• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:

    公开号:FR3017764A1
    申请号:FR1400409
    申请日:2014-02-14
    公开日:2015-08-21
    发明作者:Pierre Luc Georgy
    申请人:Astrium SAS；
    IPC主号:
    专利说明:

    [0001] The present invention relates to a multispectral image capture apparatus, which comprises a filter wheel, and a method for collecting a multispectral image. There are several methods for capturing multispectral images using a single image capture device. One of them consists in using several spectral filters that are alternately interposed in the path of a light beam used to form each image that is captured. Such a multispectral image capture apparatus usually comprises: - an image forming optics, which is adapted to form an image in a focal plane; at least one two-dimensional image sensor, comprising a photosensitive surface which is bounded by a peripheral contour and located in the focal plane; a filter wheel, which comprises a plurality of spectral filters without overlaps between two adjacent filters; and a drive system, which is arranged to rotate the wheel about an axis of rotation, so as to bring each of the filters into the light beam. The filter wheel is commonly arranged so that the filters are fed into a pupil of the imaging optics. But it is also known to arrange the wheel so as to maintain the filters in a focusing plane of the light beam. Such a focusing plane may correspond to an intermediate image which is formed by the imaging optics. In this case, the focusing plane is commonly called the intermediate image plane. Usually, the filters are not exactly located in the intermediate image plane, but close to this plane, to prevent a fault that is present on the filter appearing distinctly in the image that is captured. Alternatively, the plane of focus may be the focal plane in which the photosensitive surface of the image sensor is located. The filter wheel is then located in close proximity to the photosensitive surface, but with an intermediate space to prevent the filters from rubbing the photosensitive surface. For such devices existing before the present invention, each image is captured by the sensor while only one of the filters covers its entire photosensitive surface, or covers a portion of the intermediate image plane that is optically conjugated with the photosensitive surface. entire image sensor. The rotation of the wheel then successively brings each filter into this position. FIGS. 1 and 2 illustrate such an apparatus, with the following meanings of the references which are indicated in these figures: multispectral image capture apparatus 1 objective 2 ZZ re-imaging system optical axis of the capture apparatus multispectral images F light beam forming the captured image 3 image sensor 31 photosensitive elements of the image sensor 3, corresponding to the image points that are acquired individually at each exposure of the image sensor C3 peripheral contour of the surface photosensitive image sensor 3 PF focal plane of the imaging optics, in which is placed the photosensitive surface of the image sensor 3 PI intermediate image plane, which constitutes a focusing plane for the light beam F, additional to the focal plane PF portion of the intermediate image plane PI which is optically conjugated by the re-imaging system 2 with the photose surface entire image sensor 3 C30 peripheral boundary of intermediate image plane portion 30 PI 4 filter wheel AA rotational axis of filter wheel 4 5 5 rotation drive system of wheel 4 41- 46 spectral filters carried by the wheel 4, for example six in number The objective 1 and the re-imaging system 2 together constitute the imaging optics. This optic may be centered along the Z-Z optical axis. For such a constitution of the image forming optics, the objective 1 forms an intermediate image, in the plane PI, of a scene which is contained in the input field of this optic, then the system of reflection. In turn, from this intermediate image, the imager 2 forms, in turn, the final image in the focal plane PF, which is captured by the sensor 3. The peripheral contour 15 C3 of the photosensitive surface of the sensor 3 is optically conjugated by the re-imaging system 2 with the limit C30 inside the intermediate image plane PI. The wheel 4 is disposed near the intermediate image plane PI, with the axis of rotation A-A of the wheel which is parallel to the optical axis Z-Z. In known apparatuses prior to the present invention, one of the filters 41-46 completely covers the portion 30 of the intermediate plane PI which lies within the limit C30, for certain predetermined positions of the wheel 4 around the axis AA. FIG. 2 shows the wheel 4 in the position in which the filter 41 is active for the image that is captured by the sensor 3. Adequate rotations of the wheel 4 make it possible to replace the filter 41 in this position 25 with one of the other filters 42-46. Thus, six images can be successively captured from the same scene that is contained in the input field of the imaging optics, to constitute a multispectral image of this six-component spectral scene. In the remainder of the present description, an image is called a set of read values of the photosensitive elements 31, which results from a single exposure of all the photosensitive elements 31 of the image sensor 3. The term Spectral image is reserved to designate each spectral component of a multispectral image. In a multispectral image capture apparatus which is in accordance with FIGS. 1 and 2, each image is directly a spectral image.
