Reconfigurable optical interconnections via dynamic computer-generated holograms

• US 5,539,543 A
• Filed: 01/27/1994
• Issued: 07/23/1996
• Est. Priority Date: 01/27/1994
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Zhou, Shaomin, Liu, Hua-Kuang
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): Schuberg, Darren E.
• Application Number:
  US08/192,476
• Time in Patent Office: 908 Days
• Field of Search: 359/9, 359/11, 359/15, 359/21, 359/22, 359/298, 359/320, 365/64, 382/31, 395/25
• US Class Current: 359/15
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 1/0005 Adaptation of holography to specific applications holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2225/32 Phase only
• CPC Class Codes: G06E 3/006 Interconnection networks, e.g. for shuffling

Abstract

A system for optically providing one-to-many irregular interconnections, and strength-adjustable many-to-many irregular interconnections which may be provided with strengths (weights) w_ij using multiple laser beams which address multiple holograms and means for combining the beams modified by the holograms to form multiple interconnections, such as a cross-bar switching network. The optical means for interconnection is based on entering a series of complex computer-generated holograms on an electrically addressed spatial light modulator for real-time reconfigurations, thus providing flexibility for interconnection networks for large-scale practical use. By employing multiple sources and holograms, the number of interconnection patterns achieved is increased greatly.

Claims

1. A system for providing dynamically programable optical interconnections comprising

a spatial light modulator having a K₁ ×

K₁ array of areas of transmittance pixels, said pixels of each area being adapted to separately modify transmittance of light through each pixel thereof in response to a plurality of separate subholograms defined by a pattern of electrical signals, one subhologram for each area of said K₁ ×

K₁ array,

means for producing a plurality of parallel light beams, including a single source of light and a multiple beam splitter for producing said plurality of parallel light beams, one light beam for each of a plurality of areas of said spatial light modulator, each area having a separate array of pixels, each light beam illuminating for transmittance a separate one of said K₁ ×

K₁ areas of said spatial light modulator, and

an array of light detectors positioned to receive said light beams transmitted through said K₁ ×

K₁ areas of said spatial light modulator, whereby light detected at each of said light detectors provides conduction in response to light received, thereby providing many irregular interconnections in response to a plurality of light beams in patterns determined by said plurality of subholograms,

a computer for generating said plurality of subholograms for producing rapid reconfigurable interconnections at said array of light detectors, and

a binary spatial light filter positioned in the path of light through said spatial light modulator to impose a pattern of pixel spots of no light transmitted through said spatial light modulator, thereby increasing the number of patterns of irregular interconnections producible at said array of detectors.

2. A system for providing dynamically programmable optical interconnections comprising

a spatial light modulator having a K₁ ×

K₁ array of areas of transmittance pixels, said pixels of each area being adapted to separately modify transmittance of light through each pixel thereof in response to a plurality of separate subholograms defined by a pattern of electrical signals, one subhologram for each area of said K₁ ×

K₁ array,

means for producing a plurality of parallel light beams, each light beam illuminating for transmittance a separate one of said K₁ ×

K₁ areas of said spatial light modulator, and

an array of light detectors positioned to receive said light beams transmitted through said K₁ ×

K₁ areas of said spatial light modulator, whereby light detected at each of said light detectors provides conduction in response to light received, thereby providing many irregular interconnections in response to a plurality of light beams in patterns determined by said plurality of subholograms,

a computer for generating said plurality of subholograms for producing rapid reconfigurable interconnections at said array of light detectors,

a plurality of different columns of cells in said spatial light modulator, each column of cells receiving a separate computer generated subhologram, and including

a plurality of sources of light, s_i,

means for extending and collimating in one direction each of said sources of light to illuminate corresponding ones of said plurality of columns of pixels in said spatial light modulator,

means for recombining light transmitted by said plurality of columns of pixels to produce a plurality of individual beams, one beam for each row, and

said array of detectors comprises a column of detectors, d_j, one for each of said individual beams,

thereby producing from each detector an interconnection, the strength of conduction of each interconnection of each N detectors being equal to ##EQU10## whereby each column of cells in said spatial light modulator receives a separate computer generated subhologram to generate 1×

j(j=0,1, . . . N-1) beams transmitted to 1×

j=(j=0,1, . . . N-1) detectors in response to i×

i=(i=0,1, . . . N-1) sources of light and w_ji is the j^ith element of an interconnection weight matrix determined by said computer generated subholograms, thereby providing weighted interconnections at said detectors.

3. A system for providing dynamically programmable optical interconnections comprising

a spatial light modulator having a K₁ ×

K₁ array of areas of transmittance pixels, said pixels of each area being adapted to separately modify transmittance of light through each pixel thereof in response to a plurality of separate subholograms defined by a pattern of electrical signals, one subhologram for each area of said K₁ ×

K₁ array,

means for producing a plurality of parallel light beams, each light beam illuminating for transmittance a separate one of said K₁ ×

K₁ areas of said spatial light modulator, and

an array of light detectors positioned to receive said light beams transmitted through said K₁ ×

K₁ areas of said spatial light modulator, whereby light detected at each of said light detectors provides conduction in response to light received, thereby providing many irregular interconnections in response to a plurality of light beams in patterns determined by said plurality of subholograms, including a plurality of cascaded spatial light modulators between said light sources and said detectors for providing multistage crossover interconnections, wherein the light beams of each spatial light modulator become the sources of light beams for the next spatial light modulator in cascade, and the j^th output permutation of the power of the crossover is represented by

space="preserve" listing-type="equation">d.sub.j.sup.(1) =s.sub.j +s.sub.N-1-j

for the first stage where the stage number is denoted by the superscript in parenthesis, and N must be an integral power of two, wherein the output of the first stage is used as input to the second stage the permutation of the second stage output d_j.sup.(2) may be written as ##EQU11## and so forth to the permutation of the last stage.