| Summary: | 碩士 === 中華大學 === 電機工程學系(所) === 97 === Traditional optical fingerprint reader uses a right-angled prism and
an imaging lens. This thesis studies the optical design of an improved
fingerprint reader which uses a spherical lens on the output side of a
prism and a symmetrical aspheric lens as the imaging lens. An LED light
source normally illuminates the hypotenuse side of the prism and the
finger pressed on the bottom side of the prism. The results show the
distortion has been improved. We follow the design processes: (1)
calculating first-order optical structure parameters, (2) using ZEMAX
optical software to optimize the system, (3) using Monte Carlo method to
analyze tolerance and obtain yield rate. The systems with 60mm, 65mm,
and 70mm total lengths are designed. Considering spot size and taking
RMS diameter as a metric, we have 100% probability for the three
systems that their spot sizes are within detector pixel size. Considering
MTF, we have more than 98% probability for the 65mm and 70mm
systems that their MTFs meet design requirements. The probability for
the 60mm system that the MTF meets design requirements is only 80%.
The main factor influence yield rate is distortion. The yield rates are 44%,
76%, and 95% for The systems with 60mm, 65mm, and 70mm total
lengths, respectively.
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