    [0002] But such a multispectral image capture device has the following drawbacks: the surface of each filter is large enough, and it is all the more difficult and expensive to produce a filter of sufficient optical quality, free of point defects and homogeneous as to its filtering characteristic, that its surface is large; the acquisition time of a complete multispectral image, consisting of several spectral image acquisitions for different positions of the filter wheel, can not be reduced below a minimum duration which is imposed by the speed of rotation of the filter wheel. But using a drive system that is faster, and therefore more powerful, causes greater vibrations that are troublesome elsewhere; the number of filters that are arranged in the wheel is limited by the size thereof, and a larger wheel also requires increasing the power of the drive system, to turn the wheel with an angular speed that remains the same ; - The capture of high definition images requires the use of sensors whose photosensitive surface is larger. The filters must themselves be larger, and therefore the same for the wheel that holds them; - The capture of high definition images requires even more to reduce the vibration of the device, including those produced by the rotary drive system of the filter wheel. Such a requirement therefore appears contrary to the increase in the power of the drive system; - the evolution of multispectral imaging missions, especially in the field of space imaging, is towards an increase in the number of filters; and - 5 - the total duration of capture of a multispectral image is sought as short as possible, both to increase the frequency of capture of multispectral images, to reduce artifacts caused by the camera shake, or by moving elements that are present in the acquired scene.
    [0003] From this situation and new needs in multispectral imaging, the present invention aims to reduce the aforementioned disadvantages and limitations of prior devices. More particularly, a first object of the invention is to increase the number of filters that are carried by the wheel, without increasing the size of the wheel as much as for a filter wheel as known from the prior art. A second particular object of the invention is to allow faster rotation of the filter wheel, without significantly increasing the power of its drive system.
    [0004] A third particular aim of the invention is to make it possible to grasp successive multispectral images more quickly. Finally, a fourth object of the invention is to reduce the effective duration between the capture times of two spectral images that are part of the same multispectral image, in order to reduce color artifacts that appear for moving objects in the field. input field of the imaging optics. To achieve at least one of these or other objects, a first aspect of the invention proposes to modify a multispectral image capture apparatus as recalled above, wherein the filters are held by the wheel parallel to and near the focal plane or the intermediate image plane of the imaging optics. According to the modifications introduced by the invention, at least one of the filters, called a narrow angular sector filter, has an angular extension which is smaller than the angular extent of the photosensitive surface of the image sensor when the filters are close to the focal plane. Alternatively, the angular extent of the narrow angular sector filter is smaller than that of a portion of the intermediate image plane which is optically conjugated with the entire photosensitive surface by the re-imaging portion of the formation optics. image. For this, the angular extensions are measured relative to the axis of rotation of the wheel. In other words, at least one of the filters that is carried by the wheel does not cover the entire optical field of the image sensor when an image is captured. The surface of this filter is thus reduced, so that its manufacture is facilitated and its cost is reduced, for the same requirement of optical quality of the filter. Indeed, it is easier to manufacture filters with reduced sizes, which are free of spot defects, flatness defects and inhomogeneities of spectral filtering, compared to filters which each cover the entire optical field of the sensor. picture. Preferably, the narrow angular sector filter may be located in the wheel between two other filters, and close to them so that for any position of the wheel about the axis of rotation such that at least a portion of the narrow-sector sector filter is effective for a part of the image contained within the peripheral contour of the photosensitive surface of the image sensor, then a portion of at least one of the other two filters is simultaneously effective for a another part of the same image contained within the peripheral contour of the photosensitive surface. In other words, portions of several filters are located simultaneously within the optical field of the image sensor. The image that is captured during an exposure of the sensor thus contains a part of this image that is captured through one of the filters, and also at least another part of the same image that is captured through another of the images. filters. A complete spectral image, which is uniformly filtered by only one of the filters, can be reconstructed by bringing together the parts of images which are related to this filter, and which were captured during the successive exposure of the image sensor. Preferably, the angular extension of the narrow angular sector filter and the respective angular extensions of the two other filters may be such that for at least one position of the wheel about the axis of rotation, respective portions of the narrow angular sector filter and the other two filters are simultaneously effective for three separate portions of the image contained within the peripheral contour of the photosensitive surface. More generally, it may be preferable for respective portions of a larger number of filters to be simultaneously in the optical field of the detector, in order to reduce the individual size of each filter. In addition, the filters are advantageously brought closer to each other in the wheel, with areas of the wheel that are minimal between two adjacent filters, to reduce the portion of the optical field of the image sensor which is masked by the zones of the wheel. wheel that are filter-free, at each exposure. Such an arrangement of the filters makes it possible to bring them closer to the axis of rotation of the wheel, so that the wheel can be smaller and lighter. At equal power of the rotational drive system of the wheel, it can rotate faster, or the rotational drive system can be reduced by maintaining an identical speed of rotation of the filter wheel. In simple embodiments of the invention, the respective angular extensions of the narrow angular sector filter and the two other filters which are adjacent with it in the wheel, with respect to the axis of rotation of the wheel and for the same radial distance from this axis of rotation, may be equal. In certain embodiments of the invention, the drive system can be adapted to bring the wheel to successive positions around the axis of rotation, and to immobilize it in each of these positions for at least one exposure time of the image sensor. In other embodiments of the invention, the drive system may be adapted to rotate the wheel continuously while multiple images are successively captured by the image sensor. In this case, and when the image sensor comprises a plurality of separate photosensitive elements adapted to operate each according to an acquisition sequence which comprises successively at least one signal accumulation phase and a reading phase of a accumulated signal, the angular extension of the narrow angular sector filter may advantageously be greater than an angle of rotation which is traveled by the wheel during the sum of a total duration of the acquisition sequence and a phase duration d additional accumulation. Thus, each photosensitive element of the image sensor can individually perform at least one complete image point value acquisition sequence, while this element is exposed to the light beam through the narrow angular sector filter.
