JP5063243B2 - Main focus correction optical system and reflection telescope using the same - Google Patents

Description

  The present invention relates to a main focus correction optical system for correcting aberrations of a main mirror of a reflective telescope.

  In observations other than the zenith, astronomical observations cause a shift in the star image due to the wavelength of light due to atmospheric dispersion. A main focus correction optical system for a reflective telescope having a function of correcting such atmospheric dispersion is disclosed in Patent Document 1.

In Patent Literature 1, atmospheric dispersion is corrected by moving a compound lens composed of a pair of lenses made of materials having different dispersions. As a result, both the aberration of the main mirror and the chromatic aberration due to atmospheric dispersion are satisfactorily corrected while achieving downsizing of the entire lens system.
Japanese Patent No. 3057946

  The viewing angle of the reflecting telescope using the main focus correction optical system of Patent Document 1 is 0.5 °. In recent years, it has been desired to further improve the survey capability of the telescope. For this reason, it is desired to further increase the field of view of the main focus correction optical system.

  In addition, in the main focus correction optical system disclosed in Patent Document 1, 3 to 5 types of optical glasses are used. However, if the viewing angle is increased by 3 to 4 times, the diameter of each lens constituting the main focus correction optical system increases. In particular, a large diameter is required for the two single lenses from the side closer to the primary mirror. For this reason, it was common to select quartz instead of optical glass for the two single lenses because of manufacturing problems.

  According to the study by the inventors, when both of these single lenses are made of quartz, it has been found that it is difficult to widen the field of view sufficiently because chromatic aberration remains in the visible region to the near infrared region. .

  It is an object of the present invention to provide a main focus correction optical system that can correct a chromatic aberration well and can realize a reflecting telescope having a larger viewing angle than conventional ones.

  The present invention relates to a main focal point correction optical system for a reflective telescope having a compound lens including a pair of lenses having different dispersions, the compound lens being movable so as to have a component in a direction perpendicular to the optical axis. It is.

In such a main focus correction optical system, in one example of the present invention, constitute one quartz two single lenses from closer to the primary mirror, the other optical glass, none of the two single lenses It is a positive lens .

In another example of the present invention, when one of the pair of lenses included in the compound lens has a refractive index of nd and an Abbe number of νd,
1.538 ≦ nd ≦ 1.558
44.8 ≦ νd ≦ 46.8
It is characterized by comprising an optical glass that satisfies the following conditions.

The refractive index nd is a refractive index with respect to d-line (587.6 nm). The Abbe number νd is defined by:
νd = (nd−1) / (nF−nC)
However, refractive index for nd: d line (587.6 nm) nF: refractive index for F line (486.1 nm) nC: refractive index for C line (656.3 nm)

  According to the present invention, a reflective telescope having a larger viewing angle than that of the prior art can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram of a main part of a reflecting telescope according to a first embodiment of the present invention.

  In FIG. 1, M1 is a main mirror, and 100 is a main focus correction optical system. The primary mirror M1 is a concave rotating hyperboloid. The main focus correction optical system 100 is disposed in the vicinity of the focus of the main mirror M1, and corrects aberrations generated by the main 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, forms an image via the main focus correction optical system 100.

  FIG. 2 is a diagram showing the configuration of the main focus correction optical system 100 in more detail. The main focus correction optical system 100 includes lenses L11 to L18. G is a glass block representing a filter for selecting a transmission wavelength band.

  The two single lenses L11 and L12 from the side closer to the main mirror M1 are very large lenses having an effective diameter exceeding φ500 mm. One of the features of the present invention is that the materials constituting the lenses L11 and L12 are appropriately set. Specifically, one lens L11 is made of quartz, and the other lens L12 is made of optical glass. Thus, by devising the materials constituting the lenses L11 and L12, the chromatic aberration is corrected well, and a reflective telescope having a large viewing angle is realized. In addition, the signs of the refractive power (power) are positive in both the lenses L11 and L12.

  L15 is a compound lens for correcting atmospheric dispersion. Color shift due to atmospheric dispersion is corrected by moving the compound lens L15 in a direction (arrow direction in the figure) perpendicular to the optical axis by a moving mechanism (not shown). Note that the moving direction of the compound lens L15 is not limited to the direction orthogonal to the optical axis, but may be rotated around a predetermined point on the optical axis. That is, if the compound lens L15 is configured to be movable so as to have a component in a direction perpendicular to the optical axis, the atmospheric dispersion can be corrected.

