WO2017060409A1

WO2017060409A1 - Device and system for remote sensing

Info

Publication number: WO2017060409A1
Application number: PCT/EP2016/073968
Authority: WO
Inventors: Patrick Pirim; Frederic Villain
Original assignee: Demand Side Instruments
Priority date: 2015-10-08
Filing date: 2016-10-07
Publication date: 2017-04-13
Also published as: EP3359931A1; FR3042271A1; FR3042271B1

Abstract

The present invention relates to a remote sensing device (20), in particular for tracking changes in agricultural crops, comprising a single optical channel (4, 5) and a plurality of elementary sensors (8_xy) that are arranged in a matrix array (8) of preset shape, wherein each elementary sensor (8_xy) is a multi-spectral sensor, in particular sensitive in a plurality of spectral bands, preferably at least in one spectral band in the visible domain (B, G, R) and one spectral band in the near infrared (IR). The present invention also relates to a remote sensing system employing such a remote sensing device (20).

Description

REMOTE SENSING DEVICE AND SYSTEM

The present invention relates to a remote sensing device, in particular for monitoring the evolution of agricultural crops. The present invention relates more particularly to a remote sensing device and a remote sensing system associated with it on the ground in a fixed position.

The need to follow the evolution of agricultural crops is at the origin of remote sensing, which is a process consisting essentially of taking images over several spectral bands in order to extract relevant information on scanned cultures. Depending on the size of the crops and the needs of the monitoring, it is known to carry out the remote sensing processes by means of sensors embedded on board satellites, planes, ULM or drones, or by means of sensors on the ground. fixed station.

In known remote sensing methods, the combination of information recovered over several spectral bands makes it possible to create vegetation indices that can be used to estimate the state of the scanned cultures. Thus, depending on the reflection in the visible and near infrared, these vegetation indices can be used to estimate biomass, leaf density, chlorophyll content or other information related to the scanned cultures.

Conventionally, the recording of remote sensing images over several spectral bands is achieved by separating the optical source into several optical paths, each incorporating an objective, a sensor and an optical filter associated and specific to a single spectral band. Thus, conventional systems require up to four different optical channels, or even more, for filtering light, for example in the visible and / or near-infrared domains. Such conventional systems require complex precision mechanics to implement and are also difficult to miniaturize in view of the space required for the incorporation of the different optical channels, sensors and associated filters.

There is therefore a need for improvement and simplification of existing remote sensing devices. In particular, there is a need for improvement and simplification of remote sensing devices on the ground stationary. This objective is achieved by a remote sensing device according to the present invention, in particular for monitoring the evolution of agricultural crops, comprising a single optical channel, and a plurality of elementary sensors arranged according to a matrix of predetermined shape, in which each elementary sensor is a multi-spectral sensor, in particular sensitive on a plurality of spectral bands, preferably at least on a spectral band in the visible range (B, V, R) and a spectral band in the near infrared (IR).

Thus, the remote sensing device according to the present invention satisfies the aforementioned problem by keeping only one optical channel and integrating the optical filters in each of the elementary sensors of the camera. In other words, the present invention proposes to use only one optical channel with a single integrated sensor, or mosaic of sensors, including the necessary filters in an integrated manner. Instead of taking an image of the same field through several optical channels, for example four optical channels, each corresponding to one of the spectral bands studied, which conventionally results in a plurality of images, for example. example four images in the conventional case of four optical channels, each comprising information in a single spectral band, the present invention allows to have all the information in one shot. In other words, the present invention makes it possible to directly obtain a single image comprising the information in all the spectral bands studied at once.

Advantageously, the remote sensing device according to the present invention may therefore comprise a sensor of the type normally used for colorimetry, making it possible to recover information associated with several spectral bands on each element of the sensor at the same time. The simplification of the device, which includes only one optical channel and a single sensor incorporating all the filters, makes it possible to overcome the multiple individual calibrations required in the case of conventional remote sensing devices comprising several optical channels.

In addition, other conventional remote sensing devices alternatively incorporate prism (s) and / or splitter (s) and / or other separating optics to separate the light into several downstream optical paths. Such conventional devices therefore always include a plurality of associated individual filters and sensors. By comparison, the present invention also advantageously makes it possible to overcome any prism or separating plate or similar device conventionally used to separate an optical source into several channels. Thus, it is possible, thanks to the present invention, also to overcome the filters conventionally associated with each of the optical paths. Consequently, the present invention makes it possible to make a remote sensing device more compact and simpler than the remote sensing devices known from the state of the art. Advantageously, the matrix of multispectral elementary sensors may be provided with a geometry function of the shooting form. Thus, it is possible to adapt the size of the matrix of elementary sensors so that, in a preferred embodiment, its height corresponds to the two extreme points of view of the system. Preferably, the elementary sensors can be arranged substantially coplanarly. It is therefore possible to easily reproduce an essentially flat scanned surface, such as the surface of a field of agricultural crops.

Advantageously, the single optical channel may comprise an optical element, preferably of the convergent type, for example an objective of the type comprising a convergent lens, and the matrix of multispectral elementary sensors may be arranged on a focal plane of said element. optical. As mentioned above, the present invention advantageously allows to have only one optical channel. Thus, by adapting the lens to the input of said single optical path, it is possible to make a remote sensing device even more compact than conventional devices. Preferably, the width of the matrix may then be about twice the focal length of said optical element. Since the shooting height is low compared to the maximum distance of analysis, the inclination of the optical axis must be measured in order to correct the position of the distant pixels. A field of a large area can thus be scanned more easily than with conventional devices. In addition, according to a preferred embodiment, the remote sensing device according to the present invention may further comprise a housing, preferably light-tight, provided such that the optical element is mounted frontally on an opening of said housing, and an electronic board mounted on a bottom of said housing opposite said optical element and supporting the matrix of elementary sensors. A compact and lightweight device can be made, which can be adapted to remote sensing embedded on satellite, aircraft, ULM, drone or other air medium, but also to remote sensing ground stationary. In addition, according to an advantageous variant of the remote sensing device according to the present invention, the outside of the housing can be configured to produce a Faraday cage, thus protecting the inside of the housing from lightning. Such protection is particularly advantageous when the remote sensing device according to the present invention is used in a ground system fixed station, high, preferably of the order of 5 to 6 m minimum. Thus, in an embodiment in which the housing would be of plastic or the like, it may be advantageous to attach strips of conductive material to the outside of the housing.

In addition, according to a preferred embodiment, the remote sensing device according to the present invention may comprise one, in particular a single control unit. It is therefore possible to analyze the data recovered by the matrix of multispectral elementary sensors and to control other electronic elements using the same control unit.

The objective is also achieved by a stationary ground type remote sensing system comprising a remote sensing device according to the present invention mounted on a mast. Because of its compactness and simplicity, the remote sensing device according to the present invention is particularly suitable for installation in a fixed station on the ground.

Preferably, the remote sensing device is rotatably mounted on the mast. It is therefore possible to scan a surface easily by installing the system at the center of the surface to be scanned. In particular, according to a preferred aspect of the remote sensing device according to the present invention, the shooting can be performed by a succession of contiguous sectors, in particular 90 °, which ensures a good compromise between the geometric aberration of the wide angle and the reduced number of shots needed to cover a control area. Thus, depending on the geometry of the sensor and the optical channel input of the remote sensing device according to the present invention, it is possible to shoot on the ground over a large area, in particular of the order of one hectare. (00 m * 100 m), which makes it possible to scan areas of dimensions adapted to agriculture.

According to a preferred aspect of a remote sensing system comprising the remote sensing device according to the present invention, basic elements of a weather station can be integrated outside the housing of the device, and a transfer of information can be realized by a magnet. In a preferred embodiment, the remote sensing system may therefore further include an integrated airspeed sensor. In a variant or alternatively, the remote sensing system may therefore further include a rain sensor. In addition, in the remote sensing system, the remote sensing device may further comprise at least one magnetic sensor, and the airspeed sensor and / or the rain sensor may comprise a magnetized zone. In addition, still in advantageous variants, the magnetic field of said magnetized zone can control an electronic component in order to output an electronic signal in relation to the angular position of the airspeed sensor and / or the rain sensor.

In addition, when the remote sensing system and the remote sensing device comprise a single control unit, the electronic signals can be analyzed by the single control unit. The present invention thus further simplifies and saves space and material cost over conventional remote sensing systems.

In addition, according to another advantageous aspect, the entire remote sensing system, in particular the remote sensing device, can be at very low energy. In an advantageous embodiment, it is therefore possible to use a small solar panel to power the device and the inventive system, which can be arranged for example outside the housing of the remote sensing device.

According to yet another preferred aspect of the remote sensing device according to the present invention, the transfer of the multi-spectral images can be done by hertzian transmission, preferably by Bluetooth.

The invention will be explained in more detail in the following by means of advantageous embodiments and by relying on the following accompanying figures, in which: - Figure 1 schematically illustrates an example of an embodiment of a remote sensing device according to the present invention, in cross sections according to a front view and a side view;

FIG. 2 diagrammatically illustrates an example of different wavelengths perceived by an elementary sensor of a matrix of elementary sensors; - Figure 3 schematically illustrates an example of an embodiment of the installation of a remote sensing device according to the present invention; - Figures 4a and 4b schematically illustrate the geometric perception acquired by the sensor of a remote sensing device according to an embodiment of the present invention;

- Figure 5 schematically illustrates a block diagram of an embodiment of a remote sensing device according to the present invention; and

- Figure 6 schematically illustrates an example of integration of a weather station according to an aspect of an embodiment of a remote sensing device on the present invention.

Figure 1 schematically illustrates, in a cross-section according to a front view (left in Figure 1) and a side view (right in Figure 1), respectively, an example of an embodiment of a remote sensing device 20 according to one aspect of the present invention. The remote sensing device 20 comprises a multi-spectral sensor 8 composed of a plurality of sensor elements or elementary sensors 8 ^, where the indices x and y represent the respective line or column of an elementary sensor in the matrix of the sensor. sensor 8, for example for lines, x = 0, 1, ..., n; and for columns, y = 0, 1, ..., p.

In addition, according to one aspect of the present invention, the matrix 8 of multi-spectral elementary sensors 8 is coupled to a single optical input channel which, in a preferred embodiment, can be realized by an optical element. 4, in the direction of the optical axis 5. The optic element 4 may preferably be an objective or simply a lens or any convergent type of optical element, in the following an objective 4 on the optical axis 5 , said box 21 may advantageously be hermetically sealed to light, and furthermore comprise an electronic card 3 integrating the elementary sensors 8 ^ and keeping them preferably at the focal length of the objective 4, on a wall of the box 21 opposite to the input or single optical path formed by the direction of the optical axis 5 of the lens 4.

In the case of the monitoring of agricultural crops, it appears advantageous to configure the matrix 8 of 8xy elementary sensors coplanarly. The electronic card 3 can therefore advantageously maintain the matrix 8 essentially on a focal plane of the objective 4, as is apparent from the cross section on the right-hand part of FIG. As illustrated in the view of the left-hand part of FIG. 1a, showing a cross section in a front view of the remote-sensing device 20, the elementary sensors 8 can be arranged according to a matrix 8 of predetermined size so that the dimension in the width direction can be about twice the focal length of the lens 4 in order to have a field of 90 °, and the perpendicular dimension in the direction of the height can correspond to the two extreme points of view 6 and 7 .

In addition, according to the present invention, the remote sensing device 20 frees itself from physical filters, as well as prism (s) and / or separator blade (s), since it comprises a matrix 8 of elementary sensors 8 ^ multi-spectral associated with the unique optical input channel. Each of the elementary sensors 8 ^ can thus integrate several filters adapted to different predetermined wavelength bands, adjustable according to the need of the measurement to be made. FIG. 2 is a graph showing schematically an exemplary and non-limiting selection of filters R, V, B in the visible range and IR in the near infrared, the abscissa of the graph representing the wavelengths of the different filters, and FIG. ordinate of the graph representing the normalized ratio of perceived values. Each of the elementary sensors 8 ^ of the matrix 8 may therefore advantageously comprise such a set of integrated filters.

