CN101532953A - Method for accurately measuring optical parameters of edible oil - Google Patents
Method for accurately measuring optical parameters of edible oil Download PDFInfo
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- CN101532953A CN101532953A CN200910097283A CN200910097283A CN101532953A CN 101532953 A CN101532953 A CN 101532953A CN 200910097283 A CN200910097283 A CN 200910097283A CN 200910097283 A CN200910097283 A CN 200910097283A CN 101532953 A CN101532953 A CN 101532953A
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Abstract
The invention discloses a method for accurately measuring optical parameters of edible oil by using Terahertz time-domain spectroscopy. By using a transmission-type Terahertz time-domain spectroscopy (THz-TDS) device, the THz time domain spectroscopy of dry paper is measured as a reference signal and the THz time domain spectroscopy of the paper immersed in the edible oil is measured as a sample signal, Flourier transform values of the sample signal and the reference signal are calculated, and refractive index and absorption coefficient of the edible oil in Terahertz waveband is obtained by means of the formula. The invention is low in experimental cost and is simple and convenient in operation as well as reduces multiple reflections and FP effect of the THz wave transmitted in a far-infrared quartz cuvette and efficiently improves measurement accuracy of the optical parameters of the edible oil. The method is fast, convenient and accurate and can measure the optical parameters of the edible oil fast and simply, and the invention can provide a detection method for quality assessment and ingredient analysis of the edible oil.
Description
Technical field
The invention belongs to edible oil quality and constituent analysis detection technique field, relate to a kind of THz wave accurate measuring method of optical parameter of edible oil.
Background technology
Terahertz (Terahertz or THz) ripple typically refers to the electromagnetic wave of frequency in 0.1～10THz interval, and the energy of its photon is about 1～10meV, just in time with molecular vibration and rotational energy level between the energy of transition roughly suitable.Radiation has strong absorption to THz for most of polar molecules such as hydrone, amino molecule etc., and the vibrational energy level of many organic macromolecules (DNA, protein etc.) and the transition between the rotational energy level are also just in time in the THz wavelength band.Therefore, the THz spectrum of material (comprising emission, reflection and transmitted spectrum) includes abundant physics matter and chemical information, it absorbs and dispersion characteristics can be used for doing the detection and the identification of chemistry such as explosive, medicine and biological sample, has important use value at aspects such as physics, chemistry, biomedicine, uranology, material science and environmental sciences.
The action mode that THz spectrum and imaging technique are unique to biomolecule, water, nonpolar object etc. can make this novel detection technique make a breakthrough at agricultural product and food quality detection range.From as seen-fluorescence spectrum, Fourier transform infrared spectroscopy (FTIR), ultra-violet absorption spectrum, to the x-ray imaging analysis etc., spectral analysis and imaging technique are indispensable important means in agricultural product and the food analysis research.With respect near infrared and middle-infrared band, the advantage of THz radiation is that its wavelength is longer, and the scattering of object is less, and the most of nonpolar objects of THz radiation energy transmission are transparent and have only few medium near infrared and intermediate infrared radiation.Utilize comprehensively optical parametric such as refractive index, absorption coefficient and specific inductive capacity etc. that THz time-domain spectroscopic technology (THz-TDS) can obtain sample simultaneously, for quantitatively and multianalysis more useful informations are provided.THz can obtain widespread use at agricultural product and food inspection field as a kind of novel quick, harmless, in the future cheap detection technique.
Edible oil is important agricultural product and raw-food material, can calculate very important optical parametrics such as absorption coefficient, refractive index, specific inductive capacity by measuring its THz time domain spectrum, is used for quality evaluation and analysis of components, has important practical value.Existing edible oil THz wave detection method mainly is edible oil to be put in the measuring vessel (far infrared quartz cuvette) measure.Repeatedly reflection and FP effect when THz wave is propagated in the far infrared quartz cuvette are all brought very big error to measurement result.The current cuvette measurement edible oil that utilizes mainly adopts two kinds of computation models that the optical parametric of edible oil is analyzed.A kind of computation model is a FP effects of not considering measuring vessel, has certain error, and the result of calculation out of true is unfavorable for accurately detection by quantitative occasion such as measurement and constituent analysis; Another computation model is to consider the FP effect, utilization contains container at three layers of interior transition function model, use Nelder-Mead optimizing method and trusted zones smoothing method match sample measured value at the terahertz wave band transmission coefficient, thereby obtain the refractive index and the absorption coefficient of edible oil, though this computation model has taken into full account the multipath effect when the THz ripple is propagated in the multilayered medium, improved measuring accuracy, but very complicated for the processing of test data of experiment, processing procedure is time-consuming.
