A linear free piston Stirling machine having an overstroke prevention mechanism for the power piston. The outputs of the phase-locked loops are monitored for errors comprising high frequency transients or differences in clock signal outputs from a reference frequency. A rotor insert is rotatably supported within the spinning rotor coaxially to the rotor axis. The difference value between the two adjacent pixels is varied depending on a difference in an interference point on the image sensor corresponding to a diffraction angle of the light that has passed through the diffraction grating. The first and second layers are stacked one on top of the other such that the at least one lateral edge of the first layer is positioned between the opposite lateral edges of the second layer.