Method and device for the customization of a helmet with night vision optical device

The disclosed method provides for the precise positioning of the night vision device with respect to the helmet to which it has to be fixed, in order that the user may enjoy optimum viewing conditions. This method consists in determining the position of the support of the device with respect to significant points of the user's head, in contact with the helmet, and then in copying these relative positions on a supporting tool bearing the helmet and the support of the night vision device, and in forming thickness shims between the helmet and the support.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and device for the customization 
of a helmet with a night vision optical device. 
Helmets for pilots of military aircraft that have to carry out night 
missions are fitted out with night vision devices provided with electronic 
light intensifiers. The earliest night vision devices fixed to these 
helmets were relatively bulky &lt;&lt;binocular&gt;&gt; type devices. They gave way to 
more compact &lt;&lt;eyeglass&gt;&gt; type devices with folded optical paths. 
These night vision devices have to be adapted to the vision of each user, 
and their settings are limited and relatively complicated to make, 
especially as the size of their pupil is relatively small (generally with 
a diameter of 10 to 15 mm). This makes it necessary to achieve the precise 
positioning of their eyepieces in relation to the pilot's eyes. 
Now, these night vision devices are linked to the helmet, and there is very 
little precision in the position of the helmet with respect to the pilot's 
head, even when the helmet is provided with elements for easy wear and 
customization (generally consisting of the injection of foam between the 
inner shell and the user's head). Furthermore, the very geometry of the 
helmet is such that it is not possible to obtain a very precise 
positioning of the inner shell with respect to the fastening base of the 
night vision device, which is fixed to the outer shell. 
To resolve these problems of relative positioning, firstly between the 
pilot's head and the inner shell and, secondly, between the inner shell 
and the outer shell, it could be planned to add different adjusting 
devices for adjustment according to the different degrees of freedom 
(inter-pupil distance and geometrical orientation with major lengths of 
travel to compensate for the different positioning errors and 
manufacturing tolerance values). Such approaches have two major drawbacks. 
The first drawback is the substantial mass of these setting devices. The 
second drawback, in the case of the use of night vision eyeglasses, is the 
fact that disparities in position between the optical module of these 
eyepieces and the helmet have repercussions on the relative position 
between these eyepieces and the visor: this visor, which is linked to the 
helmet, should be capable of passing in front of these eyepieces without 
catching them. The result thereof is that these approaches result in an 
increased complexity of the hinging mechanism of the visor and/or greater 
bulk in the visor and/or greater bulk in the helmet. 
SUMMARY OF THE INVENTION 
An object of the present invention is a method used for the precise 
positioning of the optical system of a helmet night vision device, and 
especially its pupil, with respect to the user's eyes, a device that is 
simple to implement and hardly complicates or burdens the helmet. An 
object of the present invention is also a device for the implementation of 
this method. 
In the method according to the invention, after the user's eye has been 
positioned with respect to reference zones of the inner surface of the 
helmet, these reference zones are copied on a support tool, the helmet 
being placed on these zones in a position corresponding to the position 
that it would have on the user's head, and then the fastening support of 
the night vision device is fixed to the supporting tool in a position 
corresponding to said position of the eye with respect to the reference 
zones, and a thickness shim is formed between the fastening support of the 
night vision device and the outer shell of the helmet. 
The device according to the invention comprises a measuring stand 
comprising adjustable support means for the helmet, adjustable stops 
copying the relative positions of reference zones corresponding to 
particular points of support of the inner surface of the helmet on the 
user's head, and an adjustable fastening element for the support of the 
night vision optical system.

MORE DETAILED DESCRIPTION 
First of all, the user's eye is positioned in a manner known per se (for 
example on an optical stand for the customization of helmets) with respect 
to the inner surface of the helmets. In practice, it is enough to have 
four reference zones of this inner surface to define it in the context of 
the invention. These four reference zones are, for example, those 
corresponding to the top of the user's cranium, and three zones of the 
front edge of the helmet (the tip of this edge and the two zones of the 
user's temples that are opposite to each other) for example. 
FIGS. 1 and 2 show the measuring stand 16 of the invention, used to fix the 
relative positions of the night vision device and of the helmet. 
In FIG. 1, the helmet C is taken to be transparent in order to simplify the 
drawing, it being understood that, during the use of the stand 16, the 
helmet is whole, its two shells being definitively fixed to each other. 
The axis of longitudinal symmetry of the base 17 of the stand 16 is 
referenced 17a. This axis is parallel to the longitudinal axis of the 
helmet when it is placed on the stand 16. An intermediate fastening 
element 18 is fixed to the base 17, to its front part, substantially 
perpendicular to this base and symmetrical with respect to the axis 17a. A 
rod 19 is fixed to the intermediate fastening element 18, near its base. 
This rod 19 is placed so as to be perpendicular to the axis 17A and 
symmetrical to it. The rod 19 is fixed to the intermediate fastening 
element 18 by means of collars 20, 21. The screws that fasten these 
collars 20, 21 to the intermediate fastening element 18 are able to move 
in buttonholes 20A, 21A, made in the intermediate fastening element 18, 
perpendicularly to the base 17. Small bars 22, 23 are attached to the rod 
19, symmetrically with respect to the axis 17A. The resting position of 
these small bars is substantially horizontal. These small bars 22, 23 are 
fixed by one of their ends to the rod 19 and are oriented towards the rear 
of the base 17. 
Three rectangular-sectioned rods 24, 25 and 26 are fixed to the upper part 
of the intermediate fastening element 18. These three rods have 
longitudinal buttonholes through which their fastening screws pass. This 
makes it possible to position these three rods longitudinally. The rod 24 
is perpendicular to the base 17 and its longitudinal axis intersects the 
axis 17A. The rods 25, 26 are affixed so as to be parallel to the base 17 
and symmetrical with the axis 17A. 