  The compound lens L15 is composed of a pair of lenses L151 and L152 having a refractive index close to each other and different in dispersion from each other with a slight air layer therebetween. Specifically, the material constituting the lens L151 has a refractive index nd of 1.51633 and an Abbe number νd of 64.2. The material constituting the lens L152 has a refractive index nd of 1.54814 and an Abbe number νd of 45.8.

In this embodiment, the lens L152 constituting the compound lens L15 is
1.538 ≦ nd ≦ 1.558 (1)
44.8 ≦ νd ≦ 46.8 (2)
It consists of optical glass that satisfies the following conditions.

  Necessary when correcting the atmospheric dispersion by moving the compound lens L15 in a direction orthogonal to the optical axis by configuring the lens L152 with optical glass that satisfies the conditional expressions (1) and (2). An amount of chromatic aberration can be generated.

In addition, the lens L151 constituting the compound lens L15 is
1.506 ≦ nd ≦ 1.526 (3)
63.2 ≦ νd ≦ 65.2 (4)
It consists of optical glass that satisfies the following conditions.

  By configuring the lens L151 with an optical glass that satisfies the conditional expressions (3) and (4), it is possible to correct monochromatic aberration generated in the lens L152. Further, when combined with a lens L152 made of optical glass that satisfies the conditional expressions (1) and (2), the compound lens L15 is moved in a direction orthogonal to the optical axis to correct atmospheric dispersion. The necessary amount of chromatic aberration is generated.

  The lens L151 has a flat object side (primary mirror side) surface, and the lens L152 has a flat image surface side lens surface. That is, the light incident surface and the light exit surface of the compound lens L15 are both flat.

  Thereby, the change of monochromatic aberration when the compound lens L15 is moved in the direction orthogonal to the optical axis is kept small.

  Next, Table 1 shows numerical data of Example 1. In the table, R represents a radius of curvature, and d represents a surface interval. Quartz and two types of optical glass are used for the lens material. Specifically, quartz has a refractive index nd of 1.45846 and an Abbe number νd of 67.8, optical glass A has a refractive index nd of 1.51633, an Abbe number νd of 64.2, and optical glass B has a refractive index nd. 1.54814 and the Abbe number νd is 45.8.

  In the table, the atmospheric dispersion correction compound lens L15 is indicated as ADC (meaning Atmospheric Dispersion Compensator).

  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 of

It is expressed by the following formula.

  Further, f is a combined focal length of the main mirror and the main focus correction optical system, FNO is an F number, ω is a half field angle, and 2ω is a full field angle (viewing angle).

(Table 1)
f = 19958.9 FNO = 2.43 2ω = 1.9 °

Surface number Effective diameter R d Material
1 8200.0 30000.000 (Aspherical surface) 13335.002 (Primary mirror)
2 970.0 1092.370 79.115 Quartz
3 970.0 1471.448 (Aspherical surface) 100.000
4 879.5 814.514 94.096 Optical glass B
5 850.5 1211.660 (Aspherical surface) 265.290
6 705.9 14987.577 (Aspherical surface) 45.000 Optical glass B
7 636.1 544.594 172.391
8 635.7 -1037.525 40.000 Optical glass A
9 648.9 -2624.444 (Aspherical surface) 100.000
10 664.9 ∞ 40.000 Optical glass A (ADC)
11 673.3 1000.000 3.000
12 675.0 1000.000 100.000 Optical glass B (ADC)
13 677.9 ∞ 400.299
14 712.1 -1076.827 (Aspherical) 50.000 Quartz
15 750.5 -2289.929 30.000
16 828.8 690.734 (Aspherical surface) 197.447 Quartz
17 826.6 -2341.440 187.738
18 771.4 ∞ 10.000 Optical glass A (Filter)
19 769.8 ∞ 50.000
20 759.1 -2748.545 (Aspherical) 109.884 Quartz
21 751.3 -959.790 10.000

(Aspherical)
Surface k A (4th order) B (6th order) C (8th order)
1 -1.00835 0.00000 0.00000 0.00000

