JPH03243967A - Exposure light quantity irregularity correction device for recorder - Google Patents

Abstract

PURPOSE:To improve image quality and to remarkably facilitate the correcting work of the irregularity of light quantity by correcting the irregularity of the light quantity in the axial direction of a photosensitive body and making brightness potential uniform. CONSTITUTION:A light transmitting member 10 whose light transmissivity is varied according to impressed voltage divided for plural blocks in a direction which is in parallel with the axial direction of the photosensitive body 13 is arranged to an optical path which guides image light to the body 13. Simultaneously, a surface potential sensor 16 which can be moved in parallel with the surface of the body 13 is provided and the surface potential of the body 13 is detected at plural positions. Then, the surface potential of the body 13 when it is exposed is detected by light reflected from a reference density reflecting member 10b. According to the detected result, the voltage impressed on the respective blocks of the light transmitting member 10 is respectively independently controlled by a control means 31. In such a way, the surface potential is detected by the sensor 16 and the light transmissivity of an optical reflecting mirror 10 is varied so as to make the detected potential constant in the axial direction of the photosensitive body. Thus, the irregularity of the exposure light quantity is quickly and accurately corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an axial light amount unevenness correction device in an exposure device of a recording device, for example, an electrophotographic copying machine.

[Conventional technology]

Conventionally, in self-recording devices, such as electrophotographic copying machines, a light source that is long in the main scanning direction scans the surface of the document in sub-scans, and the reflected light is passed through an optical system consisting of mirrors, lenses, etc. to a drum-shaped or belt-shaped photoreceptor. The image is exposed to light to form an electrostatic latent image, which is then developed with toner. In this case, when a halogen lamp or the like is used as a light source, unevenness in the light intensity distribution occurs in the optical axis direction due to unevenness in the distribution of the amount of emitted light.

If exposure light intensity unevenness occurs, it will have a significant negative effect on the image quality of the copy, and especially when the document contains low-density line images (such as characters), adjusting the density button so that all the line images are reproduced will improve the background texture. If you adjust the density button to prevent stains on the background, some line images (letters, etc.)
There was a problem where the ``failure'' could not be reproduced.

Conventional methods for correcting such unevenness in the amount of light in the axial direction of exposure equipment include methods of making the amount of light irradiated onto the photoreceptor constant by changing the shape of the exposure slit, and placing an electrochromic element in the optical path. , which corrects the unevenness of the exposure light amount due to the influence of the lens by adjusting the light transmittance by changing the applied voltage (Japanese Patent Application Laid-Open No. 1987-
No. 228240) has been proposed.

[Problem to be solved by the invention]

However, with the method of changing the shape of the exposure slit, it is necessary to check the reproducibility of the ejected copies and modify the angle of the slit depending on the operator's experience. It was necessary to repeat the process of opening, correcting the slit, and making copies, which was very time-consuming and time-consuming, and the accuracy was not good.

Further, even in the case of using an electrochromic element, since the adjustment is made while confirming the reproducibility of the ejected copies, there is a problem in that it takes time and effort to correct the unevenness of the exposure light amount. In addition, a liquid crystal shutter is provided to limit the exposure area (Japanese Unexamined Patent Publication No. 63-149
No. 671) has also been proposed, but it does not take into account correction of exposure unevenness.

One object of the present invention is to solve the above problems.

An object of the present invention is to quickly and accurately correct unevenness in the amount of exposure light in the axial direction, which has a significant adverse effect on image quality.

Another object of the present invention is to easily eliminate unevenness in the amount of exposure light in the axial direction by treating the level of exposure light as the surface potential of the photoreceptor and controlling it to eliminate the unevenness in the surface potential of the photoreceptor in the axial direction. It is.

Another object of the present invention is to make it possible to easily correct unevenness in the amount of exposure light in the axial direction while checking the amount of light adjustment on a display panel.

[Means and Effects for Solving the Problems] To achieve this, the present invention provides an optical path in which image light is guided to a photoreceptor, in accordance with applied voltages divided into a plurality of blocks in a direction parallel to the axial direction of the photoreceptor. In addition to arranging a light transmitting member with variable transmittance,
A surface potential sensor that can move parallel to the photoconductor surface is provided to detect the photoconductor surface potential at multiple positions, and the photoconductor surface potential is detected when the photoconductor is exposed to light reflected from the reference density reflecting member. The present invention is characterized in that the voltage applied to each block of the light transmitting member is independently controlled by the control means in accordance with the detection result. In this way, the control means controls the light transmittance of each block of the light transmitting member so that the surface potential of the photoreceptor during exposure by the light reflected from the reference density reflecting member is approximately uniform in the axial direction. It is possible to quickly, easily, and highly accurately correct unevenness in the amount of exposure light in the direction.

In addition, a means is provided to select a block of the light transmitting member and set the amount of light amount adjustment without providing a surface potential sensor, and the selected block and the amount of light amount adjustment are displayed on the display panel. It becomes possible to easily correct the unevenness of the exposure light amount in the axial direction while looking at the image.

