A wave plate phase calibration device

Abstract

The invention discloses a wave plate phase calibration device, comprising a laser arranged in sequence according to an optical path, a vortex phase plate for phase modulating a light beam, a wave plate placement frame to be measured, a reflector, a quarter wave plate for converting linear polarized light into circular polarized light, and an objective lens; after the light beam is phase modulated by the vortex phase plate once, it passes through the wave plate to be measured and the quarter wave plate to reach the objective lens for imaging. The invention greatly simplifies the structure of the wave plate measurement device and improves the measurement accuracy and versatility of the wave plate phase delay.

Description

Technical Field

[0001] The invention relates to the field of optical instruments, and in particular to a wave plate phase calibration device. Background Art

[0002] Wave plates can cause phase delay between two mutually perpendicular components of polarized light, and are very important devices in polarization optics. The amount of phase delay is related to many factors such as the thickness of the wave plate and stress birefringence. It is a very important optical property of the wave plate, which directly determines the quality of the wave plate and will directly or indirectly affect the performance of the optical system. Therefore, how to accurately calibrate the phase delay of the wave plate is very important.

[0003] Wang Jing of Qufu Normal University published a master's degree thesis titled "Re-study of Intelligent Measurement Technology for Wave Plate Phase Delay" in April 2007, which proposed to use the four-step phase shift method to measure the phase delay of the wave plate. However, the four-step phase shift method has problems such as low accuracy and complicated operation in measuring phase delay. Zhang Ying of Beijing University of Posts and Telecommunications published a doctoral thesis titled "System Design and Development Based on Single-wavelength Laser to Measure Multi-wavelength Wave Plate Phase Delay" in February 2015, which proposed to use a single-wavelength laser to measure the phase delay of multi-wavelength wave plates. Although the measurement accuracy is improved, there is still a problem of complex structure. In addition, the existing wave plate calibration device has problems such as complex device structure, weak versatility, and low measurement accuracy. Summary of the invention

[0004] The present invention aims at solving the problems of the current wave plate measurement system, such as complex structure, weak versatility, low measurement accuracy, etc., and proposes a novel wave plate phase calibration device. The structure is relatively simple and the wave plate phase delay can be measured quickly and accurately.

[0005] A wave plate phase calibration device comprises a laser, a vortex phase plate, a wave plate placement frame to be measured, a reflector, a quarter wave plate, and an objective lens which are arranged in sequence according to an optical path;

[0006] The fast axis direction of the wave plate to be tested when placed is the x-axis direction, and the slow axis direction is the y-axis direction, a reference coordinate system is established, the angle between the linear polarization direction of the linear polarized light beam emitted by the laser and the x-axis is α, the light beam passes through the vortex phase plate, and after being modulated by the vortex phase plate, the light beam has a vortex phase wavefront, and the emitted light beam passes through the wave plate to be tested placed on the wave plate to be tested placement frame and then is reflected by the reflector; the polarization state of the linear polarized light beam is modulated into circular polarization through the quarter wave plate, and after being focused by the objective lens, an elliptical hollow light spot is formed on the focal plane; the angle between the major axis of the elliptical hollow light spot and the x-axis is the azimuth angle Ψ; the phase delay amount η of the wave plate to be tested can be obtained by Calculated.

[0007] The vortex phase plate is a 0-2π vortex phase plate, the optical thickness of the vortex phase plate is equal to the rotation azimuth angle, and the outgoing light beam after the incident light beam passes through the vortex phase plate has a vortex phase wavefront.

[0008] The azimuth angle Ψ changes with the change of the phase delay η of the wave plate to be measured; when α=0° and the wave plate to be measured is not placed, the major axis and the minor axis are equal, forming a circular hollow light spot.

[0009] Preferably, a half wave plate is added between the laser and the vortex phase plate to adjust α.

[0010] As a preferred choice, α=30° is generally selected. At this time, the ratio of the major and minor axes of the elliptical hollow spot is the largest, which is conducive to calibrating the azimuth angle Ψ. .

[0011] Compared with the prior art, the present invention has the following beneficial technical effects:

[0012] 1. The device of the present invention has a simple structure and is easy to operate;

[0013] 2. The present invention can detect the phase delay of any wave plate;

[0014] 3. The measurement of the present invention is of high accuracy and efficiency.

