JP2011166568A - Adjustment reference chart for image reader and optical evaluation method employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adjustment reference chart with which a pattern for measuring geometrical characteristics and resolution characteristics are easily disposed on one substrate. <P>SOLUTION: The present invention relates to an adjustment reference chart to be used for adjusting the position of a member constituting an image reader which reads image information formed by an image forming optical system by means of a one-dimensional photoelectric transducer obtained by arraying a plurality of elements in a one-dimensional direction. The adjustment reference chart has first and second resolution evaluation sections, including grid patterns comprised of an aggregate of a plurality of grids, being parallel to each other for evaluating image information formed by the image forming optical system. When a smaller angle formed from the grid pattern of the first resolution evaluation section and a direction of arraying the elements of the one-dimensional photoelectric transducer is defined as α and a smaller angle formed from the grid pattern of the second resolution evaluation section and the direction of arraying the elements of the one-dimensional photoelectric transducer is defined as β, the conditions of 5°≤α≤45° and 45°≤β≤85° are satisfied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an adjustment reference chart for an image reading apparatus used when adjusting members constituting the image reading apparatus and an optical evaluation method using the same. Particularly, it is suitable when assembling each member of an image scanner, a copying machine, and an image reading apparatus such as a facsimile.

  In a conventional image reading apparatus, image information of a document placed on a document table surface is converted into an illumination system, a plurality of reflecting mirrors, an imaging optical system, a carriage in which reading means and the like are integrally stored, such as a motor. Scanning in the sub-scanning direction by the drive mechanism and reading in two dimensions. The read image information of the document is sent to an external device such as a personal computer through an interface.

  In order to improve the image quality of the image information imaged by the imaging optical system, this type of image reading apparatus is strongly required not only to improve the design performance but also to adjust the assembly of each member with high accuracy. Yes. The assembly adjustment method of each member is as follows. First, the members are temporarily assembled on the carriage, and then the positions of the imaging optical system and the one-dimensional photoelectric conversion element (CCD) are changed. Adjustment is performed using an element position adjusting device. Adjustment items include magnification adjustment, centering in the main scanning direction, centering in the sub-scanning direction, rotational alignment with the optical axis as a reference axis, focus alignment, and the like. In order to adjust these items, a chart is arranged on the surface of the original, and an image of the chart is projected onto a one-dimensional photoelectric conversion element by an imaging optical system. The positions of the imaging optical system and the one-dimensional photoelectric conversion element are adjusted so as to obtain characteristics. In order to efficiently perform so-called geometric characteristics, such as magnification adjustment, centering in the main scanning direction, centering in the sub-scanning direction, rotation alignment using the optical axis as a reference axis, Patent Document 1 discloses an adjustment chart arrangement, for example. The method used is known (see Patent Document 1).

  A chart for adjusting the focus position of the imaging optical system is known (see Patent Document 2). In Patent Document 2, a main scanning pattern in which a plurality of grids (lines) extending in a direction perpendicular to the main scanning direction and a plurality of grids (lines) extending in an oblique direction with respect to the main scanning direction are arranged in parallel. A chart having a scanning pattern is disclosed.

  A chart disclosed in Patent Document 1 is shown in FIG. 9A, and a chart disclosed in Patent Document 2 is shown in FIG. 9B. In FIG. 9A, A to E are patterns. In FIG. 9B, 32 and 34 are patterns. As is clear from FIG. 9A, the diagonal lattice (line), which is a geometric characteristic adjustment pattern indicated by reference numerals B and D, has a wide width in the main scanning direction and is indicated by reference numeral 34 in FIG. 9B. The focus alignment (resolving power) pattern shown is also wide in the main scanning direction. Therefore, in order to arrange these patterns as one chart, it is necessary to reduce the size of each pattern.

  As an image reading apparatus, a so-called A3 size for reading a 305 mm width in the main scanning direction and a so-called A4 size for reading a 216 mm width in the main scanning direction are generally used according to the type of the original document size. In particular, in the case of an image reading apparatus with an A4 size reading width, the items that must be adjusted are the same as those for the A3 size, but the width in which a pattern can be arranged is about 2/3 that of the A3 size. There is only.

