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Optical Engineering

Projection optics design for tilted projection of fringe patterns
Author(s): Yuan Shu; Ronald Chi-kit Chung; Zheng Tan; Jun Cheng; Edmund Yin-Mun Lam; Kenneth S. M. Fung; Fan Wang
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Paper Abstract

A challenge in the semiconductor industry is 3-D inspection of the miniaturized solder bumps grown on wafers for direct die-to-die bonding. An inspection mechanism proposed earlier requires the projection of a binary fringe grating to the inspected surface from an inclined angle. For high speed and accuracy of the mechanism, the projection optics has to meet these requirements: (1) it allows a tilt angle between the inspected surface and the projector's optical axis; (2) it has a high bandwidth to let high-spatial-frequency harmonics contained in the binary grating pass through the lens and be projected onto the inspected surface properly; (3) it has a high modulation transfer function; (4) it has a large field of view; and (5) it has an adequate depth of field that matches the depth range of the inspected surface. In this paper, we describe a projection optics design, consisting of a fringe grating and several pieces of spherical lens, that addresses the requirements. To reduce the lens aberrations, the grating is laid out with an angle chosen specifically to make the grating, the lens, and the average plane of the inspected surface intersect in the same line. Performance analysis and tolerance analysis are shown to demonstrate the feasibility of the design.

Paper Details

Date Published: 1 May 2008
PDF: 10 pages
Opt. Eng. 47(5) 053002 doi: 10.1117/1.2931457
Published in: Optical Engineering Volume 47, Issue 5
Show Author Affiliations
Yuan Shu, The Chinese Univ. of Hong Kong (Hong Kong China)
Ronald Chi-kit Chung, The Chinese Univ. of Hong Kong (Hong Kong China)
Zheng Tan, Xi'an Jiaotong Univ. (China)
Jun Cheng, The Chinese Univ. of Hong Kong (Hong Kong China)
Edmund Yin-Mun Lam, The Univ. of Hong Kong (Hong Kong China)
Kenneth S. M. Fung, ASM Assembly Automation Ltd. (Hong Kong China)
Fan Wang, ASM Assembly Automation Ltd. (Hong Kong China)

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