CN112461790B - Diffuse reflection spectrum detection device and detection method - Google Patents
Diffuse reflection spectrum detection device and detection method Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/47—Scattering, i.e. diffuse reflection
- G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
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- G—PHYSICS
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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- G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/47—Scattering, i.e. diffuse reflection
- G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
- G01N21/474—Details of optical heads therefor, e.g. using optical fibres
Abstract
A diffuse reflection spectrum detection device comprises a sample real-time measurement light path, a background spectrum calibration light path, a wavelength calibration light path, a light path switching device and a spectrometer, wherein the sample real-time measurement light path, the background spectrum calibration light path and the wavelength calibration light path are switched through the light path switching device and transmitted to the spectrometer through optical fibers for light splitting detection. The calibration light source and the detection light source are placed in a close distance, so that the preheating time of the calibration light source can be shortened, the time of calibrating the wavelength is shortened, the service life of the calibration light source is prolonged, the internal temperature stability of the instrument is ensured, and the accuracy of the measured value of the sample is not influenced by wavelength calibration.
Description
Technical Field
The invention relates to the technical field of optical detection, in particular to a diffuse reflection spectrum detection device and a detection method.
Background
Spectroscopic detection is a widely used technique in research and production. With the improvement of the technical level of spectral detection in China and the increase of the demand of China on spectral analyzers in a plurality of fields such as food detection, environmental monitoring and the like in recent years, the scale of the spectral analyzer industry in China is continuously expanded. The existing spectral analysis instrument mainly has the following problems: 1. depending on import, the high price of imported products and disjointed after-sale technical service hinder the popularization of the technology in China and seriously affect the development of the technical level in China. 2. By adopting a plurality of conversion mechanisms to realize the switching of the sample light, the background light and the calibration light path, the long-time online use can cause the reduction of the conversion performance. 3. The device is easily interfered by background light during measurement, and the wavelength is easily shifted during use.
Disclosure of Invention
In view of the above, the main objective of the present invention is to provide a diffuse reflectance spectrum detection apparatus and detection method, which are intended to partially solve at least one of the above technical problems.
In order to achieve the above object, as an aspect of the present invention, a diffuse reflection spectrum detection apparatus is provided, which includes a sample real-time measurement optical path, a background spectrum calibration optical path, a wavelength calibration optical path, an optical path switching apparatus, and a spectrometer, wherein the sample real-time measurement optical path, the background spectrum calibration optical path, and the wavelength calibration optical path are switched by the optical path switching apparatus, and transmitted to the spectrometer through an optical fiber for spectroscopic detection.
The real-time sample measuring optical path comprises a detection light source, a reflection cup, a second reflector and a condensing lens; the light signal of the detection light source is reflected to a sample to be detected by the reflection cup, is diffusely reflected to the second reflector by the sample to be detected, is reflected by the second reflector, and is converged into the optical fiber by the condenser lens, so that the optical signal enters the spectrometer for spectral analysis.
The background spectrum calibration light path comprises a detection light source, a reflection cup, a first reflector, a second reflector, a standard reflector plate and a condensing lens; the light signal of the detection light source is reflected to the first reflector by the reflection cup, the light signal is reflected to the standard reflector by the first reflector, is diffused and reflected to the second reflector by the standard reflector, is reflected by the second reflector, and is converged to enter the optical fiber through the condensing lens, so that the optical signal enters the spectrometer for spectroscopic analysis.
The wavelength calibration light path comprises a calibration light source, a first reflector, a second reflector, a standard reflector plate and a condensing lens; the optical signal emitted by the calibration light source is diffused and reflected to the first reflector through the standard reflector, reflected to the second reflector through the first reflector, reflected through the second reflector, and converged into the optical fiber through the condensing lens, so that the optical signal enters the spectrometer for spectral analysis.
The calibration light source is a light source with a stable characteristic spectral line at a required wave band.
