42 results about "Nonlinear scattering" patented technology

Methods and instruments for suppression of multiple scattering noise and extraction of nonlinear scattering components with measurement or imaging of a region of an object with elastic waves, where elastic wave pulse complexes are transmitted towards said region where said pulse complexes are composed of a high frequency (HF) and a low frequency (LF) pulse with the same or overlapping beam directions and where the HF pulse is so close to the LF pulse that it observes the modification of the object by the LF pulse at least for a part of the image depth. The frequency and/or amplitude and/or phase of said LF pulse relative to said HF pulse varies for transmitted pulse complexes in order to nonlinearly manipulate the object elasticity observed by the HF pulse along at least parts of its propagation, and where received HF signals are picked up by transducers from one or both of scattered and transmitted components of the transmitted HF pulses. Said received HF signals are processed to form measurement or image signals for display, and where in the process of forming said measurement or image signals said received HF signals are one or both of delay corrected with correction delay in the fast time (depth-time), and pulse distortion corrected in the fast time, and combined in slow time to form noise suppressed HF signals or nonlinear scattering HF signals that are used for further processing to form measurement or image signals. The methods are applicable to elastic waves where the material elasticity is nonlinear in relation to the material deformation.

New methods of ultrasound imaging are presented that provide images with reduced reverberation noise and images of nonlinear scattering and propagation parameters of the object, and estimation of corrections for wave front aberrations produced by spatial variations in the ultrasound propagation velocity. The methods are based on processing of the received signal from transmitted dual frequency band ultrasound pulse complexes with overlapping high and low frequency pulses. The high frequency pulse is used for the image reconstruction and the low frequency pulse is used to manipulate the nonlinear scattering and/or propagation properties of the high frequency pulse. A 1st method uses the scattered signal from a single dual band pulse complex for filtering in the fast time (depth time) to provide a signal with suppression of reverberation noise and with 1st harmonic sensitivity and increased spatial resolution. In other methods two or more dual band pulse complexes are transmitted where the frequency and/or the phase and/or the amplitude of the low frequency pulse vary for each transmitted pulse complex. Through filtering in the pulse number coordinate and corrections of nonlinear propagation delays and optionally also amplitudes, a linear back scattering signal with suppressed pulse reverberation noise, a nonlinear back scattering signal, and quantitative nonlinear scattering and forward propagation parameters are extracted. The reverberation suppressed signals are further useful for estimation of corrections of wave front aberrations, and especially useful with broad transmit beams for multiple parallel receive beams. Approximate estimates of aberration corrections are given. The nonlinear signal is useful for imaging of differences in tissue properties, such as micro-calcifications, in-growth of fibrous tissue or foam cells, or micro gas bubbles as found with decompression or injected as ultrasound contrast agent.

The invention relates to a temperature-measuring system of distributed fibers, aiming at the continuous monitoring of temperature parameters of underground electromechanical transport equipment. The temperature-measuring system of distributed fibers comprises a singlechip control board, a fiber temperature field information acquisition module, a photoelectric detector and a circuit signal post-processing module, wherein the fiber temperature field information acquisition module comprises a pulse fiber laser and a wavelength division multiplexer; the circuit signal post-processing module comprises an acquisition card and a personal computer (PC); the singlechip control board is connected with the pulse fiber laser and the acquisition card by leads; the wavelength division multiplexer is connected with the pulse fiber laser and the photoelectric detector by fibers; incident light emitted by the pulse fiber laser is output to the sensing fiber by the wavelength division multiplexer; the sensing fiber feeds backward scattered light with temperature variance information of mine equipment back to the wavelength division multiplexer; and the wavelength division multiplexer extracts two scattered light beams of anti-Stokes and Stokes from the backward scattered light to restrain Rayleigh scattered light and other non-linear scattered light; and the photoelectric detector is connected with the acquisition card by a lead.

