Fabrication of Micro Lens Array by Excimer Laser Micromachining

Abstract

Micro Lens arrays are widely used in optical devices such as photo-sensors, digital projectors, photovoltaic cells, 3D imaging etc. These have traditionally been fabricated by photolithography, moulding and embossing, reactive ion etching and electroforming. These processes are wet processes and require expensive setup and running cost. A novel method is presented in this work that allows fabrication of micro lens array using excimer laser micromachining. The fabrication has been done using mask projection with work piece scanning. A KrF excimer laser has been used to micro machine lenses on a poly (methyl methacrylate) substrate. The surface profile of the lens array is measured and then related to the laser-material coupling and the energy of the laser pulses. Using this method, it is possible to fabricate micro lenses down to a diameter of 5 µm over a considerably large area.

Analytical study for the selection of mask size and shape for obtaining high machining quality of complex features

“…Using the contour mask, researchers have fabricated complex features such as a microlens array. 24 Furthermore, in the literature, studies had been carried out to understand the effect of the spot overlap on the machined channel roughness at an oblique angle and concluded that roughness decreases with the increase in the overlap. 25 However, in the literature, the researchers had not discussed the effect of varying spot overlap on the machining time “T m .” Given that machining time is an essential factor in an industrial environment where a high production rate is required along with superlative quality of the product, a study for optimum spot overlap is required.…”

A Microlens Array with Different Focal Lengths Fabricated by Roll-To-Roll UV Lithography

“…The function of such arrays is dominated by the spacing between the cells, as well as the geometries of the individual microstructure cells. In previous research, various methods have been proposed for fabricating the microlens arrays, including photoresist thermal reflow 6 , non-ionic poly(vinyl chloride)/dibutyl adipate gels 7 , overplating in electroforming 8 , gray-scale photolithography 9 , projection photolithography 10 , excimer laser micromachining 11 , hot embossing 12 , wet etching 13 , etc. However, these processes are complicated and time consuming.…”