From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Wed, 2 Sep 2020 17:57:12 -0700
Subject: Re: [OT] Red monochromatic LED flashlights and/or light bulbs
Thread-Topic: [OT] Red monochromatic LED flashlights and/or light bulbs
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I let it through. Thanks for the contribution, Sean!
Friendly regards, Bob

________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of Sean B=
reheny=20
Sent: Wednesday, September 2, 2020 4:55 PM
To: Microcontroller discussion list - Public.
Subject: Re: [OT] Red monochromatic LED flashlights and/or light bulbs

I doubt it is really relevant to the topic at hand (the physiological
effects of light) since the cones of the eye are not capable of
distinguishing monochromatic light from somewhat broader spectrum sources
but LEDs are not very monochromatic. I was playing around with a simple
spectrometer a few months ago and I tested a bunch of sources. Among them
were a Cree red LED, a red laser diode, and some narrow optical bandpass
filters (which I illuminated with a halogen bulb). I have attached a small
image which I hope is not too big for the listserv. It shows the laser
diode on the left, the red LED in the middle, and a 10nm-wide green
bandpass filter on the right. The laser was more monochrome than the
resolution of my simple spectrometer and shows the approximate resolution
of the device (which was just a digital camera, two razor blades forming a
thin slit, a diffraction grating, and an opaque plastic box. I
post-processed the images using a python script to produce the graphs.

Sean


[image: led spectrum.jpg]

On Wed, Sep 2, 2020 at 5:41 PM madscientistatlarge  wrote:

> P.S. afaik all leds not designed to be white or R/G/B or bicolor are
> fairly monochromatic, if I recall about 20nm half power on the curve.  Mo=
st
> of the variation in center wavelength is thermal.
>
>
>

--=20
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