Tuesday, March 19, 2013

R7 baffle being laser cut

Check it out!  This is the baffle for the R7 StreetView camera.  The final apertures are being cut with a laser.  These apertures have to line up with the view cone of the cameras fairly tightly, in order to clip off a ghost reflection in the lens that I missed during optical design.  The ghost only hits the sensor when the sun is in a 5 degree wide band just outside the field of view.  I suspect it's a fairly complex internal reflection path, since a simple double bounce ghost ought to sweep through the center of the lens as the sun does.

I had the idea of welding the whole baffle together and then as a final operation cutting the apertures, with the hope that the metal would stop moving around once we'd cut smaller apertures and finished welding.  It didn't really work out perfectly.  There was a fair bit of tolerance stackup between the internal lenses and this external baffle.  Also, the baffle mounted to 8 screws, and those 8 points would tend to get significantly out of alignment, so that the baffle shape that you ended up with depended on what order you tightened the screws.  As a result we had to open up some extra margin on the baffle openings.  I know for a fact that the sun can leak into the corners.  After a quick check, I can't find any examples of the ghost, though, so the baffle is doing a decent job.

R7 at work:

R7 at play.  Hi Ryan!  Note the ears on top.  Those are the twin GPS antennae... the way I intended all R7s to be.