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One of the main constituent parts of optical coherent measuring apparatus is laser as source with stable performance of
frequency, radiation intensity, and light beam uniformity. At present time semiconductor lasers are rather attractive devices
in view of there low prices, small size, serviceability. Progress in its quality leads to including them not only in lightheads,
but as lighting unit in measuring apparatus. In order to guarantee accuracy of measuring instruments, all parts of them must
have stable performance, and in this respect semiconductor laser demand stabilization more that one characteristic quantity
at once. And frequency stability on the one hand is overwhelmingly important for constancy of optical measuring
instruments, on the other hand our investigations show that its regulatory control is very arduous task. Both holographic
methods and phase modulated speckle interferometry clearly recognize smooth frequency shift and frequency jumping
depending on pumping current and temperature. And for repeatability it's required to return both of them. So it is necessary
laser frequency testing during working. For interferometric comparison circuit it is frequency variation that exerts influence
on fringes pattern generation, so just this parameter should be traced in the course of measuring. Specially prepared test
object, introduced in holographic scheme, allows to uncover frequency variation, if they had have place, and to reproduce
coherence function of laser source. Complicated coherence function of semiconductor lasers can destroy interference pattern
or foul the interpretation of it. So this coherence calibration is also very useful for results validity. Phase modulated speckle
interferometry method allows to build phase correlation portraits, analogical to interferograms, hence multiwavelength
contour generation masks the picture of intrinsic object information too. Both real wavelength change and nonresolution
area, when coherence length is less then path-length difference, may be obtained with the help of known wedge incline near
the measured object. Since measured and testing image will be entered at the same time, test results will be applied in
interpretation of measurement results. Thus on-line testing of laser characteristic quantities allows using unstable sources
and increasing of measurement precision.
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