VIEWING SYSTEM WITH ADJUSTABLE MAGNIFICATION

Description

Technical field:

[0001] The invention relates to clear viewfinders and more particularly to clear viewfinders with adjustable magnification. Previous technique:

[0002] Riflescopes are mechanical or optical systems that allow the infantryman to align his rifle with a target via a line of sight.

[0003] This line of sight can be materialized by the alignment of a rear sight and a front sight in the case of an exclusively mechanical sight. It can also correspond to the axis defined by a reticle placed at the focus of a collimating optic, in the case of an optical shooting scope.

[0004] Many electronic, software or network functions underlying the proposed optical architecture can complement this basic function. Examples of these underlying functionalities include: Optoelectronic functionalities: display of augmented reality or virtual reality information including: symbology, image fusion for example with a night imaging channel (light intensification or thermal imaging) or with an external video stream, Software and network functionalities: edge detection, shape recognition, target tracking, geolocation, compass, exchange of video data or metadata with third parties, collaborative combat, threat detection.

[0005] To combine or separate these functionalities into different optical imaging paths, existing solutions typically use intensity separations, pupil separations, mechanical switching, or digital fusion. Intensity separation results in a reduction in luminance on each imaging path. Pupil separation results in a reduction in the pupil size (or field of view, in this case, field separation) on each imaging path. Mechanical switching does not allow simultaneous image viewing on both paths. Finally, electronic fusion often requires separate optics, and increases in size, mass, and cost.

[0006] Furthermore, shooting glasses are usually separated into two categories:

[0007] "Clear sights", also known by the Anglo-Saxon terms "reflex sight" or "red dot sight",

[0008] Monocular shooting glasses, also known by the Anglo-Saxon terms "Telescopic scope" or "Rifle scope",

[0009] Clear sights offer "both eyes open" aiming, without imaging optics, which allows the infantryman to continue monitoring his immediate environment while aiming at a target. They are also suitable for situations requiring high responsiveness and rapid aiming, unlike monoculars for which the infantryman must position his eye at the correct distance from the scope, in its exit pupil, to be able to aim. Clear sights are generally supplemented by an external magnifying afocal system which increases their size and mass. The addition of this element then transforms the clear sight into a monocular and the infantryman loses the advantages specific to reflex sighting.It therefore loses in comfort of use because for high magnification values, for example greater than x3 or x4, the eye circle is very often less than Ø10 mm and this forces him to position his eye precisely in this eye circle, behind a monocular, to be able to aim. In certain environments, when aiming, the infantryman can also be bothered by vitreous reflections on bodies of water, windows of buildings or vehicles, etc. It is certainly possible to add a polarizer at the input of the sights to overcome this problem, but this addition reduces the optical transmission by a factor of 2 on the direct optical path, which reduces the range of the sight.

[0010] Monoculars, on the other hand, have other advantages over clear viewfinders. Some of them, for example, incorporate a bi-afocal magnification system, such as the Elcan Specter DR 1X / 4X scope, without significantly changing their size. Other scopes, such as the Sightron SIII SS832X56LRZSMD / CM, incorporate a continuous magnification system.

[0011] The solution proposed by the invention is a clear viewfinder that advantageously exploits the polarization states of light to achieve a compact and lightweight system making it possible to easily vary the magnification of the image returned to the eye while combining several functionalities. Documents WO 2018 / 057872 A1 and US 2018 / 275410 A1 fall within the scope of the prior art of the present invention. Summary of the invention:

[0012] For this purpose, an object of the invention is a shooting scope observing a scene, said shooting scope comprising a first optical sub-assembly, called an afocal module and a second optical sub-assembly, called a display module, said afocal module comprising: a removable and switchable rectilinear polarizer, so as to transmit at least a first rectilinear polarization state of light coming from said scene, called state A, or a second rectilinear polarization state of the light, called B, said state B being orthogonal to said state A; a first polarization splitter element arranged to reflect a polarization state A of light transmitted by said rectilinear polarizer; an afocal optical system arranged to collect light reflected by said first polarization splitter element, said afocal optical system comprising: ∘ a first and a second catadioptric sub-assemblies located on either side of the first polarization splitter element, ∘ a first and a second so-called afocal delay plates arranged on the path of the reflected light, on either side of the first polarization splitter element,respectively arranged between the first polarization splitter element and the first sub-assembly and between the first polarization splitter element and the second sub-assembly, said afocal optical system being adapted to form an image of the scene with an orientation identical to an orientation of the scene observed by said telescope, with a magnification greater than 1, called magnified image, the first polarization splitter element being further arranged to reflect light from the second sub-assembly, called AG light with a polarization state A, transporting said magnified image so that the line of sight of the AG light is collinear with a path of light transmitted by the first polarization splitter element, called direct light, with a polarization state B; said display module comprising: a half-wave plate called a distribution plate, arranged on the path of the AG light and the direct light,after the first polarization splitter element; a display adapted to form a display image by emitting radiation called display light; an optical objective adapted to collimate said display light; a second polarization splitter element arranged after the half-wave distribution plate, to transmit a polarization state B, direct light or AG light, by spatially combining it with the collimated display light, so that said telescope superimposes said non-magnified image or said direct light with said display image.

[0013] According to a variant of the invention, the glasses of the invention comprise a third module, called a video module comprising: a quarter-wave plate called an imaging plate, and a mirror adapted to transform a polarization state A of the AG light and the direct light reflected by the second polarization splitter element into a polarization state B, forming a so-called imaging light, the mirror being further arranged so that said imaging light passes through said objective in order to form said magnified image or an image of the scene from the direct light called the non-magnified image in an image focal plane of said objective; a third polarization splitter element arranged to reflect a polarization state A of the display light; a matrix photodetector arranged in the focal plane of said objective adapted to detect said magnified image or said non-magnified image of the scene, the matrix photodetector and the display being located on either side of the third polarization splitter element.

[0014] Preferably, in this variant, an orientation of a slow axis of said half-wave distribution plate has a modifiable orientation relative to a plane of incidence of the second polarization splitter element and, optionally, the matrix photodetector is connected to a processor adapted to apply post-processing methods of said image of the scene.