[0015] Therefore, compared with the prior art, the technical solution of the invention can improve the accuracy and versatility of wave plate phase delay measurement and simplify the device structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 An optical path diagram of an embodiment of the present invention;

[0017] Among them: 1. Laser; 2. Vortex phase plate; 3. Wave plate holder to be tested; 4. Reflector; 5. Quarter wave plate; 6. Objective lens.

[0018] Figure 2 It is an elliptical hollow light spot when α=30° and the phase delay of the wave plate to be measured is 0° in the embodiment.

[0019] Figure 3 It is an elliptical hollow light spot when α=30° and the phase delay of the wave plate to be measured is 45° in the embodiment. DETAILED DESCRIPTION

[0020] The present invention is described below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0021] like Figure 1The figure shows an optical path diagram of a wave plate phase calibration device according to an embodiment of the present invention. The wave plate phase calibration device according to the embodiment comprises: a laser 1, a vortex phase plate 2, a wave plate placement frame 3, a reflector 4, a quarter wave plate 5, and an objective lens 6.

[0022] The laser 1 emits continuous laser light with a wavelength of 532 nm.

[0023] The vortex phase plate 2 is a 0~2π vortex phase plate, the optical thickness of the vortex phase plate is equal to the rotation azimuth angle, and the outgoing light beam of the incident plane wave passing through the vortex phase plate has a vortex phase wavefront.

[0024] The light beam emitted by the laser 1 with a wavelength of 532nm passes through the 0~2π vortex phase plate 2. After being modulated by the 0~2π vortex phase plate 2, the light beam has a vortex phase wavefront, and the emitted light beam passes through the wave plate to be tested placed on the wave plate to be tested placement frame 3 and is reflected by the reflector 4; the polarization state of the linearly polarized light beam is modulated into circularly polarized light by the quarter wave plate 5, and after being focused by the objective lens 6, an elliptical hollow light spot is formed on the focal plane; the angle between the major axis of the elliptical hollow light spot and the x-axis is the azimuth angle Ψ; the phase delay amount η of the wave plate to be tested can be obtained by Calculated.

[0025] The angle α between the linear polarization direction of the incident light beam and the x-axis is 30°.

[0026] The wave plate with a phase delay of 0° is placed on the wave plate to be measured. The elliptical hollow spot formed on the focal plane is as follows: Figure 2 As shown, the azimuth angle Ψ=0° is calibrated with the long axis. According to the relationship between the phase delay η when α=30°: , we can get the phase delay of the wave plate to be measured η=0°.

[0027] The wave plate with a phase delay of 45° is placed on the wave plate to be measured. The elliptical hollow spot formed on the focal plane is as follows: Figure 3 As shown, the azimuth angle Ψ=10.278° is calibrated with the long axis. According to the relationship of the phase delay η when α=30°: , we can get the phase delay of the wave plate to be measured η=45°.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention, and should be included in the spirit and scope of the present invention, and should be included in the scope of the claims of the present invention.

Claims

1. A wave plate phase calibration device, characterized in that: It includes a laser, a vortex phase plate, a wave plate placement frame to be tested, a reflector, a quarter wave plate, and an objective lens which are arranged in sequence according to an optical path; The fast axis direction of the wave plate to be tested when placed is the x-axis direction, and the slow axis direction is the y-axis direction, a reference coordinate system is established, the angle between the linear polarization direction of the linear polarized light beam emitted by the laser and the x-axis is α, the light beam passes through the vortex phase plate, and after being modulated by the vortex phase plate, the light beam has a vortex phase wavefront, and the emitted light beam passes through the wave plate to be tested placed on the wave plate to be tested placement frame and then is reflected by the reflector; the polarization state of the linear polarized light beam is modulated into circular polarization through the quarter wave plate, and after being focused by the objective lens, an elliptical hollow light spot is formed on the focal plane; the angle between the major axis of the elliptical hollow light spot and the x-axis is the azimuth angle Ψ; the phase delay amount η of the wave plate to be tested can be obtained by It is calculated that a half wave plate is added between the laser and the vortex phase plate to adjust α.

2. A wave plate phase calibration device according to claim 1, characterized in that: The vortex phase plate is a 0-2π vortex phase plate, the optical thickness of the vortex phase plate is equal to the rotation azimuth angle, and the outgoing light beam of the incident light beam passing through the vortex phase plate has a vortex phase wavefront.

3. A wave plate phase calibration device according to claim 1, characterized in that: The azimuth angle Ψ changes with the change of the phase delay η of the wave plate to be measured; when α=0° and the wave plate to be measured is not placed, the major axis and the minor axis are equal, forming a circular hollow light spot.

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