A Structure of Optical See-Through Head Mounted Display

Abstract

In the paper, we suggest the optical see-through head mounted display (OST-HMD) for self-contained augmented reality (AR) environment. In the OST-HMD system, several types of optical architectures such as microprojector, spatial light modulator (SLM), diffraction optical elements (DOE), polarized beam splitter (PBS) are used. For comfortable use, HMDs should have small size, light weight, better mobility, no screen door effect, and minimum burden on skin. Technologically HMDs should provide higher resolution, less latency, wider field of view (FOV), wider color gamut, sufficient refresh rate, reliable eye tracking method and higher pixel per degree (PPD). Existing HMDs use optical combiners in front of projection optics, which reduce the visibility of the real-world and thus harm the sense of realistic interaction with the surronding world. Instead of the front optical combiner, we used transparent projection optics, PBS, and SLM for better view of the environment through the optical components and they enhanced the sense of reality in interaction with objects in the environment. We also used the pinhole array structure to increase FOV and resolution. To interact with the surronding world in AR, we adopted the 6 degrees of freedom (6DOF) microelectromechanical system inertial measurement unit (MEMS IMU) in the center of the HMD and created a depth map of real objects using time of flight (TOF) method. Figure 1. shows the concept of OST-HMD (left of Figure. 1) and the optical structure in the paper. (right of Figure. 1). We suggested the OST-HMD optical structure with transparent projection optics and MEMS IMU, which increased real-world visibility and the sense of presense. We will further improve the performance and simplify the structure by using ray tracing and image processing methods.