Omnidirectional optronic system with two rotary axes

Description

[0001] The invention relates to an omnidirectional optronic system, or line-of-sight orientation head, with two axes of rotation comprising an imaging path and a laser path.

[0002] The optronic system is a device that allows a combat platform to detect guided missiles fired in its direction equipped with an optical seeker head, and capable of generating a laser beam directed towards the seeker head of these missiles in order to neutralize them and divert them from their target.

[0003] Documents EP 1946350 B1, US 20070075182 A1, US2003098387A1 and US 8334490 B2

[0004] disclose various embodiments of a dual-axis rotation omnidirectional optronic system for a combat aircraft designation pod. As illustrated in the figure 1 , which is a figure of the two-axis line of sight comprises a laser emission pupil 1 eccentric with respect to the carrier axis 2 and a reception pupil 3 centered on the carrier axis 2. These two pupils 1, 3 are spatially separated. The disadvantage of this solution is that the laser is transported to the carried axis 2 by means of an optical fiber and consequently this transport introduces too much power loss on the wavelengths emitted in the infrared. Documents US 20070075182 A1 and US 8334490 B2 supplement document EP 1946350 B1 by introducing a mirror off the carrier axis to correct the aberrations introduced by an external porthole in the shape of a spherical dome on the laser path which is eccentric.

[0005] Also known is document US 6779753 B2 which discloses an omnidirectional optronic system with two rotation axes for a combat aircraft designation pod, as illustrated in the figure 2 , corresponding to the figure 1 of document US 6779753 B2. The two-axis optical line of sight comprises a laser emission pupil 66 eccentric with respect to the carrier axis 16 and a reception pupil 58 centered on the carrier axis 16. The laser and reception imaging assembly is presented as being fixed. This imposes a significant optomechanical complexity, in particular for the deflection prism 86 which must remain fixed between the rotating part along the carrier axis (vertical axis passing through the center of the dome-shaped porthole 12) and the laser deflection mechanism consisting of a set of prisms and mirrors 86, 72 and 74 (synchronous with the rotation of the carrier axis). This prism makes a complete 360° rotation impossible over several turns and involves complete reversals at the limit of the rotation domain (risk of loss of maintenance of the line of sight on an object during the reversal).In addition, this system requires a complex double motorization on the carrier axis which would significantly increase the size.

[0006] State-of-the-art systems include a direction with a singular point to avoid, or, in other words, to avoid, that when the targeted object arrives on the carrier axis, there is an ambiguity and that this forces an instantaneous 180° rotation of the carrier axis.

[0007] One aim of the invention is to overcome the problems mentioned above, and in particular to be able to improve compactness, and to limit the occultation of the imaging path by the laser path.

[0008] According to one aspect of the invention, there is proposed an omnidirectional optronic system, with two axes of rotation, a carrier axis and a carried axis perpendicular to each other, comprising an imaging path and a laser path, in which the laser path at the injection at the input of the system and the imaging path are concentric along the carrier axis, comprising: for the laser path: a first reflecting surface, arranged at the input of the injection system, configured to separate the laser path from the optical path by reflecting the injected laser beam so as to move it away from the carrier axis of the system; a second reflecting surface for deflecting the laser beam reflected by the first reflecting surface towards the spherical dome-shaped output window, offset from the optical path; an expander configured to increase the diameter of the laser beam reflected by the second reflecting surface and reduce its divergence; a deflector configured to modify the angular direction of the laser beam within a cone with an apex angle of between 3° and 6°; a third reflecting surface and a fourth reflecting surface configured to direct the expanded laser beam towards the spherical dome-shaped output window parallel to the carrier axis;and a compensation device configured to compensate for aberrations of the spherical dome-shaped exit window; for the imaging path: a first lens group and a second lens group arranged in a Kepler afocal arrangement; a fifth reflective surface, a sixth reflective surface, a seventh reflective surface, and an eighth reflective surface, arranged between the two lens groups; ; the first reflecting surface, the second reflecting surface, the expander, the deflector, the third reflecting surface, the fifth reflecting surface, the sixth reflecting surface, the seventh reflecting surface forming a first assembly linked in rotation along the carrier axis; and the fourth reflecting surface, the eighth reflecting surface, the second group of lenses, and the compensator forming a second assembly linked in rotation along the carrier axis.

[0009] Such a system makes it possible to completely isolate the two optical paths (imaging and laser) while effectively limiting the photometric disturbance of the imaging path by the laser path (optimization of backscattering and back-reflections from the laser towards the imaging path).

[0010] Furthermore, having a common injection axis for the laser path and the tracking imaging path on the carrier axis of a two-axis line-of-sight orientation head allows for 360° travel without limitation of the number of turns in a reduced footprint), and thus avoids the presence of a singular point.

[0011] According to one embodiment, the system comprises a first stage movable in rotation along the carrier axis, allowing rotation of the line of sight along the carrier axis.

[0012] In one embodiment, the system comprises a second stage movable in rotation along the carried axis, allowing rotation of the line of sight along the carried axis.

[0013] Thus, the line of sight can be oriented in an angular space greater than 2πsr.

[0014] According to one embodiment, the Kepler afocal device has a magnification in the range of values ​​[-2; -0.5].

[0015] This afocal allows the pupil to be transported through the rotation axes to the vicinity of the laser / imaging splitter located on the carrier axis. Thus, the propagation of the imaging beams can be carried out without vignetting using components with minimized dimensions, and the volume of the line-of-sight orientation device is optimized. In addition, placing the splitter in the vicinity of a pupillary plane minimizes the disturbance of the imaging path thus generated by the splitter.

[0016] In one embodiment, the Kepler afocal device has a magnification of -1.

[0017] According to one embodiment, the expander comprises a diverging / converging afocal device.

[0018] For example, the diverging / converging afocal device includes lenses (classical Galilean afocal), or mirrors (off-axis Cassegrain afocal).

[0019] This type of device makes it possible to reduce divergence without an intermediate focusing point and therefore without the risk of breakdown.

[0020] In one embodiment, the deflector includes a diasporameter, or a two-axis mirror, for orienting the laser line of sight in the instantaneous imaging field.

[0021] Thus, the deflector makes it possible to improve the compensation of residual motion defects of the motorized line of sight orientation device to ensure the quality of beam pointing in a tracking loop using the laser return seen by the imaging channel.

[0022] The deflector also allows the directions of the laser and imaging optical axes to be harmonised. Finally, placing this device as close as possible to the output makes it possible to minimise the size of the output laser optical components and therefore of the line-of-sight orientation device.

[0023] According to one embodiment, the compensator comprises at least one off-center spherical or aspherical dioptric component.

[0024] The compensator is an optical component that corrects aberrations introduced by the eccentricity of the laser pupil relative to the dome, thereby ensuring the quality of the laser beam.

[0025] Also provided, according to another aspect of the invention, is a platform provided with a system as described above.

[0026] For example, the platform may be a combat aircraft, a transport aircraft, a military aircraft, a drone, a building, a ground vehicle, or a ship.

[0027] The invention will be better understood by studying a few embodiments described as non-limiting examples and illustrated by the attached drawing in which: [ Fig.1 ] schematically illustrates an omnidirectional optronic system, according to the state of the art; [ Fig.2 ] schematically illustrates another omnidirectional optronic system, according to the state of the art; and [ Fig.3 ] schematically illustrates an omnidirectional optronic system, according to one aspect of the invention.

[0028] On the figure 3An omnidirectional optronic system is illustrated, with two axes of rotation, a carrier axis 1 and a carrier axis 2 perpendicular to each other. The system comprises an imaging channel 3 and a laser channel 4, in which the laser channel 4 at the injection or emission at the input of the system and the imaging channel 3 are concentric along the carrier axis 1.

[0029] Laser track 4 includes: a first reflecting surface 5, arranged at the input of the injection system, configured to separate the laser path 4 from the imaging path 3 by reflecting the injected laser beam so as to move it away from the carrier axis 1 of the system; a second reflecting surface 6 for deflecting the laser beam reflected by the first reflecting surface 5 towards the output window 7 in the shape of a spherical dome, offset from the imaging path 3; an expander 8a configured to increase the diameter of the laser beam reflected by the second reflecting surface 6 and reduce its divergence; a deflector 8b configured to modify the angular direction of the laser beam within a cone with an apex angle of between 3° and 6°; a third reflecting surface 9 and a fourth reflecting surface 10 configured to direct the expanded laser beam towards the output window 7 in the shape of a spherical dome parallel to the carrier axis 1;and a compensator 11 configured to compensate for aberrations of the spherical dome-shaped exit window 7; ;

[0030] Imaging pathway 3 includes: a first lens group 12 and a second lens group 13 arranged in a Kepler afocal arrangement; and a fifth reflecting surface 14, a sixth reflecting surface 15, a seventh reflecting surface 16, and an eighth reflecting surface 17, arranged between the two lens groups 12, 13.

[0031] The imaging 3 and laser 4 channels are concentric on the carrier axis 1 when injected onto the latter.

[0032] They are separated just after the injection of the laser beam 4 in order to have at the output of the system two collinear axes, the carrier axis 1 and the laser emission axis 20 but physically separated to avoid, on the one hand, the parasitic coupling in the atmosphere between these channels, and on the other hand, that the laser passes through the intermediate focal plane of the Kepler afocal device of the imaging channel 3 and to introduce excessively high power densities in this intermediate image which could disturb both the imaging channel 3 and the beam quality of the laser channel 3.

