Analysis and design of wedge projection display based on ray tracing method

We proposed the new optical design of the wedge projection display to enhance the quality of image. Since the thickness of the wedge plate can be thin enough, this technology makes up for the bulky property in projection type display. However, the image quality is heavily influenced by "dark zone". The dark zone means the repeated region that the rays cannot escape from the waveguide. Thus, these regions present nothing and the image quality is very low. To reduce the problems, we analyzed the principle of the image formation by the geometrical retracing from the wedged surface to the aperture of waveguide. The bundle of rays converging into an imaging point on the wedged surface have the same image information, but can have the different initial position and the angle when started from the aperture. Therefore, each ray is classified by the position of the imaging points on the inclined surface and the number of reflection. Based on the classified data, we can obtain the equivalent imaging point which is the intersection when the set of the rays with the same condition does not experience the reflection at the interface. Because this point is equivalent to the imaging point on the inclined surface, we can display the image by projecting on the equivalent imaging point. In this paper, the optimized set of equivalent imaging points is analyzed by retracing method and we designed the improved imaging system of the wedge projection display by modifying the shape of aperture to equip the optical components in the on-axis.