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Re: [Microscope] Re: LEDs

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  • J. Forster
    Compressing and expanding LASER beams? Sure. It s common in optics labs and is used in some products. You can buy high quality beam expanders on eBay for $100
    Message 1 of 36 , Mar 30, 2013
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      Compressing and expanding LASER beams? Sure. It's common in optics labs
      and is used in some products. You can buy high quality beam expanders on
      eBay for $100 +/-.

      -John

      ================


      > I see. I guess it does add to the complexity a bit. Is anyone doing this
      > now?
      >
      > --- In Microscope@yahoogroups.com, "J. Forster" <jfor@...> wrote:
      >>
      >> LASER beams can be expanded (or compressed) pretty much at will. It just
      >> takes two reasonable quality lenses, properly spaced.
      >>
      >> -John
      >>
      >> ==================
      >>
      >> > Interesting point about diffraction. My last message was garbled for
      >> some
      >> > reason; but what I tried to ask was whether a 1mm diameter laser light
      >> > source was useful in transmitted light microscopy. I can see how it
      >> might
      >> > be useful in EPI.
      >> >
      >> > --- In Microscope@yahoogroups.com, "Randall Buck" <rbuck@> wrote:
      >> >>
      >> >> All true,
      >> >> In addition to which you would be illuminating everything (i.e., the
      >> >> subject
      >> >> and all dust particles in the light path) with coherent light. That
      >> >> will
      >> >> guarantee an incomprehensible mesh of overlapping diffraction rings
      >> at
      >> >> the
      >> >> exit pupil.
      >> >>
      >> >> Randall
      >> >>
      >> >> -----Original Message-----
      >> >> From: Microscope@yahoogroups.com
      >> [mailto:Microscope@yahoogroups.com]On
      >> >> Behalf Of David Martindale
      >> >> Sent: Friday, March 29, 2013 6:55 AM
      >> >> To: Microscope@yahoogroups.com
      >> >> Subject: [Microscope] Re: LEDs
      >> >>
      >> >>
      >> >> That ebay auction sells only the necessary wavelength-selective
      >> mirrors.
      >> >> To
      >> >> actually build this, you need the red, green, and blue lasers, the
      >> >> optics
      >> >> necessary to collimate the beams parallel and the same diameter, some
      >> >> sort
      >> >> of positioning hardware to align the 3 beams in position and
      >> direction,
      >> >> a
      >> >> lens to focus the light onto the entrance of the fiber, and some way
      >> of
      >> >> mounting all of it rigidly enough that it will stay in alignment.
      >> This
      >> >> is
      >> >> not simple.
      >> >>
      >> >> Also, if any of the 3 lasers are capable of more than about 5 mW of
      >> >> output
      >> >> power, just working on the assembly is an eye hazard. Better read up
      >> on
      >> >> laser safety practices and buy the necessary protective eyewear.
      >> >>
      >> >> If you do build all this and get it working, you won't want to change
      >> >> distances between lasers and mirrors. It won't have much effect on
      >> >> colour
      >> >> anyway since the beams are nearly parallel, and it will mess up the
      >> >> alignment of the system. Instead, just use a small movable piece of
      >> >> metal
      >> >> near each laser to block a variable fraction of each beam.
      >> >>
      >> >> - Dave
      >> >>
      >> >> --- In Microscope@yahoogroups.com, "rich_guy_looker"
      >> <rich_guy_looker@>
      >> >> wrote:
      >> >> >
      >> >> > Alan, look at Ebay item no.
      >> >> > 251240936216, which uses 3 lasers
      >> >> > (red, green + blue) to produce
      >> >> > a white-beam.
      >> >> >
      >> >> > Then run the laser output
      >> >> > into a lens to focus it
      >> >> > into a single, solid-stand, 1 millimeter
      >> >> > diameter fiber-optic, with a collimator
      >> >> > at the other end of the fiber-optic,
      >> >> > wherein the collimator-output
      >> >> > feeds into the input
      >> >> > of your condenser.
      >> >> >
      >> >> > The really wonderful thing
      >> >> > about this is that you can adjust the lasers
      >> >> > for many different shades + hues of colors,
      >> >> > simply by varying the distance
      >> >> > of the different lasers to the
      >> >> > dichroic mirrors.
      >> >> >
      >> >> > NOTE: Make sure each of your 3 lasers
      >> >> > has built-in "APC," for
      >> >> > "automatic current control," and make
      >> >> > sure they're built for "continuous on"
      >> >> > operation.
      >> >> >
      >> >> > rich
      >> >> >
      >> >>
      >> >>
      >> >>
      >> >>
      >> >> ------------------------------------
      >> >>
      >> >> Yahoo! Groups Links
      >> >>
      >> >
      >> >
      >> >
      >>
      >
      >
      >
    • Bob Spez
      Chris, Thanks for the clarification. After doing some searching I realized I wasn t going to find an led replacement for the standard 6v15w projector bulb that
      Message 36 of 36 , Apr 1, 2013
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        Chris,

        Thanks for the clarification. After doing some searching I realized I
        wasn't going to find an led replacement for the standard 6v15w projector
        bulb that is used in the leitz stand.

