JP2005084624A - Image reading optical device and method for adjusting reflective surface in the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading optical device capable of correcting a difference between a main scanning directional image surface position and a sub scanning directional image surface position by an easy operation and to provide a method for adjusting a reflective surface in the image reading optical device. <P>SOLUTION: The image reading optical device scans the surface of an original in the sub scanning direction X while irradiating the surface of the original one-dimensionally in the main scanning direction Y and allows reflected light from the surface of the original to form an image on a CCD 40 which is a one-dimensional imaging element. The image reading optical device is provided with a reflective optical unit 20 having a plurality of reflective surfaces from first mirror 21 to fourth mirror 24 successively from the original side. At least one of the mirrors 21-24 has the reflected surface whose power is different in the main scanning direction and the sub scanning direction. Further, at least one of the mirrors 21-24 is rotated around an axis parallel to the main scanning direction and the rotation angle is adjusted. Otherwise, preferably at least one of the mirrors 21-24 is moved in parallel to the direction vertical to the main scanning direction and the position is adjusted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading optical device, in particular, an image reading optical device that reads an image of a document placed on a platen glass while scanning in one direction with a one-dimensional image sensor, and a method of adjusting a reflecting surface in the device. About.

  Conventionally, as an image reading optical device of a scanner or a digital copying machine, a document placed on a platen glass is scanned in the sub-scanning direction while irradiating one-dimensionally in the main scanning direction, and its reflected original image Is read by a one-dimensional image sensor in the main scanning direction.

  In this type of image reading optical apparatus, the adjustment of the image plane is disclosed in Patent Document 1. The optical system disclosed in this document 1 is a refractive optical system, and adjusts the tilt of the image plane by rotating the lens around the optical axis, and moves the lens in the optical axis direction to adjust the focus. Configured to adjust.

  However, when free-form surface mirrors having different powers in the main scanning direction and the sub-scanning direction are used in the optical system, the image plane position and the sub-scanning direction in the main scanning direction are caused by a manufacturing error of the surface shape or an arrangement error of each optical element. There is a possibility that the image plane position in the scanning direction may be deviated. This makes it impossible to secure a sufficient depth of focus, which is a practical problem.

In response to the recent demand for miniaturization, correction of chromatic aberration has become important, particularly in a full-color image reading optical apparatus. However, in order to correct chromatic aberration in the refractive optical system, it is necessary to use a special and expensive glass material or to greatly increase the number of refracting surfaces, resulting in an increase in size and cost.
JP 2002-296499 A

  SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide an image reading optical device that can correct the difference between the image plane position in the main scanning direction and the image plane position in the sub-scanning direction with a simple operation and that does not require correction of chromatic aberration. It is to provide.

  In addition to the first object, a second object of the present invention is to provide an image reading optical device having a simple and compact configuration.

  A third object of the present invention is to provide a method of adjusting a reflecting surface that can correct the difference between the image plane position in the main scanning direction and the image plane position in the sub-scanning direction with a simple operation.

  In order to achieve the above object, an image reading optical device according to a first aspect of the present invention is disposed in the main scanning direction with an illuminating unit that scans in the sub-scanning direction while irradiating the original surface one-dimensionally in the main scanning direction. A photoelectric conversion unit including a plurality of photoelectric conversion elements, and a reflection optical unit that forms an image of a document illuminated by the illumination unit and reflected on the document surface on the photoelectric conversion unit, the reflection optical unit comprising: A plurality of reflecting surfaces having at least one reflecting surface having different powers in the main scanning direction and the sub-scanning direction, wherein at least one of the plurality of reflecting surfaces is centered on an axis parallel to the main scanning direction; It is characterized in that it has been adjusted for rotation or adjusted for translation in a direction perpendicular to the main scanning direction.

  In the image reading optical apparatus according to the first invention, by adjusting all or a part of the plurality of reflecting surfaces provided in the reflecting optical unit by rotating around an axis parallel to the main scanning direction, or By adjusting by parallel translation in the direction perpendicular to the main scanning direction, the image plane position in the main scanning direction and the image plane position in the sub-scanning direction change as the height of the light beam hitting the reflecting surface changes. It is possible to correct the difference in image plane position between the main scanning direction and the sub-scanning direction in a reflection system having a curved surface. In addition, the high aberration correction capability of the reflection system can be fully utilized.

