High-sensitivity raman detection method and device based on moems scanning grating

Abstract

The application discloses a high-sensitivity Raman detection method and device based on a MOEMS scanning grating, and belongs to the technical field of optical detection, and the technical solution points of the application are as follows: a continuous laser light source is used for emitting continuous laser light; a light chopper is used for pulse-modulating the continuous laser light, and the pulse-modulated laser beam is incident to a light splitting sheet or a silicon photodiode; a spectrometer is used for splitting the pulse Raman scattering light signal, obtaining a measured signal, and inputting the measured signal into a phase-locked amplifier, and the spectrometer comprises a MOEMS scanning grating structure; and the phase-locked amplifier is used for obtaining the amplitude of the pulse Raman scattering light signal according to the measured signal, wherein the application modulates the continuous laser light through a double-ring light chopper, two reference signals with a 90-degree phase difference are obtained by using the physical structure of the light chopper, the MOEMS scanning grating splitting technology is adopted, the vector operation is combined with the double-path phase-locked amplification technology, the real signal amplitude is extracted, and the influence of phase drift is eliminated.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and more specifically to a high-sensitivity Raman detection method and apparatus based on a MOEMS scanning grating. Background Technology

[0002] The core of Raman spectroscopy is to identify the composition of a sample by analyzing the wavelength changes of the scattered light through laser irradiation. However, current Raman spectroscopy techniques use continuous-wave lasers, which output a continuous laser intensity. When the laser irradiates a surface, it produces Rayleigh scattering and STOKES Raman scattering. The wavelength of Rayleigh scattering is exactly the same as the incident laser wavelength; therefore, Rayleigh scattering only reflects the elastic scattering characteristics of the incident light and does not carry information about the molecular structure of the sample, making it unsuitable for component identification. In contrast, the wavelength of STOKES Raman scattering differs from the incident laser wavelength, and its wavelength change is related to the vibrational and rotational energy levels of the sample's molecules. Different samples exhibit unique wavelength distributions (Raman spectra) in their STOKES Raman scattering, and analyzing these spectra allows for precise identification of the sample's composition. However, the intensity of the excited STOKES Raman spectrum is only about 1 / 10 of the intensity of the Rayleigh scattering. 6 It is easily obscured by noise and stray light, therefore, traditional detection must be carried out in a dark room or a sealed dark box.

[0003] To detect weak Raman scattering signals, traditional techniques typically employ two methods: one is to increase the intensity of the excited Raman spectrum, often by increasing the laser intensity, for example, by increasing the laser power to 500mW. While this increases the intensity of the Raman spectrum, it often causes damage or denaturation to the sample. The other method is to use long-time integration, accumulating spectral data multiple times, which theoretically can improve the signal-to-noise ratio. The number of times N is the number of samplings. However, the long excitation time, in addition to causing low detection efficiency, also makes the sample state prone to change during the excitation period, leading to sample damage or denaturation. Therefore, the existing technology has shortcomings. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high-sensitivity Raman detection method and apparatus based on a MOEMS scanning grating. A specially designed chopper modulates a continuous laser beam to form a pulsed laser beam with a 1:1 duty cycle. Although the effective laser time is halved, subsequent lock-in amplification significantly improves the signal-to-noise ratio, offsetting the intermittent loss of the pulsed laser and reducing damage to the sample caused by prolonged high-energy input. Furthermore, the present invention employs a MOEMS scanning grating structure, resulting in a short scanning time across the entire wavelength range (790nm-1050nm), eliminating the need for long-term integration to enhance the signal and preventing sample state changes such as volatilization, oxidation, and denaturation under prolonged illumination, thereby avoiding sample damage.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a high-sensitivity Raman detection device based on a MOEMS scanning grating, comprising:

[0007] A continuous laser source, used to emit continuous laser light;

[0008] A beam splitter is used to pulse modulate the continuous laser and incident the modulated pulsed laser beam onto a beam splitter or a silicon photodiode.

[0009] A spectrometer is used to disperse pulsed Raman scattered light signals to obtain a measured signal, and input the measured signal to a lock-in amplifier. The spectrometer includes a MOEMS scanning grating structure.

[0010] A lock-in amplifier is used to obtain the amplitude of the pulsed Raman scattered light signal based on the measured signal.

[0011] As a further improvement of the present invention, the light chopper includes an outer ring light-transmitting hole, an inner ring light-transmitting hole, and a motor shaft hole, wherein the edge of the inner ring light-transmitting hole is located at the center of the outer ring light-transmitting hole.

