JPS5886582A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To obtain a clear copy of a picture for either a transmitted light type and a reflected light type original, by changing charging conditions, development conditions, etc., of a photoreceptor according to whether an image is formed by transmitted or reflected light. CONSTITUTION:When a signal of a photosensor 9 detecting an original being light-transmissive is inputted, a more current of the discharging electrode of a charging device 19 than for a reflective original flows under the control of a control circuit CONT to increase the amount of surface charging of a photoreceptor. Further, the bias voltage of the magnetic brush 20 of a devloping device is also raised to prevent a decrease in maximum copying density due to transmitted light projection. Therefore, a clear copy of a picture for either of an transmitted light type and a reflected light type original is taken. Further, only conditions of either charging or development are controlled to obtain the same effect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a light source for projecting an image using transmitted light of an original;
The present invention also relates to a novel electrophotographic copying apparatus that is capable of projecting an image using transmitted light or reflected light depending on the type of light transmittance of an original.

2. Description of the Related Art Conventional electrophotographic copying apparatuses include those that project images using reflected light from an original, and those that project images using transmitted light from an original.

The present invention is capable of image projection using any of the following devices,
Moreover, the present invention provides an electrophotographic copying apparatus that can obtain clear copied images even when the original is transparent and the transmitted light is used.

The electrophotographic copying apparatus of the present invention is an electrophotographic copying apparatus equipped with a light source for projecting an image using transmitted light from an original and a light source for projecting an image using one reflected light, and the electrophotographic copying apparatus is equipped with The present invention is characterized in that at least one of the conditions can be changed between when projecting an image using transmitted light and when projecting an image using reflected light. In other words, in the electrophotographic copying apparatus of the present invention, the process conditions for charging and development can be changed depending on whether an image is projected using transmitted light or when an image is projected using reflected light, so that clear copies can be obtained in both cases. It is possible to obtain an image.

Hereinafter, the present invention will be explained based on illustrated examples.

Fig. 1 is a longitudinal side view showing an example of a copying apparatus of the present invention, Fig. 2 is a control block circuit diagram, and Figs. 3 and µ show process conditions such as charging and development, and conditions for image projection using reflected light. Figures 5 and 5 show the γ-curve diagram of image projection by reflected light and the γ-curve diagram of image projection by transmitted light when . γ curve diagram of image projection by transmitted light when raised; Figures 7 and R are vertical sectional side views and bottom views showing different examples of the platen cover; Figure 9 is a partial plane view showing different examples of the optical system unit. It is a diagram.

In FIG. 1, l is a platen cover, 2 is a transmitted light source,
3 is a transmitted light source unit with a transmitted light source attached, l is a guide shaft of the transmitted light source unit 3, 3 is a bracket attached to the platen cover/ and supports the guide shaft l, and B is attached to the platen cover/ via a compression spring. An attached diffuser plate that also serves as a document holder, 7 is a transparent document mounting table,
t is a reflected light source, 9 is a photo sensor for detecting the light transmittance of the original, /θ is a projection slit, //, /2,
/3 is a mirror, /4I is a main lens, 15 is an auxiliary lens, /6 is a fixed mirror, /7 is a dustproof glass, 1g is a photoreceptor, /q is a charging device, 〃 is a magnetic brush of a developing device,
``G'' is an optical system unit disposed from the reflected light source r to the auxiliary lens /S, and 〃 is a guide shaft of the optical system UNISOTONO/.

According to the electrophotographic copying apparatus shown in FIG. Copies can be made with simple operations similar to those in a photocopying machine. That is, by raising the platen cover l, placing the original at a fixed position on the original placing table 7, closing the platen cover, and pressing the copy start button, copying is performed. In the state where this copying can be started, the transmitted light source unit 3
and optical system unit 2/ are both located at one end side of each guide shirt (17) and (2) as shown in the figure, and when a document is placed in a fixed position, its end is connected to the photo sensor 9 from the transmitted light source. The relationship is such that it blocks the optical path that reaches the . When the copy start button is pressed, the transmitted light source is first turned on.

