CN110764272B

CN110764272B - Method for adjusting off-axis parabolic mirror system by using lens confocal point

Info

Publication number: CN110764272B
Application number: CN201911053252.XA
Authority: CN
Inventors: 张德保; 游冠军
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2021-07-16
Anticipated expiration: 2039-10-31
Also published as: CN110764272A

Abstract

The invention relates to a method for adjusting an off-axis parabolic mirror system by using a lens confocal point, which comprises the following steps: s1, adjusting the pitch angle of the off-axis parabolic mirror by two beams of parallel lasers with equal height to ensure that the emergent light height of the off-axis parabolic mirror is equal; s2, replacing an off-axis parabolic mirror with a plane mirror, and enabling two beams of parallel laser with equal height to pass through the plane mirror to simulate a beam propagation path of an off-axis parabolic mirror system to be adjusted to form an optical loop; and S3, adding a lens in the optical circuit, moving the off-axis parabolic mirror by using a lens confocal alignment method, and replacing the plane mirror with the off-axis parabolic mirror. Compared with the prior art, the method solves the problem that the off-axis parabolic mirror is difficult to adjust in the actual light path adjusting process, effectively replaces the common off-axis parabolic mirror adjusting method, has higher accuracy and practicability, and can greatly reduce the adjusting time and difficulty.

Description

Method for adjusting off-axis parabolic mirror system by using lens confocal point

Technical Field

The invention relates to an adjusting method of an off-axis parabolic mirror system, in particular to a method for adjusting the off-axis parabolic mirror system by using a lens confocal point.

Background

As early as the 17 th century, parabolic mirrors began to be used in the reflective telescopic system. Both theory and practical application reflect that the reasonable use of the parabolic mirror obviously helps to improve the performance of the device. The parabolic mirror has the characteristic of no spherical aberration when imaging a target at infinity, and solves the problem of optical error that a dispersed light spot (commonly called a fuzzy circle) can be formed at an ideal image plane on a main shaft after a monochromatic conical light beam emitted from a certain object point on the main shaft to an optical system is refracted by the optical series, but the problems of coma and central blocking exist. Therefore, for higher accuracy requirements, off-axis parabolic mirrors have been manufactured, which retain the advantages of parabolic mirrors and solve some problems such as central obscuration. However, imaging due to off-axis is no longer perpendicular to the optical axis, resulting in great difficulties and inaccuracies for optical practitioners to adjust off-axis parabolic mirrors in the optical path. Off-axis parabolic mirror systems are often used in the collection portion of the optical path, such as terahertz time-domain spectroscopy systems. The accuracy and simplicity of the adjustment of the device greatly affect the accuracy of the experimental result, even the key point of success of the experiment.

Therefore, the off-axis parabolic mirror system adjusting method which is convenient to realize and high in accuracy is designed, and has important significance in the aspect of light path design adjustment

Disclosure of Invention

The invention aims to overcome the defects in the prior art, provides a method for adjusting an off-axis parabolic mirror system by using a lens confocal point, solves the problem of difficult adjustment of the off-axis parabolic mirror in the actual light path adjusting process, effectively replaces the common off-axis parabolic mirror adjusting method, has higher accuracy and practicability, and can greatly reduce the adjusting time and difficulty.

The purpose of the invention can be realized by the following technical scheme:

a method for adjusting an off-axis parabolic mirror system by using a lens confocal point utilizes a laser beam emitted by a laser emitter to form two parallel beams through a beam splitter and a plane reflector. The whole adjusting method comprises three steps, wherein the first step is to adjust the pitching angle of the off-axis parabolic mirror by using two beams of parallel laser. And secondly, two beams of laser are utilized to carry out plane mirror simulation positioning, and a beam propagation path of an off-axis paraboloid which needs to be adjusted actually is simulated by using a plane mirror to form an optical loop. And thirdly, the off-axis parabolic mirror is replaced by adding a lens. The adjustment completion degree is determined based on the confocal point, the coincidence of the optical circuits, and the beam quality at infinity. The diaphragm and the optical baffle are also used for auxiliary calibration in the adjusting process.

Preferably, the laser emitter is a 510nm solid state semiconductor laser.

Preferably, the reflection efficiency of the plane mirror is 96% gold-plated mirror surface.

Preferably, the beam splitting of the beam splitting sheet is 5: 5.

