Scanner module and method

Abstract

There is disclosed a scanner module (10) and method of scanning by an airborne or spaceborne platform. The scanner module (10) may have a base (12) which may be shaped to be attached to the platform. A pivotable structure (14) is pivotally coupled to the base (12) about a pivot axis (16) to be pivotally moveable about the pivot axis (16) in relation to the base (12). The pivotable structure (14) may include or hold one or more of a camera (38), a scanner, an imager, and an optical assembly. An actuator (18) is capable of pivoting the pivotable structure (14) in a first direction (24) about the pivot axis (16) and in a second and opposite direction (26). The actuator (18) is arranged to pivot the pivotable structure ( 14) at a near-constant angular speed for at least a portion of its pivotal movement.

Description

[0001] SCANNER MODULE AND METHOD

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application claims priority from United Kingdom patent application number 2403089.2 filed on 4 March 2024, which is incorporated by reference herein.

[0004] FIELD

[0005] The present disclosure relates to the field of space optics, and more particularly to airborne or satellite remote sensing performed with a scanning optical imaging sensor.

[0006] BACKGROUND

[0007] Mechanical scanning of Earth’s surface by remote sensing satellites were the norm just a few decades ago, but progressively dropped out of favour in the visual and near infrared regions with the advent of charge-coupled device (CCD) linear arrays. The failure of the Landsat-7 scanning mechanism in 2003 further weakened the case argued by proponents of mechanical scanning.

[0008] Shortly afterwards, the NewSpace revolution was born into the era of large imaging arrays. This has brought about reductions in form factor, mass, and cost of spaceborne imaging systems. Pushbroom-related imaging techniques have become the workhorse for optical remote sensing by small satellites such as the CubeSat class.

[0009] These techniques use the forward motion of the satellite in low or medium Earth orbit to scan the surface with a linear array of detectors directed in a cross-track direction of satellite motion, much like a document scanner scans a document. Different detectors may accomplish pushbroom-type imaging i.e., linear arrays, matrix (2D) detectors or time delay integration (TDI) detectors. The primary drawback of these techniques is the limited swath they afford. The swath width is constrained to the field of view of the optical system i.e., the optics and the length of the imaging detector in the cross-track direction determines swath width. With these pushbroom-type systems, the swath width is a constant width across the direction of travel of the satellite and it is “pushed” along the earth’s surface as the satellite travels. This has the drawback that it only covers a narrow strip of ground with each orbit of the satellite. Despite their loss of favour in recent years, various mechanisms and means of scanning have been proposed and / or employed to increase the imaged swath.

[0010] Driven oscillating scanners, for example electric motor driven oscillators, are used onboard satellite and airborne platforms. They can attain virtually any desired scanning speed profile. However, they require careful design, for example to mitigate cogging, and precise control. Furthermore, they actively consume power to reverse scanning direction and to match the required scanning speed profile.

[0011] Resonant scanners are sometimes used onboard satellite and airborne platforms due to relatively low power usage even under high-speed scanning at high operational duty cycle or continuous operation. Resonant scanners typically present a sinusoidal positional and speed profile. The angular position may for example follow a simple sinusoidal pattern, oscillating back and forth around the zero-point, which is often the nadir point.

[0012] In order to collect sufficient light under high-speed scanning operations, TDI (Time Delay Integration) imaging is often preferred. However, TDI imaging degrades severely when performed under highly variable scanning speeds such as a typical resonant scanner with a sinusoidal rotational speed profile.

[0013] The applicant considers there to be room for improvement.

[0014] The preceding discussion of the background is intended only to facilitate an understanding of the present disclosure. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

[0015] SUMMARY

[0016] In accordance with an aspect of the present disclosure there is provided a scanner module for an airborne or spaceborne platform, the scanner module comprising: a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform; a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more of a camera, an imager, a scanner, a mirror, and an optical assembly; an actuator capable of pivoting the pivotable structure in a first direction about the pivot axis from a first angular position towards a second angular position and / or back from the second angular position towards the first angular position in a second and opposite direction, wherein the actuator is arranged to actuate the pivotable structure so as to pivot at a nearconstant angular speed for at least a portion of its pivotal movement.

[0017] The scanner module may have a disengaged state and an engaged state. In the engaged state the scanner module may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. In the disengaged state the scanner module may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base.

[0018] The disengaged state of the scanner module may be provided by free pivotal movement of the pivotable structure between a first and a second biasing device. The pivotable structure may be arranged to bounce back and forth between the first and second biasing devices. During its pivotal movement the pivotable structure may pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices that may provide the engaged state of the scanner module. The biasing devices may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base.

[0019] The actuator may be arranged to apply a torque for initiating pivotal movement of the pivotable structure in one of the first and second directions.

[0020] The actuator may be configured to apply a pulsed torque for initiating pivotal movement of the pivotable structure in one of the first and second directions.

[0021] The actuator may be configured for driving the pivotable structure to steady state motion.

[0022] The actuator may apply a torque for maintaining pivotal movement of the pivotable structure by replacing dissipated energy.

[0023] Reversal of pivotal movement of the pivotable structure may be attained by way of a biasing arrangement which may also be termed a passive biasing arrangement. Passive biasing or the biasing arrangement may be provided, e.g., by one or more spiral torsion springs, coiled springs, or non-linear springs.

[0024] The scanner module may include at least one torsion spring which may be arranged as a passive biasing device that can reverse pivotal movement of the pivotable structure in relation to the base. The present disclosure may implement one or more magnets and / or one or more compression springs or other types of springs as biasing devices. Any one or more of these may form part of a biasing arrangement, e.g., to facilitate pivotal movement of the pivotable structure.

[0025] The biasing arrangement may further be configured to apply near-zero torque during the nearconstant angular speed portion of the pivotal movement of the pivotable structure, thereby enabling the pivotable structure to pivot with a near-constant angular speed and a near-zero angular acceleration (e.g., in relation to the base).

[0026] The actuator may be arranged to oscillate or resonate the pivotable structure. The actuator may be arranged to swing or pivot the pivotable structure back and forth, or from one side to the other.

[0027] The actuator may be arranged to apply near-zero torque during the near-constant angular speed portion of the pivotal movement of the pivotable structure. The actuator may enable the pivotable structure to pivot with a near-constant angular speed and a near-zero angular acceleration.

[0028] The scanner module may include a clutch which has a disengaged state and an engaged state. In the engaged state the clutch may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. In other words, in the engaged state, the clutch may slow down pivotal movement of the pivotable structure in relation to the base, or the clutch may in some instances speed up movement of the pivotable structure in relation to the base, e.g., once the direction of movement is reversed. In the disengaged state, the clutch may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base.

[0029] The clutch may include a projection that pivots with the pivotable structure during the disengaged state, until the projection engages (or comes into contact) with a stop formation which causes the clutch to engage and to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. The stop formation may, for example, be provided on the base.

[0030] The scanner module may include a first stop formation for engaging the clutch during pivotal movement of the pivotally moveable structure in the first direction. A second stop formation may be provided for engaging the clutch during pivotal movement of the pivotally moveable structure in the second and opposite direction. The projection of the clutch may pivot with the pivotable structure during the disengaged state of the clutch in either of, or both of, the first and second directions of pivotal movement of the pivotable structure.

[0031] The clutch may include, or be connected to, a biasing arrangement or a biasing device. The biasing arrangement or biasing device may be configured to decelerate and / or accelerate pivotal movement of the pivotable structure e.g., when the clutch is in its engaged state. In other words, the biasing arrangement may slow down pivotal movement of the pivotable structure in relation to the base, or the biasing arrangement may in some instances speed up movement of the pivotable structure in relation to the base, e.g., once the direction of movement is reversed.

[0032] The near-constant angular speed of the pivotable structure may be facilitated by the disengaged state of the clutch.

[0033] The clutch may be configured to facilitate reversal of the direction of pivotal movement of the pivotable structure.

[0034] The scanner module may include one or more centring biasing device(s) for centring the pivotable structure in a neutral position in relation to the base.

[0035] The biasing arrangement or centring biasing device(s) may include one or more springs such as torsion springs, coil springs or the like. As an alternative to springs, one or more magnets may be implemented to facilitate biasing of one component of the scanner module relative to another component of the scanner module.

[0036] The scanner module may further include a counterweight. The counterweight may be pivotally coupled to the base about the pivot axis so as to be pivotable independently of the pivotable structure in relation to the base.

[0037] The counterweight may be a spindle, or it may be shaped like a spindle. The counterweight may also be termed a counter-mass. The counterweight may have a major axis which may, for example extend along the pivot axis in use. The counterweight or spindle may have a disc-shaped portion that extends radially from the pivot axis in use. In other words, the disc-shaped portion may extend radially from a major axis of the counterweight. However, the counterweight may also have other suitable shapes such as oval, rounded, rectilinear, rectangular, triangular, or any other shape. The scanner module may include a clutch which has a disengaged state and an engaged state. In the engaged state, the clutch may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the counterweight. In other words, in the engaged state, the clutch may slow down pivotal movement of the pivotable structure in relation to the base, or the clutch may in some instances speed up movement of the pivotable structure in relation to the base, e.g., once the direction of movement is reversed. In the disengaged state the clutch may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base.

[0038] The clutch may include a projection that pivots with the pivotable structure during the disengaged state, until the projection engages (or comes into contact) with a stop formation. The stop formation may be provided on the counterweight. Engagement or contact with the stop formation by the projection may cause the clutch to engage and to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. In other words, in the engaged state, the clutch may slow down pivotal movement of the pivotable structure in relation to the base, or the clutch may in some instances speed up movement of the pivotable structure in relation to the base, e.g., once the direction of movement is reversed.

[0039] The scanner module may include a first stop formation for engaging the clutch during pivotal movement of the pivotally moveable structure in the first direction. A second stop formation may be provided for engaging the clutch during pivotal movement of the pivotally moveable structure in the second and opposite direction. The first and second stop formations may, e.g., be provided on the counterweight.

[0040] The counterweight may be arranged such that if the pivotable structure is operatively pivoted by the actuator, the counterweight automatically reacts by pivoting in an opposite direction to the pivotable structure so as to counteract a substantial portion of angular momentum of the pivotable structure and any components that are attached thereto, during pivotal movement thereof.

[0041] The counterweight may be arranged such that if the pivotable structure is operatively pivoted by a biasing arrangement or passive biasing arrangement, the counterweight automatically reacts by pivoting in an opposite direction to the pivotable structure so as to counteract a substantial portion of angular momentum of the pivotable structure and any components that are attached thereto, during pivotal movement thereof.

[0042] The scanner module itself may further be operable in a disengaged state and in an engaged state. In the engaged state of the scanner module, the scanner module may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. In its disengaged state, the scanner module may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base. In other words, in the engaged state, the scanner module may slow down pivotal movement of the pivotable structure in relation to the base, or the scanner module may in the engaged state, in some instances, speed up movement of the pivotable structure in relation to the base, e.g., once the direction of movement is reversed.

[0043] The disengaged state of the scanner module itself may be provided by free pivotal movement of the pivotable structure between a first and a second biasing device. The pivotable structure may be arranged to bounce back and forth between the first and second biasing devices. During its pivotal movement the pivotable structure may pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices that may each or both provide an engaged state of the scanner module. The biasing devices may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base (i.e., in an engaged state of the scanner module itself).

[0044] The disengaged state of the scanner module may alternatively, or in addition, be provided by a non-linear torsion spring between the pivotable structure and the base. Pivotal movement for a portion of the spring deflection with a near zero-spring constant may provide the disengaged state of the scanner module, and the engaged state may be provided by the torsion spring when it deflects beyond a certain threshold.

[0045] The actuator may be an electric motor or another type of device that can pivot the pivotable structure. For example, one or more magnets or electromagnets may be implemented. The actuator may also include one or more electric motors, magnets, or electromagnets.

[0046] The actuator may include one or more permanent magnet / s mounted on one of the base and the pivotable structure. The actuator may include one or more electromagnet / s mounted on the other of the base and the pivotable structure.

[0047] The actuator may include one or more permanent magnet / s mounted on one of the base, the pivotable structure, and the counterweight. The actuator may, additionally or alternatively include one or more electromagnet / s mounted on another of the base, the pivotable structure, and the counterweight.

[0048] The electric motor and / or electromagnet(s) may be arranged to be powered by a power source onboard the airborne or spaceborne platform. The actuator may include one or more permanent magnets mounted on one of the base and the counterweight. The actuator may include one or more electromagnets mounted on the other of the base and the counterweight.

[0049] The actuator may be arranged to pivot the pivotable structure in relation to the base. Alternatively, or in addition, the actuator may be arranged to pivot the pivotable structure in relation to the counterweight, or to pivot the counterweight in relation to the base. In other words, the actuator may be arranged to pivot any one of the pivotable structure and the counterweight relative to each other, or relative to the base. Pivotal movement of these components may be performed about the pivot axis, or about a major axis of the scanner module.

[0050] The actuator may be arranged to pivot the pivotable structure in the first direction from the first angular position to the second angular position. The pivotable structure and / or counterweight may be arranged to automatically return back from the second angular position to the first angular position in the second and opposite direction. In other words, the actuator may be arranged to pulse, actuate or move the pivotable structure in one direction after which it may return by itself to again be pulsed, actuated or moved by the actuator.

[0051] The pivotable structure may be shaped and / or configured so as to have a camera, a scanner, or other optical equipment attached thereto, or the pivotable structure may include or hold the camera, scanner, imager, an optical assembly (e.g., having one or more lenses), or other optical equipment in use. One or more mirrors, lenses or other imaging equipment may for example be mounted to the pivotable structure so as to pivot therewith in use (e.g., when actuated by the actuator).

[0052] The actuator may be arranged to oscillate the pivotable structure or the counterweight. Alternatively, the actuator may be arranged to pivot the pivotable structure or the counterweight following a regular pattern of angular movement, or an irregular pattern of angular movement. The actuator may pivot the pivotable structure at a constant angular speed, i.e., with near zero angular acceleration for at least a portion of the pivotal movement thereof (in other words, the portion of constant angular speed of the pivotable structure or counterweight may be implemented by the actuator irrespective of whether or not the movement follows a regular or irregular pattern).

[0053] The scanner module and / or the scanner system of the present disclosure may include one or more biasing arrangement / s. Reversal of pivotal movement of the pivotable structure may be attained by way of the biasing arrangement / s. The biasing arrangement may, for example, include one or more magnets. The biasing arrangement may include one or more opposing or repelling magnets, such as permanent magnets.

[0054] The biasing arrangement may include one or more spring / s, such as compression springs. In other words, one or more spring / s may be used as an alternative to the one or more magnet / s of the biasing arrangement.

[0055] In accordance with another aspect of the present disclosure there is provided a method of scanning by a scanner module onboard an airborne or spaceborne platform, the method comprising: providing a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform; providing a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more of a camera, an imager, a scanner, and an optical assembly; by an actuator, pivoting the pivotable structure in a first direction about the pivot axis from a first angular position towards a second angular position and / or back towards the first angular position in a second and opposite direction, and actuating the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement.

[0056] The optical assembly may be an optical train or an optical assembly tube, and it may have one or more lenses.

[0057] The method may include providing a disengaged state and an engaged state of the scanner module. In the engaged state the scanner module may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. In the disengaged state the scanner module may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base. The disengaged state of the scanner module may be provided by free pivotal movement of the pivotable structure between a first and a second biasing device. The pivotable structure may be arranged to bounce back and forth between the first and second biasing devices, and during its pivotal movement it may pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module. The biasing devices may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. The present disclosure extends to a scanner module for an airborne or spaceborne platform, the scanner module comprising: a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform; a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more mirrors; a resonant oscillator capable of driving and oscillating the pivotable structure so as to overcome its frictional losses, wherein the resonant oscillator is arranged to oscillate the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement.

[0058] The scanner module may further have a disengaged state and an engaged state. In the engaged state the scanner module may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base. In the disengaged state the scanner module may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base.

[0059] The disengaged state of the scanner module may be provided by free pivotal movement of the pivotable structure between a first and a second biasing device. The pivotable structure may be arranged to bounce back and forth between the first and second biasing devices, and during its pivotal movement it may pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module. The biasing devices may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base.

[0060] Embodiments of the technology will now be described, by way of example only, with reference to the accompanying drawings.

[0061] BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In the drawings:

[0063] Figure 1 is a graph illustrating movement of an exemplary conventional resonant oscillatory scanner, with angular position (6), speed (co) and acceleration (codot) of the scanner shown as functions of time, and point A and point B indicate where constant-speed sections are to be inserted according to aspects of the present disclosure;

[0064] Figure 2 is a graph illustrating features of an exemplary scanner module or scanner system according to aspects of the present disclosure, with angular position (0), speed (co), acceleration (codot), and torque (e.g., of a spiral spring) shown as functions of time, also illustrating section A1 -A2 that has been inserted at point A in Figure 1 , and section B1 -B2 that has been inserted at Point B in Figure 1 ;

[0065] Figure 3 is a three-dimensional view of an exemplary scanning system according to aspects of the present disclosure, showing a scanner module carrying a payload, e.g., a camera or a scan mirror;

[0066] Figure 4 is a three-dimensional view of an exemplary scanner module or scanning mechanism that may form part of the scanning system of Figure 3, the scanning mechanism having a pivotable structure and a base;

[0067] Figure 5 is a three-dimensional view of the exemplary scanner module of Figure 4, showing a diagrammatic cross-section of the pivotable structure thereof, taken along line V-V in Figure 4;

[0068] Figure 6 is another three-dimensional view of the exemplary scanner module of Figure 4, showing a diagrammatic cross-section of the pivotable structure and an exemplary sectional view of a clutch;

[0069] Figure 7 is a three-dimensional cross-sectional view of the exemplary scanner module of Figure 4, illustrating exemplary spiral torsional springs that may be implemented;

[0070] Figures 8-10 are diagrams that illustrate an exemplary half-cycle of scanning oscillation or pivotal movement of the exemplary scanner module of Figure 4, showing pivotal movement of the pivotable structure in relation to the base by 0°, 30° and 42° respectively;

[0071] Figure 11 is a three-dimensional view of another exemplary scanning system, showing a scanner module carrying a payload, e.g., a camera or a scan mirror;

[0072] Figure 12 is a three-dimensional view of an exemplary scanner module or scanning mechanism that may form part of the scanning system of Figure 1 1 , the scanner module having a pivotable structure, a spindle, and a base;

[0073] Figures 13-14 are three-dimensional views of the exemplary scanner module of Figure 12, showing diagrammatic cross-sections of the pivotable structure and base thereof;

[0074] Figure 15 is a cross-sectional view of the exemplary scanner module of Figure 12, showing more detail of its internal components;

[0075] Figures 16-18 are diagrams that illustrate an exemplary half-cycle of scanning oscillation of the exemplary scanner module of Figure 12, showing pivotal movement of the pivotable structure in relation to the base by 0°, 30° and 42° respectively; Figure 19 is a high-level flow diagram of an exemplary method of scanning by a camera onboard an airborne or spaceborne platform;

[0076] Figures 20-21 are top and front views, respectively, of another exemplary scanner module or scanner system according to aspects of the present disclosure; and

[0077] Figures 22-23 are top and front views, respectively, of yet another exemplary scanner module or scanner system according to aspects of the present disclosure.

[0078] DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

[0079] In embodiments of the present disclosure a constant or near constant speed resonant oscillation technique may be applied to a scanner rotating relative to a reference body such as a host satellite platform. However, rotation relative to a counter-mass, which in turn rotates relative to a reference body such as the host platform as disclosed in the applicant’s co-pending United Kingdom patent application number 2310793.1 , the contents of which are incorporated herein by reference, may also be employed. The latter may have an additional benefit of minimized disturbance torque to the host platform.

[0080] Near constant speed as opposed to constant speed may arise from physical constraints such as the effect of bearing frictional torque or centring springs’ torque. It may also be by design, for example by purposely tapering the speed profile somewhat towards the outer swath for example to improve performance or to aid yaw steering.

[0081] The present disclosure extends to a resonant scanner module for an airborne or spaceborne platform, the scanner module delivering a scan speed profile with a constant-speed section. The present disclosure further extends to a resonant oscillating mechanism for scanning a payload onboard a host platform at constant speed for a part of the oscillatory period. The present disclosure may enable minimizing disturbance torque to the host platform, e.g., by implementing a counterweight which pivots or rotates in an opposite direction to the scanner.

[0082] Figure 1 shows an angular position (theta 0), angular speed (omega co) and angular acceleration (omega dot codot) of a conventional resonant oscillator, as function of time. Conventional resonant oscillatory scanners are, for example used onboard satellites and airborne platforms. Resonant scanners typically present a sinusoidal positional and speed profile such as that illustrated in Figure 1. The angular position (0) may for example follow a simple sinusoidal pattern, oscillating back and forth around a zero-point, which is often the nadir point (e.g., when the scanner points straight down). The nadir point may for example correspond to the scanner pointing towards the earth, and it may be designated by 0° in the graph. A scanner or camera may thus be oscillated around the nadir point following the sinusoidal path of angular position (0).

[0083] Still referring to Figure 1 , point A and point B indicate where near-constant speed sections may be inserted in each cycle, according to exemplary aspects of the present disclosure. In other words, features of a scanner module and scanner system may be arranged so as to implement near-constant speed portions as will be described in more detail below.

[0084] Figure 2 shows angular position (0), angular speed (co) and angular acceleration (codot) of a constant-speed resonant oscillator or scanner module according to exemplary aspects of the present disclosure. Section A1 -A2 has been inserted at point A in Figure 1. Section B1 -B2 has been inserted at point B in Figure 1. As can be seen from the graph, angular speed (co) remains substantially constant between point A1 and point A2, as well as between point B1 and point B2. Angular acceleration (codot) also remains substantially constant between points A1 and A2, and between points B1 and B2. In this example, angular acceleration (co) is near zero during these portions of pivotal movement of a scanner, while angular speed (co) remains substantially constant.

[0085] An exemplary scanner system (100) according to aspects of the present disclosure is shown in Figure 3. An exemplary scanner module (10) that may form part of the scanner system is shown in Figure 4. The scanner module (10) may also be termed a scanning mechanism, and it may, in use, have scanning or imaging equipment attached thereto. Figure 3 shows a scanner configured to oscillate or pivot a payload, such as a camera, an imager, a scanner, an optical lens, an optical assembly (e.g., having one or more lense(s)), an optical train, or a scan mirror, back and forth in a scanning action about a rotational axis also termed a pivot axis.

[0086] The scanner module (10) of the scanner system (100) may be arranged to be implemented on or by an airborne or spaceborne platform. The airborne or spaceborne platform is not shown for the sake of brevity, but it will be appreciated by those skilled in the art that this may be a satellite, aeroplane, drone, other flying or gliding machine, or the like. The payload, carried by the oscillating scanner may be rotatably mounted on the base which may be static in relation to the payload. The static base could represent a host satellite or airborne platform, with the term static used in reference to the rotating I scanning mechanism’s moving parts. The scanner may be configured to perform a one-dimensional scanning action or a scanning motion in a single plane (e.g., in a plane normal to the pivot axis). The scanner module may include a base (12) which may be shaped to be attached to the airborne or spaceborne platform. Embodiments may be possible wherein the base forms part of the airborne or spaceborne platform, or wherein the airborne or spaceborne platform itself may be the base. A pivotable structure (14) is, in the present embodiment, pivotally coupled to the base about a pivot axis (16), so as to be pivotally moveable about the pivot axis (16) in relation to the base (12). In the present embodiment, the pivotable structure (14) includes or holds a camera (38). However, it will be appreciated that other payloads may be held, contained or mounted to the pivotable structure (14), such as a camera, a scanner, an imager, an optical assembly having one or more lenses, an optical lens or telescope or an optical train. The scanner module may further include an actuator (18), an example of which is shown in the sectional view of Figure 5. The actuator (18) may, for example include a permanent magnet (20) and an electromagnet (22) (also shown in Figure 5). The electromagnet may, e.g., be in the form of one or more coils and / or one or more poles with coils (not shown) and / or one or more solenoids.

[0087] In the present embodiment, the actuator (18) is connected to the pivotable structure (14) (or is electromagnetically coupled thereto). However, the actuator need not be connected to the pivotable structure and external actuation (e.g., by a booster, thruster or control surface or other actuating device of the airborne or spaceborne platform) may be performed. The actuator (18) may be capable of pivoting or actuating the pivotable structure (14) in a first direction (24) (e.g., counterclockwise in Fig .4) about the pivot axis (16) from a first angular position (e.g., 19 at about 0 = -42°, see Fig.2) to or towards a second angular position (e.g., 21 at about 0 = +42°, see Fig.2). Preferably, the actuator may further be configured to pivot or actuate the pivotable structure (14) back from the second angular position (e.g., 21 ) to or towards the first angular position (e.g. ,19) in a second and opposite direction (26) (e.g., clockwise in Fig.4 - following the graph in the left portion of Figure 2). It will be appreciated that the first angular position (19) may correspond to a pivoting angle of about -42° from nadir (i.e., from 0°) and it may for example be a maximum pivotal angle. Other angles are of course also possible. The second angular position (21 ) may correspond to a pivoting angle of about +42° from nadir (which may be the maximum in an opposite direction).

[0088] As the scanner module pivots by the actuator, the scanner or pivotable structure (14) may pivot in a counterclockwise direction (24) from the first exemplary angular position (19) to the second exemplary angular position (21 ), and back to the first exemplary angular position (e.g., following the angular positional path in the left half of Figure 2 which may correspond to clockwise pivotal movement (26) in Figure 4). It will, however, be appreciated that the first and second angular positions may be taken anywhere in the exemplary graph in Figure 2. For example, A1 may be taken as the first angular position, and A2 may be taken as the second angular position. Similarly, B1 may be the first angular position and B2 may be the second angular position, and so forth. In other words, numeral (19) may be the first angular position (or, e.g., any other point on the angular position graph), and numeral (21 ) may be the second angular position (or e.g., any other point on the angular position graph).

[0089] Point B1 (6 ~= -30° from nadir) in Figure 2 may also be termed the first angular position, and point B2 in Figure 2 (0 ~= +30° from nadir) may also be termed the second angular position. It will be appreciated that the actuator may move or pivot the scanner module or pivotable structure in first direction (24) (counterclockwise in Fig .4) during pivotal movement from the first angular position (B1 in this case) to the second angular position (B2 in this case). The actuator may further be arranged to pivot the pivotable structure (14) back from the second angular position (B2) to the first angular position (B1 ) in the second and opposite direction (26) (clockwise in Fig.4). This may happen as the pivotable structure is pivoted following the angular position path in the left half of Figure 2. In other words, pivotal movement from A1 to A2 may be equivalent to pivotal movement back from B2 to B1 , because A1 may correspond to the same pivot angle (0 ~= +30° from nadir) as B2, and A2 (0 ~= -30° from nadir) may correspond to the same pivot angle as B1 . The pivotable structure may of course also follow the partially sinusoidal path near the maximum positive and negative 0 values in Figure 2, but it may follow a substantially constant angular speed while pivoting through portions (28, 30) of its pivotal movement. This is described in more detail below.

[0090] Embodiments of the present disclosure may enable the actuator (e.g., 18) to be arranged to pivot or actuate the pivotable structure (14) at a near-constant angular speed (co) for at least a portion (28, 30) of its pivotal movement. More specifically, the actuator (e.g., 18) may be arranged to pivot or actuate the pivotable structure (14) so as to pivot it at a near-constant angular speed (co) for a first portion (28) of its pivotal movement, e.g., in the first direction (24, counterclockwise in Fig.4) from B1 to B2 in Fig 2 (i.e., from a first angular position to a second angular position). The actuator may also be arranged to pivot or actuate the pivotable structure (14) at a near-constant angular speed (co) for a second portion (30) of its pivotal movement e.g., in the second and opposite direction (26, clockwise in Fig. 4) from A1 to A2 in Fig.2 (i.e., from a first angular position to a second angular position). Further features of the actuator and scanner module will become apparent from the present disclosure.

[0091] A desired speed profile such as that shown in Figure 2 may be created as follows. Firstly, an offset in angular position may be introduced or selected, for example 30° in this case. Angular offset may be added to angular position of the exemplary standard resonant oscillator of Figure 1. At point A1 of a constant-speed resonant oscillator, or a scanner module according to exemplary aspects of the present disclosure, the angular position is, in this example, 30°. Then the constant-speed section (A1 -A2) of the new profile may be generated. Within section A1 -A2, the angular acceleration (codot) may be set to zero. A torque (e.g., of the actuator) may also be set to zero during this portion (30) of the pivotal movement (or during portion 28). Moreover, a torque of a spiral spring (48, explained in more detail below with reference to Figure 5) may also be substantially zero during first and second portions (28, 30). Hence, the angular speed (co) may remain constant within this section (30) or portion. This may be implemented by aspects of the present disclosure, and it may also be beneficial to TDI imaging. In this section (30), angular position (0) reduces or changes at constant rate until a desired negative angular offset is reached at Point A2, -30° in this case.

[0092] The scanner module (10) may reverse its direction of pivotal movement between points A2 and B1 in Figure 2 (i.e., through the partially sinusoidal profile at 19) and it may then repeat the above procedure for the other half-cycle, inserting a constant speed section from point B1 to point B2 (but of course with pivotal movement in another direction, counterclockwise in this instance, as described above). This procedure may repeat for a duration of steady state operation of the scanner module (10).

[0093] Referring to Figure 3, the scanner module (10) of the scanner system (100) may also include one or more bearings. A scanner-base bearing (32) may be provided to mount the pivotable structure (14) to a central rod (34) that extends from the base (12) (or that may form part of the base). The central rod (34) may be fixed to the base (12) and it may extend along the major axis or along the pivot axis (16) of the scanner module (10).

[0094] In Figure 4 is shown an encoder ring (36) which may be provided or fixed around a periphery of the pivotable structure (14), e.g., to facilitate a reader or sensor (not shown) to generate data relating to the pivotal movement and / or pivot angle(s) (0) of the pivotable structure (14). Oscillation or pivotal movement may be performed about the pivot axis (16). The pivotable structure (14) may be arranged to carry or hold imaging or scanning equipment. This may be termed a “payload”. The payload may e.g., be a camera (38) or a scan mirror.

[0095] In Figure 5 is shown a detailed sectional view of the scanner module (10) of Figure 4 showing exemplary internal components. The pivotable structure (14) of the scanner is, in the present embodiment, rotatably or pivotably mounted on the base (12) or host platform. The base may be fixed, or static, in relation with the pivotable structure (14) (but the base (12) may of course move with the airborne or spaceborne platform in use). The pivotable structure (14) is diagrammatically illustrated by the dotted pattern in Figure 5. The actuator (18, 20, 22) may be arranged to apply a pulsed torque for initiating pivotal movement of the pivotable structure (14) in one of the first and second directions (24, 26). In exemplary implementations, the actuator may be arranged to oscillate or resonate the pivotable structure. In other words, the actuator may be arranged to swing or pivot the pivotable structure back and forth, or from one side to the other. However, the oscillation may be performed regularly or irregularly by the actuator. Preferably, the near-constant speed may be achieved for at least a portion of the pivotal movement of the pivotable structure.

[0096] The actuator (18, 20, 22) may be arranged to apply near-zero torque during the near-constant angular speed portion (e.g., 28 in Figure 2) of the pivotal movement of the pivotable structure (14). The actuator may enable the pivotable structure to pivot with a near-constant angular speed and a near-zero angular acceleration. This period of near-zero torque may also facilitate more efficient power usage of the actuator which may be beneficial in many implementations, for example on a satellite or drone where power capacity and weight is limited.

[0097] As can be seen in Figure 5, the scanner module (10) may include a clutch (40). In the present embodiment, the clutch (40) has a disengaged state (42) (see Figure 8) and an engaged state (44) (see Figure 9). In the engaged (44) state, the clutch (40) may be arranged to block, inhibit or slow down pivotal movement of the pivotable structure (14) in relation to the base (12). In the disengaged state (42), the clutch (40) may be arranged to permit the pivotable structure (14) to pivot substantially freely in relation to the base (12). The clutch (40) is rotatably or pivotably mounted on the base (12). Rotatable / pivotable parts (the clutch, the base and the pivotable structure) are shown in an exemplary neutral (centred or zero) position in Figure 5. This may, e.g., correspond to a nadir pointing (0=0°) angular position of the pivotable structure (14). Bearing securing nut(s) (e.g., 46) may be used to secure the scanner-base bearing(s) (32) (presently a pair of bearings).

[0098] A spiral torsion spring (48) may couple the clutch (40) with the pivotable structure (14). The spiral torsion spring is designated by the horizontal hatch line pattern in Figure 5. An outer end (50) of the spiral torsion spring may be attached to the pivotable structure (14) of the scanner. An inner end (52) of the spiral torsion spring (48) may be attached to the clutch (40) of the scanner module. A centring spring (54) or other biasing device may be used to couple the pivotable structure (14) to the base (12). As an alternative to the centring spring, a wire-wrap (not shown) may be used. The centring spring (54) is merely shown diagrammatically in Figure 5, and is described in more detail below. The clutch (40) may include or be connected to a projection (56) or lug that may pivot together with the pivotable structure during the disengaged state (42) of the clutch (40). The projection (56) may e.g., be termed a clutch pin or a lug. In use, the projection (56) may pivot until it encounters or abuts a first stop formation (58) which causes the clutch (40) to engage and to inhibit or slow down further pivotal movement of the pivotable structure (14) in relation to the base (12). The stop formation (58) may, for example, be provided on the base (12).

[0099] The scanner module (10) may include the first stop formation (58) for engaging the clutch (40, 56) during pivotal movement of the pivotally moveable structure (14) in the first direction (24, counterclockwise in Fig .4). A second stop formation (60) may be provided for engaging the clutch (40, 56) during pivotal movement of the pivotally moveable structure (14) in the second and opposite direction (26, clockwise in Fig .4) . The first and second stop formations (58, 60) may also be termed clutch engager pins or blocking structures.

[0100] Referring to Figures 4-6, the base extends upwards to the top of the drawing in Figure 4, in the form of a pivot. The scanner and clutch may be arranged to rotate about the pivot (i.e., the central rod of the base), each with one or more bearings (presently, pairs of bearings 32, 62). The scanner module may include the spiral torsion spring (48) which may be contained in a central chamber of the pivotable structure (14). The central chamber may be disc shaped, so as to occupy minimal space and / or volume. The spiral torsional spring (48) may be arranged to act as a biasing arrangement for reversal of the scan direction, i.e., to urge the pivotable structure (14) to pivot in an opposite direction when the clutch is engaged (i.e., when the clutch pin (56) engages either stop formation (58, 60, as the case may be)). The outer end (50) of the spiral torsion spring is, in the present embodiment, fixed to the scanner’s pivotable structure (14), while the inner end (52) is fixed to the clutch (40).

[0101] In a hypothetical case where the inner end of the spiral torsion spring was fixed to the pivot (base) instead, with no clutch mechanism, the scanner would oscillate about the pivot at its natural frequency (e.g., similarly to a conventional resonant oscillator, as per Figure 1 ). Losses would damp the oscillation, but these could be overcome by the electric actuator (e.g., a motor, or one or more magnets / electromagnets) (not shown) that drives the pivotable structure (14).

[0102] A purpose of the clutch (40) may be to introduce the constant-speed sections or portions A1 -A2 (30) and B1 -B2 (28) shown in Figure 2 into the oscillation (of the pivotable structure (14) of the scanner module (10)). The clutch pin or projection (56) may be rigidly fixed to the clutch, and it may rotate or pivot along with the clutch. In the present embodiment, the clutch engager pins (58, 60) are rigidly fixed to the base (12). Turning now to Figure 6, a clutch-base bearing pair (62) may be provided to pivotably mount the clutch (40) to the base (12) (i.e., to the central rod thereof), e.g., to minimize frictional losses. The clutch (40) is diagrammatically designated by the diagonal hatched pattern in Figure 6 (and the projection (56) is not shown in Figure 6). One or more mounting holes (64) may be provided to mount the base to the airborne or spaceborne platform.

[0103] Figure 7 shows the spiral torsion spring in more detail in a diagrammatic three-dimensional cross- sectional view. As before, the spiral torsion spring is designated by the horizontal line hatch pattern.

[0104] Figures 8-10 are diagrams showing one example configuration of the scanner module in accordance with aspects of the present disclosure. The lower plots are duplicates of Fig. 2. Within the -30° to + 30° region, the clutch rotates freely with virtually no torsion in the spiral spring (48), rotational speed is constant or near-constant, and TDI imaging may be performed accurately and efficiently. When the scanner rotates beyond + or - 30° the clutch may be engaged, the torsion spring (48) may deflect, and reversal torque on the rotation / pivotal movement may be initiated.

[0105] With reference to Figures 8-10 and Table 1 below, exemplary features of the clutch are further illustrated.

[0106] Table 1 : Half-cycle of scanning oscillation of the exemplary scanning system of Figures 3-4.

[0107] In Figures 8-10 and in Table 1 , Point 0 corresponds to 0° (e.g., in line with nadir), Point 1 to 30°, and Point 2 to 42° of rotation / pivotal movement of the pivotable structure (14) of the scanner module (10) in relation to the base (12). It will be appreciated that the “scanner” in Table 1 may be construed to refer to the pivotable structure (14) of the scanner module. Table 1 illustrates the states (of the scanning system) at each of Points 0, 1 and 2 for the exemplary scanning system of Figure 3.

[0108] Figures 8-10 illustrate one half-cycle of scanning oscillation or pivotal movement of the scanning system of Figure 3. The lower plots (graphs) of Figures 8-10 are duplicates of Figure 2, showing Point 0 (6 = 0°), Point 1 (6 = 30°) and Point 2 (6 = 42°) thereon.

[0109] Point 0 coincides with the neutral or resting position of the oscillator or scanner module. Oscillation is initiated by the electric actuator (e.g., an electric motor or other actuator that moves the pivotable structure (14)). It may take several cycles for the mechanism to reach steady state oscillation illustrated in Figure 2.

[0110] Under steady state operation, the scanner or pivotable structure (14) passes through Point 0 with the clutch freely following (rotating along with) the scanner due to very light torque (relating to the clutch-base bearings’ losses) exerted via the torsion spring. Note that the outer end of the spiral torsion spring is fixed to the scanner and the inner end fixed to the clutch, which allows the disengaged clutch to follow the scanner in rotation.

[0111] As is evident from Figure 9, the angle 0 can be measured between the scanner (pivotable structure (14)) and base (12), in an anti-clockwise direction. For example, the pivot angle 0 of the pivotable structure (14) may be defined as an angle measured from a first axis (49) normal to the pivot axis (16) (the first axis (49) extending perpendicularly to a neutral / nadir angle) to a second axis (51 ) which extends straight through the pivotable structure and normal to a field of view of the scanner in use. During pivotal movement from the orientation of the pivotable structure in Figure 8 to that of Figure 9, the clutch (40) is disengaged and freely follows the scanner until 0 reaches its predetermined offset angle, in this case 30° from the zero point (Point 0). The entire section (28 see Fig.2) between -30° and 30°, may be where the clutch (40) pivots substantially freely. This may be termed the constant-speed section (28) indicated as B1 -B2 in Figure 2, and it may be where TDI imaging may be best performed (which may also be the case for section A1 - A2). For this entire section (28), the angular rotational speed (co) may remain nominally constant or near-constant, and angular acceleration (codot) may be zero (or near-zero). The spiral torsion spring’s (48) deflection and conveyed torque may be practically zero, or near-zero during this section (28) of near-constant velocity which may result from the clutch-base bearings’ (62) minimal frictional losses. Still referring to Figure 9, Point 1 is reached when 0 equals its predetermined offset angle, in this case 30°. At this point the clutch pin reaches the clutch engaging pin or projection (fixed to the base) and the clutch engages. The clutch may be inhibited from rotating any further. The inner end (52) of the spiral torsion spring (fixed to the clutch) is effectively locked to the base while the outer end (50) of the spring (fixed to the scanner / pivotable structure) continues its rotation. As rotation continues from Point 1 to Point 2, the spiral torsion spring deflects, torsion builds, and a reversing torque is applied to the scanner’s pivotable structure (14). Negative angular acceleration (deceleration) increases along with torque applied by the spiral torsion spring to the scanner’s pivotable structure (14). Torque applied by the actuator is not illustrated in the graph of Figure 2, however, it will be appreciated that the actuator may, for example, apply a pulsed torque at some point during, before or after the clutch engages. In other words, the actuator may apply a light torque to the pivotable structure to assist steady state pivotal movement of the pivotable structure. This torque applied by the actuator may be implemented just after pivotal movement of the pivotal structure has been reversed (e.g., under bias from the torsional spring), and the torque of the actuator may be applied in either pivotal movement direction (24 or 26, in Fig .4 , as the case may be). In an exemplary embodiment, the motor or actuator may switch off during the nearconstant angular speed sections (28, 30), e.g., to conserve energy, or more particularly, the actuator may be essentially switched off during these sections (28, 30) so as to avoid disturbing the near-constant speed.

[0112] In the case of a lightly driven resonant oscillator, at least two possible configurations may be implemented by the system and / or scanner module (100, 10) to implement the near-constant angular speed sections (28, 30):

[0113] 1. The actuator is completely off (during the sections (28, 30)), so as to facilitate zero (or near-zero) applied torque and therefore (near)zero acceleration or deceleration of the pivotable structure (14). This may enable near-constant speed, with slight deceleration due to losses (bearing friction, centring springs, etc.); or

[0114] 2. The actuator drives the scanner (preferably very lightly with minimal torque) so as to maintain perfect or near-perfectly constant angular speed.

[0115] T urning now to Figure 10, at Point 2, spiral torsion spring deflection and therefore torque reaches its maximum value, and the scanner briefly comes to rest before reversing direction. Thereafter the scanner continues in the opposite direction, the deflection angle of the spiral torsion spring reduces along with torque applied to the scanner. When angle 0 reaches 30° again, the clutch disengages and rotation speed (co) remains nominally constant under (near-) zero angular acceleration (e.g., during portion (30) in Figure 2). TDI imaging may be best performed in this constant-speed section, until 0 reaches -30° (A2 in Fig.2), where the clutch engages again and the aforementioned direction-reversal sequence can be repeated.

[0116] The centring spring (54) is diagrammatically illustrated in Figure 5. This may represent any means of centring the scanner’s pivotable structure (14) in relation to the base (12). It could, for example, be a torsion spring (or a coil spring) with a spring constant much smaller than the main spiral torsion spring (48). Another type of biasing device may also be used. A wire wrap may serve a dual purpose of supplying electrical connections to the electric actuator’s electromagnet and / or the payload while also facilitating centring of the scanner module and its pivotable structure (14).

[0117] The electric actuator (18) may be arranged to replenish energy lost to bearing friction, centring springs, wire wraps, slip rings and the like. The electric actuator facilitates continued oscillation at desired amplitude and constant speed within the TDI imaging period. The actuator may take various different forms. In the present embodiment the actuator is represented by the permanent magnet (20) fixed to the scanner module’s pivotable structure (14), and the electromagnet (22) fixed to the base (12). Various forms and variants of an electric motor or actuator, limited angle torque motor, or another driving arrangement may also be used as actuator as will be appreciated by those skilled in the art.

[0118] The scanner optionally carries the encoder ring (36), the reading head of which is not shown in Figures 4-5. The reading head is typically fixed to the base (12), in close proximity to the encoder ring. It will be appreciated that the encoder is an optional component of the scanner module, and it may provide positional and speed feedback / data to the electric actuator for the purpose of controlling oscillations and / or pivotal movement. This feedback data may also be transmitted to a TDI imager, where it may serve as TDI trigger and / or metadata may be generated e.g., for geolocation of imagery captured.

[0119] Referring again to Figure 5, the projection (56) of the clutch (40) may pivot with the pivotable structure (14) during the disengaged state (42) of the clutch (40) in either of, or both of, the first and second directions (24, 26) of pivotal movement of the pivotable structure (14). The clutch (40) may include, or be connected to, a biasing device such as the biasing torsional spring (48), or another type of biasing arrangement may be implemented (e.g., using magnetic bias). The biasing arrangement or biasing device may be configured to inhibit or to slow down pivotal movement of the pivotable structure e.g., when the clutch is in its engaged state (e.g., 44). It will be appreciated that the engaged state of the clutch may be implemented in both directions (24, 26), depending on which of the first and second stop formations (58, 60) is engaged by the clutch (40) and its projection (56). The near-constant angular speed (e.g., 28, 30) of the pivotable structure (14) may be facilitated by the disengaged state (42) of the clutch (40). The clutch (40) may be configured to facilitate reversal of the direction of pivotal movement of the pivotable structure (14). The scanner module (10) may include one or more centring biasing device(s) (e.g., 54) for centring the pivotable structure in a neutral position in relation to the base. The biasing arrangement or centring biasing device(s) may include one or more springs such as torsion springs, coil springs or the like.

[0120] As an alternative to a clutch and torsional spring, one or more magnets may be implemented to facilitate biasing of one component of the scanner module (10) relative to another component of the scanner module, i.e., magnets may be configured to passively facilitate reversal of the direction of pivotal movement of the pivotable structure (14). This is described with reference to an example of Figures 22-23.

[0121] An exemplary scanner module (410) and scanner system (400) that implements magnets or magnetic biasing is illustrated in Figures 22-23. This example of a scanner system (400) and scanner module (410) may be implemented in accordance with various aspects of the present disclosure. In the present scanner system (400), opposing magnets (489, 490), in this case a base or stator magnet (489), and a pivotable structure or rotor or payload magnet (490) are implemented. The base or stator magnet (489) may be mounted or attached to mounting blocks (487) or another attachment structure for housing the magnets and attaching or fixing them to the base (412). Le., the mounting structure (487) may be fixed or attached to the base (412). As with some or all of the other embodiments, the base (412) may be considered to be static or fixed (at least in relation to some of the other components of the scanner system). As with the other embodiments, a payload or pivotable structure (414) is provided. The payload (414) or pivotable structure may again house a camera, an imager, a scanner, a mirror, an optical assembly and / or mirror / s, etc.

[0122] The pivotable structure (414) may be pivotable about a pivot axis (416). In other words, the pivotable structure (414) may be pivotally mounted or attached about the pivot axis to the base (412). The pivot axis (416) preferably passes through the payload’s centre of mass (i.e., it may pass through a centre of mass of the pivotable structure (414)).

[0123] A second set of base or stator magnet and rotor or payload magnet may also be provided on an opposite side of the scanner system (400). This may enable the payload or pivotable structure (with its rotor magnets 490.1 , 490.2) to bounce between the stator / base magnets (489.1 , 489.2). Exemplary polarities or poles (North “N” and South “S”) of the magnets (489.1 , 489.2, 490.1 , 490.2) are shown for illustrative purposes. It will be appreciated that other arrangements are possible. The scanner module (410)_and / or scanner system (400) may include an actuator capable of pivoting the pivotable structure (414) in a first direction (424) about the pivot axis (416) from a first angular position towards a second angular position and / or back from the second angular position towards the first angular position in a second and opposite direction (426). The actuator may be arranged to actuate the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement. The actuator is presently not shown, but typically it may be a coil (e.g., an electromagnet and / or solenoid and / or a motor) which can e.g., be pulsed to inject energy into oscillation of the pivotable structure (414).

[0124] The direction (424) may, e.g., be counterclockwise in Figs. 22-23. In other words, the payload (414) or pivotable structure may be arranged to pivot counterclockwise (424) under steady state, with its angular speed being constant (or near constant) until it approaches the (stator) magnet (489.1 ), which may be arranged to reverse direction of movement of the pivotable structure (414) (i.e., decelerating it (414) up to a stop, and then accelerating it (414) in the opposite direction (426)). The system (400) may be arranged to work vice versa for a second direction (426), e.g., when the pivotable structure or payload pivots clockwise (426).

[0125] Presently, in Figures 22-23, the scanner module (410) may further have a disengaged state and an engaged state. In the engaged state the scanner module may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base (e.g., by way of the magnets (489.1 , 489.2, 490.1 , 490.2). In the disengaged state, the scanner module (410) may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base (412), (e.g., while the magnets are not substantially affecting movement of the pivotable structure 414). The disengaged state of the scanner module (410) may be provided by free pivotal movement of the pivotable structure (414) between a first and a second biasing device (in this case first and second opposing magnet pairs 489.1 , 490.1 and 489.2 and 490.2). In other words, a first biasing device may be considered to be a first rotor magnet (490.1 ) and its interaction with the opposing first stator magnet (489.1 ). This may also be termed a first biasing arrangement (489.1 , 490.1 ). Similarly, a second biasing device may be considered to be the second rotor magnet (490.2) and its interaction with the opposing second stator magnet (489.2). This may also be termed a second biasing arrangement (489.2, 490.2). The first and second biasing arrangements may each include one or more opposing or repelling magnets, such as permanent magnets.

[0126] The pivotable structure (414) may be arranged to bounce back and forth between the first and second biasing devices and during its pivotal movement it may pivot substantially freely in relation to the base until it (414) engages with either of the first and second biasing devices (i.e., magnet 489.1 engaging (or interacting with the magnetic field of) magnet 490.1 ; or magnet 489.2 engaging (or interacting with the magnetic field of) 490.2). In other words, the first and second biasing devices may be arranged to provide the engaged state of the scanner module (410) and scanner system (400) - i.e., by engaging or interacting with the pivotable structure (414) (and accelerating or decelerating it, as the case may be). The biasing devices (489.1 , 489.2, 490.1 , 490.2) may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base (412). The second stator magnet (489.2) may also have an associated mounting block for attaching or fixing it to the base 412. The magnets may be arranged to achieve reversal of direction of the pivotable structure, e.g., with minimal or near-zero frictional losses. In other words, the magnets (e.g., 489.1 and 490.1 ) may reverse pivotal movement of the pivotable structure, even without the pivotable structure actually making contact with the magnet (489.1 ) or its mounting structure (487). It may be possible to implement permanent magnets or electromagnets. Permanent magnets (e.g., Neodymium or Samarium cobalt magnets) may be preferable in some circumstances.

[0127] Figures 22-23 illustrate one of many possible configurations using magnets for passive reversal of direction (e.g., reversing pivotal movement of the pivotable structure). One further example may use a single elongated magnet to replace pivotable structure magnets (490.1 and 490.2), e.g., with its south pole on the left side of the pivotable structure (414) of Figure 22 (i.e., where magnet (490.2) is located) and its north pole on the right side (i.e. where magnet (490.1 ) is located). It will be appreciated that the polarities of the magnets may be the other way around in some implementations.

[0128] Figures 22-23 show magnets attached directly to a main body of the pivotable structure. This serves as a diagrammatic and functional illustration of the use of magnets as passive biasing devices. Various physical configurations and mounting options, which may, for example, include fixing the magnets to appendages or projecting structures, may be implemented.

[0129] The present embodiment of Figures 22-23, or the embodiment of Figure 5 may serve its purpose well in several scenarios, but in certain cases, such as with small satellite platforms, it may be desirable to minimise disturbance torque applied by the scanner to the host platform. This is an advantage that may, e.g., be achieved by an embodiment shown in Figures 1 1 -18 described in more detail below.

[0130] Referring to Figure 11 , another exemplary scanner system (200) and scanner module (210) is shown. The present embodiment may be similar to the embodiment of Figures 1 -10, however there are some differences. Similar features may be designated by similar reference numerals. The present embodiment (200, 210) shares several commonalities with the embodiment of Figures 1 -10. The differences and commonalities between the two will become apparent from what follows. This section explains the present embodiment (200, 210) with reference to the previous embodiment (100, 10), and explains differences between the them.

[0131] The scanner module (210) may include a counterweight (270). The counterweight (270) may be pivotally coupled to a base (212) about a pivot axis (216), so as to be pivotable independently of a pivotable structure (214) of the scanner module (210) in relation to the base (212).

[0132] The counterweight may be a spindle or it may be shaped like a spindle. The counterweight may have a major axis which may, for example, extend along the pivot axis in use. The counterweight or spindle may have a disc-shaped portion (217) that extends radially from the pivot axis (216) in use. In other words, the disc-shaped portion may extend radially from a major axis of the counterweight. However, the counterweight may also have other suitable shapes such as oval, rounded, rectilinear, rectangular, square, triangular, or any other shape.

[0133] Similarly to the embodiment of Figures 1 -10, in the present embodiment of the scanner module (210) it may include a clutch (240) which has a disengaged state (242) (see Fig.16) and an engaged state (244) (see Fig. 17). However, the present embodiment differs from that of Figs. 1 - 10 in that, in the engaged state (244), the clutch (240) may be arranged to inhibit or slow down pivotal movement of the pivotable structure (214) in relation to the counterweight (270) or spindle (i.e., not necessarily in relation to the base). In the disengaged state (242) the clutch (240) may be arranged to permit the pivotable structure (214) to pivot substantially freely in relation to the base (212) and / or in relation to the counterweight (270).

[0134] The clutch may include a projection (256) that pivots with the pivotable structure during the disengaged state, until the projection comes into contact with a stop formation (e.g., a first stop formation (258)). In the present embodiment of the scanner module (210), the stop formation (258) may be provided on the counterweight (270), e.g., on the disc shaped portion (217) thereof. Engagement or contact with the stop formation by the projection (256) may cause the clutch to engage and to inhibit or slow down further pivotal movement of the pivotable structure (214) in relation to the base (212). In the present embodiment, the scanner module (210) may include a first stop formation (258) for engaging the clutch during pivotal movement of the pivotally moveable structure in a first direction (e.g., counterclockwise (224) in Fig. 12). A second stop formation (260) may be provided for engaging the clutch during pivotal movement of the pivotally moveable structure in the second and opposite direction (e.g., clockwise (226) in Fig. 12). The first and second stop formations (258, 260) may, e.g., be provided on the counterweight (270).

[0135] The counterweight (270) may be arranged such that if the pivotable structure (214) is operatively pivoted by an actuator (218) or by a passive biasing device (248), the counterweight (270) automatically reacts by pivoting in an opposite direction to the pivotable structure (214) so as to counteract a substantial portion of angular momentum of the pivotable structure and any components that are attached thereto, during pivotal movement thereof. As before, the actuator (218) may e.g., include a permanent magnet (220) and an electromagnet (222). Throughout the present disclosure, it will be appreciated that the present embodiment of Figures 1 1 -18 may include or implement one or more features of the embodiment of Figures 1 -10 and vice versa.

[0136] The present embodiment (210) is differentiated by an additional rotational component, namely the spindle or counter-mass / counterweight (270) which may be rotatably or pivotally mounted on the static base (212). The pivotable structure (214) of the scanner module (210), may, in turn, be rotatably or pivotably mounted in the same rotational axis or pivot axis (216) upon the spindle or counter-mass. An advantage that may be achieved by the present embodiment is a reduced disturbance torque on the host platform, or base. In other words, if the pivotable structure (224) of the scanner module is operatively pivoted by the actuator, the counterweight may automatically react by pivoting in an opposite direction to the pivotable structure, so as to counteract a substantial portion of angular momentum of the pivotable structure (and its attached components, camera, etc.) during its pivotal movement. The counter-mass (270) may hence reduce or inhibit disturbance torque which may be advantageous on airborne or spaceborne craft.

[0137] In Figures 12-15 is shown more detail of the present embodiment. The pivotable structure (214) of the scanner module (210) and the clutch (240) are both rotatably or pivotally mounted on the spindle or counter-mass (270). The spindle or counter-mass (270), in turn, is rotatably or pivotally mounted on the base (212). All three pivotable parts (214, 240, 270) are shown in a neutral (centred or zero) position in Figures 12-15.

[0138] Figures 12-15 shows that the present embodiment (200, 210) may be differentiated by the addition of the spindle or counter-mass (270). The pivotable structure (214) of the scanner, and the clutch (240) no longer rotate / pivot directly relative to the fixed base, but instead rotate / pivot relative to the spindle (270) which, in turn, rotates / pivots relative to, or in relation to, the base (212). In other words, the pivotable structure and clutch pivots in relation to the spindle, and the spindle pivots in relation to the base, so effectively the pivotable structure may be regarded as pivoting indirectly in relation to the base. Once the clutch engages, the pivotable structure may pivot independently of the clutch which would then pivot together with the counter-mass. Stated differently, the pivotable structure (214) of the scanner system (200), and the clutch (240) no longer rotate / pivot directly on, or relative to the fixed base (212). Instead, these components (214, 240) rotate / pivot on or relative to the spindle (270) which, in turn, rotates / pivots on or relative to, or in relation to, the base (212).

[0139] The pivotable structure (214) of the scanner module (210) and spindle (270) need not have similar moments of inertia, although practical considerations benefit from the pivotable structure (214) of the scanner module (210) and spindle (270) having similar moments of inertia. In case of identical moments of inertia as assumed here, the pivotable structure (214) rotates through an angle 0 relative to the base, while the spindle rotates in the counter / opposite direction through angle - 0. In other words, the spindle acts as a counter-mass to rotation of the pivotable structure (214) of the scanner, or the spindle may rotate reactively relative to the pivotable structure of the scanner.

[0140] As disclosed in the applicant’s co-pending United Kingdom patent application number 2310793.1 , the contents of which are incorporated herein by reference, a transfer of reactive torque to a spindle instead of the base or host platform, may minimise disturbance(s) to the host platform. Reactive torque conveyed to the host platform may be limited to that relating to bearing friction and centring springs, wire wraps, slip rings and the like.

[0141] As with the previous embodiment, the present embodiment (210) may include an encoder ring (236) which may be fixed to a periphery of the pivotable structure (214) of the scanner module (210). Further features of the encoder may be similar to those described with reference to Figures 1 -10. In Figure 13 is shown a top end (272) and a bottom end (274) of the spindle or countermass (270). Bearing securing nuts (276, 278) may be provided to secure a spindle-base bearing or bearing pair (280), and a pivotable structure-spindle bearing (or bearing pair (282)) respectively. As before, the pivotable structure (214) is designated by the dotted pattern in Figure 13, and the spiral torsion spring (248) by horizontal hatch line patterns. An outer end (250) of the torsion spring may be affixed to the pivotable structure (214). An inner end (252) of the torsion spring (248) may be affixed to the clutch (240). A centring spring (254) may be provided between the pivotable structure (214) and the spindle or counterweight (270). In the present embodiment (210), a further centring spring (255) may be provided between the counter-mass (270) and the base (212). These centring springs or biasing devices are merely shown diagrammatically in Figure 13, and it will be appreciated that practical implementations may look different. For example, these centring springs (254, 258) may alternatively, or in addition, be (or include) wire wraps. As with the previous embodiment of Figs. 1 -10, the base (212) may include one or more mounting holes (264). Also shown in Figures 14-15 are a bearing securing nut (284) for a clutch- spindle bearing pair (286), as well as a spindle-base bearing pair (280) and a corresponding securing nut thereof.

[0142] Further features of the scanner system (200) of Figure 11 are explained with reference to Figure 2, Figures 16-18 and Table 2 below.

[0143] Turning to Figures 16-18, an exemplary half-cycle of pivotal movement or scanning oscillation of the present embodiment (210) is diagrammatically illustrated. The illustrations of Figs. 16-18 show an exemplary, non-limiting configuration. The lower plots are duplicates of Figure 2. Within the - 30° to + 30° region, the clutch rotates freely with no torsion in the spiral spring, rotational speed is constant and TDI imaging may be performed. When the scanner rotates beyond + or - 30° and the spindle rotates by - or + 30° (i.e. in the opposite direction), the clutch is engaged, the torsion spring deflects and reversal torque on the rotation is initiated.

[0144] Note that the lower plots (graphs) in Figures 16-18 are duplicates of Figure 2 showing Points 0, 1 and 2 thereon for the system of Figure 11 .

[0145] Table 2: Half-cycle of pivotal movement of the pivotable structure or scanning oscillation of the exemplary scanning system of Figure 1 1 .

[0146] When passing through Point 0 in steady state operation, both the pivotable structure of the scanner and spindle are passing through their neutral or resting positions, as when centred by the centring springs. Both may be pivoting / rotating at a near-constant speed (co) under substantially zero acceleration. This may be an ideal operational region for TDI imaging. Point 1 is reached when 0 equals its predetermined offset angle, in this case 30°. In other words, the pivotable structure of the scanner has rotated + 30° (in the anti-clockwise direction) and the spindle or counter-mass has rotated - 30° (in the clockwise direction). At this point the clutch pin reaches the clutch engaging pin (fixed to the spindle) and the clutch engages. The inner end (252) of the spiral torsion spring (fixed to the clutch (240)) may essentially be locked to the spindle (270), and it may further rotate clockwise along with the spindle, while the outer end (250) of the spring continues its anti-clockwise rotation along with the pivotable structure (214) of the scanner. As rotation continues from Point 1 to Point 2, the spiral torsion spring deflects with angle equal to the angular differential between the pivotable structure of the scanner and the spindle. By the time it reaches Point 2, the scanner has rotated through an additional 12° (in this example) in the anti-clockwise direction while the spindle has rotated through an additional 12° (in this example) in the clockwise direction, for the spiral torsion spring to reach a maximum deflection angle of 24°. Torsion subsequently builds during this rotation from Point 1 to Point 2 and a reversing torque is generated. Negative angular acceleration (deceleration) of the scanner and spindle increases along with relative torque applied by the spiral torsion spring between the pivotable structure (214) of the scanner and spindle or counter-mass (270).

[0147] At Point 2, spiral torsion spring deflection and therefore torque (of the torsional spring) reach their maximum value and both the pivotable structure of the scanner and spindle briefly come to rest before reversing their pivotal direction of movement. Thereafter, they continue in the opposite directions, the deflection angle of the spiral torsion spring reduces along with relative torque applied between the scanner and spindle. When angle 0 reaches 30° again, the clutch disengages and rotation speed (co) remains essentially or nominally constant under zero (or near-zero) angular acceleration (codot in Figure 2). TDI imaging may be best performed in this constant speed section (or near-constant angular speed section), until 0 reaches -30°, where the clutch engages again and above direction-reversal sequence is repeated.

[0148] In case of the scanning system of Figure 1 1 , the electric actuator may act between the scanner and spindle. Also, a first centring spring may centre the spindle relative to the base while a second centring spring may centre the scanner relative to the spindle. Once again, the centring springs and / or wire wraps are not shown in all drawings, for the sake of clarity. As stated elsewhere in the present disclosure, many other configurations are possible. For example: an actuator acting between the base and the spindle; or an actuator acting between the base and the scanner module / pivotable structure.

[0149] It will be appreciated that the angular profile (position, speed and acceleration) shown in Figure 2, may for example be achieved by appropriate control of an electric motor alone, without any resonant components. However, a benefit of resonant components (e.g., springs counterweight, pivotable structure, etc.) of the present disclosure, may be a reduced power consumption that these components afford. Embodiments of the present disclosure may therefore rely on resonant components as a low-power means of reversing the constant-speed scanning motion. Resonance and energy conservation may be implemented by the main spiral torsion spring (e.g., 48 and 248), and of course the pivotable structure (14, 214). The counter-mass may be an optional component, which may be implemented so as to minimise disturbances, but not necessarily to conserve energy.

[0150] Resonant oscillators do however need to overcome their losses, notably bearing friction and losses relating to centring springs, wire wraps or sliprings. For this reason, the constant-speed resonant oscillator or scanner module may include or implement actuator components, e.g., to lightly drive the scanner or pivotable structure so as to overcome losses and assist in maintaining constant speed (which may be preferable for imaging).

[0151] The scanner module may also be termed a constant-speed resonant oscillator. However, it will be appreciated that the scanner module need not be resonant, and the actuator may drive the pivotable structure in any suitable speed profile, whether a regular or irregular pattern. The scanner module of the present disclosure may benefit from low energy usage when reversing rotational direction, along with a constant-speed section (e.g., 28, 30) which may facilitate clearer and / or more efficient TDI imaging.

[0152] A fairly constant speed of the scanner module may enable preservation of MTF (modulation transfer function) in a forward scan direction, especially under a high number of TDI stages e.g. 50 or more. High-speed TDI scanning may benefit from a resonant scanner with a section of the speed profile being at a constant rotational / pivotal angular speed. The scanning action may be accomplished by different means, such as oscillation of a scan mirror(s), of which various types have been proposed and used, or oscillation of the entire camera or parts thereof.

[0153] It will be appreciated that the following features may be implemented in either of the embodiments of Figures 1 -10, or 11 -18, or a combination of both. The actuator may be an electric motor or another type of device that can pivot the pivotable structure. For example, one or more magnets or electromagnets may be implemented. The actuator may also include one or more electric motors, magnets, or electromagnets. The actuator may include one or more permanent magnet / s mounted on one of the base and the pivotable structure. The actuator may include one or more electromagnet / s mounted on the other of the base and the pivotable structure. The electric motor and / or electromagnet / s may be arranged to be powered by a power source onboard the airborne or spaceborne platform.

[0154] The actuator may include one or more permanent magnet / s mounted on one of the base and the counterweight. The actuator may include one or more electromagnet / s mounted on the other of the base and the counterweight. The actuator may be arranged to pivot the pivotable structure in relation to the base. Alternatively, or in addition, the actuator may be arranged to pivot the pivotable structure in relation to the counterweight, or to pivot the counterweight in relation to the base. In other words, the actuator may be arranged to pivot any one of the pivotable structure and the counterweight relative to each other, or relative to the base. Pivotal movement of these components may be performed about the pivot axis, or about a major axis of the scanner module.

[0155] The actuator may be arranged to pivot the pivotable structure in the first direction from the first angular position to the second angular position. The pivotable structure and / or counterweight may be arranged to automatically return back from the second angular position to the first angular position in the second and opposite direction. In other words, the actuator may be arranged to pulse, actuate or move the pivotable structure in one direction after which it may return by itself to again be pulsed, actuated or moved by the actuator. The pivotable structure may be shaped and / or configured so as to have a camera, a scanner, or other optical equipment attached thereto. One or more mirrors, lenses or other imaging equipment may for example be mounted to the pivotable structure so as to pivot therewith in use (e.g., when actuated by the actuator).

[0156] The actuator may be arranged to oscillate the pivotable structure or the counterweight. Alternatively, the actuator may be arranged to pivot the pivotable structure or the counterweight following a regular pattern of angular movement, or an irregular pattern of angular movement. The actuator may pivot the pivotable structure at a constant angular speed, i.e., with near zero angular acceleration for at least a portion of the pivotal movement thereof (in other words, the portion of constant angular speed of the pivotable structure or counterweight may be implemented by the actuator irrespective of whether or not the movement follows a regular or irregular pattern).

[0157] In exemplary configurations, the actuator may include one or more permanent magnet / s mounted on one of the base, the pivotable structure, and the counterweight; and one or more electromagnet / s mounted on another of the base, the pivotable structure, and the counterweight.

[0158] It will be appreciated that the actuator of the various embodiments of the present disclosure may instead be an actuator onboard the airborne or spaceborne platform. For example, in the case of a spaceborne platform a booster or thruster may be used as actuator to “jolt” a satellite body (i.e., the platform itself) slightly, rather than injecting energy by a motor or magnet-type actuator. This jolt or sudden pivotal movement may be utilised to provide pivotal energy to the pivotable structure and / or a resonance may be maintained by way of this ‘jolting’. Similarly, control surfaces of an airborne platform may be used as actuators to jolt or move the platform.

[0159] Implementations of the present disclosure may be possible without a physical clutch as such. At least three other possible configurations may be possible, namely: a) Two pairs of permanent magnets, with the pivotal structure rotationally ‘bouncing’ back and forth between the two of them, and no physical clutch may need to be used. The pivotable structure may be enabled to pivot freely (i.e., a disengaged state of the scanner module) for the constant speed section. See Figures 22-23. It may also be possible to implement a plurality of magnets, and not necessarily two pairs of magnets. E.g., one magnet may be implemented at the pivotable structure with at least one or more further magnets provided at the base or extending therefrom. This is also described in more detail elsewhere in the present disclosure. b) Similarly, two springs (e.g., linear springs) may be implemented with the pivotal structure rotationally ‘bouncing’ back and forth between the two of them. E.g., see Figures 20- 21. c) A non-linear torsion spring (preferably an extremely non-linear one) may be used. One could consider a portion of spring deflection with near zero spring constant as being a disengaged state of the scanner module (i.e., enabling substantially free pivotal movement of the pivotable structure).

[0160] In other words, in embodiments of the present disclosure, the scanner module itself may have a disengaged state and an engaged state, wherein, in the engaged state the scanner module may be arranged to inhibit or slow down pivotal movement of the pivotable structure in relation to the base, and in the disengaged state the scanner module may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base. The disengaged state of the scanner module may be provided by free pivotal movement of the pivotable structure between a first and a second biasing device (e.g., opposing magnet / s or magnet pairs as per Figures 22-23; or compression springs as per Figures 20-21 ), the pivotable structure being arranged to bounce back and forth between the first and second biasing devices and during its pivotal movement it pivots substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module. These biasing devices may be arranged to inhibit or slow down pivotal movement of the pivotable structure in relation to the base (i.e., in an engaged state of the scanner module). The scanner module itself may be operable in a disengaged state and in an engaged state. The disengaged state of the scanner module itself may, alternatively, be provided by a non-linear torsion spring between the pivotable structure and the base, wherein pivotal movement for a portion of the spring deflection with a near zero-spring constant may provide the disengaged state of the scanner module, and the engaged state of the scanner module may be provided by the torsion spring when it deflects beyond a certain threshold.

[0161] The present disclosure extends to a scanner module for an airborne or spaceborne platform. The scanner module may include a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform. A pivotable structure may be pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base. The pivotable structure may include or hold one or more mirrors, e.g., for scanning by way of the mirror(s). A resonant oscillator may be implemented, and it may be capable of driving and oscillating the pivotable structure so as to overcome its frictional losses. The resonant oscillator may be arranged to oscillate the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement.

[0162] Reversal of pivotal movement of the pivotable structure may be attained by way of a biasing arrangement which may also be termed a passive biasing arrangement (i.e., the biasing arrangement reacts when an object (such as the pivotable structure) engages therewith, but it is otherwise passive). Passive biasing or the biasing arrangement may be provided, e.g., by one or more spiral torsion springs, coiled springs, non-linear springs or opposing magnet / s or opposing magnet pairs. These may be provided to urge or bias the pivotable structure in either of the first or second directions.

[0163] The (passive) biasing arrangement may further be configured to apply near-zero torque during the near-constant angular speed portion of the pivotal movement of the pivotable structure, thereby enabling the pivotable structure to pivot with a near-constant angular speed and a nearzero angular acceleration (e.g., in relation to the base).

[0164] The counterweight may be arranged such that if the pivotable structure is operatively pivoted by a biasing arrangement, the counterweight automatically reacts by pivoting in an opposite direction to the pivotable structure so as to counteract a substantial portion of angular momentum of the pivotable structure and any components that are attached thereto, during pivotal movement thereof.

[0165] The systems (e.g., 100, 200, 300, 400) and scanner modules (e.g., 10, 210, 310, 410) described herein may implement a method of scanning by a scanner module onboard an airborne or spaceborne platform. An exemplary method (1900) of scanning by a scanner module onboard an airborne or spaceborne platform is illustrated in the flow diagram of Figure 19.

[0166] The method (1900) may include providing (1910) a base which is capable of being attached to, or forms part of, the airborne or spaceborne platform. The method may further include providing (1912) a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more of a camera, an imager, a scanner, a mirror, and an optical assembly having one or more lenses. The optical assembly which may be attached to (or may form part of) the pivotable structure may also be termed an optical tube assembly which may include any number of lense(s) and / or mirror(s). The method may yet further include, by an actuator, pivoting (1914) the pivotable structure in a first direction about the pivot axis from a first angular position towards a second angular position. The method may optionally include pivoting (1916) the pivotable structure back towards the first angular position in a second and opposite direction. This backwards pivoting may be performed by the actuator, or optionally it may happen automatically, e.g., as result of the counterweight, or as result of a biasing mechanism that automatically pivots the pivotable structure back in the opposite direction. The method may further include pivoting or actuating (1918) the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement.

[0167] Optionally, the method may further include providing (1920) a disengaged state and an engaged state of the scanner module. The method may include, by the scanner module, in its engaged state, decelerating (1922) and / or accelerating pivotal movement of the pivotable structure in relation to the base. The method (1900) may further include, by the scanner module, in its disengaged state, permitting (1924) the pivotable structure to pivot substantially freely in relation to the base. The method may further include, in the disengaged state of the scanner module, providing (1926) free (or substantially free) pivotal movement of the pivotable structure between a first and a second biasing device. The method may include enabling (1928) the pivotable structure to bounce back and forth between the first and second biasing devices. During said pivotal movement, the pivotable structure may be enabled (1930) to pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module. The method may include, by the biasing devices, decelerating (1932) and / or accelerating pivotal movement of the pivotable structure in relation to the base.

[0168] The constant speed (or near-constant angular speed) resonant oscillation profile of Figure 2 may be accomplished in several different ways. One such technique, is using one or more torsional spring(s) or biasing device(s) as discussed in the present disclosure. Similar speed profiles could be attained by various and very different resonator arrangements. For example: i) Two pairs of opposing or repelling magnets, separated by some distance may be used, with the scanner or scanner module oscillating (bouncing in a rotational arc) between the two. An example of such a scanner module according to exemplary aspects is described below with reference to Figures 22-23. ii) Two compression springs separated by some distance may be used, with the scanner or scanner module oscillating (bouncing in a rotational arc) between the two. An example of such a scanner module according to exemplary aspects is described below with reference to Figures 20-21. iii) Alternatively, a spiral spring configuration using a central tube with the scanner rotating around (the outside of) a counter-mass i.e. concentric bearing arrangements around the central tube rather than a sequential or linear arrangement of bearings may be implemented. iv) Various configurations utilising non-linear springs, which could include compression, spiral or other types of springs may be implemented. Non-linear refers here to springs where the spring constant or the force to position ratio (or the torque to angular position ratio) deviate substantially from a constant value, while linear springs refer to those with a nominally constant ratio. In other words, force or torque exerted by the main spring may differ substantially as function of position or angular position in order to achieve or approximate the desired speed profile.

[0169] Turning now to Figures 20-21 (e.g., with reference to example ii) above), there is shown another example of a scanner system (300) and scanner module (310) according to aspects of the present disclosure. In the present scanner system (300), opposing springs (388), in this case compression springs, are implemented. These springs may be mounted or attached to mounting blocks (387) or another attachment structure for housing the springs and attaching them to the base (312). Le., the mounting structure 387 may be fixed or attached to the base (312). As with some or all of the other embodiments, the base may be considered to be static or fixed (at least in relation to some of the other components of the scanner system). As with the other embodiments, a payload or pivotable structure (314) is provided. The payload (314) or pivotable structure may again house a camera, an imager, a scanner, an optical assembly and / or mirror / s, etc.

[0170] The pivotable structure may be pivotable about a pivot axis (316). In other words, the pivotable structure (314) may be pivotally mounted or attached about the pivot axis to the base (312). The pivot axis (316) preferably passes through the payload’s centre of mass (i.e., it may pass through a centre of mass of the pivotable structure (314)). Optionally, the scanner module (310)and / or scanner system (300) may include an actuator capable of pivoting the pivotable structure (314) in a first direction (324) about the pivot axis (316) from a first angular position towards a second angular position and / or back from the second angular position towards the first angular position in a second and opposite direction (326). The actuator may be arranged to actuate the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement. The actuator is presently not shown, but typically it may be a coil (e.g., an electromagnet and / or solenoid and / or a motor) which can e.g., be pulsed to inject energy into oscillation of the pivotable structure (314).

[0171] The direction (324) may, e.g., be counterclockwise in Figs. 20-21. In other words, the payload (314) or pivotable structure may be arranged to pivot counterclockwise under steady state, with its angular speed being constant (or near constant) until it strikes the spring (388). The spring may then be arranged to reverse direction of the pivotable structure (i.e., decelerating it up to a stop, and then accelerating it in the opposite direction (326)). In other words, the scanner module and springs may work vice versa for the second direction (326), e.g., clockwise in Figures 20-21 .

[0172] Presently, in Figures 20-21 , the scanner module (310) may further have a disengaged state and an engaged state. In the engaged state the scanner module may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base (e.g., by way of the springs 388). In the disengaged state, the scanner module (310) may be arranged to permit the pivotable structure to pivot substantially freely in relation to the base (312) (e.g., while the springs are not substantially affecting movement of the pivotable structure 314). The disengaged state of the scanner module (310) may be provided by free pivotal movement of the pivotable structure (314) between a first and a second biasing device (388.1 , 388.2). The pivotable structure (314) may be arranged to bounce back and forth between the first and second biasing devices and during its pivotal movement it may pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices (388.1 , 388.2). In other words, the first and second biasing devices may be arranged to provide the engaged state of the scanner module (310) and scanner system (310) - i.e., by engaging the pivotable structure 314 (and accelerating or decelerating it, as the case may be). The biasing devices may be arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base (312). The second biasing device (compression spring 388.2 in this instance) may also have an associated mounting block.

[0173] It will be appreciated that any one or more of the aspects of the present disclosure may be implemented in conjunction with any one or more of the other aspects. For example, aspects of the scanner module of Figures 1 to 10 may be used in conjunction with aspects of the scanner module of Figures 10 to 18 and vice versa. Moreover, aspects of the scanner module of any one of Figures 20-21 and / or Figures 22-23 may be used in conjunction with aspects of the scanner module of Figures 10 to 18 and / or in conjunction with aspects of the scanner module of Figures 1 -10.

[0174] The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the technology to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.

[0175] The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the present disclosure be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the present disclosure is intended to be illustrative, but not limiting, of the scope of any accompanying claims.

[0176] Finally, throughout the specification and any accompanying claims, unless the context requires otherwise, the word ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

CLAIMS:

1. A scanner module for an airborne or spaceborne platform, the scanner module comprising: a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform; a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more of a camera, an imager, a scanner, a mirror, and an optical assembly; and an actuator capable of pivoting the pivotable structure in a first direction about the pivot axis from a first angular position towards a second angular position and / or back from the second angular position towards the first angular position in a second and opposite direction, wherein the actuator is arranged to actuate the pivotable structure so as to pivot at a nearconstant angular speed for at least a portion of its pivotal movement, wherein the scanner module further has a disengaged state and an engaged state, wherein, in the engaged state the scanner module is arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base, and in the disengaged state the scanner module is arranged to permit the pivotable structure to pivot substantially freely in relation to the base, and wherein the disengaged state of the scanner module is provided by free pivotal movement of the pivotable structure between a first and a second biasing device, the pivotable structure being arranged to bounce back and forth between the first and second biasing devices and during its pivotal movement it pivots substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module, the biasing devices being arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base.

2. The scanner module as claimed in claim 1 , wherein the actuator is configured to apply a torque for initiating pivotal movement of the pivotable structure in one of the first and second directions.

3. The scanner module as claimed in claim 1 or claim 2, wherein the actuator is configured to apply a pulsed torque for initiating pivotal movement of the pivotable structure in one of the first and second directions.

4. The scanner module as claimed in any one of the preceding claims, wherein the actuator is configured for driving the pivotable structure to steady state motion.

5. The scanner module as claimed in any one of the preceding claims, wherein the actuator applies a torque for maintaining pivotal movement of the pivotable structure by replacing dissipated energy.

6. The scanner module as claimed in any one of the preceding claims, wherein the actuator is further configured to apply near-zero torque during the near-constant angular speed portion of the pivotal movement of the pivotable structure, thereby enabling the pivotable structure to pivot with a near-constant angular speed and a near-zero angular acceleration.

7. The scanner module as claimed in any one of the preceding claims, wherein reversal of pivotal movement of the pivotable structure is attained by way of a biasing arrangement.

8. The scanner module as claimed in claim 7, wherein the biasing arrangement is further configured to apply near-zero torque during the near-constant angular speed portion of the pivotal movement of the pivotable structure, thereby enabling the pivotable structure to pivot with a nearconstant angular speed and a near-zero angular acceleration.

9. The scanner module as claimed in claim 1 , wherein the scanner module includes a torsion spring which is arranged as a passive biasing device that can reverse pivotal movement of the pivotable structure in relation to the base.

10. The scanner module as claimed in any one of the preceding claims, wherein the scanner module further includes a clutch which has a disengaged state and an engaged state, wherein, in the engaged state the clutch is arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base, and in the disengaged state the clutch is arranged to permit the pivotable structure to pivot substantially freely in relation to the base.1 1 . The scanner module as claimed in claim 10, wherein the clutch includes a projection that pivots with the pivotable structure during the disengaged state, until the projection comes into contact with a stop formation on the base which causes the clutch to engage and to decelerate and / or accelerate further pivotal movement of the pivotable structure in relation to the base.

12. The scanner module as claimed in claim 11 , wherein the scanner module includes a first stop formation for engaging the clutch during pivotal movement of the pivotally moveable structurein the first direction, and a second stop formation for engaging the clutch during pivotal movement of the pivotally moveable structure in the second and opposite direction.

13. The scanner module as claimed in any one of claims 10 to 12, wherein the clutch includes or is connected to a biasing arrangement which is configured to decelerate and / or accelerate pivotal movement of the pivotable structure when the clutch is in its engaged state, and wherein the near-constant angular speed of the pivotable structure is facilitated by the disengaged state of the clutch.

14. The scanner module as claimed in any one of the preceding claims, wherein the scanner module includes one or more centring biasing device(s) for centring the pivotable structure in a neutral position in relation to the base.

15. The scanner module as claimed in claim 1 , wherein the scanner module further includes a counterweight which is pivotally coupled to the base about the pivot axis so as to be pivotable independently of the pivotable structure in relation to the base.

16. The scanner module as claimed in claim 15, wherein the counterweight is a spindle with a disc-shaped portion that extends radially from the pivot axis in use.

17. The scanner module as claimed in claim 15 or claim 16, wherein the scanner module further includes a clutch which has a disengaged state and an engaged state, wherein, in the engaged state the clutch is arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the counterweight, and in the disengaged state the clutch is arranged to permit the pivotable structure to pivot substantially freely in relation to the base.

18. The scanner module as claimed in claim 17, wherein the clutch includes a projection that pivots with the pivotable structure during the disengaged state, until the projection comes into contact with a stop formation on the counterweight which causes the clutch to engage and to decelerate and / or accelerate further pivotal movement of the pivotable structure in relation to the base.

19. The scanner module as claimed in claim 17 or claim 18, wherein the scanner module includes a first stop formation for engaging the clutch during pivotal movement of the pivotally moveable structure in the first direction, and a second stop formation for engaging the clutch during pivotal movement of the pivotally moveable structure in the second and opposite direction.

20. The scanner module as claimed in any one of claims 15 to 19, wherein the counterweight is arranged such that if the pivotable structure is operatively pivoted by the actuator, the counterweight automatically reacts by pivoting in an opposite direction to the pivotable structure so as to counteract a substantial portion of angular momentum of the pivotable structure and any components that are attached thereto, during pivotal movement thereof.21 . The scanner module as claimed in any one of claims 15 to 19, wherein the counterweight is arranged such that if the pivotable structure is operatively pivoted by a biasing arrangement, the counterweight automatically reacts by pivoting in an opposite direction to the pivotable structure so as to counteract a substantial portion of angular momentum of the pivotable structure and any components that are attached thereto, during pivotal movement thereof.

22. The scanner module as claimed in any one of the preceding claims, wherein the actuator is an electric motor.

23. The scanner module as claimed in any one of claims 1 to 14, wherein the actuator includes: a permanent magnet mounted on one of the base and the pivotable structure; and an electromagnet mounted on the other of the base and the pivotable structure.

24. The scanner module as claimed in any one of claims 15 to 22, wherein the actuator includes: a permanent magnet mounted on one of the base, the pivotable structure, and the counterweight; and an electromagnet mounted on another of the base, the pivotable structure, and the counterweight.

25. The scanner module as claimed in any one of claims 1 to 8, or in claim 15 or in claim 16, or in any one of claims 20 to 24, wherein reversal of pivotal movement of the pivotable structure is attained by way of a biasing arrangement including one or more magnets.

26. The scanner module as claimed in claim 25, wherein the biasing arrangement includes one or more opposing or repelling permanent magnets.

27. The scanner module as claimed in any one of claims 1 to 8, or in claim 15 or in claim 16, or in any one of claims 20 to 24, wherein reversal of pivotal movement of the pivotable structure is attained by way of a biasing arrangement including one or more compression springs.

28. The scanner module as claimed in claim 1 , wherein the disengaged state of the scanner module is provided by a non-linear torsion spring between the pivotable structure and the base,wherein pivotal movement for a portion of the spring’s deflection with a near zero-spring constant provides the disengaged state of the scanner module, and the engaged state is provided by the torsion spring when it deflects beyond a certain threshold.

29. A method of scanning by a scanner module onboard an airborne or spaceborne platform, the method comprising: providing a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform; providing a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more of a camera, an imager, a scanner, a mirror, and an optical assembly; by an actuator, pivoting the pivotable structure in a first direction about the pivot axis from a first angular position towards a second angular position and / or back towards the first angular position in a second and opposite direction, and actuating the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement; providing a disengaged state and an engaged state of the scanner module; by the scanner module, in its engaged state, decelerating and / or accelerating pivotal movement of the pivotable structure in relation to the base; by the scanner module, in its disengaged state, permitting the pivotable structure to pivot substantially freely in relation to the base and providing free pivotal movement of the pivotable structure between a first and a second biasing device, and enabling the pivotable structure to bounce back and forth between the first and second biasing devices; during said pivotal movement, enabling the pivotable structure to pivot substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module; and by the biasing devices, decelerating and / or accelerating pivotal movement of the pivotable structure in relation to the base.

30. A scanner module for an airborne or spaceborne platform, the scanner module comprising: a base which is capable of attachment to, or which forms part of the airborne or spaceborne platform; a pivotable structure which is pivotally coupled to the base about a pivot axis so as to be pivotally moveable about the pivot axis in relation to the base, wherein the pivotable structure includes or holds one or more mirrors; anda resonant oscillator capable of driving and oscillating the pivotable structure so as to overcome its frictional losses, wherein the resonant oscillator is arranged to oscillate the pivotable structure so as to pivot at a near-constant angular speed for at least a portion of its pivotal movement, wherein the scanner module further has a disengaged state and an engaged state, wherein, in the engaged state the scanner module is arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base, and in the disengaged state the scanner module is arranged to permit the pivotable structure to pivot substantially freely in relation to the base, and wherein the disengaged state of the scanner module is provided by free pivotal movement of the pivotable structure between a first and a second biasing device, the pivotable structure being arranged to bounce back and forth between the first and second biasing devices and during its pivotal movement it pivots substantially freely in relation to the base until it engages with either of the first and second biasing devices that provide the engaged state of the scanner module, the biasing devices being arranged to decelerate and / or accelerate pivotal movement of the pivotable structure in relation to the base.

Images