87 results about "Thz time domain spectroscopy" patented technology

An apparatus and method for measuring Raman-type spectra using optical dispersion to convert an optical spectrum into a waveform which can be detected directly in the time domain without the use of a conventional spectrometer. In the example of stimulated Raman spectroscopy, the apparatus and method exposes a sample to a chirped, pulsed probe beam and a Raman pump beam and the resulting Raman spectra is detected by an optical detector in the time domain, and analyzed. Alternatively, the Raman spectra from the probe and pump beams is chirped with a dispersive element prior to detection and analysis. Each probe pulse provides a snapshot of the Raman spectrum that is sampled in time so that neither repetitive waveforms nor static samples are required. Therefore, high speed acquisitions and high throughput assays can be conducted. To facilitate detection, these spectral signals can also be amplified using distributed Raman amplification directly in the dispersive element.

A method for detecting specific associations between a tethered molecule and an untethered target molecule. The method comprises (1) selecting a tethered molecule; (2) alternately impinging THz radiation onto the tethered molecule and onto a sample including the tethered and untethered target molecules; (3) detecting the radiation impinged on the tethered molecule to form a reference signal and the radiation impinged on the sample to form a sample signal; and (4) comparing the reference signal with the sample signal to generate a specimen signal indicative of an association between the selected tethered and target molecules. The method will detect whether a selected tethered molecule and the desired target exhibit any affinity or, in cases where the affinity is known, will detect the presence of the target molecule in a sample. Also provided is an apparatus for detecting specific associations between a tethered molecule and an untethered target molecule.

The invention relates to a method for measuring concentrations of sulfate, nitrate solutions by utilizing the terahertz time-domain spectroscopy. The method comprises the following steps: sample cells are selected, standard solution samples with different concentrations are prepared, terahertz time-domain spectra of the standard solution samples are measured, a terahertz time-domain spectra database of the standard solution samples is built, and the database comprises time-domain spectra, frequency-domain spectra, relation spectra of concentrations and absorption coefficients, relation spectra of concentrations and refractive indexes, relation spectra of concentrations and extinction coefficients of the standard solution samples. Terahertz time-domain spectra of the solutions to be measured are measured, the data is processed to obtain absorption coefficients of the solutions to be measured, and according to the terahertz time-domain spectra database of the standard solution samples, the concentrations of the solutions to be measured are analyzed and determined. The method utilizes the terahertz time-domain spectroscopy to measure solution concentrations, and is advantaged by simple operations, rapid measurement, simple data processing procedures, good repeatability, and high accuracy of results.

The invention discloses a nondestructive testing method for absorption coefficient and refractive index of a pesticide. The method comprises the following steps of: testing nitrogen and a pesticide test sample by using a transmission-type terahertz time domain spectroscopy (THz-TDS) to obtain time domain spectrums of the nitrogen and the pesticide test sample respectively; and performing data processing to obtain refractive index spectrum and absorption spectrum of the pesticide test sample at the THz wave band of between 0 and 2.5THz, wherein the pesticide comprises chlorpyriphos methyl, baygon and fenvalerate. By the method, rapid nondestructive testing of the pesticide can be realized; and the method has the advantages of simple sample preprocessing, easiness of operation, high repeatability, simple data processing, relatively accurate testing result and the like. The method has great significance to detection of pesticide residue on fruits and vegetables by using the terahertz time domain technology based on fingerprint spectrums of the three pesticides obtained by the method.

The invention provides an erosion morphology test method of a thermal barrier coating based on a terahertz technology. The method comprises the following steps of vertically emitting terahertz pulsesby using a reflective terahertz time-domain spectroscopy system to the thermal barrier coating; obtaining a time domain spectrogram; extracting the moment value of the front three times of reflectionpeaks in the spectrogram; obtaining the time delay of the two adjacent peaks; performing Fourier transform on the front three times of reflection peaks to obtain a frequency domain spectrogram; calculating the refractive index and the thickness of the ceramic layer of the thermal barrier coating; performing erosion on the thermal barrier coating; performing scanning; using the time-domain spectroscopy system for measurement so as to obtain a plurality of time-domain spectrograms; extracting the moment value of the first time reflection peak in the spectrogram; calculating the difference from the moment value of the first time reflection peak; calculating the thinning thickness value of the thermal barrier coating according to the difference value; obtaining the erosion morphology of the thermal barrier coating. The test method has the advantages that the step of measuring the refractive index of the thermal barrier coating is omitted; the thinning thickness of the thermal barrier coating after the erosion is calculated, so that the calculation by using the refractive index of the thermal barrier coating is not needed; therefore the error is reduced.

