High accuracy cross bar location subpixel algorithm implementation

Some controls realised during TV manufacturing need real time high accuracy measurement of cross bar intersection positions. In order to meet these constraints a subpixel approach has been needed and a hybrid architecture featuring new image processing technologies has been developed. 1024×1024 pixels images are delivered by a CCD camera at 2×25 MHz.pixel data rate. In order to process this information, a subpixel algorithm implementation study has been made. The first part of the algorithm which deals with pixels has been implemented on FPGAs. It is composed of a fast intersection area detection. For each detected area, a precise calculation using centre of mass on horizontal and vertical bars is performed to reach subpixel accuracy. The second part of the algorithm consists of horizontal and vertical line´s calculation on two Texas Instrument TMS320C40 DSPs using least mean square algorithm applied to the above mentioned centre of mass. These lines modelise the bar near intersection. Centres of mass are received via communication ports and are parallelized with line calculations. Both line parameters are grouped on one DSP for intersection position calculation. At the end of the camera image scanning (20 ms), all calculations are completed and results are available for retrospective effect