62 results about "Laser Doppler vibrometer" patented technology

A non-contact method and apparatus for continuously monitoring a physiological event in a human or animal, such as blood pressure, which involves utilizing a laser-based interferometer system to produce a waveform that is representative of continuous blood pressure in a subject. The invention may preferably utilize a laser Doppler vibrometer which is oriented to produce a laser beam directed toward the subject substantially perpendicular to a skin surface of the subject wherein the skin surface is moveable in response to blood pressure. The vibrometer is sensitive to motion of the skin surface in a direction parallel to the laser beam and produces a signal representative of this motion. By plotting the velocity of the skin surface movement in the direction parallel to the laser beam with respect to time, a waveform is produced that has been found to be representative of the blood pressure waveform and highly defined to thereby permit accurate timing analysis thereof relating to cardiac cycles.

A multi-beam laser Doppler vibrometer simultaneously measures velocity, displacement, and vibration history of multiple locations on an object. A beam of coherent light is split into an object beam and a reference beam. The object beam is divided into a plurality of object beams to simultaneously illuminate multiple locations on the object under inspection. The reference beam is frequency shifted and split into a corresponding plurality of frequency-shifted reference beams. A portion of each object beam is reflected by the object as a modulated object beam. The plurality of modulated object beams are collected and respectively mixed with the plurality of frequency-shifted reference beams to provide a plurality of beam pairs. Each beam pair may be focused onto a photodetector or an optical fiber connected to a photodetector.

The invention provides a laser dynamic deflection survey vehicle. The survey vehicle comprises a mobile measuring table, a measuring cross beam, a running wheel, a velocity measuring wheel, an accelerometer and a data acquiring and processing device. The laser dynamic deflection survey vehicle provided by the invention has the following advantages: according to the laser Doppler velocity measurement principle and the inertia measurement principle, during the driving process of the vehicle at a normal traffic velocity (15-80km/h), a plurality of laser Doppler vibration meters arranged in the front of loading wheels of the vehicle synchronously measure the relative movement velocity of various measuring points on a road surface; the instantaneous deflection deformation velocity of the road surface is obtained through inertia compensation calculation; and a dynamic deflection value of the road surface is obtained through inversion by utilizing a road layered elastic mechanical model and used for general investigation and assessment of the bearing capacity of a road network.

Systems and methods for laser based measurement of air parameters are disclosed. An example system includes a coherent source of radiation, a transceiver, an optical mixer, and an intelligent optical device. The coherent source produces a coherent radiation beam that is then transmitted to a target region by the transceiver. The transceiver is further configured to receive a scattered radiation signal from the target region. The optical mixer is configured to receive the scattered radiation signal from the transceiver, receive a reference radiation beam from the coherent source, and to determine a difference between the scattered radiation signal and the reference radiation beam. In certain embodiments, the intelligent optical device is configured to steer, modulate, or condition, at least one of the coherent radiation beam, the scattered radiation signal, and the reference radiation beam.

An apparatus and method for non-determination of the surface velocity of a target using optical interference and Doppler shifting of the light reflected from the target are disclosed. It may be used to measure small-amplitude, acoustic frequency surface vibrations as well as non-periodic surface vibration.

The invention relates to an unsteady cavitation flow-excited vibration multi-field synchronous measurement system for a water tunnel experiment and belongs to the ship and underwater vehicle engineering and water conservancy and hydropower engineering technology field. The system is composed of an experimental section, an experimental model, a high-speed camera, a synchronous trigger switch, a laser Doppler vibration meter, a data acquisition instrument, a data processing system/computer and display assembly and a light source. According to the system of the invention, rising edge voltage signals are generated through the synchronous trigger switch, trigger signals are controlled by using the voltage signals, and therefore, the signal acquisition starting instructions of the high-speed camera and the laser Doppler vibration meter are controlled quantitatively and precisely, and the quantitative and accurate synchronous measurement of an unsteady cavitation flow field and a structure field can be realized; and data obtained through multi-physical field synchronous acquisition are subjected to preprocessing, time-domain analysis, frequency-domain analysis and time-frequency analysis,and therefore, reliable analysis experimental data can be provided for the study of fluid-structure interaction characteristics.

The invention discloses a method for detecting a sound field parameter in a fluid medium by using a laser vibrometer. A transmitting transducer is arranged in a measured water pool through a mounting and positioning mechanism, a laser vibrometer probe is mounted on the surface of the water pool through a three-dimensional positioning device, laser is vertically projected onto an interface of water in the water pool and air, and the sound axes of the laser beam and the transmitting transducer coincide; and the interface between the liquid medium and the air is used as a reflection face of a laser beam, and the sound field parameter is detected by an optical method to obtain a sound pressure. The method has the advantages that: the need of arranging reflecting and sound transmitting membrane in a sound field is obviated, and the measurement steps are simplified. As it is unnecessary for a measuring light beam to pass through the inside of fluid, the value of real vibrating velocity of amass point can be obtained without taking the influences of an acoustooptic effect on the light beam into consideration nor correcting the test result; the value of the sound pressure can be obtaineddirectly according to the relationship between the sound pressure and the mass point; and the efficiency of the measurement is improved.

