阅读说明：本技术 一种提高测量旋转体角速度干涉条纹衬比度的光学系统 (Optical system for improving contrast of interference fringes for measuring angular velocity of rotating body ) 是由 董毅 田娅 张艳玲 于 2019-11-28 设计创作，主要内容包括：本发明的提高测量旋转体角速度干涉条纹衬比度的光学系统,包括激光光源、第一和第二偏振分束镜、分光棱镜、光电探测器和被测旋转物体,第一偏与第二偏振分束镜之间设置有螺旋相位片,第二偏振分束镜与待测旋转物体之间设置有四分之一波片；第一偏振分束镜反射的信号光经螺旋相位片转换为线偏振涡旋光,信号光与参考光经第二分光棱镜的反射和透射发生光外差干涉,光电探测器用于检测信号光与参考光的差频信号。本发明的光学系统,通过转动半波片可调节经第一偏振分束镜的反射光束与透射光束的光强比,使得照射于分光棱镜上的参考光与信号光的光强相等,使得干涉条纹衬比度最大,以准确反映待测旋转物体的转动角速度。(The invention relates to an optical system for improving contrast of angular velocity interference fringes of a measurement rotator, which comprises a laser light source, a first polarization beam splitter, a second polarization beam splitter, a beam splitter prism, a photoelectric detector and a rotation object to be measured, wherein a spiral phase plate is arranged between the first polarization beam splitter and the second polarization beam splitter, and a quarter wave plate is arranged between the second polarization beam splitter and the rotation object to be measured; the signal light reflected by the first polarization beam splitter is converted into linearly polarized eddy optical rotation through the spiral phase plate, the signal light and the reference light are reflected and transmitted through the second beam splitter prism to generate optical heterodyne interference, and the photoelectric detector is used for detecting a difference frequency signal of the signal light and the reference light. According to the optical system, the light intensity ratio of the reflected light beam and the transmitted light beam passing through the first polarization beam splitter can be adjusted by rotating the half-wave plate, so that the light intensities of the reference light and the signal light irradiated on the beam splitter prism are equal, the contrast of interference fringes is maximized, and the rotation angular speed of the rotating object to be measured is accurately reflected.)

1. An optical system for improving contrast of interference fringes of angular velocity of a measurement rotator comprises a laser source (1), a first polarization beam splitter (4), a second polarization beam splitter (8), a beam splitter prism (7), a photoelectric detector and a measured rotator (11), wherein the laser source is used for generating linear polarization laser; a half-wave plate (3) is arranged between the laser source and the first polarization beam splitter, laser emitted by the laser source is irradiated on the first polarization beam splitter (4) after the polarization direction of the laser is rotated by the half-wave plate, and reflected light and transmitted light of the first polarization beam splitter are respectively used as signal light and reference light; the method is characterized in that: a spiral phase plate (6) is arranged between the first polarization beam splitter and the second polarization beam splitter, and a quarter wave plate (9) is arranged between the second polarization beam splitter (8) and a rotating object (11) to be measured; the signal light reflected by the first polarization beam splitter is converted into linearly polarized vortex rotation through the spiral phase plate, and the vortex light is incident on the second polarization beam splitter (8); the second polarization beam splitter realizes total reflection of incident vortex rotation, vortex signal light reflected by the second polarization beam splitter is irradiated on a rotating object (11) to be detected after passing through the quarter-wave plate (9), and the polarization direction of the signal light reflected by the rotating object rotates for 90 degrees relative to the initial vortex rotation after passing through the quarter-wave plate again;

the signal light with the polarization direction rotating by 90 degrees is irradiated on the second polarization beam splitter (8) for transmission, the transmitted signal light is irradiated on the beam splitter prism (7), and the reference light formed by the transmission of the first polarization beam splitter is irradiated on the beam splitter prism; the signal light and the reference light are reflected and transmitted through the second beam splitter prism to generate optical heterodyne interference, and the photoelectric detector is used for detecting a difference frequency signal of the signal light and the reference light.

2. The optical system for improving the contrast of interference fringes for measuring the angular velocity of a rotating body according to claim 1, characterized in that: a beam expander (2) is arranged between the laser source (1) and the half-wave plate (3), and linear polarization laser emitted by the laser source (1) is expanded by the beam expander and then irradiates the first polarization beam splitter (4).

3. The optical system for improving the contrast of interference fringes for measuring the angular velocity of a rotating body according to claim 1 or 2, characterized in that: a first total reflector (5) is arranged between the first polarization beam splitter (4) and the beam splitter prism (7), and a second total reflector (10) is arranged between the quarter-wave plate (9) and the rotating object (11) to be measured; reference light formed by transmission of the first polarization beam splitter is reflected by the first total reflector and then irradiates the beam splitter prism (7), and vortex light transmitted by the quarter-wave plate and vortex rotation reflected by the rotating object to be measured (11) are reflected by the second total reflector (10).