The invention discloses an ultrafast RF spectrum measuring method and an ultrafast RF spectrum measuring system based on all-optical Fourier transform and time-domain amplification. The ultrafast RF spectrum measuring method comprises the steps of: fully broadening an ultrashort optical pulse through dispersion to obtain a time-domain spectrum thereof; loading an RF signal to be measured onto the time-domain spectrum through intensity modulation; realizing inverse time-domain Fourier transform through subjecting the modulated time-domain spectrum to dispersion and compression; subjecting an optical signal carrying spectrum information of the signal to be measured in the time domain to time-domain stretching by adopting a time-domain lens magnification technology; and converting the obtained optical signal into an electrical signal, and acquiring accurate spectrum information through scaling and calibration. The ultrafast RF spectrum measuring system comprises a first ultrashort pulse light source, a first dispersion-compensation optical fiber, an MZ intensity modulator, a first single-mode optical fiber, a time-domain lens magnifying system, a photoelectric detector and a real-time oscilloscope. The ultrafast RF spectrum measuring method and the ultrafast RF spectrum measuring system have the advantages of realizing ultrafast RF spectrum measurement while ensuring high spectral resolution, having measurement frame rate up to 100 MHz, and are of great significance in application scenarios such as dynamic spectrum monitoring and transient spectrum capturing.

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.

A non-contact, free-space method for determining the index of refraction of a thin film at a desired angular frequency. The method includes generating an input desired-frequency pulse and an optically detectable probe pulse. The thin film is moved in and out of the path of the input pulse, creating an output pulse that alternates between a transmitted signal, created when the film intercepts the input pulse path, and a reference signal, created when the sample is outside the input pulse path. The output pulse modulates the probe pulse, which is then detected with a photo detector, and the difference between the transmitted signal and the reference signal is calculated. The above steps are repeated over a plurality of delay times between the input pulse and the probe pulse until a complete field waveform of the differential signal is characterized. The index of refraction is calculated as a function of a ratio between the differential signal for the thin film and the reference signal. A complete field waveform of the reference signal may be characterized by repeating the above steps for a reference plate identical to the sample except having a non-transmissive film instead of the thin, transmissive film.

The invention relates to a device for improving the test accuracy of spectrum absorbance on the basis of terahertz optical combs. The device is characterized in that one of two ultrafast laser pulse beams with set repeat frequency difference is transmitted through a terahertz wave generating system to generate terahertz waves, terahertz wave signals and the other ultrafast laser pulse beam are respectively focused and are jointly transmitted into a photoconductive detection antenna, the terahertz waves can be quickly scanned by the aid of tiny repeat frequency difference between pump beams and probe beams, a digital converter is controlled by the aid of a cross-correlation instrument and a rubidium atom frequency standard, the signal acquisition time is prolonged to obtain time-domain spectra of continuous terahertz pulse chains, terahertz comb-shaped spectra are obtained by means of Fourier transformation, accurate change of the optical combs is compared before and after sample placement, and accordingly terahertz absorption spectrum lines of samples can be obtained. The device has the advantages that the shortcoming of excessive scanning time consumption of mechanical delay devices can be overcome, the problem of inaccuracy of existing terahertz super-continuous spectra due to laser pulse time jitter can be solved, and the test accuracy of the terahertz spectrum absorbance can be improved.

An apparatus for incorporation into time-domain spectroscopy systems that creates a continuous reference whereby a sample pulses' phase and amplitude can be tracked and corrected employs a beam splitter to generate sample and reference pulses. A detector is positioned for receiving the reference radiation pulses that do not interact with the sample. The same detector is also positioned for receiving the sample radiation pulses that emerge from the sample. The apparatus can be readily implemented by being configured between the emitter and detector of a terahertz time-domain spectrometer. The reference pulse is used to trace the changes in time and amplitude of the sample pulse. Since any changes in the reference pulse will most likely manifest in the sample pulse, the reference pulse is monitored and used to correct the sample pulse and thereby reduce the effects of jitter.