〔Example〕

Although the present invention is applicable to various recording devices such as printers, facsimile machines, and copying machines, a copying machine will be described below as an example.

FIG. 1 is a diagram showing the overall configuration when the present invention is applied to a copying machine, FIG. 2 is a diagram showing the exposure system, FIG. The figure is a diagram for explaining the movement mechanism of the surface potential sensor. In the figure, 1 is a platen glass, 2 is a base density reflector, 3 is an exposure device,
5.6.7 is a reflector, 8 is a lens, 9 is a shutter, 10
11 is an optical reflection mirror, 11 is a power source, 12 is a light transmission semi-variable device, 13 is a photoreceptor, 15 is a charging device, 16 is a surface potential sensor, 17 is a developing device, 18 is a paper conveyance path, and 19 is a transfer/printer. Corotron, 20 is a paper transport device, 21 is a cleaner, 22 is an erase lamp, 30 is a switch, 31
CPUJ32 is ROM.

33 is a RAM, 34 is an amplifier, 35 is an A/D converter, 3
6 is a D/A converter, 37 is a multiplexer, 38 is a high voltage power supply, 40 is a sensor holder, 41 is a support shaft, 42
is the feed screw, 43 is the mounting bracket, 44 is the motor,
45.46 is a gear.

In the illustrated copying machine, a document is placed on a platen glass 1, an exposure device 3 consisting of a fluorescent lamp, a halogen lamp, etc. is scanned to illuminate the surface of the document, and the reflected light is reflected by mirrors 5, 6, 7,
A photoreceptor 13 charged to a predetermined potential is exposed to light through a lens 8 and an optical reflection mirror 10 to form an electrostatic latent image, and a toner is developed in a developing device 17 to form a toner image on a sheet of paper sent through a paper conveyance path 18. After the copy paper is transferred by the transfer/button corotron 19, the copy paper is transported by the paper transport device 20 to a fixing device (not shown). The toner on the photoreceptor after transfer is removed by the cleaner 21, the erase lamp 15 removes the charge, and the charging device 15 charges the toner, and the next copying operation is performed in the same manner.

By the way, as shown in FIG. 2, the light source 3 is long in the main scanning direction.
In particular, when a halogen lamp or the like is used, the light emitting characteristics in the axial direction are not uniform, resulting in uneven exposure in the axial direction of the photoreceptor 13. Therefore, in the present invention, this correction is performed as follows. Do it like this.

Press a specific key switch 30 to enter the self-diagnosis mode, enter a predetermined code number, such as ##1, manually on the numeric keypad, and then press the copy start key to rotate the photoreceptor 13 and start normal charging operation. be done. Then, the exposure lamp 3 moves below the reference density reflector 2 and turns on with a predetermined light intensity, and the reflected light from the reference density reflector 2 is reflected by the optical reflection mirror 10 via the optical system to illuminate the photoreceptor 13. Expose. The optical reflection mirror 10 is a reflection mirror 10b formed by vapor deposition on the back surface of a light control glass 10a, as shown in FIG. 10a-1 as transparent divided electrode 10a-2
, a transparent common electrode 10a-3 is sandwiched between them, and both sides thereof are sandwiched between glass plates 10a-4 and 10a-5. This light control glass 10a changes the light distribution of liquid crystal molecules by changing the voltage applied between the electrodes, and the light transmittance changes. Therefore, as shown in FIG. 3(a), light enters the light control glass and is reflected. The intensity of the emitted light reflected by the mirror 10b can be changed. Note that the optical reflection mirror 10 may be formed of only the light control glass 10a and used as a transmission type instead of a reflection type. In that case, the light control glass is placed after the lens and the transmitted light is reflected by another reflection type. The light may be reflected by a mirror and exposed onto the photoreceptor. And photoreceptor 130
A surface potential sensor 16 detects the surface potential. The surface potential sensor 16 is movable in the axial direction of the photoreceptor, and is controlled by the CPU 31 so as to stop at a predetermined position and detect the surface potential. For example, as shown in FIG. 4, the potential sensor is moved by rotating a feed screw 42 via a step motor 44 attached to a bracket 43 and gears 45, 46, and slidably supported on a support shaft 41. This is done by moving the sensor holder along the shaft 41. The position where the potential sensor is stopped is set, for example, at a position where the effective charging length in the axial direction of the photoconductor is divided into seven equal parts, and when the potential sensor 16 moves all the way to the back, the optical home A position sensor (not shown) is used to determine a reference position. Further, like the photoreceptor 13, the optical reflection mirror 10 is also divided into seven equal blocks in its entire length so that the amount of transmitted light can be controlled.

Then, the surface potential sensor 16 is first moved to the center in the axial direction of the photoconductor to detect the photoconductor surface potential, and for example, the surface potential sensor 16 detects the surface potential of the photoconductor.
Then, the surface potential sensor 16 is moved to a predetermined position at either end of the photoreceptor in the axial direction to detect the surface potential, and this is defined as, for example, VBKG·1. These detection results are amplified by an amplifier 34 and sent to the A/
The data is A/D converted by the D converter 35 and read into the CPU 31. And VBKG −REF−VBKG−1≦Δ
The light transmission speed variable device 1 is controlled by the CPU 31 via the D/A converter 36 and the multiplexer 37 so that the signal becomes VBKG.
The light transmittance of the light control glass of a predetermined block is controlled by adjusting one of 2a to 12n (FIG. 2).

