Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1998-06-03
1999-10-19
Pham, Hoa Q.
Optics: measuring and testing
By polarized light examination
With light attenuation
356374, 250237G, 382149, G01B 1130
Patent
active
059698195
ABSTRACT:
A two-dimensional array of phase values is calculated from digitized phase-shifted shadow moire fringe patterns that are indicative of the flatness of the surface of an object. The light intensity "I.sub.1 " of a pixel in a first of such shadow moire fringe patterns is approximated by I.sub.0 +Acos.o slashed., the light intensity "I.sub.2 " of the pixel in a second of such shadow moire fringe patterns is approximated by I.sub.0 +Acos[.o slashed.+(.pi./2)], the light intensity "I.sub.3 " of the pixel in a third of such shadow moire fringe patterns is approximated by I.sub.0 +Acos[.o slashed.+.pi.], and the light intensity "I.sub.4 " of the pixel in a fourth of such shadow moire fringe patterns is approximated by Acos[.o slashed.+(3.pi.)/2)]. The phase values ".o slashed." are equal to arctan((I.sub.2 -I.sub.4)/(I.sub.1 -I.sub.3), and a first two-dimensional array of phase values are calculated. A plurality of two-dimensional arrays of image values are calculated from a first two-dimensional array of phase values, and the two-dimensional arrays of image values are filtered. A second two-dimensional array of phase values is calculated from the filtered two-dimensional arrays of image values. Discontinuities between adjacent phase values in the second two-dimensional array of phase values are identified by searching along a plurality of one-dimensional arrays of the two-dimensional array of phase values, and those discontinuities are adjusted. After the first row and, thereafter, the first column are searched, the other rows are sequentially searched, and thereafter the other columns may be sequentially searched.
REFERENCES:
patent: 4025195 (1977-05-01), Ebersole et al.
patent: 4714348 (1987-12-01), MaKosch
patent: 4794550 (1988-12-01), Greivenkamp, Jr.
patent: 5085502 (1992-02-01), Womack et al.
patent: 5202749 (1993-04-01), Pfister
patent: 5307152 (1994-04-01), Boehnlein
patent: 5309222 (1994-05-01), Kamei et al.
patent: 5311286 (1994-05-01), Pike
patent: 5345514 (1994-09-01), Mahdavieh et al.
patent: 5383025 (1995-01-01), Forrest
patent: 5581632 (1996-12-01), Koljonen et al.
patent: 5583632 (1996-12-01), Haga
patent: 5601364 (1997-02-01), Ume
patent: 5835223 (1998-11-01), Zwemer et al.
Ming Chang et al., "High Precision Deformation Measurement by Digital Phase Shifting Holographic Interferometry," Applied Optics, vol. 24., No. 22, pp. 3780-3783, Nov. 15, 1985.
John B. Brownwell et al., "Automated Fringe Analysis for Moire Interferometry," SPIE Code, 1554, pp. 162, 1990.
Yinyan Wang et al., "Measurement Thermal Deformation of BGA Using Phase-Shifting Shadow Moire," Society of Experimental Mechanics, Jun. 3, 1997.
John Sullivan, "Phase-Stepped Fractional Moire," Dec., 1991, Experimental Mechanics, pp. 373-381.
M. Chang et al., "Phase-Measuring Profilometry Using Sinusoidal Grating," Jun. 1993, Experimental Mechanics, pp. 117-122.
C.A. Sciammarella et al., "A Computer Based Method for Fringe Pattern Analysis," 1984.
Chiu-Ching Tsang et al., "Real Time Measurement of Printed Wiring Board Flatness in a Simulated Manufacturing Environment," Believed to be "known . . . by others" withing the meaning of 35 U.S.C. .sctn. 102 (a) before Dec. 30, 1996, Georgia Institute of Technology Publication.
Electronics Packaging Services Ltd. Co.
Pham Hoa Q.
LandOfFree
Measuring surface flatness using shadow moire technology and pha does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measuring surface flatness using shadow moire technology and pha, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measuring surface flatness using shadow moire technology and pha will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2063185