JP2015004644A - Eccentric quantity calculation method of optical system and optical system adjustment method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric quantity calculation method of an optical system capable of readily measuring precision in assembling of optical elements constituting the optical system even if the optical system that is an object of measurement is large in size, and performing optical adjustment of eccentricity or the like of each of the optical elements so that desired image formation performance can be attained.SOLUTION: Included are a first process in which: a first measurement system allows a luminous flux to enter an optical system, and the luminous flux having passed through the optical system is used to measure a wave front aberration of the optical system; and a second measurement system allows a luminous flux to enter the optical system along an optical path different from an optical path along which the luminous flux emanating from the first measurement system has passed through the optical system, and the luminous flux having passed through the optical system is used to measure the wave front aberration of the optical system, and a second process in which an eccentric quantity of each of the optical elements constituting the optical system is calculated based on the wave front aberration obtained by the first measurement system and the wave front aberration obtained by the second measurement system.

Description

  The present invention can easily calculate the amount of eccentricity of an optical system, and can easily adjust the position of each optical element constituting the optical system, and an adjustment using the method. Regarding the method.

  In an optical system having high optical performance, each optical element constituting the optical system is required to have little decentration. When an optical system is constructed by assembling a plurality of optical elements such as lenses and mirrors, it is necessary to adjust the eccentricity generated by assembling each optical element according to the image height and angle of view to be used. Incident light is incident on the optical system. It is known that optical evaluation of the optical system is performed using light that has passed through the optical system, and the eccentricity of each optical element is adjusted so as to obtain desired imaging performance (Patent Document 1).

  In the aberration correction system of Patent Document 1, a light beam that matches the image height and field angle to be used is incident on the optical system to measure wavefront aberration, and each optical element is rotated so as to correct the as component of the Zernike polynomial. Alternatively, each optical element is eccentrically adjusted with respect to the optical axis so as to correct the coma component of the Zernike polynomial.

  On the other hand, in a reflective telescope for astronomical observation or the like, a large amount of chromatic aberration occurs due to atmospheric dispersion. 2. Description of the Related Art Conventionally, there is known a main focus correction optical system that is disposed in the vicinity of an image forming position of a main mirror (reflection mirror) in a reflection telescope and corrects chromatic aberration due to atmospheric dispersion well (Patent Document 2).

JP-A-6-230274 JP 2009-036976 A

  Optical system that measures light according to the image height and angle of view used in large optical systems such as reflective telescopes for astronomical observation and aberration correction optical systems that correct aberrations in combination with other optical systems In order to make the light incident on the optical system, a larger optical system is required. In addition, it is necessary to use another optical system whose aberration has been confirmed in advance. The former is difficult to measure because it uses a large optical system. In the latter case, since it is necessary to prepare another optical system in advance, the measurement is still difficult.

  For example, when adjusting the optical elements by measuring the decentration of each optical element that constitutes the aberration correction optical system that corrects aberrations generated by the large primary mirror that forms part of the astronomical observation telescope, Therefore, it is necessary to make the light beam adapted to the image height and angle of view used for the incident light enter the aberration correction optical system. For this purpose, a large primary mirror or a separate complicated optical system is required. It is very difficult to measure the optical performance of a reflective telescope using a large primary mirror or a complex optical system.

  An object of the present invention is to provide an optical system eccentricity calculation method capable of easily measuring the assembly accuracy of optical elements constituting an optical system even when the optical system to be measured is large. Further, a method for adjusting an optical system capable of optical adjustment such as decentration of an optical element so as to obtain a desired imaging performance, and a method for evaluating the optical performance of the optical system capable of obtaining the optical performance of the optical system as a whole The purpose is to provide.

  The method of calculating the amount of eccentricity of the optical system according to the present invention is configured such that a light beam is incident on the optical system from the first measurement system, the wavefront aberration of the optical system is measured using the light beam via the optical system, and the second measurement system. The light beam from the first measurement system is incident on the optical system through an optical path different from the optical path passing through the optical system, and the wavefront aberration of the optical system is measured using the light beam via the optical system. A first step, and a second step of calculating a decentering amount of each optical element constituting the optical system from the wavefront aberration obtained by the first measurement system and the wavefront aberration obtained by the second measurement system. It is characterized by that.

