CN104422680A - Raman signal acquisition device - Google Patents

Abstract

The invention relates to a Raman signal acquisition device, which can efficiently collect Raman signals excited by samples, and at the same time has the functions of focusing laser light on the sample, filtering out interference signals such as stray light and Rayleigh lines, and has a small volume , High transmission efficiency and so on. Combined with lasers and spectrometers, it can form a Raman spectrometer. Using ultraviolet optical components, combined with ultraviolet lasers and ultraviolet spectrometers, can form an ultraviolet Raman spectrometer.

Description

A Raman signal acquisition device

technical field

The invention relates to a Raman signal acquisition device, which can efficiently collect Raman signals excited by samples, and has the functions of focusing laser light on samples and filtering out interference signals such as stray light and Rayleigh lines. Combined with lasers and spectrometers, it can form a Raman spectrometer. Using ultraviolet optical components, combined with ultraviolet lasers and ultraviolet spectrometers, can form an ultraviolet Raman spectrometer.

Background technique

Raman spectroscopy, known as molecular fingerprinting, allows fast and accurate analysis of samples. Raman spectroscopy is widely used in the detection of food, security inspection, document inspection materials, minerals, environment, chemistry, materials, biology and other fields. Sample types include solid, powder, liquid, gas, interface, colloid and other forms. At present, the importance of Raman spectroscopy is gradually being recognized by everyone, and its application is becoming more and more extensive.

The principle of Raman spectroscopy is: a photon interacts with a molecule. If the energy of the molecule absorbing the photon transitions from a low energy level in a vibration or rotational state to a high energy level, then according to the law of energy conservation, the energy lost by the photon and the vibration or vibration of the molecule The energy required for the energy level transition of the rotation is equal, and the vibration frequency changes after the photon loses energy. The change law of the photon frequency is recorded by the Raman spectrometer, which is the Raman spectrum.

The probability of Raman scattering phenomenon is very low. 10 ⁸ photons interact with sample molecules, and at most only one photon can form Raman scattering. Raman scattered photons, and realize the high-efficiency transmission of Raman signals and other functions.

There are currently three types of Raman spectrometers on the market: one is a three-grating Raman spectrometer (patent No. 98113710.5), which uses a lens or a reflective ellipsoid to collect Raman signals, and the first two gratings are filtered by addition or subtraction The interference of stray light caused by Rayleigh scattering is suitable for excitation light sources in various bands such as deep ultraviolet, ultraviolet, visible, and near-infrared. Especially in the ultraviolet region, a reflective ellipsoid mirror (patent No. 98113709.1) is used to collect Raman signals, which can Improve collection efficiency and eliminate the influence of chromatic aberration. However, the three-grating Raman spectrometer also has the disadvantages of large volume, low Raman signal transmission efficiency, and difficulty in debugging and maintenance. The second is the confocal Raman spectrometer used in the laboratory. It uses a microscope to collect Raman signals and filters out the interference of stray light. It has the advantages of small size, high collection and transmission efficiency, but the volume of the microscope used for collection is relatively large. Large, high cost, and the acquisition system and filter system are independent structures, which must be purchased together with spectrometers from specific manufacturers during use, and it is impossible to build Raman spectrometers according to the needs of users. The third is the fiber optic Raman spectrometer, which uses optical fiber to collect Raman signals, and uses Raman filters to filter out stray light. It has the advantages of small size, portability, and remote measurement. However, the optical fiber transmission efficiency is low, it is not suitable for the ultraviolet band, and the confocal function cannot be realized.

