Real-time sub-pixel cross bar position metrology

Many measurement application fields need to calculate cross bar intersection locations of horizontal and vertical bars. The system we developed and that we present in this paper is an embedded system that measures cross bar positions with sub-pixel accuracy on 1024 x 1024 pixel images delivered by a camera at a 50 MHz data rate in real time. This is done using an algorithm that looks for intersection areas and then locally calculates two lines representing horizontal and vertical bars. The two line intersection is considered to be the bar intersection. To achieve real time, we developed a hybrid architecture in which low level processes are implemented into FPGAs and others into DSPs. As a result, at the end of the camera scanning (20 ms), all calculations are completed and the results are available. (C) 2002 Published by Elsevier Science Ltd.