The optical path switching device comprises a first reflector, a standard reflector, a motion mechanism and a control circuit; the first reflector and the standard reflector are arranged on the movement mechanism according to a certain angle, the control circuit controls the position of the movement mechanism, and different light paths are switched by changing the positions of the first reflector and the standard reflector to realize wavelength calibration, background spectrum calibration, dark noise calibration and real-time measurement; and/or
The optical path switching device enables the optical signal received by the spectrometer to be strongest by adjusting the included angle between the first reflector and the standard reflector.
As another aspect of the present invention, there is provided a diffuse reflectance spectrum detection method, including the steps of:
starting up the machine to supply power to the mercury lamp and carry out wavelength calibration;
closing the mercury lamp when the wavelength calibration is finished, and carrying out dark noise calibration;
when the dark current calibration is finished, supplying power to the halogen lamp for background calibration to obtain the background light intensity;
detecting the diffuse reflection spectrum of the sample to be detected to obtain the light intensity of the sample to be detected after diffuse reflection;
and calculating the absorbance of the sample to be detected in real time by using an absorbance calculation formula according to the background light intensity and the light intensity of the sample to be detected after diffuse reflection, and further calculating the content of the substance in the sample to be detected.
Wherein the dark noise calibration comprises: when all the light sources are in the off state, dark noise calibration is carried out; when the movement mechanism returns the first reflector and the standard reflector to the inside of the instrument, the second reflector receives the optical signal after the diffuse reflection of the sample, and the spectrometer receives the optical signal after the diffuse reflection of the sample to be detected so as to realize the collection of the optical signal after the diffuse reflection of the sample to be detected; and/or the presence of a gas in the gas,
when the movement mechanism transmits the first reflector to the standard reflector, the first reflector reflects the light emitted by the detection light source to the standard reflector, and the spectrometer receives a background light signal so as to calibrate the background light; and/or the presence of a gas in the gas,
when the movement mechanism transmits the standard reflecting plate to the position capable of receiving the optical signal sent by the calibration light source, the standard reflecting plate diffuses and reflects the light of the calibration light source to the first reflecting mirror, the second reflecting mirror receives the optical signal reflected by the first reflecting mirror, and the spectrometer receives the calibration optical signal so as to calibrate the wavelength.
The calibration of the wavelength, the calibration of the background light and the calibration of the dark noise have no requirement in sequence, and the calibration can be respectively calibrated at fixed time in the using process; and/or
When the wavelength calibration is needed, the calibration light source can be turned on in advance to preheat, and the optical signal emitted by the calibration light source does not influence the real-time measurement result of the sample.
The wavelength calibration method comprises the steps of selecting a plurality of representative wavelengths to carry out wavelength calibration, recording the positions of selected corresponding pixel points and corresponding intensity values, and simultaneously recording the positions of the left pixel point and the right pixel point of the selected pixel points and the intensity values thereof, wherein the calculation formula is as follows:
λ X ＝A 3 ×X 3 +A 2 ×X 2 +A 1 ×X+A 0 (2)；
x in the formula (1) is the actual pixel point position of the wavelength corresponding point to be searched, and X is 0 For directly reading pixel positions, I 0 Is a position X 0 At the corresponding intensity value, I R Is X 0 Intensity value corresponding to the right pixel point, I L Is X 0 The intensity value corresponding to the left pixel point;
in the formula (2) < lambda > X For each pixel point corresponding wavelength obtained by polynomial fitting, coefficient A 0 -A 3 And obtaining the wavelength corresponding to the selected wavelength calibration lamp spectral line and the actual pixel point corresponding to the wavelength calibration lamp spectral line through fitting.
Based on the technical scheme, compared with the prior art, the diffuse reflection spectrum detection device and the detection method have at least one of the following beneficial effects:
1. the calibration light source and the detection light source are placed in a close distance, so that the preheating time of the calibration light source can be shortened, the time of calibrating the wavelength is shortened, the service life of the calibration light source is prolonged, the internal temperature stability of the instrument is ensured, and the accuracy of the measured value of the sample is not influenced by wavelength calibration.
