11 Nov
2013
11 Nov
'13
2:47 p.m.
(Also posted to Noisebridge. Skip if you are experiencing deja-vu.)
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.j…
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
--
There's neither heaven nor hell,
save what we grant ourselves.
There's neither fairness nor justice,
save what we grant each other.
12 Nov
12 Nov
12:42 a.m.
You might want to repeat the question on the Counter Culture Labs mailing
list:
https://counterculturelabs.org/
On Mon, Nov 11, 2013 at 2:47 PM, Peter Kwangjun Suk <
peter.kwangjun.suk(a)gmail.com> wrote:
(Also posted to Noisebridge. Skip if you are
experiencing deja-vu.)
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.j…
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
--
There's neither heaven nor hell,
save what we grant ourselves.
There's neither fairness nor justice,
save what we grant each other.
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
9:59 a.m.
I will check with folks at the East Bay Astronomical Society up at Chabot
Space & Science Center. There is some amount of spectroscopy equipment
around up there. Though much of it is very old, and intended for
astronomical observations (attached to a telescope), something might be
useful, and there might be someone who is interested in helping out.
-steve
On Tue, Nov 12, 2013 at 12:42 AM, Marc Juul <juul(a)labitat.dk> wrote:
You might want to repeat the question on the Counter
Culture Labs mailing
list:
https://counterculturelabs.org/
On Mon, Nov 11, 2013 at 2:47 PM, Peter Kwangjun Suk <
peter.kwangjun.suk(a)gmail.com> wrote:
--
-steve
(Also posted to Noisebridge. Skip if you are
experiencing deja-vu.)
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.j…
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
--
There's neither heaven nor hell,
save what we grant ourselves.
There's neither fairness nor justice,
save what we grant each other.
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
10:05 a.m.
Another thought. How about one of those monitor calibration devices like
the Datacolor Spider. I've got one you could borrow. Here's an article
about how to use it with Linux.
http://www.gdargaud.net/Hack/LinuxSpyder.html
They use software called dispcal http://dispcalgui.hoech.net/
I'd guess that if you dig into the source for that you can find code to
control and read color data from the Spyder.
-steve
On Tue, Nov 12, 2013 at 9:59 AM, Steve Berl <steveberl(a)gmail.com> wrote:
I will check with folks at the East Bay Astronomical
Society up at Chabot
Space & Science Center. There is some amount of spectroscopy equipment
around up there. Though much of it is very old, and intended for
astronomical observations (attached to a telescope), something might be
useful, and there might be someone who is interested in helping out.
-steve
On Tue, Nov 12, 2013 at 12:42 AM, Marc Juul <juul(a)labitat.dk> wrote:
--
-steve
You might want to repeat the question on the
Counter Culture Labs mailing
list:
https://counterculturelabs.org/
On Mon, Nov 11, 2013 at 2:47 PM, Peter Kwangjun Suk <
peter.kwangjun.suk(a)gmail.com> wrote:
--
-steve
(Also posted to Noisebridge. Skip if you are
experiencing deja-vu.)
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.j…
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
--
There's neither heaven nor hell,
save what we grant ourselves.
There's neither fairness nor justice,
save what we grant each other.
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
10:35 a.m.
On Tue, Nov 12, 2013 at 10:05 AM, Steve Berl <steveberl(a)gmail.com> wrote:
Another thought. How about one of those monitor
calibration devices like
the Datacolor Spider. I've got one you could borrow. Here's an article
about how to use it with Linux.
http://www.gdargaud.net/Hack/LinuxSpyder.html
They use software called dispcal http://dispcalgui.hoech.net/
I'd guess that if you dig into the source for that you can find code to
control and read color data from the Spyder.
Nifty thought, but the kind of measurement we need can't be done with RGB
light producing devices or RGB light sensing devices. In fact, the
knee-jerk-didnt-think-it-through criticism that will be raised will use the
inherent limitations of RGB devices to try and discredit this instrument.
This is why true monochromatic sources, diffraction gratings, and
non-synthetic true pan-chromatic sensors are needed.
