DE2228236C3 - Mirror lens - Google Patents

Description

The invention relates to an optical system with a mirror lens which has an annular concave Contains main mirror and a secondary mirror that carries the light from the main mirror to the area of the image plane reflects near the center opening of the main mirror.

A mirror lens contains one or more reflective surfaces, hereinafter referred to as mirrors and contribute to the generation of an image in a desired image plane. A well-known one Lens of this type contains an annular, concave main mirror that captures the incoming rays on a secondary mirror of smaller diameter, which is on the optical axis in front of the Primary mirror, d. H. between the main mirror and the object. The secondary mirror throws that Light from the main mirror back to the area of the image plane near the central opening of the main mirror.

In such a known mirror objective, the central area of the secondary mirror is not exploited because the beam hitting it has a circular cross-section after being reflected on the main mirror Has.

It is the object of the invention to specify an optical system in which the middle area of the secondary mirror is used to improve performance.

This object is achieved according to the invention for an optical system of the type mentioned at the beginning solved that within the central area formed by the inner diameter of the secondary mirror an independent, axially arranged, imaging optical system is provided.

The invention therefore uses the middle area of the secondary mirror to create a second to arrange the optical system with the mirror lens on a common optical axis.

Mirror lenses have a wide range of uses and generally always will used when a relatively small field of view (not larger than approx. 15 °) with a relatively large aperture ratio, for example of 1: 1.0, should be included, especially if a small focal length on the image side is required. These applications are, for example, targeting or direction finding devices and Given night vision devices that can work with infrared radiation. The terms "radiation", "Representing", "reflecting" etc. should be understood in this sense in the following description.

If the dps mirror lens is used, for example, in a target device, another optical system a crosshair fade-in system can be provided. In this case, the images of the the object recorded with the mirror lens and the cross-hairs recorded with the fade-in system superimposed on each other in the image plane, this area for example by the cathode surface of a Image intensifier tube can be formed.

In other applications, the mirror objective can be used as an axially arranged, imaging optical table System, a second lens, such as an inverted telephoto type lens, is provided so that the object can be viewed at different magnifications. ! r this case can the overall system contain a diaphragm or a shutter, whereby only the mirror lens or the additional lens is switched on. Inverted telephoto type lenses are used in the the following are referred to for short as inverted telephoto lenses.

The axially arranged, imaging optical system can have at least one lens together with the mirror objective. For example, the mirror lens can contain a lens in front of the main mirror which carries the secondary mirror on its rear side and is also part of the inverted telephoto lens. A front lens may be provided which is also part of the inverted telephoto lens and is located in front of the lens carrying the secondary mirror. Furthermore, the mirror objective can contain at least one lens for correcting the astigmatism and the curvature of field between the secondary mirror and the image plane. This also forms part of the further optical system. In connection with these possibilities it should be pointed out that the terms "front" and "rear" are to be understood in relation to the direction of entry of the light into the mirror lens, ie the light that falls from the front onto the main mirror.
Embodiments of the invention are in

described below with reference to the figures. It shows

F i g. 1 a mirror lens,

2 shows a lens in the manner of an inverted telephoto lens, which in the case of a mirror lens according to FIG F i g. 1 can be used,

F i g. 3 and 4 show another way of using an inverted telephoto type lens in FIG a mirror lens,

F i g. 5 and 6 show another way of using an inverted telephoto type lens in FIG a mirror lens and

F i g. 7 a mirror lens which is suitable for the installation of a crosshair fade-in system

Numerical data for four exemplary embodiments of a mirror lens are given together with numerical data for examples of a simultaneously used inverted telephoto lens 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, successively arranged ticks of the Objectives where the light falls and that

