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Process for holography involving tilt compensation
| Details |
Inventors: Curtis, Kevin Richard; Tackitt, Michael C;
Assignee: Lucent Technologies Inc. (Murray Hill, NJ)
Primary Examiner: Henry; Jon
Assistant Examiner:
Attorney, Agent or Firm:
The invention involves a holographic system containing a photopolymer-type storage medium located in the system's optical path, where the medium is rotated around a first axis such that the surface of the medium is in a non-orthogonal relationship with the optical path, and a spatial light modulator also located in the optical path, where the modulator is rotated around a second axis that is substantially orthogonal to the first axis, and wherein the surface of the modulator is in a non-orthogonal relationship with the optical path. This arrangement compensates for at least a portion of aberration introduced by the photopolymer media, thereby allowing presentation of a flatter, more focused, and less distorted image at the sensor. |
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DETAILED DESCRIPTION The invention provides a process and apparatus for holography in which aberrations introduced by storage media, particularly photopolymer-type media, are substantially reduced.
Specifically, as reflected in FIG.
3, photopolymer-type media 56 are generally placed at an angle to the optical path 64 in a holographic system, in order to reduce the effects of writing-induced shrinkage.
This angular placement, however, introduces aberrations into the relayed image of the system, including astigmatic aberration, i.
e.
, a tilt in the plane of focus 62.
This tilt causes the page of data to match up poorly to the plane of the sensor 60, thereby affecting the accuracy of read-out.
It has been discovered, however, that it is possible to compensate for at least a portion of such aberration by introducing an orthogonal tilt in the spatial light modulator, as shown in FIG.
4.
The rotation of the SLM 70 creates a similar aberration in the plane orthogonal to the plane tilted by the medium, and thereby makes the data page come into a sharper focus over the entire page.
This effect allows presentation of a flatter, more focused, and less distorted image 80 at the sensor 82, and leads to better matching of each encoded pixel to its target pixel.
The invention therefore involves a holographic system containing (a) a storage medium (74) located in the system's optical path (84), where the medium is rotated around a first axis (76) such that the surface of the medium is in a non-orthogonal relationship with the optical path, and (b) a spatial light modulator (70) also located in the optical path, where the modulator is rotated around a second axis (72) that is substantially orthogonal to the first axis, and wherein the surface of the modulator is in a non-orthogonal relationship with the optical path.
(Optical path indicates a path from the spatial light modulator through the medium and onto the sensor, and is also referred to in the art as the central ray.
) The invention is particularly useful for 4F imaging systems
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Optical Systems 
