CN101101369A - A Method of Accurately Determining the Coaxial Reference of Laser Transceiver by Using Zernike Coefficient - Google Patents

Abstract

The invention relates to a method for accurately determining the coaxial reference of laser transceivers by using Zernike coefficients. The invention relates to a method for determining the coaxiality of a transmitting optical path and a receiving optical path of an optical system where the transmitting and receiving optical systems share the same antenna. It overcomes the defect that the existing method cannot meet the high-precision application requirements due to the limitation of the machining accuracy and difficulty of the corner prism. It includes the following steps: the laser beam is emitted by the interferometer, and the beam passes through the emitting optical path assembly of the optical system under test, the beam splitter and the optical antenna in turn, and then exits; a plane mirror is arranged outside the exit of the optical antenna perpendicular to its optical axis, so that from the optical antenna The laser beam emitted onto the surface of the plane mirror returns to the interferometer along the original optical path; when adjusting the plane mirror, monitor the interference fringes in the interferometer so that Zernike is less than λ/10; the laser beam incident on the plane mirror, after being reflected by the plane mirror, passes through the beam splitter The reflection of the light beam is incident into the receiving optical path assembly of the optical system under test, and the optical axis of the receiving optical path assembly is adjusted based on this light beam.

Description

A Method of Accurately Determining the Coaxial Reference of Laser Transceiver by Using Zernike Coefficient

technical field

The invention relates to a method for determining the coaxiality of the transmitting optical path and the receiving optical path of an optical system that share the same antenna for transmitting and receiving.

Background technique

When developing an optical system that transmits and receives the same antenna, the coaxiality of the transmitting optical path and the receiving optical path is one of the important parameters that are strictly required. In the existing adjustment method, the light field is output from the transmitting light path through the antenna, and the angular prism is used to reflect it back to the receiving antenna along the original path and enter the receiving light path. Taking the incident light as the reference axis, the receiving light path is adjusted to ensure the transmission and reception. The coaxiality of the optical path. Due to the limitation of the processing accuracy of the corner prism, the emitted light field does not return strictly according to the original path, so that the coaxiality accuracy of the emitted and received optical paths can only reach tens of μrad, which cannot meet the requirements of high-precision applications. On the other hand, because the large-aperture angular prism is difficult to process, this method is difficult to be applied in the large-aperture antenna optical system.

Contents of the invention

The purpose of the present invention is to provide a method for accurately determining the coaxial reference of laser transmitting and receiving by using Zernike coefficients, so as to overcome the defect that the existing method cannot meet the high-precision application requirements due to the limitation of the processing accuracy and difficulty of the corner prism. It includes the following steps: 1. The laser beam is emitted by the interferometer 1, and the beam passes through the emitting optical path assembly 2-1, the beam splitter 2-2 and the optical antenna 2-3 of the optical system 2 in turn, and then emerges; 2. A plane mirror 3 is arranged perpendicular to its optical axis outside the exit of the optical antenna 2-3, and the plane mirror 3 is installed on the adjustment mechanism 4, and the verticality of the plane mirror 3 relative to the incident laser beam is adjusted by the adjustment mechanism 4, so that from the optical antenna 2 -3 The laser beam emitted on the surface of the plane mirror 3 returns to the interferometer 1 along the original optical path; when the plane mirror 3 is adjusted by the adjustment mechanism 4, the interference fringes in the interferometer 1 are monitored so that the wavefront error polynomial tilt coefficient Zernike is less than λ/ 10; 3. The laser beam incident on the plane mirror 3, after being reflected by the plane mirror 3, is reflected by the beam splitter 2-2, and enters the receiving optical path component 2-4 of the optical system 2 under test, and adjusts the receiving optical path based on this beam Optical axis of components 2-4.

