JPS61122622A - Projection reader - Google Patents

Abstract

PURPOSE:To reduce a vignetting generated by a Fresnel lens with a luminous flux from an original picture by placing a field lens by shifting it from the position of an image of the first image forming optical system forming an intermediate image of the original picture. CONSTITUTION:By the first optical means 12 for projecting an original picture 11, and the second optical means 15 for forming its projected image on a read means 16, a magnified image of said original picture 11 is formed on the read means 16, and also a Fresnel lens 13 operated as a field lens placed between said first optical means 12 and the second optical means 15 is placed by shifting it from a position 14 where the image of the original picture 11 is formed by the first optical means 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an apparatus for scanning and reading a projected image of an original image using a separate reading optical system.

(Prior Art) FIG. 3 is a schematic diagram showing a projection reading device already proposed by the applicant of the present invention.

In FIG. 3, a film 1 illuminated by an illumination system (not shown) is enlarged and projected by a projection lens 2. A Fresnel lens 3 is placed on the image plane projected by the lens 2, and since this Fresnel lens is focused on the exit pupil of the projection lens 2, the light emitted from the Fresnel lens 3 is made parallel to the optical axis of the projection lens. , passes through the document table glass 4. The light passing through the document platen glass 4 is imaged onto the solid-state image sensor 6 by the imaging lens 5. The imaging lens 5 and the solid-state image sensor 6 together constitute a head 7, which moves in the direction of the arrow 8, making it possible to read the entire projected image. In this configuration, since the field lens is constituted by a Fresnel lens, there is a problem in that shadows appear due to Fresnel grooves.

FIG. 4 is a diagram for explaining this. FIG. 4 shows how light rays a, b, and c from the projection lens 2 enter the Fresnel lens 3. Since the Fresnel lens 3 has an outer circumferential surface 9 and an inner circumferential surface 10, in the rays a, b, and c, a and C pass through the outer circumferential surface 9, but b goes to the inner circumferential surface 10, so this The light rays are totally reflected by the inner circumferential surface 10 of the Fresnel (Summary of the Invention) The object of the present invention is to improve the above-mentioned drawbacks and provide a projection reading device in which the light beam from the original image is less vignetted by the Fresnel lens. There is a particular thing.

The present invention aims to achieve the above object by disposing a Fresnel lens acting as a field lens offset from the position of the image of the first imaging optical system that forms an intermediate image of the original image.

(Example) FIG. 1 is a diagram showing the principle of the apparatus of the present invention. In FIG. 1, the Fresnel lens is spaced from the image plane of the projection lens 2 by a distance g1. Therefore, the light beam does not converge at the Fresnel groove, but rather has a certain diameter. luminous flux d
, e, and f are imaged at one point on the document surface 4, but the Fresnel lens 3 has a width as shown in the figure.

Therefore, the vignetting caused by Fresnel is limited to the shaded area, and the vignetting caused by Fresnel is alleviated. However, since the focal length of the Fresnel lens 3 is made to match the exit pupil of the projection lens 2, the chief ray exiting from the Fresnel lens is parallel to the optical axis of the projection lens 2.

FIG. 2 is a diagram showing an embodiment of the projection reading device of the present invention.

In FIG. 2, a light beam emitted from the film 11 illuminated by an illumination system (not shown) is imaged onto the document table glass 14 by the projection lens 12. Projection lens 12 and document table glass 14
A Fresnel lens 13 is disposed between them, and the focal point of the lens 13 coincides with the exit pupil of the projection lens 12. Therefore, the focal length of the Fresnel lens is fLz. The magnification of the projection system is β2227 sentences,! 13 is the amount of shift of the Fresnel lens 13 from the image plane of the projection lens 12. The principal ray is made parallel to the optical axis of the projection lens 12 by the Fresnel lens 13, and the image of the film 11 formed on the document platen glass 14 is focused on the CCD 16 by the imaging lens 15.
is imaged.

The imaging lens 15 and the CCD 16 together constitute a reading head 17, which is scanned in the direction of i-g 1 g, and enlarged images are sequentially formed and read on the CCD. As explained in , it has become possible to alleviate the shadow of the Fresnel lens as a field lens.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of a projection reading device according to the present invention, FIG. 2 is a diagram showing an embodiment of the projection reading device according to the present invention,
FIG. 3 and FIG. 4 are diagrams for explaining a projection reading device already proposed by the applicant of the present invention. 11-m-film, 12-m-projection lens, 13-m
- Fresnel lens, 14-m-document glass, 15-m-imaging lens, 16
---CCD, 17--Reading head.

Claims (1)

[Claims] (1) The first optical means for projecting the original image and the second optical means for forming the projected image on the reading means form an enlarged image of the original image on the reading means, and A projection reading device characterized in that a field lens arranged between an optical means and a second optical means is arranged offset from a position where an image of an original image is formed by the first optical means.