    [0005] In various embodiments of the invention, the following improvements can be implemented, separately or by combining several of them: the narrow angular sector filter can have two straight edges which each extend radially with respect to the axis of rotation of the wheel.
    [0006] Its cutting is then facilitated, in a larger filter plate which is initially produced; the wheel may be provided with at least three filters respectively corresponding to three spectral filtering windows which are different; the filters can constitute several identical groups. In this case, the filters of the same group may be all neighbors in the wheel so that each group of filters is collected in one sector of the wheel without intercalation of a filter which belongs to another group; the apparatus may furthermore comprise a system for locating the position of the wheel around the axis of rotation; the wheel may comprise a pattern between two of the filters that are adjacent, so that a position of this pattern appears in an image that is grasped while respective portions of these two neighboring filters are simultaneously effective for separate parts of the image. image contained within the peripheral contour of the photosensitive surface of the image sensor; and the drive system and an image sensor controller can be adapted so that two images that are successively captured by the sensor have overlap between respective parts of these images that are captured through one and the same filters.
    [0007] The apparatus may include a spectral image reconstruction unit adapted to produce spectral images each corresponding to the entire photosensitive surface of the image sensor, each spectral image being produced as a juxtaposition of portions of the image sensor. images that are captured by the image sensor through the same filters during at least two different exposures, with a rotation of the wheel between these exposures. Such a reconstruction unit may be located near the image sensor, with a hardware connection that connects them to each other. Alternatively, the spectral image reconstruction unit can be moved away from the image sensor with a wireless transmission system that is provided to transmit the image data between the image sensor and the reconstruction unit. An apparatus which is in accordance with the invention can in particular be used for a spatial imaging application. In this case, it can be adapted to be on board an aircraft, a spacecraft or a satellite. An apparatus according to the invention can be adapted to obtain colorized images. Such a colorized image is constructed by combining a panchromatic image, i.e. that has been captured with a large spectral window, with images that have been captured with narrow spectral windows and included in the wide window. For this, three of the filters that are carried by the wheel and which respectively correspond to three different spectral filter windows, are the narrow angular sector filter and said two other filters already mentioned above. The wheel then comprises at least one additional spectral filter which has a broad spectral window including those of the narrow angular sector filter and said two other filters. This additional spectral filter itself has an angular extension which is greater than the angular extent of the photosensitive surface of the image sensor when the filters are close to the focal plane, or which is greater than the angular extension of the portion of the intermediate image plane which is optically conjugated with the entire photosensitive surface by the reimaging part of the image forming optics, the angular extent of the additional spectral filter being also measured with respect to the axis of rotation of the image wheel. The additional spectral filter is the panchromatic filter, and each panchromatic image can thus be captured during a single acquisition sequence that is executed by the image sensor while the wheel is immobilized. A second aspect of the invention provides a method of collecting a multispectral image, which comprises receiving at a station installed on Earth, image data relating to images captured by an apparatus according to the first aspect of the invention. , this aircraft being on board an aircraft in flight, a spacecraft located in space or a satellite in orbit when the images have been captured. The image data is then transmitted by electromagnetic radiation or laser signals from the aircraft, space vehicle or satellite to the station on Earth.
    [0008] Such a collection method may include the step of reconstructing the spectral images that together form the multispectral image. During this reconstruction step, each spectral image corresponding to the entire photosensitive surface of the image sensor, is produced as a juxtaposition of the image portions that are captured by the image sensor through one of the filters at the same time. at least two different exposures, with a rotation of the wheel between these exposures. Such a reconstruction step can be performed on board the aircraft, the spacecraft or the satellite, but it can be preferably performed on Earth from the image data that is received at the station.
