June 5, 2013

Elphel new camera calibration facility

by Andrey Filippov

Fig.1. Elphel new calibration pattern

Elphel has moved to a new calibration facility in May 2013. The new office is designed with the calibration room being it’s  most important space, expandable when needed to the size of  the whole office with the use of wide garage door.  Back wall in the new calibration room is covered with the large, 7m x 3m  pattern, illuminated with bright fluorescent lights.  The length of the room allows to position the calibration machine 7.5  meters away from the pattern. The long space and large pattern will allow to calibrate Eyesis4π positioned far enough from the pattern to be withing depth of field of its lenses focused for infinity, while still keeping wide angular size, preferred for accuracy of measurements.

We already hit the precision limits using the previous, smaller pattern 2.7m x 3.0m. While the software was designed to accommodate for the pattern where each of the nodes had to have individually corrected position (from the flat uniform grid), the process assumed that the 3d coordinates of the nodes do not change between measurements.