Rotating speed measurement system and method based on metasurface light modulator

Abstract

The invention particularly relates to a rotating speed measuring system and method based on a metasurface light modulator, and aims at solving the problems that an existing rotating Doppler rotating speed measuring system is numerous in optical elements, complex in structure and low in optical efficiency. Comprising a single-mode fiber laser, and a metasurface light modulator, a half-wave plate and a polarization splitting prism which are arranged on an emergent light path of the single-mode fiber laser, a quarter-wave plate and a rotating target object to be measured are sequentially arranged on a transmission light path of the polarization splitting prism, and a photoelectric detector and a measuring terminal connected with the output end of the photoelectric detector are arranged on a reflection light path of the polarization splitting prism. The metasurface light modulator is used for directly generating a vortex beam carrying topological charge conjugate superposition photon orbital angular momentum, and the rotating speed of a rotating target is measured by using the rotating Doppler effect. Compared with an existing system, an extra 4F optical filtering system or an annular interference light path is not needed, and the system has the advantages of being simple in light path, compact in structure and high in optical efficiency.

Description

Technical Field

[0001] The invention relates to a rotation speed measuring device, and in particular to a rotation speed measuring system and a measuring method based on a metasurface light modulator. Background Art

[0002] The rotational Doppler effect generated by the interaction between a vortex beam carrying the orbital angular momentum of photons and a rotating target provides a new perspective for speed measurement. The speed measurement method based on this principle has the characteristics of fast response, wide measurement range and non-contact operation, and has been a hot topic of research in recent years. Since the rotating target will produce radial jitter or compound motion during the detection process, the process of detecting the reflected echo signal of the rotating target will inevitably be affected by the linear Doppler effect, making the process of extracting the rotational Doppler shift complicated; therefore, in the measurement, it is necessary to use a vortex beam carrying the topological charge conjugate superposition of the orbital angular momentum of photons to interact with the rotating target, thereby generating the same linear Doppler shift and the opposite rotational Doppler shift, so that the linear Doppler shift is offset in the beat signal, while the rotational Doppler shift is multiplied in the beat signal.

[0003] At present, many devices and methods for realizing rotational speed measurement based on the rotational Doppler effect of topological charge conjugate vortex beams have been proposed. However, the spatial light modulator and digital micromirror device commonly used to generate topological charge conjugate vortex beams will generate beams of multiple diffraction orders, and an additional 4F optical filter system is required to extract its first-order beam and eliminate the remaining irrelevant items; while the use of vortex wave plates and spiral phase plates can only generate a single topological charge vortex beam, and in practical applications, an additional annular interference optical path is required to generate a topological charge conjugate vortex beam. The optical path of the above-mentioned conventional rotational speed measurement system using the rotational Doppler effect of topological charge conjugate vortex beams is very complicated, requiring a large number of optical components, which is not conducive to system integration, and is prone to cause significant loss of light intensity during the measurement process, especially when the volume and payload are limited, which greatly limits the feasibility of the existing rotational speed measurement system in practical applications. Summary of the invention

[0004] The main purpose of the present invention is to solve the problems that the existing rotational speed measurement system based on topological charge conjugate vortex beam is too complex in structure, has low optical efficiency, and is not conducive to integration and application, and to provide a rotational speed measurement system and measurement method based on a metasurface light modulator.

[0005] The idea of ​​the present invention is to use a metasurface light modulator to directly generate a photon orbital angular momentum vortex light signal carrying a conjugated superposition of topological charges. The metasurface light modulator is an innovative two-dimensional optical element that can be used to manipulate light fields with high precision, thereby being able to control the phase, amplitude and polarization state of light on a subwavelength scale. At the same time, the metasurface light modulator performs local phase control on the light beam through its internal nanocolumn unit, and can generate various special structured light fields, including the photon orbital angular momentum vortex light signal carrying a conjugated superposition of topological charges required by the present invention, thereby eliminating the need for an additional 4F optical filtering system or annular interferometer optical path for further extraction, thereby reducing light intensity loss while simplifying the optical path structure.

