A single laser displacement excitation differential spectrometer

Abstract

A single-laser displacement excitation differential spectrometer includes an optical path, a temperature control module, a control module, and a display interaction module. The optical path generates 780-790nm near-infrared light through a temperature-controlled adjustable wavelength near-infrared laser light source, and realizes the excitation and collection of Raman scattered light through an excitation focusing collection optical path. The original Raman spectrum is obtained by using a symmetrical cross-type Czerny-Turner optical path structure as a split optical path. After the laser wavelength is adjusted through a temperature control system, multiple groups of Raman spectra of different excitation lights of the same substance are input to a ZYNQ chip for differentiation, reconstruction, and baseline correction to obtain the displacement excitation differential Raman spectrum of the sample. The interactive display with the user is completed by connecting to the display module through an HDMI multimedia interface. The device of the present invention is portable and convenient, reduces the complex design and cost of the differential Raman spectrometer on the laser, uses the displacement excitation differential Raman technology to meet the needs of on-site real-time detection, and can complete the real-time Raman spectrum detection of the sample.

Description

Technical Field

[0001] The invention relates to a Raman detection device, in particular to a Raman detection device based on a temperature-controlled wavelength-adjustable laser and displacement-excitation differential Raman technology. Background Art

[0002] Raman spectroscopy is a spectral analysis technique that uses laser light to irradiate a sample, causing the sample's molecular bonds to vibrate and energy level transitions to occur, causing the scattered light to change in wavelength, giving the Raman spectrum the special effect of "molecular fingerprints". However, when the concentration of the target sample is low, there is strong fluorescence interference or spectral noise, the Raman peak of the target sample may be overwhelmed by the rest of the noise signal and is difficult to identify.

[0003] Shifted excitation differential Raman causes a shift in the Raman spectrum through a slight change in the excitation wavelength, while the fluorescence part does not change. And by calculating the difference between the Raman spectra, all wavelength-independent signals are removed. This method can effectively remove not only fluorescence, but also ambient light, isothermal and any other constant sources.

[0004] For shift excitation differential Raman spectrometers, the emission laser must be dual-wavelength, and both wavelengths can be controlled separately. The difference between the two wavelengths should be close to the half-width of the strongest peak signal of the Raman peak of the sample under study. Currently, most shift excitation differential Raman spectrometers have three solutions: using a tunable laser light source, a fixed-frequency dual-frequency laser light source, or a single laser light source and then adjusting the emission wavelength through an external diffraction grating. The tunable laser light source is too large to meet the portable requirements and is expensive. The fixed laser frequency cannot achieve the optimal adaptation for all samples. The external diffraction grating requires additional external grating elements and must be mechanically adjusted. Summary of the invention

[0005] In order to overcome the problems that ordinary Raman spectrometers have poor detection effect or cannot detect samples with low concentration or high fluorescence background, and that traditional Raman spectroscopy detection instruments are complex, large in size, and poor in portability, which are not conducive to on-site real-time measurement, the present invention proposes a displacement-excitation differential Raman spectroscopy detection device with a temperature-controlled wavelength adjustable laser.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A single laser displacement excitation differential spectrometer, comprising a detection optical path, a control module, a temperature control module, an adjustable wavelength near-infrared laser light source and a display module; wherein the detection optical path comprises:

[0008] The excitation focusing collection optical path allows the light emitted by the adjustable wavelength near-infrared laser light source to be incident on the sample and collects the Raman scattered light scattered by the sample;

[0009] The light splitting path splits the light collected by the excitation focusing and collecting light paths to obtain the Raman scattering spectrum of the sample;

[0010] A splitting optical path is used to split the light collected by the excitation and collection optical path, thereby obtaining the Raman scattering spectrum of the sample;

[0011] The adjustable wavelength near-infrared laser light source provides a light source for the excitation focusing and collecting optical path, and the temperature control module is used to cool the linear array CCD in the splitting optical path to eliminate thermal noise interference;

[0012] The control module comprises:

[0013] The ZYNQ chip in the computing and control center, the data cache module, the multimedia HDMI interface connected to the display module, the driver module for driving the cooling module, the light source driver module for driving the adjustable wavelength near-infrared laser light source, and the Gigabit network port and USB interface connected to the PC during debugging;

