Jinx wrote:

> Talk of printing encoders reminded me of a project at the back of
> the cupboard.
>
> I got part-way through an optical ruler, which I wanted to have very
> fine resolution. Originally I tried a printed transparent scale but
> couldn't get the lines small or sharp enough.
>
> Is it possible that I could use a sliding Vernier scale with the fixed
> scale, and if so can anyone suggest how to achieve the best results
> with a micro ? I'm thinking of a ruler with a pointer at the '0' position
> and a pointer on the movable section, the distance between the two
> displayed on an LCD. Perhaps I'm re-inventing the wheel -- is there
> already a product around like this ?
>
> Now that laser diodes are so cheap do you think it feasible to measure
> short (500mm) distances on a ruler using light interference techniques,
> and again, if so, what detection method could be used for a micro ?
>
You can buy digital verniers over here pretty cheap these days, I've seen a
pair for as little as 35 UKP.

Mike