[0006] In order to achieve the above invention objectives and complete the above invention concepts, the present invention provides the following technical solutions:

[0007] A rotation speed measurement system based on a metasurface light modulator, which is special in that:

[0008] It includes a single-mode fiber laser, and a metasurface light modulator, a half-wave plate and a polarization beam splitter prism which are sequentially arranged on the output light path of the single-mode fiber laser; the polarization beam splitter prism is used to transmit horizontal polarized light and reflect vertical polarized light;

[0009] It also includes a quarter wave plate arranged on the transmission light path of the polarization beam splitter prism, a photoelectric detector arranged on the reflection light path of the polarization beam splitter prism, and a measurement terminal connected to the output end of the photoelectric detector; the rotating target object to be measured is arranged on the output light path of the quarter wave plate;

[0010] The working mode of the metasurface light modulator is set to a photon orbital angular momentum conjugate output mode; the metasurface light modulator is composed of a silicon circular nanorod and a silicon dioxide substrate, and has two metasurface structures designed to be mutually nested using a time-domain finite difference method, wherein a topological charge modulated by one metasurface structure is +m, and a topological charge modulated by the other metasurface structure is -m, so that the laser incident on the metasurface light modulator can be modulated into a photon orbital angular momentum vortex light signal carrying a topological charge conjugate superposition, and its topological charge is ±m, where m is a natural number greater than zero;

[0011] The working wavelengths of the half wave plate and the quarter wave plate are both the same as the central wavelength of the laser emitted by the single-mode fiber laser; the half wave plate is used to convert the incident photon orbital angular momentum vortex light signal carrying the conjugate superposition of topological charges into a horizontally polarized photon orbital angular momentum vortex light signal and inject it into the polarization beam splitter prism; the quarter wave plate is used to convert the horizontally polarized photon orbital angular momentum vortex light signal that is fully transmitted through the polarization beam splitter prism into a left-handed circularly polarized photon orbital angular momentum vortex light signal, and convert the right-handed circularly polarized photon orbital angular momentum vortex light signal obtained after being reflected by the rotating target object to be measured into a vertically polarized photon orbital angular momentum vortex light signal and inject it into the polarization beam splitter prism;

[0012] The photoelectric detector is used to receive the vertical polarized photon orbital angular momentum vortex light signal completely reflected by the polarization splitter prism, and transmit it to the measurement terminal, which calculates the received vertical polarized photon orbital angular momentum vortex light signal to obtain the rotation speed Ω of the rotating target object to be measured.

[0013] Furthermore, the measurement terminal includes a Fourier transform unit and a calculation unit. The Fourier transform unit is used to perform a fast Fourier transform on the received vertically polarized photon orbital angular momentum vortex light signal to obtain a spectrum Δf of the photon orbital angular momentum signal, and transmit the spectrum Δf to the calculation unit; the calculation unit calculates the relationship between the spectrum Δf of the photon orbital angular momentum signal, the topological charge number ±m and the rotation speed Ω, that is, Calculation is performed to obtain the rotation speed Ω of the rotating target object to be measured.

[0014] Furthermore, the laser emitted by the single-mode fiber laser is linearly polarized light, with a central wavelength of 1550±10nm and a line width of less than 250Hz.

[0015] Furthermore, the half-wave plate is a phase delay 1550nm polymer true zero-order half-wave plate, where λ 1 is the operating wavelength of the half-wave plate, λ 1 =1550nm.

[0016] Furthermore, the quarter wave plate is a phase delay 1550nm polymer true zero-order quarter-wave plate, where λ 2 is the operating wavelength of the quarter-wave plate, λ 2 =1550nm.

[0017] Furthermore, the polarization beam splitter prism is a near-infrared polarization beam splitter cubic prism with an extinction ratio greater than 1000:1.

[0018] Furthermore, the photodetector is an InGaAs biased detector, which is used to receive light signals with wavelengths in the near-infrared range.

[0019] At the same time, the present invention also provides a rotation speed measurement method based on a metasurface light modulator, which adopts the above-mentioned rotation speed measurement system based on a metasurface light modulator, and its special feature is that it includes the following steps:

[0020] Step 1, turn on the single-mode fiber laser and level its optical path, the emitted laser is incident into the metasurface light modulator, the metasurface light modulator modulates the incident laser, and obtains a photon orbital angular momentum vortex light signal carrying a conjugate superposition of topological charges, whose topological charge number is ±m, where m is a non-zero natural number;

[0021] Step 2, the photon orbital angular momentum vortex light signal carrying the conjugated superposition of topological charges is incident on a half-wave plate, and the half-wave plate converts the polarization direction of the photon orbital angular momentum vortex light signal carrying the conjugated superposition of topological charges into horizontal polarization, thereby obtaining a horizontally polarized photon orbital angular momentum vortex light signal;