[0014] The temperature control module includes an ADN8835 constant current source and a variable resistor module required by a PID temperature control system, and controls the required temperature through a cooling drive module to complete adjustable temperature control of a linear array CCD and an adjustable wavelength near-infrared laser light source;

[0015] The adjustable wavelength near-infrared laser light source includes a high-performance fiber-coupled semiconductor laser K785AFLFN-0.600W produced by China Kaplin Corporation and an aluminum heat sink bonded with thermal grease to help dissipate heat and achieve temperature control;

[0016] The display interaction module is provided with a touch screen for information display, user interaction and operation input, and is connected to the multimedia HDMI interface.

[0017] The near-infrared semiconductor butterfly package laser light source controls the excitation laser wavelength through the PID temperature control system, and is incident on the sample pool through the focusing part of the excitation focusing collection optical path. The Raman signal generated by the incident laser in the sample pool is input to the improved cross-symmetrical Czerny-Turner spectroscopic optical path through the collection part of the excitation focusing collection optical path by optical fiber. The CCD in the optical path collects the received Raman light signal and converts it into an electrical signal and transmits it to the control module. The control module transmits it to the display module to complete the display, completing one acquisition. Differential processing requires modifying the working temperature of the near-infrared semiconductor butterfly package laser light source through the PID temperature control system. After completing two acquisitions, the ZYNQ processor in the control module completes the differential, denoising, reconstruction, and baseline correction of the Raman spectrum data, and finally obtains the differential spectrum of the sample.

[0018] Furthermore, the excitation focusing and collecting optical path includes: a collimating lens for collimating incident light; a narrow bandpass filter for filtering out ambient light other than the laser light source; a silver-coated high-efficiency reflector for simplifying the optical path; a specially designed dielectric multilayer coating capable of completing the reflection of the laser light with a wavelength of about 785nm generated by a near-infrared laser light source incident at 45 degrees and completing the transmission of the incident sample Raman signal, a dichroic mirror; a focusing collection lens for aggregating the incident light and simultaneously converging the sample Raman signal; filtering the reflected light, including ambient light, Rayleigh scattering, and a high-pass filter; a converging lens for converging the filtered Raman signal to the optical fiber coupling port; allowing the Raman signal of sufficient light intensity to enter the splitting optical path, which is connected to the splitting optical path through an optical fiber;

[0019] Furthermore, the splitting light path includes: a slit, which serves as the entrance of the splitting light path and is used to control the amount of light entering; a collimator to collimate the incident light so that the light can be incident on the surface of the plane holographic diffraction grating in parallel; after the plane holographic diffraction grating disperses and splits the light, the light is focused by a focusing lens onto the linear array CCD image sensor.

[0020] Further, the control module includes: a ZYNQ chip in the computing and control center to complete the differential, denoising, reconstruction, and baseline correction processing of the Raman spectrum data, a data cache module as a data cache center, a multimedia HDMI interface connected to the display module, a driver module for driving the refrigeration module, a light source driver module for driving the adjustable wavelength near-infrared laser light source, and a Gigabit network port and a USB interface for connecting to the PC side during debugging;

[0021] Furthermore, the adjustable wavelength near-infrared laser light source includes a high-performance fiber-coupled semiconductor laser K785AFLFN-0.600W produced by China Kaiplin Company and an aluminum heat sink bonded with thermal grease underneath to help dissipate heat. The temperature control of the laser is used to achieve differential control of the laser wavelength. The near-infrared laser light source that adjusts the wavelength by driving the refrigeration module can ensure the accuracy of the laser center wavelength while being able to adjust within the range of 780nm to 790nm and work stably, reducing the volume of the laser light source and simplifying the use process of changing the laser wavelength.

[0022] For spectral difference reconstruction, one-dimensional integration is used and baseline correction is performed to obtain the final Raman spectrum. The total spectral signal S obtained usually contains Raman signal, laser signal, stray light and dark current noise in the photoelectric sensor. The total signal S can be expressed as:

[0023] S(v,v i )=L(v,v i )+R(v,v i )

[0024] where v iDifferent incident laser frequencies, L(v, v i ) and R(v,v i ) represents the noise intensity and Raman intensity.

