Hybrid reflection hologram

Abstract

Hybrid white-light viewable holograms and methods for making them. The holograms are hybrid reflection holograms made using the diffractive structures or gratings of a holographic object such as a transmission hologram or holographic optical element (HOE). The wavefronts of the diffractive structures are converted into a reflection hologram by scanning them with a coherent light source having a profiled narrow beam. The hybrid reflection hologram can exhibit display parameters including the multiple colors, solidity, and color stability of white light reflection holograms, the diffractive color shifting of a white light transmission hologram, three dimensional imaging and a wide variety of dynamic changes. Different areas or images with each of these effects can be combined in a single hologram. These hybrid reflection holograms are ideal for security and forgery prevention applications.

1 . A method for producing a reflection hologram, the method comprising the steps of: 
 providing an object hologram;    disposing the object hologram proximate to a photosensitive material;    scanning the object hologram with light from a coherent light source, the light passing through the photosensitive material; and    reflecting the light back through the photosensitive material, thereby forming a reflection hologram viewable in white light.    
   
   
       2 . The method of  claim 1  wherein the scanning step comprises scanning a laser beam having a beam thickness substantially less than a length of the object hologram.  
   
   
       3 . The method of  claim 1  wherein the scanning step comprises scanning a laser beam having a width greater than or equal to a width of the object hologram.  
   
   
       4 . The method of  claim 1  further comprising the step of metallizing the front surface of the object hologram, the rear surface of the object hologram, or a support for the object hologram.  
   
   
       5 . The method of  claim 4  wherein the reflecting step comprises reflecting the light from the metallized front surface of the object hologram.  
   
   
       6 . The method of  claim 4  wherein the reflecting step comprises passing the light through the object hologram, reflecting the light from the metallized back surface of the hologram or the metallized support, and passing the reflected light back through the object hologram.  
   
   
       7 . The method of  claim 1  further comprising the step of exposing different hologram areas of the object hologram with different apertures.  
   
   
       8 . The method of  claim 7  wherein one of the apertures is open.  
   
   
       9 . The method of  claim 7  further comprising the step of selecting a color of a hologram area by modifying the aperture.  
   
   
       10 . The method of  claim 1  wherein the scanning step comprises scanning the light at an angle of incidence selected from the group consisting of approximately a reference angle used to manufacture the object hologram, approximately Brewster's angle, approximately the appropriate playback angle to produce an orthoscopic view, approximately perpendicular to the object hologram, and between approximately zero and approximately five degrees.  
   
   
       11 . The method of  claim 10  wherein the reflection hologram comprises an edge lit reflection hologram when the angle of incidence is between approximately zero and approximately five degrees.  
   
   
       12 . The method of  claim 1  wherein the steps are repeated for a second object hologram.  
   
   
       13 . A reflection hologram comprising one or more hologram areas which exhibit color shifting as a viewing angle is changed when viewed in light comprising a plurality of wavelengths.  
   
   
       14 . The reflection hologram of  claim 13  wherein a range of colors exhibited during color shifting comprises only a subset of the plurality of wavelengths.  
   
   
       15 . The reflection hologram of  claim 14  wherein a size of the subset is substantially smaller than a number of the wavelengths.  
   
   
       16 . The reflection hologram of  claim 13  wherein the plurality of wavelengths comprises a continuous range of wavelengths.  
   
   
       17 . The reflection hologram of  claim 13  further comprising at least one hologram area which does not exhibit color shifting as a viewing angle is changed when viewed in light comprising a range of wavelengths.  
   
   
       18 . The reflection hologram of  claim 17  wherein said at least one hologram area comprises a plurality of solid colors.  
   
   
       19 . The reflection hologram of  claim 13  which is lit from the front of the hologram with white light.  
   
   
       20 . The reflection hologram of  claim 13  comprising an anti-counterfeiting label.  
   
   
       21 . The reflection hologram of  claim 13  comprising a plurality of images which are viewable from a plurality of viewing angles.  
   
   
       22 . The reflection hologram of  claim 21  wherein a particular image is viewable only from a predetermined viewing angle.  
   
   
       23 . The reflection hologram of  claim 21  wherein stored information is accessible only from a predetermined angle.  
   
   
       24 . The reflection hologram of  claim 13  comprising an edge lit reflection hologram.