[0015] Preferably, in this variant, the telescope comprises an electronically controllable liquid crystal cell adapted to introduce a phase delay varying from 0° to 180° modulo 360°, said liquid crystal cell being arranged on the optical path of the light coming from said scene, after the rectilinear polarizer and before the first polarization splitter element, said telescope comprising a switch connected to a voltage generator controlling said liquid crystal cell. Preferably, a direction of passage of the rectilinear polarizer is orthogonal to a plane of incidence of the first polarization splitter element, a slow axis of the liquid crystal cell being oriented at 45° modulo 90° of the plane of incidence of the first polarization splitter element.

[0016] Preferably, the telescope comprises a so-called upstream half-wave plate, upstream of the rectilinear polarizer adapted to have a slow axis parallel to the direction of passage of the rectilinear polarizer when the latter transmits a polarization state B and to have a slow axis having an orientation at 45° to the direction of passage of the rectilinear polarizer when the latter transmits a polarization state A.

[0017] Preferably, the afocal module and the video module are removable.

[0018] According to a first embodiment of the invention M1, the first and second subassemblies of the afocal optical system are adapted to form respectively a first and a second real intermediate image of the scene, and in which the first and second afocal delay plates are quarter-wave plates, the afocal system further comprising: a first mirror adapted to reflect the reflected light having passed through the first sub-assembly so as to return it to the first sub-assembly, a second mirror adapted to reflect the reflected light having passed through the second sub-assembly so as to return it to the second sub-assembly.

[0019] According to a second embodiment of the invention M2, the first subassembly of the afocal optical system is adapted to form a real intermediate image of the scene, and in which the first and second afocal delay plates are half-wave plates, the afocal system further comprising: a first reflective element adapted to reflect the reflected light having passed through the first sub-assembly so as to return it to the first sub-assembly, a second reflective element adapted to reflect the reflected light having passed through the second sub-assembly so as to return it to the second sub-assembly, the first and / or the second reflective element being adapted to carry out a vertical and horizontal inversion of a field of view of the reflected light.

[0020] According to a particular embodiment of the second embodiment M2, the first and second reflective elements are reflecting prisms, the first and second reflective elements being adapted to respectively achieve the vertical and horizontal inversion of the field of view of the reflected light or vice versa.

[0021] Alternatively, according to a particular embodiment of the second embodiment M2, the first reflective element is a cube corner adapted to achieve the vertical and horizontal inversion of the field of view of the reflected light and the second element is a mirror or in which the first reflective element is a mirror and the second element is a cube corner adapted to achieve the vertical and horizontal inversion of the field of view of the reflected light.

[0022] According to a third embodiment of the invention M3, the first sub-assembly of the afocal optical system does not form any real intermediate image of the scene, and in which the first and second afocal delay plates are quarter-wave plates, the first sub-assembly being formed by a concave mirror adapted to reflect the reflected light having passed through the first quarter-wave plate, the second sub-assembly being formed by a convex mirror adapted to reflect the reflected light having passed through the second quarter-wave plate.

[0023] According to a particular embodiment of the third embodiment M3, the afocal optical system further comprises an asymmetrical refractive component adapted to correct eccentricity aberrations introduced by the first polarization splitter element during passage by the reflected light. Brief description of the figures:

[0024] Other characteristics, details and advantages of the invention will emerge from reading the description given with reference to the appended drawings given by way of example and which represent, respectively: [ Fig. 1 ], a schematic view of an LT shooting scope according to the invention, [ Fig. 2A ] And [ Fig. 2B ], the optical path of light in the LT telescope when the polarizer lets through polarization A and polarization B respectively, [ Fig. 3A ], a preferred variant of the invention in which the LT bezel comprises the third removable module called video module 3, [ Fig. 3B ], the preferred variant of the invention in which the LT lens comprises the third removable module called video module 3, and in which the orientation of the polarizer POL1 is equal to i POL 1 = 45° and the orientation of the slow axis of the HP distribution blade is worth i l / 2 = 45°, [ Fig. 3C], the preferred variant of the invention in which the LT lens comprises the third removable module called video module 3, and in which the orientation of the polarizer POL1 is equal to i POL 1 = 45° and the orientation of the slow axis of the HP distribution blade is worth i l / 2 = 0°, [ Fig. 3D ], the preferred variant of the invention in which the LT lens comprises the third removable module called video module 3, and in which the orientation of the polarizer POL1 is equal to i POL 1 = 0° and the orientation of the slow axis of the HP distribution blade is worth i l / 2 = 0°, [ Fig. 4A ] And [ Fig. 4B ], a variant of the invention, in which the LT telescope comprises an electronically controllable liquid crystal cell Cell adapted to introduce a phase delay varying from 0° to 180° modulo 360°, [ Fig. 5A ], [ Fig. 5B ] And [ Fig. 5C], a schematic view of a first embodiment of the invention M1 in which the afocal optical system has dual field and pupil transport, [ Fig. 6A ] And [ Fig. 6B ], a schematic view of a second embodiment of the invention M2 in which the afocal optical system is of the double-crossing Kepler telescope type, [ Fig. 7A ] And [ Fig. 7B ], a schematic view of a third embodiment of the invention M3 in which the afocal optical system is of the double-crossing Galileo telescope type.

[0025] References to figures, when identical, correspond to the same elements.

[0026] In the figures, unless otherwise indicated, the elements are not to scale. Detailed description:

[0027] There figure 1represents a schematic view of a LT shooting scope according to the invention. This scope is used by a user U who observes a scene (not shown in the figure 1 ) located at infinity relative to the LT riflescope. This LT riflescope comprises a first optical subassembly 1, called the afocal module, and a second optical subassembly 2 called the display module.

[0028] By an inventive optical architecture of the display module 2 and the afocal module 1, the LT glasses of the invention advantageously exploit the polarization states of the light L in which comes from the observed scene in order to obtain a compact, modular and lightweight system making it possible to easily vary the magnification of the image returned to the user's eye U.

