Spatial Heterodyne Dual-Channel Polarization Raman Spectroscopy Testing Device and Method

Abstract

The present invention relates to the field of spectral detection technology, and particularly to a spatial heterodyne dual-channel polarization Raman spectroscopy testing device and method, including: a laser for emitting a laser beam; a half-wave plate, a liquid crystal polarization rotator, a dichroic filter, and an imaging objective lens sequentially arranged along the optical path of the laser beam to the target to be measured; a spatial heterodyne dual-channel interference module arranged in the transmission optical path between the target to be measured and the dichroic filter; a controller; wherein, the liquid crystal polarization rotator is connected to the controller. The present invention uses a liquid crystal polarization rotator to replace the traditional rotating polarizer and wave plate, with fewer optical elements and no mechanical moving parts inside, realizing the polarization modulation of the excitation laser signal and the Stokes Raman spectrum, having a fast modulation speed, a stable structure, and good robustness; in addition, a spatial heterodyne interference dual-channel interference module is used to realize the synchronous detection of Raman spectra in two perpendicular polarization states, improving the detection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral detection, and particularly to a spatially heterodyne dual-channel polarization Raman spectroscopy testing device and method. Background Art

[0002] A polarization Raman spectrometer can obtain the Raman spectral information of the vertical polarization state of a target to be measured, and then can calculate the Raman spectra of two mutually perpendicular polarization states. From this, the polarization states of the molecular structures of different substances can be analyzed, and the polarization characteristics of the lattice structures of various crystals can be tested, which is widely used for the chemical and physical property analysis of various materials.

[0003] Usually, the method of rotating a linear polarizer, a wave plate, and a polarization beam splitting prism is used for polarization modulation. Only the Raman spectral signal of one polarization state can be tested at a time. To complete the detection of four polarization state Raman spectra, four tests are required, and the detection time is long. In addition, mechanical structures are used for adjustment, and the rotating mechanical structures increase the complexity and control complexity of the polarization Raman spectrometer, reducing the robustness and stability of the system. Summary of the Invention

[0004] Aiming at the defects and deficiencies in the prior art, the purpose of the present invention is to use a liquid crystal polarization rotator to replace the traditional rotating polarizer and wave plate, to realize the polarization modulation of the excitation laser signal and the Stokes Raman spectrum, with fast modulation speed, no mechanical moving parts inside, stable structure, and good robustness.

[0005] The present invention provides a spatially heterodyne dual-channel polarization Raman spectroscopy testing device, including:

[0006] A laser for emitting a laser beam;

[0007] A half-wave plate, a liquid crystal polarization rotator, a dichroic filter, and an imaging objective lens are sequentially arranged along the optical path of the laser beam to the target to be measured;

[0008] A spatially heterodyne dual-channel interference module is arranged in the transmission optical path between the target to be measured and the dichroic filter;

[0009] A controller;

[0010] Wherein, the liquid crystal polarization rotator is connected to the controller, and the liquid crystal polarization rotator is configured to be controlled by the controller to modulate the polarization direction of the laser, so that the Raman spectra incident on the spatially heterodyne dual-channel interference module are in different polarization directions.

[0011] Preferably, the liquid crystal polarization rotator responds to the controller and can adjust the polarization direction of the incident laser, wherein the adjustment range is 0° to 90°.

[0012] Preferably, the spatial heterodyne dual-path interference module includes a first beam splitter, a reflector, a reflection grating, a second beam splitter, a first polarizer, a second polarizer, a first area array camera, and a second area array camera;

[0013] Among them, the first beam splitter divides the incident light into two coherent light beams. The first coherent light beam is reflected by the reflector and then forms a first interference beam and a second interference beam through the second beam splitter. The second coherent light beam is reflected by the reflection grating and then forms a third interference beam and a fourth interference beam through the second beam splitter. Among them, the first interference beam and the fourth interference beam pass through the first polarizer at the same time and form interference fringes on the first area array camera, and the second interference beam and the third interference beam pass through the second polarizer at the same time and form interference fringes on the second area array camera.