The invention discloses a glass fiber composite defect detecting method based on terahertz time-domain spectroscopy. The method comprises the following steps: firstly, using a terahertz wave probe to scan a sample with the stepping frequency of 0.1mm / each time to 1mm / each time so as to obtain the terahertz time-domain transmission pulse of each scanning point of the sample; then analyzing the obtained time-domain transmission pulse data so as to obtain the time-domain transmission pulse amplitude Ii of each scanning point of the sample; comparing the time-domain pulse amplitude Ii of all samples so as to obtain the maximal value and the minimum value of the time-domain pulse amplitude of the sample; setting Imin corresponding gray value and Imax corresponding gray value for the obtained pulse amplitude Ii of each sample point, and solving the corresponding image gray value of the sample point i; and calculating the corresponding image gray values of all sample points so as to generate the gray-scale map of the sample. According to the invention, a transmission type terahertz time-domain spectral system is adopted to detect the composite material to extract the time-domain spectral data without the need of obtaining frequency domain data, the operation procedure is simple, and data acquisition is convenient.

The invention discloses a method for increasing the resolution ratio of a terahertz absorption spectrum by a time-domain repair technology, wherein the frequency-domain resolution ratio is increased by removing the influence of reflection peaks and increasing the effective length of a terahertz time-domain signal through time-domain correlation locating, scale transformation and delay subtraction. The method comprises the following steps: step 1, obtaining time corresponding to the initial points, the valley points and the peak value points of main peaks and the reflection peaks; step 2, finding out the positions of the initial points, the valley points and the peak value points; step 3, extracting the peak values of the main peaks and the reflection peaks; step 4, calculating an attenuation factor; step 5, repairing a time-domain spectroscopy; step 6, obtaining a spectrogram; and step 7, calculating an absorption coefficient, and comparing absorption spectrograms before and after repair. The method is capable of accurately removing the reflection peaks of the time-domain signal, and effectively increasing the resolution ratio of the terahertz absorption spectrum.

The invention discloses a terahertz time-domain spectrograph based on a femtosecond laser. The terahertz time-domain spectrograph has two modes of a transmission-type system and a reflection-type system. A terahertz wave generated by the focusing of the femtosecond laser is focused on a sample through a second off-axis parabolic mirror after being collimated by a first off-axis parabolic mirror, transmission or reflection mode measurement is carried out, the terahertz wave of the sample is focused on a detection crystal through a fourth off-axis parabolic mirror after being collected by a third off-axis parabolic mirror, and the terahertz time-domain spectrograph is obtained. The second off-axis parabolic mirror and the third off-axis parabolic mirror as well as a sample stand are integrated as a measuring module on a base plate. Two short-focus off-axis parabolic mirrors and a transmission sample stand are integrated into a transmission measuring module. Two long-focus off-axis parabolic mirrors and a reflection sample stand are integrated into a reflection measuring module. A five-dimensional adjusting device is adopted for clamping the first off-axis parabolic mirror and the fourth off-axis parabolic mirror, and is used for quickly recovering the optimum positions of the first off-axis parabolic mirror and the fourth off-axis parabolic mirror when a transmission mode or a reflection module is switched. The terahertz time-domain spectrograph disclosed by the invention is simple and quick in adjustment process, and integration and user operation of the terahertz time-domain spectrograph are facilitated.

The invention discloses a Fresnel matrix THz wave propagation model based high-precision thickness detection method for coatings. Based on a electromagnetic field theory model, a reflecting propagation one-dimensional electric field model of normal incidence THz wave in a multi-layer medium structure is established according to a reflecting type THz time domain spectrum system used in coating thickness detection. On this basis, a Fresnel coefficient matrix and a phase matrix are introduced and a Fresnel matrix THz wave propagation model is proposed and validated. Quantitative detection of coating thickness is realized by utilizing the Fresnel matrix THz wave propagation model based LS (Least Squares) thickness optimization method and the coating thickness is solved through iterative optimization so as to minimize the minimal residual sum of squares of a simulation result and a measurement result and to realize the high precision optimization of thickness parameters. A distance parameter DTS between a THz emitter and a to-be-measured piece is introduced and visible treatment is performed on distance errors between the THz emitter and the to-be-measured piece, so that the accuracy ofcoating thickness detection is improved further.