The invention discloses an optical fiber Brillouin optical time domain analyzer, which is made based on optical fiber broadband nonlinear light amplification effect and strain, temperature effect and optical light domain analysis principle of coherent amplified Brillouin scattering. The optical fiber Brillouin optical time domain analyzer comprises a narrowband single-frequency fiber laser, a fiber beam splitter, a pulse modulator, two optical fiber circulators, a heterodyne receiver, a digital signal processor, a fiber-grating filter, a monomode fiber and a continuous-operating fiber Raman pump laser. The continuous-operating high-power fiber Raman pump laser is used as the pump light source of the Brillouin optical time domain analyzer, which can overcome the difficulty in strictly locking the frequency of a detection laser and the pump laser of the Brillouin optical time domain analyzer; and boardband fiber nonlinear scattering amplification is used for substituting for narrowband Brillouin amplification to increase the gain of stimulated Brillouin scattering with back amplification, thus improving the S/N ratio of the system, increasing the measurement length, and improving the accuracy for simultaneous measurement of stain and temperature.

Measurement or imaging of elastic wave nonlinear scatterers with a memory of scattering parameters comprises selecting LF pulses having characteristics to change the scattering parameters of nonlinear scatterers. A transmit time relation is selected so that the incident HF pulse propagates sufficiently close to the LF pulse that the effect of the incident LF pulse on its scatterer parameters is observed by the HF pulse. At least two elastic wave pulse complexes comprising a high frequency (HF) pulse and a selected low frequency (LF) pulse are transmitted towards the region. Received HF signals are combined to form nonlinear HF signals representing the scatterers with memory, with suppression of received HF signals from other scatterers. At least one of the received HF signals may be corrected by time delay correction and/or speckle correction with a speckle correction filter, determined by movement of the scattering object. Systems are also disclosed.

Methods for chemically-resolved optical microscopy are presented. The methods can provide a wide-field, spatial interference imaging using multiple nonlinear scattering channels to produce multiple, spatially coherent anti-Stokes Raman scattering (CARS).

The invention discloses an ultra-long distance distribution type optical fiber sensor and a method for measuring temperature and vibration signals. The ultra-long distance distribution type optical fiber sensor adopts a multi-stage relay amplifier, and a high-power pulse light source enters a detecting optical fiber stage by stage through proportional allocation of a plurality of optical fiber couplers and transmission of transmission fibers, and re-amplifies the pulse of the detecting light at a specified length, thereby improving the signal to noise ratio of the system in terms of 'source', being capable of avoiding non-linear scattering caused by overrun light which enters a detecting optical cable directly on one hand, and being capable of reducing higher energy loss caused by continuous light transmission on the other hand. The ultra-long distance distribution type optical fiber sensor adopts the staged design, thereby greatly reducing the requirement on receiving sensitive and dynamic range of a receiving circuit. In addition, the ultra-long distance distribution type optical fiber sensor adopts the expandable design, thereby being capable of conveniently realizing short-distance detection, long-distance detection and ultra-long distance detection in sequence.

An optical transmission line connection system includes a light source unit that outputs laser light, a pump light generation unit that allows the laser light outputted from the light source unit to pass through one end of an optical transmission line and be made incident on one end of another optical transmission line as pump light, a measurement unit that measures non-linear scattered light components contained in reflected light, and a control unit that evaluates a spectrum of the non-linear scattered components observed by the measurement unit, and controls positions of optical axes of the one end of the one optical transmission line and the one end of the other optical transmission line so as to position the optical axes and maximize an intensity of the non-linear scattered light components.

The invention relates to the technical field of surface coatings, nonlinear optics and laser protection, in particular to a broadband laser protection method and structure. The broadband laser protection structure is obtained through the series of steps of preparation of vanadium pentoxide, design of a sapphire shell, preparation of carbon nanotube suspension liquid, and injection and sealing of the suspension liquid. The broadband laser protection structure is widely applied to the technical field of optic intelligent windows and laser protection. The broadband laser protection structure is characterized in that composite multi-element protection is adopted, combined with wave band characteristics of existing various nonlinear optical limiting materials, intensive laser interference signals can be attenuated more effectively through thermally induced phase-transition optical limiting and nonlinear scattering methods, and therefore continuous and adjustable laser protection on the visible light wave band and the near infrared wave band is achieved. The method provided by the invention has the advantages that the process is simple, the rate of finished products is high, and the method is mature and reliable.

