A ranging system based on vector light fields

Abstract

The present invention discloses a ranging system based on vector optical fields, which includes a diagonal linearly polarized light generator with collimation and beam expansion functions, a generating system for arbitrary structured vector beams, a vector quality factor measurement system, and a CCD receiving device. A Digital Micromirror Devices (DMD) is provided in the vector beam generating system. By using digital control technology, a circular Airy vortex vector beam with a vector quality factor (VQF) varying regularly with distance can be generated. Through the acquisition of the VQF parameters by the vector quality factor measurement system, the detection of the longitudinal transmission distance is realized, so that it can be applied to industries that require distance monitoring. It has the characteristics of low cost of the detection device, easy integration, flexible regulation, and wide application range.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technologies, and particularly to a ranging system based on a vector light field. Background Art

[0002] As one of the greatest inventions of mankind in the 20th century, lasers have been widely used in fields such as medicine, industry, and laser weapons. Due to the advantages of good monochromaticity and strong directivity of lasers, using lasers as light sources to measure the distance to targets is a commonly used method for distance measurement. Light has multiple properties (amplitude, phase, spatial mode, frequency, polarization, etc.). Utilizing the rich properties of light to develop new laser ranging technologies is of great significance for promoting the progress of human society. Among them, the polarization state, as one of the important properties of light, provides a reliable technical approach for the realization of many laser technologies.

[0003] Coupling the spatial mode and the polarization degree of freedom in an inseparable manner can obtain a class of structured light fields with spatially varying polarization. Due to the non-uniformity of their transverse polarization distribution, such light fields are also called vector light fields. Vector light fields have spatially varying polarization states at different positions on the same wavefront. Such unique spatial-polarization coupling properties have given rise to more extensive applications for laser technologies. At the same time, in view of the problems of low flexibility, high cost, small applicable range, and low ranging efficiency in conventional ranging methods, the present invention designs a ranging system based on a vector light field that can perform rapid ranging and has a wide range of applicable scenarios. Summary of the Invention

[0004] In order to overcome the defects in the above-mentioned prior art, the present invention provides a ranging system based on a vector light field, which can utilize the vector quality factor (VQF) of a circular Airy vortex vector light field to achieve rapid distance measurement.

[0005] Technical Solution

[0006] A ranging system based on a vector light field includes a linearly polarized light generator with a collimation and beam expansion function arranged in the diagonal direction from left to right, a generating system for any vector beam, a vector quality factor measurement system, and a CCD receiving device. A digital micromirror device DMD for digitally regulating the light field parameters is provided in the generating system.

[0007] Further, the linearly polarized light generator includes a set of collimation and beam expansion lenses. The collimation and beam expansion lenses include a first lens with a focal length of 20 mm and a second lens with a focal length of 200 mm. The linearly polarized light generator further includes a laser.

[0008] Further, the linearly polarized light generator further includes a half-wave plate.

[0009] Furthermore, the generation system includes a Wollaston prism disposed on the right side of the linearly polarized light generator.

[0010] Furthermore, the generation system further includes a quarter-wave plate, and the generation system further includes a lens three with a focal length of 100 mm and a lens four with a focal length of 100 mm.

[0011] Furthermore, the generation system further includes a digital micromirror device (DMD). The hologram loaded on the digital micromirror device (DMD) includes a digital grating. By adjusting the grating coefficient, two circularly polarized light beams with left and right hand polarizations can be made to propagate along the same transmission path.

[0012] Furthermore, the circular Airy vortex vector beam generated by the generation system is expressed as:

[0013]

[0014] where cosθ, is a weight factor, (r, φ) are cylindrical coordinate parameters, and are the left and right circular polarization basis vectors. Additionally, is the phase difference between the two polarization basis vectors, and serve as two orthogonal spatial mode basis vectors, which are circular Airy vortex beams carrying orbital angular momentum respectively, and h is Planck's constant.

[0015] Furthermore, the circular Airy vortex beam can be expressed as:

[0016]

[0017] where Ai() represents the Airy function; r is the radius, r 0 is the radius of the main ring of the beam; a is the cut-off factor; ω is the beam waist radius; m is the topological charge; v is the initial emission angle parameter.

[0018] Furthermore, without changing any optical components in the optical path, the circular Airy vortex vector beam can dynamically regulate the transverse polarization distribution of the vector light field by changing the hologram parameters loaded on the digital micromirror device (DMD).

[0019] Furthermore, the vector quality factor measurement system includes an angle-tunable analyzer and a quarter-wave plate.

[0020] Furthermore, by using different optical components of the vector quality factor measurement system alone or simultaneously, four groups of light intensity projection measurement values required for calculating the four Stokes parameters can be obtained respectively.

[0021] Furthermore, the vector quality factor of the vector beam can be derived and calculated through four Stokes parameters.

