CMOS based optical focusing stage with phase grating Fresnel lens

This study reports a CMOS based optical focusing stage, which incorporates a binary phase-grating Fresnel-lens (PF-Lens). This PF-Lens is the first time implemented in CMOS micro stage. It exploits the superior fine line width and transparent dielectric thin film of CMOS process. Diffraction efficiency of PF-Lens is theoretically fourfold better than that of typical binary amplitude-grating Fresnel-lens (AF-Lens). In addition, by dispensing UV curable transparent polymer onto Fresnel-lens, the resulted compound lens can achieve a shorter focal length of 648 mum (HeNe laser). The integrated micro stage is thermally actuated. It provides 12 mum stroke alone optical-axis and 17.3 mum across optical-axis. It is sufficient to compensate optical alignment error and to speed up precision focus tracking.