[0029] For this, the afocal module 1 comprises a removable and switchable rectilinear polarizer POL1, so as to transmit a first rectilinear polarization state of the light L in called state A or a second rectilinear polarization state of the light, called B, state B being orthogonal to state A. More precisely, the polarizer POL1 of the telescope according to the invention can take at least two different orientations θ POL1 separated by an angle of 90° in order to transmit a polarization A or B of the light L in . For a given luminance L 0 at the input of the afocal module, the polarizer POL1 transmits at the output a luminance L 0 *cos 2< (θ POL1 ) on the polarization A and a luminance L 0 *(1 - cos 2< (θ POL1 )) on the polarization B, for a rotation value θ POL1 (orientation) which is equal to 0° when the direction of passage of the polarizer is perpendicular to the xy plane. As a non-limiting example, in the figure 1, when the orientation of POL1 is 0° (modulo 180°), the direction of passage of the polarizer is perpendicular to the plane of incidence (xy plane) and POL1 transmits an A polarization. When the orientation of POL1 is 90° (modulo 180°), the direction of passage of the polarizer is parallel to the xy plane and POL1 transmits a B polarization. In the rest of the description, the orientation of the delay plates and the polarizers will be given with the same reference, that is to say that they will have a zero rotation angle when their direction of passage or the direction of the slow axis is orthogonal to the xy plane.

[0030] According to a particular embodiment, the polarizer POL1 is adapted to transmit a rectilinear polarization state of the light L in TE or TM. In the remainder of the description, for the sake of brevity, only the general case of polarizations A or B will be mentioned, but it is understood that the invention can be implemented with any orthogonal rectilinear polarizations.

[0031] The afocal module further comprises a first polarization splitter element LS1 arranged to reflect a polarization state A of the light transmitted by the linear polarizer POL1 (and therefore reflect the polarization A). This element LS1 can be a polarization splitter cube or a polarization splitter plate.

[0032] Furthermore, the afocal module comprises an afocal optical system arranged to collect light reflected L r by the first polarization splitter element LS1 (polarized A). The afocal system comprises a first SAG1 and a second SAG2 catadioptric subassemblies located on either side of the first polarization splitter element LS1 and a first and a second so-called afocal delay plates LR 1 , LR 2 arranged on the path of the reflected light Lr, on either side of the first polarization splitter element LS1. These afocal plates LR 1 , LR 2 are respectively arranged between the first polarization splitter element (LS1) and the first subassembly and between the first polarization splitter element (LS1) and the second subassembly.

[0033] The afocal plates LR 1 , LR 2 are conventional delay plates, for example birefringent plates. Depending on the embodiment of the invention, these plates LR 1 , LR 2 are quarter-wave plates (first and third embodiments, see below) or half-wave plates (second embodiment, see below).

[0034] The afocal optical system is adapted to form an image of the scene with an orientation identical to an orientation of the scene observed with the LT telescope, with a magnification greater than 1. This image is called a magnified image. Preferably, the magnification is greater than 3, or even 5. figures 5A to 7B present three embodiments of the invention each comprising a different afocal optical system with distinct advantages.

[0035] Thanks to the arrangement of the blades LR 1 , LR 2 , the collimated light coming from the second sub-assembly SAG2, called AG light (noted L AG in figure 1) has an A polarization after passing through the plate LR 1 . This AG light carries the magnified image of the scene (with a "straight" orientation). The first polarization splitter element LS1 is arranged to reflect the AG light, so that the line of sight of the AG light is collinear with a path of the light transmitted by the first polarization splitter element, called direct light L TM . This L TM light carries the field of view of the scene coming from infinity, not magnified by the afocal optical system. Thus, the judicious use of the polarization state of the light makes it possible to obtain a compact afocal module forming the magnified image of the scene - when the polarizer POL1 lets the A polarization pass - and letting the direct light with a B polarization pass when the polarizer POL1 lets the B polarization pass.

[0036] By way of non-limiting illustration, in the figure 1, when the orientation of the polarizer makes an angle of 90° modulo 180° relative to the vertical (at the yz plane on the figure 1 ), it transmits a B polarization and the telescope provides a non-magnified image (clear viewfinder configuration). Conversely, when the orientation of the polarizer makes an angle of 0° modulo 180° relative to the vertical, it transmits an A polarization and the telescope provides a magnified image (monocular viewfinder configuration).

[0037] The LT telescope further comprises a display module 2 for superimposing an image of the scene with visual information. This display module 2 comprises a display EA adapted to emit radiation called display light L EA. The display EA makes it possible to display an image, for example a symbol such as a red dot, text or even a reticle to be combined with the magnified image or the non-magnified field of view in order to facilitate the user's aiming or to provide him with information. The light from the display can be unpolarized or directly polarized A or it can be polarized A by a rectilinear polarizer placed in the path of the display light if this light is not polarized.

[0038] The display module 2 comprises an optical objective Obj adapted to collimate said display light, called collimated display light L EA,O , and thus form the image of the display returned to infinity. In addition, the display module 2 comprises a second polarization splitter element LS2 arranged after the half-wave distribution plate HP on the optical path. This element LS2 is adapted to transmit a polarization state B, direct light or light AG, by spatially combining it with the collimated display light L EA,O forming a light called optical direct path VDO.

[0039] To achieve the combination of the afocal module and the display module, the display module comprises a half-wave plate called HP distribution plate arranged on the path of the AG light and the direct light, after the first polarization splitter element LS1. The orientation of the slow axis of this HP half-wave plate is adapted so that the AG light or the direct light has a non-zero polarization component B after passing through the HP plate so that it is transmitted by LS2. As a non-limiting example, the slow axis of the HP plate makes an angle of 22.5° modulo 45° relative to the vertical so that the polarization of the AG light is rectilinear with an angle of -45° modulo 45° relative to the vertical after passing through the HP plate.

[0040] The combination of the afocal module and the display module therefore makes it possible to obtain a telescope that can switch from a clear viewfinder configuration (non-magnified field of view) to a monocular viewfinder (magnified image) and vice versa by simply controlling the orientation of the POL1 polarizer, this orientation being able to be easily modified by the user, for example using a simple actuator (such as a wheel or a vernier) located on the telescope (see below).