  According to the present invention, even if the optical system to be measured is large, the assembly accuracy of the optical elements constituting the optical system can be easily measured, and the desired optical performance can be obtained. Thus, a method for calculating the amount of eccentricity of the optical system capable of optical adjustment such as decentration is obtained.

3 is a flowchart of an optical system eccentricity calculation method and the like according to the present invention. It is a principal part schematic of the reflective telescope which has an optical system. It is a detailed view of a correction optical system. (A), (B) It is the schematic of the measurement form of a wavefront aberration. FIG. 5 is a diagram (transverse aberration) in which the calculated eccentricity is incorporated into an optical model and optical performance is evaluated. It is explanatory drawing of the 1st, 2nd measurement system of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. The optical system eccentricity calculation method of the present invention includes the following first and second steps. In the first step, a light beam is incident on the optical system from the first measurement system, and the wavefront aberration of the optical system is measured using the light beam via the optical system. At the same time, the second measurement system causes the light beam from the first measurement system to enter the optical system through an optical path different from the optical path passing through the optical system, and uses the light beam via the optical system to reduce the wavefront aberration of the optical system. taking measurement. In the second step, the amount of eccentricity of each optical element constituting the optical system is calculated from the wavefront aberration obtained by the first measurement system and the wavefront aberration obtained by the second measurement system.

  The optical system adjustment method of the present invention includes a third step of adjusting the position of each optical element constituting the optical system using the eccentric amount calculated in the second step of the optical system eccentricity calculation method. . In the optical performance evaluation method of the present invention, an eccentric optical model for each optical element of the optical system is created using the eccentric amount calculated in the second step in the optical system eccentricity calculating method. Then, using the created decentered optical model, a simulation is performed assuming that the optical system is actually used by being mounted on a part of another optical system, and the optical performance of the optical system is evaluated by the simulation.

  First, the configuration of the optical system in the optical system eccentricity calculation method of the present invention will be described. Here, the optical system is, for example, a correction optical system that is used together with the primary mirror of the reflective telescope when performing astronomical observation. The correction optical system has a function of correcting aberration of the main mirror and correcting chromatic aberration due to atmospheric dispersion.

  FIG. 2 is an explanatory diagram of an optical arrangement of a reflective telescope having an optical system (correction optical system) that is an object of calculation of the amount of eccentricity by the method of calculating the amount of eccentricity of the optical system of the present invention. FIG. 3 is an enlarged explanatory view of the optical system of FIG. In FIG. 2, 1 is a reflective telescope. M1 is a primary mirror having an imaging function, and 100 is an optical system. The primary mirror M1 is a concave rotating hyperboloid (reflecting mirror). The optical system 100 is disposed at or near the focal point of the primary mirror M1, and corrects aberrations generated by the primary mirror M1. The light beam from the celestial body is incident on the main mirror M1 from the right side in the figure, and after being reflected by the main mirror M1, the image is formed on the image pickup surface C1 on which the image pickup element (image pickup means) is arranged via the optical system 100.

  The configuration of the optical system 100 shown in FIG. 3 will be described. The optical system 100 includes lenses (optical elements) L11 to L15 and a compound lens (optical element) A1. In the reflecting telescope 1, the shapes of the five lenses L11 to L15 are optimized. Specifically, the optical system is a compound lens for correcting atmospheric dispersion (for correcting atmospheric color separation) composed of a first lens L11, a second lens L12, and two single lenses in order from the main mirror M1 toward the imaging surface C1. (ADC) A1 is included. Furthermore, it has the 3rd lens L13, the 4th lens L14, and the 5th lens L15.

