[ros-users] camera_calibration

Vijay Pradeep vpradeep at willowgarage.com
Tue Apr 6 21:39:16 UTC 2010


Hi Patrick,

Is the checkerboard 8x6 corners?  If so, make sure that you always keep the
target in a 'landscape' orientation.  If the checkerboard gets close to a
'portrait' orientation, the OpenCV detector may mess up the correspondence
between both cameras (thus, making the calibration routine want to rotate
one of the cameras 180 degrees).

This rotational ambiguity can also be solved by using a checkerboard with
[odd]x[even] corners.

Vijay

On Tue, Apr 6, 2010 at 2:01 PM, Patrick Beeson <beeson.p at gmail.com> wrote:

> Sorry, I just checked and I am actually using the trunk, not latest.
> The problem is that I'm getting large rotational values, and I'm only
> ever seeing a horizontal offset in T (top right value in projection
> matrix) as non-zero, even though the cameras are at slightly different
> heights.  I can send the saved tar.gz file that contains the images used
> and the ost.txt created if it helps.
>
> Patrick Beeson wrote:
> > I checked out latest and had to do a small bit of changes to sync the
> > timestamps of the two cameras whenever frames have very close
> > timestamps.  So they aren't EXACTLY synced, but VERY closely synced.  I
> > can try to send you a screen shot of the output.  Note, I am testing
> > this with a quite small checkerboard (your checkerboard, but with 26mm
> > squares).  Maybe that's the problem?  Maybe I'm sampling a space too
> > close to the cameras?
> >
> > Eric Perko wrote:
> >> Patrick,
> >>
> >> What version of camera_calibration are you using? Boxturtle?
> >>
> >> - Eric
> >>
> >> On Tue, Apr 6, 2010 at 4:31 PM, Patrick Beeson <beeson.p at gmail.com>
> >> 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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