High Voltage Forum

Electromagnetic radiation => Light, Lasers and Optics => Topic started by: klugesmith on April 05, 2020, 08:20:08 AM

Title: Optical flatness inspection
Post by: klugesmith on April 05, 2020, 08:20:08 AM

While doing some spring cleaning I found an unfinished optical-flatness-testing project.  Can't even remember what I wanted to measure, but it got me to buy a couple of reference flat-faced glass disks on ebay. 

The monochromatic illuminator came from a flea market many years ago. Green filter was obvious, and for some reason I thought there might be a helium lamp inside.  Nope, plain old mercury.  The filter suppresses all lines except 546 nm, whose half-wavelength is 10.7 millionths of an inch, as stated on nameplate.

Here's the whole setup, with 4 inch reference flat and a scrap of plate glass.  The flat came in wooden box, lined with foam rubber that has seen better days.

Here are my big and little optical flats together.  With today's Internet, it's probably easy to find out why the fringes aren't always a set of equally spaced parallel lines.