Estimation of time of day

Abstract

A system and method for estimating a time of day. A signal responsive to an amount of ambient infrared radiation detected by an infrared sensor is received and processed to estimate the time of day.

Description

[0001] ESTIMATION OF TIME OF DAY

[0002] FIELD OF THE INVENTION

[0003] The invention relates to the field of estimating a time of day.

[0004] BACKGROUND OF THE INVENTION

[0005] Many connected lighting systems (e.g. internet-connected lighting systems) include integrated sensors that allow the lighting systems to provide “smart” lighting functions. The smart lighting functions provided by a connected lighting system may vary according to the time of day.

[0006] Non-connected lighting systems may also include integrated sensors. However, the lack of a synchronized clock in a non-connected lighting system limits the capabilities of non-connected lighting systems.

[0007] JP2004281327A relates to a lamp lighting walkers at night by using electromotive force generated by a solar cell in the daytime. It uses value of an output voltage of the solar cell to determine day and night time.

[0008] KR20230175030A relates to an LED lighting device and a method of operating the same that can adjust brightness according to the illuminance of the surrounding environment and reduce power use both during the day and at night. D2 discloses use an IR sensor to detector IR signal and determine its night or day based on the detected IR signal strength.

[0009] There is therefore a need for a method for estimating a time of day without requiring connection to a network.

[0010] SUMMARY OF THE INVENTION

[0011] The invention is defined by the claims.

[0012] According to examples in accordance with an aspect of the invention, there is provided a processing system for estimating a time of day, the processing system being configured to: receive, from an infrared sensor located in an indoor environment, an ambient infrared strength signal responsive to an amount of ambient infrared radiation detected by the infrared sensor; and process the ambient infrared strength signal to estimate a time of day. The inventors have recognized that the ambient infrared strength of an indoor environment having a window changes according to the time of day, and that the ambient infrared strength may therefore be used to estimate a time of day.

[0013] An estimation of the time of day may, for example, comprise an estimation as to whether the time is morning, afternoon or nighttime. The ambient infrared strength of an indoor environment starts to increase at sunrise, reaches a peak around noon and then decreases, remaining at a low level during the night.

[0014] The infrared sensor may, for example, be provided in a lighting device.

[0015] In some examples, the infrared sensor is an infrared time-of flight sensor.

[0016] The inventors have further recognized that infrared time-of-flight sensors are used in some lighting systems (for example, to detect motion), and that these sensors may additionally be used to provide an ambient infrared strength signal (i.e. a signal responsive to an intensity of infrared radiation from sources other than the infrared time-of-flight sensor), and thus to estimate a time of day.

[0017] In some examples, the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify one or more moments of noon in the ambient infrared strength signal; and estimating the time of day based on at least the identified one or more moments of noon.

[0018] In some examples, the ambient infrared strength signal is acquired during a plurality of days preceding a current day; and the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify a past moment of noon for each day in at least a subset of the plurality of days preceding a current day; and estimating the time of day based on at least the identified past moments of noon.

[0019] Moments of noon may be identified as peaks in the ambient infrared strength signal. Moments of noon may be detected more reliably than moments of sunrise and sunset on cloudy days.

[0020] In some examples, the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify one or more moments of sunrise in the ambient infrared strength signal; and estimating the time of day based on at least the identified one or more moments of sunrise.

[0021] In some examples, the ambient infrared strength signal is acquired during a plurality of days preceding a current day; and the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify a past moment of sunrise for each day in at least a subset of the plurality of days preceding a current day; and estimating the time of day based on at least the identified past moments of sunrise.

[0022] In some examples, the processing system is configured to identify a moment at which the ambient infrared strength signal rises to and crosses a predetermined ambient infrared strength threshold as a moment of sunrise. The predetermined ambient infrared strength threshold may be determined based on an ambient infrared strength signal for the indoor environment recorded over at least a 24 hour period.

[0023] In some examples, the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify one or more moments of sunset in the ambient infrared strength signal; and estimating the time of day based on at least the identified one or more moments of sunset.

[0024] In some examples, the ambient infrared strength signal is acquired during a plurality of days preceding a current day; and the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify a past moment of sunset for each day in at least a subset of the plurality of days preceding a current day; estimating the time of day based on at least the identified past moments of sunset.

[0025] In some examples, the processing system is configured to identify a moment at which the ambient infrared strength signal falls to and crosses a predetermined ambient infrared strength threshold as a moment of sunset.

[0026] The inventors have recognized that, although the ambient infrared strength in an indoor environment during the day varies according to the weather, the level of ambient infrared strength between sunset and sunrise is approximately the same each night, for a given indoor environment. A threshold based on the ambient infrared strength for the indoor environment over at least a 24 hour period, and in particular on the level of ambient infrared strength during one or more previous nights, may therefore be used to identify sunrise and / or sunset.

[0027] In some examples, the processing system is further configured to control a lighting device responsive to the estimated time of day.

[0028] In this way, a lighting device that is not part of a connected lighting system (and that therefore does not have a synchronized clock) may be controlled according to the time of day.

