Design of a stray-light-free waveguide near-eye display using a pin-mirror array and multiple thin plates

Abstract

It has been proved that waveguide near-eye displays with a pin-mirror array can extend the depth of field (DOF) for part of field of view (FOV), which can alleviate the vergence-accommodation conflict (VAC) to a certain extent. During the usage, stray light has been treated as a pivotal factor affecting the image display quality of this waveguide structure, leading to image ghosting or flipping problems. In this paper, we propose a stray-light-free waveguide near-eye display using a pin-mirror array and multiple thin plates. A two-step optimization method has been used to eliminate stray light. Firstly, the effects of the parameters of near-eye displays have been investigated, such as eye relief, pin-mirror size, and spacing size; further, the position and range of total reflection on the front and rear surfaces of the waveguide for the residual stray light are quantitatively analyzed. According to the position and range of the total reflection, multiple thin plates can be introduced to optimize the stray-light paths. To minimize the proportion of stray light in the eye box, the thickness and height of the plates can be optimized. Finally, a compact waveguide near-eye display with stray-light ratio below 0.1% across the eye box is obtained, which can effectively improve the display quality of virtual image. To verify the effectiveness of the method, image simulation was performed, and the results are consistent with the analysis. This method can also improve the vertical FOV while eliminating the stray light, which is very helpful to improve the performance of this kind of waveguide structure.