[0012] As a further improvement of the present invention, the spectrometer includes:

[0013] The second mirror is used to receive the pulsed Raman scattered light signal entering from the entrance slit and reflect the pulsed Raman scattered light signal to the MOEMS scanning grating structure.

[0014] The MOEMS scanning grating structure is used to split the pulsed Raman scattered light signal reflected by the second mirror to obtain the measured signal, and then reflect the measured signal to the third mirror.

[0015] The third reflecting mirror is used to reflect the measured signal to the unit detector;

[0016] A unit detector is used to transmit the measured signal through the exit slit to the lock-in amplifier.

[0017] As a further improvement of the present invention, the silicon photodiode includes:

[0018] The first silicon photodiode is used to receive the second pulsed laser beam output by the chopper to obtain a 90° reference signal;

[0019] The second silicon photodiode is used to receive the third pulsed laser beam output by the chopper to obtain a 0° reference signal.

[0020] As a further improvement of the present invention, the lock-in amplifier includes:

[0021] A preamplifier is used to receive and amplify the measured signal;

[0022] A bandpass filter is used to filter the amplified test signal to obtain the effective component in the pulsed Raman scattered light signal, and the effective component is input to a sine multiplier and a cosine multiplier.

[0023] Shaping circuitry is used to receive and correct the 90° reference signal and the 0° reference signal;

[0024] The multiplier is used to perform multiplication operations based on the corrected 90° reference signal, the corrected 0° reference signal, and the effective components to obtain the co-directional and quadrature components of the pulsed Raman scattering light signal; the multiplier includes a sine multiplier and a cosine multiplier:

[0025] A low-pass filter integrator is used to integrate the in-phase and quadrature components;

[0026] The vector operation module is used to perform vector operations on the same-direction components and orthogonal components after integration processing to obtain the amplitude of the measured signal.

[0027] As a further improvement of the present invention, the continuous laser includes a first beam and a second beam, the modulated pulsed laser beam includes a first pulsed laser beam, a second pulsed laser beam, and a third pulsed laser beam, and the beam splitter includes:

[0028] The first beam splitter is used to split the continuous laser into a first beam and a second beam, and transmit the first beam to a chopper for pulse modulation to obtain the first pulsed laser beam, and reflect the second beam to the third beam splitter;

[0029] The second beam splitter is used to reflect the first pulsed laser beam to the fifth beam splitter;

[0030] The third beam splitter is used to split the second beam into a third beam and a fourth beam, reflect the third beam to the chopper for pulse modulation to obtain the second pulsed laser beam, and transmit the fourth beam to the fourth beam splitter;

[0031] The fourth beam splitter is used to reflect the fourth beam to the chopper for pulse modulation to obtain the third pulsed laser beam;

[0032] The fifth beam splitter is used to reflect the first pulsed laser beam to the sample to be tested and to transmit the pulsed Raman scattered light from the sample to the lens.

[0033] As a further improvement of the present invention, the high-sensitivity Raman detection device further includes:

[0034] A lens is used to focus the pulsed Raman scattered light onto a Raman filter;

[0035] A Raman filter is used to filter the pulsed Raman scattered light to obtain the pulsed Raman scattered light signal, and the pulsed Raman scattered light signal is incident on the spectrometer through the incident slit.

[0036] This invention provides a high-sensitivity Raman detection method based on a MOEMS scanning grating, applied to the aforementioned high-sensitivity Raman detection device based on a MOEMS scanning grating, comprising:

[0037] Based on the continuous laser source and the chopper, the 0° reference signal, the 90° reference signal, and the pulsed Raman scattering light signal are obtained.

[0038] The measured signal is obtained based on the pulsed Raman scattering light signal and the spectrometer.

[0039] Used to obtain the amplitude of the measured signal based on the lock-in amplifier, the 0° reference signal, the 90° reference signal, and the measured signal.

[0040] As a further improvement of the present invention, the step of obtaining the 0° reference signal, the 90° reference signal, and the pulsed Raman scattering light signal based on the continuous laser source and the chopper includes:

[0041] A first beam and a second beam are obtained based on the continuous laser source and the first beam splitter;

[0042] The pulsed Raman scattering signal is obtained based on the first beam and the sample to be tested;

[0043] The 0° reference signal and the 90° reference signal are obtained based on the second beam.

