P3D Re: beamsplitter mirrors

[John Ohrt <johrt@xxxxxxx>]

P3D Mark J. Shields wrote:
> Or is there another
> beamsplitter that (1) has large enough front mirrors and (2) a thin,
> well-beveled joining of the inner mirrors, so as to avoid the
> problem of darkening at _both_ edges of each stereo image?
> 

My appologies for such a tardy reply, but my computer has been down for
weeks.

Actually, I think the term "image combiner" is a better term than
"beamsplitter", but That is an aside.

The design approach you are discussing is typical of a low cost
"beamsplitter".

A much better approach is to use a right-angled "prism" coated with a
good front surface mirror coating.  You must darken the centre "edge" of
the prism to avoid stray light.  In a pinch, a black ink "technical" pen
will do.  The outer mirrors are modestly oversized as is the prism so
that a field stop will clip all outer edges.

In the case of a simple camera system, the field stop is the light tight
seal at the film.

The entire assembly inner surfaces should be coated with flat black
paint etc. to suppress stray light.

Edmund Scientific should have all the mirrored prism if you are an
optics hacker.  Otherwise, you'll just have to look for a bargin!!!

Regards,
--
John Ohrt,
Toronto * Ontario * Canada


------------------------------