ANGLE POSITION DETECTION BASED ON AMORPHOUS-SILICON 4 QUADRANT ORIENTATION DETECTOR

Using the amorphous silicon active hollow FOur QUadrant Orientation De tector (FOQUOD) which can be used to determine the contrast edge posit ion of the image of an object and its orientation with respect to a ho rizontal line, two methods are devised to extract the angular position s of an image. The first method uses a signal processing technique to filter the Line orientations and two data filter masks to extract the angular position of an image. The second method is to project a test i mage onto two active hollow FOQUOD arrays in juxtaposition simultaneou sly with a small relative shift. Then by comparing the position and or ientation values of the corresponding cells, the angular position can be extracted. Both methods achieve an accuracy of over 90%. Based on t hese two methods, a double FOQUODdevice which can be used to determine the angle position is designed and fabricated for the first time. The accuracy of determining the angle positions of an arbitrary feature e xceeds 60%.