CN106770345A - The near-infrared diffusing reflection detecting system and detection method of a kind of automatic correction - Google Patents

Abstract

An automatic correction near-infrared diffuse reflectance detection system and detection method, the system includes an optical system, the optical system includes a light source system and a spectrum collection system, the spectrum collection system includes a spectrum collection window, the light source system is located around the spectrum collection system, and the spectrum collection system Located directly above the sample to be measured. The detection system also includes a correction system. The correction system includes a correction head, a moving shaft, and a motor. The correction head includes a partition and a whiteboard. The motor drives the partition and the whiteboard through the moving shaft to pass directly below the spectrum collection window. The size of the spectrum collection window is less than The size of the bulkhead. The detection method of the system is to adjust the position of the calibration head by the motor to obtain the background spectrum, reference spectrum, and original spectrum, thereby calculating the near-infrared absorption spectrum. In order to realize the automatic correction of the background spectrum and the reference spectrum, and realize the remote measurement of the sample.

Description

An automatic correction near-infrared diffuse reflectance detection system and detection method

technical field

The invention relates to the technical field of automatic correction of near-infrared diffuse reflection spectrum, in particular to an automatic correction near-infrared diffuse reflection detection system and detection method.

Background technique

The near-infrared spectroscopy and Raman spectroscopy techniques in the optical property analysis method can conduct non-destructive analysis of samples, and have the characteristics of non-contact, non-destructive, high detection sensitivity, short time, small amount of samples required and no need for sample preparation. , will not cause chemical, mechanical, photochemical and thermal decomposition of the sample during the analysis process, and is one of the research hotspots in the field of analytical science. In recent years, near-infrared spectroscopy technology has made great progress in agriculture, medicine, food and other industries. There have been researches on the application of near-infrared reflection spectroscopy analysis technology in agriculture, chemical industry and other fields at home and abroad. Near-infrared light (NIR) refers to electromagnetic waves with a wavelength in the range of 780-2526nm (wavenumber 12820cm-1-3959cm-1), which is between visible light (VIS) and mid-infrared light (MIR). Near-infrared spectrum absorption is Molecular vibrational energy level transitions (accompanied by rotational energy level transitions), and molecular vibrational energy level transitions include fundamental frequency transitions, double frequency transitions and combined frequency transitions. The near-infrared light emitted by the light source is irradiated on the substance composed of molecules. If the energy absorbed by the near-infrared light changes in the vibration state of the molecule or the transition of the vibration state between different energy levels is equal to the energy of the photon at a certain wavelength in the near-infrared spectral region, then Will produce near-infrared spectral absorption. In the near-infrared spectrum range, the measurement is mainly the double frequency and combined frequency absorption of the vibration of the hydrogen-containing functional group X-H (X=C, N, O, S, etc.) in the molecule. This technology has the advantages of convenience, rapidity, high efficiency, accuracy, low cost, no damage to samples, no consumption of chemical reagents, and no pollution to the environment. Compared with conventional detection methods, it is more suitable for online detection.

When using near-infrared diffuse reflectance spectroscopy technology, due to the influence of fluctuations in near-infrared light sources, baseline drift and other factors, it is necessary to correct the collected near-infrared spectrum. The emissivity of spectral measurement is:

which is:

Converted to absorbance as:

Therefore, in the measurement process, it is necessary to collect reference spectra and background spectra to correct the measured reflectance and absorbance. In the actual measurement process, especially when collecting near-infrared diffuse reflectance spectroscopy, effective spectral correction cannot be performed, resulting in The measurement accuracy is not high, and some of them need to be manually corrected on site at regular intervals, resulting in a waste of time and money, and it is impossible to truly realize online detection.

Contents of the invention

The technical problem to be solved by the present invention is to provide a near-infrared diffuse reflectance detection system that can automatically correct the background spectrum and the reference spectrum, and complete the automatic calibration of the remote measurement of the sample.

The present invention adopts the following technical solutions to solve the above-mentioned technical problems:

An automatic correction near-infrared diffuse reflectance detection system includes an optical system, the optical system includes a light source system and a spectrum collection system, the spectrum collection system includes a spectrum collection window, the light source system is located around the spectrum collection system, and the spectrum collection system The system is located directly above the sample to be measured, and it is characterized in that the detection system also includes a calibration system, the calibration system includes a calibration head, a moving shaft, and a motor, the calibration head includes a partition and a whiteboard, and the motor passes through the moving shaft Drive the partition and the white board to pass directly under the spectrum collection window in sequence. The size of the spectrum collection window is smaller than the size of the partition. When the partition is located directly below the spectrum collection window, the partition completely blocks the spectrum from entering the spectrum collection window. into the spectral collection system.

Optimally, the light source system includes multiple light sources, which are evenly distributed around the spectrum collection system.