Example 1 - Table A
Mirror lens - focal length 7.194

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. Du Di ■■■ denote the axial thickness of the respective lens. Si, S ₂ ... denote the air gaps between the individual lenses. The tables contain the refractive indices / J ^ and the Abbe numbers V of the gutters used for the lenses, as well as the effective openings of the individual surfaces and, if the mirror objective fails, the diameter of the central opening of the annular surfaces. In the case of ring parts, the thickness values D _u D ₂ and the distances 5 ,, S ₂ 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 mirror objective with a simple front lens (R \, R ₂ ) on which the light is incident first, a simple second lens (Ri, Rn), a main mirror (Rj) and a secondary mirror (R _b ), which receives the light reflected at the main mirror and reflects it back onto the image plane (FIG. 1).

radius

Thickness or distance refractive index

Abbezahl V

Effective
Ö (Tn u ng

diameter
the central opening

Λ ι +12.207

Ri co D] 0.941 1.517 Ry -10.239 Si 0.8137 i R ₄ -51.21 D ₂ 0.345 1.517 ■ i R ₅ -13.693 S ₂ 4.3504 't Aluminized Flat glass R ₁ , OO Si 3.5411 Aluminized Flat glass

64.2

64.2

8.00
8.00
8.00
8.00
8.00

3.74

3.60
3.60
2.40
2.40
3.60

1.60

Table B for example I relates to an inverted telephoto lens arranged in the mirror lens according to Table A on a common optical axis. It consists of six simple lenses (R ₁ to ß _t2 ) (Fig. 2).

Example I - Table B

Inverted telephoto lens - focal length 2.00

radius

Thickness or distance refractive index

Pay off

Ri +4.630 R ₂ -27.870 Ry -26.650 R ₄ + 1.1620 Rs +4.9360 R ₆ -2.1740 Ri -6.8177

D, 0.2380

5 ₁ 0.0490
D ₂ 0.1040

5 ₂ 3.5440
Z) ₃ 0.3820
Si 0.0280
D ₄ 0.1040

27.6

64.2

64.2

27.6

Effective
opening

1,800
1,800
1,800
1,800
2.100
2.100
2.100

continuation

radius

Thickness or distance refractive index Pay off

Effective
opening

/ ?, +2.6602

Rv +21.4100

R in -2.3782

/? 11 +1.9570

R ₁ , +12.8890

5 ₄ 0.1721
D ₅ 0.3350

5 ₅ 0.0480
D ₁ , 0.3330

64.2

64.2

2.100
2.100
2.100
2.100
2.100

The mirror objective according to Table A has an image-side focal length of 3.0625, measured starting from the secondary mirror. The inverted telephoto lens according to Table B has an image-side focal length of 3.7335, measured from the vertex of the surface R] ₂ . The inverted telephoto lens, which usually consists of a diverging front group (R \ to Ra) and a converging rear group (Rs to R] ₂ ) at a large distance behind the front group, is partially, ie at the rear group, within the central openings of the front and second lens of the mirror lens attached. 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 angle of view and the respective relative aperture.

The mirror lens is corrected so that a maximum usable angle of view of 4 ° with a relative Focal ratio of 1: 0.89 is included, while the inverted telephoto lens is corrected in this way.

Example II - Table C
Mirror lens - focal length 7.117

that a maximum usable angle of view of 15 ° with a relative aperture ratio of 1: 2 is included. The complete system allows the alternate Looking at the same object at two different magnifications, and it's one adjustable aperture provided so that only one of the two lenses is switched on.

The glasses used enable the optical system to be used in the spectral range between 500 nm and 800 nm, the extremely short overall length of the mirror lens is remarkable. The image plane that can be formed by the cathode surface of an image intensifier tube is just before the vertex of the

Arranged in the concave main mirror.

