CN104316506B - Raman probe and Raman signal detection system and method capable of focusing automatically - Google Patents

Abstract

The invention provides a Raman probe and a Raman signal detection system and method capable of autofocusing. The system includes a Raman probe, a numerically controlled displacement sample stage, and a controller; the Raman probe is installed on a numerically controlled displacement sample stage, and the The Raman probe and the CNC displacement sample stage can move relatively, and the signal output side of the Raman probe is equipped with a light intensity detection unit; the output end of the light intensity detection unit is connected to the controller, and the controller judges whether the sample is At the focal point, if it is not at the focal point, an instruction is issued to control the CNC displacement sample stage to make a corresponding displacement, and this is repeated several times until the sample is adjusted at the focal length of the Raman probe or within the set accuracy range. The invention can focus precisely, and maximize and stabilize the Raman signal; compared with the existing commercial probe with a fixed-distance sleeve, the invention can directly detect samples with rough and uneven surfaces without sample pretreatment.

Description

Raman probe and autofocusable Raman signal detection system and method

technical field

The present invention relates to the field of optical machinery and instrumentation, in particular to a Raman probe, and an autofocusable Raman signal detection system and method used in laser Raman spectrum measurement or Raman spectrometer.

Background technique

The portable Raman spectrometer has the advantages of small size, fast speed, and on-site operation, and has broad application prospects in the fields of medicine, food safety, and security inspection. A portable Raman spectrometer generally consists of a small semiconductor laser, a Raman fiber probe, a spectrometer and a computer system. Among them, the function of the Raman probe mainly has two aspects. On the one hand, it efficiently transmits and focuses the laser light on the sample to be detected, and on the other hand, it efficiently collects and filters Raman scattering signals and transmits them to the spectrometer.

The excitation efficiency of Raman spectroscopy is related to the laser linewidth and energy density. In order to obtain a strong Raman signal, the laser needs to be precisely aligned and focused on the sample to obtain a high laser energy density. Therefore, a micro-focusing system is configured in large-scale Raman measurement systems, and operators use microscopic images to manually focus. At present, the commercialized portable Raman spectrometer system generally does not contain a microscopic focusing system due to volume limitations, and the Raman fiber optic probe can only focus through manual adjustment, which is cumbersome to operate and unable to focus accurately, resulting in weakened Raman intensity and unstable signals wait.

A commercially available fixed-distance probe is a new type of probe that fixes the measurement distance by installing a fixed-length sleeve in front of the probe to ensure focus. This probe simplifies the focusing operation process to a certain extent, but when using this probe for measurement, the sleeve must be in contact with the sample, and if the sample surface is uneven, it will not be able to focus accurately.

Contents of the invention

In view of the defects in the prior art, the object of the present invention is to provide a Raman probe capable of precise autofocus to maximize the collected Raman signal, a Raman signal detection system and method capable of autofocus.

According to one aspect of the present invention, a Raman probe is provided, the Raman probe includes a first lens, a first filter, a mirror, a fourth lens, a second filter, a third filter, a first Four optical filters, second lens, and light intensity detection unit; among them: after the laser is transmitted from the optical fiber into the Raman probe, it is transformed into parallel light by the first lens, and then the spectrum is purified by the first optical filter. Then the beam path is changed through the reflection of the mirror set at 45° to the parallel light and the reflection of the second filter, and finally the fourth lens focuses the laser light on the sample to be measured; Raman scattering occurs after the sample to be measured is excited by the laser , the scattered light and reflected light enter the Raman probe in the opposite direction and are collected by the fourth lens. The Raman scattered light passes through the lens group composed of the second filter and the fourth filter, and then converges and couples through the second lens. Entering the optical fiber, the non-Raman signal light is blocked and suppressed (reflected or absorbed) by the lens group composed of the second filter and the fourth filter, so it cannot reach the second lens, and the laser light reflected back by the sample is transmitted by the third lens. The filter is reflected and enters the light intensity detection unit;

The light intensity detection unit includes: a third lens, a small hole and a photoelectric conversion device, the small hole is at the focal point of the third lens; the laser light reflected by the third filter is focused by the third lens, converged and then passes through the small Holes, illuminated on the photoelectric conversion device through the small hole, are received and detected by the photodetector device.

Preferably, a third optical filter is provided after the second optical filter and before the fourth optical filter, at this time, part of the laser light reflected back by the sample is reflected by the second optical filter, and the other part is reflected by the second optical filter. The laser light reflected by the third optical filter enters the light intensity detection unit; the Raman light transmitted by the second optical filter is converged and coupled into the optical fiber through the fourth optical filter and the second lens.

