On Fri, 23 Mar 2012 01:31:39 -0000, "Arfa Daily"
wrote:

DVD lasers operate at visible red as you say, whilst CD lasers are near IR.
CD laser lenses often appear to be optically coated, but for what reason
exactly, I'm not sure.

Reflective coatings are usually to minimize reflections and/or to
improve signal to noise ratio by reducing the optical bandwidth.
http://rick_oleson.tripod.com/index-166.html

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