The present invention proposes a kind of THz wave measuring method of optical parameter of edible oil.Utilize the scraps of paper to replace the far infrared quartz cuvette, during test, the scraps of paper that soaked edible oil are tested, do not need edible oil is packed in the far infrared quartz cuvette, convenient experimental operation, needn't all to clean cuvette during each sample in test, avoid because the far infrared quartz cuvette is unholiness and the repeatedly reflection and the FP effect of THz wave when propagating in the far infrared quartz cuvette come test error.Because the scraps of paper are very thin, needn't consider the FP effect of the scraps of paper, test data is handled accurately simple.
Summary of the invention
It is loaded down with trivial details to the present invention seeks to overcome existing measurement edible oil THz wave time domain spectrum experimental implementation, and the FP effect that the far infrared quartz cuvette produces and the shortcoming of deal with data difficulty provide a kind of simple optical parameter of edible oil THz wave assay method.
The THz wave accurate measuring method of optical parameter of edible oil comprises the steps:
1) the thick dry white scraps of paper of 0.8mm is dipped in the edible oil to be measured;
2) on terahertz time-domain spectrum transmission measurement device, the time dependent time domain waveform E of terahertz-wave pulse when measuring the dry white scraps of paper
r(t), as the reference signal;
3) on terahertz time-domain spectrum transmission measurement device, measure the time dependent time domain waveform E of scraps of paper terahertz-wave pulse that has soaked edible oil
s(t), as sample signal; In order to increase signal to noise ratio (S/N ratio), the time dependent time domain waveform E of the terahertz-wave pulse of each edible oil sample
s(t) get the mean value of three measured values;
4) to reference signal E
r(t) carry out fast fourier transform, obtain reference signal E
r(t) Terahertz frequency field waveform
E
r(ω)＝A
r(ω)exp[-iφ
r(ω)]＝∫E
r(t)exp(-iωt)dt
A in the formula
r(ω) be the amplitude of reference signal electric field, φ
r(ω) be the phase place of reference signal electric field;
5) to sample signal E
s(t) carry out fast fourier transform, obtain sample signal E
s(t) Terahertz frequency field waveform
E
s(ω)＝A
s(ω)exp[-iφ
s(ω)]＝∫E
s(t)exp(-iωt)dt
A in the formula
s(ω) be the amplitude of sample signal electric field, φ
s(ω) be the phase place of sample signal electric field;
6) measuring the absorption coefficient of edible oil sample and refractive index n can obtain relatively from reference signal and sample signal
Wherein d is sample thickness (thickness of the scraps of paper), and ω is a frequency, and c is an electromagnetic wave velocity of propagation in a vacuum.
The present invention utilizes the scraps of paper to replace the far infrared quartz cuvette, during test, the scraps of paper that soaked edible oil are tested, do not need edible oil is packed in the far infrared quartz cuvette, convenient experimental operation, needn't all to clean cuvette during each sample in test, avoid because the far infrared quartz cuvette is unholiness and the repeatedly reflection and the FP effect of THz wave when propagating in the far infrared quartz cuvette come test error.Because the scraps of paper are very thin, needn't consider the FP effect of the scraps of paper, test data is handled accurately simple.Help terahertz time-domain spectrum (THz-TDS) technology is applied to detection by quantitative occasions such as edible oil analysis of components.
Description of drawings
Fig. 1 terahertz time-domain spectrum measurement mechanism figure;
THz wave reference signal and rice bran oil sample signal that Fig. 2 (a) test obtains;
The refractive index curve of Fig. 2 (b) rice bran oil;
The absorbance curves of Fig. 2 (c) rice bran oil;
THz wave reference signal and soybean oil sample signal that Fig. 3 (a) test obtains;
The refractive index curve of Fig. 3 (b) soybean oil;
The absorbance curves of Fig. 3 (c) soybean oil;
THz wave reference signal and rapeseed oil sample signal that Fig. 4 (a) test obtains;
The refractive index curve of Fig. 4 (b) rapeseed oil;
The absorbance curves of Fig. 4 (c) rapeseed oil.
