An image intensifier in which a power supply unit is arranged upstream of a photocathode

Abstract

An image intensifier (300), - an intensifier tube (350) in which at least one photocathode (310), a microchannel plate (320) and a conversion element (330) are arranged one after the other in this order; a power supply module (360) configured to supply at least one respective polarization voltage to each of the elements of the intensifier tube (350); Equipped with. According to the invention, the power supply module (360) extends on the side of the microchannel plate opposite the photocathode, in a region located upstream of the photocathode. Thus, space is freed up downstream of the intensifier tube (350) in the direction of photon and electron travel in the image intensifier (300), which makes it possible to reduce the size of the image intensifier (300), for example by bringing the eyepiece (380) closer.

Description

Technical Field

[0001] The field of the present invention is the field of image enhancement devices used for observing dim scenes, particularly night scenes.

Background Art

[0002] Image enhancement devices are based on the principle of continuous optical amplification through photon-electron conversion operated by a photocathode, an increase in the number of electrons by secondary emission, and final electron-photon conversion operated by a phosphor screen called a fluorescent screen.

[0003] FIG. 1 schematically shows an image enhancement device 100 according to the prior art. The image enhancement device includes the following elements arranged one after another in the following order, namely, - a photocathode 110, and - a microchannel plate 120, or MCP representing a "microchannel plate", and - an electron-photon conversion element 130 and.

[0004] The photocathode 110 is arranged on the input side of the image enhancement device 100. During use, the photocathode 110 is polarized by a first polarization voltage. This stage can convert an incident photon beam into an initial electron beam by the photoelectric effect.

[0005] The microchannel plate 120 is a component made of glass where a large number of microchannels intersect. During use, the microchannel plate 120 is polarized by a second polarization voltage. This stage enables an increase in charge through secondary emission. The inner field is created by the application of the second polarization voltage applied between two surfaces (input and output) of the microchannel plate. When electrons enter the microchannels and hit their walls, this causes the emission of some so-called secondary electrons. The secondary electrons are accelerated by the inner field in the microchannel plate 120 and hit the walls of the microchannels again, which causes the emission of new secondary electrons. Thus, this consists of a cascade phenomenon. In the image intensifier device 100, the microchannel plate 120 is configured to receive the initial electron beam emitted by the photocathode 110 and send a response enhanced electron beam. Each electron of the initial electron beam arriving from the photocathode generates the emission of a plurality of electrons of the enhanced electron beam.

[0006] Next, the electron-photon conversion element 130 is simply called the "conversion element". During use, the electron-photon conversion element 130 is polarized by a third polarization voltage. The electron-photon conversion element 130 is configured to receive the enhanced electron beam and, in response, emit an enhanced photon beam. Each electron in the enhanced electron beam is the origin of each photon in the enhanced photon beam. Thus, the light distribution in the enhanced photon beam corresponds to the light distribution in the incident photon beam at the photocathode and is considerably amplified by the cascade emission in the microchannel plate. Thus, an image with a low light level supplied at the photocathode is converted into an image with sufficient brilliance to distinguish the objects in the image with the naked eye. Preferably, the conversion element 130 consists of a fluorescent screen.

[0007] The photocathode 110, the microchannel plate 120, and the conversion element 130 extend successively in this order along the axis (Ox). Thus, the microchannel plate 120 is positioned between the photocathode 110 and the conversion element 130. It is possible to define the direction of the flow of photons and electrons in the image intensifier device, and that direction corresponds, in this specification, to the axis (Ox) oriented from the photocathode 110 towards the conversion element 130.

[0008] Throughout the text, the terms "upstream" and "downstream" refer to the direction of the flow of photons and electrons in the image intensifier device.

[0009] All of the photocathode 110, the microchannel plate 120, and the conversion element 130 extend inside a sealed chamber in which a very low pressure prevails, or inside the intensifier tube 150. The pressure level in the intensifier tube 150 is referred to by those skilled in the art as "ultra-high vacuum". Inside the intensifier tube 150, two regions 151, 152 extend here under ultra-high vacuum pressure. The regions 151, 152 extend respectively between the photocathode 110 and the microchannel plate 120 and between the microchannel plate 120 and the conversion element 130. In this case, the photocathode 110 consists of a coating deposited across the port hole 111, said port hole forming the input window of the intensifier tube 150.

