DE2228236A1 - Katadioptnian optical system - Google Patents

Description

Catadioptric optical system

The invention relates to a catadioptric optical system, in particular an optical system with a catadioptric lens.

A catadioptric lens contains one or more light-reflecting surfaces, which are referred to below as mirrors and are used to generate an image in a desired manner Contributing level of focus. A known lens of this type contains an annular, concave primary mirror that receives the object light and reflects it forward onto a secondary mirror of smaller diameter which is arranged on the optical axis in front of the primary mirror, i.e. between the primary mirror and the object. The secondary mirror reflects the image beam backwards onto an image receiving surface which is in the area or behind the central opening of the Primary mirror is arranged.

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Such a known catadioptric lens is a hit the middle area of the secondary mirror is not used, because the beam hitting it has a circular cross-section after reflection at the primary mirror.

According to the invention, an optical system with a catadioptric lens is provided which has an annular concave primary mirror and an annular secondary mirror for receiving the light of the primary mirror, which contains the Light is reflected in an image receiving area in the area of the central opening of the primary mirror; The axis of the catadioptric objective is within the central area defined by the inner diameter of the secondary mirror is formed, an independent imaging second device is arranged which directs light into said imaging area.

The invention thus eliminates the unused central zone of the previously customary secondary mirror and a second optical device provided with the catadioptric objective on a common optical axis.

Catadioptric lenses have a wide range of applications and are generally used whenever a relatively small angle of view (not greater than approx short back focal length is required. These applications are given, for example, with aiming or direction finding devices and with night vision devices that can work with infrared light. The designations ⁶¹ * ¹ light "," light transmitting ⁸¹ , "light reflecting" etc. are to be understood in this sense in the following description.

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For example, if the catadioptric lens is in a When aiming device is used, the independent second imaging device may be a reticle overlay system. In this case the images of the with the catadioptric Objectively recorded object and the cross-hairs recorded with the fade-in system in the image receiving area are mutually exclusive superimposed, this area for example by the Cathode surface of an image intensifier tube can be formed.

In other cases of application of the catadioptric lens For example, the second image generating device can be formed by a second optical lens, for example an inverse telephoto lens, so that the object can be viewed with different magnifications. In this case it can the overall system included an aperture or a shutter, whereby only the catadioptric or the inverse telephoto lens is effective at a given tent point.

The second imaging device can have at least one lens component in common with the catadioptric objective. For example, the catadioptric lens can contain a lens component in front of the primary mirror which carries the secondary mirror on its back and is also part of the inverse fele lens. A front lens component can be provided which is also part of the inverse telephoto lens and is located in front of the lens component carrying the secondary mirror. Furthermore, the catadioptric lens can contain at least one component for correcting the astigmatism and the curvature of field between the secondary mirror and the image receiving area. This also forms part of the second image generation device. In connection with these possibilities it should be pointed out that the designations "front ¹¹ and" rear "refer to the direction of entry of the light into the catadioptric lens

are to be understood, i.e. the light shining from the front onto the Primary level falls.

Numerical data for four embodiments of a catadioptric lens are given together with numerical data for examples of a telephoto lens used at the same time according to an overall system according to the invention in the following tables, in which R ₁ , R ₂ ... the radii of curvature of the individual surfaces of the lens arranged one after the other at which the light is incident and the positive sign indicates a curvature that is convex with respect to the front side and the negative sign indicates a curvature that is concave with respect to the front side. D ₁ , Dg ... denote the axial thickness of the individual lens components. S ₁ , Sg ... denote the axial air gaps between the individual components. The tables contain either the glass reference numbers or the mean refractive indices n ^ and the Abbe numbers V of the substances used for the lenses, as well as the inner diameter of the individual surfaces and, if applicable for the catadioptric objective, the inner diameter of the ring surfaces. In the case of ring parts, the thickness values D ₁ , Dg and the distances S ₁ , Sg in the tables are nominal values which indicate the corresponding values for the axial thickness and the distances if the respective surfaces were complete.

Table A for Example I relates to a catadioptric objective with a simple front lens (R ₁ , Rg) on which the light is incident first, a simple second lens (R ,, Ra) »a primary mirror (Rc) and a secondary mirror (Rg), which receives the light reflected forwards at the primary mirror and reflects it backwards into the image receiving area in the focal plane.

