CN114719983B - Space heterodyne Raman spectrometer - Google Patents

Abstract

The present invention provides a spatial heterodyne Raman spectrometer, comprising: a light source device, a collimating lens, a Raman filter group, an interference device and an imaging device; the light source device emits a laser and then irradiates the sample, and the sample emits a scattered light beam after being stimulated; the scattered light beam passes through the collimation of the collimating lens and the filtering of the Raman filter group and enters the refractive component to be divided into two beams; one collimated light beam is incident on the plane reflector-echelon grating of the plane reflector after being refracted by the refractive component, and is reflected, and the reflected light beam enters the refractive component; the other collimated light beam is incident on the plane reflector-echelon grating of the plane reflector-echelon grating through a prism after being refracted by the refractive component, and is diffracted, the diffracted light beam passes through the prism and enters the refractive component to interfere with the reflected light beam, and the interference light beam enters the imaging device to obtain a spatial heterodyne Raman signal. The present invention has the advantages of wide measurement band range, simple optical path adjustment, compact structure, etc.

Description

Spatial heterodyne Raman spectrometer

Technical Field

The invention relates to the technical field of spectrum analysis instruments, and in particular to a spatial heterodyne Raman spectrometer.

Background Art

Raman scattering is a natural phenomenon where light is inelastically scattered by vibrating molecules with instantaneous dipole moments. During Raman scattering, a photon contributes energy equal to the molecular vibrational mode, leaving behind an excited molecule and a photon with energy loss equal to the vibrational energy gap. Because each molecule has a unique set of vibrational modes, Raman spectroscopy can be used to unambiguously identify a wide range of compounds, including minerals, organic matter, and biomarkers.

Harlander developed a new type of spatial interferometer, called the spatial heterodyne spectrometer (SHS), which is a variation of the Michelson interferometer that can measure high-resolution scattered light spectra in a compact light footprint system. In the spatial heterodyne spectrometer, the moving mirror of the Michelson interferometer is replaced by a fixed diffraction grating. However, since the diffraction gratings are placed in the two interference arms of the interferometer, and the optical path has strict equal requirements for the position and angle of the diffraction grating, the optical path adjustment of the interferometer becomes a difficult problem. In addition, since both arms use gratings for diffraction, the wavelength range measured by the detector is very narrow.

Summary of the invention

In view of the above problems, the purpose of the present invention is to propose a spatial heterodyne Raman spectrometer, which increases the range of the measurement band by splicing a plane mirror and a medium-step grating. The present invention has a compact structure and relatively simple optical path adjustment.

To achieve the above object, the present invention adopts the following specific technical solutions:

The present invention provides a spatial heterodyne Raman spectrometer, comprising: a light source device, a collimating lens, a Raman filter group, an interference device and an imaging device;

The interference device includes a refractive component, a prism and a plane reflector-echelle grating;

The light source device emits laser light and then irradiates the sample. The sample is stimulated to emit a scattered light beam. The scattered light beam is collimated by the collimating lens and filtered by the Raman filter group, then enters the refractive component and is divided into two beams.

A collimated light beam is refracted by the refraction assembly and then incident on the plane reflector-echelon grating, where it is reflected, and the reflected light beam enters the refraction assembly;

Another collimated light beam is refracted by the refractive component and then passes through a prism to be incident on the plane reflector-echelle grating where it is diffracted. The diffracted light beam passes through the prism into the refractive component to interfere with the reflected light beam. The interference light beam enters the imaging device to obtain a spatial heterodyne Raman signal.

Preferably, the plane reflector-echelle grating is an integrated structure, comprising two columns, one column is the plane reflector, and the other column is the echelle grating.

Preferably, the refractive assembly comprises a first reflector, a second reflector and a beam splitting prism; the first reflector and the second reflector are respectively fixed on two side surfaces of the beam splitting prism and are symmetrical about a beam splitting plane in the beam splitting prism.

Preferably, the collimated light beam is split into two beams by the beam splitting surface;

A collimated light beam enters the plane reflector after being reflected by the first reflector, and the reflected light beam enters the beam splitter prism after being reflected back;

Another collimated light beam is reflected by the second reflector and then refracted by the prism before entering the echelle grating for diffraction. The diffracted light beam enters the beam splitting prism again.

The reflected and diffracted beams interfere in the beam-splitting prism.

Preferably, the imaging device comprises an imaging lens group and an area array detector, wherein the imaging lens group is located directly in front of the area array detector; the interference light beam is refracted by the imaging lens group and then forms an image in the area array detector.

