| 摘要 |
This invention is applicable to display systems, such as in a helmet mounted display or a head-up display, utilizing a holographic lens operating at a relatively large off-axis angle in order to perform the dual function of a combiner glass and an eyepiece. The holographic lens is used in conjunction with more conventional optical elements (lenses, mirrors and prisms) to present a high quality collimated virtual image of an object, such as the face of a cathode ray tube, to an observer. The aberrations inherent in a holographic lens constructed to operate at a large off-axis angle and with a large field of view are corrected both by constructing the holographic lens with aberrated wavefronts and by the optical elements used in conjunction with the holographic lens during playback. Some arrangements of the playback systems of the invention include a relay lens having cylindrical surfaces and tilted and/or decentered elements used to compensate for the axial astigmatism and axial coma in the holographic lens. The holographic lens is constructed with aberrated wavefronts primarily in order to correct a large assymetric variation of astigmatism across the field of view which arises because of a difference in tilt of the two image fields corresponding to the two mutually orthogonal line focal surfaces. The tilts of the two image fields are adjusted relative to one another in such a way that they may both be matched by a single tilt of the object surface. |