ι η 9 8 5? / η 7 ι ς

Example I - Table A Katadlontrisches Obiektlv - focal length 7.1Q4

Radius, thickness or refraction »- Illuminated inside distance index number V diameter diameter

R ₁ + 12.207 ^D 1 0.941 1.517 64. 2 8.00 3.60 R ₂ ^S 1 0.8137 8.00 3.60 ^R 3- 10.239 ^D 2 0.345 1.517 64. 2 8.00 2.40 R ₄ - 51.21 ^S 2 4.3504 8.00 2.40 ^S 3 3.5411 Aluminized
Flat glass ^R 5- 13.693 Aluminized
Flat glass 8.00 3.60 ^R 6 OO 3.74 1.60

Table B for example I relates to an inverse telephoto lens arranged on a common optical axis in the catadioptric lens according to Table A. It consists of six simple lens components (R ₁ to R ₁₂ ) *

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Example I - Table B

+ 4.630 Thick or 0.2380 - focal length 2.00 lights Inverse telephoto lens distance Glass reference number By radius - 27.870 0.0490 knife 1,800 - 26,650 ^D 1 0.1040 ^R 1 Schott SF4 1,800 ₊ 1.1620 ^S 1 3.5440 R ₂ 1,800 + 4.9360 ^D 2 0.3820 ^R 3 Schott BK7 1,800 - 2.1740 ^S 2 0.0280 H 2.100 - 6.8177 ^D 3 0.1040 ^R 5 Schott BK7 2.100 + 2.6602 ^S 3 0.1721 R ₆ 2.100 + 21.4100 ^D 4 0.3350 Schott SF4 2.100 R ₁₀ - 2.3782 ^S 4 0.0480 ^R 8 2.100 ^D 5 0.3330 Schott BK7 2.100 ^S 5 , + 1.9570 2.100 ^D 6 R ₁₂₊ 12.8890 Schott BK7 2.100

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The catadioptric lens according to Table A has a rear focal length of 3.0625, measured starting from the secondary mirror. The inverse telephoto lens according to Table B has a rear focal length of 3.7335, measured from the vertex of the surface R ₁₂ * The inverse telephoto lens, which usually consists of a diverging front group (R ₁ to R ^) and a converging rear group (R ₅ to R ₁₂ ) exists at a large distance behind the front group, is partially, ie attached to the rear group, within the central openings of the front and second components of the catadloptric lens. However, the two objectives have no common components and are each constructed in such a way that a suitable correction of aberration is achieved for the respective image angle and the respective relative aperture size.

The catadioptric objective is corrected so that a half-angle field of + 4 ° with a relative aperture of F / 0.89 is included, while the inverse telephoto lens is corrected so that a half-angle field of + 15 ° at a relative aperture of F / 2.0 is included. The complete system enables alternating viewing of the same Object with two different magnifications, and an adjustable aperture is provided so that only one of the two lenses is in operation.

The materials used enable the system to be used in the visible light range between 5000 and 8000 Ä, the extremely short overall length of the catadioptric lens. The image receiving surface that passes through the cathode surface of an image intensifier tube can be formed is in a focal plane just before the vertex of the concave primary mirror arranged.

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Table C for Example II relates to a catadioptric lens that has a simple front lens (R ₁ , R ₂ ), a simple second lens (R ^, R ^), a primary mirror (R ₅ ), a secondary mirror (R ₆ ) on the Contains back (R ^) of the second lens and three lenses (Ry to R ₁₂ ) behind the secondary mirror in front of the image plane.

