Light diffusion control by electrically reconfigurable holographic optical elements

摘要

A system and a method of displaying projected images on a projection screen of the system include one or more reconfigurable holographic optical elements (HOEs) in the screen to optically manipulate the projected images impinging on the screen. The reconfigurable HOEs may be configured to perform simple optical functions that are commonly associated with traditional optical devices, such as lenses, prisms and mirrors. However, the reconfigurable HOEs may also be configured to perform sophisticated optical manipulations, such as varying angular intensity of diffused light toward predefined viewing regions. Each reconfigurable HOE includes a hologram that is sandwiched between two electrode layers. The hologram is a holographic photopolymeric film that has been combined with liquid crystal. The hologram has an optical property that changes in response to an applied electrical field. The reconfigurable HOEs are utilized to control the diffusing characteristic of the projection screen. The diffusing characteristic can be changed by selectively setting one or more reconfigurable HOEs to a diffractive state. In one application, the reconfigurable HOEs are utilized to optimally diffuse the projected images with respect to light intensity, so that the projected images appear to be uniformly bright to multiple observers at different viewing regions. In another application, the reconfigurable HOEs are utilized to display the projected images in a stereoscopic form.