[0010] In the example shown in FIG. 1, the image intensifier device further comprises an optical fiber array 140, which extends downstream of the conversion element 130 such that the conversion element 130 is positioned between the microchannel plate 120 and the optical fiber array 140. Thus, the intensifier tube 150 is closed at that end opposite the photocathode 110 by one of the ends of the optical fiber array 140. The conversion element 130 is in the form of a multilayer of luminescent micron particles. Each luminescent particle extends across one or more optical fibers of the optical fiber array 140 on the side of the microchannel plate 120.

[0011] The optical fiber array 140 is configured to invert the input image (i.e., rotate it by 180°). In other words, the image supplied at the input of the optical fiber array is rotated by 180° about the axis (Ox) between the input and the output of the optical fiber array. The image is further transferred here along the axis (Ox) from one end of the optical fiber array 140 to the other end. The arrangement of the optical fibers at the input of the optical fiber array (on the side of the microchannel plate 120) and the arrangement of the optical fibers at the output of the optical fiber array (on the opposite side of the microchannel 120) are symmetric with respect to each other according to circular symmetry at an angle of 180° = π. The optical fiber array 140 enables, during use, the enhanced image obtained in the conversion element 130 to be pivoted by 180° so that the user sees it "right side up". Thus, the problem is to cancel the image inversion imparted by the objective lens 170, which will be mentioned later.

[0012] An assembly including the photocathode 110, the microchannel plate 120, the conversion element 130, and the optical fiber array 140 is inserted between the objective lens 170 and the eyepiece 180.

[0013] The objective lens 170 consists of one or a set of refractive optics or lenses. The objective lens 170 is configured to effect an optical coupling between the focal plane and the object surface, on which there is a scene to be observed and / or imaged, and the initial image formation plane P1 is positioned at the input of the intensifier tube 150 or inside it. In this case, the initial image formation plane P1 extends directly across the active surface of the photocathode 110 over the entire photocathode 110.

[0014] The eyepiece 180 consists of one or a set of refractive optics or lenses. The eyepiece 180 is configured to effect an optical coupling between the enhanced image formation plane P2 and an image plane positioned outside the intensifier tube 150.

[0015] The enhanced image formation surface P2, during use, refers to the surface on which the enhanced image is formed by the photons emitted from the conversion element 130. When appropriate, the enhanced image formation surface P2 meets this condition and is the surface closest to the optical output 153 of the intensifier tube 150. The optical output 153 of the intensifier tube 150, during use, refers to the junction through which the enhanced photon beam emitted by the conversion element 130 exits into free space. In this case, the optical output 153 of the intensifier tube 150 is formed by one end of the optical fiber array 140 on the side opposite to the microchannel plate 120. Therefore, the enhanced image formation surface P2 passes through the output surfaces of the optical fibers of the optical fiber array 140 on the side opposite to the microchannel plate 120. The enhanced image formed on the surface P2 corresponds to the image formed at the conversion element 130 and displaced and pivoted by the optical fiber array 140.

[0016] Preferably, the image plane corresponds to the surface that is more clearly visible to the user for a stationary eye looking through the eyepiece 180. For optimal visual comfort, the diopter of the eyepiece 180 may be adjusted. During use, the user places their eye behind the eyepiece 180 on the side opposite to the optical fiber array 140. The image plane and the retina of the eye are optically coupled by the visual system formed by the elements of the eye between the retina and the cornea and, when appropriate, vision correction optics such as contact lenses. For a emmetropic eye, the image plane extends to infinity.

[0017] Each of the photocathode 110, the microchannel plate 120, and the conversion element 130 is connected to a power supply module 160, and the power supply module 160 supplies them with respective polarization voltages (referred to as the first, second, and third polarization voltages, respectively). The power supply module 160 is connected at its input to a low-voltage power source (not shown), such as a battery. The power supply module 160 converts the thus received low voltage into at least one high voltage that forms the first, second, and third polarization voltages respectively, and is configured to supply these polarization voltages to each of the photocathode 110, the microchannel plate 120, and the conversion element 130.

[0018] The power supply module 160 and the intensifier tube 150 generally extend together inside the housing 190 in the form of a tube.

[0019] As shown in FIG. 1, the power supply module 160 extends around the optical fiber array 140.

