RU82876U1 - THREE-MIRROR OPTICAL SYSTEM WITHOUT SCREENING - Google Patents

Abstract

1. A three-mirror optical system without shielding, containing three conjugate optical components, which together create an anastigmatic optical system that builds an image and is off-axis and decentered both in the aperture and in the field angle, and in which the first component with positive optical power is a mirror turned by concavity to the object, the second component is a mirror with negative optical power, the third component with positive optical power is a mirror turned by concavity to the image iju, all three mirror surfaces are formed with a common axis of rotation, characterized in that the optical power components and air gaps between them satisfy the condition: ; ; ; ! 0.35 <d1φ <0.45; 0.4 <d2φ <0.5,! where φ1, φ2, φ3 are the optical forces of the primary, secondary, and tertiary mirrors, respectively; ! φ is the equivalent optical power of the system; ! d1 is the distance between the primary and secondary mirrors; ! d2 is the distance between the secondary and tertiary mirrors, while the reflecting surface of the primary mirror is made in the form of a segment of a concave hyperboloid, the secondary mirror is convex elliptical, and the tertiary mirror is concave spherical. ! 2. The three-mirror optical system without shielding according to claim 1, characterized in that a flat mirror mounted behind the tertiary mirror is additionally introduced into it, and the focal plane of the optical system is installed between the rear surfaces of the primary and tertiary mirrors.

Description

The proposed utility model relates to optical instrumentation, in particular, to space-based mirror and mirror-lens telescopes, topographic lenses, projection lenses, etc., and can be used to improve their technical characteristics.

Known three-mirror optical system without shielding [1], containing three mirror components, in which the first component is an elliptical mirror with positive optical power, facing concavity to the object, which sets the axis of the system, the second component is a hyperbolic mirror with negative optical power, the third component ellipsoid mirror with positive optical power, turned concavity to the image, creating in the aggregate anastigmatic optical system that builds the image and I It wishes to set up off-axis and decentered as the aperture and by field corner.

The disadvantage of the system is a small rear segment S ', the length of which is less than the distance d between the mirrors: S' <d, which forces the image receivers installed in the focal plane of the system to be placed in space in front of the main primary mirror. This significantly complicates the design of the system as a whole.

Another disadvantage is the low-tech system due to the fact that all three mirrors are aspherical.

Known axial three-mirror optical system without shielding [2], working off-axis beams along the aperture, in

which also S '<d and image receivers installed in space in front of the main primary mirror.

Closest to the technical solution of the proposed utility model is a three-mirror optical system without shielding [3], consisting of three optically conjugated components that together create an anastigmatic optical system that builds an image and is off-axis and decentered, both in aperture and field angle , and in which the first component with positive optical power is a mirror facing concavity to the object, the second component is a mirror with negative optical power, and the third nent with positive optical power - a mirror, facing concavity to the image.

All three mirrors are formed by surfaces of revolution with a common axis.

A disadvantage of the known technical solution is the small rear segment S ', the value of which is comparable with the air gap d between the primary and secondary mirrors: S' ~ d.

This limits the installation of large-sized image receivers, increases the overall system dimensions along a length of 1, which becomes comparable with a value equivalent to the focal length of the optical system.

In addition, the optical system is not technologically advanced due to the use of a third mirror made in the form of an off-axis segment of an aspherical surface.

The main task, which the utility model is aimed at, is to simplify the design, increase manufacturability, reduce dimensions and increase the reliability of the optical system, especially as a part of optical-electronic cameras of space systems.

To solve this problem, a three-mirror optical system without shielding is proposed, which, like the prototype, contains three conjugate optical components, which together create an anastigmatic optical system that builds an image and is off-axis and decentralized both in the aperture and in the field angle, and in of which the first component with positive optical power is a mirror facing concavity to the object, the second component is a mirror with negative optical power and the third component with a positive hydrochloric optical power - mirror facing concave to the image, all three mirror surfaces are formed with a common axis of rotation.

In contrast to the prototype in the proposed optical system, the optical forces of the components and the air gaps between them satisfy the condition:

0.35 <d ₁ φ <0.45; 0.4 <d ₂ φ <0.5,

where φ ₁ , φ ₂ , φ ₃ are the optical forces of the primary, secondary, and tertiary mirrors, respectively;

φ is the equivalent optical power of the system;

d ₁ - the distance between the primary and secondary mirrors;

d ₂ is the distance between the secondary and tertiary mirrors, while the reflecting surface of the primary mirror is made in the form of a segment of a concave hyperboloid, the secondary mirror is convex elliptical, and the tertiary mirror is concave spherical.

In addition, a flat mirror mounted behind a tertiary mirror is additionally introduced into a three-mirror optical system without shielding, and the focal plane of the optical system

installed between the rear surfaces of the primary and tertiary mirrors.

The essence of the proposed utility model is to select the optical powers of the components and air gaps that satisfy the condition:

0.35 <d ₁ φ <0.45; 0.4 <d ₂ φ <0.5,

where φ ₁ , φ ₂ , φ ₃ are the optical forces of the primary, secondary, and tertiary mirrors, respectively;

φ is the equivalent optical power of the system;

d ₁ - the distance between the primary and secondary mirrors;

d ₂ - the distance between the secondary and tertiary mirrors.

