JPH01968A - Exposure setting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (AL Industrial Field of Application) This invention relates to an exposure method for copying photographs, etc. more beautifully in a copying machine in which the charging potential of a photoreceptor and the bias potential applied to a developing device are switched. The present invention relates to a quantity setting device.

(b) Conventional technology When copying originals with halftones such as photographs and paintings using electrophotographic copying machines, copying can be done by switching the charging potential of the photoreceptor and the bias potential of the developing device. This prevents the entire image from becoming dark and dark, and allows midtones to be reproduced. In order to switch the charging potential and bias potential, conventional devices are equipped with a photo/document switching key for photo mode and document mode, and when the photo mode is set, the device switches to a potential that can reproduce halftones. I have to.

(C1 Problem to be Solved by the Invention In general copying machines, there is an automatic exposure adjustment function that detects the density of the original based on light reflected from the original and sets the exposure amount according to the density of the original to adjust the copy density. The automatic exposure adjustment function adjusts the exposure so that a pale copy image is obtained for a dark original, and a dark copy image is obtained for a light original.However, If a conventional copying machine equipped with the photo/document switching key described above has such an automatic exposure adjustment function,
When copying photographs, paintings, etc., and setting the charging potential and bias potential to photographic mode as described above, the exposure amount is adjusted by the automatic exposure adjustment function, resulting in the copied image becoming too white ( (Since the colors are half-tones, they are automatically adjusted to make them lighter), which had the disadvantage that accurate copying could not be performed.

The present invention provides an exposure amount setting device that can accurately copy originals such as photographs and paintings by automatically setting a manual exposure mode when a photographic mode is set. The purpose is to

(d) Means for Solving the Problems The exposure amount setting device of the present invention is a photo/document switching device that switches the charging potential of the photoreceptor and the bias potential applied to the developing device in accordance with the photo mode or the document mode. In a copying machine having an automatic exposure mode that automatically adjusts the exposure amount of a document or a manual exposure mode that sets an arbitrary exposure amount, the photo mode is set by the photo/document switching key. The present invention is characterized by comprising means for switching the automatic/manual switching key to manual exposure mode when the exposure mode is activated.

(e) Function In the exposure amount setting device of the present invention, when the document mode is set using the photo/document switching key, either automatic exposure mode or manual exposure mode can be selected by operating the automatic/manual switching key. Copying can be done in mode. Furthermore, when the photographic mode is set, the charged potential of the photoconductor and the bias potential of the developing device are set for photographic use, and the manual exposure mode is automatically set so that the exposure amount is constant regardless of the background color of the original. Since the copying is done in , the copied image will not be too whitish.

(f) Embodiment is a block diagram of a copying machine which is an embodiment of the present invention.

Overall control is performed by the CPU 1, and its processing program is stored in the ROM 12 in advance. When executing a program, the RAM 13 is used as a working area. Each control section 16 to 18 in the copying machine main body 2 is connected to the CPU II through the l1014, and the operating section 8 on the copying machine main body 2, the sensor section 9 in the copying machine main body 2, etc. are connected via the l1015. It is connected.

A drum-shaped photoreceptor 3 having a photoconductive layer formed on its surface is disposed approximately at the center of the copying machine main body 2 . Photoreceptor 3
Charger around 4. A developing device 5, a transfer device 6, etc. are provided, and are controlled by a process control section 17. Copy machine body 2
An optical system device 7 is disposed at the top and is controlled by an optical system control section 16. Furthermore, other devices within the copying machine main body 2 are controlled by their respective control sections.

The charger 4 includes a charger wire 41 that generates corona discharge, and charges the surface of the photoreceptor 3 to a constant charging potential. The developing bag W5 is provided with a developing roller 51 to which a bias potential is applied and a stirring roller 53 that stirs the toner in the developing tank 52 and triboelectrically charges it. Photoreceptor 3 and developing roller 5
The polarity of 1 and the polarity of the toner are opposite to each other, and the bias potential of the developing roller 51 is closer to O than the charging potential of the photoreceptor 3. Therefore, the charged toner first adheres to the developing roller 53, and is then attached to the photoreceptor 3 from the developing roller 53 due to the Coulomb force with the photoreceptor 3.

By increasing or decreasing the charging potential of the photoconductor 3 or increasing or decreasing the bias potential of the developing roller 53, the amount of toner that adheres to the surface of the photoconductor 3 can be adjusted. That is, as the charging potential of the photoreceptor 3 approaches 0, the amount of toner adhesion decreases, and as the bias potential approaches 0, the amount of toner adhesion increases.

The optical system bag W7 has an exposure lamp 71. It includes mirrors 72 to 75 and a lens 76, and is controlled by an optical system control section 16. Exposure lamp 71 scans the original, and the reflected light passes through mirrors 72 to 75 and lens 76 to charger 4.
and the developing device 5 onto the corresponding photoreceptor 3.

