anyone know anything about optical comparators? - Page 2
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  1. #21
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    LED's still put out heat, but if I understand correctly it is not radiated heat.

    If I was to go LED, I would probably go for a green LED. Have ordered some lenses from Surplus Shed. Cannot really go wrong for $4.50 each.

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    My guess is that you face at least $200 - 300 of hassle getting the comparator repaired -- and still end up with a seldom used bench hog?? An alternative might be a used stereo microscope with a reticle in one eyepiece and some sort of x-y stage underneath if you need to actually measuring things. It will find more uses, take less space, be easy to add a digital camera to, etc. Just a thought -- for about the same money and time you might be happier with a stereo scope.

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    Quote Originally Posted by RC99 View Post
    not radiated heat.
    Wasn't aware there was any other kind "technically". Convection and conduction are just nature's equivalent of English traffic-circles.

    And if they radiate not, they illuminate, not. Every wavelength of light "downshifts" to heat, eventually.



    That said - having just now put the back o' me hand up close to one of the two LED desk lamps here, it sure ain't MUCH heat.


    Cannot really go wrong for $4.50 each.
    Used to think so. No space left in the house is what can "go wrong".

  4. #24
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    Quote Originally Posted by PeteM View Post
    My guess is that you face at least $200 - 300 of hassle getting the comparator repaired
    Nope, postage for the lenses run at $5 for halfway around the world. Then LED's are dirt cheap, a few dollars there. I already have 12V DC in to collimator to run the LED's. My biggest concern will be whether the square LED array, will mean a square light output.

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    Quote Originally Posted by RC99 View Post
    ...... My biggest concern will be whether the square LED array, will mean a square light output.
    No it won't as far as the output goes, but it is not a point source so will puck up what the lens system wants to see. It may well be a sort of square outside the lens but one only cares about what hits the receiving optics.
    A lot of the light output may end up shinning on the outside like your picture and never gets to the screen. Wasted light or worse yet reflects back onto the part and then into the lens thereby dulling the edges and acting a bit like a surface illum.

    Problem here is stops in the system and putting off axis light into the receiving lens.
    It certainly will light up the screen but good luck getting .0002 accurate images without a whole nother set of optics added on the input side.
    You have to make this array look like a filament to the rest of the system.
    Zemax is your friend if you want to get it right. Or you can do the ray tracing in CAD but this misses some things a optic designer worries about.

    That said....I've done worse to imaging optics and lived with the results and playing with it is fun.
    It does depend on the receiving end also and it's ability to be telecentric and reject rays not coming in straight. It is a "system" where everybody involved plays a part in putting that image on the screen. Good receivers screen out the bad rays but yours might expect good incoming.

    I have never run your machine's optics through the numbers or any analysis so I know jack shit about the real world here.
    THINK......and

    Mostly, what the heck, try it, see how you like it.
    What mag are we talking? 10-20x usage is different than 100X.
    Bob

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    Quote Originally Posted by RC99 View Post
    biggest concern will be whether the square LED array, will mean a square light output.
    Guess one could put a fat Lucite light-pipe or a whole bundle of skinny fibres to each LED and bring the whole array down to a concentrated "point", but this is starting to throw time and money into a hole in the spectrum.. or something hungry.

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    Monarchist
    Isfycs-cdtblwasowstboyoi.HyeccatcoMawtnEej?Yctpftttfvatou wsuqpwbbi.AymtcasPMgoetaawucc.IopafPMs.TVM.R

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    Sorry.
    Monarchist.
    I sometimes find your contributions semi-comprehensible due to being littered with abbreviations some of which seem to be of your own invention. Have you ever considered creating a table consisting of Monarchist abbreviations with the normal English equivalent juxtaposed? You could then paste from this table the full version and those of us who still use quill pens would become better informed. Alternatively you might like to create a special PM glossary of engineering terms and abbreviations which users could consult. Instead of performing a full PM search. TVM. Rich

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    lenses should be taken out and cleaned with extensive care to rinse off the cleaner so the ink does not get soft...a soft brush is much better that any rag wiping for the same reason....

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    Quote Originally Posted by ManicMetalBasher View Post
    Sorry.
    Monarchist.
    I sometimes find your contributions semi-comprehensible due to being littered with abbreviations some of which seem to be of your own invention. Have you ever considered creating a table consisting of Monarchist abbreviations with the normal English equivalent juxtaposed? You could then paste from this table the full version and those of us who still use quill pens would become better informed. Alternatively you might like to create a special PM glossary of engineering terms and abbreviations which users could consult. Instead of performing a full PM search. TVM. Rich
    L E D

    Light Emitting Diode

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    Our Jones and Lambson comparator has a Mercury Arc projector that's starting to fail. All the lenses and what-not are there though. I tried removing the bulb and putting a Big generic LED cluster in it's place (wired from elsewhere) and didn't get near the necessary illumination. I know you can get LED retrofits for these things but they are built to be bright and concentrated. Having a dark room is a plus. Ours is in the Inspection crib which is just a caged in area of the shop floor, so I'm going to make a hood for it out of plywood and some black-out curtains. I plan on just dropping the $1000 and getting a projection retrofit kit from J&L. That way it works they way it's supposed to and there's no guesswork.

