Method for Generating Video Holograms in Real Time by Means of Subholograms

Abstract

A method for generating video holograms in real time for a holographic playback device comprising at least one light modulator means, into which a scene divided into object points is encoded as an entire hologram and can be seen as a reconstruction from a visibility region, which is located within a periodicity interval of the reconstruction of the video hologram, the visibility region defining a sub-hologram together with each object point of the scene to be reconstructed, and the entire hologram being generated from a superposition of contributions of sub-holograms, is characterized in that for each object point the contributions of the sub-holograms in the entire reconstruction of the scene can be determined from at least one look-up table.

1 . Method for generating video holograms in real time for a holographic display device with at least one light modulator means on which a scene which is divided into object points is encoded as a total hologram and which can be seen as a reconstruction from a visibility region which lies within one periodicity interval of the reconstruction of the video hologram, where the visibility region defines a sub-hologram together with each object point of the scene to be reconstructed, and where the total hologram is formed by way of a superimposition of contributions of sub-holograms, where the contributions of the subholograms to the entire reconstruction of the scene can be retrieved from at least one look-up table for each object point. 
   
   
       2 . Method according to  claim 1  where the position and viewing direction of an observer define a view of the scene and where the observer is assigned with at least one visibility region, which lies near the eyes in an observer plane, and which—after a three-dimensional discretisation of the scene into visible object points—comprises the following process steps:
 Finding the position and size of the sub-hologram for each object point,   Determination of the contributions of the corresponding sub-hologram from at least one look-up table,   Repetition of these two steps for all object points, where the sub-holograms are superimposed so to form a total hologram for the reconstruction of the entire scene.   
   
   
       3 . Method according to  claim 1  where at least one of data values of the sub-holograms and the total hologram are modulated with brightness values or where at least one of data values of the sub-holograms and the total hologram are modulated with colour values. 
   
   
       4 . Method according to  claim 3  where at least one of data values of the sub-holograms and the total hologram are modulated with brightness values from at least one look-up table or where at least one of data values of the sub-holograms and the total hologram are modulated with colour values from at least one look-up table. 
   
   
       5 . Method according to  claim 1  where correction values are added to the data values of the sub-holograms and/or of the total hologram. 
   
   
       6 . Method according to  claim 1  where the position of the subhologram is determined such that the centre of the sub-hologram lies on the straight line through the object point to be reconstructed and the centre of the visibility region. 
   
   
       7 . Method according to  claim 6  where the size of the sub-hologram is determined by tracing back the visibility region through the object point to the light modulator means. 
   
   
       8 . Method according to  claim 1  where for colour representation the values of the primary colours can be retrieved from respective look-up tables. 
   
   
       9 . Method according to  claim 1  where the complex hologram values are converted into pixel values of the light modulator means. 
   
   
       10 . Method according to  claim 9  where the complex hologram values are converted into Burckhardt components or two-phase components or any other suitable code. 
   
   
       11 . Method according to  claim 1  for a holographic display device with a screen means, where the screen means is either the light modulator means itself on which the hologram of the scene is encoded, or an optical element on to which a hologram or wave front of the scene encoded on the light modulator means is projected. 
   
   
       12 . Method according to  claim 11  where the optical element of the display device is a lens or mirror. 
   
   
       13 . Method according to  claim 1  where the hologram values of the sub-hologram of an object point are determined by propagating the wave front which is emitted by the object point into the visibility region. 
   
   
       14 . Method according to  claim 1  where the look-up table is generated by determining the corresponding entry of the sub-hologram for each possible object point in a defined space by propagating the wave front which is emitted by the object point into the visibility region and by backtransforming it into the hologram plane where the light modulator means is situated. 
   
   
       15 . Method according to  claim 1  where the look-up table is generated by determining the corresponding entry of the sub-hologram for each possible object point in a defined space with the help of the ray tracing method. 
   
   
       16 . Method according to  claim 1  where the look-up table is generated by determining the corresponding entry of the sub-hologram for each possible object point in a defined space with the help of optimisation or approximation methods.