Holographic Waveguide Optical Tracker

Abstract

There is provided an object tracker comprising: a first waveguide; a source of illumination light; a detector optically coupled to said waveguide; and at least one grating lamina formed within said waveguide. Illumination light propagating along a first optical path from said source to an object in relative motion to the object tracker. Image light reflected from at least one surface of an object is deflected by said grating lamina into a second optical path towards said detector.

1 . An object tracker for tracking an object comprising:
 a first waveguide;   a source of light for illuminating said object having at least one surface;   a detector optically coupled to said first waveguide; and   a first grating formed within said first waveguide,   wherein image light reflected from said at least one surface of said object is deflected by said first grating into a total internal reflection (TIR) path towards said detector,   wherein said first grating comprises a plurality of grating elements, each having a grating vector configured to provide a unique perspective view of said object.   
     
     
         2 . The object tracker of  claim 1 , wherein said object tracker and said object are in relative motion. 
     
     
         3 . The object tracker of  claim 1  wherein said first grating element switchable between a diffracting state and a non-diffracting state. 
     
     
         4 . The object tracker of  claim 1 , wherein said first grating comprises at least one switchable grating element having a diffracting state and a non-diffracting state, wherein said at least one switchable grating element in said diffracting state deflects said image light into said TIR path towards said detector. 
     
     
         5 . The object tracker of  claim 1 , wherein said first grating comprises at least one elongated grating element with a longer dimension aligned perpendicular to a principal waveguide path defined within the first waveguide. 
     
     
         6 . The object tracker of  claim 1 , further comprising at least one selected from the group consisting of:
 an input grating or a prism for coupling light from said source of light into said first waveguide; and   a fold grating.   
     
     
         7 . The object tracker of  claim 1 , wherein said first grating is one selected from the group consisting of: a switchable Bragg grating, a switchable grating recorded in a holographic polymer dispersed liquid crystal, a switchable grating recorded in a reverse mode holographic polymer dispersed liquid crystal, a surface relief grating, a non-switching Bragg grating, a grating encoding optical power, and a grating encoding light diffusing properties. 
     
     
         8 . The object tracker of  claim 1 , wherein said object is an eye and said image light is reflected from at least one selected from the group consisting of: the cornea, lens, iris, sclera, and retina of said eye. 
     
     
         9 . The object tracker of  claim 1 , wherein:
 said detector is one selected from the group consisting of: a single element detector, a linear array, and a two-dimensional array; and   said source is one selected from the group consisting of: a laser and a light emitting diode.   
     
     
         10 . The object tracker of  claim 1 , wherein light from said source is directed towards said object by a second grating. 
     
     
         11 . The object tracker of  claim 10  wherein said first and second gratings are configured as at least one selected from the group consisting of: disposed in a single layer, disposed with said first grating at least partially overlapping said second grating, disposed adjacent to each other, and disposed in separate and at least partially overlapping waveguides. 
     
     
         12 . The object tracker of  claim 10 , wherein said second grating comprises a plurality of grating elements for diffracting said light into a plurality of illumination beams, providing at least one selected from the group consisting of: beams substantially normal to said second grating, beams converging onto said object, beams having average directions varying cyclically across said second grating, beams having diffusion distributions around an average direction, and beams having diffusion distributions around an average direction that varies across said second grating. 
     
     
         13 . The object tracker of  claim 10 , wherein said second grating is formed in a second waveguide, said second waveguide comprising at least one selected from the group consisting of:
 an input grating or a prism for coupling light from said source into a second TIR path in said second waveguide;   an output grating or a prism for deflecting said image light out of said second TIR path towards said detector; and   a fold grating.   
     
     
         14 . The object tracker of  claim 10 , wherein said second grating comprises at least one switchable grating element having a diffracting state and a non-diffracting state, wherein said at least one switchable grating element in said diffracting state deflects said image light towards said object. 
     
     
         15 . The object tracker of  claim 10 , wherein said a second grating comprises at least one elongated switchable beam deflection element with a longer dimension aligned perpendicular to a principal waveguide path defined within the first waveguide. 
     
     
         16 . The object tracker of  claim 10 , wherein said second grating is one selected from the group consisting of: a switchable Bragg grating, a switchable grating recorded in a holographic polymer dispersed liquid crystal, a switchable grating recorded in a reverse mode holographic polymer dispersed liquid crystal, a surface relief grating, a non-switching Bragg grating, a grating encoding optical power, and a grating encoding light diffusing properties. 
     
     
         17 . The object tracker of  claim 1 , wherein said detector is connected to:
 an image processing apparatus for determining at least one spatio-temporal characteristic of an eye movement; and   an image processing system which includes at least one of an edge finding algorithm, a centroid detection algorithm or a neural network.   
     
     
         18 . The object tracker of  claim 1 , wherein said source emits in the infrared band. 
     
     
         19 . The object tracker of  claim 1 , wherein said image light comprises a characteristic selected from the group consisting of: specular reflection, incoherent scatter, and speckle. 
     
     
         20 . The object tracker of  claim 1 , implemented in a device selected from the group consisting of: an eye tracker, a LIDAR, an eye-slaved display, a display implementing foveated rendering, and a display using gaze vector data to adjust a displayed image to provide vergence accommodation related depth cues.