JP2005091601A - Image reading optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image reading optical device equipped with a reflection optical unit constituted of simple and compact constitution and capable of effectively eliminating a harmful light component. <P>SOLUTION: In the image reading optical device, an original surface is scanned in a direction X while it is one-dimensionally irradiated with light in a direction Y, and reflected light from the original surface is made to form an image on a CCD 40 being a one-dimensional imaging device in the direction Y. The optical device is equipped with the reflection optical unit 20 having a plurality of reflection surfaces from a 1st mirror 21 to a 4th mirror 24 successively from an original side. Incident light P1 and emitted light P3 are positioned nearly on a line on an axial light beam passing through the center of the original in the direction Y and forming the image at the center of the CCD 40. The mirrors 21 to 24 are surrounded by a light shielding casing 30, and a light shielding member is provided between the 1st mirror 21 and the 4th mirror 24 or near the 1st mirror 21 and/or the 4th mirror 24, and an aperture diaphragm 25 is installed between the mirrors 22 and 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading optical apparatus, and more particularly to an image reading optical apparatus that reads an image of a document placed on a platen glass with a one-dimensional image sensor while scanning the image in one direction.

  Conventionally, refractive optical systems have been widely employed as optical units incorporated in scanners, image reading optical devices of digital copying machines, and the like. In response to the recent demand for miniaturization, correction of chromatic aberration has become important especially in a full-color image reading optical apparatus. However, in order to correct chromatic aberration in a refractive optical system, it is necessary to use a special and expensive glass material or to greatly increase the number of refractive surfaces, resulting in an increase in size and cost.

  As a solution to such a problem, recently, as disclosed in Patent Documents 1 to 5, there is a reflective optical unit that is configured relatively compactly with a small number of reflection surfaces by effectively using an eccentric reflection surface. Several proposals have been made.

  However, each of the reflection optical units disclosed in Patent Documents 1 to 5 is configured to decenter the imaging device with respect to the incident light beam, and there are many complicated changes when incorporated in an image reading optical device. turn into. In addition, there is a problem that the thickness (height) of the apparatus increases because the optical paths of incident light and outgoing light are shifted.

Further, in this type of reflective optical unit, it is also an important subject to eliminate harmful light components other than the effective light flux. However, at present, sufficient measures are not necessarily taken.
JP 2003-57549 A JP 2002-335375 A Japanese Patent Laid-Open No. 11-23971 JP-A-10-307260 Japanese Patent Laid-Open No. 9-329747

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image reading optical apparatus having a reflection optical unit that has a simple and compact configuration and can effectively eliminate harmful light components.

  In order to achieve the above object, the image reading optical apparatus according to the present invention scans in the X direction orthogonal to the Y direction while irradiating the original surface in a one-dimensional manner in the Y direction, and reflects light from the original surface. Is an image reading optical device that forms an image on a one-dimensional image sensor in the Y direction, and includes a reflective optical unit having a plurality of reflective surfaces from the first reflective surface to the final reflective surface sequentially from the original side, and In the axial ray that forms an image at the center of the one-dimensional image sensor through the center of the first axis, the axial ray incident on the reflection optical unit and the outgoing axial ray are positioned substantially in a straight line, and the first reflection A light shielding member is provided between the surface and the final reflection surface, or in the vicinity of the first reflection surface and / or the final reflection surface.

  In the image reading optical apparatus according to the present invention, since the incident light and the emitted light on the reflection optical unit are positioned substantially in a straight line, the reflection optical unit can be configured to be flat and compact, and one-dimensional imaging can be performed. There is no need to place the elements eccentrically.

  Further, since the light shielding member is provided between the first reflecting surface and the final reflecting surface or in the vicinity of the first reflecting surface and / or the final reflecting surface, the light reflected on the reflecting optical unit is reflected by the reflecting surface. Therefore, harmful light components that reach the one-dimensional image sensor by going around the reflecting surface can be effectively eliminated, and the high aberration correction capability of the reflecting system can be fully utilized.

