A time-sharing device and method for photoacoustic polarization light broadband spectrum detection

Abstract

The application relates to the field of polarized light detection, and discloses a time-sharing device for polarized light wide-spectrum detection based on photoacoustic effect, which comprises a polarized light source module, a light spot adjusting module, an anisotropic absorber module, a unit signal detection module and an information processing module connected in sequence through optical signals, the polarized light source module is used for generating original polarized pulse light, the light spot adjusting module is used for adjusting the polarization state and the light energy density of the original polarized light, the anisotropic absorber module is used for responding to the adjusted polarized light and generating photoacoustic signals, the unit signal detection module is used for detecting the photoacoustic signals emitted by the anisotropic absorber module, and the information processing module is used for filtering, amplifying, collecting and post-processing the detected signals.The application has the capabilities of fast response and wide-spectrum response, the device structure of the method is simple, the method is convenient to use, and the method can be widely applied to various polarized light detection related fields.

Description

A time-division device and method for polarized broadband detection based on photoacoustics Technical Field

[0001] This application relates to the field of polarized light, and more particularly to a time-division device and method for broadband polarized light detection based on photoacoustics. Background Technology

[0002] Polarization is an important property of light. As an intrinsic high-dimensional information, polarized light is widely used in optical communication, remote sensing, spectroscopy, and diagnostic medicine. Therefore, detecting the polarization information of light is of great significance.

[0003] Traditional polarization detection techniques use photoelectric detectors, which are limited by the narrow response spectrum of photoelectric materials. Although they have high sensitivity, they cannot detect a sufficiently wide spectrum of light polarization information. While photothermal detectors can broaden the response spectrum, their response speed is slower and they are more susceptible to environmental noise. On the other hand, photoelectric detection relies on the unique photoelectric response of special materials, which imposes significant material limitations.

[0004] It is evident that current polarization detection technology still lacks polarization detection methods with sufficiently broad spectral response and low material selectivity.

[0005] Therefore, further improvements are needed to existing polarization detection technologies to address the problems of slow detection response speed and significant material limitations. Summary of the Invention

[0006] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a photoacoustic-based polarized broadband detection method and detection device.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A photoacoustic-based polarized broadband detection time-division device, comprising at least a polarization source module, a spot adjustment module, an anisotropic absorber module, a unit signal detection module, and an information processing module connected sequentially via optical signals, wherein:

[0009] The polarization light source module is used to generate raw polarized pulse light;

[0010] The light spot adjustment module is used to adjust the polarization state and light energy density of the original polarized light;

[0011] The anisotropic absorber module is used to respond to the adjusted polarized light and generate a photoacoustic signal;

[0012] The unit signal detection module is used to detect the photoacoustic signals emitted by the anisotropic absorber module;

[0013] The information processing module is used to filter, amplify, acquire, and perform post-processing on the detected signals.

[0014] Preferably, it also includes an information angle change and detection module, which is disposed between the anisotropic absorber module and the unit signal detection module, and is connected to the anisotropic absorber module and the unit signal detection module respectively through optical signals;

[0015] The information angle change and detection module is used to drive the absorber to rotate so as to obtain different polarization components at different times.

[0016] The angle change and detection module includes an FPGA, a motor, and a transmission mechanism connected in sequence.

[0017] Preferably, the polarization light source module includes a pulsed laser, a quarter-wave plate, and a half-wave plate connected sequentially via an optical path;

[0018] The information processing module includes a filter, an amplifier, a high-speed ADC acquisition module, and a host computer connected in sequence.

[0019] Preferably, in one embodiment, the light spot adjustment module includes a microlens group, the anisotropic absorber module is an orthogonally stacked anisotropic absorber module, which includes orthogonally stacked broadband absorption line grid polarizers, and the unit signal detection module is a dual-unit signal detection module, which includes a dual-unit transducer probe.

[0020] The microlens group is placed above an orthogonally stacked broadband absorption linear grid polarizer;

[0021] The orthogonally stacked broadband absorption line grid polarizer is placed above the dual-unit transducer probe;

[0022] The signal processing module consists of a dual-unit transducer probe connected in front of an amplifier.

