CN107576631A - Method based on Terahertz Optical transmission spectrum detection rape leaf moisture state - Google Patents
Method based on Terahertz Optical transmission spectrum detection rape leaf moisture state Download PDFInfo
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Abstract
The invention discloses a kind of method based on Terahertz Optical transmission spectrum detection rape leaf moisture state, including：Gather the terahertz time-domain spectroscopy of reference spectra and rape leaf sample；It is converted into Terahertz Optical transmission spectrum；Using the moisture content and relative moisture content for drying weight method calculating rape leaf sample；Establish the Terahertz Optical transmission spectrum and rape leaf moisture content and the Quantifying model of relative moisture content of rape leaf；The terahertz time-domain spectroscopy of the rape leaf of unknown moisture state is obtained, is converted into Terahertz Optical transmission spectrum, input model is predicted to leaf water state.The present invention utilizes tera-hertz spectra detection technique, study the quantitative analysis to normal growth rape leaf moisture state under natural conditions, dynamic monitoring, fine-grained management, raising rapeseed quality and raising rapeseed yield to moisture state have certain theory and practice directive significance, illustrate application prospects of the THz in plant moisture detection field.
Description
Technical field
The present invention relates to the detection method of plant leaf blade moisture state, more particularly to one kind to be based on Terahertz optical transmission spectra
The method of technology for detection rape leaf moisture state.
Background technology
Rape is one of the most important oil seed production raw material in China and industrial crops, accounts for China's oil plant industrial crops gross area
More than 40%, more than the 30% of total oil-bearing crops.Rape mainly produces crop as oil plant, rich in oil in its rapeseed oil
The unrighted acids such as acid, linoleic acid, there is prevention of cardiovascular disease and reduce the health-care efficacies such as serum cholesterol in humans.Water
One of an important factor for point being photosynthesis during growth of rape, transpiration and nutrient transport, and the life that rape is important
Manage one of index.The healthy growth of rape needs appropriate moisture dosage, and during more than certain limit, its normal physiological processes will
It is interfered, or even is damaged plant, this water deficit is referred to as water stress or Water Stress.When excess moisture,
Its aerobic respiration can be hindered and plant is damaged；When hypohydration, plant water content declines, the flow of water and turgescence
It is corresponding to reduce, the generation of some diseases, such as yellowing leaf, withered, necrosis can be caused.Moisture in rape leaf is not only
The growth of plant is directly affected, or even crop yield can be influenceed, but also is had to the safe storage of rapeseed quality and seed
Vital effect.Therefore, to rape leaf determination of moisture to study the plant physiology situation, growing way, character surveillance,
Water-saving irrigation has great importance with intelligent management.
Traditional water content in plant leaf assay method mainly has seasoning, the way of distillation, karl-Fischer method, such inspection
Survey method is required a great deal of time in sample preparation and energy, some waste liquid discarded objects etc. causes serious dirt to environment
Dye, and destructive test will be such that growing process does not continue, while long detection time can not ensure the timeliness of data
Property and the synchronism between different sample measurement data.With the fast development of spectral technique, near infrared spectrum detection method, bloom
Spectrum detection method, Electromagnetic Wave Detection method and Terahertz wave spectrum (Terahert, THz) detection method are widely used in plant leaf surface moisture content
The research of detection.Because the vibration of substantial amounts of macromolecular and rotational energy level are all in terahertz wave band (0.1~10THz), in terahertz
Hereby wave band shows very strong absorption and resonance, and the tera-hertz spectra of material includes abundant physical message and chemistry is believed
Breath.The low photoionization for avoiding biological cell of Terahertz photon energy damages.Tera-hertz spectra has water imbibition, most of poles
Property molecule such as hydrone has strong absorption to terahertz emission.In addition, Terahertz has stronger penetrability, can penetrate as oil
This relatively thin biological specimen of dish leaf piece.Therefore, tera-hertz spectra detection technique has certain on detection rape leaf moisture
Advantage.
The present invention carries out rape using THz high-hydroscopicity, high-penetration, low damaging using THz time domain spectrum technology
The detection of leaf water state.Fresh blade is cut placement by experiment from the rapeseed plants of healthy growth from rapeseed plants
In laboratory environments, the change of continuous monitoring leaf water and the situation of change of THz spectrum, discussion utilize THz time domain spectrum skill
The response pattern that art detection changes for different leaves moisture state, and carry out the rape leaf moisture state of different water cut
Quantitative modeling analysis, dynamic monitoring, fine-grained management to moisture state, improve rapeseed quality and improve rapeseed yield and have
There is certain theory and practice directive significance.
The content of the invention
To overcome the problems of prior art, detected the invention provides one kind based on terahertz time-domain spectroscopic technology
The method of rape leaf moisture state.
