Activating an electrical device using time of flight sensor data

Abstract

A mechanism for activating an electrical device using time-of-flight sensor data. One or more time-of-flight parameters, derived from the time-of-flight sensor data, are monitored over a plurality of updates to the time-of-flight sensor data. In particular, two or more thresholds are monitored to determine whether or not any threshold is breached (by a corresponding time-of-flight parameter) for more than a predetermined number of consecutive updates to the time-of-flight sensor data. The predetermined number of consecutive updates is different for each threshold. Responsive to a positive determination that a threshold has been breached for at least a predetermined number of consecutive updates, the electrical device is activated.

Description

[0001] Activating an electrical device using time of flight sensor data

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of time-of-flight sensing, and in particular to the activation of an electrical device responsive to time-of-flight sensor data.

[0004] BACKGROUND OF THE INVENTION

[0005] There is an increasing demand for accurate activation of one or more electrical devices (such as lamps) responsive to the presence of an individual or subject in the vicinity of the electrical device(s).

[0006] A typical approach makes use of a PIR sensor to detect motion. Through appropriate design, it is possible to detect motion in the vicinity of the electrical device to trigger the activation of the electrical device. However, a PIR sensor relies upon continual detection of motion, particularly large motion such as walking. It is common for electrical devices to switch off if no motion is detected, which can disadvantageous^ deactivate the electrical device even if the individual is still in the vicinity of the electrical device - e.g., but making little motion.

[0007] US2019172189A1 relates to a sensing and alert system includes a time of flight (ToF) sensor arranged to capture real-time image data, and a processor operatively coupled to the ToF sensor and to a lighting module. The processor compares real-time image data from the ToF sensor to the stored calibration image data and activate the light module if the difference is greater than a predetermined amount.

[0008] US2016345407A1 relates to gesture control. For gestures performed from each of a plurality of different positions, a different control policy is selected based on being associated with the detected gesture and detected position. The gesture of users could be detected by a ToF sensor by capturing a depth-aware or three-dimensional image of the space, including the user and his or her gestures.

[0009] EP24421962A2 employs a time-of-flight sensor to detect movement of a body part of the user, ascertaining whether or not the movement of the body part conforms to a recognized movement of the body part, interpreting the recognized movement of the body part as a performable action, and thereafter actuating industrial machinery to perform the performable action.

[0010] There is a desire to provide an improved and more reliable mechanism for controlling the operation of an electrical device responsive to the presence of an individual or subject within the vicinity of the electrical device.

[0011] SUMMARY OF THE INVENTION

[0012] The invention is defined by the claims.

[0013] According to examples in accordance with an aspect of the invention, there is provided a computer-implemented method for activating an electrical device using a time-of- flight sensor.

[0014] The computer-implemented method comprises obtaining time-of-flight sensor data comprising a time-of-flight measurement for each of a plurality of spatial regions interrogated by the time-of-flight sensor, wherein the time-of-flight sensor data is iteratively updated and each time-of-flight measurement is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region of the time-of-flight measurement; monitoring one or more time-of-flight parameters, derived from the time-of-flight sensor data; defining at least two thresholds, each threshold being associated with one of the one or more time-of-flight parameters and each threshold being associated with a different predetermined number of consecutive updates; and responsive to at least one of the thresholds being and remaining breached by the value of its associated time-of-flight parameter for at least the associated predetermined number of consecutive updates to the time-of-flight sensor data, activating the electrical device.

[0015] The present disclosure therefore proposes to monitor two or more thresholds for one or more time-of-flight parameters, derived from time-of-flight sensor data, for activating the electrical device. The time-of-flight parameters are parameters that are expected to change in response to the entry of an individual into the field of view of the time- of-flight sensor, and may represent an extreme value of the time-of-flight measurements (e.g., a maximum or minimum value).

[0016] Each threshold is associated with a different number of consecutive updates to the time-of-flight sensor data. Only when the threshold is breached for the corresponding number of consecutive updates will the electrical device be activated. This advantageously reduces or avoids a risk of noise or natural variations in the sensor data falsely triggering the activation of the electrical device. By using different numbers of consecutive updates, the sensitivity of the activation to different thresholds can be tweaked - e.g., to facilitate quick activation for highly probable entry of an individual and slower activation for less probable entry of an individual into the field of view of the sensor data.

[0017] A detectable object is further than a baseline position within the spatial region of the time-of-flight measurement if it is more distant from the time-of-flight sensor (within the spatial region) than the baseline position.

[0018] In some examples, at least one time-of-flight parameter is derived from time- of-flight measurements of active blocks, wherein: each active block comprises a contiguous group of two or more spatial regions that contain an active object. For each spatial region, an active object is any detectable object that lies between the baseline position of the spatial region and the time-of-flight sensor.

[0019] In some examples, the one or more time-of-flight parameters comprises an active depth parameter, the active depth parameter having the value of the time-of-flight measurement for the spatial region that: belongs to an active block; and the distance between the active object and the baseline position of said spatial region is the greatest amongst all spatial regions belonging to any active block.

[0020] The active depth has been herein identified as a good indicator of the presence of an individual within the field of view. Thus, accuracy of identifying an individual and correctly triggering the activation of the electrical device is achieved.

[0021] The at least two thresholds may comprise: a first threshold associated with the active depth parameter, wherein the first threshold is associated with a first predetermined number of consecutive updates to the time-of-flight sensor data; and a second, different threshold associated with the active depth parameter, wherein the second threshold is associated with a second, different predetermined number of consecutive updates to the time- of-flight sensor data.

[0022] The first threshold may be associated with a greater distance from a baseline position than the second threshold; and the first predetermined number of updates is less than the second predetermined number of consecutive updates. This increases a speed of activation of the electrical device for scenarios in which it is highly likely that an individual has entered the field of view of the time-of-flight sensor (and has approached close to the sensor, whilst reducing false triggering of the electrical device.

[0023] In particular, this technique provides an improved balance between activation speed and reduced false triggering. By using different thresholds for a same parameter (with the different thresholds needing to be breached for different numbers of consecutive updates), activation can be performed reliably, and at high speed for occasions when there is increased certainty that the breach is caused by an individual (e.g., when there is an object further from the baseline position).