(It will work, because we are exploiting bandpass filters built into the
camera, so the criticisms aren't valid. But true monochromatic sources and
pan-chromatic sensors will be needed to validate and measure the true
response.)
11:50 a.m.
On Tue, Nov 12, 2013 at 11:06 AM, Hol Gaskill <hol(a)gaskill.com> wrote:
What's the badwidth you're interested in?
Call me Kenneth, then ask me the frequency. A band around 470nm is what we
need to detect.
Shooting from the hip, I'd recommend a
photodiode
http://media.digikey.com/pdf/Data%20Sheets/Opto%20Diode/ODD-470W.pdf if
you just need a coarse signal that detects the band centered on 470nm.
Also, you could use an analog to digital converter or even just a properly
dialed-in comparator to cut out the heads and tails of the spectrum.
Not bad for a shot from the hip, but if you read the background, you might
find it doesn't quite fit the distribution model. Making this out of a
photodiode and other hardware will make this far less accessible and
convenient than a smartphone app. The more accessible and convenient such
measurement is, the more such data will be mentioned in reviews. The more
such data is mentioned in reviews, the more careful marketers and
manufacturers will be with measuring their products. (Also, non-maker
insomniacs deserve good sleep too.)
12:10 p.m.
I'm not sure why people are so obsessed by 470nm specifically. If you look
back at the original literature, you'll see that the response is quite
broad, and is actually a fairly good match for the overall blue channel
response you posted earlier.
Compare:
http://www.jneurosci.org/content/21/16/6405/F5.expansion.html
http://www.maxmax.com/images/Cameras/Technical/NikonD200_SpectralResponse.j…
So yeah, for marketing purposes, it's probably more effective if you can
tap into the hype around 470nm. But if you really want an app that's
effective against insomnia, you might as well measure the blue channel all
by itself...
Patrik
PS: Also, simply subtracting the red channel from the blue gives you such
an incredibly crude measure of the light incoming at any one particular
frequency, that using highly precise measurement equipment to validate the
result is rather nonsensical. The DIY spectroscope Public Lab really gives
you more than enough precision for what you need (although perhaps not
enough for what your customers *want*, but what do they know...)
On Tue, Nov 12, 2013 at 11:50 AM, StCredZero <stcredzero(a)gmail.com> wrote:
On Tue, Nov 12, 2013 at 11:06 AM, Hol Gaskill <hol(a)gaskill.com> wrote:
What's the badwidth you're interested
in?
Call me Kenneth, then ask me the frequency. A band around 470nm is what we
need to detect.
Shooting from the hip, I'd recommend a
photodiode
http://media.digikey.com/pdf/Data%20Sheets/Opto%20Diode/ODD-470W.pdf if
you just need a coarse signal that detects the band centered on 470nm.
Also, you could use an analog to digital converter or even just a properly
dialed-in comparator to cut out the heads and tails of the spectrum.
Not bad for a shot from the hip, but if you read the background, you might
find it doesn't quite fit the distribution model. Making this out of a
photodiode and other hardware will make this far less accessible and
convenient than a smartphone app. The more accessible and convenient such
measurement is, the more such data will be mentioned in reviews. The more
such data is mentioned in reviews, the more careful marketers and
manufacturers will be with measuring their products. (Also, non-maker
insomniacs deserve good sleep too.)
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
12:35 p.m.
On Tue, Nov 12, 2013 at 12:10 PM, Patrik D'haeseleer <patrikd(a)gmail.com>wrote;wrote:
I'm not sure why people are so obsessed by 470nm
specifically. If you look
back at the original literature, you'll see that the response is quite
broad, and is actually a fairly good match for the overall blue channel
response you posted earlier.
I have had this in mind while designing this app. If I thought I needed
real precision, I wouldn't have tried at all, because I have some idea of
the limits of the setup. However, 470nm is supposed to be the frequency
that people react most strongly to, and people who have read popular
interest articles on the subject will be familiar with this.
