JP2011160070A - Method of adjusting image reader, and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image reading apparatus adjustment method and an image reading apparatus capable of obtaining a good image by a short time adjustment method.
SOLUTION: A slit portion for restricting a light beam from an original illuminated by a light source means, a plurality of mirrors for reflecting the light beam that has passed through the slit portion, and an optical element having an optical surface rotationally asymmetric with respect to the optical axis. An image forming optical system that forms an image of a light beam reflected by a plurality of mirrors, and a carriage that holds a reading unit disposed at an image forming position of the image forming optical system is moved relative to the original to thereby read the image information of the original. In the adjustment method of the image reading apparatus for reading the image, an adjustment chart having an evaluation pattern extending in the main scanning direction is placed at a position corresponding to the document table, and based on the geometric characteristics of the image of the adjustment chart imaged on the reading means Adjusting at least two positions of the slit portion, the plurality of mirrors, the imaging optical system, and the reading means, and adjusting image information read by the reading means.
[Selection] Figure 1

Description

  The present invention relates to an adjustment method and an image reading apparatus for an image reading apparatus that illuminates a document surface and reads an image in a line sequential manner. It is particularly suitable for image reading devices such as image scanners, copying machines, and facsimiles.

  A conventional image reading apparatus is a motor for a document placed on a platen glass surface by a carriage in which an illuminating device (light source means), a plurality of reflecting mirrors, an imaging optical system, and reading means are integrally housed. The image information of the document is read by scanning in the sub-scanning direction by a driving mechanism such as the above. The read image information is sent to an external device such as a personal computer through an interface.

  Lighting devices often use LED arrays. However, the lighting device is not limited to the LED array, and a xenon tube, a halogen lamp, or the like may be used. The reading means is composed of a linear sensor such as a CCD (Charge Coupled Device), and has a configuration in which light receiving elements are arranged in a one-dimensional direction (main scanning direction).

  In order to give priority to the imaging performance of a wide area in the main scanning direction in the imaging optical system with a wide angle of view, the area in the main scanning direction has a wide range of high resolution characteristics. It becomes narrower in the area. Also, in the carriage-integrated image reading apparatus, the positional accuracy of each part is maintained high in view of the large number of components and the fact that the carriage is made by resin molding, resulting in large variations in molding accuracy. It becomes difficult.

  To sum up these points, in the carriage-integrated image reading apparatus, when an imaging optical system having a narrow imaging region in the sub-scanning direction is introduced, the following problems occur. For example, in the carriage-integrated image reading apparatus shown in FIG. 17, when the position of each part is correct, the reading optical path follows a locus indicated by a one-dot chain line and reaches (images) on the CCD 177 plane. However, for example, when a positional deviation occurs in the reflection mirror 175c, the reading optical path follows the locus of a two-dot chain line from the reflection mirror surface and reaches the vicinity of the CCD 177. For this reason, the conventional image reading apparatus receives the image information of the original by shifting the CCD 177 in the sub-scanning direction in order to obtain good image information.

  However, when a rotationally asymmetric refracting surface or reflecting surface is used as the imaging optical system, if the shift adjustment as described above is performed, the CCD 177 deviates from the imaging region in the sub-scanning direction of the imaging optical system 176, which is good. There arises a problem that image information cannot be obtained.

  Conventionally, an adjustment chart that can evaluate the resolving power in the sub-scanning direction is placed on the platen glass, and the relative positional relationship in the sub-scanning direction of the slit, imaging optical system, and reading means is aligned. It is adjusted by adjusting means. Various methods for adjusting an image reading apparatus using an adjustment chart have been proposed. (See Patent Document 1).

  Further, a rotationally asymmetric optical surface has a problem that distortion in the sub-scanning direction due to a manufacturing error is more likely to occur than a rotationally symmetric optical surface. Recently, even in non-coaxial optical systems, a compact imaging optical system in which aberrations are corrected has been constructed by introducing the concept of a reference axis and making the constituent surface an asymmetric aspherical surface.

  These non-coaxial optical systems include off-axial optical systems (including curved surfaces that set a reference axis along a ray passing through the image center and the pupil center and whose surface normal at the intersection with the reference axis of the component surface is not on the reference axis. In the optical system defined as an optical system, the reference axis has a bent shape). In this off-axial optical system, the constituent surface is generally non-coaxial, and no vignetting occurs even on the reflecting surface. Therefore, an optical system using the reflecting surface is easy to configure. In general, the reflective optical system does not generate chromatic aberration, so that problems such as axial chromatic aberration and lateral chromatic aberration do not occur.

  On the other hand, if there is a manufacturing error or position error on the component surface in an off-axial optical system, the focal position shift of the image plane in the main scanning direction (main scanning section) and the focal position shift of the image plane in the sub scanning direction (sub scanning section). In this case, distortion occurs and magnification shift occurs. These cause a problem of bending of the reading line. In particular, there is a problem that distortion in the sub-scanning direction is very likely to occur as compared with a configuration including a rotationally symmetric coaxial lens system.

  Hereinafter, a deviation in the sub-scanning direction due to a magnification deviation in the reading result of the CCD 177 is defined as “sub-scanning magnification deviation”, and a deviation in the main scanning direction is defined as a “main scanning magnification deviation”. Further, in any line sensor, the deviation of the reading result in the sub-scanning direction on and off the axis is defined as “scanning line bending”.

JP 2005-101739 A

  The adjustment method of the image reading apparatus disclosed in Patent Document 1 described above tends to take a lot of time for adjustment. In the adjustment method of the image reading apparatus disclosed in Patent Document 1, the signal output from the CCD is displayed on the screen of the adjustment tool, and the relative position of the CCD in the sub-scanning direction so that the resolution performance is good based on the display result. Adjust the relationship. In order to obtain a positional relationship that provides better resolution performance, the CCD is adjusted in the sub-scanning direction while monitoring the display result of the screen.

