Virtual image display having a high efficiency grid beamsplitter

Abstract

A focusable virtual image display system employing a focusable image source such as a cathode ray tube and imaging optics to provide a virtual image. The virtual image is viewable by a user and its effective range may be changed without changing the apparent field of view or resolution. By placing the focus point of the imaging optics at the design eye, the image source is moved backwards and forwards, thus effectively changing the range of the virtual image observed by the user without changing the apparent field of view or resolution. The present invention allows the user to adjust the focus position of the virtual image of the image source by moving it relative to the imaging optics, while maintaining the size and resolution of the image. If the user wants to move the image further away, when the image source is moved, the imaging optics moves the virtual image further away and magnifies the image such that the angular field of view stays the same. The user cannot distinguish between the sizes, although the focus will be more comfortable for a particular accommodation range. The relative cost of the virtual image display system is relatively less expensive than large screen monitors due to the nature and complexity of the smaller components. By including a focus adjustment mechanism, the focusable virtual image display monitor has an added feature that a conventional large screen monitor does not provide.

Dependencies are inferred from the claim text.