[0029] In some examples, the processing system may use the estimated time of day in combination with further information relating to the indoor environment in order to control the lighting device. For example, the processing system may obtain information from one or more other sensors, e.g. a motion sensor.

[0030] For instance, the processing system may be configured to control the lighting device to provide light in response to a determination that it is nighttime and a determination that information from another sensor indicates that a person is moving within / around the indoor environment.

[0031] In some examples, the infrared sensor is a time-of-flight infrared sensor; and the processing system is further configured to: receive, from the infrared time-of-flight sensor, a distance signal responsive to a time of flight of infrared radiation emitted by the infrared time-of-flight sensor and reflected back to the infrared time-of-flight sensor; process the distance signal to detect a movement in the indoor environment; and control the lighting device responsive to the estimated time of day and the detected movement.

[0032] In this way, a single sensor may be used both to estimate the time of day and to detect movement in the indoor environment.

[0033] In some examples, the processing system is configured to control the lighting device to provide light in response to a determination that, at a time of the detected movement, the estimated time of day is nighttime.

[0034] For instance, the processing system may determine that the estimated time of day is nighttime in response to the estimated time of day being between an estimated moment of sunset and an estimated moment of sunrise, or in response to the ambient infrared strength signal failing to exceed a predetermined threshold.

[0035] In some examples, the processing system is configured to control the lighting device not to provide light in response to a determination that, at a time of the detected movement, the estimated time of day is daytime.

[0036] For instance, the processing system may determine that the estimated time of day is daytime in response to the estimated time of day being between an estimated moment of sunrise and an estimated moment of sunset, or in response to the ambient infrared strength signal exceeding a predetermined threshold.

[0037] In some examples, the processing system is further configured to identify a moment of uncovering a window of the indoor environment by: processing the ambient infrared strength signal to identify a moment at which a rate of increase in ambient infrared strength exceeds a predetermined increase threshold; and identifying the moment at which the rate of increase in ambient infrared strength exceeds the predetermined increase threshold as the moment of uncovering the window. In some examples, the processing system is further configured to identify a moment of covering a window of the indoor environment by: processing the ambient infrared strength signal to identify a moment at which a rate of decrease in ambient infrared strength exceeds a predetermined decrease threshold; and identifying the moment at which the rate of decrease in ambient infrared strength exceeds the predetermined decrease threshold as the moment of covering the window.

[0038] There is also proposed a lighting system comprising: a lighting device; an infrared sensor; and the processing system described above.

[0039] According to another aspect of the invention, there is provided a computer- implemented method for estimating a time of day, the computer-implemented method comprising: receiving, from an infrared sensor located in an indoor environment, an ambient infrared strength signal responsive to an amount of ambient infrared radiation detected by the infrared sensor; and processing the ambient infrared strength signal to estimate a time of day.

[0040] There is also proposed 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 described above.

[0041] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

[0042] BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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:

[0044] Fig. 1 illustrates a lighting system, according to an embodiment of the invention;

[0045] Fig. 2 illustrates a graph of ambient infrared strength for an indoor environment over a six-day period;

[0046] Fig. 3 illustrates a graph of ambient infrared strength for the indoor environment for one day of the six-day period;

[0047] Fig. 4 illustrates a graph of ambient infrared strength for an indoor environment over a period of time during which a window is uncovered and covered several times; Fig. 5 illustrates a graph of ambient infrared strength for another indoor environment over a period of time during which a window is uncovered and covered several times; and

[0048] Fig. 6 illustrates a computer-implemented method for estimating a time of day, according to an embodiment of the invention.

[0049] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The invention will be described with reference to the Figures.

[0051] 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.

[0052] The invention provides a system and method for estimating a time of day. A signal responsive to an amount of ambient infrared radiation detected by an infrared sensor is received and processed to estimate the time of day.

[0053] Embodiments are at least partly based on the realization that an ambient infrared strength of an indoor environment varies according to the time of day, and that, despite some variation in ambient infrared strength due to other factors (e.g. the weather, opening / closing curtains or blinds, etc.), an underlying pattern in ambient infrared strength due to the time of day may be recognized and used to estimate a time of day.

[0054] Illustrative embodiments may, for example, be employed in non-connected lighting systems.

[0055] Figure 1 illustrates a lighting system 100, according to an embodiment of the invention. The lighting system comprises a lighting device 110, an infrared sensor 120 and a processing system 130. The processing system 130 is, itself, an embodiment of the invention.

[0056] The lighting system 100 is a non-connected lighting system; that is, a lighting system that is not connected to a computing network, and, in particular, is not connected to the internet. The lighting system may be installed in an indoor environment, such as a room in a user’s home (e.g. a bedroom or bathroom). The lighting device 110 may be any device capable of emitting light. In Figure 1, the lighting device is a table lamp, however, the lighting system 100 is not limited to use with table lamps, and any other kind of lighting device (e.g. a ceiling light, a floor lamp, etc.) may be used in the lighting system 100.

