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

Ken,

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

--- In CAD_CAM_EDM_DRO@y..., Ken Jenkins <kjenkins@m...> wrote:
> So I made these scales on film ... now what :-)
>
> The file I made and sent out to the imagesetter specs the lines
> at .0003937008" x 1" (i.e. close to 1/2540). Did they come out that
> size? Damned if I know, I don't have the optics (either instrumental
> or biological to tell). The lines are very opaque and from what I
can
> seem very uniform. Like I say, if this works I can generate these
> for almost nothing by running them in the waste part of production
> galleys I just need to test what I've got. I don't have the HEDS
unit
> to do it and don't want to buy one I can't use if I have to end
> up going with a disk because I can't get something linear that¹s
> high enough resolution.
>
> Ken Jenkins
> kjenkins@m...