    [0009] Finally, in order to obtain colorized images, the wheel is equipped with a panchromatic filter in addition to the three narrow spectral window filters introduced above according to the invention. The method then further comprises a colorization step in which spectral images that have been captured respectively through the narrow angular sector filter and said two other filters are combined with an image that has been captured with the additional spectral filter. Thus an enriched image is obtained, called colorized, which has a spectral information that is directly visible to an observer of this enriched image. Other features and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the accompanying drawings, in which: FIG. 1, already described, symbolically represents a data entry device; multispectral images as known before the invention, and which may be modified in accordance with the present invention; FIG. 2, already described, represents a filter wheel as known before the present invention; - Figures 3a to 3d show four filter wheels according to the present invention; and FIG. 4 illustrates a possible use of a multispectral image capture apparatus according to the invention. For the sake of clarity, the dimensions of the elements represented in these figures correspond neither to actual dimensions nor to ratios. real dimensions. In addition, identical references which are indicated in different figures designate identical elements or which have identical functions.
    [0010] In a multispectral image capture apparatus 10 as shown in FIG. 1, the filter wheel of FIG. 2 can be replaced by one of the wheels of FIGS. 3a to 3c, to apply the invention. It is understood that although the objective 1 and the re-imaging system 2 are each represented in the form of a single lens, they may have any constitutions, based on one or more lenses, of one or more mirrors, or possibly a combination of at least one lens and at least one mirror. For example, the wheel 4 of FIG. 3a can be used in the apparatus of FIG. 1. It comprises several filters referenced 41,... 46,..., Which are effective in transmission and which can have forms of cutting that are identical. Each filter may occupy an angular sector which is between two spokes coming from the axis of rotation A-A, and be between a hub of the wheel 4 and a circular peripheral edge thereof. The width of the angular sector of each filter, which is noted a in FIG. 3a, may be less than 15 ° (degree), or even less than 10 °, for example equal to about 4 °. In addition, two adjacent filters can be brought angularly to each other, as much as possible depending on the mode of maintenance of the filters on the wheel, but without overlap between them. In such an embodiment of the invention, at least two of the filters 41,... 46,... Are always superimposed simultaneously with the portion 30 of the plane PI, which corresponds to the image as captured by the sensor. 3. Such a superposition is illustrated in FIGS. 3a to 3c by indicating the limit C30 which is conjugated with the peripheral contour C3 of the photosensitive surface of the detector 3. Several modes of capture of a multispectral image can be used alternately, depending commands that are applied to the drive system 5 and the image sensor 3. According to a first operation of an apparatus according to the invention, the wheel 4 can be immobilized while each image is captured by the sensor 3, and turned between two seizures of successive images. For this, the images must be captured with respective exposure periods of the image sensor which are separated in time. Then, portions of images that belong to two images seized successively, corresponding to one of the filters, may advantageously have an overlap with respect to the observed scene. For this, the rotation of the wheel 4 between the two images is less than the width a of each of the angular sectors occupied by the filters 41-46. Thanks to such recoveries, the parts of images which are associated with the same filter, coming from images seized separately, can be easily combined in the form of a continuous spectral image. This then forms one of the components of the multispectral image.
    [0011] Typically, the covers may themselves have an individual angular width that is less than one-tenth of the width a. The rotation of the wheel 4 between two successive exposures of the image sensor 3 is less than that which is necessary with a filter wheel as shown in FIG. 2. The two successive exposures of the entire image sensor 3 can thus be executed with an intermediate waiting time which is shorter, so that the multispectral image is generally acquired more quickly. This overall acquisition time, which is reduced for the complete multispectral image, is particularly advantageous when the apparatus and the observed scene are moving relative to one another. Such a situation exists in particular for images of the Earth that are captured from a non-geostationary satellite, for example a satellite in low orbit. Moreover, it may be useful to know or confirm which of the filters 41-46 is effective for each part of an image as captured by the sensor 3. A first possibility for this is to use an additional system for locating the sensor. angular position of the wheel 4. Such systems are well known to those skilled in the art. They can be integrated in the drive system 5, or separated from it. Another possibility is to add patterns 40 on the wheel 4, at wheel locations that are located between neighboring filters. Since the wheel 4 is close to the intermediate image plane PI, each pattern 40 can appear distinctly in the image that is captured by the sensor 3, when the wheel 4 is in a position such that this pattern is in the 3. In the image captured, the pattern 40 makes it possible to precisely