WAVEFRONT RECONSTRUCTION

• US 3,580,655 A
• Filed: 10/23/1965
• Issued: 05/25/1971
• Est. Priority Date: 04/23/1964
• Status: Expired due to Term

• Current Assignee: Mellon Bank National Association A National Banking Association
• Original Assignee: Emmett N. Leith, Upatnieks Juris
• Inventors: Leith, Emmett N., UPATNIEKS JURIS
• Application Number:
  US04/503,993
• Time in Patent Office: 2,040 Days
• US Class Current: 359/28
• CPC Class Codes: G01B 9/021 using holographic techniques
• CPC Class Codes: G01C 1/00 Measuring angles
• CPC Class Codes: G01S 15/89 for mapping or imaging
• CPC Class Codes: G01V 1/00 Seismology; Seismic or acoustic prospecting or detecting
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 1/00 Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
• CPC Class Codes: G03H 1/20 Copying holograms by holographic , i.e. optical means
• CPC Class Codes: G03H 1/26 Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
• CPC Class Codes: H04N 5/89 using holographic recording H04N5/91 takes precedence
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

This invention is directed to methods and apparatus for capturing various patterns of electromagnetic energy emanating from or as they are transformed after passing through an object and reproducing or reconstructing those patterns in their original configuration to produce images identical in appearance to the object itself.

Claims

1. A method of producing an off-axis hologram comprising the steps of:

a. directing a beam of coherent radiation onto diffusion means to produce a diffused portion and a nondiffused portion of said coherent radiation;

b. transmitting both of the diffused and nondiffused portions through focusing means for focusing only the nondiffused portion of said coherent radiation to a point;

c. positioning an object to receive the diffused portion of said coherent radiation, said object being positioned in a plane that includes the focus point of said nondiffused portion of radiation and to one side thereof so that the radiation emanating from said object as an object-bearing beam and from said focus point as a diverging reference beam are directed along axes angularly displaced to interfere with each other in a plane parallel to said first-named plane; and

d. recording in said plane parallel to said first-named plane the pattern of interference fringes produced by the interference of the radiation emanating from said object and from said focus point.

2. A method of producing an off-axis hologram comprising the steps of:

a. illuminating a partially diffusing means with coherent light concurrently to produce diffused light and nondiffused light;

b. directing both the diffused and nondiffused light to a first lens for focusing only the nondiffused light to a point;

c. positioning an object to receive the diffused light transmitted through said first lens from said partially diffusing means, said object being positioned in a plane that includes the focus point of said first lens and to one side thereof;

d. directing the light emanating from said object as an object-bearing beam and the nondiffused light from said focus point as a diverging reference beam onto a second lens and along axes angularly displaced to interfere with each other in a predetermined plane; and

e. positioning a detector sensitive to light to receive and record the light passing through said second lens from the object and said focus point, said object light and point focus light producing a pattern of interference fringes at said detector.

3. Apparatus for producing an off-axis hologram comprising:

a. a coherent light source for producing an incident beam of light;

b. a partially diffusing plate positioned for illumination on one side thereof by said coherent light concurrently to produce at the other side thereof diffused light and nondiffused light;

c. a first lens positioned to receive both the diffused and the nondiffused light for focusing only the nondiffused light to a point;

d. means for positioning an object to receive the diffused light from said partially diffusing plate, the object being positioned in a plane that includes the focus point of said first lens and to one side thereof;

e. a second lens positioned to receive the light emanating from the object and the diverging beam of nondiffused light from said focus point for direction thereof along axes angularly displaced to interfere with each other in a predetermined plane; and

f. photosensitive recording means positioned to receive a record of the light passing through said second lens from said object and said focus point so that said object light and said point focus liGht produce a pattern of interference fringes at said photosensitive recording means.

4. A method of producing an off-axis hologram according to claim 1 including the step of collimating the radiation from the reference beam prior to its arrival at the recording plane.

5. A method of producing an off-axis hologram and reconstructing one or more images of an object recorded by said off-axis hologram comprising the steps of:

a. directing a beam of coherent radiation onto diffusion means to produce a diffused portion and a nondiffused portion of said coherent radiation;

b. transmitting both of the diffused and nondiffused portions through focusing means for focusing only the nondiffused portion of said coherent radiation to a point;

c. positioning an object to receive the diffused portion of said coherent radiation, said object being positioned in a plane that includes the focus point of said nondiffused portion of radiation and to one side thereof so that the radiation emanating from said object as an object-bearing beam and from said focus point as a diverging reference beam are directed along axes angularly displaced to interfere with each other in a plane parallel to said first-named plane;

d. recording in said plane parallel to said first-named plane the pattern of interference fringes produced by the interference of the radiation emanating from said object and from said focus point;

e. illuminating the hologram with coherent radiation as an illuminating beam, thereby producing at least one image of the object; and

f. detecting said image of the object along an axis displaced from the illuminating beam by an angle corresponding substantially to the angular displacement between the object-bearing beam and the reference beam when said hologram was produced.

6. A method of producing an off-axis hologram according to claim 1 including positioning a light blocking screen in said first-named plane, said screen having a pinhole located at said focus point for blocking the remainder of the diffused light while allowing the nondiffused light from the pinhole and the diffused light received by the object to pass to said plane parallel to said first-named plane.

7. Apparatus for producing an off-axis hologram according to claim 3 including a light blocking screen positioned in said first-named plane, said screen having a pinhole located at the focus point of said first lens for blocking the remainder of the diffused light while allowing the nondiffused light from the pinhole and the diffused light received by the object to pass to said second lens.