Polygon Scanner Systems
Polygon scanning is well known in the graphic art industry but still pretty new in advanced micromachining processes using high power USP (ultra-short-pulse) lasers. Utilizing a polygon scan system demands, just like galvo based scan heads, more than the deflector itself.
Current scanning solutions for high precision processing with uniform spot size need a f-Theta telecentric lens. Processing larger work pieces – usually above 50 to 80 mm – will lead to more expensive optics or a step & repeat approach with increased stitching complexity. Such a scanning approach proves to be less cost efficient when processing at high density and high speeds.
The novel SCANLAB approach deflects the incoming laser beam by means of a multifaceted mirror or polygon. The 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 scan 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.
SCANLAB’s polygon solution, lineSCAN 300 scan heads, maximize throughput onlarge formats without compromising processing accuracy.
Full Telecentric Optics
Combining a linear stage movement with the one-dimensional f-Theta lens enables the construction of a simple yet very capable system. The reflective f-Theta system is fully telecentric and highly linear. Telecentricity provides for a 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 12 μm (4 sigma).
The LSE controller is the heart of the set-up. The controller is regulating 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.
- Polygon scanner providing 100 to 400 scanned lines per second and more
- Substrate scan speeds: 25 to 100 m/s up to 400 m/s with airbearing solution
- Full telecentric mirror based f-theta optics
- Scan line length 300 mm or more by custom stitching solutions
- Supports NIR/VIS and UV wavelengths
- Diffraction limited quality optics providing small focused spot sizes
- Includes control electronics for easy integration with lasers and linear stages