JPS63151973A - Electrophotographic printing device - Google Patents

Abstract

PURPOSE:To prevent the generation of a structure line and to improve the reproducibility of a fine line and a whole picture quality by detecting a potential on the bright part of a photosensitive body after irradiation of optical beams and controlling the quantity of laser beams in accordance with the detected result so that the potential on the bright part is included within the tolerance range of an objective value. CONSTITUTION:The surface of the photosensitive body 1 rotated in an arrow (a) direction, is uniformly charged with a charging corotron 2 to obtain photosensitivity. The photosensitive body 1 is modulated by an image signal 13 and exposed by laser beams 12 generated from a laser beam generating part 3 to form an electrostatic latent image corresponding to the image signal 13. The electrostatic latent image is developed with toner and then transferred to transfer paper 9 by a transfer corotron 10. At that time, the surface potential of the photosensitive part 1 prior to development is detected by a surface potentiometer 4, its detecting signal 5 is inputted to a control part 7 and the bright part potential of an image to be formed is detected by the control part 7. The control part 7 controls the quantity of laser beams 12 generated from the laser beam generating part 3 so that the detected bright part potential is included within the tolerance range of the objective value. Thus, an excellent visual image can be obtained.

Description

Detailed Description of the Invention [Industrial Application Field] This defense forms a latent image by scanning a light beam modulated with an image signal on the surface of a photoreceptor, and develops this latent image to create a visible image. This invention relates to an electrophotographic printing device that prints images.

[Prior art 1] Conventionally, a laser beam generated from a laser beam generator is modulated with an image signal, and the modulated laser beam is deflected by a rotating polygon mirror and scanned on the surface of the photoconductor. Forms a latent image on the surface corresponding to the input image signal,
Electrophotographic printing 81 is known in which the latent image is developed with toner or the like and transferred and recorded on transfer paper.

[Problems to be solved by the amount of light] - However, in conventional devices, the amount of laser light generated from the laser beam generator is kept at a constant amount without any control.
For example, environmental temperature.

Due to changes in the exposure characteristics of the photoconductor and changes in light due to deterioration of the optical system placed in the optical path of the laser beam, the bright area potential formed on the photoconductor surface changes, causing fogging phenomenon in bright areas and thin lines. There was a problem in that a thinning phenomenon occurred and the image quality deteriorated.

The purpose of this light amount is to solve these problems and provide an electrophotographic printing device that can produce good visible images.

[Means for Solving the Problems] The present invention includes a measuring means for measuring the bright area potential on the surface of a photoreceptor after irradiation with a light beam, and a measuring means for measuring the bright area potential at a target value based on a signal of the measurement result of the measuring means. A control means is provided for controlling the light amount of the light beam so that it falls within the tolerance range.

[Operation] The light intensity of the light beam is controlled according to the measurement result of the bright area potential so that it is within the tolerance range of the target value.

[Embodiment 1] Fig. 1 is a block diagram showing an embodiment of the present invention, in which the surface of a photoreceptor 1 rotating in the direction of arrow a is uniformly charged by a charge corotron 2 to impart photosensitivity. . Then,
The photoreceptor 1 is modulated by an image signal 13 and exposed to a laser beam 12 generated from a laser beam generator 3, so that an electrostatic latent image corresponding to the image signal 13 is formed. This electrostatic latent image is developed by supplying toner from a developing device 8, and then transferred onto transfer paper 9 by a transfer corotron 10. The transfer paper 9 after the image transfer is then peeled off from the photoreceptor 1 by a peeling corotron 11.

In this series of steps, the surface potential of the photoreceptor 1 before the phenomenon is detected by the surface electrometer 4, the detection signal 5 is input to the control section 7, and the bright area potential of the image to be formed is detected by the control section 7. Detected in

The control unit 7 controls the laser beam 1 to be R1 from the laser target light generating unit 3 so that the detected bright area potential is within the tolerance range of the target value.
Control the amount of light in step 2.

By the way, if Vcnin is the minimum potential contrast required to obtain a sharp image in the photoreceptor 1 which shows a bright decay curve as shown in FIG. Because of the lack of potential contrast between the bright potential and the bright potential, linear fog (hereinafter referred to as LD line), which is characteristic of laser beam printers, occurs. Furthermore, when the light Q is increased and the portion shown in (b) is used, sufficient potential contrast can be obtained and a clear image can be obtained. However, if the light amount is further increased and the portion shown in (c) is used, sufficient potential contrast can be ensured and there is no concern about the generation of structural lines, but on the contrary, the It lines become thinner and a clear image cannot be obtained.

This is due to the following reasons. That is, it is generally known that the laser beam 12 has a Gaussian distribution. Therefore, the surface potential of the bright area has an uneven distribution in the circumferential direction of the photoreceptor 1, as shown in FIG. 3(a). Therefore, if the potential contrast is insufficient,
In contrast to the part shown by (d) in FIG. 3(b), the part shown by (e) has a high potential, and becomes a file and @ wire construction. On the other hand, the surface potential when reproducing a thin line corresponding to one dot of a laser beam is as shown in FIG. 4<a). When the amount of laser beam light is too strong, the development contrast in the portion shown by (f) in FIG. 4(b) becomes small, and the reproducibility of the image (particularly the a-line) becomes poor.

The present invention measures the potential of the bright area and variably sets the amount of light to the optimum amount to keep the potential of the bright area constant, so that a clear image can always be colored blue.

FIGS. 5(a) and 5(b) show the control section 7 that controls the laser beam Q.
This is a flowchart showing the operation. In the figure, VR indicates a laser light control voltage for the laser light generating section 3, and VM indicates a bright area potential.