[0041] Depending on the orientation of the polarizer POL1, the user U therefore perceives at the output of the LT telescope in the direct VDO channel a magnified or non-magnified image (formed by direct light) spatially superimposed (“augmented”) with the image of the display. The telescope of the invention therefore has a compact and modular architecture which can be easily combined with another so-called video module, making it possible to detect the magnified or non-magnified image in order to carry out image processing with shape recognition algorithms, target tracking, etc. (see figure 3A ). To facilitate understanding, the light flux from the scene and transmitted by the afocal system (L TM ) is called the unmagnified image (G=1), although the afocal system does not "form" this image.

[0042] In prior art glasses, the addition of an afocal subassembly makes it possible to apply a magnification G > 1 on the direct optical path, within the limit set by the laws of conservation of geometric extent: if the field on the eye side is extended by a factor G, then the dimension of the exit pupil of the afocal will be reduced to a minimum by a factor G as well. This results in a smaller exit pupil when G > 1, and often an obligation for the user to rigorously position his eye in the plane of this exit pupil, with good alignment, otherwise his field of view will be reduced due to vignetting.

[0043] THE figure 2A And 2B illustrate the optical path of light in the telescope when the polarizer lets polarization A and polarization B pass respectively.

[0044] In the figure 2A , the polarizer POL1 has an orientation i POL 1= 0° ( module 180°). It therefore allows an A polarization of the scene light to pass through. The afocal module therefore forms a magnified image of the scene. The HP half-wave plate has an orientation adapted so that the AG light passing through it has a non-zero B polarization state. As a non-limiting example, the HP plate has an orientation i l / 2 = 22.5° so that the polarization of the AG light is rectilinear with an angle of -45° modulo 45° relative to the vertical after crossing the HP plate. Half of the luminous flux of the AG light is therefore transmitted by the LS2 element in the VDO optical path. The VDO path perceived by the user is therefore the spatial superposition of the magnified image of the scene and the display image.

[0045] In the figure 2B , the polarizer POL1 has an orientation i POL 1 = 90° ( module180°). It therefore allows a polarization B of the scene light to pass through. The afocal module therefore transmits the direct light L TM . The HP half-wave plate has an orientation adapted so that the direct light passing through it has a non-zero polarization state B. As a non-limiting example, the HP plate has an orientation i l / 2 = 22.5° so that the polarization of the direct light is rectilinear with an angle of 45° modulo 45° relative to the vertical after passing through the HP plate. Half of the luminous flux of the direct light is therefore transmitted by the LS2 element into the VDO optical path. The VDO light perceived by the user is therefore the spatial superposition of the unmagnified field of view of the scene and the display image.

[0046] Preferably, the HP blade has an orientation that can be modified and controlled by the user using a wheel, for example, in order to be able to control the ratio of the light intensity of L TM and L AG transmitted relative to the intensity of the collimated display light L EA,O, by the LS2 element.

[0047] According to a particular embodiment, the first polarization splitter element LS1 is adapted to reflect a polarization state A equal to TE and to transmit a polarization state B equal to TM. This mode is preferred because thus the polarizer POL1 partially or totally eliminates the propagation of possible natural vitreous reflections (reflections on vehicle windshields, on bodies of water, etc.) through the shooting scope for the non-magnified image. Indeed, the vitreous reflections are generally partially or totally polarized TE for incidences in the vicinity of the Brewster incidence (incidence of 56.3° for a refractive index equal to 1.5). Preferably, in this embodiment, the scope comprises a so-called upstream half-wave plate, upstream of the rectilinear polarizer POL1. This upstream plate has a modifiable orientation.It is adapted to present a slow axis parallel to the direction of passage of the rectilinear polarizer POL1 when the latter transmits a TM polarization state and to present a slow axis having an orientation at 45° to the direction of passage of the rectilinear polarizer POL1 when the latter transmits a TE polarization state. This upstream plate thus makes it possible to eliminate vitreous reflections for the magnified image.

[0048] According to one embodiment, a third polarization splitter element LS3 is added (as illustrated in figure 1 ), optional and arranged to reflect a polarization state A of the display light towards the objective Obj. This LS3 element allows to have a folded display light path, thus giving a more compact telescope.

[0049] The polarizer POL1 is a conventional polarizer chosen from a dichroic polarizer, a grid polarizer, a Brewster incidence polarizer, a thin film polarizer or any other polarizer known to those skilled in the art.

[0050] There figure 3Aillustrates a preferred variant of the invention in which the telescope LT comprises the third removable module called video module 3. This module comprises a quarter-wave plate called imaging QP, and a mirror M. These elements are arranged to transform a polarization state A of the light AG L AG and the direct light L TM reflected by the second polarization splitter element LS2 into a polarization state B, forming a light called imaging L im . In order to make the telescope more compact and to limit the number of optical components, the mirror M is arranged so that the imaging light passes through the objective Obj in the opposite direction to the path of the light L EA . The objective thus forms the magnified image or an image of the scene from the direct light called the unmagnified image, in the image focal plane of the objective.

[0051] In order to detect this magnified or non-magnified image of the scene, the video module comprises a matrix photodetector C (or sensor) arranged in the focal plane of the lens. To spatially separate the position of the detector C and the display EA, which are both placed in a focal plane of the lens, the video module comprises a third polarization splitter element LS3 arranged to reflect a polarization state A of the display light. The matrix photodetector and the display are located on either side of the third polarization splitter element LS3.

[0052] Preferably, the HP blade has a modifiable orientation in order to be able to control the luminous intensity of the light AG L AG or direct L TM transmitted by the second splitter element LS2 relative to the intensity of the collimated display light L EA,O, reflected by the second splitter element LS2. Thus, the orientation of the HP blade makes it possible to adjust the relative luminance level of the light AG or direct relative to that of the display to return a brighter image to the user in conditions of low illumination of the scene for example.

[0053] In addition, the orientation of the HP blade makes it possible to control the ratio R of the light intensity of the light AG L AG or direct L TM transmitted by the second separating element LS2 towards the user compared to the intensity returned to the sensor C. This has the effect of modulating the quantity of light in the direct optical channel VDO or towards the video recording channel, whether for the non-magnified or magnified image. Indeed, for a given luminance L 1, at the output of the afocal module, the HP half-wave plate transmits a luminance L 1 *cos 2< (2*θ λ / 2 ) of the non-magnified or magnified image towards the user and transmits a luminance L 1 *(1 - cos 2< (2*θ λ / 2 )) towards the video recording channel. For reference, the angle θ λ / 2 is equal to 0° when the slow axis of the half-wave plate is orthogonal to the xy plane. The ratio R is therefore R= cos 2< (2*θ λ / 2 ) / (1 - cos 2< (2*θ λ / 2 )).