4. The optical system for improving the contrast of interference fringes for measuring the angular velocity of a rotating body according to claim 1 or 2, characterized in that: the photoelectric detector comprises a first photoelectric detector (14) and a second photoelectric detector (15), and the signal light is interfered with the reflected light of the reference light through the beam splitter prism (7), converged by the first converging lens (12) and then irradiated on the first photoelectric detector (14); the signal light and the reference light are interfered by the reflected light of the beam splitter prism, and then are converged by a second converging lens (13) and irradiated on a second photoelectric detector (15).

5. The optical system for improving the contrast of interference fringes for measuring the angular velocity of a rotating body according to claim 4, characterized in that: if the number of angular quanta of the spiral phase plate (6) is l, and a difference frequency signal obtained after random noise is filtered by the first photoelectric detector (14) and the second photoelectric detector (15) is delta f, the following conditions are met:

from equation (1):

wherein l is the angular quantum number of the spiral phase plate, and Δ f is the frequency of the difference frequency signal measured by the detector.

Technical Field

The present invention relates to an optical system for measuring an angular velocity of a rotating body, and more particularly, to an optical system for improving contrast of interference fringes for measuring an angular velocity of a rotating body.

Background

The angular velocity can reflect the motion characteristics of a rotating object, and the angular velocity of the rotation of the object is required to be accurately measured in various occasions, such as the rotation speed of a motor shaft, the rotation speed of a scanning reflector, the particle spinning, the spiral-like motion of sperms in semen, the rotation and orbital motion of celestial bodies and the like. Conventional methods for measuring angular velocity, such as gyroscopes, encoders, etc., are limited in many applications. For example, the measurement of particles in liquid, aerospace moving targets and celestial body angular velocity in the starry sky is difficult to achieve by using conventional measurement means.

Vortex is one of the most common phenomena in nature and is commonly found in classical macroscopic systems such as water, clouds, and cyclones. A number of theories and experiments confirm that vortices also exist in the light wave field. The vortex light is singular light with a spiral wave front structure, and the center of the light beam of the vortex light is provided with a phase singularity, so that the light intensity of the cross section of the vortex light is distributed in an annular hollow shape. Vortex rotation, which is a form of wave motion, has orbital angular momentum due to a helical phase structure. The phase of the vortex rotation contains an azimuthal term

Wherein l is the number of angular quantum of vortex rotation,

is the azimuth angle. The awareness of optical vortices has reached a new height into the 21 st century. Unlike the linear doppler effect, when a vortex light having orbital angular momentum is perpendicularly irradiated onto a rough surface of a rotating body along the rotation axis, a frequency shift phenomenon, called rotational doppler shift, also occurs. By means of the rotating doppler effect, a measurement of the angular velocity of the rotor can be achieved. The method for measuring the angular velocity by using the transverse Doppler effect of the vortex rotation has the remarkable advantages of high precision, short response time, non-contact measurement and the like. However, this method has certain drawbacks. Because the light intensity of the scattered light is too weak, the fringe contrast of the interference light field is not high, and the signal-to-noise ratio of the differential frequency shift signal acquired by the photoelectric detector is not high.

Disclosure of Invention

The present invention provides an optical system for improving the contrast of interference fringes for measuring the angular velocity of a rotating body, which overcomes the defects of the technical problems.

The invention relates to an optical system for improving contrast of interference fringes of angular velocity of a measuring rotator, which comprises a laser source, a first polarization beam splitter, a second polarization beam splitter, a beam splitter prism, a photoelectric detector and a measured rotator, wherein the laser source is used for generating linear polarization laser; a half-wave plate is arranged between the laser source and the first polarization beam splitter, laser emitted by the laser source is irradiated on the first polarization beam splitter after the polarization direction of the laser is rotated by the half-wave plate, and reflected light and transmitted light of the first polarization beam splitter are respectively used as signal light and reference light; the method is characterized in that: a spiral phase plate is arranged between the first polarization beam splitter and the second polarization beam splitter, and a quarter wave plate is arranged between the second polarization beam splitter and the rotating object to be measured; the signal light reflected by the first polarization beam splitter is converted into linearly polarized vortex rotation through the spiral phase plate, and the vortex light is incident on the second polarization beam splitter; the second polarization beam splitter realizes total reflection of incident vortex rotation, vortex signal light reflected by the second polarization beam splitter is irradiated on a rotating object to be detected after passing through the quarter-wave plate, and the polarization direction of the signal light reflected by the rotating object rotates by 90 degrees relative to the initial vortex rotation after passing through the quarter-wave plate again;

the signal light with the polarization direction rotating by 90 degrees is irradiated on the second polarization beam splitter for transmission, the transmitted signal light is irradiated on the beam splitter prism, and the reference light formed by the transmission of the first polarization beam splitter is irradiated on the beam splitter prism; the signal light and the reference light are reflected and transmitted through the second beam splitter prism to generate optical heterodyne interference, and the photoelectric detector is used for detecting a difference frequency signal of the signal light and the reference light.