The invention discloses a method for identifying a microcrack direction in a plate based on a nonlinear frequency mixing technology of Lamb waves. The method includes, firstly, extracting a sum frequency signal and a difference frequency signal in a damage response signal by adopting a pulse inversion method; obtaining a directional mode pattern of a nonlinear scattering coefficient beta through the extracted sum frequency signal and difference frequency signal; and determining the maximum forward scattering point and the minimum backward scattering point of the Lamb wave, and taking the direction vertical to the connecting line of the maximum forward scattering point and the minimum backward scattering point of the Lamb wave as the direction of the micro-crack, thereby realizing the identification of the direction of the micro-crack. According to the invention, the Lamb wave excited by frequency mixing interacts with the nonlinear medium to generate a new frequency component; the sumfrequency and difference frequency effective frequency components in the damage response signal are effectively extracted through a pulse inversion method, the microcrack direction is recognized by researching the nonlinear scattering degree of Lamb waves in different directions of the microcrack, and the technical problems that the amplitude is too small, and the sum frequency and difference frequency signals with weak signals are not easy to extract and recognize are effectively solved.

The invention provides a preparation method of sulfur-nitrogen codoped carbon quantum dots. The preparation method comprises the following steps: mixing phenothiazine, sodium nitrite, dichloromethaneand acetic acid, and performing a nitration reaction to obtain 3,7-dinitrophenothiazine; mixing the 3,7-dinitrophenothiazine and alkaline liquid, sequentially performing a hydrothermal reaction and dialysis to obtain sulfur-nitrogen codoped carbon quantum dots. According to the preparation method, firstly, nitrification is performed on a nitrogen source and a sulfur source, so that the nitrogen content of the carbon quantum dots can be increased; then, the 3,7-dinitrophenothiazine and the alkaline liquid are mixed, and the hydrothermal reaction is performed to obtain the sulfur-nitrogen dopedcarbon quantum dots. The carbon quantum dots have the nitrogen content of 3.45-9.69wt% and the sulfur content of 0.51-0.83wt%, show very strong nonlinear scattering performance and have very good optical limiting performance.

The present architecture utilizes a Nonlinear Scattering Aperture Combiner that does not need to be optically multiplexed and then drives a Direct Compressor stage that produces a large temporal compression ratio to pump a Fast Compressor. This eliminates the need for a separate array of ATDMs, multiplexing optical elements, and, at the approximate 10⁷ joule energy output required for ICF, reduces the number of mechanical elements and gas interfaces from the order of 10³ to about 10. In addition, this provides a large reduction of the volume of the gas containment region. In order to accomplish this, a technique for transversely segmenting by color and/or polarization of the optical extraction beams of the Direct Compressor has been invented. In particular, it emphasizes the simplicity and uniqueness of design of the Direct Compressor. The Direct Compressor is unique in terms of high fluence, high temporal compression ratios, and high stage gain, leading to a very large reduction in laser costs. It may separately have many other applications than ICF.

The present architecture utilizes a Nonlinear Scattering Aperture Combiner that does not need to be optically multiplexed and then drives a Direct Compressor stage that produces a large temporal compression ratio to pump a Fast Compressor. This eliminates the need for a separate array of ATDMs, multiplexing optical elements, and, at the approximate 10⁷ joule energy output required for ICF, reduces the number of mechanical elements and gas interfaces from the order of 10³ to about 10. In addition, this provides a large reduction of the volume of the gas containment region. In order to accomplish this, a technique for transversely segmenting by color and/or polarization of the optical extraction beams of the Direct Compressor has been invented. In particular, it is directed towards the integration of the Direct Compressor with the Primary Laser Source and Fast Compressor. The embodiments describe how the high operating fluence are addressed in terms of avoiding optical damage and how to integrate the stages in fluid mechanical and optical aspects.