[0054] By way of non-limiting example, in the figure 3A, the slow axis of the HP blade makes an angle of θ λ / 2 =22.5° modulo 45° so that the ratio R is 1, when the polarizer transmits an A or B polarization.

[0055] Thanks to the video module of the glasses of the figure 3A , it is possible to record images or videos of the scene via video which can then be used for shape recognition, target tracking, or simply image capture for operational debriefing while simultaneously observing an image of the scene via the direct optical channel (VDO).

[0056] As mentioned above, it is the orientation of the polarizer POL1 that determines whether the sensor C detects the magnified image or the unmagnified image. Thus, the same unmagnified image is returned to the direct optical channel and the video channel when the orientation of the polarizer POL1 makes an angle of 90° modulo 180° with respect to the vertical (i.e. i POL1 = 90° modulo 180°) and when the slow axis of the HP blade has an orientation i l / 2 = 22.5° for example (as in figure 2B ). Alternatively, the same magnified image is returned to the direct optical channel and the video channel when the orientation of the polarizer POL1 makes an angle of 0° modulo 180° relative to the vertical (i.e. i POL 1 = 0° modulo 180°) and when the slow axis of the HP blade has an orientation i l / 2 = 22.5° for example (as in figure 2A ). This operating mode allows images and videos to be recorded simultaneously while the user is viewing.

[0057] Alternatively, it is possible to return the entire non-magnified image to the C sensor and, at the same time, return the entire magnified image to the direct optical VDO channel. This allows the user to have very good visual pointing accuracy in the direct optical VDO channel thanks to a narrow field of view, and to apply target tracking algorithms over a wide field on the video channel. Thus, if the target leaves the narrow field of view in the direct optical channel, it can continue to be tracked in the video channel and the target tracking information is then displayed by augmented reality via the AF display. As a non-limiting example illustrated in figure 3B , this is possible when the orientation of the polarizer POL1 is equal to i POL 1 = 45° modulo 90° and when the orientation of the slow axis of the HP distribution blade is worth i l / 2 = 45° modulo 45°.

[0058] It is also possible to return the unmagnified image in its entirety to the sensor C and, at the same time, return the magnified image in its entirety to the direct optical path VDO by a different arrangement. Thus, according to another embodiment, the rectilinear polarizer POL1 has been removed from the telescope, so that the afocal optical system transmits both direct light and AG light. and the half-wave distribution plate has a slow axis oriented i l / 2 = 45° modulo 90° so that the direct light is totally reflected towards the sensor C and the AG light is totally transmitted by the second polarization splitter element.

[0059] Moreover, in the bezel of the figure 3A, it is possible to return the non-magnified image in its entirety to the eye and, at the same time, return the magnified image in its entirety to the video channel, for example to increase the precision of the recognition or detection algorithms on the video image recorded by the sensor C. As a non-limiting example illustrated in figure 3C , this is possible when the orientation of the polarizer POL1 is equal to i POL 1 = 45° modulo 180° and when the orientation of the slow axis of the distribution blade is worth i l / 2 = 0° modulo 45°.

[0060] In one embodiment of the bezel of the figure 3A , illustrated in 3D figure, the matrix photodetector C is connected to the display and to a processor) adapted to apply post-processing methods of the image of the scene detected in video channel. This embodiment is of interest with a magnified image. More precisely, in this embodiment, the display forms a virtual image of the magnified scene detected by the photodetector which will be transmitted to the user U. This image is enriched or processed by algorithms in order to transmit more information to the user than the “naked” magnified image. This operating mode is a “virtual reality” mode. In this operating mode, the orientation of the HP distribution blade is adapted so that 100% of the light intensity of the light L AG is returned to the sensor C, i.e. reflected by the second polarization splitter element LS2.No direct light L TM reaches the user, the only image visible to the user is the virtual image of the display EA. For 100% of the light intensity of the light L AG to be returned to the sensor C and 0% of the light intensity of the light L TM to reach the user, the orientation of the polarizer POL1 must be identical to that of the slow axis of the distribution plate HP and . i POL 1 = θ l / 2 = O ° modulo 180°. In this embodiment, the exit pupil will maintain a constant and maximum diameter regardless of the magnification applied: this diameter is that of the exit pupil of the objective Obj. The eye pull of the LT telescope is therefore not modified when changing magnification and remains significant regardless of the magnification chosen (G=1 or G>1).

[0061] THE figures 4A and 4Billustrate a variant of the invention, in which the telescope LT comprises an electronically controllable liquid crystal cell Cell adapted to introduce a phase delay varying from 0° to 180° modulo 360°. This liquid crystal cell is arranged on the optical path of the light L in coming from the scene, after the rectilinear polarizer POL1 and before the first polarization splitter element. In addition, the telescope comprises a switch connected to a voltage generator controlling the liquid crystal cell. Thus, the change in magnification is operated electronically by the user, by a remote switch rather than manually by rotating the input polarizer as mentioned previously.

[0062] In the figure 4A, no voltage supplies the cell Cell which is subjected to a zero electric field E and the liquid crystals have their molecules oriented parallel to the faces of the cell, presenting a birefringence such that for a cell of given thickness e, the cell introduces a phase shift equal to π + 2kπ (k integer) along the optical axis of the viewfinder. The liquid crystal cell then behaves like a half-wave plate which transmits a polarization state orthogonal to the incident state. That is to say that the direction of passage of the polarizer POL1 is orthogonal to a plane of incidence of the first polarization splitter element ( i POL 1 = 0°) and that a slow axis of the liquid crystal cell is oriented at 45° modulo 90° of the plane of incidence of the first polarization separating element ( θ Cell = 45° modulo 90°). The afocal module transmits the light coming from the scene, to simplify it is considered that it then “forms” an unmagnified image of the scene.