Preferably, the light source device comprises: a laser and a converging lens, wherein the converging lens is located directly in front of the laser, and after the laser is emitted, the laser is converged by the converging lens and then emitted into the sample.

Preferably, the sample is located at the front focus of the collimating lens.

Compared with the existing technology, the present invention has the following advantages by splicing a plane reflector and an echelle grating:

1. The present invention adopts a plane reflector-echelon grating to realize spatial heterodyne measurement. The two columns of plane reflector and echelon grating are equivalent to two interference arms, which can realize the simultaneous adjustment of the angle and distance of the two interference arm gratings, avoiding the problem of complex optical path calibration.

2. The plane reflector and the echelle grating are manufactured on the same blank, which improves the stability of the optical path. The grating surface of the echelle grating is not parallel to the reflecting surface of the plane reflector and has a certain angle, which replaces the traditional double grating measurement, increases the light flux and measurement band, and avoids interference between the echelle levels.

3. The reflector is glued to the beam splitter prism, and there is no need to coat the beam splitter prism with a reflective film, which simplifies the manufacturing process and improves stability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of the optical path structure of a spatial heterodyne Raman spectrometer provided according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a refraction component in a spatial heterodyne Raman spectrometer provided according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of the structure of a plane reflector-echelle grating in a spatial heterodyne Raman spectrometer provided according to an embodiment of the present invention.

The figure marks include: laser 1, converging lens 2, collimating lens 3, Raman filter group 4, first reflector 501 and second reflector 502, first mirror surface 5011, second mirror surface 5022, third mirror surface 5033, beam splitting surface 5044, beam splitting prism 6, prism 7, plane reflector-medium-step grating 8, plane reflector 8-1, medium-step grating 8-2, imaging lens group 9, area array detector 10 and sample 11.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

FIG. 1 shows the optical path structure of a spatial heterodyne Raman spectrometer provided according to an embodiment of the present invention.

As shown in FIG. 1 , the spatial heterodyne Raman spectrometer provided by the embodiment of the present invention includes: a light source device, a collimating lens 3 , a Raman filter set 4 , an interference device and an imaging device.

The light source device comprises: a laser 1 and a converging lens 2 ; the converging lens 2 is arranged behind the laser 1 , and the converging lens 2 is used to converge the laser light emitted by the laser 1 and then inject it into the sample 11 .

After being excited, the sample 11 emits a scattered light beam.

The collimating lens 3 is used to collect the scattered light beam containing the Raman signal emitted by the sample 11 and collimate it, and the collimated parallel light beam is emitted into the Raman filter set 4 .

The Raman filter set 4 is used to filter the Rayleigh scattered light and other wavelength bands of fluorescence and stray light emitted by the sample 11. The collimated light beam after filtering is injected into the interference device.

The interference device comprises: a refractive component, a prism 7 and a plane reflector-echelon grating 8; the prism 7 is used to expand the field angle of the instrument and increase the range of off-axis light that can be detected by the instrument.

FIG. 2 shows the structure of a refractive assembly according to an embodiment of the present invention.

As shown in Figure 2, the refractive assembly includes: a first reflector 501, a second reflector 502 and a beam splitter prism 6; the first reflector 501 and the second reflector 502 are symmetrically fixed on the first mirror surface 5011 and the second mirror surface 5022 of the beam splitter prism 6, respectively, and are symmetrical about the beam splitting surface 5044 of the beam splitter prism 6, and the beam splitting surface 5044 is perpendicular to the third mirror surface 5033.

FIG. 3 shows the structure of a plane reflector-echelle grating provided according to an embodiment of the present invention.

As shown in FIG3 , the plane reflector-echelle grating 8 includes two columns, one column is the plane reflector 8-1, and the other column is the echelle grating 8-2. The plane reflector and the echelle grating can be adjusted at the same time to avoid the problem of difficulty in adjusting the optical path. The plane reflector 8-1 and the echelle grating 8-2 in the plane reflector-echelle grating 8 are an integrated structure and are manufactured from the same blank. The grating surface of the echelle grating 8-2 is not parallel to the reflecting surface of the plane reflector 8-1 and forms a certain angle θ, thereby increasing the light flux and the measurement band, while avoiding interference between the echelle levels. The engraved line direction of the echelle grating 8-2 is parallel to the z-axis.

The prism 7 is located in front of the echelle grating 8 - 2 in the plane reflector-echelle grating 8 .

After the collimated light beam enters the interference device, it enters the beam splitting prism 6 perpendicular to the first mirror surface 5011, and the beam splitting prism 6 splits the collimated light beam into two beams;

After a collimated light beam is reflected by the first reflector 501 , it passes through the prism 7 and enters the plane reflector 8 - 1 in the plane reflector-echelle grating 8 . The reflected light beam then enters the beam splitting prism 6 perpendicularly to the third mirror surface 5033 .