D (10th order) E (12th order) F (14th order) G (16th order)
0.00000 0.00000 0.00000 0.00000

Surface k A (4th order) B (6th order) C (8th order)
3 -3.22896 6.6052E-11 -1.1048E-16 1.0281E-21

D (10th order) E (12th order) F (14th order) G (16th order)
-8.8648E-27 3.5872E-32 -6.5041E-38 3.7813E-44

Surface k A (4th order) B (6th order) C (8th order)
5 -0.95945 1.7788E-11 6.1297E-18 -3.0669E-21

D (10th order) E (12th order) F (14th order) G (16th order)
3.6607E-26 -1.9341E-31 4.3481E-37 -2.6201E-43

Surface k A (4th order) B (6th order) C (8th order)
6 0.00000 1.1843E-10 -4.2951E-16 -4.3113E-21

D (10th order) E (12th order) F (14th order) G (16th order)
1.5894E-25 -1.6823E-30 7.6776E-36 -1.1866E-41

Surface k A (4th order) B (6th order) C (8th order)
9 0.00000 -3.3629E-10 -5.6891E-16 2.1443E-22

D (10th order) E (12th order) F (14th order) G (16th order)
6.9908E-26 -5.1635E-31 -1.5727E-36 2.3225E-41

Surface k A (4th order) B (6th order) C (8th order)
14 0.00000 -7.7726E-10 -3.0771E-15 1.2786E-20

D (10th order) E (12th order) F (14th order) G (16th order)
-1.1774E-25 1.7348E-30 -1.3055E-35 3.8106E-41

Surface k A (4th order) B (6th order) C (8th order)
16 0.00000 -4.7809E-10 1.0608E-15 -1.5397E-20

D (10th order) E (12th order) F (14th order) G (16th order)
8.3166E-26 -5.6815E-31 2.3582E-36 -4.6811E-42

Surface k A (4th order) B (6th order) C (8th order)
20 0.00000 2.2644E-09 -1.8848E-14 1.2763E-19

D (10th order) E (12th order) F (14th order) G (16th order)
-1.2070E-24 1.0334E-29 -4.4522E-35 7.4863E-41

  As is clear from the above numerical data, the main focus correction optical system of the present embodiment includes a lens made of optical glass that satisfies the above conditional expressions (1) and (2) in addition to the lens L152. Yes. Specifically, the lenses L12 and L13 are made of this material. Thereby, when the compound lens L15 is not moved in the direction orthogonal to the optical axis, the chromatic aberration remaining in the compound lens L15 can be corrected well.

  In addition to the lens L151, the main focus correction optical system of the present embodiment includes a lens made of optical glass that satisfies the above conditional expressions (3) and (4). Specifically, the lens L14 is made of this material. Thereby, when the compound lens L15 is not moved in the direction orthogonal to the optical axis, the chromatic aberration remaining in the compound lens L15 can be corrected well.

  3 and 4 are aberration diagrams of the reflecting telescope of Example 1. FIG. FIG. 3 is a longitudinal aberration diagram, and FIG. 4 is a lateral aberration diagram. As is apparent from the aberration diagrams, by using the main focus correction optical system of the present embodiment for the reflecting telescope, a good imaging performance is obtained over the entire viewing angle of 1.9 degrees.

  FIG. 5 is a diagram illustrating a configuration of the main focus correction optical system according to the second embodiment. The main focus correction optical system 200 in the figure is arranged near the focus position of the main mirror, similarly to the main focus correction optical system 100 of Example 1 in FIG.

  In FIG. 5, the main focus correction optical system 200 includes lenses L21 to L28. G is a glass block representing a filter for selecting a transmission wavelength band.

  As with the first embodiment, the two lenses L21 and L22 from the side closer to the main mirror M1 both have an effective diameter exceeding φ500 mm. In this embodiment, the lens L21 is made of optical glass, and the lens L22 is made of quartz. In this way, in the present embodiment as well, by devising the material of the two lenses from the side closer to the main mirror M1, chromatic aberration is corrected well, and a reflecting telescope with a large viewing angle is realized. The sign of the refractive power (power) is positive for both the lenses L21 and L22.

