WO2017193681A1

WO2017193681A1 - Optical system for use in laser interferometer for measuring large distance

Info

Publication number: WO2017193681A1
Application number: PCT/CN2017/075818
Authority: WO
Inventors: 刘龙为; 张和君; 张珂; 黄庭总
Original assignee: 深圳市中图仪器股份有限公司
Priority date: 2016-05-13
Filing date: 2017-03-07
Publication date: 2017-11-16
Also published as: CN205785113U

Abstract

An optical system for use in a laser interferometer for measuring a large distance comprises: a reference light path assembly (1); an optical assembly for measuring a large distance (2); and a first pyramid-shaped reflector (3). The optical assembly for measuring a large distance (2) is disposed between the reference light path assembly (1) and the first pyramid-shaped reflector (3). The optical assembly for measuring a large distance (2) comprises an emitting optical element and a receiving optical element. The emitting optical element of the optical assembly for measuring a large distance (2) shifts, by means of a rhomboid prism (201), a light beam upwards by a certain distance, such that an increase in the size of a laser light spot due to a large transmission distance does not result in overlapping of a light spot of an outgoing light beam with a light spot of a reflected light beam, and as a result the emitting optical element enables a laser beam to be propagated farther. Use of a large-diameter structure for a back-reflected light beam of a second telescope (203) of a receiving optical element, can maximally ensure a signal intensity of a back-reflected light beam, and can significantly reduce processing requirements for optical members.

Description

Optical system for measuring long distance by laser interferometer

Technical field

The present invention relates to an optical system, and more particularly to an optical system for measuring a long distance using a laser interferometer.

Background technique

Due to the inherent properties of the laser, after a certain distance of transmission, the spot of the laser will be diverged, which will cause the signal of the photoreceiver to be greatly weakened. At short distances (about 20m), the attenuation of this signal does not affect the measurement of the signal. However, when the measured distance is greater than 30m, the attenuation of the signal seriously affects the reception of the detector signal. Therefore, the measurement of the long distance must take into account the signal attenuation problem; at the same time, after the laser is transmitted over a long distance, the spot size will become larger, which will easily cause the spot to be reflected back into the laser, resulting in the laser not working.

In the prior art, some remote measurement schemes directly intercept part of the signal light, which makes the originally weak signal light become weaker, although the signal can be amplified by electronic processing, but this will Increasing electronic noise makes electronic processing more difficult. And because of the problem of laser divergence, the method of directly intercepting part of the signal makes the signal more weak. This method of intercepting signals directly requires high requirements for electronic circuits. The main problem is that the strength of the signal is relatively weak. Therefore, it is necessary to perform gain amplification processing on the circuit, and gain amplification will lead to an increase in noise. It also leads to a decrease in measurement speed; the most critical, this method does not enhance the signal from the source, but is realized by electronics and software, and due to the existence of the laser divergence angle, the laser transmission is also a long distance and then retroreflected. The energy of the laser is weakened.

In another remote measurement scheme of the prior art, a telescope is used to directly expand the incident light, thereby reducing the divergence angle of the laser, and the telescope can be used as a beam reduction mirror when the signal light is retroreflected, which can be maximized. The intensity of the signal light back. However, this method requires very high precision telescopes and is difficult to manufacture. This method also requires high mechanical installation, which not only increases the difficulty of design, but also increases the difficulty of lens manufacturing and mechanical packaging. In addition, After long-distance transmission, the spot size of the laser becomes large, which may cause the laser to return to the light-emitting hole of the laser head, resulting in harmful laser feedback, causing the laser to lose the lock.

Summary of the invention

The technical problem to be solved by the present invention is to provide a laser capable of avoiding the weakening of the measurement signal due to the large divergence of the spot and the reflection of the reflected light to the laser due to the large reflection spot. The problem of frequency stabilization and the like is used for measuring the long-distance optical system by the laser interferometer, thereby ensuring the long-distance measurement of the laser interferometer, and also reducing the design and processing requirements for the optical component.