Embodiment
The terahertz time-domain spectrum measurement mechanism of test optical parameter of edible oil as shown in Figure 1, it is that 800nm, repetition frequency are that 80MHz, pulse width are the LASER Light Source of 100fs that titanium sapphire femtosecond mode locking pulse laser instrument produces centre wavelength, output power 960mW.After entering the THz system, light beam is divided into stronger pump light and more weak detection light through beam splitter.Pump light is modulated by chopper, and directive photoconductive antenna gallium arsenide (GaAs) crystal excites the THz pulse after lens focus.The THz pulse is thrown face mirror collimation through two from the axle metal and is incided on the sample, throws the face mirrors through other two metals again and focuses on and arrive the thick zinc telluridse ZnTe crystal of 2mm, converges with detection light through lag line.At this moment the electric field of THz pulse of electromagnetic radiation is surveyed polarization state and is changed thereupon by the index ellipsoid of linear electro-optic effect modulation electric luminescent crystal ZnTe, is surveyed by the balance diode, and signal is sent into lock-in amplifier and amplified.And the method for passing through the change delay line length is surveyed the whole time domain waveform of THz signal.In order to prevent of the influence of water in air steam, be sealed in the casing that is filled with nitrogen to this section light path of crystal detection ZnTe from GaAs, the sample cell that produces the THz signal to the THz signal.Relative humidity in the case is less than 4%, and temperature is 294K.In the signal scanning process, the signal to noise ratio (S/N ratio) of experimental system is 1000, and spectral resolution is better than 40GHz.
The THz wave accurate measuring method of optical parameter of edible oil comprises the steps:
1) the thick dry white scraps of paper of 0.8mm is dipped in the edible oil to be measured;
2) on terahertz time-domain spectrum transmission measurement device, the time dependent time domain waveform E of terahertz-wave pulse when measuring the dry white scraps of paper
r(t), as the reference signal;
3) on terahertz time-domain spectrum transmission measurement device, measure the time dependent time domain waveform E of scraps of paper terahertz-wave pulse that has soaked edible oil
s(t), as sample signal; In order to increase signal to noise ratio (S/N ratio), the time dependent time domain waveform E of the terahertz-wave pulse of each edible oil sample
s(t) get the mean value of three measured values;
4) to reference signal E
r(t) carry out fast fourier transform, obtain reference signal E
r(t) Terahertz frequency field waveform
E
r(ω)＝A
r(ω)exp[-iφ
r(ω)]＝∫E
r(t)exp(-iωt)dt
A in the formula
r(ω) be the amplitude of reference signal electric field, φ
r(ω) be the phase place of reference signal electric field.
5) to sample signal E
s(t) carry out fast fourier transform, obtain sample signal E
s(t) Terahertz frequency field waveform
E
s(ω)＝A
s(ω)exp[-iφ
s(ω)]＝∫E
s(t)exp(-iωt)dt
A in the formula
s(ω) be the amplitude of sample signal electric field, φ
s(ω) be the phase place of sample signal electric field.
6) measuring the absorption coefficient of edible oil sample and refractive index n can obtain relatively from reference signal and sample signal
Wherein d is sample thickness (thickness of the scraps of paper), and ω is a frequency, and c is an electromagnetic wave velocity of propagation in a vacuum.
Embodiment 1
Measure the optical parametric of rice bran oil
The vegetable oil sample is a rice bran oil, earlier the thick dry white scraps of paper of 0.8mm is put into the sample position of THz wave time domain spectrometry device, measures THz wave time domain spectrum conduct when placing the dry white scraps of paper with reference to signal; Then the 0.8mm thick paper that has soaked rice bran oil is put into the sample position of terahertz time-domain spectrum measurement mechanism, measurement has been soaked the 0.8mm thick paper THz wave time domain spectrum of rice bran oil as sample signal, and THz wave reference signal that obtains and sample signal are shown in Fig. 2 a.Use method of the present invention to calculate the refractive index and the absorption coefficient (shown in Fig. 2 b and Fig. 2 c) of rice bran oil at last, the mean refractive index of rice bran oil is 1.481.
