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<div class="moz-cite-prefix">John,<br>
<br>
Interesting post. Also great to see you out and about at the
last competition. And dinner. Robots + Mexican food ==
DoublePlusGoodness.<br>
<br>
I will start by saying that you, being by nature an inquisitive
and research-oriented kinda guy, should certainly be encouraged to
delve into this and find us a superior method of finding colored
objects, be they fluorescent orange or any other color. By all
means.<br>
<br>
But I think perhaps there is a misunderstanding here. You wrote:<br>
<br>
"I think we have a conceit that orange is unique enough because it
looks dramatic to our eyes." <br>
<br>
Instead, fluorescent orange is used precisely because there is
otherwise so little of it naturally in the environment. The
software can be tuned to recognize any arbitrary color. But most
of those colors are present in copious amounts in nature. Which
makes the recognition task much harder. Not much fluorescent
orange in the average outdoor scene.<br>
<br>
The digital cameras we use are in fact most sensitive to light in
the infrared, because of the nature of the CCD tech. And
everything outdoors has a significant infrared signature because
of the nature of the illumination, i.e., the sun. As a result
all modern digital cameras, including the one in your phone as
well as those used by professional photographers, have an infrared
filter on the front end. Otherwise the infrared swamps out
everything else. (In fact if you want a camera that can see into
the infrared, to see heat and such, all you need to do is remove
that filter. There are hacks on the internet to do that very
thing.)<br>
<br>
The reason that fluorescent orange works so well with these
cameras is not because of human conceit, but rather because there
is so little of it naturally in the environment to confuse the
recognition algorithm. So the signal to noise ratio is very
high, and the likelihood of false detections is commiserately low.
<br>
<br>
In fact, this is true for all the fluorescent colors, not just
orange. <br>
<br>
The cameras and recognition algorithms we use work equally well
with fluorescent blue and fluorescent green. Again, because
there is so little else in the environment that are those
colors. ( Just kind of hard to find fluorescent blue and
fluorescent green traffic cones, though we could paint some those
colors if so desired.)<br>
<br>
In some early experiments I added a 1 million candle-power
flashlight to the robot in order to try to smooth out the wide
range of lighting differences in outdoor situations. But I found
after a lot of experimentation that it wasn't really needed.<br>
<br>
As an aside, a biology professor once told me that the reason that
our eyes are optimized for "visible" light which, as you point
out, is less than an "ocatve" of the electromagnetic spectrum, is
because eyeballs evolved underwater, and indeed are full of water,
and water is transparent to those frequencies. Birds and insects
can also see into the ultraviolet, but ultraviolet causes cancers,
and only critters with short life spans have that capability:
they don't live long enough for the cancers to be a problem. <br>
<br>
But as I say, if you can come up with a different type of sensor
or sensor plus illuminator that works better, bring it on! We're
all interested.<br>
<br>
cheers,<br>
dpa<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On 12/05/2016 06:07 PM, John Swindle wrote:<br>
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<div><font face="sans-serif">Dave Anderson and others,<br>
<br>
Some time back I asked why visible light cameras are used to
locate the traffic cones. I think the answers were that such
cameras are cheap, and something to the effect that the
color of the cone is notable.<br>
<br>
I don't think I made my point: As with sonar operating at a
frequency that we think is noise-free because we don't hear
all the interfering noise that exists above our hearing, I
think we have a conceit that orange is unique enough because
it looks dramatic to our eyes. But visible light is such a
tiny part of the usable spectrum. What I was suggesting is
that there might be a characteristic of the cones that could
be exploited to give fantastic distinction to the cone's
location, even if the exploit is unique to the cones that
are being used that day. The exploit might require the robot
to illuminate the cone. (Or, shall I say, irradiate the
cone? The group might find that disturbing.)<br>
<br>
My comments are motivated by several things:<br>
<br>
. The problems of using visible light cameras to guide a
self-driving vehicle, where radar, LIDAR, and other
approaches are much more foolproof.<br>
<br>
. "Alternate light sources" cited in the forensic TV shows.
A fancy name for colored light and some beyond-visible
stuff.<br>
<br>
. Tricorders and ship's sensors.<br>
<br>
Later,</font><br>
John Swindle<br>
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