[0057] In some examples, the infrared sensor 120 may be an infrared time-of-flight sensor. An infrared time-of-flight sensor both emits and detects infrared radiation: by detecting infrared radiation that has been emitted by the infrared time-of-flight sensor and reflected by an object in the indoor environment in which the lighting system is installed, the distance between the infrared time-of-flight sensor and the object may be determined. This allows motion in the indoor environment (e.g. due to a person moving in the indoor environment) to be detected.

[0058] A ID (or “single zone”) infrared time-of-flight sensor or a 3D (or “multizone”) infrared time-of-flight sensor may be used in the lighting system 100. A ID infrared time-of-flight sensor is capable of determining the distance to one or more objects; a 3D infrared time-of-flight sensor is capable of determining the size of an object and its position in 3D space. Alternatively, the infrared sensor 120 may be a passive infrared sensor (i.e. an infrared sensor that only receives infrared radiation, and does not emit infrared radiation).

[0059] In Figure 1, the infrared sensor 120 and processing system 130 are illustrated as separate elements to the lighting device 110. However, in some examples, one or both of the infrared sensor and the processing system may be integrated in the lighting device.

[0060] The processing system 130 is configured to receive an ambient infrared strength signal 125 from the infrared sensor 120. The ambient infrared strength signal is responsive to an amount of ambient infrared radiation detected by the infrared sensor. Ambient infrared radiation is infrared radiation that originates from sources other than the infrared sensor (e.g. infrared radiation originating from sunlight that has entered the room).

[0061] Where the infrared sensor 120 is an infrared time-of-flight sensor, the infrared time-of-flight sensor may detect both ambient infrared radiation from the indoor environment, and infrared radiation emitted by the infrared time-of-flight sensor and reflected by objects in the indoor environment back to the infrared time-of-flight sensor. The ambient infrared strength signal is responsive to the infrared radiation detected by the infrared time- of-flight sensor, excluding the infrared radiation emitted by the infrared time-of-flight sensor and reflected back to the infrared time-of-flight sensor.

[0062] Many infrared time-of-flight sensors are capable of directly outputting a signal responsive to ambient infrared strength. The processing system may therefore receive the ambient infrared strength signal 125 from the infrared time-of-flight sensor. Alternatively, the processing system may receive from the infrared time-of-flight sensor an initial signal responsive to all infrared radiation detected by the infrared sensor, and process the initial signal to remove infrared radiation emitted by the infrared time-of-flight sensor and reflected back, thereby generating the ambient infrared strength signal. Any existing technique may be used to remove the infrared radiation emitted by the infrared time-of-flight sensor; for instance, the wavelength(s) of infrared radiation emitted by the infrared time-of-flight sensor may be excluded from the ambient infrared strength signal.

[0063] Where the infrared sensor 120 is a passive infrared sensor, any infrared radiation detected by the passive infrared sensor may be considered to be ambient infrared radiation. The ambient infrared strength signal may therefore simply be a signal responsive to an amount of infrared radiation detected by the passive infrared sensor.

[0064] Having received the ambient infrared strength signal 125, the processing system 130 is configured to process the ambient infrared strength signal to estimate a time of day. The underlying principle behind the use of ambient infrared strength in estimating a time of day is illustrated by Figure 2, which shows a graph 200 of ambient infrared strength (in kilo counts per second) for an indoor environment, measured using an infrared time-of-flight sensor located in the indoor environment, over a six-day period.

[0065] For each day, the graph 200 shows the same trend in ambient infrared strength. During the night (i.e. before sunrise and after sunset), the ambient infrared strength of the indoor environment remains at a low level, experiencing very little variation. During daytime (i.e. between sunrise and sunset), the ambient infrared strength increases from the low nighttime level, reaches a peak at around noon, and then returns to the low nighttime level around sunset.

[0066] In addition to this general trend, the ambient infrared strength experiences a high amount of variation during the day, due to changes in the weather that affect the amount of sunlight entering the indoor environment. Similarly, the peak in ambient infrared strength varies from day to day, due to changes in the weather. However, the ambient infrared strength at nighttime has approximately the same value each night.

[0067] The inventors have recognized that this pattern may be used to estimate a time of day. In particular, the inventors have recognized that the pattern may be used to determine one or more moments of sunrise, noon and / or sunset in the ambient infrared strength signal, from which a current (approximate) time of day may be inferred. The ambient infrared strength of the indoor environment on Day 5 of the six- day period is shown in more detail in Figure 3, which shows a graph 300 of ambient infrared strength for the indoor environment from 00:00 to 23:59 on Day 5. The actual times of sunrise (05:58) and sunset (18:06) have been marked on the graph 300.

[0068] Between 00:00 and 05:58 (sunrise), the ambient infrared strength remains at a low level, slightly under 2.00 kilo counts per second. Shortly after sunrise at 05:58, the ambient infrared strength starts to increase gradually, reaching a peak in the early afternoon (around 14:00). Between 05:58 and 14:00, the ambient infrared strength increases and decreases several times, due to changes in the weather. After reaching its peak, the ambient infrared strength gradually decreases, reaching a steady low value, of slightly under 2.00 kilo counts per second, again at around sunset (18:06). Between 14:00 and 18:06, the ambient infrared strength again increases and decreases several times, due to changes in the weather.

[0069] Returning to Figure 1, the processing system 130 may be configured to estimate the time of day by processing the ambient infrared strength signal 125 to identify one or more predefined moments in the ambient infrared strength signal, and estimating the time of day based on at least the identified one or more predefined moments. The one or more predefined moments may comprise one or more moments of sunrise, one or more moments of noon, and / or one or more moments of sunset. Preferably, the one or more predefined moments may comprise more than one type of predefined moment (e.g. one or more moments of noon and one or more moments of sunset; one or more moments of sunrise and one or more moments of sunset; one or more moments of sunrise and one or more moments of noon; or one or more moments of sunrise, one or more moments of noon and one or more moments of sunset).

[0070] In some examples, the ambient infrared strength signal 125 may be acquired during a plurality of days preceding a current day. The plurality of days preceding the current day may, for example, include a day immediately preceding the current day (e.g. the ambient infrared strength signal may be acquired over a period of days or weeks leading up to the current day). However, this is not necessarily the case: in some examples, an ambient infrared strength signal may be acquired during an initial period of use of the lighting system in the indoor environment, and subsequent estimations of the time of day may be based on the ambient infrared strength signal acquired during the initial period.

[0071] The processing system 130 may estimate the time of day by processing the ambient infrared strength signal 125 to identify at least one predefined moment (e.g. at least one of a past moment of sunrise, a past moment of noon and / or a past moment of sunset) for each day in at least subset of the plurality of days preceding the current day, and estimating the time of day based on at least the identified predefined moments.

[0072] The estimation of the time of day may be based on at least identified past moments of noon for at least a subset of the plurality of days preceding the current day. The moments of noon may be identified by dividing the ambient infrared strength signal into a plurality of 24-hour periods, and, for each of at least a subset of the 24-hour periods, identifying a peak in the ambient infrared strength signal for the 24-hour period as the moment of noon for the 24-hour period.

[0073] The estimation of the time of day may be based on at least identified past moments of sunrise for at least a subset of the plurality of days preceding the current day. The moments of sunrise may be identified by dividing the ambient infrared strength signal into a plurality of 24-hour periods, and, for each of at least a subset of the 24-hour periods, identifying a moment in the ambient infrared strength signal for the 24-hour period at which the ambient infrared strength signal rises to and crosses a predetermined ambient infrared strength threshold as the moment of sunrise for the 24-hour period.

[0074] The estimation of the time of day may be based on at least identified past moments of sunset for at least a subset of the plurality of days preceding the current day. The moments of sunset may be identified by dividing the ambient infrared strength signal into a plurality of 24-hour periods, and, for each of at least a subset of the 24-hour periods, identifying a moment in the ambient infrared strength signal for the 24-hour period at which the ambient infrared strength signal falls to and crosses the predetermined ambient infrared strength threshold as the moment of sunset for the 24-hour period.

[0075] As the skilled person will appreciate, a suitable threshold value for identifying a moment of sunrise and / or a moment of sunset will depend on characteristics of the indoor environment (e.g. a geographical location of the indoor environment, a number and size of windows of the indoor environment, etc.) and on the position of the infrared sensor 120 within the indoor environment (in particular, a distance of the infrared sensor from a window). The predetermined ambient infrared strength threshold may therefore be determined based on the ambient infrared strength signal. For instance, the predetermined ambient infrared strength signal may be set as a value slightly higher (e.g. 5-15% higher) than the lowest value of ambient infrared strength over the plurality of days, or a value slightly higher (e.g. 5-15% higher) than the lowest value of ambient infrared strength within the 24-hour period for which the moment of sunrise and / or moment of sunset is being identified (or within an immediately preceding 24-hour period). On some days, due to weather conditions, the ambient infrared strength signal 125 may fluctuate around the predetermined ambient infrared strength threshold during the daytime (i.e. during the hours between sunrise and sunset). In other words, for some 24-hour periods, there may be more than one moment in the ambient infrared strength signal at which the ambient infrared strength signal rises to and crosses the predetermined ambient infrared strength threshold, and more than one moment in the ambient infrared strength signal at which the ambient infrared strength signal falls to and crosses the predetermined ambient infrared strength threshold.

[0076] The processing system 130 may, in response to identifying more than one moment at which the ambient infrared strength signal 125 rises to and crosses the predetermined ambient infrared strength threshold in a 24-hour period, select, as the moment of sunrise for the 24-hour period, whichever of the identified moments correspond to the longest period below the predetermined ambient infrared strength threshold in the signal during the 24-hour period (i.e. the moment at which the signal rises to and crosses the threshold immediately after the longest period below the threshold).

[0077] Similarly, the processing system 130 may, in response to identifying more than one moment at which the ambient infrared strength signal 125 falls to and crosses the predetermined ambient infrared strength threshold in a 24-hour period, select, as the moment of sunset for the 24-hour period, whichever of the identified moments correspond to the longest period below the predetermined ambient infrared strength threshold in the signal during the 24-hour period (i.e. the moment at which the signal falls to and crosses the threshold immediately before the longest period below the threshold).

[0078] The at least one predefined moment may be identified for any day in the plurality of days for which it is possible to detect the predefined moment with a predefined degree of confidence. The degree of confidence to which moments of sunrise, noon and / or sunset can be identified in the ambient infrared strength signal depends on the weather at the time of the relevant sunrise, noon or sunset. In particular, these moments (especially sunrise) may be more difficult to identify in an ambient infrared strength signal acquired on a cloudy day. For instance, in the graph 200 of Figure 2, the increase in ambient infrared strength after sunrise is smaller and more gradual on Day 1, during which the weather was cloudy, than on other days. The moment of sunrise for Day 1 cannot therefore be determined from the ambient infrared strength signal to a high degree of confidence.

[0079] The processing system 130 may estimate the time of day based on at least the identified predefined moments by determining a length of time between a current time and a most recent identified past moment of sunrise, most recent identified past moment of noon and / or most recent identified past moment of sunset. For instance, if the plurality of days includes a day immediately preceding the current day, and an identified past moment of sunrise for the day immediately preceding the current day was 26 hours before a current time, the processing system may estimate the current time as “daytime” or, more specifically, “morning”. Similarly, if an identified past moment of noon for the day immediately preceding the current day was 24 hours before a current time, the processing system may estimate the current time as “noon”, while if an identified past moment of sunset for the day immediately preceding the current day was 20 hours before a current time, the processing system may estimate the current time as “daytime” or, more specifically, “afternoon”.

[0080] In some examples, the processing system 130 may process the ambient infrared strength signal 125 to identify one or more predefined moments (e.g. moments of sunrise, noon and / or sunset) as they occur (i.e. in real time or near real time). In other words, the processing system may identify a moment of sunrise and / or a moment of sunset for a current day. The processing system may estimate the time of day based on the identified moment of sunrise and / or moment of sunset for the current day.

[0081] For instance, the processing system 130 may estimate the time of day as “daytime” for a predetermined number of hours following the identified moment of sunrise for the current day, or as “nighttime” if the length of time since the identified moment of sunrise for the current day exceeds the predetermined number of hours or if a moment of sunrise for the current day has not yet been identified in the ambient infrared strength signal. The processing system may estimate the time of day as “nighttime” for a predetermined number of hours following the identified moment of sunset for the current day, or as “daytime if a moment of sunset for the current day has not yet been identified in the ambient infrared strength signal. If the processing system is configured to identify both moments of sunrise and sunset, the processing system may estimate the time of day as “daytime” following an identified moment of sunrise until a moment of sunset is identified, and as “nighttime” following an identified moment of sunset until a moment of sunrise is identified.

[0082] In some examples, the processing system 130 may use the identified one or more predefined moments for the current day in combination with identified past predefined moments for a plurality of days preceding the current day. In some examples, the processing system may estimate the time of day based on the identified one or more predefined moments for the current day if the one or more predefined moments are identified with a predefined degree of confidence, and based on the identified past predefined moments for a plurality of days preceding the current day if the one or more predefined moments for the current day are not identified with a predefined degree of confidence. This allows the ambient infrared strength signal for the current day to be used on days where the weather conditions allow the identification of sunrise and / or sunset in the ambient infrared strength signal, while also enabling a reliable estimation of the time of day on days where the weather conditions do not allow the identification of sunrise and / or sunset in the ambient infrared strength signal.

[0083] The processing system 130 may, for example, identify a moment at which the ambient infrared strength signal rises to and crosses a predetermined ambient strength threshold as the moment of sunrise for the current day. In some examples, the processing system may identify a moment at which the ambient infrared strength signal rises to and crosses the predetermined ambient infrared strength threshold as the moment of sunrise only if, immediately prior to crossing the predetermined ambient infrared strength threshold, the ambient infrared strength signal had remained below the predetermined ambient infrared strength threshold for a predetermined length of time (e.g. at least an hour). This reduces a likelihood that a variation in ambient infrared strength during the day (e.g. due to changes in the weather or covering and then uncovering a window of the indoor environment) is misidentified as a moment of sunrise.

[0084] Similarly, the processing system 130 may identify a moment at which the ambient infrared strength signal falls to and crosses a predetermined ambient strength threshold as the moment of sunset for the current day. In some examples, the processing system may identify a moment at which the ambient infrared strength signal falls to and crosses the predetermined ambient infrared strength threshold as the moment of sunset only if, immediately following crossing the predetermined ambient infrared strength threshold, the ambient infrared strength signal remains below the predetermined ambient infrared strength threshold for a predetermined length of time (e.g. at least an hour).

[0085] The predetermined ambient strength threshold used to identify a moment of sunrise and / or a moment of sunset for the current day may be determined based on the ambient infrared strength signal. For instance, if the ambient infrared strength signal has been acquired over a period of at least 24 hours immediately preceding the current time, the predetermined ambient infrared strength threshold may be determined based on the lowest value of ambient infrared strength over the preceding 24 hours, e.g. the predetermined ambient infrared strength threshold may set as a value 5-15% higher than the lowest value.