  FIG. 18 is a conceptual diagram of a conventional image reading apparatus adjustment method. Regarding the sub-scan movement of the CCD, the direction approaching the document surface from a predetermined CCD position is defined as plus, and the direction moving away from the document surface is defined as minus. The position of the CCD in the sub-scanning direction is shifted from the inflection point e1 to the point e2 by the reflection mirror being displaced from a predetermined position. In order to obtain good resolution performance, the point e2 is moved in the positive or negative direction in the sub-scanning direction. If the resolution increases, the CCD moves in the same direction, and if it decreases, the CCD moves in the opposite direction. Then, to determine the position where good resolution is obtained, the CCD is moved as long as the resolution continues to increase. Then, when a position (e1) in a certain sub-scanning direction moves to a point e3 as a boundary, the resolving power starts to decrease. This inflection point e1 is a CCD position where a good resolving power can be obtained. In order to obtain the inflection point e1, it is necessary to drive the CCD position while monitoring the display result. As a result, the adjustment takes a lot of time.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus adjustment method and an image reading apparatus capable of obtaining a good image with a short time adjustment method.

  The adjustment method of the image reading apparatus according to the present invention includes: a light source unit that illuminates a document placed on a document table; a slit unit that restricts passage of a light beam from the document illuminated by the light source unit; Imaging optics that includes a plurality of mirrors that reflect the light flux that has passed and an optical element having an optical surface that is rotationally asymmetric with respect to the optical axis, and that forms image information of the original from the light flux reflected by the plurality of mirrors In an adjustment method of an image reading apparatus for reading image information of the original by moving a carriage holding a reading unit disposed at an image forming position of the system and the imaging optical system relative to the original, An adjustment chart in which an evaluation pattern extends in the main scanning direction is placed at a corresponding position on the table, and the slit portion and the complex are formed based on the geometric characteristics of the image of the adjustment chart imaged on the reading means. Mirrors, the imaging optical system, and of the reading means, it is characterized in that adjusting at least two positions to adjust the image information read by the reading means.

  ADVANTAGE OF THE INVENTION According to this invention, the adjustment method and image reading apparatus of an image reading apparatus which can obtain a favorable image with a short time adjustment method can be achieved.

(A) The figure which shows the outline | summary of Example 1 of this invention, (B) The figure which shows the outline | summary of the position shift of a reflective mirror. Enlarged view around the slit Illustration of evaluation pattern (A) The figure which shows the evaluation pattern (reflective mirror predetermined position) by the sub-scan magnification deviation by this invention, (B) The figure which shows the evaluation pattern (reflection mirror position deviation) by the sub-scan magnification deviation by this invention Mirror sectional view of Example 1 Graph of sub-scanning angle of view and R-G and B-G intervals Graph of sub-scanning magnification deviation and CCD deviation from a specified position (A) The figure which shows the outline | summary of Example 2 of this invention (rotationally asymmetrical reflective surface), (B) Mirror sectional drawing of Example 2 of this invention (A) The figure which shows the outline | summary of Example 2 of this invention (rotationally asymmetrical refracting surface), (B) Lens sectional drawing of Example 2 of this invention (A) The figure which shows the evaluation pattern (reflecting mirror predetermined position) by the scanning line bending by Example 2 of this invention, (B) The evaluation pattern (reflection mirror position shift) by the scanning line bending by Example 2 of this invention is shown. Figure Graph of scanning line bending amount and CCD deviation amount from predetermined position of Example 2 of the present invention Graph of scanning line bending of Example 2 of the present invention Graph of scanning line bending of Example 2 of the present invention Graph of scanning line bending amount and CCD deviation amount from predetermined position of Example 2 of the present invention Graph of scanning line bending of Example 2 of the present invention Graph of scanning line bending of Example 2 of the present invention The figure which shows the adjustment method of the conventional image reading apparatus Graph of adjustment method of conventional image reading apparatus

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The imaging optical system (imaging means) of the present invention uses an off-axial optical system. For this reason, in order to clarify the configuration and numerical values of the embodiments of the imaging optical system, the off-axial optical system used in this specification and the reference axis that forms the framework thereof are defined as follows.

[Definition of reference axis]
In general, an optical path of a light beam having a reference wavelength that is a reference from an object to an image plane is defined as a reference axis in the optical system. This alone leaves ambiguity in how to select a reference ray, so that the reference ray, ie the reference axis, is usually set according to one of the following two principles.

  In the case where an axis having symmetry is present even partially in the optical system, and aberrations can be collected with good symmetry, a light beam passing through the symmetry axis is set as a reference light beam. In general, aberrations cannot be collected with good symmetry when there is no symmetry axis in the optical system, or even if there is a partial symmetry axis. At that time, out of the rays from the center of the object plane (the center of the object to be photographed and the observation range), the rays that pass through the optical system in the order of the specified surface of the optical system and pass through the aperture center defined in the optical system are used as a reference. Set as a ray. The distance between the members along the reference beam is referred to as the distance (length) of the reference beam axis.

  The reference axis defined in this way is generally a bent shape. A curved surface whose surface normal does not coincide with the reference axis at a point where the reference axis defined as described above intersects with the curved surface is defined as an off-axial curved surface, and an optical system including the off-axial curved surface is defined as an off-axial optical system. (However, even if the reference axis is simply bent by the plane reflecting surface, the surface normal does not coincide with the reference axis, but the plane reflecting surface does not impair the symmetry of the aberration, so it is excluded from the off-axial optical system. To do.)

  In the embodiments of the present invention, the reference axis serving as the reference of the optical system is set as described above. However, the method of determining the axis serving as the reference of the optical system is based on the optical design, the arrangement of aberrations, or the optical system. An axis convenient for expressing each surface shape may be employed.