  After the light coming from the celestial body is reflected by the primary mirror M1, it passes through the first lens L11, the second lens L12, the compound lens (A1), the third lens L13, the fourth lens L14, and the fifth lens L15 of the optical system 100. After passing in order, an image of a celestial body is formed on the imaging surface C1. As a result, aberrations are favorably corrected within a viewing angle range of 1.6 degrees. The optical system 100 has an effective viewing angle of 1.5 degrees. F1 and W1 are parallel plane plates corresponding to the thickness of the filter for selecting the transmission wavelength band and the window material of the CCD dewar.

  The compound lens A1 is composed of two lenses A11 and A12 made of materials having different dispersions in order to correct atmospheric dispersion. The compound lens A1 is moved by the actuator (moving mechanism) so as to have a component in the direction orthogonal to the optical axis (in the direction of the arrow in the figure), thereby correcting the color shift due to atmospheric dispersion.

The compound lens A1 has a structure in which a pair of lenses A11 and A12 made of materials having different refractive indexes and close to each other are joined or arranged adjacent to each other with a slight air gap (air layer). Specifically, the material constituting the lens A11 (trade name BSL7Y) has a refractive index nd of 1.51633 and an Abbe number νd of 64.2. The material constituting the lens A12 (trade name PBL1Y) has a refractive index nd of 1.54814 and an Abbe number νd of 45.8. At this time, the ratio of the refractive indexes of the materials of the lenses A11 and A12 is
1.51633 / 1.54814 = 0.979
It is. That is, the refractive indexes are 2.1% different from each other.

  The compound lens A1 of the present embodiment has a positive lens (lens A12) and a negative lens (lens A11) that have different refractive indexes of 0.5% or more (preferably within a range of 0.5% to 5%). They are arranged adjacent to each other in the direction. The combination of these materials and the opposite lens surfaces have the same degree of curvature (difference within ± 5% in radius of curvature). As a result, when the compound lens A1 is moved in the direction orthogonal to the optical axis to correct atmospheric dispersion, a necessary amount of chromatic aberration is generated. The refractive index nd is a refractive index with respect to the d line (587.6 nm). The Abbe number νd is defined by:

νd = (nd−1) / (nF−nC)
However, nd: refractive index with respect to d-line (587.6 nm) nF: refractive index with respect to F-line (486.1 nm) nC: refractive index with respect to C-line (656.3 nm) Lens A11 is a surface on the object side (primary mirror M1 side) Is flat, and the lens A12 has a flat lens surface on the imaging surface (IP) side. That is, the light incident surface and the light exit surface of the compound lens A1 are both flat.

  As a result, for monochromatic light, the term when the compound lens A1 is moved in the direction orthogonal to the optical axis is not much different from that when a simple flat glass is moved, and the change in monochromatic aberration is reduced. I keep it.

  Next, Table 1 shows numerical data of the reflecting telescope 1. The surface numbers in the table are numbers assigned to the respective surfaces in the order of light flux from the celestial side. i indicates the order of the surfaces from the celestial body. Ri represents the radius of curvature of each surface, and di represents the distance between the i-th surface and the (i + 1) -th surface. R1 is a primary mirror, and R2 to R15 are surfaces of the optical system 100.

  Quartz (SILICA), trade name BSL7Y and trade name PBL1Y are used as the material. Specifically, quartz (SILICA) has a refractive index nd of 1.45846 and an Abbe number νd of 67.8. The material BSL7Y has a refractive index nd of 1.51633 and an Abbe number νd of 64.2. The material PBL1Y has a refractive index nd of 1.54814 and an Abbe number νd of 45.8. Although the glass name of OHARA INC. Was used as the material name in the examples, an equivalent product may be used.

  The optical system 100 of the present embodiment has five aspheric surfaces. The aspherical shape is the z axis in the optical axis direction, the h axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, k is the conic constant, and A to G are the 4th to 16th orders. When the aspheric coefficient is

It is expressed by the following formula. In Table 1, f represents the combined focal length of the primary mirror M1 and the optical system 100, FNO represents the F number, and 2ω represents the total field angle (viewing angle) (degrees).