2. The invention can turn on the calibration light source in advance to preheat before calibrating the wavelength, shortens the time of calibrating the wavelength and does not influence the measurement of other optical signals.
3. The optical system of the invention has no moving parts basically, thus reducing the loss of elements and greatly improving the stability of the instrument.
4. The diffuse reflection type measurement is adopted, the sample is not damaged, the operation is simple, no interference is caused, and the cost is low.
5. The sample optical signal, the background optical signal and the calibration optical signal are in the same environment and pass through the same optical system, so that the measurement of the spectrum is more accurate.
Drawings
FIG. 1 is a schematic diagram of a background calibration light path;
FIG. 2 is a schematic illustration of a wavelength calibration optical path;
FIG. 3 is a schematic diagram of a sample detection optical path;
FIG. 4 is a schematic view of an optical path switching apparatus;
FIG. 5 is a graph of the spectrum of a mercury lamp at 900-1650 nm;
FIG. 6 is a dark current spectrum of a spectrometer in the near infrared band in the absence of illumination;
FIG. 7 is a spectral plot of the spectrometer collected in the near infrared band when measuring background light;
FIG. 8 is a spectrum of a near infrared band acquired by a spectrometer after soybean diffuse reflection;
FIG. 9 is a graph of absorbance in the near infrared band of soybeans after dark current calibration.
Detailed Description
The diffuse reflection spectrum detection device disclosed by the invention sequentially comprises a detection light source, a calibration light source, a reflection cup, a reflector 1, a reflector 2, a diffuse reflection plate, a condensing lens, an optical fiber, a light path switching device and a spectrometer. The light path switching device is provided with a reflector, a standard reflecting plate, a motion mechanism and a control circuit. The control circuit controls the position of the movement mechanism, and different light paths are switched by switching the positions of the reflector and the standard reflector to realize wavelength calibration, background spectrum calibration, dark noise calibration and real-time measurement. The influence caused by background interference and wavelength drift can be automatically corrected in the using process of a user, and the detection precision and reliability are improved. The device has the advantages of low price, easy maintenance and good stability.
The invention discloses a diffuse reflection spectrum detection device, which comprises a sample real-time measurement light path, a background spectrum calibration light path, a wavelength calibration light path, a light path switching device and a spectrometer, wherein the sample real-time measurement light path, the background spectrum calibration light path and the wavelength calibration light path are switched through the light path switching device and transmitted to the spectrometer through optical fibers for light splitting detection.
The real-time sample measuring optical path comprises a detection light source, a reflection cup, a second reflector and a condensing lens; the light signal of the detection light source is reflected to a sample to be detected by the reflection cup, is diffusely reflected to the second reflector by the sample to be detected, is reflected by the second reflector, and is converged into the optical fiber by the condenser lens, so that the optical signal enters the spectrometer for spectral analysis.
The background spectrum calibration light path comprises a detection light source, a reflection cup, a first reflector, a second reflector, a standard reflector plate and a condensing lens; the light signal of the detection light source is reflected to the first reflector by the reflection cup, the light signal is reflected to the standard reflector by the first reflector, is diffused to the second reflector by the standard reflector, is reflected by the second reflector, and is converged into the optical fiber by the condensing lens, so that the optical signal enters the spectrometer for spectral analysis.
The wavelength calibration light path comprises a calibration light source, a first reflector, a second reflector, a standard reflector plate and a condensing lens; the optical signal emitted by the calibration light source is diffused and reflected to the first reflector through the standard reflector, reflected to the second reflector through the first reflector, reflected through the second reflector, and converged into the optical fiber through the condensing lens, so that the optical signal enters the spectrometer for spectral analysis.
The calibration light source is a light source with a stable characteristic spectral line at a required wave band.