The invention provides a method for detecting amino acid content in grain by use of terahertz frequency-domain spectrum technology. The method comprises the steps of grinding grain samples to be tested and then tableting the grain samples to be tested, directly testing the grain samples to be tested by use of a terahertz time-domain spectrum system in a transmission measurement mode under a nitrogen atmosphere to obtain the terahertz time-domain spectrum signals of the samples, performing Fourier transform on the time-domain spectrums to obtain the frequency-domain spectrums of the samples, performing normalization spectrum preprocessing on all the obtained frequency-domain spectrums, and finally, dividing the preprocessed frequency-domain spectrums of the grain tableted samples to be tested into calibration set frequency-domain spectrums and verification set frequency-domain spectrums, and establishing a quantitative analysis model by use of the partial least squares regression method so as to obtain the quantitative detection values of the various grain samples to be tested. The method for detecting the amino acid content in the grain by use of the terahertz frequency-domain spectrum technology is simple in sample preparation, simple to operate, and capable of truly and effectively realizing fast and accurate quantitative detection on the amino acids in the grain.

The invention discloses a matched test system for detecting spectrum characters generated by a sample under electron beam excitation and belongs to the detection field of detection on THz radiation spectrum characters. The system includes: a vacuum chamber, a vacuumizing system, a rotation control rod, and an electron gun. The vacuumizing system supplies a high-vacuum test environment to the sample under free electron beam excitation; the rotation control rod not only can fix the electron gun but also can control angle and position of the sample under electron beam excitation; a pair of observation windows, which are mounted in the upper and lower parts of the vacuum chamber, can be used for performing real-time detection and analysis on a radiation field generated by the sample under the electron beam excitation in a THz time-domain spectroscopy analyzer conveniently, and a pair of observation windows, which are mounted in the front and rear parts of the vacuum chamber, allows a test operator to conveniently observe the situation in the interior of the vacuum chamber. The whole system has reasonable design. The system, when being matched with the THz time-domain spectroscopy analyzer, can conveniently detect the characters of THz radiation spectrum generated by the sample under the free electron beam excitation.

The invention discloses a method for detecting insect fragments in wheat flour based on Terahertz time domain spectra. First, wheat flour samples containing the insect fragments are made and divided into a correcting sample set and a verifying sample set. The Terahertz time domain spectra of all the samples are collected, Fourier transformation is carried out on obtained time domain spectrum data so as to obtain a Terahertz frequency domain spectrum data group, and a spectral data group of Terahertz absorption coefficients is calculated. The insect fragments in the wheat flour are estimated based on Terahertz absorption spectra in combination with PLSR (Partial-Least-Squares Regression), optimal factor number in the PLSR is determined through the utilization of cross validation, and the rapid detection of the insect fragments in the wheat flour is realized. Modeling is carried out by introducing PLSR in the Terahertz absorption spectra, the problems that the independent variables of the Terahertz spectra are multiple and multiple correlations exist among the independent variables are solved, and the quantitative analysis problem of the Terahertz spectrum data is solved. The method has important practice meaning in ensuring the quality of the flour and sequent food.

Disclosed are a method and an apparatus for measuring terahertz time-domain spectrum, which relate to the field of terahertz time-domain spectrum. The method comprises the steps of: generating a first pulse laser beam from a first femtosecond laser device at a preset repetition frequency to generate THz pulses; generating a second pulse laser beam from a second femtosecond laser device at the repetition frequency; measuring electric field intensities of the THz pulses at respective phase differences between the first pulse laser beam and the second pulse laser beam; and obtaining a THz time-domain spectroscopy by performing Fourier transformation of data representative of the electric field intensities. Compared with prior art, THz spectrum measured according to the method and apparatus of present invention has higher spectroscopy resolution and broader detection range, which makes the technology of present invention have stronger capability for discriminating substances.

The invention provides an ultra-wide frequency spectrum terahertz wave time domain spectrum coherent detection method and device, and belongs to the field of optoelectronics application. According to the method provided by the invention, the electric field time domain waveform signal of a Terahertz wave pulse is detected through laser secondary harmonic signals generated by the non-linear effect of the laser pulse electric field and the Terahertz wave pulse electric field with air atoms / molecules in air media; the method belongs to a coherent detection method. A frequency doubling light signal generated in the device comprises optical intrinsic oscillation frequency doubling light generated in nonlinear crystals beta-BBO by using detection laser and also comprises detection laser and laser frequency doubling light generated by the Terahertz wave pulse electric field in the air media. The intrinsic oscillation source is generated by using beta-BBO crystals; the size of the oscillation source can be controlled through rotating an inclined angle formed between a fast shaft of the beta-BBO crystals and the polarization direction of the detection laser; the intrinsic oscillation source generation by using an external voltage modulator is not used; the cost is reduced; the detection method is simpler and more convenient; the detection can be performed under the all optical element conditions.