[0020] FIG. 1 also shows an arrow 101, denoted by a symbol, representing the required distance between the back focus of the eyepiece 180, or, in other words, the enhanced image formation plane P2 (at the output of the optical fiber array 140 in this specification), and the eyepiece 180 at the level of the interface surface 181 of the eyepiece 180 positioned opposite the conversion element 130. The back focus 101 corresponds to a distance that allows the eyepiece 180 to achieve an optical coupling between the enhanced image formation plane P2 and the image plane clearly visible to the user. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0021] An object of the present invention is to provide an image intensifying device that can have a reduced size compared to an image intensifying device according to the prior art. MEANS FOR SOLVING THE PROBLEMS

[0022] This object is an image intensifier comprising an intensifier tube and a power supply module, wherein the intensifier tube - at least one photocathode configured to convert an incident photon beam into an initial electron beam, - a microchannel plate configured to generate a plurality of secondary electrons in response to receiving incident electrons during use, receive the initial electron beam, and generate an intensified electron beam in response, - a conversion element configured to receive the intensified electron beam and emit an intensified photon beam in response, the conversion element being a microchannel plate positioned between the photocathode and the conversion element, - a power supply module configured to supply at least one respective voltage to each of the photocathode, the microchannel plate, and the conversion element and the power supply module is achieved in an image intensifier that extends in a region positioned upstream of the photocathode on the side of the photocathode opposite the microchannel plate.

[0023] The conversion element may be referred to as a "photon - electron conversion element".

[0024] During use, each incident electron in the microchannel plate preferably generates the emission of a large number of secondary electrons, more than 10.

[0025] One solution for reducing the size of the image intensifier of the type shown in Figure 1 is to shorten the length of the fiber optic array. In fact, recent developments have enabled the fabrication of arrays of fibers with a shortened length while maintaining the optical transmission and contrast requirements that can invert the input image and ensure consistent image quality.

[0026] FIG. 2 shows an image intensifier 100' that differs from that of FIG. 1 only in that the optical fiber array 140' has a reduced length. Similar to the prior art, the conversion element 130' extends at the input of the optical fiber array, and the enhanced image formation plane P2 is positioned at the output of the optical fiber array 140'. Due to the reduced length of the optical fiber array 140', the enhanced image formation plane P2 is considerably retracted with respect to the outlet of the housing 190'. To maintain the necessary distance between the enhanced image formation plane P2 and the eyepiece lens 180', it is necessary to bring the housing 190' and the eyepiece lens 180' closer to each other. The eyepiece lens 180' can be brought closer to the housing 190' up to the most extreme position where the eyepiece lens 180' is pressed against the outlet edge 191' of the housing 190'. The outlet edge 191' of the housing 190' refers to the edge of the housing 190' that is furthest from the objective lens 170. If the reduction in the length of the bundle of optical fibers 140' is significant, even at this most extreme position, it is impossible to obtain that the distance between the enhanced image formation plane P2 and the eyepiece lens 180' is equal to the back focus 101' of the eyepiece lens (see FIG. 2). Therefore, a person skilled in the art may consider reducing the length L of the housing 190' in order to reduce the distance between the enhanced image formation plane P2 and the outlet edge 191' of the housing 190'. However, a person skilled in the art is limited by the size of the power supply module 160'. An obvious solution to overcome this problem is to miniaturize the power supply module 160'.

[0027] Therefore, the idea at the origin of the present invention is to reexamine the overall arrangement of different elements in the image intensifier, and instead of just changing the dimensions of the power supply module, to move the power supply module. According to the present invention, the power supply module is moved towards a region positioned on the upstream side of the photocathode (i.e., the side of the photocathode opposite to the microchannel plate) according to the direction of the flow of photons and electrons in the image intensifier. This new location can, without constraint, bring the enhanced image formation surface P2 closer to the exit edge 191' of the housing 190'. Thus, while having a bundle of optical fibers with a shortened length, it becomes possible to match the required distance between the enhanced image formation surface and the eyepiece. Furthermore, since the power supply module is moved rather than miniaturized, it is not necessary to change the whole in order to incorporate miniaturized internal components of the power supply module.

[0028] Moving the power supply module is not an obvious solution to those skilled in the art. Those skilled in the art are rather encouraged to maintain the previous arrangement, specifically to avoid the need to resize different housings and caps in the image intensifier, and to avoid the need to reexamine the problem of electrical insulation not only around the power supply module but also around the connectors (high-voltage power supply lines carrying a very small current).

