Angle position detection based on amorphous silicon four quadrant orientation detector

Using the amorphous silicon active hollow FO ur QU adrant O rientation D etector (FOQUOD) which can be used to determine the contrast edge position of the image of an object and its orientation with respect to a horizontal line, two methods are devised to extract the angular positions 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 image onto two active hollow FOQUOD arrays in juxtaposition simultaneously with a small relative shift. Then by comparing the position and orientation values of the corresponding cells, the angular position can be extracted. Both methods achieve an accuracy of over 90%. Based on these two methods, a double FOQUOD device 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 exceeds 60%.