[Table 1]
f = 18334.3mm FNO = 2.25 2ω = 1.5 °
Surface number Curvature radius R Surface spacing d Material Effective diameter
1 (Primary mirror) 30000.0000 (Aspherical surface) 13456.4205 8200.0
2 760.000 100.0000 SILICA 820.0
3 1375.5000 (Aspherical) 372.8500 801.0
4 -3530.0000 (Aspherical) 46.0000 BSL7Y 320.8
5 656.2498 318.0000 574.6
6 (ADC) Plane 40.0000 BSL7Y 611.0
7 (ADC) 1058.0000 3.0000 611.0
8 (ADC) 1040.0000 82.0000 PBL1Y 611.9
9 (ADC) Plane 274.3000 611.2
10 -840.0002 (Aspherical) 40.0000 PBL1Y 552.2
11 9800.0000 90.00000 568.9
12 480.0000 (Aspherical) 102.0000 BSL7Y 628.0
13 4021.4590 100.2000 628.0
14 4176.7483 88.0000 SILICA 616.0
15 -1272.8222 (Aspherical) 90.0412 616.0
16 (Filter) ∞ 15.0000 SILICA 520.6
17 (Filter) ∞ 32.5000 510.3
18 (Window) ∞ 37.0000 SILICA 520.6
19 (Window) ∞ 15.0000 510.3
20 Image plane ∞ --- --- 500.3

(Aspherical)
Face 1
k = -1.00835 A (4th order) = 0.00000 B (6th order) = 0.00000 C (8th order) = 0.00000
D (10th order) = 0.00000 E (12th order) = 0.00000 F (14th order) = 0.00000 G (16th order) = 0.00000

Surface 3
k = 0.00000 A (4th order) =-1.49749E-11 B (6th order) =-7.57907E-17
C (8th order) =-7.70529 E-22 D (10th order) = 1.026626E-26 E (12th order) =-7.07883E-32
F (14th) = 2.559601E-37 G (16th) =-3.76155E-43

Face 4
k = 0.00000 A (4th order) = 6.914718E-11 B (6th order) = 6.03728E-16
C (8th order) = -1.53262E-20 D (10th order) = 3.61811E-25 E (12th order) = -4.74168E-30
E (12th order) = 3.217309E-35 G (16th order) = -8.85988E-41

Face 10
k = 0.00000 A (4th order) = 2.768476E-09 B (6th order) =-4.8556E-14
C (8th order) = 7.176113E-19 D (10th order) = -1.07637E-24 E (12th order) = 1.187443E-28
F (14th) =-7.98382E-34 G (16th) = 2.393557E-39

Surface 12
k = 0.00000 A (4th order) =-4.35553E-09 B (6th order) = 3.635868E-14
C (8th order) =-5.95127E-19 D (10th order) = 7.658840E-24 E (12th order) =-7.19412E-29
F (14th order) = 3.942821E-34 G (16th order) =-9.54343E-40

Surface 15
k = 0.00000 A (4th order) =-1.06469E-09 B (6th order) = 3.377750E-14
C (8th order) = -1.10265E-19 D (10th order) = 2.282369E-24 E (12th order) = -2.74304E-29
F (14th) = 1.755771E-34 G (16th) = -4.82195E-40

  Next, the method for calculating the amount of eccentricity of the optical system, the method for adjusting the optical system, the method for displaying the optical performance of the optical system, etc. (hereinafter referred to as “the method for adjusting the optical system”) will be described. The optical system according to the present invention is an optical system that is large and heavy, such as a reflective telescope for astronomical observation, and whose optical performance is difficult to measure in its original use state.

  FIG. 1 is a flowchart of an optical system adjustment method and the like according to the present invention. The flow chart of FIG. 1 is intended for an optical system (correction optical system) used in the reflective telescope 1 shown in FIG. 2 as an example. In this embodiment, an optical system in which optical performance cannot be evaluated with an angle of view (observation field of view) close to the original application and image height, a first measurement system and a second measurement that radiate optical paths that pass through the optical system are different from each other. The wavefront aberration of the optical system is measured by the two measurement systems (step S1). The coma component of the zernike coefficient is calculated from the two wavefront aberrations (step S2).