[0023] Preferably, in another case, the light spot adjustment module includes a parabolic reflector and an xyz axis displacement mechanism, with the parabolic reflector fixed on the displacement mechanism;

[0024] The anisotropic absorber module includes a broadband absorption grating polarizer and an absorber fixing mechanism 3-2, with the broadband absorption grating polarizer fixed on the absorber fixing mechanism;

[0025] The unit signal detection module includes a focused piezoelectric ultrasonic transducer, and the focused piezoelectric ultrasonic transducer is also connected in front of the filter.

[0026] A photoacoustic-based polarized light broadband detection method, employing the aforementioned photoacoustic-based polarized light broadband detection time-division device, comprises the following steps:

[0027] S1. The polarized pulse light generated by the polarization light source module is sent to the spot adjustment module to adjust its polarization state and light energy density and then irradiates the anisotropic absorber module to generate a photoacoustic signal.

[0028] The photoacoustic signal contains information about the angle between the polarization angle and the maximum absorption angle of the anisotropic absorber.

[0029] S2, the unit signal detection module is used to detect the photoacoustic signals emitted by the anisotropic absorber module;

[0030] S3. The information processing module analyzes the detected photoacoustic signal in two ways: one is to take the maximum value of the photoacoustic signal intensity; the other is to obtain the spectrum of the photoacoustic signal through Fourier transform and integrate the spectrum.

[0031] S4. The information processing module obtains the polarization information of the photoacoustic signal by analyzing the detection through a specific algorithm.

[0032] Preferably, in step S1, the field intensity of the generated photoacoustic signal... Light polarization angle and the characteristic angle of in-plane anisotropic absorbers The following relationship exists:

[0033] ;

[0034] in, The angle is The photoacoustic field generated by the interaction of light with anisotropic absorbers The signal amplitude at that location; and The absorption coefficients are orthogonal and parallel to the optical axis; It represents the amount of luminous flux emitted.

[0035] Preferably, in step S2, the photoacoustic signal is acquired using a data acquisition card or an oscilloscope.

[0036] Preferably, in step S3,

[0037] The intensity of the acoustic signal is taken to its maximum value. ;

[0038] The spectrum of the sound wave signal is obtained by Fourier transform and then integrated. .

[0039] Preferably, in step S4, at least four angular information points within a 360° range are detected and calculated using the following algorithm:

[0040] ;

[0041] ;

[0042] ;

[0043] in, These are the first three components of the Stokes parameter, from which parameters such as polarization angle, ellipticity, and degree of polarization can be calculated, including the degree of polarization. Calculation formula:

[0044] .

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] This invention has the ability to respond quickly and with a wide spectrum of response. The device for implementing this method has a simple structure and is easy to use, and can be widely applied in various fields related to polarization detection.

[0047] The method of this invention utilizes the photoacoustic polarization response characteristics of in-plane anisotropic absorbers and innovatively applies them to polarized light detection. This method inherits the excellent broadband response capability of photoacoustics and relaxes the restrictions on the selection of response materials. Attached Figure Description

[0048] Figure 1 is a schematic diagram of the structure of a time-division device for polarized light broadband detection based on photoacoustics according to Embodiment 1 of the present invention;

[0049] Figure 2 shows the signal diagrams of the upper and lower layers of anisotropic absorbers responding to different polarized light irradiation under different polarized light illumination in a time-division device based on photoacoustic polarized light broadband detection according to Embodiment 1 of the present invention, in which they are arranged in an orthogonal stacked array.

[0050] Figure 3 is a schematic diagram of the structure of a time-division device for polarization broadband detection based on photoacoustics according to Embodiment 2 of the present invention;

[0051] Figure 4 shows the polarization data of a total of 720 sampling angles obtained by a time-division device for polarized light detection based on photoacoustics in Embodiment 2 of the present invention for detecting linearly polarized light.

[0052] Figure 5 is a schematic flowchart of a photoacoustic-based polarized broadband detection method according to Embodiment 3 of the present invention;

[0053] Figure 6A shows the polarization response absorption spectrum of the anisotropic absorber used in a photoacoustic-based polarized light broadband detection method according to Embodiment 3 of the present invention.

