A pixel array structure includes scan lines, data lines, first pixels, and second pixels. In some embodiments, the compact laser system can be scanned over a broad range. The nozzle part is sealingly inserted into an opening in the cylinder head and a cross brace is fixed to the cylinder head in a deflection-resistant manner, overlapping with at least one injector device. The contrasts of images formed by the respective photographing systems are evaluated while the two focusing lenses are being moved, and a position corresponding to the maximum value of the contrasts is determined as the focusing position. In some embodiments, nitride near the top of the gate stack is removed by removing the upper portion of the gate stack.