Method and system for waking up a device

Abstract

A method for determining the presence of a person, comprising receiving an IR sensor signal and determining a smoothed IR signal using the IR sensor signal, determining a threshold value as an offset from the smoothed IR signal in a first mode, wherein in the first mode the presence determination is carried out by comparing the IR sensor signal with the threshold value, and wherein in a second mode the presence determination is carried out by comparing the IR sensor signal with the smoothed IR signal, wherein a switch from the first mode to the second mode is triggered when the IR sensor signal exceeds the threshold value, and a switch from the second mode to the first mode is triggered when a variability of the IR sensor signal is below a variability threshold value.

Description

Technical Field

[0001] This invention relates to systems and methods for detecting the presence of a person using infrared radiation, and particularly to systems and methods for waking up devices. Background Technology

[0002] Presence detection is the ability of a device or system to detect the presence of a person. It is well known that IR sensors are used for non-contact presence detection by detecting body heat. Presence detection can be used, for example, to regulate the operation of equipment, such as turning the device on or off. Examples of devices using non-contact presence detection include heating / air conditioning systems that enter energy-saving mode, and lighting devices (such as lamps) that automatically turn on when a person is present.

[0003] A thermopile is an IR sensor that can deliver an output as absolute temperature, not just temperature changes. However, when using thermopiles for presence detection, it has been shown that thermopiles are difficult to calibrate relative to background IR radiation in the room, especially in “noisy” environments with fluctuating room temperature.

[0004] US20150185806 describes presence detection using a thermopile with a predetermined threshold. Summary of the Invention

[0005] In a first aspect of the invention, a method for determining the presence of a person is provided, wherein the method relates to a system that can be in a state of presence or absence, the method comprising:

[0006] Receive the IR sensor signal and use it to determine the smoothed IR signal.

[0007] In the first mode, the threshold is determined as the offset from the smoothed IR signal.

[0008] In the first mode, presence determination is performed by comparing the IR sensor signal with a threshold, and

[0009] In the second mode, presence determination is performed by comparing the IR sensor signal with a smoothed IR signal.

[0010] When the IR sensor signal exceeds a threshold, a switch occurs from the first mode to the second mode, and

[0011] When the variability of the IR sensor signal falls below the variability threshold, a switch occurs from the second mode to the first mode.

[0012] Two different detection modes avoid state changes triggered by fluctuating background temperature when someone approaches or moves away from the IR sensor, while providing high sensitivity.

[0013] Preferably, the smoothed IR signal is modulated into an IR sensor signal over time at a first rate in a first mode, and over time at a second rate in a second mode, wherein the first rate is lower than the second rate.

[0014] This increases sensitivity in the second mode while preventing the threshold from "running out of control" when someone approaches the sensor.

[0015] In the first mode, presence determination is performed by comparing the IR sensor signal with a threshold, such that when the IR sensor signal exceeds the threshold, a transition from a non-existent state to a present state occurs. In the second mode, presence detection is performed by comparing the IR sensor signal with a smoothed IR signal, such that when the IR sensor signal exceeds the smoothed signal, a transition from a present state to a non-existent state occurs.

[0016] In the first mode, the upper threshold can be determined as the smoothed IR signal plus the offset value, and the lower threshold is determined as the smoothed IR signal minus the offset value, wherein in the first mode, the upper threshold is used to determine the transition from the non-existent state to the existent state, and the lower threshold is used to determine the transition from the existent state to the non-existent state.

[0017] In the second mode, when the IR sensor signal exceeds the smoothed IR signal, a transition from a non-existent state to a present state and a transition from a non-existent state to a present state can occur.

[0018] At the start of this method, the system can be predefined as either existing or non-existent. This leads to a self-learning system.

[0019] The IR sensor is preferably a thermopile.

[0020] Thermopile has the advantage that it can respond quickly to temperature changes and report absolute temperature values.

[0021] The status (existence or non-existence) is preferably updated repeatedly, preferably at predetermined time intervals, which are preferably at least one second.

[0022] Preferably, in the first mode, the presence determination is performed by comparing the IR sensor signal with a threshold and not by comparing the IR sensor signal with a smoothed signal, and in the second mode, the presence determination is performed by comparing the IR sensor signal with a smoothed IR signal and not by comparing the IR sensor signal with the threshold of the first mode.

