System for identifying at least one beacon

Abstract

A system for identifying at least one beacon (B) includes a night vision goggle or night vision device integrating an image amplifier tube (13). The image amplifier tube (13) includes a diffraction grating (20) disposed between an input window (15) and a photocathode (16) to diffract photons in the photocathode and enable the photocathode to have a quantum efficiency (QE) greater than 1% in the imaging wavelength range; and in a detection wavelength range different from the imaging wavelength range, ranging from 0.001% to 1%, wherein the detection wavelength range is at least from 1,000 nm to 1,100 nm; the image amplifier tube is configured to capture electromagnetic radiation emitted by the beacon in the second detection wavelength range.

Description

Technical Field

[0001] The technical field of this invention relates to systems for identifying beacons, particularly in dimly lit conditions, using night vision goggles or night vision devices. Beacons can be carried by individuals, animals, vehicles, or placed in strategic locations.

[0002] This invention is particularly advantageous for military applications. In fact, battlefield friend-or-foe identification is also known as "Identification, Friend or Foe" (IFF), and beacons can be carried by soldiers. In this context, this invention enables soldiers equipped with observation devices or goggles to reliably and discreetly identify friendly forces. Therefore, this system enables the prevention of friendly firefights and optimizes coordination between friendly units, while providing responsiveness suitable for various operational scenarios. Background Technology

[0003] In the context of military operations, the use of night vision device 110 is known. (As in the prior art...) Figure 1 and Figure 3 As illustrated in the diagram, the night vision device 110 is typically in the form of an observation device, which is intended to be placed in front of the sensor or the user's eyes, or, when two devices are arranged side by side to form a night vision goggle (also known as the abbreviation NVG), placed in front of both of the user's eyes.

[0004] The night vision device 110 integrates multiple elements along the optical axis α1 of a single eye of the sensor or user to transform the image of the observed scene. More specifically, starting from the scene outside the sensor or user's eye, the observer includes a lens 12, an image intensifier tube 130, and an eyepiece 14. The lens 12 typically includes one or more lenses that enable the capture of photons of electromagnetic radiation from the observed scene. Similarly, the eyepiece 14 includes one or more lenses that enable the capture and incidental visualization of photons of the light signal transmitted by the image intensifier tube 130.

[0005] The image intensifier tube 130 includes at least three different elements: a photocathode 16, an electron multiplier 18, and a fluorescent screen 20.

[0006] The photocathode 16 is in the form of a semi-transparent photosensitive layer that receives photons of incident electromagnetic radiation (i.e., photons transmitted by the lens 12). For this purpose, the input window 15 transmits photons from the lens 12 to the photocathode 16 while ensuring the tightness of the outer wall 23 of the image intensifier tube 130.

[0007] The photocathode 16 is typically made in the form of a thin metal or semiconductor film placed against a glass layer or a light-transmitting material layer. The material of the photocathode 16 is chosen based on its sensitivity to the image of the observed scene. The interaction between photons of the incident electromagnetic radiation of the observed scene and the photocathode 16 causes the emission of electrons (called photoelectrons) through the photoelectric effect.

[0008] These photoelectrons are then subjected to a first electric field within the first acceleration region 17, which guides them toward the electron multiplier 18. This first electric field is created by applying a voltage, typically on the order of 50 to 500 volts, between the photocathode 16 and the electron multiplier 18 to ensure the electrons follow the straightest possible path.

[0009] An electron multiplier 18, also known as an electronic amplifier, typically comprises a microchannel plate 25 covered with electrodes. This microchannel plate is also known as the abbreviation MCP in English literature or GMC in French literature. It takes the form of a plate of resistive or dielectric material with a thickness typically ranging from 0.2 to 1 mm.

[0010] The microchannel 25 of the plate has a rotation axis α2 that is tilted at an angle α3 of a few degrees (typically between 4 and 12 degrees) relative to the normal of the surface of the electron multiplier 18, so as to induce multiple collisions of photoelectrons 28 in the microchannel 25.

