Practical development questions of 3D shape shearography technique for surface strain inspection of curved objects are discussed. Results of a global cameras-projector system calibration and different methods of shear distance estimation in 3D are presented.
In short-range optical detection-and-ranging systems in which the maximum distances to the objects are 10-15 m, it becomes possible to reduce the required radiation energy or the size of the optical receiver system while maintaining the specified detection-probability characteristics by noise synchronization of the emission time. The signal in this case is received on the interval between noise bursts-i.e., on a time interval in which a false alarm is less probable. This article presents a statistical analysis of the probability distributions of the noise intervals, used as the basis for defining the principle by which the detection-probability characteristics are calculated. It is shown that, when the threshold/noise ratio equals unity, the radiation energy required to ensure a skip probability equal to 0.01 is almost a factor of 3 less than in classical detection, and, when the threshold/noise ratio equals 2, it will be a factor of 23 less.In optical detection-and-ranging systems, the optimum filtering is used to maximize the SNR under conditions of Gaussian noise statistics. With a uniform energy spectrum of the noise, the pulse response gt of the optimum (matched) filter is a mirror image of the input signal s 1 t:The signal at the output of the filter in this case is determined by Duhamel's integral,Consequently, if a pulsed radiator is triggered at the instant that a noise burst with a negative derivative at the output of the receiver-amplifier channel intersects a fairly low level, while the reflected signal is received on the interval between bursts of a random output process, it becomes possible to substantially reduce the radiation energy required for reliable detection.When the temporal extension to the object to be detected is comparable with the signal duration, the working interval of observation is equal to twice the signal duration. The probability that a noise burst with a positive derivative that exceeds the operating level will appear on this interval will in this case correspond to the false-alarm probability, which can be defined by the relationship α Z 2T 0 0 W τ; C 1 dτ;(1)where W τ; C 1 is the probability density of intervals between bursts of a random process at the output of the detector-amplifier channel when the C 1 level is crossed, and T 0 is the maximum temporal extension to the object to be detected. The general exact expression of the probability density of the intervals between the bursts of a random process when the constant level C 1 is crossed (Fig. 1) is determined by the "crossover-counter" method 1,2 and is extremely complex, since it involves slowly convergent infinite series whose terms are integrals of infinitely increasing multiplicity.There is interest in short time intervals for calculating the false-alarm probability. In this case, approximate methods can be used to determine the probability density of the intervals between bursts of random processes, 2,3where W 2 C 1 ; y; t 0 and W 4 C 1 ; y; C 1 ; t 0 ; t 0 τ are, respectively, the two-dimensional and four-dimensio...
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