Fabrication of microlenses with a Novolak-type polymer

In this work, the fabrication of arrays of parabolic convergent and divergent microlenses is presented. The used material is the Novolak-based polymer All-Resist AR P322, which can be used both for optical UV lithography and for electron beam direct write lithography. Gratings of parabolic divergent microlenses with f-number of 0.5 were fabricated using traditional optical lithography, employing the diffraction characteristics of de-focussed light during the photolithography exposure. Direct write electron beam lithography was used to obtain convergent parabolic microlenses, with different diameters and different heights, allowing the control of the focal length of these lenses. The same technique was employed to manufacture gratings of parabolic convergent microlenses with different diameter and focal length, what enables one to control the intensity of the different orders of the diffracted light. These structures have several applications in the fields of pattern recognition, robotic vision and optical sensors.