EYE POSITION MEASURING TECHNIQUE

• US 3,864,030 A
• Filed: 07/11/1972
• Issued: 02/04/1975
• Est. Priority Date: 07/11/1972
• Status: Expired due to Term

• Current Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Tom N. Cornsweet
• Inventors: Cornsweet, Tom N.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/270,639
• Time in Patent Office: 938 Days
• Field of Search: 351/6,7 356/4,5,152
• US Class Current: 351/210
• CPC Class Codes: A61B 3/113 for determining or recording eye movement

Abstract

Apparatus and method for determining the relative position of an eye with respect to some apparatus. In the exemplary embodiment, relative eye positions in all three directions may be simultaneously monitored in both direction and magnitude. Displacements along any of the usual x, y and z coordinate directions are detected by processing the image of a light source reflected from the eye cornea which acts as a partially reflecting convex mirror. Eye displacements in a plane (x, y plane) perpendicular to the optic axis of the eye are measured by detecting the phase and magnitude of corneal reflections with respect to the phase of driving signals used to periodically energize a plurality of light sources in a predetermined sequence. Eye displacements along the eye optical axis (z axis) are measured by measuring the percentage of amplitude modulation introduced by corresponding movements of the reflected corneal image in the z direction between two light chopping devices. If displacements along only one coordinate axis are to be detected, subcombinations of the apparatus and techniques disclosed in the exemplary embodiment for simultaneous three dimensional detection of eye displacements may be utilized individually in a simplified fashion to obtain measurements of eye displacements along any desired number of coordinate directions.

Claims

1. An eye position measuring device for detecting relative eye position by measuring reflections from the eye'"'"''"'"'s cornea, said device comprising:

source means for selectively providing light energy emanating from different ones of at least two physically distinct positions and for providing a synchronization signal representative of the sequence with which light is caused to emanate from the distinct positions, light transmitting means for directing said light energy onto said cornea, light receiving means for collecting a portion of said light energy after reflection from said cornea, photodetecting means for converting reflected light passed by said receiving means into a photodetector output signal, said photodetecting means being aligned with the receiving means to provide substantially equal illumination thereof due to light emanating from either of said distinct positions when the cornea center is in alignment with an optical axis of said receiving means, and phase sensitive detecting means electrically connected to said source means and to said photodetectinG means for comparing the phase of said photodetector output signal with that of said synchronization signal to thereby provide a signal representing the relative direction of cornea displacement from an aligned position and hence representative of a corresponding relative eye position.

2. An eye position measuring device as in claim 1, wherein said source means comprises:

an array of at least two light sources, and electrical driving means connected thereto for alternately energizing said at least two light sources and for providing said synchronization signal.

3. An eye position measuring device as in claim 1, adapted to simultaneously monitor eye position displacements along both x and y axes in an orthogonal x, y, coordinate system, said x and y axes being perpendicular to the eye'"'"''"'"'s optical axis, wherein:

said source means includes means for alternately producing light energy from positions corresponding to the positive and negative x-axis directions and for producing an x-axis synchronization signal, said source means also includes means for alternately producing light energy from positions corresponding to the positive and negative y-axis directions and for producing a y-axis synchronization signal, said phase sensitive detecting means includes a first detector for comparing the phase of said photodetector output signal with said x-axis synchronization signal to produce an x-axis displacement signal representative of the direction and magnitude of eye movement along the x-axis, and said phase sensitive detecting means also includes a second detector for comparing the phase of said photodetector output signal with said y-axis synchronization signal to produce a y-axis displacement signal representative of the direction and magnitude of eye movement along the y-axis.

4. An eye position measuring device as in claim 3, wherein the source means interleaves the alternate production of light in the x-axis directions with the alternate production of light in the y-axis direction.

5. A closed loop servo system including an eye position measuring device as in claim 1 for automatically maintaining a predetermined physical relationship between another optical apparatus and said device, said system further comprising:

positional servo control means for physically adjusting the relative physical relationship between said optical apparatus and said device, and said positional servo control means being connected to and controlled by said signal representing the relative direction of cornea displacement.

6. An eye position measuring device for detecting relative eye position by measuring reflections from the eye'"'"''"'"'s cornea, said device comprising:

source means for selectively providing light energy emanating from different ones of at least two physically distinct positions and for providing a synchronization signal representative of the sequence with which light is caused to emanate from the distinct positions, light transmitting means for directing said light energy onto said cornea, light receiving means for collecting a portion of said light energy after reflection from said cornea, photodetecting means for converting reflected light passed by said receiving means into a photodetector output signal, said photodetecting means being aligned with the receiving means to provide substantially equal illumination thereof due to light emanating from either of said distinct positions when the cornea center is in alignment with an optical axis of said receiving means, phase sensitive detecting means electrically connected to said source means and to said photodetecting means for comparing the phase of said photodetector output signal with that of said synchronization signal to thereby provide a signal representing the relative direction of cornea displacement from an aligned position and henCe representative of a corresponding relative eye position, said source means comprising an array of at least two light sources, and electrical driving means connected thereto for alternately energizing said at least two light sources and for providing said synchronization signal, said array comprising four separate light sources arranged in a square array, and said electrical driving means comprising circuits for sequentially energizing the sources to effect rotation of the areas emanating light, said rotation being about an axis normal to the plane of said planar array and passing through its center thereby permitting substantially simultaneous measurement of eye movements in two coordinates within a plane perpendicular to the eye'"'"''"'"'s optical axis.

7. An eye position measuring device as in claim 6, wherein said electrical driving means includes means for simultaneously energizing two adjacent ones of said light sources during said rotation.

8. An eye position measuring device for detecting relative eye position by measuring reflections from the eye'"'"''"'"'s cornea adapted to simultaneously monitor eye position displacements along x, y, and z axes in an orthogonal x, y, z coordinate system, said x and y axes being perpendicular to the eye'"'"''"'"'s optical axis, and the z axis being directed along the eye'"'"''"'"'s optical axis, said device comprising:

source means for selectively providing light energy emanating from different ones of at least two physically distinct positions and for providing a synchronization signal representative of the sequence with which light is caused to emanate from the distinct positions, light transmitting means for directing said light energy onto said cornea, light receiving means for collecting a portion of said light energy after reflection from said cornea, photodetecting means for converting reflected light passed by said receiving means into a photodetector output signal, said photodetecting means being aligned with the receiving means to provide substantially equal illumination thereof due to light emanating from either of said distinct positions when the cornea center is in alignment with an optical axis of said receiving means, phase sensitive detecting means electrically connected to said source means and to said photodetecting means for comparing the phase of said photodetector output signal with that of said synchronization signal to thereby provide a signal representing the relative direction of cornea displacement from an aligned position and hence representative of a corresponding relative eye position, said source means including means for alternately producing light energy from positions corresponding to the positive and negative x-axis directions and for producing in x-axis synchronization signal, said source means also including means for alternately producing light energy from positions corresponding to the positive and negative y-axis directions and for producing a y-axis synchronization signal, said phase sensitive detecting means including a first detector for comparing the phase of said photodetector output signal with said x-axis synchronization signal to produce an x-axis displacement signal representative of the direction and magnitude of eye movement along the x-axis, said phase sensitive detecting means also including a second detector for comparing the phase of said photodetector output signal with said y-axis synchronization signal to produce a y-axis displacement signal representative of the direction and magnitude of eye movement along the y-axis, light chopping means for alternately chopping light passing through said receiving means at predetermined locations on each side of a focussed corneal reflection image whereby the degree of modulation produced in light passing through the light chopping means is dependent upon the relative distances between the focussed corneal reflection image and said predetermined locations, the envelope of the modulation being in-phase with the light chopping at the nearest of said predetermined locations, said light chopping means also producing a z-axis synchronization signal representing the timing of the alternate chopping at said predetermined locations, and a third detector for comparing said photodetector output signal with said z-axis synchronization signal to produce a z-axis displacement signal representative of the direction and magnitude of eye movement along the z-axis.

9. An eye position measuring device as in claim 8, wherein said light chopping means comprises:

a rotatable transparent disk having alternate sectors of spaced light blocking stripes therein on each side of the disk, a sector of stripes on one surface being opposite a transparent sector on the other surface, and said disk surfaces being located in planes respectively passing through said predetermined locations.

10. An eye position measuring device as in claim 8, wherein:

said first and second detectors are connected to receive said photodetector output signal through a filter circuit for blocking the modulation frequency introduced by said chopping means, and said third detector is connected to receive said photodetector output signal through another filter circuit for blocking the signal frequencies caused by the sequential changes of light emanating from said source means.

11. A method for detecting eye displacements by measuring reflections from the eye'"'"''"'"'s cornea, said method comprising:

alternately illuminating different parts of said cornea, collecting at least a first portion of the light reflected from the cornea when in a nominally centered position and illuminated on a first part thereof, collecting at least a second portion of the light reflected from the cornea when in a nominally centered position and illuminated on a second part thereof, said first and second portions being substantially equal when the cornea is in said nominally centered position, converting said first and second portions into an electrical signal which is substantially d.c. signal when the cornea is in said nominally centered position, and comparing the phase relationships between said electrical signal and said alternate illumination of different parts of the cornea to measure the direction of eye displacements.

12. A method as in claim 11, further comprising:

measuring the amplitude of said electrical signal to provide a measurement of the magnitude of said eye displacements.

13. A method as in claim 11, further comprising:

controlling the relative positioning between an optical apparatus and said eye in response to said electrical signal.

14. A method as in claim 11, further comprising:

forming an image at a predetermined image location when the cornea is in said nominally centered position, of light reflected from said cornea, chopping said reflected light at a first position displaced from said image location, measuring the percentage of modulation introduced in said electrical signal at the frequency of said chopping to provide a measurement of the magnitude of eye displacements along the optical axis of the eye.

15. A method as in claim 14, wherein:

said chopping step comprises alternate chopping at both said first position and another second position, said image location being half way therebetween, and said measuring step comprises detecting the envelope of said modulation and comparing its phase with the phase of the alternate chopping to derive a measurement of the direction of eye displacements along the optical axis of the eye.