As shown in FIG. 3, a remote sensing device 20 as described in the above embodiment may be mounted in a ground-based remote sensing system, i.e. top of a mast 2 of height H so as to aim along its optical axis 5 an area situated at a distance d ,, where i = 0, 1, ..., n, and thus cover a distance between d ₀ and d _n , corresponding to the extreme viewpoints 6, 7 of the remote sensing device 20 in a single shot, each interval between the distances d ₀ , di, ..., d _n thus covered corresponding to each of the n lines of the matrix of elementary sensors 8 ^. In practice, it is generally preferable to configure the optical path, that is to say the geometry of the objective 4, as well as the geometry of the matrix 8 so that d ₀ is of the order of 2 m, and that d _n be of the order of 50 m, for a mast height H of about 5 to 6 m minimum. As illustrated in FIG. 4a, the field of view can thus advantageously correspond to a triangle 11 of dimensions d _n * 2 d _n on a plane 1 of scanned cultures. In the above example, the triangle 11 can be of dimensions corresponding to about 50 m ^χ 100 m. It is then possible, by associating the remote sensing device 20 with a rotating means 12, to rotate the shooting of an angle equivalent to the angle of view to cover plan 1 in its entirety. Thus, as is apparent from FIG. 4a, the remote sensing device 20 mounted on the mast 2 at the position 0 can successively scan the triangle 1 1 of base AB, then, according to the direction of the desired rotation, hourly or counterclockwise, allotted by means of rotation 12, those of base BC, CD and DA or DA, CD and BC, respectively. Still in the above example, it is therefore possible to cover an area of the order of one hectare (100 m * 100 m) by successive rotations 90 ° of the remote sensing device 20 associated with the rotating means 12.

FIG. 4b represents a portion of the field 1 perceived for each 8 _xy multi-spectral elementary sensor which can thus display an elementary zone 9 of the triangle 11, where a notation similar to that of the elementary sensors 8 is used to identify the zones elementary 9 _np , with x = 0, 1, ..., n; and y = 0, 1, ..., p.

The block diagram of Figure 5 details an example of an embodiment of the operation of a remote sensing device according to the present invention. It may therefore be the remote sensing device 20 previously described embodiments or a variant or another embodiment. By keeping the notations and the reference signs of the previous embodiments, in the example detailed in FIG. 5, the shooting can be done along the optical axis 5 and can then be transmitted to the matrix 8 of elementary sensors. multi-spectral 8 ^ via a single input optical channel, here the objective 4. As indicated above, the electronic card 3 can support and drive the 8xy elementary sensors to extract information from spectral intensity of each of the scanned sources. This information can be transmitted to a general control unit 23 which can then transmit to a user this formatted information by means of a transmission unit 25, for example by radio, infrared or other wired or wireless network, in particular by Bluetooth .

Moreover, as is also apparent from FIG. 5, in a preferred embodiment, the general control unit 23 can also manage the rotation control, notably at the end of the shooting cycle, via position control units 27a to 27d.

As is evident from FIG. 5, in a preferred embodiment, the general control unit 23 can also retrieve orientation information 26. (compass) and / or tilt and / or albedo, in order to apply the necessary corrections to the information sent.

Given the low power consumption of the remote sensing device 20 according to the present invention, the energy required for these different units can be recovered by a power receiver 24, as shown in FIG. induction or solar collector. In this way, the remote sensing device 20 and the associated remote sensing system can be autonomous.

All the units described above in relation to the example illustrated in FIG. 5 can be preferably grouped together in the box 21, which can be mobile about a vertical axis of rotation, here the mast 2, as described in relation in Figure 3, and driven by a motor 35, also shown in Figure 5.

In addition, in an advantageous embodiment, as also apparent from FIG. 5, another part 22, which can be fixed, in particular with respect to the mast 2, can include an electronic unit 30 integrating a controller 31 able to drive the motor. 35 via a motor control unit 33 as a function of information from the position sensor 36 exchanged via an input / output unit 32, ie I / O. This electronic unit 30 can then receive energy via an external power supply cable 37 and send this energy back to the receiver 24 at high frequency by means of a power transfer unit 34. FIG. The rotating units (box) 21 and stationary 22 may be electrically connected and may be covered with electrically conductive areas 38, for example copper strips or other electrically conductive material, in order to provide a grounding and / or a Faraday cage to protect against lightning strikes, especially when the remote sensing device 20 is mounted on a mast 2 at least 5 or 6 m from the ground.

FIG. 6 represents another example of a preferred embodiment of the present invention, in which elements of a weather station are integrated in the remote sensing device 20, in particular to the structure of the box 21, which advantageously makes it possible to eliminate external cabling and use the same single 23 controller for these related functions. In an advantageous embodiment, this arrangement can therefore be combined with a ground remote sensing system fixed station as described above so as to achieve a station integrating remote sensing and weather. Thus, as also emerges from the exemplary embodiment illustrated in FIG. 6, in an advantageous variant of a preferred embodiment of the present invention, a rain gauge 40 with a cup 43, comprising a receptacle 44, can oscillate a magnet 41 in front of a magnetic sensor 42 arranged inside the cabinet 21 and can be connected to the single control unit 23.

Likewise, in another advantageous variant or in addition to the preceding variant, as also illustrated in FIG. 6, an anemometer 47 having one of its blades different from the other (s) may make it possible to measure the wind speed as well as its direction with the aid of a magnet 45 and a magnetic sensor 46, the latter can also be arranged inside the box 21 and be connected to the single control unit 23.

In summary, by its synergistic effect between the adoption of a single input optical channel and a matrix of multi-spectral elementary sensors, the present invention makes it possible to dispense with conventional systems combining several optical paths of conventional systems comprising multiple lenses or separating optics such as prisms or splitter plates, in which each resulting optical path is associated with a single spectral band. This results in a device and a remote sensing system improved and simplified compared to conventional devices. Finally, it will be appreciated by those skilled in the art that the various exemplary embodiments of the present invention described above may be combined with one another in order to realize other embodiments still within the scope of the present invention.

Claims

1. A remote sensing device (20), in particular for monitoring the evolution of agricultural crops, comprising: a single optical channel (4, 5), and a plurality of elementary sensors (8 ^) arranged in a matrix (8) ) of predetermined shape, wherein each elementary sensor (8 _xy ) is a multi-spectral sensor, in particular sensitive to a plurality of spectral bands, preferably at least on a spectral band in the visible range (B, V, R) and a near infrared spectral band (IR).

A remote sensing device (20) according to claim 1, wherein the matrix (8) of multi-spectral elementary sensors (8 ^) is provided with a geometry depending on the shooting shape.

Remote sensing device (20) according to one of claims 1 or 2, wherein the elementary sensors (8 ^) are arranged substantially coplanar.

A remote sensing device (20) according to any one of claims 1 to 3, wherein the single optical channel comprises an optical element (4), preferably of convergent type, and the matrix (8) of elementary sensors mu! Ti -spectral (8 ^) is arranged on a focal plane of said optical element (4).

The remote sensing device (20) of claim 4, wherein the width of the array (8) is about twice the focal length of said optical element (4).

The remote sensing device (20) according to one of claims 4 or 5, further comprising: a housing (21), preferably light-tight, provided such that the optical element (4) is mounted frontally on an opening of said housing (21), and an electronic card (3) mounted on a bottom of said housing (21) opposite said optical element (4) and supporting the matrix (8) of elementary sensors (8 ^).

The remote sensing device (20) according to claim 6, wherein the outside of the housing (21) is configured to provide a Faraday cage. 8. A remote sensing device (20) according to any one of the preceding claims, comprising one, in particular a single, control unit (23).

9. A remote sensing system comprising a remote sensing device (20) according to any one of claims 1 to 8 mounted on a mast (2).

A remote sensing system according to claim 9, wherein the remote sensing device (20) is rotatably mounted on the mast (2).

11. Remote sensing system according to one of claims 9 or 10, further comprising an air sensor (47).

The remote sensing system of any of claims 9 to 11, further comprising a rain sensor (40). The remote sensing system according to one of claims 11 or 12, wherein the remote sensing device (20) further comprises at least one magnetic sensor (42, 46), and wherein the air sensor (47) and / or the rainfall sensor (40) comprises a magnetic zone (41, 45).

The remote sensing system of claim 13, wherein the magnetic field of said magnet area (41, 45) controls an electronic component for outputting an electronic signal in relation to the angular position of the airspeed sensor (47) and / or the rain sensor (40).

The remote sensing system of claim 14, in combination with a remote sensing device according to claim 8, wherein the electronic signals are analyzed by the single control unit (23).