Preferably, the focal length f of the off-axis paraboloid is 10 cm.

Preferably, the focal length f of the lens₁Is 5 cm.

Preferably, the horizontal scale on the optical barrier should contain the height of the emergent light.

Compared with the prior art, the method solves the problem that the off-axis parabolic mirror is difficult to adjust in the actual light path adjusting process, effectively replaces the common off-axis parabolic mirror adjusting method, has higher accuracy and practicability, and can greatly reduce the adjusting time and difficulty.

Drawings

FIG. 1 is a schematic view of a beam splitting parallel light of the laser of the present embodiment;

FIG. 2 is a schematic diagram of an object of the off-axis parabolic mirror system of the present embodiment;

FIG. 3 is a propagation diagram of a plane mirror simulated off-axis parabolic mirror system according to the present embodiment;

fig. 4(a) and 4(b) are schematic diagrams of two processes of pitch adjustment of the off-axis parabolic mirror according to the embodiment, respectively;

FIGS. 5(a) and 5(b) are schematic diagrams illustrating two processes of replacing the plane mirror for the lens and the off-axis parabolic mirror according to the present embodiment;

FIG. 6 is a diagram illustrating the effect of the present embodiment after the adjustment is completed;

fig. 7 is a flowchart of the adjusting method of the present embodiment.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Examples

This embodiment describes a method for adjusting an off-axis parabolic mirror system using a lens confocal point.

All diaphragms are preset according to the initial light height before adjustment.

As shown in fig. 1, the single laser beam is split into parallel beams:

1. laser emitted by the laser emitter is changed into two beams of laser through the beam splitting sheet, and the laser beams are reflected and transmitted.

2. A plane reflector is arranged on the light path of the reflected laser beam to enable the transmitted laser beam to be parallel to the reflected laser beam, and the distance between the beam splitting sheet and the plane mirror is delta x.

As shown in fig. 2, the target schematic of the off-axis parabolic mirror system:

1. the attached target schematic is an example of the applicable scope of an off-axis parabolic mirror system, and is not limited to the use of such off-axis parabolic mirrors.

2. The focal lengths of the four off-axis parabolic mirrors are the same, and the distance between them is twice the focal length, i.e. 2 f.

3. The light beam is firstly focused and then diverged to the position of the off-axis parabolic mirror C through the off-axis parabolic mirror A, the light beam characteristics are kept unchanged between the off-axis parabolic mirrors C and D, and the light beam is firstly focused and then diverged to the off-axis parabolic mirror B through the off-axis parabolic mirror D, so that the quality of the light beam is kept unchanged and the light beam is continuously transmitted.

FIG. 3 is a propagation diagram of a flat mirror simulated off-axis parabolic mirror system:

1. the two parallel beams of light after the beam splitter are directed into the conceptual diagram position of an ideal parabolic mirror system with two plane mirrors a1 and B1 and collimated. The distance between the plane mirror a1 and the plane mirror B1 in the x-axis direction is d, which is 2 f.

2. The two lights introduced into the conceptual diagram positions are reflected in the direction shown by the plane mirrors C1 and D1. The distance from the plane mirror a1 to the plane mirror C1 is D, and the distance from the plane mirror B1 to the plane mirror D1 is Δ x + D.

3. Two diaphragms were placed between the mirrors C1 and D1 for x-axis collimation, and the light rays should be projected from D1 to the center of the mirror C1, as set at the previous position.

4. The plane mirror C1 is calibrated in the horizontal direction, and the left knob and the right knob are adjusted to make the two beams of light beams completely coincide.

After operations 1 to 4, the positions of the flat mirrors a1, C1, D1 are now coincident with the conceptual map position of the off-axis parabolic mirror system.

In this embodiment, the off-axis parabolic mirror is mounted on the mirror mount and the pitch knob is used to adjust the pitch angle of the mirror. Fig. 4(a), 4(b) are preparation works before the whole system adjustment work-off-axis parabolic mirror pitch adjustment:

1. the pitching calibration of the off-axis parabolic mirror is firstly carried out, two parallel light beams with equal height are used for emitting onto the parabolic mirror, and a graduated optical baffle is arranged in the reflection direction of the off-axis parabolic mirror.