Preferably, the second optical filter and the third optical filter are dichroic mirrors, which are arranged at an angle of 45° to the optical path, and the second optical filter and the third optical filter are not parallel to each other. Laser light is reflected and Raman scattered light is transmitted.

Preferably, the reflector, the second filter and the third filter all form an angle of 45° with the optical path; the first filter and the fourth filter form an angle of 90° with the optical path.

For the above-mentioned Raman probe, when the sample to be measured is not at the focus of the Raman probe, the laser light will converge at the front or rear of the small hole through the optical path, and only a small part of the light energy will pass through the small hole. The farther the sample is from the focus, the energy The less reflected light passes through the small hole; only when the laser spot is just focused on the object, the reflected laser spot will converge on the small hole through the optical path, and almost all the reflected light energy will pass through the small hole, and the photoelectric conversion device receives The light intensity signal is maximum. Due to the spatial selectivity of the small holes, most of the energy can pass through the small holes in the focusing state, and the photoelectric conversion device can obtain the maximum light intensity at this time. In this way, a focused ranging problem is transformed into an optically quantified light intensity measurement problem.

According to the second aspect of the present invention, there is provided an auto-focusing Raman signal detection system composed of the above-mentioned Raman probe, including a Raman probe, a numerically controlled displacement sample stage, and a controller; the Raman probe is installed on a numerically controlled displacement sample On the stage, the Raman probe and the numerical control displacement sample stage can move relatively, and the signal output side of the Raman probe is provided with a light intensity detection unit; the output end of the light intensity detection unit is connected to the controller, and the controller according to the The output signal of the light intensity detection unit compares and judges whether the sample is at the focal point. If it is not at the focal point, an instruction is issued to control the numerical control displacement sample stage to make corresponding displacements, and this is repeated many times until the sample is adjusted at the focal length of the Raman probe or the set accuracy within range.

According to a third aspect of the present invention, there is provided an autofocusable Raman signal detection method, the method steps are as follows:

a) Place the sample to be tested on the numerical control displacement sample stage;

b) Place the Raman probe above the digitally controlled displacement sample stage at a place greater than the focal length of the Raman probe;

c) Turn on the laser to output a laser, enter the Raman probe through the optical fiber, turn it into parallel light by the first lens, then purify the spectrum through the first filter, and then pass through the reflection of the mirror and the second filter in turn The laser beam is reflected to change the beam path, and finally the fourth lens focuses the laser light on the sample to be measured;

d) Raman scattering occurs after the measured sample is excited by the laser, the scattered light and reflected light enter the Raman probe in the opposite direction and are collected by the fourth lens, and the Raman scattered light passes through the second filter and the fourth filter The lens group composed of the second optical filter and the fourth optical filter is blocked and suppressed by the lens group composed of the second optical filter and the fourth optical filter, so the non-Raman signal light cannot reach the second lens, where it is The laser light reflected by the sample enters the light intensity detection unit after being reflected by the third filter;

e) The light intensity detection unit outputs the signal to the controller, and the controller controls the movement of the digitally controlled displacement sample stage until the collected signal reaches the maximum and the focusing is completed.

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

The technical innovation in the present invention avoids manual operation, can focus accurately, and maximizes and stabilizes the Raman signal; compared with the existing commercial probe with a fixed distance sleeve, the technology of the present invention can be used for samples with rough and uneven surfaces Perform direct detection without sample preparation.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is a schematic structural diagram of a Raman detection device with autofocus function according to an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a light intensity detection unit in an embodiment of the present invention;

Fig. 3 is an adjustment flowchart of the displacement adjustment device in an embodiment of the present invention;

Figure 4 is the distance and light intensity relationship curve between the focal plane of the probe and the sample when the small hole is 100 microns;

In the figure: 100 is the Raman probe, 200 is the digital control displacement sample stage, 300 is the controller; 1 is the optical fiber, 2 is the first lens, 3 is the first filter, 4 is the mirror, 5 is the fourth lens, 6 is the second filter, 7 is the third filter, 8 is the fourth filter, 9 is the second lens, 10 is the light intensity detection unit, 11 is the sample, 12 is the sample stage, 13 is the controller , 14 is the third lens, 15 is the small hole, and 16 is the photodetection device.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

As shown in Figure 1, it is a schematic structural view of an embodiment of a Raman detection device with autofocus function in the present invention, including a Raman probe 100, a numerically controlled displacement sample stage 200, and a controller 300; the Raman probe 100 is installed on a numerically controlled On the shifting sample stage 200, the Raman probe 100 and the numerical control shifting sample stage 200 can move relatively.

