On Wed, 29 Apr 2015 08:56:55 -0700, wrote:

To all you optics type folks,
I am converting a camera to a full spectrum camera. This mainly
involves removing the IR blocking filter in the camera. This has been
done. But the CCD sensor needs to be kept approximately the same
distance away from the sensor in order for the autofocus to work. I
have two options. Since the filter is partly made from tinted glass
just removing the coating won't work. So another piece of glass the
same thickness could be put in the filter's place. The other option is
to make an aluminum spacer the same thickness as the filter. There is
a rubber gasket that sits on the filter and that the sensor actually
rests against. If I make a frame that is the same dimensions it would
not block any light. I will be using the camera mostly for IR, there
will be a filter at the front of the camera. Since IR light will focus
a little farther away from the lens than visible light should a spacer
be a little thicker than the filter? Or will it make practically no
difference? Since it looks like I might need to make something I might
as well as make it correctly.

Why not just swap out the no-IR glass for an IR-only glass they use
for IR cameras? Just a WAG.

--
"I believe there are more instances of the abridgment of the freedom
of the people by gradual and silent encroachments of those in power
than by violent and sudden usurpations."
--James Madison, Virginia Convention, June 16, 1788