Measure the optical parametric of soybean oil
The vegetable oil sample is a soybean oil, earlier the thick dry white scraps of paper of 0.8mm is put into the sample position of THz wave time domain spectrometry device, measures THz wave time domain spectrum conduct when placing the dry white scraps of paper with reference to signal; Then the 0.8mm thick paper that has soaked soybean oil is put into the sample position of THz wave time domain spectrometry device, measurement has been soaked the 0.8mm thick paper THz wave time domain spectrum of soybean oil as sample signal, and THz wave reference signal that obtains and sample signal are shown in Fig. 3 a.Use method of the present invention to calculate the refractive index and the absorption coefficient (shown in Fig. 3 b and Fig. 3 c) of soybean oil at last, the mean refractive index of soybean oil is 1.484.
Measure the optical parametric of rapeseed oil
The vegetable oil sample is a rapeseed oil, earlier the thick dry white scraps of paper of 0.8mm is put into the sample position of THz wave time domain spectrometry device, measures THz wave time domain spectrum conduct when placing the dry white scraps of paper with reference to signal; Then the 0.8mm thick paper that has soaked rapeseed oil is put into the sample position of THz wave time domain spectrometry device, measurement has been soaked the 0.8mm thick paper THz wave time domain spectrum of rapeseed oil as sample signal, and THz wave reference signal that obtains and sample signal are shown in Fig. 4 a.Use method of the present invention to calculate the refractive index and the absorption coefficient (shown in Fig. 4 b and Fig. 4 c) of rapeseed oil at last, the mean refractive index of rapeseed oil is 1.486.
Claims (1)
1, a kind of THz wave accurate measuring method of optical parameter of edible oil is characterized in that comprising the steps:
1) the thick dry white scraps of paper of 0.8mm is dipped in the edible oil to be measured;
2) on terahertz time-domain spectrum transmission measurement device, the time dependent time domain waveform E of terahertz-wave pulse when measuring the dry white scraps of paper
r(t), as the reference signal;
3) on terahertz time-domain spectrum transmission measurement device, measure the time dependent time domain waveform E of scraps of paper terahertz-wave pulse that has soaked edible oil
s(t), as sample signal; In order to increase signal to noise ratio (S/N ratio), the time dependent time domain waveform E of the terahertz-wave pulse of each edible oil sample
s(t) get the mean value of three measured values;
4) to reference signal E
r(t) carry out fast fourier transform, obtain reference signal E
r(t) Terahertz frequency field waveform
E
r(ω)＝A
r(ω)exp[-iφ
r(ω)]＝∫E
r(t)exp(-iωt)dt
A in the formula
r(ω) be the amplitude of reference signal electric field, φ
r(ω) be the phase place of reference signal electric field;
5) to sample signal E
s(t) carry out fast fourier transform, obtain sample signal E
s(t) Terahertz frequency field waveform
E
s(ω)＝A
s(ω)exp[-iφ
s(ω)]＝∫E
s(t)exp(-iωt)dt
A in the formula
s(ω) be the amplitude of sample signal electric field, φ
s(ω) be the phase place of sample signal electric field;
6) measuring the absorption coefficient of edible oil sample and refractive index n can obtain relatively from reference signal and sample signal
Wherein d is sample thickness (thickness of the scraps of paper), and ω is a frequency, and c is an electromagnetic wave velocity of propagation in a vacuum.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2009100972835A CN101532953B (en) | 2009-04-02 | 2009-04-02 | Method for accurately measuring optical parameters of edible oil |
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|---|---|---|---|
| CN2009100972835A CN101532953B (en) | 2009-04-02 | 2009-04-02 | Method for accurately measuring optical parameters of edible oil |
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| CN101532953B CN101532953B (en) | 2010-08-04 |
