rpw3@fortune.UUCP (12/28/83)
#R:sri-arpa:-1488600:fortune:21500005:000:1215
fortune!rpw3 Dec 28 01:51:00 1983
Please clarify what you mean by "get close to the focal point of the
optical system". For any lens system I've used (both cameras and TVs),
the imaging surface (the film or the sensor) already IS at the focal point.
As I recall, the formula (for convex lenses) is:
1 1 1
--- = --- + ---
f obj img
where "f" is the focal length of the lens, "obj" the distance to the "object",
and "img" the distance to the (real) image. Solving for minimum "obj + img",
the closest you can get a focused image to the object (using a lens) is 4*f,
with the lens midway between the object and the image (1/f = 1/2f + 1/2f).
Not sure what a bundle of fibers would do for you, since without a lens each
fiber picks up all the light around it within a cone of its numerical
aperture (NA). Some imaging systems DO use fiber bundles directly in contact
with film, but that's generally going the other way (from a CRT to film).
I think Tektronix has a graphics output device like that. I suppose you
could use it if the object were self-luminous...
Rob Warnock
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