Apparatus and method for generating diffractive element using liquid crystal display

An apparatus for accepting an electromagnetic radiation from an external radiation source and for generating an interference pattern from physical wave interference of components of said radiation at an output plane;

• said apparatus comprising:
• a control receiving said radiation beam for selectively passing or blocking passage of said received electromagnetic radiation beam;
• a spatial filter receiving said radiation beam and generating an output beam of said radiation having a spatial frequency content;
• a liquid crystal display (LCD) panel having a two-dimensional array of addressable pixel elements for dynamically and in substantially real-time receiving a first plurality of data sets from an external data source and for presenting said data sets in a two dimensional array of picture elements, said output beam simultaneously impinging on each one of picture elements in said array of pixel elements;
• a display controller for receiving said data stream comprising data values for each pixel and for generating pixel drive signals at each said addressable pixel location to produce a pixel optical characteristic at said location corresponding to said data values;
• each said data set including a second plurality of data values associated with a corresponding second plurality of spatial locations at which each said data value is displayed, each said displayed data value presenting an optical characteristic related to said corresponding data value in the path of said selectively passed electromagnetic radiation beam,
• a diffraction grating rotatably mounted in said radiation beam for optically processing said beam prior to said beam impinging on said display means, said diffraction grating causing diffraction of said radiation beam into at least one diffracted beam;
• means coupled to said computer and to said rotatably mounted grating for controllably rotating said grating in a predetermined manner;
• optical means for simultaneously receiving said at least one diffracted beam and for redirecting said at least one diffracted beam to overlap with any other order of diffracted beam including with a zeroth order beam in said output plane and for forming a real image of said display means at said output plane, said simultaneous overlap resulting in the formation of a set of interference fringes over a predetermined spatial region of said output plane, the spatial frequency being related to relative phase difference between said overlapping beams;
• recording means for recording said real image of said display means and said interference fringes over said predetermined region;
• and
• composite image generation means for generating a mosaic of a plurality of recorded interference fringes, said composite image generation means including composite control means for dynamically altering said data set communicated to said display means, and positioning means for changing the location at which said interference fringes are recorded for each said data set.

An optical diffraction element for forming a real image composed of interference fringes at an output plane, said diffractive element comprising:

• a memory for storing a data set representative of a two dimensional optical diffraction pattern;
• a display controller coupled to said memory for receiving said stored data set and for translating said received data set into a plurality of drive signals;
• a liquid crystal display panel for receiving said drive signals and for displaying said representation of said diffraction pattern as discernable optical characteristic variation values;
• and
• optical means directing an input illumination beam to an input face of said liquid crystal display and receiving an output of said liquid crystal display including output components diffracted by said liquid crystal display panel and generating a real image from at least selected spatial frequency components of said liquid crystal display panel and said spatial filter components creating said interference fringes at said output plane.

A recording system, said system comprising:

• a two-dimensional display displaying a data set representing a two-dimensional diffractive pattern wherein said diffractive pattern is displayed as variations in optical characteristics in a two-dimensional array;
• a first optical system receiving an external radiation beam and presenting said radiation beam to said two-dimensional display;
• a second optical system receiving a plurality of output beams from said two-dimensional display including at least one diffracted beam and selectively passing components of said output to form interference fringes in a real-image of at least a portion of said two-dimensional display at a recording plane;
• recording means for receiving and recording said interference fringes and said real image at said recording plane.

A system for recording a diffractive element, said system comprising:

• a computer for generating a data set representative of a diffractive pattern;
• display means coupled to said computer for receiving said data set and for displaying said data set as said diffractive pattern as optical characteristics in a two-dimensional array;
• a radiation source for generating a radiation beam;
• first optical system means for processing said radiation beam output by said source and for presenting said processed beam to said display means;
• second optical system means for receiving an output from said display means and for selectively passing components of said display output and forming a real-image at an output plane;
• detection means for receiving said radiation at said output plane and for detecting said real-image of the interference pattern formed at said output plane;
• and
• said display means further comprising an LCD configured to display a graphic element for dynamically adding two-dimensional image information to a diffracted beam.

A method for recording a diffractive element;

• said method comprising:
• (A) generating a first data set representative of a first two-dimensional diffraction grating having predetermined first diffraction characteristics;
• (B) communicating said first data set to a LCD display to cause presentation of said two-dimensional diffraction grating representation as optical characteristic variations on said LCD;
• (C) allowing a beam of radiation to impinge on said LCD in a predetermined manner for a predetermined period of time such that said incident beam is diffracted by said LCD diffraction pattern;
• (D) optically imaging said LCD at an output focal plane;
• (E) optically collecting and redirecting selected components of said diffracted radiation to overlap and generate interference fringes at said output focal plane;
• and
• (F) recording said interference fringes at said output focal plane to form said diffractive element.