In this regard, the present invention provides an optical system for measuring a long distance by a laser interferometer, comprising: a reference optical path assembly, a remote measuring optical component, and a first pyramid mirror, the remote measuring optical component being disposed in the Between the reference optical path assembly and the first pyramidal mirror, wherein the remote measuring optical component comprises an exiting optical component and a receiving optical component.

According to a further improvement of the present invention, the reference optical path assembly includes a polarization beam splitting prism and a second pyramid mirror, and the second pyramid mirror is disposed above the polarization beam splitting prism.

According to a further improvement of the present invention, the polarization beam splitting prism is disposed directly in front of the exiting optical member and the receiving optical member.

According to a further refinement of the invention, the exiting optical component comprises a bevel prism and a first telescope, the flared port of the first telescope being disposed at a beam exit of the rhombic prism.

A further improvement of the present invention is that the receiving optical component includes a second telescope disposed on a receiving optical path of the first pyramid mirror.

A further improvement of the present invention is that the clear aperture of the convex lens in the second telescope is larger than the clear aperture of the convex lens in the first telescope.

According to a further improvement of the present invention, the clear aperture of the convex lens in the second telescope is 1.1 to 2 times the clear aperture of the convex lens in the first telescope.

A further improvement of the present invention is that the clear aperture of the convex lens in the second telescope is 1.25 times the clear aperture of the convex lens in the first telescope.

A further improvement of the invention is that both reflective surfaces of the first pyramid mirror are at an angle of 45 to the measurement light emitted by the reference optical path assembly.

A further improvement of the invention is that the first telescope comprises a negative lens and a positive lens.

Compared with the prior art, the invention has the beneficial effects that the remote measuring optical component is disposed between the reference optical path component and the first pyramid mirror, and the outgoing optical component in the remote measuring optical component The beam is moved up by a diagonal prism, so that the laser spot becomes larger due to the long transmission distance, and does not cause the coincidence of the emitted spot and the reflected spot, and the laser beam can be made by the expansion of the first telescope. Spreading farther, on the basis of this, through the large-diameter beam return structure of the second telescope, the second telescope of the receiving optical component has a larger aperture than the small aperture of the first telescope, so that Maximum range The signal intensity of the retroreflected light is ensured.

DRAWINGS

1 is a schematic structural diagram of a system according to an embodiment of the present invention;

2 is a schematic view showing the structure of a light-passing aperture of an exiting optical component and a receiving optical component of a remote measuring optical component according to an embodiment of the present invention.

detailed description

The preferred embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, this example provides an optical system for measuring a long distance by a laser interferometer, comprising: a reference optical path assembly 1, a remote measuring optical component 2 and a first pyramidal mirror 3, said remote measurement The optical assembly 2 is disposed between the reference optical path assembly 1 and the first pyramid mirror 3, wherein the remote measuring optical assembly 2 includes an outgoing optical component and a receiving optical component.

As shown in FIG. 1, the reference optical path assembly 1 includes a polarization beam splitting prism 101 and a second pyramid mirror 102. The second pyramid mirror 102 is disposed above the polarization beam splitting prism 101. The prism 101 and the second pyramid mirror 102 constitute a reference light portion of the laser interferometer measuring system; the polarization beam splitting prism 101 is disposed directly in front of the exiting optical member and the receiving optical member.

The reference optical path assembly 1 has the same structure as the conventional linearly measured interference optical splitting system. The measurement light is partially transmitted as the measurement light at the polarization beam splitting prism 101, and the other portion is reflected upward. As the reference light, the reference light reflected by the PBS is again located in the PBS. The upper second pyramid mirror 102 reflects along with the retroreflected signal light into the detection system of the laser interferometer.

As shown in FIG. 1, the exiting optical component of this example includes a bevel prism 201 and a first telescope 202, and a beam expanding port of the first telescope 202 is disposed at a beam exit of the rhombic prism 201; the receiving The optical component includes a second telescope 203 disposed on a receiving optical path of the first pyramid mirror 3. The two reflecting surfaces of the first pyramid mirror 3 are preferably at an angle of 45 with the measuring light emitted by the reference optical path assembly 1; the first telescope 202 preferably includes a negative lens and a positive lens.