[0063] In the figure 4B , the switch is actuated and the cell Cell is supplied with a voltage and is subjected to an electric field E such that the liquid crystals are oriented so as to cancel their birefringence along the optical axis of the LT telescope. The polarization state transmitted by the cell is therefore unchanged, the afocal module then forms a magnified image of the scene. and the magnified image is returned to the user's eye and / or to the video recording channel.

[0064] It is of course possible to reverse the direction of operation of the cell, so that the cell does not modify the polarization of the light in zero E field and behaves like a half-wave plate which transmits a polarization state orthogonal to the incident state in the presence of a particular E field. However, the operating mode illustrated in the figure 4Ais preferred because, in the event of a voltage generator malfunction, the unmagnified image is seen by the user. This is a more versatile operating mode and therefore the preferred default mode.

[0065] THE figure 5A , 5B And 5C schematically illustrate a first embodiment of the invention M1 in which the afocal optical system has dual field and pupil transport. More precisely, the figure 5A represents the ray tracing when the afocal module forms a magnified image. The figure 5B represents the states of polarization and the direction of propagation of light rays when the telescope forms a magnified image. The figure 5C represents the polarization states and the direction of propagation of light rays when the telescope forms an unmagnified image. The previously detailed components will not be described again for the sake of brevity.

[0066] In the first embodiment M1, the first and second subassemblies SAG1, SAG2 of the afocal optical system are adapted to form respectively a first and a second real intermediate image I 1 , I 2 of the scene. In addition, the first and second afocal delay plates LR1, LR2 are quarter-wave plates. The afocal system further comprises a first mirror M R1 adapted to reflect the reflected light Lr having passed through the first subassembly so as to return it to the first subassembly and a second mirror M R2 adapted to reflect the reflected light Lr having passed through the second subassembly so as to return it to the second subassembly. By way of non-limiting example, in the first embodiment, the mirrors M R1 and M R2 are configured not to modify the polarization of the light.Otherwise, the thin-film treatments on the catadioptric elements of the telescope as well as the phase delays and orientations of the delay blade elements will be optimized so as to maximize the overall optical transmission on the different imaging channels.

[0067] The light L in first passes through the polarizer POL1 which transmits only the rectilinear polarization state along the polarizer passage axis. The user can freely modify the orientation of the polarizer passage axis. In the case of the figure 5B , i POL 1 = 0° and polarization A is transmitted while in the figure 5C , i POL 1 = 90° and polarization B is transmitted. In the figure 5B, the polarization state B is reflected by the first polarization splitter element then passes through the LR1 delay plate (quarter-wave plate), which transforms it into right circular polarization. The light then passes through the SAG1 sub-assembly for the first time, which does not affect the polarization states, then is reflected on the MR1 mirror, which transforms the polarization state into left circular by reversing the direction of propagation of the light, then passes through the SAG1 sub-assembly again, then the LR1 plate, to finally emerge polarized B. The first image of the intermediate field I1 is formed when passing through this first optical block.

[0068] The B-polarized light passes through the first polarization splitter element LS1 and transforms into left circular polarization after passing through the phase-delay plate LR2 (a quarter-wave plate here). This light is reflected on the mirror MR3, then passes through the sub-assembly SAG2 for the first time, which does not affect the polarization states, then is reflected on the mirror MR2, which transforms the polarization state into right circular by reversing the direction of propagation of the light, then passes through the sub-assembly SAG2 again, then the plate LR2, to finally emerge polarized A. The second image of the intermediate field I2 is formed when passing through this second optical block, allowing the image of the scene formed by the afocal module to be straightened. The mirror MR3 is optional and allows the optical path to be bent in order to make the afocal module more compact.

[0069] In the embodiment where the reflective treatment of the mirror MR3 phase-shifts the A-polarized light relative to the B-polarized light, it is preferable to position the quarter-wave plate LR2 between this mirror MR3 and the second sub-assembly SAG2, so that this mirror is intercepted only by A or B waves, and not by circular polarizations, which will make it possible not to affect the polarization states during reflection on its surface.

[0070] Preferably, the first subassembly SAG1 is designed such that the crossing of the first element LS1 is done at low numerical aperture in order to minimize the eccentricity aberrations introduced by LS1. Typically, this numerical aperture is preferably less than 0.10.

[0071] The rest of the device works as previously mentioned. As a non-limiting example, in the figure 5B And 5C, the orientation of the slow axis of the quarter-wave plates LR1, LR2 is i LR 1, LR 2 = 45° so that the polarization of the reflected light changes from A to B or from B to A before passing through the LS1 element again. In addition, the HP half-wave plate is rotated by an angle i l / 2 =22.5°, and the transmitted polarization is rectilinear oriented at 45°. Thus, when the direct light or AG intercepts the second element LS2, half of the polarized luminous flux B is transmitted towards the user's eye and the other polarized half B is returned to the video channel (ratio R=1). Thus, in the figure 5B , 50% of the AG light intensity is returned to the video channel and 50% is transmitted into the direct optical channel VDO. In the figure 5C, 50% of the direct light is returned to the video channel and 50% is transmitted into the direct optical channel VDO. The first embodiment M1 has a simple and robust architecture allowing the image of the scene formed by the afocal module to be rectified. However, having to reform a double image of the field and the pupil requires the use of numerous optical components to achieve good correction of aberrations, and can be a disadvantage in the case where one wishes to reduce the mass and size of this afocal subassembly.

[0072] THE figure 6A And 6B schematically illustrate a second embodiment of the invention M2 in which the afocal optical system is of the double-crossing Kepler telescope type. More precisely, the figure 6A represents the ray tracing within the telescope when the afocal module forms a magnified image. The figure 6Brepresents the polarization states and the direction of propagation of the light rays when the telescope forms a magnified image. The operating principle being similar to that of the M1 mode afocal, only the modifications made by the M2 mode afocal with respect to the M1 mode afocal will therefore be described below.

[0073] In the M2 mode, the first sub-assembly SAG1 of the afocal optical system is adapted to form a real intermediate image I 1 of the scene, this image being formed in any plane. In the M2 mode, the first and second afocal delay plates LR1, LR2 are half-wave plates. The afocal optical system further comprises a first reflective element P R1 adapted to reflect the reflected light Lr having passed through the first sub-assembly SAG1, so as to return it to the first sub-assembly. In addition, a second reflective element P R2 is adapted to reflect the reflected light Lr having passed through the second sub-assembly SAG2 so as to return it to the second sub-assembly. The first and / or the second reflective element P R1, P R2 are adapted to perform a vertical and horizontal inversion of a field of view of the reflected light so that the afocal optical system forms a rectified magnified image of the scene.For this purpose, the first and second reflective elements are reflecting prisms as illustrated in the . figure 6A And 6B . One of the prisms P R1 , P R2 must perform an image inversion (up / down) by folding in the horizontal xy plane, the other prism must perform a reversion (left / right) by folding in the vertical yz plane. However, for the sake of simplification, the folds performed by these two prisms have both been represented in the horizontal xy plane. The up / down image rectification can be performed by the prism P R1 or the prism P a2 and vice versa for the left / right image rectification.

[0074] Alternatively, the first reflective element P R1 is a cube corner adapted to achieve vertical and horizontal inversion of the field of view of the reflected light and the second reflective element P R2 is a mirror. The opposite is of course possible, that is, the first reflective element is a mirror and the second element is a cube corner adapted to achieve vertical and horizontal inversion of the field of view of the reflected light.

[0075] The rest of the device works as previously mentioned.

[0076] By way of non-limiting example, in the figure 6B , the half-wave blades have a slow axis oriented at an angle i l / 2 =22.5° so that the light having re-crossed SAG1 and intercepting LS2 is polarized B and the light having re-crossed SAG2 and intercepting LS2 is polarized A. In addition, the polarizer POL1 has an orientation i POL1 = 0° and HP half-wave plate is rotated by an angle i l / 2 =22.5°, and the transmitted polarization is rectilinear oriented at 45°. Thus, when the light AG intercepts the second element LS2, half of the polarized luminous flux B is transmitted towards the user's eye and the other polarized half B is returned to the video channel (ratio R=1).

[0077] This M2 mode architecture has the advantage of reforming only one intermediate image of the field, which makes the correction of aberrations easier than in the M1 embodiment and the disadvantage of being dependent on the phase shifts introduced by the reflections on the faces of the elements Pr1, Pr2 and MR3 which can result in a loss of optical transmission through the complete afocal system. But this disadvantage can be minimized by optimizing the phase delays introduced during these reflections as well as those of the LR1 and LR2 delay plates.

[0078] THE figure 7A And 7B schematically illustrate a third embodiment of the invention M3 in which the afocal optical system is of the double-crossing Galileo telescope type. More precisely, the figure 7A represents the ray tracing within the telescope when the afocal module forms a magnified image. The figure 7B represents the polarization states and the direction of propagation of the light rays when the telescope forms a magnified image returned at 100% to the video channel. The operating principle being similar to that of the afocal of the M1 and M2 mode, only the modifications made by the afocal of the M3 mode with respect to the afocal of the M1 and M2 mode will therefore be described below. Unlike the optical architecture of the M2 mode, the Galilean telescope does not reform a real image of the field; it is therefore not necessary to carry out image rectification.

[0079] This telescope has the advantage of being very compact, but the disadvantage of having a virtual exit pupil which results in a greatly reduced field of view in direct optical VDO for the magnified image, including for small eye pulls. The eye pull and the field of view in direct optical VDO are however not affected for direct light and the non-magnified image, since the optical path in this case does not pass through the Galilean telescope.

[0080] In embodiment M3, the afocal optical system does not form any real intermediate image of the scene and the first and second afocal delay plates LR1, LR2 are quarter-wave plates (see figure 5Bfor a description of the polarization states within the telescope). In this M3 mode, the first sub-assembly is formed by a concave mirror MC1 adapted to reflect the reflected light Lr having passed through the first quarter-wave plate and the second sub-assembly is formed by a convex mirror MC2 adapted to reflect the reflected light Lr having passed through the second quarter-wave plate.

[0081] The first element LS1 is crossed by the light reflected by the concave mirror MC1 in a convergent beam which introduces strong eccentricity aberrations on the field imaging. Preferably, these eccentricity aberrations are compensated by introducing an asymmetrical element for example an asymmetrical refractive component Cor, without adding eccentricity chromatism or angular deviation on the field imaging.

[0082] According to one embodiment, the aiming axis of the telescope when the afocal module forms a magnified image can be adjusted by decentering the mirrors MC1 or MC2 or by adjusting the rotation angle of the Cor component in the horizontal xy or vertical yz plane.

[0083] According to one embodiment, the concave mirror MC1 can be replaced by a Mangin mirror to compensate for the residual spherical aberration.

[0084] Preferably, the LT scope of the M3 mode solves the problem of the greatly reduced field of observation in the direct optical VDO channel for the magnified image, by returning all of the light passing through the afocal module to the video imaging channel (virtual reality mode previously mentioned). Thus, the display connected to the sensor C returns this image in the form of virtual reality to the user's eye. This operating mode is illustrated in figure 7B. As a non-limiting example, this mode of operation is possible when the orientation of the polarizer POL1 is identical to that of the slow axis of the HP distribution blade and i POL 1 = θ l / 2 = O °. This M3 mode architecture has the advantage of being more compact, lighter and of better optical quality than the M1 and M2 modes. It has the disadvantage of being poorly suited to direct viewing of the magnified image because the exit pupil of the afocal subassembly is virtual. It is then preferable to use a "virtual reality" mode to view the magnified image on the direct path, which allows on the one hand to have a large exit pupil and a large eye pull, and to be able to adjust the brightness of the display according to external conditions. However, this mode brings an additional power consumption by the simultaneous use of the camera and the display.

Claims

1. A scope (LT) observing a scene, said scope comprising a first optical subset (1), called afocal module, and a second optical subset (2), called display module, said afocal module (1) comprising: - a removable and switchable linear polariser (POL1) so as to transmit at least a first linear polarisation state of light (Lin) coming from said scene, called state A, or a second linear polarisation state of said light, called B, said state B being orthogonal to said state A; - a first polarisation-splitting element (LS1) arranged to reflect a polarisation state A of light transmitted by said linear polariser; - an afocal optical system arranged to collect light (Lr) reflected by said first polarisation-splitting element, said afocal optical system comprising: ∘ a first (SAG1) and a second (SAG2) catadioptric subset, located on either side of the first polarisation-splitting element, ∘ first and second retardation plates (LR1, LR2) that are called afocal and that are arranged on the path of the reflected light (Lr), on either side of the first polarisation-splitting element (LS1), respectively disposed between the first polarisation-splitting element (LS1) and the first subset (SAG1) and between the first polarisation-splitting element (LS1) and the second subset (SAG2), said afocal optical system being adapted to form an image of the scene with an orientation identical to an orientation of the scene observed by said scope, with a magnification greater than 1, which is called the magnified image, the first polarisation-splitting element (LS1) further being arranged to reflect light emanating from the second subset (SAG2), which is called AG light (LAG), with a polarisation state A, transporting said magnified image such that the axis of sight of the AG light is collinear with a path of light transmitted by the first polarisation-splitting element, which is called direct light (LTM), with a polarisation state B; said display module comprising: - a half-wave plate, called distribution half-wave plate (HP), that is arranged on the path of the AG light and direct light, after the first polarisation-splitting element; - a display (EA) adapted to form a display image by emitting radiation called display light (LEA); - an optical objective (Obj) adapted to collimate said display light; - a second polarisation-splitting element (LS2) arranged, after the distribution half-wave plate, to transmit a polarisation state B, of the direct light or of the AG light, by spatially combining it with the collimated display light (LEA,O), so that said scope superposes said unmagnified image or said direct light with said display image.

2. The scope according to claim 1, further comprising a third module, called the video module (3), comprising: - a quarter-wave plate, called imaging quarter-wave plate (QP), and a mirror (M) that are adapted to convert a polarisation state A of the AG light and direct light reflected by the second polarisation-splitting element into a polarisation state B, forming a light called imaging light (Lim), the mirror being further arranged so that said imaging light passes through said objective in order to form said magnified image or an image of the scene emanating from direct light, which is called the unmagnified image, in an image focal plane of said objective; - a third polarisation-splitting element (LS3) arranged to reflect a polarisation state A of the display light; - a matrix-array photodetector (C) arranged in the focal plane of said objective and adapted to detect said magnified image or said unmagnified image of the scene, the matrix-array photodetector and the display being located on either side of the third polarisation-splitting element.

3. The scope according to the preceding claim, wherein an orientation of a slow axis of said distribution half-wave plate (HP) has an orientation that is modifiable with respect to a plane of incidence of the second polarisation-splitting element (LS2).

4. The scope according to the preceding claim, wherein the matrix-array photodetector is connected to a processor adapted to apply post-processing methods to said image of the scene.

5. The scope according to any one of the preceding claims, comprising an electronically controllable liquid-crystal cell (Cell) adapted to introduce a phase delay ranging from 0° to 180° modulo 360°, said liquid-crystal cell being arranged on the optical path of the light (Lin) coming from said scene, after the linear polariser (POL1) and before the first polarisation-splitting element, said scope comprising a switch connected to a voltage generator controlling said liquid-crystal cell.

6. The scope according to the preceding claim, wherein a passing direction of the linear polariser is orthogonal to a plane of incidence of the first polarisation-splitting element, a slow axis of the liquid-crystal cell being oriented at 45° modulo 90° to the plane of incidence of the first polarisation-splitting element.

7. The scope according to any one of the preceding claims, comprising a half-wave plate, called upstream plate, that is located upstream of the linear polariser (POL1) adapted to have a slow axis parallel to the passing direction of the linear polariser (POL1) when the latter transmits a polarisation state B and to have a slow axis having an orientation of 45° to the passing direction of the linear polariser (POL1) when the latter transmits a polarisation state A.

8. The scope according to any one of claims 2 to 7, wherein the afocal module and the video module are removable.

9. The scope according to any one of the preceding claims, wherein the first and second subsets (SAG1, SAG2) of the afocal optical system are adapted to form a first and a second real intermediate image (I1, I2) of the scene, respectively, and wherein the first and second afocal retardation plates are quarter-wave plates, the afocal system further comprising: - a first mirror (MR1) adapted to reflect the reflected light (Lr) having passed through the first subset so as to send it back to the first subset, - a second mirror (MR2) adapted to reflect the reflected light (Lr) having passed through the second subset so as to send it back to the second subset.

10. The scope according to any one of claims 1 to 8, wherein the first subset (SAG1) of the afocal optical system is adapted to form a real intermediate image (I1) of the scene, and wherein the first and second afocal retardation plates are half-wave plates, the afocal system further comprising: - a first reflective element (PR1) adapted to reflect the reflected light (Lr) having passed through the first subset so as to send it back to the first subset, - a second reflective element (PR2) adapted to reflect the reflected light (Lr) having passed through the second subset so as to send it back to the second subset, the first and / or second reflective element (PR1, PR2) being adapted to perform a vertical and horizontal inversion of a field of view of the reflected light.

11. The scope according to the preceding claim, wherein the first and second reflective elements are deflecting prisms, the first and second reflective elements (PR1, PR2) being adapted to perform the vertical and horizontal inversion of the field of view of the reflected light or vice versa, respectively.

12. The scope according to claim 10, wherein the first reflective element is a corner retroreflector adapted to perform the vertical and horizontal inversion of the field of view of the reflected light and the second element is a mirror or wherein the first reflective element is a mirror and the second element is a corner retroreflector adapted to perform the vertical and horizontal inversion of the field of view of the reflected light.

13. The scope according to any one of claims 1 to 8, wherein the first subset (SAG1) of the afocal optical system does not form any real intermediate image of the scene, and wherein the first and second afocal retardation plates are quarter-wave plates, the first subset being formed by a concave mirror (MC1) adapted to reflect the reflected light (Lr) having passed through the first quarter-wave plate, the second subset being formed by a convex mirror (MC2) adapted to reflect the reflected light (Lr) having passed through the second quarter-wave plate.

14. The scope according to the preceding claim, wherein the afocal optical system further comprises an asymmetric refractive component adapted to correct eccentricity aberrations introduced by the first polarisation-splitting element as reflected light passes therethrough.