[0022] Step 3, the horizontally polarized photon orbital angular momentum vortex light signal is incident on a polarization beam splitter prism, and after being transmitted through the polarization beam splitter prism, the horizontally polarized photon orbital angular momentum vortex light signal is incident on a quarter wave plate, and the quarter wave plate converts the polarization direction of the horizontally polarized photon orbital angular momentum vortex light signal into left-handed circular polarization, thereby obtaining a left-handed circularly polarized photon orbital angular momentum vortex light signal;

[0023] Step 4, incident the left-handed circularly polarized photon orbital angular momentum vortex light signal onto the surface of the rotating target object to be measured, and after being reflected by the surface of the rotating target object to be measured, obtaining the right-handed circularly polarized photon orbital angular momentum vortex light signal;

[0024] Step 5, the rotating target object to be measured reflects the right-handed circularly polarized photon orbital angular momentum vortex light signal back to the quarter wave plate; the quarter wave plate converts the polarization direction of the right-handed circularly polarized photon orbital angular momentum vortex light signal into vertical polarization, thereby obtaining a vertically polarized photon orbital angular momentum vortex light signal;

[0025] Step 6, the vertically polarized photon orbital angular momentum vortex light signal is incident on a polarization beam splitter prism, and is reflected by the polarization beam splitter prism into a photodetector;

[0026] Step 7, transmit the vertically polarized photon orbital angular momentum vortex light signal detected by the photodetector to the measurement terminal; the measurement terminal calculates the vertically polarized photon orbital angular momentum vortex light signal to obtain the rotation speed Ω of the rotating target object to be measured, and completes the rotation speed measurement based on the metasurface light modulator.

[0027] Furthermore, step 7 is specifically as follows:

[0028] Step 7.1, transmitting the vertically polarized photon orbital angular momentum vortex light signal detected by the photodetector to a measurement terminal;

[0029] Step 7.2, using the Fourier transform unit in the measurement terminal to perform fast Fourier transform on the vertically polarized photon orbital angular momentum vortex light signal to obtain a spectrum Δf, and the spectrum Δf is transmitted to the calculation unit;

[0030] Step 7.3, using the calculation unit according to the relationship between the spectrum Δf, the topological charge ±m and the speed Ω The rotation speed Ω of the rotating target object to be measured is calculated, and the rotation speed measurement based on the metasurface light modulator is completed.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a rotation speed measurement system and method based on a metasurface light modulator, which uses a metasurface light modulator to directly generate a vortex light beam carrying the orbital angular momentum of topological charge conjugate superposition photons, and then uses the rotational Doppler effect to achieve the rotation speed measurement of the rotating target. Compared with the prior art, it does not require an additional 4F optical filtering system or annular interference optical path, has the characteristics of simple optical path, compact structure and high optical efficiency, and has important application value in the field of target rotational motion state sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of an embodiment of a rotation speed measurement system based on a metasurface light modulator of the present invention;

[0034] Figure 2 This is a schematic diagram of the working principle and process of a metasurface light modulator in an embodiment of a rotational speed measurement system based on a metasurface light modulator of the present invention; wherein, Figure (a) is a schematic diagram of the superposition principle of two mutually nested metasurface structures modulating light beams; and Figure (b) is a schematic diagram of the process of the metasurface light modulator modulating the incident laser.

[0035] Description of reference numerals:

[0036] 1-single-mode fiber laser; 2-metasurface light modulator; 3-half-wave plate; 4-polarization beam splitter prism; 5-quarter-wave plate; 6-rotating target object to be measured; 7-photodetector; 8-measurement terminal. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0038] A rotation speed measurement system based on a metasurface light modulator, such as Figure 1 As shown, it includes a single-mode fiber laser 1, and a metasurface light modulator 2, a half-wave plate 3 and a polarization beam splitter prism 4 which are sequentially arranged on the outgoing light path of the single-mode fiber laser 1; a quarter-wave plate 5 is arranged on the transmission light path of the polarization beam splitter prism 4, and a photodetector 7 is arranged on the reflected light path; the output end of the photodetector 7 is connected to a measuring terminal 8; a rotating target object 6 to be measured is arranged on the outgoing light path of the quarter-wave plate 5, and can be a rotating mirror reflector or a diffuse reflector;

[0039] The central wavelength of the linearly polarized laser emitted by the single-mode fiber laser 1 is 1550±10nm, and the line width is less than 250Hz;

[0040] The working mode of the metasurface optical modulator 2 is the photon orbital angular momentum conjugate output mode; it adopts two metasurface structures designed by mutual nesting using the time-domain finite difference method. The modulation principle and process are as follows Figure 2 As shown, the topological charge modulated by one metasurface structure is +m, and the topological charge modulated by the other metasurface structure is -m. The incident laser is modulated by the two metasurface structures and then superimposed to obtain a photon orbital angular momentum vortex light signal carrying a conjugate superposition of topological charges, whose topological charge is ±m, where m is a natural number greater than zero.