[0025] S1 and S2 represent the total signal obtained by two incident lasers of different wavelengths. Slight changes in the wavelength of the incident laser will cause R(v, v i )The Raman intensity term is shifted, and L(v, v i ) The noise term will not change with the incident laser frequency, and we can get

[0026] ΔS=S2-S1=R(v, v1)-R(v, v2)

[0027] That is, the spectrum after differentiation. Under this condition, the differential spectrum can be obtained by one-dimensional integral reconstruction. However, as the temperature of the laser changes, not only will the output laser shift, but also the output power will change. Specifically, the higher the temperature, the lower the output power, which will produce a baseline-like deviation in the differential spectrum. The present invention uses the BEADS algorithm for baseline correction and uses the ZYNQ core to complete differentiation, reconstruction and baseline correction.

[0028] The CCD (1205) of the light splitting path adopts the S13256 linear array CCD sensor of Hamamatsu, which has 2048 pixels and a pixel size of 14x1000μm. The sensor has high quantum efficiency and image resolution in the near-infrared region, and has built-in TEC cooling, and PID temperature control is achieved through the thermoelectric cooling controller ADN8835.

[0029] Furthermore, the adjustable wavelength near-infrared laser light source 4000 includes a high-performance fiber-coupled semiconductor laser K785AFLFN-0.600W produced by China Kaplin Corporation and an aluminum heat sink block bonded with thermal conductive silicone grease below to help dissipate heat and achieve temperature control;

[0030] The present invention proposes a material detector based on a temperature-controlled wavelength adjustable laser and displacement excitation differential Raman technology, which is highly practical and portable. A near-infrared laser light source whose wavelength can be adjusted by temperature control is adopted, and an appropriate wavelength can be selected for excitation as needed. The excitation, filtering and collection of Raman light are realized through a dichroic mirror and a filter group, which effectively improves the signal-to-noise ratio and detection sensitivity. The improved symmetrical Czerny-Turner structure is adopted as the light splitting optical path, which can accurately split the excitation light and ensure the accuracy and resolution of the spectrum. In terms of spectrum acquisition, a linear array CCD image sensor is adopted, which has the characteristics of fast speed and high sensitivity and can quickly obtain spectral information. The ZYNQ processor platform provides stable timing drive and efficient spectral differential reconstruction baseline correction calculation, as well as display interaction function, so that the instrument is easy to operate and can display the detection results in real time. The optical path structure of the instrument is simple, and an external probe is designed, which makes on-site detection more convenient and quick. This instrument does not need to be connected to a computer (PC), but uses the computing and display functions of the embedded platform itself to realize a truly portable Raman micro-detection instrument. It can meet the needs of on-site real-time detection and realize a truly portable displacement-excitation differential Raman detector.

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

[0032] 1. The temperature control of the laser is used to achieve differential control of the laser wavelength. Compared with the traditional tunable laser, it reduces the cost and improves portability. Compared with the fixed dual-wavelength laser, the wavelength can be adjusted to adapt to the incident laser wavelength difference required by different test samples. The near-infrared laser light source that adjusts the wavelength through temperature control can adjust the range of 780nm to 790nm and work stably while ensuring the accuracy of the laser center wavelength.

[0033] 2. Data processing is convenient. The interference of ambient light, dark pixels and fluorescence noise is eliminated by differential analysis of the original spectrum. After baseline correction, an accurate Raman spectrum can be obtained. No additional program processing is required. After measuring the original spectrum twice, the ZYNQ motherboard can obtain an accurate Raman spectrum through differential analysis, reconstruction and baseline correction.

[0034] 3. High resolution and accuracy, using Hamamatsu's S13256 linear array CCD sensor, with 2048 pixels and 14x1000μm pixel size. The sensor has high quantum efficiency and image resolution in the near-infrared region, and built-in TEC cooling, and PID temperature control is achieved through the thermoelectric cooling controller ADN8835. Through this sensor, the instrument can achieve high-resolution spectral acquisition and accurately capture and analyze the Raman spectral characteristics of the sample.