The optical path switching device comprises a first reflector, a standard reflector, a motion mechanism and a control circuit; the first reflector and the standard reflector are arranged on the movement mechanism according to a certain angle, the control circuit controls the position of the movement mechanism, and different light paths are switched by changing the positions of the first reflector and the standard reflector to realize wavelength calibration, background spectrum calibration, dark noise calibration and real-time measurement; and/or
The optical path switching device enables the optical signal received by the spectrometer to be strongest by adjusting the included angle between the first reflector and the standard reflector.
The invention also discloses a diffuse reflection spectrum detection method, which comprises the following steps:
starting up the machine to supply power to the mercury lamp and carry out wavelength calibration;
when the wavelength calibration is finished, the mercury lamp is turned off to carry out dark noise calibration;
when the dark current calibration is finished, supplying power to the halogen lamp for background calibration to obtain the background light intensity;
detecting the diffuse reflection spectrum of the sample to be detected to obtain the light intensity of the sample to be detected after diffuse reflection;
and calculating the absorbance of the sample to be detected in real time by using an absorbance calculation formula according to the background light intensity and the light intensity of the sample to be detected after diffuse reflection, and further calculating the content of substances in the sample to be detected.
Wherein the dark noise calibration comprises: when all light sources are in a closed state, dark noise calibration is carried out; when the movement mechanism returns the first reflector and the standard reflector to the inside of the instrument, the second reflector receives the optical signal after the diffuse reflection of the sample, and the spectrometer receives the optical signal after the diffuse reflection of the sample to be detected so as to realize the collection of the optical signal after the diffuse reflection of the sample to be detected; and/or the presence of a gas in the gas,
when the movement mechanism transmits the first reflector to the standard reflector, the first reflector reflects the light emitted by the detection light source to the standard reflector, and the spectrometer receives a background light signal so as to calibrate the background light; and/or the presence of a gas in the atmosphere,
when the moving mechanism transmits the standard reflecting plate to the position capable of receiving the optical signal sent by the calibration light source, the standard reflecting plate diffusely reflects the light of the calibration light source to the first reflecting mirror, the second reflecting mirror receives the optical signal reflected by the first reflecting mirror, and the spectrometer receives the calibration optical signal so as to calibrate the wavelength.
The calibration of the wavelength, the calibration of the background light and the calibration of the dark noise have no sequential requirements, and the calibration can be respectively calibrated at fixed time in the using process; and/or
When the wavelength calibration is needed, the calibration light source can be turned on in advance for preheating, and the optical signal emitted by the calibration light source does not influence the real-time measurement result of the sample.
The wavelength calibration method comprises the steps of selecting a plurality of representative wavelengths to carry out wavelength calibration, recording the positions and the corresponding intensity values of selected corresponding pixel points, and simultaneously recording the positions and the intensity values of the left and the right two pixel points of the selected pixel points, wherein the calculation formula is as follows:
λ X ＝A 3 ×X 3 +A 2 ×X 2 +A 1 ×X+A 0 (2)；
x in the formula (1) is the actual pixel point position of the wavelength corresponding point to be searched, and X is 0 For directly reading pixel positions, I 0 Is a position X 0 At the corresponding intensity value, I R Is X 0 Intensity value corresponding to the right pixel point, I L Is X 0 The intensity value corresponding to the left pixel point;
in the formula (2) < lambda > X For each pixel point corresponding wavelength obtained by polynomial fitting, coefficient A 0 -A 3 And obtaining the wavelength corresponding to the selected wavelength calibration lamp spectral line and the actual pixel point corresponding to the wavelength calibration lamp spectral line through fitting.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the accompanying drawings in combination with the embodiments.
Fig. 1-3 are schematic diagrams illustrating an optical path structure of the apparatus for detecting diffuse reflection spectrum in near infrared band according to the present embodiment.