[0014] Preferably, the first area array camera and the second area array camera are connected to the controller, so that the obtained interference fringes are inverted by the controller to obtain the Raman spectrum. Among them, the first area array camera obtains the polarized Raman spectrum SP(0° - 90°, 0°); the second area array camera obtains the polarized Raman spectrum SP(0° - 90°, 90°).

[0015] Preferably, the 1 / 2 wave plate is used to adjust the polarization direction of the laser emitted by the laser to 0°.

[0016] Preferably, the optical axis direction of the first polarizer is adjusted to 0°, and the optical axis direction of the second polarizer is adjusted to 90°.

[0017] Preferably, the dichroic filter is configured to reflect the laser emitted by the laser and transmit the Stokes Raman spectrum generated by the stimulated target to be measured.

[0018] Preferably, a Raman filter is provided between the dichroic filter and the spatial heterodyne dual-path interference module, and the Raman filter is used to filter out the Rayleigh scattering noise in the Stokes Raman spectrum excited by the target to be measured.

[0019] In the second aspect of the present invention, a technical solution is proposed, a spatial heterodyne dual-path polarized Raman spectrum testing method, using the above-mentioned spatial heterodyne dual-path polarized Raman spectrum testing device, including the following steps:

[0020] Step 1, adjusting parameters: making the polarization direction of the laser passing through the 1 / 2 wave plate be 0°, and controlling the liquid crystal polarization rotator through the controller to modulate the polarization direction of the laser passing through the liquid crystal polarization rotator to 0°;

[0021] Step 2: Laser emission: The laser emits laser light, which is modulated by a half-wave plate and a liquid crystal polarization rotator and then reflected by a dichroic filter to an imaging objective lens, and then focused on the target to be measured, so that the Stokes Raman spectrum excited by the target can pass through the dichroic filter and enter the spatial heterodyne dual-path interference module;

[0022] Step 3: Beam splitting and spectroscopy: The Stokes Raman spectrum forms two coherent light beams after passing through the first beam splitter. The first coherent light beam is reflected by a mirror and then passes through the second beam splitter to form a first interference beam and a second interference beam. The second coherent light beam is reflected by a reflection grating and then passes through the second beam splitter to form a third interference beam and a fourth interference beam. The formed interference beams form interference fringes on the area array camera and are inverted by the controller to obtain the first Raman spectrum;

[0023] Step 4: Polarization direction modulation: The controller controls the liquid crystal polarization rotator to modulate the polarization direction of the laser passing through the liquid crystal polarization rotator to 90°, and repeat Steps 2-3 to obtain the second Raman spectrum.

[0024] Preferably, in Step 3, the first interference beam and the fourth interference beam simultaneously pass through the first polarizer and then form interference fringes on the first area array camera, and the second interference beam and the third interference beam simultaneously pass through the second polarizer and then form interference fringes on the second area array camera;

[0025] The first area array camera obtains the polarized Raman spectrum SP(0°, 0°); the second area array camera obtains the polarized Raman spectrum SP(0°, 90°);

[0026] In Step 4, the first area array camera obtains the polarized Raman spectrum SP(90°, 0°); the second area array camera obtains the polarized Raman spectrum SP(90°, 90°).

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] The present invention uses a liquid crystal polarization rotator to replace the traditional rotating polarizer and wave plate, with fewer optical elements and no mechanical moving parts inside, realizing the polarization modulation of the laser signal for excitation and the Stokes Raman spectrum, having a fast modulation speed, a stable structure and good robustness; in addition, a spatial heterodyne interference dual-path interference module is used to realize the synchronous detection of Raman spectra in two perpendicular polarization states, improving the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are not intended to be drawn to scale. In the drawings, each identical or approximately identical component shown in each figure may be represented by the same reference numeral. For clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the drawings, where:

[0030] Figure 1 is a schematic structural diagram of a spatially heterodyne dual-channel polarization Raman spectroscopy test device provided by an embodiment of the present invention; Detailed implementation manners

[0031] To better understand the technical content of the present invention, specific embodiments are hereby given and described in conjunction with the accompanying drawings as follows.