[0044] As a further improvement of the present invention, the method for obtaining the amplitude of the measured signal based on the lock-in amplifier, the 0° reference signal, the 90° reference signal, and the measured signal includes:

[0045] The effective component is obtained based on the measured signal and the bandpass filter;

[0046] The same-direction component is obtained based on the 0° reference signal and the active ingredient;

[0047] Orthogonal components are obtained based on the 90° reference signal and the effective components;

[0048] The amplitude of the measured signal is obtained based on the same-direction component and the quadrature component.

[0049] This invention uses a pulsed laser to detect the substance under test. A 0° reference signal and a 90° reference signal are generated through a double-circle chopper structure. Combined with a MOEMS scanning grating, each wavelength is controlled to be emitted onto the unit detector. Phase-sensitive detection and demodulation are achieved for each wavelength, thereby accurately detecting weak Raman scattered light signals in the presence of large noise and interference. This solves the problems of small Raman scattering, large stray light, low signal-to-noise ratio and susceptibility to external interference in traditional Raman spectroscopy detection. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of a traditional Raman spectrometer;

[0051] Figure 2 This is a schematic diagram of the device structure of the present invention;

[0052] Figure 3 This is a schematic diagram of the structure of a light chopper;

[0053] Figure 4 This is a schematic diagram of the spectrometer of the present invention;

[0054] Figure 5 This is a diagram of a traditional single-channel lock-in amplifier circuit.

[0055] Figure 6 This is a circuit diagram of a traditional dual-channel lock-in amplifier.

[0056] Figure 7 This is a circuit diagram of the dual-channel lock-in amplifier of the present invention. Detailed Implementation

[0057] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof.

[0058] Identical parts are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions toward or away from the geometric center of a specific part, respectively.

[0059] The term "and / or" in the following text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0060] like Figure 1 The diagram shows the structure of a traditional Raman spectrometer, where LD1 is a continuous laser source, M is a mirror, F is a beam splitter, F2 is a Raman notch filter, SP is the sample to be tested, SPM is the spectrometer, SL1 is the entrance slit, AD1 is the array detector, PG is the concave grating, and L... 1 For collimating lens, L 2 It is a converging lens, where L 1 L 2 A concave reflector can also be used instead.

[0061] The specific principle is as follows: the laser emitted by LD1 is reflected by a mirror and a beam splitter before illuminating SP, exciting the sample to generate Rayleigh scattering and STOKES Raman scattering. These Rayleigh and STOKES Raman scatterings are transmitted through F to F2, where F2 filters out the extremely strong Rayleigh scattering, retaining only the weak Raman scattering. The Raman scattering then enters SPM through SL1, and is further processed by L... 1 After collimation, the light is split by PG (light of different wavelengths is separated due to different diffraction angles), and then by L. 2 Focusing on AD1, multi-wavelength signals are ultimately acquired through AD1 to form Raman spectra.

[0062] However, array detectors need to receive mixed signals of multiple wavelengths simultaneously (each wavelength corresponds to a different Raman peak), and the output is a composite signal of multiple wavelengths superimposed. Since the principle of lock-in amplification technology is to perform phase-sensitive detection on a single specific frequency signal, thereby separating the target signal from strong noise, array detectors cannot use lock-in amplification technology to improve the signal-to-noise ratio. They can only rely on inefficient means such as increasing laser power or long-term integration, which can easily lead to problems such as sample damage and long detection time.

[0063] Based on this, embodiments of this application provide a high-sensitivity Raman detection device based on a MOEMS scanning grating, comprising:

[0064] A continuous laser source, used to emit continuous laser light;

[0065] A beam chopper is used to pulse-modulate continuous laser light and direct the modulated pulsed laser beam onto a beam splitter or silicon photodiode.

[0066] A spectrometer is used to disperse pulsed Raman scattered light signals to obtain the measured signal, and input the measured signal to a lock-in amplifier. The spectrometer includes a MOEMS scanning grating structure.

[0067] A lock-in amplifier is used to obtain the amplitude of the pulsed Raman scattered light signal based on the measured signal.

[0068] This embodiment uses a pulsed laser to detect the substance under test. A 0° reference signal and a 90° reference signal are generated through a dual-circle chopper structure. Combined with a MOEMS scanning grating, each wavelength is controlled to be emitted onto the unit detector. Phase-sensitive detection and demodulation are achieved for each wavelength, thereby accurately detecting weak Raman scattered light signals in the presence of large noise and interference. This solves the problems of small Raman scattering, large stray light, low signal-to-noise ratio and susceptibility to external interference in traditional Raman spectroscopy detection.