Since the method of the present invention does not use a corner prism with high processing precision and difficulty, it overcomes the defects of the prior art. The present invention proposes a high-precision laser emission/reception system reference axis determination technology, using an interferometer, a high-precision adjustment mechanism, and a high-precision plane mirror to accurately measure the Zernike tilt coefficient, and determine the laser receiving optical path assembly according to the optical axis of the laser emitting optical path assembly The optical axis reference can improve the coaxiality between the reference axis of the laser receiving optical path and the emitting optical path to the order of 0.1μrad, and this technology can be widely used in optical transceiver systems with large aperture optical antennas.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

Specific Embodiment 1: The present embodiment will be specifically described below with reference to FIG. 1 . This embodiment is composed of the following steps: 1. The laser beam is emitted by the interferometer 1, and the beam sequentially passes through the emitting optical path assembly 2-1, the beam splitter 2-2 and the optical antenna 2-3 of the optical system 2 to be tested and then emerges; Two, a plane mirror 3 is arranged perpendicular to its optical axis outside the exit of the optical antenna 2-3, and the plane mirror 3 is installed on the adjustment mechanism 4, and the verticality of the plane mirror 3 relative to the incident laser beam is adjusted by the adjustment mechanism 4, so that from The laser beam emitted by the optical antenna 2-3 onto the surface of the plane mirror 3 returns to the interferometer 1 along the original optical path; when the plane mirror 3 is adjusted by the adjustment mechanism 4, the interference fringes in the interferometer 1 are monitored, so that the wavefront error polynomial tilt coefficient Zernike Less than λ/10; 3. The laser beam incident on the plane mirror 3, after being reflected by the plane mirror 3, is reflected by the beam splitter 2-2, and enters the receiving optical path component 2-4 of the optical system 2 under test, taking this beam as a reference Adjusting the optical axis of the receiving optical path assembly 2-4 can ensure that the misalignment between the emitting optical path and the receiving optical path of the optical system 2 under test is less than (λ/10)/φ. φ is the effective aperture of the optical antenna 2-3, and λ is the wavelength of the laser beam.

When the optical axis of the plane mirror 3 does not coincide with the optical axis of the emission light path of the optical antenna 2-3, the polynomial coefficient Zernike tilt of the wavefront error is not zero, and the fringes of the interferometer 1 will appear left-right and up-down asymmetry.

While monitoring the fringes of the interferometer 1, adjust the adjustment mechanism 4, so that the wavefront error polynomial tilt coefficient Zernike is less than λ/10, which can ensure that the angle between the optical axis of the plane mirror 3 and the optical axis of the emission light path is less than (λ/10)/φ, and the incident plane mirror 3 of the laser beam, after being reflected by the plane mirror 3, enters the receiving optical path of the optical system 2 under test, and adjusting the receiving optical path of the optical system 2 under test with this beam as a reference can ensure that the misalignment of its transmitting and receiving systems is less than ( λ/10)/φ.

When using it, you can choose a flat mirror with a diameter of φ300mm as the reflector, and the surface accuracy RMS is 1/70λ. You can choose the GHI-4”HS interferometer produced by ZYGO Company of the United States to emit the reference beam and detect the interference fringes between the reflected wavefront and the reference wavefront. The interferometer produced by ZYGO Company has a CCD detector, which can convert the interference fringe image Direct input to the computer with data acquisition card for image processing. The main parameters of the interferometer produced by ZYGO company are: diameter φ300mm, working wavelength 632.8nm, two-dimensional high-precision adjustment frame with horizontal rotation and pitch rotation can be selected as the adjustment mechanism4 Adjust the angle of the plane mirror.

Claims (1)

1, utilization Zernike coefficient is accurately determined the method for laser transmitting-receiving coaxial reference, it is characterized in that it comprises the steps: one, launches laser beam by interferometer (1), this light beam sees through emission optical path component (2-1), spectroscope (2-2) and optical antenna (2-3) the back outgoing of tested optical system (2) successively; Two, vertical its optical axis is provided with a level crossing (3) outside the outlet of optical antenna (2-3), level crossing (3) is installed on the adjusting mechanism (4), by adjusting mechanism (4) level crossing (3) is adjusted with respect to the verticality of incident laser light beam, turned back to the interferometer (1) along original optical path so that shine the lip-deep laser beam of level crossing (3) from optical antenna (2-3); When utilizing adjusting mechanism (4) to adjust level crossing (3), monitor the interference fringe in the interferometer (1), make wavefront error polynomial expression inclination coefficient Zernike less than λ/10; Three, the laser beam of plane of incidence mirror (3), after level crossing (3) reflection, through the reflection of spectroscope (2-2), incide in the receiving light path assembly (2-4) of tested optical system (2), be the optical axis that benchmark is adjusted receiving light path assembly (2-4) with this light beam.

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