[0024] In some examples, for each spatial region and when a detectable object is located between the time-of-flight sensor and the baseline position and is more than a predetermined distance away from the baseline position, the value of the time-of-flight measurement is a difference between: a time-of-flight distance between the time-of-flight sensor and the baseline position; and a time-of-flight distance between the time-of-flight sensor and the closest, to the time-of-flight sensor, detectable object located between the time-of-flight sensor and the baseline position.

[0025] The predetermined distance may be no less than 150 mm, e.g., no less than 200 mm, e.g., 200mm.

[0026] In some examples, the step of monitoring one or more time-of-flight parameters comprises: for each active block, determining a summed value for the active block by summing the time-of-flight measurements for all spatial regions in the active block, wherein the one or more time-of-flight parameters comprises an active volume parameter, the active volume parameter having the value of the largest summed value amongst the active blocks.

[0027] In some examples, each active block comprises a contiguous group of three or more spatial regions that contain an active object. This significantly reduces a likelihood of noise or natural variation in the sensor data contributing to the active depth, thereby reducing the risk of false triggering of the activation of the electrical device.

[0028] The number of contiguous spatial regions that form an active block may be defined in view of the size of object to be detected. This may depend upon the specific use case design for the computer-implemented method and / or electrical device.

[0029] In some examples, for each spatial region, the value of each time-of-flight measurement is zero, or lower than a threshold representing the noise or measuring error of the time-of-flight sensor, when no detectable object is located between the baseline position and the time-of-flight sensor.

[0030] In some examples, for each spatial region, the baseline position is responsive to the position of one or more objects within the spatial region during a calibration of the time-of-flight sensor.

[0031] The electrical device may be a lamp. The plurality of spatial regions may comprise no fewer than 5 spatial regions, e.g., no fewer than 20 spatial regions. The plurality of spatial regions may be arranged in a grid-like formation.

[0032] There is also provided a computer program product comprising computer program code means which, when executed on a computing device having a processing system, cause the processing system to perform all of the steps of any herein disclosed method.

[0033] There is also provided a processing system for activating an electrical device using a time-of-flight sensor.

[0034] The processing system is configured to: obtain time-of-flight sensor data comprising a time-of-flight measurement for each of a plurality of spatial regions interrogated by the time-of-flight sensor, wherein the time-of-flight sensor data is iteratively updated and each time-of-flight measurement is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region of the time-of-flight measurement; monitor one or more time-of-flight parameters, derived from the time-of-flight sensor data; define at least two thresholds, each threshold being associated with one of the one or more time-of-flight parameters and each threshold being associated with a different predetermined number of consecutive updates; and responsive to at least one of the thresholds being and remaining breached by the value of its associated time-of-flight parameter for at least the associated predetermined number of consecutive updates to the time-of-flight sensor data, activate the electrical device.

[0035] The skilled person would be readily capable of adapting the processing system to perform the function(s) of any herein disclosed method, and vice versa.

[0036] There is also provided a lighting system comprising: the processing system; a lighting device configured to emit light when activated; and the time-of-flight sensor, wherein the lighting device functions as the electrical device for activation by the processing system. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0039] Fig. 1 illustrates a scenario in which embodiments may be employed; Fig. 2 illustrates example time-of-flight sensor data;

[0040] Fig. 3 is a flowchart illustrating a proposed method;

[0041] Fig. 4 illustrates a first time-of-flight parameter for a first set of updates to the time-of-flight sensor data;

[0042] Fig. 5 illustrates the first time-of-flight parameter for a second set of updates to the time-of-flight sensor data;

[0043] Fig. 6 illustrates a second time-of-flight parameter for a third set of updates to the time-of-flight sensor data;

[0044] Fig. 7 illustrates the first time-of-flight parameter for the third set of updates to the time-of-flight sensor data;

[0045] Fig. 8 illustrates a processing system; and

[0046] Fig. 9 illustrates a lighting system.

[0047] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The invention will be described with reference to the Figures.

[0049] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0050] The invention provides a mechanism for activating an electrical device using time-of-flight sensor data. One or more time-of-flight parameters, derived from the time-of- flight sensor data, are monitored over a plurality of updates to the time-of-flight sensor data. In particular, two or more thresholds are monitored to determine whether or not any threshold is breached (by a corresponding time-of-flight parameter) for more than a predetermined number of consecutive updates to the time-of-flight sensor data. The predetermined number of consecutive updates is different for each threshold. Responsive to a positive determination that a threshold has been breached for at least a predetermined number of consecutive updates, the electrical device is activated. Figure 1 illustrates an environment 10 in which proposed embodiments may be employed. The environment 10 comprises an electrical device in the form of a lamp 100. The environment also comprises one or more objects 101, 102, here: a desk 101 and a chair 102.

[0051] To improve visibility for a user of the one or more objects 101, 102, it would be desirable for the lamp 100 to automatically switch on or activate (i.e. , emit light) responsive to the presence of an individual within the vicinity of the lamp. Of course, it is common for a lamp to deactivate responsive to failure to identify the presence of an individual, e.g., for a minimum time period.

[0052] Existing lamps with automatic activation functionality usually make use of a passive infrared (PIR) sensor to detect motion. Existing designs for a PIR sensor are configured to realize reasonably good detection range control, such that only big motions (e.g., resulting from an individual walking) in close vicinity of the sensor / lamp will be detected. This reduces a risk of false triggering of the lamp, e.g., people walking in a distance leading to turning on of the lamp which is not desired.

[0053] However, PIR sensors perform poorly when detecting small / minor motions. There are a number of use case scenarios where this is disadvantageous. For example, if a lamp is positioned to illuminate a workstation (e.g., a desk 101 and chair 102 for a child), then if the individual is relatively still (e.g., quietly studying), then the PIR sensor is unlikely to detect small motions such as hand movements during writing or page turning. As a result, the lamp may undesirably turn off or deactivate while the individual is still using the workstation.

