Lightweight device to stimulate and monitor human vestibulo-ocular reflex

A helmet formed of a rigid shell is disclosed. The shell is lined with several air filled bladders to contact firmly the head of a user. The shell has a rigid chin bar supporting a bite bar connected fixedly to a mouthpiece bearing against the teeth and hard palate to firmly anchor the helmet without movement. The outer shell surface supports various air pumping bulbs and accelerometers. Separate left and right visor pivot on the side guided in a central tongue and groove track to move optical lens mounts into the user's field of vision. The chin bar is connected to the shell by a pair of releasable clasps. A safety lanyard connects to the clasps to quickly pull pins from the clasps to enable quick release in case of motion sickness.

BACKGROUND OF THE INVENTION 
1. Technical Field of the Invention 
The field of invention of this invention is a specialty helmet for 
supporting optical equipment in close proximity to the eyes of a subject 
for making specific eye stimulation and reflex measurements. It is 
extremely important that the optical equipment be fixed relative to the 
helmet and the helmet in turn fixed relative to the head of the subject. 
Slippage or movement between the subject's head and the helmet creates 
incorrect data and to this end, the present apparatus is a structure which 
can be coupled to the head of the subject (by rigid attachment to the 
skull without slippage) such that accurate data can be obtained. Moreover, 
it selectively mounts and dismounts as required appropriate optical 
equipment for making measurements of the subject. 
2. Discussion of Background Art 
References known to exist and having a bearing on the subject matter of the 
present disclosure include Jencks, U.S. Pat. No. 4,035,846. This shows an 
inflatable stabilization system located on the interior of an outside 
rigid helmet shell. There is an inflatable bladder having a number of 
fingers. The bladder is inflatable by operation of a manifold system 
connected to the bladder within the helmet. 
Chaise U.S. Pat. No. 4,581,774 is a protective motorcycle helmet disclosing 
a collar and cooperative fastener below the collar. Helmer U.S. Pat. No. 
3,082,765 shows a football helmet or the like having a chin strap with a 
cooperative mouthpiece adapted for protection of the mouth and teeth. 
Littler U.S. Pat. No. 4,274,161 shows a collar which has a tubular body 
enabling it to fit around a neck to conform beneath a crash helmet 
typically worn by a motorcycle driver. Poon U.S. Pat. No. 4,586,200 is a 
motorcycle driver helmet having a multiple skin construction in the helmet 
shell which enables air to be captured in bubbles within the structure. It 
conforms more readily to the fit, size and shape of the user's head. 
Taesler U.S. Pat. No. 4,259,747 is a helmet for aircraft pilots. It has a 
mounting system for electronic communication devices. It includes cushions 
for supporting the head. Goggles are also supported on the helmet by means 
of appended arms. 
BACKGROUND OF THE PRESENT DISCLOSURE 
This disclosure is directed to a helmet which is particularly intended for 
use in measuring head and eye movement and also to enable the 
incorporation of an optical stimuli for neurosensory investigations. It 
requires significant design compromise to obtain such a helmet. The first 
criteria of the present invention is that it be fixed rigidly to the head. 
In large measure, helmets which are rigidly and snugly fixed to the head 
must fully enclose or envelope the head. Such helmets are available as for 
example for motorcycle drivers. They have secure latches and chin straps 
and fully encompass and enclose the head. However, such encompassing 
helmets are not acceptable for the kind of investigations which are 
necessary particularly in neurosensory investigations for astronauts. A 
large portion of the neurosensory investigation helmet must be cut away 
for electrodes, subject comfort, and also for extending visual field. In 
fact, so much of the helmet must be cut away that it is really not capable 
of fixedly attaching to the skull. 
One of the important uses of the helmet of the present disclosure and one 
which necessitates a cut away helmet construction is investigation of 
human vestibulo-ocular reflex. This data relates to investigation and 
prevention of space adaptation syndrome. This refers generally to the fact 
that a significant portion of astronauts, that is personnel undergoing 
space travel in a near zero gravity field, experience in some fashion 
motion sickness. Typical motion sickness investigation primarily focuses 
on observations of the eyes of the personnel. One of the problems relating 
to an all encompassing helmet where the shell completely envelops the head 
is the possibility of space adaptation syndrome induced sickness which, in 
certain personnel, is manifested by nausea or vomiting. In view of that 
risk, it is necessary that the helmet dismount readily to free the person. 
