KEYWORDS: Digital holography, Holograms, 3D image reconstruction, Gas lasers, Carbon monoxide, Sensors, Phase measurement, 3D image processing, Digital recording, Infrared sensors
Digital holography in the mid infrared range is shown to be a feasible technique for optical metrological applications.
The technique allows to reconstruct both amplitude and phase of wavefronts scattered by a 3D object. Experimental
results of the method applied to the reconstruction of digitally holograms recorded at CO2 laser wavelength of 10.6
micron are reported. It is show that good reconstructions can be obtained even with the lower spatial resolution of IR
recording detectors compared to visible CCD array. The results show that new prospective can be exploited by using
high power CO2 laser sources in optical metrological applications.
An optical Fourier system comprising two Fourier lenses arranged in a 4 - f configuration, a CCD camera coupled to an Analogue Digital (A/D) converter and interfaced to a computer, has been found effective to image and discriminate real etched alpha tracks and artifacts on LR-115. The choice of the optical components enhanced the system's sensitivity and the field of view of detector area (1.4 cm2). The use of spatial filters in the Fourier plane deforms the tracks and introduces phase variation of the Fourier transform signal. In addition narrow bandwidth filters could not cover broader range of all the tracks. Image analysis before track counting improves signals to noise ratio and increase the selectivity of the tracks signal size. The system can handle higher track density and other types track detectors.
We report the use of lateral vibration of speckle patterns in studying the particle sizing of bulk powdery clay sample. A two-exposure recording was made on a high-resolution holographic plate placed in the observation plane. The first exposure was taken when the laser-speckles without the sample vibrated laterally and the second when the laser-speckles and the sample vibrated laterally together. The plate was photographically processed to obtain a specklegram. The analysis of the fringe pattern from the decoded specklegram gave the particle sizes in the sample.
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