[0054] Instead of using a PIR sensor, it is possible to use a radar sensor such as a 5.8G doppler radar. These sensors are able to reliably detect not only big motions but also small / minor motions. However, it is very difficult for a doppler radar sensor to control the detection range or region of interest (ROI). This is especially true if the radar sensor is located at a relatively high location (e.g., on the head of the lamp), which leads to a large signal coverage of the radar sensor. Consequently, the sensor may detect motions from afar leading to false triggers.

[0055] The present disclosure proposes an alternative sensing mechanism for activating an electrical device, such as a lamp, that overcomes at least some of these disadvantages. More particularly, there is proposed a mechanism that achieves highly accurate activation of an electrical device responsive to the presence of an individual within the vicinity of the electrical device or sensor for the electrical device. The proposed approach makes use of time-of-flight sensor data generated or produced using a time-of-flight sensor. The time-of-flight sensor is configured to interrogate a plurality of spatial regions (e.g., defining pixels of the time-of-flight sensor). Each spatial region is a portion of an interrogated volume by the time-of-flight sensor. A time-of-flight measurement is generated for each spatial region. Thus, the time-of-flight sensor data comprises a plurality of time-of-flight measurements.

[0056] It will be appreciated that the time-of-flight sensor data will be iteratively or continuously updated. For instance, the time-of-flight sensor may iteratively capture frames, each frame comprising a plurality of time-of-flight measurements, each time-of-flight measurement being associated with a respective spatial region interrogated by the time-of- flight sensor, and therefore a respective pixel of the time-of-flight sensor.

[0057] In general, a time-of-flight measurement of a spatial region will be responsive to a distance between a nearest detectable object within said spatial region and the time-of- flight sensor.

[0058] A time-of-flight measurement may, for instance, be defined using a temporal measure (e.g., seconds, ms, ps or ns) or a distance measure (e.g., m or mm). Usually, the time-of-flight measurement takes the form of a distance measure.

[0059] In some examples, each time-of-flight measurement may be derived from a respective raw time-of-flight measurement produced by the time-of-flight sensor. A raw time-of-flight measurement may represent a time between emission of a signal (e.g., an infrared light signal, an electromagnetic signal and so on) into a particular spatial region and detection of a reflection of the emitted signal. As another example, each raw time-of-flight measurement may represent a distance conversion of this detected time (e.g., converting the time to a distance using the speed of light). The emission of the signal may represent an interrogation by the time-of-flight sensor.

[0060] For the present disclosure, the time-of-flight measurement of a spatial region is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region. The baseline position may, for instance, be defined in a calibration of baseline defining procedure for the time-of-flight sensor.

[0061] As an example, a baseline time-of-flight measurement may be obtained for each spatial region. The baseline time-of-flight measurement for a spatial region may represent a distance between the time-of-flight sensor and a nearest detectable object in the spatial region during a calibration procedure (e.g., when the interrogated volume contains only background or baseline objects - such as the desk 101 or chair 102). For each spatial region, this nearest detectable object may be labelled a baseline object. More particularly, each baseline time-of-flight measurement may be a raw time-of-flight measurement for the spatial region during a calibration procedure.

[0062] In some examples, a subsequently obtained time-of-flight measurement for a spatial region may then be obtained or defined by determining a difference between the baseline time-of-flight measurement and a raw time-of-flight measurement. In this way, each time-of-flight measurement for a spatial region may effectively represent the distance between the position of the nearest detectable object in the spatial region and the baseline position of the spatial region. In this example, the baseline position within a spatial region may be effectively defined as the position of the baseline object of the spatial region.

[0063] In preferred examples, a time-of-flight measurement for a spatial region may be obtained or defined as being equal to the difference between the baseline time-of-flight measurement and a raw time-of-flight measurement when the difference exceeds some threshold (i. e. , representing a predetermined distance from the baseline object within the spatial region), and a predetermined value (e.g., 0 or “null”) otherwise. The predetermined distance may, for instance, be a distance of no less than 150 mm or no less than 200 mm. This reduces a risk of false activation of the electrical device.

[0064] In other examples, the time-of-flight measurement for a spatial region may be defined as being equal to the raw time-of-flight measurement when the difference between the raw time-of-flight measurement and the baseline time-of-flight measurement exceeds some threshold (i.e. , representing a predetermined distance from the baseline object within the spatial region), and a predetermined value (e.g., 0, “null” or an extremely large value) otherwise. In this example, the baseline position within a spatial region is effectively defined as a position that lies between the position of the baseline object of the spatial region and the time-of-flight sensor, and has the predetermined distance from the baseline object.

[0065] The predetermined distance may, for instance, be a distance of no less than 150 mm or no less than 200 mm. This reduces a risk of false activation of the electrical device.

[0066] Figure 2 illustrates an example approach for generating a time-of-flight measurement for each of a plurality of spatial regions. Each spatial region is represented by a different entry in a grid. In this embodiment of the present disclosure, the time-of-flight sensor is an infrared depth sensor that defines 64 zones or pixels (arranged as an 8 x 8 grid). Each zone corresponds to an entry in a grid as shown in Figure 2. Each zone corresponds to a spatial region in the environment, and contains or defines a time-of-flight measurement for the corresponding spatial region.

[0067] A first frame 210 illustrates baseline time-of-flight measurements generated during a calibration process of the time-of-flight sensor. The first frame effectively provides a 3D map of the space covered by the field of view of the time-of-flight sensor when the interrogated area is unoccupied (i.e., does not contain any individuals or humans).

[0068] Example values for baseline time-of-flight measurements are illustrated in Figure 2. A first set 211 of baseline time-of-flight measurements represents time-of-flight measurements for spatial regions for which the nearest detectable object to the time-of-flight sensor is a first object (e.g., a desk). A second set 212 of baseline time-of-flight measurements represents time-of-flight measurements for spatial regions for which the nearest detectable object to the time-of-flight sensor is a second, different object (e.g., a chair). Other time-of-flight measurements represent spatial regions in which a nearest detectable object is further away (e.g., the floor).

[0069] Each baseline time-of-flight measurement effectively represents the baseline position of a spatial region.

[0070] A second frame 220 illustrates raw time-of-flight measurements generated for a first period or point in time during subsequent use of the time-of-flight sensor data.

[0071] A third frame 230 illustrates time-of-flight measurements for the first period or point in time, which are calculated by, for each spatial region, determining a difference between the raw time-of-flight measurement for the spatial region and the baseline time-of- flight measurement for the spatial region.

[0072] In this example, if the value of the difference is below a predetermined threshold (here: 200) then the value of the time-of-flight measurement is set to 0. This reduces or attenuates noise in the time-of-flight measurements.

[0073] By determining the difference between the baseline time-of-flight measurement of a spatial region and the raw time-of-flight measurement, then any new objects (i.e., not present during the calibration procedure), or movement of any object that was present during the calibration procedure, within the field of view of the time-of-flight sensor are captured by the difference.

[0074] Any spatial region having a non-zero value time-of-flight measurement can be labelled as an active spatial region. Thus, each active spatial region will contain a detectable object between the baseline position of said active spatial region and the time-of-flight sensor. Later described embodiments recognize some active spatial regions are (artificially) created by (natural) variations in raw time-of-flight measurements (e.g., caused by reflections from dust particles or simple noise in the time-of-flight sensor).

[0075] Other approaches for defining each time-of-flight measurement using raw time-of-flight measurements and baseline time-of-flight measurements have been previously disclosed.

[0076] The present disclosure provides a mechanism for predicting whether or not a new object (particularly an individual) has entered the field of view of the time-of-flight sensor and activating an electrical device responsive thereto.

[0077] Figure 3 is a flowchart that illustrates a computer-implemented method 300 according to an embodiment. The computer-implemented method is for activating an electrical device (such as a lamp) using a time-of-flight sensor.

[0078] The computer-implemented method 300 comprises a step 310 of obtaining time-of-flight (TOF) sensor data. The time-of-flight sensor data comprises a time-of-flight measurement for each of a plurality of spatial regions interrogated by the time-of-flight sensor.

[0079] The time-of-flight sensor data is iteratively updated. Thus, in practice, step 310 may be iteratively repeated independently of any other step of the method.

[0080] As previously explained, each time-of-flight measurement is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region of the time-of-flight measurement. Suitable examples of time-of-flight measurements (e.g., derived from baseline and raw time-of-flight measurements) have been previously disclosed.

[0081] The computer-implemented method 300 also comprises a step 320 of monitoring one or more time-of-flight parameters, derived from the time-of-flight sensor data. Thus, the time-of-flight parameter(s) are derived or produced from the time-of-flight measurements of the time-of-flight sensor data. A time-of-flight parameter is a parameter having a value that changes responsive to one or more of the time-of-flight measurements in the time-of-flight sensor data.

[0082] As a simple example, the time-of-flight parameter may have the value of the time-of-flight measurement, amongst all time-of-flight measurements, indicating the furthest object from the baseline position of its corresponding spatial region.

[0083] As another example, the time-of-flight parameter may have the value of the time-of-flight measurement closest to the time-of-flight sensor amongst all time-of-flight measurements. A number of other suitable and preferred examples of time-of-flight parameters will be described later in this disclosure.

[0084] The computer-implemented method 300 also comprises a step 330 of defining at least two thresholds, each threshold being associated with one of the one or more time-of- flight parameters and each threshold being associated with a different predetermined number of consecutive updates.

[0085] The at least two thresholds may be associated with a same time-of-flight parameter, different time-of-flight parameters or a mixture of the two (e.g., two or more associated with a same first time-of-flight parameter and one or more associated with a second time-of-flight parameter.

[0086] The computer-implemented method 300 also comprises an activation check process 340. The activation check process 340 comprises, responsive to at least one of the thresholds being and remaining breached by the value of its associated time-of-flight parameter for at least the associated predetermined number of consecutive updates to the time-of-flight sensor data, activating the electrical device.

[0087] Thus, two or more thresholds are continually monitored during the iterative updates to the time-of-flight sensor data. Each threshold is associated with a particular time- of-flight parameter. If at least one of these thresholds is breached (i. e. , becomes breached and remains breached) by the value of its associated time-of-flight parameter for a predetermined (to the threshold) number of consecutive updates to the time-of-flight sensor data, then the electrical device is activated. The predetermined number of consecutive updates is different for at least two of the thresholds.

[0088] In effect, the detection of the breach of a threshold for more than the predetermined number of consecutive updates functions as a detection of the presence of an individual.

[0089] The activation check process 340 may therefore comprise determining, in a step 341, whether any of the thresholds have been breached for their corresponding predetermined number of consecutive updates. Responsive to a positive determination, process 340 activates the electrical device in a step 342. Responsive to a negative determination, process 340 ends (e.g., the method reverts back to step 310).

[0090] It has previously been described how the value(s) of one or more time-of- flight parameters are compared to a threshold to decide whether or not to activate the electrical device. In preferred examples, at least one (e.g., each) time-of-flight parameter is derived from time-of-flight measurements of active blocks.

[0091] An active block is any contiguous group of two or more spatial regions that contain an active object. An active object is any detectable object (to the time-of-flight sensor) that lies between the baseline position of the spatial region and the time-of-flight sensor. The identification of time-of-flight measurements containing an active object can be trivially achieved.

[0092] Put another way, each active block comprises a contiguous group of two or more active spatial regions. Each active spatial region contains a detectable object between the baseline position of said active spatial region and the time-of-flight sensor.

[0093] A contiguous group of spatial regions is a group of spatial regions in which each spatial region immediately / directly abuts or neighbors another spatial region in the same contiguous group. A contiguous group will include all spatial regions that immediately abut or (directly) neighbor any of the spatial regions in the contiguous group. Thus, when considered as a whole, a contiguous group will only directly abut or neighbor one or more spatial regions that do not contain an active object.

[0094] In preferred examples, each active block comprises a contiguous group of three or more (active) spatial regions, more preferably four or more (active) spatial regions, that contain an active object. This reduces a probability that noise or other natural variations will affect or influence the value of the time-of-flight parameter, reducing a risk of false triggering or activating of the electrical object.

[0095] The use of time-of-flight parameters derived from time-of-flight measurements of only active blocks reduces the likelihood of noise or other variations contributing to the time-of-flight parameter(s). In particular, it can be assumed that an individual will occupy more than one spatial region, and that a likelihood of noise significantly affecting contiguous spatial regions is low. This effect is particularly enhanced when each active block comprises three or more spatial regions, and even more enhanced when each active block comprises four or more spatial regions.

