Optical display systems utilizing holographic lenses
First Claim
1. A display system having a holographic lens constructed with two coherent sources located relatively close to entrance and exit pupils thereof, and which deviates the axial ray coming from an object surface through an off-axis angle into an exit pupil and which has a focal surface with axial coma and axial astigmatism, said display system havingfirst means along said axial ray between said object surface and said holographic lens to compensate said axial coma, andsecond means along said axial ray between said object surface and said holographic lens to compensate said axial astigmatism.
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Abstract
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.
The invention herein described was made in the course of or under a Contract or Subcontract thereunder with the Department of the Air Force.
282 Citations
25 Claims
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1. A display system having a holographic lens constructed with two coherent sources located relatively close to entrance and exit pupils thereof, and which deviates the axial ray coming from an object surface through an off-axis angle into an exit pupil and which has a focal surface with axial coma and axial astigmatism, said display system having
first means along said axial ray between said object surface and said holographic lens to compensate said axial coma, and second means along said axial ray between said object surface and said holographic lens to compensate said axial astigmatism.
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12. Holographic lens construction apparatus used to construct a reflective holographic lens with aberrated wavefronts in order to compensate for the variation of astigmatism across the field of view which otherwise arises because the two focal surfaces of said holographic lens would be incorrectly tilted relative to one another, said holographic lens construction optics comprising
a holographic lens recording material on a substrate, a source of a first laser wavefront incident on said holographic lens recording material, which is divergent from a point source located close to the desired exit pupil of the holographic lens, and is aberrated by passing through tilted cylindrical lenses, and a source of a second laser wavefront incident on said holographic lens recording material from the opposite side as the first laser wavefront, and which is coherent with the first wavefront, is convergent on a point close to the desired entrance pupil of said holographic lens and is aberrated by passing through tilted cylindrical lenses.
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17. Holographic lens construction apparatus used to construct a reflective holographic lens with aberrated wavefronts in order to compensate for the variation of astigmatism across the field of view which otherwise arises because the two focal surfaces of said holographic lens would be incorrectly tilted relative to one another, said holographic lens construction apparatus comprising
first and second tilted cylindrical lenses, a holographic lens recording material on a substrate, a source of a first laser wavefront incident on said holographic lens recording material, which is divergent from a point source located close to the desired exit pupil of the holographic lens, and is aberrated by passing through said first tilted cylindrical lens, and a source of a second laser wavefront incident on said holographic lens recording material from the opposite side as the first laser wavefront, and which is coherent with the first wavefront, is convergent on a point close to the desired entrance pupil of said holographic lens, and is aberrated by passing through said second tilted cylindrical lens.
Specification