Compare:
http://www.jneurosci.org/content/21/16/6405/F5.expansion.html
http://www.maxmax.com/images/Cameras/Technical/NikonD200_SpectralResponse.j…
Unfortunately, the Nikon D200 is not the target platform. It's the iPhone 4
and newer models and I'm having a hard time finding spectral response data
on the newer models. (AFAIK, they are variants of the IMX145, and I don't
know if the IMX145 datasheet would apply.) Looking at the spectral response
of other hardware is good enough to validate this *might* work. However, I
really should validate the resulting instrument by accurately measuring
what its response actually is. "Yeah, it's probably good enough" is ok for
my personal use, but it's really a different story if I'm going to
distribute it.
So yeah, for marketing purposes, it's probably
more effective if you can
tap into the hype around 470nm. But if you really want an app that's
effective against insomnia, you might as well measure the blue channel all
by itself...
As I said before, if I thought I really needed much more accuracy than
that, then I would not have proceeded with this. Even so, I really need to
be able to tell people precisely what they are getting. What if the peak
turned out to be more like 450nm and dropped off unexpectedly quickly? A
user would want to know. If I know exactly what the curve is and can
provide that information, knowledgeable people like you can make an
informed decision about how well this works.
PS: Also, simply subtracting the red channel from the
blue gives you such
an incredibly crude measure of the light incoming at any one particular
frequency,
The intent has always been to create a relatively crude instrument.
that using highly precise measurement equipment to
validate the result is
rather nonsensical.
Uh, no. Home audio equipment is comparatively crude, and most consumers
know this, but equipment of decent precision is still used to measure its
performance. This isn't nonsensical. It's providing good information to
users. Really, they have enough uncertainty to deal with when making
decisions and unlike yourself, they don't necessarily have a lot of
experience gauging how inaccuracies can stack in a system. The more of that
kind of judgement you can remove from their process, the easier it is for
them.
The DIY spectroscope Public Lab really gives you more
than enough
precision for what you need (although perhaps not enough for what your
customers *want*, but what do they know...)
It's what they can *know* not what they can make an educated guess at in a
field they know relatively little about. I don't think, you're really
putting yourself in the shoes of the target demographic.
1:49 p.m.
On Tue, Nov 12, 2013 at 12:10 PM, Patrik D'haeseleer <patrikd(a)gmail.com>wrote;wrote:
using highly precise measurement equipment to validate
the result is
rather nonsensical.
Also, being able to accurately measure spectral response would also allow
one to accurately characterize something like a particular piece of blue
cellophane or an inexpensive set of blue goggles as a suitable light
filter, both of which (combined with the Mk-I eyeball) would be more
accessible and convenient for a wider pool of users. This in in contrast to
just hazily telling people, "well, you could *probably* use a piece of blue
cellophane and it would probably be good enough to crudely tell you..."
11:52 a.m.
On Tue, Nov 12, 2013 at 11:06 AM, Hol Gaskill <hol(a)gaskill.com> wrote:
What's the badwidth you're interested in?
Shooting from the hip, I'd
recommend a photodiode
http://media.digikey.com/pdf/Data%20Sheets/Opto%20Diode/ODD-470W.pdf if
you just need a coarse signal that detects the band centered on 470nm.
Also, you could use an analog to digital converter or even just a properly
dialed-in comparator to cut out the heads and tails of the spectrum.
This could be a viable device for people who don't have a smartphone,
however.
12:26 p.m.
i was asking about bandwidth, not center frequency.
good luck on your app, kenneth.
Nov 12, 2013 11:50:29 AM, stcredzero(a)gmail.com wrote:
On Tue, Nov 12, 2013 at 11:06 AM, Hol Gaskill
hol(a)gaskill.com> wrote:
What's the badwidth you're interested in?
Call me Kenneth, then ask me the frequency. A band
around 470nm is what we need to detect.
Shooting from the hip, I'd recommend a
photodiode http://media.digikey.com/pdf/Data%20Sheets/Opto%20Diode/ODD-470W.pdf if you
just need a coarse signal that detects the band centered on 470nm. Also, you could use an
analog to digital converter or even just a properly dialed-in comparator to cut out the
heads and tails of the spectrum.