Otherwise, there is a significant risk of choking, requiring the person to 
simultaneously attempt to pull off the helmet when they are gagging, 
thereby running the risk of choking to the person while simultaneously 
requiring complicated helmet removal activities. 
One correction for such a helmet dismounting problem is to use a helmet 
which is substantially cut away. In other words, the total portion of 
helmet is reduced as, by example enlarging the face area, cutting back 
around the neck, and otherwise reducing the amount of shell. When this is 
done, the helmet typically becomes loose or slack on the head of the 
subject. Movement between the helmet and head of the subject during 
investigation creates false data. The present invention overcomes this 
handicap by providing a neurosensory investigation helmet with a plurality 
of inflatable bladders on the interior and a quick release chin bar 
connected to a mouthpiece securing the helmet in place. The bladders are 
placed on the interior so that they can be inflated pneumatically and 
thereby expand. The bladders enable the helmet to grip the head of the 
subject firmly. This assists in holding the helmet snugly on the head of 
the user. An important added factor is to fasten the helmet on the head of 
the user rigidly with respect to the skull. Clamping devices which engage 
the skull are terribly uncomfortable. However, it has been determined that 
the present apparatus can firmly grip and engage the skull by means of a 
mouthpiece constructed to fit around the upper teeth of the user and to 
bear against the hard palate just behind the front upper teeth. This is an 
area which is relatively insensitive, thereby permitting firm contact and 
engagement without discomfort to the user. Moreover, this type 
construction anchors the helmet so that it is not free to slide backwardly 
on the head of the user. This mouthpiece type construction in conjunction 
with inflatable bladders on the interior of the rigid shell permits the 
helmet of the present disclosure to be anchored firmly in place. That is, 
it is fixed but in a comfortable fashion to the head, even to the skull of 
the user. A release lanyard is provided to permit the user to quickly 
disengage the chin bar mouthpiece in the event of any distress. 
The helmet of the present disclosure incorporates left and right visors 
which move independently of each other. They are adapted to pivot on the 
side of the helmet with a segment or wedge rotating in front of the eyes. 
There is a raised position where they are out of the way and there is a 
second position where they are immediately over the eye. The visors are 
constructed with a round opening. The opening is equipped with a lens 
mount such as the mounting ring commonly found for mounting lenses on a 
camera body. The size is such that a suitable optical system can be 
mounted to undertake experiments measuring space adaptation syndrome. This 
measurement particularly involves obtaining accurate, error free data from 
various devices which are fixed to the head by means of the helmet of the 
present disclosure. All relative movement is eliminated between the head, 
the helmet and the various sensors and measuring devices mounted on the 
helmet. This can be done in a comfortable, lightweight helmet enabling 
rather easy electrical and mechanical disconnection. Various stimulus 
modules and sensor modules are attached to the helmet at the visors. They 
can be connected on either visor, that is the visor over the left eye or 
the symmetrical visor over the right eye. The visors affix easily, rotate 
into and out of position and support interchangeable and detachable 
modules. 
So that a full set of data can be obtained, ear phones are included inside 
the helmet so that communications can selectively be maintained with the 
subject. In the absence of communications, typically white noise is 
broadcast to the subject to mask off noise which might otherwise create 
noise triggered false data. There may also be variable tones (cadence) 
used to prompt the subject to make appropriate head movements. Likewise, 
the helmet is constructed with selected flat spots at proper locations for 
mounting accelerometer clusters at the indicated locations. The 
accelerometers are at right angles to one another in the cluster. This 
sensor indicates head movement so that it can be correlated with the 
optical measurements made at the eye, thereby assuring sufficient data for 
analysis of motion sickness. 