[0011] In addition to the first electric field created between the photocathode 16 and the electron multiplier 18, a second electric field is created between the input and output of the electron multiplier 18 by electrodes placed on either side of the input and output of the microchannel plate 25.

[0012] This electric field enables the charging of the internal semiconductor layer of the microchannel 25, causing multiple collisions of photoelectrons 28 within the microchannel 25 to generate a large number of secondary electrons 29. This electric field also accelerates the primary and secondary electrons 29 within the microchannel 25, causing them to collide again with the surface of the microchannel 25, generating more secondary electrons 29, and so on, thus generating a large number of secondary electrons 29 through this physical process. Furthermore, it allows for the acceleration of the secondary electrons 29 through energy input, guiding them from the input section to the output section of the microchannel 25. Typically, photoelectrons 28 in the electron multiplier 18 are charged at a rate of 10... 2 Up to 10 4 The multiplier increases within the range.

[0013] At the output of the microchannel 25, under the influence of the third electric field generated between the output of the electron multiplier 18 and the fluorescent screen 20, these secondary electrons 29 then linearly shift toward the fluorescent screen 20 within the second acceleration region 19. This third electric field is typically generated by a voltage in the range of 4kV to 10kV.

[0014] The fluorescent screen 20 enables the conversion of secondary electrons 29 into photons that generate light intensity. It takes the form of a layer of luminescent material or a fluorescent layer deposited on a substrate typically made of glass. At the output of the fluorescent screen 20, the formed image is transmitted to the eyepiece 14 via optical elements (typically a fiber optic network 21), which may allow the image formed on the fluorescent screen 20 to be flipped to obtain a correct view of the observed scene.

[0015] To generate three electric fields, the electronic components 22 are typically arranged around the internal vacuum housing 24. The resulting night vision system 110 thus includes optical elements, the electronic components 22, and an optional system for viewing the observed scene through the eyepiece 14.

[0016] Currently available night vision systems 110 are typically capable of capturing and amplifying photons in the wavelength range λ from 450 nm to 900 nm. More specifically, the operating wavelength range λ of the night vision system 110 is primarily modulated by the sensitivity spectrum of the photocathode 16.

[0017] like Figure 2 As illustrated, the sensitivity spectrum of the photocathode 16 is defined based on the wavelength of the photons received by the photocathode 16 and on the quantum efficiency (also known as the abbreviation QE) (i.e., the ratio of the number of photoelectrons 28 generated to the number of photons received by the photocathode 16). For the sensitivity spectrum of the prior art night vision system 110, the quantum efficiency QE is typically greater than 1% between 450 nm and 900 nm and less than 0.001% outside this operating wavelength range λ.

[0018] In addition to the photons observed in the scene, the operating wavelength range λ can also capture signals.

[0019] For example, as described in document EP 0560470, an IFF (Identification of Foe / Friendly) system can be implemented by using night vision goggles (NVG) to detect beacons B carried by an ally. (Prior art) Figure 4A possible implementation of the teachings in document EP 0560470 is illustrated. In this example, the night vision goggles (NVG) are associated with a device 310 for activating beacon B. Therefore, the activation device 310 generates a signal Sa for activating beacon B, causing beacon B to generate a performance signal Sm detectable by the night vision goggles (NVG). For this purpose, beacon B can use an infrared diode that, when activated, flashes within the operating wavelength range λ of the night vision goggles (NVG).

[0020] Other similar solutions are described in documents US5299227, US5375008, US20070236384 and WO2022 / 103941.

[0021] In all these solutions, beacon B is detected within the operating wavelength range λ of the night vision system 110. However, detecting beacon B within the operating wavelength range λ inevitably degrades the quality of the acquired image because the signal received from beacon B replaces information about the observed scene.

[0022] Furthermore, the development of the night vision system 110 on the battlefield has led to a decrease in the concealment of the beacon B carrier, as the opponent / enemy may be equipped with night vision goggles NVG, which can also detect the performance signal Sm emitted by the beacon B. This is because night vision goggles NVG are actually sensitive in the wavelength range λ from 450 nm to 900 nm.