  In the image reading optical apparatus according to the first invention, the plurality of reflecting surfaces may be integrally held by a holding portion, and the rotation adjustment or the parallel movement adjustment may be performed on the holding portion. . In this case, the reflective optical unit may have a stop, and the photoelectric conversion unit may be held by the holding unit.

  The plurality of reflecting surfaces are configured to reflect a document image reflected by the document surface so as to be away from the document surface, and a document image reflected by the first mirror substantially parallel to the document surface. A second mirror that reflects in this manner, a third mirror that reflects the original image reflected by the second mirror so that it approaches the original surface, and an original image that is reflected by the third mirror is substantially the same as the original surface. And a fourth mirror that reflects so as to be parallel. Thus, the reflection optical unit can be configured compactly with the minimum number of reflection surfaces, and the photoelectric conversion element need not be arranged eccentrically.

  Further, an axial ray that forms an image at the center of the photoelectric conversion unit through the center of the document in the main scanning direction, and incident light incident on the first mirror and outgoing light emitted from the fourth mirror are It is preferable to lie on a substantially straight line. A flat image reading optical device can be obtained.

  The first, second, third and fourth mirrors may be configured to have power in the main scanning direction and the sub-scanning direction, respectively. In this case, the rotation adjustment or the parallel movement adjustment may be made with respect to the first mirror, or may be made with respect to the second mirror.

  According to a second aspect of the present invention, there is provided a reflecting surface adjustment method comprising: a plurality of reflecting surfaces having at least one reflecting surface having different powers in the main scanning direction and the sub-scanning direction, and an original surface illuminated in the main scanning direction The method of adjusting the reflecting surface in an image reading optical device that forms an image of the original image reflected on the image on a photoelectric conversion unit comprising a plurality of photoelectric conversion elements arranged in the main scanning direction, wherein at least one of the plurality of reflecting surfaces By rotating and adjusting around one axis parallel to the main scanning direction with respect to one reflecting surface, or by adjusting the parallel movement in the direction orthogonal to the main scanning direction, the photoelectric conversion unit in the main scanning direction The image plane position is matched with the image plane position in the sub-scanning direction.

  In the reflecting surface adjustment method according to the second invention, as in the image reading optical apparatus according to the first invention, the main scanning direction image plane position and the sub-scanning direction image plane position in the reflecting system having a free-form surface are also provided. Can be corrected by a simple operation, and the high aberration correction capability of the reflection system can be fully utilized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an image reading optical device according to the present invention and a reflection surface adjusting method in the device 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 photoelectric conversion element.

  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).

  Among the plurality of mirrors, the first mirror 21 reflects the document image (incident light P1) reflected by the document surface so as to be away from the document surface. The second mirror 22 reflects the document image reflected by the first mirror so as to be parallel to the document surface. The third mirror 23 reflects the document image reflected by the second mirror so as to approach the document surface. Further, the fourth mirror 24 reflects the document image reflected by the third mirror so as to be parallel to the document surface (emitted light P3), and forms an image on the CCD 40.

(Refer to the first example of the reflective optical unit, FIG. 2 and FIG. 3)
Here, the reflective optical unit 20A as the first example will be described with reference to FIGS.

  Each of the mirrors 21 to 24 is fixed / held by the light shielding casing 30, and the light shielding casing 30 is fixed on the base plate 35 of the apparatus 10. The base plate 35 is provided with a pair of holding blocks 36, 36. The shading casing 30 has support shafts 33 projecting on both sides thereof fitted into receiving groove portions 36 a of the holding block 36, and an arrow a around the support shaft 33. The installation angle is adjusted by rotating in the direction.

  The support shaft 33 is arranged parallel to the main scanning direction at the surface vertex of the first mirror 21, and the mirrors 21 to 24 are integrated on the axis by adjusting the rotation angle of the light shielding casing 30 around the support shaft 33. The rotational position with respect to the light beam is adjusted.

  Each of the mirrors 21 to 24 has power in the main scanning direction and the sub-scanning direction, respectively, as shown as construction data below, and the light beam that strikes the first mirror 21 by adjusting the rotation angle as described above. Accordingly, the image plane position in the main scanning direction and the image plane position in the sub-scanning direction in the CCD 40 change accordingly, and the difference in image plane position can be corrected. In addition, the high aberration correction capability inherent in the reflection system is fully utilized.

  Further, in the reflective optical unit 20A, since the incident light P1 and the outgoing light P3 are positioned on a straight line, the reflective optical unit 20A can be configured to be flat and compact, and the CCD 40 needs to be arranged eccentrically. Disappears. Further, since the aperture stop 25 is provided between the second mirror 22 and the third mirror 23, it is possible to effectively block the peripheral light.

