CN114660792A - A reflective afocal optical system - Google Patents

Abstract

The invention discloses a reflective afocal optical system, which comprises a primary mirror, a secondary mirror, a tertiary mirror, a plane mirror A and a plane mirror B, wherein the focal powers of the primary mirror, the secondary mirror and the tertiary mirror are all not zero and are arranged on the same optical axis to form a common optical axis A; the middle of the primary mirror is provided with a through hole; the secondary mirror receives the light beam reflected by the primary mirror, reflects the light reflected by the primary mirror again and emits the light from the primary mirror through hole; the three mirrors receive the light beams reflected by the secondary mirror; the plane mirror A receives the light beams reflected by the three mirrors and reflects and turns the light beams, and meanwhile, a middle through hole A for the reflected light beams of the secondary mirror to pass through is formed in the middle of the plane mirror A; the plane mirror B receives the light beam reflected by the plane mirror A, reflects and turns the light beam, and forms an optical axis B after turning, wherein the optical axis B is perpendicular to the optical axis A; the invention reduces the volume of the whole system and is more beneficial to arranging the image stabilizing element.

Description

A reflective afocal optical system

technical field

The invention relates to the field of optics, in particular to a reflective afocal optical system.

Background technique

In order to obtain more information, distinguish more details, and collect more energy, modern photoelectric sighting equipment continues to expand in the direction of multi-band, long focal length, and large aperture. On this basis, improving multi-spectral integration and product stability accuracy is also an important development trend. In principle, the more optical paths shared by multiple spectral segments, the higher the integration and coaxial stability. For airborne photoelectric sighting equipment, in addition to the above characteristics, the size and weight of the system are as important as performance indicators. For long focal length systems, optical axis control measures are also required to solve the problems caused by platform motion or vibration. image instability problem.

The reflective design does not introduce chromatic aberration, and is also conducive to the lightweight of large-diameter optical systems, which is very suitable for multi-spectral optical systems with common optical paths. Although the reflection system has many advantages, the reflection system always faces the problem of beam blocking. Patents CN205899119U, CN110850592A, CN110989152A, CN214151221U, CN110221420A, CN112485793A, CN112859313A, CN102928077B all adopt off-axis design to avoid beam blocking. The off-axis design can avoid blocking, but the manufacturing difficulty of the off-axis system is significantly increased, and the volume is also increased, which is not conducive to compact design. Patents CN107843980A, CN107843979A, CN104793324B, CN103278916B, CN201964957U, etc. use mirrors at the largest aperture to reduce volume and weight, and follow-up hybrid design is adopted to avoid second blocking. The catadioptric hybrid design introduces more variables, which brings convenience to the design, but the refractive elements in the common aperture part must introduce chromatic aberration, which is not conducive to broadband and multispectral imaging. Patent CN107167904A uses a reflective design, the primary and secondary mirrors are coaxial, in order to avoid secondary occlusion, only the off-axis half field of view is used, especially the meridional field of view is significantly compressed. The American Optical Handbook, Volume 1, Chapter 18, Section 7, discloses a coaxial reflective afocal system. The primary mirror, secondary mirror and third mirror all have optical power and are coaxial, and the fourth mirror is The plane mirror is arranged at an angle of 45° to the optical axis, with a hole in the center, and the primary image is located at the hole in the plane mirror. Although the design has two blockings, the blocked beams overlap, so the blocking amount is not increased. If this design is used for airborne sighting, it has two disadvantages. First, it is difficult to use a flat mirror as an image stabilization element, because the beam incident angle is large, and it is only suitable for image stabilization in one direction; Second, the primary image is farther to the right of the primary mirror, making the system relatively bulky.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a reflective afocal optical system, which compresses the volume of the entire system and is more convenient for arranging image stabilization elements.