First, in the case of the first print after turning on the power, the control section 7 outputs the initial value VRi of VR, and sets the laser light control voltage of the laser light generation section 3 to VRi (step 14.
15>. Next, after setting the flag F for distinguishing whether or not it is the first print to F=0, a predetermined period of time (approximately 1
000m5) and then detects the VM (steps 16 to 18). Note that if this is not the first printing after the power is turned on, the control section 7 starts the operation from step 17.

Next, the control unit 7 determines whether the flag F is F=0 or F=1 (step 19), and if F=O, feedback control is performed to bring VR within the tolerance range of the target value by the operations from step 20 onwards. In other words, the target value at Vl is VS, the coefficient is D
Then, a new VR is set by VR-VR+D (VM-VS) (1) (step 20).

Then, it is determined whether this new VR is larger than the maximum value VRnax or smaller than the minimum value VRn1n1 in step 21>, and if VR>Vflax, an error message indicating this (M A X error display) is displayed. is performed, and the subsequent printing operation is stopped (step 47).

Conversely, if VR<VRninl, VR=V R1i
n1 (step 48), and outputs this new VR (step 24).

On the other hand, in the judgment at step 19, if F=1, V
After setting R to the value VROLD used during the previous printing, set F=O and output VR=VROLD (
Steps 22-24). Also, F=0teari, VRll
If inl<VR<VRHAX, the VR obtained in step 20 is output.

If you repeat this operation up to 3 times, the specified time (1
After 70ms) has elapsed, proceed to step 25 to detect the VM.
28>, when VM falls below the lower limit value (■5-X) of the target value ■S, VR is reduced by ΔVR (step 30), and conversely, when VM exceeds the upper limit value (VS+X) of the target value ■S If so, VR is increased by ΔVR (step 31). However, when VS-X<VM<VS+X, VR is determined again (step 32).

In this judgment, if VR<V RHAX, an error display (MAX error display) is performed (step 47).
, if VR<VRlinl, then VR= VRlinlin
Output as l <Step 49.33>. However, under other conditions, VR is output as is (step 3
3).

If the 11 operations of steps 27 to 33 are repeated 4 times (step 34), 1iVM is detected again after a predetermined period of time (1701s) has passed, and it reaches the upper limit of the target value [j(VS+X
) and below the lower limit value (VS-X) (steps 34 to 37).

As a result, if VM<VS-X, then VR is determined,
If it is equal to or higher than the second lower limit VAV R1in2 of VR, a control error is displayed and the subsequent printing operation is stopped (step 43.50>. However, if VR<VRnin
If it is 2, F=O is set (step 44), and after 170 ns has elapsed, VM is detected, control of the laser light quantity is ended, and the process shifts to print mode (steps 45 to 46).

On the other hand, if VM>VS+X, a control error is displayed and the printing operation in the trace is stopped (step 37
．． 50).

However, if the VM is between the upper and lower limits of the setting point S, after setting VROl, D=VR, VR= (VR+
C1) Increase VR by a certain amount by xC2/100-C1-(2) (step 39).

Here, CI and C2 are constants.

Then, if the new VR is within V RHAX, this
Output the VR at step 40.41), then F
= 1 (step 42). Then 17010
After S elapses, VM is detected, control of the laser light amount is ended, and the process shifts to print mode (steps 45 to 46).
). However, if VR>VRHAX in step 40, an error is displayed and the printing operation is stopped (step 40.47).

In summary, for the first print [VM-VS
The laser control 'aO voltage VR is feedback-controlled in three stages according to J, and then VM is set to the upper limit 1 (VS+
The laser control tip voltage VR is controlled in four stages so as to be between the lower limit fir(VS-X) and (1).

Therefore, even if the optical system in the laser beam optical system deteriorates or the exposure characteristics of the photoreceptor change, the photoreceptor can always be exposed with the optimal laser light amount (laser light 41 whose bright area potential is constant). It is possible to prevent the occurrence of structural lines and improve the reproduction lines of the KU gland.

[Effect of the Invention 1] As explained above, according to the present invention, the bright area potential of the photoreceptor after the light beam irradiation 94 is detected, the laser beam is controlled according to the result, and the bright area potential reaches the target value. Since it is made to be within the tolerance range, it is possible to prevent the occurrence of structural lines and improve the reproducibility of fine lines, which has the effect of improving the overall image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram that does not show one embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the relationship between the laser beam D, the surface potential of the photoreceptor, and the current bias, and FIG. Figure 4 is an explanatory diagram to explain the generation of partial potential and structure lines. Figure 4 is an explanatory diagram to explain the reproducibility of bright area potential and fine lines. Figure 5 is an illustration of the operation of the control unit that controls the laser beam Φ. FIG. 1...Photoreceptor, 2...Charge corotron, 3...
- Laser light generating section, 4... Surface electrometer, 7... Control section, 8... Developing device, 9... Transfer paper, 10... Transfer corotron. Fig. 1 Fig. 2 124 yen 11Q,)'1 m□ φ ni Fuenen no ku - Fig. 3 Drum, PI force direction □ de'74FII11 haiku□ Fig. 4 Section 5 (0)

Claims (1)

[Claims] An electrophotographic printing device that forms a latent image by scanning a light beam modulated with an image signal on the surface of a photoreceptor, and obtains a visible image by developing the latent image, comprising: a light beam; A measuring means for measuring the bright area potential of the surface of the photoreceptor after irradiation, and controlling the light amount of the light beam so that the bright area potential is within a tolerance range of a target value based on a signal of the measurement result of this measuring means. An electrophotographic printing device comprising a control means.