Re: A sense of humor needs to be restored to these proceedings
Posted by
Jon Elson
on 1999-06-08 12:26:49 UTC
Elliot Burke wrote:
normal rated power, they will last a very long time. They are VASTLY
more collimated than LEDs.
one, a larger spot is less sensitive to a speck of dust or a small defect in the
scale grating.
whole image! There will be all sorts of periodic and some non-periodic
errors. These things are made to set type for newspapers, not make
measuring scales with .0001" accuracy!
People try to make printed circuit boards this way, and are horrified
when the two sides don't match up better than .020" or worse over
a 12" wide board.
Jon
> In spite of the request to forgo handwaving, that's where I'll begin:Visible red lasers are now available for about $9. By running them below
> The light source is the easiest part, but there are some subtlies: the
> light should be nearly collimated. The simplest way to achieve this is to
> use a LED with a narrow beam angle. The standard T1 3/4 lamps are 5 mm in
> diameter and have a beam a bit smaller than that. There are some larger
> diameters which could be handy.
normal rated power, they will last a very long time. They are VASTLY
more collimated than LEDs.
> Detectors are another issue. You can use 2 or 4 detectors. I prefer the 4From a purely electronic/mechanical viewpoint, yes, but from an operational
> detector approach, since the electronics then don't have to be as stable.
> There are some 4 detector packages, for example the UDT SPOT-4DMI and the
> FIL-S4DG, these have detector sizes of 0.5 mm square and 1.3 mm square,
> respectively.
> It is desirable to have the detectors cover as little area as possible, so
> that the system will be less sensitive to angular misalignment.
one, a larger spot is less sensitive to a speck of dust or a small defect in the
scale grating.
> The enterprising builder might remove the quadrant detector from a CDTotal GARBAGE! You will be lucky to get registration of .01" over the
> player. Personally I don't like fussing with surface mount packages.
>
> Now on to getting patterns printed on plastic. Forgive me if this is too
> elementary, but there may be some out there who don't know this trick. The
> trick is to use the Linotronic (type) film printer at a printing service.
whole image! There will be all sorts of periodic and some non-periodic
errors. These things are made to set type for newspapers, not make
measuring scales with .0001" accuracy!
People try to make printed circuit boards this way, and are horrified
when the two sides don't match up better than .020" or worse over
a 12" wide board.
> These print on mylar film very high contrast stable patterns. The machinesResolution is not accuracy!
> have resolutions from between 1200 and 3600 dpi.
> They are used by Mac zealots, and only understand file formats that arePlain PostScript.
> popular in the graphic arts world.
Jon