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Measuring the Spectral Characteristics of a Light Therapy Lamp

48 points by jamesbowman 9y ago

Y_Y 9y ago
The conclusion about the UV diffuser isn't quite right. It clearly preferentially attenuates around 365nm for example. Good article and solid conclusion though.
- joshvm 9y ago
  Really the absorption measurement should have been taken using a broadband lamp (an old light bulb would do). Using a CFL, the signal to noise in the attenuation region is pretty poor to begin with. A lot of plastics (e.g. Polycarbonate) attenuate UV - you have to go out of your way to find windows that will pass it. For example: http://www.randombio.com/clear-lucite-spectra.png http://www.randombio.com/clear-lucite-spectra.png
- emeraldd 9y ago
  Big Clive had a reasonably comprehensive video on UV sources and some of the dangers https://www.youtube.com/watch?v=CpRMud6EFtE https://www.youtube.com/watch?v=CpRMud6EFtE
- SiempreViernes 9y ago
  Yes, and it's not clear it attenuates total transmitted power significantly on other wavelengths. Just putting in a diffuser you expect more light scattering out of the rays going towards (what I presume is a) optical fibre, but most of that power just goes somewhere else, it is not absorbed.
smartbit 9y ago
Can anyone tell how to measure the R1-R14 [0] values of a LED lamp? It seems like a sort of a Gretag-Macbeth [1] card is used. Can I use a photospectrometer [2]? I'd like to measure R9 [3] & R13 myself. [0] http://gc-lighting.com/led-education/lighting-guide/ http://gc-lighting.com/led-education/lighting-guide/ [1] https://en.wikipedia.org/wiki/ColorChecker https://en.wikipedia.org/wiki/ColorChecker [2] https://en.wikipedia.org/wiki/Spectrophotometry https://en.wikipedia.org/wiki/Spectrophotometry [3] http://leapfroglighting.com/why-the-led-r9-value-isnt-important/ http://leapfroglighting.com/why-the-led-r9-value-isnt-import...
- andreareina 9y ago
  There seems to be little overlap in the Munsell colors between the two[1][2]. There does appear to be a variant that uses some ColorChecker patches[3], or there's another calculation that just goes directly off of the light's emission spectrum[4], assuming your spectrometer has enough resolution. I think in practice, an ad-hoc comparison of the ColorChecker under daylight/D65 and the light in question will yield good enough results. [1] https://en.wikipedia.org/wiki/Color_rendering_index#Test_color_samples https://en.wikipedia.org/wiki/Color_rendering_index#Test_col... [2] https://en.wikipedia.org/wiki/ColorChecker#Colors https://en.wikipedia.org/wiki/ColorChecker#Colors [3] https://en.wikipedia.org/wiki/Color_rendering_index#New_test_color_samples https://en.wikipedia.org/wiki/Color_rendering_index#New_test... [4] https://en.wikipedia.org/wiki/Color_rendering_index#Example https://en.wikipedia.org/wiki/Color_rendering_index#Example
stedaniels 9y ago
I'd love to see the something from Lumie [0] analysed/reviewed like this in the UK. For instance the Lumie Vitamin L [1] is an LED version I'm interested in getting. I suffer for terrible migraine with aura [2] verging on chronic [3] that's started to beat my maximum dose of beta blockers, so I'll try anything! [0] https://www.lumie.com/ https://www.lumie.com/ [1] https://www.amazon.co.uk/Lumie-Vitamin-Lightbox-Effective-Therapy/dp/B073P2WNDS/ https://www.amazon.co.uk/Lumie-Vitamin-Lightbox-Effective-Th... [2] https://www.migrainetrust.org/about-migraine/types-of-migraine/migraine-with-aura/ https://www.migrainetrust.org/about-migraine/types-of-migrai... [3] https://www.migrainetrust.org/about-migraine/types-of-migraine/chronic-migraine/ https://www.migrainetrust.org/about-migraine/types-of-migrai...
- clauraform 9y ago
  I suffered frequently from terrible migraine until a chiropracter worked my spine. After that it was gone, except for one time months later. That was in my teenage years following a growth spurt and neuroactive narcotics abuse. The closest I got to feeling like that again was from too little sleep and work out, coupled with too much coffee and cigarettes. I'm still luzzled how likely blocked arteries figure into this. Still I get a numb hand from time to time.
giarc 9y ago
"bone-chilling,.... Vancouver winter" I guess temperature really is relative.
- LeifCarrotson 9y ago
  It makes me wonder if there are geographic/climactic components to seasonal affective disorder. In Vancouver, it's going to be in the "bone-chilling" upper 40s today, while a few degrees south near me it will be in the low 20s. A few degrees south means that even though we have colder weather, we'll have more hours of brighter sunlight. In England, further north than either of our locations, it will be in the low 50s (those temperature ranges are 8, -6, and 11 degrees Celsius, respectively). Would more people suffer from SAD in more northern locations because there's simply less sun, but they'll choose to live there because it's warm enough as a result of proximity to ocean currents? Or would fewer people suffer from SAD because they can spend more time outside where it's warmer?
  - TheCondor 9y ago
    There does seem to be some correlation. People in more southern places are less likely to have the condition.
pmlnr 9y ago
True(ish) sunlight lamps are freakin' expensive, no wonder 70$ is a scam.
nate_meurer 9y ago
Oddly, the article neglects to mention the whole rationale for boosting the blue light in these kinds of therapy lamps: blue light (wavelengths in the low to mid 400 nm range) has the greatest effect on circadian rhythm. Google "blue light circadian" for loads of data.