    These things are remarkably simple, but also very sensitive.

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    Well I have some progression and learning about LEDS.

    You can get single die high brightness LEDS. Depends on how big your pocket is though.

    A company called Luminus makes these LEDS Luminus Devices: High Brightness White LEDs

    However prices for them are impressive. The Luminus SST-90 would be the one to use, but it is that old it is hard to find.

    CREE make a single die LED called the XHP35. Which might be suitable, but it low cost compared to the Luminus ones.

    Another company Lumileds have just released a single die LED the Luxeon V, but does not seem to be available anywhere yet. LUXEON V High Power CSP LED Emitter | Lumileds

    Here is an old thread where a person used s SST-90 to relight an old comparator

    http://www.chaski.org/homemachinist/...195140#p195140

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    Quote Originally Posted by M.B. Naegle View Post
    Our Jones and Lambson comparator has a Mercury Arc projector that's starting to fail. All the lenses and what-not are there though. I tried removing the bulb and putting a Big generic LED cluster in it's place (wired from elsewhere) and didn't get near the necessary illumination. I know you can get LED retrofits for these things but they are built to be bright and concentrated. Having a dark room is a plus. Ours is in the Inspection crib which is just a caged in area of the shop floor, so I'm going to make a hood for it out of plywood and some black-out curtains. I plan on just dropping the $1000 and getting a projection retrofit kit from J&L. That way it works they way it's supposed to and there's no guesswork.

    These things are remarkably simple, but also very sensitive.
    Not that I'd really recommend this but.. had a similar need ages ago. What I needed seemed unobtanium - at least "quickly".

    Thanks to GE Nela Park training, knew that a certain High density, commonly stocked, Metal Halide lamp had a powerful mercury vapor element at core, and in its own tough envelope.

    Carefully broke the outer envelope away, used the guts for the project.

    Doesn't suit this need. Similar sources that do may exist.

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    What lens mag are you running? What tolerance do you expect it to do?
    X-Y point to point on the stage or overlay work? These things matter a lot.
    The shown comparator is not in the same class with yours and yes I have owned one and seen many like yours.
    (Trust everyone but always cut the deck) Good luck or use by others may not be good luck for you.
    Bob

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    It only has a 10X and 20X mag lens fitted.

    My screen only has a faint cross hail. I do not even have the angle measuring capability, which I really would like.

    Generally all I go to measure point to point. Put point 1 on the cross hair. A dial indicator on the table. Move point two to the cross hair and measure the distance on the dial indicator.

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    This gives you lots of room to play with on the light source end.
    You want to check linear dims being right on both round and square parts. The light rays may "wrap around" the part making it measure smaller than it is.
    The other direction gives you not so nice edges when measuring a gage block but you are down in fairly easy to deal with mags and do not need a super bright source.

    You can print an angle/radius chart on your inkjet/laser on transparency film.
    Form stuff too but you may have to calibrate the X and Y and offset correct for "stretch/shrink" of one or both axis when printing.
    We do this all the time, know the constants to use in the CAD for each printer and place calib. marks on the sheet for double checking.
    Bob

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    Thanks Bob. I have decided to go with the SST-90 LED. It certainly is not the cheapest, but is the most powerful. I just need to find a suitable driver for it.

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    Quote Originally Posted by RC99 View Post
    I just need to find a suitable driver for it.
    Digi-Key and Mouser may have driver PCB's as well as the LED. Nuisance to find stuff, though. Too many SKU.

    Ebay sources have them too @ ten bucks US to forty bucks. Apparently they are being used in battery-powered hand torches, (flashlights for the Septics), as well.

    Might see if buying AS such a packaged torch is faster and easier to find, locally.

    Doesn't suit the comparator, still useful for jacklighting 'roos or not tripping on the way to the outhouse of a dark night.


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    While I wait on parts to arrive I am starting to see the issues with LED lights.

    Looking at the radiation charts they emit light not in a uniform manner. The high intensity bulbs commonly used emit their light in a sort of uniform spherical pattern.

    Thus with conventional bulbs used with lenses the same intensity light hits the outer area of the lens as hits the middle. With LED's more light radiation hits the middle then hits the outer edges, so you might end up with a really bright centre and dull outer edges.

    In saying that looks like some new optical comparators do use LED technology.

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    Quote Originally Posted by RC99 View Post
    While I wait on parts to arrive I am starting to see the issues with LED lights.

    Looking at the radiation charts they emit light not in a uniform manner. The high intensity bulbs commonly used emit their light in a sort of uniform spherical pattern.
    LEDs also have rather narrow spectral bands, even the 'white' and 'warm white' ones.

    They 'fake it' to seem otherwise, vs the genuinely seamless output of an incandescent. Lenses process those a bit differently.
    In saying that looks like some new optical comparators do use LED technology.
    Someone has had to work on that.

    No idea how 'portable' their methods, but "not very" suspected if they had to do it at all.


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