[0035] 4. High portability. The design of timing control and data calculation through the ZYNQ platform makes the present invention free from the dependence of the traditional Raman detection platform on the computer (PC), easy to carry, with an external probe, and can perform real-time on-site detection. It adopts a near-infrared light source device, a temperature control device, an excitation focusing collection optical path, and a splitting optical path in conjunction with the ZYNQ module. It has a simple structure, common components, affordable prices, and accurate Raman detection effects, which is conducive to the promotion of Raman spectroscopy technology in the field of public safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the light splitting path of the present invention.

[0037] Figure 2 It is a schematic diagram of the optical path of the Raman probe of the present invention.

[0038] Figure 3 It is a schematic structural diagram of the main part of the present invention.

[0039] Figure 4 It is a system flow chart of the present invention.

[0040] Figure 5 It is a functional schematic diagram of the main control module of the present invention. DETAILED DESCRIPTION

[0041] A further detailed description is given below in conjunction with the accompanying drawings.

[0042] A detection device based on a temperature-controlled wavelength adjustable laser and displacement-excited differential Raman technology, comprising a detection optical path 1000, a control module 2000, a temperature control module 3000, an adjustable wavelength near-infrared laser light source 4000 and a display module 5000; wherein the detection optical path 1000 comprises:

[0043] The excitation focusing collection optical path 1100 is used to direct the light emitted by the near-infrared laser light source with adjustable wavelength into the sample and collect the Raman scattered light scattered by the sample;

[0044] The light splitting optical path 1200 is used to split the light collected by the excitation focusing collection optical path, so as to obtain the Raman scattering spectrum of the sample;

[0045] The adjustable wavelength near-infrared laser light source 4000 is used to provide a light source for the excitation focusing collection optical path 1100, and the temperature control module 3000 is used to cool the linear array CCD in the splitting optical path 1200 to eliminate thermal noise interference;

[0046] The excitation focusing and collecting optical path 1100 includes: a collimating lens 1101 for collimating incident light; a narrow bandpass filter 1102 for filtering out ambient light outside the laser light source; a silver-coated high-efficiency reflector 1103 for simplifying the optical path; a specially designed dielectric multilayer coating that can complete the reflection of the laser light with a wavelength of about 785nm generated by a near-infrared laser light source incident at 45 degrees and complete the transmission of the incident sample Raman signal, a dichroic mirror 1104; a focusing collection lens 1105 for aggregating the incident light and simultaneously converging the sample Raman signal; filtering the reflected light, including ambient light and Rayleigh scattering, a high-pass filter 1106; a converging lens that converges the filtered Raman signal to the optical fiber coupling port 1107; allowing the Raman signal of sufficient light intensity to enter the splitting optical path, which is connected to the splitting optical path 1200 through an optical fiber;

[0047] The splitting optical path 1200 includes: a slit 1201, which serves as the entrance of the splitting optical path and is used to control the amount of incoming light; a collimator 1202 that collimates the incident light so that the light can be incident on the surface of the plane holographic diffraction grating in parallel; and after the plane holographic diffraction grating 1203 disperses and splits the light, the light is focused by a focusing mirror 1204 to a linear array CCD image sensor 1205.

[0048] The control module 2000 includes:

[0049] The computing and control center ZYNQ chip 2001, the data cache module 2002, the multimedia HDMI interface 2003 connected to the display module 5000, the driver module 2004 driving the cooling module 3000, the light source driver module 2005 driving the adjustable wavelength near-infrared laser light source 4000, and the Gigabit network port 2006 and USB interface 2007 used to connect to the PC side during debugging;

[0050] The temperature control module 3000 includes an ADN8835 constant current source and a variable resistor module required by a PID temperature control system, and controls the required temperature through a cooling drive module 2004 to complete the adjustable temperature control of the linear array CCD1205 and the adjustable wavelength near-infrared laser light source 4000;

[0051] The adjustable wavelength near-infrared laser light source 4000 includes a high-performance fiber-coupled semiconductor laser K785AFLFN-0.600W produced by China Kaplin Corporation and an aluminum heat sink bonded with thermal grease below to help dissipate heat and achieve temperature control;

[0052] The display interaction module 5000 is provided with a touch screen for information display, for interaction with the user and operation input, and is connected to the multimedia HDMI interface 2003 .