  L25 is a compound lens for correcting atmospheric dispersion, and is movable in a direction orthogonal to the optical axis. The compound lens L25 is configured by arranging a pair of lenses L251 and L252 having a close refractive index and different dispersion from each other with a slight air gap therebetween. Specifically, the refractive index nd of the material constituting the lens L251 is 1.51633, and the Abbe number νd is 64.2. The material constituting the lens L252 has a refractive index nd of 1.54814 and an Abbe number νd of 45.8.

  As described above, the lens L252 of this embodiment is also made of a material that satisfies the conditional expressions (1) and (2), as in the first embodiment. As a result, the same effect as in the first embodiment is obtained.

  Similarly to the first embodiment, the lens L251 is also made of a material that satisfies the conditional expressions (3) and (4). As a result, the same effect as in the first embodiment is obtained.

  The lens L251 has a flat object side (primary mirror side) surface, and the lens L252 has a flat image surface side lens surface. That is, the light incident surface and the light exit surface of the compound lens L25 are both flat.

  Next, Table 2 shows numerical data of Example 2. The meaning of the symbols is the same as in the first embodiment. The lens material is quartz and two types of optical glass. Specifically, quartz has a refractive index nd of 1.45846 and an Abbe number νd of 67.8, optical glass A has a refractive index nd of 1.51633, an Abbe number νd of 64.2, and optical glass B has a refractive index nd. 1.54814 and the Abbe number νd is 45.8.

(Table 2)
f = 19524.8 FNO = 2.38 2ω = 1.9 °

Surface number Effective diameter R d Material
1 8200.0 30000.000 (Aspherical surface) 13335.002 (Primary mirror)
2 970.0 1833.240 72.260 Optical glass B
3 970.0 3367.768 (Aspherical) 10.000
4 892.5 679.598 93.106 Quartz
5 860.6 824.106 (Aspherical surface) 329.604
6 710.4 73720.599 (Aspherical surface) 45.000 Optical glass B
7 655.9 730.893 182.334
8 646.9 -1035.164 40.000 Optical glass A
9 655.6 -4281.669 (Aspherical) 10.000
10 657.9 ∞ 40.000 Optical glass A (ADC)
11 664.3 1000.000 3.000
12 665.9 1000.000 100.000 Optical glass B (ADC)
13 668.1 ∞ 500.000
14 702.0 -1486.270 (Aspherical surface) 73.254 Quartz
15 745.6 -4682.392 10.000
16 807.0 727.104 (Aspherical surface) 201.105 Quartz
17 806.1 -1731.620 176.269
18 748.7 ∞ 10.000 Optical glass A (Filter)
19 747.0 ∞ 50.000
20 743.2 -1243.666 (Aspherical surface) 111.380 Quartz
21 736.3 -824.163 10.000

(Aspherical)
Surface k A (4th order) B (6th order) C (8th order)
1 -1.00835 0.00000 0.00000 0.00000

D (10th order) E (12th order) F (14th order) G (16th order)
0.00000 0.00000 0.00000 0.00000

Surface k A (4th order) B (6th order) C (8th order)
3 -15.02165 2.1808E-11 1.3009E-16 -1.4478E-22

D (10th order) E (12th order) F (14th order) G (16th order)
-4.8157E-27 3.3280E-32 -8.6566E-38 7.9762E-44

Surface k A (4th order) B (6th order) C (8th order)
5 -0.73222 7.4816E-11 -4.3973E-16 -1.7855E-21

D (10th order) E (12th order) F (14th order) G (16th order)
2.8523E-26 -1.7469E-31 3.7468E-37 -1.2026E-43

Surface k A (4th order) B (6th order) C (8th order)
6 0.00000 9.5582E-11 -2.7429E-16 -1.7607E-21

D (10th order) E (12th order) F (14th order) G (16th order)
1.0935E-25 -1.1671E-30 5.0868E-36 -6.4398E-42

Surface k A (4th order) B (6th order) C (8th order)
9 0.00000 -1.3795E-10 4.1569E-16 5.4029E-21

D (10th order) E (12th order) F (14th order) G (16th order)
3.6686E-26 -3.8061E-31 -6.8045E-37 1.6815E-41

Surface k A (4th order) B (6th order) C (8th order)
14 0.00000 -1.8943E-09 7.7835E-15 -6.2111E-20

