HK1160931B - A method for automatically calibrating a raman spectrum detecting system and the system - Google Patents

Description

Method for automatically calibrating Raman spectrum detection system and Raman spectrum detection system

Technical Field

The invention relates to a Raman spectrum detection system and a method for automatically calibrating the Raman spectrum detection system. The invention also relates to a method for detecting an object by using the self-calibration Raman spectrum detection system.

Background

Light is scattered when it strikes a substance. When scattering occurs, the wavelength of most scattered light does not change, and the scattering with unchanged wavelength is called Rayleigh scattering; the wavelength of a small portion of the scattered light increases or decreases, and this wavelength-shifted scattering is called raman scattering, and the corresponding spectrum is called raman spectrum. The raman spectrum belongs to a vibration spectrum of a molecule, and it is possible to know which substance is or contains which component by detecting the raman spectrum of a substance, and therefore, the raman spectrum can be used as a "fingerprint" for identifying a substance. Therefore, the Raman spectrum can be applied to the fields of medicine, food safety, cultural relic gem identification, safety inspection and the like. Meanwhile, as the application of raman spectroscopy in these fields is increasingly widespread, a raman spectrometer capable of performing on-site rapid detection is urgently needed to adapt to different environments of various application occasions.

However, the characteristics of the laser light, such as frequency and power, used for exciting the material to generate raman scattering change with the change of the environmental temperature and the increase of the usage time, so that the measured raman spectrum also changes. In addition, for the raman spectrometer which is moved frequently, the optical path structure of the system may be changed due to vibration and the like in the transportation and use processes, so that the excitation efficiency of exciting raman light and the signal collection efficiency are changed, and the raman spectrum of the system measuring the same sample at different times and in different environments may be changed. Most of Raman spectrometers for scientific research use a laser with stable frequency and power as an excitation light source, and have strict requirements on the use environment and the like. However, the laser with stable frequency and power is expensive, which is not favorable for the popularization of the raman spectrometer. Even a laser with stable frequency and power will experience some attenuation of its power over time, resulting in an uncertain measurement.

Disclosure of Invention

It is therefore an object of the present disclosure to provide a raman spectroscopy detection system and method for eliminating the effect of changes in system performance due to environmental factors, critical device changes, etc. on the measured raman spectra, thereby improving the accuracy of substance identification.

According to an aspect of the present disclosure, there is provided a raman spectroscopy detection system comprising: a light source for emitting excitation light for exciting the object to be detected to emit Raman light; an external optical path system for irradiating the light emitted by the light source onto the object to be detected and collecting the Raman light emitted by the object to be detected; the optical detection device is used for receiving the Raman light collected by the external optical path system and detecting the Raman light to obtain spectral data of the Raman light; a control device for controlling the excitation light source to provide the excitation light, controlling the detection of Raman light by the light detection device, receiving the spectral data output from the light detection device and analyzing the spectral data to identify the object to be detected; and the automatic calibration device is used for automatically calibrating the Raman spectrum detection system.

According to a preferred embodiment of this aspect of the disclosure, the automatic calibration device comprises a standard sample and a reduction fixture for the standard sample.

According to a preferred embodiment of this aspect of the disclosure, the return fixture is a spring.

According to a preferred embodiment of this aspect of the present disclosure, the control device further includes a calibration unit for determining a current characteristic of the system by analyzing raman spectrum data of the standard sample received from the light detection device, and calibrating the raman spectrum data of the test object based on the current characteristic.

According to a preferred embodiment of this aspect of the disclosure, the outer optical path system comprises: a mirror that reflects excitation light from the light source; a filter that reflects the excitation light reflected by the mirror and transmits raman light having a wavelength longer than that of the excitation light; a collecting lens that focuses the excitation light from the filter onto the object and collects raman light emitted from the object; a collection lens that focuses the Raman light collected by the collection lens into a light detection device.

According to a preferred embodiment of this aspect of the disclosure, the optical filter is a dichroic mirror, or is a notch filter.

According to a preferred embodiment of this aspect of the present disclosure, further comprising an alarm device for receiving the recognition result of the control device and outputting a prompt or an alarm.

According to a preferred embodiment of this aspect of the disclosure, the characteristics include the frequency and power of the light source and the excitation efficiency and signal collection efficiency of the external optical path system.