The choice of optical forces and air gaps in these conditions allows you to perform the following parameters:

1. provide a preset value of the focal length;

2. provide correction of the image curvature for which the conditions must be met: φ ₁ + φ ₂ + φ ₃ = 0;

3. Ensure that a large rear segment is obtained: the S 'distance from the tertiary mirror to the image plane, which is about 2 times the distance d between the primary and secondary, and secondary and tertiary mirrors, i.e. S '~ (1.8 ÷ 2) d.

This allows you to install an additional flat mirror and transfer the image plane to the area of the rear of the primary and tertiary mirrors and thereby install image receivers without shielding light beams and increasing the size of the optical system.

In the proposed optical system, there are seven parameters to ensure overall characteristics and aberration correction, three

the radius of curvature of the mirrors, or three optical forces φ ₁ , φ ₂ , φ ₃ , two air gaps between the mirrors d ₁ and d ₂ and two eccentricities of the mirrors - primary e ₁ and secondary e ₂ .

This is enough to correct five aberrations (spherical, coma, astigmatism, image curvature and distortion) and two overall characteristics - the focal length and the back segment -S '. Therefore, a tertiary mirror can be made spherical, which significantly increases the manufacturability of its manufacture.

Thus, the combination of the above features of the proposed three-mirror optical system without shielding allows you to solve the problem.

The proposed utility model is illustrated by a drawing, where in Fig. 1, a general optical diagram of a three-mirror optical system without shielding is presented, and Appendix I shows the design parameters and calculation results of a specific optical system.

A three-mirror optical system without shielding consists of three components. Component 1 is made in the form of an off-axis segment of a concave hyperboloid. Component 2 is made in the form of a convex ellipsoid, component 3 - in the form of a spherical concave mirror.

In the three-mirror optical system, an additional flat deflecting mirror 4 is installed behind the tertiary mirror 3, and the focal plane of the optical system 5 is installed between the rear surfaces of the primary 1 and tertiary 3 mirrors.

The operation of a three-mirror optical system without shielding is as follows.

Rays emanating from an infinitely distant object at an angle β ₀ to the optical axis in the meridional plane fall on the primary mirror 1. The angle β ₀ forms the center of the image field. After reflection from the primary mirror and secondary mirror 2, the rays fall on the tertiary mirror 3, the flat mirror 4 and are focused in the focal plane

optical system 5. After reflection from the primary mirror 1 and the secondary mirror 2, the image — an imaginary, tertiary mirror 3 — builds a real image. A significant rear segment after the tertiary mirror 3 allows the flat mirror 4 to transfer the image between the primary and tertiary mirrors for their rear parts.

Appendix I shows the results of calculating a specific optical system with the following parameters:

- focal length of the lens = 3900 mm;

- diameter of the entrance pupil - 390 mm;

- angular field - 2β = 6 ⁰ ;

- angle - β ₀ = 5.9 °;

- the ratio of optical forces and air gaps:

d ₁ φ ₁ = 0.389; d ₂ φ = 0.4356.

Image quality is close to diffraction.

Thus, in the proposed three-mirror optical system without shielding, design simplification, technological improvement, reduction in size and reliability of the optical system, especially in the composition of optical-electronic cameras of space systems, have been achieved.

INFORMATION SOURCES

1. USA, patent No. 4265510, NKI: 359/366, 1981

2. E.R. Malamed. Design of space-based optical devices. SPG 2002, publishing house SPITMO (Technical University), p.208.

3. Russian Federation, patent No. 23237194, IPC: G02B 17/06, 2008 - prototype.

Claims (2)

1. A three-mirror optical system without shielding, containing three conjugate optical components, which together create an anastigmatic optical system that builds an image and is off-axis and decentered both in the aperture and in the field angle, and in which the first component with positive optical power is a mirror turned by concavity to the object, the second component is a mirror with negative optical power, the third component with positive optical power is a mirror turned by concavity to the image iju, all three mirror surfaces are formed with a common axis of rotation, characterized in that the optical power components and air gaps between them satisfy the following condition:

;

;

; 0.35 <d ₁ φ <0.45; 0.4 <d ₂ φ <0.5, where φ ₁ , φ ₂ , φ ₃ are the optical forces of the primary, secondary, and tertiary mirrors, respectively; φ is the equivalent optical power of the system; d ₁ - the distance between the primary and secondary mirrors; d ₂ is the distance between the secondary and tertiary mirrors, while the reflecting surface of the primary mirror is made in the form of a segment of a concave hyperboloid, the secondary mirror is convex elliptical, and the tertiary mirror is concave spherical. 2. The three-mirror optical system without shielding according to claim 1, characterized in that a flat mirror mounted behind the tertiary mirror is additionally introduced into it, and the focal plane of the optical system is installed between the rear surfaces of the primary and tertiary mirrors.