The remote measuring optical component 2 increases the center distance of the emitted light of the laser interferometer and the reflected signal light, and compresses the divergence angle of the emitted light, so that the laser beam can be transmitted farther, and the receiving area of the signal light is increased. The maximum possible increase in the intensity of the signal light.

After the measurement light of the reference optical path assembly 1 enters the remote measurement optical component 2, the measurement light is first shifted upward by a diagonal prism 201, and the two reflection surfaces of the oblique prism 201 are both 45 with the measurement light. ° Angle, such angle is greater than the critical angle of total reflection of the prism, to avoid the loss of energy to the utmost extent; at the same time, it also ensures that the measurement light only has translation, after being translated by the oblique prism 201, it enters the first telescope 202, The first telescope 202 consists of a negative lens and a positive lens, which have no real focus in the middle of the telescope lens compared to two telescopes in the form of positive lenses. Because of laser optics: ω·θ=const; after the telescope is expanded, the divergence angle of the corresponding laser beam is also reduced, and the size of the spot after the laser transmits a distance: ω _z ∝ θ; that is, the size and divergence of the spot The angle is proportional, which requires that the divergence angle of the spot be compressed as much as possible so that the laser beam travels farther. Nevertheless, the light spot is inevitably increased after the laser is transmitted over a long distance. At this time, a reverse telescope can function to compress the light spot, and the convex lens of the second telescope 203 has the largest possible aperture. The reflected laser signal can be collected to the maximum extent to ensure that the signal of the laser interferometer can be measured.

In this example, the first pyramid mirror 3 and the second pyramid mirror 102 are both prismatic mirrors, which may also be referred to as pyramids; in order to ensure that the first pyramid mirror 3 can cover the measurement light after the center becomes larger And the signal light reflected by the first pyramid mirror 3, where the first pyramid mirror 3 should be larger than the size of the commonly used pyramid mirror.

As shown in FIG. 2, the clear aperture of the convex lens in the second telescope 203 is larger than the clear aperture of the convex lens in the first telescope 202; preferably, the clear aperture of the convex lens in the second telescope 203 1 to 2 times of the clear aperture of the convex lens in the first telescope 202, the pass aperture of the convex lens in the second telescope 203 is 1.25 times the aperture of the convex lens in the first telescope 202. The best results.

In this example, when measuring the linear information of the long distance, the remote measuring optical component 2 is mounted on the reference optical path assembly 1, and the measuring light emitted by the reference optical path assembly 1 is offset upward by the oblique prism 201 by the oblique direction. After the prism 201, the beam of the measuring light is expanded by the first telescope 202. Since the beam of the measuring light is incident from the center of the first telescope 202, it is only necessary to consider the spherical aberration of the system, and the laser spot is Generally small, the spherical aberration of the system is also relatively small.

When the light beam of the measuring light is reflected by the first pyramid mirror 3, since the light beam is transmitted through a long distance, the light spot is larger than the light spot emitted, the light passing aperture of the convex lens in the second telescope 203 is larger than that in the first telescope 202. The clear aperture is large, and the clear aperture of the second telescope 203 here is 1.25 times the aperture of the first telescope 202 compared to the clear aperture of the first telescope 202, as shown in FIG. This facilitates the maximum reflected signal light, ensures the intensity of the signal light, and also ensures the accuracy of long-distance measurement.