[0054] Figure 6B is a characterization image of the linear response capability of optical power of a photoacoustic-based polarized broadband detection method in Embodiment 3 of the present invention.

[0055] Figure 6C is a characterization image of the light polarization angle detection using a photoacoustic-based polarized light broadband detection method according to Embodiment 3 of the present invention.

[0056] Figure 6D shows the characterization of the detection capability of a photoacoustic-based polarized light broadband detection method with different polarization degrees in Embodiment 3 of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0058] It should be noted that, unless there is a conflict, the various features in the embodiments of this application can be combined with each other, all of which are within the protection scope of this application. Furthermore, although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than the module division in the device or the order in the flowchart. Moreover, the terms "first," "second," and "third" used in this application do not limit the data or execution order, but only distinguish identical or similar items with essentially the same function and effect.

[0059] The present invention will now be described in detail through specific embodiments.

[0060] Example 1

[0061] As shown in Figures 1 and 2, a time-division multiplexing device for polarized broadband detection based on photoacoustics includes a polarization source module, a spot adjustment module, an anisotropic absorber module, a unit signal detection module, and an information processing module, which are sequentially connected by optical signals.

[0062] The polarization light source module is used to generate original polarized pulsed light. Specifically, the polarization light source module includes a pulsed laser 1-1, a quarter-wave plate 1-2, and a half-wave plate 1-3 connected sequentially through an optical path.

[0063] The light spot adjustment module is used to adjust the polarization state and light energy density of the original polarized light. The light spot adjustment module includes a microlens group 7-1.

[0064] Specifically, the microlens group 7-1 consists of two microlenses. In the light spot adjustment module, the two microlenses are attached to the top of two sets of orthogonally stacked anisotropic absorber modules and cannot be moved. The focal point of the microlens is on the surface of the anisotropic absorber directly below each array unit to ensure sufficient power to generate photoacoustic signals.

[0065] The anisotropic absorber module is used to respond to the adjusted polarized light and generate a photoacoustic signal. The anisotropic absorber module is an orthogonally stacked anisotropic absorber module, which consists of two sets of anisotropic absorbers with orthogonal polarization response angles and horizontally placed along the normal direction. A certain gap is left in the middle to distinguish the signal peaks of the two axially placed orthogonal absorbers in the signal time domain. The two sets of polarization response angles are {0°, 90°} and {45°, 135°}, respectively. Since they are orthogonally placed, the upper layer will not cause crosstalk to the polarization information of the lower layer.

[0066] In the orthogonally stacked anisotropic absorber module, the absorbers are positioned directly below the microlenses of the corresponding light spot adjustment modules, and the area of ​​each set of orthogonal absorbers is less than or equal to the surface area of ​​the microlens. The coupling medium between the two orthogonally placed absorber layers is matched with its own material, which can reduce sound loss.

[0067] Below the anisotropic absorber module is the unit signal detection module. The unit signal detection module is used to detect the photoacoustic signal emitted by the anisotropic absorber module. The unit signal detection module adopts dual-unit signal detection, which consists of a dual-unit transducer probe 9-1 and a coupling medium. The dual-unit detector faces two sets of orthogonal absorbers, with the coupling medium sandwiched in between.

[0068] In the dual-unit signal detection module, each independent unit has an area equivalent to an absorber. Its acoustic focus and light focus are confocal on the surface of the absorber, and the distance between them is close enough to avoid signal crosstalk between horizontally adjacent orthogonal absorber groups.

[0069] The information processing module is used to filter, amplify, acquire, and post-process the detected photoacoustic signals. The information processing module includes a filter 6-1, an amplifier 6-2, a high-speed ADC acquisition module 6-3, and a host computer 6-4 connected in sequence. The amplifier 6-2 is connected to the dual-unit transducer probe 9-1 of the unit signal detection module at the front and to the high-speed ADC acquisition module 6-3 at the rear.