A kind of method based on Terahertz Optical transmission spectrum detection rape leaf moisture state, comprises the following steps：
(1) using terahertz time-domain spectroscopy system acquisition reference spectra and the terahertz time-domain spectroscopy of rape leaf sample；
The terahertz time-domain spectroscopy of gained is changed and handled, obtains corresponding Terahertz Optical transmission spectrum；
(2) using the moisture content and relative moisture content for drying weight method calculating rape leaf sample；
(3) the Terahertz Optical transmission spectrum and rape leaf moisture content and the quantitative of relative moisture content for establishing rape leaf are returned
Return model；
(4) terahertz time-domain spectroscopy of the rape leaf of unknown moisture state is obtained, through handling and changing, corresponding to extraction
Terahertz Optical transmission spectrum, established Quantifying model is then inputted after Pretreated spectra again, to the moisture content of blade
It is predicted with relative moisture content state.
Time domain tera-hertz spectra transmission-type scanning system (THz-TDS) can be used by implementing the inventive method, and laser is titanium
Jewel femtosecond laser oscillator；Wavelength：800nm；Repetition rate：80MHz；Frequency range：0.1~3.5THz；Pulse width：
50fs；Mean power：500m W；
Preferably, the rape variety selected in step (1) is fresh oil 6.
Preferably, blade complete, no disease and pests harm and new are selected in step (1) from the rapeseed plants of healthy normal growth
Fresh rape leaf is as the rape leaf sample.Select grow fine, blade is complete, new similar in no disease and pests harm, size
Fresh rape leaf.
Preferably, being directed to every rape leaf sample in step (1), once referred at interval of a period of time duplicate measurements
The terahertz time-domain spectroscopy of spectrum and rape leaf, gathered every time the weight that measures blade after terahertz time-domain spectroscopy immediately and
Thickness.
For same blade, its first time is weighed as fresh weight, is dried to the dry weight that is weighed as after weight, it is middle
During be weighed as the real-time weight of blade；Measure the thickness parameter that vane thickness is used for the conversion of follow-up spectrum.Blade
Weight uses precision to be weighed for 0.0001g electronic balance；The thickness of blade uses vernier caliper measurement of the precision for 0.01mm.
Each interval time is 20min~40min；Preferably 30min.
Preferably, collection every time, the point position of the rape leaf of selection is mesophyll part, avoids vein part, adopts every time
3 different point positions are chosen when collecting the terahertz time-domain spectroscopy of rape leaf sample to be acquired, it is each to put position repeated acquisition three
Secondary spectrum.
For each rape leaf sample, 9 time-domain spectroscopies are gathered altogether, this 9 spectrums are taken average final as the blade
Time-domain spectroscopy.The time of integration is 40ps, and the sampling number of time-domain spectroscopy is 1000, temporal resolution 39.2fs.
Preferably, in detection process, drying nitrogen is filled into pattern detection storehouse, and using terahertz time-domain spectroscopy system
The transmission scan module of system obtains the reference spectra using nitrogen as background, and obtains the terahertz of rape leaf in a nitrogen environment
Hereby time-domain spectroscopy.Further preferably, start to detect when filling drying nitrogen air humidity into pattern detection storehouse less than 5%.
Preferably, the conversion and processing in step (1) are：The terahertz time-domain spectroscopy gathered is subjected to Fourier's change
Change, be converted into corresponding Terahertz frequency domain spectra, Terahertz Optical transmission spectrum is then extracted according to Terahertz frequency domain spectra, then it is right
Terahertz Optical transmission spectrum is smoothed.Further preferably, the method for the smoothing processing is put down for Savitzky-Golay
It is sliding.
Preferably, the temporal resolution of terahertz time-domain spectroscopy is 39.2fs (femtosecond)；After being fourier transformed too
The frequency resolution of hertz frequency domain spectra is 25.5GHz, and spectral range is 0.1~3.5THz.
Preferably, after extraction Terahertz transmissivity spectrum, chosen spectrum scope is that 0.1~2THz spectral coverage is modeled,
The Quantifying model is PLS models.
After extracting Terahertz Optical transmission spectrum, in order to ensure the validity of spectral information and high s/n ratio, and modeling
The optimization of precision, choose 0.1~2THz (frequency resolutions：Spectral information in the range of 25.5GHz), in Savitzky-Golay
PLS modeling analysis is carried out on the basis of smoothing processing again.
Preferably, select 50 samples from all 80 sample sets every time by the way of grab sample in step (3)
This collects as calibration set, remaining 30 sample as checking, carries out PLS modeling analysis.Modeling is repeated 10 times, then by 10 times
Model result takes average as final model result.For moisture content, calibration set is respectively with checking collection coefficient correlation
0.8920th, 0.8052, root-mean-square error is respectively 0.0822,0.1166；For relative moisture content, calibration set is related to checking collection
Coefficient is respectively 0.8976,0.8213, and root-mean-square error is respectively 0.1253,0.1884.
