Methods and systems of rapid focusing and zooming for volumetric 3D displays and cameras

摘要

This invention relates in general to methods and systems of rapid focusing and zooming for the applications in the projection of volumetric 3D images and in the imaging of 3D objects. Rapid variable focusing or zooming is achieved by rapid and repeated change of the object distance or the spacing between lens groups of the projection lens or a combination of both. One preferred approach inserts thin wedge prisms into the optical path and changes their positions relative to the optical path. This changes the thickness traveled through by the optical path and results in effective optical path length change. Another approach folds an optical path by mirrors and moves the mirrors to change the optical path length. For focusing purpose, small and precise displacement is achieved by moving a wedge-shaped optical device obliquely with respect to the optical path. The wedge-shaped optical device can be a thin wedge prism or a mirror on a wedge-shaped base. Optical layout analysis shows that the changes of the object distance, of the spacing between two lens groups and of the image distance are almost in proportion and can be correlated by linear relations. Therefore, the same type of motion function can be used to change these three optical path lengths to achieve focusing and constant magnification.