  However, in general, the path of the light beam passing through the center of the image plane or the observation plane, the stop, the entrance pupil or the exit pupil, or the center of the first surface or the center of the final surface of the optical system is used as the reference of the optical system. Is set as the reference axis. The order of each surface is set so that the reference axis rays are reflected. Accordingly, the reference axis finally reaches the center of the image plane while changing its direction in accordance with the law of reflection along the set order of each surface.

  All of the tilt surfaces constituting the optical system of each embodiment of the present invention are basically tilted within the same plane. Therefore, each axis of the absolute coordinate system is determined as follows.

Z-axis: Reference axis passing through the origin toward the first surface Y-axis: Straight line passing through the origin and forming 90 ° counterclockwise with respect to the Z-axis in the tilt plane X-axis: passing through the origin and perpendicular to the Z and Y axes In addition, in order to represent the surface shape of the i-th surface constituting the optical system, the local coordinates with the origin at the point where the reference axis and the i-th surface intersect are represented by the shape of the surface in the absolute coordinate system. Setting the system and expressing the surface shape of the surface in the local coordinate system is easier to understand when recognizing the shape. Therefore, in the embodiment displaying the configuration data of the present invention, the surface shape of the i-th surface is expressed in the local coordinate system.

  Further, the tilt angle of the i-th surface in the YZ plane is represented by an angle θi (unit: °) with the counterclockwise direction being positive with respect to the Z axis of the absolute coordinate system. Therefore, in each embodiment of the present invention, the origin of the local coordinates of each surface is on the YZ plane. There is no surface eccentricity in the XZ and XY planes. Further, the y and z axes of the local coordinates (x, y, z) of the i-th surface are also inclined by the angle θi in the YZ plane with respect to the absolute coordinate system (X, Y, Z). Set as follows.

z-axis: A straight line that passes through the origin of the local coordinate and forms an angle θi in the counterclockwise direction in the YZ plane with respect to the Z-axis direction of the absolute coordinate system. y-axis: A straight line that passes through the origin of the local coordinate and passes through the origin of the local coordinate. A straight line that forms 90 ° in the counterclockwise direction in the x axis: a straight line that passes through the origin of the local coordinate system and is perpendicular to the YZ plane. The imaging optical element in the embodiment of the present invention has a rotationally asymmetric aspherical surface. The shape is shown by the following equation.

  The spherical surface has a shape represented by the following formula.

Since the curved surface formula is only an even-order term with respect to x, the curved surface defined by the curved surface formula is a plane-symmetric shape with the yz plane as the symmetry plane. It is difficult to directly calculate the focal length based on paraxial theory. Therefore, the converted focal length f _eq according to the following definition is used.

By definition, when there are an odd number of reflecting surfaces, the sign of the focal length is expressed opposite to the normal sign. Where h _{1 is} the incident height a _k ′ of the light beam incident on the first surface parallel to the reference axis and infinitely incident on the reference axis, and is the angle that the light beam makes with the reference axis when exiting from the final surface. Also, in the numerical examples, Di is a scalar quantity representing the distance between the origins of the local coordinates between the i-th surface and the (i + 1) -th surface, and Ndi is the medium between the i-th surface and the (i + 1) -th surface. Refractive index.

[Example 1]
FIG. 1A is a main part schematic diagram illustrating the adjustment method of the image reading apparatus according to the first embodiment of the present invention. FIG. 1B is a main part schematic diagram illustrating an outline of positional deviation of the reflecting mirror according to the first embodiment of the present invention.

  In the figure, reference numeral 12 denotes an original table (original table glass), and an adjustment chart 11 having a positional deviation detection pattern is placed at a corresponding position of the original table 12. As shown in FIG. 3 to be described later, the adjustment chart 11 is formed by extending an evaluation pattern (image evaluation pattern) 31 in the main scanning direction. Reference numeral 18 denotes a carriage, which includes an illumination device 13, a slit portion 14, a plurality of reflection mirrors 15a, 15b, 15c, and 15d, and an imaging means 16 as an imaging optical system. Further, the carriage 18 holds a one-dimensional photoelectric conversion element (CCD) 17 as reading means, and is moved relative to the original by a driving device (not shown) such as a sub-scanning motor to read the image information of the original. Yes.

  The illumination device 13 has light source means such as a xenon tube, a halogen lamp, and an LED array. The slit part 14 restricts the passage of the light beam (light beam width) from the adjustment chart 11. The first, second, third, and fourth reflecting mirrors 15a, 15b, 15c, and 15d bend the optical path of the light beam from the adjustment chart 11 inside the carriage 18. The imaging optical system 16 includes an optical element (off-axial optical element) having an optical surface rotationally asymmetric with respect to the optical axis, and reads image information of a document from a light beam reflected by a plurality of mirrors (CCD) 17 surface The image is formed on the top. The reading means (CCD) 17 has at least three line sensors (one-dimensional photoelectric conversion elements), and is arranged at the imaging position of the imaging optical system 16. Reference numeral 19 denotes a CCD adjustment device as adjustment means, which is attached to the CCD 17 and adjusts the position of the CCD 17 in the sub-scanning direction.

  Reference numeral 10 denotes a mirror adjusting device as an alignment adjusting means, which is attached to the fourth reflecting mirror 15d, and adjusts the angle of the fourth reflecting mirror 15d in the sub-scanning direction.

  In this embodiment, by adjusting the angle of the fourth reflecting mirror 15d in the sub-scanning direction, the relative positional relationship of the slit portion 14, the imaging optical system 16, and the CCD 17 in the sub-scanning direction is adjusted. .

  FIG. 2 is an enlarged explanatory view around the slit portion shown in FIGS. In the figure, L is the opening width of the slit portion 14 in the sub-scanning direction, and M is the center line. Here, an area having a width L / 2 including the center line M as a center is defined as a “slit center”.