[0070] The sampling rate of the high-speed ADC module 6-3 in the information processing module should satisfy the Nyquist sampling theorem with the frequency of the photoacoustic signal, that is, it should be at least twice the frequency of the sound. The host computer 6-4 used can be a microcontroller, FPGA, PC or other devices. It processes the two sets of four angle data contained in the acquired photoacoustic signal to obtain the optical polarization parameters.

[0071] The algorithm for obtaining the optical polarization parameters of the photoacoustic signal is as follows:

[0072] ;

[0073] ;

[0074] ;

[0075] in, Indicates the first One corner, These are the first three components of the Stokes parameter.

[0076] The working principle of the device in this embodiment is as follows:

[0077] The pulsed light output by the pulsed laser 1-1 of the polarization light source module is linearly polarized. It first passes through a quarter-wave plate 1-2. Adjusting the angle of the quarter-wave plate 1-2 allows for the generation of light with different degrees of polarization, ranging from linearly polarized to circularly polarized and elliptically polarized light. Then, it passes through a half-wave plate 1-3. Adjusting the half-wave plate 1-3 changes the polarization direction (major axis of elliptically polarized light) without altering the degree of polarization. Therefore, by adjusting the quarter-wave plate 1-2 and the half-wave plate 1-3, polarized light with different degrees and directions of polarization can be output.

[0078] In this example, the pulsed laser 1-1 used is a solid-state laser with a wavelength of 532nm and a pulse width of 10ns; the quarter-wave plate 1-2 and half-wave plate 1-3 used are dedicated to the 532nm wavelength; the parabolic reflector 2-1 used has a wavelength range of 450nm-20000nm; the dual-unit transducer probe 9-1 used has a main frequency of 5MHz, and each unit has a receiving area of ​​1mm*1.5mm; the amplifier 6-2 used is a 40dB gain RF amplifier; and the high-speed ADC acquisition module 6-3 has a sampling rate of 125MSPS.

[0079] The original polarized light with arbitrary polarization degree and polarization angle output from the polarization light source module first reaches the microlens group 7-1 of the spot adjustment module, and then is focused on the surface of the orthogonally stacked broad spectrum absorption line grid polarizer 8-1 to obtain an irradiation energy density sufficient to generate photoacoustic signals; the polarized light irradiates the upper and lower layers of the orthogonally stacked broad spectrum absorption line grid polarizer 8-1 to generate photoacoustic signals respectively.

[0080] Photoacoustic signal field intensity With the angle of light polarization The upper-layer broadband absorption grating polarizer has a polarization angle of [missing information]. The following relationship exists:

[0081] ;

[0082] .

[0083] in, and The absorption coefficients are orthogonal and parallel to the optical axis. Represents the amount of luminous flux emitted. The angle is The photoacoustic field generated by the interaction of light with the upper broadband absorption grating polarizer is in The signal amplitude at that location, The angle is The signal amplitude of the photoacoustic field generated by the interaction of light with the lower broadband absorption grating polarizer at the same location.

[0084] The total photoacoustic field is a linear superposition of the two:

[0085] ;

[0086] in This is caused by the non-negligible positional difference between the photoacoustic sources due to the spacing between them. This also allows for the simultaneous acquisition of different responses from the upper and lower layers in a single time-domain signal axis, as shown in Figure 2, when the polarized light direction only responds to the lower absorber (left) and only responds to the upper absorber (right).

[0087] The dual-unit transducer probe 9-1 detects the sound field generated by the orthogonally stacked broadened spectral absorption line grid polarizer 8-1. The generated electrical signal is amplified by amplifier 6-2, then acquired by high-speed ADC acquisition module 6-3 and transmitted to host computer 6-4.

[0088] During a single irradiation, the response signals of the two sets of polarizers in four directions acquired by the high-speed ADC acquisition module 6-3 can be parsed in the host computer 6-4 using the following algorithm:

[0089] ;

[0090] ;

[0091] ;

[0092] Where i represents the i-th angle, These are the first three components of the Stokes parameter, from which optical polarization parameters such as polarization angle, ellipticity, and degree of polarization can be calculated, including the degree of polarization. Calculation formula:

[0093] .