D (10th order) E (12th order) F (14th order) G (16th order)
8.9982E-26 3.0721E-30 -2.7670E-35 7.7861E-41

Surface k A (4th order) B (6th order) C (8th order)
16 0.00000 4.9017E-10 -9.4345E-15 6.2787E-20

D (10th order) E (12th order) F (14th order) G (16th order)
-3.1845E-25 5.4220E-31 1.5115E-36 -6.8053E-42

Surface k A (4th order) B (6th order) C (8th order)
20 0.00000 2.8218E-09 -4.0460E-14 5.1195E-19

D (10th order) E (12th order) F (14th order) G (16th order)
-4.9045E-24 3.2607E-29 -1.2290E-34 1.9533E-40

  As is clear from the above numerical data, the main focus correction optical system of the present embodiment includes a lens made of optical glass that satisfies the above conditional expressions (1) and (2) in addition to the lens L252. Yes. Specifically, the lenses L21 and L23 are made of this material. Thereby, the effect similar to Example 1 is acquired.

  In addition to the lens L251, the main focus correction optical system of the present embodiment includes a lens made of optical glass that satisfies the above conditional expressions (3) and (4). Specifically, the lens L24 is made of this material. Thereby, the effect similar to Example 1 is acquired.

  6 and 7 are aberration diagrams of the reflecting telescope of Example 2. FIG. FIG. 6 is a longitudinal aberration diagram, and FIG. 7 is a lateral aberration diagram. As is apparent from the aberration diagrams, by using the main focus correction optical system of the present embodiment for the reflecting telescope, a good imaging performance is obtained over the entire viewing angle of 1.9 degrees.

  FIG. 8 is a diagram illustrating a configuration of the main focus correction optical system according to the third embodiment. The main focus correction optical system 300 in the figure is arranged near the focus position of the main mirror, similarly to the main focus correction optical system 100 of Example 1 in FIG.

  In FIG. 8, the main focus correction optical system 300 includes lenses L31 to L38. G is a glass block representing a filter for selecting a transmission wavelength band.

  The two lenses L31 and L32 from the side closer to the main mirror M1 both have an effective diameter exceeding φ500 mm, as in the first embodiment. In this embodiment, the lens L31 is made of optical glass, and the lens L32 is made of quartz. In this way, in the present embodiment as well, by devising the material of the two lenses from the side closer to the main mirror M1, chromatic aberration is corrected well, and a reflecting telescope with a large viewing angle is realized. The sign of the refractive power of the lens L31 is positive, and the sign of the refractive power of the lens L32 is negative.

  L35 is a compound lens for correcting atmospheric dispersion, and is movable in a direction orthogonal to the optical axis. The compound lens L35 is configured by arranging a pair of lenses L351 and L352 having a refractive index close to each other and different in dispersion from each other with a slight air gap therebetween. Specifically, the material constituting the lens L351 has a refractive index nd of 1.51633 and an Abbe number νd of 64.2. The material constituting the lens L352 has a refractive index nd of 1.54814 and an Abbe number νd of 45.8.

  As described above, the lens L352 of the present embodiment is also made of a material that satisfies the conditional expressions (1) and (2), as in the first embodiment. As a result, the same effect as in the first embodiment is obtained.

  Similarly to the first embodiment, the lens L351 is made of a material that satisfies the conditional expressions (3) and (4). As a result, the same effect as in the first embodiment is obtained.

  The lens L351 has a flat object side (primary mirror side) surface, and the lens L352 has a flat image surface side lens surface. That is, the light incident surface and the light exit surface of the compound lens L35 are both flat.

  Table 3 shows numerical data of Example 3. The meaning of the symbols is the same as in the first embodiment. The lens material is quartz and two types of optical glass. Specifically, quartz has a refractive index nd of 1.45846 and an Abbe number νd of 67.8, optical glass A has a refractive index nd of 1.51633, an Abbe number νd of 64.2, and optical glass B has a refractive index nd. 1.54814 and the Abbe number νd is 45.8.

