JPH0442379A - Optical reader - Google Patents

Abstract

PURPOSE:To make the control of magnification easy and to improve accuracy for magnification by controlling a lens block by using jig or the like before mounting the block onto a main body case. CONSTITUTION:A lens block 26 is formed by a solid-state image pickup element which is composed of a CCD 22, lens 24 and holding member 25 to hold the solid-state image pickup element and the lens 24 so as to relatively move them. This lens block 26 is mounted onto a main body case 1 so as to be attached, detached and moved on an optical path. On the other hand, a position control means 41 is provided to control the position of the lens block 26. The length of the optical path is decided corresponding to the set magnification of the lens 24 in the lens block 26 and according to the length of the optical path, an MTF is controlled to be optimum by suitably relatively moving the lens 24 and the solid-state image pickup element. Thus, the magnification can easily be controlled and the accuracy for the magnification can extremely be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical reading device having an optical system such as an image scanner.

[Conventional technology] FIG. 4 shows the general configuration of a conventional optical reading device.

In the figure, reference numeral 10 denotes a translucent document table on which a document is placed. Further, 20 is an optical system, and the document table 1
0, so that the image of the document P on the document table 10 can be optically read at a predetermined magnification.

Here, the optical system 20 is provided in the main body case 2, and includes a light source 21 that irradiates light onto the original P through the original platen 10, and a C0D 22 that converts reflected light from the original P into an electrical signal.
1. An optical path L refracted between the document table 10 and the CCD 22.
a plurality of mirrors 23 for forming a mirror 2;
It is generally comprised of a lens 24 and the like for imaging the reflected light from the COD 2.2 onto the COD 2.2 surface.

In addition, the main body case 2 is connected to the upper main body case 3.

It consists of a lower body case 4 slidably connected to the upper body case 3, and a mirror 23 is connected to the lower body case 4, and a light source 21. CCD22 and lens 2
4 is provided in the upper main body case 3.

However, in the optical reading device described above, the lens 2
4. Magnification errors occur due to body errors and optical path length errors.

This situation will be explained based on the schematic diagrams of FIGS. 5 and 6. (However, to simplify the explanation, the lens 24 will be considered as a thin lens.) The lens at 0 focuses the reflected light from the voice on the original P onto point 02 on C0D22. The magnification β at this time is 2 /, +1, 2
-0+S, j 202S). Here, if a lens with a focal length error of f'(<f) is used as the lens 24, the image will be formed at the 0□' point, resulting in C0D22
Don't put an image on it. So,,o,′,6 is CCD,2
When focusing by moving the lens 24 to the right in the figure so that the lens 24 is above the lens 2, the magnification β' becomes approximately 112'# (1.l12'-〇2'S). This results in a magnification error Δβ(−β−
β′) occurs.

On the other hand, in FIG. 6, if an error in the optical path length (LT) occurs due to a mounting error of the mirror (23), for example, if the document P is located at a position closer to C0D22 by a distance X than the set position (0,'S- 0,S), point 0.S on the document P. The image forming point is 03', and strictly speaking, no image is formed on the CCD 22. However, if the amount of positional deviation (x) of the original P is about +1 rnm, it is thought that the resolution will hardly deteriorate, and the magnification β'' in that case is l13'/, I!2 (tap, 4
1 s′””03S). Therefore, the magnification error Δ
β(−ββ″) is generated.

In order to reduce the magnification error Δβ mentioned above, the lens 2
4, the mounting accuracy of the mirror 23, etc. may be improved, but increasing these precisions increases costs and is not practical.

Therefore, the magnification is usually adjusted by appropriately varying the optical path length LT and the lens mounting position.

For example, in the optical reading device shown in FIG. 4, when adjusting the magnification, first coarsely adjust the MTF and coarsely adjust the reading line (adjust where on the document P the CCD 22 is looking).
After doing so, check the magnification.

Here, the magnification is generally checked by reading an image having a length of 85 inches in the main scanning direction and determining how many pixels of the C0D 22 should receive it. For example, if the optical reading device is a 300DPI machine, 300X
When 8□5=2550 pixels, the magnification error Δβ is 0 (
%).

