winsor wrote:
>>
Not sure what you are saying here. Focal length, field of view and
intended use all affect your stated cost elements. I think you left out
the cost of the materials themselves unless you lumped that into
something else. ED glass is much pricier than other glass. Optical
glass is pricier than optical plastic.
<<
Plastic lenses are harder to coat than those made of glass so by the time
they are coated the cost may not be that different. Also they are difficult
to make in large sizes because of shrinkage, so are usually made as hybrids
with glass which again raises price, although if aspherical it can cut
number of elements thereby potentially cutting cost. Another problem is that
plastic lenses are not available with a wide range of dispersion, so it is
tough to make achromats etc. (there is no ED plastic!)
The latest "Photonics Spectra" magazine (a technical electro-optics trade
publication)has a very pro plastic lens article by a vendor of plastic
lenses, but all the examples given and pictures are for smart bombs etc.,
where ruggedness and weight are very important.
There is a very old paper by Kodak in the SPIE proceedings (more than 10yrs
ago)discussing the issue of cost of manufacturing digital cameras using
smaller size sensors, in which they say, that the lenses are cheaper to make
intitally as you reduce sensor (& hence lens) size but eventually tighter
and tighter mechanical manufacturing tolerances actually raise lens cost.
Evidently centering alignment becomes a major issue.
Regards,
Tim Hughes
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