[0023] In a second aspect of the invention, a system configured to perform the method according to the first aspect of the invention is provided. The system can be configured to determine whether a person is present in the field of view of an IR sensor. The system includes a signal processing module, threshold determination logic, and presence determination logic. The signal processing module is configured to receive a voltage from the IR sensor and determine an IR signal and a smoothed IR signal, and is further configured to determine the variability of the IR sensor signal. The threshold determination logic is configured to determine a threshold as an offset from the smoothed IR signal, and the presence determination logic is configured to determine presence in a first mode by comparing the IR sensor signal with the threshold.

[0024] It is configured to determine presence in a second mode by comparing an IR sensor signal with a smoothed IR signal, wherein a switch from a first mode to a second mode occurs when the IR sensor signal exceeds a threshold, and a switch from a second mode to a first mode occurs when the variability of the IR sensor signal is below a variability threshold.

[0025] In a third aspect of the invention, a powered device is provided that includes a system according to a second aspect of the invention. This device may, for example, be an access control device. The device may be configured to put the device into a power-saving mode when the system receives information indicating that no one is present, or to wake the device from the power-saving mode when the system receives information indicating that a person is present. Attached Figure Description

[0026] The accompanying drawings form part of the specification and schematically illustrate preferred embodiments of the invention, and serve to demonstrate the principles of the invention.

[0027] Figure 1 This is a schematic diagram of the system.

[0028] Figure 2 This is a schematic diagram of a memory.

[0029] Figure 3 It is a diagram of the system and people.

[0030] Figure 4a It is a schematic diagram of a system including a display and a person.

[0031] Figure 4b This is a schematic diagram of a laptop computer.

[0032] Figure 4c This is a schematic diagram of the system used to detect proximity.

[0033] Figure 5 This is a flowchart illustrating the method.

[0034] Figure 6a There are two graphs.

[0035] Figure 6b It is a schematic graph.

[0036] Figure 7 This is a schematic diagram. Detailed Implementation

[0037] Figure 1 An embodiment of a presence determination system 1 including an IR sensor 2 is shown. This IR sensor is preferably an IR sensor capable of measuring absolute temperature values, and preferably a thermopile 2. A useful thermopile is described in WO20040968256, but other types of thermopile can also be used. However, any suitable type of IR sensor can be used, such as a calorimeter. The thermopile 2 is capable of detecting IR radiation and supplying voltage to a subsystem 3. The subsystem 3 can be implemented in hardware or software, or a combination thereof, and... Figure 1 An embodiment implemented in hardware and software is shown. Subsystem 3 includes an input interface 4 for receiving voltage from IR sensor 2. Subsystem 3 also includes a processor 5, a memory 6, and an output interface 7.

[0038] System 1 may also include one or more of a signal filter, amplifier, A / D converter, and similar devices known in the field of signal processing, particularly for processing voltages from IR sensor 2. System 1 is powered by a power supply. Subsystem 3 may be installed in the same device as IR sensor 2 or may be separate from IR sensor 2. In one embodiment, all steps of the method described herein are performed by the same processor 5.

[0039] Reference Figure 2 The memory 6 is capable of storing data such as IR sensor data 8 and threshold data 9, presence status data 12, mode data 20, and smoothed IR signal data 21. The memory 6 has threshold determination logic 10 and presence determination logic 13. The memory 6 also has a signal processing module 11. Generally, and as described elsewhere herein, these components can be implemented using any suitable combination of hardware and software.

[0040] System 1 is typically able to output information about at least two states: "person exists" and "person does not exist," or alternatively, information about transitions from "existence" to "non-existence" and from "existence" to "non-existence." The current state (existence / non-existence) of System 1 is stored in memory 6 as existence state data 12.

[0041] System 1 can also switch between a first mode and a second mode, and then switch back, as described in more detail below. This is also implemented by the existence determination logic 13, as described in more detail below. Therefore, the existence determination logic 13 can compare the IR sensor signal 50 with thresholds 52 and 53, and compare the IR sensor signal 50 with the smoothed IR signal 51. The existence determination logic 13 also uses the variability 54 of the IR sensor signal 50 and compares the variability 54 with the variability threshold 55. The existence determination logic 13 can output a state to the output interface 7 and output a mode to the signal processing module 11 (the signal processing module 11 uses this state to know how to determine the smoothed IR signal 51).

