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Anybody build Dan Gelbart angled laser centre finder?
vtsteam:
--- Quote from: Baron on April 12, 2015, 01:06:30 PM ---
--- Quote from: vtsteam on April 12, 2015, 10:29:49 AM ---I'm just kind of curious -- at the distances we're talking about, small spot size, and using lenses, etc., why does it have to be a laser?
--- End quote ---
Unlike an ordinary light source a laser beam is a single essentially parallel beam of light. The light from an incandescent bulb is scattered in all directions.
--- End quote ---
Baron I appreciate that, but it no longer holds true once you add a filter (which scatters to some degree) and a lens (which converges light).
Also it's entirely possible to make a dot with conventional non-coherent light at a 12" focal length. Every kid knows this when he focuses a spot of sunlight with a magnifying glass on a leaf. Collimators, focusing lenses for ordinary lght -- these have been around forever. I can see the advantage of a laser's coherent beam (no lens or filter) for a long distance dot. But not for a short distance dot. At least not for this relatively crude purpose.
Also, if you want the dot smaller (or rounder) with an overly bright laser, can't you just use a pinhole?
Arbalist:
Have another look at the video in post #1. Dan moves the laser up and down to achieve the required pattern on the workpiece. This clearly wouldn't be very practical if you had to keep refocusing. The filter I used didn't appear to scatter the light at all, that's not to say it didn't but I couldn't see it. Others are already using a pinhole to reduce the dot size and make it more round.
PekkaNF:
Uuh...
Semiconductor laser beam from the chip is not round and even.
http://www.thorlabs.de/tutorials.cfm?tabID=38696
I'm using the laser module that has regulator, laser diode, optics and all that stuff to keep stuff simple and compact. I have no interest to mate regulator and laser diode (and for the same reason I don't want to use cheap laser pointer because they might have such a bad regulator that it fry laser if you change different size/type of batteries).
There probably would be a way of using normal HIPO LED, condencer and all that stuff, but it's not for me. Looks too involved and bulky, even though underlying principles are simple.
This laser approach has very complicated physics (and specially the laser diode regulator electronics) but it's all in a small and cheap commercial componenet.
All this talk about the lense is when laser pointer or a laser module that has no "adjustable focus" is chosen.
I have tested this unit with a prism and it seems to work also....it would bring some complication but it would also produce more compact unit as per original Dan design.
If I'll mange to get out of work early today, I'll gobble up something and borrow my daughters camera. My camera got dust on imaging sensor and it has been on shop two weeks allready.
Pekka
Fergus OMore:
--- Quote from: Arbalist on April 13, 2015, 01:49:23 AM ---Have another look at the video in post #1. Dan moves the laser up and down to achieve the required pattern on the workpiece. This clearly wouldn't be very practical if you had to keep refocusing. The filter I used didn't appear to scatter the light at all, that's not to say it didn't but I couldn't see it. Others are already using a pinhole to reduce the dot size and make it more round.
--- End quote ---
But this is 're-inventing the wheel' or worse. I recall Peter Rawlinson writing in Model Engineer- years ago- getting there.
Again, CentreCam was there. Part of it is still on the 'net. Trethewey WAS going to have another go- but for reasons unknown, hasn't.
I was going through the video again. There is something similar to what 'we were doing in production' in the early 1950's. We'd got to screw threads and spinning the threads- and they were not only sealing against liquids but air- and could vent. It was long before lasers! We used, if my memory is lasting out- a hacksaw, a file and an old M&W 0-1" Mike to test.
I'm simply left wondering.
Cheers
Norman
Arbalist:
It's just a centre finder Norman.
It's something most of us can make for a few pounds or dollars though rather than the $125+ that the commercial ones cost. If the commercial ones were a bit smaller and cost £20 I'd probably already be using one.
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