Kinematic Mount Selection for Optical Scanning Assemblies
Kinematic mount selection for optical scanning assemblies isolates substrates from thermal and dynamic distortions while maintaining sub-microradian repeatability.
Polygon Scan Head
Meaning
High speed optical assemblies utilizing a rotating multi faceted mirror allow for rapid raster scanning of a laser beam across a target area. The polygon scan head achieves significantly higher line rates than oscillating galvanometers because the motion is continuous and unidirectional. It is the primary instrument for high throughput applications such as laser printing and large area surface texturing.
Scanning Velocity
Speed of the rotating mirror determines the pixel clock and the spacing between consecutive laser pulses. A polygon scan head can reach surface speeds of hundreds of meters per second. This capability is matched against the pulse repetition rate of the laser to ensure uniform coverage.
Dynamic Balance
Centrifugal forces at high rotations require the mirror assembly to be perfectly balanced to prevent vibration. Any wobble in the axis of rotation causes periodic errors in the scan line spacing. Bearings for these systems are often air based or high precision ceramic to handle the thermal load.
Process Integration
Synchronization of the laser trigger with the facet position is handled by a specialized controller and an optical start of line sensor. The polygon scan head requires a flat field lens to correct for the change in focus across the wide scan path. Managing the timing jitter is the most difficult part of achieving high quality results at these speeds.