  With respect to the optical system, design value models taking into account the actually measured refractive index, refractive index distribution, surface shape, and lens thickness are created (Table 4). The calculated coma aberration is a target, and the eccentricity of each lens (each optical element) of the optical system is used as a variable, and is optimized by optical design software. The decentering amount of each lens after optimization is the decentering amount with reference to the optical axis of the optical system (Table 5) (step S3).

  Here, when the amount of eccentricity is not allowable, the optical system is reassembled (adjusted) (step S4a). When the determination cannot be made only by the decentration amount or when more detailed determination is performed, an eccentric optical model is created (step S4). Next, the optical performance of the optical system is evaluated by simulation, taking into account the eccentricity in addition to the designed value that takes into account the actually measured refractive index, refractive index distribution, surface shape, and lens thickness (step S5). Thereafter, the process is completed (step S6).

  FIGS. 4A and 4B are conceptual diagrams showing wavefront measurement in two measurement forms of a first measurement system and a second measurement system that emit light beams with different optical paths passing through the optical system 100. Reference numerals 1100a and 110b denote a first measurement system and a second measurement system, respectively. The first measurement system 1100 a emits a light beam that passes through the center of the optical axis of the optical system 100.

  The second measurement system 1100b radiates a light beam that passes through the entire effective diameter of the optical system 100. The first measurement system 1100a and the second measurement system 1100b each have an interferometer. L1 and L2 are measurement optical systems that correct the wavefront aberration of the optical system 100 in the respective wavefront measurement forms. M2 and M3 are mirrors (concave mirrors) that fold the light beam that has passed through the optical system 100 back to the measurement system side. Table 2 shows numerical data of the measurement optical system L1 in the wavefront measurement mode 1 of FIG.

[Table 2]
Surface number Curvature radius R Surface spacing d Material Effective diameter
1 plane 89.564
2 -97.428 10.000 BSL7Y 52
3 -446.097 20.000 56
4 -131.553 15.000 BSL7Y 68
5 -88.858 30.000 74
6 1272.822 (Aspherical) 88.000 SILICA 661
7 -4176.748 100.200 661
8 -4021.459 (Aspherical) 102.000 BSL7Y 646.26
9 -480.000 (Aspherical) 90.000 674
10 -9800.000 40.000 PBL1Y 610
11 840.000 (Aspherical) 274.300 561.62
12 Plane 82.000 PBL1Y 636
13 -1040.201 3.000 636
14 -1058.165 40.000 BSL7Y 618
15 Plane 318.000 638
16 -656.249 46.000 BSL7Y 626
17 3530.000 (Aspherical surface) 372.85 662
18 -1375.500 (Aspheric) 100.000 SILICA 821.24
19 -760.0000 156.400 854
20 -1700 -156.4 MIRROR 960
21 -760.0000 -100.000 SILICA 854
22 -1375.500 (Aspherical surface) -372.85 821.24
23 3530.500 (Aspherical) -46.000 BSL7Y 662
24 -656. 249 -318.000 626
25 Plane -40.000 BSL7Y 638
26 -1058.165 -3.000 618
27 -1040.201 -82.000 PBL1Y 636
28 Plane 274.300 636
29 840.000 (Aspherical) -40.000 PBL1Y 561.62
30 -9801.893 -90.000 610
31 -480.000 (Aspherical) -102.000 BSL7Y 674
32 -4021.459 (Aspherical) -100.200 646.26
33 -4176.798 -88.000 SILICA 661
34 1272.838 (Aspherical)-30.000 661
35 -88.8581 -15.000 BSL7Y 74
36 -131.553 -20.000 68
37 -446.097 -10.000 BSL7Y 56
38 -97.4287 -89.564 52
39 plane

(Aspherical)
Surface 18, 22
k = -1.00835 A (4th order) = 0.00000 B (6th order) = 0.00000 C (8th order) = 0.00000
D (10th order) = 0.00000 E (12th order) = 0.00000 F (14th order) = 0.00000
G (16th) = 0.00000

