JPS5993469A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To adjust at least either of copy density and contrast by detecting the surface potential of recording information on a photosensitive body after exposure and adjusting the amount of exposure of the 2nd exposing means according to the detected value. CONSTITUTION:An original 14 is exposed to the surface of the photosensitive drum 4 to form an electrostatic latent image on the drum 4. The potential of this latent image is detected by a surface potential detecting means 20. The detecting means 20 consists of plural PLZT elements, etc., so as to measure the latent images as divided picture elements. Signals from the respective elements of the detecting means are operated by an operation control means 22 and then stored. The 2nd exposing means 21 have light emitting diodes corresponding to the elements of the detecting means. When said latent image reaches the 2nd exposure position, respective elements are driven by the stored signals and the amount of the 2nd exposure is adjusted for every picture element. The 2nd exposing means 21 may consist of the 2nd light source and elements which vary in the quantity of transmitted light with impressed voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a so-called plain paper copying electrophotographic apparatus that makes copies on plain paper using an electrophotographic method.

Structure of the conventional example and its problems FIG. 1 is a side sectional view of the main part of an example of a conventional electrophotographic apparatus. In the figure, 1 is a light source, 2 is a document mounting table, 3 is a lens as an imaging means, 4 is a photosensitive drum, and 5 is a uniform charging device that uniformly charges the photosensitive drum 4 by corona discharge. A corotron, 6 is a toner reservoir for development, 7 is a developing sleeve that conveys the toner 16 to the surface of the photoreceptor drum 40, 8 is a copy paper, 9a and 9b are used to transfer the copy paper 8 to the photoreceptor drum 4
1Q is a transfer corotron for transferring the developed toner on the photosensitive drum 4 onto the copying paper 8; 111L and 11b are rollers for the heating surface E that fixes the toner on the copying paper 8. , 12 is a corotron for static elimination, and 13 is a blade for scraping off residual toner transfer.

The operation of the conventional electrophotographic apparatus configured as described above will be described next.

When the original 14, which has been straightened so that its copying surface is in contact with the transparent original placing table 2, is scanned by moving the original placing table 2 to the right, the light emitted from the light source 1 is reflected by the copying surface of the original 14 as a reflective surface. After being reflected and passing through the lens 3, a copy image is formed on the photosensitive drum 4.

The photosensitive drum 4 rotates in the direction of arrow A, and is charged to a uniform potential by a uniform charging corotron 5 before being irradiated with the reflected light. The potential of the exposed portion decreases depending on the amount of irradiated light. Therefore, scanning 61 of the original 4. When the reflected light is irradiated onto the photoreceptor drum 4 while changing the reflective surface sequentially as the angle of the image changes to −2°, an electrostatic latent image corresponding to the recording surface of the original 14 is recorded on the surface of the photoreceptor drum 4. be done. A developing section including a toner reservoir 6 and a developing sleeve 7 transfers charged toner 15 to the photoreceptor drum 4.
After applying a layer to the electrostatic latent image of soil and developing it, the transport roller 91L
, 9b is inserted between the developed photoreceptor drum 4 and the transfer corotron 1o, and the transfer corotron 10 removes the toner on the surface of the photoreceptor drum 4 by corona discharge. The toner is electrostatically attracted to the surface of the copy paper 80, and the toner is transferred onto the copy paper 8. The copy paper 8 to which the toner has been transferred is heated and pressed by a heating and pressing roller 11! It is fixed by L, 11b.

On the other hand, the photoreceptor drum 4 after the transfer is transferred to the corotron 1 for static elimination.
After the charge is removed by step 2, the remaining toner is scraped off by the blade 13, and the device returns to its initial state of waiting for uniform charging.

Since such electrophotographic copying machines can easily make copies on plain paper, they are rapidly becoming popular and are used in a wide range of fields. However, when copying a single prefecture manuscript with low contrast, there are problems such as the same low contrast, or in extreme cases, the copy cannot be made and the copy becomes whitish with no contrast. There is. For this reason, current countermeasures include adjusting the potential on the toner side during development, increasing the electrostatic attraction between the charged surface on the photoreceptor drum surface and the toner, and increasing the overall density. However, even with this method, the white part of the original (18 minutes) may turn dark due to copying, resulting in background smudges, and it is not a fundamental countermeasure.

OBJECTS OF THE INVENTION The present invention solves such conventional problems, and includes detecting the surface potential of information recorded on the photoreceptor surface by the first photoreceptor as an electric signal by using the surface potential detecting means; By adjusting the exposure by the second exposure means in accordance with the electric signal.