Example II - Table C

K & tadiODtriech.ee lens - focal length 7.117

radius

Thickness or spacing

Glass reference lights inside number Diameter diameter

10.7100

39.9100

D ₁ 0.750 Schott BK7 S ₁ 6.712

R - 7.4690

R ₄ - 72.0000 R ₅ - 11.6200 R ₆ - 72.0000

D ₂ 0.250 bulkhead BK7

S ₂ 3.049 S, 3.049 1.582

Aluminized flax

Aluminized glass

2.6300

D, 0.400 bulkhead SF4

- 10.4400

R ₉ - 8.1511 R _in + 2.6600

S-0.060

D ^ 0.100 Schott SF6 S ₆ 0.748

8,200 8,200 6,200 6,200 6,200 2,960 2,200 2,200 2,200 2,200

3.00 1.48

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R ₁₁ + 2.2210

D ₅ 0.125 Schott SF6 R ₁₂ + 46.5200 ν

1,100
1,100

Table D for Example II relates to an inverse telephoto lens on the optical axis of the catadioptric objective according to Table C placed 1st and nine components consists, namely eight simple components (R ₁ to R ₁ 5) and a
rear double component (R ₁₇ to R ₁ Q) *

Example II - Table D
Inverse telephoto lens - focal length 2.00

radius

Thick or refractive Abbe number lights
Distance index V diameter

R ₁ + 10.7100

R ₂ + 39.9100

R ₃ + ■ 4.695

R ₄ - 5.6077

R _{5 to} 5.176

1.065

D ₁ 0.750

5 ₁ 0.505

D ₂ 0.280 1.755

5 ₂ 0.004

D ₃ 0.122 1.518

OO

5 ₃ 2.761 D ₄ 0.500

5 ₄ 0.125

1.519

Schott BKT ^

27.6

64.1

60.4

(8.20) (8.20) 1.60 1.60 1.60 1.60 1.85 1.85

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R ₉ + 137.7 ^D 5 0.389 1.518 64.1 1.85 ^R 10 * 2.025 ^S 5 0.082 1.85 R ₁₁ - 7.625 ^D 6 0.100 1,755 27.6 1.85 R ₁₂ + 2.594 ^S 6 0.118 1.85 ^R 13 + 10, 825 D ₇ 0.473 1.518 64.1 1.85 ^R 14 - 2.850 S ₇ 0.044 1.85 R ₁₅ + 2.0453 ^D 8 0.539 1.518 64.1 1.85 ^R 16 + 602.41 ^S 8 0.471 2.00 R ₁₇ - 72,000 ^D 9 0.200 1.518 64.1 2.00 ^R 18 - 7.469 ^D 10 0.250 Schott BK7 (6.20) ^R 19 - 72,000 (6.20)

The catadioptric lens according to Table C has a rear focal length of 0.061, the focal plane is located just behind the apex of the surface Re of the primary mirror. This objective includes a half angle of + 4 ° with a relative aperture of F / 0.89. The small diameter components just before the focal plane are of particular interest. The double lens (R ^ to R ₁₀ ) is primarily used to correct the primary spherical aberration and astigmatism created by the primary mirror and the larger diameter components in front of it. The last component (R ₁₁ , R ₁ ?) * ^S * ^ n primarily a flattened lens. Through the areas Ry to R

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a sufficient degree of freedom is achieved to enable a high aberration correction and, at the same time, a curvature value for the rear surface (R ^) of the second component, which _{ensures that the secondary mirror (R 6} ) is supported.

The inverse telephoto lens according to Table D contains the front and the second component (R ₁ , R ₂ and IU, R ^) of the catadioptric lens as the front component (R ₁ * R ₂ ) and the rear element (K ₁₀ R ^ _Q ) its double rear component. The other components of the inverse telephoto lens are arranged in an adapted manner between the two mentioned components of the catadioptric lens. However, it can also be the case that the above-mentioned components of small diameter of the catadioptric lens likewise form part of the inverse telephoto lens. The relatively small distance between these components and the image plane, which is the same for the inverse telephoto lens and the catadioptric lens, means that these components have little effect on the focusing of light rays that enter through the inverse telephoto lens. The construction of the effective components of this objective is of course done for good aberration correction, taking into account the small diameter components of the catadioptric objective. It is therefore possible, with a catadioptric objective with components behind the secondary mirror which are further removed from the image plane, to utilize these components as an essential part of the second image generating device which operates in the area of the central zone of the catadioptric objective.

The inverse telephoto lens according to Table D includes a half angle of + 15 ° with a relative aperture of F / 2.0. The complete system is to be used in the range of visible light, and according to Example I a diaphragm is arranged in such a way that the two objectives are selectively alternating

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are reversible to the same lens with different To look at enlargements. Furthermore, a mechanism for moving the primary mirror and for focusing the Katadioptrisehen lens can be provided. By the front component backwards occurring "constriction" For example, the focusing mechanism can be provided behind the front component within its nominal overall diameter.