[0086] In some examples, the processing system 130 is further configured to control the lighting device 110 responsive to the estimated time of day. For instance, the processing system may control one or more properties of light provided by the lighting device (e.g. color, brightness, a lighting-up period and / or a dimming-down period) responsive to the estimated time of day. For example, the processing system may control the lighting device (when turned on) to provide light with a first color and / or first brightness when the estimated time of day is early morning, and a second color and or second brightness when the estimated time of day is evening.

[0087] In some examples, the processing system 130 may be configured to turn the lighting device 110 on and / or off. The processing system may be configured to control the lighting device to turn on and / or off responsive to both the estimated time of day and additional information relating to the indoor environment (e.g. motion information). In some examples, the processing system may receive the additional information relating to the indoor environment from one or more further sensors (e.g. a motion sensor).

[0088] In examples in which the infrared sensor 120 is an infrared time-of-flight sensor, the processing system 130 may further receive, from the infrared time-of-flight sensor, a distance signal responsive to the time of flight of infrared radiation emitted by the infrared time-of-flight sensor and reflected by objects in the indoor environment back to infrared time-of-flight sensor. For instance, the time-of-flight sensor may emit short pulses of infrared radiation, and the distance signal may directly measure the time of flight of each short pulse. Alternatively, the time-of-flight sensor may emit a continuous wave of modulated infrared radiation; the phase of the distance signal would then depend on the time of flight of the infrared radiation.

[0089] The processing system 130 may process the distance signal to detect a movement (e.g. motion of a person) in the indoor environment. In some examples, the processing system may additionally determine a type of detected movement, e.g. by processing the distance signal to determine a posture of a moving person. For example, the processing system may detect that a person is walking in the indoor environment or that a person is sitting and working (e.g. typing).

[0090] The use of a time-of-flight sensor in detecting movement, and determining a type of detected movement, is well known, and suitable techniques for processing the distance signal will be apparent to the skilled person.

[0091] The processing system 130 may be configured to control the lighting device 110 responsive to both the estimated time of day and a detected movement (and optionally, a type of detected movement). For example, the processing system 130 may control the lighting device 110 to provide light in response to detecting movement at a time of day at which sunlight levels are determined to be low or zero. A time of day at which sunlight levels are determined to be low or zero may include nighttime, early morning (e.g. up to an hour after sunrise), and late afternoon or evening (e.g. less than two hours before sunset). The processing system may control the lighting device not to provide light in response to detecting movement at other times of day (i.e. when sunlight levels are estimated to be high).

[0092] This would, for example, enable the lighting system 100 to automatically provide light in response to a user getting up during the night to use the bathroom, getting up in the morning before there is sufficiently sunlight not to need artificial lighting or sitting at a desk (e.g. working or studying) late in the afternoon or evening.

[0093] In some examples, the processing system 130 may be configured to control one or more properties of light provided by the lighting device 110 responsive to both the estimated time of day and a detected movement. The one or more properties of the light provided by the lighting device may, for instance, comprise a brightness, color and / or lighting-up period (i.e. a time taken to reach a final brightness level from when the lighting device is switched on).

[0094] For instance, in response to a determination that a person is moving in the indoor environment during the night, the processing system 130 may control the lighting device 110 to provide light with a low brightness, in order to allow the person to see well enough to move about safely without causing unnecessary disruption to sleep. In response to a determination that a person is getting up in the morning, the processing system 130 may control the lighting device 110 to have a long lighting-up period (i.e. slowly increasing in brightness), in order to help the person to wake up.

[0095] In some examples, the processing system 130 may be further configured to process the ambient infrared strength signal to determine a status of a window of the indoor environment (i.e. whether the window is currently uncovered or covered, e.g. by curtains or blinds).

[0096] The underlying principle behind the use of ambient infrared strength in determining a status of a window of an indoor environment is illustrated by Figure 4, which shows a graph 400 of ambient infrared strength (in kilo counts per second) for an indoor environment over a period of time during which the window of the indoor environment is uncovered (by opening the curtains) and then covered again (by closing the curtains) several times.

[0097] The graph 400 shows that the ambient infrared strength quickly increases to a much higher value each time the window is uncovered (to an ambient infrared strength about 20 times greater than before the window was uncovered within a few seconds), and quickly decreases to a much lower value each time the window is covered.

[0098] Figure 5 shows another graph 500 of ambient infrared strength (in kilo counts per second) for a different indoor environment over a period of time during which the window of the indoor environment is uncovered and then covered again several times. The infrared sensor used to measure the ambient infrared strength for graph 500 was further from the window of the indoor environment than the sensor used to measure the ambient infrared strength for the graph 400 of Figure 4.

