intensity to be emitted to an opposite side of the photosensitive body 9 of the line head 8 is detected by an optical sensor 12. In accordance with the output of the optical sensor 12, a light intensity control means 17 corrects accurately an output from a drive means 18 to the line head 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a large number of edge emitting ELs.
The present invention relates to an image forming apparatus that forms an electrostatic latent image on an outer peripheral surface of a photoconductor by a line head having elements arranged in a straight line.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a thin film active layer 1 made of zinc sulfide containing an active element has been used as a dielectric layer.
, And the plate electrodes 4 and 4 on the surface of these dielectric layers 2 and 3.
There is an edge emitting EL element 6 in which 5 is laminated and a flat light flux is emitted from the end surface of the active layer 1 by applying a voltage to these flat plate electrodes 4 and 5. As shown in FIG. 4, such an edge emitting EL element 6 is formed by linearly arranging it on a substrate 7 by a thin film technique or the like,
By making a rod lens array (not shown) face the tip of each edge emitting EL element 6, the line head 8
Is formed.

Then, the above-mentioned line head 8 is opposed to the photoconductor, and in the process of rotating the photoconductor, an electric charge is applied to the surface of the photoconductor to charge it, and the line head 8 is attached to the charged portion.
There is an image forming apparatus that forms an electrostatic latent image on the surface of a photoconductor by irradiating light based on an image signal from the photoconductor. On the other hand, if the sensitivity of the photoconductor is deteriorated with the lapse of time or the emission intensity of the line head 8 is lowered, the image density of the electrostatic latent image is lowered and the print quality is affected.

Therefore, an optical sensor is provided in the vicinity of the outer periphery of the photosensitive member in the non-image forming area, the optical intensity from the line head 8 is detected by this optical sensor, and the light intensity is input to the line head 8 according to the detection result. There is an image forming apparatus that adjusts the density of an image by correcting the output. However, the photoconductor and the line head 8 must be placed close to each other in a narrow space, which makes it difficult to support the optical sensor.

From the above, Japanese Patent Laid-Open No. 3-4416
As described in Japanese Unexamined Patent Publication No. 4 (1998), an optical sensor is closely attached to a surface orthogonal to the light emitting surface of the edge-emitting EL element 6, and light leaking from the edge-emitting EL element 6 is detected by the optical sensor. There is an invention in which the input to the line head 8 is corrected based on the result.

[0006]

However, Japanese Unexamined Patent Publication No. 3-4.
As described in Japanese Patent No. 4164, edge-emitting type E
When the optical sensor is closely attached to the surface orthogonal to the light emitting surface of the L element 6, the optical sensor receives light that is considerably attenuated with respect to the light intensity from the end surface of the edge emitting EL element 6. .. The attenuation factor is influenced by the transmittances of the dielectric layers 2 and 3 and the flat plate electrodes 4 and 5, and varies greatly because there are many factors of attenuation. Therefore, the light intensity of the line head 8 cannot be accurately grasped.

[0007]

SUMMARY OF THE INVENTION The present invention is a line head in which a photoconductor rotatably provided and a large number of edge emitting EL elements are arranged along a straight line parallel to the axis of the photoconductor. A driving means to which the edge emitting EL element is connected, an optical sensor arranged on an end surface of the line head on the side opposite to the photoconductor, and a driving means of the driving means according to the output of the optical sensor. It is composed of a light intensity control means for correcting the output.

[0008]

According to the present invention, the edge emitting type EL element of the line head is caused to emit light by the driving means, and the edge emitting type EL element is driven.
An electrostatic latent image is formed by irradiating the outer peripheral surface of the photoconductor with light from one end of the element, and light from the other end of the edge-emitting EL element is detected by an optical sensor, and the light is detected based on the detection result. The intensity control means corrects the output from the driving means to the line head. In this case, since a light amount equal to the amount of light emitted from the line head to the photoconductor can be input to the optical sensor, the output to the line head can be corrected accurately, and therefore the electrostatic latent image can be corrected. The concentration of can be constant.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The same parts as those described in FIGS. 4 and 5 are designated by the same reference numerals, and the description thereof will be omitted. 8 is a line head. The substrate 7 of the line head 8 is provided with a rod lens array 10 that converges the light of each edge-emitting EL element 6 onto the photoconductor 9 and a circuit board 11 on which a drive circuit including a matrix circuit is formed. The circuit board 11 holds an optical sensor 12 facing the end surface of the line head 8 on the side opposite to the photoconductor 9 of the specific edge emitting EL element 6.

The optical sensor 12 is connected to a light amount detection circuit 13. The output side of the light amount detection circuit 13 and the output side of the oscillation circuit 14 are provided with a plurality of AND gates 15a, 15
It is connected to an applied voltage control circuit 17 which is a light intensity control means via b and 15c and an OR gate 16. The applied voltage control circuit 17 is connected between a drive means 18 having a plurality of transistors for driving the individual edge emitting EL elements 6 of the line head 8 and a power supply 19.
Further, each transistor of the driving means 18 performs a switching operation when the output from the S / P (serial / parallel) conversion circuit 20 is input as a base, and the S / P conversion circuit 20 uses the print data or the data shift clock. (CL
It has an input gate for inputting K).