Here, ΔVBKG is a predetermined value such as IOV, for example.

When this control is completed, the control value (digital value) is stored in a RAM 33 or the like with a backup power source. The same operation is repeated by moving the surface potential sensor 16 to a predetermined position in the axial direction of the photoreceptor. The program for this control procedure is RO
It is stored in M32.

Note that if the output of the high-voltage power supply 38 to the charging device 15 that charges the photoreceptor 13 is kept constant, a cycle down of the charging characteristics of the photoreceptor 13, that is, a phenomenon in which the dark potential decreases as the number of times of charging increases. Therefore, it is necessary to close the shutter 9 from time to time, detect the dark potential with the surface potential sensor 16, and control the output of the high-voltage power supply 38 so that the dark potential is stabilized.

In this way, the surface potential sensor 16 detects the surface potential,
By changing the light transmittance of the optical reflection mirror 10 so that the detected potential is constant in the axial direction of the photoreceptor, it is possible to correct the unevenness of the exposure light amount quickly and with high precision.

FIG. 5 is a diagram showing another embodiment of the present invention.

In the figure, 50 is a liquid crystal display panel, 51 is an operation button, 52
is a block display mark, 53 is an adjustment amount display mark, 54
is the scale.

In this embodiment, the amount of light transmitted through the optical reflection mirror is manually controlled without using a surface potential sensor. That is, the block to be adjusted is selected by left and right operations of the operation buttons, and at this time, the selected block is indicated by the block display mark 52 on the liquid crystal display panel 50. Next, by operating the operation button 51 up and down, one of the light transmission speed variable devices 12a to 12n shown in FIG. Indicated by mark 53. This operation is adjusted so that the copy quality of ejected copies of a predetermined original (not shown), for example, the reproducibility of low-density line images, is approximately uniform in the axial direction.

〔Effect of the invention〕

As described above, according to the present invention, by correcting the unevenness in the amount of light in the axial direction of the photoconductor and making the bright potential uniform, it is possible to improve the image quality by making the reproducibility of lines uniform, etc. The work of correcting light intensity unevenness is significantly easier than with conventional methods, and furthermore, no special tools are required and the work can be carried out in a short time, achieving excellent effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration when the present invention is applied to a copying machine, FIG. 2 is a diagram showing the exposure system, FIG. 3 is a diagram showing the configuration of an optical reflection mirror with variable light transmission speed, and FIG. The figure is a diagram for explaining the moving mechanism of the surface potential sensor, and FIG. 5 is a diagram showing another embodiment of the present invention. 2... Reference density reflecting plate, 3... Exposure device, 10...
- Optical reflection mirror, 12... Light transmission speed variable device, 13
...Photoreceptor, 15.Charging device, 16.Surface potential sensor, 31.CPU, 32.-ROM, 33.
...RAM.

Claims (4)

[Claims] (1) In an apparatus that exposes a photoreceptor charged to a predetermined potential by a charging means to image light to form an electrostatic latent image and develop and record the image, the device is disposed in an optical path that guides the image light to the photoreceptor; A light transmitting member that is divided into a plurality of blocks in a direction parallel to the axial direction of the photoreceptor and whose light transmittance is variable depending on the applied voltage, a surface potential detection means that is movable parallel to the surface of the photoreceptor, and a surface potential detecting means that is movable parallel to the surface of the photoreceptor. comprising a control means for controlling a voltage applied to the light transmitting member according to a detection result, and a reference concentration reflecting member,
The photoreceptor is exposed to the light reflected from the reference density reflecting member, the surface potential detection means is moved to detect the surface potential of the photoreceptor at multiple positions, and each of the light transmitting members is controlled by the control means based on the detection results at the multiple positions. 1. An exposure light amount unevenness correction device for a recording device, characterized in that the light transmittance of each block is independently controlled. (2) The exposure light amount unevenness correcting device according to claim 1, further comprising means for storing and retaining the light transmittance control amount at a plurality of positions. (3) The exposure light amount unevenness correcting device according to claim 1, further comprising means for detecting the dark potential of the photoreceptor by the surface potential detecting means and controlling the charging means based on the detection result. (4) In an apparatus in which a photoreceptor charged to a predetermined potential by the charging means is exposed to image light, an electrostatic latent image is formed, and the image is developed and recorded. , selecting a light transmitting member that is divided into a plurality of blocks in a direction parallel to the axial direction of the photoreceptor and whose light transmittance is variable according to an applied voltage, and a block of the light transmitting member;
The present invention includes a selection adjustment means capable of adjusting the light transmittance by changing the applied voltage stepwise, and a display means, and displays the block selected by the selection adjustment means and the amount of light transmittance adjustment. An exposure light amount unevenness correction device for a recording device, characterized in that: