[ros-users] camera_calibration

Eric Perko wisesage5001 at gmail.com
Wed Apr 7 17:26:12 UTC 2010

I can't speak for how Patrick's cameras work, but for anyone else like
me using PGR Flea2 or Firefly 1394 cameras, they claim to
autosychronize if they are on the same 1394 bus (haven't gotten around
to testing this, so I'm basing this on the spec sheet and promotional
materials from PGR). If anyone knows this to be false, please let me
know. My assumption in this case would be that it would actually be
possible to match up two frames that should have been captured within
125us of each other and avoid motion-dependent differences between the
two cameras. Mainly, I would like to be able to reuse the existing
camera1394 (or any other camera driver that implements the
camera_driver API) and not have to implement a separate stereo driver
for the case when I am using a pair in stereo.

Perhaps we actually need a node that could take two camera driver
nodes that provide a polled_camera interface and that polls them
synchronously. This node could also provide a plugin type API for
custom external triggering logic if required. Something like a general
stereo_driver node. Does anything similar exist already?

- Eric

On Wed, Apr 7, 2010 at 12:53 PM, Blaise Gassend <blaise at willowgarage.com> wrote:
> With two threads this morning discussing calibration with unsynchronized
> cameras, I can't help wondering how well the camera_calibration code
> will work if the cameras aren't being triggered simultaneously. If
> camera_calibration decides to use a pair of frames in which the
> checkerboard was moving, I imagine that you might be trying to match
> checkerboards that were actually at different positions, which would
> certainly lead to poor calibration.
> I have no idea if this is a reasonable worry to have, and James could
> probably say more about this than I could. I imagine that motion blur
> would tend to discourage the use of frames in which the target is
> moving.
> On Tue, 2010-04-06 at 15:31 -0500, Patrick Beeson wrote:
>> I'm trying to calibrate two identical 1394 cameras that are sitting next
>> to each other.  The stereo calibration from camera_calibration converges
>> to VERY bad R and T matrices, rotating the frames and
>> the warping the images drastically.  I've tried several times, with no luck.
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