The device comprises a halogen lamp, a mercury lamp, a reflector cup, a reflector 1 (namely a first reflector), a reflector 2 (namely a second reflector), a diffuse reflection plate, an aspheric lens, an optical fiber, an optical path conversion device and a spectrometer, wherein as shown in fig. 4, the optical path conversion device is a schematic diagram of the optical path conversion device, and the optical path conversion device is provided with the reflector, a standard reflector, a movement mechanism (namely a guide rail) and a control circuit (not shown). The reflector and the standard reflecting plate are arranged on the moving mechanism according to a certain angle. The control circuit controls the position of the movement mechanism, and different light paths are switched by changing the positions of the reflector and the standard reflector so as to realize the operations of real-time measurement, background spectrum calibration, wavelength calibration and dark noise calibration in the use process.
The method comprises the following steps:
1. when the spectrometer is started, wavelength calibration is carried out, namely, the mercury lamp is powered on firstly, the moving mechanism is moved to the position shown in figure 2, light emitted by the mercury lamp is diffusely reflected to the reflector 1 by the standard reflector, reflected to the reflector 2 by the reflector 1 and reflected by the reflector 2, the calibration light signal is converged by the aspherical mirror, and the converged light signal is transmitted to the spectrometer for spectral analysis by the optical fiber. The wavelength calibration can be performed regularly during the measurement process.
2. And when the wavelength calibration is finished, closing the mercury lamp and carrying out dark current calibration.
3. When the dark current calibration is finished, the halogen lamp is powered to carry out background calibration. The movement mechanism is moved to the position shown in figure 1, light emitted by the halogen lamp irradiates the reflector 1 after being reflected by the reflecting cup, is reflected to the standard reflecting plate by the reflector 1, is diffusely reflected to the reflector 2 by the standard reflecting plate, is reflected by the reflector 2, converges background light signals by the aspherical mirror, and transmits the converged light signals to the spectrometer for spectral analysis by the optical fiber.
4. When the background signal is collected, the movement mechanism is moved to the position shown in fig. 3 to collect the sample light signal, the light emitted by the halogen lamp is reflected by the reflection cup and then irradiates the soybean, the light signal after the soybean diffuse reflection is reflected by the reflector 2, the sample light signal is converged by the aspherical mirror, and the converged light signal is transmitted to the spectrometer through the optical fiber for spectral analysis.
5. When the wavelength calibration is carried out again, the control circuit turns on the mercury lamp, turns off the halogen lamp at the same time, moves the movement mechanism to the wavelength calibration position, and at the moment, the spectrometer receives a wavelength calibration signal and applies a wavelength calibration formula to carry out wavelength calibration.
6. And (5) repeating the steps (2), (3) and (4) after the wavelength calibration is finished.
7. The absorbance of the soybean can be calculated in real time by using an absorbance calculation formula according to the obtained background light intensity and the light intensity after the diffuse reflection of the sample, and the content of substances in the soybean is further calculated.
Wherein the absorbance of the sample is calculated according to the following formula:
wherein A is the absorbance of the sample in the measuring wave band, R is the optical signal reflectance after the optical signal is reflected by the sample, I 0 The intensity of light received by the spectrometer during background calibration is shown as I, and the intensity of light received by the spectrometer after diffuse reflection of the sample is shown as I. I is a The absorbance of the measured sample is calculated for the intensity of the spectrometer without incident light, and the content of the substance in the sample is further calculated.
The wavelength calibration method in this embodiment is as follows: selecting four representative wavelengths to carry out wavelength calibration, recording the positions of the four pixel points and corresponding intensity values, recording the positions of the left and right two pixel points of the four pixel points and the intensity values of the two pixel points, and solving the wavelength corresponding to each actual pixel point by the following formula. The calculation formula is as follows:
λ X ＝A 3 ×X 3 +A 2 ×X 2 +A 1 ×X+A 0 (2)
the actual pixel position of the point corresponding to the wavelength to be found in the formula (1) X, X 0 For directly read pixel location (obtained by peak finding), I 0 Is X 0 Corresponding intensity value, I R Is X 0 Intensity value corresponding to the right pixel point, I L Is X 0 The intensity value corresponding to the left pixel point. In the formula (2) < lambda > X The coefficient A is obtained by fitting the wavelength corresponding to each pixel point through a polynomial, and the wavelength corresponding to the selected wavelength calibration lamp spectral line and the actual pixel point corresponding to the wavelength calibration lamp spectral line are fitted for three times.
