Compact, energy-efficient sensing array

Abstract

An optical sensing system (20) includes an array (32) of optical transceiver units (34) arranged in a plurality of groups (A, B, C, D) that emit respective beams of outgoing optical radiation toward a target scene and receive and sense incident optical radiation from the target scene. An optical switching network (38) selectively delivers the outgoing optical radiation from the laser (54) to the group. A controller (48) configured to activate the system to sense the target scene during a series of activation periods (70) interleaved with a sleep period (72), such that during each activation period, the controller turns on the laser and then controls the light switching network to continuously deliver the outgoing light radiation to the plurality of groups during the activation period, the laser is activated to be transmitted by the optical transducers in each group, and then the laser is turned off after an activation period.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application 63 / 426,054, filed on November 17, 2022. This application also relates to PCT Patent Applications PCT / US2022 / 40526 and PCT / US2022 / 40527, both filed on August 17, 2022. The disclosures of all these related applications are incorporated herein by reference.

[0003] Field

[0004] The present invention generally relates to systems and methods for optical sensing, and in particular, to integrated optical sensing devices.

[0005] Background

[0006] In many optical sensing applications, one or more beams of light irradiate multiple points on a target, and the reflected radiation from each point is processed to analyze the characteristics of the target. In some applications, such as optical coherence tomography (OCT) and continuous - wave (CW) LiDAR, coherent light beams are transmitted towards the target, and the reflected radiation is sensed and processed coherently with the transmitted radiation. To sense the characteristics of the target with high resolution, the transmitted beam can be scanned within the target area, or a receiver array can be used to simultaneously transmit and sense an array of multiple beams.

[0007] As used in this specification and the claims, the terms "optical", "light", and "optical radiation" refer to electromagnetic radiation in any one of the visible, infrared, and ultraviolet spectral ranges.

[0008] Summary

[0009] Embodiments of the invention described below provide improved systems, devices, and methods for optical sensing.

[0010] Accordingly, embodiments of the present invention provide an optical sensing system that includes an array of optical transceiver units arranged in multiple banks and configured to emit respective beams of outgoing optical radiation toward a target scene and receive and sense incoming optical radiation from the target scene. A laser is configured to generate the outgoing optical radiation. An optical switching network is coupled to selectively transfer the outgoing optical radiation from the laser to the banks for transmission by the optical transceiver units. A controller is configured to activate the system to sense the target scene during a series of activation periods interleaved with sleep periods such that, during each activation period, the controller turns on the laser and then controls the optical switching network during the activation period to continuously transfer the outgoing optical radiation to the multiple banks for transmission by the optical transducers in each bank, and then turns off the laser after the activation period.

[0011] In some embodiments, the duty cycle of the activation periods relative to the sleep periods is less than 50% or even less than 10%.

[0012] In the disclosed embodiments, the optical transceiver units are configured to measure the range to corresponding points in the target scene by performing coherent sensing of the incoming optical radiation.

[0013] In some embodiments, the optical switching network includes a hierarchy of active optical switches set by the controller to select the banks to receive the outgoing optical radiation. In one embodiment, the optical transceiver units in each bank are arranged in multiple columns, and the optical switching network further includes passive beam splitters coupled to distribute the outgoing optical radiation from the optical switches among the columns in each bank. Additionally or alternatively, the array of optical transceiver units and the optical switching network are disposed on a photonic integrated circuit (PIC) and interconnected by optical waveguides on the PIC.

[0014] In some embodiments, the optical transceiver units have respective fields of view into which respective beams of outgoing optical radiation are emitted, and the system includes a scanner configured to scan the fields of view across corresponding portions of the target scene. In one embodiment, the controller is configured to control the scanner such that, in a first sensing mode, the scanner is inactive, whereby the transceiver units sense a matrix of points in the target scene at a first resolution determined by the pitch of the transceiver units, and in a second sensing mode, actuate the scanner to sense the target scene at a second resolution finer than the first resolution. Generally, in the first sensing mode, the controller activates the laser only during the activation periods interleaved with the sleep periods, while in the second sensing mode, the controller continuously activates the laser.

[0015] According to an embodiment of the present invention, there is also provided an optical sensing system, which includes an array of optical sensing units having corresponding fields of view. A scanner is configured to scan the fields of view of the optical sensing units across corresponding portions of a target scene. A controller is configured to operate the system in a low power mode of operation, in which the optical sensing units sense a matrix of points in the target scene at a first resolution in a staring configuration, and to switch the system to a high power mode of operation, in which the scanner scans the fields of view of the optical sensing units to sense the target scene at a second resolution finer than the first resolution.

[0016] In some embodiments, the optical sensing unit includes an optical transceiver unit, which is configured to emit a beam of corresponding outgoing light radiation towards the target scene and receive incoming light radiation from the target scene. In the disclosed embodiments, the optical transceiver unit is configured to measure the range to a point in the target scene by performing coherent sensing of the light radiation reflected from the target scene.

[0017] In some embodiments, in the low power mode, the controller activates the system during a series of activation periods to sense the target scene, the activation periods being interleaved with sleep periods during which the system is inactive. In the disclosed embodiments, the controller activates the system to operate continuously when in the high power mode.

[0018] In some embodiments, the controller is configured to detect an interesting feature in an image captured by the array of optical sensing units when operating in the low power mode, and to switch the system to the high power mode in response to the detected feature. In one embodiment, the controller is configured to control the array of optical sensing units and the scanner so as to sense a portion of the target scene containing the interesting feature in the high power mode.

[0019] In the disclosed embodiments, the scanner is inactive in the low power mode of operation. Alternatively or additionally, the scanner is configured to move the fields of view of the sensing units frame by frame in the low power mode of operation.

[0020] Further alternatively or additionally, the controller is configured to change the frame rate and change the second resolution of the system in the high power mode of operation.

[0021] According to an embodiment of the present invention, there is additionally provided a method for optical sensing, which includes providing an optical sensing device including an array of optical sensing units, the array of optical sensing units having corresponding fields of view. The device operates in a low power mode, in which the sensing units sense a matrix of points in the target scene at a first resolution in a staring configuration. The device can be switched to a high power mode, in which the scanner scans the fields of view of the optical sensing units to sense the target scene at a second resolution finer than the first resolution.

[0022] The present invention will be more fully understood from the following detailed description of embodiments of the invention in conjunction with the accompanying drawings, in which: Brief Description of the Drawings

[0024] Figure 1A is a block diagram schematically showing an optical sensing system according to an embodiment of the present invention;

[0025] Figure 1B is Figure 1A a schematic diagrammatic view of an optical sensing system of

[0026] Figure 2 is a block diagram schematically showing details of an optical sensing device according to an embodiment of the present invention;

[0027] Figure 3 is by Figure 2 an optical sensing device according to an embodiment of the present invention in a low power mode a schematic front view of the created sensing pattern;

[0028] Figure 4 is schematically showing according to an embodiment of the present invention Figure 2 an optical sensing device according to an embodiment of the present invention in a low power mode a timing diagram of the operating mode; and

[0029] Figure 5 is a flowchart schematically showing a method for optical sensing according to an embodiment of the present invention.

[0030] Detailed Description

[0031] As previously mentioned, in some coherent sensing applications, multiple beams of light radiation are simultaneously directed towards a target scene, and an array of receivers senses the light radiation reflected from the target scene. The sensing resolution is limited by the pitch between the transmitter array and the receiver array, which in turn is limited by the size of the transmitters and receivers themselves. The resolution can be enhanced by scanning the field of view of the receivers within a small angle range, for example, as described in the PCT patent application cited above, but at the cost of reducing the frame rate (due to the increased length of time required to scan the entire scene).

[0032] Some embodiments of the present invention address these issues by providing an array of sensing units and a scanning system having a low-power mode and a high-power mode. The low-power mode can be used to sense a matrix of points in a target scene at a low resolution in a staring mode at a high frame rate. In response to a trigger condition, the system switches to the high-power mode and operates at a lower frame rate and a higher resolution. In the high-power mode, the field of view of the sensing units in the array is scanned within a small angle to cover the target scene at a resolution finer than the physical pitch of the sensing unit array (i.e., finer than the pitch projected onto the scene by the imaging optics). For example, the trigger condition can be based on the detection of an object or event of interest by analyzing frames captured in the low-power mode. Alternatively or additionally, the trigger condition can be invoked by another command or event.

[0033] The scanning speed, resolution, and frame rate of the high-power mode can be fixed, or alternatively, these parameters can be variable to allow a user or system controller to select the optimal trade-off between resolution, frame rate, and power consumption for each sensing scenario and application.

[0034] In some embodiments, when the sensing array operates in the low-power mode, the field of view of the sensing units moves in small increments frame by frame. For example, the same scanner used to scan the field of view within each frame in the high-power mode can be used to move the field of view frame by frame in the low-power mode. Alternatively or additionally, when the sensing array is mounted on a moving platform, the movement of the platform will inherently cause the field of view of the sensing units to move. Thus, even in the low-power mode, a high-resolution image will be gradually built up, and objects and events of interest can be detected with higher precision.

[0035] This embodiment uses an array of photon sensing units. In some embodiments, the array includes transceiver units, where each unit includes optical and optoelectronic components and auxiliary electronics for transmitting a radiation beam and for receiving and detecting the reflected radiation. In other embodiments, the unit can include components only for receiving and detecting radiation.

[0036] In the embodiments described below, the beam to be emitted and / or the beam to be mixed with the reflected radiation for coherent detection is centrally generated and modulated by a core transceiver engine and then distributed among the transceiver units. An optical switching network time-division multiplexes the beam among different groups of units. This approach is useful in reducing the size, power, and complexity requirements of the transceiver units and the array as a whole. In the high-power mode, the scanner scans the field of view of all the units on a corresponding portion of the target scene at a resolution finer than the physical pitch of the transceiver unit array, as described above. Any suitable scanning mechanism can be used for this purpose, such as an optomechanical scanning device or a tunable laser source having a grating disposed between the projection lens and the target scene.

[0037] In some embodiments, the system operates in a low-power mode at a low duty cycle (less than 50% and possibly less than 10%). In other words, the optical transceiver unit actively senses the target scene during short activation intervals interleaved with longer sleep periods, thereby reducing the power consumption of the system. As described above, this power reduction scheme is particularly useful when the system switches between the low-power mode and the high-power mode of operation. Alternatively, this scheme can also be used to reduce power consumption even in the absence of a high-power scanning mode.

[0038] Thus, in these embodiments, the optical transceiver units in the array are arranged in multiple groups. The optical switching network selectively delivers the outgoing optical radiation from the laser to the groups for transmission by the optical transceiver units. The controller activates the system to sense the target scene during a series of activation periods interleaved with sleep periods. During each activation period, the controller turns on the laser and then controls the optical switching network during the activation period to continuously deliver the output optical radiation to the multiple groups for transmission by the optical transducers in each group. After the activation period, the controller then turns off the laser to save power.

[0039] Figure 1A and Figure 1B An optical sensing system 20 according to an embodiment of the present invention is schematically shown. Figure 1A is a block diagram, while Figure 1B shows a diagrammatic view.

[0040] In system 20, a core transceiver (TRx) engine 22 includes one or more laser light sources and photonics and electronics circuitry for controlling, modulating, and distributing the coherent radiation generated by the light sources. The TRx engine 22 can implement various different modulation schemes, such as by controlling the drive current supplied to one or more lasers or by modulating the light output by one or more lasers. The TRx engine 22 is connected to a photoelectric sensing device 28 formed on a substrate 30 through one or more optical waveguides 24 and possibly also through an electrical bus 26.

[0041] In some embodiments, the apparatus 28 is fabricated using Photonic Integrated Circuit (PIC) technology and the substrate 30 comprises a silicon die, e.g., in a Silicon-On-Insulator (SOI) configuration. Optionally, the substrate 30 may comprise other kinds of semiconductor or dielectric materials. The core TRx engine 22 may also be disposed on the substrate 30, in which case the waveguides 24 and the bus 26 may be conveniently formed on the substrate 30, e.g., formed on the substrate 30 by a lithography process. Optionally, the core TRx engine 22 may be coupled to the substrate 30 via one or more edge couplers or one or more grating couplers (not shown). Additionally, optionally, the waveguides 24 and the bus 26 may comprise optical fibers and electrical wires, respectively.

[0042] The apparatus 28 includes an array 32 of transceiver units 34 formed on the substrate 30. Each transceiver unit 34 includes an optical transducer 36 that couples light into and out of the unit together with photonics and electronics components, e.g., as detailed in the above PCT patent application. The transceiver unit 34 includes photonics components for transmitting and receiving light such that the transducer 36 both emits light towards a target and receives light reflected from the target. The optical transducer 36 may include, for example, a grating coupler for a surface-coupling configuration of the apparatus 28, or an edge coupler for an edge-coupling configuration.

[0043] The transceiver unit 34 has a corresponding field of view that is defined by a corresponding optical aperture of the optical transducer 36 and focusing optics 44 that projects the optical aperture onto a target scene. A scanner 46 scans the field of view above the target. Each transducer 36 emits (and receives) a cone of light that is collimated by the optics 44, and the resulting light beam from each transducer is projected at a different angle in the field of view. Additionally, the scanner 46 may scan the light beam to control the coverage density of the field of view of the system 20, including changing the coverage density in different regions of the field of view. In this way, even when the field of view of the transducer 36 itself only sparsely covers the target, the coverage density can be filled as needed over the entire target scene or over regions of interest within the target scene.

[0044] In the illustrated embodiment, scanner 46 includes an electromechanical motion assembly that moves optics 44 in small increments in a direction transverse to the optical axis, for example, by means of an electromagnetic or piezoelectric actuator. Such a motion assembly with two-dimensional shifting capabilities is used in cameras to achieve optical image stabilization (OIS) and can be adapted for use in system 20. Alternatively or additionally, the motion assembly can be configured to move sensing device 28 relative to optics 44. Additionally or alternatively, other kinds of scanners can be used in system 20, such as one or more rotating mirrors, or any other suitable type of mechanical, optical, or wavelength-based scanner known in the art.

[0045] Switching network 38 on substrate 30 distributes the light received via waveguide 24 among a plurality of optical buses 40, which include waveguides that are coupled to deliver light to different, respective groups of transceiver units 34. Switching network 38 can also couple electrical signals between electrical bus 26 and electrical bus 42 for delivering electrical signals to and from transceiver units 34. In the embodiment described below with reference to Figure 2 Switching network 38 includes an optical distribution tree that includes an active optical network that includes optoelectronic components that select the bus 40 to which the light will be distributed, followed by a passive optical splitter array. Alternatively, other kinds of optical distribution networks can be used to distribute the light output by core transceiver engine 22 among transceiver units 34.

[0046] Processor 48 controls the operation of system 20 and receives the signals output by transceiver units 34 in response to the light received by device 28. Processor 48 generally includes a general-purpose microprocessor with suitable analog and digital interfaces for controlling and receiving signals from the components of system 20. Optionally or additionally, processor 48 can include dedicated digital logic and other hardware components, which can be hardwired or programmable. Processor 48 processes the signals output by transceiver units 34 to measure, for example, using techniques of coherent LIDAR, the range and / or velocity of points in a target scene relative to system 20. These measurements can be used, in particular, in applications of simultaneous localization and mapping (SLAM).

[0047] In one embodiment, processor 48 switches system 20 between a low-power mode and a high-power mode of operation. In the low-power mode, scanner 46 is fixed in place such that each transducer unit 34 interrogates a single corresponding point in the target scene. In this mode, the sensing resolution is typically limited by the spacing of the optical transducers 36 in array 32. In the high-power mode, processor 48 actuates scanner 46 to laterally (typically in two dimensions) move the field of view of the optical transducers to interrogate the target scene at a finer spacing. These modes of operation are described further below.

[0048] In an alternative embodiment, scanner 46 may be omitted from system 20. In this case, array 32 operates only in a staring mode. This system configuration has the advantages of smaller size and lower power consumption, although at the cost of reduced resolution.

[0049] Figure 2 is a block diagram schematically showing details of sensing device 28 according to an embodiment of the present invention. In this embodiment, transceiver units 34 are arranged in an array of sixteen columns 50, with thirty-two units in each column. Each column is served by a corresponding bus 52 that supplies a coherent light beam from laser 54 in core transceiver engine 22 to all the units in the column. In the illustrated embodiment, transceiver units 34 are edge-coupled and thus direct the corresponding outgoing light radiation beam to turning mirror 55, which directs the beam to the target, and incoming light radiation from the target back to the transceiver units. Alternatively, as described above, the transceiver units may be surface-coupled.

[0050] The laser beam is distributed between columns 50 by switching network 38, which in this embodiment includes a hierarchy of three active switches (SW) 56 (such as thermo-optic switches), followed by two layers of passive beam splitters 58. The setting of active switches 56 defines four groups of transceiver units 34, labeled A, B, C, and D, with four columns in each group. When a given group is selected, the passive beam splitters 58 in the lower layer of network 38 distribute the light beam among the four columns 50 in the group. Multiplexing the laser beam among groups of transceiver units in this way helps reduce the number of laser devices required for sensing within a given range, as well as the number of signal processing channels required.

[0051] In the switching network 38, the specific arrangement of the active switch 56 and the passive beam splitter 58, as well as the number of light sources, depend on the specific application requirements and trade - offs, and are particularly determined by the link budget and the number of signal - processing channels available in the system. In addition, the active switch 56 consumes electrical power and is optically more lossy than the passive beam splitter. Reducing the number of switches increases the number of required passive beam splitters and the number of signal - processing channels needed to process signals simultaneously. Using this trade - off and other trade - offs, various systems with different optimization goals can be designed, for example, as an example, lower power consumption versus a smaller number of signal - processing channels.

[0052] Figure 3 is a schematic front - view of a sensing pattern 60 created by the sensing device 28 in the low - power mode according to an embodiment of the present invention. Each frame captured by the device 28 contains 512 pixels corresponding to the respective fields of view 62 of the transceiver units 34 in all four groups A, B, C, and D without scanning.

[0053] Figure 4 is a timing diagram schematically showing the operating mode of the sensing device 28 in the low - power mode according to an embodiment of the present invention. To capture a frame with a sensing pattern 60 as Figure 3 shown, the sensing device 28 is activated for a short activation period 70 of duration T F within each frame period of duration T S . After the activation period 70 within each frame, there is a long sleep period 72. The duty cycle of the activation period, relative to the sleep period, is typically less than 50% of the frame period and can be as low as 10% or less. For example, T S can be 250 μs, while the frame period T F is 10 ms, resulting in a duty cycle of 2.5% assuming a capture rate of 100 frames per second.

[0054] During each activation period 70, first the laser 54 is turned on and stabilized for a stabilization period 74 (e.g., 50 μs). Then, the switching network 38 ( Figure 2 ) continuously distributes the laser beam to each of the four groups A - D during respective sensing periods 76, 78, 80, 82 (each 50 μs in this example). Alternatively, the sensing device 28 can operate at a higher or lower duty cycle and frame rate, depending on factors such as the target sensing range and sensitivity, as well as other application requirements.

[0055] Figure 5 is a flow chart schematically showing a method for optical sensing with variable resolution according to an embodiment of the present invention. For clarity, the method is described below with reference to the components of the system 20, but it can alternatively be implemented in other systems with a suitable sensing array and scanning capabilities.

[0056] Initially, in an initial image acquisition step 90, system 20 operates in a low-power mode, in which the sensing device acquires an image at a low resolution. In this step, as described above, the sensing device 28 operates intermittently in a staring mode (during the activation period 70) without scanning. In a processing step 92, the processor 48 processes the low-resolution image output by the sensing device 28 to extract features that may be of interest. In a feature detection step 94, the processor 48 tests the extracted features to detect any features that meet the criteria requiring high-resolution sampling and analysis. As long as no features meeting the criteria are detected, the sensing device 28 continues to operate in the low-power mode of step 90.

[0057] When a feature of interest is detected in step 94, in a scan activation step 96, the processor 48 switches system 20 to operate in a high-power scan mode. In this mode, the laser 54 operates continuously, and the scanner 46 (FIG. 1) is driven in a raster pattern to move the field of view defined by the transducer 36 in order to fill Figure 3 the gaps between the columns and rows of the sensing pattern shown. In this way, for example, in a high-resolution acquisition step 98, a sensing frame with a resolution of 1 million pixels (960×960 pixels) can be captured at a capture rate of approximately 2.5 frames per second. Alternatively, the frame rate can be increased at the cost of reduced resolution. The achievable frame rate and resolution depend on factors such as the optical design of system 20, the optical power available from the laser 54, and the range of distances and angles to be covered.

[0058] Additionally or alternatively, when the device 28 is operating in the low-power mode and a feature of interest is identified in step 94 in a certain part of the frame, the optical switching network 38 can be controlled to feed the laser beam in the high-power mode only to one or more sets of transceiver units 34 covering the area containing the feature of interest. Thus, in step 98, a high-resolution image is captured in the area of the field of view of system 20 that is found to contain one or more features of interest.

[0059] The specific physical configuration of system 20 and the sensing device 28 and the operating parameters of the low-power mode and the high-power mode of operation have been described above only by way of example. Other system and array configurations and other sets of operating parameters can alternatively be used for similar purposes and are considered to be within the scope of the present invention.

[0060] Accordingly, it should be understood that the embodiments described above are cited by way of example, and the present invention is not limited to those embodiments specifically shown and described above. Rather, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications of these features that would occur to those skilled in the art upon reading the foregoing description and that are not disclosed in the prior art.

Claims

1. An optical sensing system, comprising: An array of optical transceiver units, which are arranged in multiple groups and configured to emit a beam of corresponding outgoing light radiation towards a target scene and receive and sense incident light radiation from the target scene; A laser, which is configured to generate the outgoing light radiation; An optical switching network, which is coupled to selectively transfer the outgoing light radiation from the laser to the groups for transmission by the optical transceiver units; And A controller, which is configured to activate the system to sense the target scene during a series of activation periods interleaved with sleep periods, such that during each activation period, the controller turns on the laser and then controls the optical switching network during the activation period to continuously transfer the outgoing light radiation to the multiple groups for transmission by the optical transducers in each group, and then turns off the laser after the activation period.

2. The system according to claim 1, wherein The duty cycle of the activation period relative to the sleep period is less than 50%.

3. The system according to claim 2, wherein The duty cycle is less than 10%.

4. The system according to claim 1, wherein, The optical transceiver units are configured to measure the range to corresponding points in the target scene by coherently sensing the incident light radiation.

5. The system according to claim 1, wherein, The optical switching network includes a hierarchy of active optical switches, which are set by the controller to select the groups to receive the outgoing light radiation.

6. The system according to claim 5, wherein The optical transceiver units in each group are arranged in multiple columns, and wherein the optical switching network further includes a passive beam splitter, which is coupled to distribute the outgoing light radiation from the optical switch among the columns in each group.

7. The system according to claim 1, wherein The array of optical transceiver units and the optical switching network are disposed on a photonic integrated circuit (PIC) and interconnected by optical waveguides on the PIC.

8. The system according to any one of claims 1-7, wherein, The optical transceiver units have corresponding fields of view, and the beam of the corresponding outgoing light radiation is emitted into the corresponding fields of view, and wherein the system includes a scanner, which is configured to scan the fields of view across corresponding portions of the target scene.