A small intermediate fastening element 27 is attached to the rear face of 
the intermediate fastening element 18, in its upper part. This small 
intermediate fastening element 27 is perpendicular to the surface of the 
intermediate fastening element 18 and parallel to the axis 17A. A foot 28 
is fixed to this small intermediate fastening element 27. This foot 28 
consists of a plate 29 and a sole 30, substantially perpendicular to the 
plate 29. The plate 29 has longitudinal buttonholes 29A, through which 
there pass fastening screws, making it possible to adjust the height at 
which it is fastened with respect to the base 17. The upper surface of the 
sole 30 is convex and its shape corresponds to the shape of the inner 
surface of the inner shell of the helmet supported on this surface. 
A support pedestal 31 is fixed to the rear of the base 17. This support 
pedestal 31 supports an arm 32 that is oriented upwards and is hinged with 
respect to the pedestal 31 about an axis 31A parallel to the base 17 and 
perpendicular to the axis 17A. The plane of symmetry of the arm 32 passes 
through the axis 17A. The arm 32 bears a V-shaped cap 33 that is 
symmetrical with respect to the plane of symmetry of the arm 32. The 
distance from the V-shaped cap 33 to the arm 32 can be adjusted by means 
of a screw 34, connecting the cap to the arm. One end of an adjusting 
screw 35 is connected to the arm 32, approximately in the middle of this 
arm, by means of a hinged link 32A. At its other end, the screw 35 has a 
stop 36 into which it is screwed. The stop 36 rests on a protuberance 37 
of the support 31. Thus, the elements 35 to 37 form an adjustable stop for 
the arm 32 in its rotation towards the rear of the base 17. The cap 33 
takes support on the rear upper part of the helmet when it is in position 
on the tool 16, and is designed to adjust its symmetry with respect to a 
plane perpendicular to the base 17 and passing through the axis 17A. 
FIG. 1 shows the helmet in position on the tool 16. The cap 33 is tilted 
towards the rear to enable the positioning of the helmet. The inner shell 
38 takes support on the sole 30 (whose position corresponds substantially 
to the top of the user's cranium) and on the front faces of the ends of 
the rods 24 to 26 (which are in contact with the front edge of the shell 
38). The lower ends 39, 40 of the helmet take support on the free ends of 
the small bars 22, 23 which enable an adjustment of rolling motion (about 
an axis substantially parallel to the axis 17A) of the helmet. 
The locations of the front surfaces 24A to 26A of the rods 24 to 26 are set 
to correspond to said reference zones of the front edge of the inner shell 
of the helmet. 
With the helmet taking support on the surfaces 24A to 26A and 30, the 
position of the small bars 22 and 23 is set so that the ends 39 and 40 of 
the helmet are in the same horizontal plane, without the helmet's losing 
contact with the surfaces 24A to 26A and 30. The setting of the position 
of the cap 33 is used to provide greater precision to the setting of the 
symmetry of the helmet with respect to a vertical plane passing through 
the axis 17A, its setting being done after that of the small bars 22, 23. 
With the position of the helmet C being set with respect to the reference 
surfaces (24A to 26A, 30), it can be estimated that it is practically the 
same as the accurate position of the helmet on the user's head. The 
fastening support 8 of the night vision device (not shown) can then be 
positioned on the helmet in its optimum position. Indeed, the respective 
spatial positions of the user's head and of the night vision device, and 
especially of the fastening support 8 of this device, are known as 
precisely as possible. With the helmet being in contact with surfaces of 
the user's head at least in the characteristic zones, the respective 
relative positions of the helmet and of the night vision device are 
deduced therefrom. Consequently, it is enough to fasten the night vision 
device to the stand 16 in the same spatial position with respect to the 
surfaces 24A to 26A and 30 that it occupied on the stand 1 with respect to 
the surfaces of the characteristic zones, for it to be accurately 
positioned with respect to the helmet and therefore with respect to the 
user's eyes. 
As can be seen in FIG. 2, to position the support 8 on the stand 16, a 
bracket 41 is fixed to the base 17, before the intermediate fastening 
element 18, symmetrically with respect to the axis 17A. This bracket 41 
has adjustment means (not shown) used to adjust the spatial position of 
the support 8 that it bears at its end. FIG. 2 also shows two plates 42, 
43 fixed to the base 17, perpendicularly to this base, laterally framing 
the helmet, symmetrically with respect to the axis 17A, at a short 
distance from the helmet. These plates 42, 43 each carry an adjustable 
short rod supporting a small surface applied to the side corresponding to 
the helmet, approximately at the level of the user's eyes. In FIG. 2, only 
the rod 44 and surface 45 relating to the plate 42 (corresponding to the 
left-hand side of the helmet) can be seen. When the position of the helmet 
on the stand 16 is properly set, as described here above, the surface 45 
and the corresponding right-hand surface are applied to the helmet to keep 
it properly in position. With the position of the support 8 being also 
properly set, it is observed that, for a series of helmets, given the 
manufacturing tolerance values, and the tolerance values of the 
positioning of the inner shell with respect to the outer shell, the 
support 8 is generally located at a variable distance (a few millimeters) 
from the outer shell CE. Consequently, one or more shims 46 are inserted 
between the support 8 and the outer shell of the helmet. The thickness of 
these shims corresponds to said variable distance. This shim may be 
metallic or may be made of a plastic material that is hard enough so as 
not to be crushed during the fastening of this support 8. When the shim 46 
is in position, this support 8 is fastened, for example by means of three 
screws as can be seen in FIG. 2. Naturally, instead of using only one shim 
46 for which the thickness must be adjusted by machining, it is possible 
to use several thinner shims, chosen from a set of various assorted shims.