Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
...
> Ok, So lets stick to conventional top side drilling. The problem I see 
> now is the lens system cannot be perpendicular to the plane of the PCB. 
> Did your lens experiment work ok when viewing the PCB at a angle ?
> What diameter was your lens ?
> How about just a large diameter lens without worrying about a screen ?
...

Two laser pointers with some kind of vibrating mirrors (or surplus
barcode scanners) aimed to make a crosshair on the board? With each
properlly aligned, board thickness won't matter as where the lines
cross will still be in the center. If you don't find a laser pointer
with a head that makes a single line, a mirror attached to a small
speaker, one end in the center, other end on the rim of the speaker
will turn a beam into a line. Surplus small front surface mirrors are
inexpensive. Last I checked, Goldmine Electric and Hosfelt had some.

Otherwise, a camera off of perpendicular means the center of the
screen is only the drill point of the board is the same thickness as
when it was calibrated and there is no curve to the board. This is not
a killer, though, as there are only a few different thicknesses of
boards and it can be "calibrated" for each thickness you use.

Steve Greenfield