Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics

Ellingson, W A; Brada, M P

Title: Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics

Full Record
Other Related Research

Abstract

A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser`s wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered light is detected by an optical train consisting of a charge coupled device (CCD), or vidicon, television camera which, in turn, is coupled to a video monitor and a computer for digitizing the image. An analyzing polarizer in the optical train allows scattered light at a given polarization angle to be observed for enhancing sensitivity to either surface or near-subsurface defects. Application of digital image processing allows subtraction of digitized images in near real-time providing enhanced sensitivity to subsurface defects. Storing known ``feature masks`` of identified defects in the computer and comparing the detected scatter pattern (Fourier images) with the storedmore »« less

Inventors:: Ellingson, W A; Brada, M P

Issue Date:: 1995-06-20

Research Org.:: Univ. of Chicago, IL (United States)

OSTI Identifier:: 87733

Patent Number(s):: 5426506

Application Number:: PAN: 8-036,320

Assignee:: Univ. of Chicago, IL (United States)

DOE Contract Number:: W-31109-ENG-38

Resource Type:: Patent

Resource Relation:: Other Information: PBD: 20 Jun 1995

Country of Publication:: United States

Language:: English

Subject:: 42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; CERAMICS; NONDESTRUCTIVE TESTING; USES; DEFECTS; SCATTERING; FREQUENCY SELECTION; VISIBLE RADIATION; OPTICAL SYSTEMS; DIGITIZERS; AUTOMATION; DATA PROCESSING

Citation Formats


                    Ellingson, W A, and Brada, M P. Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics.  United States: N. p., 1995. 
        Web.

Copy to clipboard


                    Ellingson, W A, & Brada, M P. Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics.  United States.

Copy to clipboard


                    Ellingson, W A, and Brada, M P. Tue .  
        "Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics".  United States.

Copy to clipboard


                    
@article{osti_87733,

  title        = {Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics},

  author       = {Ellingson, W A and Brada, M P},

  abstractNote = {A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser`s wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered light is detected by an optical train consisting of a charge coupled device (CCD), or vidicon, television camera which, in turn, is coupled to a video monitor and a computer for digitizing the image. An analyzing polarizer in the optical train allows scattered light at a given polarization angle to be observed for enhancing sensitivity to either surface or near-subsurface defects. Application of digital image processing allows subtraction of digitized images in near real-time providing enhanced sensitivity to subsurface defects. Storing known ``feature masks`` of identified defects in the computer and comparing the detected scatter pattern (Fourier images) with the stored feature masks allows for automatic classification of detected defects. 29 figs.},

  doi          = {},

  journal      = {},
number       = ,

  volume       = ,

  place        = {United States},

  year         = {1995},

  month        = {6}

}

Copy to clipboard

Patent:

Search for the full text at the U.S. Patent and Trademark Office

Save / Share:

Export Metadata

Save to My Library

Similar Records in DOE Patents and OSTI.GOV collections:

Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics

Patent Ellingson, William A [Naperville, IL]; Brada, Mark P [Goleta, CA]

A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser's wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered lightmore »« less
Full Text Available
Optical method and apparatus for detection of defects and microstructural changes in ceramics and ceramic coatings

Patent Ellingson, William A [Naperville, IL]; Todd, Judith A [Hinsdale, IL]; Sun, Jiangang [Westmont, IL]

Apparatus detects defects and microstructural changes in hard translucent materials such as ceramic bulk compositions and ceramic coatings such as after use under load conditions. The beam from a tunable laser is directed onto the sample under study and light reflected by the sample is directed to two detectors, with light scattered with a small scatter angle directed to a first detector and light scattered with a larger scatter angle directed to a second detector for monitoring the scattering surface. The sum and ratio of the two detector outputs respectively provide a gray-scale, or "sum" image, and an indication ofmore »« less
Full Text Available
Detection of subsurface defects in machined silicon nitride ceramics by optical scattering methods

Conference Ellingson, W A; Ayaz, D M; Brada, M P; ...

Si{sub 3}N{sub 4} materials, from two manufacturers in the form of texture test bars, were studied by optical Fourier scattering methods. Subsurface defects were synthesized by either ultrasonically drilling or by grinding slots parallel to the surface. Because of unique optical transmission properties of ceramics subsurface defects, such as those likely to be caused by machining may be detected. S-polarized He-Ne laser light ({lambda} = 0.6328 {mu}m) was used as the light source. Specular reflections were detected by an optical Fourier method which incorporated cross-polarization. Analysis of scattered laser light was accomplished using a CCD-array camera, an 8-bit A/D converter,more »« less
Full Text Available
Detection of subsurface defects in machined silicon nitride ceramics by optical scattering methods

Conference Ellingson, W A; Ayaz, D M; Brada, M P; ...

Si[sub 3]N[sub 4] materials, from two manufacturers in the form of texture test bars, were studied by optical Fourier scattering methods. Subsurface defects were synthesized by either ultrasonically drilling or by grinding slots parallel to the surface. Because of unique optical transmission properties of ceramics subsurface defects, such as those likely to be caused by machining may be detected. S-polarized He-Ne laser light ([lambda] = 0.6328 [mu]m) was used as the light source. Specular reflections were detected by an optical Fourier method which incorporated cross-polarization. Analysis of scattered laser light was accomplished using a CCD-array camera, an 8-bit A/D converter,more »« less
Full Text Available
Fiber optic apparatus for detecting molecular species by surface enhanced Raman spectroscopy

Patent Angel, S M; Sharma, S K

Optrode apparatus for detecting constituents of a fluid medium includes an optical fiber having a metal coating on at least a portion of a light transmissive core. The metal is one, such as silver, gold or copper, which enhances emission of Raman signal frequencies by molecules adsorbed on the surface of the coating when monochromatic probe light of a different frequency is scattered by such molecules and the metal coating is sufficiently thin to transmit light between the absorbed molecules and the core of the fiber. Probe light is directed into one end of the fiber and a detector analyzesmore »« less

Similar Records