NON-FT PLANE ANGULAR FILTERS
Non-Fourier Transform (FT) plane angular filters and their use in holographic storage systems or devices for angular filtering of a data beam prior to recording holographic data or for angular filtering of a recovered beam prior to detecting the recovered holographic data. The non-FT plane filters may be a macrotube array, an etalon, a multi-layer thin film interference coating on a curved surface, a lenslet array device, a waveguide-like array, or a combination thereof. Also provided are methods for carrying out angular filtering using such filters for data storage and/or data recovery.
1 . A holographic storage system or device comprising:
one or more of:
a data beam source for generating a data beam or
a recovered beam source for generating a recovered beam comprising holographic data recorded in a holographic storage medium;
a non-Fourier Transform plane angular filter for carrying out on or more of:
angular filtering of the data beam prior to recording holographic data in a holographic storage medium or
angular filtering of the recovered beam prior to detecting the recovered holographic data by a detector;
wherein the non-Fourier Transform plane angular filter comprises a macrotube array, an etalon, a multi-layer thin film interference coating on a curved surface, a lenslet array device, a waveguide-like array, or a combination thereof.
2 . The system or device of claim 1 , wherein the non-Fourier Transform plane angular filter comprises a macrotube array.
3 . The system or device of claim 2 , wherein the macrotube array comprises macrotubes etched in silicon.
4 . The system or device of claim 1 , wherein the non-Fourier Transform plane angular filter comprises an etalon at the image plane.
5 . The system or device of claim 1 , wherein the non-Fourier Transform plane angular filter comprises a multi-layer thin film interference coating on a curved surface.
6 . The system or device of claim 5 , wherein the interference coating comprises from about 1 to about 40 layers of a dielectric material.
7 . The system or device of claim 5 , wherein the interference coating includes a patterned surface.
8 . The system or device of claim 6 , wherein the interference coating is on the curved surface of a lens.
9 . The system or device of claim 8 , wherein the lens is an objective lens.
10 . The system or device of claim 1 , wherein the non-Fourier Transform plane angular filter comprises a lenslet array device.
11 . The system or device of claim 10 , wherein the lenslet array device comprises a lenslet array imaging assembly wherein each lenslet of the lenslet array focuses incident rays: (a) onto a light-absorptive coating surrounding an array of apertures, wherein incident rays having a small enough angle of incidence pass through the apertures, and wherein incident rays having an angle of incidence which is too large are filtered out by the absorptive coating; or (b) through incident ray focusing tubes having spaced apart light-absorbing walls, wherein the tubes are long enough so that incident rays having a small enough angle of incidence pass through the tubes, while incident rays having an angle of incidence which is too large are filtered out by the tubes.
12 . The system or device of claim 1 , wherein the non-Fourier Transform plane angular filter comprises a waveguide-like array.
13 . The system or device of claim 12 , wherein the waveguide-like array comprises a fiber optic faceplate comprising a plurality of optical fibers, each of the optical fibers having a light-absorbing outer layer.
14 . A method for recording holographic data comprising the following the steps:
(a) providing a data beam; and
(b) passing the data beam through a non-Fourier Transform plane angular filter to carry out angular filtering of the data beam prior to recording holographic data in a holographic storage medium, wherein the non-Fourier Transform plane angular filter comprises: a macrotube array, an etalon, a multi-layer thin film interference coating on a curved surface, a lenslet array device, a waveguide-like array, or a combination thereof.
15 . The method of claim 14 , wherein the non-Fourier Transform plane angular filter is located in the image space, and wherein the non-Fourier Transform plane angular filter limits the angular bandwidth emitted by a pixel element of a spatial light modulator.
16 . The method of claim 14 , which comprises the further step of multiplexing the holographic data into the holographic storage medium after angular filtering of the data beam during step (b).
17 . The method of claim 14 , wherein the holographic data is multiplexed by angle multiplexing, polytopic multiplexing, or angle-polytopic multiplexing.
18 . A method for recovering holographic data comprising the following steps:
(a) providing a recovered beam comprising recovered holographic data; and
(b) passing the recovered beam through a non-Fourier Transform plane angular filter to carry out angular filtering of the recovered beam prior to detecting the recovered holographic data by a detector, wherein the non-Fourier Transform plane angular filter comprises: a macrotube array, an etalon, a multi-layer thin film interference coating on a curved surface, a lenslet array device, a waveguide-like array or a combination thereof.
19 . The method of claim 18 , wherein the non-Fourier Transform plane angular filter is located in the image space, and wherein the non-Fourier Transform plane angular filter limits the angular bandwidth accepted into a pixel element of a detector.
20 . The method of claim 18 , wherein the recovered beam of step (a) is generated by phase conjugate reconstruction.
21 . The method of claim 18 , wherein the recovered beam of step (a) is generated by recovering multiplexed holographic data from the holographic storage medium.