  In order to further improve the adjustment accuracy, measures such as increasing the area of the pattern or providing the pattern at multiple locations are required, and more and more patterns are accommodated on a single chart. It has become difficult.

Japanese Patent Publication No. 8-34530 US Pat. No. 6,282,331

  For the above purpose, it is necessary to reduce the size of the pattern used for the chart. Therefore, in the detection of the position of each member constituting the image reading apparatus, the measurement accuracy can be increased, and the measurement accuracy can be improved and the number of patterns can be reduced by using the chart pattern capable of measuring a plurality of items. It becomes necessary.

  A conventional main scanning pattern in which a plurality of grids extending in a direction perpendicular to the main scanning direction is arranged in parallel can evaluate the resolving power in the main scanning direction, but has no further function. Further, the main scanning pattern is not orthogonal to the sub-scanning pattern in which a plurality of lattices extending in an oblique direction with respect to the main scanning direction are arranged in parallel, and the two-dimensional resolution can be completely separated. It was difficult.

  As described above, it is difficult to obtain a chart in which patterns that can measure both geometric characteristics and resolving power characteristics with high accuracy are provided in one chart. More specifically, first, the pattern for evaluating the resolution and the pattern for evaluating the geometric characteristics each have only a single function, and it is difficult to reduce the number of patterns. Second, since the pattern for evaluating the resolution evaluates the two-dimensional resolution without completely separating the resolution in the independent direction, it is difficult to increase the adjustment accuracy.

  An object of the present invention is to provide an adjustment reference chart in which a resolution evaluation unit that measures geometric characteristics and resolution characteristics can be easily arranged on a single substrate. It is another object of the present invention to provide an image reading apparatus capable of reading high-quality image information adjusted with the adjustment reference chart.

The adjustment reference chart of the present invention adjusts the position of a member constituting an image reading apparatus that reads image information imaged by an imaging optical system by a one-dimensional photoelectric conversion element in which a plurality of elements are arranged in a one-dimensional direction. The adjustment reference chart is used in the process, and the adjustment reference chart includes a lattice pattern including a collection of a plurality of parallel lattices for evaluating image information imaged by the imaging optical system. 1 and a second resolving power evaluation unit, and α represents the smaller angle formed by the lattice pattern of the first resolving power evaluation unit and the arrangement direction of the elements of the one-dimensional photoelectric conversion element. When the smaller angle between the lattice pattern of the resolving power evaluation unit and the arrangement direction of the elements of the one-dimensional photoelectric conversion element is β,
5 ° ≦ α ≦ 45 °
45 ° ≦ β ≦ 85 °
It is characterized by satisfying the following conditions.

  According to the present invention, it is possible to achieve an adjustment reference chart in which a resolution evaluation unit that measures geometric characteristics and resolution characteristics can be easily arranged on a single substrate. Further, it is possible to achieve an image reading apparatus capable of reading high-quality image information adjusted by the adjustment reference chart.

The figure which shows the adjustment reference | standard chart of Example 1 of this invention Diagram showing spot diagram characteristics on the optical axis of the imaging lens Diagram showing spot diagram characteristics when the plane mirror is deformed The figure which shows the adjustment reference | standard chart of the comparative example of this invention The figure which shows the CTF characteristic of the comparative example of this invention The figure which shows the CTF characteristic of Example 1 of this invention. The figure which shows the adjustment reference | standard chart of Example 2 of this invention The figure which shows the CTF characteristic of Example 2 of this invention. The figure which shows the conventional adjustment reference | standard chart pattern 1 is a schematic diagram of a main part of an adjustment device and an image reading device according to a first embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Embodiments of an adjustment reference chart for an image reading apparatus according to the present invention, an optical evaluation method using the same, and an image reading apparatus adjusted using the same will be described below with reference to the drawings.

[Example 1]
FIG. 1 is an explanatory diagram of an adjustment reference chart according to the first embodiment of the present invention. The adjustment reference chart of this embodiment adjusts the position of a member constituting an image reading apparatus that reads image information imaged by an imaging optical system by a one-dimensional photoelectric conversion element in which a plurality of elements are arranged in a one-dimensional direction. Used when.