In this embodiment, the Raman probe 100 includes a first lens 2, a first filter 3, a mirror 4, a fourth lens 5, a second filter 6, a third filter 7, a fourth filter A light sheet 8 , a second lens 9 , and a light intensity detection unit 10 ; the light intensity detection unit 10 includes: a third lens 14 , a small hole 15 and a photoelectric conversion device 16 .

Among the figure: the first lens 2, the first optical filter 3, the reflection mirror 4, the second optical filter 6, and the fourth lens 5 used for laser focusing are used as the transmission laser assembly one, which is used as the Raman light collection The fourth lens 5, the second optical filter 6, the third optical filter 7, the fourth optical filter 8, and the second lens 9 are used to transmit Raman light and suppress stray light components 2, which are used as laser collimation The fourth lens 5, the second optical filter 6, the third optical filter 7, and the light intensity detection unit 10 constitute the laser automatic ranging focusing assembly three. Component one, component two and component three constitute a Raman probe 100 , and the Raman probe 100 is installed on a digitally controlled displacement sample stage 200 .

The first lens 2, the first optical filter 3 and the reflector 4 are sequentially arranged along the direction of the output light of the optical fiber 1, the first lens 2, the first optical filter 3 are perpendicular to the optical path, and the reflector 4 is at 45 degrees to the optical path. The second optical filter 6 is arranged at 45 degrees along the direction of the reflected light of the reflector 4, the second optical filter 6 is arranged in parallel with the reflector 4, and the fourth lens 5 is vertically arranged on the reflected light path of the second optical filter 6, The third optical filter 7 , the fourth optical filter 8 and the second lens 9 are sequentially arranged along the optical path direction of the fourth lens 5 and the second optical filter 6 , and an optical fiber is arranged on the other side of the second lens 9 . The third optical filter 7 is arranged at 45 degrees with the optical path, the fourth optical filter 8 and the second lens 9 are perpendicular to the optical path, and the third lens 14 and the small hole are arranged successively along one side of the reflection optical path of the third optical filter 7 15 and the photoelectric conversion device 16 , the third lens 14 , the pinhole 15 and the photoelectric conversion device 16 constitute the light intensity detection unit 10 .

After the laser light is transmitted from the optical fiber 1 into the Raman probe 100, it is converted into parallel light by the first lens 2, and then the spectrum is purified by the first filter 3, and then it is reflected at 45° to the parallel light in turn. Mirror 4 reflection, second filter 6 reflection to change the beam path, and finally the fourth lens 5 focuses the laser on the sample under test, where the fourth lens 5 plays the role of laser focus; the sample under test 11 is excited by the laser After that, Raman scattering occurs, and the scattered light and reflected light enter the Raman probe 100 in the opposite direction and are collected by the fourth lens 5, and the Raman scattered light is transmitted through the second filter 6, the third filter 7 and the fourth filter. The lens group formed by the optical filter 8 is converged and coupled into the optical fiber through the second lens 9 perpendicular to the optical path; the non-Raman signal light is formed by the second and third optical filters 6 and 7 and the fourth optical filter 8 The suppression (reflection or absorption) is blocked by the lens group, so it cannot reach the second lens 9, wherein part of the laser light reflected by the sample is reflected by the second filter 6, and the other part is reflected by the third filter 7, and the third filter The laser light reflected by the light sheet 7 enters the light intensity detection unit 10 .

The signal from the light intensity detection unit 10 is sent to the controller 300 after pre-processing, amplification, and AD conversion. The controller 300 judges whether the sample is at the focus according to the signal comparison. The corresponding displacement is repeated many times until the sample is adjusted at the focal length of the probe or within the set accuracy range. At the same time, the digitally controlled displacement sample stage 200 can also be adjusted in another two dimensions, so that the probe can work on a fixed plane.

