Tunable Lens for AR Headset

The mismatch between positions of virtual images and a see-through view constitute a serious problem in virtual and augmented reality optical systems with a single projection plane. These issues may lead to a user's discomfort: eye fatigue, headache and nausea. In order to solve these problems a tunable lens forming several projection planes at different locations can be used. Developed varifocal lens consists of two tunable liquid crystal cells. The first cell for fine adjustment varies optical power from 1 D to 3 D, the second cell for coarse adjustment varies power from 0.25 D to 1 D. The total dioptric range is -4 D ... +4 D with an equidistant step of 0.25 D that forms 33 projection planes. Electrode pattern made of indium zinc oxide consists of rings corresponding to Fresnel zones, each zone is divided to multiple sub-zones. In order to minimize the number of control electrodes (bus lines) and keep high diffraction efficiency, the bus lines shunt together all of the corresponding sub-zones in all of the zones. Developed lens is tested with AR glasses based on a holographic waveguide. Displacement of virtual image from 250 mm to 1 meter is demonstrated.