[0029] This new location of the power supply module liberates the space positioned on the downstream side of the conversion element, depending on the direction of the flow of photons and electrons in the image intensifier. By liberating the space, it becomes possible to reduce the size of the image intensifier. For example, liberating this space makes it possible to shorten the distance between the conversion element and auxiliary elements such as the eyepiece. This technical advantage is found in the presence of a bundle of optical fibers downstream of the conversion element, but can also be found in the absence of such a bundle of optical fibers.

[0030] Advantageously, the power supply module extends around the periphery of the objective lens, as described with reference to FIG. 1. The diameter of the objective lens may be smaller than the diameter of the intensifier tube, and it is possible to utilize the space around the objective lens in order to accommodate the power supply module without increasing the overall diameter of the image intensifier device.

[0031] Preferably, the power supply module extends outside the intensifier tube.

[0032] Preferably, the device according to the invention further comprises a first set of lenses called objective lenses, configured to optically couple a focal plane positioned outside the intensifier tube and an initial image formation plane positioned at the input of the intensifier tube or inside thereof, and the power supply module extends around the periphery of the objective lenses.

[0033] Advantageously, the power supply module does not protrude beyond the objective lens along an axis parallel to the optical axis of the objective lens on either side of the objective lens.

[0034] Preferably, the power supply module comprises a through-opening extending opposite the photocathode. The power supply module may have an annular shape.

[0035] According to an advantageous embodiment, the device according to the invention further comprises a bundle of optical fibers arranged downstream of the conversion element in the direction of propagation of photons and electrons in the image intensifier device, such that the optical fibers of the bundle of optical fibers pivot the image supplied at the input of the bundle of optical fibers in itself, and the output surface of the bundle of optical fibers on the side opposite the conversion element forms a surface called an enhanced image formation surface.

[0036] According to another advantageous aspect, the device of the invention further comprises a transparent support, and the conversion element is formed by a coating covering at least a part of one face of the transparent support, and the face of the transparent support forms a surface called an enhanced image formation surface.

[0037] The device according to the invention may further comprise a second set of lenses, called an eyepiece, configured to optically couple an enhanced image formation surface and an image surface positioned outside the intensifier tube. The device according to the invention may further comprise not only a complementary image formation module configured to provide a complementary image, but also a partially reflective element extending between the eyepiece and the enhanced image formation surface and configured to superimpose the complementary image and the enhanced image formed on the enhanced image formation surface.

[0038] According to an advantageous variant, the device according to the invention may further comprise an offset element configured to laterally displace the enhanced image directly or indirectly derived from the enhanced image formation surface. The offset element may be at least partially transparent in the visible region in order to allow an overlap of the enhanced image displaced by the offset element in the field of view of the transparency of the surrounding landscape.

[0039] The present invention will be better understood by reading the description of the embodiments provided solely for the purpose of indication without limitation, with reference to the accompanying drawings.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0041] For greater clarity, the axes of the orthonormal reference system (Oxyz) are shown in the figure. In this case, the axis (Ox) corresponds to the direction of light propagation in the image enhancement device according to the invention.

[0042] FIG. 3 schematically shows, in cross section, an image enhancement device 300 according to a first embodiment of the invention. The image enhancement device 300 will be described only with respect to its differences compared to the embodiment of FIG. 1.

[0043] In this case, the power supply module 360 does not extend around the optical fiber array 340, and the optical fiber array 340 has a reduced length.

[0044] The power supply module 360 extends around the objective lens 370 in a region located upstream of the photocathode 310, that is, on the side of the photocathode 310 opposite the microchannel plate 320 and the conversion element 330.

[0045] As before, the photocathode 310, the microchannel plate 320, and the conversion element 330 extend inside the intensifier tube 350 as described in the introduction. The intensifier tube 350 itself extends inside the housing 390 together with the optical fiber array 340. Each of the photocathode 310, the microchannel plate 320, and the conversion element 330 extends here in a plane parallel to the plane (Oyz).

[0046] As before, an output edge 391 is defined in the housing 390, is positioned laterally of the optical fiber array 340, and faces the eyepiece 380. The output edge 391 of the housing 390 extends here in a plane (yOz) parallel to the plane of the microchannel plate 320.