[0094] Example 2

[0095] As shown in Figure 3, the difference between this embodiment and embodiment 1 is that, based on the existing modules in embodiment 1, the device in this embodiment further includes an information angle change and detection module. The information angle change and detection module is located between the anisotropic absorber module and the unit signal detection module, and is connected to the anisotropic absorber module and the unit signal detection module respectively through optical signals.

[0096] The information angle change and detection module is used to drive the absorber to rotate so as to obtain different polarization components at different times.

[0097] Furthermore, the structure of each module in this embodiment is as follows:

[0098] The polarization light source module is used to generate original polarized pulsed light. Specifically, the polarization light source module includes a pulsed laser 1-1, a quarter-wave plate 1-2, and a half-wave plate 1-3 connected sequentially through an optical path.

[0099] The light spot adjustment module consists of a parabolic reflector 2-1 and an xyz-axis displacement mechanism 2-2. The parabolic reflector 2-1 is fixed to the xyz-axis displacement mechanism 2-2 by a fixing mechanism. The three-dimensional movement of the parabolic reflector 2-1 can be achieved by adjusting the displacement mechanism. By moving the parabolic reflector 2-1 in the z-direction through the displacement mechanism, the power density of the light spot illuminating the surface of the absorber is adjusted, thereby expanding its detectable energy range. By moving the parabolic reflector in the xy-direction through the displacement mechanism, the range of the illuminating light spot is adjusted to cover the acoustic focal point.

[0100] The anisotropic absorber module consists of a broadband absorption grating polarizer 3-1 and an absorber fixing mechanism 3-2. The broadband absorption grating polarizer 3-1 is fixed on the absorber fixing mechanism 3-2. In the anisotropic absorber module, the normal direction of the absorber surface is coaxial with the light beam and the sound beam. The absorber fixing mechanism 3-2 has a mechanical structure coupled with the transmission mechanism.

[0101] The angle change and detection module includes an FPGA 4-1, a motor 4-2, and a transmission mechanism 4-3 connected in sequence. The FPGA 4-1 controls the movement of the motor 4-2, which is either a stepper motor or a Hall effect brushless motor. The transmission mechanism 4-3 connects the absorber fixing mechanism 3-2 and the motor 4-2, and drives the absorber to rotate through the motor 4-2.

[0102] The unit signal detection module consists of a focused piezoelectric ultrasonic transducer 5-1 and a coupling medium. The acoustic focus of the focused piezoelectric ultrasonic transducer 5-1 is placed on the surface of the absorber. The coupling medium is located between the absorber and the focused piezoelectric ultrasonic transducer 5-1, and is used for acoustic matching while propagating the acoustic signal. In the unit signal detection module, the bandwidth of the focused piezoelectric ultrasonic transducer 5-1 covers the frequency of the photoacoustic signal generated by the absorber. The sound beam is coaxial with the beam and the normal direction of the absorber. The coupling is used for acoustic matching and propagates the photoacoustic signal generated by the absorber to the focused piezoelectric ultrasonic transducer 5-1.

[0103] The information processing module includes a filter 6-1, an amplifier 6-2, a high-speed ADC acquisition module 6-3, and a host computer 6-4 connected in sequence. The filter 6-1 is connected to a focused piezoelectric ultrasonic transducer 5-1 in front and to the amplifier 6-2 in the rear. The amplifier 6-2 is connected to the high-speed ADC acquisition module 6-3 in the rear.

[0104] In this embodiment, the pulsed light output by the pulsed laser 1-1 of the polarization light source module is linearly polarized light. It first passes through a quarter-wave plate 1-2. By adjusting the angle of the quarter-wave plate 1-2, light with different degrees of polarization, such as linearly polarized light to the two extremes of circularly polarized light and the intermediate state of ellipsoidally polarized light, can be obtained. Then, it passes through a half-wave plate 1-3. By adjusting the half-wave plate 1-3, its polarization direction (major axis of ellipsoidal polarization) can be changed without changing the degree of polarization of the light. Therefore, by adjusting the quarter-wave plate 1-2 and the half-wave plate 1-3, polarized light with different degrees of polarization and polarization directions can be output.

