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Claims  |
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Having thus defined our invention, we claim:
1. A system for viewing an external scene visually observed through at
least one eye of an observer thereof comprising:
(a) helmet means for mounting on the head of an observer;
(b) a field-of-view camera mounted on said helmet and having a
field-of-view camera axis generally perpendicular to the optic axis of the
obserber's eye in the sense that said field-of-view camera's optic axis
intersects said eye's optic axis;
(c) an especially configured visor mounted on said helmet directly in front
of said eye, said visor at least partially transparent to light from said
scene transmitted to said eye of the observer along said optic axis and
reflecting said light from said scene as a mirror image to said
field-of-view camera; and
(d) adjustment means associated with said visor, said field-of-view camera
and said helmet means for spacing the visor at equal distances between
said eye and said field-of-view camera measured from said intersection of
said optic axis, and adjusting the angle between said visor and said
field-of-view camera axis, to be equal to the angle between said visor and
said eye's optic axis said angles being measured from the same side of
said visor so that parallax is minimized to permit the point-of-view
camera to accurately record said external scene as visualized by said eye.
2. The system of claim 1 wherein said visor includes an infrared reflective
layer for reflecting light of about infrared frequencies along said
field-of-view camera's axis, said field-of-view camera being a
monochromatic camera sensitive to said reflected light.
3. The system of claim 2 wherein said visor is a glass laminate including a
glass substrate having said infrared layer as a coating on one surface
thereof reflecting light of about infrared wavelength, a polycarbonate
substrate adjacent said glass substrate on the side of said glass
substrate opposite said infrared coating, and means to attach said
polycarbonate substrate to said glass substrate.
4. The system of claim 3 wherein the thickness of said visor is no more
than about 3 mm.
5. The system of claim 4 wherein said visor is sized to yield about a 45
degree vertical.times.55 degree horizontal field-of-view.
6. The system of claim 5 wherein said visor has a vertical distance of
about 4" and the focal length of the lens of said field-of-view camera is
about 8 mm.
7. The system of claim 1 wherein said visor includes a metallic reflecting
film on the backside of said visor for reflecting light of visible
wavelength along said camera's axis, said camera being a camera capable of
recording visible light.
8. The system of claim 7 wherein said visor further includes a polarizing
film adjacent said metallic film for transmitting polarized light to the
eye of said observer, said camera having a polarized filter adjacent the
lens thereof and a filter for preventing light of near infrared wavelength
from being transmitted through the lens of said camera.
9. The system of claim 8 wherein said visor is a glass laminate including a
glass substrate, an infrared layer applied to the front side of said visor
facing the eye of said observer for reflecting light of about infrared
wave length, a polycarbonate substrate adhesively secured to the back side
of said glass substrate, a polarizing film secured to the back side of
said polycarbonate substrate, and said metallic film affixed to the back
side of said polarizing film.
10. The system of claim 9 wherein said polarizing film is removably clipped
to said glass and polycarbonate substrates.
11. The system of claim 9 wherein said polarizing film is adhesively
secured to the back side of said polycarbonate substrate.
12. The system of claim 9 wherein said visor is no more than about 4.5 mm
thick.
13. The system of claim 12 wherein said visor is sized to yield about a 45
degree vertical.times.55 degree horizontal field-of-view.
14. The system of claim 13 wherein said visor has a vertical distance of
about 4" and the focal length of the lens of said field-of-view camera is
about 8.0 mm.
15. The system of claim 1 further including eye tracking means for
determining the point of gaze of said eye of said observer.
16. The system of claim 15 wherein said eye tracking means includes
illuminator means for transmitting a light source at near infrared
wavelength frequency in a given direction, an eye monitor camera disposed
with its lens axis coaxial with said direction of said light source, said
illuminator means reflected by said visor towards the pupil of said eye as
a light beam and reflected back as a bright pupil disc and corneal
reflection spot beam by said visor to said eye monitor camera whereby the
corneal and pupil reflection of the eye of said observer is recorded as a
point of gaze spot by said eye monitor camera and means for projecting
said point of gaze spot onto said scene as recorded by said point-of-view
camera.