The present apparatus is worn as a conventional helmet. It is placed on the 
head and then a chin bar is placed across the front. The chin bar supports 
an individualized mouthpiece which engages the front teeth and hard palate 
behind the teeth. To further couple the helmet and head, the helmet is 
provided with foam liners and air bladders. Integral air bladders are 
inflated to firmly yet gently grip the head of the user so that the entire 
system is fixed on the head with no possibility of movement between the 
head and helmet. Varied sized and interchangeable liners accommodate 
different head sizes. The various optical sensors and optical measuring 
devices are affixed to the visors so that the response of the subject can 
then be tested, observed and analyzed. 
An important feature of the helmet of the present disclosure is that a 
lightweight device has been provided. At first blush, one might assume 
that the helmet is to be used in zero gravity circumstances and hence mass 
would therefore be meaningless. In actuality, mass is still meaningful 
because it is desirable to reduce inertia to the greatest extent possible. 
Accordingly, the disclosed helmet is reduced in weight by reducing the 
amount of shell around the head. Also, the accessories mounted on the 
helmet are also reduced. To this end, the helmet includes wiring and a 
plug for connection with a socket connecting to electrical conductors for 
remote location of most of the circuitry associated with the test 
accessories. 
When the amount of helmet is reduced, lateral light leakage becomes more of 
a problem. In the event the helmet wraps completely around the head, 
outside light can be shut out. The cut away construction which is used in 
the present apparatus runs the risk of light leakage. Outside light is 
undesirable because it creates a false stimulus to the test subject. 
However, the use of the internal foam padding along the bridge of the nose 
and encircling the face along the cheekbones significantly cuts down the 
amount of leaked light. When the subject is undergoing experimentation, 
the risk of distraction from leaked light is then reduced. 
In summary, the present apparatus is a cut away helmet with a reduced mass 
which nevertheless snugly and fixedly attaches to the head with comfort. 
It is attached in such a way that it is rigidly coupled to the skull. It 
is fixed by means of inflatable bladders and foam lining snugly gripping 
the back and sides of the head. The helmet cannot slide on the head by 
virtue of a chin bar supported customized mouthpiece bearing against the 
teeth and hard palate to fix the helmet firmly in place. The chin bar and 
mouthpiece are easily dismounted by a quick release lanyard pulling latch 
pins from the connectors on the helmet. The helmet includes left and right 
symmetrical visors which pivot on the sides of the helmet, the visors 
supporting circular eye openings which can selectively receive lenses for 
viewing or mount optical equipment for undergoing tests. An inflation 
system is included for the various bladders to assure clamping when the 
helmet is put on. The helmet also supports pairs of accelerometers to 
measure orientation in space.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Attention is directed to FIG. 1 of the drawings where the numeral 10 
identifies the helmet of the present disclosure. It is constructed with an 
outer shell 11 of solid plastic material, the ideal material being a 
lightweight elastomeric product, one acceptable material being 
polyethylene. The helmet interior is shaped to conform with the head and 
is sized dependent on the size of the head of the user. The shell is 
constructed with a padded border 12 which has the form of a bead which 
covers the shell edge. It is shaped generally in the fashion of a pilot's 
helmet with several modifications as will be noted. For instance, in FIG. 
1 there is a flat spot 13 at the back to enable mounting of accelerometers 
14 and 15 at right angles to one another. Likewise, there is an additional 
flat spot 16 on the top of the helmet for mounting of similar 
accelerometers 17 and 18 arranged at right angles to one another. Last of 
all, there is a flat spot 19 which again is provided for mounting of 
accelerometers 20 and 21 at right angles to one another. On the opposite 
side of the helmet but obscured, there is an additional flat spot similar 
to the region 19 for mounting another pair of orthogonal accelerometers or 
other sensors. The helmet is cut away so that the bottom or edge of the 
helmet at 22 is comparatively high with respect to motorcycle helmets and 
the like. The bottom edge extends forwardly to a region which is 
identified at 23 which, when on the head of a user, is located forward and 
slightly below the ear. This will be described as the cheek piece 23 for 
purposes of nomenclature. The cheek piece 23 protrudes forwardly and 
slightly downwardly to thereby position a two part clasp 24 at this area. 
The clasp 24 supports a chin bar 25 which extends forwardly, downwardly 
and in a curving fashion to encircle the lower chin of the user. The two 
part clasp includes a U-shaped sliding lock portion fitting on three sides 
against an upstanding, conforming clasp base anchored on the shell 11. The 
two are releasable locked together by a pin 26 inserted into aligned holes 
in the clasp portions. The pin is frictionally held in place but it is 
easily pulled out by a lanyard 28. The two ends of the lanyard connect to 
duplicate pins at duplicate clasps on both ends of the chin bar 25. 
The chin bar 25 is symmetrical with similar left and right portions on both 
sides as shown in FIG. 2 of the drawings. The central portion 27 dips 
below a cut away area which is immediately in front of the mouth of the 
user. The chin bar 25 supports a demountable bite bar 29 which spans the 
gap above the central chin bar portion 27. The bite bar 29 includes the 
rectangular frame with a central mounting mechanism to be discussed in 
regard to FIG. 3. Individualized bite bars are mounted releasably on the 
frame for quick conversion. The demountable system thus contemplates an 
individualized and shaped mouthpiece (to be described) which is supported 
on the bite bar and extends rearwardly so that it can be gripped 
comfortably in the fashion of a mouthpiece. This system enables more than 
one person to use the helmet 10 and yet each person can easily have a 
customized system for their head shape. An important feature is the quick 
disconnect system operated by pulling downwardly on the lanyard 28. In the 
event of nausea or motion sickness symptoms, the user can quickly pull 
downwardly on the lanyard, removing the clasp pins 26 and thereby 
unlatching the chin bar and supported mouthpiece. This quickly clears the 
mouth and reduces risk of choking the user with the mouthpiece. 
It will be observed that the upper edge of the chin bar 25 is equipped with 
cloth and back material 31, this serving as a light seal which will 
cooperate with the lower edges of the respective visors to be described. 
In FIG. 1 of the drawings, a left eye visor 32 is shown in a pivoted 
position. It is supported at a rotatable pivot 33 which is affixed to the 
side of the helmet. The visor inscribes an angle appropriate to provide 
sufficient height for an eyepiece 34. The eyepiece 34 supports an 
encircling ring 35. The ring is a mount for a lens so that the user may 
look through the visor or alternatively through other equipment to be 
described. The mount ring 35 is constructed in the fashion of mounting 
rings on cameras, the preferred form permitting lenses or other optical 
devices to thread to the mounting ring for support on the visor. Examples 
of the devices will be given later. The diameter of the opening is 
sufficient that the user has an adequate field of vision through the 
opening. 
The visor 32 is a wedge shaped curving plastic section. It is constructed 
to conform to the exterior curving shape of the helmet. It is built with 
an upper edge bead 36 which is thicker and again is made of softer 
material. A contoured edge 37 is located along the lower edge of the visor 
to mesh with the cloth and hook material 31 along the top of the chin bar 
25. The bead 36 snugly contacts against the outer skin of the helmet shell 
11 to limit light leakage which might otherwise pass under the visor. In 
this sense, the visor assists in forming a light leak barrier to avoid 
distraction of the user from lateral light entry into the helmet. The 
visor encircles or inscribes an angle of approximately 90.degree. around 
the periphery of the helmet. Thus it is fastened at the pivot 33 at one 
end. It is larger at the opposite end and terminates at a tongue for 
engaging a tongue and groove guide or track 40. The track 40 is 
symmetrical along the center line of the helmet and is positioned 
immediately over the bridge of the nose and curves to the top of the 
helmet. It is an arc of a circle so that the visor may pivot around the 
pivot point 33 as shown in FIG. 1. The track 40 incorporates an undercut 
groove 41 as best shown in FIG. 1 and the groove cooperates with a 
protruding tongue along the edge of the visor. The tongue portion is 
received in the groove 41 to define a tongue and groove guide channel. 
Thus, one end of the visor is anchored for pivotal movement while the 
other end is guided in sliding movement in the track 40. This permits the 
visor to rotate through an arc of approximately 60.degree. or 75.degree. 
so that it has two positions. One position is shown in FIG. 2 where the 
left visor is located over the eye while the right visor has been rotated 
upwardly to a position out of sight of the wearer. 
The visor construction shown in FIG. 2 enables the visor to rotate upwardly 
and discloses a larger eye socket on the shell 11. This is bordered with a 
light blocking bead 43 which covers over the edge of the shell 11. This 
extends forwardly to the lower end of the track 40. There, it tucks under 
the track where the track terminates at its lower extremity 44. This is 
located at the tip of the nose of the wearer when placed on their head. 
In FIG. 2 of the drawings, a locking groove 45 is shown for one of the two 
visors. Both visors are provided with locking grooves. The locking groove 
curves along the shell 11 to define a narrow channel. The visor supports a 
pivotally mounted look pin 46 which is moved by a lever 47 (see FIG. 1). 
This pin passes through the visor and extends into the groove 45. When 
raised, easy movement of the visor is permitted. When the pin is extended, 
it inserts sufficiently into the groove 45 to engage internal groove 
surfaces to retard movement of the visor. 
Attention is now directed to FIGS. 3 and 4 to be considered jointly. A 
reverse nape strap 48 loops forward of the forehead of the user to assist 
in firm helmet placement. A top bladder 50 is located inside the shell 11. 
The bladder contacts the crown of the head to the rear of the strap 48. It 
preferably is an inflatable bladder which supports a removable thin foam 
layer for contact against the top of the head of the user. The thin foam 
and bladder 50 are located in t he top central portion of the helmet. 
Another bladder 51 is included around the edge of the helmet and is 
constructed somewhat in the fashion of a horseshoe to encircle the back of 
the head at the neck and to extend along the side edges of the helmet near 
the ears. The bladder 51 supports a removable foam layer in the shape of a 
concentric horseshoe having suitable ear matching notches for headphones. 
This foam layer is removable to permit users with different size heads to 
wear the helmet. This serves as a forward anchor point to the helmet 10. 
The second bladder is generally U-shaped to provide lateral locking. It 
has been determined that additional bladders of relatively small volume 
can be used to fill out the remaining regions of contact against the head 
of the user. For instance, in one embodiment of the present apparatus, a 
total of four individual bladders beneath the shell and in contact 
(through foam layers) with the head of the user has been found acceptable. 
Each bladder is individually filled. To this end, they connect by suitable 
conduits (not shown) to externally located manifolds 52 and 53. The 
manifold 52 supports a squeeze bulb 54, and a bleed valve with an 
adjustable knob 55 is connected with the bulb 54. The bulb 54 is hand 
operated to pump air into one of the bladders and the knob 55 is closed to 
prevent drainage. In similar fashion, the manifold 53 supports an 
individualized squeeze bulb, again used in the same fashion. Ideally, an 
individual squeeze bulb is provided for each bladder so that they can be 
filled and yet not over filled. At the time of mounting the helmet, all of 
the various bladders are deflated; then, the bladders are filled and the 
helmet is then held snugly but comfortably against the head of the user. 
User's control of filling assures tailored comfort. It is extremely 
important to provide comfort because the helmet 10 of the present 
invention may be worn for many hours. Comfort is assured by the use of the 
inflatable bladders which yield, thereby conforming to the contours and 
shape of the skull. 
An important feature is the incorporation of the bite bar support of the 
mouthpiece. It supports a small rod 58 which in turn supports an 
individualized mouthpiece 60. The mouthpiece grips the front and back 
surfaces of the upper front teeth and contacts the hard palate behind the 
front teeth. It is rigidly fixed by the bar 58 to the bite bar and hence 
to the helmet 10. This anchor point is very important to provide 
stability. This stability assures that the helmet is anchored without 
slippage and is otherwise immobilized on the head of the user. Because it 
is in contact with the hard palate, it can properly be described as 
anchored to the skull and hence relative motion between the helmet and the 
head of the user is impossible. Moreover this is achieved with a high 
level of comfort. That is the head is clamped and held but it is not 
brutalized by the incorporation of hard contacts against the head. The 
firmness of anchoring is accomplished with significant comfort to the 
user. 
Another important factor shown in FIG. 4 is the incorporation of an 
externally accessed electrical connector 64. This will be used for a 
number of sensors to provide electrical continuity to the exterior 
Going now to FIG. 5 of the drawings, this schematic block diagram shows the 
location of various components and accessories to be described Briefly, 
the helmet 10 supports headphones on the interior positioned over the 
ears, this being identified at 65. The several accelerometers are 
identified at 66. They are wired in the helmet on the interior of the 
shell and connect to the exterior through the electrical fitting 64. The 
head phones are used for communication with the subject. Additionally, and 
just as importantly, they are often used in experiments to transmit white 
noise and various tones to the subject to blank off audio stimuli This 
permits the experiments to proceed without audio interference. The helmet 
thus supports these components with wiring on the interior. 
