|
I believe that most of us are familiar with the
A-B-C method for making optical flats, but you can extend that method a bit to
make fairly accurate 90 degree corners on prisms.
Start with three prisms that have one of the two 90
degree faces ground flat. Use a sharpie pen to mark these faces A,
B, and C.
Clamp face A against face B, and grind the two
remaining faces an a flat lap.
Then clamp face B against face C and grind the two
remaining faces on a flat lap.
Then clamp face C against face A and grind the two
remaining feces on a flat lap.
Repeat this cycle several times, and you end up
with a pretty darn good 90 degree corner. I hardly see any light
through a diemaker's square. (OK, OK, just a little bit of
light...)
I have not seen this documented anywhere, but there
it is one of those processes like mirror grinding where the process itself
creates the accuracy. That means you can do it on a desert island or
after the final near-extinction of humanity, mutation, apocalypse, and collapse
of civilization in you Idaho bomb shelter. The prisms may be needed for
periscopes or gun sights to defend against, hunt down, and destroy the mutant
ninjas.
. . . Richard
|