Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/12—Reflex reflectors
  • G02B5/122—Reflex reflectors cube corner, trihedral or triple reflector type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41G—WEAPON SIGHTS; AIMING
  • F41G3/00—Aiming or laying means
  • F41G3/22—Aiming or laying means for vehicle-borne armament, e.g. on aircraft
  • F41G3/225—Helmet sighting systems
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
  • G01S17/87—Combinations of systems using electromagnetic waves other than radio waves
  • G01S17/875—Combinations of systems using electromagnetic waves other than radio waves for determining attitude
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
  • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
  • G02B19/0028—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
  • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
  • G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
  • G02B19/0061—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED
  • G02B19/0066—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED in the form of an LED array
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/0093—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/10—Beam splitting or combining systems
  • G02B27/14—Beam splitting or combining systems operating by reflection only
  • G02B27/144—Beam splitting or combining systems operating by reflection only using partially transparent surfaces without spectral selectivity
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/10—Beam splitting or combining systems
  • G02B27/14—Beam splitting or combining systems operating by reflection only
  • G02B27/145—Beam splitting or combining systems operating by reflection only having sequential partially reflecting surfaces

Definitions

• Optical reflector with semi-reflective blades for a helmet position detection device and a helmet comprising such a device
• the field of the invention is that of optical devices for detecting the instantaneous position and orientation of the helmet worn by an aircraft pilot.
• posture in the rest of the text a position and a particular orientation of the helmet.
• the pilots' helmets are equipped with visualization devices making it possible to generate information in the pilot's field of vision concerning the piloting, the navigation or the weapon system.
• These helmet visuals are generally coupled with helmet position and orientation detection systems.
• systems for locating the position of a helmet there are different systems for locating the position of a helmet.
• systems based on the analysis of optical signals representing the position of the helmet are used.
• These systems necessarily include one or more sources of light emission and one or more light receiving sources.
• the emission sources may be light patterns or light emitting diode type point sources fixed to the helmet in a particular arrangement, such as a triangle.
• the position of the helmet in a given area is then obtained by analyzing the images of the diodes received by cameras from several points of view and by geometric calculation, we deduce the position of the head in space.
• Such devices have been made by the company Karl Zeiss / Denel.
• photoresensor strips or photodiodes can be arranged on the helmet and illuminated by particular image projectors in such a way that the spatial or temporal analysis of the signals received by the different photodiodes can be analyzed. detectors allows to find posture information of the helmet.
• the detected signal is disturbed by solar irradiance. Indeed, a part of the solar illumination is diffused by the helmet towards the cameras of recognition. It is known that solar illumination can reach 70,000 lux in the case of a cockpit canopy with a 70% transmission. The detected signal becomes not very exploitable as soon as the solar illumination received by the helmet is important.
• the emission sources are on the headphones, their signal is embedded in the sunlight.
• the photo-detectors are on the helmet, the signal received from the source is embedded in the solar illumination.
• the means conventionally used to improve the detection consists in providing a significant source power. It can also emit and receive in a wavelength range located outside the visible solar radiation, that is to say located either in the infrared or in the near ultraviolet.
• solar irradiance levels are still high in the infrared and ultraviolet bands and this type of solution requires specific emission and reception sources that necessarily increase the costs of the detection system.
• FIG. It consists in arranging on the helmet 1 patterns 3 represented by triangles in this figure and comprising at least a first optical element 5 of the "retro-reflector" type having a very high retro-reflection coefficient and a very low diffusion coefficient in the visible domain.
• the detection device comprises a set of fixed cameras 2 associated with an image processing system. Thus, the solar radiation R s is necessarily returned in the direction of the sun as can be seen in Figure 1 and can not reach the detection cameras 2.
• the detection device comprises a set of sources of fixed lights 6 illuminating the helmet, the catadiopter 5 having a very high retro-reflection coefficient and a very low diffusion coefficient in the source emission domain.
• Opto-mechanical means 61 and 62 for producing an image of the light source 6 on the optical axis of the camera 2 complete the device.
• Opto-mechanical means 61 and 62 for producing an image of the light source 6 on the optical axis of the camera 2 complete the device.
• a "cube corner” 5 as shown in Figure 2 consists of three plane mirrors 51 orthogonal to each other. So, a light brush emitted by the party emitting and illuminating the reflector 5 is re-emitted in the same direction to the receiving part with excellent performance as seen in Figure 3.
• This figure represents the propagation of light rays L from a point source S in a cube corner 5.
• the propagation of the rays is in a plane parallel to one of the three mirrors constituting the cube. In this plane, the light rays undergo only two reflections on the mirrors 51. It is easily demonstrated that the image of the source S is a source S 'located on an axis SC passing through the source S and the center C of the cube corner and at equal distance D thereof. In the same way, any light beam that does not come from the source and strikes the reflex reflector, produces, as a rule, almost no illumination towards the receiving part.
• the fidelity of the relative position of the points has a direct impact on the accuracy of the position measurement. Indeed, it can be shown that any defect in the geometry of the tetrahedron is original or due to an evolution of the structure will not only degrade the measurement accuracy but also introduce new ambiguities on the discrimination of points. For example, an angular deviation of 0.5 mrad on the position of a point of the tetrahedron causes an error of 1 mrad on the measurement.
• the rigidity of the support which guarantees the respect of the relative points of points, is so crucial. This is a handicap for systems that, being mounted on the head of the user, must remain as light as possible.
• the purpose of the device according to the invention is to provide an optical position and orientation detection system using particular retro-reflectors that make it possible to generate the detection tetrahedra by means of a single component.
• the device is easily used in a wide range of illuminations, daytime with illuminations of the order of 100,000 lux and night, with illuminations of the order of 0.01 lux, it implements tetrahedron shaped sights, making it easy to determine the position and orientation of the helmet in the space.
• This solution also has the advantage of not requiring power supply for the sights carried by the pilot's helmet, to be particularly simple and robust and to give high signal / noise ratios regardless of the illumination. It is therefore perfectly adapted to the environment of aircraft cockpits.
• the subject of the invention is an optical component for an optical device for position / orientation detection of a helmet comprising an optical "cube corner", that is to say a trirectangular trihedron of flat surfaces, characterized in that that each of the three plane surfaces comprises a plane blade having a first face and a second face parallel to each other, the first face being merged with the flat surface on which it rests, the interface between this first face and said surface comprising a treatment semi-reflective.
• the "cube corner" is a flat-faced prism made of a transparent material
• the semi-reflective treatment may be identical or different for the three interfaces and the second face of the blades may comprise a reflective treatment.
• the invention also relates to a helmet comprising at least one light diffusing coating and an optical component as defined above.
• the invention finally relates to an optical device for detecting the position / orientation of a helmet, said device comprising at least one fixed camera associated with an image processing system, a source of fixed light, opto-mechanical means for producing an image of the light source on the optical axis of the camera and the helmet carrying at least one optical component as defined above.
• Figure 3 shows the optical operation of this cube corner
• Figure 4 is an exploded view and a perspective view of a cube corner according to the invention.
• FIG. 5 represents the operating principle of a cube corner according to the invention in a plane
• Figure 6 shows the principle of operation of a cube corner according to the invention in perspective
• Figure 7 shows the different images generated in a cube corner according to the invention.
• FIG. 8 represents a detection position system according to the invention.
• the component according to the invention creates N virtual images of a single source S by means of a particular arrangement represented in the two views of FIG. see in the left view of Figure 4 is disposed on the three planar faces 51 of a cube corner 5 three blades 7 flat and parallel faces.
• the first face 71 of each blade 7 is disposed on a face 51, the interface between this first face 71 and the surface 51 comprising a semi-reflective treatment.
• the second face 72 of each blade is reflective.
• the right view of Figure 4 shows the component 8 according to the invention, once the cube corner 5 and the three blades 7 assembled and the corners of the cube corner being folded (dashed parts in this view).
• FIGS. 5 and 6 respectively represent the image given by the cube corner 5 and only one of the three blades 7, then the image given by the entire corner of the cube and three blades.
• a point source S is aligned on an axis SC passing through the source and the center of the initial cube corner 5.
• S is considered to be in the optical medium of the corner of initial cube or in other words, the source S is the image of a source S 0 not shown in Figure 5 and located in the air.
• the light rays from the source S will therefore be partly reflected by the surface 51 and partly transmitted.
• the addition of the semi-reflective plate 7 thus creates a second corner of optical cube C1 vertex.
• the first cube corner gives the source S a first image S 'as previously explained.
• the second cube corner gives from source S a second image S1.
• S1 is shifted by twice the offset of CC1 along the same axis, ie to the total e.V2, where e is the thickness of the attached plate 7.
• the angle at which S1 is viewed from S is the same as that under which C1 is seen since S is e / (SCV2).
• This component is therefore optically equivalent to four cube corners arranged in a tetrahedron.
• the semi-reflecting plane plate generates not only the two images S 'and S1 but also a plurality of images resulting from the multiple reflections between the faces of the blade. In this figure, only one of the three blades is shown.
• Ri and R 2 the reflection coefficients of the two faces, it is shown that the reflection coefficients of the different images are successively Ri, R 2. (1 -Ri) 2 , Ri.R 2 2. (1 -Ri) 2, R 2 .R 3 February. (1 -R) 2, ...
• only images S 'and S1 have significant reflection coefficients.
• FIG. 8 represents a view of a complete position detection system whose helmet comprises the components 8 according to the invention.
• the device comprises a helmet 1 carried by a mobile user in a given area 4.
• the device according to the invention is well suited to operate in an aviation environment such as an aircraft cockpit. In this case, the user is a driver. However, this device can be used for all applications requiring knowledge of the posture of the user's head.
• the helmet 1 has a matte diffusing coating, advantageously light in color and comprises a set of components 8.
• Each component 8 is represented by a tetrahedron in FIG. 8.
• the detection of the quadruplets of images given by the optical components 8 is provided by a set of cameras 2.
• a single camera is shown in FIG. 8.
• the cameras are arranged in such a way that, whatever the movements of the user's head, a number of components 8 are constantly in the field of the cameras. It is generally estimated that three cameras are sufficient.
• the cameras can be CCD (Charge Coupled Device).
• the focal length and aperture of the camera lens should be chosen small enough so that the images of the sources are constantly sharp on the photosensitive surface.
• the resolution of the camera must be adapted to the desired detection accuracy.
• the sensitivity of the camera must be sufficient for the images given by the sources to be exploitable.
• the detection device also comprises one or more fixed light sources 6 distributed in the cockpit and associated with the cameras 2. These sources 6 have an angle of illumination adapted to that of the cameras. These sources 6 must operate in the sensitivity range of the cameras 2. These sources 6 are preferably light-emitting diodes which have the triple advantage of great compactness, robustness and good reliability.
• the detection device comprises opto-mechanical means for producing an image of each light source 6 on the optical axis of the associated camera.
• these means are simply a mirror 61 and a semi-reflective plate 62 ensuring the mixing of the two source-camera channels.
• the radiation of the source 6 illuminating the catadioptric component 8 returns to the camera.
• the reflector then gives four images appearing bright on a dark background, symbolized by the four arrows in Figure 8. It is possible, with the general provisions described above, to make a number of changes to improve the detection.
• the light source can be modulated temporally, it can be sweeping, be slaved to illuminate particular areas of the helmet.
• the tetrahedron uses the catadioptric and photometric properties of the cube corner and returns the flux from the source to the source, aligned with the camera and thus to the camera, where another system would introduce a dependence of the emission lobe the source;
• the formed tetrahedron is very accurate. Indeed cube corners and faces are manufactured with very large accuracies up to one second of arc, the thickness of the facets can be very regular in both thickness and flatness. Such precision can not be achieved with a real tetrahedron composed of four components or four mechanically independent sources;
• the formed tetrahedron is monolithic: the deformation causes its destruction, which makes it possible to detect any variation of conformation;
• the formed tetrahedron is virtual. It can be located "in the head of the operator" seen from the camera, which allows a latitude of choice of the position of the much larger optical component;

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Electromagnetism (AREA)
• General Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Helmets And Other Head Coverings (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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ID=43332536

Family Applications (1)

Country Status (6)

Cited By (4)

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Citations (6)

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• 2009
  • 2009-12-04 FR FR0905866A patent/FR2953604B1/fr not_active Expired - Fee Related
• 2010
  • 2010-12-02 IN IN4897DEN2012 patent/IN2012DN04897A/en unknown
  • 2010-12-02 WO PCT/EP2010/068749 patent/WO2011067341A1/fr not_active Ceased
  • 2010-12-02 RU RU2012127813/28A patent/RU2543680C2/ru not_active IP Right Cessation
  • 2010-12-02 US US13/513,856 patent/US8605295B2/en not_active Expired - Fee Related
  • 2010-12-02 EP EP10787106.3A patent/EP2507655B1/fr not_active Not-in-force

Patent Citations (6)

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