Explicit raytracing for gimbal-based gazepoint trackers

• US 7,997,730 B2
• Filed: 03/09/2010
• Issued: 08/16/2011
• Est. Priority Date: 04/04/2005
• Status: Active Grant

• Current Assignee: Eyegaze, Inc.
• Original Assignee: LC Technologies Incorporated
• Inventors: Cleveland, Dixon
• Primary Examiner(s): Mack; Ricky L
• Assistant Examiner(s): Sahle; Mahidere S
• Application Number:
  US12/719,924
• Publication Number:
  US 20100220288A1
• Time in Patent Office: 525 Days
• Field of Search: 351209-210, 348/E13.014, 348/E13.025, 382/103, 345/419
• US Class Current: 351/210
• CPC Class Codes: A61B 3/113 for determining or recording eye movement
• CPC Class Codes: G02B 27/0093 with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking
• CPC Class Codes: G03B 15/16 for photographing the track of moving objects high-speed photography G03B39/00
• CPC Class Codes: G03B 17/48 adapted for combination with other photographic or optical apparatus
• CPC Class Codes: G06F 3/013 Eye tracking input arrangements G06F3/015 takes precedence
• CPC Class Codes: G06V 40/18 Eye characteristics, e.g. of the iris

Abstract

A system for determining a three-dimensional location and orientation of an eye within a camera frame of reference includes a camera, an illuminator, and a processor. The camera captures an image of the eye. The illuminator generates a reflection off of a corneal surface of the eye. The processor computes a first two-dimensional location of a pupil reflection image and a corneal reflection image from the image of the eye. The processor predicts a second two-dimensional location of a pupil reflection image and the corneal reflection image as a function of a set of three-dimensional position and orientation parameters of the eye within the camera frame of reference. The processor iteratively adjusts the set until the first two-dimensional location is substantially the same as the second two-dimensional location. The set is the three-dimensional location and orientation of an eye.

Claims

1. A system for determining a three-dimensional location and orientation of an eye within a camera frame of reference, comprising:

a camera, wherein the camera captures an image of the eye;

an illuminator, wherein the illuminator generates a reflection off of a corneal surface of the eye; and

a processor, wherein the processor computes a first two-dimensional location of a pupil reflection image and a corneal reflection image from the image of the eye, wherein the processor predicts a second two-dimensional location of a pupil reflection image and the corneal reflection image as a function of a set of three-dimensional position and orientation parameters of the eye within the camera frame of reference, wherein the processor iteratively adjusts the set until the first two-dimensional location is substantially the same as the second two-dimensional location, wherein the set is the three-dimensional location and orientation of an eye, and wherein the processor predicts the second two-dimensional location using optical ray-tracing functions that model an eye shape and camera optics,

wherein the optical ray-tracing functions employ an ellipsoidal model for the corneal surface of the eye, the ellipsoidal model further comprising;

a nominal radius of curvature at a center of a cornea, a parameter defining a flattening of a corneal curvature toward corneal edges, and a parameter defining a degree of astigmatism on the corneal surface.

2. The system of claim 1, wherein the ellipsoidal model further comprising a parameter defining an angle of astigmatism on the corneal surface.

3. The system of claim 1, wherein the optical ray-tracing functions account for a refraction of a pupil image that results from the camera viewing a pupil of through a curved corneal surface.