  In the figure, reference numeral 1 denotes an adjustment reference chart, which has first and second resolving power evaluation units (patterns) S and M including at least a lattice pattern composed of a collection of a plurality of lattices parallel to each other. Hereinafter, the first resolving power evaluation unit is also referred to as a pattern S, and the second resolving power evaluation unit is also referred to as a pattern M.

  In this embodiment, the arrangement direction of the elements of the one-dimensional photoelectric conversion element (CCD) is the main scanning direction. Of the angles formed by the lattice and the arrangement direction of the one-dimensional photoelectric conversion elements, the smaller angle is employed. At this time, the pattern S has a lattice pattern s1 made up of an assembly (aggregation part) of a plurality of lattices (white lines and black lines) parallel to each other inclined at an angle α. The pattern M has a lattice pattern m1 composed of an aggregate (aggregate portion) of a plurality of lattices (white lines and black lines) parallel to each other inclined at an angle β. Here, the angles α and β are positive.

  The grid patterns s1 and m1 constituting the two patterns S and M of the present embodiment are configured such that the white line and the black line have a width of 0.085 mm and CTF measurement can be performed at a frequency of 5.9 lppm.

In this embodiment, the angles α and β are 5 ° ≦ α ≦ 45 °, respectively (1)
45 ° ≦ β ≦ 85 ° (2)
To satisfy the following conditions.

  In this embodiment, the angle (tilt angle) α of the lattice pattern s1 of the pattern S is set to 8 ° so as to satisfy the conditional expression (1). Further, the angle (tilt angle) β of the lattice pattern m1 of the pattern M is set to 82 ° so as to satisfy the conditional expression (2). Thus, in this embodiment, the two patterns S and M can be used to measure (evaluate) the resolving power characteristics (resolving power performance) in different directions of the imaging optical system.

  Further, in the present embodiment, the adjustment reference chart has two patterns S and M in which the lattice pattern is inclined with respect to the main scanning direction as described above. Thus, by measuring the phase when the adjustment reference chart is projected onto the CCD, position information in a direction (sub-scanning direction) orthogonal to the main scanning direction (element arrangement direction) of the CCD can be obtained. Thus, in this embodiment, the measurement (evaluation) of the geometric characteristics can be performed.

  In the present embodiment, it is more desirable to set the numerical ranges of the conditional expressions (1) and (2) as follows.

8 ° ≦ α ≦ 45 ° (1a)
45 ° ≦ β ≦ 82 ° (2a)
In this embodiment, when the angle (relative angle) formed by the arrangement direction of the lattice pattern s1 of the pattern S and the lattice pattern m1 of the pattern M is γ,
85 ° <γ ≦ 90 ° (3)
To satisfy the following conditions. The angle γ is a positive value.

  In this embodiment, the angle γ is 90 ° so that the conditional expression (3) is satisfied, and the two lattice patterns s1 and m1 are orthogonal to each other. Thus, in this embodiment, the resolution characteristics in the directions orthogonal to each other can be properly evaluated, and the measurement of the two-dimensional resolution characteristics is facilitated.

  In addition, by making the lattice patterns s1 and m1 of the two patterns S and M orthogonal to each other, the original plate for chart production can be shared by both patterns, and one type of original plate whose outer periphery is a square is rotated by 90 °. Thus, it is easy to create two types of patterns.

  More preferably, the numerical range of the conditional expression (3) should be set as follows.

87 ° <γ ≦ 90 ° (3a)
Next, the adjusting device of the present embodiment will be described. FIG. 10A is a schematic diagram of a main part of an adjusting device that adjusts the resolving power characteristics and the geometric characteristics of the imaging optical system using the adjustment reference chart of this embodiment.