  In the image reading optical apparatus according to the present invention, it is preferable that an aperture stop is provided between at least a pair of adjacent reflecting surfaces among the plurality of reflecting surfaces. Ambient light can be blocked.

  The reflective optical unit is preferably surrounded by a light shielding member having an opening through which an effective light beam passes. It can block harmful light components from the outside.

  Further, the reflecting surface has at least first to fourth reflecting surfaces, and the axial light beam reflected by the second reflecting surface and incident on the third reflecting surface is divided into incident light and outgoing light to the reflecting optical unit. An aperture stop may be provided between the second reflecting surface and the third reflecting surface, which is substantially parallel to the straight line formed. The thickness (height) of the reflective optical unit can be minimized with a small number of constituent surfaces such as the first to fourth reflective surfaces, and the aperture stop can be arranged in a space-efficient manner.

  Embodiments of an image reading optical device according to the present invention will be described below with reference to the accompanying drawings.

(Overall configuration of image reading optical device, see FIG. 1)
1 shows an overall configuration of an embodiment of an image reading optical device according to the present invention. The image reading optical device 10 reads a document (not shown) placed on a platen glass 11 in the X direction (sub-scanning direction), and generally includes an illumination lamp 13 and a mirror 14. The first slider 12, the second slider 15 including the mirrors 16 and 17, the reflection optical unit 20 including the mirrors 21 to 24, and the CCD 40 are included.

  At the time of image reading, the first slider 12 moves at a predetermined speed v in the X direction, and the second slider 15 moves at a speed v / 2 in the X direction. The reflective optical unit 20 and the CCD 40 are fixed in position. The light irradiated one-dimensionally from the illumination lamp 13 in the Y direction (main scanning direction) is reflected by the document surface placed on the document table glass 11 and reflected through the mirrors 14, 16, and 17. The light enters the optical unit 20, is sequentially reflected by the mirrors 21 to 24, and forms an image on the CCD 40. The CCD 40 is a well-known one-dimensional image sensor.

  The reflective optical unit 20 includes a first mirror 21, a second mirror 22, a third mirror 23, a fourth mirror 24, and an aperture stop 25 in order from the document side, and these mirrors are surrounded by a light shielding casing 30. The light shielding casing 30 is completely shielded from light except for the entrance opening 31 and the exit opening 32. The aperture stop 25 is provided between the second mirror 22 and the third mirror 23.

  If the light beam that passes through the center of the original in the Y direction and forms an image on the center of the CCD 40 is an axial light beam, the incident light P1 and the outgoing light P3 of this axial light beam are positioned on a straight line. Further, the axial ray P2 reflected by the second mirror 22 and incident on the third mirror 23 is parallel to the axial ray (incident light P1, outgoing light P3).

(Specific examples of the reflective optical unit, see FIGS. 2 to 4)
Hereinafter, specific examples (first example, second example, third example) of the reflective optical unit 20 will be described in detail.

  As shown in FIG. 2, the reflective optical unit 20 </ b> A that is the first example is one in which a light shielding plate 35 is installed between the first mirror 21 and the fourth mirror 24.

  As shown in FIG. 3, the reflective optical unit 20 </ b> B as the second example is one in which light shielding plates 36 and 37 are installed on the back of the first mirror 21.

  As shown in FIG. 4, the reflective optical unit 20 </ b> C as the third example is provided with a light shielding part 38 between the first mirror 21 and the fourth mirror 24 by deforming the ceiling part of the light shielding casing 30 inward. A light shielding plate 39 is installed.

  In each of the reflective optical units 20 (20A, 20B, 20C), the incident light P1 and the outgoing light P3 are positioned on a straight line, so that the reflective optical unit 20 can be configured to be flat and compact, There is no need to place the CCD 40 eccentrically.

  In the first example, a light shielding plate 35 is provided between the first mirror 21 and the fourth mirror 24, in the second example, light shielding plates 36 and 37 are provided on the back of the first mirror 21, and in the third example, the first mirror 21 is provided. Since the light shielding portion 38 and the light shielding plate 39 are provided between the first mirror 24 and the fourth mirror 24, the light that enters the reflective optical unit 20 wraps around the reflecting surface without being reflected by the first mirror 21 and reaches the CCD 40. The light component can be effectively eliminated, and the high aberration correction capability of the reflection system can be fully utilized. In the second example, a light shielding plate may be installed on the back of the fourth mirror 24 instead of or in combination with the light shielding plates 36 and 37.

