Laser fringe

In very high resolution spectrometers, such as the dynamic alignment spectrometer mentioned above, three laser beams are run in parallel to the infrared beam. These three laser beams are positioned at the apices of an equilateral triangle. Laser fringe measurements are taken on all three beams and any error, (that is, if all the zero crossings are not simultaneous) is corrected by tilting the fixed mirror. By this method, both mirror tilt and sampling frequency measurement are accomplished. 

N.S. Hong, and A.R. Jones, A Light Scattering Technique for Particle Sizing Based on Laser Fringe Anemometry, J. Phys. D Appl. Phys., 9 (1976) 1839-1848. 

The advent of lasers allowed optical interferometry to become a useful and accurate technique to determine surface motion in shocked materials. The two most commonly used interferometric systems are the VISAR (Barker and Hollenbach, 1972) and the Fabry-Perot velocity interferometer (Johnson and Burgess, 1968 Durand et al., 1977). Both systems produce interference fringe shifts which are proportional to the Doppler shift of the laser light reflected from the moving specimen surface. Both can accommodate a speci-... 

Experimentally, this technique is very similar to the TDI technique described above. A laser beam is incident normally on a diffraction grating or a preferentially scratched mirror deposited on the surface to obtain the normally reflected beam and the diffracted beams as described above. Instead of recombining the two beams that are located symmetrically from the normally reflected beam, each individual beam at an angle d is monitored by a VISAR. Fringes Fg produced in the interferometers are proportional to a linear combination of both the longitudinal U(t) and shear components F(t) of the free surface velocity (Chhabildas et al., 1979), and are given by... 

In the intersection space (optical probe) of two coherent laser beams, planar interference fringes are formed. These are normal to the plane of beams, parallel to the beam bisector, and of a known uniform distance. 

If the detected frequency of the flashing light scattered by a microscopic object when crossing the fringes is multiplied by the fringe distance, the veltKity component of the scattering object normal to the beam bisector and parallel to the laser beam plane is determined. 

Optical anemometer An instrument for measuring gas flow rate using a laser, in which small frequency shifts are visualized as interference fringes. 

Mattheyses, A. L., Shaw, K. and Axelrod, D. (2006). Effective elimination of laser interference fringing in fluorescence microscopy by spinning azimuthal incidence angle. Microsc. Res. Tech. 69, 642-7. 

In the interferometric dilatometer, the change in length of the sample causes the movement of interference fringes. Knowing the laser wavelength and counting the moved fringes, it is possible to deduce the dilatation of the sample. Hereafter, we shall briefly describe a very simple interferometric dilatometer used for the measurement of the linear contraction coefficient of Torlon. For a more detailed description of this dilatometer, see ref. [53],... 

Fig. 7.10 Interference spectrum of the fs laser fabricated fiber inline FPI device. Insert interfer ence fringe plotted in dB scale. Reprinted from Ref. 18 with permission. 2008 Optical Society of America...

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