Novel resistive electrode structure for liquid crystal modal lens shifting

摘要

Miniaturization of image sensors and increase of their resolution creates a demand for new miniature optical components providing classical functions in optics, like auto-focus (AF) and optical image stabilization (OIS). Several routes have been explored in order to realize AF and OIS functions in miniaturized components, for example electro-wetting liquid lenses, MEMS components and liquid crystal (LC) lenses. Our recent attempt to provide OIS with LC lenses showed the possibility to shift an image but limitations appeared. The sectorization of the electrodes generates aberrations due to the discontinuities of the electric field at the junction between two sectors. To overcome these limitations, we propose a new structure featuring a resistive electrode. This structure consists in substrates with thin electrodes joined with a ring-shaped resistive electrode (10kΩ/sq.) made of PEDOT-PSS and etched by oxygen plasma. A high resistivity layer (10MΩ/sq.) is then coated on the optical aperture and the cell is assembled like a classical LC modal lens. With this electrode structure, we succeeded to linearize the electric potential between the electrodes and reduce aberrations of the resulting wavefronts. First we simulated the lens by finite elements method to study the impact of the ring-shaped resistive electrode and to calibrate the physical parameters of each components (metallic electrodes, ring-shaped electrode, high resistivity layer, LC...). Then, we realized lenses and we characterized them in terms of focus, deviation angle and aberrations.