  In this embodiment, when assembling the image reading apparatus, necessary members (parts) are first temporarily assembled on the carriage 58. Then, the positions of the imaging optical system 56 and the one-dimensional photoelectric conversion element 57 are adjusted by using the imaging optical system position adjustment device 66 and the one-dimensional photoelectric conversion element position adjustment device 67, respectively. As adjustment items, at least magnification alignment, center alignment in the main scanning direction, center alignment in the sub-scanning direction, rotation alignment using the optical axis as a reference axis, and focus alignment are required. In order to adjust these items, the image of the above-described adjustment reference chart 1 arranged on the document surface is projected onto the one-dimensional photoelectric conversion element 57 through the imaging optical system 56. Then, the positions of the imaging optical system 56 and the one-dimensional photoelectric conversion element 57 are adjusted so as to obtain desired characteristics while confirming the electric signal obtained by reading the image. For example, the optical axis direction, the direction orthogonal to the optical axis, the rotation direction with respect to the optical axis, the tilt direction, and the like are adjusted.

  Next, the image reading apparatus of this embodiment will be described. FIG. 10B is a schematic diagram of a main part of an image reading apparatus manufactured by the adjustment apparatus of FIG.

  In the figure, a document 51 placed on the surface of the document table glass 52 is irradiated with a light beam from an illumination device 53. Image information of the original 51 is imaged on a reading means (CCD) 57 by an imaging optical system 56 through a slit 54 and a plurality of reflecting mirrors 55a to 55d. A carriage 58 in which these members 53 to 57 are integrally stored is scanned in the sub-scanning direction by a drive mechanism 59 such as a motor. As a result, the image information of the document 51 is read. Then, the read image information of the document 51 is sent to an external device (not shown) such as a personal computer through an interface.

  In this embodiment, an optical element including an anamorphic surface is used for the imaging optical system 56, and the imaging performance is improved while shortening the optical path length.

  Table 1 shows design numerical values of the imaging optical system (image reading lens) 56. In Table 1, f is the focal length of the imaging optical system, Fno is the F number, m is the imaging magnification, Y is the maximum image height, and ω is the half field angle. In the imaging optical system shown in Table 1, the surface number i indicates the order of the surfaces from the document surface side, Ri is the radius of curvature of each surface, Di is a member 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 with respect to the d-line, respectively.

G1, G2, G3, and G4 are first, second, third, and fourth lenses, respectively, that form the imaging optical system 56 in order. The incident / exit surface of the fourth lens G4 is an anamorphic surface. C1 is a platen glass and C2 is a cover glass. The shape of the anamorphic surface is an aspherical shape described below using the coefficients shown in Table 2. In Table 2, “E−x” indicates “10 ^−x ”.

  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. The axis orthogonal to the optical axis in the sub-scan section is taken as the z-axis. At this time, the bus 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 1]
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 2]
0 8 side 9 side
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

Generally, when the two-dimensional resolving power in the main scanning direction and the sub-scanning direction of the imaging optical system is obtained using the adjustment reference chart, the two-dimensional resolving power is separated if the two lattice patterns s1 and m1 are not orthogonal to each other. Cannot be determined.

  Next, a problem when the two-dimensional resolving power cannot be separated in the orthogonal direction will be described with reference to FIGS. FIG. 2 is a diagram showing spot diagram characteristics on the optical axis of an imaging optical system used in the image reading apparatus. When the imaging optical system is assembled as an image reading apparatus, it is often used in combination with a plurality of plane mirrors (reflection mirrors) as shown in FIG.

  Figure shows a spot diagram when a flat mirror placed at a distance of 34.1 mm on the left side (document side) of the imaging optical system changes to a toric reflection surface (concave surface) with a radius of curvature of 10,000 mm in the main scanning direction, for example. 3 shows. Due to the variation of the plane mirror, the spot diagram is enlarged in the main scanning direction as compared with the state without warping. The flat mirror has a rectangular shape that is long in the main scanning direction, and is held at both ends thereof. Since the holding interval is long, warping in the main scanning direction is likely to occur. In the assembling process, attention is paid to the holding structure and the assembling work method so that warpage does not occur, but it cannot be completely prevented. Therefore, there is a need for an optical evaluation method that can reduce as much as possible the influence of warpage that has occurred in the assembly process.

  FIGS. 4 and 5 show comparative examples in which the imaging optical system having the spot diagram characteristics as shown in FIG. 3 is subjected to CTF evaluation using the pattern exemplified in Patent Document 2. FIG.