  The construction data including the free curved surface of the first to fourth mirrors 21 to 24, the original table glass 11, and the CCD 40 are shown in Tables 1, 2 and 3 below. The aspheric coefficients of these free-form surfaces are as shown in the following equations.

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

  FIG. 6 shows a through focus curve of the design value MTF (modulation transfer function) of the construction data shown in Table 1. FIG. 7 shows an MTF through focus curve when there is an error in the mirror surface shape and arrangement. FIG. 8 shows the MTF through focus curve after adjusting the rotation angle of the mirror as described above.

  In the first example, the case where the axis of the support shaft 33 is arranged at the surface vertex of the mirror 21 is shown, but the same effect can be obtained even if it is set at another position.

(Refer to the second example of the reflective optical unit, FIG. 9)
Next, the reflective optical unit 20B as the second example will be described with reference to FIG. The reflection optical unit 20B basically has the same configuration as that of the first example, except that the CCD 40 is held by the light shielding casing 30. As described in the first example, the rotation adjustment is performed around the free-form surface data of each of the mirrors 21 to 24 and the support shaft 33. Therefore, the function and effect are the same as in the first example.

(Refer to the third example of the reflective optical unit, FIG. 10 and FIG. 11)
As shown in FIGS. 10 and 11, the reflective optical unit 20 </ b> C, which is the third example, is fitted with support shafts 37 provided on both end faces of the first mirror 21 in parallel with the main scanning direction in the receiving groove portions 38 a of the holding block 38. The angle is adjusted by rotating in the direction of arrow b around the support shaft 37. The holding block 38 is fixed to a light shielding casing (not shown in FIG. 10).

  The support shaft 37 is arranged in parallel with the main scanning direction at the surface vertex of the first mirror 21, and the rotation angle of the first mirror 21 is adjusted around the support shaft 37. The construction data of each of the mirrors 21 to 24 is as shown in the first example. By adjusting the rotation angle of the first mirror 21, the height of the light beam hitting the first mirror 21 changes, and accordingly the CCD 40 In this case, the image plane position in the main scanning direction and the image plane position in the sub-scanning direction are changed, and the difference in image plane position in any direction can be corrected.

  The other configuration is the same as that of the first example. In FIG. 10, the same components as those in FIG. The CCD 40 may be provided separately from the light shielding casing, or may be held by the light shielding casing.

(Refer to the fourth example of the reflective optical unit, FIG. 12)
Next, a reflective optical unit 20D as a fourth example will be described with reference to FIG. In the reflection optical unit 20D, the angle of the second mirror 22 is adjusted by rotating it in the direction of the arrow c around the support shaft 37 ′, like the first mirror 21 in the third example. The support shaft 37 ′ is arranged in parallel with the main scanning direction at the surface vertex of the second mirror 22, and the rotation angle of the second mirror 22 is adjusted around the support shaft 37 ′.

  The construction data of each of the mirrors 21 to 24 is as shown in the first example. By adjusting the rotation angle of the second mirror 22, the height of the light beam hitting the second mirror 22 changes, and accordingly the CCD 40 In this case, the image plane position in the main scanning direction and the image plane position in the sub-scanning direction are changed, and the difference in image plane position in any direction can be corrected.

  Other configurations are the same as those in the first example, and in FIG. 12, the same components as those in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. The CCD 40 may be provided separately from the light shielding casing, or may be held by the light shielding casing.

(Refer to the fifth example of the reflective optical unit, FIG. 13)
Next, a reflective optical unit 20E as a fifth example will be described with reference to FIG. In the reflective optical unit 20E, the position of the first mirror 21 is adjusted by translating it in the arrow d direction perpendicular to the main scanning direction. This parallel movement adjustment is performed by providing a guide function to a holding member (not shown) that holds both end portions of the first mirror 21 and moving the first mirror 21 in parallel.

  The construction data of each of the mirrors 21 to 24 is as shown in the first example. By adjusting the parallel movement of the first mirror 21, the height of the light beam hitting the first mirror 21 changes. The image plane position in the main scanning direction and the image plane position in the sub-scanning direction respectively change, and the difference in image plane position in any direction can be corrected.

  The other configuration is the same as that of the first example, and in FIG. 13, the same components as those in FIG. The CCD 40 may be provided separately from the light shielding casing, or may be held by the light shielding casing.

