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.

Development of a Multi-Channel Piezoelectric Acoustic Sensor Based on an Artificial Basilar Membrane

Abstract: In this research, we have developed a multi-channel piezoelectric acoustic sensor (McPAS) that mimics the function of the natural basilar membrane capable of separating incoming acoustic signals mechanically by their frequency and generating corresponding electrical signals. The McPAS operates without an external energy source and signal processing unit with a vibrating piezoelectric thin film membrane. The shape of the vibrating membrane was chosen to be trapezoidal such that different locations of membrane have different local resonance frequencies. The length of the membrane is 28 mm and the width of the membrane varies from 1 mm to 8 mm. Multiphysics finite element analysis (FEA) was carried out to predict and design the mechanical behaviors and piezoelectric response of the McPAS model. The designed McPAS was fabricated with a MEMS fabrication process based on the simulated results. The fabricated device was tested with a mouth simulator to measure its mechanical and piezoelectrical frequency response with a laser Doppler vibrometer and acoustic signal analyzer. The experimental results show that the as fabricated McPAS can successfully separate incoming acoustic signals within the 2.5 kHz–13.5 kHz range and the maximum electrical signal output upon acoustic signal input of 94 dBSPL was 6.33 mVpp. The performance of the fabricated McPAS coincided well with the designed parameters.

Ultrasonic bonding apparatus and quality monitoring method

Abstract: An ultrasonic bonding apparatus comprises an ultrasonic wave controller, a bonding system including a bonding head, a laser oscillator, a laser optics, a vibration monitoring system including a vibrometer, and a mechanism for feeding a result of monitoring back to a bonding condition.

Use of readback signal modulation to measure head/disk spacing variations in magnetic disk files

Abstract: -A new method is developed for measuring the dynamics of the head/disk interface in magnetic disk files. This method utilizes the modulation of a sinusoidal readback signal that results from head/ disk spacing variation. Measurements of slider dynamics using this readback signal modulation (RSM) technique are compared with measurements made with the laser-Doppler vibrometer (LDV) for transient slider motions that are introduced by several different means of slider disturbance. The RSM measurements are calibrated experimentally by use of the LDV together with the functional form provided by the Wallace equation, which expresses the dependence of the readback voltage on various recording parameters including the head/disk spacing. The RSM technique for head/disk spacing measurement variation has a resolution of 50 nm without correction, and this can be improved to 5 nm by removal of the systematic error that is associated with the recorded signal. A frequency range of 20 Hz to 100 kHz is achievable. Since the read/write head of the disk file is used as the measurement transducer without modification, and relatively simple and inexpensive additional instrumentation is required for the implementation of the RSM technique, it is expected that this method may become a useful tool in the research and development of magnetic disk files.

Analysis of Atmospheric Laser Doppler Velocimeters

Abstract: Fundamental relationships between backscattered power, range, wavelength, and number of scatter centers in the probe volume for the self-aligning, dual-scatter, laser doppler velocimeter are developed. It is shown that not all power scattered from the velocimeter probe volume contributes to a doppler signal. This fact leads to significant deviations in calculations involving signal-to-noise power ratios as compared to the case when only gross backscattered power is considered.

Optically pumped FIR lasers: Frequency and power measurements and laser magnetic resonance spectroscopy

Abstract: Optically pumped FIR lasers are currently in use in both frequency metrology and laser magnetic resonance spectroscopy programs in the NBS Boulder labs. The laser for use in frequency metrology is a CW 71 μm methyl alcohol waveguide laser with over 100 mW output for frequency synthesis. Another laser with an intracavity absorption cell for laser spectroscopy has been constructed and is nearly transversely pumped. The metrology technique used to measure the frequency of these lasers is briefly reviewed and a unique power meter is described.