Re: [CAD_CAM_EDM_DRO] Optical DRO

Hi Arne,

Hilger and Watts were a manufacturer of high end optical equipment -
surveying stuff and the like.
I think what Jon might have been talking about was moire fringes - if you
draw a series of parallel lines on two sheets of transparent stuff (glass,
tracing paper etc) and tilt one of them a little with respect to the other
and then move the tilted one in the direction of the straight lines on the
other one, you will see a series of dark lines or bars moving at an angle to
the motion. These effectively form a vernier type of readout and could be
read with photocells. The degree of accuracy can be altered by changing the
spacing of the lines and the angle between the two sheets of material. Have
a play with it and you'll see how it works.

Ian

--
Ian W. Wright
Sheffield UK

----- Original Message -----
From: Arne Chr. Jorgensen <instel@...>
> Well, you proposed something, using some old Hilger&Watts gratings, - I
have
> no clue what these are. Further, I didn't understand what you meant by
> tilting them and how you would read them. You also mentioned glass
scales.
> Would you care to try explaining it again. ( I am a little thick headed
> sometimes :)