[0053] Figure 3The overall structure diagram of the present invention is given, and the overall structure is, from top to bottom, a display interaction module (5000), a light splitting path (1200), an adjustable wavelength near-infrared laser light source and a heat sink (4000), a temperature control module (3000), and a control module (2000).

[0054] The excitation focusing collection optical path 1100 is connected to an adjustable wavelength near-infrared laser light source through an optical fiber, and the collected Raman scattering signal is input to the splitting optical path (1200) through the optical fiber. The optical fiber connection port is a circular hole on the outside of the shell.

[0055] Figure 4 The system flow chart of the present invention is given. When the system is turned on, the instrument automatically completes initialization, including the refrigeration module adjusting the adjustable wavelength near-infrared laser light source to the preset temperature to work, helping the ZYNQ chip to complete startup and buffer the linear array CCD data. In the next step, the user chooses whether to perform data differentiation. When selecting data acquisition, the user needs to set the laser temperature first, then place the sample for spectral data acquisition, and complete the preservation of the original data. When entering data differentiation, it is necessary to input two sets of measurement data completed by the same substance at different temperatures. The ZYNQ chip will complete the work including data differentiation, reconstruction and baseline correction and return the final Raman spectrum data.

[0056] Figure 5 Schematic diagram of the control module function, including the ZYNQ chip (2001) with main computing functions, the data cache module (2002), the multimedia HDMI interface (2003) for connecting the display module 5000, the driving module (2004) for driving the refrigeration module 3000, the light source driving module (2005) for driving the adjustable wavelength near-infrared laser light source 4000, and the Gigabit network port (2006) and USB interface (2007) for connecting to the PC during debugging.

Claims

1. A single laser displacement excitation differential spectrometer, characterized in that: The invention comprises a detection optical path (1000), a control module (2000), a temperature control module (3000), an adjustable wavelength near-infrared laser light source (4000) and a display module (5000); wherein the detection optical path (1000) comprises: The excitation focusing collection optical path (1100) allows the light emitted by the near-infrared laser light source with adjustable wavelength to be incident on the sample and collects the Raman scattered light scattered by the sample; A light splitting optical path (1200) is used to split the light collected by the excitation focusing collection optical path, thereby obtaining a Raman scattering spectrum of the sample; The adjustable wavelength near-infrared laser light source (4000) provides a light source for the excitation focusing collection optical path (1100), and the temperature control module (3000) is used to cool the linear array CCD in the splitting optical path (1200) to eliminate thermal noise interference; The control module (2000) comprises: A ZYNQ chip (2001) of the computing and control center, a data cache module (2002), a multimedia HDMI interface (2003) connected to the display module (5000), a cooling drive module (2004) of the temperature control module (3000), a light source drive module (2005) driving an adjustable wavelength near-infrared laser light source (4000), and a Gigabit network port (2006) and a USB interface (2007) connected to the PC side during debugging; The temperature control module (3000) includes an ADN8835 constant current source and a variable resistor module required by a PID temperature control system, and adjusts and controls the required temperature through a cooling drive module (2004) to complete adjustable temperature control of a linear array CCD (1205) and an adjustable wavelength near-infrared laser light source (4000); The display module (5000) is provided with a touch screen for information display, user interaction and operation input, and is connected to a multimedia HDMI interface (2003); The adjustable wavelength near-infrared laser light source (4000) controls the excitation laser wavelength through the temperature control module (3000), and is incident on the sample pool through the focusing part of the excitation focusing collection light path (1100). The Raman signal generated by the incident laser in the sample pool is input to the splitting light path (1200) through the optical fiber through the collecting part of the excitation focusing collection light path (1100). The linear array CCD in the splitting light path (1200) collects the received Raman light signal and converts it into an electrical signal and transmits it to the control module (2000). The control module transmits it to the display module (5000) to complete the display, and completes one acquisition. The differential processing requires the PID temperature control system to modify the working temperature of the adjustable wavelength near-infrared laser light source. After completing two acquisitions, the ZYNQ processor in the control module completes the differential, denoising, reconstruction, and baseline correction processing of the Raman spectrum data, and finally obtains the differential spectrum of the sample.