According to the optical system for improving the contrast of the interference fringes for measuring the angular velocity of the rotator, the beam expander is arranged between the laser source and the half-wave plate, and linear polarization laser emitted by the laser source is expanded by the beam expander and then irradiates the first polarization beam splitter.

The invention relates to an optical system for improving contrast of interference fringes of angular velocity of a measured rotator, wherein a first total reflector is arranged between a first polarization beam splitter and a beam splitter prism, and a second total reflector is arranged between a quarter-wave plate and the rotator to be measured; the reference light formed by the transmission of the first polarization beam splitter is reflected by the first total reflector and then irradiates the beam splitter prism, and the vortex light transmitted by the quarter-wave plate and the vortex rotation reflected by the rotating object to be measured are reflected by the second total reflector.

The invention relates to an optical system for improving contrast of interference fringes of angular velocity of a measuring rotating body, wherein a photoelectric detector comprises a first photoelectric detector and a second photoelectric detector, signal light is interfered with reflected light of a reference light by a light splitting prism through transmitted light of the light splitting prism, and then the signal light is irradiated on the first photoelectric detector after being converged by a first converging lens; the signal light and the reference light are interfered by the reflected light of the beam splitter prism, and then are converged by the second converging lens to irradiate the second photodetector.

The optical system for improving the contrast of the interference fringes of the angular velocity of the measured rotating body is provided with the angular quantum number of the spiral phase plate as l, and a difference frequency signal obtained after random noise is filtered by the first photoelectric detector and the second photoelectric detector as delta f, so that the following requirements are met:

from equation (1):

wherein l is the angular quantum number of the spiral phase plate, and Δ f is the frequency of the difference frequency signal measured by the detector.

The invention has the beneficial effects that: in the optical system, linearly polarized light generated by a laser light source rotates the polarization direction through a half-wave plate, and then laser is divided into two paths with mutually vertical polarization directions through a first polarization beam splitter, wherein one transmitted path is used as reference light, and the other reflected path is used as signal light; the signal light is converted into vortex light with a certain angle quantum number through the spiral phase plate, the vortex light penetrates through the quarter-wave plate after being totally reflected by the second polarization beam splitter, the vortex light is irradiated on a rotating object to be detected and reflected back to pass through the quarter-wave plate again, the polarization direction of the vortex light can rotate 90 degrees relative to the initial vortex light, the vortex light rotating in the polarization direction of 90 degrees is consistent with the polarization direction of the reference light, heterodyne interference can be generated between the signal light and the reference light, and the rotating speed of the rotating object to be detected is obtained by the photoelectric detector through obtaining a difference frequency signal. The light intensity ratio of the reflected light beam and the transmitted light beam passing through the first polarization beam splitter can be adjusted by rotating the half-wave plate, so that the light intensity of the reference light and the light intensity of the signal light irradiated on the beam splitter prism are equal, the contrast of the interference fringes is maximum, the signal-to-noise ratio of the difference frequency signal detected by the photoelectric detector is improved, and the rotation angular speed of the rotating object to be detected is accurately reflected.

Drawings

FIG. 1 is a schematic diagram of an optical system for improving contrast of interference fringes for measuring angular velocity of a rotating body according to the present invention.

In the figure: the device comprises a laser light source 1, a beam expander 2, a half-wave plate 3, a first polarization beam splitter 4, a first holophote 5, a spiral phase plate 6, a beam splitter prism 7, a second polarization beam splitter 8, a quarter-wave plate 9, a second holophote 10, a rotating object to be detected 11, a first convergent lens 12, a second convergent lens 13, a first photoelectric detector 14 and a second photoelectric detector 15.

Detailed Description

The invention is further described with reference to the following figures and examples.