If the original is light-transmitting like photographic film, is it transmitted light when lit? Since the light M2 passes through the document and reaches the photo sensor 9, the photo sensor 9 outputs a signal indicating that the document is transparent, and this signal prohibits the reflection light source r from turning on. The transmitted light source unit 3 and the optical system unit 2/ are moved to the right, that is, the projection scanning movement is performed. During the projection scanning movement, the transmitted light source 2 continues to be lit, and its light passes through the original and the projection slit /θ, and further passes through the mirrors //, /2, /3, main lens lg, auxiliary lens /3. Fixed mirror 16 and dustproof glass 1
7, the image is scanned and projected onto the surface of the photoreceptor.

As shown in Figure 1, a plurality of photosensors 9 are arranged in parallel, so if even one of them detects the light from the transmitted light source, the document is determined to be light-transmissive. That signal will be output.

When the original is plain paper (the light from the transmitted light source d1 is blocked by the original and does not reach the photosensor 9), the reflected light source 1 is turned on after a predetermined time elapses after the transmitted light source is turned on. Subsequently, the projection scanning movement of the transmitted light source unit 3 and the optical system unit 2/ is performed.As a result, an image is projected onto the surface of the photoreceptor 7g using the document reflected light from the reflected light source r that passes through the projection line )/θ. be exposed. In this case, since the transmitted light R is blocked by the document and is not related to image projection, the transmitted light source 2 may be left on during the scanning movement, or may be turned off.

As described above, according to the copying apparatus shown in FIG. 1, depending on whether the document is light-transmissive or non-transparent, image projection is automatically performed using transmitted light or reflected light. When the original is an X-ray photographic film, a copy with excellent halftone reproducibility can be obtained by using transmitted light. but,
If the charging conditions and development conditions of the photoreceptor are the same for image projection using transmitted light and image projection using reflected light, if the original is light-transmissive like photographic film and transmitted light is used, This method has a problem in that the maximum density of copies is lower than when the original is not transparent to light and only uses reflected light, such as a single sheet of paper.

Fig. 3 and Fig. q show the above-mentioned relationship. In the case of reflected light projection, as shown in Fig. 3, the rise of the γ curve is steep and the halftone reproducibility is poor, but the copy density CD is Maximum concentration D
1 is high, whereas in the case of transmitted light projection, as seen in the first example, the rise 9 of one curve is gentle and the halftone reproducibility is excellent, but the maximum density D2 is low.

Therefore, in the copying apparatus shown in FIG. 1, as shown in FIG. When a signal indicating that is transparent to light is input, the current of the discharge electrode of the charging device 19 is increased based on the signal to increase the amount of surface charge of the photoreceptor 1g compared to the case of reflected light projection. The developing bias voltage applied to the outer sleeve of the magnetic brush is also increased.

This solves the problem that the maximum density of a copy in transmitted light projection is low, but also causes image fog.

Figures 3 and 6 show the relationship.

That is, when the surface charge amount of the photoreceptor/g is increased, the maximum density of the gamma curve determined by transmitted light projection becomes higher than the maximum density D2 in FIG. 9, as shown in FIG. However, on the other hand, the copy density CD with respect to the original density 0D=0.00 is also as high as D4, causing image fog. Therefore, by increasing the developing bias voltage, as shown in FIG. 6, the CD of 0D=0.00 is lowered to the same extent as in FIG. 9 or FIG. 3, and the maximum density D5 is reduced.
can be maintained at a level higher than the maximum density D2 in FIG. 3 and close to the maximum density D1 in FIG. therefore,
Clear copies with high maximum density, excellent halftone reproducibility, and no image fog can be obtained by transmitted light projection.

The present invention is not limited to the examples described above, and is not limited to automatically switching between transmitted light projection and reflected light projection. In this case, only one of the charging conditions and the developing conditions may be changed. Such a case can be detected by the relationship between the light amounts of the transmitted light source 2 and the reflected light source 1.

