Super bright LEDs for lens disk scanner

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Super bright LEDs for lens disk scanner

Postby Steve_McVoy » Thu Jul 26, 2012 3:59 am

Some time ago I researched using a super bright LED in place of a crater lamp in my Western lens disk set:

http://www.earlytelevision.org/western_empire.html

I have a working crater lamp, but don't want to use it much because they are impossible to find.

At that time I discovered that bright LEDs had too large an aperture to produce the spot light source I need.

Does anyone have any ideas, or are there new LEDs now that I might use?
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Re: Super bright LEDs for lens disk scanner

Postby Harry Dalek » Thu Jul 26, 2012 10:59 am

Steve_McVoy wrote:Some time ago I researched using a super bright LED in place of a crater lamp in my Western lens disk set:

http://www.earlytelevision.org/western_empire.html

I have a working crater lamp, but don't want to use it much because they are impossible to find.

At that time I discovered that bright LEDs had too large an aperture to produce the spot light source I need.

Does anyone have any ideas, or are there new LEDs now that I might use?


Hi steve why don't you use a clear Luxeon ? the area of light will be small enough.
I recall Marcus was selling the lamps your after for 10 dollars on this forum
http://www.taswegian.com/NBTV/forum/vie ... php?t=1416
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby Steve_McVoy » Thu Jul 26, 2012 12:51 pm

I will contact him. I have a 40s crater lamp used for early fax transmission, but the aperture is about .04 inches, while I need about .01. If the Luxeons have a small enough aperture they would be perfect.
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Postby Steve_McVoy » Thu Jul 26, 2012 1:00 pm

I looked at Luxeons before. Their aperture is too large - I need something about .01 inch.
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Postby gary » Thu Jul 26, 2012 3:54 pm

Have you tried the old trick of grinding off the lens portion? (often used to create a point source).
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Postby Steve Anderson » Thu Jul 26, 2012 5:50 pm

Depending on the application and optics used a laser-diode may fit the bill but there's a limited range of colours, primarily (excuse the pun) red, green and (expensive) blue.

Harry has done quite a bit of work with these...

Steve A.

Having actually bothered looking at the link in the first posting I realize that a laser-diode is unsuitable. Oh well.
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Postby Steve_McVoy » Fri Jul 27, 2012 2:24 am

Yes, I tried grinding the lens off. Same problem - aperture is too big.

I notice on the Luxeon specs that the lens is about .1 inch across. I may try masking it to .01 and see if I get enough brightness.
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Postby Panrock » Fri Jul 27, 2012 3:39 am

Would, I wonder, a .1 inch luxeon followed up by a telescope eyepiece, placed beyond its focus and acting like a diminishing lens, be of any use here?

I would try for the widest possible angle-of-view eyepiece (to gather in the most of the luxeon's light. The shorter its focal length though, the closer it could sit to the luxeon (whilst remaining outside its own focal point). A wide angle, short focus 'Nagler' comes to mind...

I'm later going to have a related problem myself with obtaining a sufficiently hair-fine line of light for my mirror screw. Only in that case, an acrylic rod should do the job (I hope!).

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Postby Steve_McVoy » Fri Jul 27, 2012 10:05 am

The problem with putting a lens in front of the LED is that I need the light to be radiated about 20 degrees off center in each direction. The crater lamp sits a couple of inches behind the lenses in the disk, which are in a spiral a bit more than 1/2 inch high. The light from the crater lamp must illuminate all the lenses in the spiral.
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Postby Panrock » Fri Jul 27, 2012 3:52 pm

I've just had a play with a 9mm Celestron orthoscopic eyepiece that fell to hand, and a torch. Once the barrel is unscrewed and removed, such an eyepiece easily fits into this gap and a 40 deg field of view is achievable too. This comes at the price of the apparent position of the spot through the eyepiece changing very slightly when moving from one side to the other.

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Postby Steve_McVoy » Sat Jul 28, 2012 1:47 am

Interesting. I'll give it a try. Thanks, Steve.
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