JPS59148069A - Copying machine - Google Patents

Abstract

PURPOSE:To vary easily gamma characteristics by a user according to a difference in original or taste and to obtain a proper picture by varying the electrification potential of a photosensitive body and also varying interlockingly the quantity of exposure. CONSTITUTION:The output changeover switch 6 of a high voltage power source 5 is interlocked with the changeover switch 9 of a power source 8 connected to an exposure lamp 7. Switches on a panel are operated to vary the electrostatic charge potential and the quantity of exposure successively, varying the gamma characteristics. When the gamma characteristics of this device are maximum, the surface potential of the photosensitive body is set to 900V and the voltage of the exposure lamp is set to 55V, and when the gamma characteristics are minimum, they are set to 500V and 48V respectively. Therefore, a character original is reproduced with good contrast in 7-8 gradations when the gamma characteristics are maximum, and the original is reproduced in 10-11 gradations when the gamma value is minimum; the copy original is reproduced with fidelity and the operation is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a copying apparatus capable of variable image gradation.

Conventional Structure and Problems In the conventional copying apparatus, the density of the image can be varied depending on the difference in the original document or the preference of the user. Examples of this method include changing the developing bias voltage and changing the exposure amount.

Conventional copying machines use selenium as a photoreceptor,
As the developer, a high-resistance toner containing a magnetic material with an average grain size of about 10 μm and a high-resistance carrier containing a magnetic material with an average particle size of about 40 μm are used. The magnetic roll rotates at a high speed, causing the sleeve to rotate at a slower speed. ``Furthermore, although the charging coroton is connected to a high voltage power source, it is generally not possible for the user to freely control it. In such a conventional configuration, in order to change the shading of an image, the amount of exposure is changed by controlling the power supply connected to the exposure lamp, or the power supply for incubation bias connected to the sleeve is controlled. etc.

However, with the above configuration, there are various types of documents, such as documents containing only text and photographs with subtle shading, and it is difficult to obtain the image desired by the user simply by changing the shading. In other words, for manuscripts that mainly consist of text, sharp images with high contrast and high gamma (representing the degree of gradation reproduction) are preferred, and for manuscripts that include many photographs, it is better to have low gamma and rich gradation. -Full tones can be subtly reproduced, resulting in images that are faithful to the original. To solve this problem, it is necessary to change the gamma characteristics as necessary, but it has been difficult to change the gamma with the conventional configuration.

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 variable image gradation by gamma switching with improved operability.

Structure of the Invention In order to achieve the above object, the copying apparatus of the present invention is configured to change the charging position of the photoreceptor or the developing bias voltage and to change the exposure amount in conjunction with the change. This allows the user to vary the gradation of the image depending on the type of document or preference.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic diagram of a copying apparatus according to an embodiment of the present invention. In Figure 1, 1 is a selenite photoreceptor, 4 is a coroton for charging, 6 is a high voltage power source, and 7
8 is an exposure lamp, and 8 is a power supply for the exposure lamp, and the changeover switch 6 of the high-voltage power supply 5 and the changeover switch 9 of the exposure lamp power supply 8 are designed to be interlocked. On the other hand, the sleeve 3 is completely connected to the bias voltage 1o.

The operation of the copying apparatus of this embodiment configured as described above will be explained below. FIG. 2 shows the relationship between original density and image density when the toner density of the developer is kept constant and the charge level of the photoreceptor is varied.

The saturation image fJa degree is different between the photoconductor's fourth charge of 900V and 600V, but the gamma value is also greatly different. 5o
For oV, gamma 1 is high (600V is low. Therefore, for text originals, 9oOv is appropriate, and for photographic originals, 5ooV is appropriate.

In FIG. 3, like FIG. 2, the toner density is changed and the charge level of the photoreceptor is changed, but the exposure amount is also adjusted at the same time. The difference from FIG. 1 is that there is almost no difference in the change in gamma value, but the rising point of the gamma value is different. In FIG. 2, the charging potentials are 900 V and 500 V, and the gamma value rises at points A and B, which are different, whereas in FIG. 3, they are at the same point C. In Figure 2,
In this case, characteristics with a low gamma value suitable for photographic originals are rich in gradation, but because the rising point of the gamma value is shifted to the right, the low-density portions of the original become dull. Therefore, when the gamma characteristics are changed, it is necessary to readjust the exposure amount in order to obtain a proper image.

In this embodiment, the output selector switch 6 of the high voltage power supply 5 and the selector switch 9 of the power supply 8 connected to the exposure lamp 7 are linked, and the user operates the switches etc. on the operation panel. Then, the band potential and the exposure amount change in the 1i order, and the gamma characteristics change as shown in FIG. With this device, when the gamma value is at its highest, the surface potential of the photoreceptor is set to 900 ■, and the exposure lamp voltage is set to ssV, and when the gamma value is at its lowest, the surface potential of the photoreceptor is set to esooV, and the exposure lamp voltage is set to ssV. I set the voltage to 48v and tried creating an image. As a result, at the highest gamma value, the gradation ranges from 7 to 8 steps, and text manuscripts can be reproduced with good contrast, and at the lowest gamma value, the gradation ranges from 10 to 11 steps. Not only was it able to faithfully reproduce photographic originals, it was also easy to operate.

As described above, according to Honjitsu MFLJ, the output selector switch 6 of the high-voltage power supply 6 and the output selector switch 9 of the exposure lamp power supply 8 are operated in conjunction with each other, resulting in good operability and a single image. A copying apparatus capable of switching gradations can be realized.

Next, an embodiment of the pond of the present invention will be described.

In this embodiment, the phenomenon bias consideration source 10 is provided with an output changeover switch 11, and this output changeover switch 11 and the output changeover switch 9 of the exposure lamp power supply 8 are linked. When the user operates a switch on the operation panel,
As the developing bias voltage and exposure amount are changed sequentially, the gamma characteristics in particular change as shown in FIG. When the bias voltage is low, the gamma value is high, and text originals can be reproduced with good contrast, while when the bias voltage is high (-1, the gamma value is low, gradation reproducibility is good, and photographic originals can be reproduced faithfully. Can be reproduced.

Effects of the Invention As is clear from the above explanation, the present invention is configured to change the charging potential of the photoreceptor and change the exposure amount in conjunction with it, so that it is possible to
The user can easily change the gamma characteristics according to his/her preference, and can easily obtain appropriate images for both high-contrast documents and multi-tone documents such as photographs. Furthermore, instead of changing the charging potential of the photoreceptor, the same excellent effect as described above can be obtained by changing the developing bias and the exposure amount in conjunction with each other.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of a copying machine in one-shot processing of the present invention, Fig. 2 is a gamma characteristic curve diagram due to changes in the charged potential of the photoreceptor, and Figs. 3 to 6 are illustrations of the operation of this embodiment. A gamma characteristic curve diagram is shown. 1...Photoreceptor, 2-...Magnet roll, 3
... Sleeve, 4... Coroton for charging, 5.
...4-voltage power supply, 6...- selector switch, 7-...
・Exposure lamp, 8... Power supply for exposure lamp, 9-
Selector switch, 10---・Development bias power supply, 11・
...Selector switch. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Rinzumi thickening 0'°' Door 4 helmet soaking (00)

Claims (1)

[Scope of Claims] 0) A copying apparatus characterized in that it is possible to change the gradation of an image by changing the charge level of a photoreceptor and changing the amount of exposure in conjunction therewith. B)) A copying apparatus characterized in that it is possible to vary the gradation of an image by changing the developing bias voltage and changing the exposure amount in conjunction with the developing bias voltage.