Further, FIG. 7 and FIG. 1 show a platen cover l having a built-in transmissive surface light source n consisting of an array of pXm KL lamps. It may also be used in place 9 of l. When such a platen cover 7 is used, first, for example, n EL lamps in the leftmost column are turned on, and when the 6-optical system unit I starts scanning movement, the EL lamps in the adjacent right column are sequentially turned on. It is only necessary to scan and light up n EL lamps. In this case, depending on the size of the document, the number of lights out of n columns corresponding to the size of the document may be turned on, thereby reducing power consumption. However, all the KL lamps may be turned on from the beginning until the optical system unit completes the scanning movement.

Furthermore, in the copying apparatus shown in FIG. 1, if the transmitted light source (n) is not turned off during the scanning movement, or if the transmitted surface light source (n) is turned on in a scanning manner or on the entire surface, the document changes from light transmitting to midway. If it is something that becomes opaque, use a reflective light source for the light-transmitting part! The image is projected using the light from the transmitted light source 2 or the transmitted surface light source n without turning on the light source, and when it hits a light-opaque area, the reflective light source l is turned on based on the signal from the photosenosade to project the image. can do. This makes it possible to obtain clear copies of both the light-transmitting and non-transparent parts of the document.

However, if the document changes from light-opaque to transparent, the arrangement of the reflected light source t, photosensor 9, and projection slit lθ as shown in FIG. Since it is difficult to prevent the reflected light from entering the photosensor 9, it is not possible to turn off the reflected light Hz using the signal from the photosensor 9 even if the original becomes light-transmissive.

In this regard, the arrangement relationship of the reflected light source l, the photosensor 9, and the projection slit 10 in the optical system unit 2/ shown in Fig. 2 is such that the above-mentioned problem is solved and the original changes from light-opaque to transparent. In this case, the reflected light Hz can be turned on or off according to the signal from the photosensor 9. That is, since the photo sensor 9 and the projection slit /θ are provided on opposite sides of the reflected light source, it is possible to easily prevent the light from the reflected light source r and its reflected light from entering the photo sensor 9 using the reflective shade. can. Therefore, the photo sensor 9 detects whether or not the light from the transmissive surface light source n passes through the document, regardless of whether the reflective light source t is lit.
It is possible to easily turn off and turn on the reflective light source according to the opacity.

In the case of switching between transmitted light projection and reflected light projection midway as described above, the difference between the charging position of the photoreceptor/g, the image projection position, and the developing position must be taken into consideration. In this regard, it is difficult to change the charging conditions between transmitted light projection and reflected light projection because charging is done before image projection.

Therefore, in the case of switching during the process, it is preferable to change the developing conditions and also the projection conditions such as the amount of light from the light source.

According to the present invention, as described above, an excellent effect can be obtained in that a sharp copy can be obtained for both light-transmitting and non-transparent originals.

Figures 5 and 6 show a γ curve diagram for image projection using reflected light and a γ curve diagram for image projection using transmitted light when the processing conditions are conditions for image projection using reflected light, with the amount of charge increased from the above process conditions. 7 and 1 are longitudinal sectional side views and bottom views showing different examples of platen covers, and FIG. FIG. 7 is a partial plan view showing a different example of the optical system unit.

l...Platen cover, 2...Transmitted light source, 3...
Transmitted light source unit, l...Guide shaft, 7 Original table, r-, 9 Reflected light source, Ta...Photo sensor, IO...Projection slit, //, /ノ, /3 Mirror, /41...
Main lens, /S - auxiliary lens, 16... fixed mirror, 1g... photoreceptor, 19... charging device,
〃...magnetic brush, 〃...optical system unit, n
...Guide shaft, n...Transmissive surface light source.

Patent applicant: Konishiroku Photo Industry Co., Ltd. Figure 1 %2 figure Figure 3 O.D. Figure 5 °%4 figure p Figure 6

Claims (1)

[Claims] An electrophotographic copying apparatus comprising a light source for projecting an image using transmitted light from an original and a light source for projecting an image using reflected light, the electrophotographic copying apparatus comprising at least one of photoreceptor charging conditions and developing conditions. An electrophotographic copying apparatus characterized in that it can change between projecting an image using transmitted light and projecting an image using reflected light.