Table S for Example III relates to a catadioptric Lens similar to that in Table C with the difference that the double lens and the flattened lens are behind the secondary mirror (Rg) by a thick single component (Ry, Ro) are replaced.

Example III - Table £ Catadioptric ^ Lens - Focal length e 7.15

Radius Thickness or Refraction Illuminated Inside Distance index number V diameter diameter

R ₁ + 13.85 ^D 1 1.07 1.569 56, 8.198 , 13 8.198 , 07 5.66 2.86 R ₂ - 39.89 ^S 1 5.298 5.66 Flat glass 5.64 2.86 ^R 3 * 9.012 ^D 2 0.232 1.699 30, Glaf R ₄ - 52.90 ^S 2 2.923 Aluminized ι 2.84 R ₅ - 12.65 ^S 3 2.923 2.73 Aluminized R ₆ - 52.90 ^S 4 1.129 1.28

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+ 3 , 005 D: ,8th 5 1, ■ " 439 13th 1 - 42 , 84 1 2228236 R ₇ , 88 f - 128 5 ° ' 4347 , 567 1 ^R 8 , 88 * ° » 080 1 56 , 13 1 * 9 , 38 , 569 ^{1 R} 10 , 38

Table F for example III relates to an inverse telephoto lens on the optical axis of the catadioptric lens according to Table E. This inverse telephoto lens has * eight components, seven single components (R ₁ to R ₁₄ ) and a rear double component (R ₁ C to R ₁₇ ) ·

Example III - Table F Inverse Telephoto Lens - Focal Length 2,000

Radius, thickness or refraction «- Abbezahl lights Distance index V diameter

1.40 27.6

1.40

1.40 64.2

1.40

1.85 60.4

1.85

1.85

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R ₁ + 4.265 ^D 1 0.186 1 , 755 R ₂ - 7.0713 ^S 1 0,201 ^R 3 * 4,445 ^D 2 0.100 1 , 517 R ₄ + 1.075 ^S 2 2.517 ^R 5 »3 0.500 1 , 519 ^R 6 cP ^S 3 0.125 R ₇ - 25.75

■ ^D 4 1.992 S ₄ 49.613 8.28 ^D 6 ^S 7 9.012 ^D 9 52.90 0.325 1.517 64.2 1.85 ^R 8 - ^D 5 2.9236 5.6077 2.8055 ^S 6 ^D 8 0.010 1.85 Rg - ^S 5 1.8107 D ₇ 0.100 1,755 27.6 1.85 ^R 10 ⁺ 7,053 0.113 1.85 R ₁₁ + 0.321 1.517 64.2 1.85 ^R 12 " 0.010 1.85 R _{13 +} 0.369 1.517 64.2 1.85 R ₁₄ + 0.946 1.85 ^R 15- 0.200 1,699 30.1 (5.66) ^R 16- 0.232 1,699 30.1 (5.66) R ₁₇ -

The catadioptric objective according to Table E has a rear one Focal length of 0.0312, the plane of focus is located just behind the apex of the surface (Hc) of the primary mirror. The objective includes a half angle of + 4 ° with a relative aperture of F / 0.89. The one used to correct the Astigmatism serving double lens of the objective according to Table C is replaced by the simple, thick component (R «, Rg), which serves the same purpose. At the same time it causes a flattening, so a special component for this purpose is not required. Instead, a translucent plate is placed very close to the focal plane.

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The front component of the catadioptric lens is annular, making the inverse telephoto lens (Table F). can be passed through, but this contains the second component (R ^, R ^) of the catadioptric lens as a rear element (R ₁ 6 >> ₁ 7) of ^the rear double component.

The complete system is intended for use in the visible light range and contains a diaphragm and, if necessary, a focusing device. This mechanism can be provided in a unit, which consists of the primary mirror, the second component with the secondary mirror and the thick Component behind the secondary mirror exists, so that both lenses can be focused depending on the alternating activation. The inverse telephoto lens closes a half angle of ± 15 ° at a relative temperature of F / 2.0. It is designed to produce an image on the same plane as the catadioptric lens. Both lenses have high performance in terms of aberration correction.

