Uncalibrated two-view metrology

A method of visual metrology from uncalibrated cameras is proposed in this paper, whereby a camera, which captures two images separated by a (near) pure translation, becomes a height measurement device. A novel projective construction allows accurate affine height measurements to be made relative to a reference plane, given that the reference plane planar homography between the two views can be accurately recovered. To this end a planar homography estimation method is presented, which is highly accurate and robust and based on a novel reciprocal-polar (RP) image rectification. The absolute height of any pixel or feature above the reference plane can be obtained from this affine height once the camera´s distance to the reference plane, or the height of a second measurement in the image is specified. Results from our data show a mean absolute error of 6.9 mm and with two outliers removed this falls to 1.5 mm.