17. The system of claim 16 wherein said visor includes an infrared
reflective layer for reflecting light of about infrared frequencies along
said camera's axis, said camera being a monochromatic camera sensitive to
said reflected light.
18. The system of claim 17 wherein said visor is a glass laminate including
a glass substrate having said infrared layer as a coating on one surface
thereof reflecting light of about infrared wavelength, a polycarbonate
substrate adjacent said glass substrate on the side of said glass
substrate opposite said infrared coating, and means to attach said
polycarbonate substrate to said glass substrate.
19. The system of claim 18 wherein the thickness of said visor is no more
than about 3 mm.
20. The system of claim 19 wherein said visor is sized to yield about a 45
degree vertical.times.55 degree horizontal field-of-view.
21. The system of claim 20 wherein said visor has a vertical distance of
about 4" and the focal length of the lens of said field-of-view camera is
about 8 mm.
22. The system of claim 16 wherein said visor includes a metallic
reflecting film on the backside of said visor for reflecting light of
visible wavelength along said camera's axis, said camera being a camera
capable of recording visible light.
23. The system of claim 22 wherein said visor further includes a polarizing
film adjacent said metallic film for transmitting polarized light to the
eye of said observer, said camera haing a polarized filter adjacent the
lens thereof and a filter for preventing light of near infrared wavelength
from being transmitted through the lens of said camera.
24. The system of claim 23 wherein said visor is a glass laminate including
a glass substrate, an infrared layer applied to the front side of said
visor facing the eye of said observer for reflecting light of about
infrared wave length, a polycarbonate substrate adhesively secured to the
back side of said glass substrate, a polarizing film secured to the back
side of said polycarbonate substrate, and said metallic film affixed to
the back side of said polarizing film.
25. The system of claim 24 wherein said polarizing film is removably
clipped to said glass and polycarbonate substrates.
26. The system of claim 24 wherein said polarizing film is adhesively
secured to the back side of said polycarbonate substrate.
27. The system of claim 26 wherein said visor is no more than about 4.5 mm
thick.
28. The system of claim 27 wherein said visor is sized to yield about a 45
degree vertical.times.55 degree horizontal field-of-view.
29. The system of claim 28 wherein said visor has a vertical distance of
about 4" and the focal length of the lens of said field-of-view camera is
about 8 mm.
30. A head-mounted eye-movement system for monitoring an observer's view of
any external scene as seen through at least one of the observer's eyes,
said system comprising:
(a) a field-of-view camera positioned vertically on one side of the optic
axis of said eye for recording said scene;
(b) eye tracking means including an eye tracking source of near infrared
light for recording the position of said eye as said observer views said
scene vertically positioned on the opposite side of the eye's optic axis;
(c) a visor positioned vertically between said field-of-view camera and
said eye tracker means at the intersection of said eye's optic axis with
said field-of-view camera's optic axis, said visor transparent to visible
light to permit said observer to view said scene while looking through
said visor;
(d) optical coating means on said visor, said coating means reflecting said
eye tracker light to actuate said eye tracking means while reflecting
light from said scene to said field-of-view camera to simultaneously
permit said field-of-view camera to record said scene.
31. The head-mounted system of claim 30 wherein said eye tracking means
includes an eye tracker camera having an optic axis, said eye tracking
source of light generally coaxial with said eye tracker camera's optic
axis.
32. The head-mounted system of claim 30 further including adjustment means
for adjusting the distance between said observer's eye and said visor to
be approximately equal to the distance between the aperture of said
field-of-view camera lens and said visor, and the angle formed between and
by the intersection of said optic axis of said field-of-view camera with
said visor being approximately equal to the angle formed between and by
the intersection of said optic axis of said observer's eye with said
visor, said angles, for reference purposes, measured on the same side of
said visor whereby parallax is minimized.
33. The head-mounted system of claim 32 wherein said eye tracking means
includes an eye tracker camera having an optic axis, said eye tracking
source of light generally coaxial with said eye tracker camera's optic
axis.
34. The head-mounted system of claim 33 wherein said eye tracker camera's
optic axis is approximately parallel to said field-of-view camera's optic
axis.
35. The head-mounted system of claim 32 wherein said field-of-view camera
has an 8 mm focal length lens.
36. The head-mounted system of claim 35 wherein said eye tracker means is
reflective to track the movement of said eye over a 55 degree horizontal
and 45 degree vertical field-of-view.
37. The head-mounted system of claim 36 wherein said eye tracking means
includes an eye tracker camera having an optic axis, said eye tracking
source of light generally coaxial with said eye tracker camera's optic
axis.
38. The head-mounted system of claim 37 wherein said eye tracker camera's
optic axis is approximately parallel to said field-of-view camera's optic
axis.
39. The head-mounted system of claim 30 wherein said optical coating means
includes an infrared optical coating for reflecting light having near
infrared wavelength, said infrared optical coating reflecting said
infrared source light on one side thereof for actuating said eye tracking
means while reflecting scene light of near infrared wavelength to said
field-of-view camera for recording said scene, said field-of-view camera
being a monochromatic infrared camera.
40. The head-mounted system of claim 39 further including adjustment means
for adjusting the distance between said observer's eye and said visor to
be approximately equal to the distance between the aperture of said
field-of-view camera lens and said visor, and the angle formed between and
by the intersection of said optic axis of said field-of-view camera with
said visor being approximately equal to the angle formed between and by
the intersection of said optic axis of said observer's eye with said
visor, said angles, for reference purposes, measured on the same side of
said visor whereby parallax is minimized.
41. The head-mounted system of claim 40 wherein said eye tracking means
includes an eye tracker camera having an optic axis, said eye tracking
source of light generally coaxial with said eye tracker camera's optic
axis.
42. The head-mounted system of claim 41 wherein said eye tracker camera's
optic axis is approximately parallel to said field-of-view camera's optic
axis.
43. The head-mounted system of claim 30 wherein said optical coating means
includes an infrared optical coating for reflecting light having near
infrared wavelength on one side of said visor for actuating said eye
tracking means and a visible light optical coating on the opposite side of
said visor for reflecting scene light of visible wavelength to said
point-of-view camera, said point-of-view camera being a camera capable of
recording a visible light.
44. The head-mounted system of claim 43 wherein said visor has a polarizing
film adjacent said visible light optical coating for polarizing said scene
light, and said field-of-view camera having a polarizing filter lens and
an infrared cut filter lens preventing transmission of light having near
infrared wavelength to said field-of-view camera.
45. The head-mounted system of claim 44 further including adjustment means
for adjusting the distance betweem said observer's eye and said visor to
be approximately equal to the distance between the aperture of said
field-of-view camera lens and said visor, and the angle formed between and
by the intersection of said optic axis of said field-of-view camera with
said visor being approximately equal to the angle formed between and by
the intersection of said optic axis of said observer's eye with said
visor, said angles, for reference purposes, measured on the same side of
said visor whereby parallax is minimized.
46. The head-mounted system of claim 45 wherein said eye tracking means
includes an eye tracker camera having an optic axis, said eye tracking
source of light generally coaxial with said eye tracker camera's optic
axis.
47. The head-mounted system of claim 46 wherein said eye tracker camera's
optic axis is approximately parallel to said field-of-view camera's optic
axis.
48. The head-mounted system of claim 47 further including head position
means for sensing the position of the head of said observer and means for
combining data from said eye-tracker camera, said field-of-veiw camera and
said head position means to determine said observer's absolute
point-of-gaze.
49. In a head-mounted eye monitor system including an eye tracker camera,
an external eye tracker source of near infrared light, and a field-of-view
camera for recording the external scene viewed by at least one eye of the
observer, the improvement comprising:
(a) means for mounting at least the lens of said eye tracker camera, in
fixed relationship to the head of the observer, vertically spaced from and
on one side of the optic axis of said observer's eye;
(b) means for mounting at least the lens of said field-of-view camera in
fixed relationship to the head of the observer vertically spaced from and
on the opposite side of the optic axis of said observer's eye from that of
said eye tracker camera;
(c) a visor positioned at the intersection of the optic axis of said
observer's eye with the optic axis of said field-of-view camera and
transparent to visible light from said external scene; and
(d) reflective means on said visor for reflecting said eye tracker light
from one side of said visor to said eye tracker camera for recording the
positions of said observer's eye and reflecting light from said external
scene from the opposite side of said visor and in the opposite direction
to said field-of-view camera for recording said external scene as viewed
by said observer's eye.
50. The system of claim 49 further including adjustment means for adjusting
the distance between said observer's eye and said visor to be
approximately equal to the distance between the aperture of said
field-of-view camera lens and said visor, and for adjusting the angle
formed between and by the intersection of said optic axis of said
field-of-view camera with said visor to be approximately equal to the
angle formed between and by the intersection of said optic axis of said
observer's eye with said visor, said angles, for reference purposes,
measured on the same side of said visor whereby parallax is minimized.
51. The head-mounted system of claim 50 wherein said eye tracking means
includes an eye tracker camera having an optic axis, said eye tracking
source of light generally coaxial with said eye tracker camera's optic
axis.
52. The head-mounted system of claim 51 wherein said eye tracker camera's
optic axis is approximately parallel to said field-of-view camera's optic
axis.
53. The head-mounted system of claim 52 wherein said optical coating means
includes an infrared optical coating for reflecting light having near
infrared wavelength, said infrared optical coating reflecting said
infrared source light on one side thereof for actuating said eye tracking
means while reflecting scene light or near infrared wavelength to said
field-of-view camera for recording said scene, said field-of-view camera
being a monochromatic infrared camera.
54. The head-mounted system of claim 52 wherein said optical coating means
includes an infrared optical coating for reflecting light having near
infrared wavelength on one side of said visor for actuating said eye
tracking means and a visible light optical coating on the opposite side of
said visor for reflecting scene light of visible wavelength to said
point-of-view camera, said point-of-view camera being a camera capable of
recording a visible light.
55. The head-mounted system of claim 54 wherein aid visor has a polarizing
film adjacent said visible light optical coating for polarizing said scene
light, and said field-of-view camera having a polarizing filter lens and
an infrared cut filter lens preventing transmission of light having near
infrared wavelength to said field-of-view camera.
56. An eye-movement monitoring system comprising
an eye-tracker camera,
an external eye-tracker source of near infrared light,
a field-of-view camera for recording the external scene viewed by at least
one eye of an observer,
means for mounting at least the lens of said eyetracker camera, vertically
spaced from and on one side of the optic axis of said observer's eye;
means for mounting at least the lens of said field-of-view camera
vertically spaced from and on the opposite side of the optic axis of said
observer's eye from that of said eye-tracker camera;
a visor positioned at the intersection of the optic axis of said observer's
eye with the optic axis of said field-of-view camera and transparent to
visible light from said external scene; and
reflective means on said visor for reflecting said eye-tracker light from
one side of said visor to said eyetracker camera for recording the
positions of said observer's eye and reflecting light from said external
scene from the opposite side of said visor and in the opposite direction
to said field-of-view camera for recording said external scene as viewed
by said observer's eye.
57. The eye-movement monitoring system of claim 56 wherein said means for
mounting includes a mounting affixed to the head of said observer. |
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Claims |
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Description |
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This invention relates generally to an eye-movement measurement system and
more particularly to eye monitoring systems adapted to be mounted to the
observer's head.
The invention is particularly applicable to an eyemovement measurement
system which utilizes an eye tracker in combination with a point-of-view
camera to determine the observer's point of gaze and will be described
with particular reference thereto. However, it will be appreciated by
those skilled in the art that the invention may have broader application
and may be applied in any situation where a picture, preferably a video
recording, of the external scene actually viewed by the observer is
desired. Additionally, it will be appreciated by those skilled in the art
that while the invention has particular application to a headmounted
system, the arrangement disclosed can easily be adapted for use in a floor
mounted or remote eye-movement measurement system.
INCORPORATION BY REFERENCE
The following documents are incorporated herein by reference as background
material and form a part hereof:
(1) An article entitled "Eye-Movement Measurement Techniques" by L. R.
Young & David Sheena appearing in American Psychologist, Volume 30, No. 3,
dated March 1975, Pages 315-330;
(2) Methods & Design - Survey of Eye Movement Recording Methods" by Young &
Sheena, Behavior Research Methods & Instrumentation, 1975, Vol. 7 (5),
Pages 397-429;
(3) "Eye-Trac" Catalog by Applied Science Laboratories, copyright 1982,
pages 1-31;
(4) U.S. Pat. No. 4,034,401 to Mann;
(5) U.S. Pat. No. 3,542,457 to Balding et al;
(6) European Patent Application Publication No. 0-125-808 dated Nov. 21,
1984;
(7) European Patent Application Publication No. 0-157-973 dated Nov. 16,
1985;
(8) U.S. Pat. No. 4,755,045 by the present inventors; and
(9) U.S. Ser. No. 848,154, filed Apr. 4, 1986 and assigned to Applied
Science Laboratories.
BACKGROUND
There are a large number of eye-movement measuring techniques in the art
and the principal ones are disclosed in the Young & Sheena articles which
are incorporated by reference herein. This invention relates to those
eyemovement measuring techniques which use an external light source,
generally at near infrared wavelength, which is reflected from some
portion of the eye to obtain a measurement of eye position or fixation.
Generally, such techniques are classified as corneal reflection per se,
corneal reflection-pupil center, corneal reflection-double Purkinje image,
pupil tracking per se, limbus (i.e., the boundary between the iris and the
sclera) tracking, eyelid tracking and combinations thereof. When used
throughout this specification, reference to "eye tracker" or "eye tracker
means" or "eye tracker mechanism" means any and all conventional
mechanisms which utilize any of the aforementioned tracking techniques
principally be measuring reflection of light from or over a portion of the
eye. This is in distinction to electrooculography and contact lens
eye-movement measurement techniques which do not fall within the
definition of an eye tracker as used herein.
Eye trackers of the type to which this invention relates, may be further
classified as (i) head-mounted, in the sense that the principal
measurement instruments are secured by a helmet or head band to the
observer's head or (ii) "remote" or floor mounted in the sense that no
instruments are applied to the observer's head even though chin rests or
other devices might be used to immobilize the observer's head movement of
(iii) a combination of "head-mounted" and "remote" or "hybrid" devices
which do not exist in a practical, commercial sense, but are present in
any theoretical consideration.
A totally "remote" eye tracker system is produced by Applied Science
Laboratories, the assignee of the present invention, in its 1996 and 1998
model lines which are further described in our U.S. Pat. No. 4,755,045,
U.S. patent application Ser. No. 848,154, and in ASL's Eye Trac Catalog,
all incorporated by reference herein. In the 1998 model, the position of a
servo controlled tracking mirror is controlled to maintain the eye image
within the eye camera field-of-view so that eye line-of-gaze can be
determined with the pupil center to corneal reflection technique. In this
manner, rapid, unrestrained movements of the head will not result in loss
of eye measurement even with as much as one foot of lateral or vertical
head motion. Because there are no head-mounted instruments nor any other
distracting instrumentation present to the observer, the 1996 and 1998
systems are ideal for eye tracking measurements where the observer is
seated, such as in the cockpit of a flight trainer or in a chair watching
video commercials, etc. However, there are countless research, industrial
and military applications where it is desired to accurately see what a
person is looking at instead of projecting a predetermined scene and
monitoring the reaction of the observer to the projected scene. Such
applications typically use headmounted systems to monitor eye-movements.