The present invention is realized by constructing a reflective afocal optical system, including a primary mirror, a secondary mirror, a third mirror, a plane mirror A and a plane mirror B, wherein the optical power of the primary mirror, the secondary mirror and the third mirror is not zero And they are arranged on the same optical axis to form a common optical axis A;

There is a through hole in the middle of the primary mirror;

The secondary mirror is located on the reflection side of the primary mirror, receives the light beam reflected by the primary mirror, reflects the light beam reflected by the primary mirror again, and emits the light beam from the primary mirror through hole;

The three mirrors are located on the reflection side of the secondary mirror and behind the primary mirror, and receive the light beam reflected by the secondary mirror;

The plane mirror A receives the light beam reflected by the three mirrors and is located between the secondary mirror and the third mirror. The angle between the normal of the plane mirror A and the optical axis A is not zero, and the middle of the plane mirror A is provided with the secondary mirror for reflection. The middle through hole A through which the light beam passes;

The plane mirror B receives the light beam reflected by the plane mirror A and turns the light beam to form an optical axis B, and the optical axis B is perpendicular to the optical axis A;

Preferably, an image stabilization control unit is installed at the rear end of the plane mirror A or the plane mirror B, and the angle of the plane mirror A or the plane mirror B is adjusted through the image stabilization control unit to adapt to a more complex use environment.

Preferably, the reflection surface of the primary mirror adopts a concave paraboloid, the reflection surface of the secondary mirror adopts a convex hyperboloid, and the reflection surface of the third mirror adopts a concave paraboloid.

满足

的关系； Preferably, the aperture D of the primary mirror is the same as the refractive power of the primary mirror.

Satisfy

Relationship;

，主镜的口径D与

满足

的关系； The optical power of the subsystem composed of the primary mirror and the secondary mirror is

, the aperture D of the primary mirror and

Satisfy

Relationship;

，

与

满足

的关系。 The optical power of the three mirrors is

,

and

Satisfy

Relationship.

，λ为工作波 长。 Preferably, the wave aberration of the zero-degree field-of-view primary image formed by the optical axis A and the incident light is less than

, λ is the working wavelength.

Preferably, the angle between the normal of the reflecting surface of the plane mirror A and the optical axis A is less than 45 degrees, and more preferably, the angle is less than 30 degrees.

Further, the primary mirror, secondary mirror and third mirror are replaced by spherical or high-order aspheric surfaces, or free-form surfaces, and the image stabilization control unit is arranged on the plane mirror A, and the plane mirror B is a dichroic mirror.

The present invention has the following advantages:

1. The present invention compresses the length from the secondary mirror to the third mirror;

2. Compared with the traditional technology flat reflector B, which has no central hole and sufficient back space, it is more suitable for use as an image stabilization control unit;

3. The focal length of the primary mirror and the secondary mirror is reduced, and the primary image formed by the same field of view is smaller, thereby reducing the size of the central hole of the plane mirror A and further reducing the loss of light;

4. If the plane mirror A is used as the optical axis stability control unit, the plane mirror B can be replaced with a dichroic mirror, so that the whole system can handle more spectral bands.

Description of drawings

FIG. 1 is a schematic diagram of the principle of Embodiment 1 of the present invention

Fig. 2 is the principle schematic diagram of the second embodiment of the present invention;

In the figure: 100, primary mirror; 200, secondary mirror; 300, three mirrors; 400, plane mirror A; 500, plane mirror B; 600, optical axis B; 700, optical axis A; 800, rotating mechanism.

Detailed ways

The present invention will be described in detail below with reference to Fig. 1 and Fig. 2, and the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the implementations. example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1:

As shown in FIG. 1, a reflective afocal optical system includes a primary mirror 100, a secondary mirror 200, a third mirror 300, a plane mirror A400 and a plane mirror B500, wherein the optical power of the primary mirror 100, the secondary mirror 200 and the third mirror 300 is are not zero and are arranged on the same optical axis, forming a common optical axis A700;

There is a through hole in the middle of the primary mirror;