[0041] Half wave plate 3 is the phase delay The 1550nm polymer true zero-order half-wave plate is used to convert the incident photon orbital angular momentum vortex light signal carrying topological charge conjugation superposition into a horizontally polarized photon orbital angular momentum vortex light signal and incident it to the polarization beam splitter prism 4; the quarter-wave plate 5 is the phase delay The 1550nm polymer true zero-order quarter-wave plate is used to convert the horizontally polarized photon orbital angular momentum vortex light signal transmitted by the polarization beam splitter prism 4 into a left-handed circularly polarized photon orbital angular momentum vortex light signal, and convert the right-handed circularly polarized photon orbital angular momentum vortex light signal obtained after being reflected by the rotating target object 6 to be measured into a vertically polarized photon orbital angular momentum vortex light signal and incident on the polarization beam splitter prism 4; wherein, λ 1 , 2 are the operating wavelengths of the half wave plate 3 and the quarter wave plate 5, respectively, and both are the same as the central wavelength of the laser emitted by the single-mode fiber laser 1, that is, λ 1 =λ 2 =1550nm;

[0042] The polarization beam splitter prism 4 is a near-infrared polarization beam splitter cubic prism with an extinction ratio greater than 1000:1, which is used to transmit horizontal polarized light and reflect vertical polarized light;

[0043] The photodetector 7 is an indium gallium arsenide biased detector, which can receive light signals with wavelengths in the near-infrared range; in this embodiment, the photodetector 7 is used to receive the vertically polarized photon orbital angular momentum vortex light signal reflected by the polarization beam splitter prism 4, and transmit it to the measurement terminal 8;

[0044] The measurement terminal 8 includes a Fourier transform unit and a calculation unit. The Fourier transform unit is used to perform a fast Fourier transform on the received vertically polarized photon orbital angular momentum vortex light signal to obtain a spectrum Δf and transmit it to the calculation unit; the calculation unit calculates the spectrum Δf according to the relationship between the topological charge ±m and the rotation speed Ω. Calculation is performed to obtain the rotation speed Ω of the rotating target object 6 to be measured.

[0045] At the same time, based on the above-mentioned rotation speed measurement system based on the metasurface light modulator, this embodiment also provides a rotation speed measurement method based on the metasurface light modulator, including the following steps:

[0046] Step 1, turn on the single-mode fiber laser 1 and level its optical path, the emitted laser is incident on the metasurface light modulator 2, the metasurface light modulator 2 modulates the incident laser to obtain a photon orbital angular momentum vortex light signal carrying a conjugate superposition of topological charges, and its topological charge number is ±m, where m is a non-zero natural number;

[0047] Step 2, the photon orbital angular momentum vortex light signal carrying the conjugated superposition of topological charges is incident on the half wave plate 3, and the half wave plate 3 converts the polarization direction of the photon orbital angular momentum vortex light signal carrying the conjugated superposition of topological charges into horizontal polarization, thereby obtaining a horizontally polarized photon orbital angular momentum vortex light signal;

[0048] Step 3, the horizontally polarized photon orbital angular momentum vortex light signal is incident on the polarization beam splitter prism 4, and the horizontally polarized photon orbital angular momentum vortex light signal is incident on the quarter wave plate 5 after being transmitted through the polarization beam splitter prism 4, and the quarter wave plate 5 converts the polarization direction of the horizontally polarized photon orbital angular momentum vortex light signal into left-handed circular polarization, thereby obtaining a left-handed circularly polarized photon orbital angular momentum vortex light signal;

[0049] Step 4, incident the left-handed circularly polarized photon orbital angular momentum vortex light signal onto the surface of the rotating target object 6 to be measured, and after being reflected by the surface of the rotating target object 6 to be measured, a right-handed circularly polarized photon orbital angular momentum vortex light signal is obtained;

[0050] Step 5, the rotating target object 6 to be measured reflects the right-handed circularly polarized photon orbital angular momentum vortex light signal back to the quarter wave plate 5; the quarter wave plate 5 converts the polarization direction of the right-handed circularly polarized photon orbital angular momentum vortex light signal into vertical polarization, thereby obtaining a vertically polarized photon orbital angular momentum vortex light signal;