[0023] Therefore, there is a need to improve existing beacon recognition systems in order to ensure image quality and maintain the concealment of beacon carriers. Summary of the Invention

[0024] The present invention provides a solution to this technical problem by using a night vision goggle or observation device that integrates a tube with an extended operating wavelength range to perform beacon detection outside the wavelength range used to form scene images.

[0025] More specifically, the present invention stems from the observation that the use of a diffraction grating inserted between the input window and the photocathode enables modification of the shape of the operating wavelength range and the attainment of quantum efficiency in the range of 0.001% to 1% in a specific wavelength range from 1,000 nm to 1,100 nm, preferably from 1,050 nm to 1,075 nm.

[0026] Therefore, the present invention provides a beacon using a performance signal emitted between 1,000 and 1,100 nanometers, preferably between 1,050 and 1,075 nanometers, which is associated with a night vision goggle or observation device integrating an image amplifier tube that operates in a first wavelength range (referred to as the imaging wavelength range) to observe a scene and in a second wavelength range (referred to as the detection wavelength range) to detect the beacon.

[0027] In fact, although the quantum efficiency is insufficient to form an image of the scene in the detection wavelength range from 1,000 nanometers to 1,100 nanometers, it is sufficient to capture the beacon performance signal.

[0028] Therefore, the present invention relates to a system for identifying at least one beacon, the beacon integrating means for emitting electromagnetic radiation with wavelengths in the range of 1,000 nanometers to 1,100 nanometers, the system comprising a night vision goggle or observation device integrating an image amplifier tube, the image amplifier tube comprising:

[0029] An input window, configured to receive and transmit photons;

[0030] A photocathode, which is incorporated into the inner surface of the input window, is capable of converting photons transmitted through the input window into photoelectrons; the photocathode has a sensitivity spectrum defined according to the wavelength of the photons received by the photocathode and according to the quantum efficiency of the photocathode, wherein the quantum efficiency is the ratio of the number of photoelectrons generated by the photocathode to the number of photons received.

[0031] An electron multiplier capable of multiplying the photoelectrons into secondary electrons; and

[0032] A fluorescent screen that converts the secondary electrons into photons.

[0033] The present invention is characterized in that the image amplifier tube further includes a diffraction grating placed between the input window and the photocathode to diffract photons in the photocathode and enable the photocathode to exhibit the following quantum efficiency:

[0034] Higher than 1% in the imaging wavelength range; and

[0035] In a detection wavelength range different from the imaging wavelength range, in the range from 0.001 to 1%, the minimum detection wavelength range is from 1,000 to 1,100 nanometers;

[0036] The image amplifier tube is configured to capture electromagnetic radiation emitted by the beacon within the detection wavelength range.

[0037] It will be understood that the characteristic of a detection wavelength range of at least 1,000 to 1,100 nanometers is related to the wavelength of the beacon. Therefore, based on this characteristic, the detection wavelength range of the photocathode corresponds at least to the emission wavelength range of the beacon selected between 1,000 and 1,100 nanometers.

[0038] Therefore, the present invention enables the detection of beacons without degrading the formed image, since the beacon detection wavelength is not included in the imaging wavelength range, for example, from 450 nm to 900 nm.

[0039] Furthermore, this invention improves the concealment of the beacon carrier. In fact, conventional night vision goggles, which detect photons in the wavelength range of 450 nm to 900 nm, cannot capture the beacon's performance signal in the wavelength range of 1,000 to 1,100 nm, preferably from 1,050 to 1,075 nm. Preferably, the image amplifier tube is configured to capture the performance signal originating from at least one beacon at a wavelength of 1,064 nm.

[0040] Preferably, in order to obtain effective detection in the detection wavelength range, a photocathode is formed based on antimony and at least one alkali metal (such as NaKCs, SbNaKCs, SbNaK, SbKCs, SbRbKCs or SbRbCs alloys, etc.).

[0041] In addition to the image amplifier tube, the night vision goggles or observation device may also include a beacon activation device. Preferably, the beacon activation device is configured to emit an activation signal, while the beacon includes a module for receiving the activation signal in order to emit electromagnetic radiation in the range of 1,000 nm to 1,100 nm as a response to the activation signal emitted by the activation device.

[0042] For example, the beacon activation device can be formed by an RF transmitter or an optical transmitter, with the beacon receiving module corresponding to an antenna or an optical receiver. For an optical transceiver, the optical transmitter can be a laser diode with wavelengths ranging from 1,400 nm to 1,800 nm, and the beacon receiving module can correspond to a photodiode capable of capturing wavelengths in the same range. In fact, transmitting and receiving the activation signal within this wavelength range also ensures significant stealth for the beacon carrier.

[0043] Furthermore, to improve detection range, night vision goggles or observers can be configured to observe a scene in which a specific observation area is defined by the emission angle of the activation device and the field of view of the night vision goggles or observers, and detection of the beacon is performed only within that specific observation area. In practice, by targeting a specific area of ​​its observation area, the emission angle of the activation device can be reduced to improve the range of the activation signal. Typically, this strategy can achieve beacon detection over a distance of more than three kilometers (1.86 miles).

[0044] Furthermore, the image amplifier tube may include a mechanism for adjusting the light gain to suit the tube's output brightness. This function, referred to in the literature as "auto-gating," limits saturation and improves dynamic range in scenes with drastic light intensity changes. This mechanism relies on rapid detection of light changes to adjust photoelectron generation within milliseconds and stabilizes the brightness at the image intensifier tube's output (typically between 6 and 12 candela / m²) depending on the type of phosphor used (green P43 or white P45). 2 between).

[0045] The automatic gating mechanism is implemented by periodically adjusting the potential of the photocathode. Therefore, when a significant brightness change is detected at the output of the image intensifier tube, the automatic gating mechanism intervenes to modify the duty cycle of the periodic voltage applied to the photocathode within milliseconds. This modification of the duty cycle allows for adjustment of the number of photoelectrons generated by the photocathode and subsequently multiplied by the electron multiplier. The voltage applied across the electron multiplier itself is adjusted to regulate the number of secondary electrons, and thus, the output brightness of the tube.

[0046] This principle of adjusting the internal charge of the tube ensures that it does not exceed a predetermined brightness threshold. This threshold is, for example, the MOB threshold, an abbreviation for "Maximum of Brightness".

[0047] This dynamic control of magnification not only protects the image intensifier tube from the risks associated with excessive light intensity, but also provides better vision of the observed scene by adapting the image resolution to ambient conditions, without saturation or visual dizziness. Therefore, operators benefit from clearer and more stable night vision, even in the face of sudden changes in light, which is crucial for applications such as military or surveillance operations.

[0048] However, the activation period of the photocathode level specific to the automatic gating mechanism causes the image amplifier tube to be unable to detect the beacon during certain phases. To avoid the beacon emitting a signal only outside the detection range of the image amplifier tube, the beacon can be configured to emit a signal for a significantly longer period than the specific activation period of the automatic gating mechanism.

[0049] However, this solution increases power consumption and thus the size of the beacon. To address this issue in asynchronous detection, the activation device can have a variable activation period. Using this embodiment, the beacon can be detected when a specific activation period of the image amplifier tube occurs simultaneously with the activation period of the activation device. This solution limits the necessary transmission time of the beacon but may introduce a delay in the beacon detection speed, i.e., the time between the simultaneous occurrence of these two activation periods.

[0050] To avoid this delay, synchronization detection can be performed by connecting the activation device to a device for managing a specific activation period of the automatic gating mechanism. In this embodiment, the activation device has an activation period that is synchronized with the specific activation period of the automatic gating mechanism of the image amplifier tube. Attached Figure Description

[0051] The invention will be better understood by reading the following description, given only by way of example and in conjunction with the accompanying drawings, wherein the same reference numerals denote the same or similar elements, and wherein:

[0052] Figure 1 A simplified cross-sectional view of a prior art night vision device is shown;

[0053] Figure 2 It shows Figure 1 Changes in the quantum efficiency of night vision devices;

[0054] Figure 3 It shows Figure 1 A perspective view of a night vision device;

[0055] Figure 4 This demonstrates the implementation of two Figure 1 A simplified view of existing beacon recognition systems for night vision devices;

[0056] Figure 5 A simplified cross-sectional view of the night vision device according to the present invention is shown;

[0057] Figure 6 It shows Figure 5 Changes in the quantum efficiency of night vision devices;

[0058] Figure 7 This demonstrates the implementation of two Figure 5 A simplified view of a night vision device and a beacon identification system according to the present invention;

[0059] Figure 8 It shows the integration of Figure 7 Examples of images observed through the night vision goggles of two night vision devices;

[0060] Figure 9 It shows the use of Figure 7 The four timing diagrams of the asynchronously triggered beacon identification system; and

[0061] Figure 10 It shows the use of Figure 7 The identification system synchronously triggers four timing diagrams of the beacon. Detailed Implementation

[0062] Figure 5 A night vision device 11 integrating an image intensifier tube 13 according to the present invention is shown. (As in the prior art) Figure 1 The illustrated night vision device 11 is typically in the form of an observation instrument, intended to be placed in front of the eyes of a sensor or user, or, when two devices are arranged side-by-side to form night vision goggles, in front of both eyes of the user. The night vision device 11 integrates multiple elements along the optical axis α1 of a single eye of the sensor or user to transform the image of the observed scene. More specifically, starting from the scene outside the eyes of the sensor or user, the observation instrument includes a lens 12, an image intensifier tube 13 of the present invention, and an eyepiece 14.

[0063] As previously described, lens 12 includes one or more lenses that enable the capture of photons of electromagnetic radiation from the observed scene. Similarly, eyepiece 14 includes one or more lenses that enable the capture and incidental visualization of photons of the optical signal transmitted by image intensifier tube 13.

[0064] The image intensifier tube 13 includes at least three different components integrated in an internal vacuum housing 24: a photocathode 16, an electron multiplier 18, and a fluorescent screen 20.

[0065] As previously described, the photocathode 16 appears as a semi-transparent photosensitive layer that receives photons from incident electromagnetic radiation (i.e., photons transmitted by the lens 12). To this end, the input window 15 transmits photons from the lens 12 to the photocathode 16 while ensuring the tightness of the outer wall 23 of the image intensifier tube 13.

[0066] The photocathode 16 is typically made in the form of a thin metal or semiconductor film placed against a glass layer or a light-transmitting material layer. The material of the photocathode 16 is chosen based on its sensitivity to the image of the observed scene. The interaction between photons of the incident electromagnetic radiation of the observed scene and the photocathode 16 induces electron emission through the photoelectric effect.

[0067] More specifically, the photocathode 16 is integrated into the diffraction grating 30, which itself is integrated into the inner surface of the input window 15.

[0068] The diffraction grating 30 is formed by a periodic arrangement of patterns (e.g., indentations, recesses, grooves, notches, or stripes) formed in the input window 15. The diffraction material is preferably placed between the patterns of the diffraction grating 30 in the input window 15 to form a planar surface for depositing the photocathode 16. For example, the input window 15 may be made of glass, quartz, or borosilicate glass. The patterns of the diffraction grating 30 in the input window 15 can be formed using known etching techniques, such as holography, ion etching, and / or diamond etching.

[0069] The pattern is then preferably filled with a diffractive material having an optical refractive index n different from that of the input window 15, such as Al2O3 (n~1.7), TiO2 (n~2.3-2.6), Ta2O5 (n~2.2), or HfO2. This diffractive material can be deposited using known physical vapor deposition techniques, such as cathode sputtering, evaporation, or electron beam physical vapor deposition (also known as EBPVD).

[0070] The difference between the optical index of the diffractive material present in the pattern and the optical index of the material in the input window 15 is preferably greater than or equal to 0.2.

[0071] The photocathode 16 is preferably made of a semiconductor material (preferably an antimony-based alkaline compound). Such alkaline materials can be selected from the following: SbNaKCs, SbNa2KCs, SbNaK, SbKCs, SbRbKCs, or SbRbCs. Preferably, the photocathode 16 is made of antimony and sodium.

[0072] At the output of the photocathode 16, the emitted electrons (called photoelectrons) are then subjected to a first electric field within the first acceleration region 17, which guides the photoelectrons to the electron multiplier 18. This first electric field is formed by applying a voltage between the photocathode 16 and the electron multiplier 18, typically in the range of 50 to 500 volts, to ensure a straight path for the electrons.

[0073] In addition to the first electric field created between the photocathode 16 and the electron multiplier 18, a second electric field is created between the two surfaces of the electron multiplier 18 by electrodes placed on either side of the microchannel plate 25.

[0074] This electric field enables the charging of the internal semiconductor layer of the microchannel 25, causing multiple collisions of photoelectrons 28 within the microchannel 25 to generate a large number of secondary electrons 29. This electric field also accelerates the primary and secondary electrons 29 within the microchannel 25, causing them to collide again with the surface of the microchannel 25, generating more secondary electrons 29, and so on, thus generating a large number of secondary electrons 29 through this physical process. Furthermore, it allows for the acceleration of the secondary electrons 29 through energy input, guiding them from the input section to the output section of the microchannel 25. Typically, photoelectrons 28 in the electron multiplier 18 are charged at a rate of 10... 3 Up to 10 6 The electrons are multiplied within the range of electron multipliers. At the output of the microchannel 25, under the influence of a third electric field generated between the electron multiplier 18 and the fluorescent screen 20, these secondary electrons 29 are then linearly displaced toward the fluorescent screen 20 within the second acceleration region 19. This third electric field is typically generated by a voltage in the range of 4kV to 10kV.

[0075] The fluorescent screen 20 enables the conversion of secondary electrons 29 into photons that generate light intensity. It appears in the form of a light-emitting material layer or a fluorescent layer deposited on a substrate typically made of glass.

[0076] At the output of the fluorescent screen 20, the formed image is transmitted to the eyepiece 14 via optical elements (typically fiber optic network 21), which may enable the image formed on the fluorescent screen 20 to be flipped to obtain a correct view of the observed scene.

[0077] To generate three electric fields, the electronic components 22 are typically arranged around the internal vacuum casing 24. The resulting night vision system 11 thus includes optical elements, the electronic components 22, and possibly a system for viewing the observed scene through the eyepiece 14.

[0078] like Figure 6 The illustrated image intensifier tube 13, formed by using a correlated photocathode 16 and a diffraction grating 30, has a sensitivity spectrum with a maximum quantum efficiency QE that is less than the maximum quantum efficiency QE of prior art image intensifier tubes 130.

[0079] Furthermore, the sensitivity spectrum has been broadened. Therefore, photons between 400 nm and 1,064 nm can be detected, instead of those between 450 nm and 900 nm.

[0080] More specifically, according to the present invention, the image intensifier tube 13 thus formed has the following quantum efficiency QE:

[0081] Higher than 1% in the imaging wavelength range; and

[0082] In a detection wavelength range different from the imaging wavelength range, the detection wavelength range is from 0.001% to 1%, with the minimum range being from 1,000 nm to 1,100 nm, and preferably from 1,050 nm to 1,075 nm.

[0083] This detection wavelength range enables the capture of the performance signal Sm of at least one beacon B. Therefore, as Figure 7 As illustrated, the present invention provides a night vision goggle (NVG) or night vision device using an image intensifier tube 13 integrated as described above, to capture the performance signal Sm from at least one beacon B within the detection wavelength range. Preferably, the beacon B transmits the performance signal Sm at a precise wavelength of 1,064 nanometers.

[0084] Beacon B can be formed by an electronic package that integrates a power supply and a device (such as an infrared diode) for transmitting the performance signal Sm.

[0085] Furthermore, beacon B can permanently emit the manifestation signal Sm, or it can emit it in response to the activation signal Sa. Preferably, as Figure 7 As illustrated, the activation signal Sa can be emitted from the night vision goggle NVG or night vision device. For this purpose, the night vision goggle NVG or night vision device integrates the activation device 31.

[0086] The activation device 31 can be formed by a tube integrating a power supply and a device for transmitting the activation signal Sa. It should be noted that the power supply for the activation device 31 can be provided by a night vision goggle (NVG) or night vision device, for example, by electronic component 22. The activation signal Sa can be an optical or radio frequency signal. Therefore, when the activation device 31 of beacon B integrates a radio frequency transmitter, beacon B integrates an antenna, and the signal Sm is transmitted only in response to the reception of the activation signal Sa.

[0087] As a variant, when the activation device 31 of beacon B integrates a light emitter (e.g., a laser diode), beacon B integrates a light receiver (e.g., a photodiode), and the performance signal Sm is also emitted only in response to the reception of the activation signal Sa. The laser diode and photodiode can be configured to operate at wavelengths in the range of 1,400 nm to 1,800 nm (e.g., 1,550 nm).

[0088] In order for beacon B to receive the activation signal Sa, it is necessary to adjust the propagation range and propagation angle F31 of the activation signal Sa so that the activation signal Sa reaches beacon B. In the same way, the power and propagation angle Fb of beacon B must be configured so that the signal Sm reaches the detection angle Fnvg of the night vision goggles NVG or night vision device.

[0089] To increase the detection range of beacon B, the propagation angle F31 of the activation signal Sa can be reduced. Alternatively, a propagation angle F31 of the activation signal Sa smaller than the viewing angle Fnvg of the night vision goggles NVG or night vision device can be used. In this embodiment, beacon B can only be detected within a specific observation area Zp of the image observed by the night vision goggles NVG or night vision device.

[0090] exist Figure 8 In the example, the night vision goggles NVG enable the viewing of binocular night images, and in these images, a specific central viewing area Zp enables the detection of beacon B.

[0091] Furthermore, the night vision goggles (NVG) or night vision device can integrate an optical gain adjustment mechanism, also referred to in the literature as "automatic gating," to limit the on-time of the image amplifier tube 13 to specific activation periods Pal of the automatic gating mechanism. To prevent beacon B from emitting the performance signal Sm only outside the detection range of the image amplifier tube 13, beacon B can be configured to emit signals for a significantly longer period than the specific activation period Pal of the automatic gating mechanism.

[0092] As a variant, utilizing such Figure 9 The illustrated asynchronous detection allows the activation device 31 to have a variable activation period P31. Using this embodiment, beacon B can be detected when a specific activation period Pal of the image amplifier tube 13 occurs simultaneously with the activation period P31 of the activation device 31. Therefore, in Figure 9 On the last timing diagram related to the detection of image amplifier tube 13, beacon B was not detected on the two first emitted performance signals Sm, but beacon B was detected on the last two performance signals Sm.

[0093] Utilize, such as Figure 10 The illustrated synchronization detection, activation device 31, is connected, for example, via electronic component 22 to a device for managing a specific activation period Pal of the automatic gating mechanism. In this embodiment, activation device 31 presents an activation period P31 synchronized with the specific activation period Pal of the automatic gating mechanism of image amplifier tube 13. Therefore, in this embodiment, in Figure 10 On the last timing diagram related to the detection of image amplifier tube 13, beacon B was detected on the four emitted performance signals Sm.

[0094] Therefore, this invention enables the detection of beacon B without degrading the image formed by the image amplifier tube 13, because the detection wavelength of beacon B is not included in the imaging wavelength range, for example, from 450 nm to 900 nm. Furthermore, this invention improves the stealth of the beacon B carrier, since the detection wavelength of beacon B cannot be detected by conventional night vision systems that capture photons in the wavelength range λ from 450 nm to 900 nm.