The present invention obtains time-domain spectroscopy of the rape leaf in 0-40ps；Time-domain spectroscopy progress Fourier transformation is obtained
Frequency spectrum in the range of 0.1~3.5THz；It is saturating in the range of 0.1 higher~2THz of extraction signal to noise ratio according to frequency spectrum
Cross rate spectrum；Quantitatively returned using the corresponding moisture state of optical transmission spectra combination rape leaf in the range of 0.1~2THz
Return modeling；Obtain the optical transmission spectra of rape leaf to be checked and input the model, obtain corresponding moisture state testing result.
The present invention utilizes tera-hertz spectra detection technique, studies quantitative point to normal growth rape leaf moisture state under natural conditions
Analysis, dynamic monitoring, fine-grained management, raising rapeseed quality and raising rapeseed yield to moisture state have certain theory
With practical advice meaning, application prospects of the THz in plant moisture detection field is illustrated.
Compared with prior art, the present invention has the advantages that：
For the quantitative detection of the rape leaf moisture state based on Terahertz optical transmission spectra, compared to other kinds of
Model, PLS models have the advantages that method is simple, precision is high, stability is good.It is based on compared to traditional blades moisture detecting method
Conventional spectral method of detection, tera-hertz spectra detection technique is due to strong water absorption character, most of polar molecules such as moisture
Son, ammonia molecule etc. have strong absorption to terahertz emission.In addition, Terahertz has strong penetration performance, rape leave can be penetrated
This kind of relatively thin biological specimen of piece, and then the transmission-type measurement higher compared to reflection measurement precision can be realized.Therefore, utilize
The water imbibition and penetrability of tera-hertz spectra are one of scientific methods for studying substance moisture content content and distribution situation.
Brief description of the drawings
Fig. 1：The flow chart of Terahertz detection of the present invention.
Fig. 2：The time-domain spectroscopy figure of rape leaf.
Fig. 3：The optical transmission spectra figure of rape leaf in the range of 0.1~2THz.
Embodiment
Implement a kind of method that leaf water state is quantitatively detected based on Terahertz optical transmission spectra herein, with reference to such as Fig. 1
Shown flow chart, comprises the following steps：
(1) sample prepares：The rapeseed plants of healthy growth are transplanted to greenhouse from big Tanaka testing previous week, protected
Hold light irradiation time 10h, 24 degree of temperature, humidity 65%.8 basins are transplanted altogether, per 3 plants of basin, apply appropriate moisture daily, to ensure oil
The normal growth of dish, and ensure that soil moisture content is 80% or so (± 4%).
(2) spectra collection：Laboratory apparatus uses CIP-THz transmission scan systems, the drying nitrogen being full of into sample storehouse,
Internal system humidity is set to be less than 5%.In whole experiment process, constant indoor temperature 294K is tested, relative humidity is permanent to be less than 20%.First adopt
Integrate the reference spectra using nitrogen as background.Then a piece of rape leaf is respectively taken from 8 basin rapeseed plants, it is taken to progress successively
The collection of sample spectrum.Each blade selects 3 different point positions (selection mesophyll part, avoid vein position), each puts position
Repeated acquisition 3 times.9 time-domain spectroscopies of acquisition are taken into the average terahertz time-domain spectroscopy as the sample.In experimentation, often
It is secondary swept THz spectrum after use precision to weigh the weight of blade for 0.0001g electronic balance immediately, and use precision for
0.01mm vernier caliper measurement vane thickness.Then blade is placed in laboratory environments, repeats to survey once every 30min
Reference spectra, rape sample spectra, leaf weight and vane thickness, 10 groups of continuous monitoring, it is obtained 10 and refers to spectral line and 80
Bars spectral line, as shown in Figure 2.
(3) moisture calculates：Using weight method is dried, the rape leaf after spectroscopic data will be gathered and be put into 65 DEG C of drying bakers
Weight is inside dried to, then calculates the moisture content and relative moisture content of blade respectively using formula (1) and formula (2).
Wherein WfreshIt is the fresh weight of blade, WdryIt is the dry weight of blade, WtimeIt is the weight of the blade during duplicate measurements
Amount.
(4) spectral manipulation：The sample terahertz time-domain spectroscopy gathered is subjected to Fourier transformation, is converted into corresponding frequency
Domain modal data, corresponding Terahertz transmitted spectrum is then extracted according to formula (6), as shown in Figure 3.Savitzky- is used again
Golay methods are composed to transmissivity and carry out smoothing denoising processing.