  Furthermore, since each aperture optical unit 20 is provided with the aperture stop 25 between the second mirror 22 and the third mirror 23, it is possible to effectively block peripheral rays. Further, since the reflection optical unit 20 is surrounded by the light shielding casing 30, harmful light components from the outside can be blocked.

  Further, an axial ray P2 reflected by the second mirror 22 and incident on the third mirror 23 is arranged in parallel to the incident light P1 and the outgoing light P3, and the second mirror 22 and the third mirror 23 Since the aperture stop 25 is provided between them, the thickness (height) of the reflective optical unit 20 can be minimized with four fewer constituent surfaces, and the aperture stop 25 can be arranged in a space efficient manner. it can.

(Construction data, see FIGS. 5 and 6)
The 1st-4th mirrors 21-24 which comprise the said reflective optical unit 20 are comprised by the free-form surface. Here, the free curved surface of each of the mirrors 21 to 24 and the construction data including the original table glass 11 and the CCD 40 are shown in the following Table 1, Table 2, and Table 3. The aspheric coefficients of these free-form surfaces are as shown in the following equations.

  FIG. 5 is a coordinate system of basic data and eccentricity data shown in Tables 1 and 2, and FIG. 6 is a coordinate system of aspherical coefficients shown in Table 3.

(Other examples)
The image reading optical apparatus according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  For example, the configuration of the light shielding casing, the shape of the light shielding portion, the shape of the light shielding plate, and the like are arbitrary. Of course, the construction data of each reflecting surface is an example.

1 is an overall configuration diagram showing an image reading optical device according to the present invention. It is sectional drawing which shows the 1st example of the reflective optical unit integrated in the image reading optical apparatus which concerns on this invention. It is sectional drawing which shows the 2nd example of the said reflection optical unit. It is sectional drawing which shows the 3rd example of the said reflection optical unit. It is a chart figure which shows the coordinate system of the basic data of each reflective surface of the said reflection optical unit, and eccentricity data. It is a chart figure which shows the coordinate system of the aspherical coefficient of each reflective surface of the said reflective optical unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image reading optical apparatus 11 ... Original plate glass 20 ... Reflection optical unit 21-24 ... Mirror (reflection surface)
25 ... Aperture stop 30 ... Light-shielding casing 31, 32 ... Opening 35, 36, 37, 39 ... Light-shielding plate 38 ... Light-shielding part 40 ... CCD (one-dimensional imaging device)

Claims (4)

An image reading optical device that scans in the X direction orthogonal to the Y direction while irradiating the original surface in one direction in the Y direction, and forms an image of reflected light from the original surface on a one-dimensional image sensor in the Y direction. There,
A reflective optical unit having a plurality of reflective surfaces from the first reflective surface to the final reflective surface sequentially from the document side;
In the axial ray that forms an image at the center of the one-dimensional image sensor through the center in the Y direction of the document, the axial ray incident on the reflection optical unit and the outgoing axial ray are positioned substantially in a straight line.
Having a light shielding member between the first reflective surface and the final reflective surface or in the vicinity of the first reflective surface and / or the final reflective surface;
An image reading optical device.   The image reading optical apparatus according to claim 1, further comprising an aperture stop between at least one pair of adjacent reflecting surfaces among the plurality of reflecting surfaces.   The image reading optical apparatus according to claim 1, wherein the reflection optical unit is surrounded by a light shielding member having an opening through which an effective light beam passes. The reflective surface has at least first to fourth reflective surfaces;
The axial ray reflected by the second reflecting surface and incident on the third reflecting surface is substantially parallel to a straight line formed by the incident light and the outgoing light to the reflecting optical unit,
Having an aperture stop between the second reflecting surface and the third reflecting surface;
The image reading optical apparatus according to claim 1, wherein the image reading optical apparatus is characterized in that:

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