A calibrated radioactive source comprises a container and a material labelled by at least one radionuclide. According to embodiments, sizes of circles from a top view of a micro-lens are measured and correlated to a change in focus depth of an optical scope. The CPLL exhibits in first order PLL dynamics without a loop filter in the feedback loop to the NCO. With the DC bias current below threshold of the laser diode and RF bias with a frequence close to the relaxation ascillation frequency of the laser diode, a periodic pulse train is emitted with constant phase. The damper module includes a frame and a plurality of vanes located in the frame. The drive member is axially movable between a dose setting position, in which the drive member is rotationally constrained to the housing, and a dose dispensing position, in which the drive member is rotationally decoupled from the housing.