Iris boundary estimation using cornea curvature

• US 10,296,792 B2
• Filed: 04/26/2017
• Issued: 05/21/2019
• Est. Priority Date: 07/14/2016
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Spizhevoy, Alexey, Amayeh, Gholamreza, Kaehler, Adrian
• Primary Examiner(s): Gilliard, Delomia L
• Application Number:
  US15/497,726
• Publication Number:
  US 20180018515A1
• Time in Patent Office: 755 Days
• Field of Search: None
• CPC Class Codes: G06V 10/245 by locating a pattern; Special marks for positioning
• CPC Class Codes: G06V 40/19 Sensors therefor
• CPC Class Codes: G06V 40/193 Preprocessing; Feature extraction
• CPC Class Codes: G06V 40/197 Matching; Classification

Abstract

Examples of systems and methods for determining a limbic boundary of an iris of an eye are provided. Properties of the corneal bulge can be computed from eye images. An intersection of the corneal bulge with the eye surface (e.g., sclera) can be determined as the limbic boundary. The determined limbic boundary can be used for iris segmentation or biometric applications. A head mounted display can include a camera that images the eye and a processor that analyzes the eye images and determines the limbic boundary.

Claims

1. A wearable display system comprising:

a display;

an image capture device configured to capture an image of an eye of a user;

non-transitory memory configured to store executable instructions; and

a hardware processor in communication with the display, the image capture device, and the non-transitory memory, the hardware processor programmed by the executable instructions to;

obtain a camera calibration;

obtain physiological parameters of the eye in a three-dimensional coordinate frame of the eye, wherein the physiological parameters comprise;

a radius of a corneal sphere comprising a cornea of the eye,

a radius of an iris of the eye, and

a distance between a center of the corneal sphere and a center of a pupil of the eye;

receive the image of the eye, the image comprising at least a portion of the cornea of the eye and the iris of the eye;

transform the image of the eye into the coordinate frame of the eye via a perspective transformation to generate a transformed image;

determine, from the transformed image, an intersection between the corneal sphere and the eye;

convert, based at least in part on the camera calibration, the intersection from the coordinate frame of the eye to a coordinate frame of the image of the eye;

determine the limbic boundary based at least in part on the intersection; and

utilize the limbic boundary in a biometric application.

2. The wearable display system of claim 1, wherein the camera calibration comprises a relationship between a camera coordinate frame and the coordinate frame of the eye.

3. The wearable display system of claim 1, wherein the camera calibration comprises a calibration matrix, wherein the calibration matrix comprises intrinsic camera parameters.

4. The wearable display system of claim 1, wherein the physiological parameters are estimated from a population of human subjects.

5. The wearable display system of claim 1, wherein to obtain the physiological parameters of the eye, the hardware processor is programmed by the executable instructions to:

determining the physiological parameters from images of the eye.

6. The wearable display system of claim 5, wherein the hardware processor is further programmed by the executable instructions to periodically re-determine the physiological parameters of the eye.

7. The wearable display system of claim 1, wherein to determine the intersection between the corneal sphere and the eye, the hardware processor is programmed by the executable instructions to:

estimate three-dimensional properties of the corneal sphere in the three-dimensional coordinate frame of the eye.

8. The wearable display system of claim 7, wherein to estimate the three-dimensional properties of the corneal sphere, the hardware processor is programmed by the executable instructions to:

estimate a center of the pupil and a center of the corneal sphere.

9. The wearable display system of claim 1, wherein to determine the intersection between the corneal sphere and the eye, the hardware processor is programmed by the executable instructions to:

determine a plurality of intersection points of the corneal sphere and the eye.

10. The wearable display system of claim 9, wherein to convert the intersection from the coordinate frame of the eye to a coordinate frame of the image of the eye, the hardware processor is programmed by the executable instructions to:

project the plurality of intersection points into the coordinate frame of the image of the eye.

11. A wearable display system comprising:

a display;

an image capture device configured to capture an image of an eye of a user;

non-transitory memory configured to store executable instructions; and

a hardware processor in communication with the display, the image capture device, and the non-transitory memory, the hardware processor programmed by the executable instructions to;

obtain physiological parameters of the eye in a three-dimensional coordinate frame of the eye, wherein the physiological parameters comprise;

a radius of a corneal sphere comprising a cornea of the eye,

a radius of an iris of the eye, and

a distance between a center of the corneal sphere and a center of the pupil of the eye;

receive the image of the eye, the image comprising at least a portion of the cornea of the eye and the iris of the eye;

transform the image of the eye into the coordinate frame of the eye via a perspective transformation to generate a transformed image;

determine, from the transformed image, an intersection between the corneal sphere and the eye; and

determining the limbic boundary based at least in part on the intersection.

12. The wearable display system of claim 11, wherein to obtain the physiological parameters of the eye, the hardware processor is programmed by the executable instructions to:

determine the physiological parameters from eye images of a particular individual.

13. The wearable display system of claim 11, wherein the image of the eye is received from the image capture device.

14. The wearable display system of claim 11, wherein to determine the limbic boundary, the hardware processor is programmed by the executable instructions to:

determine a plurality of intersection points of the corneal sphere and the eye.

15. The wearable display system of claim 11, wherein the hardware processor is further programmed by the executable instructions to:

perform a biometric application based at least in part on the limbic boundary, and wherein the biometric application comprises iris identification.