Re: [CAD_CAM_EDM_DRO] About Optical DRO
Posted by
Jon Elson
on 2000-03-20 22:20:42 UTC
"Arne Chr. Jorgensen" wrote:
by all?
Anyway, the graatings are parallel, but 'twisted' with respect to each
other. Does that
help? (With perfectly collimated light, the way Arne describes above
would work well, too,
but we want to avoid hairy optics in this, and just use LEDs as the
light source.)
have marks every .004", so
in quadrature, that would give .001". They are not too expensive, a
long time ago I got one
36" long for about $40. I'm sure, given a good grating out of an old
DRO's optical scale
I could make a fine encoder. But, I haven't run across much of this
sort of gear.
'interfered' with by vibration.
I know on my old Bridgeport optical scales, that they couldn't be read
during heavy cuts, the
screen was just a blur.
Jon
> Then Jon came along with his tilted gratings ! What a mess ! :)Arrgh! When will we have drawings easily inserted in documents, visible
>
> To both of you, - sure I have played with the same idea for years.
> By the way
> Jon, - it would be real nice it you posted a picture on your home
> page of your
> setup.
>
> Okay, here is what I messed up:
>
> I though Jon meant to tilt one of them like you should open a book
> !! I was
> playing Einstein ! I tried to imagine how it would be if I was siting
> on a
> photon, riding along with the beam of light. What on earth did Jon
> see ? I
> just could not understand why he would tilt it like that - but I have
> always
> learned that Jon use to have some real good reasons ! So then, - :)
>
by all?
Anyway, the graatings are parallel, but 'twisted' with respect to each
other. Does that
help? (With perfectly collimated light, the way Arne describes above
would work well, too,
but we want to avoid hairy optics in this, and just use LEDs as the
light source.)
>Bishop Graphics (are they still in business?) sells mylar scales that
> PS: Jon, I like the setup you explained. I didn't know that the
> gratings had
> so fine lines. I draw something on plastic sheets myself, by hand.
> I could
> measure down to such an unbelievable fractions of a mile :)
>
> Is there any made gratings, sheets, what ever you could buy cheap ? (
> I mean
> to experiment with )
have marks every .004", so
in quadrature, that would give .001". They are not too expensive, a
long time ago I got one
36" long for about $40. I'm sure, given a good grating out of an old
DRO's optical scale
I could make a fine encoder. But, I haven't run across much of this
sort of gear.
> By the way - I have also played with the idea of using a laser pointerYes, I think any sort of laser interferometer would be savagely
> on such
> an arangement - using a mirror on the moving axis, and directing it to
> a camera
> for analyzis - but vibrations would probably ruin it. - Well, back to
> bed.
'interfered' with by vibration.
I know on my old Bridgeport optical scales, that they couldn't be read
during heavy cuts, the
screen was just a blur.
Jon