Array-based imaging relay

• US 10,191,188 B2
• Filed: 03/08/2016
• Issued: 01/29/2019
• Est. Priority Date: 03/08/2016
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Powell, Karlton D.
• Primary Examiner(s): Alexander, William R
• Assistant Examiner(s): Parbadia, Balram T
• Application Number:
  US15/064,046
• Publication Number:
  US 20170261650A1
• Time in Patent Office: 1,057 Days
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G02B 30/56 by projecting aerial or floating images
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G06V 40/1312 direct reading, e.g. contactless acquisition
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

Abstract

A lens system includes a first lens array assembly including a first plurality of cells, each cell of the first plurality of cells configured to exhibit a pair of Fourier transform lenses, and a second lens array assembly including a second plurality of cells, each cell of the second plurality of cells configured to exhibit a pair of Fourier transform lenses. The first and second lens array assemblies are positioned relative to one another along an optical axis of the lens system such that an image of an object is provided at an image conjugate distance from the second lens array assembly.

Claims

1. A lens system comprising:

a first lens array assembly comprising a first plurality of cells, each cell of the first plurality of cells configured to exhibit a pair of Fourier transform lenses that implement a phase-corrected Fourier transform; and

a second lens array assembly comprising a second plurality of cells, each cell of the second plurality of cells configured to exhibit a pair of Fourier transform lenses that implement a phase-corrected Fourier transform;

wherein the first and second lens array assemblies are positioned relative to one another along an optical axis of the lens system such that an image of an object is provided at an image conjugate distance from the second lens array assembly, and

wherein a distance between the first and second lens array assemblies is dependent on an object conjugate distance of the object, the image conjugate distance, focal lengths of the Fourier transform lenses of the first and second pluralities of cells, and respective pitches of the first and second pluralities of cells.

2. The lens system of claim 1, wherein:

the image conjugate distance is established via a function of the object conjugate distance for the object, the distance between the first and second lens array assemblies, a first pitch of the first plurality of cells, a second pitch of the second plurality of cells, a first focal length of the first plurality of cells, and a second focal length of the second plurality of cells; and

the function establishes that light emanating from the object and passing through the respective cells of the first and second plurality of cells converges at the image conjugate distance.

3. The lens system of claim 1, wherein the first and second lens array assemblies are spaced apart from one another by a gap.

4. The lens system of claim 3, wherein the gap is on an order of the first and second common focal lengths.

5. The lens system of claim 1, wherein the first and second lens array assemblies are in contact with one another.

6. The lens system of claim 1, wherein the first and second pluralities of cells have a common pitch.

7. The lens system of claim 1, wherein the first and second plurality of cells have common focal lengths equal to one another.

8. The lens system of claim 1, wherein:

the first lens array assembly comprises a first pair of in-tandem microlens arrays, each microlens array of the first pair comprising a respective set of constituent lenslets, each constituent lenslet having a first common focal length;

the second lens array assembly comprises a second pair of in-tandem microlens arrays, each microlens array of the second pair comprising a respective set of constituent lenslets, each constituent lenslet having a second common focal length;

the in-tandem microlens arrays of the first pair are separated from one another along an optical axis of the lens system by the first common focal length;

the in-tandem microlens arrays of the second pair are separated from one another along the optical axis of the lens system by the second common focal length; and

the first and second pairs of in-tandem microlens arrays are positioned relative to one another along the optical axis such that the image is provided at the image conjugate distance.

9. The lens system of claim 8, further comprising:

an input microlens array disposed between the object and the first pair of in-tandem microlens arrays to collimate light emanating from the object; and

an output microlens array positioned behind the second pair of in-tandem microlens arrays along the optical axis to focus the image at an adjusted image conjugate distance closer than the image conjugate distance.

10. The lens system of claim 9, further comprising:

a transparent cover disposed forward of the input microlens array, the transparent cover having a front surface at which the object is disposed;

a light guide plate disposed between the transparent cover and the input microlens array; and

a light source disposed along an edge of the light guide plate to inject source light into the light guide plate;

wherein the light guide plate is wedge-shaped to extract the source light and illuminate the object at the surface of the transparent cover.

