Spatial light modulation with application to electronically generated holography

Apparatus for converting a holographic interference pattern to electrical signals comprising:

• first and second supports spaced a predetermined distance apart, said first support having a surface positionable to receive said interference pattern;
• a first array of parallel, electrically conductive electrodes supported in a first predetermined orientation from said first support;
• a second array of parallel, electrically conductive electrodes supported in a second predetermined orientation to define with said first array of electrodes a matrix of spaced electrode crossing locations;
• a normally opaque, dipolar electro-optical medium, transmissive in the presence of an applied electric field, positioned intermediate said first and second supports;
• control means electrically coupled with said first and second electrode arrays for sampling said matrix of locations by applying an electric field of predetermined value between selected pairs of electrodes within said first and second arrays thereof;
• means adjacent each said electrode crossing location for dissipating laterally disposed flux components of a said applied electrical field;
• and
• detecting means adjacent said second support for deriving electrical output signals corresponding with the intensity of said interference pattern at a said sampled matrix locations.

Apparatus for generating a hologram in response to holographic data derived as a sequence of electrical data signals, said data signals corresponding with the intensities of an interference pattern sampled in the scan of a matrix of uniform discrete apertures adjacent said pattern, comprising:

• first and second spaced planar supports;
• a first array of electrically conductive electrodes supported in a first predetermined orientation adjacent said first transparent support;
• a second array of electrically conductive electrodes supported in a second predetermined orientation by said second support to define with said first array of electrodes a matrix of electrode crossing locations;
• a normally opaque medium intermediate said first and second supports having a suspension of dipolar particles normally randomly dispersed therein, said particles being movable into alignment with an applied electric field of at least a threshold value to effect a transmissive condition of said medium;
• field restriction means adjacent each said electrode crossing location for dissipating flux components of a said applied electric field laterally extensible from said crossing locations;
• a first transparent, electrically conductive latching electrode adjacent said first support;
• a second transparent, electrically conductive latching electrode adjacent said second support;
• and
• control means electrically coupled with said first and second electrode arrays, responsive to said data signals for generating an electrical field of value corresponding with said data signals between electrodes of said first and second arrays at said crossing locations and for generating a latching electrical field intermediate said first and second latching electrodes having a field strength value selected below said threshold value for effecting a retention of a pre-existing said particle alignment by said threshold value electric field.

A system for constructing, transmitting and reconstructing holographs of an object comprising:

• means for providing a coherent source of light of predetermined wavelength characteristic;
• means for illuminating said object with said coherent source of light;
• means for providing a reference beam of a said coherent source of light;
• first and second substantially planar supports spaced a predetermined distance apart, said first support having a transparent receiving surface for receiving light reflecting from said illuminated object, and simultaneously, from said reference beam to form an interference pattern;
• a first array of parallel, electrically conductive electrodes supported in a first predetermined orientation by said first support;
• a second array of parallel, electrically conductive electrodes supported in a second predetermined orientation by said second support to define with said first array of electrodes a first matrix of spaced electrode crossing locations;
• a first normally opaque medium intermediate said first and second supports, having a suspension of dipolar particles normally randomly dispersed therein, said particles being movable into alignment with an applied electric field of at least threshold field strength value to effect a transmissive condition of said medium;
• a first electrically conductive layer supported adjacent said first support and having openings therein aligned with said electrode crossing locations;
• a second electrically conductive layer supported adjacent said second support, having openings therein aligned with said electrode crossing locations and being in electrically conductive communication with said first electrically conductive layer;
• first control means electrically coupled with said first and second electrode arrays for sequentially sampling said matrix of locations by generating an electrical field of predetermined value between sequentially selected pairs of electrodes of said first and second arrays and for providing a scanning synchronization signal;
• light responsive detecting means positioned with respect to said second support for deriving an electrical data signal corresponding with the light intensity of said interference pattern at a said sampled matrix location;
• means for conveying said scanning synchronization signals and said data signals;
• third and fourth transparent supports spaced a predetermined distance apart, said third support having a surface positionable for receiving light from a coherent source exhibiting said predetermined wavelength characteristics;
• a third array of parallel, electrically conductive electrodes supported in a third predetermined orientation by said third support;
• a fourth array of parallel, electrically conductive electrodes supported in a fourth predetermined orientation by said fourth transparent support to define with said third array of electrodes a second matrix of spaced electrode crossing locations geometrically corresponding with said first matrix;
• a second normally opaque medium intermediate said third and fourth supports, having a suspension of dipolar particles normally randomly dispersed therein, said particles being movable into alignment with an applied electrical field of at least threshold field strength value to effect a transmissive condition of said medium;
• a third electrically conductive layer supported adjacent said third support and having openings therein aligned with said electrode crossing locations;
• a fourth electrically conductive layer supported adjacent said fourth support, having openings therein aligned with said electrode crossing locations and being in electrically conductive communication with said third electrically conductive layer;
• a first transparent, electrically conductive latching electrode adjacent said third support;
• a second transparent, electrically conductive latching electrode adjacent said fourth support;
• and
• second control means electrically coupled with said third and fourth electrode arrays and said first and second latching electrodes, responsive to said conveyed scanning synchronization signals and said data signals for generating an electrical field of value above said threshold field strength value and corresponding with said data signals between electrodes of said third and fourth arrays at said crossing locations in a sequence regulated by said synchronizing signals and for generating a latching electric field intermediate said first and second latching electrodes having field strength value selected below said threshold value for effecting a retention of a pre-existing said particle alignment.