Several of us have been discussing the pinhole camera. We
disagreed on using the terms "image" and "focus" in conjuction with
pinhole optics. I claim a pinhole does not focus and thus there is no
image in the sense of an image formed by a system of lenses. My point is
that one should be able to treat the image formed by one optic system as
the object of another system, and that the formation of an image should
not depend of a viewing screen.
I suspect that this is one of those slippery points and I am being
a bit picky, but I looked at a few text and did not find an optical
image defined other than if an object is in plane x and an optical
sytem is at point y with optical characteristics q than the the image is
at z.
Advanced optics text refer to the mapping from the image space to
the object space and imply a one-to-one mapping. A pinhole camera is a
many-point-to-many-point mapping and is either some extreme limiting case
of the acceptable mapping or it just does not form an image.
The best term I have is "optical projection".
Similarly is a shadow an image? How about a diffraction pattern?