  A light beam based on the image of the adjustment chart 11 illuminated with the light beam emitted from the illumination device 13 passes through the center of the slit, and passes through the first, second, third, and fourth reflecting mirrors 15a, 15b, 15c, and 15d. The imaging optical system 16 forms an image on the CCD 17 surface. At this time, when each of the reflecting mirrors 15a, 15b, 15c, and 15d is attached at a predetermined position, the reading optical path indicated by the alternate long and short dash line in FIG. However, if the mounting position of the third reflecting mirror 15c is deviated as indicated by a dotted line, for example, the light beam forms an image on the CCD 17 indicated by the dotted line with an angle of view in the sub-scanning direction as compared with the one-dot chain line.

  Here, an adjustment method of the image reading apparatus of the present embodiment will be described. The adjustment method is carried out by placing an adjustment chart in which an evaluation pattern extends in the main scanning direction at a corresponding position on the document table, and making adjustments based on the geometric characteristics of the adjustment chart image formed on the reading means. Go. Here, the geometric characteristic is a magnification shift of the image reading apparatus.

  FIG. 3 is an explanatory diagram of an adjustment chart having an evaluation pattern. In FIG. 3, a vertical line 31a with respect to the main scanning direction is a pattern for detecting (evaluating) a magnification deviation (main scanning magnification deviation) in the main scanning direction, and a diagonal line 31b and a vertical line 31a are magnification deviations in the sub-scanning direction. This is a pattern for detecting (evaluating) (sub-scanning magnification deviation). The angle at which the oblique line 31b and the vertical line 31a intersect is defined as θ.

  The adjustment chart 11 of the present embodiment has an evaluation pattern 31 having a shape having two or two sides intersecting at different angles with respect to the main scanning direction, and one or one side is the extending direction of the line sensor. It is sufficient if it is orthogonal to.

  FIG. 4A is an explanatory diagram showing the position of the center of gravity of the image of the adjustment chart formed on the CCD 17 when the reflecting mirrors 15a, 15b, 15c, and 15d are attached at predetermined positions (as designed values). is there. The CCD 17 is a line sensor that reads R (red), G (green), and B (blue) colors. a is the pixel length, and is obtained by a = b / tan θ. b is the distance between the line sensors B (blue), G (green), and R (red).

  FIG. 4B is an explanatory diagram showing a state where the mounting position of the third reflecting mirror 15c is shifted as indicated by a dotted line. In the figure, the parameters a, b, c, d, e, and f are indicated by absolute values. c is a parameter for evaluating the main scanning magnification deviation between R and G, and e is a parameter for evaluating the sub scanning magnification deviation between R and G. The sub scanning magnification deviation between R and G = e− (c + a) is obtained. If e− (c + a)> 0, it is a positive sub-scanning magnification deviation amount, and if e− (c + a) <0, it is a negative sub-scanning magnification deviation amount. d is a parameter for evaluating the main scanning magnification deviation between B and G, and f is a parameter for evaluating the sub scanning magnification deviation between B and G. The sub scanning magnification deviation between B and G is calculated as f− (d + a). If f− (d + a) <0, it is a positive sub-scanning magnification deviation amount, and if f− (d + a)> 0, it is a negative sub-scanning magnification deviation amount.

  The CCD 17 is adjusted toward the position of the solid line (position in the sub-scanning direction) shown in FIG. 1B based on the amount and sign of the sub-scanning magnification deviation between R-G and B-G. Thereafter, the mirror adjustment device 10 adjusts the angle of the fourth reflecting mirror 15d in the sub-scanning direction so that the light beam passes through the center of the slit portion 14. By repeating the same operation, a good image can be obtained.

  As described above, in this embodiment, the image information read by the reading unit 17 is adjusted by using the step of adjusting at least two members 17 and 15d.

  Alternatively, the adjustment amount of the CCD 17 may be calculated from the sub-scanning magnification shift amount, and the CCD 17 may be moved to a predetermined position in the sub-scanning direction at a time. Thereafter, the same effect can be obtained by adjusting the angle in the sub-scanning direction of the fourth reflecting mirror 15d by the mirror adjusting device 10 so that the light beam passes through the center of the slit portion 14.

  In this embodiment, the step of adjusting the angle of the fourth reflecting mirror 15d in the sub-scanning direction is adjusted by the mirror adjusting device 10, but the present invention is not limited to this, and other reflecting mirrors may be used. Further, in this embodiment, in addition to the adjustment method described above, the angle in the sub-scanning direction of the imaging optical system 16 is adjusted based on the geometric characteristics of the image of the adjustment chart, and thereafter, among the plurality of mirrors You may make it adjust the angle of the subscanning direction of at least 1 mirror.

  Alternatively, the position of the reading unit 16 in the sub-scanning direction may be adjusted based on the geometric characteristics of the image on the adjustment chart, and then the position of the slit portion 14 in the sub-scanning direction may be adjusted. The imaging optical system is not limited to a rotationally asymmetric reflecting surface, and the same effect can be obtained even with a rotationally asymmetric refracting surface.

[Numerical Example 1]
Next, Numerical Example 1 of Example 1 of the present invention is shown below. In the following numerical examples, “E−x” indicates “10 ^−x ”.

Document scanning width = 305.0
Imaging magnification = -0.22
Document side NA = 0.02006
feq = 52.229
[Table 1]
I Yi Zi θi Di Ndi
1 0 0 0 175.3261 1 Object surface
2 0 176.6883 18.5 -13.695 1 Reflecting surface
3 -8.24187 165.7509 61.4113 16.5011 1 Reflecting surface
4 8.215416 166.953 85.8226 16.0017 1 Aperture
5 24.17465 168.1186 62.8366 -14.3288 1 Reflecting surface
6 14.9929 157.1182 22.4254 28.7538 1 Reflecting surface
7 17.43258 185.0038 5 1 Image plane

