Illuminator, preferably an illuminator for active range estimation device and method for illuminating a target

Abstract

Illuminator, preferably an illuminator for active range estimation device, comprising: a source of laser radiation (2-a,2-b); a conditioning optics (3-a,3-b) for the source of laser radiation (2-a,2-b); a first dot pattern generator (DPG-1) receiving laser light from the conditioning optics (3-a,3-b) and configured to produce a number Npd of first divergent rays r1a, r2a, …, ria, …, rNpda, forming a first pattern P1, and a second dot pattern generator (DPG-2) receiving laser radiation from the conditioning optics (3- a,3-b) and configured to produce a number Npd of second divergent rays forming a second pattern r1b, r2b, …, rib, …, rNpdb,. The first and second dot pattern generators (DPG-1 and DPG-2) are configured to produce Npd couples of corresponding first and second rays r1a - r1b, r2a - r2b, … ria - rib, …rNpda rNpdb that have substantially parallel axis and impact on a target to produce Npd pairs of dots D1a - D1b, D2a - D2b, …, Dia - Dib, …, DNpda - DNpdb on the target.

Description

[0001]“ILLUMINATOR, PREFERABLY AN ILLUMINATOR FOR ACTIVE RANGE ESTIMATION DEVICE AND METHOD FOR ILLUMINATING A TARGET” The present invention relates to an illuminator, preferably an illuminator for an active range estimation device and a method for illuminating a target. Background of the invention It is known to use illuminators, preferably for active range estimation devices, comprising: a source of laser radiation (typically a laser LED); conditioning optics coupled to the source of laser radiation; and dot pattern generator (DPG) element receiving laser radiation from the conditioning optics and having an engineered structure configured to produce a number of divergent rays forming a pattern that impinge on a target forming a number of dots. Such a structure can be diffractive, meaning that the DPG is a diffractive optical element (DOE), or, more broadly, a metasurface. The illuminators are rather simple, cheap and easy to produce. However, the energy of the laser is concentrated in the dots that have a high energy density. In active stereo range estimation sensors, the image of the dots is captured by a first left camera and by a second right camera. A correspondence algorithm is first used to match the dots captured by a first left camera with those of a second right camera. A centroiding algorithm is then used to estimate the centroid of each dot. A triangulation algorithm calculates the tridimensional position of the dots knowing: the spatial position of the left camera; the spatial position of the right camera; the vectors ^^^^^: pointing from the position of the left camera to centroid of the dots; the vectors : pointing from the position of the right camera to the centroid of the dots; and the distance ^^^^^^between the cameras. A calibration phase is required to estimate the distance^^^^^^and to minimize any systematic errors when estimating the vectors ^^^^^and ^^^^^. The above-described illuminators present some drawbacks when used for active stereo range estimation devices. First, in some applications it is necessary to use a quite powerful laser source to illuminate a target that is quite far (for instance 100 meters). More power requires a more powerful (and more expensive) laser. Moreover, laser power is upper- limited by laser safety limits. Second, the use of the above illuminators also introduces drawbacks in the centroiding phase as the image of each dot occupies few pixels, which makes the centroiding phase inaccurate (and noise makes centroiding even more imprecise). Finally, the use of the above-described illuminators also introduces drawbacks in the calibration phase. Calibration requires knowing the Euclidean distance between reference points (e.g., distance between chessboard corners), and such an information is not provided by the pattern generated by the aforementioned illuminators. The above-described illuminators also present some drawbacks when used for active range estimation devices based on time-of-flight estimation. In such devices, each dot has an associated short pulse laser modulation, as well as a time-of-flight sensor. The tridimensional position of each dot is thus estimated from the time elapsed between emitting and receiving one short pulse, which is referred to as time of flight. Similarly to active stereo range estimation devices, in some applications it is necessary to use quite powerful short pulses, and thus a quite powerful laser source, to illuminate a target that is quite far (for instance 100 meters). More power again requires a more powerful (and more expensive) laser. Moreover, laser power is likewise upper-limited by laser safety limits. Other proposed illuminators comprise a rotating body carrying several lasers to perform a scanning of a target. Such illuminators are quite complex, expensive and cumbersome. Object of the invention The object of the present invention is to provide an illuminator device and a method for illuminating a target, suitable to produce dots that are sufficiently bright on a far target, without violating laser safety limits, and enhancing all key stages of an active range estimation device employing the said illuminator. Moreover, the present invention aims to provide an illuminator device having a simple and inexpensive structure. Scope of the present invention The above scope is obtained by the present invention that relates to an illuminator, preferably an illuminator for an active range estimation device, as defined in claim 1. The present invention also relates to a method for illuminating a target as defined in claim 16. Description of figures The invention shall be described with reference to the drawings wherein: figures 1a, 1b show in a simplified manner an illuminator, preferably an illuminator for an active range estimation device, realized according to the teachings of the present invention; figure 2 shows the front view of a special embodiment of the illuminator of figure 1; figures 3A, 3B and 3C show the working principle of the illuminator of figure 1; figures 4 and 5 show variations to the illuminator of figure 1; figure 6 shows operations performed by a disparity- based range estimation device utilizing the illuminator of the present invention; and figure 7 shows an example of an image captured by a left camera and another image captured by a right camera, when the scene depicted at the top is illuminated by the proposed illuminator. Preferred description of the invention Numeral 1 indicates an illuminator, preferably an illuminator for an active range estimation device, comprising: ^ A first source of laser light 2-a (represented schematically) consisting of one laser source in the example (for instance a laser diode or an array of Vertical Cavity Surface Emitting Laser); ^ A first conditioning optics 3-a (represented schematically and of known kind) that receives the laser light produced by the laser source 2-a (the laser light may be supplied to the conditioning optics 3-a through a fiber optics for instance); ^ A first dot pattern generator DPG-1 that receives the conditioned laser light from the conditioning optics 3- a and that is configured to produce a number Npdof first divergent rays r1a, r2a, …, ria, …, rNpdaforming a first pattern P1 of rays. As it is known, dot pattern generators (DPGs) are optical components that are able to produce rays of light that propagate towards precise angles. An important example of such DPGs are diffractive optical elements (DOEs). Typically, DOEs are formed in a film of only a few microns thickness. A DOE may be fabricated in a broad range of materials such as aluminium, silicon, silica, and plastics, thus providing flexibility in selecting the base material for specific applications. Another important example of such DPGs are metasurfaces. A metasurface is a subwavelength- level artificially engineered 3D material that can also produce rays of light that propagate towards precise angles. According to the present invention there is also provided: ^ A second source of laser light 2-b (represented schematically) consisting of one laser source in the example (for instance a laser diode or an array of Vertical Cavity Surface Emitting Laser); ^ A second conditioning optics 3-b (represented schematically and of known kind) that receives the laser light produced by the laser source 2-b (the laser light may be supplied to the conditioning optics 3-b through a fiber optics for instance); ^ A second dot pattern generator DPG-2 that receives the laser light from the conditioning optics 3-b and that is configured to produce a number Npdof second divergent rays r1b, r2b, …, rib, …, rNpdbforming a second pattern P2 of rays. The first dot pattern generator DPG-1 and the second dot pattern generator DPG-2 are spaced, one with respect to the other, of a distance d. The first dot pattern generator DPG- 1 and the second dot pattern generator DPG-2 have a substantially identical internal structure (the structures cannot be exactly the same due to the inevitable tolerances due to production process) and are configured to produce pairs r1a -r1b, r2a -r2b, …, ria -rib, …, rNpda -rNpdbof corresponding first and second rays that have substantially parallel trajectories and extend from the illuminator 1 to a target B where the illumination of the laser on the target B produces dots of light. For substantially parallel trajectories it is meant trajectories that diverge as little as possible (e.g., 0.1 mrad), as in practice it is not possible to generate perfectly parallel trajectories, once again due to inevitable tolerances involved in assembling the illuminator. More specifically, when the rays r1a -r1b, r2a -r2b, … ria - rib, …, rNpda -rNpdbimpinge on the target B they produce Npdpairs of dots D1a -D1b, D2a -D2b, …, Dia -Dib, …, DNpda -DNpdb. According to the present invention, each of the Npddots has another dot that is projected with a parallel trajectory to form the above “pair”. The illuminator 1 may be a part of an active range estimation device 10 comprising one camera 11 (figure 1a) or two cameras 11-a, 11-b (figure 1b) configured to capture images of the dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbon the target B. An electronic system 12 has a software configured to process the images of the camera 11 / the two cameras 11-a- 11-b to estimate the physical distance of each dot D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbfrom the active range estimation device 10. This information permits to identify which object target B is, e.g., a car, a pedestrian or simply ground (in the example the target B has been schematized as a flat surface but the shape may be arbitrary – figure 7 shows cars that form targets). According to an aspect of the invention there is provided a protective casing 15 (represented schematically and partially in figure 1A with a line and detailed in figure 2) enclosing the single camera 11 of figure 1A and the illuminator 1 to protect them. A possible example of tubular protective casing is shown in figure 2. In the example of figure 2 the protective casing 15 has a tubular cylindrical shape with the camera 11 aligned on the axis of the tube and the DPG-1 and DPG-2 placed at opposite sides of the axis. The camera 11 and the DPG-1 and DPG-2 face a front opening of the case 15. Accordingly, the light generated from the front opening produces Npdpairs of dots D1a -D1b, D2a -D2b, …, Dia -Dib, …, DNpda -DNpdb. It is advantageous to integrate illuminator 1 and a camera 11 in the same casing 15, for a matter of cost, and for making calibration process more robust, as illuminator and camera 11 are physically attached. This means that extrinsic calibration between the illuminator and corresponding camera holds better over time. In the case that a stereo system is needed, two casings 15-a, 15-b are provided, each casing enclosing its camera 11a, 11b and a couple of DPGs. When the target B is close to the illuminator (for instance a range of 0 - 25 metres, for instance 5 meters) in the image captured by the cameras the dots DiaDibare separated, i.e. each dot is detected by different pixels of the camera 11 (we refer to figure 3-A). When the distance between the target B and the illuminator increases (for instance the distance is 25 meters) in the image captured by the cameras the dots DiaDib become closer (we refer to figure 3-B) as the angular separation between dots decreases with distance. When the target B is far from the illuminator (for instance a range of 75 – 200 metres, for instance 100 meters) in the image the dots DiaDibare partly overlapping, i.e., different dots may be detected by the same pixels of the cameras (we refer to figure 3-B). In this way, according to the present invention, at far range (about 100 meters for instance) each pixel of a camera 11, 11a, 11b receives twice the power with respect to prior art illuminators without increasing the power of each individual dot Diaor Dib. It is obvious that the described illuminator may produce more than two sets of parallel rays (also referred herein as pairs of parallel rays, or pairs of dots); for instance it can produce three, four or more sets of parallel rays produced by respective dot pattern generator DPG-1, DPG-2 and DPG-3; DPG-1, DPG-2, DPG-3 and DPG-4; or more. It can be demonstrated that range increases between^^^^^and ^^^^times, where ^^^^is the number of dots following with parallel trajectories. In the examples given it is considered that ^^^^= 2, and the range increases between 1,41 and 2. Of course if the number of rays is three, four or more, range is increased even further. In other words, at close range the illuminator according to the present invention produces two distinct, bright dots (more power and more pixels) that are easy to be resolved. At medium range the imaged dots are partially overlapped, and are imaged by a given number of pixels. At long range, each pixel imaged by the two dots basically receives twice as much power with respect to prior art illuminators. The two DPGs are used to increase range while keeping constant the number of dots that can be resolved at long range. This is a first evident advantage of the illuminator according to the present invention with respect to prior art illuminators using a single laser and a single DPG. Figure 4 shows three variants to the illuminator shown in figure 1. According to a first variant (figure 4, left side) the first source of laser radiation 2-a and the second source of laser radiation 2-b have outputs that are combined in a combining point 17 before being supplied to the first conditioning optics 3-a and to the second conditioning optics 3-b. The combining point 17 may be realized by using an optical combiner, either in free space or in fiber optics. The advantage of this embodiment is that even if one laser fails, the other is still operational and thus may take over the failed laser by increasing its power. According to a second variant (figure 4, center portion) a single source of laser radiation 2-c is provided, the single source of laser radiation 2-c is configured to provide laser radiation to an input 22-in of optical splitter 22 having a first output 22-out-1 providing laser radiation to the first conditioning optics 3-a and having a second output 22-out-2 providing laser radiation to the second conditioning optics 3-b. The advantage of this embodiment is that it only requires one laser source for both DPGs DPG-1 and DPG-2. According to a third variant (figure 4, right side) the first dot pattern generator DPG-1 and the second dot pattern generator DPG-2 belong to the same substrate. In this case there is provided: A first source of laser light 2-d (represented schematically) consisting of one laser source in the example; A first conditioning optics 3-d (represented schematically and of known kind) that receives the laser light produced by the laser source 2-d (the laser light may be supplied to the conditioning optics 3-d through a fiber optics for instance); The first dot pattern generator DPG-1 and the second dot pattern generator DPG-2 that are realized in the same substrate and that are configured to produce pairs r1a -r1b, r2a -r2b, …, ria -rib, …, rNpda -rNpdbof corresponding first and second rays that have substantially parallel trajectories and extend from the illuminator 1 to a target B where the illumination of the laser on the target B produces dots of light. The above variant has the advantage of presenting a very compact structure. In addition, having both dot pattern generator DPGs DPG-1 and DPG-2 realized in the same substrate makes it simpler to have pairs of rays projected with parallel trajectories, than having DPG-1 and DPG-2 in separate substrates, placed apart from one another. Figure 5 shows another variant to the illuminator shown in figure 1. In the embodiment, the laser radiation comprises a first source of laser radiation 2-a and a second source of laser radiation 2-b; a first conditioning optics 3-a optically coupled with the first source of laser radiation 2-a and a second conditioning optics 3-b optically coupled with the second source of laser radiation 2-b; the first dot pattern generator DPG-1 receiving laser radiation from the first conditioning optics 3-a and the second dot pattern generator DPG-2 receiving laser radiation from the second conditioning optics (3-b). According to the variant of figure 5 a scanning device 25 is placed at the outputs of the dot pattern generator DPG-1 and of the second dot pattern generator DPG-2 to move the dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbacross the target B. The scanning device comprises, in the example, a first scanning mirror 25-a receiving the rays arriving from the first dot pattern generator DPG-1 and a second scanning mirrors 25-b receiving the rays arriving from the second dot pattern generator DPG-2. The two scanning mirrors 25-a, 25-b must operate together such that the dots of each pair of dots follow parallel trajectories. This means that, during the scanning phase, the scanning mirrors should be substantially parallel to one another. The advantages of this embodiment are that it adds scanning capability to the disclosed illuminator, and that a fixed tilt between scanning mirrors 25-a, 25-b can be programmed to compensate any tilt between DPGs DPG-1 and DPG-2. As outlined above, the illuminator 1 may be advantageously used in an active range estimation device 10 comprising at least one sensor (the camera 11 of figure 1a, and the cameras 11a and 11b of figure 1b in the above examples) configured to capture information associated to the impact of the rays on the target surface B, and the electronic system 12 configured to process the captured information to estimate the physical distance of each dot D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpd, DNpd, or from the corresponding pairs of dots, from the active range estimation device 10. This information permits to know the shape of the target. An example of a range estimation device 10 is a disparity-based range estimation sensor, based on one camera (monocular depth estimation) two cameras (stereo estimation), or more. Without loss of generality, let us consider two cameras. In this case, the electronic system is configured to receive consecutive images IleftIrightof the two cameras (see figure 7 that provides examples of the images taken by the two cameras), in each image there is present up to Npdpairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbon a dark background (the target B). A correspondence phase (block 100 – figure 6) is executed by the electronic system 12 to find and identify on each image the Npdpairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdb. The correspondence phase can be executed by with known algorithms. Making the correspondence operation on two dots is advantageous with respect to prior art correspondence operation in which only one dot is used. In fact, two dots are associated with a greater power and a larger number of illuminated pixels; which means that the different size of different pairs of pixels can be better resolved as a pair of dots illuminates more pixels than a single dot; this enables a better correspondence. After having executed the corresponding phase of block 100 a centroiding phase is executed (block 110) to calculate the centroid C1ab, C2ab, …, Ciab, …, CNpdabof each pair of dots of each image IleftIright. As it is known the centroid is the 'average position' of each pair of dots, i.e., the arithmetic mean of all pixels illuminated by each pair of dots. The centroiding phase is executed with known algorithms. Making the centroiding operation on two dots is advantageous with respect to prior art centroiding operation in which only one dot is used. In fact, two dots are associated with a greater power and a larger number of illuminated pixels; this enables a better centroiding. Finally, a triangulation algorithm (of known kind block 120) is applied on centroids C1ab, C2ab, …, Ciab, …, CNpdabof the images Ileftand Irightto calculate the distance of the pairs of dots the active range estimation device 10. The tridimensional position of the centroids can be calculated via triangulation in a known manner, knowing the camera and illuminator parameters, including intrinsic parameters, extrinsic parameters, and distortion models. All such parameters can be estimated in a calibration phase. In the case that two casings 15-a, 15-b are provided, each casing encloses its respective camera 11a, 11b and its respective illuminator. Consequently the illuminator enclosed in the first casing 15-a and the illuminator enclosed in the second casing 15-b produce a first set of pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdband a second set of pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdb. Calibration of each camera 11a, 11b may be realized by the electronic system 12 with the pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbproduced by the illuminator associated with that camera or with the illuminator of the other camera. The advantages of the invention are therefore the following: Longer range, that increases from^^^^^to ^^^^times. Distance-dependent dot shape, which helps in correspondence. Thanks to using at least two parallel dots, its shape can be resolved up to about 100 m, whereas using only a single dot limits resolution up to about 30 m. Enhanced centroiding at short and medium ranges, as ^^^dots naturally occupy more pixels than a single dot. Improved laser safety. An active stereo system typically projects its pattern from a single point, which is critical in terms of laser safety. Such is not the case of the present invention, as the projected pattern originates from multiple elementary dot projectors. Inexpensiveness. The most expensive part of the system – the camera itself – remains the same. Only more identical dot pattern projectors are added, which are inexpensive. Calibration. In prior art techniques all dots are projected with oblique trajectories and no parameter that has a constant or known Euclidean distance may be determined. Conversely, by projecting pairs of dots in which both dots of each pair have parallel trajectories according to the invention, their Euclidean distance is known all the time. Such an information is key in enabling calibration. According to a specific embodiment, another example of a range estimation device 10 is a time-of-flight (ToF)-based range estimation sensor. In such a case, the disclosed illuminator has an associated short pulse modulation. A ToF sensor 11 (e.g., a ToF-camera) can thus be used to estimate the ToF of the pulses associated with the dots projected by the illuminator to the target B. A ToF sensor is an instrument that estimates the distance between the sensor and the framed objects or scene in real time by measuring the time it takes for a short light pulse to travel the sensor-object-sensor path (time-of-flight). In this case, the electronic system is configured to receive an image from the ToF sensor. Also depending on the number of pixels of the ToF sensor, in each image there is present up to 2×NpdToF estimations, which correspond to pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdb(the target B). A correspondence phase can be executed by the electronic system 12 to correspond each ToF estimation to the correct dot, or pair of dots. The correspondence phase can be executed by known algorithms. No further phases are required as the tridimensional position of each dot can be directly calculated from the ToF estimation, unlike as in triangulation. The advantages of the invention for such a specific embodiment are the following: Longer range, that increases from^^^^^to ^^^^times. Improved laser safety. An active range estimation device based on a ToF sensor typically projects its pattern from a single point, which is critical in terms of laser safety. Such is not the case of the present invention, as the projected pattern originates from multiple elementary dot projectors. Inexpensiveness. The most expensive part of the system – the sensor itself – remains the same. Only more identical dot pattern projectors are added, which are inexpensive. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.

Claims

CLAIMS 1. -Illuminator, preferably an illuminator for an active range estimation device, comprising: a source of laser light (2-a,2-b); a conditioning optics (3-a,3-b) for the source of laser light (2-a,2-b); a first dot pattern generator (DPG-1) receiving laser light from the conditioning optics (3-a,3-b) and configured to produce a number Npdof first divergent rays r1a, r2a, …, ria, …, rNpda, forming a first pattern P1; a second dot pattern generator (DPG-2) receiving laser light from the conditioning optics (3-a,3-b) and configured to produce a number Npdof second divergent rays r1b, r2b, …, rib, …, rNpdb, forming a second pattern P2; the first and second dot pattern generators (DPG-1 and DPG- 2) being configured to produce Npdpairs of corresponding first and second rays r1a -r1b, r2a -r2b, …, ria -rib, …, rNpda -rNpdbthat have substantially parallel trajectories and illuminate a target B to produce Npdpairs of dots D1a -D1b, D2a -D2b, …, Dia -Dib, …, DNpda -DNpdb. 2.- Illuminator as defined in claim 1, wherein said source of laser light comprises a first source of laser light (2- a) and a second source of laser light (2-b); said conditioning optics comprising a first conditioning optics (3-a) optically coupled with said first source oflaser light (2-a) and a second conditioning optics (3-b) optically coupled with said second source of laser light (2- b); said first dot pattern generator (DPG-1) receiving laser radiation from said first conditioning optics (3-a) and said second dot pattern generator (DPG-2) receiving laser radiation from said second conditioning optics (3-b). 3.- Illuminator as defined in claim 2, wherein said first source of laser light (2-a) and the second source of laser light (2-b) have outputs that are combined together in a combining point (17) before being supplied to the first conditioning optics (3-a) and to the second conditioning optics (3-b). 4.- Illuminator as defined in claim 1, wherein a single source of laser light (2-c) is provided, the single source of laser light (2-c) is configured to provide laser light to an input (22-in) of beam splitter (22) having a first output (22-out-1) providing laser light to the first conditioning optics (3-a) and having a second output (22-out-2) providing laser light to the second conditioning optics (3-b). 5.- Illuminator as defined in claim 1, wherein said source of laser light comprises a single source of laser light (2- d); the first dot pattern generator DPG-1 and the second dot pattern generator DPG-2 belong to the same substrate, receive laser light from said single source (2-d) and are configuredto produce said pairs r1a -r1b, r2a -r2b, …, ria -rib, …, rNpda- rNpdbof corresponding first and second rays that have substantially parallel trajectories and extend from the illuminator 1 to a target B where the illumination of the laser on the target B produces dots of light. 6.- Illuminator as defined in any of the preceding claims, wherein a scanning device (25) is placed at the outputs of the first dot pattern generator DPG-1 and of the second dot pattern generator DPG-2 to move the dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbaccross the target B. 7.- Illuminator as defined in claim 6, wherein the scanning device comprises a first scanning mirror (25-a) receiving the rays arriving from the first dot pattern generator DPG- 1 and a second scanning mirror (25-b) receiving the rays arriving from the second dot pattern generator DPG-2; the first and second scanning mirrors (25-a, 25-b) are configured to operate together in a synchronized manner such that the dots of each pair of dots follow substantially parallel trajectories. 8.- Illuminator as claimed in any of the preceding claims, wherein said dot pattern generators DPGs comprise one of the following: diffractive optical elements (DOEs); metasurfaces. 9.- Active range estimation device (10) comprising at leastone sensor (11,11a,11b) configured to capture information associated to the impact of the rays on the target B and an electronic system (12) configured to process said information to estimate the physical distance of the target B from the active range estimation device, characterized by comprising an illuminator (10) as defined in any of the preceding claims 1 to 8. 10.- Active range estimation device (10) as defined in claim 9, wherein said sensor comprises at least one camera (11) and said electronic system is configured to process camera images of the pairs of dots generated by the impact of the rays on said target B to estimate the physical distance of dots from the active range estimation device (10). 11.- Active range estimation device as defined in claim 10, wherein said electronic system is configured to perform: - a correspondence phase (block 100) to find and identify in each camera image the Npdpairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdb; - a centroid phase (block 110) to calculate the centroid C1ab, C2ab, …, Ciab, …, CNpdabof each pair of dots of each image; - a triangulation phase (block 120) on centroids C1ab, C2ab, …, Ciab, …, CNpdabof the images to calculate the distance of the pairs of dots from the active range estimation device (10). 12.- Active range estimation device as defined in claim 9,wherein said sensor is configured to estimate the time of flight of said rays from the illuminator to the target and back to the sensor. 13.- Active range estimation device as defined in claim 8 to 12, wherein there is provided a protecting casing enclosing said sensor and said illuminator. 14.- Active range estimation device as defined in claim 12, wherein said sensor and illuminator face a front opening of the case. 15.- Active range estimation device as defined in claim 14, wherein there are provided a first and a second casing (15- a, 15-b), each casing encloses its respective camera sensor (11a, 11b) and its respective illuminator; the illuminator enclosed in the first casing (15-a) and the illuminator enclosed in the second casing (15-b) produce a first set of pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdband a second set of pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdb; said electronic system (12) being configured to perform a calibration phase of each camera 11a, 11b aided by the pairs of dots D1a, D1b, D2a, D2b, …, Dia, Dib, …, DNpda, DNpdbproduced by the illuminator associated with that camera or with the illuminator of the other camera. 16.- Method for illuminating a target (B) comprising: generating a source of laser light (2-a,2-b); conditioning (3-a,3-b) the generated laser light (2-a,2-b);providing conditioned laser light to a first dot pattern generator (DPG-1) to produce a number Npdof first divergent rays r1a, r2a, …, ria, …, rNpdaforming a first pattern P1; providing conditioned laser light to a second dot pattern generator (DPG-2) to produce a number Npdof second divergent rays r1b, r2b, …, rib, …, rNpdb,forming a second pattern P2; the first and second dot pattern generators (DPG-1 and DPG- 2) being configured to produce Npdpairs of corresponding first and second rays r1a -r1b, r2a -r2b, …, ria -rib, …, rNpda -rNpdbthat have substantially parallel trajectories and illuminate a target B to produce Npdpairs of dots D1a -D1b, D2a -D2b, …, Dia -Dib, …, DNpda -DNpdb.

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