In a measurement of a time-domain waveform of a terahertz wave based on time-domain spectroscopy, a current signal including a component originating from the terahertz wave is detected using a photoconductive device, and a voltage signal corresponding to the detected current signal is detected. At a pre-processing stage before the voltage signal detection, an offset current included in the detected current signal and having no relation to the terahertz wave is drawn. The offset current is monitored and the magnitude of the drawn offset current is adjusted according to a result of the monitoring. A time-domain waveform of the terahertz wave is acquired based on the voltage signal detected while drawing the offset current. The monitoring of the offset current and the adjusting of the offset current are performed in a waiting state in which measurement of the time-domain waveform of the terahertz wave is not performed.

The invention discloses a defect detection method and a defect detection system based on terahertz imaging. The defect detection method comprises the steps of: dividing a detected sample into a plurality of scanning points, and carrying out stepped scanning on the plurality of scanning points by utilizing terahertz waves to obtain terahertz time-domain transmission pulses corresponding to the plurality of scanning points; analyzing the plurality of terahertz time-domain transmission pulses to obtain time-domain transmission pulse amplitude values corresponding to the plurality of scanning points; calculating grayscale values corresponding to the plurality of scanning points according to the time-domain transmission pulse amplitude values to obtain a grayscale map of the detected sample; and positioning defect parts in the detected sample according to the light and shade contrast in the grayscale map. According to the defect detection method and the defect detection system, the detectedsample is imaged based on the terahertz imaging technology, the time domain spectral data can be extracted according to the detected sample, the corresponding grayscale map is finally generated, andthe obtained grayscale map can enable the forms of various internal defects of the to-be-detected sample to be visualized, so that the defect detection can be precisely conducted on the to-be-detectedsample.

The invention relates to a terahertz imaging-based biomacromolecule content relative quantitative detection method, and belongs to the field of biomacromolecule detection. The method comprises the following steps: S1, obtaining a nitrocellulose film or a polyvinylidene fluoride film containing biomacromolecules; S2, placing the to-be-detected film on a terahertz time-domain spectrometer, and carrying out scanning imaging to obtain a time-domain spectrum of a point; S3, performing Fourier transform and smoothing processing on the time domain spectral data, and taking the processed time domain spectral data as frequency domain spectral data; S4, taking N points on each to-be-detected film, measuring the thickness of the to-be-detected film, and taking a mean value as the thickness of the to-be-detected film; and S5, calculating, analyzing and recombining the frequency domain spectral data of each pixel point of the measurement film, and converting the frequency domain spectral data intogray values of the corresponding pixel points, so as to form a visual image reflecting the spatial distribution condition of the biomacromolecule content on the film. The method has the advantages ofno need of antibodies, simple operation, fast and accurate detection speed, time saving, labor cost saving, and realization of label-free detection.

The invention relates to a terahertz strong-field time-domain spectrum. High-pulse-energy terahertz wave is efficiently produced for designing an appropriate wave tilting imaging system, and the system has strong scientific research and practical application values. According to the technical scheme adopted by the invention, a terahertz strong-field system of an ultrashort pulse pump based on a wave tilting method is composed of the following components: a convex lens, a concave lens, a plane reflection mirror, a grating, a 1 / 2 wave plate, 2 cylindrical reflecting mirrors, LiNbO3 crystals, 5 off-axis parabolic mirrors, 2 terahertz linear polarizers, a mechanical delay line, a thin film beam splitter, a detection crystal, a photoelectric balance detection module and a laser light source; the components are arranged on an optical platform, wherein the convex lens and the concave lens are combined to form a telescope system, the rear focuses of the convex lens and the concave lens are coincided, and the amplitude of a light beam I emitted by the laser light source is reduced according to focal length ratio of the two lenses. The terahertz strong-field system provided by the invention is mainly applied to a wave tilting imaging occasion.

An in vitro method of determining an analyte concentration of a sample includes placing the sample into a low-field, bench-top time-domain nuclear magnetic resonance (TD-NMR) spectrometer. The NMR spectrometer is tuned to measure a selected type of atom. A magnetic field is applied to the sample using a fixed, permanent magnet. At least one 90 degree radio-frequency pulse is applied to the sample. The radio-frequency pulse is generally perpendicular to the magnetic field. The 90 degree radio-frequency pulse is removed from the sample so as to produce a decaying NMR signal. The decaying NMR signal is measured at a plurality of times while applying a plurality of 180 degree refocusing radio-frequency pulses to the sample. The analyte concentration is calculated from the plurality of measurements associated with the decaying NMR signal and a selected model.