As a result of checking the magnification in this way, if the number of pixels is within the standard, it is judged as a pass, and if it is outside the standard, the magnification is adjusted. Specifically, if the number of pixels is larger than the standard, the magnification is adjusted by increasing the optical path length (LT) by sliding the lower body case 4 of the optical reading device to the right in FIG. In addition, if the number of pixels is smaller than the standard, the optical path length (L
Adjust the magnification by shortening T).

Note that when the lower main body case 4 of the optical reading device is slid to adjust the magnification, the optical path length etc. change, resulting in deterioration of resolution. Therefore, after adjusting the magnification, the lens 24 is
22 to adjust the MTF.

[Problem to be solved by the invention] By the way, in the optical reading device described above, when the MTF is adjusted to eliminate the deterioration of the MTF, a change in magnification occurs, and when the magnification is adjusted to eliminate the change in magnification, the MTF is deteriorated. .

Therefore, in today's world where there is a demand for a dramatic improvement in magnification accuracy, magnification adjustment and MTFIM adjustment must be performed alternately and repeatedly many times, making magnification adjustment time-consuming.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an optical reading device that can easily adjust magnification and dramatically improve magnification accuracy.

[Means for Solving the Problems 1] The present invention includes a light source that irradiates light onto a document through a document table;
A solid-state element that converts light reflected from the original into an electrical signal, a mirror that forms a refracted optical path between the document table and the solid-state image sensor, and a solid-state element that captures the reflected light from the five mirrors. In an optical reading device having an optical system including a lens, etc. for forming an image on a main body case and provided in a main body case, from the solid-state image sensor, the lens, and a holding member that holds the solid-state image sensor and the lens in a relatively movable manner. A lens block is formed, the lens block is attached to the main body case so as to be removably movable on the optical path, and a position adjustment means is provided that can adjust the position of the lens block. do.

1 Effect] In the present invention, the lens block is adjusted using a jig or the like before being attached to the main body case. That is, the optical path length is determined according to the set magnification of the lens of the lens block, and the lens and the solid-state image sensor are appropriately moved relative to each other using the optical path length.
Adjust to get the best TF. The lens block thus adjusted is attached to the main body case so that the magnification error is approximately O (%). At this time, since the MTF is the best, there is no need to adjust the MTF again.

In this way, when the magnification is adjusted so that the magnification error is around O (%), the MTF automatically becomes the best, so there is no need to repeat MTF adjustment and magnification adjustment many times as in the past. Therefore, magnification adjustment becomes easy and magnification accuracy can be dramatically improved.

[Example] An embodiment of the present invention will be described based on the drawings.

The optical reading device according to this embodiment is as shown in FIG.
The apparatus includes a document table 10, a position adjusting means for an optical system 1 having a lens block 26, which is a characteristic part of this apparatus, and the like.

Components that are the same as those shown in FIG. 4 are given the same reference numerals, and their explanations will be omitted or simplified.

Here, the optical system is provided in the main body case 1 which is movable relative to the document table 10, and includes a light source 21 and a lens block 26. The lens block 26 is
It is attached to the main body case 1 via the support member 32 so as to be removable and movable on the optical path L2. and,
The lens block 26 includes a solid-state image sensor, a lens 24, and a holding member that holds the solid-state image sensor and the lens 24 in a relatively movable manner. in particular,
The solid-state image sensor is formed from a CCD 22, and the holding member is formed from a box-shaped lens case 25. This lens case 25 is arranged so that the optical axes of the CCD 22 and the lens 24 coincide, that is, C0 is placed on the center line of the lens 24.
It is held so that the pixel center of D22 is aligned.

On the other hand, the position adjustment means is formed to be able to adjust the position of the lens block 26, and includes an adjustment screw 41. The adjustment screw 41 is screwed into a support plate 42 fixed to the main body case 1, and is configured to be able to move the lens block 26 minutely on the optical path L2 via the support member 32. Note that since the support member 32 is biased toward the adjustment screw 41 via a spring (not shown), the lens block 26 can be accurately positioned and adjusted.

Next, the effect will be explained.

First, when the lens block 26 is attached to the main body case 1, adjustment is made using the jig 5o shown in FIGS. 2 and 3 so that the magnification can be adjusted without performing the MTF adjustment.

