Re: DRO linear scales discussion

>
> What you do is take a piece of the scale and place it in a holder
> that allows you to tilt it a few degrees from parallel to the main
> scale. You put two LEDs on one side, and two photodiodes
> on the other side at some separation. When the tilt is adjusted,
> you will find a setting that causes bands of light and dark to sweep
> across the sensors such that when one sensor is at 50% brightness,
> the other is at either 0 or 100%. At that tilt, you have obtained
> a quadrature (90 degrees) phase shift.

I'm confused. You do not have to tilt the scale to get the signal
phase shift. You have to adjust the width between the LED/sensor pair
until you obtain the need shift. Then, lock it down. You could do
this with a fine pitch screw.
Or, as usual, am I missing something?