Table G for Example IV relates to a catadioptric objective consisting of an annular, concave primary mirror (R ₁ ), an annular secondary mirror (R ₂ ), and three lens components (Rx to Rg) between the secondary mirror and the focal plane.

Example IV - Table G Catadioptric «β lens - focal length 5.72

Radius Thickness or glass reference clearances Inner distance number Diameter

knife knife

R ₁ - 19 5100 i 3 , 9643 Aluminized
Flat glass 3, 80 1, 80 R ₂ + 32, 5863 Aluminized
Flat glass 2, 25th 0, 376

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5 ₂ 2.211

R ₃ - 4.4028 1.081

D ₁ 0.126 14RS-5
R ₄ + 8.2800 1.081

5 ₃ 0.002

R ₅ + 4.7536 1.081

D ₂ 0.309 14RS-5
R ₆ - 9.0472 1.081

5 ₄ 0.526

R ₇ + 5.6900 1.081

D ₃ 0.183 14RS-5
R ₈ + 538.1125 1.081

The catadioptric lens according to Table G includes a half-angle field of + 5 ° and a relative aperture of F / 1.43 a. Bs is intended for use with infrared light and has a back focal length of 1.0954, so that the image plane is arranged approx. 0.2 behind the vertex of the primary mirror.

The unused central area of the objective has a smaller cross-section than in the previous examples and is used to adapt a second image-generating device, which consists of a cross-hair fade-in system, which also works with infrared light. This system is constructed in the usual way and is therefore not specifically described. It 'is arranged so that it directs a crosshair image onto the infrared-sensitive image receiving area of the catadioptric lens, taking into account that the lenses R ₃ to Rg are present as part of the catadioptric lens. In this fourth example, the second imaging device normally operates simultaneously with the catadioptric objective, so that no diaphragm device is required. However, a focusing mechanism can be provided.

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It should be noted that the optical systems of Examples I to III can also work with crosshair fade-in devices instead of inverse telephoto lenses, which depends on the particular application.

Various developments and modifications of the exemplary embodiments described above are within the scope of the invention possible. The constructions described can be used if the parameters are changed by up to approx. + 20%. Minor changes can be made, for example other types of glass or other translucent materials can be used if the performance of the respective surfaces does not exceed + 0.5 / F and the axial lens thicknesses as well as the axial Distances cannot be changed more than 0.05F. If desired, certain aspherical surfaces can also be provided.

The two optical systems of Examples I to IV are shown in FIGS. 1 and 2, in FIGS. 3 and 4, in FIG. 5, respectively and 6 and in Flg. 7 of the drawings.

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Claims (7)

Claims Optical system with a catadioptric lens that an annular concave primary mirror and an annular secondary mirror for receiving the light of the Contains primary mirror, which the light in an image receiving area in the area of the central opening of the primary mirror reflected, characterized in that on the axis of the catadioptric lens within the central area, formed by the inside diameter of the secondary mirror, an independent imaging second device is arranged which guides light into said imaging area. 2. Optical system according to claim 1, characterized in that the image-forming second device at least has a lens component in common with the catadioptric lens. 3. Optical system according to claim 1 or 2, characterized in that that the second imaging device is an inverse telephoto lens. 4. Optical system according to claim 3, characterized in that a locking mechanism or a diaphragm for the respective Activation of only the catadioptric or only the inverse telephoto lens is provided. 5. Optical system according to claim 3 or 4, characterized in that that the catadioptric objective contains a lens component in front of the primary mirror, which the secondary mirror its back and is also part of the inverse telephoto lens. 209857/0715 6. Optical system according to claim 5, characterized in that the catadioptric lens is a front lens component which is also a part of the inverse telephoto lens and in front of the lens component provided with the secondary mirror is arranged. 7. Optical system according to one of the preceding claims, characterized in that the catadioptric lens at least one the correction of the astigmatism and the
Curvature of field supporting component between the
Secondary mirror and the image receiving area and that these component or components furthermore a part
of the second image forming device. 209857/0715 IO Blank page