[0042] System 1 can store information about which mode the system is in as mode data 20.

[0043] Reference Figure 3 As shown in Figure 4, the IR sensor 2 has a field of view 15, in which the IR sensor 2 detects IR radiation and the system 1 determines the presence of a person 16. The person 16 typically radiates IR radiation stronger than background IR radiation (e.g., caused by ambient room temperature). Therefore, the IR radiation detected in the field of view 15 can be used to determine the presence of the person 16 within the field of view 15. In a preferred embodiment, the system includes a thermopile 2. In some embodiments, the system 1 may have multiple thermopiles 2, each with a different field of view 15. Multiple IR sensors 2 may use the same subsystem 3, and the subsystem 3 can then provide data storage, signal processing, and threshold determination for each of the IR sensors 2.

[0044] System 1 can use output interface 7 to provide information about the presence or absence of a person to the second device 17. The second device 17 is preferably an electrical receiving device, and therefore it is powered by electrical power. Output interface 7 can be any suitable interface through which System 1 can provide data to the second device 17, and output interface 7 can be implemented in hardware and / or software. The second device 17 can be a computer system. The information provided from System 1 to the second device 17 can be information about a state (presence / absence) or information about a state transition from one state to another.

[0045] The second device 17 can utilize the output from system 1 in various ways. Depending on the situation, presence and absence states can be used to turn the second device 17 on or off. The second device 17 can be any type of device that can benefit from non-contact presence detection, such as, for example, a personal computer (e.g., a laptop computer), a heating system, an air conditioning system, or a ventilation system, such as ensuring that these systems are turned off or placed in power-saving mode when no one is present for a set period of time. Thus, presence or absence states can trigger timers. The second device 17 can also be a facility that provides light, such as indoor or outdoor lights. The second device 17 can also be turned on by presence states, such that a computer, information or advertising display, light, access control device, or ventilation system is turned on when a person is present. The second device 17 can also be an alarm device, such as an intrusion alarm. Generally, all of these devices can benefit from being turned on / activated, turned off, placed in power-saving mode, or woken from power-saving mode by the methods and systems described herein.

[0046] For example, the output from System 1 can be used to put the second device 17 into a power-saving mode and / or turn off the display 18. Therefore, when a person is not present, the second device 17 can be put into a power-saving mode, possibly after a minimum period of time has been detected as absent. The presence status provided by System 1 can be used to wake up the second device 17.

[0047] It should be noted that parts of subsystem 3 (such as, for example, processor 5 and / or memory 6) may be part of the second device 17, particularly when the second device 17 includes or is composed of a computer. The software described herein can then be installed on the computer's hard drive and used by the computer's CPU. Generally, parts of system 1 can be integrated with parts of the second device 17, such that processor 5 or memory 6 may be part of the second device 17. The entire system 1 may also be fully integrated into the second device 17 as a sub-part implemented with a suitable combination of hardware and software.

[0048] That is, system 1 can be installed in the second device 17, or it can be separated from the second device 17. In one embodiment ( Figure 4a As shown in the diagram, the IR sensor 2 is mounted next to the computer's display 18, which can be the display of a laptop computer, tablet computer, smartphone (such as an iPhone or Android phone), or a standalone display of a desktop computer. The field of view 15 is preferably directed at the intended position of a person 16 in front of the display 18.

[0049] Figure 4bA second device 17 is shown, which is a laptop computer in which system 1 is integrated into a laptop computer. Therefore, the methods and systems described herein can be used to wake a laptop computer from power-saving mode or to put a laptop computer into power-saving mode.

[0050] exist Figure 4c In the preferred embodiment shown, system 1 is used to detect a person 16 approaching IR sensor 2 and to activate or deactivate a second device 17. For example, system 1 may be part of an access control device or provide an output to that access control device. Thus, system 1 can be used to open or unlock a door when person 16 is detected, or to wake the access control device from sleep mode. Examples of access control devices that can be woken up include electronic locks, tag readers, fingerprint readers, or facial recognition devices. Therefore, for example, when person 16 approaches IR sensor 2, system 1 can activate the access control device, enabling person 16 to unlock the door.