A preferred embodiment of the invention provides an ultra-soft atomic force microscope device that has a nanoneedle cantilever that terminates in a smaller diameter nanofiber tip. Deflection of the nanoneedle cantilever is measured directly by a laser Doppler vibrometer. The invention simultaneously provides a very low mass nanoneedle cantilever arm with a very small diameter nanofiber tip, while being able to image the vibration and displacement. An AFM device of the invention simultaneously provides a ultra low mass and soft cantilever, the ability to accurately and directly measure vibration and deflection of the very small diameter nanoneedle cantilever with the laser Doppler vibrometer, and a sharp nanofiber tip that provides sub nanometer resolution.

The invention relates to a vibration testing system and method for a thin-wall cylindrical shell component, and belongs to the technical field of laser Doppler vibration measurement. A laser Doppler vibrometer, a test piece mounting table and a laser reflecting unit are all arranged on a base, and the laser emitting end of the laser Doppler vibrometer corresponds to the test piece mounting table. Guide rails and a lead screw of the laser reflecting unit are both fixedly arranged on a fixing support, sliding blocks are fixedly arranged on a sliding carriage, and the sliding carriage is in sliding fit with the guide rails through the sliding blocks. A nut is arranged on the lead screw in a sleeved mode, and the nut is fixedly connected to the lower surface of the sliding carriage. One end of a measurement arm is fixedly arranged on the upper surface of the sliding carriage, and the measurement arm, the lead screw and the guide rails are all arranged in parallel. A reflecting mirror is arranged at the other end of the measurement arm, a 45-degree included angle is formed between the reflecting mirror and the vertical direction, and the laser emitting end of the Doppler vibrometer corresponds to the reflecting mirror. A first drive motor is mounted between the reflecting mirror and the measurement arm, and an output shaft of the first drive motor is fixedly connected with the reflecting mirror. A second drive motor is arranged at the shaft end of the lead screw.

The invention discloses a method for measuring vibration performance of the tool nose of a micro-milling tool, which belongs to the field of micro processing. The method is characterized in that the micro-milling tool is clamped in the tool nose of a spindle, one end of a piezoelectric actuator is pasted on the tool handle of the micro-milling tool, and the other end of the piezoelectric actuator is connected with a high frequency force sensor pasted on a machine tool motion platform; a machine tool drives the micro-milling tool to conduct micro feeding to the piezoelectric actuator, certain precompression is applied between the piezoelectric actuator and the tool handle of the micro-milling tool, and the piezoelectric actuator generates shock excitation under the action of excitation of an externally-connected signal generator; and a laser Doppler vibrometer is adopted to measure the vibration performance of the tool nose of the micro-milling tool. The method provided by the invention has the advantages that harmonic excitation is only applied on the tool handle of the micro-milling tool, so that damage of the tool nose is avoided, the micro-milling tool with small diameter can be measured, the frequency is high, the vibration performance can be on-line measured, and the method is simple, easy and convenient to implement.

The invention relates to the technical field of interferometry, and discloses a heterodyne interference optical path structure based on optical fibers and a laser vibrometer. The optical path structure includes a first optical fiber coupler, an optical fiber frequency shifter, a second optical fiber coupler, an optical fiber loop detector and an optical transceiver, which are connected by opticalfibers and constitute a heterodyne interference loop. The laser vibrometer includes a measuring laser source, a balanced photoelectric detector and the optical path structure. The measuring laser source is connected with the input end of the first optical fiber coupler through an optical fiber, and the balanced photoelectric detector is connected with the output end of the second optical fiber coupler through an optical fiber. Through connection by optical fibers, the characteristics of small size and high reliability are achieved. Through the heterodyne interference optical path, the opticalpath system has high signal-to-noise ratio and anti-interference ability and can be used to measure geometric parameters such as length, displacement, straightness and flatness in the field of precision measurement.

A laser Doppler velocimeter is formed using a fiber laser as the lasing medium. Within the velocimeter, all optical signals, transmitted and received, are conveyed by optical fibers. An amplifier amplifies a source laser, which is then transmitted to one or more transceivers. The one or more transceivers, each projecting along a different axis, and each with a single optical fiber input/output interface act as both the transmission device to focus the radiation at a target region, and as the receiving system for collecting reflected radiation. The transceivers each include an amplifier to further amplify the radiation received from the laser source. The one or more transceivers transmit radiation simultaneously to the target region, and may be located remotely from the laser source. The portion of the reflected radiation collected by the receiving system is analyzed to determine the Doppler shift caused by targets at the focal point of the one or more transceivers.

An airborne wind profiler for an aloft aircraft includes a system bus for receiving a GPS signal including a time and position solution and an attitude signal representing heading, roll, pitch, and yaw of the aircraft. An optical module includes at least one laser Doppler velocimer including an mount allowing the at least one laser Doppler velocimeter to articulate in at least two axes, thereby to orient the laser Doppler velocimeter below a horizon to generate at least one first velocimeter signal. The velocimeter signal includes at least one first radial velocity of a first wind-borne aerosol and a first orientation of the at least one laser Doppler velocimeter relative to the aircraft. A processor module receives the first velocimer signal at the time from at least one laser Doppler velocimeter.

