Classifications

• • 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
  • G01S17/66—Tracking systems using electromagnetic waves other than radio waves
• • 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
  • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
  • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
  • G01S3/782—Systems for determining direction or deviation from predetermined direction
  • G01S3/785—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system
  • G01S3/786—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J1/00—Photometry, e.g. photographic exposure meter
  • G01J1/10—Photometry, e.g. photographic exposure meter by comparison with reference light or electric value provisionally void
  • G01J1/20—Photometry, e.g. photographic exposure meter by comparison with reference light or electric value provisionally void intensity of the measured or reference value being varied to equalise their effects at the detectors, e.g. by varying incidence angle
• • 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
  • G01S17/88—Lidar systems specially adapted for specific applications
• • 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
  • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
  • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
  • G01S3/782—Systems for determining direction or deviation from predetermined direction
  • G01S3/783—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived from static detectors or detector 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
  • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
  • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
  • G01S3/782—Systems for determining direction or deviation from predetermined direction
  • G01S3/783—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived from static detectors or detector systems
  • G01S3/784—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived from static detectors or detector systems using a mosaic of detectors
• • 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
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• • 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
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/481—Constructional features, e.g. arrangements of optical elements
• • 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
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/481—Constructional features, e.g. arrangements of optical elements
  • G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone

Definitions

• the present invention relates to a target tracking device using a quadrant photodetector.
• This type of detector is conventionally embedded in an aircraft such as a helicopter.
• FIG. 1 illustrates the four quadrants Q1 to Q4 of a conventional detector.
• the detector estimates a current position of a spot by weighting the light energies received by quadrants Q1 to Q4, which extend around a center C. From this current position, it is possible to deduce how the target is oriented relative to to the aircraft 1.
• the optronic set composed of the optical system and the detector 4Q must be designed so that the laser echo is projected. on the quadrants in a very small spot T, so that the spot extends only in only one of the quadrants of the detector 4Q (quadrant Q4 in the example shown in FIG. 1).
• a known solution is to move the spot T so that it simultaneously covers several quadrants of the detector 40. Such displacement is typically achieved by reorienting the device comprising the optical system and the detector 40 relative to the target.
• the reorientation of the device comprising the optical system and the detector 4Q is controlled manually by a user.
• manual control imparts rotational movement to the device comprising the optical system and the detector 40 so that the spot follows a spiral path to the center of the detector 40, as shown in FIG.
• This method is however long and tedious. Moreover, this method depends on the dexterity and the experience of the user.
• a target tracking device comprising a quadrant photodetector an optical device configured to enlarge a spot entirely contained in only one of the quadrants of a quadrant.
• photodetector 4Q This optical device is in fact a defocuser that enlarges the spot by defocusing the light beam.
• the defocator comprises a defocusing lens movable in translation relative to the photodetector 40.
• Extending the projected spot has the effect of bringing the edge of the spot closer to a boundary between two quadrants.
• the approximation caused by the enlargement is such that the spot simultaneously covers at least two of the quadrants, then a weighting can be directly implemented, and the position of the spot is accordingly estimated.
• a displacement of the spot must be implemented. Nevertheless, the displacement that must be implemented so that the spot simultaneously covers at least two of the quadrants becomes shorter after the enlargement step.
• the command that should be used to ensure this movement of the stain is much simpler after enlargement. For example, assuming that the spot can be moved on the photodetector incrementally, the number of increments required for the spot to cross at least one boundary between two neighboring quadrants is reduced.
• a defocuser is very sensitive to vibrations and temperature variations, which has adverse consequences on a possible harmonization between the tracking device used and an illuminator emitting the laser beam.
• the displacement of the defocusing lens is also energy consuming, and is not easy to control.
• a defocuser has a transmission quality perfectible.
• One aim of the invention is to be able to find the position of a projected spot on a quadrant detector more quickly, when this spot is confined to a single quadrant, by means of a device that is more robust to vibrations or to the thermal less consumer of electrical energy, easier to drive, and having a higher quality of transmission.
• a device for tracking a target comprising an optical system and a quadrant photodetector, in which the optical system is configured to project a light beam from of the target in a spot on at least one of the quadrants, wherein the photodetector is configured to estimate a current position of the spot by weighting light energies received by the quadrants, and wherein the optical system comprises an optical device configured to when the stain is entirely contained in only one of the quadrants, enlarge the stain.
• the optical device comprises a polyhedron intended to be traversed by the light beam and having a plurality of optical axes, the polyhedron being rotatable relative to the photodetector about an axis of rotation different from each of the optical axes.
• the polyhedron used is more robust to vibrations and heat than a defocusing lens, and has a better quality of transmissions.
• the tracking device according to the first aspect of the invention may further comprise the following optional features, taken alone or in combination.
• the stain can be enlarged until the stain simultaneously covers at least two of the quadrants. Thus, it is not necessary to generate displacement control of the enlarged spot so that the position of this spot can be estimated by weighting light energies received by the dials.
• the stain may be enlarged until the stain has a predetermined diameter greater than or equal to the length of one side of a quadrant.
• the enlarged spot may not immediately cover several quadrants.
• a task displacement control adapted to meet this condition is nevertheless singularly simplified by having enlarged the spot to such a diameter.
• the polyhedron may be a hexahedron, for example a cube, having three optical axes respectively comprising three diagonals of the hexahedron, the axis of rotation comprising another diagonal of the hexahedron.
• the polyhedron may have two optical axes and comprise a quadrilateral-shaped face, for example square, intended to be traversed by the light beam, the two optical axes respectively comprising two diagonals of the face and the axis of rotation being perpendicular to the face.
• the tracking device may further include a multi-stable actuator configured to place the polyhedron in different angular positions, wherein the projected spot has different sizes. Moreover, the following characteristics can be provided:
• the photodetector has a center having a predetermined central position
• Quadrants are arranged around the center
• the target tracking device is adapted to be mounted mobile on an aircraft
• the target tracking device comprises a control module configured to generate, from the estimated current position and the predetermined central position, at least one reorientation command of the tracking device with respect to the aircraft, the command being adapted for the spot to move toward the photodetector center in a substantially straight path.
• an aircraft comprising a target tracking device according to the first aspect of the invention.
• a method of tracking a target implemented by a device comprising an optical system configured to project a light beam from the target in a spot on at least one quadrant of a quadrant photodetector configured to estimate a current position of the spot by weighting light energies received by the quadrants covered by the spot, the method comprising, when the spot is entirely contained in only one of the quadrants, an enlargement of the spot by an optical device of the optical system.
• Figure 1 schematically illustrates a photodetector with four quadrants on which a light beam is projected
• FIGS. 2 and 3 schematically illustrate a device for tracking a target according to one embodiment of the invention
• FIG. 4 is a perspective view of an optical device according to a first embodiment of the invention.
• FIG. 5 is a perspective view of an optical device according to a second embodiment of the invention.
• FIG. 6 is a flowchart of steps of a target tracking method according to an embodiment of the invention
• FIGS. 7 and 8 each schematically illustrate a photodetector with four quadrants and two spots projected on this photodetector during the implementation of the tracking method according to FIG. 6.
• an aircraft 1 comprises a tracking device 2 of a target.
• the tracking device 2 is rotatably mounted on the aircraft 1, for example by means of a ball joint or a pivot connection.
• the tracking device 2 comprises internal means for rotating the tracking device 2 relative to the aircraft 1.
• These internal means typically comprise at least one motor and a control module of the or each motor. Each motor makes it possible to turn the device 2 about an axis associated with this motor. Therefore, when the internal means comprise several motors, the tracking device can be rotated about two different axes.
• the tracking device 2 of a target comprises an objective 3, an optical system 4 and a photodetector 6.
• a light beam from a target to follow can enter the tracking device 2 by this objective 3.
• the optical system 4 is configured to project a light beam received by the objective 3 on the photodetector 6 into a spot T.
• the photodetector 6 known in itself, comprises four quadrants Q1, Q2, Q3 and Q4, as shown diagrammatically in FIG.
• the four quadrants extend around a center C of the photodetector 6 whose position, said central position, is predetermined.
• Each quadrant Qi is adapted to generate an electrical signal according to the amount of light energy that it receives per unit area.
• the four quadrants may each have a quarter-circle shape, as in the example shown in FIG.
• the set formed by the four quadrants is thus in the form of a circle, and the center C is the center of this circle.
• the side of a quadrant is equal to the radius of this circle.
• the four quadrants can each have a square shape.
• the set formed by the four quadrants is also square, and the center C is in the center of this square.
• the photodetector 6 furthermore comprises (or is coupled to) a weighting device 8 configured to estimate a current position of the spot T by weighting the electrical signals. generated by the different quadrants Q1 -Q4 according to a weighting method known from the state of the art.
• the optical system 4 furthermore comprises an optical device 10 configured to modify a light beam coming from the objective 3 so as to be able to modify the size of the spot constituting the projection of the light beam on the photodetector 6.
• the tracking device 1 further comprises a control unit for generating and sending commands to the optical device 10, these commands being adapted to thereby modify the light beam.
• the control unit is for example included in the weighting 8, or coupled thereto.
• the optical device 10 comprises a translucent polyhedron intended to be traversed by a light beam received by the objective 3.
• the polyhedron has several optical axes, and is rotatable relative to the photodetector 6 about an axis different from each of its optical axes.
• Such a polyhedron to modify the beam has several advantages over a defocuser: it is more robust to vibrations or to the thermal (sensitivity of the harmonization between the tracking device 1 and the illuminator), consumes less electrical energy , and is easier to fly.
• the polyhedron has a better transmission quality than a defocusing lens.
• the tracking device 1 further comprises an actuator for rotating the polyhedron with respect to the photodetector 6.
• the actuator is configured to place the polyhedron in different angular positions, in which the projected spot on the photodetector 6 has different sizes.
• the actuator is preferably multi-stable, which allows for additional energy savings.
• the polyhedron can be declined in several variants.
• an optical device 10 comprises a polyhedron 16 according to the above, having three optical axes X2, Y2, 22.
• the polyhedron is a hexahedron: it can then be a cube, as shown in Figure 5, or a parallelepiped.
• the hexahedron has eight vertices, including: first two opposing vertices passing through a first diagonal of the hexahedron, two opposite second vertices passing through a second diagonal of the hexahedron, two opposing third vertices passing through a third diagonal of the hexahedron , and two opposite fourth vertices passing through a fourth diagonal of the hexahedron.
• the three optical axes X2, Y2, Z2 respectively comprise the first, second and third diagonals of the hexahedron.
• the hexahedron is also rotatable relative to the photodetector 6 about an axis of rotation R comprising the fourth diagonal of the hexahedron.
• a second embodiment of the optical device 10 comprises a polyhedron 18 having only two optical axes X3, Y3.
• the polyhedron has in particular a face 20 intended to be traversed by a light beam received by the objective 3.
• the face 20 is a quadrilateral, for example a square, which has four vertices including: first two opposing vertices passing through a first diagonal of the face, two opposite second vertices passing through the second diagonal of the face.
• the two optical axes X3, Y3 of the polyhedron 18 respectively comprise the first and second diagonals of the face 20.
• the polyhedron 18 is moreover rotatable relative to the photodetector 6 about an axis of rotation R3 orthogonal to the plane of the face 20.
• the axis of rotation R3 passes for example through the point of intersection of the diagonals of the face .
• the polyhedron typically has a form of thin plate measured perpendicular to the face.
• the polyhedron 18 is simpler in design and more compact than the polyhedron 16.
• a method implemented by means of the tracking device 21 comprises the following steps, to follow a target.
• the target T is illuminated by an illuminator, for example embedded in the aircraft 1.
• This illuminator is for example a laser.
• a light beam generated by the illuminator is reflected on the target T, and enters the tracking device 1 by its objective 3.
• the light beam received by the objective 3 is projected by the optical system 4 on the photodetector 6 to quadrants into a spot T.
• the optical device 10 operates in a first mode of operation, wherein the spot T formed by the projection of the light beam on the photodetector 6 is smaller than the side of a quadrant.
• the spot moves on the photodetector 6 (the aircraft 1 is indeed mobile, and the target can obviously be so).
• the photodetector 6 detects that the spot T is contained in only one of its quadrants, for example the quadrant Q1, as shown in FIG. 7. Such detection is typically performed by the unit. of weighting, by comparing the intensity of the electrical signals generated by the different quadrants of the photodetector 6 to a predetermined threshold. Such detection occurs more particularly by observing that the three electrical signals generated by three of the quadrants (here quadrants Q2, Q3, Q4) have intensities lower than the predetermined threshold, meaning that these three quadrants have not received energy. while the electrical signal generated by the quadrant Q1 has an intensity greater than the threshold, which means that the quadrant Q1 has itself received light energy in a substantial amount.
• the photodetector 6 is not able to determine precisely where the spot is, and may in particular risk leaving the field of view of the objective 3 of the tracking device 2.
• the optical device 10 is reconfigured (step 102) so as to enlarge the spot at this stage only on the quadrant Q1, until the spot covers not only the quadrant Q1, but also at least one of the three quadrants Q2, Q3, Q4.
• the spot T becomes after enlargement a spot referenced T 'at least partially covering the quadrants Q1 and Q4 simultaneously.
• the reconfiguration 102 of the optical device 10 comprises for example a generation, by the weighter, of a reconfiguration command of the optical device 10s and the transmission of this command to the optical device 10 to cause the enlargement of the spot T in the spot T .
• the magnification caused by the reconfiguration 102 is for example stopped as soon as the weighting unit detects that at least two of the four electrical signals it receives has an intensity greater than the predetermined threshold (ie two electrical signals among the four signals, either three electrical signals among the four signals generated, or the four signals). This means that the enlarged spot T 'covers several quadrants simultaneously.
• the optical device 10 is in a second mode of operation once this condition is verified.
• the weighting unit can weight the electrical signals it receives so as to estimate the current position of the center of the spot on the detector.
• control module generates, from the estimated current position and the predetermined central position, at least one reorientation control of the tracking device 2 adapted so that the spot moves towards the photodetector center 6 in a substantially path. straight.
• the generated command is transmitted to the engine (s), which causes a rotation of the tracking device 2 relative to the aircraft 1. During this rotation, the stain moves towards the photodetector center 6 along a substantially rectilinear path.
• the enlargement step is conducted until the stain has a predetermined diameter. Indeed, to enlarge too much the spot could lead to a loss of light energy (a large part of the light beam would be projected out of the photodetector 6).
• This predetermined diameter is preferably greater than or equal to the length of one side of a quadrant.
• the enlarged spot indeed covers several quadrants of the photodetector 6 as previously assumed, thus making it possible to again implement a weighting of the light energies received by the quadrants.
• FIG 8 there is shown an example of spot T in quadrant Q1.
• the spot T is distant from the neighboring quadrant Q4 by a distance L.
• the spot T has become the enlarged spot T '(shown in dotted lines) having a diameter equal to the length d one side of a quadrant.
• the enlarged spot T ' remains at a distance from the quadrants Q2, Q3 and Q4, the fact remains that this distance has been diminished by the magnification.
• the enlarged spot is distant from the Q4 quadrant of a distance L 'less than the distance L.
• two events can trigger the end of the enlargement stage: a coverage of the task on several quadrants, or the achievement a predetermined spot size (greater than or equal to the length of one side of a quadrant).

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Electromagnetism (AREA)
• Computer Networks & Wireless Communication (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Optical Communication System (AREA)
• Optical Radar Systems And Details Thereof (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (8)

Family Cites Families (18)

• 2017
  • 2017-09-19 FR FR1700947A patent/FR3071322B1/fr active Active
• 2018
  • 2018-09-19 EP EP18792854.4A patent/EP3685179A1/fr not_active Withdrawn
  • 2018-09-19 RU RU2020112492A patent/RU2733804C1/ru active
  • 2018-09-19 WO PCT/EP2018/075367 patent/WO2019057783A1/fr unknown
  • 2018-09-19 US US16/648,617 patent/US11099274B2/en active Active
  • 2018-09-19 CA CA3076400A patent/CA3076400C/fr active Active
  • 2018-09-19 KR KR1020207010879A patent/KR102154780B1/ko active IP Right Grant
• 2020
  • 2020-03-18 IL IL273383A patent/IL273383A/en active IP Right Grant

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