Surface 17, 23
k = 0.00000 A (4th order) =-1.49749E-11 B (6th order) =-7.57907E-17
C (8th order) =-7.70529 E-22 D (10th order) = 1.026626E-26 E (12th order) =-7.07883E-32
F (14th) = 2.559601E-37 G (16th) =-3.76155E-43

Face 11, 29
k = 0.00000 A (4th order) = 6.914718E-11 B (6th order) = 6.03728E-16
C (8th order) = -1.53262E-20 D (10th order) = 3.61811E-25 E (12th order) = -4.74168E-30
F (14th order) = 3.217309E-35 G (16th order) = -8.85988E-41

Surface 9, 31
k = 0.00000 A (4th order) = 2.768476E-09 B (6th order) =-4.8556E-14
C (8th order) = 7.176113E-19 D (10th order) = -1.07637E-24 E (12th order) = 1.187443E-28
F (14th) =-7.98382E-34 G (16th) = 2.393557E-39


Surface 8, 32
k = 0.00000 A (4th order) =-4.35553E-09 B (6th order) = 3.635868E-14
C (8th order) =-5.95127E-19 D (10th order) = 7.658840E-24 E (12th order) =-7.19412E-29
F (14th order) = 3.942821E-34 G (16th order) =-9.54343E-40

Face 6, 34
k = 0.00000 A (4th order) =-1.06469E-09 B (6th order) = 3.377750E-14
C (8th order) = -1.10265E-19 D (10th order) = 2.282369E-24 E (12th order) = -2.74304E-29
F (14th) = 1.755771E-34 G (16th) -4.82195E-40

Table 3 shows numerical data of the measurement optical system L2 in the wavefront measurement mode 2 of FIG.
[Table 3]
Surface number Curvature radius R Surface spacing d Material Effective diameter
1 ∞ 315.730
2 -163.089 35.000 BSL7Y 150
3 -115.189 9.100 160
4 352.573 25.000 BSL7Y 170
5 151.4205 780.000 160
6 1272.822 (Aspherical) 88.000 SILICA 661
7 -4176.748 100.200 661
8 -4021.459 (Aspherical) 102.000 BSL7Y 646.26
9 -480.000 (Aspherical) 90.000 674
10 -9800.000 40.000 PBL1Y 610
11 840.000 (Aspherical) 274.300 561.62
12 Plane 82.000 PBL1Y 636
13 -1040.201 3.000 636
14 -1058.165 40.000 BSL7Y 618
15 Plane 318.000 638
16 -656.249 46.000 BSL7Y 626
17 3530.000 (Aspherical surface) 372.85 662
18 -1375.500 (Aspheric) 100.000 SILICA 821.24
19 -760.0000 156.400 854
20 -1700 -156.4 MIRROR 960
21 -760.0000 -100.000 SILICA 854
22 -1375.500 (Aspherical surface) -372.85 821.24
23 3530.500 (Aspherical) -46.000 BSL7Y 662
24 -656. 249 -318.000 626
25 Plane -40.000 BSL7Y 638
26 -1058.165 -3.000 618
27 -1040.201 -82.000 PBL1Y 636
28 Plane -274.300 636
29 840.000 (Aspherical) -40.000 PBL1Y 561.62
30 -9801.893 -90.000 610
31 -480.000 (Aspherical) -102.000 BSL7Y 674
32 -4021.459 (Aspherical) -100.200 646.26
33 -4176.798 -88.000 SILICA 661
34 1272.838 (Aspherical surface) -780.000 661
35 151.420 -25.000 BSL7Y 160
36 352.573 -9.100 170
37 -115.189 -35.000 BSL7Y 160
38 -163.089 -315.73 150
39 ∞

(Aspherical)
Surface 18, 22
k = -1.00835 A (4th order) = 0.00000 B (6th order) = 0.00000 C (8th order) = 0.00000
D (10th order) = 0.00000 E (12th order) = 0.00000 F (14th order) = 0.00000
G (16th) = 0.00000