        So far, the only led light I have used with my microscope is the 13 watt
        dimmable led bulb (800 lumens) in my swing arm desk lamp placed a few
        inches form the standard convex microscope mirror that fits under the
        condenser.

        This light is fine for brightfield, but doesn't generate enough light for
        darkfield using a 40x or 45x objective. So today I purchased a 26 watt led
        narrow beam (25 degrees) dimmable spotlight to fit into my desk lamp. This
        bulb is rated at 1500 lumens and has a warm white light with a color rating
        of 82CRI and 3000K light. The bulb cost a whopping $70, but If it works for
        darkfield and lives up to it's advertised 25,000 hour lifespan it may be
        the last microscope bulb I ever need to buy.

        My other two sources of light, which work equally well for darkfield are a
        fiber optic wand light source, powered by a 21v 150w halogen bulb with a
        built in reflector, and the standard 6v 15W incandescent microscope
        projector lamp bulb. Both put out about 200 lumens, both cost about $10
        each, but are only rated for 200 hours of life.

        Bob.


        On Sun, Mar 31, 2013 at 3:18 PM, Chris Albertson
        <albertson.chris@...>wrote:

        > **
        >
        >
        > I think "lumen" is the total amount of light from a bulb. If you add a
        > reflector then the reflected light is added to the light that comes
        > straight from the bulb. So your projector bulb is "brighter" even if it
        > has the same number of lumens. Basically the reflector adds "gain" and
        > has a multiplier effect. This effect can be really large as in car
        > headlights.
        >
        > There are three ways to measure brightness and they all have similar names.
        > (1) the total energy from a light bulb, (2) the amount of light per solid
        > area in a given direction and (2) light per square meter that hits a
        > surface. Confusion happens the names of the units are so similar.
        >
        > Yes, there are LED projector bulbs. Some video projects use LEDs, so look
        > into replacement parts for those projectors
        >
        > I'm still not likley the spectra of LEDs. Try this: In a dark room
        > reflect the LED off a refraction grating (a DVD disc makes a decent
        > grating) and yu can see the "rainbow" image of the LED on the wall. Many
        > of the LEDs I have make bands, not rainbows. Then I confirm by using
        > halogen bult and see the expected broad spectra.
        >
        > A poor-man's spectroscope is not hard to make. use a DVD for a grating and
        > make a 4mm slit and place an SLR camera in back of the slit and watch the
        > camera's light meter as you move the DVD. The LEDs I've seen are so
        > "spiky" you can see it even in this high school level science experiment.
        > Using something this simple you can see the difference between lamps with
        > decent and with poor CRI. But it is not good enough to distinguish more
        > than just good from poor.
        >
        > With LEDs it is a trade off, the most light per watt comes from the
        > tri-color LEDs. From a flat sprectra they need phosphors inside the LED
        > and a filter to attenuate the peaks. This kills the light per watt
        > number. So they compromise and the best or those small surface mount parts
        > that look yellow.
        >
        > On Sun, Mar 31, 2013 at 11:26 AM, Bob Spez <bobspez@...> wrote:
        >
        > > **
        >
        > >
        > >
        > > I've been following this post with some interest but have more questions
        > > than answers. The whole subject of specs on lumens is a tricky one. Specs
        > > on different websites vary widely. The three types of lighting I use with
        > > my Leitz Laborlux black enamel bino scope is the original 6V15W
        > > incandescent projector bulb in the base of the Leitz stand. The second
        > type
        > > of lighting is a 13 Watt LED bulb in a swing arm desk lamp, pointed at a
        > > convex microscope mirror under the condenser. The third type is a fiber
        > > optic wand powered by a 50 watt halogen bulb. I have placed the wand tip
        > > in the same spot as the incandescent projection bulb, under the stand, or
        > > directly under the condenser, with very similar results.
        > > While all three lighting methods give similar results in Brightfield, but
        > > only the incandescent light and the 50 watt halogen fiber optic light
        > > achieve a usable darkfield, and they give similar results in lighting
        > > (though not in color).
        > > Because the 6V15W incandescent bulb is a projection type bulb, it
        > achieves
        > > much more brilliance than the lumens would predict.
        > > It seems like the type of bulb is more important than the lumens it is
        > > rated at. I wonder if they make an LED projection bulb?
        > >
        > > Bob
        > >
        > > [Non-text portions of this message have been removed]
        > >
        > >
        > >
        >
        > --
        >
        > Chris Albertson
        > Redondo Beach, California
        >
        > [Non-text portions of this message have been removed]
        >
        >
        >


        [Non-text portions of this message have been removed]
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