Table C for Example II relates to a mirror lens that has a simple front lens (R], R2), a simple second lens (Ri, Ra), a main mirror (Ri), a secondary mirror (R _b ) on the back (Ri) of the second

Jj lens and three lenses (Rj to Ru) behind the secondary mirror in front of the image plane (Fig. 3).

radius

Thickness or Absland Brech / ahl

R] + 10.7100 D] 0.750 1,517 R- +39.9100 S] 6.712 R. -7.4690 D- 0.250 1,517 Ri -72.0000 S ' 3,049 Aluminized R. -11.6200 Flat glass S; 3,049 Aluminized R, - -72.0000 Glass S ₄ 1,582 R- +2.6300 D: 0.400 1,755 R> - -10.4400 S ^ 0.060 R _n -8.1511 Z) ₄ 0.100 1.805 Rl » +2.6600 S ₁ . 0.74S R]] + 2J210 D. 0.125 1,805 R ,, +46.5200

Abbc / ahl Effective
opening diameter
the communication 64.2 8,200
8,200 64.2 6,200
6,200 6,200 3.00 2,960 1.48 27.6 2,200
2,200 25.4 2,200
Z200 25.4 1,100
1,100

Table D for example il relates to an inverted telephoto lens which is positioned on the optical axis of the Mirror lens is arranged according to Table C and

Example II - Table D

Inverted telephoto lens - focal length 2.00 consists of nine lenses, namely eight simple lenses (R \ to R ₁₆ ) and a rear double lens (R _u to R \ $) (Fig. 4).

radius + 10.7100 thickness or distance Refractive index Abbezahl V Effective opening R \ +39.9100 (8.20) D, 0.750 1.517 64.2 R: +4.695 (8.20) S ₁ 0.505 R: -5.6077 1.60 D-. 0.280 1,755 27.6 y? 4 -5.176 1.60 S ₂ 0.004 R, + 1.065 1.60 D \ 0.122 1.518 64.1 R ₁ , OO 1.60 s> 2.761 R ₁ OO 1.85 D ₄ 0.500 1.519 60.4 Rs + 137.7 1.85 Sl 0.125 R >> -2.025 1.85 D <. 0.389 1.518 64.1 Rw -7.625 1.85 Si 0.082 Ru +2.594 1.85 D ₁ , 0.100 1,755 27.6 Marg + 10.825 1.85 Si, 0.118 R [·, -2,850 1.85 D- 0.473 1.518 64.1 Ru +2.0453 1.85 Si 0.044 R ^ +602.41 1.85 Ds 0.539 1.518 64.1 Ru, -72,000 2.00 Sn, 0.471 Rr -7.469 2.00 D., 0.200 1.518 64.1 «IS -72,000 (6.20) Tuesday ₁₁ 0.250 1.517 64.2 RlV (6.20)

The mirror objective according to Table C has an image-side focal length of 0.061, the image plane is located just behind the vertex of the surface Rs of the main mirror. This lens has a maximum usable angle of view of 4 ° with a relative aperture ratio of 1: 0.89. The small diameter lenses just before the image plane are of particular interest. The double lens (R? To R \ ₀ ) is primarily used to correct the primary spherical aberration and astigmatism generated by the main mirror and the larger diameter lenses in front of it. The last lens /? N, R _u ) is primarily a lens of low refractive power. A sufficient degree of freedom is achieved through the surfaces R- to Rn to enable a high aberration correction and at the same time a curvature value for the rear surface (Ra) of the second lens, which ensures that the secondary mirror (Rb) is supported.

The inverted telephoto lens according to Table D contains the front lens and the second lens (Ru R ₂ and Ri, Ra) of the mirror lens as the front component (R \, R ₂ ) and the rear element (Rw, R] g) of its rear double lens. The remaining lenses of the inverted telephoto lens are arranged in an adapted manner between the two mentioned lenses of the mirror lens. It must be taken into account that the small-diameter surfaces R ₇ to R \ _{2 of} the mirror lens are arranged in the beam path of the inverted telephoto lens. The small distance between these surfaces R ₇ to Ru to the image plane, which is the same for the inverted telephoto lens and the mirror lens, means that these lenses (R ₇ to R \ ₂ ) practically do not affect the position of the image plane of the inverted telephoto lens, since this has a sufficiently large depth of field. The structure of the effective lenses of this lens is of course done for good aberration

ίο

tion correction taking into account the small diameter surfaces R ₇ to /? i2 of the mirror lens. It is therefore possible, with a mirror objective with lenses behind the secondary mirror, which are further away from the image plane, to use these lenses as an essential part of the axially arranged, imaging optical system which works in the area of the central opening of the mirror objective.