This example can solve the following problems: First, it can solve the problem that the laser signal becomes weak after the long-distance transmission of the laser. Due to the inherent property of the laser, the laser spot will inevitably become larger after being transmitted at one end. Ben For example, by expanding the first telescope 202 and simultaneously compressing the divergence angle of the laser, the laser spot can be reduced as much as possible; at the same time, the reflected spot back is compressed by a large telescope 203 system to ensure laser interference. The instrument's signal is strong and reduces the optical reflection surface. Secondly, the severe requirements for the processing of optical components are reduced. In this example, good spherical aberration can be achieved by correcting the spherical aberration, and the requirements for optical components are greatly reduced. Thirdly, the problem of debugging the optical path system is avoided. In the prior art, the position of the telescope, especially the upper and lower positions, is very important, and a slight deviation may cause the signal to not return to the laser head. This problem no longer exists in this example.

The exiting optical component in the remote measuring optical component 2 of the present example moves the beam upward by the oblique prism 201, so that even if the laser spot becomes larger due to the long transmission distance, the emitted spot and the reflected spot are not caused. Coincident, and by the expansion of the first telescope 202, the laser beam can be propagated further. On the basis of this, the large-diameter beam returning structure of the second telescope 203 is compared with the small aperture of the first telescope 202. The second telescope 203 of the receiving optical component has a larger aperture, which ensures the signal intensity of the retroreflected light to the utmost extent.

This example solves the problem that the laser signal becomes weak due to long-distance transmission. First, an oblique prism 201 instead of two independent triangular mirrors reduces the waste of energy reflection of the optical transmission; secondly, the first telescope 202 is located. The telescope beam expanding system compresses the divergence angle of the laser to ensure the long-distance transmission of the laser; solves the demanding price and error requirements of the optical components in the measuring optical system, and replaces a separate telescope system with a separate telescope system. The processing requirements of the optical components of the system are greatly reduced. At the same time, the flexible separation structure can also ensure the collection of signal light; the debugging and installation in the optical system for long-distance measurement is simplified, and the structure of this example can be ensured by the guarantee of the mechanical structure. Quick installation and debugging.

The embodiments described above are preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is not limited to the specific embodiments, and the shapes and structures according to the present invention are Equivalent variations are within the scope of the invention.

Claims

An optical system for measuring a long distance by a laser interferometer, comprising: a reference optical path assembly, a remote measuring optical component, and a first pyramid mirror, wherein the remote measuring optical component is disposed on the reference optical path Between the assembly and the first pyramid mirror, wherein the remote measuring optics assembly includes an exit optic and a receiving optic.
The optical system for measuring a long distance of a laser interferometer according to claim 1, wherein the reference optical path assembly comprises a polarization beam splitting prism and a second pyramid mirror, and the second pyramid mirror is disposed on Above the polarizing beam splitting prism.
The optical system for measuring a long distance by a laser interferometer according to claim 2, wherein the polarization beam splitting prism is disposed directly in front of the exiting optical member and the receiving optical member.
The optical system for measuring a long distance by a laser interferometer according to any one of claims 1 to 3, wherein the exiting optical component comprises a bevel prism and a first telescope, and the first telescope is expanded The port is disposed at a beam exit of the orthoptical prism.
The optical system for measuring a long distance for a laser interferometer according to claim 4, wherein the receiving optical component comprises a second telescope, and the second telescope is disposed at the receiving of the first pyramid mirror On the light road.
The optical system for measuring a long distance by a laser interferometer according to claim 5, wherein a clear aperture of the convex lens in the second telescope is larger than a clear aperture of the convex lens in the first telescope.
The optical system for measuring a long distance of a laser interferometer according to claim 6, wherein a clear aperture of the convex lens in the second telescope is 1.1 to 2 of a clear aperture of the convex lens in the first telescope. Times.
The optical system for measuring a long distance by a laser interferometer according to claim 7, wherein a clear aperture of the convex lens in the second telescope is 1.25 times a clear aperture of the convex lens in the first telescope.
An optical system for measuring a long distance by a laser interferometer according to any one of claims 1 to 3, characterized in that both of the reflecting surfaces of the first pyramid mirror and the measurement emitted by the reference optical path assembly The light is at an angle of 45°.
The optical system for measuring a long distance by a laser interferometer according to any one of claims 1 to 3, characterized in that the first telescope comprises a negative lens and a positive lens.