Multi-modal imaging system

Abstract

The multi-mode imaging system according to the invention is suitable for use with a platform moving at a certain speed relative to the ground surface in order to obtain image and / or video data related to an area (A) on the ground surface, and it includes an imaging unit which comprises a detector (D) having a first section (B1) containing detector rows (DS) covered with a panchromatic filter (PAN), a second section (B2) containing detector rows (DS) each covered with a different spectral optical filter; a directing unit which enables the imaging unit to be directed to monitor the said area (A) and a control unit which is connected to the imaging unit and the steering unit; and which is arranged to include more than one operating mode and to control the said imaging unit and the steering unit in accordance with the activated operating mode.

Description

[0001] MULTI-MODAL IMAGING SYSTEM

[0002] Relevant Technical Field

[0003] The present invention relates to remote imaging systems that enable taking photographs and / or videos of the earth's surface, and in particular to a multi-mode imaging system developed for use with low earth orbit satellites (LEO), manned / unmanned aerial vehicles and similar platforms.

[0004] Prior Art

[0005] Systems used for obtaining satellite images from space can be classified into three categories: frame imaging systems, linear array scanners, and microwave radar imagers. Frame imaging systems are systems that expose the entire imaged area at once. The first high-resolution images of the Earth from space were taken with this type of photographic camera on the NASA Gemini 4 space shuttle in 1965. In microwave radar imagers, the microwave energy sent by the satellite platform with an antenna attached to the transmitter is received back by the receiver on the platform after being reflected from the ground surface. The system measures the time between the sent and received signals and converts these time values into distance data. This produces a different type of image, which is a record of the system's distance to objects. Linear array scanners, which can be classified as pushbroom designs, are used with a platform (aircraft, satellite, etc.) that moves according to the area in question so that it can scan the area to be viewed from above. With the movement of the platform, the area to be imaged is exposed in successive strips. Pushbroom systems do not contain any mechanical scanner, mirror or moving part. In these systems, each row of the image is directly imaged by a one-dimensional linear detector array placed in the focal plane.

[0006] Among the imaging systems mentioned above, Pushbroom systems are preferred because they have a simple geometric structure and the image they provide has high spatial resolution, and are widely used for remote imaging in satellite systems.

[0007] In their simplest form, pushbroom imaging systems consist of a linear detector array located in the focal plane. The projection of this array onto the ground is perpendicular to the direction of flight, and scanning is provided in the direction of the trajectory track with the forward movement of the platform on which the system is located. In this way, by combining the images taken in rows, image data for a wide area is obtained. These systems usually contain a panchromatic channel that combines the entire visible spectrum and a large number of different spectrum channels. The channels mentioned can be created using at least one detector array for each spectral band and an optical filter that passes the relevant spectral band.

[0008] With the spatial imaging systems in the state of the art, image data related to the ground surface can be obtained in different formats. However, in order to obtain both video and image with these systems, the optical path is generally divided into two; this causes the light intensity to be halved and the signal-to-noise ratio to decrease. At the same time, the need to use a second detector in the optical system arises.

[0009] Object of the invention

[0010] The object of the present invention is to develop a multi-mode imaging system and method suitable for use with LEO satellites, drones and similar platforms.

[0011] Another object of the present invention is to develop a multi-mode imaging system and method that enables the acquisition of panchromatic and / or multi-spectral image and / or video data with a single detector array.

[0012] Definition of the figures

[0013] Exemplary applications of the imaging system developed with the present invention are shown in the attached figures and from these figures;

[0014] Figure 1 is an exemplary representation of the detector arrangement of the imaging system according to the present invention.

[0015] Figure 2 is an exemplary representation of the area on the ground surface scanned by the detector rows along with the platform movement.

[0016] Figure 3 is an exemplary representation of the detector arrangement of an exemplary embodiment of the invention, showing its placement according to the platform movement and the imaged area.