Claims

1. A system for identifying at least one beacon (B), the beacon (B) integrating means for emitting electromagnetic radiation in the wavelength range from 1,000 nanometers to 1,100 nanometers, the system comprising a night vision goggle, i.e., an NVG or night vision device, integrating an image amplifier tube (13), the image amplifier tube (13) comprising: An input window (15) is configured to receive and transmit photons; A photocathode (16), which is attached to the inner surface of the input window (15), is capable of converting photons transmitted through the input window (15) into photoelectrons (28); the photocathode (16) has a sensitivity spectrum defined according to the wavelength of the photons received by the photocathode (16) and according to the quantum efficiency (QE) of the photocathode (16), the quantum efficiency (QE) being the ratio of the number of photoelectrons (28) generated by the photocathode (16) to the number of photons received; An electron multiplier (18) capable of multiplying the photoelectrons (28) into secondary electrons (29); and A fluorescent screen (20) converts the secondary electrons (29) into photons; The image amplifier tube (13) is characterized in that it further includes a diffraction grating (20) placed between the input window (15) and the photocathode (16) to diffract photons in the photocathode (16) and enable the photocathode (16) to exhibit the following quantum efficiency (QE): Higher than 1% in the imaging wavelength range; and In a detection wavelength range different from the imaging wavelength range, in the range from 0.001% to 1%, the minimum detection wavelength range is from 1,000 nm to 1,100 nm; The image amplifier tube (13) is configured to capture electromagnetic radiation emitted by the beacon (B) within the detection wavelength range.

2. The system for identifying at least one beacon (B) according to claim 1, wherein the photocathode (16) is based on antimony and formed based on at least one alkali metal.

3. The system for identifying at least one beacon (B) according to claim 1 or 2, wherein the image amplifier tube (13) is configured to capture an appearance signal (Sm) originating from the at least one beacon (B), the appearance signal (Sm) having a wavelength in the range of 1,050 nm to 1,075 nm, preferably 1,064 nm.

4. The system for identifying at least one beacon (B) according to any one of claims 1 to 3, wherein the night vision goggle, i.e., NVG, or the night vision device further comprises means (31) for activating the beacon (B), which is configured to emit an activation signal (Sa), the beacon (B) comprising a module for receiving the activation signal (Sa) in order to emit electromagnetic radiation in the form of an expression signal (Sm) in the range of wavelength from 1,000 nm to 1,100 nm as a response to the activation signal (Sa) emitted by the activation means (31).

5. The system for identifying at least one beacon (B) according to claim 4, wherein the means (31) for activating the beacon (B) is formed by a radio frequency transmitter, and the module for receiving the beacon (B) is formed by an antenna.

6. The system for identifying at least one beacon (B) according to claim 4, wherein the means (31) for activating the beacon (B) is formed by an optical transmitter and the receiving module of the beacon (B) is formed by an optical receiver.

7. The system for identifying at least one beacon (B) according to claim 6, wherein, The light emitter is a laser diode with a wavelength in the range of 1,400 nanometers to 1,800 nanometers, and the receiving module of the beacon (B) is formed by a photodiode capable of capturing wavelengths in the range of 1,400 nanometers to 1,800 nanometers.

8. The system for identifying at least one beacon (B) according to any one of claims 4 to 7, wherein the night vision goggle, i.e., the NVG, or the night vision device is configured to observe a scene (Sc) in which a specific observation area (Zp) is placed, defined by the emission angle (F31) of the activation device (31) and the viewing angle (Fnvg) of the night vision goggle, i.e., the NVG, or the night vision device, and the detection of the beacon (B) is performed only in the specific observation area (Zp).

9. The system for identifying at least one beacon (B) according to any one of claims 4 to 8, wherein the image amplifier tube (13) includes an automatic gating mechanism and the activation device (31) has a variable activation period (P31-1).

10. The system for identifying at least one beacon (B) according to any one of claims 4 to 8, wherein the image amplifier tube (13) includes an automatic gating mechanism having a specific activation period (Pal), and the activation device (31) has an activation period (P31-2) synchronized with the specific activation period (Pal) of the automatic gating mechanism of the image amplifier tube (13).

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