Many high definition television (HDTV) applications improve the contrast and detail of dark image scenes by using a pupil to reduce light on the screen. One such application is Dynamic Black, utilized in many DLP® HDTV applications. Since HDTV projection lenses are generally of fixed length and have no complicated zoom or focus mechanisms, HDTV applications generally have convenient optical and mechanical access to the projection lens pupil. Optically, the pupil provides a function that minimally affects spatial uniformity. However, conventional HDTV solutions to enhance contrast and detail of dark image scenes are limited for a variety of reasons and are not universally applicable to all types of displays. For example, decreasing the aperture of the lens pupil often increases the f-number of the optical system, thereby increasing visibility of defects while reducing the high-angle rays that pass through the system. The f-number or focal ratio of an optical system expresses the diameter of the entrance pupil in terms of the effective focal length of the lens. Further, it may be desirable to enhance contrast and detail of dark images in displays in formats other than HDTV.
USPTO Backgrounds
USPTO Backgrounds