Such lens block adjustment is performed in the following steps.

■ Attach the lens block 26 to the jig 50 using the screws 51.

When the lens block 26 is attached to the jig 50, the optical path length becomes the set value LT and the magnification target T as shown in FIG.
The CC'D 22 can capture the MTF adjustment pair line PL.

(2) Roughly adjust the MTF by sliding the rinse 24 against the CCD 22 in the left-right direction in FIG.

■Read the magnification target T with C0D22 and lens 2
Measure the magnification of 2.

(2) Change the optical path length by loosening the screw 51 and sliding the lens block 26 in the direction of the optical path L2' so that the measured magnification becomes the set magnification, that is, cancel out the magnification error.

(This work is done while looking at the magnification target T.

) ■ Tighten the screw 51 to fix the lens block 26 to the jig 50 at the position where the magnification error is around O (%).

(2) In this state, make the final adjustment of the MTF and fix the lens 24.

The lens block 26 adjusted according to the above procedure has an optical path length different from the set value or a magnification error of around O (%), and has the best MTF.

Next, the adjusted lens block 26 is attached to the main body case 1 of the optical reading device shown in FIG. 1, and the magnification target T and the like are placed on the original stacking table 10, and final adjustment is performed in the following steps.

(2) Attach the lens block 26 to the support member 32 using the screws 52.

■ By rotating the adjustment screw 41, the lens block 26 slides on the optical path L2 via the support member 32, so look at the magnification target T with the CCD 22 and search for a position where the magnification error is around 0 (%). , and fix it to the main body case 1 at that position. The MTF at this time is the best.

■Loosen the screw 52 tightened with the above-mentioned bend ■ and remove the lens block 2.
6 relative to the support member 32 to make the final adjustment of the reading line, and after adjustment, fix it to the support member 32 (note that such adjustment is done while looking at the reading line dot (DT)).

).

■Magnification accuracy can be dramatically improved by simply performing steps ■ to ■ above, but in order to maximize magnification accuracy, the optical path length may change slightly due to the final adjustment of the reading line in ■. After final adjustment of the reading line, repeat steps ■ and ■ again.

However, according to this embodiment, a solid-state image sensor (CCD)
22), lens 24 and the solid-state image sensor and lens 2
4 and a holding member (lens case 25) that is relatively movable, and the lens block 26 is attached to the main body case 1 so as to be detachable and movable on the optical path L2. Moreover, since the lens block 26 is provided with a position adjustment means (adjustment screw 41) that can adjust the position of the lens block 26, the magnification can be easily adjusted and the magnification accuracy can be dramatically improved.

[Effects of the Invention] According to the present invention, a lens block is formed from a solid-state image sensor, a lens, and a holding member that holds the solid-state image sensor and lens in a relatively movable manner, and this lens block is removably attached to a main body case. In addition, since the lens block is mounted so that it can be moved along the optical path and is equipped with a position adjustment means that can adjust the position of the lens block, it is easy to adjust the magnification, and the accuracy of the magnification can be dramatically improved. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIGS. 2 and 3 are views showing a jig used for lens block adjustment, with FIG. 2 being a side view and FIG. 3 being a perspective view. FIG. 4 is a sectional view showing a conventional optical reading device. Fifth
This figure and FIG. 6 are diagrams for explaining the magnification error. DESCRIPTION OF SYMBOLS 1... Main body case, 22... CCD (solid-state image sensor), 24... Lens, 25... Lens case (holding member), 26... Lens block, 41... Adjustment screw (position adjustment means).

Claims (1)

[Claims] (1) A light source that irradiates light onto the document through the document table, a solid-state image sensor that converts light reflected from the document into an electrical signal, and a mirror that forms a refracted optical path between the document table and the solid-state image sensor. and an optical reading device having an optical system provided in a main body case, which includes a lens, etc. for forming an image of reflected light from a mirror onto a solid-state image sensor, the solid-state image sensor, the lens, and the solid-state image sensor and the lens. A lens block is formed from a holding member that holds the lens block so as to be relatively movable, and the lens block is attached to the main body case so as to be detachable and movable on the optical path, and the position of the lens block is adjustable. An optical reading device characterized by being provided with a position adjustment means.