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| CN102213682A (en) * | 2011-04-18 | 2011-10-12 | 中国计量学院 | Method for measuring transmission of interference-insensitive terahertz wave |
| CN102297848A (en) * | 2011-05-16 | 2011-12-28 | 中国科学院西安光学精密机械研究所 | Method for acquiring data for rapid terahertz pulse imaging |
| CN103235222A (en) * | 2013-04-22 | 2013-08-07 | 江南大学 | Detection method for electromagnetic absorption performance of fluid food-derived material |
| CN103364363A (en) * | 2013-06-28 | 2013-10-23 | 中国科学院西安光学精密机械研究所 | Device and method for acquiring absorption coefficient and refractive index of substance in terahertz waveband |
| CN104345040A (en) * | 2013-07-31 | 2015-02-11 | 天津智易时代科技发展有限公司 | Terahertz spectrum analysis system |
| CN104568819A (en) * | 2015-01-15 | 2015-04-29 | 南开大学 | All-fiber transmission reflection integrated terahertz time-domain spectroscopy system |
| CN104964932A (en) * | 2015-06-18 | 2015-10-07 | 东莞理工学院 | Terahertz vertical transmission spectrum and reflectance spectrum measuring integral system and application thereof |
| CN109406454A (en) * | 2018-09-11 | 2019-03-01 | 江苏大学 | A kind of improved Z scanning means |
| CN109444092A (en) * | 2018-09-14 | 2019-03-08 | 上海无线电设备研究所 | Combine the test macro and method of identification oil types with laser with Terahertz |
| CN109658583A (en) * | 2019-02-01 | 2019-04-19 | 广东工业大学 | Invoice discrimination method, device, equipment and storage medium based on tera-hertz spectra |
| WO2019127960A1 (en) * | 2017-12-28 | 2019-07-04 | 雄安华讯方舟科技有限公司 | Terahertz-based test method |
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2009
- 2009-04-02 CN CN2009100972835A patent/CN101532953B/en not_active Expired - Fee Related
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102213682A (en) * | 2011-04-18 | 2011-10-12 | 中国计量学院 | Method for measuring transmission of interference-insensitive terahertz wave |
| CN102213682B (en) * | 2011-04-18 | 2013-01-09 | 中国计量学院 | Method for measuring transmission of interference-insensitive terahertz wave |
| CN102297848A (en) * | 2011-05-16 | 2011-12-28 | 中国科学院西安光学精密机械研究所 | Method for acquiring data for rapid terahertz pulse imaging |
| CN102297848B (en) * | 2011-05-16 | 2013-04-17 | 中国科学院西安光学精密机械研究所 | Method for rapid terahertz pulse imaging |
| CN103235222A (en) * | 2013-04-22 | 2013-08-07 | 江南大学 | Detection method for electromagnetic absorption performance of fluid food-derived material |
| CN103364363A (en) * | 2013-06-28 | 2013-10-23 | 中国科学院西安光学精密机械研究所 | Device and method for acquiring absorption coefficient and refractive index of substance in terahertz waveband |
| CN104345040A (en) * | 2013-07-31 | 2015-02-11 | 天津智易时代科技发展有限公司 | Terahertz spectrum analysis system |
| CN104568819A (en) * | 2015-01-15 | 2015-04-29 | 南开大学 | All-fiber transmission reflection integrated terahertz time-domain spectroscopy system |
| CN104964932A (en) * | 2015-06-18 | 2015-10-07 | 东莞理工学院 | Terahertz vertical transmission spectrum and reflectance spectrum measuring integral system and application thereof |
| CN104964932B (en) * | 2015-06-18 | 2017-12-01 | 东莞理工学院 | A kind of integral system and application for measuring Terahertz normal transmission spectrum and reflectance spectrum |
| WO2019127960A1 (en) * | 2017-12-28 | 2019-07-04 | 雄安华讯方舟科技有限公司 | Terahertz-based test method |
| CN109406454A (en) * | 2018-09-11 | 2019-03-01 | 江苏大学 | A kind of improved Z scanning means |
| CN109444092A (en) * | 2018-09-14 | 2019-03-08 | 上海无线电设备研究所 | Combine the test macro and method of identification oil types with laser with Terahertz |
| CN109444092B (en) * | 2018-09-14 | 2021-07-20 | 上海无线电设备研究所 | Test system and method for identifying oil product types by combining terahertz and laser |
| CN109658583A (en) * | 2019-02-01 | 2019-04-19 | 广东工业大学 | Invoice discrimination method, device, equipment and storage medium based on tera-hertz spectra |
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