As shown in FIG. 2 , the light intensity detection unit 10 includes a third lens 14 having the same focal length as the fourth lens 5 , a small hole 15 and a photoelectric conversion device 16 . The light intensity detection unit 10 is used to detect the light intensity of the collecting light path, and input the signal to the controller 300, and the controller 300 adjusts the digitally controlled displacement sample stage 200 until the light intensity reaches the maximum. Specifically, the laser light of the Raman light-transmitting and stray-light suppressing components is converged by a third lens 14 having the same focal length as the fourth lens 5 , then passes through the pinhole 15 , and is finally received and detected by the photodetection device 16 . The photoelectric conversion device 16 can be a photocell, a photodiode, a CCD, a PSD or other light intensity detection devices. As shown in Figure 4, the fourth lens 5, the second optical filter 6 and the third optical filter 7, and the third lens 14 image the focal plane image of the fourth lens 5 on its conjugate plane and the small hole 14 ; Due to the spatial selectivity of the small hole, in the focusing state, most of the energy can pass through the small hole 14, and the photodetector device 16 obtains the maximum light intensity at this time. In this way, a focused ranging problem is transformed into an optically quantified light intensity measurement problem.

In a preferred embodiment, the second optical filter 6 and the third optical filter 7 are 45 ° dichroic mirrors, which are required to be set at an angle of 45 ° with the optical path, so as to reflect the laser light and not to Raman scattering light transmission. The fourth optical filter 8 is a long-wave pass component that suppresses Rayleigh scattered light, and is required to be arranged perpendicular to the optical path. That is, the mirror 4, the second filter 6 and the third filter 7 need to form an angle of 45° with the optical path; while the first filter 3 and the fourth filter 8 need to form an angle of 90° with the optical path. The laser light reflected by the second filter 6 is stray light, which is not utilized.

In the present invention, in order to make the structure more compact, reduce components, and reduce costs, the second lens 5 simultaneously serves as the laser focusing lens in component one, the Raman light collection lens in component two, and the laser collimating lens in component three, namely The same lens, due to the reversibility of the optical path, has different effects on different types of light passing through it in the forward and reverse directions, and is functionally divided into focusing laser, collecting Raman light and collimating laser. Part 5 is specifically shown in FIG. 1 . The fourth lens 5 can be arranged perpendicular to the optical path, or in other ways.

The Raman detection device with auto-focus function in the present invention is not limited to the above forms, but also includes other structural forms.

Taking the embodiment shown in Figure 1 as an example, the specific work of the light intensity detection unit 10 is as follows:

a) The laser collimated and focused through the optical path acts on the sample to be tested;

b) The laser light reflected by the object is collected by Raman through the fourth lens 5, passes through the second filter 6 placed at 45 degrees, and is partially reflected on the third filter 7, and the reflected light passes through the third lens 14 focusing, and irradiating on the photoelectric conversion device 16 through the small hole 15; the third lens 14 has the same focal length as the fourth lens 5; the small hole 15 is at the focal point of the third lens 14;

c) When the sample to be measured is not at the focal point of the probe, the reflected laser light will converge at the front or rear of the small hole 15 through the optical path, and only a small part of the light can pass through the small hole 15. The farther the sample is from the focus, the more light can pass through the small hole. The less reflected light; only when the laser spot is just focused on the object (at this time, the spot is the smallest, that is, in the focused state), the reflected laser spot will converge on the small hole 15 through the optical path, and almost all of the reflected light energy will pass through the small hole 15. Hole 15, the light intensity signal received by the detector is the largest.

In another preferred embodiment of the present invention, the numerically controlled displacement sample stage 200 is provided with a displacement adjustment device and the sample stage 12. The displacement adjustment device is a precise adjustment device that can move in three dimensions, especially a three-dimensional movement. Three-dimensional mobile devices controlled by moving stepper motors or piezoelectric ceramics. Due to the relative motion between the probe and the sample, the probe can be fixed, and the sample can move in three dimensions, or the sample can be fixed in turn, and the probe can move in three dimensions, or a combination of one-dimensional movement of the probe and two-dimensional movement of the sample can be adopted. , the sample moves two-dimensionally relative to the plane perpendicular to the output beam of the probe, which is especially suitable for the situation where multiple positions need to be scanned and detected. For example, when Raman is combined with thin-layer chromatography, it is necessary to analyze Samples at multiple positions on the laminate were measured by Raman spectroscopy.

In the Raman signal detection system capable of autofocusing in the above embodiments of the present invention, the displacement adjustment device can be fixedly connected to the Raman probe 100 and the sample stage 12 , and the Raman probe 100 can move relative to the sample stage 12 .