[0022] Furthermore, by obtaining the vector quality factor parameter, the propagation distance can be derived for ranging.

[0023] Advantageous Effects

[0024] Compared with the prior art, the present invention has the following advantageous effects:

[0025] The DMD digitally generates a vector beam with a controllable polarization state, which has the characteristics of high flexibility, fast generation rate, low cost, wide application range, etc. By generating a special vector beam, only by reconstructing its polarization state, information such as its Stokes parameters, vector quality factor, and distance can be obtained with one key through computer digital programming. Therefore, it has the advantage of fast ranging. In addition, changing the vector optical field parameters can make the system face more complex actual application scenarios. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of a ranging system based on a vector optical field according to the present invention;

[0027] Figure 2 It is a polarization state distribution diagram of a circular Airy vortex vector optical field at different propagation distances;

[0028] Figure 3 It is a curve diagram of the vector quality factor of a circular Airy vortex vector optical field changing with the propagation distance.

[0029] Reference Signs

[0030] Linear polarization light generator A, generation system B, vector quality factor measurement system C, CCD receiving device D, laser 1, lens 1 2, lens 2 3, half-wave plate 4, Wollaston prism 5, quarter-wave plate 6, lens 3 7, lens 4 8, digital micromirror device DMD9. Detailed Embodiments

[0031] To better illustrate and elaborate the content of the present invention, the following will be described in conjunction with the drawings and implementation examples:

[0032] There is Figures 1 - 3 As shown, the present invention discloses a ranging system based on a vector optical field, including a linear polarization light generator A with a collimating and beam-expanding function arranged in the diagonal (45°) direction from left to right, a generation system B for any vector beam, a vector quality factor measurement system C, and a CCD receiving device D. A digital micromirror device DMD9 for digitally regulating the optical field parameters is provided in the generation system B.

[0033] Further, the linear polarization light generator A includes a group of collimating and beam expanding lenses, the collimating and beam expanding lenses include a first lens 2 with a focal length of 20 mm and a second lens 3 with a focal length of 200 mm, the collimating and beam expanding lenses can collimate the light beam and expand its size by ten times, and the linear polarization light generator A further includes a laser 1.

[0034] Further, the linear polarization light generator A further includes a half-wave plate 4 for adjusting the polarization state of the output light beam to 45 degrees diagonally.

[0035] Further, the generating system B includes a Wollaston prism 5 arranged on the right side of the linear polarization light generator A, which is used to project the +45° linearly polarized light into two beams with equal light intensity along the horizontal and vertical polarization directions, and the transmission angle between the two beams with orthogonal polarization states is about 1.5°.

[0036] Further, the generating system B further includes a quarter-wave plate 6 for changing the horizontal and vertical linear polarization states into left-handed and right-handed circular polarization states respectively, and the generating system B further includes a third lens 7 with a focal length of 100 mm and a fourth lens 8 with a focal length of 100 mm.

[0037] Further, the generating system B further includes a digital micromirror device DMD9, and the hologram loaded on the digital micromirror device DMD9 includes a digital grating. By adjusting the grating coefficient, the left-handed and right-handed circularly polarized light beams can be transmitted along the same transmission path.

[0038] Further, the circular Airy vortex vector beam generated by the generating system B is expressed as:

[0039]

[0040] where, cosθ, is the weight factor, (r, φ) are cylindrical coordinate parameters, and are the left-handed and right-handed circular polarization basis vectors. Additionally, is the phase difference between the two polarization basis vectors, and as the two orthogonal spatial mode basis vectors, respectively carry orbital angular momentum circular Airy vortex beams, is the Planck constant.

[0041] Further, the circular Airy vortex beam can be expressed as:

[0042]

[0043] where Ai() represents the Airy function; r is the radius, r 0is the radius of the main beam ring; a is the cut-off factor; ω is the beam waist radius; m is the topological charge; v is the initial emission angle parameter.

[0044] Further, without moving any optical components, the circular Airy vortex optical field can be regulated by the digital micromirror device DMD9 and the computer to the target optical field, so as to realize the generation of vector beams with different polarization state distributions.

[0045] Further, the vector quality factor measurement system C includes a polarization analyzer with adjustable angle and a quarter-wave plate.

[0046] Further, when only the polarization analyzer with an angle of 0° is placed in the vector quality factor measurement system C, the light intensity projection in the horizontal direction, that is, Ih, can be collected by the CCD receiving device D.

[0047] Further, when only the polarization analyzer with an angle of 45° is placed in the vector quality factor measurement system C, the light intensity projection in the diagonal direction, that is, Id, can be collected by the CCD receiving device D.

[0048] Further, when a quarter-wave plate with an angle of 45° and a polarization analyzer with an angle of 0° are placed in the vector quality factor measurement system C, the light intensity projection in the right-handed circular polarization direction, that is, Ir, can be collected by the CCD receiving device D.