An apparatus for accepting an electromagnetic radiation from an external radiation source and for generating an interference pattern at an output plane;

• said apparatus comprising:
• an LCD display for dynamically receiving a first plurality of data sets from an external data source and for presenting said data sets in a two-dimensional array, each said data set including a plurality of data values associated with a corresponding plurality of spatial locations at which each said data value is displayed, each said displayed data value resulting in the presentation of an optical characteristic in the path of said electromagnetic radiation beam,
• at least one of said first plurality of data sets including data values such that said two-dimensional array of optical characteristic variation causes output a plurality of beams including diffraction of said radiation beam into at least one diffracted beam;
• a optical system for simultaneously receiving at least two of said beams and for redirecting said at least two beams to simultaneously overlap at said output plane and for forming a real image of said LCD display at said output plane, said simultaneous overlap resulting in the formation of a set of interference fringes at locations in said real image;
• recording means for recording said real image of said display means and said interference fringes;
• said LCD display is reimaged at said output plane by a factor of between about 50:1 and about 1:1000.

A recording system, said system comprising:

• a two-dimensional LCD displaying a data set representing a two-dimensional pattern wherein said pattern is displayed as variations in optical density in a two-dimensional array;
• a diffraction grating rotatably mounted to a rotation means adjacent to said LCD, said LCD configured to display at least one of a plurality of 2-dimensional selector images as said two-dimensional pattern;
• a first optical system receiving an external radiation beam and presenting said radiation beam to said diffraction grating;
• a second optical system receiving a plurality of output beams from said two-dimensional LCD including at least one diffracted beam and selectively passing components of said output to form interference fringes in a real-image of at least a portion of said two-dimensional display at a recording plane;
• recording means for receiving and recording said interference fringes and said real image at said recording plane;
• first rotation control means for driving said rotation means to a selected angular position chosen from a plurality of addressable angular position;
• second control means for coupling and controlling the angular position of said diffraction grating with a particular one of said selector images so that said selector image provides a mask for the selective passage and exposure of selected orientations of said diffraction grating through said low density regions of said selector image displayed on said LCD at said output plane;
• said rotation means being operatively coupled to said LCD so that by rotating said diffraction grating though a multiplicity of angular orientations corresponding to particular ones of said selector images, a composite output image is built up over a multiplicity of exposures;
• said first and said second optical means being configured such that each exposure provides a large LCD footprint at an output focal plane.

A holographic recording apparatus for generating an interference pattern from interference of components of an incident electromagnetic radiation beam received from an external radiation source, said apparatus comprising:

• a display for displaying a two-dimensional array of data values, each said data value causing said display to present an optical characteristic to a portion of said incident radiation beam, at least a first plurality of said data values causing generation of a first diffracted radiation and a second plurality of said data values simultaneously causing generation of a second diffracted or undiffracted radiation, said second diffracted or undiffracted radiation differing from said first diffracted radiation in having either a different diffracted spatial frequency angle or a different diffracted spatial frequency magnitude or both;
• a spatial frequency selective optical component receiving said first and second radiation and selectively passing predetermined components of said first and second radiation and selectively blocking other components of said first and second radiation;
• an optical system reimaging said display at said output plane and redirecting said selectively passed radiation to overlap within an area bounded by said reimaged display in said output plane, said overlap resulting in the formation of a set of interference fringes in said output plane related to relative phase difference between said overlapping radiation over a predetermined spatial region;
• and
• recording means for recording said interference fringes in said real image of said display.

A method of forming a holographic diffraction pattern on a recording medium, said method comprising:

• (a) providing a two-dimensional array of data values from an external data source;
• (b) displaying said array of data values on an LCD display, each said displayed data value presenting an optical characteristic to a portion of an incident radiation, at least some of said displayed data values causing a diffractive pattern to be displayed on said LCD;
• (c) irradiating said LCD display with a beam of incident coherent electromagnetic radiation, at least a first plurality of said data values causing generation of a first diffracted radiation and a second plurality of said data values simultaneously causing generation of a second diffracted or undiffracted radiation, said second diffracted or undiffracted radiation differing from said first diffracted radiation in having either a different diffracted spatial frequency angle or a different diffracted spatial frequency magnitude or both;
• (d) selectively passing predetermined components of said first and second radiation and selectively blocking other components of said first and second radiation;
• (e) forming a real-image of said LCD display at a reduced magnification on said recording medium, such real image formation causing redirection of said selectively passed radiation to overlap within an area bounded by said real-image on said recording medium, said overlap resulting in the formation of a set of interference fringes related to relative phase difference between said overlapping radiation within said real image of said liquid crystal display panel;
• (f) recording said interference fringes;
• and
• (g) repeating steps (a)-(f) a plurality of times to record a mosaic of said interference fringes on different regions of said recording medium to define a holographic diffraction pattern thereon.

