What is it about?
Fabrication of non-spherical mirrors and lenses is done with machine tools that leave smallrepeating tooling marks on the surface that act like a diffraction grating. This work describes how these errors can effect image quality, and location of a lens in a lens system with these errors changes the image quality. Simple guidelines for specification of spatial frequency and amplitude errors are provided that relate to loss in image signal to noise.
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Why is it important?
Aspheric and freeform optical surfaces can provide much better imaging system performance than spherical optics. Modern fabrication methods are reducing the cost of these surface types, and they are becoming more wide-spread. Mid-spatial frequency errors on these surfaces are inherent to the manfacturing process, and over-specification by the optical designer can reduce yield and/or increase cost. This paper provides guidelines for managing these surface artifacts.
Perspectives
Most optical designers and system fabricators are wary of non-spherical surfaces because of fabrication cost, yield, and testing. This paper attempts to provide some guidance to both system designers and optical designers to specify the surface tolerance so that system performance is met without over-specification of non-spherical optical elements.
John Tamkin
Imaging Insights LLC
Read the Original
This page is a summary of: Effects of structured mid-spatial frequency surface errors on image performance, Applied Optics, November 2010, Optical Society of America (OSA),
DOI: 10.1364/ao.49.006522.
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