The primary reason for using aspheric components is to eliminate spherical aberration (especially when there is a constraint on the number of optical surfaces and indices allowed). However, most designers still prefer to use spherical rather than aspherical surfaces. The reason has more to do with fabrication issues than anything else. Aspherics are much harder to make and measure. More time and skill are required of the optician and metrologist, thereby driving up costs. Consequently, the use of aspherics is limited to cases where (a) there is no other way, or (b) a trade-off study has shown it to be cost effective in the long run. Finally, it should be noted that the use of an aspheric does not change any of the first order design characteristics (cardinal points). All paraxial data remains the same.
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发表于 2006-8-25 03:48:00
