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20 November 2012 Extended depth of field for visual measurement systems with depth-invariant magnification
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Conventional optical imaging systems are limited by a fundamental trade-off between the depth of field (DOF) and signal-to-noise ratio. Apart from a large DOF, a constant magnification within a certain depth range is particularly essential for visual measurement systems. In this paper, we present a novel visual measurement system with extended DOF and depth-invariant magnification. A varifocal liquid lens is employed to sweep its focus within a single exposure of the detector, after which a blurred image is captured. The blurred image is subsequently reconstructed to form a sharp extended DOF image by filtering with a single blur kernel. The experimental results demonstrate that our method can extend the DOF of a conventional visual measurement system by over 10 times, while the change in the magnification within the extended DOF remains less than 1%.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yanyu Zhao and Yufu Qu "Extended depth of field for visual measurement systems with depth-invariant magnification", Proc. SPIE 8563, Optical Metrology and Inspection for Industrial Applications II, 85630O (20 November 2012);

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