Aspherical shape
R1 surface
C20: -1.14E-03 C02: -1.32E-03 C21: -5.70E-05
C03: 2.67E-06 C40: -1.10E-07 C22: 1.61E-06
C04: 3.35E-06 C41: 2.31E-08 C23: -7.19E-08
C05: 5.32E-08 C60: 4.85E-11 C42: -9.62E-10
C24: 2.15E-09 C06: -1.33E-08 C61: -8.21E-12
C43: 4.69E-11 C25: 1.20E-10 C07: -2.60E-09
C80: -2.42E-15 C62: 5.17E-13 C44: -6.70E-12
C26: 5.90E-11 C08: -2.50E-10

R2 surface
C20: 1.23E-03 C02: 2.38E-03 C21: -7.38E-05
C03: -2.86E-06 C40: -8.06E-07 C22: -1.60E-07
C04: 3.65E-06 C41: 4.01E-08 C23: -2.67E-08
C05: 9.99E-08 C60: 7.73E-10 C42: 2.00E-09
C24: 2.16E-09 C06: -2.00E-08 C61: -2.51E-11
C43: 1.27E-10 C25: -2.01E-10 C07: -3.57E-09
C80: -3.85E-13 C62: -1.56E-12 C44: -1.30E-11
C26: 1.00E-10 C08: -1.87E-10

R3 surface
C20: -2.61E-03 C02: 5.41E-03 C21: -1.61E-05
C03: 5.33E-06 C40: -1.53E-06 C22: -6.12E-06
C04: 3.88E-06 C41: -1.40E-07 C23: -3.33E-07
C05: 6.94E-07 C60: 1.58E-09 C42: 3.13E-09
C24: 6.00E-09 C06: 2.00E-07 C61: 4.91E-11
C43: -1.49E-10 C25: -9.24E-09 C07: -5.45E-08
C80: -9.24E-13 C62: -4.10E-12 C44: -1.98E-12
C26: -1.42E-09 C08: -6.02E-09

R4 surface
C20: 4.88E-03 C02: 1.00E-02 C21: -1.37E-05
C03: -1.20E-05 C40: -1.32E-06 C22: -2.08E-06
C04: 8.00E-07 C41: -8.69E-08 C23: -2.73E-07
C05: 1.26E-07 C60: -4.19E-10 C42: -7.07E-09
C24: -1.43E-08 C06: 1.43E-07 C61: -6.82E-11
C43: -4.42E-10 C25: 2.06E-09 C07: -1.30E-08
C80: 1.24E-13 C62: -5.13E-12 C44: 2.69E-11
C26: -1.33E-10 C08: -9.38E-10

In this embodiment, the imaging optical system 16 shown in FIG. 1A has four off-axial optical elements R1, R2, R3, and R4 each having a reflecting surface.

  FIG. 5 is a cross-sectional view of the main part of the imaging optical system 16 having these four off-axial optical elements (reflection mirrors) R1, R2, R3, and R4. In FIG. 5, the left side is the enlargement side and the document surface P side (the side where the read image is provided), and the right side is the reduction side and the side where the CCD (one-dimensional photoelectric conversion element) Q is provided. .

  The imaging optical system 16 includes an off-axial optical element R1, an off-axial optical element R2, an aperture S, an off-axial optical element R3, and an off-axial optical element R4 in order from the document surface P side. The image information on the document surface P is formed on the surface. P is a document (document surface) as an object, on which image information for reading is formed. Q is an image plane on which photoelectric conversion elements (CDD17) in which pixels are arranged in a one-dimensional direction are arranged. The image reading imaging optical system 16 reduces and forms image information on the document surface P on the one-dimensional photoelectric conversion element Q, and the one-dimensional photoelectric conversion element Q reads the image information.

  As shown in FIG. 1A, the CCD 17 is arranged perpendicular to the document surface, and the three line sensors are arranged in the order of R, G, and B from the top in the drawing. Regarding the sub-scanning movement of the CCD 17, the upper direction in the figure from the predetermined CCD 17 position is defined as positive, and the lower direction in the figure from the document surface is defined as negative.

  FIG. 6 is an explanatory diagram showing the relationship between the sub-scanning field angle and the sub-scanning magnification deviation amount in the axial light beam. When the reflecting mirror 15c is arranged at a predetermined position (design value position), the R-G 6a is 8.0 pixels and the B-G 6b is -8.0 pixels. When the reflection mirror 15c is displaced from a predetermined position, an angle of view is added in the sub-scanning direction. When the sub-scanning field angle is −1.6 °, the RG interval 6c is 8.3 pixels, and the BG interval 6d is −8.3 pixels. At this time, the sub-scan magnification displacement amount between RG is 0.3 pixels and the BG sub-scan magnification displacement amount is −0.3 pixels. .

  FIG. 7 is an explanatory diagram showing the relationship between the amount of sub-scanning magnification deviation between RG and BG in the axial light beam and the positional deviation of the CCD. When the reflection mirror 15c is displaced from a predetermined position, the sub-scan magnification displacement amount between R and G is 0.2 pixels, or the BG sub-scan magnification displacement amount is -0.2 pixels. At this time, the CCD 17 is displaced from the predetermined position by about 0.8 mm toward the document surface as indicated by 7a and 7b in the figure. Therefore, the CCD 17 can be adjusted by moving about 0.8 mm away from the original surface.

  When the reflection mirror 15c is displaced from a predetermined position, the amount of R-G sub-scan magnification displacement is -0.1 pixel, or the amount of B-G sub-scan magnification displacement is 0.1 pixel. At that time, the CCD 17 is displaced by about 0.4 mm from the predetermined position in the direction away from the original surface as indicated by 7c and 7d in the figure. Therefore, the CCD 17 can be adjusted by moving about 0.4 mm toward the document surface. Thereafter, the sub-scanning angle of the reflecting mirror is adjusted by the mirror adjusting device 10.

  As described above, a good image can be obtained in a short time by adjusting based on the sub-scanning color shift amount and the sign.

