High speed eye tracking device and method

• US 5,430,505 A
• Filed: 08/17/1993
• Issued: 07/04/1995
• Est. Priority Date: 01/30/1992
• Status: Expired due to Term

• Current Assignee: MÄK Technologies, Inc. (Singapore Technologies Engineering Limited)
• Original Assignee: MÄK Technologies, Inc. (Singapore Technologies Engineering Limited)
• Inventors: Katz, Warren J.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Dang, Hung Xuan
• Application Number:
  US08/107,005
• Time in Patent Office: 686 Days
• Field of Search: 351/208, 351/205, 351/209, 351/210, 351/221, 250/221, 250/216
• US Class Current: 351/208
• 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

Abstract

An eye tracking device that utilizes light detection devices for determining the visual axis and point of regard of a user. The light detection devices are arranged in such a way, such as embedded in a thin film, so as to be curved around the optical axis of the eye. In this way, the light detection devices are always coincident with source-emitted light reflected from the fovea. The curved arrangement of light detection devices are mounted onto a head or facial apparatus, which has a mild reflector on its outside surface to keep external light noise at a minimum. Conversion circuitry, such as a pyramid cascade circuit or a microprocessor circuit, determines the position of the fovea-reflected light and computes the visual axis and point of regard of the user at a very rapid rate.

Claims

1. An eye tracking device comprising a peripheral light source which emits light into a curved optical layer aligned with the optical axis of the eye, said optical layer comprised of resistive strips, the resistance of said resistive strips changing with the amount of light impinging on them, said optical layer and said resistive strips having a reflective coating on their outer surface specifically reflective to the emitted frequency of said light, so that said resistive strips do not contact with said emitted light, except that emitted light that escapes through said resistive strips emerges in the direction of the eye, whereby light reflected from the fovea impinges on the uncoated surface of said reflective strips and changes their resistance, such that the location of the fovea can be ascertained, and computing means for computing the visual axis and point of regard from said fovea-reflected light.

2. The eye tracking device of claim 1 whereby the curvature of the optical layer conforms to the curvature of the eye.

3. The eye tracking device of claim 2 whereby the curved optical layer is mounted on head apparel means and extended around said head apparel means so as to correspond to the optical axis of the eye, such that the resistive strips are always coincident with said optical axis of the eye.

4. The eye tracking device of claim 3 whereby the outside surface of the head apparel means is equipped with a mild reflector on said outside surface, said mild reflector being reflective of external light sources of the same frequency as the light emitted by the peripheral light source.

5. The eye tracking device of claim 2, wherein said device is calibrated to any individual user by measuring the curvature of said individual'"'"'s eye and curving the optical layer to parallel said eye curvature.

6. The eye tracking device of claim 1 where the computing means comprises a pyramid cascade circuit comprising a plurality of read only memory words which contain the hard coded address for each row and column of the resistive strips, a plurality of analog to digital converters for converting the voltage output of each row and column of said resistive strips to a numerical value, and a plurality of comparators between each pair of said rows and columns for comparing the numerical values and selecting the larger of the two, passing said larger numerical value and said address up to the next level of comparators, until the address with the largest numerical value is determined.

7. The eye tracking device of claim 6 whereby two pyramid cascade circuits are utilized, one for the rows of transparent resistive strips and one for the columns of transparent resistive strips.

8. The eye tracking device of claim 1 where the computing means comprises a microprocessor, said microprocessor comprising a plurality of analog to digital converters for converting the voltage output of each row and column of the resistive strips to a numerical value, and a digital multiplexor for selecting the numerical value that corresponds to its address in each row and column of said resistive strips, said microprocessor being programmed in such a way that it sorts through all of said rows and columns, determines which has the highest numerical value, and outputs the address of said row and column with said highest numerical value.

9. The eye tracking device of claim 8 whereby two microprocessor circuits are utilized, one for the rows of transparent resistive strips and one for the columns of transparent resistive strips.