The inverted telephoto lens according to Table D has a maximum usable angle of view of 15 ° with a relative aperture ratio of 1: 2. The whole The system is intended to be used in the visible light range, and according to Example I is a diaphragm $ 0 arranged that the two lenses are optional

Example III - Table E
Mirror lens - focal length 7.15

can be switched on alternately in order to display one and the same object with different magnifications regard. Furthermore, a mechanism for moving the main mirror and for focusing the Be provided mirror lens. Due to the "constriction" that occurs backwards from the front lens the focusing mechanism behind the front lens can be within its nominal overall diameter be provided.

Table E for Example III relates to a mirror lens similar to that according to Table C with the difference that the double lens and the lens of low refractive power behind the secondary mirror (Re) are replaced by a thick single lens (R ₇ , Rs) (Fig. 5) .

radius

Thickness or distance refractive index

Rl + 13.85 Tuesday 1.07 1.569 R ₂ -39.89 Si 5.298 «3 -9.012 D ₂ 0.232 1,699 Ra -52.90 S ₂ 2.923 Aluminized R ₅ -12.65 Flat glass Si 2.923 Aluminized R _b -52.90 Glass Sat 1.129 Ri +3.005 D ₁ 1,439 1.567 Rs -128.8 S ₅ 0.4347 R, OO There 0.080 1.569 R \ o OO

Abbezahl V Effective
opening diameter
the central opening 56.13 8.198
8.198 2.86
2.86 30.07 5.66
5.66 5.64 2.73 2.84 1.28

42.84

56.13

1.88
1.38
1.38

Table F for Example III relates to an inverted telephoto lens on the optical axis of the mirror lens according to Table E. This inverted telephoto lens has eight lenses, seven single lenses (R 1 to R _{! 4} ) and a rear double lens (R ₁₅ to R _n ). (Fig. 6)

Example III - Table F

Inverted telephoto lens - focal length 2,000

Kaaius

Thickness or distance Refractive index Abbe number V

+4.265 D ₁ 0.186 ^ ₂ -7.0713 Si 0,201 Ri -4,445 D ₂ 0.100 R ₄ +1.075 S ₂ 2.517 Rs DO D ₃ 0.500 Rh οα Si 0.125

1,755

1.517

1.519 27.6

64.2

60.4

Effective
opening

1.40
1.40
1.40
1.40
1.85
1.85

continuation 22nd 0.325 28 236 12th Abbezahl V Effective 11th radius opening 0.010 1.85 R ₁ -25.75 Thickness or absland Refractive index 64.2 0.100 1.85 A ₈ -1.992 D ₄ 0.113 1.517 1.85 A ₉ -49.613 27.6 Sat 0.321 1.85 / f, "+2.8055 D ₅ 0.010 1,755 1.85 A ₁₁ +8.28 64.2 S, 0.369 1.85 R ₁ , -2.9236 D _h 0.946 1.517 1.85 Λ,., +1.8107 64.2 Sb 0.200 1.85 Ru +7.053 D ₁ 0.232 1.517 1.85 /? "-5.6077 30 ,! S ₁ (5.66) Λ κ, -9.012 30.1 D, 1,699 (5.66) Λ, 7 -52.90 A, 1,699

The mirror lens according to Table E has an image-side focal length of 0.0312, the image plane is located just behind the vertex of the surface (Rs) of the main mirror. The lens has a maximum usable angle of view of 4 ° with a relative aperture ratio of 1: 0.89. The double lens of the objective used to correct the astigmatism according to Table C has been replaced by the simple, thick lens (R ₇ , Rs) , which serves the same purpose. At the same time, it causes a flattening, so that a special lens is not required for this purpose. Instead, a translucent plate is placed very close to the image plane.

The front lens of the mirror lens is ring-shaped so that the inverted telephoto lens (Table F) can be passed through, but this contains the second lens (Ri, R ^) of the mirror lens as the rear element (Rm, Ry ₇ ) of the rear double lens.