In such a configuration, in the process of rotating the photoconductor 9, the outer peripheral surface of the photoconductor 9 is charged by an unillustrated charger to be charged, and the edge emitting EL element corresponding to the input print data is charged. By making 6 emit light,
An electrostatic latent image is formed on the outer periphery of the photoconductor 9, and at this time print data is compressed and stored in a temporary storage memory (not shown), and line emission of the same pattern is repeated a plurality of times to form a main scanning line. To do. That is, each edge emitting type E
Although the L element 6 irradiates the photoconductor 9 with light with a flat light flux, a substantially square pixel is formed by repeating the light emission a plurality of times while rotating the photoconductor 9. The electrostatic latent image formed on the photoconductor 9 is developed by a developing device (not shown), and the developed image is transferred to a sheet by a transfer device (not shown).

Here, as shown in FIG. 2, the emission intensity of the edge emitting EL element 6 of the line head 8 changes according to the applied voltage, and emits light every time the polarity of the applied voltage is switched. The intensity increases and also changes with the emission frequency.

Therefore, correction of the output to the line head 8 will be described with reference to the timing chart shown in FIG. When the edge emitting EL element 6 of the line head 8 is made to emit light, the light from the edge emitting EL element 6 is detected by the light sensor 12 each time the light is emitted, and the detected value is detected by the light amount detection circuit 13 as the signal a, Converted to b and c. The signals a, b, and c and the frequencies f ₁ , f ₂ , and f from the oscillator circuit 14 are generated.
Signals output for every ₃ are AND gates 15a, 1 in sequence
5b and 15c and the OR gate 16 are input, and here the light emission amount control signal d in which the frequencies f ₁ , f ₂ and f ₃ are mixed is generated. Applied voltage control circuit 17 applies a voltage to the collector of the transistor of the driving means 18 from the power source 19 based on the input light intensity control signal _{d E (E 1, E 2} ... E n). On the other hand, the S / P conversion circuit 20 converts the input serial print data into parallel data in synchronization with the data shift clock, and outputs the parallel print data to the base of the transistor of the driving means 18. This allows
Each transistor causes the edge emitting EL element 6 to emit light while the drive voltage is controlled.

As described above, the correction of the output to the line head 8 is performed by causing the edge emitting EL element 6 corresponding to the optical sensor 12 to emit light when the power is turned on. When the purpose is only to correct the decrease in the light emission intensity of the line head 8 due to aging, the purpose can be achieved by providing only one optical sensor 12, and thus the structure for detecting the light intensity can be achieved. Can also be simplified.

[0015]

According to the present invention, a photosensitive member rotatably provided, a line head in which a large number of edge emitting EL elements are arranged along a straight line parallel to the axis of the photosensitive member, and the end surface are provided. Driving means to which a light emitting EL element is connected, an optical sensor provided on an end surface of the line head opposite to the photoconductor, and the output of the driving means is corrected according to the output of the optical sensor. Since it is constituted by the light intensity control means, the driving means causes the end surface emitting EL element of the line head to emit light, and the light from one end of the end surface emitting EL element is irradiated to the outer peripheral surface of the photoconductor to form an electrostatic latent image. An image is formed, light from the other end of the edge emitting EL element is detected by an optical sensor, and the output from the driving means to the line head is corrected by the light intensity control means based on the detection result. Sensitive from line head It is possible to input to the optical sensor the light of the light amount equal to the amount of light to be irradiated to, it is possible to accurately correct the output of the line head, thus,
This has the effect of making the density of the electrostatic latent image constant.

[Brief description of drawings]

FIG. 1 is a side view including a circuit diagram according to an embodiment of the invention.

FIG. 2 is a graph showing the relationship between emission intensity and voltage.

FIG. 3 is a timing chart.

FIG. 4 is a partial perspective view showing the configuration of a line head.

FIG. 5 is a partial perspective view showing the configuration of an edge emitting EL device.

[Explanation of symbols]

 6 Edge-Emitting EL Element 8 Line Head 9 Photoreceptor 12 Photosensor 17 Light Intensity Control Means 18 Driving Means

Claims (1)

[Claims] 1. A photosensitive member rotatably provided, and a large number of edge emitting ELs along a straight line parallel to the axis of the photosensitive member.
A line head formed by arranging elements, and the edge emitting type E
Driving means to which an L element is connected, an optical sensor arranged on an end surface of the line head opposite to the photoconductor, and a light intensity for correcting the output of the driving means according to the output of the optical sensor. An image forming apparatus comprising: a control unit.