Optical beamformers

• US 4,862,115 A
• Filed: 02/12/1988
• Issued: 08/29/1989
• Est. Priority Date: 02/12/1988
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Athale, Ravindra A., Rolsma, Peter B., Lee, John N.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US07/155,434
• Time in Patent Office: 564 Days
• Field of Search: 332/7.51, 367/61, 367/122-124, 367/129, 364/822
• US Class Current: 359/1
• CPC Class Codes: G01V 1/28 Processing seismic data, e.g. for interpretation or for event detection G01V1/48 takes precedence
• CPC Class Codes: G06E 3/00 Devices not provided for in group G06E1/00, e.g. for processing analogue or hybrid data

Abstract

Disclosed as a beamforming system, particularly useful for seismic exploration or undersea surveillance, in which data processing of the system is done optically. Sensor outputs are subjected to plural sets of time delays, and the system beams formed optically. Four embodiments are presented of the optical processing hardware.

Claims

1. A beamforming system effective to form one or more distinct system beams, said system comprising:

a plurality of sensors;

means for storing outputs of said sensors, said means for storing comprising means for transducing said outputs into a plurality of optical outputs;

means for summing one or more preselected subsets of said optical outputs into said one or more distinct system beams, said one or more preselected subsets corresponding to said one or more distinct system beams;

wherein said means for storing is effective to delay each output of each subset of said one or more subsets for a time greater than or zero;

wherein;

said system comprises a means for supplying a clocking signal to said means for storing;

said means for summing comprises a means for detection of said one or more distinct system beams;

said means for storing comprises one or more pluralities of cell means for storing said one or more preselected subsets, said one or more pluralities of cell means corresponding to said one or more distinct system beams;

each plurality of said one or more pluralities of cell means having as many as n of cell means denominated by integers 1 through n, respectively, and wherein;

for i being an integer between 1 and n inclusive, for cell means number 2 through n of said each plurality of cell means, the ith cell means is adapted to transfer any signal stored in said ith cell means to the (ith-1) cell means responsive to the presence of said clocking signal; and

for i=1, the 1st cell means of said each plurality of cell means is adapted to transfer any signal in said 1st cell means to said means for detection, said means for detection being effective to cause detection of each said one or more distinct system beams responsive to said clocking signal.

2. The system of claim 1, wherein said each plurality of said one or more pluralities of cell means is a charge coupled device, and said plurality of cell means of each said charge coupled device is plurality of charge holding cells.

3. The system of claim 2, wherein said means for storing comprises a plurality of fiber optic connections effective to store said one or more preselected subsets in preselected ones of said charge holding cells.

4. The system of claim 2, wherein said means for storing comprises:

a first lens;

a holographic mask comprising a plurality of portions, each of said portion having a pre-selected holographic grating frequency; and

a second lens;

wherein

said first lens is effective to image each of said plurality of optical outputs onto said holographic mask;

said first lens and said portions of said holographic mask are adapted to co-operate effectively to direct said one or more preselected subsets onto preselected portions of said second lens, said preselected portions of said second lens are effective to focus each said one or more subsets of said plurality of optical outputs onto a corresponding one of said one or more charge coupled devices;

said preselected portions of said second lens are further effective to focus each optical output of each said subset onto preselected ones of said charge holding cells, each of said charge holding cells being adapted to store a charge proportional to the sum of all optical outputs focused on said each of charge holding cells.

5. A beamforming system effective to form one or more distinct system beams, said system comprising:

a plurality of sensors;

means for storing outputs of said sensors, said means for storing comprising means for transducing said outputs into a plurality of optical outputs;

means for summing one or more preselected subsets of said optical outputs into said one or more distinct system beams, and one or more preselected subsets corresponding to said one or more distinct system beams;

wherein said means for storing is effective to delay each output of each subset of said one or more subsets for a time greater than or equal to zero;

wherein said means for storing comprises;

an array of light valves;

means for imaging said plurality of optical outputs onto said array of light valves;

means for selectively opening each valve of said array of light valves effective to permit said plurality of optical outputs to pass through said array of light valves;

wherein said means for storing further comprises a means for separating said plurality of optical outputs passes by said light valves into said subsets, said means for summing being effective to form said one or more distinct system beams responsive to said means for separating;

wherein said array of light valves is a liquid crystal television display, said means for transducing is a light modulator and said means for storing comprises;

means for generating periodic clock signals;

first and second lenses, said second lens being said means for separating;

an array of shift registers having an input and output, said array of shift registers being effective to store a plurality of data vectors, said shift registers being effective to shift each vector of said plurality of data vectors on register towards said output from said input responsive to the presence of each clock signal of said periodic clock signals, the data vector in said output being lost responsive to said presence of said each clock signals;

means for sampling the outputs of said plurality of sensors responsive to said presence of said each clock signal effective to form a data vector of the sampled outputs, said data vector of said sampled outputs being input into said input of said array of said shift registers;

wherein said light modulator is effective, between consecutive signals of said periodic clock signals, to;

sequentially map each data vector in said array of shift registers into said light modulator effective to transducer said each data vector into an optical data vector, all such optical data vectors constituting said plurality of optical outputs; and

said first lens is effective to image said each optical data vector onto said liquid crystal television display.

6. A beamforming system effective to form one or more distinct system beams, said system comprising:

a plurality of sensors;

means for storing outputs of said sensors, said means for storing comprising means for transducing said outputs into a plurality of optical outputs;

means for summing one or more preselected subsets of said optical outputs into said one or more distinct system beams, said one or more preselected subsets corresponding to said one or more distinct system beams;

wherein said means for storing is effective to delay each output of each subset of said one or more subsets for a time greater than or equal to zero;

wherein said means for storing comprises a Bragg cell, said Bragg cell being effective to support, responsive to said sensors, a plurality of signals propagating across said bragg cell, said Bragg cell constituting said means for transducing and being effective to transducer said plurality of signals propagating across said Bragg cell into said plurality of optical outputs.

7. The system of claim 8, wherein said means for summing is one or more optical summers corresponding to said one or more distinct system beams, and said means for storing comprises:

a holographic mask having a plurality of portions, each of said portions having a preselected grating frequency; and

a first and a second lens;

wherein

said first lens is effective to image said plurality of optical outputs of said Bragg cell onto preselected ones of said portions of said holographic mask;

said portions of said holographic mask are effective to redirect said plurality of optical outputs onto preselected portions of said second lens;

said second lens is adapted to focus said one or more subsets onto corresponding ones of said one or more optical summers effective to form said one or more distinct system beams.