JPS62144181A - Gradation correcting device for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To generate a uniform copy picture without breaks of narrow lines or the like by providing a cylindrical mask roll, which is arranged in a position after image exposure and before development and is brought into contact with or close to a photosensitive body and has light transmissive parts having optional dot patterns, and irradiating lamp arranged in the mask roll. CONSTITUTION:A mask roll 10 is brought into contact with a photosensitive body 1 or is arranged near it with a minute gap (<=1mm) between them, and many dot- shaped light transmissive parts 12 of pattern arrangement are provided on the outside peripheral surface of a cylindrical roll. When the light of an irradiating lamp 9 is irradiated as a dot pattern to an electrostatic latent image, which is formed by charging and exposure in accordance with the operation of a gradation correcting device 8, through light transmissive parts A, B, and C of the mask roll 10, the potential of the latent image on the photosensitive body is reduced in only a part to which the light is irradiated. The reduction of the latent image potential causes the edge effect peculiar to electrophotographs in highlight and middle surface potential parts. The effect of dot erase appears scarecely in a high potential part because it is a saturated development area originally.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image gradation correction device for an electrophotographic copying machine that forms an electrostatic latent image of an original image on a photoreceptor by charging, exposing, and developing a photoreceptor. It is.

Compliant copying machine! ! It is known that a self-mesh pattern screen is inserted between the contact glass and the document to correct the gradation of the ii1 image, but the self-mesh pattern screen has dots arranged uniformly, and the dots are If the size of the dots is too small, the correction will not be very effective, and if the dots are set to an effective level, the dots may lose their uniformity or cause defects in the linear portions of characters.

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a device M that can perform good gradation correction at low cost.

In order to achieve the above-mentioned object, the present invention provides a cylindrical mask roller that is placed in close contact with or near a photoreceptor at a position after image exposure and before development and forms a transparent part of an arbitrary dot pattern, and the mask. and an irradiation lamp disposed within the roller.

Details of the structure and operation of the present invention? (2) will be explained based on the embodiment shown in the figure.

In FIG. 1, an exposure position 3 of a known copying apparatus is shown in which a primary charger 2, an exposure position 3, a developing device 84, a transfer charger 5, a cleaning device 6, and a quenching device 7 are arranged around a photoreceptor 1. A tone correction device 8 is disposed between the developer device 4 and the developer device 4 .

Although FIG. 1 shows an example of a black-and-white copying machine, a color copying machine is also provided with a gradation correction device in the same manner.

The gradation correction device includes an irradiation lamp 9, a mask roller 10 rotatably arranged around the irradiation lamp 9, and a light-shielding tube 1 arranged outside the mask roller 10.

The mask roller 10 is disposed in close contact with the photoreceptor 1 or with a gap of one stroke (less than one stroke). The mask roller 10 is rotated at the same linear speed as the photoreceptor 1.

The mask roller 10 is a cylindrical roller as shown in FIG. 2, and has many dot-shaped light-transmitting portions 12 (schematically shown as dots in FIG. 2) arranged in a pattern as shown in FIG. 3 on the outer peripheral surface of the roller. Placed.

The pattern arrangement is, for example, as shown in FIG.
Divide the la+- section into 4 x 4 16 parts, and form 3 of them as transparent parts, as shown by A, B, and C, and the other 13117, 1 place as a light-shielding part. be done. This pattern of l wm x l vx sections is continuously arranged in the front, back, left and right. Transparent part A' in Figure 3
, C" is the transparent part of the adjacent pattern and A of the pattern
, C respectively. That is, A, B,
The arrangement of the transparent parts in C is repeated.

Due to the structure of the gradation correction device 8, the light from the irradiation lamp 9 hits the transparent parts A, B, and C of the mask roller 10 on the electrostatic latent image formed by being charged and exposed.

It is irradiated as a driver pattern. The latent image potential of the photoreceptor decreases only in the area irradiated with light. This reduction in latent image potential becomes an edge effect peculiar to electrophotography at surface potentials between highlights and the middle, and the correction effect is most effective.