It is an object of the present invention to provide an electrophotographic 7hage device suitable for copying on plain paper and capable of adjusting at least one of the density and contrast of the copy.

Structure of the Invention The electrophotographic apparatus of the present invention includes a photoreceptor capable of recording information using light, a first exposure means for optically irradiating information on a document surface onto the photoreceptor, and a a second exposure means for directly exposing the surface of the photoreceptor; a calculation control means for supplying the drive signal to the second exposure means; a calculation control means for detecting the surface potential of the photoreceptor; surface potential detection means for supplying a control signal corresponding to the surface potential, and the surface potential detection means and the second exposure means correspond to each other in order to process the document surface by dividing it into pixels. a pixel processing section, and for each pixel processing section, the surface potential detection section detects information about an electrostatic latent image on the surface of the document recorded by the first exposure section on the surface of the photoreceptor, and outputs the detected information as a control signal. The arithmetic control means performs a predetermined arithmetic operation based on the control signal and supplies a drive signal to the second exposure means, and the second exposure means By performing <'rp2 light on the basis of the drive signal, it is possible to adjust at least one of the density and contrast of the document if.

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

The 21st bacterium relates to one implementation of the non-invention i+t+'The safety of electrophotographic equipment V! It shows the face of I'l1llI mi. Components in FIG. 2 that are similar to those explained in FIG. 1 are designated by the same reference numerals, and redundant explanation thereof will be omitted. In FIG. 2, the first exposure means includes a light source 1
, document mounting table 2. The lens 3 records an electrostatic latent image by light irradiation on the upper surface of the photosensitive drum 4 while scanning the document 14 placed on the document mounting table 2 with the document 14 as a reflective surface. 20
is a table+r+1 position detection means that detects the surface potential of the electrostatic latent image on the front side and converts it into an electric signal, and as shown in FIG. ``Insanity Optics 9'' such as a PLZT element that outputs a voltage corresponding to the magnitude of the electric field due to the electric potential 20+! L, 20b, 20
C.

... are constructed by dividing the electrostatic latent image into pixels and arranging them to measure the surface potential.

21 is a second exposure means for irradiating light for adjusting the surface potential of the electrostatic latent image produced by the first exposure means;
As shown in the figure, elements 21a and 21b such as light emitting diodes (LEDs) whose light emission amount can be changed according to the applied voltage.
, 21c, . . . are arranged in correspondence with the elements of the surface potential detection means. Reference numeral 22 supplies the surface potential detection means 2Q with a signal corresponding to each pixel of the electrostatic latent image based on an electric signal corresponding to the surface potential of each pixel of the electrostatic latent image converted to Jl:l. This is an arithmetic control means for setting the applied voltage to control the elements of the second exposure means 21, and as illustrated in FIG.
A calculation unit 22& that performs a predetermined calculation, a memory part 22b that stores the calculation result, and a second exposure unit P that outputs a control signal at a predetermined timing based on the calculation result in the memory part.
It includes a delay fEA220 that outputs to each element of i21.

10゜Next, regarding the operation of these 9 elements, we will explain an example of a platform for copying a complete manuscript with poor contrast and unclear differences in brightness and darkness.゜Figure 4 shows an example of the exposure characteristics of a uniformly charged photoreceptor drum, where the horizontal axis represents the exposure amount (βa・5ea) and the horizontal axis represents the surface potential (V). The exposure amount (β-SθC) is the product of the light illuminance (6) and the irradiation time (sec), and since the irradiation time is generally kept almost constant, changes in the exposure amount are It is thought that it is proportional to the change in the illuminance of light. Well, the above exposure is when light from a light source is reflected from the copy surface of the original as a reflective surface, and the lower the density of the reflective surface, the lower the illuminance, and conversely, the lower the density, the higher the illumination. .

On the other hand, the higher the surface potential of the photoreceptor drum, the easier it is to attract toner, and when it approaches zero, it hardly attracts toner. Figure 4 shows that the surface potential of the photoreceptor drum tends to decrease as the amount of exposure to the photoreceptor drum increases, that is, as the illuminance of exposure increases, but this is due to the This shows that the smaller the concentration (closer to white), the lower the surface potential.
Point a in the figure is a state where the surface is uniformly charged, and point 0 is a state where sufficient illuminance is obtained and the surface potential is close to zero. Now, the surface potential detection means 20, the second exposure means 21,
When copying is performed without using the density adjustment means by the arithmetic control means 22, the high-density portion of the printed area is at point a in FIG. Because it is located between the dots, the electrostatic attraction between the photoreceptor drum and the toner during development is weak but occurs, and the toner is attracted and adhered to the paper, causing background stains on the paper surface that should be white, just like originals. occurs, and the contrast becomes low.