  FIG. 4 is a diagram showing an adjustment reference chart in the comparative example, and FIG. 5 is a diagram showing CTF characteristics in the comparative example.

  In FIG. 4, a lattice pattern m1 composed of a pattern M lattice (white line, black line) is perpendicular to the main scanning direction, and a lattice pattern s1 composed of a pattern S lattice (white line, black line) is relative to the main scanning direction. It is inclined at 45 °. The gratings of the grating patterns s1 and m1 constituting both patterns S and M have a white line and black line width of 0.085 mm and CTF measurement at a frequency of 5.9 lppm. The CTF value is calculated by the following equation using the maximum value MAX and the minimum value MIN of the image signal in the resolution evaluation pattern.

  As shown in FIG. 5, when the pattern S and the pattern M exemplified in Patent Document 2 are used, the positions where the best image formation state is different from each other, and it cannot be determined which one should be adjusted. This is because the lattice pattern s1 includes a component of the lattice pattern m1 with respect to the lattice pattern m1 perpendicular to the main scanning direction, as shown in FIG.

  On the other hand, in this embodiment, when the CTF value of the characteristic described in FIG. 3 is calculated, the CTF characteristic becomes as shown in FIG. 6, and the best when the pattern S and the pattern M are used. The focus position is different. This is because the arrangement direction of the lattice pattern m1 is close to the enlarged direction of the spot diagram characteristics exemplified. The best focus position shown when the patterns S and M are used is different. However, as described above, in this embodiment, the arrangement directions of the lattice patterns s1 and m1 of the two patterns S and M are orthogonal, and the two-dimensional resolution characteristics can be evaluated in two independent directions. The resolution characteristics of the pattern M are independent from each other.

  Therefore, in order to adjust the focus position to the smallest spot diagram, that is, the best two-dimensional focus state, an intermediate position between the best focus positions when the patterns S and M shown in FIG. 6 are used. It only has to be adjusted to the point. It is possible to easily determine the best adjustment position by utilizing that the intermediate point is the same point as the best position of the average value (two-dot chain line) of the CTF values of the pattern S and the pattern M.

  Further, since the lattice patterns s1 and m1 of the pattern S and the pattern M are inclined with respect to the main scanning direction, the geometric characteristics can be measured (adjusted) using the same pattern. The pattern M having a large grating inclination angle has a small phase change when the CCD is displaced in the direction orthogonal to the main scanning direction, and is therefore suitable for adjustment with a large amount of movement. On the contrary, the pattern S has a large phase change. It is suitable for high-precision adjustment with minute movement.

  In this embodiment, by using the adjustment reference chart having the two patterns S and M as described above, it is possible to adjust the geometric characteristics with high accuracy, and the 45 ° oblique line pattern exemplified in Patent Document 1 described above is used as the adjustment reference. There is no need to place it in the chart.

[Example 2]
FIG. 7 is an explanatory diagram of an adjustment reference chart according to the second embodiment of the present invention. In the figure, the same elements as those shown in FIG. The present embodiment is different from the first embodiment in that the arrangement directions of the lattice patterns s1 and m1 constituting the two patterns S and M are different. That is, the angles α and β with respect to the arrangement direction of the CCD elements are made different. Other configurations and optical functions are the same as those in the first embodiment, and the same effects are obtained.

  In addition, the gratings of the grating patterns s1 and m1 constituting the two patterns S and M of the present embodiment can perform CTF measurement at a frequency of 5.9 lppm with a white line and a black line having a width of 0.085 mm, as in the first embodiment. The

  That is, in this embodiment, the lattice pattern s1 constituting the pattern S is arranged with an inclination angle of α = 45 °, and the lattice pattern m1 constituting the pattern M is arranged with an inclination angle of β = 45 °. The relative angle γ in the arrangement direction of both lattice patterns s1, m1 is 90 ° and orthogonal to each other. This satisfies all the conditional expressions (1), (2), and (3) described above.