[0032] As Figure 1 shown, the spatially heterodyne dual-channel polarization Raman spectroscopy test device includes: a laser 1, a half-wave plate 2, a liquid crystal polarization rotator 3, an imaging objective 4, a dichroic filter 5, a Raman filter 6, and a spatially heterodyne dual-channel interference module 7 arranged in sequence along the optical axis.

[0033] Among them, in order to realize the synchronous detection of Raman spectra in two perpendicular polarization states, the spatially heterodyne dual-channel interference module 7 is composed of a first beam splitter 71, a reflector 72, a reflection grating 73, a second beam splitter 74, a first polarizer 75, a second polarizer 76, a first area array camera 77, and a second area array camera 78; wherein, a controller 8 is respectively connected to the liquid crystal polarization rotator 3, the first area array camera 77, and the second area array camera 78.

[0034] Specifically, the polarization direction is adjusted by the half-wave plate 2, especially the polarization direction of the laser emitted by the laser 1 is adjusted to 0°.

[0035] Furthermore, the liquid crystal polarization rotator 3 can adjust the polarization direction of the incident laser, and the adjustment range is 0° to 90°. By controlling the voltage or current of the liquid crystal polarization rotator 3 by the controller 8, the polarization direction of the incident laser can be adjusted.

[0036] Furthermore, in order to obtain Raman spectra in two perpendicular polarization states, the transmission axis direction of the first polarizer 75 is adjusted to 0°. The transmission axis direction of the second polarizer 76 is adjusted to 90°. In this way, the first interference beam and the fourth interference beam pass through the first polarizer at the same time and form a first interference fringe on the first area array camera, and the second interference beam and the third interference beam pass through the second polarizer at the same time and form a second interference fringe on the second area array camera. The first interference fringe and the second interference fringe form a perpendicular polarization state Raman spectrum.

[0037] Among them, the dichroic filter 5 reflects the laser emitted by the laser 1 and transmits the Stokes Raman spectrum generated by the target under excitation; the Raman filter 6 is used to filter out Rayleigh scattering noise.

[0038] In a preferred embodiment, the optical elements are coaxial and at the same height relative to the substrate, that is, coaxial and at the same height relative to the optical platform or the instrument base;

[0039] In a specific embodiment, the optical path of the spatial heterodyne dual-path polarization Raman spectroscopy testing device is as follows: The laser 1 emits laser light, which first passes through a half-wave plate 2 to adjust the polarization direction, and then the laser light passes through a liquid crystal polarization rotator 3 for polarization modulation. Subsequently, the modulated laser signal is reflected by a dichroic filter 5 to an imaging objective 4 and then focused on the target to be measured. The Stokes Raman spectrum excited by the target can be collimated by the imaging objective 4, then can transmit through the dichroic filter 5, and then passes through a Raman filter 6 to filter out Rayleigh scattering noise and enters the spatial heterodyne dual-path interference module 7. Subsequently, the light beam first passes through a first beam splitter 71 to form two coherent light beams. The first coherent light beam is reflected by a mirror 72 and then passes through a second beam splitter 74 to form a first interference beam and a second interference beam. The second coherent light beam is reflected by a reflection grating 73 and then passes through the second beam splitter 74 to form a third interference beam and a fourth interference beam. Among them, the first interference beam and the fourth interference beam simultaneously pass through a first polarizer 75 to form interference fringes on a first area array camera 77, and the second interference beam and the third interference beam simultaneously pass through a second polarizer 76 to form interference fringes on a second area array camera 78.