(Other examples)
The image reading optical device according to the present invention and the method of adjusting the reflecting surface in the device are not limited to the above-described embodiments, and can be variously changed within the scope of the gist.

  For example, the configuration of the light shielding casing, the holding form of each mirror, the details of the rotation adjustment or parallel movement adjustment mechanism, 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 an elevation view showing a first example of a reflection optical unit incorporated in an image reading optical device according to the present invention. It is a perspective view which shows the rotation adjustment structure of the said 1st example. 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. It is a graph which shows the through focus curve of design value MTF. It is a graph which shows a MTF through focus curve in case a mirror has an error. It is a graph which shows the MTF through focus curve after adjusting a rotation angle. It is an elevational view showing a second example of the reflective optical unit. It is an elevational view showing a third example of the reflective optical unit. It is a perspective view which shows the rotation adjustment structure of the said 3rd example. It is an elevational view showing a fourth example of the reflective optical unit. It is an elevational view showing a fifth example of the reflective optical unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image reading optical apparatus 11 ... Original platen glass 20 (20A-20E) ... Reflective optical unit 21-24 ... Mirror (reflective surface)
25 ... Aperture stop 30 ... Shading casing (holding part)
33, 37, 37 '... support shafts 36, 38 ... holding block 40 ... CCD (photoelectric converter)
Y: Main scanning direction X: Sub scanning direction a, b, c: Rotation adjustment direction d: Parallel movement adjustment direction

Claims (10)

An illumination unit that scans in the sub-scanning direction while irradiating the original surface in a one-dimensional manner in the main scanning direction;
A photoelectric conversion unit comprising a plurality of photoelectric conversion elements arranged in the main scanning direction;
A reflection optical unit that forms on the photoelectric conversion unit a document image illuminated by the illumination unit and reflected by the document surface;
The reflective optical unit includes a plurality of reflecting surfaces having at least one reflecting surface having different powers in the main scanning direction and the sub-scanning direction, and at least one of the plurality of reflecting surfaces is a main scanning direction. It has been adjusted to rotate around a parallel axis, or adjusted to translate in a direction perpendicular to the main scanning direction,
An image reading optical device.   The image reading optical apparatus according to claim 1, wherein the plurality of reflecting surfaces are integrally held by a holding unit, and the rotation adjustment or the parallel movement adjustment is performed on the holding unit.   The reflection optical unit includes a diaphragm, the diaphragm and the plurality of reflection surfaces are integrally held by a holding unit, and the rotation adjustment or the parallel movement adjustment is performed on the holding unit. The image reading optical apparatus according to claim 1.   The image reading optical apparatus according to claim 2, wherein the photoelectric conversion unit is held by the holding unit.   The plurality of reflecting surfaces reflect a document image reflected by the document surface so as to be away from the document surface, and a document image reflected by the first mirror is substantially parallel to the document surface. A second mirror that reflects, a third mirror that reflects the original image reflected by the second mirror so as to approach the original surface, and an original image that is reflected by the third mirror is substantially parallel to the original surface. The image reading optical apparatus according to claim 1, further comprising a fourth mirror that reflects the light.   An axial light beam that forms an image at the center of the photoelectric conversion unit through the center of the document in the main scanning direction, and the incident light incident on the first mirror and the outgoing light emitted from the fourth mirror are almost straight. The image reading optical apparatus according to claim 5, wherein the image reading optical apparatus is located on a line.   6. The image reading optical apparatus according to claim 5, wherein the first, second, third, and fourth mirrors have power in the main scanning direction and the sub-scanning direction, respectively.   The image reading optical apparatus according to claim 7, wherein the rotation adjustment or the parallel movement adjustment is performed on the first mirror.   The image reading optical apparatus according to claim 7, wherein the rotation adjustment or the parallel movement adjustment is performed on the second mirror. A plurality of reflecting surfaces having at least one reflecting surface having different powers in the main scanning direction and the sub-scanning direction are provided, and the document image reflected by the document surface illuminated in the main scanning direction is arranged in the main scanning direction. A method of adjusting the reflecting surface in an image reading optical device that forms an image on a photoelectric conversion unit composed of a plurality of photoelectric conversion elements,
By rotating and adjusting at least one of the plurality of reflecting surfaces around an axis parallel to the main scanning direction, or by adjusting the translation in a direction perpendicular to the main scanning direction, Matching the image plane position in the main scanning direction and the image plane position in the sub-scanning direction at the conversion unit;
Reflective surface adjustment method characterized by the above.

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