[0069] Furthermore, the aforementioned high-sensitivity Raman detection device also includes a chopper, a spectrometer and lock-in amplifier, a silicon photodiode, a beam splitter, a lens, and a Raman filter, based on... Figure 2 and Figure 4 The detection principle of the high-sensitivity Raman detection device provided in this embodiment is as follows: First, a continuous laser is emitted from a continuous laser source (LD1). After the continuous laser reaches the first beam splitter (M1), it is split into a first beam and a second beam by M1. The first beam is transmitted by M1 to a chopper (MD), which pulses it to obtain a first pulsed laser beam. This first pulsed laser beam is then emitted to the second beam splitter (M2) and reflected by M2 to the fifth beam splitter (M5). The first pulsed laser beam is then reflected by M5 to the sample to be detected (S). The sample to be detected is excited by the pulsed laser to form pulsed Raman scattered light. After being transmitted by M5, the pulsed Raman scattered light is focused by a lens (L1) to a Raman filter (F1) for filtering to obtain a pulsed Raman scattered light signal. The pulsed Raman scattered light signal enters the spectrometer (SPM) through the entrance slit (S1) via F1 to obtain the measured signal. The measured signal is then incident on a lock-in amplifier, where MT is a motor used to drive the rotation of MD.

[0070] The second beam is reflected by M1 to the third beam splitter (M3), resulting in a third and a fourth beam. M3 then reflects the third beam to the inner aperture of the MD for pulse modulation, producing a second pulsed laser beam. The MD then directs the second pulsed laser beam to the first silicon photodiode (D1) to obtain a 90° reference signal. The fourth beam is reflected by M3 to the fourth beam splitter (M4), which in turn reflects it to the outer aperture of the MD for pulse modulation, producing a third pulsed laser beam. This third pulsed laser beam is then directed to the second silicon photodiode (D2) to obtain a 0° reference signal. The silicon photodiode then directs the 90° and 0° reference signals to a lock-in amplifier. The lock-in amplifier obtains the amplitude of the Raman scattered light signal based on the measured signal, the 90° reference signal, and the 0° reference signal.

[0071] Among them, such as Figure 3 As shown, the light chopper includes an outer ring of light-transmitting holes, an inner ring of light-transmitting holes, and a motor shaft hole. The edge of the inner ring of light-transmitting holes is located at the center of the outer ring of light-transmitting holes. The motor shaft hole is used to install an adapter motor to drive the light chopper to rotate at high speed. There are multiple outer and inner rings of light-transmitting holes, all located on a concentric circle. The length ratio of the holes to the lengths of the un-holeed holes on the concentric circle is 1:1. Therefore, when the light chopper is modulated, the duty cycle of the transmitted light intensity is also 1:1. This embodiment does not limit the material or the number of holes of the light chopper. For example, the light chopper can be made of stainless steel with 40 holes in each ring, thus generating 40 pulse signals per ring.

[0072] like Figure 4 As shown, when the pulsed Raman scattered light signal enters the SPM from S1 through F1, it first reaches the second reflecting mirror (L2). L2 reflects the pulsed Raman scattered light signal to the MOEMS scanning grating structure. The MOEMS scanning grating structure includes a grating body, a MEMS driving unit, and a negative feedback piezoresistive sensor. The surface of the grating body is manufactured using nanoimprinting. The MEMS driving unit can precisely control the position of the grating surface in a quasi-static manner. The negative feedback piezoresistive sensor is used to monitor the deflection angle of the grating in real time. The MOEMS scanning grating structure can scan the 790nm-1050nm wavelength band. When the pulsed Raman scattered light signal enters the MOEMS scanning grating structure, the MOEMS scanning grating structure precisely adjusts the grating angle and uses the principle of grating diffraction to split the pulsed Raman scattered light signal. That is, by using different diffraction angles, the light of different wavelengths in the pulsed Raman scattered light signal is separated, and then the light of different wavelengths can be accurately and sequentially reflected by the third reflecting mirror (L3) and reach the unit detector (DT) from the exit slit (S2). Compared with array detectors, this method reduces costs while ensuring high splitting accuracy, while maintaining a small size. In this embodiment, due to the splitting step, multiple test signals are obtained by the spectrometer, each test signal corresponding to a wavelength, and only one test signal is input to the lock-in amplifier at a time.

