JPH0774900A - Image reader - Google Patents

Abstract

PURPOSE:To make fine adjustments extremely easy and to facilitate fixation after the adjustments by arranging the image forming lens of an image formation optical system off the optical axis of an image formation optical system. CONSTITUTION:Information on a document surface 1 is projected on a linear image pickup element 5 through the image forming lens 4 of the image formation optical system. Namely, the document surface 1 is lighted by a long-sized light source and the luminous flux which is reflected there and exits from the document surface 1 is reflected by a mirror and imaged on the linear image pickup element 5 through the image forming lens 4. Then the image forming lens 4 of the image formation optical system is shifted on a horizontal surface and arranged. Various methods for shifting the image forming lens 4 can be employed and, for example, the image forming lens 4 is arranged while rotated around the gravity center position of the image forming lens 4 on the horizontal surface by a specific angle from the optical axis 7 of the image formation optical system. Consequently, the fine adjustments are easy and the fixation after the adjustments are facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image of a document illuminated by a long light source using an image forming optical system and a one-dimensional image pickup device.

[0002]

2. Description of the Related Art In a conventional image reading apparatus, as shown in FIG. 1, an original surface 1 is illuminated by a long light source 2 having a specific light distribution characteristic, and a light beam emitted from the original surface 1 by reflection thereof is emitted. The light is reflected by the mirror 3 and is imaged on the one-dimensional image sensor 5 by the imaging lens 4. The shading correction mask 6 has a symmetrical shape, and a line of symmetry is arranged on the optical axis of the lens 4. As shown in FIG. 2, the document surface 1
When there are three resolution charts 1a, 1b, 1c in
When the resolving power appears asymmetrically as shown in FIG. 4, the one-dimensional image pickup device 5 is tilted to the left and right in the horizontal plane with the center of gravity as the center, and the optical axis of the imaging optical system is arranged as shown in FIG. By giving a predetermined angle with No. 7, the resolving power is symmetrically corrected as shown in FIG.

[0003]

However, in the conventional image reading apparatus, since the one-dimensional image pickup device 5 is arranged so as to be tilted to the left and right, not only time is required for adjustment in the manufacturing process, but also Fine adjustment was extremely difficult. That is, it is difficult for the one-dimensional image pickup device 5 to be arranged in the xy direction with respect to the optical axis 7 of the imaging optical system and in the swinging direction on a horizontal plane including the optical axis 7. Even after installation after adjustment, there were difficulties in fixing in the above three directions.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide an image reading apparatus in which fine adjustment is extremely easy and fixing after adjustment can be easily performed.

[0005]

In order to solve the above problems, the present invention provides a long light source for illuminating a document, an image forming optical system for forming an image of the illuminated document, and the above-mentioned structure. In an image reading device including a one-dimensional image pickup device arranged on an image forming plane of an image optical system, an image forming lens of the image forming optical system is arranged so as to be displaced with respect to an optical axis of the image forming optical system. Is characterized by.

[0006]

Embodiments of the present invention will be described with reference to the drawings.

The image reading apparatus of the present invention is substantially the same as the conventional apparatus shown in FIG. 1 except for the configuration of the imaging lens 4. Information (for example, resolution charts 1a, 1b, 1c) on the document surface 1 is projected onto the one-dimensional image pickup device 5 via the image forming lens 4 of the image forming optical system.

The original surface 1 is illuminated by a long light source 2.
A light flux reflected from the document surface and exiting from the document surface is reflected by the mirror 3 and is formed by the imaging lens 4 into the one-dimensional image pickup device 5
Is imaged. The mask 6 for shading correction may or may not be provided between the mirror 3 and the imaging lens 4.

According to the present invention, in the above-mentioned image reading apparatus, the image forming lens 4 of the image forming optical system is arranged so as to be displaced in the horizontal plane.

Various methods can be adopted for the method of shifting the imaging lens 4. For example, as shown in FIGS. 6 and 7,
With the center of gravity of the imaging lens 4 as the center, the imaging lens 4 is moved from the optical axis 7 of the imaging optical system at a predetermined angle (10
Rotate (less than °) and shift them.

FIG. 8 shows the embodiment of FIGS. 6-7 of the present invention more specifically. A V-shaped groove 8a is formed on the upper surface of the support member 8, and the imaging lens 4 is supported and fixed therein. Flanges 9 are provided on both sides of the support member 8 so as to project, and fixing holes 9a, 9a are formed in these. These holes 9a,
A fixing bolt (not shown) is passed through 9a to fix the apparatus at a predetermined position. The diameter of the holes 9a, 9a is set to be several millimeters larger than the outer diameter of the bolt. The rotation pin 10 is inserted into the lower surface of the support member 8 so that the support member 8 can rotate around the rotation pin 10.

In the embodiment of FIG. 8, the bolt is loosened to some extent and then the support member 8 is rotated about the rotary pin 10 by moving the flange 9 relative to the bolt. As a result, the imaging lens 4 together with the support member 8 is displaced in the horizontal plane with respect to the optical axis 7. After that, the bolt is retightened at a desired position and the support member 8 is fixed at that position.

[0013]

According to the present invention, fine adjustment is extremely easy as compared with the conventional image reading apparatus, and the fixing after the adjustment can be easily performed. As a result, the manufacturing time can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a conventional image reading apparatus.

FIG. 2 is a diagram showing an example of a resolution chart of the document surface of FIG.

FIG. 3 is a diagram showing the operation of the one-dimensional image sensor of FIG.

FIG. 4 is a diagram showing a resolving state in which resolving power is asymmetric.

FIG. 5 is a diagram showing a resolving state in which resolving power is symmetrical.

FIG. 6 is a diagram showing the operation of the imaging lens.

FIG. 7 is a diagram showing the relationship between the document surface, the one-dimensional image sensor, the optical axis, and the operation of the imaging lens.

FIG. 8 is a perspective view showing an example of means for rotating the support member of the imaging lens.

[Explanation of symbols]

 1 Original Surface 2 Long Light Source 3 Mirror 4 Imaging Lens 5 One-dimensional Image Sensor 6 Shading Correction Mask 7 Optical Axis 8 Supporting Member 9 Flange 10 Rotating Pin

Claims (1)

[Claims] 1. A long light source for illuminating a document, an image-forming optical system for forming an image of an illuminated document, and a one-dimensional image pickup device arranged on an image-forming surface of the image-forming optical system. The image reading device according to claim 1, wherein the image forming lens of the image forming optical system is arranged so as to be displaced with respect to the optical axis of the image forming optical system.