[0051] When a person 16 approaches, system 1 can be used to activate electronic display 18. Display 18 can be a display 18 fixedly installed indoors or outdoors. For example, display 18 can be a sign indicating directions, an advertising display, or a different type of information display. For example, system 1 can be used to activate display 18 on a refrigerator door. Thus, system 1 can be used to turn on the display so that it displays information.

[0052] The IR sensor voltage is provided from IR sensor 2 to subsystem 3. Subsystem 3 analyzes the sensor voltage and provides a presence / absence output to second device 17. System 1 can sample the thermal data in field of view 15 using any suitable sampling interval. Preferably, the sampling frequency ranges from once every 5 seconds to 100 times per second. The sampling of the IR sensor voltage is performed by signal processing module 11 to obtain IR sensor signal 50, which is stored as IR sensor data 8. Typically, thermopile 2 delivers its output as an output voltage. Preferably, all IR sensor data herein (thresholds, smoothed signals, etc.) is or can be converted into absolute temperature values, and therefore not relative temperature values. Therefore, preferably, thermopile is used as IR sensor 2.

[0053] Signal processing module 11 is capable of generating (providing) a smoothed IR signal 51. The smoothed IR signal 51 may be a moving average of the IR sensor signal 50. The smoothed IR signal 51 is IR sensor data 8 (which has been processed using a (preferably digital) smoothing method to remove extreme values ​​in order to show trends), and may be a moving average of the IR sensor signal 50. Examples of useful smoothing methods include moving averages or medians. In some embodiments, outliers in the IR sensor data 8 are removed. The signal processing module is also capable of determining the variability of the IR sensor signal 50 and providing it to the presence determination logic 13.

[0054] Now refer to Figures 5 to 7 This describes the method used to determine whether a person exists or does not exist. It should be understood that System 1 is configured to perform such a method. The following primarily describes how System 1 initially exists in a non-existent state and in the first mode, but the transition from the existent state to the non-existent state is accomplished according to the same principles. Similarly, the transition from the first mode to the second mode and from the second mode to the first mode is accomplished using the same principles described below.

[0055] It should be noted that this method should be implemented to keep various states and modes updated in real time or near real time.

[0056] In step 100, IR sensor 2 provides voltage to subsystem 3 to generate IR sensor signal 50, and... Figure 6a The diagram illustrates an example of how the IR sensor signal changes over time. The signal processing module 11 uses the IR sensor signal 50 to determine the smoothed IR signal 51.

[0057] The smoothed IR signal 51 represents historical IR sensor data 8, which has been processed using a (preferably digital) smoothing method to remove extreme values ​​in order to display trends. Examples of useful smoothing methods include moving averages or medians. In some embodiments, outliers in the data are removed.

[0058] The signal processing module 11 can generate a smoothed IR signal 51, for example, using a moving average of the IR sensor signal 50. The smoothed IR signal 51 can closely follow the IR sensor signal 50 (second mode) by using a moving average over a short time period, or it can follow the IR sensor signal 50 more slowly (first mode) by using a moving average over a longer time period. Therefore, it is preferred that in the first mode, the smoothed IR signal 51 is adjusted slowly, while in the second mode, the smoothed IR signal 51 is adjusted to the IR sensor signal 50 more quickly. For example, when using a moving average, a longer time period is determined in the first mode compared to the second mode. The time period in the first mode can be 3 to 100 times longer, more preferably 3 to 20 times longer, than in the second mode. For example, in the first mode, a moving average can be determined over a time period from 1 to 20 seconds, but in the second mode, a moving average can be determined over a time period from 0.5 to 0.1 seconds (e.g., 0.25 seconds). Therefore, the smoothed IR signal is adjusted at a first rate in the first mode and at a second rate in the second mode, wherein the first rate is lower than the second rate.

[0059] Moving averages are a useful method for determining smoothed IR signals, but other useful statistical methods may also exist.

[0060] In step 101, threshold determination logic 10 determines a first threshold 52 and a second threshold 53. Threshold determination logic 10 uses a smoothed signal 51 to determine the first threshold 52 and the second threshold 53. Thresholds 52 and 53 are determined as the smoothed IR signal 51 + / - offset.

[0061] First threshold = smoothed IR signal + offset.

[0062] Second threshold = smoothed IR signal – offset.