Optimally, the calibration system further includes a lower fixing plate, the lower fixing plate is provided with an optical window, the optical window is located directly below the spectrum collection system, and the sample to be detected is located directly below the optical window.

Optimally, the distance between the lowest point of the spectrum collection system and the lower fixing plate is smaller than the distance between the light source system and the lower fixing plate.

Optimally, the motor is a stepper motor.

Optimally, the whiteboard is close to the lower fixed plate, but not in contact with the lower fixed plate, and is located above the lower fixed plate, and the size of the optical window is smaller than that of the whiteboard.

Preferably, the calibration system further includes an upper fixing plate, the light source system and the spectrum collection system are fixed on the upper fixing plate, the spectrum collection system includes an optical fiber interface, and the optical fiber interface is fixed above the upper fixing plate.

Optimally, the motor is fixed on the lower fixing plate.

Optimally, it also includes a fully enclosed structure, which is combined with the upper fixing plate and the lower fixing plate to completely seal the diffuse reflectance detection system.

A method using the above-mentioned self-correcting near-infrared diffuse reflectance detection system, the steps are as follows:

(1) Start the motor;

(2) The motor drives the calibration head through the moving shaft to completely block the spectrum collection window by the partition. At this time, the spectrum collection system is completely isolated from the light source, and the background spectrum is collected;

(3) The motor drives the calibration head through the moving shaft to completely cover the optical window with the whiteboard. At this time, the light source irradiates the whiteboard to produce a reference spectrum;

(4) The motor continued to rotate, and when the whiteboard left the optical window, the light source irradiated the sample, and what the spectral collection system collected was the original spectrum of the sample;

(5) Through the collection of the background spectrum, the reference spectrum and the original spectrum of the sample, after the calculation of the reflectance and absorbance, it is converted into the near-infrared spectrum of the absorbance.

The advantages of the present invention are:

(1) The present invention uses an automatic correction system, so that the automatic correction of the background spectrum and the reference spectrum can be realized, and the remote measurement of the sample can be realized.

(2) The present invention uses multiple light source systems, which weakens the impact of near-infrared light source fluctuations in a single light source system on the detection process of near-infrared diffuse reflection.

(3) The upper fixing plate and the lower fixing plate are adopted in the present invention, which makes the whole detection system more stable.

(4) The present invention adopts a fully enclosed structure, which eliminates the influence of the outside world on the detection result, thereby improving the stability of the signal and the measurement accuracy.

(5) The detection method in the present invention can easily obtain the background spectrum, reference spectrum, and original spectrum of each sample, so that the obtained near-infrared spectrum is more accurate.

Description of drawings

Fig. 1 is the schematic diagram of the background spectrum correction of the near-infrared diffuse reflectance spectrum automatic correction system of the present invention;

Figure 2 is a schematic diagram of the reference spectrum calibration of the near-infrared diffuse reflectance spectrum automatic calibration system;

Figure 3 is a schematic diagram of the original spectrum of the near-infrared diffuse reflectance spectroscopy automatic correction system;

Fig. 4 is the background spectrum collected by the automatic calibration system;

Fig. 5 is the reference spectrum collected by the automatic calibration system;

Fig. 6 is the original spectrum collected by the automatic calibration system;

Figure 7 is the near-infrared spectrum of urea collected by the automatic calibration system;

Fig. 8 is the near-infrared spectrum of corn collected by the automatic calibration system;

Figure 9 shows the near-infrared spectrum of soybeans collected by the automatic calibration system.

detailed description

The embodiments of the present invention are described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1

As shown in Figure 1-3, an automatic correction near-infrared diffuse reflectance detection system includes an optical system, the optical system includes a light source system and a spectrum collection system, the light source system is located around the spectrum collection system, and the spectrum collection system is located at the required Measure directly above the sample.

The light source system includes a near-infrared light source 1 and an optical filter 2. The near-infrared light source 1 passes through the optical filter 2 to eliminate unnecessary wave bands. Optimally, the light source system includes multiple light sources, which are evenly distributed around the spectrum collection system, thus reducing the impact of near-infrared light source fluctuations in a single light source system on the process of near-infrared diffuse reflectance detection.

The spectrum collection system includes a spectrum collection window 5 , an optical collection lens 3 , and an optical fiber interface 18 , and the spectrum is coupled to an optical fiber through the optical collection lens 3 and the optical fiber connector 18 .