[0096] Turning back to Figure 2, it is again noted that the third frame 230 illustrates time-of-flight measurements calculated by, for each spatial region, determining a difference between the raw time-of-flight measurement for the spatial region and the baseline time-of- flight measurement for the spatial region. In this example, if the value of the difference is below a predetermined threshold then the value of the time-of-flight measurement is set to 0. Thus, for this example, identifying the time-of-flight measurement(s) associated with an active block can be trivially performed by identifying any contiguous groups of (e.g., one or more) time-of-flight measurements that have a non-zero value. Only the groups that comprise two or more time-of-flight measurements represent active blocks.

[0097] Thus, the third frame 230 may comprise four separate sets or groups 231, 232, 233, 234 of contiguous measurement(s) that could each potentially represent an active block. A first set 231 represents a first active block comprising 5 spatial regions, and a second set 232 represents a second active block comprising 2 spatial regions. A third set 233 comprises only a single spatial region (and therefore does not represent an active block) and a fourth set 234 comprises only a single spatial region (and therefore does not represent an active block).

[0098] In examples in which an active block requires no less than 3 spatial regions containing an active object, then the illustrated third frame 230 will only identify only a single set 231 of measurements (as the other previously identified sets contained fewer than 3 time-of-flight measurements).

[0099] The greater the number of spatial regions in an active block, the more likely that the active block represents a true object, such as an individual, entering the field-of-view of the time-of-flight sensor (e.g., rather than a natural variation or noise in the time-of-flight sensor data).

[0100] One example of a suitable time-of-flight parameter is an active depth. An active depth has the value of the time-of-flight measurement for the spatial region that belongs to an active block and the distance between the active object and the baseline position is the greatest amongst all spatial regions belonging to any active block.

[0101] Thus, if the value of a time-of-flight measurement increases with increased distance of a detectable object in the corresponding spatial region from the baseline position of said spatial region, then the active depth will be the largest value amongst all the time-of- flight measurements belonging to any set of measurements representing an active block.

[0102] By way of contrast, if the value of a time-of-flight measurement decreases with increased distance from of a detectable object in the corresponding spatial region from the baseline position of said spatial region, then the active depth will be the smallest value amongst all the time-of-flight measurements belonging to any set of measurements representing an active block.

[0103] In the example illustrated by the third frame 230 of Figure 2, the active depth would therefore be 1062. Another example of a suitable time-of-flight parameter is an active volume.

[0104] An active volume is determined by, for each active block, summing the time-of-flight measurements of all spatial regions in the active block to produce a summed value for each active block and defining the largest summed value of the active block(s) as the active volume.

[0105] In the example illustrated by the third frame 230 of Figure 2, the active volume would therefore be 3868 (i.e., 1062 + 916 + 820 + 722 + 348).

[0106] The use of the active depth and / or the active volume mitigates the impact of variations and / or noise on the time-of-flight parameter(s) used to control activation of the electrical device.

[0107] The proposed technique monitors one or more time-of-depth parameters using two or more criteria, each of which is able to trigger activation of the electrical device. Each criterion comprises the value(s) of a time-of-depth parameter breaching a particular (different) threshold for a different number of (temporally adjacent) consecutive updates to the sensor data. It will be clear than when a criterion is met, the electrical device is activated. A number of example criteria are here-after described.

[0108] As an example, if the value of an active depth breaches a first predetermined threshold for a first number of (temporally adjacent) consecutive updates to the sensor data, then a first condition for triggering activation of the electrical device may be met. The first predetermined threshold may, for instance, represent a minimum expected value of a time-of- flight measurement for an upright human entering the field of view of the time-of-flight- sensor. The first number of consecutive updates may, for instance, be at least 2, e.g., 2.

[0109] Figure 4 is a waveform that illustrates an example value of the active depth (AD) over a first set of updates (N) to the sensor data. The first predetermined threshold 405 is identified with a dashed line. In this example, the value of the active depth increases with increasing distance of a detectable object (defining the active depth) from a baseline position.

[0110] At a first point in time 410, during the first set of updates, some noise or natural variation in the sensor data causes the active depth to spike. Thus, the threshold 405 is breached by the example value of the active depth. However, the threshold 405 is not breached for the first number of consecutive (i.e., temporally adjacent) updates to the sensor data, as it is only breached once. Thus, at the first point in time, the first condition is not met. The requirement for the first number of consecutive updates can thereby reduce noise from undesirably meeting the first condition and triggering the activation of the electrical device. At a second point in time 420, during the first set of updates, an individual enters the field of view of the sensor data. This causes the active depth to increase (above the threshold 405) and remain there for multiple consecutive updates to the sensor data. Accordingly, the first condition is met and the electrical device is activated.

[0111] The use of the first condition allows for quick or near-immediate activation of the electrical device when a standing individual is within field of view of the time-of-flight sensor and moves close to the time-of-flight sensor. The effect of noise is significantly mitigated through the use of the active depth itself and appropriate selection of the first predetermined threshold.

[0112] As an example, if the value of an active depth breaches a second predetermined threshold for a second number of consecutive (i. e. , temporally adjacent) updates to the sensor data, then a second condition for triggering activation of the electrical device may be met. Preferably, the second predetermined threshold represents an object closer to a baseline position in a spatial region than the first predetermined threshold. In such examples, the second number of consecutive updates is preferably larger than the first number.

[0113] For instance, if the value of a time-of-flight measurement increases with increased distance from of a detectable object in the corresponding spatial region from the baseline position of said spatial region, then the first predetermined threshold may be larger than the second predetermined threshold. The second number of consecutive updates may, in a working example, be 5.

[0114] Figure 5 is a waveform that illustrates an example value of the active depth (AD) over a second set of updates (N) to the sensor data. The second predetermined threshold 505 is identified with a dashed line. In this example, the value of the active depth increases with increasing distance of a detectable object (defining the active depth) from a baseline position. By comparing Figure 4 to Figure 5, it can be seen that the second predetermined threshold 505 is below the first predetermined threshold.

[0115] In this example, the value of the second number of consecutive updates is 5.

[0116] At a third point in time 510, some noise or natural variation in the sensor data causes the active depth to spike. Thus, the threshold 505 is breached by the example value of the active depth. However, the threshold 505 is not breached for the second number of consecutive (i.e., temporally adjacent) updates to the sensor data. Thus, at the third point in time, the second condition is not met. The requirement for the second number of consecutive updates can thereby reduce noise from undesirably meeting the second condition and triggering the activation of the electrical device.

[0117] It is noted that the second condition may have been met if the second number of consecutive updates was equal to the first number of consecutive updates. This would have undesirably triggered the activation of the electrical device, i.e., creating a false trigger. Figure 5 thereby demonstrates the advantage of an embodiment in which the second number is greater than the first number, i.e., when the number of consecutive updates associated with a threshold increases as the value of the threshold tends towards a value that indicates an increased proximity to a baseline position of a spatial region.

[0118] At a fourth point in time 520, an individual enters the field of view of the sensor data. This causes the active depth to increase (above the threshold 505) and remain there for multiple consecutive updates to the sensor data. Accordingly, the second condition is met and the electrical device is activated.

[0119] This condition can be met, for instance, if an individual enters the field of view of the time-of-flight sensor, but stays some distance away from the time-of-flight sensor. Thus, there is a proximity effect in using the first and second predetermined thresholds in this way. The use of a larger value for the second number of consecutive updates advantageously reduces false triggering of the electrical device.

[0120] Thus, if the value of a time-of-flight measurement increases with increased distance from of a detectable object in the corresponding spatial region from the baseline position of said spatial region, then the value of the threshold may increase as the number of consecutive updates decreases, and vice versa.

[0121] Thus, there is proposed the use of a plurality of thresholds for the active depth. Each threshold is associated with a different number of consecutive updates. The number of consecutive updates preferably increases as the value of the threshold tends towards a value that indicates an increased proximity to a baseline position of a spatial region. The preceding description gives an example of two thresholds.

[0122] As another example, if value of an active volume breaches a third predetermined threshold for a third number of consecutive (temporally adjacent) updates to the sensor data, then a third condition for triggering activation of the electrical device may be met.

[0123] The use of the active volume helps to monitor for special situations, e.g., which may not be captured by use of an active depth or other time-of-flight parameter alone. For example, if an individual moves the chair out of the field of view of the time-of-flight sensor, then sits on the chair and moves into the field-of-view, then it is possible neither the first criterion nor the second criterion previously disclosed will be satisfied because the active depths are not big enough.

[0124] It has been herein identified that the active volume helps to capture the existence of an individual within the field of view of the time-of-flight sensor. If the active volume breaches a threshold for more than the third number of consecutive updates, then the third criterion is satisfied to confirm the entry of a person.

[0125] In some examples, if an active depth and an active volume are both compared to a respective set of one or more thresholds, then the number of consecutive updates associated with each threshold for the active volume may be greater than any number of consecutive updates associated with any threshold for the active depth. This further reduces a risk of false triggering of the activation of the electrical device.

[0126] Figure 6 is a waveform that illustrates an example value of the active volume (AV) over a third set of updates (N) to the sensor data. The third predetermined threshold 605 is identified with a dashed line. In this example, the value of the active volume increases with increasing distance of a detectable object (defining the active depth) from a baseline position.

[0127] At a fifth point in time 610, during the third set of updates, the entry of an individual into the field of view of the time-of-flight sensor causes an increase in the value of an active volume. Thus, the threshold 605 is breached by the value of the active volume. The threshold is breached for at least the third number of consecutive updates. Accordingly, the third condition is met, and the electrical device may be activated.

[0128] Figure 7 is a waveform that illustrates an example value of the active depth (AD) over the third set of updates (N) to the sensor data. The first predetermined threshold 405 and the second predetermined threshold 505 are identified with respective dashed lines. In this example, the value of the active depth increases with increasing distance of a detectable object (defining the active depth) from a baseline position.

[0129] Figure 7 demonstrates however, at the fifth point in time 610, the value of the active depth may not breach either the first nor second predetermined thresholds for at least their respective number of consecutive updates. Thus, if the active volume was not used to trigger the activation of the electrical device, the entry of an individual into the field of view of the time-of-flight sensor may have otherwise been missed.

[0130] The skilled person would be readily capable of developing a processing system for carrying out any herein described method. Thus, each step of the flow chart may represent a different action performed by a processing system, and may be performed by a respective module of the processing system.

[0131] Embodiments may therefore make use of a processing system. The processing system can be implemented in numerous ways, with software and / or hardware, to perform the various functions required. A processor is one example of a processing system which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform the required functions. A processing system may however be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions.

[0132] Examples of processing system components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0133] In various implementations, a processor or processing system may be associated with one or more storage media such as volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that, when executed on one or more processors and / or processing systems, perform the required functions. Various storage media may be fixed within a processor or processing system or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or processing system.

[0134] Figure 8 illustrates an example of a processing system 800 within which one or more parts of an embodiment may be employed. Various operations discussed above may utilize the capabilities of the processing system 800. For example, one or more parts of a system for activating an electrical device may be incorporated in any element, module, application, and / or component discussed herein. In this regard, it is to be understood that system functional blocks can run on a single processing system or may be distributed over several processing systems and locations (e.g. connected via internet).

[0135] The processing system 800 includes, but is not limited to, PCs, workstations, laptops, PDAs, palm devices, servers, storages, and the like. Generally, in terms of hardware architecture, the processing system 800 may include one or more processors 801, memory 802, and one or more I / O devices 807 that are communicatively coupled via a local interface (not shown). The local interface can be, for example but not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface may have additional elements, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Further, the local interface may include address, control, and / or data connections to enable appropriate communications among the aforementioned components.

[0136] The processor 801 is a hardware device for executing software that can be stored in the memory 802. The processor 801 can be virtually any custom made or commercially available processor, a central processing unit (CPU), a digital signal processor (DSP), or an auxiliary processor among several processors associated with the processing system 800, and the processor 801 may be a semiconductor based microprocessor (in the form of a microchip) or a microprocessor.