[0047] The enhanced image formation surface P2 as described in the introduction section is, here, positioned at the output end of the optical fiber array 340. Specifically, the enhanced image formation surface P2 consists of the surface passing through the output surface of the optical fibers of the optical fiber array 340 on the side of the optical fibers opposite to the microchannel plate 320. The enhanced image formation surface P2 is, here, a non-planar surface, and its topology follows the topology of the first boundary surface 381 belonging to the eyepiece 380, and the first boundary surface 381 is positioned on the side of the conversion element 330.

[0048] The power supply module 360 does not extend around the optical fiber array 340 and extends in the region positioned upstream of the photocathode 310. Therefore, even with the shortened length Lf of the optical fiber array 340, the output edge 391 of the housing 390 is close to the output end 341 of the optical fiber array 340. Therefore, the output edge 391 of the housing 390 is close to the enhanced image formation surface P2. Therefore, despite the optical fiber array 340 having the shortened length Lf, the distance between the enhanced image formation surface P2 and the first boundary surface 381 belonging to the eyepiece 380 is equal to the back focus 301 of the eyepiece 380 (as defined in the introduction section).

[0049] The power supply module 360 extends, here, around the periphery of the photocathode 310 in these orthographic projections in a plane parallel to the plane (Oyz).

[0050] In this case, the optical fiber array 340 protrudes slightly outside the housing 390. Therefore, the enhanced image formation surface P2 extends outside the housing 390.

[0051] The power supply module 360 is, here, positioned outside the intensifier tube 350 and the housing 390. The power supply module 360 has, here, a length Lc measured along the axis (Ox), and the length Lc is completely smaller than the length Lb of the objective lens 370 measured along the same axis. Furthermore, the power supply module 360 does not protrude beyond the objective lens 370 along the axis (Ox) (parallel to the optical axis BB' of the objective lens 370).

[0052] Figure 4A shows an image intensifier 300 in a cross-section in a plane AA' parallel to the plane (yOz) and passing through the power supply module 360. Figure 4A shows that the power supply module 360 surrounds the objective lens 370 over an angle of 360°. In other words, the power supply module 360 is provided with a through-opening 361, and the objective lens 370 extends inside the through-opening 361. The through-opening 361 is positioned opposite the photocathode 310. Preferably, the through-opening 361 is orthogonal to the plane (Oyz) of the photocathode 310 and preferably has an axially symmetric cylindrical shape with an axis of rotation passing through the center of the photocathode 310. In this case, without being limited, the power supply module 360 is shaped as a first axially symmetric cylinder and is open at the center by a through-opening 361 shaped as a second axially symmetric cylinder concentric with the first axially symmetric cylinder. In other words, the power supply module 360 has an annular shape. In a variation not shown, the power supply module 360 has any shape provided with a through-opening shaped as an axially symmetric cylinder as described above. According to yet another variation, the opening at the center does not have an axially symmetric cylindrical shape but has any shape that can allow light to pass through to the photocathode 310.

[0053] In the variation 300' shown in Figure 4B, the power supply module 360' only surrounds the objective lens 370' over an angle of 180° or less.

[0054] Many other forms of the power supply module can be implemented without departing from the scope of the present invention. Specifically, it can be implemented in a form where the power supply module is not centered on the optical axis BB'.

[0055] Preferably, the power supply module 360 does not protrude beyond the housing 390 in the orthographic projection of the power supply module 360 in the plane (Oyz). In other words, the orthographic projection of the power supply module 360 in the plane (yOz) is inscribed inside the orthographic projection of the housing 390 in the same plane. For this purpose, the maximum diameter of the objective lens 370 is strictly smaller than the outer diameter of the housing 390, and the power supply module 360 extends in a space defined by the edge of the objective lens 370 and a tube with the same diameter as the outer diameter of the housing 390. Thus, it is ensured that the power supply module 360 does not increase the overall size of the image intensifier device, specifically, does not increase the diameter of the image intensifier device.

[0056] Two embodiments in which the new arrangement of the power supply module also has advantages in the absence of an optical fiber array at the output of the intensifier tube are described hereinafter. Specifically, in these embodiments, the new arrangement of the power supply module always allows, with a reduced size, to free up space for inserting auxiliary elements and to add new functions to the image intensifier device.

[0057] FIG. 5 shows a second embodiment of an image intensifier device 500 according to the invention, in which the space freed up by the power supply module is used to add additional functions to the device without increasing its size.

[0058] The image intensifier device 500 differs from the embodiment of FIG. 3 only in that it does not comprise an optical fiber array at the output of the intensifier tube and comprises means for generating and superimposing complementary images.