The detection system also includes a correction system. The correction system includes a correction head, a moving shaft 10, and a motor 4. The correction head includes a partition 6 and a whiteboard 7. The motor 4 drives the partition 6 and the whiteboard 7 through the moving shaft 10 to pass through the spectrum collection window 5 in sequence. Directly below. The partition 6 is not smaller than the size of the spectrum collection window 5. When the partition 6 is located directly below the spectrum collection window 5, the partition 6 can completely block the near-infrared light 15 from entering the spectrum collection system from the spectrum collection window 5. The calibration system also includes a lower fixing plate 9, the lower fixing plate 9 is provided with an optical window 8, the optical window 8 is located directly below the spectrum collection system, the near-infrared light 15 irradiates the sample 16 through the optical window 8, and the sample to be detected is located at Just below the optical window 8. The whiteboard 7 is close to the lower fixed plate 9, but not in contact with the lower fixed plate 9. It is located above the lower fixed plate 9. The white plate 9 is not less than the size of the optical window 8, so as to prevent the near-infrared light 15 from irradiating the sample 16 and the white plate 9 at the same time. Collection of reference spectra.

Optimally, the motor 4 is a stepper motor and is fixed on the lower fixing plate 9 .

Optimally, the calibration system further includes an upper fixing plate 12 , on which both the light source system and the spectrum collection system are fixed, and the optical fiber interface 18 is fixed above the upper fixing plate 12 . Wherein, the distance between the lowest point of the spectrum collection system and the lower fixing plate 9 is smaller than the distance between the light source system and the lower fixing plate 9 . In this way, the partition 6 can better shield the spectrum collection window 5 .

The near-infrared reflection detection system also includes a fully enclosed structure 20, which is combined with the upper fixing plate 12 and the lower fixing plate 9 to seal the diffuse reflection detection system completely. In this way, the influence of the outside world on the detection result is eliminated, thereby improving the stability of the signal and the measurement accuracy.

Example 2

A detection method using an automatic correction near-infrared diffuse reflectance detection system, the system is consistent with the connection mode and working principle described in Embodiment 1.

The method of using the near-infrared diffuse reflectance detection system of automatic correction, its steps are as follows:

(1) Start the motor.

(2) The motor drives the calibration head through the moving shaft to completely block the spectrum collection window 5 by the partition. At this time, the spectrum collection system is completely isolated from the light source, and the background spectrum is collected.

When the calibration head moves to the position in Figure 1, the partition 6 of the calibration head is close to the spectrum collection window 5, blocking the near-infrared light 15 emitted by the light source from the spectrum collection system, and the background spectrum 13 generated at this time passes through the optical collection lens 3 and fiber optic connector 18 coupled into the optical fiber.

(3) The motor drives the calibration head through the moving shaft to completely cover the optical window 8 by the whiteboard. At this time, the light source irradiates the whiteboard to generate a reference spectrum.

When the calibration head moved to the position shown in Fig. 2, the whiteboard 7 of the calibration head was just below the spectrum collection system and directly above the optical window 8, and the near-infrared light 15 emitted by the light source was irradiated on the whiteboard 7 to generate a reference spectrum 14, The reference spectrum 14 is coupled into the optical fiber through the optical collection lens 3 and the optical fiber connector 18 .

(4) The motor continues to rotate. When the whiteboard leaves the optical window 8, the light source illuminates the sample, and the spectrum collection system collects the original spectrum of the sample.

When the calibration head moves to the position in Figure 3, the calibration head is far away from the optical window 8 and the spectrum collection system, the near-infrared light 15 emitted by the light source passes through the optical window 8 and irradiates the sample 16 to generate a near-original spectrum 17, and the original spectrum 17 of the sample 16 passes through The optical window 8 is collected by an optical collection system and coupled to an optical fiber.

(5) Through the collection of the background spectrum 13, the reference spectrum 14 and the original spectrum 17 of the sample 16, the reflectance and absorbance are calculated, and finally the near-infrared spectrum converted into absorbance is realized to automatically correct the spectral signal.

(6) The motor rotates in reverse, and the correction head resets.

Below are the near-infrared spectra of urea, soybean and corn using an auto-calibration probe.

