Re: RE: That encoder stuff.

Hi Elliot,

I haven't come across the term 'Talbot distance' before - is it a calculable
figure or only arrivable at by experiment? Presumably such a factor would
vary depending on the wavelength of the light source??

Ian
--
Ian W. Wright
Sheffield UK

> From: "Elliot Burke" <elliot@...>
>
>
> I'll give it a try.
> The light transmission through two contacted 50% duty gratings is a

triangle

> wave. Separate them and it approaches a sine wave, if you have a

non-point

> source (LED rather than laser). If spacing is increased to the Talbot
> distance, and you have a LED (extended) source, you'll get the triangle
> wave. Operating at half Talbot spacing gives close to sine wave.