[0059] The means for generating and superimposing complementary images here comprise a complementary image formation module 51 and a partial mirror 52.

[0060] The partial mirror 52 extends between the eyepiece 580 and the enhanced image formation plane P2. The partial mirror 52 reflects a part of the incident light and transmits the other part of the incident light. In this case, the partial mirror 52 is a semi-reflective mirror. The partial mirror 52 is inclined at an angle α with respect to the plane (Oyz), where α = 45°. In a variant not shown, the partial mirror 52 can be replaced by any other partial reflection element such as a splitter cube or a splitter blade.

[0061] Furthermore, the complementary image formation module 51 is configured to generate a so-called complementary image and, here, to project the complementary image along the axis (Oz) in the direction of the partial mirror 52. The complementary image formation module 51 comprises a display screen, specifically a screen based on OLED (organic light-emitting diode). The complementary image formation module 51 may further comprise a processing device that is connected to the display screen and incorporates not only the electronic equipment necessary for controlling and powering the screen, but also the electronic equipment necessary for exchanging data with the outside (for receiving data regarding the complementary image to be displayed on the screen).

[0062] The complementary image formation module 51 extends around the partial mirror 52 and, specifically, occupies at least a part of the area that was occupied in the prior art by the power supply module 560.

[0063] The partial mirror 52 is configured to superimpose the complementary image projected by the complementary image forming module 51 and the enhanced image formed on the enhanced image forming surface P2. For this purpose, the complementary image forming module 51 is configured to project the complementary image and reach the partial mirror 52 at an incidence of 45° while propagating along the axis (Oz). In use, this complementary image is at least partially reflected in the direction of the eyepiece 580. Further, the enhanced image formed at the output end of the bundle of optical fibers 540 reaches the partial mirror 52 at an incidence of 45° while propagating along the axis (Ox). In use, this enhanced image is at least partially transmitted in the direction of the eyepiece. Thus, downstream of the partial mirror 52 in the direction of the light (and electron) flow of the device 500, the complementary image is superimposed on the enhanced image.

[0064] Advantageously, the complementary image has dimensions similar to those of the enhanced image. For example, the complementary image consists of graphic symbols. For example, it is possible to superimpose symbols relating to measurements provided by additional sensors on the enhanced image (for example, display the main points, target crosshairs, etc.).

[0065] In this case, the enhanced image forming surface P2 is a planar surface in order to simplify the superimposition of the complementary image of the enhanced image. However, the present invention also encompasses variations in which the enhanced image forming surface P2 is non-planar, such as a concave surface for example.

[0066] FIG. 6 shows a third embodiment of the image enhancement device 600 according to the present invention, which is described only in terms of its differences compared to the embodiment of FIG. 3.

[0067] In this embodiment, the image enhancement device 600 does not include an optical fiber array at the output of the intensifier tube and comprises real image superimposing means.

[0068] The real image superimposing means here comprises an offset element 61 and focusing optics 62. Here, the offset element 61 extends between the enhanced image forming surface P2 and the focusing optics 62.

[0069] The focusing optics 62 here consists of a concave mirror with its optical axis parallel to the axis (Ox) and its reflecting surface positioned on the side of the enhanced image formation plane P2. The focusing optics 62 is configured to project the enhanced image P2 formed on the enhanced image formation plane P2 to infinity. In this case, the image is projected to infinity in the direction of the enhanced image formation plane P2.

[0070] The offset element 61 is here fixed in contact with the enhanced image formation plane P2. This arrangement is made possible thanks to the space freed up by the forward movement of the power supply module.

[0071] Here too, without limitation, the enhanced image formation plane P2 is a planar surface to facilitate surface contact with the offset element 61.

[0072] The offset element 61 here comprises a waveguide that covers the enhanced image formation plane P2 and projects laterally beyond this surface up to the so-called observation region RO. The waveguide is provided with an injection element and an extraction element. For example, the injection element and the extraction element each consist of a diffraction element etched on the surface of the waveguide. In this case, the injection element (not shown) extends on the side of the focusing optics, opposite to the enhanced image formation plane P2. Further, the extraction element (not shown) here extends on the side of the focusing optics towards the observation region RO.

[0073] The offset element 61 is at least partially transparent in the visible region. For example, the offset element 61 has a transmission coefficient of 95% or more over a wavelength range from 400 nm to 700 nm.