  As described above, the adjustment method in this embodiment is adjusted as follows based on the geometric characteristics of the image of the adjustment chart 11 formed on the CCD 17 as described above. In other words, in this embodiment, any two of the slit portion 14, the plurality of mirrors 15a, 15b, 15c, 15d, the image forming means 16, and the CCD 17 are adjusted by the adjusting means, so that the adjusting method can be performed in a short time. A good image is obtained. This achieves a high-quality image reading apparatus.

[Example 2]
FIG. 8A and FIG. 9A are schematic views showing the main part of the adjustment method of the image reading apparatus according to the second embodiment of the present invention. FIG. 8A shows a case where a rotationally asymmetric reflecting surface is used in the imaging optical system. FIG. 9A is a schematic diagram when a rotationally asymmetric refracting surface is used in the imaging optical system. In FIG. 8A and FIG. 9A, the same elements as those shown in FIG. Are given the same number.

  This embodiment differs from the first embodiment described above in that the adjustment chart 11 is composed of at least three evaluation patterns and the scanning line bending of the image reading apparatus is detected. Other configurations and optical actions are the same as those in the first embodiment, and the same effects are obtained.

  In other words, the adjustment chart 11 in this embodiment has at least three evaluation patterns in the main scanning direction having two or two sides that intersect at different angles with respect to the main scanning direction. From the obtained image information, the scanning line bending of the image reading apparatus is detected.

  Here, an adjustment method of the image reading apparatus of the present embodiment will be described. The adjustment method is carried out by placing an adjustment chart in which an evaluation pattern extends in the main scanning direction at a corresponding position on the document table, and making adjustments based on the geometric characteristics of the adjustment chart image formed on the reading means. Go. Here, the geometric characteristic refers to scanning line bending of the image reading apparatus.

  FIG. 10A is a diagram showing the position of the center of gravity of the image of the adjustment chart 11 in the main scanning direction formed on the line sensor when the reflecting mirrors 15a, 15b, 15c, and 15d are attached at predetermined positions. is there. When the three points of the axial light beam, the main scanning field angle (α), and the main scanning field angle (−α) are evaluated, the scanning lines are not bent because the intervals L formed on the CCD 17 coincide with each other. FIG. 10B is a diagram showing the position of the center of gravity of the image of the adjustment chart 11 in the main scanning direction formed on the line sensor when the attachment position of the third reflecting mirror 15c is shifted as indicated by the dotted line. H1 and H3 in FIG. 10B each indicate the amount of scanning line bending.

  The scanning line bending amount H1 of the main scanning field angle -α is obtained by H1 = (L−X1) × tan θ. Further, the scanning line bending amount H3 of the main scanning angle of view α is obtained by H3 = (L−X3) × tan θ. Based on the scanning line bending amounts H1 and H3 and the sign, the CCD 17 is adjusted toward the position of the solid line (position in the sub-scanning direction) shown in FIG. Thereafter, the mirror adjustment device 10 adjusts the angle of the fourth reflecting mirror 15d in the sub-scanning direction so that the light beam passes through the center of the slit portion 14. By repeating the same operation, a good image can be obtained.

  Alternatively, the adjustment amount of the CCD 17 is calculated from the scanning line bending amounts H1 and H3, and the CCD 17 is moved to a predetermined position at a time. Thereafter, the same effect can be obtained by adjusting the angle in the sub-scanning direction of the fourth reflecting mirror 15d by the mirror adjusting device 10 so that the light beam passes through the center of the slit portion 14.

  Next, Numerical Examples 2 and 3 in Embodiment 2 of the present invention will be shown. Numerical Example 2 is an imaging optical system using a rotationally asymmetric reflecting surface. Numerical Example 3 is an imaging optical system using a rotationally asymmetric refracting surface.

[Numerical Example 2]
Document scanning width = 305.0
Imaging magnification = -0.11
Document side NA = 0.00897
feq = 32.474
[Table 2]
I Yi Zi θi Di Ndi
1 0 0 0 301.1807 1 Object surface
2 0 301.1807 18.8 -17.0112 1 Reflecting surface
3 -10.3793 287.7029 37.6 -10.8365 1 Aperture
4 -16.9912 279.1173 19.22076 20.9715 1 Reflecting surface
5 -16.9535 281.6817 0.841515 1 Image plane

Aspherical shape
R1 surface
C20: -4.41E-03 C02: -3.95E-03 C21: 7.24E-05
C03: 2.48E-05 C40: 1.70E-06 C22: -1.44E-06
C04: -1.08E-07 C41: -7.67E-08 C60: -1.90E-09
C42: -2.74E-09 C24: -4.47E-09 C61: 8.54E-11
C43: -1.12E-10 C80: 2.05E-12 C62: 2.15E-11
C44: 3.97E-10 C64: -1.84E-12

R2 surface
C20: 6.95E-03 C02: 6.25E-03 C21: 1.71E-04
C03: 8.86E-06 C40: -4.56E-06 C22: 1.74E-05
C04: -3.08E-06 C41: -2.23E-07 C60: 1.11E-08
C42: -1.14E-08 C24: 5.27E-08 C61: 4.52E-10
C43: 4.69E-09 C80: -1.89E-11 C62: -2.06E-10
C44: 9.41E-09 C64: -8.90E-11

In this embodiment, the imaging optical system 16 shown in FIG. 8A has two off-axial optical elements R1 and R2 each having a reflecting surface. FIG. 8B is a cross-sectional view of the main part of the imaging optical system 16 having these two off-axial optical elements (reflection mirrors) R1 and R2. In FIG. 8B, on the drawing, the left side is the enlargement side and the document surface P side (the side where the read image is provided), and the right side is the reduction side and the CCD (one-dimensional photoelectric conversion element) Q is provided. On the side.

  The imaging optical system 16 has an off-axial optical element R1, an aperture S, and an off-axial optical element R2 in order from the document surface P side, and image information on the document surface is received on the light receiving surface of the one-dimensional photoelectric conversion element. An image is formed. P is a document (document surface) as an object, on which image information for reading is formed. Q is an image plane, and photoelectric conversion elements (CDD) Q in which pixels are arranged in a one-dimensional direction are arranged. The image reading imaging optical system 16 reduces and forms image information on the document surface P on the one-dimensional photoelectric conversion element Q, and the one-dimensional photoelectric conversion element Q reads the image information.