Not bad for a shot from the hip, but if you read the
background, you might find it doesn't quite fit the distribution model. Making this
out of a photodiode and other hardware will make this far less accessible and convenient
than a smartphone app. The more accessible and convenient such measurement is, the more
such data will be mentioned in reviews. The more such data is mentioned in reviews, the
more careful marketers and manufacturers will be with measuring their products. (Also,
non-maker insomniacs deserve good sleep too.)
12:33 p.m.
The figure <http://www.jneurosci.org/content/21/16/6405/F5.expansion.html>I
linked to earlier suggests the 50% drop-off should be around 420-520nm,
which covers pretty much all of the blue range of the spectrum.
The photodiode you listed seems pretty much a perfect match. No need to
muck around with narrow band-pass filters.
Patrik
On Tue, Nov 12, 2013 at 12:26 PM, Hol Gaskill <hol(a)gaskill.com> wrote:
i was asking about bandwidth, not center frequency.
good luck on your app, kenneth.
Nov 12, 2013 11:50:29 AM, stcredzero(a)gmail.com wrote:
Shooting from the hip, I'd recommend
a photodiode
http://media.digikey.com/pdf/Data%20Sheets/Opto%20Diode/ODD-470W.pdf if
you just need a coarse signal that detects the band centered on 470nm.
Also, you could use an analog to digital converter or even just a properly
dialed-in comparator to cut out the heads and tails of the spectrum.
On Tue, Nov 12, 2013 at 11:06 AM, Hol Gaskill
hol(a)gaskill.com> wrote:
What's the badwidth you're interested in?
Call me Kenneth, then ask me the frequency. A band
around 470nm is what
we need to detect.
Not bad for a shot from the hip, but if you read
the background, you
might find it doesn't quite fit the distribution model.
Making this out of
a photodiode and other hardware will make this far less accessible and
convenient than a smartphone app. The more accessible and convenient such
measurement is, the more such data will be mentioned in reviews. The more
such data is mentioned in reviews, the more careful marketers and
manufacturers will be with measuring their products. (Also, non-maker
insomniacs deserve good sleep too.)
_______________________________________________
sudo-discuss mailing list
sudo-discuss(a)lists.sudoroom.org
http://lists.sudoroom.org/listinfo/sudo-discuss
12:41 p.m.
On Tue, Nov 12, 2013 at 12:33 PM, Patrik D'haeseleer <patrikd(a)gmail.com>wrote;wrote:
The figure
<http://www.jneurosci.org/content/21/16/6405/F5.expansion.html>I
linked to earlier suggests the 50% drop-off should be around 420-520nm,
which covers pretty much all of the blue range of the spectrum.
This is another reason I'd like to play around with subtracting the red
signal. Depending on what the spectral response curves are, it might be
possible to play around with multipliers and get close to the shape of the
graph. (Granted, that it might also turn out to just including the blue
signal, but I really need to *know* what that is, not make an educated
guess about it.)
The photodiode you listed seems pretty much a perfect
match. No need to
muck around with narrow band-pass filters.
For the purpose of the intended distribution context and audience, I should
**avoid** requiring other to be mucking around with photodiodes. The fact
that a photodiode detector's curve matches another really doesn't change
that.
10:28 a.m.
On Tue, Nov 12, 2013 at 9:59 AM, Steve Berl <steveberl(a)gmail.com> wrote:
I will check with folks at the East Bay Astronomical
Society up at Chabot
Space & Science Center. There is some amount of spectroscopy equipment
around up there. Though much of it is very old, and intended for
astronomical observations (attached to a telescope), something might be
useful, and there might be someone who is interested in helping out.
Thanks. I appreciate it. It turns out what we need is a visible light
monochromator. Also, light meters with good sensitivity at low levels would
be helpful as well. Biology labs often have monochromators. A spectroscope
would be helpful to validate light sources, if a monochromator cannot be
found and one would have to be fabricated.
3855
days inactive
3856
days old
14 comments
6 participants
participants (6)
-
Hol Gaskill -
Marc Juul -
Patrik D'haeseleer -
Peter Kwangjun Suk -
StCredZero -
Steve Berl