[0074] During use, the enhanced image formed on surface P2 propagates through offset element 61 while reaching focusing optics 62. At the level of the focusing optics, the light is balanced and sent back in the opposite direction. In other words, the enhanced image is projected to infinity and sent back in the opposite direction. Thus, the light sent back by focusing optics 62 returns to offset element 61 at the level of the injection element as described above. Thus, the light penetrates through the inside of offset element 61 in the waveguide and starts optical guiding. In the waveguide, the light is guided along axis (Oz) to observation region RO. When the light reaches the level of the aforementioned extraction element, it is extracted from the waveguide. The extracted light is made parallel, like the light initially injected into the waveguide. Thus, offset element 61 is configured to receive the enhanced image at the input, shift this enhanced image laterally to observation region RO, and extract this enhanced image outside of offset element 61. The enhanced image shifted laterally using offset element 61 is an image directly or indirectly derived from enhanced image formation surface P2. In this case, since the enhanced image corresponds to the enhanced image formed on surface P2 and projected to infinity by focusing optics 62, it is indirectly derived from said surface P2.

[0075] During use, the user places their eye opposite offset element 61, where the enhanced image will be projected to infinity, opposite the observation region RO that has flowed through shift element 61. Thus, the user visualizes by superimposing the enhanced image brought by offset element 61 and the external scenery visible transparently through offset element 61. Thus, image enhancement device 600 forms an augmented reality viewing device for providing a scene corresponding to the superimposition of the enhanced image and the image in natural vision.

[0076] In this embodiment, image enhancement device 600 does not include an eyepiece lens disposed directly at the output of the fiber optic bundle.

[0077] Advantageously, the offset element 61 is fixed to the bundle of optical fibers 640 by direct or close coupling to the output surface of the optical fiber 640.

[0078] In a variant not shown, the focusing optics extends between the enhanced image formation plane P2 and the offset element. Therefore, the focusing optics consists of one or more refractive lenses. Also here, the focusing optics is configured to project the enhanced image formed on the enhanced image formation plane P2 to infinity. Also here, the image is projected in the direction of the offset element on the side of the focusing optics opposite to the plane P2 here. The image projected to infinity in this way enters the offset element and is brought to the observation region extracted from the offset element. The back focus of the focusing optics can be very short. Therefore, the present invention enables access to the focusing optics sufficiently close to the plane P2 thanks to the space freed up by the forward movement of the power supply module.

[0079] The present invention is not limited to the examples described above. For example, in a variant not shown, the image enhancement device does not include an optical fiber array, but includes a transparent support such as a glass block. In this case, the conversion element is in the form of a coating that extends integrally across one surface of the transparent support. The transparent support is transparent to the wavelength of the photons emitted by the conversion element. Therefore, the enhanced image formation plane coincides with the surface on which the coating forming the conversion element extends in the transparent support. The inversion of the image's "right side up" is achieved by refractive optics. The different embodiments and variants of the present invention described above can be easily combined with this variant.

[0080] According to still other variations, the intensifying device comprises a bundle of optical fibers that forms the optical input of the intensifying tube on the photocathode side. In this case, the initial image formation plane P1 as described above is formed by one end of the bundle of optical fibers on the side opposite to the photocathode. This embodiment may or may not be combined with the presence of the bundle of optical fibers at the output of the intensifying tube on the conversion element side. This embodiment can be combined with each of the examples, variations, and embodiments described above.

[0081] According to still other variations, the power supply module can be positioned inside the housing that receives the intensifying tube and the bundle of optical fibers.

[0082] The present invention also encompasses a twin system including two image intensifying devices according to the present invention, each dedicated to each user's respective eye.

[0083] The device according to the present invention can find advantageous use in the field of night vision for observing dim or dark scenes.

[0084] The present invention can be adapted to a night vision device without a microchannel plate, based on the use of a photocathode or a CMOS sensor that can convert the flow of incident electrons into an electrical measurement signal. In such a device, a power supply module that can supply a polarization voltage to the photocathode can be arranged upstream of the photocathode, so to speak, in the direction of the flow of light and electrons in the device.