identify the position of the wheel 4, and to determine which filter has been effective in each part of the image. For example, each pattern 40 may be a hole that is drilled in the wheel 4, at a radial distance measured from the axis A-A which varies according to the two filters that are adjacent to this pattern (see Figure 3a). According to a second operation of an apparatus according to the invention, the wheel 4 can be driven continuously in rotation, with an angular speed which can be constant, but not necessarily. Such continuous operation reduces the vibrations that are generated by the wheel 4 and its drive system 5. In this case, for each image that is captured by the sensor 3, some photosensitive elements 31 of the sensor 3 may have been exposed. only partially to the light beam F through one of the filters. In other words, an edge of one of the filters 41-46, which is parallel to a radial direction of the wheel 4, may have encroached on the input section of the luminous flux in one of the photosensitive elements 31 during the first phase. accumulation of this element. The measurement of the luminous flux which is then produced by this photosensitive element 31 is disturbed, or even is not significant. It may then be advantageous to limit the speed of rotation of the wheel 4 so that each photosensitive element 31 can produce at least one luminous flux measurement at each passage of one of the filters 41-46 in the individual optical field. of this element, without a filter edge encroaching on this individual field. The worst case occurs when an edge of a newly arriving filter impinges on the optical field of one of the elements 31 just after that element has started a new acquisition sequence. Each filter may be sufficiently angularly extended so that the element 31 can finish the acquisition sequence already started, then Io completely execute the accumulation phase of the following acquisition sequence, before the end edge of the filter n ' arrives in turn in the optical field of the element 31. In other words, the width a of the angular sector which is occupied by the filter is advantageously greater than the angle of rotation which is traversed by the wheel 4 for a duration equal to the sum of the total duration of the acquisition sequence to be finished, and the duration of the accumulation phase of the following acquisition sequence. In known manner, the acquisition operation of a photosensitive element of the image sensor comprises an accumulation phase during which an electrical signal is accumulated in proportion to the luminous flux which is received during a fixed accumulation period, and then a read phase during which the amplitude of the accumulated signal is detected, and then the photosensitive element is reset. However, it is not essential that all the photosensitive elements 31 be exposed through each of the filters during a phase of complete accumulation at each turn of the wheel 4. Those photosensitive elements that have been validly exposed to the light beam F can be selected, and only the playback signals that have been produced by the photosensitive elements of this selection can be retained. Those photosensitive elements 31 that have not been validly exposed through one of the filters during a turn of the wheel 4, will preferably be exposed primarily through this filter during a subsequent turn of the wheel, or when a subsequent passage of the wheel with a filter of the same spectral characteristic. Optionally, a chronological order of the photosensitive elements may be adopted, so that at least some of the elements which are photosensitive execute the acquisition sequence of a wheel 4 can by the synchronized system. compared to transitions between filters. The patterns 40 to identify the angular position of the still to be used when a continuous rotation is imposed 5 drive 5. As for the operating mode with stop wheel 4 when an image is captured, it can be advantageous, also when the rotation of the wheel 4 is continuous while several images are seized in succession, the parts of images which are related to the same filter but which belong to images seized successively, have overlaps between them. In the filter wheel of FIG. 3a, each of the filters 41-46 has two straight edges which extend radially in the wheel 4. FIG. 3b shows another configuration for the filter wheel which is compatible with the invention. This other configuration can be deduced from that of FIG. 3a, by applying to the wheel a deformation by rotation around the axis AA, with an amplitude of rotation which is variable as a function of the radial distance measured from the axis AA. The filter wheel of FIG. 3b is obtained in this way, with a rotation deformation amplitude which progressively increases as a function of the radial distance. In the filter wheels of FIGS. 3a and 3b, all the filters may be different, that is, they correspond to transmission spectral windows which are different from one another. According to an alternative embodiment of the invention, identical filters may be cyclically repeated around the axis of rotation A-A in the same wheel. For example, the ordered series of filters 41 to 45 is repeated in the wheel of Figure 3c, progressively rotating about the axis A-A. For the two image capture operations that have been described above, with stop wheel 4 during each exposure of the sensor 3 or by continuously rotating the wheel 4 while several acquisitions are made, the spectral images are then reconstructed to 3. For this, for each of the filters 41-46, portions of images corresponding to this filter are taken from the images acquired successively by the sensor 3. These image parts are then combined into a single spectral image that corresponds to this filter. This spectral image preferably covers the entire optical