Deposition of optical microlens arrays by ink-jet processes

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 mum and 2 mm, and h = 6.25 and 150 mum, respectively, conferring a focal distance varying between 100 mum 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 mum allow us to obtain lenses with diameter 800 mum, height 56 mum and focal distance of 2.9 mm. All the components have a high optical transparency (92%) within the wavelength range 300 nm-2.7 mum, 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 approximate to 40 nm. Their shape measured by profilometry and their focusing properties, determined in and near the focal plane, are reported. (C) 2001 Elsevier Science B.V. All rights reserved.