[Canberrauav] choosing cameras
Andrew Tridgell andrew at tridgell.net 
Fri Oct 3 13:07:54 EST 2014 

Hi All,

As a followup to my "next steps" post, I'd like to open a discussion on
what cameras we should look at getting.

Right now we fly a PtGrey Chameleon, which is a 1280x960 machine vision
colour camera, with USB2 connection. This camera has served us well, but
is too low resolution if we want to have a serious go at finding
"shoe-sized" objects.

The obvious next step would be a higher resolution machine vision
camera, either on USB3 or gigabit ethernet. PtGrey offers heaps of
those, but they are expensive. For example, a 6MP Grasshopper3 is $2995,
and a 9.1MP is $3495. I'm sure they are great cameras, but given we'd
need at least two of them it's a big chunk of our budget.

There are other manufacturers that offer similar cameras (many with the
same sensors inside), but at least for those that put prices on their
website the prices seem similar.

Another way to go is to use a camera that is a bit more mass-market,
which brings the cost down. A lot of people doing aerial mapping use
cameras like the Sony Nex7. The issue then is how we trigger the camera
and how we get the images into the Odroid within the aircraft.

An interesting possibility is to use one of the new range of
"lens-style" cameras, like this one:

  https://developer.sony.com/devices/cameras/sony-smartphone-attachable-lens-style-camera-dsc-qx100/

those cameras were designed to mate to a smartphone via WiFi, and are
essentially a camera built into a lens, with remote control and remote
image retrieval over WiFi. Could we use something like that in an
aircraft, with a wireless adapter on the Odroid? The protocols they talk
seem to be just JSON over HTTP, and there is extensive documentation, so
it would seem to be possible. Obviously we'd need to test to see if the
WiFi interferes with other systems (especially RC control and GPS), but
I suspect we could solve that.

These cameras incorporate the same range of sensors used in cameras like
the Nex7, but without the camera body. There are also versions that take
interchangeable lenses:

  http://store.sony.com/interchangeable-lens-style-camera-zid27-ILCEQX1/B/cat-27-catid-All-Cyber-shot-Q-Series-Cameras

That would give us a 20M sensor for 1/5 of the price of a machine vision
camera. They have quite large sensors (23.5 X 15.6mm), so I'd hope the
sensitivity would be good. By comparison the 6MP Grasshopper3 has a
12.4mm sensor, so sensor area of the "lens-style" camera is about 4x. I
haven't checked the datasheets to see if that does translate into
increased sensitivity.

Cheers, Tridge

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