[0051] Step 6, the vertically polarized photon orbital angular momentum vortex light signal is incident on the polarization beam splitter prism 4, and is reflected by the polarization beam splitter prism 4 and enters the photodetector 7;

[0052] Step 7, speed measurement

[0053] Step 7.1, transmitting the vertically polarized photon orbital angular momentum vortex light signal detected by the photodetector 7 to the measurement terminal 8;

[0054] Step 7.2, using the Fourier transform unit in the measurement terminal 8 to perform fast Fourier transform on the vertically polarized photon orbital angular momentum vortex light signal to obtain a spectrum Δf, and the spectrum Δf is transmitted to the calculation unit;

[0055] Step 7.3, using the calculation unit according to the relationship between the spectrum Δf, the topological charge ±m and the speed Ω The rotation speed Ω of the rotating target object 6 to be measured is calculated, and the rotation speed measurement based on the metasurface light modulator is completed.

[0056] 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. For ordinary professional and technical personnel in the field, the specific technical solutions recorded in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present invention.

Claims

1. A rotation speed measurement system based on a metasurface light modulator, characterized in that: The invention comprises a single-mode optical fiber laser (1), and a super-surface optical modulator (2), a half-wave plate (3) and a polarization beam splitter prism (4) which are sequentially arranged on the output light path of the single-mode optical fiber laser (1); the polarization beam splitter prism (4) is used for transmitting horizontally polarized light and reflecting vertically polarized light; It also includes a quarter wave plate (5) arranged on the transmission light path of the polarization beam splitter prism (4), a photoelectric detector (7) arranged on the reflection light path of the polarization beam splitter prism (4), and a measurement terminal (8) electrically connected to the output end of the photoelectric detector (7); the rotating target object (6) to be measured is arranged on the output light path of the quarter wave plate (5); The working mode of the metasurface light modulator (2) is a photon orbital angular momentum conjugate output mode; the metasurface light modulator (2) is composed of a silicon circular nanorod and a silicon dioxide substrate, and has two metasurface structures designed to be nested with each other, wherein the topological charge modulated by one metasurface structure is +m, and the topological charge modulated by the other metasurface structure is -m, so that the laser incident on the metasurface light modulator (2) can be modulated into a photon orbital angular momentum vortex light signal carrying a topological charge conjugate superposition, wherein the topological charge is ±m, and m is a natural number greater than zero; The operating wavelengths of the half wave plate (3) and the quarter wave plate (5) are both the same as the central wavelength of the laser emitted by the single-mode fiber laser (1); the half wave plate (3) is used to convert the incident photon orbital angular momentum vortex light signal carrying the conjugate superposition of topological charges into a horizontally polarized photon orbital angular momentum vortex light signal and to inject the signal into the polarization beam splitter (4); the quarter wave plate (5) is used to convert the horizontally polarized photon orbital angular momentum vortex light signal transmitted through the polarization beam splitter (4) into a left-handed circularly polarized photon orbital angular momentum vortex light signal, and to convert the right-handed circularly polarized photon orbital angular momentum vortex light signal obtained after being reflected by the rotating target object (6) to be measured into a vertically polarized photon orbital angular momentum vortex light signal and to inject the signal into the polarization beam splitter (4); The photoelectric detector (7) is used to receive the vertically polarized photon orbital angular momentum vortex light signal reflected by the polarization splitter prism (4), and transmit it to the measurement terminal (8). The measurement terminal (8) calculates the received vertically polarized photon orbital angular momentum vortex light signal, thereby obtaining the rotation speed Ω of the rotating target object (6) to be measured.

2. The speed measurement system based on the metasurface light modulator according to claim 1, characterized in that: The measuring terminal (8) comprises a Fourier transform unit and a computing unit. The Fourier transform unit is used to perform a fast Fourier transform on the received vertically polarized photon orbital angular momentum vortex light signal to obtain a spectrum Δf, and transmit the spectrum Δf to the computing unit. The computing unit calculates the spectrum according to the relationship between the spectrum Δf, the topological charge number ±m and the rotation speed Ω. Calculation is performed to obtain the rotation speed Ω of the rotating target object (6) to be measured.

3. The rotation speed measurement system based on the metasurface light modulator according to claim 2, characterized in that: The laser light emitted by the single-mode fiber laser (1) is linearly polarized light, with a central wavelength of 1550±10 nm and a line width of less than 250 Hz.