The light reflectance of light-colored areas of a document is high, and the amount of reflected light is also large. Furthermore, the greater the amount of exposure light in the photoconductive layer of the photoreceptor 3, the more surface charges are canceled.

Furthermore, the more charge there is on the photoreceptor 3, the more toner will adhere to it. As a result, a copy image with shading similar to the original can be obtained. Note that when the amount of exposure from the exposure lamp 71 is reduced, the amount of light reflected from the document is also reduced, making it difficult to cancel the charges on the photoreceptor 3, and the amount of toner deposited by the developing roller 51 increases.

The operation section 8 is provided with an automatic/manual switching key 81, exposure level setting keys 82, 83, 84, a photo/document switching key 85, a print switch 86, and the like.

The automatic/manual switching key 81 is a key for switching the exposure mode between automatic and manual. When the automatic exposure mode is set using this key, the document density sensor "91" of the sensor unit 9 is activated.
The optical system control section 16 automatically sets the exposure amount of the document according to the output of the image. That is, when the original density is high, the exposure amount is increased to make the copied image lighter, and when the original density is lighter, the exposure amount is decreased to make the copied image darker. Note that the original density sensor 91 is a sensor provided in the optical system device 7 and detects the density of the original based on light reflected from the original. Further, when the manual exposure mode is set, three levels of exposure amount can be fixedly set using the exposure level setting keys 82, 83, and 84. As for the exposure level setting keys, 82 is the darkest, and the exposure level setting keys are set to light in the order of 83° and 84.

The photo/document switching key 85 is a key for switching between the photo mode and the document mode. When the photo mode is set using this key, the process control unit 17 changes the charging potential of the photoreceptor 3 by the charger 4 and the developing roller. A bias potential of 51 is set for photography. In other words, the charging potential is O
, and the bias potential is set to move away from O. Further, the automatic/manual switching key 81 is also electrically switched to a manual exposure mode intermediate density (exposure level setting key 83), and the exposure amount of the exposure lamp 71 is fixedly set by the optical system control section 16. Furthermore, when the document mode is set using the photo/document switching key, the process control unit 17 sets the bias potential of the developing roller 51 so that the potential of the charger 4 moves away from 0 and the bias potential of the developing roller 51 approaches 0. .

Next, the operation will be explained.

Photo mode> When copying an original with halftones such as a photo or painting, operate the photo/document switch key 85 to set the photo mode, and then operate the print switch 86 to start copying. I do. By setting the photo mode, the charger 4
The charging potential of the photoreceptor 3, the bias potential of the developing roller 51, and the exposure amount of the exposure lamp 71 are set to predetermined potentials and amounts as described above, and the copying process is performed. That is, the charging potential of the photoreceptor 3 and the bias potential of the developing roller 51 are set for photography, and the exposure lamp 71
is set to a fixed amount and there is no variation due to the density of the original, so the copied image can be accurately reproduced without becoming white.

Document mode> When copying originals with clear contrast, such as documents,
By operating the photo/document switching key and setting the mode for documents, the charging potential of the photoreceptor 3 and the bias potential of the developing roller 51 are set for documents, so that a clear copy image with clear contrast can be obtained. Become. The exposure mode may be set to automatic exposure mode or manual exposure mode by operating the automatic/manual switching key 81.

In this embodiment, the photo/document switching key is used to switch both the charging potential of the photoreceptor 3 and the bias potential of the developing roller, but it is also possible to switch only one of them.

(Effects of the Invention According to the exposure amount setting device of the present invention, copying is performed with a fixed exposure amount in manual exposure mode by setting the photo mode, so the copied image becomes too white due to the background color of the original image. You can obtain beautiful copied images without any problems.Also, by setting the photo mode, the manual exposure mode is automatically set, so there is no need to go through the trouble of operating the auto/manual switch key. This has the advantage of requiring fewer operations.

[Brief explanation of the drawing]

The figure is a block diagram of a copying machine to which an exposure amount setting device according to an embodiment of the present invention is applied. 4-charger, 5-developing device, 71-exposure lamp, 81-automatic/manual switching key, 85-photo/document switching key.

Claims (1)

[Claims] (1) A photo/document switch key that switches the charged potential of the photoreceptor and the bias potential applied to the developing device depending on the photo mode or document mode, automatic exposure mode that automatically adjusts the original exposure amount, or arbitrary exposure mode In a copying machine having an automatic/manual switching key for switching to a manual exposure mode set to a certain amount, when a photographic mode is set by the photo/document switching key, means for switching the automatic/manual switching key to the manual exposure mode. An exposure amount setting device comprising: