PATCHWORK FRESNEL ZONE PLATES FOR LENSLESS IMAGING

• US 20150219808A1
• Filed: 08/12/2014
• Published: 08/06/2015
• Est. Priority Date: 08/28/2013
• Status: Active Grant

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Gill, Patrick R., Stork, David G., Endsley, Jay A.
• Granted Patent: US 9,746,593 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence

Abstract

Described are imaging devices that employ patchworks of diffractive structures as focusing optics. Each diffractive structure best focuses light over a relatively narrow cone of incident angles, and provides suboptimal focusing for incident angles outside that cone. Different diffractive structures best focus different angular ranges, with the patchwork thus providing an overall focusable response for the relatively broad range of angles required to image a scene. Images can be captured without a lens, and cameras can be made smaller than those that are reliant on lenses and ray-optical focusing.

Claims

1. An imaging device comprising:

an array of photoelements; and

adjacent and dissimilar diffractive structures overlying the array and each having an area at least 10 times the area of one of the photoelements, each diffractive structure best focusing light onto the array of photoelements over a respective different range of incident angles.

2. The imaging device of claim 1, wherein the diffractive structures are phase plates.

3. The imaging device of claim 2, wherein at least one order ring of a first one of the phase plates overlaps with at least one order ring of a second one of the phase plates.

4. The imaging device of claim 3, wherein a lower-order ring of the first one of the phase plates is at least partially replaced with a higher-order ring of the second one of the phase plates.

5. The imaging device of claim 1, further comprising a light-transmissive medium allowing light incident adjacent ones of the diffractive structures to intersect the same one of the photoelements.

6. The imaging device of claim 1, wherein the ranges of incident angles overlap, the imaging device further comprising an aperture spaced from the array of photoelements to constrain an outer bound of the overlapping incident angles.

7. The imaging device of claim 6, further comprising a second aperture spaced from the aperture along an axis normal to the array.

8. The imaging device of claim 1, further comprising an actuator to move the diffractive structures laterally with respect to the array.

9. A photosensor to sense incident light over a range of incident angles, the photosensor comprising:

an array of photoelements; and

overlapping diffractive structures each best focusing light onto the array of photoelements over a respective cone of incident angles, each cone covering a different portion of the range of incident angles and having a given eccentricity.

10. The photosensor of claim 9, wherein the different portions cover the range of incident angles.

11. The photosensor of claim 9, wherein a first of the diffractive structures produces two foci and a second of the diffractive structures produces one focus.

12. The photosensor of claim 9, wherein at least some of the diffractive structures are elliptical.

13. The photosensor of claim 9, wherein at least one of the diffractive structures focuses the light onto the array over the respective cone of incident angles and a second cone of incident angles.

14. The photosensor of claim 9, wherein the diffractive structures comprise zone plates.

15. The photosensor of claim 9, wherein the diffractive structures comprise phase gratings.

16. The photosensor of claim 9, wherein the overlapping diffractive structures are irregularly spaced from one another.

17. An imaging device comprising:

an array of photoelements; and

a diffractive structure overlying the array and comprising at least one of a group of diffractive structures that each best focus light over a respective different range of incident angles, and a phase antisymmetric grating that best focuses light into a collection of curved and/or straight linear segments; and

a first aperture spaced from the array of photoelements to constrain light reaching the array of photoelements substantially to light passing through the diffractive structure.

18. The imaging device of claim 17, further comprising a second aperture spaced from the first aperture along an axis normal to the array.

19. The imaging device of claim 18, wherein the first aperture is disposed between the second aperture and the array.

20. The imaging device of claim 18, wherein at least one of the first aperture and the second aperture is adjustable.