Contents of the invention

The invention provides a Raman signal acquisition device, which comprises a hollow cylindrical container with two openings, and an objective lens and a focusing lens are respectively arranged at the two opening ends of the cylindrical container, and the objective lens and the focusing lens are arranged on the same optical axis, and the objective lens and the focusing lens are arranged on the same optical axis. A filter is provided in the cylindrical container between the focusing lenses; a through hole is opened on the side wall of the cylindrical container as a light entrance hole, and the excitation light emitted by the excitation light source enters the cylindrical container through the light entrance hole. The reflection mirror in the cylindrical container is reflected to the surface of the filter, and then reflected by the filter to the objective lens, which is focused on the sample to be measured by the objective lens, and the Raman signal and Rayleigh signal scattered by the sample to be measured and the reflected The excitation light is collected by the objective lens and filtered by the filter, the reflected light and the scattered Rayleigh signal are filtered out, and the Raman signal passes through the filter and reaches the focusing lens for focusing.

Technical solution: the geometric center of the optical filter is on the optical axis of the objective lens and the focusing lens; the angle between the optical axis of the optical filter and the optical axis of the objective lens and the focusing lens is less than 10 degrees; the mirror reflects the excitation light to the optical filter center, and the mirror is not on the optical axis of the objective lens and the focusing lens, and does not affect the transmission of light between the objective lens and the optical filter; the optical filter reflects the excitation light reflected by the mirror to the objective lens along the optical axis of the objective lens; A spectrometer is arranged on one side of the focusing lens on the Raman signal acquisition device, and the focusing lens focuses the Raman signal into the light entrance hole of the spectrometer; a second filter can be added between the filter and the focusing lens to Optimize the filtering effect of Rayleigh signal and reflected light, the angle between the optical axis of the filter and the optical axis of the focusing lens is less than 10 degrees.

Beneficial effects: the present invention provides a Raman signal collection device, which can efficiently collect Raman signals excited by samples, and has the functions of focusing laser light on samples and filtering out interference signals such as stray light and Rayleigh lines. The backscattering method is used to collect Raman signals, and the collection efficiency is high; the filter not only has the function of a reflector, but also filters out stray light, which reduces the use of optical components and improves the light transmission efficiency. The main part is a fixed hollow cylindrical container, which is small in size, light in weight, and stable in structure, which is convenient for coupling with the spectrometer. It is suitable for Raman spectrum testing with fixed excitation wavelength, including Raman spectrum testing in ultraviolet, visible, and near-infrared bands.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic diagram of the structure of the present invention.

Fig. 2 is a specific application example of the present invention: a Raman spectrum diagram of diamond.

In the figure 1. light entrance hole, 2. small mirror, 3. optical filter, 4. objective lens, 5. focusing lens, 6. device housing, 7. sample.

Detailed ways

In Fig. 1, a kind of Raman signal collecting device comprises the hollow cylindrical container 6 of two end openings, and two open ends of cylindrical container 6 are respectively provided with objective lens 4, focusing lens 5, objective lens 4 and focusing lens 5 It is arranged on the same optical axis, and an optical filter 3 is arranged in the cylindrical container between the objective lens 4 and the focusing lens 5;

A through hole is opened on the side wall of the cylindrical container 6 as the light entrance hole 1 (between the objective lens 4 and the optical filter 3), and the excitation light emitted by the excitation light source enters the cylindrical container 6 through the light entrance hole 1, It is reflected to the surface of the filter 3 through the reflector 2 (between the objective lens 4 and the filter 3) provided in the cylindrical container 6, and then reflected to the objective lens 4 by the filter 3, and then focused by the objective lens 4 to the surface of the optical filter 3. On the test sample 7, the Raman signal, the Rayleigh signal and the reflected excitation light scattered by the test sample 7 are all collected by the objective lens 4 and filtered by the filter 3, and the reflected light and the scattered Rayleigh signal are filtered out, The Raman signal passes through the optical filter 3 and reaches the focusing lens 5 for focusing.