Another collimated light beam is reflected by the second reflector 502 and passes through the prism 7 to enter the echelle grating 8-2 in the plane reflector-echelle grating 8, and the diffracted light beam after emission is perpendicular to the third mirror 5033 and enters the beam splitting prism 6 for the second time.

After the reflected light beam and the diffracted light beam interfere with each other in the beam splitting prism 6, an interference light beam is formed and enters the imaging device.

The imaging device comprises: an imaging lens group 9 and an area array detector 10; the imaging lens group 9 is located directly in front of the area array detector.

The interference light beam is refracted by the imaging lens group 9 and enters the area array detector 10 for imaging, thereby obtaining a spatial heterodyne Raman signal.

The optical path of the present invention is as follows: the laser 1 emits laser light and passes through the converging lens 2 to irradiate the sample 11; the sample 11 emits a scattered light beam after being stimulated, and the scattered light beam is collimated into parallel light by the collimating lens 3, and after passing through the Raman filter group 4 to filter out stray light and other signal light, it is emitted into the beam splitting prism 6 and is split into two collimated light beams by the beam splitting surface 5044;

A collimated light beam is reflected by the first reflector 501 and then passes through the prism 7 to enter the plane reflector 8 - 1 in the plane reflector-echelle grating 8 . The reflected light beam enters the beam splitting prism 6 perpendicularly to the third mirror surface 5033 .

Another collimated light beam is reflected by the second reflector 502 and then passes through the prism 7 to enter the echelle grating 8 - 2 in the plane reflector-echelle grating 8 . The diffracted light beam enters the beam splitting prism 6 perpendicular to the third mirror 5033 .

The reflected light beam and the diffracted light beam interfere with each other in the beam splitting prism 6 to form an interference light beam, which enters the imaging lens group 9, and after being refracted by the imaging lens group 9, enters the area array detector 10 for imaging.

Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims (6)

1. A spatially heterodyne raman spectrometer, comprising: the device comprises a light source device, a collimating lens, a Raman filter set, an interference device and an imaging device;

the interference device comprises a refraction component, a prism and a plane reflector-echelle grating;

The light source device emits laser and then emits the laser into a sample, and the sample emits scattered light beams after being stimulated; the scattered light beams enter the refraction component to be split into two beams after passing through collimation of the collimating lens and filtering of the Raman filter set;

A beam of collimated light beam is refracted by the refraction component and then is incident to the plane mirror of the plane mirror-echelle grating for reflection, and the reflected light beam enters the refraction component;

The other beam of collimated light beam is refracted by the refraction component and then enters the plane reflector-echelle grating through the prism to be diffracted by the echelle grating of the echelle grating, the diffracted light beam enters the refraction component through the prism to interfere with the reflected light beam, and the interfered light beam enters the imaging device to obtain a spatially heterodyne Raman signal;

the plane reflector-echelle grating is of an integrated structure and comprises two columns, wherein one column is a plane reflector, and the other column is an echelle grating.

2. The spatially heterodyne raman spectrometer of claim 1, wherein the refractive assembly comprises a first mirror, a second mirror, and a beam splitting prism; the first reflecting mirror and the second reflecting mirror are respectively fixed on two side surfaces of the beam splitting prism and are symmetrical relative to the beam splitting surface in the beam splitting prism.

3. The spatially heterodyne raman spectrometer of claim 2, wherein the collimated beam is split into two beams by the beam splitting plane;

a beam of collimated light enters the plane reflecting mirror after being reflected by the first reflecting mirror, and the reflected light enters the beam splitting prism after being reflected back;

The other collimated beam is reflected by the second reflecting mirror, is refracted by the prism and enters the echelle grating to be diffracted, and the diffracted beam enters the beam splitting prism again;

the reflected light beam and the diffracted light beam interfere in the beam splitting prism.

4. A spatially heterodyne raman spectrometer according to claim 3 wherein the imaging device comprises an imaging lens group and an area array detector, the imaging lens group being located directly in front of the area array detector; the interference light beam is refracted by the imaging lens group and then imaged in the area array detector.

5. The spatially heterodyne raman spectrometer of claim 4, wherein the light source device comprises: the laser device comprises a laser device and a converging lens, wherein the converging lens is positioned right in front of the laser device, and the laser device emits laser and then is converged by the converging lens to be injected into a sample.

6. The spatially heterodyne raman spectrometer of claim 5, wherein the sample is located at a front focal point of the collimating lens.