Direct write grayscale lithography for arbitrary shaped micro-optical surfaces

We have developed a novel LED projection based direct write grayscale lithography system for the fabrication of micro-optical freeform surfaces, micro-lenses, diffusors and diffractive optics. In the present publication, we show the benefit of this new technology concerning the high dynamic control of the dosage in combination with a high structure depth of up to 100μm and spatial resolution below 0.5μm. As an example, we demonstrate the performance of the system by showing the fabrication of a 100% filling factor micro-lens-array where the RMS surface deviation does not exceed 0.3% of the total structure depth which means an error less than 30nm at 10μm lens sag. Further, we show that this structuring technology is suitable to generate diffractive optical elements as well as freeform optics and arrays with a high aspect ratio and structure depth showing a superior optical performance.