According to another aspect of the present disclosure, there is provided a method of inspecting an object using a raman spectroscopy detection system as described above, comprising the steps of: automatically calibrating the system by using a standard sample; controlling the excitation light to irradiate the object to excite the object to emit Raman light; detecting the raman light to obtain spectral data of the raman light; the spectral data is analyzed to identify the object.

According to a further aspect of the present disclosure, there is provided a method of automatically calibrating a raman spectroscopy detection system as described above, comprising the steps of: before detecting the detected object, controlling exciting light to irradiate the standard sample so as to excite the standard sample to emit Raman light; receiving the raman light and obtaining spectral data of the raman light; analyzing the spectral data to determine current characteristics of the system; the calibration values for the auto-calibration system are obtained by comparing the current characteristics of the system with pre-stored data.

Drawings

FIG. 1 schematically illustrates a Raman spectroscopy detection system according to an embodiment of the present invention;

FIG. 2 schematically illustrates an exemplary control arrangement of a Raman spectroscopy detection system according to an embodiment of the present invention;

FIG. 3a schematically illustrates an example configuration of an outer optical path system of a Raman spectral detection system, in accordance with an embodiment of the present invention;

FIG. 3b schematically illustrates another example configuration of an outer optical path system of a Raman spectral detection system according to an embodiment of the present invention;

FIG. 4 schematically illustrates an exemplary auto-calibration arrangement for a Raman spectroscopy detection system, in accordance with an embodiment of the present invention.

Detailed Description

FIG. 1 illustrates a Raman spectroscopy detection system, indicated generally in FIG. 1 by reference numeral 10, in accordance with an embodiment of the present invention.

In one embodiment, the raman spectroscopy detection system 10 includes a control device 11, a light source 12, an external optical path system 14, a light detection device 13, and a calibration device 15 with a standard sample.

The light source 12 emits excitation light for exciting the object to emit raman light under the control of the control device 11. In principle, any light source that can provide excitation light with a narrow line width and stable frequency and power can be used in the present invention. In one embodiment, the light source 12 employs a laser with a center wavelength of 785nm that outputs collimated parallel light. Of course, lasers with other wavelengths, such as 532nm center, may be used, in which case the external optical path system 14 and the light detection device 13 are adjusted accordingly according to the excitation wavelength.

The excitation light emitted from the light source 12 is irradiated onto the object through the external optical path system 14, thereby exciting the object to emit raman light. The raman light is collected by the external optical path system 14 and transmitted to the light detection device 13. In one embodiment, the external optical path system 14 is a fiber optic probe. In which case the light source 12 and the light detection means 13 may have an optical fiber interface. In another embodiment, the external optical path system 14 is in the form of free-space coupling, in which case the light source 12 collimates the output parallel light, and the light detection means may have no fiber optic interface.

The light detection device 13 receives the raman light of the object collected by the external optical path system 14 and detects the raman light under the control of the control device 11. In one embodiment, the light detection device 13 is a spectrometer that separates the different frequencies of the raman light and acquires the signal intensities of the different frequencies of the raman light, thereby obtaining the raman spectrum data of the object. In another embodiment, the spectrometer has a photodetector. This is described in more detail below.

The photodetector 13 transmits the obtained raman spectrum data of the test object to the controller 11. In one embodiment, the control device 11 may be a single chip microcomputer, and in another embodiment, the control device 11 may be a general purpose computer or an industrial computer. The control device 11 is equipped with an operating system and software, and a standard raman spectrum database, and analyzes and processes raman spectrum data transmitted from the light detection device 13. Specifically, the control device 11 determines whether the received raman spectrum data is the same as or similar to the raman spectrum data of contraband, such as drugs, explosives, etc., by using the standard raman spectrum database and a pre-installed pattern recognition algorithm. If yes, the detected object is determined to be contraband or contain the contraband. In this case, the control device 11 can display the recognition result via a display connected to the control device 11 and can emit an alarm signal in the form of, for example, a sound, a light or a vibration via an alarm likewise connected to the control device 11. Conversely, if it is determined that the object is not contraband or does not contain contraband, the control device 11 may also display the identification result through the display and give a security signal through a warning lamp also connected to the control device 11. The display may be a touch screen.