[0105] In this example, the pulsed laser 1-1 used is a solid-state laser with a wavelength of 532nm and a pulse width of 10ns; the quarter-wave plate 1-2 and half-wave plate 1-3 used are dedicated to the 532nm wavelength; the parabolic reflector 2-1 used has a wavelength range of 450nm-20000nm; the focusing piezoelectric ultrasonic transducer 5-1 used has a main frequency of 10MHz and an acoustic focal length of 15mm; the filter 6-1 used is a high-pass filter; the amplifier 6-2 is a 40dB gain RF amplifier; and the high-speed ADC acquisition module 6-3 has a sampling rate of 125MSPS.

[0106] In this example, polarized light with arbitrary polarization degree and angle output from the polarization light source module first reaches the parabolic reflector 2-1 of the spot adjustment module. The parabolic reflector 2-1 has a broadband focusing function. By adjusting the z-displacement axis of the parabolic reflector 2-1, light spots of different sizes can be irradiated onto the surface of the broadband absorption grating polarizer 3-1 to obtain different irradiation energy densities. By adjusting the xy-displacement axis of the parabolic reflector, the spot range can be moved to the acoustic focal point. The polarized light generates a photoacoustic signal at the irradiation point of the broadband absorption grating polarizer 3-1.

[0107] Photoacoustic signal field intensity With the angle of light polarization Broadband absorption grating polarizer polarization angle The following relationship exists:

[0108] ;

[0109] in, The angle is The photoacoustic field generated by the interaction of light with a broadband absorption grating polarizer The signal amplitude at that location, and The absorption coefficients are orthogonal and parallel to the optical axis. This represents the magnitude of the luminous flux. For non-perfectly linearly polarized light, its angular polarization components still satisfy the above relationship, and the resulting photoacoustic field intensity is the sum of all components.

[0110] The focused piezoelectric ultrasonic transducer 5-1 detects the sound field generated by the broadband absorption grating polarizer 3-1 at the sound focal point. The generated electrical signal passes through the filter 6-1 and amplifier 6-2 in sequence, and is then acquired by the high-speed ADC acquisition module 6-3 and transmitted to the host computer 6-4.

[0111] The above process describes the generation and path of signals during each subdivided angle acquisition. After acquiring an angle, the FPGA 4-1 feeds back the angle position to the host computer 6-4, and then controls the motor 4-2 to drive the absorber fixing mechanism 3-2 to rotate to the next angle through the transmission mechanism 4-3, acquiring new information to obtain information on different light polarization components.

[0112] The above process is repeated continuously. A total of 720 subdivided angles of photoacoustic signal are collected for one rotation of the motor (one signal is collected for each rotation of the motor. Here, the motor rotates 0.5 degrees each time, so 720 subdivided angles can be collected for one rotation). The effect is shown in Figure 4, which is the linear polarization light polarization diagram of 720 angle information collected in one rotation in Example 2.

[0113] Example 3

[0114] As shown in Figure 5, a photoacoustic-based polarized light broadband detection method, and the aforementioned photoacoustic-based polarized light broadband detection time-division device, are described. The steps of this method are as follows:

[0115] S1. The polarized pulse light generated by the polarization light source module is sent to the spot adjustment module to adjust its polarization state and light energy density and then irradiates the anisotropic absorber module to generate a photoacoustic signal.

[0116] The photoacoustic signal contains information about the angle between the polarization angle and the maximum absorption angle of the anisotropic absorber.

[0117] Further, step S1 specifically involves: the pulsed laser outputs original polarized light, which is then adjusted by the front-end spot adjustment module to adjust its polarization state, energy, and other parameters, so that the light irradiates the anisotropic absorber module to generate a photoacoustic signal.

[0118] The pulsed laser emits a laser with a wavelength of 532nm and a pulse width of 10ns, which is within the response range of the absorber. The polarized laser then passes through a front-end spot adjustment module to adjust the optical path. This module mainly consists of a polarization state adjustment structure composed of a 532nm polarizer, a quarter-wave plate, and a half-wave plate. This part, together with the laser, forms an adjustable polarization source. The light then illuminates a parabolic reflector, and the energy density (i.e., spot size) of the light illuminating the absorber is adjusted by z-axis displacement to generate a photoacoustic signal.

