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So, someone stole my bike light. Now I only have a
reflector. Out of interest, I took the rear reflector off my
bike and subjected it to my hideously over-specified
optical test equipment.
It's not very good. Here's why: It's a shiny metalic cube-
corner reflector, covered in red-transparent
plastic. Now
the cube-corner reflector I have no issues with. It's a good
way of getting light out in lots of directions from a light
source that may be coming in from all sorts of angles. The
red-transparent plastic is where the issues lie.
The red plastic basically acts as a low pass filter. White
light in, red light out. The whole spectrum shorter than
about 600 nm is wasted. It just warms the plastic up a
bit*.
We can do better. With fluorescence. Simply embed red-
emitting quantum dot CdSe nanoparticles in the plastic.
Much better visibility as not only the (red portion)
reflected light will be seen, but the quantum dots will
harvest some of the blue/green/orange light and emit that
back at the driver.
* or a lot of you put 600W Xenon arc light down a liquid
light guide at it.
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Annotation:
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//Now the cube-corner reflector I have no issues
with. It's a good way of getting light out in lots of
directions from a light source that may be coming
in from all sorts of angles.// |
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As I understand it, a cube-corner reflector returns
light in the direction it came from - is that not
the case? |
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But I like the fluorescence part. Qdots are
awesome, but I'm not sure if they're cheap enough
for this application. |
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The nice thing about corner cube reflectors is
that, regardless of the incoming direction, the
light goes back out on the exact reciprocal. |
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Your fluorescent dots will emit weakly (low QE of
fluorescence) and diffusely from the surface
exposed to the light. |
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I'm not saying the idea can't work, just that the
gain will be minimal, and if the dots intercept
some of the red light, might even be negative. |
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//a cube-corner reflector returns light in the
direction it came from// |
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You're correct, my description was messy. |
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//cheap enough for this application// |
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They're going to be using them for increasing the
efficiency of solar panels, I suspect they'll be
cheap soon. Also, minor gains for massive money is
a hallmark of any bike part. |
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//Your fluorescent dots will emit weakly (low QE
of fluorescence) and diffusely from the surface
exposed to the light.// |
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QD's are >80% quantum yield, actually, that's just
the ones I use and they've got biology goop all
over them, plus, it's free (red) light. QDs emit
equally in all directions. This is a very good thing.
It means that some light will go back to the
source, some light will hit the reflector, and go
back to the source, some will go out of the sides.
Now, at the sides a simple mirror can re-direct
that backward. |
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//Also, minor gains for massive money is a hallmark of
any bike part.// |
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While this is true, the ones for whom it is especially
true tend to have as little in the way of reflectors as
they can legally get away with. |
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// little in the way of reflectors as they can legally
get away with// |
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with the increased efficiency of the bs0 Quantum
Reflector*, they can shave off that precious gram!!! |
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*$299 regular $345 for the Aero model |
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<off topic> [bs0] - what are you using Qdots for?
<\ot> |
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Actually, thinking about it, I haven't noticed Qdots
being conspicuously bright (in their respective
emission colour) in ambient light - but that's indoors
(fluorescent lights - probably not a lot of blue and
very little UV). |
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Off topic. We're using them for imaging low-copy
number ion channels in the mitochondria. The
calcium uniplex / mito BK Ca2+ channels. Electro
physiology tells us that there are <10 of these per
mito sometimes, so if you want to see them you
need something that doesn't bleach. Even better if
it's 2-photonable. Better still if you can see them in
EM |
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<wildly off topic> how do you selectively bind them
to the chosen proteins? Are they antibody-coupled,
or have you got something like a streptavidin or his
tag [edit: forget I said his tag; that would be stupid]
on the channel protein? <\wot, and apologies to
innocent bystanders> |
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Absolutely bog-standard secondary antibodies. We
have well checked primaries. Not so useful for
localization, a 2 antibody chain can put you
anywhere in a 30nm sphere. |
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If you can tag your protein miniSOG is great. I can't,
tagging the proteins screws their function, native
expression levels (<10 proteins) would render them
practically invisible, overexpressing them is asking for
trouble. |
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Hmm. Hadn't heard of miniSOG, just Googled it, way
cool. Thanks! |
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//apologies to innocent bystanders//
Any science talk is good; doesn't matter when or where it shows up.
Also, where do you get (and why do you have...) a 600W Xenon arc light and a liquid light guide?
<back on topic> Can't say I know much about fluorescent quantum dots, but the idea certainly has merits. Maybe use wave guides or diffraction gratings to direct the light you don't want reflected (ie. not red) to the fluoro dots, where it gets converted to red; while the (incident) light you do want goes (more-or-less) unimpeded to the reflector. |
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Can you stick the quantum dots in a confocal etalon cavity (one etalon for each corner reflector) to increase the conversion efficiency and directionality of the red light? |
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Fireflys strapped to the handle-bars. |
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Alternatively, if all you want to know is "what's in front of the bike?" then something like sonar, or catfish with long feelers might work. |
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//where do you get (and why do you have...) a
600W Xenon arc light and a liquid light guide?// |
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You take a 300 W Sutter DG4, a need for more
light, the internet, some cowboy engineering* a
bigger fan and Boom!** you have a 600W 10,000
lumen light source with a good amount of UV. |
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*eventually some proper engineering |
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** the first time at least, the second time we put a
better power supply in. |
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