Line scan reader/writer by holographic collection

Abstract

An electro-optical scanner which can write and read with common optics by using a phase hologram near the focal plane of the scanned surface.

Having described the invention, what is claimed as new and novel and for which it is desired to secure Letters Patent is: 
     
       1. Apparatus comprising: A. a light source for providing a light beam;   B. an optical light beam splitter;   C. a first focusing lens for receiving said light beam through said beam splitter;   D. collection means placed between said first lens and a surface which includes information to be read in proximity with said surface, said collection means having an unmodulated portion through which said light beam is focused onto said surface and having a modulated portion through which diverging light from said surface is collected and directed to said beam splitter by means of said first focusing lens;   E. detector means; and   F. a second focusing lens for focusing said light received by said beam splitter from said surface for receipt by said detector means.   
     
     
       2. Apparatus as in claim 1 wherein said collection means is operable to separate signal representative of said information on said surface to be read from noise and directing said signal to said first focusing lens. 
     
     
       3. Apparatus as in claim 1 wherein said collection means is a hologram. 
     
     
       4. Apparatus as in claim 3 wherein said hologram is a phase hologram. 
     
     
       5. Apparatus as in claim 1 further comprising means for moving said surface with respect to said collection means so that all of said information on said surface may be read. 
     
     
       6. Apparatus as in claim 1 further comprising a scanning device coupled in the optical path between said beam splitter and said first focusing lens so that the operation of said scanning device causes said light beam to be focused on different portions of said surface without moving either said surface or said collection means. 
     
     
       7. Apparatus as in claim 6 wherein the operation of said scanning device causes said light beam to be focused along different portions of said surface on a first axis and further comprising means for moving said surface with respect to said collection means along a second axis thereby enabling all of said information on said surface to be read. 
     
     
       8. Apparatus as in claim 7 wherein said scanning device is a rotatable multifaceted mirror. 
     
     
       9. Apparatus as in claim 1 wherein said beam splitter is capable of being positioned in a first position or a second position, wherein said first position locates said beam splitter in the path between said light source and said first focusing lens thereby enabling said light beam to be transmitted to said source and received by said detector means from said surface so that said information may be read, and wherein said second position locates said beam splitter so that said detector means does not receive said light beam from said surface. 
     
     
       10. Apparatus as in claim 9 wherein said second position of said beam splitter enables said apparatus to write information on said surface and with other optical means, including said first and second focusing lens, enables the reading of said information on said surface. 
     
     
       11. Apparatus as in claim 10 further comprising a mirror coupled in the path between said first focusing lens and said surface so that said light beam is not received by said surface during a writing operation, but rather is received by another surface in a different location from said surface. 
     
     
       12. Apparatus as in claim 9 wherein said collection means is a phase hologram. 
     
     
       13. Apparatus as in claim 12 further comprising means for moving said surface with respect to said collection means so that all of said information on said surface may be read. 
     
     
       14. Apparatus as in claim 9 further comprising a rotatable multifaceted mirror coupled in the optical path between said beam splitter and said first focusing lens so that rotation of said mirror causes said light beam to be focused on different portions of said surface without moving either said surface or said collection means. 
     
     
       15. Apparatus as in claim 14 wherein rotation of said mirror causes said light beam to be focused along different portions of said surface on a first axis and further comprising means for moving said surface with respect to said collection means along a second axis thereby enabling all of said information on said surface to be read. 
     
     
       16. Apparatus as in claim 15 wherein said phase hologram is placed in a position substantially parallel to said surface. .Iadd. 
     