[0073] In this embodiment, there are no restrictions on the continuous laser source and the Raman filter. For example, a 785nm continuous output DFB butterfly laser can be used as the laser source, with a linewidth of 0.1nm, wavelength accuracy of ±0.5nm, power variation ≤1% / hour, and a maximum output power of 500mW. The center wavelength of the Raman filter is 785nm, the OD value (optical density) is 8, and the notch bandwidth is 5nm.

[0074] Furthermore, in this embodiment, to improve the signal-to-noise ratio and remove interference from stray light, and to avoid the influence of dark current in the unit detector itself, noise in the operational amplifier in the circuit, or DC offset, a lock-in amplification technique is used to adjust the frequency of the measured signal. Lock-in amplification utilizes the characteristic that the reference signal frequency is correlated with the input signal frequency but uncorrelated with the noise signal, allowing the extraction of useful signals from strong noise, thus greatly improving measurement accuracy. Moreover, the cross-correlation operation in lock-in amplification has strong anti-interference capabilities; therefore, this technique is widely used in weak signal detection and measurement.

[0075] like Figure 5 The diagram illustrates the circuit principle of a single-channel phase-locked amplifier in the prior art. Specifically, after the signal under test is output from the unit detector, it passes through the preamplifier circuit and the bandpass filter (BP) to reach the multiplier (PSD). The reference signal passes through the shaping circuit and the phase-shifting circuit to reach the multiplier. After the two signals are phase-sensitively detected by the multiplier, they pass through the low-pass filter integrator (LPF) to detect the weak Raman signal from the noise signal.

[0076] Theoretically, this lock-in amplification technology can improve detection sensitivity. Its advantage lies in its relatively simple circuitry and principle. However, because it requires precise phase shifting of the reference signal to ensure complete frequency and phase synchronization (phase difference = 0) between the reference signal and the measured signal, and considering the effects of temperature drift and frequency jitter in electronic components, in practice only frequency synchronization is possible, not phase synchronization. Therefore, existing technologies also include dual-channel lock-in amplification circuits, such as... Figure 6 As shown.

[0077] The principle of the dual-channel lock-in amplifier circuit is as follows: if there is no temperature drift, the measured signal is output from the unit detector, amplified by the preamplifier circuit and the bandpass filter (BP), and simultaneously input to the cosine multiplier (COSPSD) and the sine multiplier (SIN PSD). The reference signal is shaped by the shaping circuit to obtain the corrected reference signal, which is then input to the SIN PSD. At the same time, the corrected reference signal is input to the COS PSD through a 90° phase shift circuit. Multiplication is then performed on the COS PSD and SIN PSD, and the result is integrated by the LPF. The two integration results are recorded as X (same-direction component) and Y (quadrature component). Finally, the integration results are vector-operated to obtain the amplitude corresponding to the measured signal.

[0078] Its advantage is that there is no need to consider the phase relationship between the reference signal and the measured signal. It is only necessary to divide the reference signal into 0° and 90° reference signals. However, the physical characteristics of the electronic components in the phase shift circuit are sensitive to temperature, which makes the parameters of the electronic components easy to change with temperature, i.e., temperature drift is easy to occur. This makes it difficult to stabilize the phase difference at 90°, causing the two integration results to shift relative to X and Y. Ultimately, it is difficult to calculate the corresponding amplitude based on the shifted integration results.

[0079] Based on this, this embodiment uses a specially designed dual-ring chopper to achieve a precise and stable 90° phase difference through physical structure. The improved circuit diagram is as follows. Figure 7 As shown, the measured signal first passes through a preamplifier and a back amplifier (BP) to obtain the effective component of the pulsed Raman scattering light signal. Then, the effective component is simultaneously input to the SIN PSD and COS PSD. The 0° reference signal generated by D2 is shaped and then input to the COS PSD. The signal multiplied by the two signals is output via an LPF and denoted as X (same-direction component). The 90° reference signal generated by D1 is shaped and then input to the SIN PSD. The signal multiplied by the measured signal is filtered by an LPF and output as Y (orthogonal component). X and Y are vector-wise processed and output, resulting in the noise-removed measured signal. This noise-removed measured signal is then input to an A / D converter for acquisition. Finally, the data is processed by an ARM processor via an SPI interface to obtain the amplitude corresponding to the measured signal. Repeating the above steps for each measured signal yields the amplitude corresponding to each measured signal, i.e., the amplitude corresponding to each wavelength. The amplitudes are arranged in wavelength order to generate a complete Raman spectrum. The components of the sample to be tested are then identified by analyzing the Raman spectrum. This embodiment does not impose any restrictions on the A / D converter; for example, the chip of the A / D converter can be 16-bit with a 1MSPS sampling rate.