field of the sensor 3, without 5 bands that would be missing between two neighboring image parts. To ensure that each spectral image is thus complete, it is advantageous to provide overlaps between image portions that have already been described. According to FIG. 4, the multispectral image capture device 10 can be embarked on board a satellite 11 which is in orbit around the Earth, denoted T. The optical axis ZZ of the aircraft 10 is pointing towards the area of the Earth's surface that one wants to observe. The image data, denoted D in the figure, which is produced by the image sensor at each exposure is transmitted to a receiving station 12 on Earth, either directly or via a relay satellite. One of the known modes for transmitting such data through the earth's atmosphere can be used, such as radio transmission or laser signal transmission. The reconstruction of the spectral images is performed by a dedicated unit that can be alternately on board the satellite 11, or on Earth. This second solution may be preferred to reduce the load and energy consumption of the satellite 11. In this case, the data D which is transmitted between the satellite 11 and the receiving station 12 relate to the images as captured by the sensor 3 For example, for a monitoring mission from space, especially from a geostationary satellite, a filter wheel which is in accordance with the invention and in Figure 3d may be used. References 41 to 43 still denote narrow angular sector filters, each corresponding to a transmission spectral window which is narrow. For this reason, the filters 41-43 are called monochromatic. For example, the filter 41 transmits the blue color, the filter 42 the green color, the filter 43 the red color, and so on. for any number of monochromatic filters. The filters 51 and 52 are said to be panchromatic because they correspond to a broad transmission spectral window, which may include the spectral windows of the monochromatic filters 41-43. Preferably, the panchromatic filters 51 and 52 are sufficiently large to each cover the entire optical field of the image sensor. The references C30-1 and C30-2 correspond to the limit C30 for two positions of the wheel 4, for each of which the panchromatic filter 51 or 52, respectively, is active for all the image which is captured by the sensor when the same acquisition sequence. Possibly, a single panchromatic filter can be provided in the wheel 4. An advantageous method of obtaining images or color video, using such a device, can then include the following steps: / 1 / the wheel 4 is d first immobilized in the C30-1 position, and the pointing of the optical axis ZZ to a target zone on the surface of the Earth can then be stabilized, for example for about ten seconds; / 2 / then the wheel 4 is rotated continuously so that the monochromatic filters 41-43 travel in front of the image sensor, preferably without exceeding the maximum speed which is defined by the angular width of each filter so that each photosensitive element the sensor can perform a complete acquisition sequence for each of the filters 41-43. The image sensor then performs several sequences of acquisition chained while the wheel 4 rotates; / 3 / the wheel 4 is stopped in the C30-2 position, and an acquisition of the target area in video is performed for a desired observation time, for example at least 10 minutes; then / 4 / the spectral images that were captured in step / 2 / are used to colorize the panchromatic image that was captured in step / 3 /. In the case of real-time monitoring, it is necessary to have the acquisition of colors before the video: step / 2 / is executed before step / 3 /. On the other hand, if the real-time visualization is not imperative, the acquisition of the colors can be carried out after that of the video: the step / 2 / can be executed between the steps / 3 / and / 4 /. The stabilization of the score can also be omitted in the latter case. In general, for such a color video surveillance method, the rotations of the wheel 4 which are carried out for the steps / 1 / to / 3 / can be in a constant direction, or with alternating round trips. . It is understood that the invention may be reproduced by adapting it with respect to the embodiments described above, while retaining at least some of the advantages mentioned. In particular, the following adaptations can be implemented: each filter can have any shape; the filters can be close two-to-two in the wheel so that several filters are always simultaneously in the optical field of the image sensor; the filters can occupy only a small part of the wheel, and the complementary part of the wheel can be dedicated to a function other than the spectral filtering; the filter wheel may be located just in front of the image sensor, since the photosensitive surface thereof is located at the focal plane of the image forming optics, which is a focusing plane of the light beam. In this case, it is not necessary for the optics to include a re-imaging system; the invention can be applied to filters that are effective in any spectral domains, as well as to any number of different filters. In particular, it may be advantageous for the case of filters of only two types, which are alternated in the wheel in the form of narrow angular sectors. Indeed, obtaining such narrow filters with an imposed quality is facilitated by the reduction of the individual surface of each filter; and finally, the invention is compatible with matrix image sensors which are commercially available. For example, for an airborne application, especially when the aircraft is embedded in a drone, a fast matrix sensor, that is to say that is capable of capturing images at a frequency of 120 Hz (hertz) or more, can provide at least ten multispectral images per second in the case of a dozen spectral bands.