     
       17.  A reader apparatus for reading information on a surface by illuminating the surface and detecting the intensity of reflected light therefrom, such apparatus comprising A. a light source for providing a light beam,   B. first focusing means for focusing the light beam onto a surface which bears information to be read,   C. collection means disposed between the first focusing means and the surface, and proximal to the surface, the collection means having a first portion through which the light beam is focused onto the surface and having a modulated second portion through which light reflected from the surface is collected and directed along an optical path,   D. detector means for developing a signal indicative of light intensity thereon, and   E. second focusing means for focusing onto the detector means the reflected light directed by the modulated portion. .Iaddend. .Iadd.18. Apparatus as in claim 17, wherein the modulated second portion includes a hologram. .Iaddend. .Iadd.19. Apparatus as in claim 18, wherein the hologram is disposed in a region of the collection means substantially surrounding the first portion. .Iaddend. .Iadd.20. Apparatus as in claim 19, wherein the hologram is a phase hologram. .Iaddend. .Iadd.21. Apparatus as in claim 19, further comprising means for moving the surface with respect to the collection means for enabling the reading of information in a region of   
     
     
        the surface. .Iaddend. .Iadd.22.  Apparatus as in claim 19, further comprising a scanning device in an optical path between the light source and the first focusing means for directing the light beam onto different portions of the surface. .Iaddend. .Iadd.23. Apparatus as in claim 22, wherein said scanning device directs the light beam on different portions of the surface located along a first axis, and further comprising means for moving the surface with respect to the collection means along a second axis, thereby enabling the reading of information at different locations on the scanned surface. .Iaddend. .Iadd.24. Apparatus as in claim 23, wherein the scanning device includes a rotatable multifaceted scanner. .Iaddend. .Iadd.25. Apparatus as in claim 24, wherein the hologram is disposed substantially parallel to the scanned surface. .Iaddend. .Iadd.26. An improved light gathering structure for use in an optical reader of the type wherein a light beam scans a path along a surface bearing information to be read, and the light reflected from the surface is directed to a detector for developing a signal representative of the information illuminated by the beam, such light gathering structure comprising a strip hologram having a first portion through which the light beam scans the path and an adjacent modulated portion for collecting light diffusely reflected from the surface. .Iaddend. .Iadd.27. A structure as in claim 26, wherein the strip hologram includes a phase hologram. .Iaddend. .Iadd.28. A structure as in claim 27, wherein the modulated portion directs the collected light toward a fixed detector. .Iaddend. .Iadd.29. A structure as in claim 28, wherein the modulated portion has a focusing   
     
     
        property. .Iaddend. .Iadd.30.  A structure according to claim 29, wherein the strip hologram includes a first fringe pattern formed substantially parallel to the scan path. .Iaddend. .Iadd.31. A structure as in claim 30, wherein the strip hologram further includes a second fringe pattern formed substantially orthogonal to the fringes of said first pattern. .Iaddend. .Iadd.32. A light-gathering structure as in claim 26, wherein the first portion extends along the scan path and wherein the modulated portion is located adjacent thereto and comprises a first hologram fringe pattern having fringes substantially parallel to the path for collecting light diffusely reflected from the surface, and   a second hologram fringe pattern having fringes substantially orthogonal to the fringes of the first pattern, so that the two sets of fringes behave as a crossed pair of cylindrical lenses at each position along the scan path. .Iaddend. .Iadd.33. A light-gathering structure as in claim 28, wherein the first portion extends along the scan path and wherein the modulated portion is located adjacent thereto and comprises   a first hologram fringe pattern having fringes substantially parallel to the path for collecting light diffusely reflected from the surface, and   a second hologram fringe pattern having fringes substantially orthogonal to the fringes of the first pattern. .Iaddend. .Iadd.34. A light-gathering structure as in claim 28, wherein the hologram includes a fringe pattern corresponding to interference fringes formed with illumination directed through a lens along a hologram recording axis, said recording axis and said scan path defining a recording beam plane, and wherein the angle between said recording axis and said scan path is a function of position   
     
     
        along the scan path. .Iaddend. .Iadd.35.  An improved method of reading optical reflectance information born on a surface by illuminating the surface along a scan path with a scanning beam and reading the reflectance information by directing the light reflected from the surface to a detector, the improvement comprising the steps of: placing proximal to the surface a strip hologram including a first portion extending along the scan path, and also including an adjacent modulated second portion,   illuminating the surface by scanning it with the scanning beam through the first portion, and   directing through the modulated second portion, the light diffusely reflected from the surface toward the detector. .Iaddend. .Iadd.36. The method of claim 35, wherein the step of directing includes the step of directing, along an optical path substantially coaxial with the scanning beam, the light reflected from an illuminated spot on the surface. .Iaddend.