JPS63182675A - Image recorder - Google Patents

Abstract

PURPOSE:To obtain a dot pictures having no moire without using an auxiliary light source, by placing a dot screen group having each angle corresponding to each fundamental color, in its optical path, at the time of using an area gradation. CONSTITUTION:A light source 2 is projected to an original on an original placing table 1, and its reflected light passes through a color separation filter 3 and a SELFOC lens array 4, is subjected to a dot separating by a dot screen cassette 5 and projected onto a photosensitive drum 6. When a light beam whose intensity has been changed to a size of a dot by a dot screen 20 is projected an electrostatic latent image is formed on the photosensitive drum 6. In this case, the dot screen is moved by synchronizing with a rotation of the photosensitive drum 6, the color separation filter 3 is replaced successively, and also, in that case, when dot screens B, C, D and E are used in order for each separate color plate, dot electrostatic latent images whose dot angles are different from each separate color plate respectively and formed successively on the photosensitive drum 6. In such a way, the constitution is simplified, and also, a dot pictures having no moire can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a copying machine equipped with a halftone screen.

[Prior Art] In recent years, copying machines have become widely used, and not only monochrome copying machines but also color copying machines are now available. However, when a color original is separated into halftone dots for each color plate and recorded, the halftone angle of each color plate is In some cases, moiré may occur, making the image difficult to see. In the printing industry, experience has shown that moiré disappears when each halftone screen angle is 15 degrees or more.
As mentioned above, a screen with halftone dots every 15 degrees is used to separate the color plates.

Examples of halftone dot separation using a halftone screen in a copying machine include JP-A-60-100161 @ and JP-A-60-168169. Halftone dot separation was performed by performing auxiliary exposure using an auxiliary light source placed around the halftone screen.

[Problems to be Solved by the Invention] However, in this case, it is necessary to adjust the light amount of the auxiliary light source, and it is troublesome to replace the light source if it is damaged.

Furthermore, in order to perform halftone separation for each color plate, the length of the halftone dot screen becomes long and the diameter of the auxiliary light source becomes large.

[Object of the Invention] An object of the present invention is to obtain a moiré-free halftone image by arranging a halftone screen in the optical path without using an auxiliary light source.

[Example] An embodiment of the present invention will be briefly described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. At the bottom of the movable document table 1, there is a light source 2 that illuminates the document, and in the reflected optical path there is a color separation filter 3 and a SELFOC lens array 4, and a halftone screen cassette 5 whose screen surface is directly in front of the photosensitive drum 6. It is located so that it is located at Around the photosensitive drum 6, there are a toner case 7 containing toner 8, a developing sleeve 9, a charge corotron 10° static elimination lamp 11, and a cleaning member 12.
The photosensitive drum 6 is in contact with a transparent insulating film 15 rotated by a driving roller 14 and a driven roller 13 at its lower part. The transparent insulating film 15 is cleaned by a cleaning blade 16. The exposure section consists of an exposure lamp 17 and a color separation filter 18, and a paper feed cassette 19 feeds the light and pressure sensitive recording paper S to a position where it can be appropriately exposed to light from the exposure section.

Further, as shown in FIG. 2, the halftone dot screen cassette 5 includes a halftone dot screen 20 and a screen drive roll 21, and the halftone dot screen 20 is driven by the screen drive roll 21.

As shown in FIG.
There are 4 types of halftone screens B, C, and 4 sizes with different halftone angles: 30 degrees, 45 degrees, 60 degrees, and 15 degrees.
It is divided into D, E and plain film A. If you do not want the original to have halftone dots, you can copy it using this plain film A.

The operation of the apparatus configured as described above will be described below.

A light source 2 illuminates the document on the document table 1, and the reflected light passes through a color separation filter 3, a SELFOC lens array 4,
The halftone dots are separated by the halftone screen cassette 5 and transferred to the photosensitive drum 6.
irradiated on top. The photosensitive drum 6 is a cleaning member 12
After collecting the toner remaining on the surface, turn on the static elimination lamp 1.
1, and is uniformly charged by a charge corotron 10 to an initial state. When the light whose intensity is changed according to the size of the halftone dots is irradiated thereon by the halftone dot screen 20, an electrostatic latent image is formed on the photosensitive drum 6. At this time, the halftone screen is moved in synchronization with the rotation of the photosensitive drum 6. At this time, the color separation filters 3 are replaced one after another, and the halftone screens B, C,
If D and E are used, halftone electrostatic latent images with different halftone dot angles are sequentially formed on the photosensitive drum 6 for each color plate.

In this embodiment, the toner case 7 stores a black one-component toner 8, which is uniformly applied onto the developing sleeve 9, and the halftone electrostatic latent image on the photosensitive drum 6 is developed. The toner 8 developed on the photosensitive drum 6 is transferred to a transparent insulating film 15 that is moved by a driving roller 14 and a driven roller 13.
transferred on top. Transparent insulating film 1 with toner 8 on it
5 rests on a photosensitive and pressure sensitive recording paper S fed from a paper feed cassette 19, and the image on the transparent insulating film 15 is created by light passing through an exposure light source 17 and a color separation filter 18. S is exposed. After repeating this several times on one sheet of photosensitive and pressure sensitive recording paper S for each color plate,
is pressure-fixed by a pressure-fixing section (not shown) and then discharged from the apparatus.

Figure 3 shows an example of a halftone screen.
By using a cassette equipped with screens such as Noon, which have different halftone dot sizes and shapes, it is possible to obtain a variety of expressive halftone dot images.

Another embodiment is shown in FIG. That is, as shown in FIG. 4, when the reflected light from the original 51 irradiated by the light source 52 is passed through the color separation filter 56 and the condensing lens 53 and is directly exposed onto the photosensitive pressure sensitive recording paper 55, the exposure A halftone screen 54 is placed immediately in front of the document surface or directly below the document surface as shown by the chain line in the figure.

In this case, the halftone screen only needs to be driven when switching the exposure of each color plate.

In each of the embodiments detailed above, a photosensitive and pressure sensitive recording paper was used as the recording paper, but it can be applied to various applications, such as being used for RPC using color toner.

[Effects of the Invention] As detailed above, the present invention does not use an auxiliary light source and disposes a halftone screen in the optical path, so the present invention has a feature that the structure is simple and a halftone image without moiré can be obtained. have

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a detailed view of the operation, FIG. 3 is a detailed view of the halftone screen portion, and FIG. 4 is a view showing another embodiment. 5 is a halftone screen cassette, 20 is a halftone screen,
21 is a screen drive roller, A is a plain screen, and B, C, D, and E are 30 degrees, 45 degrees, and 60 degrees, respectively.
It is a halftone screen with a halftone dot angle of 15 degrees.

Claims (1)

[Claims] In a copying machine using an optical system, when area gradation representing gradation is used, an image recording device characterized in that a halftone screen group having each angle corresponding to each basic color is arranged in the optical path. .