Laser Doppler vibrometer

About: Laser Doppler vibrometer is a research topic. Over the lifetime, 6319 publications have been published within this topic receiving 76068 citations.

Laser-scanning confocal vibrometer microscope: Theory and experiments

Abstract: In this article we present a new laser-scanning confocal microscope for vibration measurements in microscopic mechanical and biological structures. Our system can map out-of-plane vibrations with picometer amplitude resolution while the locus transverse and depth resolutions are in the submicrometer regime. We have achieved this performance by using the measurement beam of a heterodyne laser-Doppler vibrometer as the scanned laser beam of a confocal microscope. The power of the heterodyne carrier is a measurement of the detected light intensity. Therefore, the laser-scanning confocal laser-Doppler vibrometer microscope (CVM) can also be used as common confocal microscope to image and measure geometries of three-dimensional structures. The focus of this article is on the analysis of the transverse resolution, which cannot be adopted from other techniques. Our realized CVM allows vibration measurements up to 20MHz. The measured minimum 1∕e2-power spot diameter of 730nm enables vibration analysis of submicro...

End-of-vector laser power control in a selective laser sintering system

Abstract: A selective laser sintering apparatus and method is disclosed, in which the laser power is controlled according to the scan velocity. The scanning system, which includes a pair of galvanometer-controlled mirrors for directing the aim of the laser beam, generates signals indicative of either the position or scan velocity of the aim of the beam, in either one or two directions. The signals are gated in the laser power control system so as to pass the signals only during those times at which the laser is to be turned on. A laser power control system receives the signals and, in the case of position signals, differentiates the signals to generate velocity signals. The velocity signals are used to derive a scan velocity, and the scan velocity is multiplied by the desired laser power at full scan velocity to produce a laser power control signal. By making the laser power dependent upon the scan velocity, a constant laser energy flux density is applied to powder at the target surface, even during acceleration and deceleration intervals at the beginning and end of a scan, respectively.

Laser beam machine for micro-hole machining

Abstract: The present invention relates to a laser beam machine having a laser oscillator, for generating a laser beam; a light path system, including galvano mirrors and an fθ lens that form a light path along which the laser beam emitted by the laser oscillator is guided to an object; and a diffractive optical element, located along the light path leading from the laser oscillator to the galvano mirrors.

Broadband optical detection of transient motion from a scattering surface by two-wave mixing in a photorefractive crystal

Abstract: A method and apparatus for optically detecting transient motion from a scattering surface. A laser beam having a predetermined frequency is directed onto such a surface to thereby scatter the laser beam and produce a scattered laser beam defining an optical wavefront and having an optical spectrum with a central peak at the laser frequency and a sideband on either side of the central peak. The scattered laser beam is caused to interfere inside a photorefractive crystal with a pump beam derived from the laser beam so as to form an index of refraction grating diffracting the pump beam into a reference beam having an optical wavefront substantially matching the wavefront of the scattered laser beam and an optical spectrum with a single peak at the laser frequency and no sidebands, whereby to produce at an exit face of the photorefractive crystal a transmitted scattered laser beam and a diffracted reference beam interfering with one another. The interfering beams at the exit face of the photorefractive crystal, or polarization components thereof, are at least temporarily out of phase, thereby obtaining an optical signal sensitive to phase perturbations produced by the transient motion, which optical signal is detected and converted into an electrical signal representative of the transient motion. The invention is particularly useful for detecting small surface formations or displacement of a material subjected to ultrasonic energy, enabling displacements ranging from a fraction of 1Å to a few hundred Å to be detected with a large etendue or light gathering efficiency and a broad frequency bandwidth extending from frequencies as low as 1 KHz, and even below.