As shown in fig. 1, a schematic structural diagram of an optical system for improving contrast of an interference fringe of an angular velocity of a measurement rotator according to the present invention is provided, and the optical system comprises a laser light source 1, a beam expander 2, a half-wave plate 3, a first polarization beam splitter 4, a first total reflector 5, a spiral phase plate 6, a beam splitter prism 7, a second polarization beam splitter 8, a quarter-wave plate 9, a second total reflector 10, a rotation object to be measured 11, a first condenser lens 12, a second condenser lens 13, a first photodetector 14, and a second photodetector 15, and centers of optical elements in all directions are coaxial. Beam expander 2 and half-wave plate 3 set gradually between laser light source 1 and first polarization beam splitter 4, and laser light source 1 is used for producing linear polarization laser, and the light source that laser light source 1 sent shines on half-wave plate 3 again after beam expanding of beam expander 2, and half-wave plate 3 is used for the polarization direction of rotatory linear polarization laser. The laser light with the changed polarization direction is irradiated on the first polarization beam splitter 4 to be transmitted and reflected, the reflected light is used as signal light, the transmitted light passing through the first polarization beam splitter 4 is used as reference light, as shown in fig. 1, the reflected light of the laser light passing through the first polarization beam splitter 4 is S-polarized light, the transmitted light is P-polarized light, and the polarization direction of the S-polarized light is perpendicular to that of the P-polarized light.

The spiral phase plate 6 is arranged between the first polarization beam splitter 4 and the second polarization beam splitter 4, the signal light generated by the reflection of the first polarization beam splitter 4 generates linear polarization vortex optical rotation with the angular quantum number of l after passing through the spiral phase plate 6, the vortex light irradiates on the second polarization beam splitter 8, and the second polarization beam splitter 8 realizes the total reflection of the vortex optical rotation. The second polarization beam splitter 8 realizes total reflection of vortex light by arranging the first polarization beam splitter 4 and the second polarization beam splitter 8 in the polarization direction of light. The vortex light irradiated on the second polarization beam splitter 8 is totally reflected, then passes through the quarter wave plate 9, and then is irradiated on the second total reflector 10 to be reflected, the reflected vortex light is irradiated on the rotating object 11 to be detected, and the reflected vortex light generates frequency shift due to the rotation of the rotating object 11 to be detected.

After the vortex light reflected by the rotating object 11 to be measured passes through the second total reflection mirror 10, the polarization direction of the vortex light after passing through the quarter-wave plate 9 again can rotate by 90 degrees relative to the polarization direction of the initial vortex optical rotation. Vortex light after 90-degree rotation is irradiated on the second polarization beam splitter 8 and then is completely transmitted, and the signal light after the vortex light is transmitted through the second polarization beam splitter 8 is changed into P-polarized light, so that the polarization direction of the signal light is the same as the vibration direction of the reference light.

Reference light transmitted by the first polarization beam splitter 4 is reflected by the first total reflector 5 and then irradiates the beam splitter prism 7, vortex signal light transmitted by the second polarization beam splitter 8 also irradiates the beam splitter prism 7, and the polarization directions of the signal light and the reference light are the same. The transmitted light of the signal light irradiated on the beam splitter prism 7 interferes with the reflected light of the reference light irradiated on the beam splitter prism 7, and is converged by the first condenser lens 12 and irradiated on the first photodetector 14, and the first photodetector 14 detects a difference frequency signal between the signal light and the reference light.

The reflected light of the signal light irradiated on the beam splitter prism 7 interferes with the transmitted light of the reference light irradiated on the beam splitter prism 7, the signal light is converged by the second converging lens 13 and then irradiated on the second photoelectric detector 15, the second photoelectric detector 15 detects the difference frequency signal of the signal light and the reference light, the difference frequency signals detected by the first photoelectric detector 14 and the second photoelectric detector 15 are equal in amplitude and same in phase, and random noise in the signal can be filtered by using a phase-reversal subtraction method to obtain a precise difference frequency signal.

When the surface of the rotating body 11 to be measured has a certain roughness, the vortex light irradiates the surface and is emitted, the light intensity of the reflected vortex light is lost, in order to obtain the best interference effect, the light intensities of the signal light and the reference light irradiated on the beam splitter prism 7 are required to be equal, therefore, the intensity of the signal light generated by the reflection of the first polarization beam splitter 4 should be greater than the intensity of the reference light generated by the transmission thereof, so as to ensure that the intensity of the signal light and the reference light which are finally interfered are equal, this is achieved by rotating the half-wave plate 3, by which the polarization direction of the linearly polarized laser light can be rotated, the proportion of the reflected light and the transmitted light of the laser through the first polarization beam splitter 4 is adjusted, so that the light intensity of the signal light and the light intensity of the reference light which are irradiated on the beam splitter prism 7 are equal, and finally the contrast of the interference fringes is optimal.

If the number of angular quanta of the spiral phase plate 6 is l, and a difference frequency signal obtained after random noise is filtered by the first photodetector 14 and the second photodetector 15 is Δ f, then the following conditions are satisfied:

from equation (1):

wherein l is the angular quantum number of the spiral phase plate, and Δ f is the frequency of the difference frequency signal measured by the detector.