  FIG. 11 is an explanatory diagram showing the relationship between the scanning line bending amount and the CCD position deviation at a field angle of ± 76.2 mm in the main scanning direction. When the reflection mirror 15c was displaced from a predetermined position, the scanning line curve was displaced by 0.011 pixel at the end of the main scanning direction ± 76.2 mm.

  FIG. 12 is an explanatory diagram showing the relationship between the main scanning direction and the scanning line curve. When the angle of view is increased in the main scanning direction from the axial light beam, the scanning line is bent, and at the edge of ± 76.2 mm in the main scanning direction, the scanning line is shifted by 0.011 pixel as shown by 12a and 12b in FIG. It becomes. At that time, the CCD 17 is displaced by about 0.44 mm from the predetermined position in the direction away from the original surface as indicated by 11a in FIG. Therefore, the CCD 17 can be adjusted by moving it about 0.44 mm in the direction approaching the document surface. When the reflection mirror 15c was displaced from a predetermined position, the scanning line curve was displaced by -0.001 pixel at the end of the main scanning direction ± 76.2 mm.

  FIG. 13 is an explanatory diagram showing the relationship between the main scanning direction and the scanning line bending. When the angle of view is increased from the axial light beam in the main scanning direction, the scanning line is bent, and at the end portion of ± 76.2 mm in the main scanning direction, the position of the scanning line is -0.001 pixel as shown by 13a and 13b in FIG. Misaligned. At this time, the CCD 17 is displaced from the predetermined position by about 0.33 mm toward the document surface side as indicated by 11b in FIG. Therefore, the CCD 17 can be adjusted by moving it about 0.33 mm away from the original surface. Thereafter, the mirror adjusting device 10 adjusts the angle of the reflecting mirror 15d in the sub-scanning direction.

  As described above, a good image can be obtained in a short time by adjusting based on the scanning line bending amount and the sign.

[Numerical Example 3]
In Table 3, f is the focal length of the image reading lens LG, Fno is the F number, m is the magnification, Y is the maximum image height, and ω is the half angle of view. In the image reading lens LG, the surface number i indicates the order of the surfaces from the document surface P side, Ri is the radius of curvature of each surface, Di is the member thickness between the i-th surface and the i + 1-th surface. Thickness or air spacing, Ndi and νdi indicate the refractive index and Abbe number of the material based on the d-line, respectively.

  The shape of the anamorphic surface is an aspherical shape described below using the coefficients shown in Table 4 of the numerical examples. The aspherical shape having a refractive power that is rotationally asymmetric with respect to the optical axis has the intersection point between the lens surface and the optical axis as the origin, the optical axis direction is the x axis, and the axis orthogonal to the optical axis in the main scanning section is the y axis. When the axis perpendicular to the optical axis in the sub-scan section is the z-axis, the generatrix shape X is

However, R is a radius of curvature k _y , B ₄ , B ₆ , B ₈ , B ₁₀ is expressed by an aspheric coefficient.

  The child wire shape S has a cross section on a plane perpendicular to the bus bar on the bus bar,

However, r ₀ is the radius of curvature in the sub-scanning direction on the optical axis (sub-wire curvature radius), and R = r ₀
D ₂ , D ₄ , D ₆ , D ₈ , D ₁₀ , E ₂ , E ₄ , E ₆ , E ₈ , and E ₁₀ are expressed by an expression that is an aspheric coefficient.

[Table 3]
f = 32.9, Fno = 6.5, m = 0.189, Y = 108, ω = 27.5

Surface number RD Nd νd
C1 C1 ∞ 3.000 1.516 64.140
C2 ∞
G1 1 10.798 3.367 1.697 55.530
2 22.980 1.140
S 3 ∞ (Aperture) 0.417
G2 4 -33.062 0.844 1.689 31.070
5 12.104 0.406
G3 6 21.425 4.755 1.786 44.200
7 -21.425 3.600
G4
(Anamo) 8 * -13.051 1.855 1.530 55.800
9 * -15.217
C2 C1 ∞ 0.700 1.516 64.140
C2 ∞

[Table 4]
8 sides 9 sides
R -1.305E + 01 -1.522E + 01
ky -6.556E + 00 -3.950E + 00
B4 -3.964E-04 -1.469E-04
B6 1.011E-06 -1.644E-06
B8 -6.217E-08 3.185E-09
B10 7.351E-10 -3.429E-11
Kz -6.556E + 00 -3.950E + 00
D4 -3.964E-04 -1.469E-04
D6 1.011E-06 -1.644E-06
D8 -6.217E-08 3.185E-09
D10 7.351E-10 -3.429E-11
r -1.305E + 01 -1.522E + 01
E2 4.790E-03 6.799E-03
E4 -6.606E-04 -4.661E-04
E6 1.638E-05 6.402E-06
E8 -3.672E-07 -1.093E-07
E10 6.724E-09 1.808E-09

FIG. 9B is a lens cross-sectional view of the imaging optical system in Numerical Example 3. In FIG. 9B, on the drawing, the left side is the enlargement side and the document surface P side (the side where the scanned image is provided), and the right side is the reduction side and the CCD (one-dimensional photoelectric conversion element) Q is provided. On the side.

  LG is an imaging optical system for image reading for imaging image information on a document surface on the light receiving surface of a one-dimensional photoelectric conversion element, and P is a document (document surface) as an object on the surface. Is formed with image information for reading. Q is an image plane, and photoelectric conversion elements (CDD) Q in which pixels are arranged in a one-dimensional direction are arranged. C1 is a platen glass, and C2 is a cover glass.

