Compact and tunable liquid crystal lens to control the propagation of light and transmit signal/data

Miniaturisation 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 stabilsation (OIS). Several routes have been explored in order to integrate AF and OIS functions in miniaturised components, for example electro-wetting liquid lenses, micro electronic mechanical systems components and liquid crystal (LC) lenses. Recent attempts to provide LC lenses with OIS showed the possibility to shift an image but limitations appeared. The sectorisation of the electrodes generates aberrations due to the discontinuities of the electric field at the junction between two sectors. To overcome these limitations, the French company proposes a new structure featuring a resistive electrode. This structure consists of glass substrates with thin Indium Tin Oxyde (ITO) electrodes joined with a ring-shaped resistive electrode (10kΩ/sq.) made of two mixed polymers PEDOT-PSS (poly(3,4-éthylènedioxythiophène) - poly(styrène sulfonate) de sodium) and etched by oxygen plasma. A high resistivity layer (10MΩ/sq.) is then coated on the optical aperture (hole pattern Chromium (Cr) electrode), then the cell is assembled like a classical LC modal lens. With this electrode structure, it became possible to linearise the electric potential between the electrodes and reduce aberrations of the resulting wavefronts. First a simulation of the lens by finite elements method was made, 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, liquid crystal...). Then, lenses were made and characterised in terms of focus, deviation angle and aberrations. The SME proposes a highly integrated and low cost active Liquid Crystal Lens for auto-focus and optical image stabilisation that offers three main interests for applications: •No moving parts - thin film technology with no encapsulated air: this technology is well suited to critical environments such as space/vacuum or underwater system. It has also low sensitivity to vibration that makes it ideal for industrial applications. •Ultra miniature design: the lens dimensions are close to the lens pupil diameter to achieve a thickness of less that 1mm. This lens is particularly well suited to auto-focus functionality in endoscopic probes or in embedded devices such as a smartphone or a wearable camera. •Low cost: the technology uses standard production processes of the Liquid Crystal Display (LCD) and semiconductor industries. It is possible to massively scale-up production so as to lower the unit price of components. The French SME aims to transfer this technology to industrial partners located in Europe, Japan, USA or South Korea. License agreements and technical cooperation agreements are sought with industrial partners in sectors such as telecommunications, medical imaging equipment, optic systems development, virtual reality helmets development.