48 points by jamesbowman 9y ago

Y_Y 9y ago

The conclusion about the UV diffuser isn't quite right. It clearly preferentially attenuates around 365nm for example. Good article and solid conclusion though.

joshvm 9y ago
Really the absorption measurement should have been taken using a broadband lamp (an old light bulb would do). Using a CFL, the signal to noise in the attenuation region is pretty poor to begin with. A lot of plastics (e.g. Polycarbonate) attenuate UV - you have to go out of your way to find windows that will pass it. For example: http://www.randombio.com/clear-lucite-spectra.png http://www.randombio.com/clear-lucite-spectra.png
emeraldd 9y ago
Big Clive had a reasonably comprehensive video on UV sources and some of the dangers https://www.youtube.com/watch?v=CpRMud6EFtE https://www.youtube.com/watch?v=CpRMud6EFtE
SiempreViernes 9y ago
Yes, and it's not clear it attenuates total transmitted power significantly on other wavelengths. Just putting in a diffuser you expect more light scattering out of the rays going towards (what I presume is a) optical fibre, but most of that power just goes somewhere else, it is not absorbed.

smartbit 9y ago

Can anyone tell how to measure the R1-R14 [0] values of a LED lamp? It seems like a sort of a Gretag-Macbeth [1] card is used. Can I use a photospectrometer [2]? I'd like to measure R9 [3] & R13 myself. [0] http://gc-lighting.com/led-education/lighting-guide/ http://gc-lighting.com/led-education/lighting-guide/ [1] https://en.wikipedia.org/wiki/ColorChecker https://en.wikipedia.org/wiki/ColorChecker [2] https://en.wikipedia.org/wiki/Spectrophotometry https://en.wikipedia.org/wiki/Spectrophotometry [3] http://leapfroglighting.com/why-the-led-r9-value-isnt-important/ http://leapfroglighting.com/why-the-led-r9-value-isnt-import...

andreareina 9y ago
There seems to be little overlap in the Munsell colors between the two[1][2]. There does appear to be a variant that uses some ColorChecker patches[3], or there's another calculation that just goes directly off of the light's emission spectrum[4], assuming your spectrometer has enough resolution. I think in practice, an ad-hoc comparison of the ColorChecker under daylight/D65 and the light in question will yield good enough results. [1] https://en.wikipedia.org/wiki/Color_rendering_index#Test_color_samples https://en.wikipedia.org/wiki/Color_rendering_index#Test_col... [2] https://en.wikipedia.org/wiki/ColorChecker#Colors https://en.wikipedia.org/wiki/ColorChecker#Colors [3] https://en.wikipedia.org/wiki/Color_rendering_index#New_test_color_samples https://en.wikipedia.org/wiki/Color_rendering_index#New_test... [4] https://en.wikipedia.org/wiki/Color_rendering_index#Example https://en.wikipedia.org/wiki/Color_rendering_index#Example

stedaniels 9y ago

I'd love to see the something from Lumie [0] analysed/reviewed like this in the UK. For instance the Lumie Vitamin L [1] is an LED version I'm interested in getting. I suffer for terrible migraine with aura [2] verging on chronic [3] that's started to beat my maximum dose of beta blockers, so I'll try anything! [0] https://www.lumie.com/ https://www.lumie.com/ [1] https://www.amazon.co.uk/Lumie-Vitamin-Lightbox-Effective-Therapy/dp/B073P2WNDS/ https://www.amazon.co.uk/Lumie-Vitamin-Lightbox-Effective-Th... [2] https://www.migrainetrust.org/about-migraine/types-of-migraine/migraine-with-aura/ https://www.migrainetrust.org/about-migraine/types-of-migrai... [3] https://www.migrainetrust.org/about-migraine/types-of-migraine/chronic-migraine/ https://www.migrainetrust.org/about-migraine/types-of-migrai...

clauraform 9y ago
I suffered frequently from terrible migraine until a chiropracter worked my spine. After that it was gone, except for one time months later. That was in my teenage years following a growth spurt and neuroactive narcotics abuse. The closest I got to feeling like that again was from too little sleep and work out, coupled with too much coffee and cigarettes. I'm still luzzled how likely blocked arteries figure into this. Still I get a numb hand from time to time.

giarc 9y ago

"bone-chilling,.... Vancouver winter" I guess temperature really is relative.

LeifCarrotson 9y ago
It makes me wonder if there are geographic/climactic components to seasonal affective disorder. In Vancouver, it's going to be in the "bone-chilling" upper 40s today, while a few degrees south near me it will be in the low 20s. A few degrees south means that even though we have colder weather, we'll have more hours of brighter sunlight. In England, further north than either of our locations, it will be in the low 50s (those temperature ranges are 8, -6, and 11 degrees Celsius, respectively). Would more people suffer from SAD in more northern locations because there's simply less sun, but they'll choose to live there because it's warm enough as a result of proximity to ocean currents? Or would fewer people suffer from SAD because they can spend more time outside where it's warmer?
- TheCondor 9y ago
  There does seem to be some correlation. People in more southern places are less likely to have the condition.

pmlnr 9y ago

True(ish) sunlight lamps are freakin' expensive, no wonder 70$ is a scam.

nate_meurer 9y ago

Oddly, the article neglects to mention the whole rationale for boosting the blue light in these kinds of therapy lamps: blue light (wavelengths in the low to mid 400 nm range) has the greatest effect on circadian rhythm. Google "blue light circadian" for loads of data.