JPH0136100B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that feeds sheet originals one by one onto a document table and illuminates them while moving them on the glass surface of the document table. As an example of the application of this document illumination method, it can be applied to a document reading section of a copying machine, a facsimile machine, and the like.

FIG. 1 shows a document illumination device of this type of conventionally known electrophotographic apparatus.

In the figure, 1 is a document table glass, 2 is a paper guide, 3 is a paper feed roller, 4 is a paper discharge roller, and 5 is an illumination lamp. During operation, the sheet original 6 is transferred from the paper feed roller 3.
is fed one by one onto the document glass 1, and while sliding on the document glass 1, it is illuminated by a lamp 5, and the projected image is irradiated onto the photosensitive drum through the lens 7, after which it is discharged from the paper discharge roller 4. be done. At this time, it is necessary to provide a slight gap between the document table glass surface and the paper guide so that the sheet document 6 can be moved smoothly. In addition, the gap must be kept within the focal depth of the imaging lens so that even if the document flaps in this gap (even if it approaches the platen glass or the paper guide), the document pattern can be projected satisfactorily onto the photosensitive drum. There is a need. For this reason, the gap is generally about 1 mm. The surface of the paper guide 2 is painted white, and when a sheet document does not pass through, the light from the illumination lamp is reflected to erase the latent image and prevent overconsumption of toner.

By the way, when copying with the illumination device configured as shown in Figure 1, there is no problem when the sheet original is made of ordinary paper, but if the original is made of transparent or translucent paper such as Mylar 2nd original or thin letter paper, there is no problem. When this occurs, the line image written on the manuscript becomes distorted. The reason for this will be explained with reference to FIG.

In FIG. 2, each number indicates the same member as in FIG.

In FIG. 2, 6 is a sheet original, 6a is an opaque portion of the sheet original, and 6b is a transparent portion. Now, when the illumination lamp 5 located obliquely below the document table glass 1 illuminates the pattern on the document sheet, a shadow 2a of the document pattern is formed on the surface of the paper guide. When there is a gap between the paper guide and the original, the original pattern and shadow pattern will be slightly △x in the X direction.
This results in the formation being shifted by a certain amount. By the way, the projection light onto the photosensitive drum is irradiated in the Y direction, but both the original pattern and the shadow pattern are within the focal depth of the imaging lens, and the two patterns overlap when viewed from the lens side. The document will not be formed clearly and will be disturbed by the amount (Δx in the figure).

SUMMARY OF THE INVENTION It is an object of the present invention to provide an illumination device that can prevent disturbances between the original pattern and the character image in transparent paper and translucent paper originals as described above.

In the present invention, a transparent plate is provided on the surface of the paper guide on the document glass side, and a light reflecting surface is formed on the back surface of this transparent plate, so that the sliding surface of the paper of the paper guide and the light reflecting surface of the document illumination light are respectively The image defect is prevented by configuring the light reflecting surface to be a separate surface and at a position outside the focal point of the lens (at a position approximately 1.5 mm or more away from the platen glass). do.

The embodiments shown in the drawings will be described below.
In the figures, the same numbers as those in FIG. 1 indicate the same members. In the figure, 8 indicates a glass surface, acrylic, or any other transparent plate attached to the paper guide. The contact surface of the paper guide with the transparent plate is painted white.
In FIG. 3, the distance between the surface of the transparent plate and the document table glass is set to about 1 mm so as not to impede the movement of the paper. At this time, as described above, even if the original sheet flaps on the original glass, the image will not be blurred because the original sheet is within the focal depth of the imaging lens.

In the arrangement shown in FIG. 3, the original sheet 6 receives the illumination light from the lamp 5 and creates a shadow of the original pattern on the white painted surface of the paper guide 2. At this time, if the thickness of the transparent plate is increased to 1.5 mm or more, the shadows will suddenly become blurred. The reason for this is that the illumination luminous flux does not come from only one direction, as shown by the solid arrow in Figure 3, but from multiple directions, including light reflected from the lamp's reflective shade, etc., as shown by the broken arrow. The light beams pass through the document sheet, and while they pass through the transparent plate 8 and reach the white painted surface of the paper guide 2, not only do the light beams themselves become blurred, but they also overlap, creating shadows. It's to make a fuss. In addition, the white painted surface of the paper guide on which the blurred shadow of the original pattern is reflected is located far enough away from the document table glass and outside the depth of focus of the lens, so the effect of the shadow on the photosensitive drum is It almost disappears.

If the thickness of the transparent plate is about 3 mm or more, fogging is likely to occur uniformly on the reproduced image. The reason for this is that since the light reflecting surface of the paper guide has moved away, less of the light that has passed through the original is reflected back onto the original. For the above reasons, it can be said that the appropriate thickness of the transparent plate is around 2 mm.

As described above, the apparatus of the present invention is configured so that the sliding surface for guiding the sheet original and the light reflecting surface for illuminating the original are separate surfaces, and the light reflecting surface is located outside the focal point of the lens. , even when illuminating a document on transparent or translucent paper, it prevents the shadow pattern of the document from being formed in a position that is shifted from the document.
Prevents image distortion from occurring. Furthermore, in the present invention, the effect becomes remarkable by making the light reflecting surface outside the focal depth of the lens.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a document illuminating device in a known electrophotographic apparatus, FIG. 2 is an explanatory diagram showing the operation of the document illuminating device shown in FIG. 1, and FIG. 3 is a diagram showing an embodiment of the illuminating device according to the present invention. show. 1...Original table glass, 2...Paper guide, 3...
Paper feed roller, 4... Paper discharge roller, 5... Illumination lamp, 6... Sheet original, 6a... Opaque part of the original, 6b... Transparent part of the original, 2a... Shadow of the original pattern, 8... Transparent board.

Claims (1)

[Claims] 1. In a device that feeds sheet originals one by one onto a document glass surface, illuminates them while moving them on the document glass surface, and projects the image onto a photosensitive member using a lens. A transparent plate is provided on the platen glass side of the guide that guides the arranged sheet original, and a light reflecting surface is formed on the back side of this transparent plate, so that the sliding surface of the original sheet and the light reflecting surface of the original illumination light are formed. are separate surfaces, and a document moving gap formed between the document table glass and the transparent plate is provided within the focal depth of the lens, and the light reflecting surface is located at a position outside the focal depth of the lens. A document illumination device characterized in that it is configured so that: