Optical system for acquiring images of a scene

Abstract

The present invention relates to an optical system (10) for acquiring images of a scene, comprising: - a first optical channel (12) for providing a first optical flow originating from the scene viewed from a first field of view, - a second optical channel (14) for providing a second optical flow originating from the scene viewed from a second field of view having a smaller dimension than the first field of view, - a polarising splitter (16) for recombining a portion of the first optical flow according to a first polarisation state with a portion of the second optical flow according to a second polarisation state in order to form a recombined optical flow, - a sensor (18) for capturing the recombined optical flow, and - an array of polarisers (20) positioned in the plane of the sensor (18).

Description

[0001] DESCRIPTION

[0002] TITLE: Optical system for acquiring images of a scene

[0003] The present invention relates to an optical system for acquiring images of a scene.

[0004] The field of the invention is that of image capture systems which offer the possibility of adjusting characteristics of the field covered by a sensor.

[0005] Such systems generally consist of a sensor, a camera lens that forms an image on that sensor, and one or more independent devices or devices integrated into the lens that allow the size and / or direction of the field covered by the sensor to be changed.

[0006] For example, optical zoom systems, as well as multifocal systems, or systems incorporating anamorphic lenses, are commonly used to vary the field of view on a camera system. We will not discuss digital zooms here, as this involves post-processing, performed "a posteriori," and therefore falls outside the scope of this invention because it is not integrated into the camera system.

[0007] In the case of optical zooms, the zoom function is achieved by continuously moving several optical sub-assemblies, typically two or more, to change the focal length of a lens while maintaining sharp focus on its associated sensor. In contrast, a bifocal system allows for capturing only two different fields of view—referred to as the "narrow field" and "wide field"—by inserting a sub-assembly into the lens's optical path that enables focal length adjustment.

[0008] Mechanically compensated zoom lenses offer the advantage of continuously adjusting the size of the framed area, unlike multifocal systems. However, when these two types of optical systems are combined with a single sensor, it is usually not possible to capture two distinct fields of view simultaneously.

[0009] In particular, to simultaneously image two distinct fields of vision, it is known from the state of the art:

[0010] One option is to use two separate sensors to simultaneously capture the two distinct fields, or to reimage these two fields side-by-side on a single sensor. However, this presents problems related to size, "dead zones" between the images of the two fields on this sensor which prevent the full use of the sensor's surface, or partial overlap (crosstalk) of one image onto the other.

[0011] The aim of the invention is therefore to propose an optical image capture system that allows two distinct fields of vision of a scene to be imaged simultaneously on the same sensor, overcoming the problems of bulk and overlap of the images of the two fields on the sensor.

[0012] To this end, the invention relates to an optical system for acquiring images of a scene, the optical system comprising:

[0013] - a first optical path designed to provide a first optical flow from the scene viewed from a first field of vision,

[0014] - a second optical path capable of providing a second optical flux from the scene viewed from a second field of vision, the second field of vision having a smaller dimension than the first field of vision,

[0015] - a polarizing separator suitable for receiving the first optical flux and the second optical flux and for recombining a portion of the first optical flux according to a first polarization state with a portion of the second optical flux according to a second polarization state to form a recombined optical flux, the second polarization state being orthogonal to the first polarization state,

[0016] - a sensor specifically designed to capture the recombined optical flux, and

[0017] - a polarizer matrix positioned in the plane of the sensor so that the recombined optical flux passes through the polarizer matrix before being captured by the sensor, the polarizers of the polarizer matrix having polarizations according to the first polarization state or according to the second polarization state.

[0018] According to other advantageous aspects of the invention, the optical system comprises one or more of the following features, taken individually or in all technically possible combinations:

[0019] - the second optical channel includes an optical scanning unit designed to modify the viewing axis perceived by the sensor for the portion of the recombined optical flow resulting from the second optical flow;

[0020] - the optical system comprises a single objective positioned between the polarizing splitter and the polarizer array so as to receive the recombined optical flux;

[0021] - the first optical path comprises a first processing unit and the second optical path comprises a second processing unit, the polarizing splitter being suitable for receiving an incident optical flux from the scene, and for separating the incident optical flux into a first intermediate optical flux sent to the input of the first processing unit, and into a second intermediate optical flux sent to the input of the second processing unit, the first processing unit being suitable for processing the first intermediate optical flux to obtain the first optical flux and for sending the first optical flux to the polarizing splitter for recombination, the second processing unit being suitable for processing the second intermediate optical flux to obtain the second optical flux and for sending the second optical flux to the polarizing splitter for recombination;

[0022] - the first processing unit includes at least one phase-delay blade suitable for modifying the polarization of the first optical flux so that the first optical flux is polarized according to the first polarization state, the second processing unit includes at least one phase-delay blade suitable for modifying the polarization of the second optical flux so that the second optical flux is polarized according to the second polarization state;

[0023] - the first processing unit includes an afocal subset with a magnification of less than one, so that the combination of the afocal subset and the single lens has a focal length less than the focal length of the single lens, allowing the obtaining of an enlarged field of view, forming the first field of view, for the first optical flow relative to the second optical flow;

[0024] - the first optical path includes a first objective for the first optical flow and the second optical path includes a second objective for the second optical flow;

[0025] - each of the first optical channel and the second optical channel includes a half-wave plate suitable for selecting the scene-side polarization directions to be captured by the sensor for each of the channels;

[0026] - the polarizing splitter is also capable of recombining a portion of the first optical flux according to the second polarization state with a portion of the second optical flux according to the first polarization state to form an additional recombined optical flux, the optical system further comprising:

[0027] - an additional sensor specifically designed to capture the additional recombined optical flux, and

[0028] - an additional matrix of polarizers positioned in the plane of the additional sensor so that the additional recombined optical flux passes through the additional matrix of polarizers before being captured by the additional sensor, the polarizers of the additional matrix of polarizers having polarizations according to the first polarization state or according to the second polarization state; - the polarizing separator is also suitable for recombining a portion of the first optical flux according to the second polarization state with a portion of the second optical flux according to the first polarization state to form an additional recombined optical flux, the optical system further comprising an eyepiece for observing an image formed from the additional recombined optical flux.

[0029] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0030] [Fig. 1] Figure 1 is a schematic view of an example of an optical system for acquiring images of a scene according to a first and a second embodiment,

[0031] [Fig. 2] Figure 2 is a schematic view of an example of a polarizer matrix,

[0032] [Fig. 3] Figure 3 is a schematic view of an example of an optical system for acquiring images of a scene according to the first embodiment, the optical system comprising a single lens,

[0033] [Fig. 4] Figure 4 is a schematic view of a more specific embodiment of the optical system of Figure 3 according to the first embodiment, and

[0034] [Fig. 5] Figure 5 is a schematic view of an example of an optical system for acquiring images of a scene according to the second embodiment, the optical system comprising two lenses, and

[0035] [Fig. 6] Figure 6 is a schematic view of a more specific example of the optical system of Figure 5 according to the second embodiment.

[0036] An optical system 10 for acquiring images of a scene is schematically illustrated in Figure 1. The scene is, for example, an environment in which there may or may not be living beings or moving or non-moving objects.

[0037] The optical system 10 is configured to simultaneously capture images from two fields of view of the scene on the same sensor.

[0038] This description first outlines the elements common to both embodiments. Each embodiment is then described in more detail.

[0039] Generic embodiment

[0040] As illustrated by Figure 1, the optical system 10 comprises a first optical channel 12, a second optical channel 14, a polarizing splitter 16, a sensor 18 and a polarizer matrix 20. The first optical channel 12 is suitable for providing a first optical flux Fi from the scene seen from a first field of view.

[0041] The second optical path 14 is designed to provide a second optical flux F2 from the scene viewed from a second field of view. The second field of view has a smaller dimension than the first field of view.

[0042] The polarizing separator 16 is suitable for receiving the first optical flux F1 and the second optical flux F2, and for recombining a portion of the first optical flux F1 according to a first polarization state with a portion of the second optical flux F2 according to a second polarization state to form a recombined optical flux FR.

[0043] The second polarization state is orthogonal to the first polarization state. For example, one of the first and second polarization states is linear polarization P (electric field polarized parallel to the plane of incidence), and the other polarization state is linear polarization S (electric field polarized perpendicular to the plane of incidence). The plane of incidence considered here is the plane of the polarizing separator 16.

[0044] The polarizing separator 16 is, for example, a polarizing cube or a polarizing separator blade.

[0045] Sensor 18 is specifically designed to capture the recombined optical flux FR.

[0046] Sensor 18 operates within a defined wavelength band. For example, sensor 18 operates in the visible spectrum. Alternatively, sensor 18 operates in the infrared spectrum.

[0047] The polarizer matrix 20 is positioned in the plane of the sensor 18 so that the recombined FR optical flux passes through the polarizer matrix 20 before being captured by the sensor 18.

[0048] The polarizer array 20 is formed of individual polarizers whose polarization directions are either in the first polarization state or in the second polarization state. This allows images of the first and second fields of view to be formed simultaneously on the sensor 18.

[0049] The polarizer array 20 is, for example, an alternation of grid polarizers having preferred polarization directions according to the first polarization state and according to the second polarization state. Each individual polarizer can cover one or more pixels of the sensor 18.

[0050] Figure 2 illustrates an example of a polarizer matrix 20 comprising, on a grid, an alternation of two types of polarizers having polarization directions of 0° and 90°. More generally, the preferred polarization directions are preferably chosen between 0°, 45°, 90°, and 135°. The sensor 18 and the polarizer matrix 20 together thus form a focal plane splitter sensor.

[0051] Optionally, the second optical channel 14 includes a scanning optical unit 24 capable of modifying the viewing axis perceived by the sensor 18 for the portion of the recombined optical flow FR originating from the second optical flow F2. In other words, the resulting image from the second optical flow F2 may have the center of its field of view modified on the sensor 18.

[0052] The 24 optical scanning unit thus allows scanning of the smallest field (second field of view). The scanning allows for horizontal and / or vertical field scanning.

[0053] The scanning optical unit 24 includes, for example, a scanning mirror.

[0054] Preferably, the scanning mirror is designed to be moved around a reference orientation to perform field scanning (of the second field of view). The reference orientation is one in which the scanning mirror receives the second optical flux F2 at normal incidence. This prevents image derotation when scanning the field of view, unlike scanning mirrors with an incidence of 45° (or close to 45°). Therefore, it is not necessary to add an additional optical sub-assembly or apply post-processing algorithms to correct image derotation if the scanning angle remains reasonable.

[0055] First method of implementation

[0056] In what follows, the specifics of the optical system 10 according to the first embodiment are described with reference to figures 1, 3 and 4.

[0057] In the first embodiment, the optical system 10 comprises a single objective 30.

[0058] Thus, in this embodiment, the first optical channel 12 and the second optical channel 14 have coaxial entrance pupils, which advantageously eliminates parallax effects in the center of the fields of these two channels.

[0059] The only 30mm lens has a fixed focal length.

[0060] As illustrated by Figures 3 and 4, the single objective 30 is positioned between the polarizing separator 16 and the polarizer matrix 20 so as to receive the recombined optical flux FR.

[0061] As illustrated in Figures 3 and 4, the first optical path 12 comprises a first processing unit 32. The first processing unit 32 is designed to form the first optical flow F1 from an incident optical flow Fi. In particular, the first processing unit 32 is such that the focal length of the entire assembly of the first processing unit 32 and the single lens 30 is less than the focal length of the single lens. This makes it possible to enlarge the field of view on the first optical path 12, and thus obtain a first optical flow Fi with the first field of view.

[0062] Similarly, the second optical channel 14 includes a second processing unit 34. The second processing unit 34 is suitable for forming the second optical flow F2 from an incident optical flow Fi.

[0063] In addition to the recombination features of the polarizing separator 16 described for the generic embodiment, the polarizing separator 16 also has features specific to the first embodiment.

[0064] In particular, the polarizing splitter 16 is suitable for receiving an incident optical flux Fi from the scene, and for separating the incident optical flux Fi into a first intermediate optical flux Fn sent into the input of the first processing unit 32, and into a second intermediate optical flux F12 sent into the input of the second processing unit 34.

[0065] The first processing unit 32 is suitable for processing the first intermediate optical flux Fn to obtain the first optical flux F1 and for sending the first optical flux F1 to the polarizing separator 16 for recombination.

[0066] In particular, the first processing unit 32 includes an afocal subset 40 with a magnification of less than one, so that the combination of the afocal subset 40 and the single objective lens 30 has a focal length shorter than that of the single objective lens 30, thus enabling the acquisition of an enlarged field of view, forming the first field of view, for the first optical flux F1 relative to the second optical flux F2. The afocal subset 40 is also suitable for directing the first optical flux F1 towards the polarizing splitter 16.

[0067] Optionally, the first processing unit 32 includes at least one phase-delay plate 42 suitable for modifying the polarization of the first optical flux F1 so that the first optical flux F1 is polarized according to the first polarization state. For example, the phase-delay plate or plates 42 are quarter-wave plates.

[0068] Typically, the first intermediate optical flux Fn is in the second polarization state. The phase-delay plate(s) of the first processing unit 32 modify the polarization of the first optical flux F1 so that it is in the first polarization state. In the examples illustrated in Figures 3 and 4, the phase-delay plate 42 transforms an S polarization state into a P polarization state.

[0069] An example of the implementation of the afocal subset 40 and the phase-delay plates 42 is illustrated by Figure 4. In this example, the afocal subset 40 comprises lenses 44A, 44B and 44C (lens assemblies in Figure 4) forming a Keplerian afocal system, quarter-wave plates 42A, 42B and 42C, a separating unit 45 and an achromatic prism doublet 46. In this example, the objective 30 is a fixed focal length objective.

[0070] The Keplerian afocal system also performs a pupil transport function, so that through this subset, the entrance pupil of the first optical channel 12 (the "wide-field" channel) is re-imaged on itself to virtually coincide with the entrance pupil of the second optical channel 14 (the "narrow-field" channel). These pupil positions precisely prevent any scanning of the entrance pupil in object space or image space when scanning the field. Furthermore, they minimize the size of the polarizing splitter 16 and / or reduce the vignetting it might cause.

[0071] The rear surfaces of lenses 44A, 44B, and 44C are coated with a mirror finish, typically a metallic coating. Their respective combination with quarter-wave plates 42A, 42B, and 42C (located at the input and output of lenses 44A, 44B, and 44C) allows a 90° rotation to be applied to the incident linear polarization state when their slow axis is oriented at 45° to this incident polarization. Quarter-wave plates 42A, 42B, and 42C are thus used in a double-through configuration.

[0072] The separation unit 45 is a polarizing separator. The separation unit 45 is, for example, a polarizing cube or a polarizing separator blade.

[0073] Typically, the passage of a converging beam through the separation unit 45 causes eccentricity aberrations – notably eccentricity coma. The achromatic prism doublet 46, in conjunction with the lenses 44A, compensates for these eccentricity aberrations without deviating the optical axis of the system.

[0074] The second processing unit 34 is designed to process the second intermediate optical flux F12 to obtain the second optical flux F2 and to send the second optical flux F2 to the polarizing separator 16 for recombination.

[0075] For this purpose, the second processing unit 34 includes, for example, a reflecting unit suitable for reflecting the second optical flux F2 formed towards the polarizing separator 16. For example, the reflecting unit is a mirror.

[0076] In a specific example, visible in Figures 3 and 4, the reference unit is the optical scanning unit 24 mentioned in the generic embodiment.

[0077] Optionally, the second processing unit 34 also includes at least one phase-delay plate 48 suitable for modifying the polarization of the second intermediate optical flux F12 so that the polarization of the second optical flux F2 is in the second polarization state. The phase-delay plate 48 is thus used in a double-pass configuration. For example, the phase-delay plate(s) 48 are quarter-wave plates. Typically, the second intermediate optical flux F12 is in the first polarization state. The phase-delay plate(s) of the second processing unit 34 allow(s) the polarization of the second optical flux F2 to be modified so that the second optical flux F2 is in the second polarization state. In the examples illustrated by Figures 3 and 4, the phase-delay plate 48, used in a double-pass configuration, allows a P polarization state to be transformed into an S polarization state.

[0078] In operation, the optical system 10 according to the first embodiment includes the separation, by the polarizing separator 16, of an incident optical flux Fi into a first intermediate optical flux Fn and a second intermediate optical flux F12.

[0079] The first intermediate optical flux Fn is then processed by the first processing unit 32 to form the first optical flux F1. In particular, magnification is applied to the first intermediate optical flux Fn to obtain the first optical flux F1. Preferably, at least one phase-delay plate 42, used in a double pass-through configuration, allows the first optical flux F1 to be brought into the first polarization state.

[0080] The second intermediate optical flux F12 is then processed by the second processing unit 34 to form the second optical flux F2. Preferably, at least one phase-delay plate 48 is used to bring the second optical flux F2 into the second polarization state.

[0081] The first optical flux F1 and the second optical flux F2 are then recombined on the polarizing separator 16. The recombined optical flux FR is formed from a portion of the first optical flux F1 in the first polarization state and a portion of the second optical flux F2 in the second polarization state.

[0082] The recombined optical flux FR is then captured by the sensor 18, after passing through the polarizer matrix 20. The use of the polarizer matrix 20 thus makes it possible to capture on the same sensor distinct images coming from the first optical flux F1 and the second optical flux F2.

[0083] Second method of implementation

[0084] In what follows, the specifics of the optical system 10 according to the second embodiment are described with reference to figures 1, 5 and 6.

[0085] In the second embodiment, as illustrated by figures 5 and 6, the first optical path 12 includes a first objective 50 from which the first optical flux F1 originates and the second optical path 14 includes a second objective 52 from which the second optical flux F2 originates.

[0086] Thus, in this second embodiment, the first optical path 12 and the second optical path 14 have disjoint entrance pupils (see in Figure 6, the entrance pupil 53 of the first objective 50, which is not coaxial with the entrance pupil 54 of the second objective 52). A slight parallax error may therefore exist between these two paths, which is a function of the distance between their respective entrance pupils and the observation distance. Depending on the application of the invention, this parallax effect can be neglected, particularly if the Wide Field (WF) and Small Field (SF) images are not to be merged during post-processing, or if the observation distance is much greater than the center-to-center distance between these two entrance pupils.

[0087] The first lens, 50, and the second lens, 52, have different focal lengths, allowing them to capture fields of view of distinct dimensions. Specifically, the focal length of the first lens, 50, is such that the first optical flow, F1, is aligned with the first field of view, and the focal length of the second lens, 52, is such that the second optical flow, F2, is aligned with the second field of view.

[0088] In particular, in the example in Figure 6, the first objective 50 is formed from an assembly of several lenses, and the second objective 52 is formed from a doublet of lenses.

[0089] The first optical channel 12 is suitable for receiving a first incident flux Fn and for forming the first flux F1 via the first objective 50. The first optical channel 12 is also suitable for sending the first formed optical flux F1 to the polarizing separator 16.

[0090] The first optical path 12 includes, for example, optics, such as lenses and / or mirrors, enabling the routing of the first optical flux F1 to the polarizing separator 16. In the example illustrated by Figure 6, the first optical path 12 includes a mirror 55.

[0091] The second optical channel 14 is suitable for receiving a second incident flux F12 and for forming the second flux accordingly via the second objective 52. The second optical channel 14 is also suitable for sending the second formed optical flux F2 to the polarizing separator 16.

[0092] The second optical path 14 includes, for example, optics, such as lenses and / or mirrors, enabling the routing of the second optical flux F2 to the polarizing separator 16. In the example illustrated by Figure 6, the second optical path 14 includes two mirrors 56, 57 and lenses 58, 59.

[0093] In the example illustrated in Figure 6, the second optical channel 14 includes a scanning optical unit 24. In this example, the scanning optical unit 24 is formed by a scanning mirror 80, a quarter-wave plate 81, and a polarizing beam splitter 82. The combination of the quarter-wave plate 81 and the scanning mirror 80 allows the linear polarization to be rotated by 90° during the double pass. The beams before and after field scanning are then separated by the polarizing beam splitter 82. Optionally, as illustrated in Figures 5 and 6, each of the first optical channel 12 and the second optical channel 14 includes a half-wave plate 70, 72 for selecting the scene-side polarization directions to be captured by the sensor 18 for each channel.This can prove advantageous in cases where one wishes to reduce the glare that could be caused by glass reflections on the stage side (reflections on a body of water, on windows, etc.).

[0094] In particular, the orientations of the half-wave plates 70, 72 are chosen for example so that the first optical flux Fi is in the first polarization state, and the second optical flux F2 is in the second polarization state.

[0095] Optionally, as illustrated in Figures 5 and 6, the polarizing splitter 16 is also capable of recombining a portion of the first optical flux F1 in the second polarization state with a portion of the second optical flux F2 in the first polarization state to form an additional recombined optical flux FRadd. In this case, the optical system 10 further comprises:

[0096] - an additional sensor 60 specifically designed to capture the additional recombined optical flux

[0097] FRadd, and

[0098] - an additional matrix of polarizers 62 positioned in the plane of the additional sensor 60 so that the additional recombined optical flux FRadd passes through the additional matrix of polarizers 62 before being captured by the additional sensor 60. The polarizers of the additional matrix of polarizers 62 have polarizations according to the first polarization state or according to the second polarization state.

[0099] Alternatively, the polarizing splitter 16 is also suitable for recombining a portion of the first optical flux F1 in its second polarization state with a portion of the second optical flux F2 in its first polarization state to form an additional recombined optical flux FRadd. In this variant, the optical system 10 includes an eyepiece for observing an image formed from the additional recombined optical flux FRadd.

[0100] Optionally, as illustrated in the example in Figure 6, each of the first optical channel 12 and the second optical channel 14 also includes polarizers 63, 64, known as cleaning polarizers, designed to strongly attenuate any polarization state orthogonal to the first polarization state for the first optical flux F1, and any polarization state orthogonal to the second polarization state for the second optical flux F2. This reduces the risk of crosstalk between the two images (from the first optical channel 12 and the second optical channel 14) captured by the sensor 18.

[0101] In operation, the optical system 10 according to the second embodiment includes obtaining and routing to the polarizing separator 16, a first optical flux Fi by the first optical channel 12 and a second optical flux F2 by the second optical channel 14.

[0102] The first optical flux F1 and the second optical flux F2 are then recombined on the polarizing separator 16. The recombined optical flux FR is formed of a portion of the first optical flux F1 in the first polarization state and a portion of the second optical flux F2 according to the second polarization state.

[0103] The recombined optical flux FR is then captured by the sensor 18, after passing through the polarizer matrix 20.

[0104] Optionally, the polarizing splitter 16 also recombines a portion of the first optical flux F1 according to the second polarization state with a portion of the second optical flux F2 according to the first polarization state to form an additional recombined optical flux FRadd. The additional recombined optical flux FRadd is then captured by the additional sensor 60, after passing through the additional polarizer array 62.

[0105] Benefits

[0106] The image capture system described in the various embodiments thus offers the possibility of simultaneously capturing two fields of view on a single sensor with fixed dimensions, resolution, and position. These two fields, called "Small Field (SF)" and "Wide Field (WF)," can be of different dimensions and have different viewing directions on the scene side.

[0107] In particular, the 20-polarizer array allows for the simultaneous visualization, on a single sensor, of two distinct images with different polarization states (orthogonal, for example). These images originate from two optical beams traversing different optical paths (e.g., observation direction, field size, focal length, aperture, resolution, spectral band, depth of field, etc.) before being recombined on this sensor.

[0108] Using only one sensor has certain advantages:

[0109] - cost first of all, especially when it comes to SWIR (Short Wavelength InfraRed, translated as near infrared), MWIR (Medium Wavelength Infrared, translated as medium infrared) or LWIR (Long Wavelength Infrared, translated as far infrared) cameras.

[0110] - bulk and mass.

[0111] - elimination of any latency effect since the images of both fields are acquired and processed simultaneously by a single sensor.

[0112] - suppression of parallax effects between the two fields if the entrance pupils of the two channels coincide (first embodiment). Furthermore, the invention also offers the possibility of choosing the observation direction of the small field within the large field by means of an angular scanning system.

[0113] The risk of crosstalk between the two captured fields can be greatly reduced given the high extinction ratios of some polarizers which can be greater than 1:10,000.

[0114] Using a focal plane split camera in which the polarizer array is intercalated between the microlens array and the photosensitive surface helps to reduce cross-talk between neighboring pixels.

[0115] This shooting system also has the advantage of being modular, as it results either from the combination of a lens and a 40mm afocal sub-assembly (operating mode 1), or from the combination of two independent lenses (operating mode 2). By modifying either of these sub-assemblies, it is possible to change the characteristics of the small and wide fields of view.

[0116] Finally, it should be noted that it is possible to add a second sensor in operating mode 2 without modifying the design of the optical system 10. This option can be used advantageously, for example, to simultaneously capture the wide and narrow fields in a spectral band other than visible, such as near-infrared (NIR) or SWIR, while retaining all the previously listed advantages in this new spectral band of interest. It will then be necessary to ensure that the optical combination maintains all its performance (optical quality, transmission, polarization extinction ratio, etc.) in these two spectral bands. The second sensor can also prove useful when the signal is disturbed in the spectral band of the first sensor, but not in that of the second sensor (fog, smoke, aerosols, vegetation, etc.).

[0117] Finally, in addition to these advantages, the second embodiment also improves optical transmission on each channel. Here, there is no need to convert the S polarization to P on channel (GC) (or vice versa), just as there is no need to convert the P polarization to S on channel (PC) (or vice versa), before re-imaging the signal on the main sensor.

[0118] Thus, the invention can, for example, be used for: target tracking; wide-field detection and recognition or identification. In this context, this system can be advantageously used: on a drone, to detect, identify, and recognize elements of the scene; on a ground vehicle, for panoramic observation (360° azimuth) in the wide-field channel, using a common front lens for both similar channels, but re-imaging both fields on a single sensor; and to improve detection by significantly reducing sensor glare caused by specular reflections. In particular, in marine environments, specular reflections of the sun on a body of water are often problematic in this respect when the sun is not at its zenith.

[0119] A person skilled in the art will understand that the embodiments and variants described above can be combined with each other provided they are technically compatible.

Claims

DEMANDS 1. Optical system (10) for acquiring images of a scene, the optical system (10) comprising: - a first optical path (12) suitable for providing a first optical flux (Fi) from the scene seen from a first field of vision, - a second optical path (14) suitable for providing a second optical flux (F2) from the scene seen from a second field of vision, the second field of vision having a dimension smaller than the first field of vision, - a polarizing separator (16) suitable for receiving the first optical flux (F1) and the second optical flux (F2), and for recombining a portion of the first optical flux (F1) according to a first polarization state with a portion of the second optical flux (F2) according to a second polarization state to form a recombined optical flux (FR), the second polarization state being orthogonal to the first polarization state, - a sensor (18) suitable for capturing the recombined optical flux (RF), and - a polarizer matrix (20) positioned in the plane of the sensor (18) so that the recombined optical flux (RF) passes through the polarizer matrix (20) before being captured by the sensor (18), the polarizers of the polarizer matrix (20) having polarizations according to the first polarization state or according to the second polarization state.

2. Optical system (10) according to claim 1, wherein the second optical channel (14) comprises an optical scanning unit (24) adapted to modify the sighting axis perceived by the sensor (18) for the portion of the recombined optical flow (FR) resulting from the second optical flow (F2).

3. Optical system (10) according to claim 1 or 2, wherein the optical system (10) comprises a single lens (30) positioned between the polarizing splitter (16) and the polarizer array (20) so as to receive the recombined optical flux (RF).

4. Optical system (10) according to claim 3, wherein the first optical channel (12) comprises a first processing unit (32) and the second optical channel (14) comprises a second processing unit (34), the polarizing splitter (16) being adapted to receive an incident optical flux (Fi) from the scene, and to separate the incident optical flux (Fi) into a first intermediate optical flux (Fn) sent to the input of the first processing unit (32), and into a second intermediate optical flux (F12) sent to the input of the second processing unit (34), the first processing unit (32) being suitable for processing the first intermediate optical flux (Fn) to obtain the first optical flux (Fi) and for sending the first optical flux (Fi) to the polarizing separator (16) for recombination, the second processing unit (34) being suitable for processing the second intermediate optical flux (F12) to obtain the second optical flux (F2) and for sending the second optical flux (F2) to the polarizing separator (16) for recombination.

5. Optical system (10) according to claim 4, wherein the first processing unit (32) comprises at least one phase-delay blade (42) adapted to modify the polarization of the first optical flux (F1) so that the first optical flux (F1) is polarized according to the first polarization state, the second processing unit (34) comprising at least one phase-delay blade (48) adapted to modify the polarization of the second optical flux (F2) so that the second optical flux (F2) is polarized according to the second polarization state.

6. Optical system (10) according to claim 4 or 5, wherein the first processing unit (32) comprises an afocal subset (40) with a magnification of less than one, such that the combination of the afocal subset (40) and the single lens (30) has a focal length less than the focal length of the single lens, enabling the obtaining of an enlarged field of view, forming the first field of view, for the first optical flow (F1) with respect to the second optical flow (F2).

7. Optical system (10) according to claim 1 or 2, wherein the first optical path (12) comprises a first lens (50) for the first optical flow (F1) and the second optical path (14) comprises a second lens (52) for the second optical flow (F2).

8. Optical system (10) according to claim 7, wherein each of the first optical channel (12) and the second optical channel (14) comprises a half-wave plate (70, 72) suitable for selecting the scene-side polarization directions to be captured by the sensor (18) for each of the channels.

9. Optical system (10) according to claim 7 or 8, wherein the polarizing splitter (16) is also suitable for recombining a portion of the first optical flux (F1) according to the second polarization state with a portion of the second optical flux (F2) according to the first polarization state to form an additional recombined optical flux (FRadd), the optical system (10) further comprising: 17 - an additional sensor (60) designed to capture the additional recombined optical flux (FRadd), and - an additional matrix of polarizers (62) positioned in the plane of the additional sensor (60) so that the additional recombined optical flux (FRadd) passes through the additional matrix of polarizers (62) before being captured by the additional sensor (60), the polarizers of the additional matrix of polarizers (62) having polarizations according to the first polarization state or according to the second polarization state.

10. Optical system (10) according to claim 7 or 8, wherein the polarizing separator (16) is also suitable for recombining a portion of the first optical flux (Fi) according to the second polarization state with a portion of the second optical flux (F2) according to the first polarization state to form an additional recombined optical flux (FRadd), the optical system (10) further comprising an eyepiece for observing an image formed from the additional recombined optical flux (FRadd).

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