(Table 3)
f = 19403.6 FNO = 2.37 2ω = 1.9 °

Surface number Effective diameter R d Material
1 8200.0 30000.000 (Aspherical surface) 13335.002 (Primary mirror)
2 970.0 873.348 157.175 Optical glass A
3 970.0 3333.244 (Aspherical surface) 158.480
4 840.5 -13212.913 50.000 Quartz
5 761.7 791.282 (Aspherical) 407.404
6 649.3 -1754.228 (Aspherical surface) 45.000 Optical glass B
7 635.2 1578.997 200.000
8 637.3 -1848.843 40.000 Optical glass A
9 646.9 -18294.701 (Aspherical) 17.370
10 650.3 ∞ 40.000 Optical glass A (ADC)
11 672.4 1000.000 3.000
12 675.2 1000.000 100.000 Optical glass B (ADC)
13 683.6 ∞ 177.657
14 727.9 -6814.108 (Aspherical) 72.001 Quartz
15 759.4 -2478.171 10.000
16 820.0 965.597 (Aspherical) 202.733 Quartz
17 820.1 -1423.173 177.305
18 753.8 ∞ 10.000 Optical glass A (Filter)
19 751.9 ∞ 50.000
20 746.7 -1313.138 (Aspherical) 114.188 Quartz
21 737.5 -839.091 10.000

(Aspherical)
Surface k A (4th order) B (6th order) C (8th order)
1 -1.00835 0.00000 0.00000 0.00000

D (10th order) E (12th order) F (14th order) G (16th order)
0.00000 0.00000 0.00000 0.00000

Surface k A (4th order) B (6th order) C (8th order)
3 -54.66745 1.1374E-10 -4.4860E-16 1.5269E-21

D (10th order) E (12th order) F (14th order) G (16th order)
-5.6784E-27 1.7056E-32 -2.9347E-38 1.9993E-44

Surface k A (4th order) B (6th order) C (8th order)
5 -0.98376 -1.8468E-11 -3.7934E-16 -2.5415E-21

D (10th order) E (12th order) F (14th order) G (16th order)
1.7136E-26 -7.6661E-32 -5.9696E-38 7.0824E-43

Surface k A (4th order) B (6th order) C (8th order)
6 0.00000 2.6517E-10 -2.3391E-16 -7.4009E-21

D (10th order) E (12th order) F (14th order) G (16th order)
2.0264E-25 -1.9829E-30 7.6322E-36 -7.1631E-42

Surface k A (4th order) B (6th order) C (8th order)
9 0.00000 6.7928E-10 1.2811E-15 2.3516E-21

D (10th order) E (12th order) F (14th order) G (16th order)
7.8333E-26 1.5698E-30 -2.5409E-35 1.0393E-40

Surface k A (4th order) B (6th order) C (8th order)
14 0.00000 -2.7301E-09 1.4387E-14 -7.8855E-20

D (10th order) E (12th order) F (14th order) G (16th order)
1.6854E-25 3.1944E-30 -2.9090E-35 7.8285E-41

Surface k A (4th order) B (6th order) C (8th order)
16 0.00000 1.7980E-09 -1.5000E-14 7.6734E-20

D (10th order) E (12th order) F (14th order) G (16th order)
-2.8399E-25 3.6952E-32 3.6417E-36 -9.9395E-42

Surface k A (4th order) B (6th order) C (8th order)
20 0.00000 2.8607E-09 -3.6761E-14 4.3135E-19

D (10th order) E (12th order) F (14th order) G (16th order)
-4.2651E-24 3.1025E-29 -1.2624E-34 2.1112E-40

  As is clear from the above numerical data, the main focus correction optical system of the present embodiment includes a lens made of optical glass that satisfies the above conditional expressions (1) and (2) in addition to the lens L352. Yes. Specifically, the lens L33 is made of this material. Thereby, the effect similar to Example 1 is acquired.

  In addition to the lens L351, the main focus correction optical system of the present embodiment includes a lens made of optical glass that satisfies the above conditional expressions (3) and (4). Specifically, the lenses L31 and L34 are made of this material. Thereby, the effect similar to Example 1 is acquired.

  9 and 10 are aberration diagrams of the reflecting telescope of Example 3. FIG. FIG. 9 is a longitudinal aberration diagram, and FIG. 10 is a lateral aberration diagram. As is apparent from the aberration diagrams, by using the main focus correction optical system of the present embodiment for the reflecting telescope, a good imaging performance is obtained over the entire viewing angle of 1.9 degrees.