Surface 17, 23
k = 0.00000 A (4th order) =-1.49749E-11 B (6th order) =-7.57907E-17
C (8th order) =-7.70529 E-22 D (10th order) = 1.026626E-26 E (12th order) =-7.07883E-32
F (14th) = 2.559601E-37 G (16th) =-3.76155E-43

Face 11, 29
k = 0.00000 A (4th order) = 6.914718E-11 B (6th order) = 6.03728E-16
C (8th order) = -1.53262E-20 D (10th order) = 3.61811E-25 E (12th order) = -4.74168E-30
F (14th order) = 3.217309E-35 G (16th order) = -8.85988E-41

Surface 9, 31
k = 0.00000 A (4th order) = 2.768476E-09 B (6th order) =-4.8556E-14
C (8th order) = 7.176113E-19 D (10th order) = -1.07637E-24 E (12th order) = 1.187443E-28
F (14th) =-7.98382E-34 G (16th) 2.393557E-39


Surface 8, 32
k = 0.00000 A (4th order) =-4.35553E-09 B (6th order) = 3.635868E-14
C (8th order) =-5.95127E-19 D (10th order) = 7.658840E-24 E (12th order) =-7.19412E-29
F (14th order) = 3.942821E-34 G (16th order) =-9.54343E-40

Face 6, 34
k = 0.00000 A (4th order) =-1.06469E-09 B (6th order) = 3.377750E-14
C (8th order) = -1.10265E-19 D (10th order) = 2.282369E-24 E (12th order) = -2.74304E-29
F (14th) = 1.755771E-34 G (16th) = -4.82195E-40

  In Tables 2 and 3, R represents the radius of curvature, and d represents the surface spacing. In Table 2, surface numbers 6 to 19 and 21 to 34 are the optical system 100, respectively. Surface numbers 2 to 5 and 35 to 38 are measurement optical systems L1, respectively. Surface number 20 is mirror M1. In Table 3, surface numbers 6 to 19 and 21 to 34 are optical systems. Surface numbers 2 to 5 and 35 to 38 are measurement optical systems L2. Surface number 20 is mirror M2.

  For convenience, in the wavefront measurement modes 1 and 2 of the first measurement system 1100a and the second measurement system 1100b in FIGS. 4A and 4B, the lenses L11 to L15 of the optical system 100 are as shown in Table 4. Is assumed to be eccentric. Further, in Table 4, the decentering amounts of the mirror M2 and the mirror M3 indicate that the decentering amounts of the mirrors M2 and M3 are corrected in order to correct the tilt components (zernike2 term, 3 term) generated by the decentering from the lenses L11 to L15. The amount is the centered amount.

[Table 4]
Lens name X eccentricity Y eccentricity L11 + 50.000um -50.000um
L12 -50.000um + 50.000um
L13 + 50.000um + 50.000um
L14 -50.000um + 50.000um
L15 + 50.000um + 50.000um
M2 -39.900um + 58.170um
M3 -56.820um + 64.570um

At this time, the calculated values of the coma component of the wavefront aberration in the wavefront measurement modes 1 and 2 are as shown in Table 5.
[Table 5]
Wavefront measurement form 1 Wavefront measurement form 2
zernike7 -1.051458λ -7.837996λ
zernike8 0.921803λ 1.738226λ
zernike14 0.068602λ -1.227027λ
zernike15 -0.032967λ -0.012590λ
zernike23 -5.1506E-4λ -0.374624λ
zernike24 -1.005759E-3λ -0.012639λ
λ = 632.8nm

Table 6 shows the calculation results optimized by optical design software with the decentering of the lenses L11 to L15 and the decentering of the mirrors M2 and M3 as variables, with the coma component of the wavefront aberration in Table 5 as a target. Become.