[0040] Specifically, the testing steps are as follows:

[0041] In the first step, the laser 1 emits laser light, which first passes through a half-wave plate 2 to adjust the polarization direction, and the polarization direction becomes 0°. Then the laser light passes through a liquid crystal polarization rotator 3 for modulation, and first modulates the polarization direction of the output laser light to 0°.

[0042] In the second step, subsequently, the modulated laser signal is reflected by a dichroic filter 5 to an imaging objective 4 and then focused on the target to be measured. The Stokes Raman spectrum excited by the target can transmit through the dichroic filter 5, and then passes through a Raman filter 6 to filter out excess Rayleigh scattering noise, and then enters the spatial heterodyne dual-path interference module 7.

[0043] In the third step, subsequently, the light beam first passes through a first beam splitter 71 to form two coherent light beams. The first coherent light beam is reflected by a mirror 72 and then passes through a second beam splitter 74 to form a first interference beam and a second interference beam. The second coherent light beam is reflected by a reflection grating 73 and then passes through the second beam splitter 74 to form a third interference beam and a fourth interference beam. Among them, the first interference beam and the fourth interference beam simultaneously pass through a first polarizer 75 to form interference fringes on a first area array camera 77, and the second interference beam and the third interference beam simultaneously pass through a second polarizer 76 to form interference fringes on a second area array camera 78. The controller 8 inversely calculates the recorded interference fringes to obtain the Raman spectrum, where the first area array camera obtains the polarization Raman spectrum SP(0°, 0°); the second area array camera obtains the polarization Raman spectrum SP(0°, 90°);

[0044] In the fourth step, the controller 8 modulates the polarization direction of the laser to 90° through the liquid crystal polarization rotator 3, repeats the third step, and then the controller 8 inversely calculates the obtained interference fringes to obtain the Raman spectrum, where the first area array camera obtains the polarized Raman spectrum SP9(0°, 0°); the second area array camera obtains the polarized Raman spectrum SP(90°, 90°).

[0045] Combined with the above embodiments, the present invention uses a liquid crystal polarization rotator to replace the traditional rotating polarizer and wave plate. It has fewer optical elements and no mechanical moving parts inside, realizes the polarization modulation of the excitation laser signal and the Stokes Raman spectrum, has a fast modulation speed, a stable structure, and good robustness; in addition, a spatial heterodyne interference dual-path interference module is used to realize the synchronous detection of Raman spectra in two perpendicular polarization states, improving the detection efficiency.

[0046] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to what is defined by the claims.

Claims

1. A spatial heterodyne dual-channel polarization Raman spectroscopy testing device, characterized in that, Comprising: A laser for emitting a laser beam; A half-wave plate (2), a liquid crystal polarization rotator (3), a dichroic filter (5), and an imaging objective lens (4) sequentially arranged along the optical path of the laser beam to the target to be measured; A spatial heterodyne dual-path interference module (7) arranged in the transmission optical path between the target to be measured and the dichroic filter (5); A controller (8); Wherein, the liquid crystal polarization rotator (3) is connected to the controller (8), and the liquid crystal polarization rotator (3) is configured to be controlled by the controller (8) to modulate the polarization direction of the laser, so that the Raman spectra incident on the spatial heterodyne dual-path interference module (7) are in different polarization directions; The liquid crystal polarization rotator (3) can adjust the polarization direction of the incident laser in response to the controller (8), wherein the adjustment range is 0° to 90°; The spatial heterodyne dual-path interference module (7) includes a first beam splitter (71), a reflector (72), a reflection grating (73), a second beam splitter (74), a first polarizer (75), a second polarizer (76), a first area array camera (77), and a second area array camera (78); Wherein, the first beam splitter (71) divides the incident light into two coherent light beams. The first coherent light beam forms a first interference beam and a second interference beam after being reflected by the reflector (72) and then passing through the second beam splitter (74). The second coherent light beam forms a third interference beam and a fourth interference beam after being reflected by the reflection grating (73) and then passing through the second beam splitter (74). The first interference beam and the fourth interference beam form interference fringes on the first area array camera (77) after passing through the first polarizer (75) at the same time, and the second interference beam and the third interference beam form interference fringes on the second area array camera (78) after passing through the second polarizer (76) at the same time; The first area array camera (77) and the second area array camera (78) are connected to the controller (8), so that the obtained interference fringes are inversed by the controller (8) to obtain Raman spectra, wherein the first area array camera (77) obtains a polarized Raman spectrum SP(0° - 90°, 0°); the second area array camera obtains a polarized Raman spectrum SP(0° - 90°, 90°); The optical axis direction of the first polarizer (75) is adjusted to 0°, and the optical axis direction of the second polarizer (76) is adjusted to 90°.