11. The lens system of claim 9, further comprising an image sensor disposed behind the output microlens array at the adjusted image conjugate distance established by the output microlens array.

12. The lens system of claim 1, wherein:

the first lens array assembly comprises a first array of graded-index microlensing structures;

each graded-index microlensing structure of the first array corresponds with a respective one of the first plurality of cells;

the second lens array assembly comprises a second array of graded-index microlensing structures; and

each graded-index microlensing structure of the second array corresponds with a respective one of the second plurality of cells.

13. A lens system comprising:

a first pair of in-tandem microlens arrays, each microlens array of the first pair comprising a respective set of lenslets, each lenslet having a first common focal length; and

a second pair of in-tandem microlens arrays, each microlens array of the second pair comprising a respective set of lenslets, each lenslet having a second common focal length;

wherein;

the in-tandem microlens arrays of the first pair are separated from one another along an optical axis of the lens system by a distance equal to the first common focal length such that the microlens arrays of the first pair are configured to provide a representation of a phase-corrected Fourier transform of light emanating from an object, the representation provided along a plane disposed between the first and second pairs;

the in-tandem microlens arrays of the second pair are separated from one another along the optical axis of the lens system by a distance equal to the second common focal length such that the microlens arrays of the second pair are configured to provide an image of the object via a phase-corrected Fourier transformation of the representation;

the first and second pairs of in-tandem microlens arrays are positioned relative to one another along the optical axis of the lens system such that the image of the object is provided at an image conjugate distance from the second pair of in-tandem microlens arrays; and

a distance between the first pair of in-tandem microlens arrays and the second pair of in-tandem microlens arrays is dependent on an object conjugate distance of the object, the image conjugate distance, the first and second common focal lengths, and respective pitches of the first and second pairs of in-tandem microlens arrays.

14. The lens system of claim 13, wherein the image conjugate distance is established via a function of the object conjugate distance for the object, the distance between the first and second pairs, the first and second common focal lengths, a first pitch of the first pair, and a second pitch of the second pair.

15. The lens system of claim 13, wherein the distance is zero such that the first and second pairs are in contact with one another.

16. The lens system of claim 13, wherein the first and second pitches are equal to one another.

17. The lens system of claim 13, wherein the first and second common focal lengths are equal to one another.

18. The lens system of claim 13, further comprising:

an input microlens array disposed between the object and the first pair to collimate light emanating from the object;

an output microlens array positioned behind the second pair along the optical axis to focus the image at an adjusted image conjugate distance closer than the image conjugate distance;

a transparent cover disposed forward of the input microlens array, the transparent cover having a front surface at which the object is disposed;

a light guide disposed between the transparent cover and the input microlens array; and

a light source disposed along an edge of the light guide to inject source light into the light guide;

wherein the light guide is wedge-shaped to extract the source light and illuminate the object at the surface of the transparent cover.

19. A fingerprint reader comprising:

a light source;

a light guide having an edge at which the light source is disposed, the light guide configured to illuminate a fingerprint pattern in front of the light guide;

first and second pairs of in-tandem microlens arrays, the respective microlens arrays of the first and second pairs being spaced apart from one another to implement a phase corrected Fourier transform, the first and second pairs of in-tandem microlens arrays being positioned relative to one another such that an image of an object is provided at an image conjugate distance from the second pair of in-tandem microlens arrays, wherein each microlens array of the first pair comprising a respective set of lenslets, each lenslet having a first common focal length, and wherein each microlens of the second pair comprising a respective set of lenslets, each lenslets having a second common focal length;

an input microlens array disposed in front of the first pair to prepare light emanating from the fingerprint pattern for the first and second pairs;

an output microlens array positioned behind the second pair to adjust the image conjugate distance; and

an image sensor disposed at the adjusted image conjugate distance to capture a representation of the fingerprint pattern;

wherein a distance between the first pair of in-tandem microlens arrays and the second pair of in-tandem microlens arrays is dependent on an object conjugate distance of the object, the image conjugate distance, the first and second common focal lengths, and respective pitches of the first and second pairs of in-tandem microlens arrays.

20. The fingerprint reader of claim 19, wherein the input microlens array is configured to collimate the light emanating from the fingerprint pattern.