    权利要求:
    Claims (18)
    [0001]
    CLAIMS1 Multispectral image capture apparatus (10), comprising: - image forming optics (1,
    [0002]
    2) adapted to form an image in a focal plane (PF); at least one two-dimensional image sensor (3), comprising a photosensitive surface limited by a peripheral contour (C3), and located in the focal plane (PF); a wheel (4) comprising a plurality of spectral filters (41-46), arranged to maintain said filters parallel to and in the vicinity of the focal plane (PF) or an intermediate image plane (PI) of the optical imaging (1, 2); and - a drive system (5), arranged to rotate the wheel (4) about an axis of rotation (A-A) so as to bring each of the filters (41-46) into the light beam (F); characterized in that at least one of the filters (41-46), referred to as the narrow angular sector filter, has an angular extension which is less than an angular extension of the photosensitive surface of the image sensor (3) when the filters are near the focal plane (PF), or which is less than an angular extension of a portion (30) of the intermediate image plane (PI) which is optically conjugated with the entire photosensitive surface by a re-imaging portion ( 2) of the image forming optics, the angular extensions being measured with respect to the axis of rotation (AA) of the wheel (4). 2. Apparatus according to claim 1, wherein the narrow angular sector filter is located in the wheel (4) between two other filters, and close to said two other filters so that for any position of the wheel around the axis of rotation (AA) such that at least a portion of the narrow angular sector filter is effective for a portion of the image contained within the peripheral contour (C3) of the photosensitive surface of the image sensor (3 ), a portion of at least one of said two other filters is simultaneously effective for another portion of the same image contained within the peripheral contour of the photosensitive surface.
    [0003]
    An apparatus according to claim 2, wherein the angular extension of the narrow angular sector filter and the respective angular extensions of said two other filters are such that for at least one position of the wheel (4) about the axis of rotation (AA), respective portions of the narrow angular sector filter and said two other filters are simultaneously effective for three separate portions of the image contained within the peripheral contour (C3) of the photosensitive surface.
    [0004]
    4. Apparatus according to claim 2 or 3, wherein respective angular extensions of the narrow angular sector filter and said two other filters, relative to the axis of rotation (AA) of the wheel (4) and for the same radial distance from said axis of rotation, are equal.
    [0005]
    5. Apparatus according to any one of claims 1 to 4, wherein the drive system (5) is adapted to bring the wheel (4) to successive positions about the axis of rotation (AA), and for immobilizing said wheel in each position for at least one exposure time of the image sensor (3).
    [0006]
    An apparatus according to any one of claims 1 to 4, wherein the drive system (5) is adapted to rotate the wheel (4) continuously while a plurality of images are successively captured by the image sensor (3). ); wherein said image sensor (3) has a plurality of photosensitive elements (31) separate and adapted to each operate in an acquisition sequence which comprises successively at least one signal accumulation phase and a read phase of an accumulated signal; and wherein the angular extent of the narrow angular sector filter is greater than an angle of rotation traveled by the wheel (4) during a sum of a total duration of the acquisition sequence and a phase duration of additional accumulation.-21 -
    [0007]
    Apparatus according to any one of the preceding claims, wherein the narrow angular sector filter has two straight edges which each extend radially with respect to the axis of rotation (A-A) of the wheel (4).
    [0008]
    8. Apparatus according to any one of the preceding claims, wherein the wheel (4) is provided with at least three filters (41-46) respectively corresponding to three filter spectral windows which are different.
    [0009]
    An apparatus according to claim 8 taken together with claim 3 or 4, wherein the three filters corresponding respectively to the three different spectral filtering windows are the narrow angular sector filter and said two other filters, and the wheel (4) comprises at least one additional spectral filter (51) having a spectral window which comprises the spectral windows of the narrow angular sector filter and said two other filters, and said additional spectral filter itself has an angular extension which is greater than the angular extent of the photosensitive surface of the image sensor (3) when the filters are close to the focal plane (PF), or which is greater than the angular extent of the portion (30) of the plane of intermediate image (PI) which is optically conjugated with the entire photosensitive surface by the re-imaging portion (2) of the imaging optics; further spectral filter being also measured relative to the axis of rotation (A-A) of the wheel (4).
    [0010]
    Apparatus according to any one of the preceding claims, wherein the filters (41-45) constitute several identical groups, and the filters of the same group are all neighbors in the wheel (4) so that each group of filters is collected in one sector of the wheel without intercalation of a filter that belongs to another group.
    [0011]
    Apparatus according to any one of the preceding claims, further comprising a system for locating the position of the wheel (4) about the axis of rotation (A-A).
    [0012]
    12. Apparatus according to any one of the preceding claims, wherein the wheel (4) has a pattern (40) between two of the filters (41-46) which are adjacent in said wheel, so that a position of said pattern appears. in an image that is captured while respective portions of said two neighboring filters are simultaneously effective for separate portions of the image contained within the peripheral contour of the photosensitive surface of the image sensor (3).
    [0013]
    Apparatus according to any one of the preceding claims, wherein the drive system (5) and a controller of the image sensor (3) are adapted so that two images that are successively captured by the sensor are overlapped. between respective parts of said images which are captured through a same filter (41-46).
    [0014]
    Apparatus according to any one of the preceding claims, further comprising: - a spectral image reconstruction unit adapted to produce spectral images each corresponding to the entire photosensitive surface of the image sensor (3), each spectral image being produced as a juxtaposition of image portions captured by the image sensor through a same filter (41-46) in at least two different exposures, with a rotation of the wheel (4) between said exhibitions.
    [0015]
    15. Apparatus according to any one of the preceding claims, adapted to be carried on board an aircraft, a spacecraft or a satellite (11).
    [0016]
    A method of collecting a multispectral image, comprising receiving at a station (12) installed on Earth (T), image data (D) relating to images captured by an apparatus (10) according to claim 14 said aircraft being on board the aircraft in flight, the space vehicle in space or the satellite (11) in orbit when the images are captured, and said image data being transmitted by electromagnetic radiation 7 7 6 4 -23- or laser signals from said aircraft, spacecraft or satellite to the station on Earth, directly or via a relay satellite.
    [0017]
    The method of claim 16, comprising a step of reconstructing spectral images together forming said multispectral image, during which each spectral image corresponding to the entire photosensitive surface of the image sensor (3) is produced as a juxtaposition of parts of images captured by the image sensor through the same filters (41-46) during at least two different exposures, with a rotation of the wheel (4) between said exposures, said reconstruction step 10 being performed on Earth (T) from the image data (D) received at the station (12).
    [0018]
    The method of claim 17, wherein the multispectral image pickup apparatus (10) is in accordance with claim 9, and the method further comprises a colorization step in which spectral images are captured respectively through the narrow angular sector filter and said two other filters are combined with an image captured with the additional spectral filter (51), to obtain an enriched image which has spectral information visible to an observer of said enriched image.
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    同族专利:
    公开号 | 公开日
    US20170180684A1|2017-06-22|
    EP3105924B1|2021-08-04|
    PL3105924T3|2022-02-07|
    DK3105924T3|2021-11-01|
    ES2895474T3|2022-02-21|
    CN106105189B|2017-10-03|
    CA2975335A1|2015-08-20|
    EP3105924A1|2016-12-21|
    WO2015120948A1|2015-08-20|
    CN106105189A|2016-11-09|
    JP2017514105A|2017-06-01|
    CA2975335C|2018-04-17|
    JP6125113B1|2017-05-10|
    FR3017764B1|2017-06-09|
    US9961308B2|2018-05-01|
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    法律状态:
    2015-02-26| PLFP| Fee payment|Year of fee payment: 2 |
    2016-02-25| PLFP| Fee payment|Year of fee payment: 3 |
    2017-02-24| PLFP| Fee payment|Year of fee payment: 4 |
    2018-03-01| PLFP| Fee payment|Year of fee payment: 5 |
    2019-02-20| PLFP| Fee payment|Year of fee payment: 6 |
    2020-02-25| PLFP| Fee payment|Year of fee payment: 7 |
    2021-02-25| PLFP| Fee payment|Year of fee payment: 8 |
    2022-02-01| PLFP| Fee payment|Year of fee payment: 9 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1400409A|FR3017764B1|2014-02-14|2014-02-14|APPARATUS FOR ENTERING MULTISPECTRAL IMAGES COMPRISING A FILTER WHEEL|FR1400409A| FR3017764B1|2014-02-14|2014-02-14|APPARATUS FOR ENTERING MULTISPECTRAL IMAGES COMPRISING A FILTER WHEEL|
    JP2016552276A| JP6125113B1|2014-02-14|2014-12-24|Multispectral imaging device with filter wheel|
    ES14824486T| ES2895474T3|2014-02-14|2014-12-24|Apparatus for capturing multispectral images comprising a filter wheel and method|
    CN201480073313.8A| CN106105189B|2014-02-14|2014-12-24|Multi-optical spectrum image collecting equipment including filter wheel|
    US15/118,136| US9961308B2|2014-02-14|2014-12-24|Multispectral image capture device comprising a filter wheel|
    CA2975335A| CA2975335C|2014-02-14|2014-12-24|Multispectral image capture device comprising a filter wheel|
    PCT/EP2014/079332| WO2015120948A1|2014-02-14|2014-12-24|Multispectral image capture device comprising a filter wheel|
    EP14824486.6A| EP3105924B1|2014-02-14|2014-12-24|Multispectral image capture device comprising a filter wheel and method|
    PL14824486T| PL3105924T3|2014-02-14|2014-12-24|Multispectral image capture device comprising a filter wheel and method|
    DK14824486.6T| DK3105924T3|2014-02-14|2014-12-24|APPARATUS FOR RECORDING MULTISPECTRAL IMAGES INCLUDING A FILTER WHEEL AND PROCEDURE|
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