Based on the probe shown in Figure 1 and the above-mentioned detection device, the auto-focusing Raman signal detection method adopted, the steps are as follows:

a) placing the sample 11 to be tested on the numerically controlled displacement sample stage;

b) Place the probe above the CNC displacement sample stage at a place about 3-5mm larger than the focal length of the probe;

c) Turn on the laser to output a laser, enter the Raman probe through the optical fiber, and turn it into parallel light by the first lens 2, then pass through the first filter 3 to purify the spectrum, and then reflect by the mirror 4 in turn, and the second The second filter 6 is reflected to change the beam path, and finally the fourth lens 5 focuses the laser light on the sample to be tested;

d) Raman scattering occurs after the measured sample 11 is excited by the laser, and the scattered light and reflected light enter the Raman probe in the opposite direction and are collected by the fourth lens 5, and the Raman scattered light is transmitted through the second filter 6 and the second filter. The lens group composed of three optical filters 7 and the fourth optical filter 8 is converged and coupled into the optical fiber through the second lens 9; the non-Raman signal light is transmitted by the second and third optical filters 6 and 7 and the fourth optical filter The lens group formed by the sheet 8 blocks suppression (reflection or absorption), so it cannot reach the second lens 9, wherein part of the laser light reflected by the sample is reflected by the second filter 6, and the other part is reflected by the third filter 7 , the laser light reflected by the third filter 7 enters the light intensity detection unit 10;

e) The light intensity detection unit 10 outputs the signal to the controller, and the controller controls the movement of the digitally controlled displacement sample stage until the collected signal reaches the maximum, and the focusing is completed.

In the above-described embodiment, the controller is implemented by a computer, and the signal of the photoelectric conversion device 16 enters the computer through the amplifying circuit and AD conversion, and the computer controls the movement of the displacement adjustment device through calculation (for example, the computer controls the displacement adjustment device to advance in the vertical direction, etc.), until The collected signal is the largest, and the focus is completed at this time.

In a preferred embodiment of the present invention, the displacement adjustment device involved in the above detection device performs displacement adjustment according to the following steps, as shown in Figure 3:

a) The Raman probe is located 3-5mm away from the focus distance outside the sample stage, and the initial light intensity signal is x ₀ ;

b) Control the displacement adjustment device to move down by one step, and measure the light intensity signal at this time as x _i ;

c) When the difference between two adjacent light intensity signals x _i -x _i-1 is greater than 0, continue to control the movement of the displacement adjustment device until x _i -x _i-1 is less than 0, and the displacement controller controls the reverse movement;

d) According to the actual focus accuracy, the step c) can be controlled to reduce the step value when x _i -x _i-1 is less than 0, and repeat it several times until the light intensity difference is less than the set minimum value esp.

FIG. 4 shows the relationship between the distance between the focal plane of the Raman probe 100 and the sample 11 and the light intensity when the aperture 15 is 100 microns. From the relationship between the light intensity and the distance of the Raman probe 100, it can be seen that the present invention can achieve precise control within 10 microns near the focal point, and the smaller the aperture 15, the higher the precision.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (6)

1. a kind of Raman probe, it is characterised in that the Raman probe include the first lens, the first optical filter, speculum, the 4th Lens, the second optical filter, the 3rd optical filter, the 4th optical filter, the second lens, light intensity detection unit；Wherein：Laser is passed from optical fiber Lead into after Raman probe, by the first lens directional light is become, then spectrum is carried out at purifying through the first optical filter Reason, then sequentially pass through speculum reflection, the reflection of the second optical filter changing beam path, finally by the 4th lens by Laser Focusing In sample；There is Raman scattering after laser excitation in sample, scattered light and reflected light opposite direction enter Raman probe Collected by the 4th lens, the lens set that Raman scattering light transmission therein is made up of the second optical filter and the 4th optical filter, then Jing Assembled by the second lens and be coupled into optical fiber, the lens set institute that non-Raman signal light is made up of the second optical filter and the 4th optical filter Stop and suppress, therefore the second lens can not be reached, wherein the laser reflected by sample is reflected by the 3rd optical filter, into light Strong probe unit；

The light intensity detection unit includes：3rd lens, aperture and electrooptical device, the aperture is in the 3rd lens Focal point；The lens focus of laser Jing the 3rd of the 3rd optical filter reflection, photoelectricity is radiated at after convergence through aperture by aperture again On switching device, the device that is photoelectrically converted receives detection；