If wavelength calibration is needed in the real-time measurement process, the calibration light source can be turned on in advance for preheating, so that the calibration light source is more stable in the wavelength calibration process, and the optical signal of the calibration light source cannot influence the real-time measurement of the sample.
The band measured in this embodiment is the near infrared band 900-1700nm, and the corresponding band can be selected according to different requirements.
In this embodiment, a halogen lamp is used as the detection light source.
The sample in this example was selected to measure the amount of material in soybeans. Any sample that needs to be measured can also be measured.
In this embodiment, the light-reflecting cup is adopted to directly receive part of the optical signals emitted by the detection light source, and a concave reflector can also be installed on the other side of the detection light source to reflect more of the optical signals emitted by the detection light source to the light-reflecting cup.
The condensing lens in this embodiment is an aspherical lens, and a combination lens may be selected according to the length of a desired focal point.
In this embodiment, the wavelength calibration signal collection light source is a mercury lamp, and the waveform diagram of the mercury lamp in the near infrared band is shown in fig. 5, and the light source can be selected according to the band to be measured.
As shown in fig. 6 to 9, they are schematic diagrams of the detection results of the present embodiment, including a dark noise spectrum, a spectrum, and an absorbance spectrum. Wherein, fig. 6 is a dark current spectrum of the spectrometer in the near infrared band without illumination when no illumination is provided, fig. 7 is a spectrum acquired by the spectrometer in the near infrared band when the background light is measured, fig. 8 is a spectrum acquired by the spectrometer in the near infrared band after soybean diffuse reflection, and data of fig. 6-8 can be obtained by using an absorbance formula
The absorbance of the soybeans in the near infrared band was calculated as shown in FIG. 9.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A diffuse reflection spectrum detection device is characterized by comprising a sample real-time measurement light path, a background spectrum calibration light path, a wavelength calibration light path, a light path switching device and a spectrometer, wherein the sample real-time measurement light path, the background spectrum calibration light path and the wavelength calibration light path are switched through the light path switching device and transmitted to the spectrometer through optical fibers for light splitting detection;
the optical path switching device comprises a first reflector, a standard reflector, a motion mechanism and a control circuit; the first reflector and the standard reflector are arranged on the movement mechanism according to a certain angle, the control circuit controls the position of the movement mechanism, and different light paths are switched by changing the positions of the first reflector and the standard reflector to realize wavelength calibration, background spectrum calibration, dark noise calibration and real-time measurement;
the diffuse reflection spectrum detection device comprises a detection light source, a reflection cup, a second reflector and a condensing lens;
under the condition that the optical path is switched to the real-time sample measuring optical path by the optical path switching device, the light reflecting cup reflects an optical signal of a detection light source to a sample to be detected, the optical signal is diffusely reflected to the second reflector by the sample to be detected, is reflected by the second reflector, and is converged into an optical fiber by the condensing lens so as to enter a spectrometer for spectroscopic analysis;
under the condition that the light path is switched to the background spectrum calibration light path by the light path switching device, the light signal of the detection light source is reflected to the first reflector by the reflection cup, the light signal is reflected to the standard reflector by the first reflector, is diffusely reflected to the second reflector by the standard reflector, is reflected by the second reflector, and is converged into the optical fiber by the condensing lens so as to enter the spectrometer for light splitting analysis;
under the condition that the optical path switching device switches the optical path to the wavelength calibration optical path, the optical signal emitted by the calibration light source is diffusely reflected to the first reflector through the standard reflector, reflected to the second reflector through the first reflector, reflected through the second reflector, and converged into the optical fiber through the condensing lens, so as to enter the spectrometer for spectral analysis.
2. The diffuse reflection spectrum detection device of claim 1, wherein the real-time sample measurement optical path comprises a detection light source, a reflective cup, a second reflector and a condenser lens.