[0017] The elements in the figures are referenced one by one and the correspondences of these elements are given below:

[0018] Detector (D)

[0019] First section (B1)

[0020] Second section (B2)

[0021] Detector row (DS)

[0022] Panchromatic filter (PAN)

[0023] First filter (F1) Second filter (F2)

[0024] Third filter (F3) Nthfilter (FN) Filter that passes the blue light spectrum (B) Filter that passes the green light spectrum (G) Filter that passes the red light spectrum (R) Filter that passes the near infrared light spectrum (NIR) Area (A) Direction of movement (1)

[0025] Detailed description of the invention

[0026] With the present invention, a multi-modal imaging system is developed to solve the above- mentioned technical problems.

[0027] The imaging system according to the invention has been developed to be used with a LEO satellite, drone or similar platform moving at a certain speed relative to the ground surface. The system in question comprises at least one imaging unit located on the platform, at least one directing unit that allows the imaging unit to be directed to monitor an area (A) to be viewed [the directing unit can perform this operation by directing the satellite or moving the imaging unit relative to the satellite], at least one control unit connected to the imaging unit and the directing unit.

[0028] The imaging unit comprises a detector (D) divided into a first section (B1) configured to acquire panchromatic image data and a second section (B2) configured to acquire multi-spectral image data. Each of the first section (B1) and the second section (B2) comprises at least two detector rows (DS). The detector rows (DS) are the sub parts of the detector (D) that are of equal size, as shown symbolically in Figure 1. The detector rows (DS) are in the form of a rectangle, with long edges positioned perpendicular to the platform's direction of movement (1) and short edges positioned parallel to the platform's direction of movement (1), and the short edges mentioned are quite small compared to the long edges. The first section (B1) of the detector (D) is covered with a panchromatic filter (PAN). Each detector row (DS) in the second section (B2) of the detector (D) is covered with a different spectral optical filter (F1-FN). The mentioned panchromatic filter (PAN) transmits all visible wavelengths of light, while preventing the passage of light outside the visible band. Each of the mentioned spectral optical filters (F1-FN) is arranged to transmit a different spectrum range from each other. In a preferred embodiment, said first section (B1) is at least half the size of the total area of the detector (D), preferably covering a bigger part of the total area of the detector (D).

[0029] An exemplary implementation of the detector (D) is shown in Figure 1. In Figure 1 , there are two representations of the same detector (D), with the placement of the detector rows (DS) on the left and the placement of the filters on the right. In the exemplary implementation, the first section (B1) and the second section (B2) each contain a plurality of detector rows (DS). The entire first section (B1) is covered by a panchromatic filter (PAN), while the second section (B2) contains N detector rows (DS) covered by a first filter (F1), second filter (F2), third filter (F3) ... and Nthfilter (FN), respectively. Light coming from an area (A) on the ground surface that is desired to be imaged falls on the surface of the detector (D) covered with the mentioned filters. The filters (PAN, F1 , F2, F3, ... FN) located on the detector (D) ensure that a certain part of the incoming light reaches the detector (D). Thus, the parts of the detector (D) covered with different filters create different image data for the imaged area (A). The filters mentioned (PAN, F1, F2, F3, ... FN) are positioned perpendicular to the direction of movement (1) of the platform in such a way that the area to be imaged (A) enters the field of view of each of the filters in sequence, with the movement of the platform. Therefore, in the implementation shown in Figure 1 , an area to be imaged (A) will first enter the field of view of the detector rows (DS) covered with the Panchromatic filter (PAN) and then the detector rows (DS) covered with the first filter (F1), the second filter (F2), the third filter (F3) ... and the Nthfilter (FN) respectively.

[0030] Figure 2 shows two exemplary representations of the area (A) on the ground surface, that the detector rows (DS) on the platform will scan in the direction of the platform’s movement (1). The image on the left in Figure 2 shows the area imaged by a single detector row (DS), while the image on the right shows the area imaged by a detector (D) containing four detector rows (DS).