On the other hand, using the concentration adjusting means, the surface potential detecting means 2
The arithmetic control means 22 controls the surface potential of the electrostatic latent image to be measured by o, and for the portions below a predetermined surface potential, the second light exposure means 21 performs exposure when the second light exposure means 21 is exposed. When operated, the surface potential of the electrostatic latent image corresponding to the paper area decreases from point B to near point C, and when development is performed, the surface potential of the paper area becomes 0 point, and the surface potential of the character area decreases. Since this is point a, it is possible to obtain a copy with very good contrast compared to the original.

FIG. 5 shows another embodiment of the present invention 1 to 1, in which a second exposure means 21' corresponding to the second exposure means 21 of the electrophotographic apparatus shown in FIG. 2 is provided with a light source 23, a lens 24, It is constructed by a light amount adjusting means 26.

The light emitted from the light source 23 forms an image on the photoreceptor drum 4 by the lens 24, but at this time, an electro-optic effect such as a PLZT element that can change the amount of light transmitted according to the applied voltage is used. Each element of the light amount adjusting means 26 is configured by arranging a plurality of elements corresponding to the elements of the surface potential detecting means 20.
By inputting a control signal in the form of voltage to the arithmetic control means 22 based on the surface potential detected by each element,
The amount of exposure by the second flashing means 21' is controlled to a predetermined value.

vane The same effects as in the example can be obtained.

Effects of the Invention As described above, according to the present invention, the surface potential of information recorded on the photoreceptor surface by the first exposure means is detected as an electric signal by the surface potential detection means, and the second exposure is performed according to the electric signal. By performing adjustment exposure using the means, it is possible to realize an electrophotographic apparatus that has an extremely excellent effect in that it is possible to easily and reliably adjust at least one of the density and contrast of a copy.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a main part of an example of a conventional electrophotographic apparatus, FIG. 2 is a side sectional view of a main part of an electrophotographic apparatus according to an embodiment of the present invention, and FIG. 3 is a main part of the main part of FIG. FIG. 4 is a diagram showing the exposure characteristics of the photosensitive drum, and FIG. 6 is a sectional side view of a main part of another embodiment of the present invention. 1...Light source, 3...Lens, 4...
... Photosensitive drum, 20 ... Surface potential detection means, 21.21' ... Second exposure means, 22
......Arithmetic control means, 23...Light source, 2
4...Lens, 26...Light amount adjustment means. Figure 1 2 [

Claims (1)

Scope of Claims: (1) a photoreceptor capable of recording information using light; a first exposure means for optically irradiating information on the surface of a document onto the photoreceptor; a second exposure means for directly exposing the surface of the photoreceptor; a calculation control means for supplying the drive signal to the second exposure means; and a calculation control means for detecting the surface potential of the photoconductor, and The surface potential detection means and the second exposure means are provided with pixel processing units corresponding to each other in order to process the document surface by dividing it into pixels. In addition, for each of the corresponding pixel processing sections, the surface potential detection means detects the electrostatic rowing information of the document surface recorded on the photoreceptor surface by the first exposure means, and outputs the information as an open leg signal. the arithmetic control means performs a predetermined arithmetic operation based on the control signal and supplies a drive signal to the second exposure means; An electrophotographic apparatus characterized in that the electrophotographic apparatus is configured to adjust the density and contrast of the document surface by at least 10,000 by performing exposure based on a self-excitation signal. <21 The surface position detection means is a compound 9i9. having a nausea optical effect. An electrophotographic apparatus according to claim 1, wherein the electrophotographic apparatus is configured to output a military air signal according to the position of one surface by each element. (3) The second exposure means includes a light source and a plurality of elements having an electro-optic effect in which the amount of light transmitted changes according to the application of a voltage, and the second exposure means includes a light source and a plurality of elements having an electro-optic effect in which the amount of light transmitted changes according to the application of a voltage, and the element having the electro-optic effect is used to emit light from the light source. An electrophotographic apparatus according to claim 1 or 2, wherein the electrophotographic apparatus is configured to adjust the amount of light and irradiate it onto a photoreceptor. (4) The electrophotographic apparatus as set forth in claim 3, page 1, item (1) or item (2), wherein the second light source means is constituted by a plurality of light emitting diodes. (6) The arithmetic control means outputs a control signal in response to an electric signal from the surface potential detection means having a predetermined surface potential or less, causes the second exposure means to perform a predetermined exposure on the photoreceptor, and increases the surface potential. An electrophotographic apparatus according to claim (1) or (2), characterized in that the electrophotographic apparatus is configured to perform control to approach zero.