The numeral 67 identifies the optokinetic module. It is constructed in an 
optically opaque container and has a threaded connection which connects 
with the ring mount 35 shown in FIG. 1. Recall that both visors are 
equipped with duplicate ring mounts 35. They are threaded so that they 
receive demountable equipment in the fashion of placing a lens on a camera 
body. The optokinetic module is thus a closed housing which threads to one 
visor or the other and is positioned in the field of vision of one eye of 
the user. This field of view sees selected objects or graphics to cause 
the user to reposition their eye. This can be used to cause the subject to 
redirect their line of vision by a specified angle. The optokinetic module 
has an opaque housing which shuts out all other light and which provides 
the optical stimulus for the user. This type device is located on one 
visor or the other so that the viewer can see the image in their field of 
vision. 
The LED module 6B is structurally similar to the module shown in FIG. 1. It 
has a closed and opaque housing which mounts in the same fashion as shown 
in FIG. 1 to the visor, and it is used to position a set of controllably 
activated LEDs across the field of view so that first one and then another 
can be illuminated. They are located so that the observer will deflect 
their vision from first one and then to another. 
Another module is identified at 69. It includes a video camera in the 
module. In addition to that, it has an integrally constructed light ring 
70. Again, the housing is shaped so that it is opaque, threadably mounted 
to the visor and within the field of vision of the user. The camera module 
is a small video camera which is aimed at the eye of the user. Since all 
light is shut out, the eye must be illuminated. The light ring 70 is 
included to provide adequate illumination for the camera. For comfort of 
the subject, one approach is to provide illumination with infrared lamps 
and to use a camera which responds to infrared light. Thus, the camera 
module is a small video camera with appropriate optics for focusing on the 
eye. 
The camera module 69 cooperates with either module 67 or 68. Fortunately, 
when an optical stimulus is provided at one eye, the other eye responds 
also. Thus, if the subject sweeps their line of vision to the right, as 
prompted by one of the optical stimuli, the other eye will deflect in like 
fashion. Because this coupling between the two eyes persists the stimulus 
can be provided to one eye and the response of the subject can be observed 
in the other eye. For this reason, the two independent visors are included 
in the helmet 10. The camera can be mounted on one visor and the module 
providing the stimulus is then mounted on the other visor. 
An important aspect of the testing of eye movements if the incorporation of 
electrodes which measure the electrooculography (EOG). EOG electrodes are 
included at 71. They are mounted on the face of the subject near the eye 
with ready access as shown in FIG. 3 of the drawings. The numeral 72 
identifies various helmet restraints. 
A helmet interface box is included at 75. It is mounted away from the 
helmet to reduce mass of the helmet. Conveniently, it can be placed on the 
back of the chair on which the subject sits. This includes an amplifier 76 
which is provided with the signals from the helmet restraint circuitry 72. 
Likewise, another amplifier system 77 is included for the EOG electrodes. 
Recall that the camera module 69 includes a video camera. The appropriate 
video and synchronization signals are provided through an interface 78. 
The light ring 70 is connected with a suitable power source which is the 
light ring interface 79. The LED module 68 is likewise provided with a 
suitable interface 80. An appropriate interface for the optokinetic module 
67 is also included at 81. The several accelerometers 66 are connected 
with appropriate amplifiers 82. All of this data is then provided by a 
wiring harness in a rotating chair 83 for convenience in conducting such 
experiments. In turn, that data is then delivered to an experiment control 
and data interface 84 which then connects the various data to a computer 
with an adequate memory system for data storage. Accordingly, the data can 
then be processed with a view of reducing space adaptation syndrome in 
motion sickness and thereby obtain an indication and hopefully a system 
for reducing motion sickness. 
While the foregoing is directed to the preferred embodiment, the scope 
thereof is determined by the claims which follow.