[Noisebridge-discuss] Spectral Response Curves

Adrian Chadd adrian.chadd at gmail.com
Mon Nov 11 20:51:33 UTC 2013

.. build your own with a lens, prism and a white wall? :-)


On 11 November 2013 12:47, StCredZero <stcredzero at gmail.com> wrote:
> Hello,
> Right now, I'm doing research for a specialized app to let consumers
> validate products that can be used to treat insomnia. Specifically, I'm
> working on a smartphone app that can act like a light detector for light in
> a narrow band around 470 nanometers. This is the frequency that has been
> shown to suppress melatonin secretion by the pineal gland.
> There are specialty products for avoiding late night 470 nanometer light
> exposure (light bulbs, screen overlays, glasses) but these are often very
> overpriced, and there is no convenient way to validate them. There are also
> "ordinary" products that serve the same purpose, but there is no good way
> for people to accurately test them. Currently, people can use a CD or DVD as
> an ad-hoc diffraction grating and look at the resulting spectrum, but even
> this isn't quite good enough. I've bought a narrow bandpass filter for 470nm
> light, and even products that have a spectrum that "looks good" (very little
> blue) can have hot-spots that leak large amounts of 470nm light, and it
> doesn't take much to suppress melatonin. (As low as 0.5 lux for prolonged
> exposures.)
> Looking generally at spectral response curves for digital cameras, it should
> be possible to "synthesize" a narrow band detector by taking the blue
> channel response and subtracting the red channel value.
> http://www.maxmax.com/images/Cameras/Technical/NikonD200_SpectralResponse.jpg
> This should effectively produce a "synthetic" instrument that has a spectral
> response curve that would be the camera's blue response, minus its red
> response. Even more helpful, the user should be able to view a synthesized
> narrowband image of the product, to be able to spot leaks and hot spots.
> What I need: I would like help in scientifically measuring the spectral
> response curve of the "synthetic instrument." I already have a (tiny) 470nm
> filter from Thorlabs, and I'm already aware of Public Lab's DIY
> spectroscope. I would like to use more accurate equipment, however. It is
> important that I can provide accurate information about the performance of
> the app and use rigorous procedures for measurement so that users know they
> can rely on the instrument.
> Does anyone have the expertise and access to equipment to help me out?
> --SCZ
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