[0031] Figure 3 shows an exemplary embodiment of the invention. In said embodiment, the second section (B2) of the detector (D) is divided into the most commonly used spectral ranges of the visible light spectrum. In this embodiment, each of the first section (B1) and the second section (B2) of the detector (D) contains four detector rows (DS), and the second section (B2) of the detector (D) is covered with a filter passing the blue light spectrum (B), a filter passing the green light spectrum (G), a filter passing the red light spectrum (R), and a filter passing the near-infrared light spectrum (NIR), respectively. The area (A) shown in Figure 3 will first enter the field of view of the panchromatic filter (PAN) and then the filters in the second section (B) sequentially, with the movement of the platform. Therefore, it becomes possible to obtain images with different spectrum characteristics for the desired area (A) with the same detector (D). The first section (B1) covered with the panchromatic filter (PAN) has a wide area, allowing a wide frame area to be imaged in each exposure. Therefore, it will be able to image the entire area (A) in question in a single exposure. In the second section (B2), the detector rows (DS), each covered with a different spectral filter, are in the form of a very narrow rectangle, so they can image the area to be imaged (A) in rows.

[0032] The control unit is arranged to include multiple operating modes for acquiring different image data, each having different characteristics of the area to be imaged (A), and to control said imaging unit and directing unit in accordance with the activated operating mode. The control unit is arranged to comprise at least a first operating mode that provides the acquisition of a multi-spectral video of the relevant area (A); and is arranged to activate the first section (B1) of the detector (D) to get the video image of the relevant area (A), deactivate the second section (B2) of the detector (D), control the directing unit to provide the tracking of the area (A) by the detector (D), during a first time interval, and thus provide the acquisition of panchromatic video data of the relevant area (A); and to deactivate the first section (B1) of the detector (D), activate the second section (B2) of the detector (D) to take a pushbroom image of the area (A), deactivate the directing unit during a second time interval that follows the first time interval and is shorter than the first time interval, and thus enable the acquisition of multi-spectral image data for the area of interest (A), and to provide multi-spectral video data for the area (A) by combining the received panchromatic video data with the multi-spectral image data, when the first operating mode is activated.

[0033] When the first operating mode is activated, the control unit controls the imaging unit and the directing unit to obtain multi-spectral video data regarding the area (A) to be displayed. When this mode is activated, the control unit divides the duration that the area (A) is within the field of view of the imaging unit into two time intervals, named as the first time interval and the second time interval. In the first time interval, the first section (B1) is active. The first (B1) section, which contains at least two detector rows (DS) and is covered with a panchromatic filter, takes the video image of the area during the first time interval. The directing unit, which is active during the first time interval, ensures that the field of view of the first section (B1) is fixed to the area in question (A) during said first time interval. Thus, panchromatic video data of the area (A) is obtained. During the second time interval following the first time interval, the directing unit is inactive. Therefore, the detector's (D) field of view changes with the movement of the platform. In this time interval, the first section (B1) is in passive state and the second section (B2) is in active state. With the movement of the platform, each detector row (DS) in the second section (B2) is provided to get image data for the relevant area (A). Each detector row (DS) receives image data for a separate spectrum band of the area (A). By combining this data with the panchromatic video data, multi-spectral video data is obtained.

[0034] In a preferred embodiment of the invention, said control unit also comprises at least a second operating mode that enables the acquisition of multi-spectral image data related to the area (A) to be imaged. The control unit is arranged to: deactivate the directing unit, activate one or more detector rows (DS) of the first section (B1) of the detector (D) which are closest to the second section (B2) of the detector and deactivate the remaining section, activate the second section (B2) of the detector (D) and to obtain multi-spectral image data of the area (A) by combining the image data received by each detector row (DS) in the active position when the second operating mode is activated.

[0035] With the specified process steps, multi-spectral image data of the area (A) is obtained with the pushbroom technique.

[0036] In a preferred embodiment of the invention, said control unit also comprises at least a third operating mode that enables the acquisition of panchromatic image data related to the area (A) to be imaged. In this embodiment, the control unit is configured to; deactivate the directing unit, deactivate the second section (B2) of the detector (D), activate the first section (B1) of the detector (D) and thus, together with the movement of the platform, to ensure that the temporal and spatial high-resolution panchromatic image data of the area (A) is acquired by the first section (B1). when the said third operating mode is activated. With the specified process steps, panchromatic image data of area (A) is obtained with the pushframe technique.