[0033] The angular coverage of the optronic system is carried out in full (>2π sr) by solving the singular point problem by means of the deflector 8b acting on the laser channel 4.

[0034] The first reflecting surface 5, the second reflecting surface 6, the expander 8a, the deflector 8b, the third reflecting surface 9, the fifth reflecting surface 14, the sixth reflecting surface 15, the seventh reflecting surface 16 forming a first assembly linked in rotation along the carrier axis 1.

[0035] The fourth reflecting surface 10, the eighth reflecting surface 17, the second group of lenses 13, and the compensator 11 form a second assembly linked in rotation along the carried axis 2.

[0036] The system also comprises a first support 18 of the assembly linked in rotation along the carrier axis 1, provided with carrier bearings allowing rotation along the carrier axis 1.

[0037] The system comprises a second support 19 of the assembly linked in rotation along the carried axis 2, provided with bearings allowing rotation along the carried axis 2.

[0038] The afocal device of Kepler 12, 13 has a magnification in the range of values ​​[-2; -0.5], for example approximately -1.

[0039] The expander is a divergent / convergent afocal device depending on the laser propagation. Such an afocal can be achieved, for example, using lenses (classical Galilean afocal) or mirrors (off-axis Cassegrain afocal).

[0040] The deflector may include a diasporameter, or a two-axis mirror to move the laser line of sight in the instantaneous imaging field.

[0041] The compensator may include one or more off-center spherical or aspherical dioptric components.

[0042] A system according to the invention is mounted on a platform which may be a combat aircraft, a transport aircraft, a military aircraft, a drone, a building, a land vehicle or a ship.

Claims

1. An omnidirectional optronic system with two axes of rotation, a carrier axis (1) and a carried axis (2), that are perpendicular to each other, comprising an imaging channel (3) and a laser channel (4), the laser channel (4) at the point of injection at the entrance of the system and the imaging channel (3) being concentric with the carrier axis (1), characterised in that the laser channel (4) comprises: - a first reflective surface (5), arranged at the entrance of the system at the point of injection, configured to split the laser channel (4) from the imaging channel (3) by reflecting the injected laser beam so as to deviate it from the carrier axis (1) of the system; - a second reflective surface (6) for deflecting the laser beam reflected by the first reflective surface (5) toward the exit window (7), shaped as a spherical dome, offset from the imaging channel (3); - an expander (8a) configured to increase the diameter of the laser beam reflected by the second reflective surface (6) and to reduce its divergence; - a deflector (8b) configured to modify the angular direction of the laser beam inside a cone of apex angle comprised between 3° and 6°; - a third reflective surface (9) and a fourth reflective surface (10) configured to direct the expanded laser beam toward the exit window (7), shaped as a spherical dome, parallel to the carrier axis (1); and - a compensator (11) configured to compensate for aberrations in the exit window (7), shaped as a spherical dome; - for the imaging channel (3): - a first group of lenses (12) and a second group of lenses (13) arranged as an afocal Kepler device; and - a fifth reflective surface (14), a sixth reflective surface (15), a seventh reflective surface (16), and an eighth reflective surface (17), arranged between the two groups of lenses (12, 13); the first reflective surface (5), the second reflective surface (6), the expander (8a), the deflector (8b), the third reflective surface (9), the fifth reflective surface (14), the sixth reflective surface (15), and the seventh reflective surface (16) forming a first assembly that rotates as one about the carrier axis (1); and the fourth reflective surface (10), the eighth reflective surface (17), the second lens assembly (13), and the compensator (11) forming a second group that rotates as one about the carried axis (2).

2. The system according to claim 1, comprising a first stage (18) that is rotatable about the carrier axis (1), allowing the line of sight to be rotated about the carrier axis (1).

3. The system according to claim 1 or 2, comprising a second mobile stage (19) that is rotatable about the carried axis (2), allowing the line of sight to be rotated about the carried axis (2).

4. The system according to one of the preceding claims, wherein the afocal Kepler device has a magnification comprised in the interval of values [-2; -0.5].

5. The system according to claim 4, wherein the afocal Kepler device has a magnification of -1.

6. The system according to one of the preceding claims, wherein the expander (8a) comprises a divergent / convergent afocal device.

7. The system according to claim 6, wherein the divergent / convergent afocal device comprises lenses, or mirrors.

8. The system according to one of the preceding claims, wherein the deflector (8b) comprises a diasporometer, or a two-axis mirror, allowing the laser line of sight to be oriented in the instantaneous imaging field.

9. The system according to one of the preceding claims, wherein the compensator (11) comprises at least one off-centre spherical or aspherical dioptric component.

10. A platform provided with a system according to one of the preceding claims.

11. The platform according to claim 10, the platform being a combat aircraft, a transport aircraft, a military aircraft, or a drone, a ship, a land vehicle or a boat.