[0080] For example, the amplitude calculation steps are as follows, assuming one of the measured signals S(t) input to the preamplifier is:

[0081]

[0082] in, The signal is a Raman signal, where A is the amplitude and ω is the angular frequency. B(t) represents the phase, B(t) represents the total noise, and t represents time. This indicates that the signal is a physical quantity that changes with time. The Raman signal is very weak compared to the noise, so the input signal is a signal with a very low signal-to-noise ratio.

[0083] 0° reference signal S r0 (t) and the 90° reference signal S r1 (t) are respectively: S r0 (t)=A r sin(ωt+δ1) and S r1 (t)=A r cos(ωt+δ2), because the two signals have a 90° phase difference, one is represented by a sine wave and the other by a cosine wave, where A r The amplitudes of the reference signals are the same for both reference signals. δ1 represents the phase of the 0° reference signal and δ2 represents the phase of the 90° reference signal.

[0084] The calculation results of COS PSD are as follows:

[0085]

[0086] The calculation results of S IN PSD are as follows:

[0087]

[0088] Because a low-pass filter (LPF) filters out all high-frequency (such as ω and 2ω) AC components and retains the DC component, the result after passing through the LPF is... Then the amplitude corresponding to the measured signal can be obtained.

[0089] The reason for setting a 90° phase difference in this embodiment is that, in actual signal detection, the phase of the signal being measured... Phase drift can easily cause random drift due to factors such as changes in the optical path and circuit interference. However, by using two orthogonal (90° phase difference) reference signals, a stable amplitude result can be obtained through the combination of X and Y, regardless of how the phase of the measured signal changes. This eliminates the interference of phase drift on signal amplitude detection. If the phase difference between the two reference signals is not 90°, the components of the two reference signals will overlap, and the influence of phase drift cannot be eliminated by simple calculation.

[0090] Based on the above analysis, the spectrometer provided in this embodiment can be summarized as follows: a second reflecting mirror, used to receive the pulsed Raman scattered light signal entering from the entrance slit and reflect the pulsed Raman scattered light signal to the MOEMS scanning grating structure; the MOEMS scanning grating structure, used to split the pulsed Raman scattered light signal reflected by the second reflecting mirror to obtain the measured signal, and reflect the measured signal to the third reflecting mirror; the third reflecting mirror, used to reflect the measured signal to the unit detector; the unit detector, used to send the measured signal through the exit slit to the lock-in amplifier. The silicon photodiode includes: a first silicon photodiode, used to receive the second pulsed laser beam output from the chopper to obtain a 90° reference signal; and a second silicon photodiode, used to receive the third pulsed laser beam output from the chopper to obtain a 0° reference signal. The two silicon photodiodes are of the same specification. The lock-in amplifier includes: a preamplifier for receiving and amplifying the measured signal; a bandpass filter for filtering the amplified measured signal to obtain the effective component of the pulsed Raman scattered light signal, and inputting the effective component to a sine multiplier and a cosine multiplier; a shaping circuit for receiving and correcting the 90° reference signal and the 0° reference signal; a multiplier for performing multiplication operations based on the corrected 90° reference signal, the corrected 0° reference signal, and the effective component to obtain the co-directional and quadrature components of the pulsed Raman scattered light signal; the multiplier includes a sine multiplier and a cosine multiplier; a low-pass filter integrator for integrating the co-directional and quadrature components; and a vector operation module for performing vector operations on the integrated co-directional and quadrature components to obtain the amplitude of the measured signal.

[0091] The continuous laser beam includes a first beam and a second beam. The modulated pulsed laser beam includes a first pulsed laser beam, a second pulsed laser beam, and a third pulsed laser beam. The beam splitter includes: a first beam splitter for splitting the continuous laser beam into a first beam and a second beam, transmitting the first beam to a chopper for pulse modulation to obtain a first pulsed laser beam, and reflecting the second beam to a third beam splitter; a second beam splitter for reflecting the first pulsed laser beam to a fifth beam splitter; a third beam splitter for splitting the second beam into a third beam and a fourth beam, reflecting the third beam to a chopper for pulse modulation to obtain a second pulsed laser beam, and transmitting the fourth beam to a fourth beam splitter; a fourth beam splitter for reflecting the fourth beam to a chopper for pulse modulation to obtain a third pulsed laser beam; and a fifth beam splitter for reflecting the first pulsed laser beam to the sample to be tested and transmitting the pulsed Raman scattered light from the sample to a lens. The lens is used to focus the pulsed Raman scattered light onto the Raman filter; the Raman filter is used to filter the pulsed Raman scattered light to obtain the pulsed Raman scattered light signal, and then the pulsed Raman scattered light signal is incident on the spectrometer through the entrance slit.