[0099] The values of ambient infrared strength in graph 500 are very different to the graph 400 of Figure 4, but the same pattern is observed when the window is uncovered and covered: the ambient infrared strength quickly increases to a much higher value each time the window is uncovered (to an ambient infrared strength 2-3 times greater than before the window was uncovered), and quickly decreases to a much lower value each time the window is covered.

[0100] The inventors have recognized that an ambient infrared strength signal may therefore be used to determine a status of a window of an indoor environment in which the ambient infrared strength signal is measured.

[0101] Returning to Figure 1, the processing system 130 may be configured to identify a moment of uncovering a window of the indoor environment by processing the ambient infrared strength signal 125 to identify a moment at which a rate of increase in ambient infrared strength exceeds a predetermined increase threshold. The moment at which the rate of increase in ambient infrared strength exceeds the predetermined increase threshold may be identified as a moment of uncovering the window. The predetermined increase threshold may, for example, be defined relative to a current value of the ambient infrared strength, such as a rate of increase equivalent to the ambient infrared strength doubling within a few seconds (e.g. within 15 seconds, or within 5 seconds).

[0102] Similarly, the processing system 130 may be configured to identify a moment of covering the window of the indoor environment by processing the ambient strength signal 125 to identify a moment at which a rate of decrease in ambient infrared strength exceeds a predetermined decrease threshold. The moment at which the rate of decrease in ambient infrared strength exceeds the predetermined decrease threshold may be identified as a moment of covering the window. The predetermined decrease threshold may also be defined relative to a current value of the ambient infrared strength, such as a rate of decrease equivalent to the ambient infrared strength halving within a few seconds (e.g. within 15 seconds, or within 5 seconds).

[0103] In some examples, the identified moment of uncovering the window and / or the identified moment of covering the window may be provided to a sleep monitoring system. The inventors have recognized that the covering of a window of a bedroom in particular (by closing the curtains / blinds) is an indication that a user is going to bed, that the uncovering of the window (by opening the curtains / blinds) is an indication that the user is getting up out of bed, and that this information may be used to improve an accuracy of a sleep monitoring system (e.g. by improving an accuracy of a time of falling asleep and / or a time of waking up determined by the sleep monitoring system).

[0104] For instance, if the processing system 130 is used in a connected lighting system, rather than a non-connected lighting system, the ambient infrared strength signal may not be needed to estimate a time of day, but moments of covering and / or uncovering a window of the indoor environment may still be detected in the ambient infrared strength signal. The system time at which moments of covering and / or uncovering the window may be recorded by the processing system, and provided to a sleep monitoring system in communication with the connected lighting system. The sleep monitoring system may use a time of covering / uncovering a window in combination with other measurements of the sleep monitoring system to improve an accuracy of an estimated time of going to sleep or an estimated time of waking.

[0105] In some examples, the processing system 130 may be configured to determine a status of the window of the indoor environment based on an identified moment of covering the window and / or on an identified moment of uncovering the window. For instance, the processing system may determine that the window is covered in response to a determination that a (most-recent) identified moment of covering the window occurred more recently than a (most-recent) identified moment of uncovering the window. Similarly, the processing system may determine that the window is uncovered in response to a determination that a (most- recent) identified moment of uncovering the window occurred more recently than a (most- recent) identified moment of covering the window.

[0106] In some examples, the processing system 130 may be further configured to control the lighting device 110 based on the determined status of the window. For instance, the processing system may control the lighting device to provide light in response to a determination that the window is covered, or to switch off the lighting device in response to a determination that the window is uncovered. In some examples, the determined status of the window may be used in combination with a detected motion in the indoor environment in order to control the lighting device. For example, the processing system may control the lighting device to provide light in response to detecting motion at a time at which the window is determined to be covered.

[0107] Figure 6 illustrates a computer-implemented method 600 for estimating a time of day, according to an embodiment of the invention.

[0108] The computer-implemented method 600 begins at step 610, at which an ambient infrared strength signal is received from an infrared sensor located in an indoor environment. The ambient infrared strength signal is responsive to an amount of ambient infrared radiation detected by the infrared sensor.

[0109] At step 620, the ambient infrared strength signal is processed to estimate a time of day. The time of day may, for example, be estimated using any of the techniques described above.

[0110] It will be understood that the disclosed methods are computer-implemented methods. As such, there is also proposed a concept of a computer program comprising code means for implementing any described method when said program is run on a processing system.

[0111] As discussed above, embodiments make use of a controller. The controller can be implemented in numerous ways, with software and / or hardware, to perform the various functions required. A processor is one example of a controller which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform the required functions. A controller 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.

[0112] Examples of controller 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).

[0113] In various implementations, a processor or controller 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 controllers, perform the required functions. Various storage media may be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller.

[0114] 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. 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.

[0115] Functions implemented by a processor may be implemented by a single processor or by multiple separate processing units which may together be considered to constitute a "processor". Such processing units may in some cases be remote from each other and communicate with each other in a wired or wireless manner.

[0116] 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.

[0117] A computer program 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.

[0118] 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.