The sample macroscopic view optical property of measurement can use complex refractivity index n~represent：
Wherein, n (ω) is the actual refractive index of sample, and it describes the dispersion of sample；K (ω) is extinction coefficient, it
The absorption characteristic of sample is described.ω=2 π f, f are frequency.Free space air refraction is 1, then reference spectra Eref
(ω) expression formula is：
L be terahertz pulse in the distance of free-space propagation, c is the light velocity, and the signal spectrum through sample is represented by：
The Optical transmission spectrum of sample is represented by：
Wherein, the frequency-domain waveform of terahertz sources is E0(ω), the transmitting frequency-domain waveform that detector directly receives are
Reference spectra Eref(ω), through sample after the frequency-domain waveform that receives of detector be sample signal Esample(ω).N (ω) is
The actual refractive index of sample.ω=2 π f, f are frequency.C is the light velocity, and d is thickness of sample, 1/ (n (ω)+1) and 2n (ω)/(n
(ω)+1) it is respectively terahertz pulse incidence sample and the transmission coefficient for being emitted sample.
(5) model is established：According to the Terahertz optical transmission spectra and corresponding moisture content and relative moisture content of rape leaf,
Corresponding offset minimum binary (PLS) regression model is established respectively.Wherein calibration set sample number is 50, and checking collection sample number is 30,
PLS models are established by 10 grab sample, then taken the result of 10 models average as final model result, such as table
Shown in 1.
Table 1：The result of PLS models under 10 grab sample
(6) moisture is predicted：For the rape leaf of unknown moisture state, gather its terahertz time-domain spectroscopy and carry out frequency domain turn
Change, then input the transmission spectrum of extraction into the PLS models established, you can predict corresponding moisture content and relative hydration
Rate.
Claims (10)
- A kind of 1. method based on Terahertz Optical transmission spectrum detection rape leaf moisture state, it is characterised in that including as follows Step：(1) using terahertz time-domain spectroscopy system acquisition reference spectra and the terahertz time-domain spectroscopy of rape leaf sample；To institute The terahertz time-domain spectroscopy obtained is changed and handled, and obtains corresponding Terahertz Optical transmission spectrum；(2) using the moisture content and relative moisture content for drying weight method calculating rape leaf sample；(3) the Terahertz Optical transmission spectrum and rape leaf moisture content and the quantitative recurrence mould of relative moisture content of rape leaf are established Type；(4) terahertz time-domain spectroscopy of the rape leaf of unknown moisture state, through handling and changing, terahertz corresponding to extraction are obtained Hereby Optical transmission spectrum, established Quantifying model is then inputted after Pretreated spectra again, to the moisture content and phase of blade Moisture content state is predicted.
- 2. method according to claim 1, it is characterised in that it is complete from the rapeseed plants of healthy normal growth to select blade Whole, no disease and pests harm and fresh rape leaf is as the rape leaf sample.
- 3. method according to claim 1, it is characterised in that every rape leaf sample is directed in step (1), at interval of one The terahertz time-domain spectroscopy of section reference spectra of time duplicate measurements and rape leaf, has gathered terahertz time-domain spectroscopy every time Measure the weight and thickness of blade immediately afterwards.
- 4. method according to claim 3, it is characterised in that the weight of hinge uses electronic balance of the precision for 0.0001g Weigh；The thickness of blade uses vernier caliper measurement of the precision for 0.01mm.
- 5. method according to claim 1, it is characterised in that the point position of the rape leaf of selection is mesophyll part, is adopted every time 3 different point positions are chosen when collecting the terahertz time-domain spectroscopy of rape leaf sample to be acquired, it is each to put position repeated acquisition three Secondary spectrum.
- 6. method according to claim 1, it is characterised in that in detection process, drying nitrogen is filled into pattern detection storehouse, And reference spectra of the transmission scan module acquisition of terahertz time-domain spectroscopy system using nitrogen as background is used, and in nitrogen ring The terahertz time-domain spectroscopy of rape leaf is obtained under border.
- 7. method according to claim 6, it is characterised in that drying nitrogen air humidity is filled into pattern detection storehouse and is less than Start to detect when 5%.
- 8. method according to claim 1, it is characterised in that conversion and processing in step (1) are：The terahertz that will be gathered Hereby time-domain spectroscopy carries out Fourier transformation, is converted into corresponding Terahertz frequency domain spectra, is then carried according to Terahertz frequency domain spectra Terahertz Optical transmission spectrum is taken, then Terahertz Optical transmission spectrum is smoothed.
- 9. method according to claim 8, it is characterised in that the temporal resolution of terahertz time-domain spectroscopy is 39.2fs；Through The frequency resolution of Terahertz frequency domain spectra after Fourier transformation is 25.5GHz, and spectral range is 0.1~3.5THz.
- 10. method according to claim 1, it is characterised in that after extraction Terahertz transmissivity spectrum, chosen spectrum scope is 0.1~2THz spectral coverage is modeled, and the Quantifying model is PLS models.
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