Re: Make your own DRO scales ...ok ... I did

What about substituting a solid state laser in order to achieve
the collimation? These are very cheap now and surprisingly
powerful?


Ken J.

> You don't need a HEDS unit if you can do what you have done. All you
> have to do is make 2 fixed gratings with the same line pitch as the
> scale but one offset from the other by 1/4 line pitch. Place two
> narrow angle LEDs above and two phototransistors underneath. The
> fixed gratings will act as a shutter to the movable scale grating as
> long as the distance between them is very small or the LED light beam
> is collimated (narrow angle output). The phototransistor outputs will
> be in quadrature.
>
> Mariss