3rd optical filter is set after second optical filter and before the 4th optical filter, now, is reflected by sample The laser part returned is reflected by the second optical filter, and another part is reflected by the 3rd optical filter, and what the 3rd optical filter reflected swashs Light enters light intensity detection unit；The Raman light of the second filter transmission assembles coupling via the 4th optical filter, the second lens again Conjunction enters optical fiber；

Second optical filter and the 3rd optical filter are 45 ° of dichroic mirrors, are arranged with light path angle at 45 °, and described second filters Piece and the 3rd optical filter are not parallel, and both are highly transmissive to Raman diffused light to laser high reflection；

The speculum, the second optical filter, the 3rd optical filter, with light path angle at 45 °；First optical filter, the 4th filter Piece is then in 90 ° with light path, and the 4th optical filter is the logical part of long wave for suppressing Rayleigh scattering light.

2. Raman probe according to claim 1, it is characterised in that when sample is not in the focus of the Raman probe During place, laser will be converged at the front or behind of aperture by light path, and only fraction luminous energy by aperture, get over by sample focal point Far, the reflected light that can pass through aperture is fewer；Only when laser facula is just focused on object, the hot spot of the laser of reflection will be logical Cross light path and converge at aperture, most reflection luminous energy will be by aperture, and the light intensity signal that electrooptical device is received is most Greatly.

3. it is a kind of comprising Raman probe described in any one of claim 1-2 can auto-focusing Raman signal detection system, its It is characterised by, the system includes Raman probe, numerical control displacement sample stage, controller；The Raman probe is installed on numerical control position Move on sample stage, Raman probe and numerical control displacement sample stage can relative movement, the signal output side of the Raman probe is provided with light Strong probe unit；The output end of the light intensity detection unit is connected to controller, and controller is defeated according to the light intensity detection unit Whether go out signal multilevel iudge sample in focal point, if not in focal point, sending instruction control numerical control displacement sample stage and making phase The displacement answered, it is so repeated multiple times, until sample is adjusted at Raman probe focal length or in the accuracy rating of setting.

4. it is according to claim 3 can auto-focusing Raman signal detection system, it is characterised in that the numerical control displacement Displacement adjustment device and sample stage are provided with sample stage, the displacement adjustment device is a kind of accurate adjustment dress that can be moved in three-dimensional Put, the displacement adjustment device is fixedly connected with Raman probe and sample stage, Raman probe can be with sample stage relative movement.

5. Raman probe described in a kind of any one of employing claim 1-2 can auto-focusing Raman signal detection method, its It is characterised by that methods described step is as follows：

A) testing sample is placed on numerical control displacement sample stage；

B) Raman probe is placed in into numerical control displacement sample stage top more than at Raman probe focal length；

C) open laser instrument and export a laser, Jing optical fiber enters Raman probe, by the first lens directional light, Ran Houjing are become Crossing the first optical filter carries out purification process to spectrum, then sequentially passes through speculum reflection, the reflection of the second optical filter changing light beam Path, finally by the 4th lens by Laser Focusing in sample；

D) there is Raman scattering after laser excitation in sample, and scattered light and reflected light opposite direction enter Raman probe by the 4th Lens are collected, the lens set that Raman scattering light transmission therein is made up of the second optical filter and the 4th optical filter, then via second Lens are assembled and are coupled into optical fiber；Non- Raman signal light stops suppression by the lens set that the second optical filter and the 4th optical filter are constituted System, therefore the second lens can not be reached, wherein visiting into light intensity after the laser reflected by sample is reflected by the 3rd optical filter Survey unit；

E) light intensity detection unit outputs a signal to controller, via controller control numerical control displacement sample stage movement, until collecting The signal for arriving is maximum, completes focusing.

6. it is according to claim 5 can auto-focusing Raman signal detection method, it is characterised in that the controller control Numerical control displacement sample stage movement processed, the numerical control displacement sample stage is provided with displacement adjustment device and sample stage, and the displacement is adjusted According to following steps when device carries out adjustment of displacement：

A) Raman probe is located at the outer 3-5mm of the outer focal length of sample stage, and initial beam intensity signal is x₀；

B) command displacement adjusting means moves down a step pitch, and now light intensity signal is x for measurement_i；

C) when adjacent light intensity signal difference x twice_i-x_i-1During more than 0, continue the movement of command displacement adjusting means, until x_i-x_i-1 Less than 0, displacement controller control reverse movement；

D) according to actual focusing precision, can control x during step c)_i-x_i-1Step value is reduced during less than 0, and it is repeated multiple times, directly To light intensity difference less than minimum of a value esp for setting.