[0037] In a preferred embodiment of the invention, the control unit also includes a fourth operating mode that enables the acquisition of panchromatic video data related to the area (A) to be displayed. In this embodiment, the control unit is configured to; control the directing unit by tracking the location and ensuring that the area (A) is monitored by the detector (D), deactivate the second section (B2) of the detector (D), activate the first section (B1) of the detector (D) to take the video image of the relevant area (A), thus enabling the acquisition of panchromatic video data related to the area (A), when the said fourth operating mode is activated.

[0038] In an exemplary implementation of the invention, the control unit is integrated with a communication unit and the operating mode to which the control unit will switch is determined in line with the commands coming from the ground.

[0039] The system in question is preferably positioned on a platform that is a low earth orbit (LEO) satellite and moves at a certain speed relative to the ground surface. The system in question provides the acquisition of multispectral and / or panchromatic image and / or video data related to a region of the ground surface that is desired to be imaged, together with the movement of the platform on which it is positioned. It is possible to obtain multispectral I hyperspectral I ultraspectral image data by increasing the number of filters related to different spectrum ranges in the detector.

Claims

CLAIMS1. A multi-mode imaging system suitable for use with a platform moving at a certain speed relative to the ground surface, to obtain image and / or video data regarding an area (A) on the ground surface comprising; at least one imaging unit having a detector (D) with a first section (B1) comprising at least two detector rows (DS) covered with a panchromatic filter (PAN), a second section (B2) comprising at least two detector rows (DS), each covered with a different spectral optical filter, at least one directing unit that allows the imaging unit to be oriented to monitor said area (A), and at least one control unit which is in connection with the imaging unit and the directing unit; and which is arranged to have more than one operating mode and is arranged to control said imaging unit and the directing unit in accordance with the activated operating mode, wherein, the imaging system is characterized by comprising the said control unit which has at least a first operating mode, that enables obtaining a multi-spectral video of said area (A) and which is arranged in such a way that, when said first operating mode is activated: it will activate the first section (B1) of the detector (D) to take the video image of the relevant area (A), it will deactivate the second section (B2) of the detector (D), it will control the directing unit to provide the tracking of the area (A) by the detector (D), during a first time interval, and thus provide the acquisition of panchromatic video data of the relevant area (A); and it will deactivate the first section (B1) of the detector (D), it will activate the second section (B2) of the detector (D) to take a pushbroom image of the area (A), it will deactivate the directing unit during a second time interval that follows the first time interval and is shorter than the first time interval, and thus enable the acquisition of multi-spectral image data for the area (A), and it will provide multi-spectral video data for the area (A) by combining the received panchromatic video data with the multi-spectral image data,2. An imaging system according to claim 1 ; comprising said control unit which has at least one second operating mode that enables obtaining a multi-spectral image data related to the area (A) to be imaged and which is arranged in such a way that, when said second operating mode is activated: it will deactivate the directing unit, it will activate one or more detector rows (DS) of the first section (B1) of the detector (D) closest to the second section (B2) of the detector (D) and deactivate the remaining part, it will activate the second section (B2) of the detector (D) and it will obtain multi-spectral image data related to the area (A) by combining the image data received by each detector row (DS) in active position.

3. An imaging system according to any of Claims 1 or 2; comprising said control unit which has at least one third operating mode that provides for receiving panchromatic image data related to the area (A) to be imaged and which is arranged in such a way that, when said third operating mode is activated, it will deactivate the directing unit, it will deactivate the second section (B2) of the detector (D), it will activate the first section (B1) of the detector (D) and thus, together with the movement of the platform, it will enable the acquisition of temporal and spatial high-resolution panchromatic image data of the area (A) by the first section (B1).

4. An imaging system according to any of the preceding claims comprising said control unit which has at least one fourth operating mode that provides for receiving panchromatic video data related to the area (A) to be imaged and which is arranged in such a way that, when said fourth operating mode is activated, it will control the directing unit by tracking the location and ensuring that the area (A) is monitored by the detector (D), it will deactivate the second section (B2) of the detector (D), it will activate the first section (B1) of the detector (D) to take the video image of the relevant area (A), thus will enable the acquisition of panchromatic video data related to the area (A).

Images