The complete system is for use in the visible light range and contains a screen and optionally a focusing device. This mechanism can be provided in a Einheil that from the main mirror, the second lens with the secondary mirror and the thick lens behind the There is a secondary mirror so that both lenses can be focused depending on whether they are switched on alternately.

The inverted telephoto lens has a maximum usable angle of view of 15 ° with a relative Focal ratio of 1: 2. It is built so that it creates an image on the same plane as the mirror lens. Both lenses have a high Performance in terms of aberration correction.

Table G for Example IV relates to a mirror objective which consists of an annular, concave main mirror (R \), a secondary mirror (R2), which reflects the light from the main mirror to the area of the image plane near the central opening of the main mirror, and three lenses (R3 to Ks) between the secondary mirror and the image plane (FIG. 7).

Example IV - Table G Focal length 5.72 3.9643 Glass Effective By Mirror lens - 1 Thickness or spacing opening knife the radius Middle- 2.211 opening Aluminized 3.80 1.80 0.126 Flat glass If ₁ -19.5100 S ₁ Aluminized 2.25 0.376 Flat glass If ₂ +32.5863 S ₂ 1.081 Thallium R ₃ -4.4028 D ₁ Bromoiodide

continuation

radius Thick or spaced gins Effective By opening knife the Coat opening

+8.2800
+4.7536

-9.0472
+5.6900

+538.1125

5 ₃ 0.002
D ₂ 0.309

5 ₄ 0.526
Dy 0.183

Thallium bromoiodide

Thallium bromoiodide

1.081
1.081

1.081
1.081

1.081

The mirror lens according to Table G has a maximum usable angle of view of 5 ° with a relative aperture ratio of 1: 1.43. It is intended for use with infrared radiation and has a Image-side section of 1.0954, so that the image plane is located approx. 0.2 behind the vertex of the main mirror is.

The unused central area of the objective has a smaller cross-section than in the previous examples and is used to adapt an axially arranged optical system which consists of a crosshair fade-in system which also works with infrared radiation. This system is constructed in the usual way and is therefore not specifically described. It is arranged in such a way that it directs a crosshair image onto the infrared-sensitive area of the image plane of the mirror lens, taking into account that the lenses R3 to Rg are present as part of the mirror lens. In this fourth example, the axially arranged optical system normally operates simultaneously with the mirror lens, so that no diaphragm device is required. However, a focusing mechanism can be provided.

jo It should be noted that the optical systems of the Examples I to III likewise with cross-hair fade-in devices instead of inverted telephoto lenses can work, which depends on the respective application.

For this purpose 3 BIuU drawings

Claims (7)

Patent claims: 1. Optical system with a mirror lens that has an annular concave main mirror and a secondary mirror contains the light from the main mirror to the area of the image plane in the Reflects near the central opening of the main mirror, characterized in that within the central area formed by the inner diameter of the secondary mirror an independent, axially arranged imaging optical system is provided. 2. Optical system according to claim 1, characterized in that the axially arranged optical System has at least one lens together with the mirror lens. 3. Optical system according to claim 1 or 2, characterized in that the axially arranged optical system is an inverted telephoto type lens. 4. Optical system according to claim 3, characterized in that a locking mechanism or a diaphragm for switching on only the mirror lens or only the inverted telephoto lens is provided. 5. Optical system according to claim 3 or 4, characterized in that the mirror lens contains a lens in front of the main mirror, which carries the secondary mirror on its rear side, and furthermore is part of the inverted telephoto lens. 6. Optical system according to claim 5, characterized in that the mirror lens has a Has front lens that is part of the inverted telephoto lens and in front of the secondary mirror provided lens is arranged. 7. Optical system according to one of the preceding claims, characterized in that the Mirror objective at least one which supports the correction of the astigmatism and the curvature of field Lens between the secondary mirror and the image plane and that this lens is part of the axial arranged imaging optical system is.