[0092] Furthermore, embodiments of this application provide a high-sensitivity Raman detection method based on a MOEMS scanning grating, comprising:

[0093] Based on the continuous laser source and the chopper, the 0° reference signal, the 90° reference signal, and the pulsed Raman scattering light signal are obtained.

[0094] The measured signal is obtained based on the pulsed Raman scattering light signal and the spectrometer;

[0095] It is used to obtain the amplitude of the measured signal based on the lock-in amplifier, the 0° reference signal, the 90° reference signal and the measured signal.

[0096] The steps for obtaining the 0° reference signal, 90° reference signal, and pulsed Raman scattering signal based on a continuous laser source and a chopper include:

[0097] The first beam and the second beam are obtained based on the continuous laser source and the first beam splitter;

[0098] Based on the first beam and the sample to be tested, the pulsed Raman scattering signal is obtained;

[0099] Based on the second beam, the 0° reference signal and the 90° reference signal are obtained.

[0100] The step of obtaining the amplitude of the measured signal based on the lock-in amplifier, the 0° reference signal, the 90° reference signal, and the measured signal includes:

[0101] The effective component is obtained based on the measured signal and the bandpass filter;

[0102] The same-direction component is obtained based on the 0° reference signal and the active ingredient;

[0103] Orthogonal components are obtained based on the 90° reference signal and the effective components;

[0104] The amplitude of the measured signal is obtained from the same-direction and quadrature components.

[0105] This application provides a high-sensitivity Raman detection method and system based on a MOEMS scanning grating. It employs a continuous-wave laser, which overcomes the drawbacks of pulsed lasers, such as high cost, narrow pulse width, small duty cycle, and low light intensity utilization. Continuous-wave lasers are low-cost, and this embodiment modulates the continuous-wave laser using a dual-circle chopper to form an 8kHz pulsed laser beam with a 1:1 duty cycle, shifting the frequency from DC to a higher frequency range. Since external interference light intensity generally changes slowly and does not reach the modulated frequency, the effects of stray light, detector dark current, and amplifier DC offset are avoided. Therefore, the Raman spectroscopy detection in this embodiment is unaffected by external light intensity, eliminating the need for a darkroom or sealed black box. Furthermore, because the DC and low-frequency components are filtered out, the operational amplifier can be configured to amplify the signal by a larger gain.

[0106] Furthermore, since this embodiment uses a MOEMS scanning grating, it eliminates the need for array detectors found in existing technologies, instead using a unit detector. This allows for the use of lock-in amplification technology, significantly improving the signal-to-noise ratio and ensuring high spectroscopic accuracy while reducing costs. Additionally, this embodiment employs dual lock-in amplification technology, avoiding the requirement of single lock-in amplification technology where the reference signal must be strictly in phase and frequency with the measured signal. Maintaining the same frequency is sufficient. Moreover, the use of a dual-circuit chopper allows for a 90° phase difference to be maintained through physical structure, rather than a 90° phase-shifting circuit, thus avoiding phase drift. In summary, the spectrometer in this embodiment can achieve high-precision substance detection with lower excitation light intensity and shorter detection time.

[0107] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0108] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0109] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0110] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-sensitivity Raman detection device based on a MOEMS scanning grating, characterized in that, include: A continuous laser source, used to emit continuous laser light; A chopper is used to pulse modulate the continuous laser and incident the modulated pulsed laser beam onto a beam splitter and a silicon photodiode; the silicon photodiode includes a first silicon photodiode and a second silicon photodiode, the first silicon photodiode is used to receive the second pulsed laser beam output by the chopper to obtain a 90° reference signal, and the second silicon photodiode is used to receive the third pulsed laser beam output by the chopper to obtain a 0° reference signal. A spectrometer is used to disperse pulsed Raman scattered light signals to obtain a measured signal, and input the measured signal to a lock-in amplifier. The spectrometer includes a MOEMS scanning grating structure. A lock-in amplifier is used to obtain the amplitude of the pulsed Raman scattered light signal based on the measured signal; The light chopper includes an outer ring light-transmitting hole, an inner ring light-transmitting hole, and a motor shaft hole, with the edge of the inner ring light-transmitting hole located at the center of the outer ring light-transmitting hole. The lock-in amplifier includes: A preamplifier is used to receive and amplify the measured signal; A bandpass filter is used to filter the amplified test signal to obtain the effective component in the pulsed Raman scattered light signal, and the effective component is input to a sine multiplier and a cosine multiplier. Shaping circuitry is used to receive and correct the 90° reference signal and the 0° reference signal; A multiplier is used to perform multiplication operations based on the corrected 90° reference signal, the corrected 0° reference signal, and the effective components to obtain the in-phase and quadrature components of the pulsed Raman scattering light signal; the multiplier includes a sine multiplier and a cosine multiplier; A low-pass filter integrator is used to integrate the in-phase and quadrature components; The vector operation module is used to perform vector operations on the same-direction components and orthogonal components after integration processing to obtain the amplitude of the measured signal.