[Table 6]
Lens name X eccentricity calculation result Y eccentricity calculation result L11 + 50.000um -50.000um
L12 -50.000um + 50.000um
L13 + 50.000um + 50.000um
L14 -50.000um + 50.000um
L15 + 50.000um + 50.000um
M2 -39.900um + 58.170um
M3 -56.820um + 64.570um

  The numerical values in Tables 4 and 6 agree with each other, and it can be seen that the optical design optimization method calculated for obtaining the eccentricity is correct and reliable. From Tables 4 and 5, the eccentricity (Table 5) from the lens L11 to the lens L15 of the optical system can be correctly calculated from the results of wavefront measurement in the two measurement forms of the first measurement system 1100a and the second measurement system 1100b. I understand.

  FIG. 5 is a lateral aberration obtained by incorporating the calculation result (calculation method) of the eccentricity calculated in Table 5 into an optical software model and calculating the optical performance of the reflecting telescope 1 shown in FIG. 2 by simulation.

  In the optical system adjustment method and the like of the present invention, not only adjustment to improve the wavefront aberration of the optical system is performed, but also the eccentricity of each lens is obtained and incorporated in the optical software model. As a result, as shown in FIG. 5, the optical performance can be evaluated by simulation even when measurement is not possible with the angle of view and image height as shown in FIG.

  FIG. 6 is an explanatory diagram of a Fizeau interferometer as an example used in the first measurement system 1100a and the second measurement system 1100b of the embodiment shown in FIGS. 4 (A) and 4 (B). In FIG. 6, laser light (wavelength 632.8 nm) emitted from the laser light source 11 becomes parallel light by the beam expander 12 and the collimator lens 13 and enters the half mirror 14. Part of the laser light that has passed through the half mirror surface 14 a of the half mirror 14 is reflected by the reference surface 15 a made up of the half mirror of the reference optical system 15, becomes reference light, is reflected by the half mirror surface 14 a, and is collected by the imaging lens 16. The light is incident on the detection means 17.

  On the other hand, the laser beam that has passed through the reference optical system 15 is collected and then enters the measurement optical system L1 (L2) shown in FIG. As shown in FIGS. 4A and 4B, the laser light that has passed through the measurement optical system L1 (L2) returns via the optical system 100 and the mirror M1 (M2), and the reference optical system 15, the half mirror 14a, and the connection result. The light enters the detection means 17 through the image lens 16. Then, it interferes with the laser beam reflected by the reference surface 15a to form an interference pattern. The wavefront aberration of the optical system 100 is measured by detecting the fringe of the interference pattern by the detection means 17 (step 1 in FIG. 1).

  The measurement of the wavefront aberration of the optical system 100 is not limited to this interference method, and any method may be used.

  As described above, according to the present invention, it is possible to easily measure the assembly accuracy of the optical elements constituting the optical system even when the optical system to be measured is large, and to obtain desired imaging performance. Thus, optical adjustment such as decentration of the optical element can be easily performed.

DESCRIPTION OF SYMBOLS 1 Reflective telescope 100 Optical system L11-L15 Optical member M1, M2 Mirror 1100a 1st measurement system 1100b 2nd measurement system L1, L2 Measurement optical system

Claims (3)

A light beam is incident on the optical system from the first measurement system, and the wavefront aberration of the optical system is measured using the light beam via the optical system, and the optical of the light beam from the first measurement system is measured by the second measurement system. A first step in which a light beam is incident on the optical system in an optical path different from an optical path passing through the system, and a wavefront aberration of the optical system is measured using the light beam via the optical system;
A second step of calculating a decentering amount of each optical element constituting the optical system from the wavefront aberration obtained by the first measurement system and the wavefront aberration obtained by the second measurement system. A method for calculating the amount of eccentricity of an optical system.   A third step of adjusting the position of each optical element constituting the optical system using the amount of eccentricity calculated in the second step in the method of calculating the amount of eccentricity of the optical system according to claim 1 is provided. Adjustment method of optical system.   A decentered optical model for each optical element of the optical system is created using the decentration amount calculated in the second step of the decentration amount calculation method for the optical system according to claim 1, and the decentered optical model is used to create the decentered optical model. A method for evaluating an optical system, wherein simulation is performed assuming that the optical system is actually used by being mounted on a part of another optical system, and the optical performance of the optical system is evaluated.