Light intensity distribution control element for high-brightness projectors using solid-state light sources

By replacing mercury lamps with solid-state light sources as the light sources of projectors, advantages such as long-life, mercury-free, instantaneous lighting, and high-color-rendering characteristics can be obtained, but low brightness is a problem. In a solid-state light source projector in which blue semiconductor lasers and a yellow phosphor are combined and the phosphor plane and screen are optically conjugate with each other, if the blue laser beam on the phosphor plane is expanded using a diffusion plate to avoid a decrease in the luminous efficiency of the phosphor, the light utilization efficiency decreases and the light intensity distribution becomes non-uniform on the phosphor plane. In this research, a computer-generated hologram, a free-form element, and a polarizing free-form element were designed as light intensity distribution control elements to improve the above two characteristics. The use of each light intensity distribution control element showed an improvement over the diffusion plate through a numerical simulation.