The field of the invention is that the helmet display systems. These systems are also known under the name Anglo-Saxon "See-Through HMD", "HMD" being the acronym for "Head Mounted Display". They are intended for different applications. As examples, they can be worn by aircraft pilots or infantry.

These systems are intended to be projected toward the eye of the user an aerial image collimated at infinity and superimposed on the external landscape. The projected image can have a representative symbology information on tasks, the task at hand or the external environment and / or the image data by a camera. The latter may be a camera in low-light or an infrared camera or thermal camera.

These systems can be monocular or binocular as the user perceives the image of one eye or both eyes.

These systems generally comprise a high-resolution small display on which is displayed the image to be projected, a relay optic and a "combiner" or optical mixer that ensures both the reflection of the projected image and collimated towards eye of the user and the transmission of the outside landscape. This combiner is integrated with a screen or a face shield or goggles. a transparent curved element arranged in front of the eyes of the user by means visor or shield and whose primary function is to protect the user's eyes while providing a good visibility from the outside. This protection is mechanical but can also be optical if the visor has special treatment. In the following text,

In most applications, the visual field of the display system to be important is to say between 20 degrees and 40 degrees. However, in most of the proposed solutions, the combiner is an optical element with a non-significant axis so as to ensure a good transmission and to leave as little as possible of optical elements in the

visual field. Building a good quality optical solution with out important axis is the first difficulty.

A second difficulty of this type of visualization system is the integration of the combiner on the screen should minimize disruption to the vision of the outside, the human eye is naturally large field. Thus, the human visual field reaches 200 degrees in a lateral plane to 1 25 degrees in a vertical plane. The combiner should introduce the least possible visual masks and have a shape that the best facial contours. It also requires that the system be compatible port corrective eyeglasses.

Finally, the weight and bulk of the system must remain low so that it can easily fit in the front of a helmet, or set directly on the face as a mask, like masks Ski or protective masks, or using a cap or headband adapted.

public viewing systems mounted on eyeglass branches do not fulfill all these conditions.

Various technical solutions have been proposed. A first type of solution consists in implementing the whole system side, the entire system is contained in a substantially horizontal plane. The display and the relay optics are located on one of the lateral sides of the head of the user. As examples include the devices described in WO 201 0/089495 entitled "The portable heads-up display and augmented reality" and WO 2009/1 36393 entitled "Wide Angle helmet mounted display system". These solutions have the drawbacks of being complex, bulky and present a side mask, which can be significant.

A second type of solution consists in implementing the whole system in front, the entire system is contained in a substantially vertical plane above the observer's eye. As examples include the devices described in WO 201 3/036888 entitled "Night vision devices and methods" and US 5,341,242 entitled "Helmet mounted display." As can be seen in the various figures of these applications, optical solutions implemented are complex. Their integration into the front of the helmet is not simple. Moreover, they are essentially monocular solutions and the transition in binocular version of these solutions is problematic.

The head display system according to the invention does not have these disadvantages. It can be monocular or binocular. It includes optical said crossed. That is to say, in the case of a binocular system, if an optical mixer is arranged in front of the right eye of the user, the relay optic and the corresponding display are arranged in frontal position -Dessus of the user's left eye and under the optical mixer on the left side. This arrangement is obtained by judiciously selecting the geometric parameters of the different optical elements, their curvatures and form of their surfaces. This optical architecture has many advantages both in construction simplicity as clutter and fits easily in the front of

More specifically, the invention relates to a viewing system comprising a first display and a first optical unit comprising a first relay optics and a first semi-transparent optical combiner, the first optical assembly being arranged to form a second image on the infinity a first image displayed by the first display, the display system being adapted to be carried by the head of a user, the first optical mixer being disposed in front of one eye of said user conditions for use, output optical pupil of the first set being disposed at said eye, the optical axis of the first optical assembly corresponding to light ray of the central field of vision passing through the center of the optical pupil, characterized in that:

The first optical combiner is a thin plate substantially parallel curved faces, each face being defined by a polynomial relationship or a file of points defining a free surface,

The inclination of the first optical mixer on the optical axis is substantially equal to 35 degrees,

The distance between the exit pupil of the point of intersection between the optical axis and the first optical mixer is about 60 millimeters;

The optical mixer has an optical power almost zero transmission not to deform direct vision.

In the use position, the inclination of the average optical axis between the first optical combiner and the first end lens in a vertical plane and with respect to a straight line joining the centers of the eyes is approximately 25 degrees, so the first relay optic is located at the forehead and over the other eye of the user, in crossed position with the first optical combiner.

Advantageously, the first relay optics comprising a first front lens, the first surface of said first front lens located closest to the combiner is defined by a polynomial relationship or a file of points defining a free form.

Advantageously, the second surface of the first front lens is aspherical or is defined by a polynomial relationship or a file of points defining a free form.

Advantageously, the first display is LCD screen type or "LCD" stands for "Liquid Crystal Display", or the type emissive screen or "OLED" stands for "Organic Light Emitting Diode," the first relay optics includes only, starting from the first optical combiner to the first display, the first end lens, convergent-divergent lens doublet spherical surfaces and a biconvex lens eccentric spherical surfaces.

Advantageously, the first display operating in reflection and being of the type "LCOS" stands for "Liquid Crystal on Silicon", the system comprising an illumination source, first relay optics is of the telecentric type and comprises only, starting from first optical combiner to the first display, the first end lens, convergent-divergent lens doublet spherical surfaces, a positive meniscus lens eccentric spherical surfaces, a separator cube adapted to reflect light from the light source to the first display and a biconvex lens eccentric spherical surfaces.

Advantageously, the splitter cube is a separator reflection type "PBS", acronym "Polarizer Beam Splitter".

Advantageously, in its binocular Alternatively, the system comprises a second display and a second optical assembly including a second relay optics and a second semi-transparent optical combiner, the second display being different from the first display, the second optical assembly being identical to the first optical assembly, the second display and the second optical assembly being arranged symmetrically with respect to the first display and the first optical assembly, so that the second optical combiner is arranged in front of the other eye of the user, the first relay optic being disposed above the second optical combiner and the second relay optic being disposed above the first optical mixer, the mirror plane being the median plane of the head.

The shape and orientation of "combiners" oriented in a direction generally following the general curvature of the face, allow to extend the right and left screens beyond the areas "useful" semi reflective to form a one-piece screen providing function protection for the face and especially the eyes. Thus, the continuous shape of the screen in a generally convex curve following the facial keeps direct vision through the screen without alterations.

The invention will be better understood and other advantages will appear on reading the description which follows, given without limitation and from the appended figures among which:

1 shows a front view of a first monocular display system according to the invention;

2 shows a profile view of the previous monocular display system;

Figure 3 shows a front view of the binocular version of the previous visualization system;

4 shows a sectional view of the first monocular display system;

5 shows a front view of a second monocular display system according to the invention;

6 shows a sectional view of the second monocular display system.

A display system according to the invention is intended to be carried by the head of a user. The mechanical support of the viewing system carried by the head may be a headset, a pair of glasses or other head support.

The visualization system available in monocular or binocular release. Each monocular block includes:

- a display, and

- an optical assembly having a dioptric relay optics and an optical combiner or mixer partially transparent, semi-transparent typically integrated with a display, a helmet visor or goggles and functioning by reflection. The optical mixer is a thin blade with curved faces and substantially parallel to each other which does not introduce little or no distortion of the external landscape. This mixer has no optical power transmission.

In the remainder of the description, the term optical axis, the virtual axis corresponding to light ray of the central field of vision passing through the center of the optical pupil.

The operation of a monocular block is as follows. The optical assembly is arranged to form a second collimated image or "optical infinity" of a first image displayed by the display, the optical output of the optical assembly being disposed pupil at the eye the observer. It is larger than the diameter of the eye pupil to allow a comfortable use and adaptation to changes in inter-pupillary distance. This image is perceived by the user superimposed on the exterior landscape transmitted by the optical mixer.

For the general layout of a display system according to the invention on a support of the possible ergonomic and easier to perform, the optics are said crossed. That is to say, in the case of a binocular system, if an optical mixer is arranged in front of the right eye of the user, the relay optic and the corresponding display are arranged in frontal position -Dessus of the user's left eye and under the optical mixer on the left side.

For this implementation is possible, it is necessary that:

- The angle of the first optical mixer on the optical axis is substantially equal to 35 degrees, that is to say that the reflected optical axis makes an angle of about 70 degrees with the incident optical axis. A lower angle requires a greater distance between the eye and the optical combiner involving larger dimensions. A greater angle requires higher optical corrections, difficult to master. It is preferable that this angle of inclination is between 33 degrees and 37 degrees. It is essential that the optical mixer is or not axisymmetric surface defined by a polynomial law or this surface "free-form" defined by a point file. Indeed, a spherical combiner provides excessive geometrical aberrations for that

- The distance between the exit pupil of the point of intersection between the optical axis and the first optical mixer is about 60 millimeters. This distance is necessary so that, in the case of a binocular application, the relay optics of the first optical system can be housed between the front and the combiner of the second optical system. It also allows the user to wear glasses;

- In position of use, the inclination of the average optical axis between the first optical combiner and the first front lens of the relay optics in a vertical plane and with respect to a straight line joining the centers of both eyes is d about 25 degrees, so that the first relay optic is located at the forehead and over the other eye of the user, in crossed position with the first optical combiner. A smaller angle causes the relay optics to be too low on the other eye and introduces visual masks. A larger angle causes the relay optics to be too high and can not be positioned under the front part of the helmet. It is preferable that this angle of inclination is between 20 degrees and 30 degrees.

polynomial or be like "free form" defined by a file of points in order to reduce residual geometric aberrations of the combiner.

Optical components such as highly eccentric combiner according to the invention exhibit very significant geometrical aberrations if they are simply tilted spherical mirrors. As has been said, it is essential that the surface of the optical mixer is a non-axisymmetric surface or "free form", that is to say that the curvature of its surface is defined by a polynomial law or a point file to compensate for aberrations at best eccentric.

However, this correction is not sufficient to completely correct the geometric aberrations of the combiner. The relay optics should compensate the residual aberrations. The relay optics has a first front lens located closest to the combiner, the first surface is also defined by a polynomial law. It corrects "closer" aberrations of the combiner. In order to avoid multiple surface lenses "free-form" or aspheric, it also uses the eccentricity or tilting spherical surface lenses to correct the residual aberrations at best. It should be noted that the distortion aberration is corrected in terms of optics. This correction is made directly on the image generated by the display by image processing from the laws of optical distortion. The latter comprises an inverse distortion exactly compensates for the distortion of the optical assembly.

Establishing accurate and optimization of optical components is done using optical computing codes, well known to the art.

A first implementation of a system according to the invention on a helmet H is shown in Figures 1, 2 and 3. In these different figures, the screen or the helmet visor are not shown. 1 shows a front view and Figure 2 a side view of a monocular system profile. In these two figures, the display 1 and the relay optics 2 are on the left of the helmet and the combiner 3 side sends an image on the right eye of the user.

As shown in Figure 3, the binocular system includes two identical sets symmetrical to each other with respect to a vertical plane. Thus, the second assembly comprises a display 1a, optical-relay Complete 2a and a combiner 3a.

This first implant works with a display operated by transmission or emission. This display can be passive. It may be a "LCD" type display, an acronym for "Liquid Crystal Display." It can also be active, type "OLED", which stands for "Organic Light-Emitting Diode".

A sectional view of the entire optical architecture for a monocular assembly comprising such a display is shown in Figure 4. This example is not limiting. It comprises a display 1, a relay optics comprising four lenses L1, L2, L3 and L4 and a combiner 3 forming an image collimated at the pupil P. In this figure and in FIG 6, the contours of the components are represented bold strokes. Three light rays in fine lines are drawn. They represent average rays passing through the center of the pupil corresponding to center field following the optical axis and the two extreme fields.

The general characteristics of this monocular set are:

- Display Type: LCD or OLED 8 mm x 5 mm

- Field: 32 degrees x 1 horizontal vertical 8 °

- Dimensions pupillaires : 1 0 mm x 1 0 mm

- Dimensions: Length L T : 86 mm width and the T 54 mm

Features of the combiner:

- Thin section with curved faces and parallel to each semi-reflective treated

- Average Radius of curvature: 48 mm

- polynomial type of area

- Tilt angle: 36 degrees

Characteristics of four lenses of the relay optics. The lens L1 is closer to the combiner and the lens L4 is closest to the display.

Lens L1 centered

o Material: PMMA type plastic

o First area: the type of polynomial average radius of curvature 10 mm - Second area: Type aspherical means radius 2000mm

o Central Thickness: 10 mm

Doublet centered L2-L3

o Materials: glasses

o First area: spherical radius of curvature: 14 mm

- Second area: spherical radius of curvature of: - 8 mm - Third area: spherical curvature radius:

- 90 mm

o First Central thickness: 6 mm - Second central thickness 6 mm

Eccentric lens L4 and tilted

o Material: Glass

o First area: spherical radius of curvature: 20 mm

- Second area: spherical radius of curvature of: - 55 mm

o Central Thickness: 5 mm

a display system can also be used according to the invention with a display operating in reflection of light. For example, this display may be of the "LCOS" acronym "Liquid Crystal On Silicon". One difficulty is that, by nature, light must pass through the relay optics. To this end, one introduces a separator cube within the same relay optics which provides both the illumination of the display and transmission of the light reflected by the latter. Generally, this cube is of the "PBS" acronym "Polarizing Beam Splitter". Optically, this cube corresponds to the addition of a thick glass plate with plane and parallel faces. In addition, the relay optics must be telecentric to ensure uniform illumination.

Figure 5 shows a front view of a monocular display system operating with a display "LCOS". As seen in this figure, the separator cube implantation constraints lead to an optical solution more complicated and much more compact.

A sectional view of the entire optical architecture for a monocular assembly comprising such a LCOS display is shown in Figure 6. It comprises a display 1, a relay optic comprising five lenses L1, L2, L3, L4, L5 and a separator cube and a combiner 3 forming an image collimated at the pupil P.

The general characteristics of this monocular set are:

- Display Type: LCOS 12mm x 9mm

- Field: 32 degrees x 18 degrees horizontal vertical

- Dimensions pupillaires : 15 mm x 10 mm

- Dimensions: Length L T 1 62 mm width and the T 60 mm combiner features:

- Thin section with curved faces and parallel to each semi-reflective treated

- Average Radius of curvature: 70 mm

- polynomial type of area

- Tilt angle: 35 degrees

Characteristics of five lenses and cube the relay optic splitter. The lens L1 is closer to the combiner and the lens L5 is closest to the display.

- centered lens L1

o Material: PMMA type plastic

First o Size: Type polynomial average radius of curvature 42 mm - Second Size: Type aspherical average radius of curvature -43 mm

o Central Thickness: 26 mm

- Doublet eccentric L2-L3

o Materials: glasses

o First area: spherical radius of curvature: 74 mm - Second area: spherical radius of curvature of: - 28

mm - Third area: spherical curvature radius:

- 88 mm

o First Central thickness: 26 mm - Second central thickness: 1 mm

L4 meniscus lens converge eccentric

o Material: Glass

o First area: spherical radius of curvature: 38 mm

- Second area: spherical radius of curvature of 1 60 mm

o Central Thickness: 10 mm

cube separator

o Material: Glass

o Thickness: 21 mm

L5 lens

o Material: Glass

o First area: spherical radius of curvature: 16 mm

- Second area: spherical radius of curvature of: - 65 mm

o Central thickness: 7 mm

CLAIMS

1. viewing system comprising a first display (1) and a first optical unit comprising a first relay optic (2) and a first optical mixer (3) partially transparent, said first optical relay (2) having a first front lens, the first optical assembly being arranged to form a second image at infinity from a first image displayed by the first display, the display system being adapted to be carried by the head of a user, the first optical mixer being disposed in front of a of both eyes of said user conditions, the optical output of the first pupil being disposed at said eye, the

The first optical combiner is a thin plate substantially parallel curved faces, each face being defined by a polynomial relationship or a file of points defining a free form;

The inclination of the first optical mixer on the optical axis is approximately 35 degrees,

The distance between the exit pupil of the point of intersection between the optical axis and the first optical mixer is about 60 millimeters;

In the use position, the inclination of the average optical axis between the first optical combiner and the first end lens in a vertical plane and with respect to a straight line joining the centers of the eyes is approximately 25 degrees, so the first relay optic is located at the forehead and over the other eye of the user, in crossed position with the first optical mixer.

2. The display system according to claim 1, characterized in that the first relay optics (2) having a first front lens (L1), the first surface of said first front lens located closest to the mixer is defined by a law polynomial or a file of points defining a free form.

3. The display system according to claim 2, characterized in that the second surface of the first front lens (L1) is aspheric and is defined by a polynomial relationship or a file of points defining a free form.

4. The display system according to one of the preceding claims, characterized in that the first display (1) being of the type

"LCD" or "OLED" the first relay optics (2) comprises only, starting from the first optical combiner to the first display, the first front lens (L1), a convergent-divergent lens doublet (L2, L3) spherical surfaces and a biconvex lens (L4) eccentric spherical surfaces.

5. The display system according to one of claims 1 to 3, characterized in that the first display (1) being of the type "LCOS", the system comprising an illumination source, first relay optics is of the telecentric type of and only comprises, starting from the first optical combiner to the first display, the first front lens (L1), a convergent-divergent lens doublet (L2, L3) at the spherical surfaces, a positive meniscus lens (L4) which is eccentric to spherical surfaces, a separator cube (PBS) adapted to reflect light from the light source to the first display and a biconvex lens (L5) eccentric spherical surfaces.

6. The display system according to claim 5, characterized in that the separator cube is the "PBS" type.

7. The display system according to one of the preceding claims, characterized in that the system being binocular, it comprises a second display (1a) and a second optical unit comprising a second relay optic (2a) and a second optical mixer (3a) partially transparent, the second display being different from the first display, the second optical assembly being identical to the first set

optics, the second display and the second optical assembly being arranged symmetrically with respect to the first display and the first optical assembly, so that the second optical combiner is arranged in front of the other eye of the user, the first relay optic being disposed above the second optical combiner and the second relay optic being disposed above the first optical mixer, the mirror plane being the median plane of the head.