Patent ID: 6285449
Filing Date: 2001-09-04
Classification: G01N

Abstract:
Apparatus for detecting surface and subsurface defects and microstructural changes in translucent ceramic-based materials and coatings, said apparatus comprising:a tunable laser providing an output beam of high intensity light having a variable wavelength varying between a lower wavelength limit and an upper wavelength limit;optical means for directing said output beam onto a specimen of a ceramic-based material or coating and for receiving light scattered from the specimen, wherein the specimen is disposed in a machine, said optical means including polarizing means for polarizing said output beam prior to incidence upon the specimen, wherein the wavelength of said output beam varies between said lower and upper wavelength limits allowing said output beam to penetrate from the surface to a given depth of the specimen, and wherein said given depth corresponds to said upper wavelength limit;first polarization maintaining optical fiber means disposed between said optical means and the specimen for directing the output beam onto the specimen without removing the specimen from said machine, and wherein said polarization maintaining optical fiber means further directs light scattered by the specimen to said optical means to permit distinguishing surface defects and microstructural changes from subsurface defects and microstructural changes by comparing polarization states of the output beam and the light scattered by the specimen;first detector means for receiving light scattered at small scattering angles from the specimen's surface or subsurface being investigated and providing a first output signal representing light scattered at small scattering angles;second detector means for receiving light scattered at larger scattering angles from the specimen's surface or subsurface for providing a second output signal representing light scattered at larger scattering angles, wherein larger surface or subsurface defects and microstructural changes exhibit larger scattering angles than the scattering angles from smaller surface or subsurface defects and microstructure changes; anddisplay processing means coupled to said first and second detectors for processing said first and second output signals and visually displaying defects and microstructural changes on and below the surface of the specimen.