| Summary: | 碩士 === 中華大學 === 電機工程學系碩士班 === 98 === As information technologies advance in recent years, personal security and data protection are important problem issue. The use of biological feature is a way to solve this problem. Common utilized biometric features are fingerprint, facial, iris, voiceprint, in which fingerprint identification is the most widely used method.
Traditional fingerprint reader comprises a prism and an imaging lens set, There is the projection distortion due to the total reflection from the prism. This paper consider an improved optical design, in which the image exit edge of the prism is an aspherical lens surface, and the imaging lens is also an apherical. The light from source perpendicularly incidents on the slant surface of the prism and then incidents on the finger on a bottom surface of the prism in 45 degrees, after twice total reflections, the distortion of the fingerprint image can be significantly reduced.
In this paper, the first step of the optical design process is to find the first order optical parameters, The second step, is to optimize the lens parameters by ZEMAX optical design software, The third step is to perform tolerance analysis for the optimized design by the use of Monte Carlo method built in ZEMAX. From the sampling examples of the Monte Carlo method, we have the aberration data. We use MATLAB to fit the aberration distribution function so that the aberration probability density function can be obtained. From the distribution function, we are able to analyze its characteristics and calculate accurate yield rate.
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