JPS6043669A - Copying machine - Google Patents

Abstract

PURPOSE:To perform picture quality switching with improved operativity and reproductibility by providing a means which switches the electrostatic charging potential and exposure amount of a phtosensitive body in plural stages. CONSTITUTION:The output voltage of a high voltage power source 8 connected to an electrostatic charge corotron 7 is switched with the switch 9 of a panel to vary the charge potential of the photosensitive body 1, and the voltage of the power source 11 of an exposure lamp 10 is switched associatively with said switching to make an automatic adjustment. The density of an image is switched with ten gradations and a developing device which varies gamma is used to vary the image quality easily according to the difference of originals or by preference. Therefore, a proper image is obtained easily by varying the charge potential and exposure amount of the photosensitive body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a copying apparatus in which image quality can be changed depending on the original to be copied or preference.

2. Description of the Related Art Conventional Structures and Problems There are conventional copying apparatuses in which the shading of an image can be varied depending on the original or the user's preference. However, there are various types of originals, such as texts only or photographs with subtle shading, and it is difficult to obtain the desired image by simply varying the shading.

For manuscripts containing only text, the so-called black-and-white with high gamma produces a clear contrast, making even thin text appear darker and making the image easier to read. On the other hand, for originals with many photographs, a lower gamma and the ability to subtly reproduce halftones will produce a more faithful image.

In conventional copying apparatuses, priority is given to image quality for text originals, and therefore, for photographic originals, the image quality is often blacked out and subtle halftones are not reproduced.

OBJECTS OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples, and to provide a copying apparatus that realizes image quality switching with improved operability and reproducibility.

Structure of the Invention In order to achieve the above object, the copying apparatus of the present invention includes a developing device capable of changing gamma characteristics, a charging agent for a developer, and a photoreceptor.
This device includes a means for changing the exposure amount in conjunction with the change in the exposure level, and thereby allows the user to switch the image quality depending on the difference in the original document or his/her preference.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a characteristic diagram showing the relationship between original density and image density when the toner density is set to 15% and the charging potential of the photoreceptor and the exposure amount are varied, and FIG. FIG. 2 is a configuration diagram of main parts of an embodiment.

In FIG. 2, the drum-shaped photoreceptor 1 is made of selenium-tellurium, and the developer 2 is a high-resistance toner containing a magnetic material with a diameter of 10 μm, and a high-resistance carrier containing a magnetic material with a diameter of 40 μm. It consists of The magnet roll 4 of the developing device 3 rotates in the direction of arrow A at 160 rpm, and the sleeve 6 rotates in the direction of arrow B at 160 rpm. The distance between the surface of photoreceptor 1 and the surface of sleeve 5 is: , 6πm, and the distance between the sleeve 60 surface and the doctor blade 6 is 0.
．． It is the 5th end. The photoreceptor 1 is rotating in the direction of arrow C at a peripheral speed of 165 sugars/sec.

As is clear from Figure 1, the charging potential is AOOV and 5oo
v, the saturated image density is slightly different between 1.4 and 1.2, but the original density is 0.3 to 1. The gamma value differs greatly in the Q range, being high at 700V and almost 1 at 500V.
It's low.

Therefore, the text image has a large contrast of 70
0V is appropriate, and for photographic images, 5oov with a gamma value close to 1 is appropriate. The former and latter images are named document mode and photo mode image quality, respectively.

To change the charging potential of the photoreceptor, use the Charging Corotro/7
The output voltage of the high-voltage power supply 8 connected to the printer is switched by operating a switch 9 on the control panel of the copying machine. At this time, the exposure amount of the photoreceptor is automatically adjusted by switching the voltage of the meramp power supply 11 connected to the exposure lamp 1o in conjunction with the switching of the high voltage output. Further, although not shown, the exposure amount of the six steno lenses cannot be changed in each of the document/photo mode and the photo mode so that the shading of the image can be varied.

For example, in the document mode where the charging potential is 7oov, the lamp voltage is switched in 5 steps in the range of 60 to 70V, and in the photo mode of 600V, the lamp voltage is switched in 5 steps in the range of 55 to 65T/.

This makes it possible to reduce the difference in image density between document mode and photo mode at low document densities 01 to o3.

When I copied an image using the device described above, in document mode, it had eight levels of gradation and high contrast, and even faint text was clearly reproduced.

When in photo mode, halftones in photos were reproduced with high fidelity in 10 levels of gradation.

Effects of the Invention As is clear from the above description, the present invention provides a developing device and a developer that have the characteristic of changing gamma, and a child actor that can change the charging potential of the photoreceptor and change the exposure amount in conjunction with the developing device and developer. Because the configuration includes the
Appropriate images can be easily obtained from documents with multiple gradations, such as photographs.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing an example of gradation changes when the charging potential of the photoreceptor is changed, and FIG. 2 is a diagram showing the main part of an embodiment of the present invention. 1...Photoreceptor, 2...Developer, 3...
...Developer, 4... Magnet roll, 6
...Sleeve, 6... ...Doctor Blade, 7...Charged Corotro/,
8...High voltage power supply, 9...Switch, 1
o...Exposure lamp, 11.Moe.Lap power supply. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Zurin manuscript collection

Claims (4)

[Claims] (1) A copying apparatus characterized by comprising two image quality switching means: photo mode and document mode. (2) The copying apparatus according to claim (1), wherein the switching means is configured to switch the charging potential of the photoreceptor by switching the high voltage output. (3) The copying apparatus according to claim (1), characterized in that a plurality of steps are provided for switching the exposure amount of the photoreceptor for each of the two image quality switches. (4) The sleeve rotates at low speed, the magnet roll rotates at high speed, and the distance between the photoreceptor and the sleeve is 0.3~0.
It is characterized by having a developing device with a length of 6 ff 1 m and a distance between the sleeve and the doctor blade of 0.4 to 0, s t nm, and a developing agent consisting of an insulating magnetic toner and a small-diameter carrier. Particularly ``a copying apparatus according to claim (1), (2), or (3).