As noted, hybrid head-mounted - remote systems exist in the literature. For
example, in EPC application No. 0157973, the external light source for
directing the near infrared light for eye measurement purposes is mounted
in the observation room while the corneal reflection instrument is
attached to eyeglass frames affixed to the observer, who is viewing a
scene projected on a screen. In U.S. Pat. No. 4,034,401, both the near
infrared light source and the eye tracker camera (which is of the limbus
tracking type) are reflected off a pilot's helmet to locate the eye
position relative to an externally generated weapons pointing display
reflected on the windshield of the aircraft. In both applications, the
observer is seated or stationary and looking at a scene which is projected
in front of him. To partially mount some of the eye tracker mechanism to
the head of the observer simply encumbers the observer without presenting
any enhancement of the system when compared with the ASL 1998 model used
either in an airplane cockpit environment or in a seated environment for
viewing artificially projected scenes such as commercials and the like.
For such reasons, "hybrid" eye measurement systems are not commercially
practical.
This then leaves head-mounted systems to satisfy those applications, i.e.,
observer movement and/or real life scene viewing, which cannot be
addressed by head-free systems. A head-mounted, eye monitoring system as
thus defined herein requires a field-of-view or scene camera which records
any external scene as actually viewed by the observer and an eye tracker
mechanism, both items secured by an appropriate head band or helmet to the
head of the observer. Different, head-mounted systems have been developed
in the art for different eye measuring techniques, principally limbus
tracking and corneal reflection.
One typical limbus tracking arrangement uses eyeglasses with an infrared
source of illumination mounted at the bottom of the lens and flanked on
either side by photo cells which electrically record the light reflected
to generate an eye image. A field-of-view camera is then added to the
eyeglasses to obtain a point-of-gaze display. Examples of such
head-mounted limbus tracking systems may be found in ASL's Eye Trac
Catalog and in several embodiments disclosed in European Patent
Application No. 0,125,808, which also discloses use of CCD chips for
imaging. As noted by Young & Sheena, the eyeglass limbus tracking
arrangement is suitable for some applications, but is limited with respect
to vertical eye-movement measurement. Also, the field-of-view camera is
mounted on one side of the eyeglass frame while the eye position
measurement instruments are located on the other side and this
side-by-side mounting arrangement introduces a parallax error, which may
or may not present a problem.
To obtain more precise eye measurement over both horizontal and vertical
eye-movement, corneal reflex cameras have been used in head-mounted eye
monitoring systems which also employ field-of-view cameras to obtain point
of gaze information from an observer having freedom of movement. As
disclosed in the Young & Sheena articles, early head-mounted corneal
reflex eye monitoring systems used a periscope arrangement with the bottom
of the scope carrying the infrared light source and scope lenses which
reflected the infrared image to the top of the scope. The top of the scope
was mounted on top of the observers head and carried the scene lens and an
eye tracker camera in combination with a beam splitter prism for
superimposing the corneal reflection as a spot of light onto the scene
recorded from the field-of-view camera. Because of difficulties
encountered in maintaining the infrared light source appropriately
centered relative to the cornea, this concept has been modified into a
side-by-side arrangement where the field-of-view camera is mounted on one
side of the observer's head while the eye tracker mechanism with
appropriate optics is mounted on the opposite side. Fiber optics have been
used to lighten the helmet weight. One example of such an arrangement is
disclosed in U.S. Pat. No. 3,542,457, incorporated by reference herein. As
best illustrated in U.S. Pat. No. 3,542,457, a dichroic fixed mirror is
used to reflect light from an infrared lamp to the eye spot or eye track
camera for subsequent superimposition on the scene viewed by the
field-of-view camera, the eye also viewing the scene through the dichroic
mirror which is transparent to visible light. As in the earlier periscope
version of the helmet, U.S. Pat. No. 3,542,457 uses a complicated optic
system to reflect the light to the cornea and back to the eye tracker
camera.
It should also be noted that in the literature, specifically for one of the
embodiments disclosed in EPA No. 125-808-A, the concept of using an eye
tracker camera on the "limbus tracking" eyeglass frame for recording
corneal reflection without complicated optics is used. However, that
disclosure fixed the infrared lamp to the bridge of the eyeglass frame and
would be suspect to the errors and inaccuracies of the earlier corneal
reflex head-mounted systems which used a light source simply positioned in
front of the eye.
