ATM Adjustable focal length mirror?

[Jerry <jerryu@mindspring.com>]

If  you had a flat mirror made of the same material as the convex
security mirrors you see in stores (which have excellent optical
propeties) and you supported the edge and pulled the center down with a
screw adjustment what would you have?  These mirrors are very light
weight and are some what flexable since they are made of some type of
plastic materail.

The edge would not be attached but just supported.  You could also use
more than one
adjusting screw by attaching as many as you wanted to the back.  The
screws and edge
support would hold it in place.  You can get these mirrors with
reflecting surfaces on both sides which means that the reflecting
material has to be on the suface rather than behind the plastic
substrate for some of  them.  They are not cheap I found one priced for
$97.  I think the ad said polycarbonate.  And I think it was 16"  in
diameter.