The secondary mirror 200 is located on the reflection side of the primary mirror 100, receives the light beam reflected by the primary mirror 100, collects the light beam reflected by the primary mirror 100, and reflects it from the through hole;

The three mirrors are located on the reflection side of the secondary mirror and behind the primary mirror, and receive the light beam reflected by the secondary mirror;

The plane mirror A400 receives the light beam reflected by the three mirrors, and is located between the secondary mirror 200 and the third mirror 300. The angle between the normal of the plane mirror A400 and the optical axis A is not zero, and the middle of the plane mirror A400 is provided with a secondary The middle through hole A through which the mirror-reflected beam passes;

The plane mirror B500 receives the light beam reflected by the plane mirror A400 and turns the light beam to form an optical axis B600, the optical axis B600 is perpendicular to the optical axis A700;

In this embodiment, the reflection surface of the primary mirror adopts a concave paraboloid, the reflection surface of the secondary mirror adopts a convex hyperboloid, and the reflection surface of the third mirror adopts a concave paraboloid.

满足

的关 系； In this embodiment, the aperture D of the primary mirror and the refractive power of the primary mirror

Satisfy

Relationship;

，主镜的口径D与

满足

的关系； The optical power of the subsystem composed of the primary mirror and the secondary mirror is

, the aperture D of the primary mirror and

Satisfy

Relationship;

，

与

满足

的关系。 The optical power of the three mirrors is

,

and

Satisfy

Relationship.

，λ为工作波 长。 Preferably, the wave aberration of the zero-degree field-of-view primary image formed by the optical axis A and the incident light is less than

, λ is the working wavelength.

In this embodiment, the included angle between the normal line of the reflecting surface of the plane mirror A and the optical axis A is less than 45 degrees, preferably, the included angle is less than 30 degrees.

On the basis of the coaxial three-mirror design, the present invention adds two plane mirrors (plane mirror A and plane mirror B), and the two plane mirrors jointly deflect the optical axis by 90 degrees, so that the deflected optical axis is the same as that of the coaxial three-mirror. The optical axis is vertical.

Specifically, in this implementation, the optical system data is shown in the following table:

Embodiment 2:

As shown in FIG. 2, a reflective afocal optical system includes a primary mirror 100, a secondary mirror 200, a third mirror 300, a plane mirror A400 and a plane mirror B500, wherein the optical power of the primary mirror 100, the secondary mirror 200 and the third mirror 300 is are not zero and are arranged on the same optical axis, forming a common optical axis A700;

There is a through hole in the middle of the primary mirror;

The secondary mirror 200 is located on the reflection side of the primary mirror 100, receives the light beam reflected by the primary mirror 100, collects the light beam reflected by the primary mirror 100, and reflects it from the through hole;

The three mirrors are located on the reflection side of the secondary mirror and behind the primary mirror, and receive the light beam reflected by the secondary mirror;

The plane mirror A400 receives the light beam reflected by the three mirrors, and is located between the secondary mirror 200 and the third mirror 300. The angle between the normal of the plane mirror A400 and the optical axis A is not zero, and the middle of the plane mirror A400 is provided with a secondary The middle through hole A through which the mirror-reflected beam passes;

The plane mirror B500 receives the light beam reflected by the plane mirror A400 and turns the light beam to form an optical axis B600, the optical axis B600 is perpendicular to the optical axis A700;

In this embodiment, the reflection surface of the primary mirror adopts a concave paraboloid, the reflection surface of the secondary mirror adopts a convex hyperboloid, and the reflection surface of the third mirror adopts a concave paraboloid.

满足

的关 系； In this embodiment, the aperture D of the primary mirror and the refractive power of the primary mirror

Satisfy

Relationship;

，主镜的口径D与

满足

的关系； The optical power of the subsystem composed of the primary mirror and the secondary mirror is

, the aperture D of the primary mirror and

Satisfy

Relationship;

，

与

满足

的关系。 The optical power of the three mirrors is

,

and

Satisfy

Relationship.