[0119] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A processing system (130) for estimating a time of day, the processing system being configured to: receive, from an infrared sensor (120) located in an indoor environment, an ambient infrared strength signal (125) responsive to an amount of ambient infrared radiation detected by the infrared sensor over one or more days; processing the ambient infrared strength signal (125) to identify one or more moments of noon in the ambient infrared strength signal by identifying one or more peaks in the ambient infrared strength signal; and estimating the time of day based on at least the identified one or more moments of noon.

2. The processing system (130) of claim 1, wherein: the ambient infrared strength signal (125) is acquired during a plurality of days preceding a current day; and the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify a past moment of noon for each day in at least a subset of the plurality of days preceding the current day by dividing the ambient infrared strength signal into a plurality of 24-hour periods, and, for each of at least a subset of the 24-hour periods, identifying a peak in the ambient infrared strength signal for the 24-hour period as the moment of noon for the 24-hour period ; and estimating the time of day based on at least the identified past moments of noon.

3. The processing system (130) of any of claims 1 to 2, wherein the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal (125) to identify one or more moments of sunrise in the ambient infrared strength signal by identifying a moment at which the ambient infrared strength signal rises to and crosses a predetermined ambient infrared strength threshold as a moment of sunrise; andestimating the time of day based on at least the identified one or more moments of sunrise.

4. The processing system (130) of claim 3, wherein: the ambient infrared strength signal (125) is acquired during a plurality of days preceding the current day; and the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify a past moment of sunrise for each day in at least a subset of the plurality of days preceding the current day by dividing the ambient infrared strength signal into a plurality of 24-hour periods, and, for each of at least a subset of the 24-hour periods, identifying a moment in the ambient infrared strength signal for the 24-hour period at which the ambient infrared strength signal rises to and crosses a predetermined ambient infrared strength threshold as the moment of sunrise for the 24-hour period; and estimating the time of day based on at least the identified past moments of sunrise.

5. The processing system (130) of any of claims 1 to 4, wherein the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal (125) to identify one or more moments of sunset in the ambient infrared strength signal by identify a moment at which the ambient infrared strength signal falls to and crosses a predetermined ambient infrared strength threshold as a moment of sunset; and estimating the time of day based on at least the identified one or more moments of sunset.

6. The processing system (130) of claim 5, wherein: the ambient infrared strength signal (125) is acquired during a plurality of days preceding the current day; and the processing system is configured to estimate the time of day by: processing the ambient infrared strength signal to identify a past moment of sunset for each day in at least a subset of the plurality of days preceding the current day by, for each of at least a subset of the 24-hour periods, identifying a moment in the ambient infrared strength signal for the 24-hour period at which the ambient infrared strength signalfalls to and crosses the predetermined ambient infrared strength threshold as the moment of sunset for the 24-hour period; and estimating the time of day based on at least the identified past moments of sunset.

7. The processing system (130) of any of claims 1 to 6, wherein the processing system is further configured to control a lighting device (110) responsive to the estimated time of day.

8. The processing system (130) of claim 7, wherein: the infrared sensor (120) is a time-of-flight infrared sensor; and the processing system is further configured to: receive, from the infrared time-of-flight sensor, a distance signal responsive to a time of flight of infrared radiation emitted by the infrared time-of-flight sensor and reflected back to the infrared time-of-flight sensor; process the distance signal to detect a movement in the indoor environment; and control the lighting device (110) responsive to the estimated time of day and the detected movement.

9. The processing system (130) of claim 8, wherein the processing system is configured to control the lighting device (110) to provide light in response to a determination that, at a time of the detected movement, the estimated time of day is nighttime.

10. The processing system (130) of any of claims 1 to 9, wherein the processing system is further configured to identify a moment of uncovering a window of the indoor environment by: processing the ambient infrared strength signal (125) to identify a moment at which a rate of increase in ambient infrared strength exceeds a predetermined increase threshold; and identifying the moment at which the rate of increase in ambient infrared strength exceeds the predetermined increase threshold as the moment of uncovering the window.

11. The processing system (130) of any of claims 1 to 10, wherein the processing system is further configured to identify a moment of covering a window of the indoor environment by: processing the ambient infrared strength signal (125) to identify a moment at which a rate of decrease in ambient infrared strength exceeds a predetermined decrease threshold; and identifying the moment at which the rate of decrease in ambient infrared strength exceeds the predetermined decrease threshold as the moment of covering the window.

12. A lighting system (100) comprising: a lighting device (110) located in an indoor environment; an infrared sensor (120) located in the indoor environment; and the processing system (130) of any of claims 1 to 11.

13. A computer-implemented method (600) for estimating a time of day, the computer-implemented method comprising: receiving, from an infrared sensor (120) located in an indoor environment, an ambient infrared strength signal (125) responsive to an amount of ambient infrared radiation detected by the infrared sensor over a plurality of days; and processing the ambient infrared strength signal to estimate a time of day by dividing the ambient infrared strength signal into a plurality of 24-hour periods, and, for each of at least a subset of the 24-hour periods, identifying a peak in the ambient infrared strength signal for the 24-hour period as the moment of noon for the 24-hour period.

14. 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 (600) according to claim 13.

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