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Electro-Optic Surface Profiler

IP.com Disclosure Number: IPCOM000046835D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Buechele, JW: AUTHOR [+2]

Abstract

An Electro-Optic Surface Profiler (EOSP) for multilayer ceramic (MLC) greensheet inspection is arranged to provide rapid, noncontact precision measurement of depth simultaneously with surface coordinate distances, including detecting contrasting detail or structure, its geographic location and extent. The depth displacement Z of the EOSP is derived by electro-optically sensing the focal shift. One electro-optical arrangement is shown in Fig. 1. A focused light beam (or illuminated aperture) is projected onto the object surface, as shown. A cylindrical lens L3 splits the image projected by L1 and L2 into two orthogonal "lines", F2' and (F2F3)', separated along the axis by the astigmatism introduced by L3.

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Electro-Optic Surface Profiler

An Electro-Optic Surface Profiler (EOSP) for multilayer ceramic (MLC) greensheet inspection is arranged to provide rapid, noncontact precision measurement of depth simultaneously with surface coordinate distances, including detecting contrasting detail or structure, its geographic location and extent. The depth displacement Z of the EOSP is derived by electro-optically sensing the focal shift. One electro-optical arrangement is shown in Fig. 1. A focused light beam (or illuminated aperture) is projected onto the object surface, as shown. A cylindrical lens L3 splits the image projected by L1 and L2 into two orthogonal "lines", F2' and (F2F3)', separated along the axis by the astigmatism introduced by L3. A quadrant detector is placed, as shown, between the focal lines such that each focal line bisects diametrically opposed detector quadrants. Axial displacement of the object surface shifts the focal lines proportionally and changes the outputs of the detector quadrants. The outputs of each pair of diametrically opposed detector quadrants are summed, and the difference in the sums is the measure of the object's surface displacement in the height dimension. Normalizing this difference by multiplying it with the reciprocal of the sum of the four quadrants renders the system immune to reflectivity differences across the object surface, such as occurs in rapid scanning of depressions (vias) or bumps (lines) in screened MLC greensheets. Although depth sensing remains unaffected by object contrast, the summed four detector signals indicate the differences in reflectivity as contrasting detail is scanned. The presence of marks, e.g., line structure, smudges imprinted (embedded) or indented into the surface, their position and extent in the X, Y, Z coordinates are sensed. Where excessive changes in reflectivity are present so t...