9. The system according to claim 8, wherein, The controller is configured to control the scanner such that in a first sensing mode, the scanner is inactive, whereby the transceiver units sense a matrix of points in the target scene at a first resolution determined by the pitch of the transceiver units, and in a second sensing mode, actuates the scanner to sense the target scene at a second resolution finer than the first resolution.

10. The system according to claim 9, wherein, In the first sensing mode, the controller activates the laser only during the activation periods interleaved with the sleep periods, and wherein, in the second sensing mode, the controller continuously activates the laser.

11. An optical sensing system, comprising: An array of optical sensing units, which have corresponding fields of view; A scanner, which is configured to scan the fields of view of the optical sensing units across corresponding portions of a target scene; And A controller configured to operate the system in a low-power mode of operation, in which the optical sensing unit senses a matrix of points in the target scene at a first resolution in a staring configuration, and to switch the system to a high-power mode of operation, in which the scanner scans the field of view of the optical sensing unit to sense the target scene at a second resolution finer than the first resolution.

12. The system according to claim 11, wherein, The optical sensing unit includes an optical transceiver unit configured to emit corresponding outgoing light radiation beams towards the target scene and to receive incoming light radiation from the target scene.

13. The system according to claim 12, wherein, The optical transceiver unit is configured to measure the range to the points in the target scene by coherently sensing the light radiation reflected from the target scene.

14. The system according to claim 11, wherein, In the low-power mode, the controller activates the system during a series of activation periods to sense the target scene, the activation periods being interleaved with sleep periods during which the system is inactive.

15. The system according to claim 14, wherein, The controller activates the system to operate continuously when in the high-power mode.

16. The system according to any one of claims 11-15, wherein, The controller is configured to detect an interesting feature in an image captured by the array of the optical sensing unit when operating in the low-power mode, and to switch the system to the high-power mode in response to the detected feature.

17. The system according to claim 16, wherein, The controller is configured to control the array of the optical sensing unit and the scanner to sense a portion of the target scene containing the interesting feature in the high-power mode.

18. The system according to any one of claims 11-15, wherein, The scanner is inactive in the low-power mode of operation.

19. The system according to any one of claims 11-15, wherein, The scanner is configured to move the field of view of the sensing unit frame by frame in the low-power mode of operation.

20. The system according to any one of claims 11-15, wherein, The controller is configured to change the frame rate and change the second resolution of the system in the high-power mode of operation.

21. A method for optical sensing, comprising: Providing an optical sensing device including an array of optical sensing units, the array of optical sensing units having respective fields of view; Operating the device in a low-power mode, in which the sensing units sense a matrix of points in the target scene at a first resolution in a staring configuration; And Switching the device to a high-power mode, in which a scanner scans the field of view of the optical sensing unit to sense the target scene at a second resolution finer than the first resolution.

22. The method according to claim 21, wherein, Providing the optical sensing device includes measuring the range to the points in the target scene by coherently sensing the light radiation reflected from the target scene.

23. The method according to claim 21, wherein Operating the device in the low-power mode includes activating the array during a series of activation periods to sense the target scene, the activation periods being interleaved with sleep periods during which the array is inactive.

24. The method according to claim 23, wherein switching the device includes operating the device continuously when in the high-power mode.

25. The method according to claim 23, wherein The duty cycle of the activation periods relative to the sleep periods is less than 50%.

26. The method according to claim 25, wherein, The duty cycle is less than 10%.

27. The method according to any one of claims 21-26, wherein, Switching the device includes detecting an interesting feature in an image captured by the array of the optical sensing unit when operating in the low power mode, and switching the device to the high power mode in response to the detected feature.

28. The method according to claim 27, wherein, Switching the device includes controlling the device to sense a part of the target scene including the interesting feature in the high power mode.

29. The method according to any one of claims 21-26, wherein The scanner is inactive in the low power mode.

30. The method according to any one of claims 21 to 26, wherein, Operating the device in the low power mode includes moving the field of view of the sensing unit frame by frame by the scanner in the low power mode.

31. The method according to any one of claims 21 to 26, wherein Switching the device to the high power mode includes changing the frame rate and changing the second resolution in the operating high power mode.

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