[0119] The photoacoustic signal generated at the irradiation point, and the field intensity of the photoacoustic signal. With the angle of light polarization Characteristic angles of in-plane anisotropic absorbers The following relationship exists:

[0120] ;

[0121] in, The angle is The photoacoustic field generated by the interaction of light with anisotropic absorbers The signal amplitude at that location, and The absorption coefficients are orthogonal and parallel to the optical axis. This represents the magnitude of the luminous flux. For non-perfectly linearly polarized light, its angular polarization components still satisfy the above relationship, and the resulting photoacoustic field intensity is the sum of all components.

[0122] S2, the unit signal detection module is used to detect the photoacoustic signals emitted by the anisotropic absorber module;

[0123] Specifically, a focused ultrasonic sensor is used to detect the generated photoacoustic signal. The focused ultrasonic sensor uses PZT piezoelectric ceramic material, has a main frequency of 10MHz, an acoustic focal length of 15mm, and uses a gel-like ultrasonic coupling agent as the coupling medium between it and the absorber. The detected signal is acquired by a 125Msps acquisition card mounted in the host computer.

[0124] S3. The information processing module analyzes the detected photoacoustic signal in two ways: one is to take the maximum value of the photoacoustic signal intensity; the other is to obtain the spectrum of the photoacoustic signal through Fourier transform and integrate the spectrum.

[0125] Specifically, this involves analyzing the photoacoustic signal data collected in S2. The signal is processed, and its intensity is directly related to the optical polarization angle. The signal is analyzed in two ways:

[0126] One approach is to take the maximum value of the audio signal intensity. ;

[0127] One method is to obtain the signal's spectrum through Fourier transform and then integrate the spectrum. The values ​​obtained by both methods can be used to refer to the signal strength at a specific angle.

[0128] S4. The unit signal detection module detects photoacoustic signals within 360° of the motor's rotation. The information processing module obtains the polarization information of the photoacoustic signal by analyzing the detection through a specific algorithm.

[0129] The specific algorithm is as follows: detect the total area within 360°. The signals at each angle are calculated using the following algorithm:

[0130] ;

[0131] ;

[0132] ;

[0133] in, Indicates the first One corner, Stokes parameters are four real numbers that describe the intensity and polarization state of a beam of fully polarized, partially polarized, or unpolarized light. Together they form a four-dimensional real vector. The first three components of the equation are used to calculate parameters such as polarization angle, ellipticity, and degree of polarization, including the degree of polarization. Calculation formula:

[0134] ;

[0135] As shown in Figure 6A, by using the maximum intensity as a reference for the signal intensity at a specific angle, the increasing power polarized light is detected, and the photoacoustic signal exhibits a good linear response.

[0136] As shown in Figure 6C, by rotating the half-wave plate in the front-end optical path adjustment, light with four specific polarization angles (0°, 45°, 90°, 135°) is obtained and detected. It can be seen that this method has good accuracy in angle detection.

[0137] As shown in Figure 6D, by rotating a quarter-wave plate in the front-end optical path adjustment, light with different polarization degrees is obtained and detected. It can be seen that this method has good accuracy in polarization degree detection.