In one embodiment of the invention, the control device 11 also has a calibration unit, which is shown at 110 in fig. 2. The calibration unit 110 may automatically calculate calibration parameters of the system based on the standard sample, so that the control device 11 may consider the calibration parameters when analyzing and processing the raman spectrum data of the test object. As will be described in detail below.

In addition, Raman spectrum detection system 10 may further include a sample chamber for placing an object to be detected to eliminate the influence of ambient stray light. A replaceable rechargeable battery may also be included for powering the raman spectroscopy detection system 10 without an external power source and for recharging in the presence of an external power source.

Fig. 2 shows a detailed schematic diagram of the control device 11 according to an embodiment of the present invention.

In this embodiment, the control device 11 is a control circuit board with an arm9 chip, for example, pre-installed with a winCE operating system. The control device 11 receives commands and parameters from the input peripheral, transmits control signals to the light source 12 and the light detection device 13, and receives spectral data from the light detection device 13. After the spectral data are identified, the identification result is transmitted to a display, and if necessary, an alarm signal is sent out. In one embodiment, the input peripheral may be a key, a switch or a keyboard, and is used for setting parameters of each component of the raman spectrum detection system 10 by inputting instructions to the control device 11 and transmitting operation instructions to the raman spectrum detection system 10.

In one embodiment, the control device 11 may also have a power supply unit 111 and a data transmission unit 112 as needed. The power supply unit 111 is used to convert an external power supply into a power supply required by the raman spectrum detection system 10. The power supply unit 111 may also charge an optional battery through which the raman spectroscopy detection system 10 is powered in the absence of an external power source. The data transmission unit 112 is used for receiving data input from the raman spectroscopy detection system 10 and transmitting the data. The data transmission unit 112 may be a serial interface, a parallel interface, a USB interface, a network interface, or a wireless network interface, such as bluetooth.

Through the data transmission unit 112, a plurality of raman spectrum detection systems 10 and control centers according to embodiments of the present invention can form a network system for detection. The control center utilizes the network communication function of the raman spectrum detection system 10 to update the system database, set parameters, and the like. The raman spectrum detection system 10 of the embodiment of the present invention can transmit the detection data and the detection result to the control center through the network, or export the data to a usb disk or other storage device through the data transmission unit 112, or connect a printer through the data transmission unit 112 to print the detection result.

Fig. 3a schematically illustrates an example configuration of the outer optical path system 14 of the raman spectroscopy detection system 11 in accordance with an embodiment of the present invention.

In this example configuration, the outer optical path system 14 employs free-space coupling. The external optical path system 14 includes a reflecting mirror 140, an excitation light narrowband filter 141, a dichroic mirror 142, a long pass filter 143, a collecting lens 144, and a condensing lens 145. Excitation light emitted from the light source 12 of the laser device shown in fig. 1 is reflected by the reflecting mirror 140, passes through the excitation light narrowband filter 141, and is reflected by the dichroic mirror 142. The reflected light is focused by the collection lens 144 onto an object placed in the sample chamber, for example. The signal light thus excited by the object is collected by the same collecting lens 144, passes through the dichroic mirror 142 and the long-pass filter 143, is focused by the condensing lens 145 onto the light detection device 13, for example, at the slit of the spectrometer, and enters the light detection device 13.

In this example, an excitation light narrowband filter 141 is employed to filter out stray light in the laser light other than the excitation wavelength, which stray light is mainly derived from the spontaneous emission of the laser. The center wavelength of the filter 141 corresponds to the selected laser. If the stray light of the selected laser does not affect the detection of the raman spectrum, the excitation light narrowband filter 141 may not be used.

In this example, the dichroic mirror 142 reflects the excitation light, filters out rayleigh scattered light having the same wavelength as the excitation light in the signal light, and transmits raman light having a longer wavelength than the excitation light. The dichroic mirror 142 is preferably a filter having an incident angle of 45 degrees. Of course, the dichroic mirror 142 may be selected to have an incident angle of other angles, for example, about 5 degrees, so that when incident at this angle, light having a longer wavelength than the excitation light is transmitted while reflecting the excitation light.

