Bidirectional holographic lens
A device can determine a distance to an object. The device can use the determined distance to vary a focal length of a first adjustable element so that the first adjustable element directs light from the object into a first waveguide and onto a detector, and forms an image of the object at the detector. The device can produce an image, such as augmented content, on a panel. The device can direct light from the panel into a second waveguide. The device can use the determined distance to vary a focal length of a second adjustable element so that the second adjustable element directs light out of the second waveguide and forms a virtual image of the panel in a plane coincident with the object. The device can operate as an augmented reality headset. The adjustable elements can be phase modulators, or acoustically responsive material with surface acoustic wave transducers.
1. A device for forming an image of an object, the object positioned at a finite distance away from the device, comprising:
a top waveguide having a top surface facing the object, a bottom surface parallel to the top surface, and a first end along an edge of the top waveguide;
a multi-pixel detector disposed at the first end of the top waveguide;
a top multi-region phase modulator positioned along the top surface of the top waveguide;
a controller configured to receive position data corresponding to the finite distance to the object, the controller further configured to energize the top multi-region phase modulator in response to the position data such that when energized, the top multi-region phase modulator directs at least a first fraction of light from the object into the top waveguide and forms an image of the object on the multi-pixel detector;
a bottom waveguide having a top surface positioned proximate the bottom surface of the top waveguide, a bottom surface parallel to the top surface of the bottom waveguide, and a first end along an edge of the bottom waveguide;
a multi-pixel image panel disposed at the first end of the bottom waveguide; and
a bottom multi-region phase modulator positioned along the bottom surface of the bottom waveguide;
wherein the controller is further configured to energize the bottom multi-region phase modulator in response to the position data such that when energized, the bottom multi-region phase modulator directs at least a second fraction of light from the multi-pixel image panel out of the bottom waveguide and forms a virtual image of the multi-pixel image panel in a plane coincident with the object, and
wherein the controller is further configured such that the bottom lens pattern extends only partially over the bottom multi-region phase modulator in an area corresponding to a position of the object in a field of view.
2. The device of claim 1 , wherein the controller is further configured to energize the top multi-region phase modulator in a top lens pattern having a focal length selected to form the image of the object in a plane coincident with the multi-pixel detector.
3. The device of claim 2 , wherein the top lens pattern includes at least portions of a first plurality of concentric circles, the first plurality of concentric circles becoming more closely spaced at increasing distances from a center of the first plurality of concentric circles.
4. The device of claim 2 , wherein:
the controller is further configured to select the first fraction of light directed by the top multi-region phase modulator into the top waveguide; and
the first fraction of light corresponds to a first order diffraction efficiency of the top lens pattern.
5. The device of claim 4 , wherein:
the top waveguide and the top multi-region phase modulator are at least partially transparent when viewed through the bottom and top surfaces; and
the transparency of the top waveguide and the top multi-region phase modulator correspond to a zeroth order diffraction efficiency of the top lens pattern.
6. The device of claim 2 , wherein the controller is further configured such that the top lens pattern extends fully over the top multi-region phase modulator.
7. The device of claim 2 , wherein the controller is further configured such that the top lens pattern extends only partially over the top multi-region phase modulator in an area corresponding to a position of the object in a field of view.
8. The device of claim 1 , wherein the controller is further configured to energize the bottom multi-region phase modulator in a bottom lens pattern having a focal length selected to form the virtual image of the multi-pixel image panel in the plane coincident with the object.
9. The device of claim 8 , wherein the bottom lens pattern includes at least portions of a second plurality of concentric circles, the second plurality of concentric circles becoming more closely spaced at increasing distances from a center of the second plurality of concentric circles.
10. The device of claim 9 , wherein:
the controller is further configured to select the second fraction of light directed by the bottom multi-region phase modulator out of the bottom waveguide; and
the second fraction of light corresponds to a first order diffraction efficiency of the bottom lens pattern.
11. The device of claim 10 , wherein the top waveguide, the top multi-region phase modulator, the bottom waveguide, and the bottom multi-region phase modulator are at least partially transparent when viewed through the bottom surface of the bottom waveguide to the top surface of the top waveguide.
12. The device of claim 1 , wherein the top surface of the bottom waveguide is spaced apart from the bottom surface of the top waveguide.