In addition, it is known and disclosed in ASL's Eye Trac Catalog and
discussed in some length by Young & Sheena that any number of different
sensors, i.e., magnetic head, optic, mechanical, etc., may be applied to
the observer's head to measure the orientation of the eye in space to
obtain the point-of-gaze (the angle of gaze relative to a reference point
in the visual field) relative to ground.
In summary, the limbus tracking eyeglasses are limited in their ability to
measure eye-movement and the helmet mounted corneal reflection cameras
require optics which somewhat tend to distort the spot image projection
and require extensive calibration and readjustment. More importantly, all
head-mounted, eye-movement measurement systems heretofore mounted the
field-of-view or scene camera short distance from the eye (or eyes) whose
movement was being recorded in a manner which introduced a perspective or
parallax error. The parallax error could allow the field-of-view camera to
see an object which is actually hidden and thus not visible to the
observer. This difference in field-of-view is significantly noticeable at
short distances and somewhat insignificant at infinity. When an eye
tracker is used with the field-of-view camera in a head-mounted system,
the system must be calibrated to the scene distance viewed if accurate
point-of-gaze data is to be obtained. That is the field-of-view scene
recorded must be adjusted for parallax for the distance of the particular
viewed scene and the eye tracker than adjusted relative to the adjusted
field-of-view scene thus recorded if accurate point-of-gaze information in
space which is depended on absolute eye position, is to be obtained.
Heretofore, mechanical and/or optical conflicts have either resulted in
camera incompatibility with a head-mounted eye tracker or limitations of
eye tracker performance to a specifically calibrated distance.
SUMMARY OF THE INVENTION
Accordingly, it is one of the principal objects of the present invention to
provide a head-mounted eye-movement monitoring system which provides
accurate recording of the observer's eye-movement relative to the external
scene as actually viewed by the observer.
This feature, along with other features of the invention, is achieved in a
head-mounted eye-movement system which monitors an observer's view of any
external scene as seen through at least one of the observer's eyes. The
system includes a field-of-view camera positioned vertically on one side
of the optic axis of the eye for recording the scene. An eye tracker
mechanism which includes an eye tracking source of near infrared light for
recording the position of the eye as the observer views the scene is
vertically positioned on the opposite side of the eye's optic axis. A
visor is vertically positioned at an angle between the field-of-view
camera and the eye tracker mechanism at the intersection of the eye's
optic axis with the field-of-view camera's optic axis. The visor is
transparent to visible light to permit the observer to view the external
scene while looking through the visor. An optical coating arrangement is
provided on the visor which reflects the near infrared eye tracker light
from the eye of the observer to actuate the eye tracker mechanism in
accordance with standard practice while simultaneously reflecting light
from the external scene to the field-of-view camera for recording the
external scene viewed by the observer. The two way, oppositely directed,
reflective reverse mirror views of the visor (actually a three way
utilization) permits a stable, vertical mount arrangement with all
measuring instrumentation positioned over or under the eye whose movement
is to be recorded. Thus the system can be easily modified to include a
second field-of-view camera for the other eye in combination with an
additional eye tracker mechanism so that the movement of both eyes can be
easily recorded. In such an arrangement the visor would simply be
laterally extended across the face of the observer. In addition, when the
eye tracker mechanism utilized any of the corneal reflection techniques,
the general arrangement described permits a very simple optic system,
essentially comprising only the visor, to reflect a coaxial infrared light
source to the eye and back to the eye tracker camera avoiding the
intricacies of the prior art helmet mounted optics and inherently
resulting in a clearer eye tracker picture which maintains proper eye
alignment irrespective of eye-movement.
In accordance with another principal feature of the invention, a helmet or
head band arrangement is provided which precisely mounts the field-of-view
camera in a fixed relationship to the eye of the observer. More
particularly, adjustment mechanisms associated with the visor,
field-of-view camera and the helmet space the visor at equal distances
between the eye and the field-of-view camera. This distance is measured
from the intersection point of the eye's optic axis with the field-of-view
camera's opt | | |
