Quote: Hey..I have a question...some folks are setting their KE so it splits the light exiting the LED before it strikes the mirror. Does it make much difference if you split the light after it hits the mirror and is returning to the tester?
Say what? In a slitless tester the KE used for reading the mirror also cuts across the LED. That's how you produce the "virtual slit". Maybe this diagram will help explain it? (edit - I had the virtual slit upside down - now it's correct.)