，λ为工作波 长。 Preferably, the wave aberration of the zero-degree field-of-view primary image formed by the optical axis A and the incident light is less than

, λ is the working wavelength.

In this embodiment, the included angle between the normal line of the reflecting surface of the plane mirror A and the optical axis A is less than 45 degrees, preferably, the included angle is less than 30 degrees.

In this embodiment, a rotating mechanism 800 is installed on the back of the plane mirror A400, and the angle of the plane mirror A400 is adjusted through the rotating mechanism to adapt to various environments; at the same time, the plane mirror B500 can be changed to a dichroic mirror to reflect a part of the spectrum and transmit through another part of the spectrum.

In this embodiment, specifically, in this embodiment, the optical system data is shown in the following table:

The difference between the second embodiment and the first embodiment is that in the second embodiment, a rotating mechanism is installed on the back of the plane mirror A400, and the angle of the plane mirror A400 can be adjusted in real time through the rotating mechanism, so that the moving target can be kept still on the image plane (someone said that At the same time, the plane mirror B500 can be changed to a dichroic mirror, which reflects part of the spectrum and transmits the other part of the spectrum; the others remain unchanged.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A reflective afocal optical system, characterized by: the device comprises a primary mirror, a secondary mirror, a third mirror, a plane mirror A and a plane mirror B, wherein the focal powers of the primary mirror, the secondary mirror and the third mirror are all not zero and are arranged with an optical axis to form a common optical axis A;

the middle of the primary mirror is provided with a through hole;

the secondary mirror is positioned on the reflection side of the primary mirror, receives the light beam reflected by the primary mirror, reflects the light beam reflected by the primary mirror again and emits the light beam from the through hole;

the three mirrors are positioned on the reflecting side of the secondary mirror and behind the primary mirror and receive the light beams reflected by the secondary mirror;

the plane mirror A receives the light beam reflected by the three mirrors, is positioned between the secondary mirror and the three mirrors, the included angle between the normal of the plane mirror A and the optical axis A is not zero, and meanwhile, the middle of the plane mirror A is provided with a middle through hole A for the reflected light beam of the secondary mirror to pass through;

the plane mirror B receives the light beam reflected by the plane mirror A and reflects and turns the light beam to form an optical axis B, and the optical axis B is perpendicular to the optical axis A.

2. The reflective afocal optical system of claim 1, wherein: the reflecting surface of the primary mirror adopts a concave paraboloid, the reflecting surface of the secondary mirror adopts a convex hyperboloid, and the reflecting surfaces of the three mirrors adopt concave paraboloids.

3. A reflective afocal optical system according to claim 2, characterized in that: the aperture D of the primary mirror and the focal power of the primary mirror

Satisfy the requirement of

The relationship of (1);

the focal power of a subsystem consisting of the primary mirror and the secondary mirror is

Aperture D of primary mirror and

satisfy the requirement of

The relationship of (1);

optical focus of the three mirrorsDegree of

，

And

satisfy the requirement of

The relationship (2) of (c).

4. A reflective afocal optical system according to claim 3, characterized in that: the wave aberration of the zero-degree view field primary image formed by the optical axis A and the incident light is less than

And λ is the operating wavelength.

5. The reflective afocal optical system of claim 1, wherein: and the included angle between the normal of the reflecting surface of the plane mirror A and the optical axis A is less than 45 degrees.

6. The reflective afocal optical system of claim 4, wherein: and the included angle between the normal of the reflecting surface of the plane mirror B and the optical axis B is less than 30 degrees.

7. The reflective afocal optical system of claim 1, wherein: the primary mirror, the secondary mirror and the tertiary mirror can be replaced by spherical surfaces or high-order aspheric surfaces or free-form surfaces.

8. The reflective afocal optical system of claim 1, wherein: and a rotating mechanism for stabilizing the image is arranged on the back of the plane mirror A.

9. The reflective afocal optical system of claim 8, wherein: the plane mirror B is a dichroic mirror.

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