Aiming at correcting chromatic aberrations in a far-infrared band, the fabrication of a hybrid microlens array with one-step lithography is proposed, by using a coding grey-level mask. The designed hybrid microlens consists of a refractive microlens and a diffractive microlens in physics. Its structure parameters, in order to achieve the best correction of chromatic aberrations, are evaluated and optimized with the software OSLO to design the layout the grey-level mask. Based on the theory of partial coherent light, the photoresist exposure model and development model, the profile of hybrid microlens in the photoresist have been simulated, the nonlinear errors in the lithography process can be pre-compensated by correcting the mask design. A hybrid microlens array is fabricated through use of the designed mask.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.