How it works
The novel NST approach deflects the incoming laser beam by means of a multifaceted mirror or polygon. The patent pending one dimensional large field f-Theta optics keeps the spot focused on the substrate.
By nature rotating scanners are one dimensional scanners. They produce a scanned line and to obtain a 2D scanning system a secondary linear motion is required. The direction of the secondary motion is perpendicular to the line scanned by the polygon scanner. This is synchronized in speed with the latter rotational speed to obtain a line by line scan of the target surface. Since the polygon is rotating at a constant speed, in contrast to the back and forward motion of the galvo mirror scanners, a higher number of scanned lines per second over a larger area can be realized.
Combining a linear stage movement with the one dimensional f-Theta lens enables the construction of a simple yet very performant system. The reflective f-Theta system is fully telecentric and highly linear. Telecentricity provides for constant light matter interaction across the scan. The impeding beam is circular, constant in size and constant in peak intensity across the scan. Due to the mirror based optics the scan grid shows no pincushion distortion and no error compensation tables are required to achieve accuracy better than 5 μm. The LSE170A system demonstrates its performance over a scan line of 170 mm.
The LSE controller is the heart of the set-up. The controller is controlling the position of the laser beam and takes care of the fine time synchronization between the rotating polygon, the laser pulsing and material transport. The ‘image’ data or laser pulsing pattern is prepared in a black and white bitmap (a windows.bmp) file. The highest repetition accuracy in spot positioning is delivered through proprietary SuperSync™ controls.
The system controller is controlled by a set of operator defined parameters. The operator sets the laser repetition rate, the horizontal (fast direction) pulse spacing and vertical (slow direction) line spacing. It is this parameter set that controls the actual dimension of the scribed bitmap and sets the laser writing speed.