| Abstrakt: |
We discuss and demonstrate the optimal scanning functions of a galvanometer-based scanner (GS) from an optomechanical point of view. Triangular versus sawtooth and sinusoidal scanning functions are reviewed briefly. From this discussion, we focus on triangular functions with linear active portions and as fast as possible non-linear stop-and-turn portions, necessary to obtain an as high as possible duty cycle. We have studied analytically the performances of these return portions for various sinusoidal, parabolic and higher order polynomial equations. Contrary to what is pointed out in the literature, where linear + sinusoidal scanning function was considered best, we demonstrated that actually the linear + parabolic function provides the highest duty cycle (i.e. time efficiency of the scanning process). The second part of the study approaches the command function, given by the input voltage of the GS that has to provide the optimal scanning function discussed above. This command function is considered in relationship with the active torque that drives the device. This torque is studied with regard to the constructive parameters of the device (moment of inertia, damping coefficient and elastic coefficient of the torsion springs), and to the imposed parameters of the scanning regime (scan frequency, amplitude, velocity and duty cycle). Especially the trade-off that can be done between the various - and contradictory - requirements one has for the device is of interest. The main one is between the duty cycle and the maximum value of the command voltage, in order to minimize the maximum input electrical signal for the device with a minimum loss in what concerns the scan efficiency. Thus, this modeling of the active torque can show the practical limits of the duty cycle, after the study concerning the scanning function has demonstrated its theoretical limitations. |
