Defocusing simulations on a retinal scanning display for quasi accommodation-free viewing

The limited depth of focus (DOF) is one of the main problems of today's head mounted displays. This paper investigates ways to overcome this drawback by using the retinal scanning technology. Based on an accommodation-dependent schematic eye model the contrast function of a retinal scanning display is evaluated as a function of eye accommodation, eye position and scanning beam width. The display's defocusing properties and the design trade-off between resolution, depth of focus and maximum image field are analyzed and discussed. The analysis indicates that an elliptically shaped scanning beam is most favorable to provide a quasiaccommodation free viewing. This elliptical beam shape is caused by the asymmetry in the scan pattern.