2. The spatially heterodyne dual-channel polarization Raman spectroscopy testing device according to claim 1, wherein The half-wave plate (2) is used to adjust the polarization direction of the laser emitted by the laser (1) to 0°.

3. The spatially heterodyne dual-channel polarization Raman spectroscopy test device according to claim 1, characterized in that, The dichroic filter (5) is configured to reflect the laser emitted by the laser (1) and transmit the Stokes Raman spectrum generated by the target to be measured under excitation.

4. The spatially heterodyne dual-path polarization Raman spectroscopy test device according to any one of claims 1-3, characterized in that, A Raman filter (6) is provided between the dichroic filter (5) and the spatial heterodyne dual-path interference module (7), and the Raman filter (6) is used to filter out the Rayleigh scattering noise in the Stokes Raman spectrum excited by the target to be measured.

5. A spatial heterodyne dual-channel polarization Raman spectroscopy testing method, characterized in that, Using the spatial heterodyne dual-path polarized Raman spectrum testing device according to any one of claims 1 - 4, comprising the following steps: Step 1, Adjust parameters: Make the polarization direction of the laser passing through the half-wave plate (2) be 0°, and control the liquid crystal polarization rotator (3) through the controller (8) to modulate the polarization direction of the laser passing through the liquid crystal polarization rotator (3) to 0°; Step 2, Emit laser: The laser is emitted by the laser (1), and after being modulated by the half-wave plate (2) and the liquid crystal polarization rotator (3), it is reflected by the dichroic filter (5) to the imaging objective lens (4), and then focused on the target to be measured, so that the Stokes Raman spectrum excited by the target can pass through the dichroic filter (5) and enter the spatial heterodyne dual-path interference module (7); Step 3, Beam split and spectrum: The Stokes Raman spectrum forms two coherent light beams after passing through the first beam splitter (71). The first coherent light beam is reflected by the mirror (72) and then passes through the second beam splitter (74) to form the first interference light beam and the second interference light beam. The second coherent light beam is reflected by the reflection grating (73) and then passes through the second beam splitter (74) to form the third interference light beam and the fourth interference light beam. The formed interference light beams form interference fringes on the area array camera and are inverted by the controller (8) to obtain the first Raman spectrum; Step 4, Polarization direction modulation: The controller (8) controls the liquid crystal polarization rotator (3) to modulate the polarization direction of the laser passing through the liquid crystal polarization rotator (3) to 90°, and repeat Steps 2 - 3 to obtain the second Raman spectrum.

6. The spatially heterodyne dual-channel polarization Raman spectroscopy testing method according to claim 5, characterized in that In Step 3, the first interference light beam and the fourth interference light beam pass through the first polarizer (75) at the same time and form interference fringes on the first area array camera (77), and the second interference light beam and the third interference light beam pass through the second polarizer (76) at the same time and form interference fringes on the second area array camera (78); The first area array camera obtains the polarized Raman spectrum SP(0°, 0°); the second area array camera obtains the polarized Raman spectrum SP(0°, 90°); In Step 4, the first area array camera obtains the polarized Raman spectrum SP(90°, 0°); the second area array camera obtains the polarized Raman spectrum SP(90°, 90°).

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