The detection process of this embodiment is: this implementation case adopts three near-infrared light sources, and the energy is 5W halogen tungsten lamps 1, 1', 1" (halogen tungsten lamp 1 "can not be seen in the figure), through the filter sheet 2, 2', 2" (filter 2" cannot be seen in the picture), filter out the bands other than 1000-2500nm, and the three light sources are evenly distributed around the spectrum collection system. The moving shaft 10 of the stepping motor 4 drives the calibration head to move. When the partition 6 of the calibration head moves to the right below the spectrum collection system, the length and width of the partition are 40mm. The near-infrared light 15 is blocked from entering the spectrum collection system through the collection window 5 with a diameter of 30 mm, and transmitted to the spectrometer through an optical fiber for splitting and detection. At this time, the background spectrum 13 is collected, and the collected spectrum is shown in FIG. 4 . When the whiteboard 7 of the correction head moves to the right below the spectrum collection system and directly above the optical window 8 with a diameter of 30mm, the near-infrared light 15 emitted by the light source is irradiated on the whiteboard 7 with a length and width of 40mm to generate a reference spectrum 14. The spectrum 14 passes through the collection window 5 and is coupled to the optical fiber through the optical collection lens 3 with a diameter of 30mm and the optical fiber connector 18, and the reference spectrum 14 transmitted to the spectrometer for spectroscopic and detection is shown in FIG. 5 . When the calibration head is far away from the directly below the spectrum collection system and directly above the optical window 8, the near-infrared light emitted by the light source irradiates the sample 16 through the optical window 8 to produce an original spectrum 17 corresponding to the sample, and the actual measurement position of the sample 16 is the same as The difference between the optical windows 8 is 30 mm, and the original spectrum 17 is coupled into the optical fiber through the collection system and transmitted to the spectrometer. The measured spectrum is shown in FIG. 6 . The collected background spectrum 13 , reference spectrum 14 and original spectrum 17 can be calculated by reflectance and absorbance to obtain a near-infrared absorption spectrum corresponding to urea, as shown in FIG. 7 .

According to the above method, the background spectrum 13, the reference spectrum 14 and the original spectrum 17 of corn can be collected respectively, and the near-infrared diffuse reflectance absorption spectrum of corn can be obtained according to the formula in the background art, as shown in FIG. 8 . The near-infrared diffuse reflectance absorption spectrum of soybean obtained by the same method is shown in Fig. 9 .

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (10)

1. A near-infrared diffuse reflectance detection system for automatic correction, comprising an optical system, the optical system comprising a light source system and a spectrum collection system, the spectrum collection system comprising a spectrum collection window, the light source system being positioned around the spectrum collection system, The spectrum collection system is located directly above the sample to be measured, and it is characterized in that the detection system also includes a calibration system, the calibration system includes a calibration head, a moving shaft, and a motor, and the calibration head includes a partition and a whiteboard, and the motor passes through The moving shaft drives the partition and the whiteboard to pass directly under the spectrum collection window in turn. The size of the spectrum collection window is smaller than the size of the partition. When the partition is located directly below the spectrum collection window, the partition completely blocks the spectrum from the spectrum collection window. into the spectral collection system. 2. The self-correcting near-infrared diffuse reflectance detection system according to claim 1, wherein the light source system comprises a plurality, and is evenly distributed around the spectrum collection system. 3. the near-infrared diffuse reflectance detection system of automatic correction according to claim 1, is characterized in that, described correction system also comprises lower fixed plate, and described lower fixed plate is provided with optical window, and described optical window is positioned at Directly below the spectrum collection system, the sample to be detected is located directly below the optical window. 4. The near-infrared diffuse reflectance detection system for automatic correction according to claim 2, wherein the distance between the lowest point of the spectrum collection system and the lower fixed plate is smaller than the distance between the light source system and the lower fixed plate. 5. The automatic correction near-infrared diffuse reflectance detection system according to claim 1, wherein the motor is a stepping motor. 6. The near-infrared diffuse reflectance detection system of automatic correction according to claim 3, wherein the whiteboard is close to the lower fixed plate, but not in contact with the lower fixed plate, and is positioned above the lower fixed plate, and the optical window The size of the sheet is smaller than the size of a whiteboard. 7. The near-infrared diffuse reflectance detection system of automatic correction according to claim 3, characterized in that, the correction system also includes an upper fixed plate, and the light source system and the spectrum collection system are all fixed on the upper fixed plate, and the The spectrum collection system includes an optical fiber interface, and the optical fiber interface is fixed above the upper fixing plate. 8. The near-infrared diffuse reflectance detection system for automatic correction according to claim 5, wherein the motor is fixed on the lower fixing plate. 9. The near-infrared diffuse reflection detection system for automatic correction according to claim 5, further comprising a fully enclosed structure, the fully enclosed structure is combined with the upper fixing plate and the lower fixing plate to completely seal the diffuse reflection detection system . 10. A method for detecting using the self-correcting near-infrared diffuse reflectance detection system according to any one of claims 1-9, wherein the steps are as follows: (1) Start the motor; (2) The motor drives the calibration head through the moving shaft to completely block the spectrum collection window by the partition. At this time, the spectrum collection system is completely isolated from the light source, and the background spectrum is collected; (3) The motor drives the calibration head through the moving shaft to completely cover the optical window with the whiteboard. At this time, the light source irradiates the whiteboard to produce a reference spectrum; (4) The motor continued to rotate, and when the whiteboard left the optical window, the light source irradiated the sample, and what the spectral collection system collected was the original spectrum of the sample; (5) Through the collection of the background spectrum, the reference spectrum and the original spectrum of the sample, after the calculation of the reflectance and absorbance, it is converted into the near-infrared spectrum of the absorbance.