Since the high potential area is originally a saturated development area, the effect of dosotoy erase is not so great. FIG. 4 is a diagram showing the difference between erase correction and before no correction.

In the figure, the & axis shows the original density and the dark blue axis shows the copy density.

Curve A shows the characteristic curve when no correction is made, and curve B shows the characteristic curve when corrected.

If the material of the mask roller 10 is metal, the light-transmitting portion is formed as a through hole. If the resin film is torn, a silver salt film can also be used, and a pattern can be formed by screen printing or the like, and there is no particular need for through holes.

When the mask roller 10 is formed of a resin film, it is flexible, so the mask roller 10 is formed along the photoreceptor surface.
Is it possible to make surface contact between the two surfaces? Therefore 11α
This makes it possible to reduce the upfront cost for one lamp.

If the mask roller 10 is made of metal, it is necessary to insulate it or provide a gap between it and the photoreceptor 17).

1 lamp 9 stored inside the mask roller lO
It is preferable to make sure that the irradiated light is directed only in the direction of the photoreceptor 1. As an example, a light-shielding tube 11 is placed outside the mask roller 10 to prevent light from being emitted to areas other than those required.

Instead of the example shown in FIG. 1, the light shield 7 is placed inside the mask roller 10 as shown in FIG. Make it emit.

By providing the light-shielding tube 11, the light emitted from the light passing portion of the mask roller 10 is regulated so that it does not become blurred on the surface of the photoreceptor 1.

Providing the light-shielding tube 11 inside the mask roller 10 as shown in FIG. 5 has the advantage that the device can be made smaller.

The mask roller 10 is flexible, and when it comes into surface contact with the photoreceptor 1, the photoreceptor surface is not irradiated with light other than the transparent portion of the mask roller 10, and the irradiated light is not blurred. Moreover, since the irradiation time can be gained, the number of vehicles ahead of the irradiation lamp 9 can be reduced.

When the inside of the mask roller 10 is ventilated by a blowing means via means not shown, it is possible to prevent the temperature inside the mask roller from rising. In this case, the functionality of the present invention is not diminished.

In order to drive the mask roller 10 at the same linear speed as the photoreceptor 1, it is necessary to select an appropriate method depending on the material of the mask roller 10. There is a structure in which a gear is provided to rotate integrally with the gear and meshes with the gear in a 1:1 relationship to drive the gear. As another example, among the mask rollers 10 (11, 11
A rubber roller is disposed at , and a mask roller 10 is sandwiched between the rubber roller and the photoconductor to obtain Tg! There is a friction drive method.

Naturally, when rotating the mask roller 10, holding the irradiation lamp 9 and the light shielding surface 11 stationary in the examples shown in FIGS. 1 and 5 can be easily carried out using known technical means.

Since then, the present invention has made it possible to create a uniform copy image without defects such as fine lines by correcting the latent image by erasing using pattern irradiation. Good correction results can now be obtained with a simple device without requiring any special structure.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts of a copying machine equipped with a gradation correction device according to the present invention, FIG. 2 is a perspective view of a mask roller, FIG. 3 is an enlarged partial view of a pattern on the surface of the mask roller, and FIG. The figure is a characteristic diagram showing the difference in the relationship between original density and copy density depending on the presence or absence of correction, and FIG. 5 is a partial front view of a modified example of the correction device. l...-Photoreceptor 2...Primary charger 3...
Exposure position 4...Developing device 8...Tone correction device 9...Irradiation lamp 10...Mask roller 1
1... Light-shielding tube, Figure 4, Shogaku no Arashi -

Claims (1)

[Claims] In an electrophotographic copying machine that forms an electrostatic latent image of an original image on a photoreceptor by charging, exposing, and developing the photoreceptor,
It is characterized by having a cylindrical mask roller that is placed in close contact with or in close proximity to the photoreceptor at a position after image exposure and before development and that forms a transparent part of an arbitrary dot pattern, and an irradiation lamp that is placed inside the mask roller. A gradation correction device for an electrophotographic copying machine.