Accurate three dimensional eye tracker

• US 4,373,787 A
• Filed: 11/13/1980
• Issued: 02/15/1983
• Est. Priority Date: 02/28/1979
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Crane, Hewitt D., Steele, Carroll M.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Bovernick, Rodney B.
• Application Number:
  US06/206,489
• Time in Patent Office: 824 Days
• Field of Search: 351/1, 351/6, 351/7, 351/13, 351/16
• US Class Current: 351/210
• CPC Class Codes: A61B 3/113 for determining or recording eye movement
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

A three dimensional eye tracker, for measuring as a function of time the point in three dimensional space on which the eye is fixed, includes a portion which functions as a two dimensional double Purkinje eye tracker for measuring movement of the eye in rotation and translation, an automatic optometer portion for measuring the refractive power of the eye, and a common optical path simultaneously to provide corrections for both portions of the instrument. The two dimensional eye tracker portion incorporates a means for directing a beam into the eye, thereby forming first and fourth Purkinje images, and measuring means responsive to the first and fourth Purkinje images to generate output signals indicative of eye rotation and translation. The automatic optometer portion alternately directs a light beam through different areas of the eye lens and includes a mechanism for altering the directed light beam until the image on the retina does not move. The common optical path for the light beams includes elements that stabilize the eye image in a way to make alignment of the subject in the instrument relatively easy and also to avoid errors both in measurement of refractive power and for direction of gaze due to translation and axial movement of the eye. Polarizers and mechanical stops are incorporated in the optometer portion to provide optical isolation between the eye tracker and the optometer portions, and electrical filtration is provided in both portions of the instrument further to avoid interference.

Claims

1. A three dimensional eye tracker for measuring, as a function of time, the point in three dimensional space on which the eye is fixed, including

a two dimensional double Purkinje image eye tracker portion for measuring movement of the eye in rotation and translation, said eye tracker incorporating means for forming and directing a beam containing images of first and fourth Purkinje images, measuring means responsive to said first and fourth Purkinje images to generate output signals indicative of eye rotation and translation, optical focusing and positioning means positioned in the path of said images and responsive to said output signals to maintain the position of the first Purkinje image relative to the said eye and focus images from the eye, and

an automatic optometer portion for measuring the refractive power of the eye, having beam generating means for forming an image at the eye and refractive power measuring means responsive to an image containing beam from the eye, at least a portion of said optometer beam path traversing a path including at least a portion of the said optical focusing and positioning means, whereby images formed by the said optometer portion are maintained in focus and stabilized in position.

2. A three dimensional eye tracker as defined in claim 1, wherein optical isolation means is provided for eliminating interference between beams formed in the said eye tracker and optometer portions and the means for generating output signals.

4. A three dimensional eye tracker as defined in claim 2, wherein optical isolation means is provided for eliminating interference between beams formed in the said eye tracker and optometer portions and the means for generating output signals.

3. A three dimensional eye tracker for measuring, as a function of time, the point in three dimensional space on which the eye is fixed, including

a two dimensional double Purkinje image eye tracker portion for measuring movement of the eye in rotation and translation, said eye tracker incorporating means for forming and directing an eye tracker input light beam to said eye, thereby forming first and fourth Purkinje images,

means for forming and directing an eye tracker output beam containing the said first and fourth Purkinje images,

optical image locating means adjustably positioned in both the said input and output beams for simultaneously stabilizing the position of the directed image on the eye and the position of the said output beam,

optical image focusing means adjustably positioned in the said output beam to determine focus of the said images,

Purkinje image location measuring means positioned to receive at least a portion of the said output beam from the said optical focusing means and image locating means, said Purkinje image location means being responsive to the said Purkinje images to generate output signals indicative of eye rotation and translation,

image location determining servo means connected to receive the said output signals indicative of eye rotation and translation and connected to stabilize both the position of the directed image on the eye and the position of the said output beam,

image condition of focus measuring means positioned to receive at least a portion of the said output beam from the said optical focusing means and image locating means and generate an output focus signal indicative of the condition of focus of at least one of the said images at a given location,

image focus determining servo means connected to receive the said output focus signal indicative of the condition of focus of the said images and connected to reposition the said optical image focusing means in response to the said signal, thereby to focus the said images at the said given position,

an automatic optometer portion for measuring the refractive power of the eye including optometer input light beam generating means for projecting a refracting image to the eye, and

means for projecting an optometer output beam containing said image from the eye back into the said optometer, whereby a measure of the refractive power of the eye may be made, a portion of each said optometer input and output beams and the said eye tracker output beam having a common path with each other which includes the said optical image focusing means and the said image locating means, whereby the focus and location of the said refracting image at the eye and position of the output beam are thereby stabilized.