[0137] The memory 802 can include any one or combination of volatile memory elements (e.g., random access memory (RAM), such as dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and non-volatile memory elements (e.g., ROM, erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), programmable read only memory (PROM), tape, compact disc read only memory (CD-ROM), disk, diskette, cartridge, cassette or the like, etc.). Moreover, the memory 802 may incorporate electronic, magnetic, optical, and / or other types of storage media. Note that the memory 802 can have a distributed architecture, where various components are situated remote from one another, but can be accessed by the processor 801.

[0138] The software in the memory 802 may include one or more separate programs, each of which comprises an ordered listing of executable instructions for implementing logical functions. The software in the memory 802 includes a suitable operating system (O / S) 805, compiler 804, source code 803, and one or more applications 806 in accordance with exemplary embodiments. As illustrated, the application 806 comprises numerous functional components for implementing the features and operations of the exemplary embodiments. The application 806 of the processing system 800 may represent various applications, computational units, logic, functional units, processes, operations, virtual entities, and / or modules in accordance with exemplary embodiments, but the application 806 is not meant to be a limitation.

[0139] The operating system 805 controls the execution of other computer programs, and provides scheduling, input-output control, file and data management, memory management, and communication control and related services. It is contemplated by the inventors that the application 806 for implementing exemplary embodiments may be applicable on all commercially available operating systems. Application 806 may be a source program, executable program (object code), script, or any other entity comprising a set of instructions to be performed. When a source program, then the program is usually translated via a compiler (such as the compiler 804), assembler, interpreter, or the like, which may or may not be included within the memory 802, so as to operate properly in connection with the O / S 805. Furthermore, the application 806 can be written as an object oriented programming language, which has classes of data and methods, or a procedure programming language, which has routines, subroutines, and / or functions, for example but not limited to, C, C++, C#, Pascal, BASIC, API calls, HTML, XHTML, XML, ASP scripts, JavaScript, FORTRAN, COBOL, Perl, Java, ADA, NET, and the like.

[0140] The I / O devices 807 may include input devices such as, for example but not limited to, a mouse, keyboard, scanner, microphone, camera, etc. Furthermore, the I / O devices 807 may also include output devices, for example but not limited to a printer, display, etc. Finally, the I / O devices 807 may further include devices that communicate both inputs and outputs, for instance but not limited to, a NIC or modulator / demodulator (for accessing remote devices, other files, devices, systems, or a network), a radio frequency (RF) or other transceiver, a telephonic interface, a bridge, a router, etc. The I / O devices 807 also include components for communicating over various networks, such as the Internet or intranet.

[0141] The I / O devices 807 may comprise a connector for an electrical device, e.g., for connecting or controlling the operation of an external electrical device. This facilitates control over the operation or activation of the electrical device.

[0142] If the processing system 800 is a PC, workstation, intelligent device or the like, the software in the memory 802 may further include a basic input output system (BIOS) (omitted for simplicity). The BIOS is a set of essential software routines that initialize and test hardware at startup, start the O / S 805, and support the transfer of data among the hardware devices. The BIOS is stored in some type of read-only-memory, such as ROM, PROM, EPROM, EEPROM or the like, so that the BIOS can be executed when the processing system 800 is activated.

[0143] When the processing system 800 is in operation, the processor 801 is configured to execute software stored within the memory 802, to communicate data to and from the memory 802, and to generally control operations of the processing system 800 pursuant to the software. The application 806 and the O / S 805 are read, in whole or in part, by the processor 801, perhaps buffered within the processor 801, and then executed. When the application 806 is implemented in software it should be noted that the application 806 can be stored on virtually any computer readable medium for use by or in connection with any computer related system or method. In the context of this document, a computer readable medium may be an electronic, magnetic, optical, or other physical device or means that can contain or store a computer program for use by or in connection with a computer related system or method.

[0144] The application 806 can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a "computer-readable medium" can be any means that can store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium.

[0145] Figure 9 illustrates a lighting system 900 in which embodiments may be performed.

[0146] The lighting system comprises a processing system 800, a lighting device 910 and a time-of-flight sensor 920.

[0147] The processing system 800 is configured to perform the steps of any herein described method. Accordingly, the processing system is configured to obtain time-of-flight sensor data comprising a time-of-flight measurement for each of a plurality of spatial regions interrogated by the time-of-flight sensor, wherein the time-of-flight sensor data is iteratively updated and each time-of-flight measurement is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region of the time-of-flight measurement; monitor one or more time-of-flight parameters, derived from the time-of-flight sensor data; define at least two thresholds, each threshold being associated with one of the one or more time-of-flight parameters and each threshold being associated with a different predetermined number of consecutive updates; and responsive to at least one of the thresholds being and remaining breached by the value of its associated time-of-flight parameter for at least the associated predetermined number of consecutive updates to the time-of-flight sensor data, activate the electrical device. The processing system 800 may be embodied as a previously described processing system. In particular, the processing system 800 may be configured to communicate with the lighting device 910, which functions as the electrical device, to control the activation of the lighting device 910.

[0148] The lighting device 910 is configured to emit light of a first intensity when activated and emit light of a second, different intensity when deactivated. In some examples, the second intensity is preferably less than the first intensity, e.g., zero. The value of the first intensity may, for instance, be modifiable by an operator of the lighting system.

[0149] Examples of suitable lighting devices are well known in the art, and may comprise any form of lamp, such as a LED arrangement, a halogen bulb and / or a fluorescent light.

[0150] The lighting device functions as the electrical device for activation by the processing system.

[0151] The time-of-flight sensor 920 is the sensor used to generate or produce the time-of-flight sensor data for obtaining and processing by the processing system. Examples of suitable time-of-flight sensors are well established in the art, and have been previously outlined in this disclosure.

[0152] Although above-described embodiments have been described in the context of activating a lamp or light source, the skilled person will readily appreciate that the proposed mechanisms can be configured for activating any form of electrical device (e.g., a camera, a further sensor, an alarm, a virtual assistant system and so on).