3. The diffuse reflectance spectrum detection apparatus according to claim 1, wherein the background spectral calibration optical path comprises a detection light source, a reflector cup, a first reflector, a second reflector, a standard reflector plate and a condenser lens.
4. The diffuse reflectance spectrum detection apparatus according to claim 1, wherein the wavelength calibration light path comprises a calibration light source, a first mirror, a second mirror, a standard reflecting plate, and a condenser lens.
5. The diffuse reflectance spectrum detection apparatus according to claim 4, wherein the calibration light source is a light source having a stable characteristic spectrum line at a desired wavelength band.
6. The diffuse reflection spectrum detection device of claim 1, wherein the light path switching device makes the light signal received by the spectrometer strongest by adjusting the angle between the first reflector and the standard reflector.
7. A detection method using the diffuse reflectance spectrum detection apparatus according to any one of claims 1 to 6, comprising the steps of:
starting up the machine to supply power to the mercury lamp and carry out wavelength calibration;
closing the mercury lamp when the wavelength calibration is finished, and carrying out dark noise calibration;
when the dark current calibration is finished, supplying power to the halogen lamp for background calibration to obtain the background light intensity;
detecting the diffuse reflection spectrum of the sample to be detected to obtain the light intensity of the sample to be detected after diffuse reflection;
and calculating the absorbance of the sample to be detected in real time by using an absorbance calculation formula according to the background light intensity and the light intensity of the sample to be detected after diffuse reflection, and further calculating the content of substances in the sample to be detected.
8. The detection method of claim 7, wherein the dark noise calibration comprises: when all light sources are in a closed state, dark noise calibration is carried out; when the movement mechanism returns the first reflector and the standard reflector to the inside of the instrument, the second reflector receives an optical signal reflected by a sample in a diffuse manner, and the spectrometer receives the optical signal reflected by the sample to be detected in the diffuse manner at the moment so as to realize the collection of the optical signal reflected by the sample to be detected in the diffuse manner; and/or the presence of a gas in the gas,
when the movement mechanism transmits the first reflector to the standard reflector, the first reflector reflects the light emitted by the detection light source to the standard reflector, and the spectrometer receives a background light signal so as to calibrate the background light; and/or the presence of a gas in the atmosphere,
when the moving mechanism transmits the standard reflecting plate to the position capable of receiving the optical signal sent by the calibration light source, the standard reflecting plate diffusely reflects the light of the calibration light source to the first reflecting mirror, the second reflecting mirror receives the optical signal reflected by the first reflecting mirror, and the spectrometer receives the calibration optical signal so as to calibrate the wavelength.
9. The detection method according to claim 7, wherein the calibration of the wavelength, the calibration of the background light and the calibration of the dark noise have no sequential requirements, and the calibration can be respectively performed at regular time during the use process; and/or
When the wavelength calibration is needed, the calibration light source is turned on in advance to preheat, and the optical signal emitted by the calibration light source does not influence the real-time measurement result of the sample.
10. The detection method according to claim 7, wherein the wavelength calibration method comprises selecting a plurality of representative wavelengths for wavelength calibration, recording positions and corresponding intensity values of selected corresponding pixels, and recording positions and intensity values of two pixels on the left and right of the selected pixels, and the calculation formula is as follows:
λ X ＝A 3 ×X 3 +A 2 ×X 2 +A 1 ×X+A 0 (2)；
x in the formula (1) is the actual pixel point position of the wavelength corresponding point to be searched, and X is 0 For directly reading pixel positions, I 0 Is a position X 0 At the corresponding intensity value, I R Is X 0 Intensity value corresponding to the right pixel point, I L Is X 0 The intensity value corresponding to the left pixel point;
in the formula (2) < lambda > X For each pixel point corresponding wavelength obtained by polynomial fitting, coefficient A 0 -A 3 And obtaining the wavelength corresponding to the selected wavelength calibration lamp spectral line and the actual pixel point corresponding to the wavelength calibration lamp spectral line through fitting.
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