light meter

[MKLEPPER]

New to forum, I am looking for advice on a proper light meter. I am inventing a medical device that uses light 400-470 nm by LED and fiber optic. I need a meter that will give me light power data regarding how much light energy a given set up generates at various distances and locations from the source. The light output for these systems ranges from 50 millicandela to more that 10,000 millicandela. I have no idea what the fibers put out. So it needs to have a low light power sensitivity. While I am at it (day job is physician so there you go) I want to drive the fibers with a luxeon star. How do I best focus and collimate (learned that word today) the light into the fiber or bundle? thanks. Oh I just got a bunch of MKO LED die from Bridgelux. Conceptually I want to affix wires with conductive epoxy and make a series of 2 or 3 in a string separated by 1cm each. What am I in for? I bought a microscope. Thanks MK

 

[Bullzeyebill]

New to forum, I am looking for advice on a proper light meter. I am inventing a medical device that uses light 400-470 nm by LED and fiber optic. I need a meter that will give me light power data regarding how much light energy a given set up generates at various distances and locations from the source. The light output for these systems ranges from 50 millicandela to more that 10,000 millicandela. I have no idea what the fibers put out. So it needs to have a low light power sensitivity. While I am at it (day job is physician so there you go) I want to drive the fibers with a luxeon star. How do I best focus and collimate (learned that word today) the light into the fiber or bundle? thanks. Oh I just got a bunch of MKO LED die from Bridgelux. Conceptually I want to affix wires with conductive epoxy and make a series of 2 or 3 in a string separated by 1cm each. What am I in for? I bought a microscope. Thanks MK

Welcome to CPF. Google is your friend if you can narrow the search down when looking for a light meter. Those of us that use light meters on CPF often use the Meterman LM631, a sort of general purpose light meter that reads in fc and lux. It may not be sensative or accurate enough for your uses. Google light meters and see what you come up with.

Bill

 

[precisionworks]

General purpose light meters have a spectral response which covers the CIE Photopic Curve (black line in graph, green line is the Scotopic luminosity):

Because you want to measure only in the 400-470 nm range (purple to blue as seen by the human eye) you'll need a filter that does not pass any wavelength above 470 nm ... and does not pass anything below 400 nm. These are called Bandpass Filters, and any number of companies will make one (or one million) for you. You need a bandpass width of only 70 nm, which is well within the range available (most can cover up to 150 nm).

Here's one place to get a quote, but there are many others:

http://www.newport.com/webrequest/d...o=Bandpass-Filters&lang=1033&type=6&page=main

Once the bandpass filter is in place, a lightmeter will "see" only the 400-470 nm output of the LEDs. I believe a meter like the Extech 403125 would work:

http://www.extech.com/instruments/resources/datasheets/403125.pdf

A call to Extech would confirm suitability. They may be able to suggest a meter with greater sensitivity in that part of the spectrum.

 

[MKLEPPER]

thanks Any experience with how to "funnel" light into a fiber. Sounds like a collimator but most I see and on tip of fiber to focus beam. Wonder about simply reversing the proper wavelength device and projecting LED beam into "other end" of collimator and focusing light at the fiber tip?

 

[gadget_lover]

I saw a post where they talked of using a pair of optics (nx05) head to head to focus the light from an LED onto a fiber.

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fiber optic-optic led

Dan