2. The high-sensitivity Raman detection device based on the MOEMS scanning grating according to claim 1, characterized in that, The spectrometer includes: The second mirror is used to receive the pulsed Raman scattered light signal entering from the entrance slit and reflect the pulsed Raman scattered light signal to the MOEMS scanning grating structure. The MOEMS scanning grating structure is used to split the pulsed Raman scattered light signal reflected by the second mirror to obtain the measured signal, and then reflect the measured signal to the third mirror. The third reflecting mirror is used to reflect the measured signal to the unit detector; A unit detector is used to transmit the measured signal through the exit slit to the lock-in amplifier.

3. The high-sensitivity Raman detection device based on the MOEMS scanning grating according to claim 1, characterized in that, The continuous laser beam includes a first beam and a second beam, the modulated pulsed laser beam includes a first pulsed laser beam, a second pulsed laser beam, and a third pulsed laser beam, and the beam splitter includes: The first beam splitter is used to split the continuous laser into a first beam and a second beam, and transmit the first beam to a chopper for pulse modulation to obtain the first pulsed laser beam, and reflect the second beam to the third beam splitter; The second beam splitter is used to reflect the first pulsed laser beam to the fifth beam splitter; The third beam splitter is used to split the second beam into a third beam and a fourth beam, reflect the third beam to the chopper for pulse modulation to obtain the second pulsed laser beam, and transmit the fourth beam to the fourth beam splitter; The fourth beam splitter is used to reflect the fourth beam to the chopper for pulse modulation to obtain the third pulsed laser beam; The fifth beam splitter is used to reflect the first pulsed laser beam to the sample to be tested and to transmit the pulsed Raman scattered light from the sample to the lens.

4. The high-sensitivity Raman detection device based on the MOEMS scanning grating according to claim 3, characterized in that, The high-sensitivity Raman detection device also includes: A lens is used to focus the pulsed Raman scattered light onto a Raman filter; A Raman filter is used to filter the pulsed Raman scattered light to obtain the pulsed Raman scattered light signal, and the pulsed Raman scattered light signal is incident on the spectrometer through the incident slit.

5. A high-sensitivity Raman detection method based on a MOEMS scanning grating, applied to the high-sensitivity Raman detection device based on a MOEMS scanning grating as described in any one of claims 1-4, characterized in that, include: Based on the continuous laser source and the chopper, the 0° reference signal, the 90° reference signal, and the pulsed Raman scattering light signal are obtained. The measured signal is obtained based on the pulsed Raman scattering light signal and the spectrometer. Used to obtain the amplitude of the measured signal based on the lock-in amplifier, the 0° reference signal, the 90° reference signal, and the measured signal.

6. The high-sensitivity Raman detection method based on MOEMS scanning grating according to claim 5, characterized in that, The process of obtaining the 0° reference signal, 90° reference signal, and pulsed Raman scattering signal based on a continuous laser source and a chopper includes: The first beam and the second beam are obtained based on the continuous laser source and the first beam splitter; The pulsed Raman scattering signal is obtained based on the first beam and the sample to be tested; The 0° reference signal and the 90° reference signal are obtained based on the second beam.

7. The high-sensitivity Raman detection method based on a MOEMS scanning grating according to claim 6, characterized in that, The method for obtaining the amplitude of the measured signal based on the lock-in amplifier, the 0° reference signal, the 90° reference signal, and the measured signal includes: The effective component is obtained based on the measured signal and the bandpass filter; The same-direction component is obtained based on the 0° reference signal and the active ingredient; Orthogonal components are obtained based on the 90° reference signal and the effective components; The amplitude of the measured signal is obtained based on the same-direction component and the quadrature component.

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