In this example, a long-pass filter 143 is preferably used to further filter the rayleigh scattered light in the signal light. The long pass filter 143 has a high reflectance for the excitation light wavelength and a high transmittance for light having a longer wavelength than the excitation light. The long-pass filter can also be replaced by a notch filter, the notch filter only has high reflectivity for the light with the exciting light wavelength, and has high transmissivity for the light with other wavelengths, and the incidence angle of the notch filter is determined according to the use requirement.

In this example, the collecting lens 144 is preferably a quartz convex lens, which focuses the excitation light on the object and collects the signal light emitted from the object. The fluorescent effect of the quartz convex lens is small, and interference on signal light of an object to be detected is avoided.

In this example, the condensing lens 145 is preferably an achromatic lens. The converging lens focuses the signal light onto the optical detection device 13, for example, into the slit of the spectrometer, and the ratio (F/D) of the focal length to the clear aperture preferably matches the numerical aperture (F #) of the spectrometer, so as to achieve the best signal light utilization.

Fig. 3b schematically illustrates another example configuration of an outer optical path system of a raman spectroscopy detection system in accordance with an embodiment of the present invention.

This example configuration differs from that shown in fig. 3a in that fig. 3b uses a sheet of notch filters 146 instead of the dichroic mirror 142 and long-pass filter 143 in fig. 3 a. The notch filter 146 is preferably a filter having an incident angle of about 10 degrees.

In the embodiment of the present invention, the light detection device 13 employs a spectrometer. In the example configuration of fig. 3a and 3b, the spectral range of the spectrometer has to match the chosen excitation light wavelength and to be able to cover the raman spectral range of the object. For example, if 785nm excitation light is selected, a test object 200-2000cm is detected^-1The spectrum range which can be measured by the spectrometer needs to cover 797nm-932 nm; if 532nm excitation light is selected, the same test object is measured at 200-2000cm^-1The inner Raman peak, the spectral range of the spectrometer must cover 537nm-596 nm. In this embodiment, the spectrometer has a photodetector. The photodetector is preferably a linear or area array detector such as a CCD, and the widths of the grating and the slit are selected so that the Raman peak of the object can be resolved and the signal intensity is high.

FIG. 4 schematically illustrates an exemplary auto-calibration device 15 of Raman spectroscopy detection system 10, in accordance with an embodiment of the present invention.

The automatic calibration device 15 is, for example, a movable shutter, on which a standard sample is coated. The movable stop is attached to one end of a spring, and the other end of the spring is fixed to, for example, the housing of the raman spectroscopy detection system 10.

Prior to detection, the raman spectroscopy detection system 10 is in an idle state. The movable shutter 15, now coated with the standard sample, is located at the exit of the system, with the spring in the rest position. If a calibration instruction is input through an input peripheral, the control device 11 of the raman spectroscopy detection system 10 controls the light source 12 to emit light, and the emitted excitation light is irradiated onto the standard sample through the external optical path system 14. The raman signal light emitted from the standard sample is then collected by the external optical path system 14 and transmitted to the light detection device 13 configured as a spectrometer. The photodetector 13 detects the signal light, obtains raman spectrum data, and transmits the data to the controller 11. The control device 11 analyzes the data to obtain calibration parameters to complete the calibration of other components of the raman spectroscopy detection system 10.

In one embodiment, the light detection device 13 detects the Raman spectrum of the standard sample and transmits it to the calibration unit 110 of the control device 11. The calibration unit 110 automatically identifies the peak position and the peak intensity of the raman peak of the standard sample, and calculates the difference between the detected peak position and the peak position of the raman peak of the pre-stored standard sample, which is the frequency difference between the raman peak of the detected object and the real peak at this time, and is referred to as a frequency calibration value. The frequency calibration value is subtracted from the frequency of the Raman peak of the detected object, so that the real frequency of the Raman peak of the detected object can be obtained, and the calibration of the Raman peak frequency is realized. The calibration unit 110 further calculates a ratio of the measured peak intensity value to a pre-stored peak intensity value, which is a ratio between the raman peak intensity of the detected object and the real peak intensity, and is referred to as an intensity calibration value herein. The real peak intensity of the Raman peak of the detected object can be obtained by dividing the peak intensity of the Raman peak of the detected object by the intensity calibration value, thereby realizing the calibration of the Raman peak intensity.