2. The single laser displacement excitation differential spectrometer according to claim 1, characterized in that: The excitation focusing and collecting optical path (1100) comprises: a collimating lens (1101) for collimating incident light; a narrow-bandpass filter (1102) for filtering out ambient light other than the adjustable wavelength near-infrared laser light source; a silver-coated high-efficiency reflector (1103) for simplifying the optical path, the silver-coated high-efficiency reflector (1103) comprising a dielectric multilayer coating, capable of completing the reflection of laser light with a wavelength of about 785 nm generated by the adjustable wavelength near-infrared laser light source incident at 45 degrees and completing the transmission of the incident sample Raman signal; a dichroic mirror (1104); a focusing collection lens (1105) for aggregating the incident light and simultaneously converging the sample Raman signal; a high-pass filter (1106) for filtering the reflected light, the filtered light comprising ambient light and Rayleigh scattering; and a converging lens for converging the filtered Raman signal to the optical fiber coupling port (1107), so that the Raman signal with sufficient light intensity enters the light splitting optical path, which is connected to the light splitting optical path (1200) via the optical fiber.

3. The single laser displacement excitation differential spectrometer according to claim 1, characterized in that: The light splitting optical path (1200) comprises: a slit (1201) serving as an entrance to the light splitting optical path for controlling the amount of incoming light; a collimator (1202) for collimating incident light so that the light can be incident on the surface of the plane holographic diffraction grating in parallel; and a plane holographic diffraction grating (1203) for focusing the light after dispersion and splitting onto a linear array CCD (1205) via a focusing lens (1204).

4. The single laser displacement excitation differential spectrometer according to claim 1, characterized in that: The control module (2000) comprises: a ZYNQ chip (2001) as a computing and control center for completing the differential, denoising, reconstruction and baseline correction processing of Raman spectrum data; a data cache module (2002) as a data cache center, a multimedia HDMI interface (2003) connected to a display module (5000), a refrigeration drive module (2004) of a temperature control module (3000), a light source drive module (2005) for driving an adjustable wavelength near-infrared laser light source (4000), and a gigabit network port (2006) and a USB interface (2007) for connecting to a PC during debugging.

5. The single laser displacement excitation differential spectrometer according to claim 1, characterized in that: The adjustable wavelength near-infrared laser light source (4000) uses temperature control of the laser to achieve differential control of the laser wavelength. The adjustable wavelength near-infrared laser light source that adjusts the wavelength through the temperature control module (3000) can adjust within the range of 780nm to 790nm while ensuring the accuracy of the laser center wavelength and can operate stably, thereby reducing the volume of the adjustable wavelength near-infrared laser light source and simplifying the use process of changing the laser wavelength.

6. The single laser displacement excitation differential spectrometer according to claim 1, characterized in that: For spectral difference reconstruction, one-dimensional integration is used and baseline correction is performed to obtain the final Raman spectrum. The total spectral signal S obtained usually contains Raman signal, laser signal, stray light and dark current noise in the photoelectric sensor. The total signal S can be expressed as: in Different incident laser frequencies, and It represents the noise intensity and Raman intensity; use , represents the total signal obtained by two incident lasers of different wavelengths, V1 and v2 represent the frequencies of two incident lasers of different wavelengths; slight changes in the wavelength of the incident laser will cause The noise term does not change with the incident laser frequency, and can be obtained S= - = , that is, the spectrum after differentiation. Under this condition, the differential spectrum can be obtained by one-dimensional integral reconstruction; A baseline-like deviation is generated in the differential spectrum; the baseline is corrected using the BEADS algorithm, and the ZYNQ core is used to complete the difference, reconstruction, and baseline correction.

7. The single laser displacement excitation differential spectrometer according to claim 3, characterized in that: The linear array CCD (1205) of the split light path has 2048 pixels and a pixel size of 14x1000μm; the sensor has high quantum efficiency and image resolution in the near-infrared region, and has built-in TEC cooling, and PID temperature control is achieved through the thermoelectric cooling controller ADN8835.

8. The single laser displacement excitation differential spectrometer according to claim 1, characterized in that: The adjustable wavelength near-infrared laser light source (4000) includes a high-performance fiber-coupled semiconductor laser K785AFLFN-0.600W and an aluminum heat sink bonded with thermal grease below to help dissipate heat and achieve temperature control.

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