A new type holographic display based on a wedge-shaped waveguide and its keystone predistortion

The wedge display is a piece of wedge-shaped waveguide. Each time a ray reflects in the wedge, its angle relative to the opposite side increases so that the critical angle is eventually reached and the ray emerges. Therefore, how far the ray travels before emerging is determined by its injection angle. As a kind of projection display, the wedge-shaped waveguide is a natural fit to holographic projection. In this paper, a new type of holographic display based on the wedge panel is reported. The hologram projected into the wedge is generated by computer with a Spatial Light Modulator (SLM 1280*1024), illuminated by a He-Ne laser. A method taking advantage of reverse ray tracing to correct keystone distortion of the wedge display is introduced. By setting special patterns on the screen of the wedge panel and replacing the projector at its thick end with a camera, keystone distortion information is recorded. The predistortion process adds the distortion pattern from the camera to the original input images. Images with less distortion are shown on the screen after the predistortion process.