  In the first to third embodiments described above, the example of the viewing angle of 1.9 ° has been described, but the viewing angle is not limited to this value and can be implemented. For example, the present invention can be applied to other viewing angles such as a viewing angle of 1.5 ° or 2 °.

  In Examples 1 to 3, as the optical glass, optical glass A (refractive index nd is 1.51633, Abbe number νd is 64.2) and optical glass B (refractive index nd is 1.54814, Abbe number). νd is 45.8), but is not limited thereto. The two optical glasses constituting the composite lens can be applied as long as they are optical glasses having similar refractive indexes and different dispersions. Optical glass other than the glass shown in the embodiments can be applied to other lenses.

  In the above-described embodiment, an example in which atmospheric dispersion is corrected by moving a compound lens in a direction orthogonal to the optical axis using a compound lens having both end surfaces flat as the compound lens has been described. However, other types of compound lenses may be used. For example, as described in Patent Document 1, a method of correcting atmospheric dispersion by using a compound lens having both concentric spherical surfaces and rotating the compound lens around the center of curvature may be used. .

It is the schematic of the astronomical telescope of Example 1 of this invention. It is a figure which shows the main focus correction | amendment optical system used for the astronomical telescope of Example 1. FIG. FIG. 4 is a longitudinal aberration diagram of the astronomical telescope of Example 1. 3 is a lateral aberration diagram of the astronomical telescope of Example 1. FIG. It is a figure which shows the main focus correction | amendment optical system used for the astronomical telescope of Example 2. FIG. FIG. 6 is a longitudinal aberration diagram of the astronomical telescope of Example 2. 6 is a lateral aberration diagram of the astronomical telescope of Example 2. FIG. It is a figure which shows the main focus correction | amendment optical system used for the astronomical telescope of Example 3. FIG. It is a longitudinal aberration diagram of the astronomical telescope of Example 3. 6 is a lateral aberration diagram of the astronomical telescope of Example 3. FIG.

Explanation of symbols

M1 main mirror 100, 200, 300 main focus correction optical system L11, L21, L31 first lens L12, L22, L32 second lens L15, L25, L35 compound lens L151, L251, L351 first lens constituting compound lens L152 , L252, L352 Second lens constituting the compound lens G filter

Claims (8)

In a main focus correction optical system of a reflective telescope having a compound lens including a pair of lenses having different dispersions and configured to be movable so that the compound lens has a component in a direction perpendicular to the optical axis.
One of the two single lenses from the side close to the primary mirror is made of quartz and the other is made of optical glass .
2. The main focus correction optical system according to claim 1, wherein both of the two single lenses have a positive refractive power . When one of the pair of lenses constituting the compound lens has a refractive index of nd and an Abbe number of νd,
1.538 ≦ nd ≦ 1.558
44.8 ≦ νd ≦ 46.8
The main focus correction optical system according to claim 1, wherein the main focus correction optical system is made of an optical glass that satisfies the following conditions. The other of the pair of lenses constituting the compound lens,
1.506 ≦ nd ≦ 1.526
63.2 ≦ νd ≦ 65.2
3. The main focus correction optical system according to claim 2, wherein the main focus correction optical system is made of an optical glass that satisfies the following conditions. Other than one of the pair of lenses constituting the compound lens, 1.538 ≦ nd ≦ 1.558
44.8 ≦ νd ≦ 46.8
4. The main focus correction optical system according to claim 2 , further comprising a lens made of an optical glass that satisfies the following condition. Other than the other lens of the pair of lenses constituting the compound lens, 1.506 ≦ nd ≦ 1.526
63.2 ≦ νd ≦ 65.2
The main focus correction optical system according to claim 2 to 4 any one, characterized in that it comprises a structure lenses of optical glass satisfying the following condition. The compound lens, the main focus correction optical system according to any one of claims 1 to 5, characterized in that configure the pair of lenses arranged close via an air layer. The main focus correction optical system according to any one of claims 1 to 6, characterized in that it constitutes a light incident surface and light exit surface in the plane of the compound lens. A reflecting telescope comprising: a main mirror; and the main focus correcting optical system according to claim 1 .

Images