[0049] Further, when no optical element is placed in the vector quality factor measurement system C, the total light intensity of the beam, that is, I 0 .

[0050] Further, by calculating with the four obtained light intensities (Ih, Id, Ir, I 0 ), four Stokes parameters (S 0 , S 1 , S 2 , S 3 ) can be obtained. The specific relationship is:

[0051] S 0 = I 0 , S 1 = 2I h - S 0 , S 2 = 2I d - S 0 , S 3 = 2I r - S 0

[0052] Further, according to the four Stokes parameters (S 0 , S 1 , S 2 , S3 ) It is possible to reconstruct the transverse polarization state distribution of the target vector optical field.

[0053] Furthermore, by locally integrating the four Stokes parameters (S 0 , S 1 , S 2 , S 3 ), the integral values of S 0 , S 1 , S 2 , S 3 can be obtained.

[0054] Furthermore, through the four Stokes integral values (S 0 , S 1 , S 2 , S 3 ), the vector quality factor (VQF) can be obtained. The specific relationship is as follows:

[0055]

[0056] Furthermore, the propagation distance can be deduced through VQF, thereby realizing ranging.

[0057] Furthermore, without changing the optical path, the circular Airy vortex vector beam can realize the regulation of the VQF change curve only by changing the emission angle parameter in the circular Airy vortex vector beam loaded on the digital micromirror device DMD9.

[0058] Specifically, when the light source is a 532 nm laser source and it is modulated into a circular Airy vortex vector optical field, distance measurement can be realized;

[0059] Figure 2 shows the transverse polarization distribution diagrams of the circular Airy vortex vector optical field at transmission distances of z1 = 0 mm, z2 = 80 mm, and z3 = 580 mm respectively. Among them, the line segment represents linear polarization, the circle with a right arrow represents right-handed elliptical polarization, and the circle with a left arrow represents left-handed elliptical polarization. As the transmission distance increases, the polarization state of the circular Airy vortex vector beam gradually evolves from the initially uniformly distributed linear polarization to left- and right-handed elliptical polarizations, and finally becomes left- and right-handed circular polarizations distributed in inner and outer circular rings;

[0060] Figure 3 shows the change curve of the vector quality factor VQF of the circular Airy vortex vector optical field with distance. As the transmission distance increases, VQF varies between [0, 1]. Therefore, distance measurement can be realized by obtaining the VQF value.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the technical solutions of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A ranging system based on vector optical fields, characterized in that: it includes a linearly polarized light generator (A) with collimation and beam expansion functions in the diagonal direction, an arbitrary vector beam generation system (B), a vector quality factor measurement system (C), and a CCD receiving device (D) arranged in sequence from left to right. The linearly polarized light generator (A) includes a laser (1), a set of collimation and beam expansion lenses, and a half-wave plate (4) for adjusting the polarization state of the output beam to 45 degrees in the diagonal direction. The collimation and beam expansion lenses include a lens one (2) with a focal length of 20 mm and a lens two (3) with a focal length of 200 mm. The generation system (B) includes a Wollaston prism (5), a quarter-wave plate (6) for changing the polarization state of the beam, a lens three (7) with a focal length of 100 mm, a lens four (8) with a focal length of 100 mm, and a digital micromirror device DMD (9) for digitally regulating the optical field parameters. The vector quality factor measurement system (C) includes an angle-tunable analyzer and a quarter-wave plate; The circular Airy vortex vector beam generated by the generation system (B) is expressed as: where cosθ, are weight factors, (r, φ) are cylindrical coordinate parameters, and are the left- and right-handed circular polarization basis vectors. Additionally, is the phase difference between the two polarization basis vectors, and serve as two orthogonal spatial mode basis vectors, which are circular Airy vortex beams carrying orbital angular momentum respectively, is the Planck constant; The circular Airy vortex beam can be expressed as: where \(Ai()\) represents the Airy function; \(r\) is the radius, \(r\) 0 is the radius of the main ring of the light beam; \(a\) is the cut-off factor; \(\omega\) is the beam waist radius; \(m\) is the topological charge; \(v\) is the initial emission angle parameter; On the premise of keeping the optical path unchanged, the transverse polarization distribution of the circular Airy vortex vector optical field can be regulated by digitally regulating the target optical field through the digital micromirror device DMD (9) and a computer; Multiple light intensity projection measurements by the vector quality factor measurement system (C) can achieve the reconstruction of the transverse polarization distribution of the target vector optical field, thereby obtaining four Stokes parameters: S 0 , S 1 , S 2 , S 3 ; The four Stokes parameters measured by the vector quality factor measurement system (C) can be used to obtain the vector quality factor of the vector optical field; The propagation distance is deduced through the vector quality factor of the vector optical field, so as to carry out ranging.

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