[0153] It will be understood that disclosed methods are preferably computer- implemented methods. As such, there is also proposed the concept of a computer program comprising code means for implementing any described method when said program is run on a processing system, such as a computer. Thus, different portions, lines or blocks of code of a computer program according to an embodiment may be executed by a processing system or computer to perform any herein described method.

[0154] There is also proposed a non-transitory storage medium that stores or carries a computer program or computer code that, when executed by a processing system, causes the processing system to carry out any herein described method.

[0155] In some alternative implementations, the functions noted in the block diagram(s) or flow chart(s) may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0156] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0157] A single processor or other unit may fulfill the functions of several items recited in the claims. If a computer program is discussed above, it may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0158] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A computer-implemented method (300) for activating an electrical device (100, 910) using a time-of-flight sensor (920), the computer-implemented method comprising: obtaining (310) time-of-flight sensor data (230) comprising a time-of-flight measurement for each of a plurality of spatial regions interrogated by the time-of-flight sensor, wherein the time-of-flight sensor data is iteratively updated and each time-of-flight measurement is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region of the time-of-flight measurement; monitoring (320) one or more time-of-flight parameters (AD, AV), derived from the time-of-flight sensor data; defining (330) at least two thresholds (405, 505, 605), a first threshold and a second threshold, each threshold being associated with one of the one or more time-of-flight parameters and the first threshold being associated with a first predetermined number of consecutive updates and the second threshold being associated with a second predetermined number of consecutive updates; and responsive to at least one of the thresholds being and remaining breached by the value of its associated time-of-flight parameter for at least the associated predetermined number of consecutive updates to the time-of-flight sensor data, activating (342) the electrical device; wherein the first threshold is associated with a greater distance from the baseline position than the second threshold; and the first predetermined number of updates is less than the second predetermined number of consecutive updates.

2. The computer-implemented method (300) of claim 1, wherein at least one time-of-flight parameter is derived from time-of-flight measurements of active blocks (231, 232), wherein: each active block comprises a contiguous group of two or more spatial regions that contain an active object; andfor each spatial region, an active object is any detectable object that lies between the baseline position of the spatial region and the time-of-flight sensor.

3. The computer-implemented method (300) of claim 2, wherein the one or more time-of-flight parameters comprises an active depth parameter (AD), the active depth parameter having the value of the time-of-flight measurement for the spatial region that: belongs to an active block; and the distance between the active object in said spatial region and the baseline position of said spatial region is the greatest amongst all spatial regions belonging to any active block.

4. The computer-implemented method (300) of any of claims 1 to 3, wherein, for each spatial region and when a detectable object is located between the time-of-flight sensor and the baseline position and is more than a predetermined distance away from the baseline position, the value of the time-of-flight measurement is a difference between: a time-of-flight distance between the time-of-flight sensor and the baseline position; and a time-of-flight distance between the time-of-flight sensor and the closest, to the time-of-flight sensor, detectable object located between the time-of-flight sensor and the baseline position.

5. The computer-implemented method (300) of claim 4, wherein the predetermined distance is no less than 150 mm.

6. The computer-implemented method (300) of any of claims 2 or 3, wherein the step of monitoring one or more time-of-flight parameters comprises, for each active block, determining a summed value for the active block by summing the time-of-flight measurements for all spatial regions in the active block, and wherein the one or more time-of-flight parameters comprises an active volume parameter (AV), the active volume parameter having the value of the largest summed value amongst the active blocks.

7. The computer-implemented method (300) of any of claims 2 to 6, wherein each active block comprises three or more spatial regions.

8. The computer-implemented method (300) of any of claims 1 to 7, wherein, for each spatial region, the value of each time-of-flight measurement is zero when no detectable object is located between the baseline position and the time-of-flight sensor.

9. The computer-implemented method (300) of any of claims 1 to 8, wherein, for each spatial region, the baseline position is responsive to the position of one or more objects within the spatial region during a calibration of the time-of-flight sensor.

10. The computer-implemented method (300) of any of claims 1 to 9, wherein the electrical device is a lamp (100).

11. A computer program product comprising computer program code means which, when executed on a computing device having a processing system, cause the processing system to perform all of the steps of the method (300) according to any of claims 1 to 10.

12. A processing system (800) for activating an electrical device (100, 910) using a time-of-flight sensor (920), the processing system being configured to: obtain (310) time-of-flight sensor data (230) comprising a time-of-flight measurement for each of a plurality of spatial regions interrogated by the time-of-flight sensor, wherein the time-of-flight sensor data is iteratively updated and each time-of-flight measurement is non-responsive to any changes in the position of any detectable object further than a baseline position within the spatial region of the time-of-flight measurement; monitor (320) one or more time-of-flight parameters (AD, AV), derived from the time-of-flight sensor data; define (330) at least two thresholds (405, 505, 605), a first threshold and a second threshold, each threshold being associated with one of the one or more time-of-flight parameters and the first threshold being associated with a first predetermined number of consecutive updates and the second threshold being associated with a second predetermined number of consecutive updates; and responsive to at least one of the thresholds being and remaining breached by the value of its associated time-of-flight parameter for at least the associated predeterminednumber of consecutive updates to the time-of-flight sensor data, activate (342) the electrical device; wherein the first threshold is associated with a greater distance from the baseline position than the second threshold; and the first predetermined number of updates is less than the second predetermined number of consecutive updates.

13. The processing system (800) of claim 12, wherein at least one time-of-flight parameter is derived from time-of-flight measurements of active blocks (231, 232), wherein: each active block comprises a contiguous group of two or more spatial regions that contain an active object; and for each spatial region, an active object is any detectable object that lies between the baseline position of the spatial region and the time-of-flight sensor.

14. The processing system (800) of claim 13, wherein the one or more time-of- flight parameters comprises an active depth parameter (AD), the active depth parameter having the value of the time-of-flight measurement for the spatial region that: belongs to an active block; and the distance between the active object in said spatial region and the baseline position of said spatial region is the greatest amongst all spatial regions belonging to any active block.

15. A lighting system (900) comprising: the processing system (800) of any of claims 12 to 14; a lighting device (910) configured to emit light when activated; and the time-of-flight sensor (920), wherein the lighting device functions as the electrical device for activation by the processing system.

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