An apparatus for accepting an electromagnetic radiation from an external radiation source and for generating an interference pattern from wave interference of components of said radiation at an output recording plane;

• said apparatus comprising:
• display means for dynamically receiving a first plurality of data sets from an external data source and for presenting said data sets in a two dimensional data element array, and for receiving an incident radiation beam;
• each said data set including a plurality of data values associated with a corresponding plurality of spatial locations at which each said data value is displayed, each said displayed data value presenting an optical characteristic related to said corresponding data value in the path of said selectively passed radiation beam,
• at least one of said first plurality of data sets including data values such that said two-dimensional array of optical characteristic variation causes diffraction of said radiation beam into at least one diffracted beam having a particular diffracted angle relative to a plane of said display means and spatial frequency components associated with said or each diffracted beam;
• mask filter means receiving said or each diffracted beam and selectively passing a first predetermined one or ones of said beam or beams and selectively blocking second one or ones of said beams different from said first one or ones;
• optical means for reimaging said display means as a real image at said output plane and simultaneously redirecting said first beams to overlap within a region bounded by said real image in said output plane, said simultaneous overlap resulting in the formation of a set of interference fringes within said region bounded by said real image related to relative phase difference between said overlapping beams;
• recording means for recording said interference fringes;
• and
• composite image generation means for generating a mosaic of a plurality of said sets of recorded interference fringes, said composite image generation means including composite control means for dynamically altering said data set communicated to said display means, and positioning means for changing the location at which said interference fringes are recorded for each said data set.

A recording device for recording at least one holographic element on a recording media, said device being of the type receiving coherent radiation from a radiation source, and having a controller for controlling exposure of said recording media, and a diffractive element for generating a plurality of diffracted radiation beams from said radiation, said recording device characterized in that:

• said diffraction element comprises a liquid crystal display (LCD) simultaneously displaying within a two-dimensional array of pixels a first region generating a diffractive sub-element and a second region generating another sub-element different from said first region;
• said coherent radiation being directed toward said LCD from said radiation source to simultaneously intersect each of said first and second regions, said first region diffractive sub-element dividing the portion of said radiation incident thereupon into at least two output beams by diffraction;
• and
• an optical element for redirecting said at least two output beams to overlap as a real-image of said diffraction element at an output plane substantially coincident with a location of said recording media.

A system for recording a diffractive element, said system comprising:

• a liquid crystal display presenting two-dimensional data representing an optical diffractive pattern, said optical diffraction pattern generating a plurality of output beams when illuminated by an incident illumination beam;
• an optical system receiving at least some of said plurality of output beams and generating a real image of at least a portion of said liquid crystal display at an output image plane;
• and
• said plurality of output beams generating an interference pattern within and coincident with said real image of said at least a portion of said liquid crystal display.

A system for recording a diffractive element, said system comprising:

• a liquid crystal display presenting two-dimensional data;
• a diffraction grating having a grating spatial frequency and rotatable about an axis aligned substantially perpendicular to the plane of said liquid crystal display, said diffraction grating generating a plurality of diffracted beams when illuminated by an external illumination source;
• said plurality of diffracted beams being directed to impinge on said liquid crystal display;
• said two-dimensional data defining a masked portion and an unmasked portion of said liquid crystal display, said unmasked portion transmitting said impinging diffracted beams incident thereupon and said masked portion not transmitting said impinging diffracted beams;
• an optical system receiving at least some of said plurality of diffracted beams and generating a real image of said unmasked portion of said liquid crystal display at an output image plane;
• said plurality of diffracted beams generating an interference pattern within and coincident with said real image of said at least a portion of said liquid crystal display.

A method for producing a document having a multi-level security authentication feature thereupon, wherein said multi-level security authentication feature includes a diffractive component and a non-diffractive text portion embedded within said diffractive portion;

• said method comprising:
• displaying a two-dimensional data set as a pattern on a liquid crystal display having an outer boundary, a diffractive region creating a diffractive optical characteristic when illuminated by light, and a non-diffractive region not generating a diffractive optical characteristic when illuminated by light;
• illuminating said liquid crystal display with a converging beam of light;
• imaging selected spatial frequency components of said liquid crystal display onto a recording medium at a demagnified scale to reproduce a real image representation of said outer boundary and a real image representation of at least an outline of said non-diffractive region displayed on said display;
• generating interference fringes from physical wave interference of light diffracted by said illuminating of said diffractive region, said interference fringes being generated within said outer boundary and in areas corresponding to said diffractive region of said liquid crystal display;
• recording said real image representation and said interference fringes on a recording medium.