Deposition of optical microlens arrays by ink-jet processes

Abstract Ink-jet processes using either a drop-on-demand or a dosing system have been applied to the deposition of single lenses and large arrays of high optical property refractive microlenses. The lenses are made of a silica based inorganic–organic material which can be densified either thermally or by UV irradiation at low temperature. Microlense diameter d and height h made with a single drop can be varied between approximately d =50 μm and 2 mm, and h =6.25 and 150 μm, respectively, conferring a focal distance varying between 100 μm and approximately 10 mm, respectively. Large arrays of lenses have been realized with a minimum separation between the lenses as small as 5% of their diameter. Single lenses and arrays of lenses made with multidrops were also obtained. Microdrops (1000) with d =50 μm allow us to obtain lenses with diameter 800 μm, height 56 μm and focal distance of 2.9 mm. All the components have a high optical transparency (92%) within the wavelength range 300 nm–2.7 μm, are highly homogeneous and have very low stress and astigmatism. The index of refraction can be tailored by modifying the sol composition. The lens average surface roughness is R a ≈40 nm. Their shape measured by profilometry and their focusing properties, determined in and near the focal plane, are reported.