The geometric center of the optical filter 3 is on the optical axis of the objective lens 4 and the focusing lens 5;

The angle between the optical axis of the optical filter 3 and the optical axis of the objective lens 4 and the focusing lens 5 is less than 10 degrees, the efficiency of the optical filter 3 to reflect the excitation light is greater than 90%, and the efficiency of filtering out the interference signal is about 99.99%. Raman Signal transmittance greater than 80%;

The mirror 2 reflects the excitation light to the center of the optical filter 3 , and the mirror is not on the optical axis of the objective lens 4 and the focusing lens 5 , and does not affect the light transmission between the objective lens 4 and the optical filter 3 .

The optical filter 3 reflects the excitation light reflected by the mirror 2 to the objective lens 4 along the optical axis of the objective lens 4, so that the use of the objective lens 4 achieves a common optical axis effect.

A spectrometer is arranged on the outside of the focusing lens 5 on the Raman signal collection device (that is, the side away from the hollow cylindrical container 5-6), and the focusing lens 5 focuses the Raman signal into the light entrance hole of the spectrometer.

A second optical filter can be added between the optical filter 3 and the focusing lens 5 to optimize the filtering effect of the Rayleigh signal and reflected light, and the angle between the optical axis of the optical filter and the optical axis of the focusing lens 5 is less than 10° Spend.

In the embodiment shown in Figure 2, the Raman spectrum of diamond is recorded, the excitation light source is a 355nm solid-state laser, the abscissa in the figure is the Raman frequency shift, and the experimental conditions are: excitation wavelength, 355nm solid-state laser.

Claims (7)

1. A Raman signal acquisition device, comprising a hollow cylindrical container (6) with two open ends, characterized in that: two open ends of the cylindrical container (6) are respectively provided with an objective lens (4), a focusing lens ( 5), the objective lens (4) and the focusing lens (5) are arranged on the same optical axis, and a filter (3) is arranged in the cylindrical container (6) between the objective lens (4) and the focusing lens (5); A through hole is opened on the side wall of the cylindrical container (6) as the light entrance hole (1). The excitation light emitted by the excitation light source enters the cylindrical container (6) through the light entrance hole (1), and passes through the The reflection mirror (2) in the cylindrical container (6) is reflected to the surface of the optical filter (3), and then reflected by the optical filter (3) to the objective lens (4), and the objective lens (4) focuses on the sample to be tested (7 ), the Raman signal, Rayleigh signal and reflected excitation light scattered by the sample to be measured (7) are collected by the objective lens (4) and filtered by the filter (3), and the reflected light and scattered Rayleigh signal After being filtered out, the Raman signal passes through the filter (3) and reaches the focusing lens (5) for focusing. 2. The Raman signal acquisition device according to claim 1, characterized in that: the geometric center of the optical filter (3) is on the optical axis of the objective lens (4) and the focusing lens (5). 3. The Raman signal acquisition device according to claim 1 or 2, characterized in that: the angle between the optical axis of the optical filter (3) and the optical axis of the objective lens (4) and the focusing lens (5) is less than 10 Spend. 4. The Raman signal acquisition device according to claim 1, characterized in that: the mirror (2) reflects the laser light to the center of the filter (3), and the mirror (2) is not between the objective lens (4) and the focusing The optical axis of the lens (5) does not affect the transmission of light between the objective lens (4) and the optical filter (3). 5. The Raman signal acquisition device according to claim 1, characterized in that: the filter (3) reflects the excitation light reflected by the mirror (2) to the objective lens along the optical axis of the objective lens (4) (4). 6. The Raman signal acquisition device according to claim 1, characterized in that: a spectrometer is arranged outside one side of the focusing lens (5) on the Raman signal acquisition device, and the focusing lens (5) focuses the Raman signal to in the light entrance of the spectrometer. 7. The Raman signal acquisition device according to claim 1, characterized in that: a second filter can be added between the filter (3) and the focusing lens (5) to optimize the Rayleigh signal and reflection For the filtering effect of light, the included angle between the optical axis angle of the optical filter and the optical axis of the focusing lens (5) is less than 10 degrees.