4. The rotation speed measurement system based on the metasurface light modulator according to claim 3 is characterized in that: The half wave plate (3) is a phase delay A 1550nm polymer true zero-order half-wave plate, wherein λ1 is the working wavelength of the half-wave plate (3), λ1 = 1550nm.

5. The rotation speed measurement system based on the metasurface light modulator according to claim 4, characterized in that: The quarter wave plate (5) is a phase delay A 1550nm polymer true zero-order quarter-wave plate, wherein λ2 is the working wavelength of the quarter-wave plate (5), λ2=1550nm.

6. The rotation speed measurement system based on metasurface light modulator according to claim 1, characterized in that: The polarization beam splitting prism (4) is a near-infrared polarization beam splitting cubic prism with an extinction ratio greater than 1000:

1.

7. The rotation speed measurement system based on the metasurface light modulator according to claim 5, characterized in that: The photodetector (7) is an indium gallium arsenide bias detector, which is used to receive light signals with a wavelength in the near-infrared range.

8. A rotation speed measurement method based on a metasurface light modulator, using a rotation speed measurement system based on a metasurface light modulator according to any one of claims 1 to 7, characterized in that: The steps include: Step 1, turning on the single-mode fiber laser (1) and leveling its optical path, the emitted laser is incident on the metasurface light modulator (2), the metasurface light modulator (2) modulates the incident laser, and obtains a photon orbital angular momentum vortex light signal carrying a conjugate superposition of topological charges, wherein the topological charge number is ±m, where m is a non-zero natural number; Step 2, the photon orbital angular momentum vortex light signal carrying the conjugated superposition of topological charges is incident on a half wave plate (3), and the half wave plate (3) converts the polarization direction of the photon orbital angular momentum vortex light signal carrying the conjugated superposition of topological charges into horizontal polarization, thereby obtaining a horizontally polarized photon orbital angular momentum vortex light signal; Step 3, the horizontally polarized photon orbital angular momentum vortex light signal is incident on a polarization beam splitter prism (4), the horizontally polarized photon orbital angular momentum vortex light signal is transmitted through the polarization beam splitter prism (4), and then is incident on a quarter wave plate (5), the quarter wave plate (5) converts the polarization direction of the horizontally polarized photon orbital angular momentum vortex light signal into left-handed circular polarization, and obtains a left-handed circularly polarized photon orbital angular momentum vortex light signal; Step 4, incident the left-handed circularly polarized photon orbital angular momentum vortex light signal onto the surface of the rotating target object (6) to be measured, and after being reflected by the surface of the rotating target object (6) to be measured, obtaining the right-handed circularly polarized photon orbital angular momentum vortex light signal; Step 5, the rotating target object to be measured (6) reflects the right-handed circularly polarized photon orbital angular momentum vortex light signal back to the quarter wave plate (5); the quarter wave plate (5) converts the polarization direction of the right-handed circularly polarized photon orbital angular momentum vortex light signal into vertical polarization, thereby obtaining a vertically polarized photon orbital angular momentum vortex light signal; Step 6, the vertically polarized photon orbital angular momentum vortex light signal is incident on the polarization beam splitter prism (4), and is reflected by the polarization beam splitter prism (4) and enters the photodetector (7); Step 7, transmitting the vertically polarized photon orbital angular momentum vortex light signal detected by the photodetector (7) to the measurement terminal (8); the measurement terminal (8) calculates the received vertically polarized photon orbital angular momentum vortex light signal to obtain the rotation speed Ω of the rotating target object (6) to be measured, thereby completing the rotation speed measurement based on the metasurface light modulator.

9. The method for measuring rotation speed based on a metasurface light modulator according to claim 8, characterized in that: Step 7 is as follows: Step 7.1, transmitting the vertically polarized photon orbital angular momentum vortex light signal detected by the photodetector (7) to the measurement terminal (8); Step 7.2, using the Fourier transform unit in the measurement terminal (8) to perform fast Fourier transform on the vertically polarized photon orbital angular momentum vortex light signal to obtain a spectrum Δf, and the spectrum Δf is transmitted to the calculation unit; Step 7.3, using the calculation unit according to the relationship between the spectrum Δf, the topological charge ±m and the speed Ω Calculation is performed to obtain the rotation speed Ω of the rotating target object (6) to be measured, thereby completing the rotation speed measurement based on the metasurface light modulator.

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