Self-learning Laser Beam Positioning to Track Moving Objects
In biology applications a laser beam is used for cell stimulation. First the laser beam is redirected onto 2 mirrors then directed to the cells. An important requirement, to hold the laser beam onto the cell is very difficult to achieve due to thermal effects or external vibration. The position of the laser beam needs to be controlled in real-time to track the motion of the cell.
For this task a system with two piezo-driven mirrors and two position-sensitive 4-quadrant diodes is used. The mirrors adjust a laser beam in any direction defined by the 4-quadrant-diodes. The signals are used to operate the PKS1 piezostage for stabilizing the position of the laser beam on the cell.
The regulation of the controller uses frequencies up to 100 Hz. The piezo stage needs to be 3 to 5 times faster than the frequency. piezosystem jena uses the mirror tip- and tilting piezostage PKS1. This piezo stage adjusts the direction of the mirror in milliseconds with a frequency between 300 and 1000 Hz. For a coarse adjustment the tilting platform can be moved up to +/-2 degree manually.