Explanation of Signs

[0085] 51 Complementary image formation module 52 Partial mirror 61 Offset element 62 Focusing optics 100’ Image intensifying device 101’ Back focus 130’ Electron-photon conversion element 140’ Optical fiber array, optical fiber 160' Power supply module 180' Eyepiece 190' Housing 191' Outlet edge 300, 300' Image intensifier 301 Back focus 310 Photoelectric cathode 320 Microchannel plate 330 Conversion element 340 Optical fiber array 341 Output end 350 Intensifier tube 360 Power supply module 361 Through opening 370, 370' Objective lens 380 Eyepiece 381 First boundary surface 390 Housing 391 Output edge 500 Image intensifier 540 Optical fiber 560 Power supply module 580 Eyepiece 600 Image intensifier 640 Optical fiber AA' Plane BB' Optical axis L Length of housing 190' Lb Length of objective lens 370 Lc Length of power supply module 360 Lf Length of optical fiber array 340 RO Observation area P2 Enhanced image formation surface

Claims

1. An image intensifying device (300; 300'; 500; 600) comprising an intensifying tube (350) and a power supply module (360; 360'; 560), wherein the intensifying tube (350) comprises at least one photocathode (310) configured to convert an incident photon beam into an initial electron beam, a microchannel plate (320) configured to generate a plurality of secondary electrons in response to reception of incident electrons during use, receive the initial electron beam, and in response, generate an intensified electron beam, a conversion element (330; 530) configured to receive the intensified electron beam and, in response, emit an intensified photon beam by means of the microchannel plate (320) positioned between the photocathode (310) and the conversion element (330; 530), a first set of lenses (370), called an objective lens, configured to optically couple a focal plane positioned outside the intensifying tube (350) to an initial image formation plane (P1) positioned at or inside the input of the intensifying tube (350), comprising the power supply module (360; 360'; 560) is configured to supply at least one respective bias voltage to each of the photocathode (310), the microchannel plate (320), and the conversion element (330; 530), the power supply module (360; 360'; 560) extends in a region positioned completely upstream of the photocathode (310) on the side of the photocathode opposite the microchannel plate at the periphery of the objective lens (370). An image intensifying device (300; 300'; 500; 600) characterized by that.

2. The power supply module (360; 360'; 560) does not protrude beyond the objective lens (370) along an axis parallel to the optical axis (BB') of the objective lens (370) on either side of the objective lens (370). The image intensifying device (300; 300'; 500; 600) according to Claim 1, characterized by that.

3. The power supply module (360; 560) comprises a through opening (361) extending opposite the photocathode (310). The image intensifying device (300; 500; 600) according to Claim 1 or 2, characterized by that.

4. The image enhancement device (300; 500; 600) according to claim 3, characterized in that the power supply module (360; 560) has an annular shape.

5. The image enhancement device (300; 300'; 500; 600) further comprises an optical fiber bundle (340; 540; 640) arranged downstream of the conversion element (330; 530) in the direction of propagation of photons and electrons in the image enhancement device, such that the optical fibers of the optical fiber bundle (340; 540; 640) pivot the image supplied at the input of the optical fiber bundle by themselves, and the output surface of the optical fiber bundle on the side opposite to the conversion element (330; 530) forms a surface called the enhanced image formation surface (P2). The image enhancement device (300; 300'; 500; 600) according to any one of claims 1 to 4.

6. The image enhancement device further comprises a transparent support, the conversion element is formed by a coating covering at least a part of one surface of the transparent support, and the other surface of the transparent support forms a surface called the enhanced image formation surface. The image enhancement device according to any one of claims 1 to 4.

7. The image enhancement device (300; 300'; 500) further comprises a second set of lenses (380; 580), called an eyepiece lens, configured to optically couple the enhanced image formation surface (P2) and an image surface positioned outside the intensifier tube (350). The image enhancement device (300; 300'; 500) according to claim 5 or 6.

8. The image enhancement device (500) further comprises a complementary image formation module (51) configured to provide a complementary image, and a partial reflection element (52) extending between the eyepiece lens and the enhanced image formation surface (P2) and configured to superimpose the complementary image and the enhanced image formed at the enhanced image formation surface (P2). The image enhancement device (500) according to claim 7.

9. The image enhancement device (600) further comprises an offset element (61) configured to laterally shift the enhanced image directly or indirectly derived from the enhanced image formation surface (P2). The image enhancement device (600) according to claim 5 or 6.

10. The image enhancement device (600) according to claim 9, wherein the offset element (61) is at least partially transparent in the visible region in order to enable overlapping of the enhanced image shifted by the offset element in the field of view of the transparency of the surrounding scenery.

Images