2. As shown in fig. 4(a), the parabolic mirror is rotated according to the inclination angle θ of the optical baffle, so that the line between the two light spots is parallel to the parallel light beam.

3. As shown in fig. 4(b), when the pitch knob of the off-axis parabolic mirror is rotated, the two light beams move in parallel, and the pitch angle of the off-axis parabolic mirror is adjusted to make the two parallel light beams have the same height.

As shown in fig. 5(a) and 5(b), the lens and the off-axis parabolic mirror replace the plane mirror:

1. as shown in fig. 5(a), the lens is placed between the plane mirrors a1 and C1, and the distance between the lens and the plane mirror C1 is f + f1, and f1 is the focal length of the lens.

2. The off-axis parabolic mirror C is moved so that the transmitted light from the lens and the reflected light from the plane mirror D1 should intersect and be at 90 deg..

3. The center of the off-axis parabolic mirror C is placed at the intersection of the two rays (directly observing whether the convergence points on the parabolic surfaces coincide).

4. Adjusting the horizontal knob of the off-axis parabolic mirror according to the following criteria:

as shown in fig. 5(b), a card is placed at the focus between the lens and the off-axis parabolic mirror, and the two light paths are shielded in sequence to see whether the focus positions are overlapped;

theoretically, since the distance between the lens and the off-axis parabolic mirror should be f + f1, the light coming out of the off-axis parabolic mirror should be parallel light. However, the discrimination of the focus coincidence may cause an error in the discrimination of the human eye. Therefore, a reflector is added between the off-axis parabolic mirror C and the plane mirror D1, and whether the distance between the off-axis parabolic mirror C and the plane mirror D1 is satisfied is judged according to whether the size of the light spot at infinity is changed.

The following steps can be repeated for each plane mirror to replace the off-axis parabolic mirror.

The optical shutter in fig. 5(B) is to prevent laser injury to the operator during operation, and therefore shields the light emitted from B1 when not in use.

Claims

1. A method for adjusting an off-axis parabolic mirror system using a lens confocal point, comprising the steps of:

s1, adjusting the pitch angle of the off-axis parabolic mirror by two beams of parallel laser with equal height to make the emergent light height of the off-axis parabolic mirror equal,

s2, using a plane mirror to replace the off-axis parabolic mirror, making two parallel lasers with equal height pass through the plane mirror, simulating the light beam transmission path of the off-axis parabolic mirror system to be adjusted, forming an optical loop,

s3, adding a lens in the optical loop, moving the off-axis parabolic mirror by using a lens confocal alignment method, and replacing the plane mirror with the off-axis parabolic mirror;

the lens confocal alignment method specifically comprises the following steps: placing a lens on an optical circuit, enabling the distance between the lens and a plane mirror to be the sum of the focal length of the lens and the focal length of an off-axis parabolic mirror, then removing the plane mirror, replacing the plane mirror with the off-axis parabolic mirror, and enabling emergent light of the off-axis parabolic mirror to be parallel light;

two parallel lasers are generated by the following method: the beam emitted by the laser emitter is divided into a transmitted beam and a reflected beam by the beam splitting piece, and the reflected beam is parallel to the transmitted beam by using a plane reflector.

2. A method for adjusting an off-axis parabolic mirror system with a lens confocal point according to claim 1, wherein the splitting ratio of the beam splitter is 5: 5.

3. The method of claim 1, wherein the distance between two parallel laser beams is less than the parabolic width of the off-axis parabolic mirror.

4. The method for adjusting an off-axis parabolic mirror system using lens confocal according to claim 1, wherein the two parallel lasers in step S2 are equal in height to the two parallel lasers in step S1.

5. The method of claim 1, wherein in step S1, an optical baffle with horizontal scale is placed on the outgoing light path of the off-axis parabolic mirror to assist in adjusting the pitch angle of the off-axis parabolic mirror.

6. A method for confocal adjustment of an off-axis parabolic mirror system according to claim 1, wherein the laser is visible light.

7. A method for adjusting an off-axis parabolic mirror system with a lens confocal point according to claim 1, wherein the step S2 is performed by using a diaphragm placed on the optical loop formed by the plane mirrors to collimate the light.

8. A method for using a lens to adjust an off-axis parabolic mirror system with a common focus according to claim 1, wherein said flat mirrors are gold coated mirrors with a reflection efficiency of 96%.