  The imaging optical system LG for image reading reduces and forms image information on the document surface P on the one-dimensional photoelectric conversion element Q, and reads the image information by the one-dimensional photoelectric conversion element Q.

  An imaging optical system LG for reading an image has a meniscus first lens G1 having a positive refractive power (hereinafter abbreviated as “positive”) with a convex surface facing the document surface P side in order from the document surface P side, a diaphragm. S, a negative second lens G2 whose both lens surfaces are concave, and a positive third lens G3 whose both lens surfaces are convex. Further, the telephoto type has four meniscus positive fourth lenses G4 having a convex surface facing the image surface. In the fourth lens G4, the light entrance / exit surfaces (first and second surfaces) are anamorphic surfaces.

  FIG. 14 is an explanatory diagram showing the relationship between the amount of bending of the scanning line and the positional deviation of the CCD. When the reflection mirror 15c was displaced from a predetermined position, the scanning line curve was displaced by 3.1 pixels at the main scanning end of ± 77.7 mm.

  FIG. 15 is an explanatory diagram showing the relationship between the main scanning direction and the scanning line bending. When the angle of view is added to the main scanning from the axial light beam, the scanning line is bent, and at the main scanning end of ± 77.7 mm, the scanning line is shifted by 3.1 pixels as indicated by 15a and 15b in FIG. At that time, the CCD is displaced from the predetermined position by about 0.76 mm toward the original surface as shown by 14a in FIG. Therefore, the CCD 17 can be adjusted by moving it about 0.76 mm away from the original surface. When the reflection mirror 15c was displaced from a predetermined position, the scanning line curve was displaced by −1.6 pixels at the end of the main scanning direction ± 77.7 mm.

  FIG. 16 is an explanatory diagram showing the relationship between the main scanning direction and the scanning line curve. When the angle of view is increased from the axial light beam in the main scanning direction, the scanning line is bent, and at the end of the main scanning direction of ± 77.7 mm, the scanning line bending is at a position of −1.6 pixels as shown by 16a and 16b in FIG. Misaligned. At that time, the CCD 17 is displaced by about 0.38 mm from the predetermined position in the direction away from the original surface as indicated by 14b in FIG. Therefore, the CCD 17 can be adjusted by moving it about 0.38 mm in the direction approaching the document surface. Thereafter, the mirror adjusting device 10 adjusts the angle of the reflecting mirror 15d in the sub-scanning direction.

  As described above, a good image can be obtained in a short time by adjusting based on the scanning line bending amount and the sign.

  In this embodiment, in addition to the adjustment method described above, the angle in the sub-scanning direction of the imaging optical system 16 is adjusted based on the geometric characteristics of the image on the adjustment chart, and then, among the plurality of mirrors, You may make it adjust the angle of the subscanning direction of at least 1 mirror.

  Alternatively, the position of the reading unit 16 in the sub-scanning direction may be adjusted based on the geometric characteristics of the image on the adjustment chart, and then the position of the slit portion 14 in the sub-scanning direction may be adjusted.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

  10 mirror adjustment device, 11 adjustment chart, 12 document table, 12 light source means, 14 slit section, 15a, 15b, 15c, 15d reflecting mirror, 16, 176 imaging optical system, 17 reading means (CCD), 18 carriage, 31 Evaluation pattern

Claims (7)

Light source means for illuminating a document placed on a document table, a slit portion for restricting passage of light flux from the document illuminated by the light source means, a plurality of mirrors for reflecting light flux that has passed through the slit portion, An imaging optical system that includes an optical element having an optical surface rotationally asymmetric with respect to the optical axis and that forms image information of the original from light beams reflected by the plurality of mirrors, and imaging of the imaging optical system In an adjustment method of an image reading apparatus for reading image information of the original by moving a carriage holding a reading unit arranged at a position relative to the original,
An adjustment chart in which an evaluation pattern extends in a main scanning direction is placed at a corresponding position on the document table, and the slit portion, the geometrical characteristics of the image of the adjustment chart imaged on the reading unit, An adjustment method for an image reading apparatus, comprising: adjusting at least two positions of a plurality of mirrors, the imaging optical system, and the reading means, and adjusting image information read by the reading means.   The reading unit includes at least three line sensors, and the adjustment chart includes an evaluation pattern having a shape having two or two sides intersecting at different angles with respect to the main scanning direction. 2. The magnification shift in the sub-scanning direction of the image reading apparatus is detected from image information obtained by the book or one side orthogonal to the straight direction of the reading unit and image information obtained from the reading unit. Method for adjusting image reading apparatus.   The reading unit includes at least three line sensors, and the adjustment chart includes at least an evaluation pattern having a shape having two or two sides intersecting at different angles with respect to the main scanning direction in the main scanning direction. The method according to claim 1, wherein the reading unit detects a scanning line curve of the image reading device from image information obtained from the shape.   The adjustment method of the image reading apparatus adjusts the position of the reading means in the sub-scanning direction based on the geometric characteristic of the image of the adjustment chart imaged on the reading means, and then adjusts the position of the mirrors. 4. The method of adjusting an image reading apparatus according to claim 1, wherein a step of adjusting an angle of at least one mirror in the sub-scanning direction is used.   The adjustment method of the image reading apparatus adjusts the angle in the sub-scanning direction of the imaging optical system based on the geometric characteristics of the image of the adjustment chart imaged on the reading means, and then the plurality of sheets The method for adjusting an image reading apparatus according to claim 1, wherein a step of adjusting an angle of at least one of the mirrors in the sub-scanning direction is used.   In the adjustment method of the image reading device, the position of the reading unit in the sub-scanning direction is adjusted based on the geometric characteristics of the image of the adjustment chart imaged on the reading unit, and then the sub-scan of the slit portion is performed. The method for adjusting an image reading apparatus according to claim 1, wherein a step of adjusting a position in the direction is used.   An image reading apparatus adjusted using the method for adjusting an image reading apparatus according to claim 1.