On Saturday 03 May 2014 12:39:35 Jon Elson did opine: > On 05/03/2014 06:23 AM, andy pugh wrote: > > On 3 May 2014 03:56, Jon Elson <[email protected]> wrote: > >> Hmm, well, a 4 second lag is pretty bad, if you are using it to > >> center parts under the spindle. What resolution is that > >> camera? It seems the lower res ones may have faster > >> update. > > > > I bought this one: > > http://www.ebay.co.uk/itm/270975087407 > > (They have since got even cheaper, and the quality seems to have > > improved, this one might even have a brass shell option: > > http://www.ebay.com/itm/360803447528 ) > > > > There is no lag at all. > > Here is a sample picture (of the mm scale of my micrometer) > > http://imagebin.ca/v/1L8Lftd4YXkq > > Well, that's the problem, this thing is NOT a microscope, it > has a field of view of over 20 MM! That is huge. I want a > field > of view of a couple mm, max. I can do this with those > little PC board video cameras by screwing the lens out > from the chip, but it has the disadvantage of having to > add a video monitor to the system. I use one for > alignment of the centering jaws on my pick and place > machine. > > So, I'm going to look for a unit that is specifically sold > as a microscope, even if they cost more. > > Jon
I think you can make arguments both ways Jon. You are looking for accuracy that exceeds the machines accuracy in most cases, and the depth of field of those ranges downward from 2mm or worse depending of the F-stop of the lens. I think what one wants isn't the microscope, but something with effectively a long telephoto, so you can get far enough away from the work to see what you are doing visually too, not to mention having the camera far enough away that you can just leave it there full time like I do. Compared to the chip size, the equivalent of a 250mm or even longer lens on a 35mm camera, but scaled down to the usual 7mm colonoscopy sized camera. I would say that is about what I have with the $22 version I have. And its in decent focus from about 20mm to 45mm from the work, and once adjusted, zero parallax as I move Z up & down, which seems to be the most important as you can then look at and locate a work piece of any thickness clamped to the table by running the spindle(z) up and down to suit. Its a good idea to remove the tool as you may run it into the work while doing the locating though. Everyday usability ratings carry the highest priority IOW. A microscope, with a 6mm focal length F2.8 lens, and a .1mm depth of focus just won't cut it IMO. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available. Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
