METHOD AND APPARATUS FOR RECORDING AND PROJECTING HOLOGRAMS

• US 3,834,786 A
• Filed: 05/01/1972
• Issued: 09/10/1974
• Est. Priority Date: 05/01/1972
• Status: Expired due to Term

• Current Assignee: Carlsen W. John
• Original Assignee: Carlsen W. John
• Inventors: Carlsen, W. John
• Primary Examiner(s): Stern, Ronald J.
• Application Number:
  US05/249,324
• Time in Patent Office: 862 Days
• Field of Search: 350/3.5,162SF
• US Class Current: 359/24
• CPC Class Codes: G03H 1/0406 Image plane or focused image holograms, i.e. an image of the object or holobject is formed on, in or across the recording plane
• CPC Class Codes: G03H 1/24 using white light , e.g. rainbow holograms
• CPC Class Codes: G03H 1/28 superimposed holograms only
• CPC Class Codes: G03H 2001/221 Element having optical power, e.g. field lens
• CPC Class Codes: G03H 2001/2218 being perpendicular to optical axis
• CPC Class Codes: G03H 2001/2265 Achromatic holobject
• CPC Class Codes: G03H 2210/20 2D object
• CPC Class Codes: G03H 2210/30 3D object
• CPC Class Codes: G03H 2222/18 RGB trichrome light
• CPC Class Codes: G03H 2223/12 Amplitude mask, e.g. diaphragm, Louver filter

Abstract

A method and apparatus for recording and projecting single color or multiple color encoded image-plane carrier holograms are described. An object is illuminated with a coherent collimated laser beam. The parallel spatially modulated rays are focused on a monochrome recording medium located in a recording plane with the rays maintained essentially parallel. A collimated reference beam, which is coherent with the object beam, is directed at the recording medium to form an image-plane hologram having a single discrete spatial carrier frequency in case of a single color laser or additional spatial carrier frequencies for as many colors as are in the laser. The processed image-plane hologram is projected by directing a generally collimated beam of incoherent white light upon the hologram to form separated wavefront reconstructions of parallel rays. A lens projects the parallel rays in a viewing plane after their convergence at a focal spot in a focal plane. A spatial filter located in the focal plane provides selection of desired color images and blocks undesired ghosts. A control for moving and adjustment of the spatial filter is provided to attain hue and saturation control as well as brightness of the projected image. An embodiment for recording of image-plane holograms of diffuse objects or diffusely illuminated objects as well as three-dimensional objects is described.

Claims

1. A projector for reconstructing a projectable color imageplane hologram recorded on a medium where the color information carrying hologram is formed with color related constant spatial carrier frequencies which are amplitude modulated by a focused image by interfering spatially modulated coherent object light beams including different colors at a recording angle with corresponding reference beams coherent with the object beams comprising means for producing an incoherent beam of generally parallel light and having a light spectrum which includes color wavelengths present in the light of the object beams used to form the hologram, said incoherent beam being directed to illuminate said image-plane hologram on the medium at an angle which is the recording angle which the reference beams make with the spatially modulated coherent object light beams, the intensity of said incoherent beam being selected sufficiently high to enable projection of a reconstructed image in a remote viewing plane, means responsive to generally parallel light rays reconstructed by the hologram along a path which extends generally at the recording angle from the incoherent beam for focusing the generally parallel rays after passage through a focal spot in a viewing plane, a spatial filter formed of an opaque stop having an aperture, said spatial filter being located generally in the plane of the focal spot to form a color projection of aperture selected reconstructed parallel rays in the viewing plane, means for moving the spatial filter within its plane to select reconstructed parallel light rays from the hologram for projection;

and means for adjusting the size of the aperture in the spatial filter to control the brightness of the image projected from the hologram.

2. A method for reconstructing and projecting an image-plane color hologram recorded on a transparent medium where the color information carrying hologram on a transparent medium where the color information carrying hologram is formed with color related constant spatial carrying frequencies which are amplitude modulated by a focused image by intErfering spatially modulated coherent object light beams including different colors at a recording angle with corresponding reference beams coherent with object beams comprising the steps of directing a generally collimated source of white light upon a hologram recorded on said transparent medium along a direction which the reference beams made with the spatially modulated coherent object light beams, selecting the intensity of the source of white light sufficiently high to enable a projection of a reconstructed image upon a remote viewing plane, focusing parallel rays generally emanating along a path forming a recording angle with the source of white light and reconstructed by the illuminated hologram in the transparent medium in an image in a viewing plane after passing the parallel rays through a focal point in a focal plane, and spatially filtering the rays within the focal plane to project an image of a selected color on the viewing plane by positioning an apertured stop within the focal plane to select a desired color hue for the projected image, and adjusting the size of the aperture in the stop to select the desired brightness of the image,

3. A system for recording and projecting color image-plane holograms comprising means for producing an essentially collimated coherent object light beam formed of different color wavelengths and spatially modulated by an object means for interfering said collimated coherent object light beam in a recording plane at a recording angle with a collimated reference beam coherent with the object beam to form a hologram on a recording medium of a discrete constant spatial carrier frequency, means for illuminating the hologram on a developed recording medium with a collimated beam of incoherent light along an angular direction which the reference beam made with respect to the object light beam and producing separated wavefront reconstructions formed of parallel rays emanating along a path which generally extends at the recording angle from the beam of illuminating incoherent light, means for imaging the parallel rays after passage through focal points in a focal plane on a viewing plane for display, spatial filtering means located in said focal plane to pass selected parallel rays for imaging on the viewing plane with a desired color display, means for moving said spatial filtering means in the focal plane to select the color hue of the projected image on the viewing plane;

and means for adjusting the number of rays passed by the spatial filtering means to select the color saturation of the projected image.