In actual detection, the object to be detected is placed in the light outlet of the system, for example, in the sample chamber. The standard sample is pushed open by the object to be detected, and the spring is compressed. At this time, the raman spectrum detection system 10 is in a detection state, and detects the object according to a detection procedure of a generally known raman spectrometer.

And after the detection is finished, taking the sample to be detected out of the light outlet of the system. The compressed spring then returns to its original shape and pushes the baffle coated with the standard back and the raman spectroscopy detection system 10 returns to the idle state.

Through the description of the embodiment of the present invention, those skilled in the art can understand that the disclosed raman spectrum detection system 10 has a fast automatic calibration function, so that the requirements of a raman spectrometer, especially a portable raman spectrometer, on a laser serving as a light source are reduced, and the cost of the device is effectively reduced. The automatic calibration function improves the detection accuracy, improves the adaptability of the Raman spectrometer to the environment and enlarges the application range of the Raman spectrometer.

The foregoing detailed description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the detailed description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are merely illustrative of the principles of this invention and that various modifications may be implemented by those skilled in the art without departing from the spirit and scope of the invention.

Claims (9)

1. A raman spectroscopy detection system comprising:

a light source for emitting excitation light for exciting the object to be detected to emit Raman light;

the external optical path system is used for focusing the light emitted by the light source on the detected object and collecting the Raman light emitted by the detected object;

the optical detection device is used for receiving the Raman light collected by the external optical path system and detecting the Raman light to obtain spectral data of the Raman light;

a control device for controlling the light source to provide the excitation light, controlling the detection of the Raman light by the light detection device, receiving the spectral data output from the light detection device and analyzing the spectral data to identify the object;

an automatic calibration device for automatically calibrating the Raman spectrum detection system,

wherein the automatic calibration device comprises a standard sample, and the automatic calibration device is arranged at a light outlet of the outer optical path system to receive light from the outer optical path system and collect Raman light emitted by the standard sample by the outer optical path system,

wherein the outer optical path system comprises:

a mirror that reflects excitation light from the light source;

a filter that reflects the excitation light reflected by the reflecting mirror and transmits raman light having a wavelength longer than that of the excitation light, the filter being a dichroic mirror;

a collecting lens that focuses the excitation light from the filter onto the object and collects raman light emitted from the object;

a condensing lens that focuses the Raman light collected by the collecting lens into a light detection device,

wherein an exciting light narrow-band filter used for filtering stray light is arranged between the reflector and the filter, a long-pass filter used for filtering Rayleigh scattered light is arranged between the filter and the converging lens,

wherein the collection lens is a quartz convex lens and the collection lens is an achromatic lens.

2. A raman spectroscopic detection system according to claim 1 wherein said automatic calibration means further comprises a repositioning fixture for said standard sample.

3. A raman spectroscopic detection system according to claim 2 wherein said reset fixture is a spring.

4. The raman spectrum detection system according to claim 2, wherein the control device further comprises a calibration unit for determining a current characteristic of the system by analyzing the raman spectrum data of the standard sample received from the light detection device, and calibrating the raman spectrum data of the object based on the current characteristic.

5. A Raman spectrum detection system according to any one of claims 1 to 4, further comprising an alarm device for receiving the identification result of the control device and outputting a prompt or alarm.

6. A Raman spectral detection system according to claim 4, wherein said characteristics include frequency and power of the light source and excitation efficiency and signal collection efficiency of the external optical path system.

7. A method of inspecting an object using the raman spectroscopy detection system of claim 1 comprising the steps of:

automatically calibrating the exciting light by using a standard sample;

controlling the excitation light to irradiate the object to excite the object to emit Raman light;

detecting the raman light to obtain spectral data of the raman light;

the spectral data is analyzed to identify the object.

8. A method of automatically calibrating the raman spectroscopy detection system of claim 1 comprising the steps of:

before detecting the detected object, controlling exciting light to irradiate the standard sample so as to excite the standard sample to emit Raman light;

receiving the raman light and obtaining spectral data of the raman light;

analyzing the spectral data to determine current characteristics of the system;

the calibration values for the auto-calibration system are obtained by comparing the current characteristics of the system with pre-stored data.

9. The method of claim 8, wherein the characteristics include frequency and power of the light source and excitation efficiency and signal collection efficiency of the external optical path system.