The laser speckle patterns taken from grinded work-piece surface of a glass plane is processed to obtain the data results related to surface roughness using a visual user interface which has been developed with an experimental setup mainly consisting of He-Ne laser and CCD. The functions of processing the speckle images with the user interface are presented such as smooth the images by Gauss filter before other processions, and make the binary images by the threshold got with OSTU and present its histogram. We give the fitting curve of laser speckles' probability density distribution and their parameters, and Calculate their texture characteristic parameters such as angle-second moment, inertia (contrast), correlation and entropy value. The user interface of computer is developed using GUIDE from MATALB. We also present to compare the experimental results produced from laser speckle patterns at different detective angles and distance with the theory. The studies are useful to processing data for the measurement of surface roughness and profile of the work-piece using laser speckle method.
A new quick processing method to obtain the statistical properties of the weak laser speckle in free-space diffraction field whose speckle contrast V is less than 1 has been presented in this paper. During the process of experimental work, the conventional hypothesis of the laser speckle statistical regularity of keeping roundness was used. Based on the hypothesis, many images of laser speckle in different detection angles by a CCD sensor on the surface of samples coated with thermal sprayed with ZrO28Y2O3 have been processed. The density distribution of probability and the contrast of speckles were obtained. Even though the processing experimental data is gray-matrix but the intensity-matrix, the results are the same. The rationality of the process and the density distribution of probability are discussed in this paper. The experimental results accord well with the theoretical analysis and indicate that the method is feasible. This method makes the measurement of the surface roughness by laser speckle more convenient.
The light spot images on the coating rough surface with the plasma-thermal sprayed coating materials ZrO28Y2O3 and NiCrAlY when the laser beam (visible, wavelength is 632.8 nm, power is 2 mw) with different diameter shined on it have been studied and its experimental demonstration has also been presented in this paper. The Charge Coupled Device camera is applied to detect the light spot image field distribution, and 3D distribution of the light spot images have been obtained by computer. Above experiment results give us some basis knowledge to measure the coating thickness in the next step, which shows the physical behavior of the light spot. In addition, the different profiles of Gauss laser spot image on the rough surface for ZrO28Y2O3 and NiCrAlY coating have been analyzed.
The optical scattering characteristics of two kinds of the rough costing surface with different materials ZrO2 8Y2O3 and NiCrAlY applied the plasma-thermal spraying are studied in this paper. The micrographs with different magnification of the thermal sprayed coating surfaces have been taken by a scan electron microscope (SEM). In addition, the intensity distribution of the spatial scattering has also been gotten using an He-Ne laser beam to irradiate the rough surface of the plasma-sprayed coating and compared with others spatial scattering out of reflection spot of a smooth glass plane. The experiment results shown that different coating material and the plane have different scattering distribution in space and can use a laser system with Gauss-shaped which have different light spot diameter to project on the rough surface of the thermal sprayed coating to measure some parameters.
A new method of reprography and detection employing scan electron microscope (SEM) for the non-destructive testing the micro-cracks with width about 1 μm on the inner surface of the pinhole has been presented in this paper. The results show that the new method is a feasible approach to test the micro-cracks of the inner surface of the pinhole with sub-millimeter aperture.
The physical phenomenon of the perturbation on the water surface caused by underwater acoustic signals has been analyzed in this paper. A laser probe detection system in laboratory with a semiconductor laser to measure signal underwater from the water surface was developed. Meanwhile, the synchronous measurement utilized a -200dB standard hydrophone was also done.The signal frequencies from 200Hz to 10KHz was measured and the results have been given. The experimental results show that the system is available.
KEYWORDS: Ronchi rulings, Gaussian beams, Near field, Helium neon lasers, Argon ion lasers, Laser applications, Near field optics, Electronics, Data processing, Optical testing
Up to now, as large as seven times of Rayleigh-range or more is needed in measuring the far-field Gaussian beam divergency. This method is very inconvenient for the determination of the output beam divergency of the industrial product such as He-Ne lasers and the measuring unit will occupy a large space. The measurement and the measuring accuracy will be greatly influenced by the environment. Application of the Ronchi ruling to the measurement of far-field divergency of Gaussian beam in near-field is analyzed in the paper. The theoretical research and the experiments show that this measuring method is convenient in industrial application. The measuring system consists of a precision mechanical unit which scans Gaussian beam with a microdisplaced Ronchi ruling, a signal sampling system, a single-chip microcomputer data processing system and an electronic unit with microprinter output. The characteristics of the system is stable and the repeatability errors of the system are low. The spot size and far-field divergency of visible Gaussian laser beam can be measured with the system.
A method to measure the divergency of a singlemode TEMoo laser Gaussian beam using grating with a range of Q parameters is presented through computation with theoretical error about 1%, which is from error analysis using one-dimension regression equations.
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