A non-contact biometric sensing device is described. The device includes a processing device, a user interface communicatively coupled to the processing device, a display communicatively coupled to the processing device, a laser doppler vibrometer sensor communicatively coupled to the processing device, and an infrared camera communicatively coupled to the processing device. The processing device is programmed to utilize mechanical motion data received from the laser doppler vibrometer sensor and thermal distributions data from the infrared camera to calculate biometric data, when signals originating from the laser doppler vibrometer sensor and the infrared camera are reflected back towards the device from a target.

The invention discloses a landmine multi-modal vibration mode measurement device and method. The landmine multi-modal vibration mode measurement device comprises a signal generator, a sound emission unit, a sound level meter, a laser Doppler vibrometer, a multi-channel data acquisition card, a computer and a caisson, wherein the signal generator is connected with the sound emission unit through a data line; the sound level meter and the laser Doppler vibrometer are sequentially connected with the multi-channel data acquisition card and the computer through data lines; high-intensity and low-frequency sound waves with continuous sweep frequency are emitted out through the signal generator and the sound emission unit, the sound level meter and the laser Doppler vibrometer detect the sound pressure level of the upper end face of a landmine and an amplitude-frequency characteristic curve of the vibration speed respectively, and the multi-order inherent frequency of the landmine is measured out; the signal generator and the sound emission unit emit high-intensity sound wave signals with the inherent frequency of the landmine as the output frequency, and the laser Doppler vibrometer, the multi-channel data acquisition card and the computer detect, display and record a multi-modal vibration mode of the landmine. The landmine multi-modal vibration mode measurement device and method achieve non-contact type rapid and accurate measurement of the multi-modal vibration mode of the landmine.

The invention relates to a device for the optical non-contact oscillation measurement of an oscillating object, comprising a laser Doppler vibrometer that has a laser (1) as the light source for a laser beam, a first beam splitter assembly (S1) for splitting the laser beam into a measuring beam (2) and a reference beam (3), a means (4) for shifting the frequency of the reference beam (3) or of the measuring beam (2) in a defined manner, a second beam splitter assembly (S2, S3) by means of which the measuring beam (2) back-scattered by the oscillating object (6) is merged with the reference beam (3) and superimposed on the same, and a detector (5) for receiving the superimposed measuring and reference beam (7) and for generating a measurement signal, wherein the laser (1) is provided with a polarization filter arranged inside the optical resonator of the laser and the frequency of the dominating mode can be kept constant by a control to the beat signal.

The invention discloses a landmine inherent frequency acousto-optic measurement device and method. The landmine inherent frequency acousto-optic measurement device comprises a signal generator, a sound wave emission system, a laser Doppler vibrometer, a data collection card, a computer, a landmine box, a soil sample and a small reflector, wherein the signal generator is connected with the sound wave emission system through a lead wire; the laser Doppler vibrometer is sequentially connected with the data collection card and the computer through a data line; the soil sample is placed in the landmine box; and the small reflector is placed on the soil sample placed in the landmine box. The signal generator emits continuous frequency sweeping low-frequency sound waves, vibration signals on the small reflector are detected through the laser Doppler vibrometer, amplitude-versus-frequency curves of the vibration signals with and without landmine sample burying are obtained, and the landmine inherent frequency is obtained in a ratio solving method. The landmine inherent frequency acousto-optic measurement device and method can achieve non-contact, fast and accurate measurement of the landmine inherent frequency.

The invention relates to the technical field of photoelectric transient state testing and provides an optical control system, a control method and a laser Doppler velocimeter. The optical control system includes an optical power reference value input module, a reflected light power detection module, a controller and an optical power adjusting module. According to the technical scheme provided by the invention, dynamic adjustment of emitted light power can be performed according to the change of reflected light power, so that the reflected power is kept constant and is equal to or in a fixed proportion with the reference light power; amplitude stability and base line stability of coupling interference signals of reflected light and reference light can be ensured; a condition that a to-be-detected object can reflect light of sufficient power can be ensured; testing signal quality can be improved; signal-to-noise ratio of signals can be improved; and a phenomenon of signal loss caused by too weak reflected light can also be inhibited; and the testing reliability is improved.

The invention discloses a propellant charge exhaust plume flow velocity measurement device, which solves the problem that the existing laser Doppler velocimeter and particle image velocimeter can only measure the particle velocity in the fluid, rely on tracer particles and cannot be accurately characterized Fluid velocity issues. The invention includes a tunable semiconductor laser, a laser control system, an optical system, and a data acquisition and processing unit. The invention can realize the measurement of the exhaust plume flow velocity of the solid, liquid, colloid and paste propellant charge within the high precision and wide velocity measurement range (0-3000m/s). The invention is applicable to the measurement of the flow velocity of the exhaust plume generated when different kinds of propellants are burned in the engine, and has important significance for the optimization of the propellant composition, the design of the propellant charge and the design of the engine.