  When the CTF value of the characteristic described in FIG. 3 is calculated as in the first embodiment, the CTF characteristic is as shown in FIG. 8, and the best focus position for each of the patterns S and M is as follows. Match. In the present embodiment, since the enlargement direction shown in FIG. 8 is a substantially intermediate direction between the arrangement directions of the lattice patterns s1 and m1 of the pattern S and the pattern M, the best focus position matches. Of course, as described above, the arrangement directions of the two patterns S and M of the lattice patterns s1 and m1 of the present embodiment are also orthogonal. Thereby, since the two-dimensional resolution characteristics can be evaluated in two independent directions, the resolution characteristics of the pattern S and the pattern M are independent of each other.

  Although the focus position in the best two-dimensional imaging state in this embodiment is clear, the position is the average value (two-dot chain line) of the CTF values of the patterns S and M described in the first embodiment. Even if it is the best position, there is no misjudgment. Further, since the lattice pattern s1 of the pattern S and the lattice pattern m1 of the pattern M are inclined with respect to the main scanning direction, measurement (adjustment) of the geometric characteristics can be performed using the same pattern.

  The lattice pattern s1 of the pattern S and the lattice pattern m1 of the pattern M are both at an inclination angle of 45 ° with respect to the main scanning direction, but since the inclination directions are opposite, the CCD is misaligned in a direction perpendicular to the main scanning direction. In this case, the directions of phase change are opposite to each other. Therefore, by calculating both phase shift amounts, the positional shift in the direction orthogonal to the main scanning direction can be measured with high accuracy, and other effects can be calculated. This facilitates highly accurate adjustment of geometric characteristics and eliminates the need to arrange the 45 ° oblique line pattern exemplified in Patent Document 1 described above in the adjustment reference chart.

  In each embodiment, the resolution characteristics and the geometric characteristics are measured (adjusted) with high accuracy by inclining and orthogonalizing the lattice patterns of the two patterns S and M. However, the present invention is not limited to this. . Either one of the measurements can contribute to improving the image quality of the image information read by the image reading apparatus, which is the object of the present invention. In addition, the inclination angle and line width of the lattice of the lattice pattern are not limited to the values set in each embodiment, and in particular, the inclination angles α and β are other ranges as long as they satisfy the conditional expressions (1) and (2), respectively. Even in the form, it is effective.

  As described above, in this embodiment, patterns for measuring geometric characteristics and resolving power characteristics are easily arranged in one adjustment reference chart as described above. Further, by using this adjustment reference chart, it is possible to realize an adjustment device that can adjust the resolution characteristic and the geometric characteristic with high accuracy. Further, an image reading apparatus capable of reading a high-quality image can be manufactured by the adjusting device.

  DESCRIPTION OF SYMBOLS 1 Adjustment reference | standard chart, S 1st resolving power evaluation part, M 2nd resolving power evaluation part, s1, m1 Grid pattern

Claims (6)

An adjustment reference chart used to adjust the position of a member constituting an image reading apparatus that reads image information formed by an image forming optical system by a one-dimensional photoelectric conversion element in which a plurality of elements are arranged in a one-dimensional direction. There,
The adjustment reference chart includes first and second resolving power evaluation units including a lattice pattern composed of a collection of a plurality of parallel lattices for evaluating image information imaged by the imaging optical system. And
The smaller angle formed by the lattice pattern of the first resolving power evaluation unit and the arrangement direction of the elements of the one-dimensional photoelectric conversion element is α, the lattice pattern of the second resolving power evaluation unit, and the one-dimensional photoelectric conversion When the smaller angle formed by the arrangement direction of the elements is β,
5 ° ≦ α ≦ 45 °
45 ° ≦ β ≦ 85 °
An adjustment reference chart characterized by satisfying the following condition. When the smaller angle formed by the arrangement direction of the lattice pattern of the first and second resolving power evaluation units is γ,
85 ° <γ ≦ 90 °
The adjustment reference chart according to claim 1, wherein the following condition is satisfied.   An optical evaluation method, comprising: measuring the resolving power characteristics of the imaging optical system using the adjustment reference chart according to claim 1.   An optical evaluation method comprising measuring the geometric characteristics of the imaging optical system using the adjustment reference chart according to claim 1.   An image reading apparatus adjusted using the adjustment reference chart according to claim 1.   An image reading apparatus adjusted using the optical evaluation method according to claim 3.