[0138] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A time-division device for polarized light broadband detection based on photoacoustics, characterized in that, The device includes at least a polarization source module, a spot adjustment module, an anisotropic absorber module, a unit signal detection module, and an information processing module, all connected sequentially via optical signals. Specifically: the polarization source module generates raw polarized pulse light; the spot adjustment module adjusts the polarization state and energy density of the raw polarized pulse light; the anisotropic absorber module responds to the adjusted polarized light and generates a photoacoustic signal; the unit signal detection module detects the photoacoustic signal emitted by the anisotropic absorber module; and the information processing module filters, amplifies, acquires, and processes the detected signal. The spot adjustment module includes a microlens group; the anisotropic absorber module includes an orthogonally stacked broadband absorption grating polarizer; and the unit signal detection module is a dual-unit signal detection module, consisting of a dual-unit transducer probe and a coupling medium. The microlens group is placed on top of the orthogonally stacked broadband absorption grating polarizer. The orthogonally stacked broadband absorption line grid polarizer is placed above the dual-unit transducer probe; the information processing module is connected to the dual-unit transducer probe from the front of the amplifier; the microlens group consists of two microlenses, and the two microlenses in the spot adjustment module are attached to the top of the two sets of orthogonally stacked anisotropic absorber modules and cannot be moved; the orthogonally stacked anisotropic absorber module consists of two sets of anisotropic absorber broadband absorption line grid polarizers with orthogonal polarization response angles and placed horizontally along the normal, with a certain gap in the middle to distinguish the signal peaks of the two axially placed orthogonal absorbers in the signal time domain; the absorber in the orthogonally stacked anisotropic absorber module is placed directly below the microlens of the corresponding spot adjustment module, and the area of ​​each set of orthogonal absorbers is less than or equal to the surface area of ​​the microlens; in the dual-unit signal detection module, the area of ​​each independent unit is equivalent to that of the absorber, and its acoustic focus and light are confocal on the surface of the absorber, and the distance is close enough to avoid signal crosstalk between horizontally adjacent orthogonal absorber groups.

2. The photoacoustic-based polarization broadband detection time-division device as described in claim 1, characterized in that, It also includes an information angle change and detection module, which is located between the anisotropic absorber module and the unit signal detection module, and is connected to the anisotropic absorber module and the unit signal detection module respectively through optical signals; the information angle change and detection module is used to drive the absorber to rotate so as to obtain different polarization components at different times; the angle change and detection module includes an FPGA (4-1), a motor (4-2) and a transmission mechanism (4-3) connected in sequence.

3. A time-division device for polarized broadband detection based on photoacoustics as described in claim 1 or 2, characterized in that, The polarization light source module includes a pulsed laser (1-1), a quarter-wave plate (1-2), and a half-wave plate (1-3) connected sequentially through an optical path; the information processing module includes a filter (6-1), an amplifier (6-2), a high-speed ADC acquisition module (6-3), and a host computer (6-4) connected sequentially.

4. A photoacoustic-based polarized broadband detection method, employing a photoacoustic-based polarized broadband detection time-division device as described in any one of claims 1 to 3, characterized in that, The method steps are as follows: S1. The polarized pulse light generated by the polarization light source module is sent to the spot adjustment module to adjust its polarization state and light energy density, and then irradiates the anisotropic absorber module to generate a photoacoustic signal; the photoacoustic signal contains the angle information between the polarization angle and the maximum absorption angle of the anisotropic absorber; S2. The unit signal detection module is used to detect the photoacoustic signal emitted by the anisotropic absorber module; S3. The information processing module analyzes the detected photoacoustic signal in two ways: one is to take the maximum value of the photoacoustic signal intensity; the other is to obtain the spectrum of the photoacoustic signal through Fourier transform and integrate the spectrum; S4. The information processing module analyzes the polarization information of the detected photoacoustic signal through an algorithm; the detection range is within 360°. The signals at each angle are calculated using the following algorithm: ； ； ;in, Indicates the first One corner, These are the first three components of the Stokes parameter, from which the polarization angle, ellipticity, and degree of polarization can be calculated. The degree of polarization... Calculation formula: 。 5. The photoacoustic-based polarized broadband detection method as described in claim 4, characterized in that, In step S1, the field intensity of the generated photoacoustic signal Light polarization angle and the characteristic angle of in-plane anisotropic absorbers The following relationship exists: ;in, The angle is The photoacoustic field generated by the interaction of light with anisotropic absorbers The signal amplitude at that location; and The absorption coefficients are orthogonal and parallel to the optical axis; It represents the amount of luminous flux emitted.

6. The photoacoustic-based polarized broadband detection method as described in claim 5, characterized in that, In step S2, the photoacoustic signal is acquired using a data acquisition card or an oscilloscope.

7. The photoacoustic-based polarized broadband detection method as described in claim 6, characterized in that, In step S3, the intensity of the photoacoustic signal is taken as the maximum value. The spectrum of the sound wave signal is obtained by Fourier transform and then integrated. 。

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