[0063] The offset can be predetermined. It can be determined for a specific application and the IR sensor 2 used. The offsets for the upper threshold 52 and the lower threshold 53 can be the same or different, but in a preferred embodiment, the same offset (the absolute value of the offset) is used for both the upper threshold 52 and the lower threshold 53. The offset is selected based on the configuration of the IR sensor and the choice of amplifier and A / D converter, and can be determined using a specific configuration of system 1. Empirically, the offset can be approximately 10% to 70% of the typical difference between the signal strength measured in the presence and absence states.

[0064] In the absence of certain conditions, the IR sensor signal 50 and the smoothed IR signal 51 can fluctuate with ventilation, sunlight, open windows, etc. An offset should be selected to avoid erroneous triggering from the first mode to the second mode, as well as erroneous triggering due to presence / absence. The determined thresholds 52 and 53 are continuously updated (see below) and stored in memory 6 as threshold data 9. Steps 100 and 101 can be repeated to dynamically change the smoothed IR signal 51 and the thresholds 52 and 53.

[0065] In the first mode, in step 102, the IR sensor signal 50 is repeatedly checked to see if it exceeds or falls below a first threshold 52 or a second threshold 53. This can be done by using an IR sensor value determined after the threshold is determined, preferably immediately after the threshold is determined (in subsequent cycles). If the IR sensor signal 50 is above the upper threshold 52, the presence of a person is determined. A single measurement of the IR sensor signal 50 above the threshold 52 (and therefore exceeding the threshold) may be sufficient, but it may also be necessary to exceed the threshold 52 for a minimum duration, such as continuously or repeatedly. Preferably, the determination of presence is performed at the same frequency as updating the thresholds 52, 53.

[0066] If the system is in a non-existent state and the IR sensor signal 50 exceeds the upper threshold 52, two things happen: 1) the mode changes from the first mode to the second mode, and 2) the state changes from non-existent to present. If the lower threshold 53 is exceeded, nothing happens because system 1 is already in a non-existent state. However, the mode can change to the second mode.

[0067] Changes in state are stored as state data 12. These changes can be output using output interface 7. Changes in mode are stored as mode data 20 in memory 6. Changes in mode do not need to be output from system 1.

[0068] In a similar manner, when system 1 is in the existent state, if the lower threshold 53 is exceeded, it will change to the non-existent state and will also change to the second mode.

[0069] Figure 6a The diagram illustrates how the IR sensor signal 50 changes over time, where initially no person 16 is in the field of view 15, and system 1 is initially in a non-existent state, i.e., the first mode. Then, person 16 enters the field of view 15, remains in the field of view 15, and then leaves the field of view 15. See... Figure 6aSystem 1 is initially in a non-existent state, i.e., mode one. In this particular example, there is no person 16 in the field of view 15, and system 1 only detects the background temperature. However, person 16 enters the field of view 15 at 29 seconds, causing a sharp increase in IR radiation in the field of view 15. At 29 seconds, the IR sensor signal 50 thus exceeds the upper threshold 52. This triggers a change in state from non-existent to present, and also triggers a change in mode from mode one to mode two. Therefore, from time point 29 seconds to time point 38, the smoothed IR signal 51 is modulated to the IR sensor signal 50 more quickly, which can be seen in how quickly the smoothed IR signal 51 rises after time point 29 seconds.

[0070] In the second mode, the change from a non-existent state to an existent state (and from an existent state to a non-existent state) is not accomplished using thresholds 52 and 53, but rather by comparing the IR sensor signal 50 with the smoothed IR signal 51. Therefore, when the existence determination logic 13 detects a sensor signal value 50 lower than the smoothed IR signal 51, the system changes the state from existent to non-existent (if it is not already in a non-existent state). Figure 6b The diagram illustrates an illustrative example of this situation, where a non-existent state is triggered at time T, and if existence determination logic 13 detects a value higher than the smoothed IR signal from IR sensor signal 50, the system changes the state from non-existent to existent (if it is not already in the existent state).

[0071] Furthermore, in the second mode, the variability of the IR sensor signal 50 is determined. Figure 6a The lower graph in the figure shows how the variability 54 of the IR sensor signal 50 changes over time for the IR sensor signal 50 in the upper graph. Figure 6a The lower part of the graph also shows the variability threshold 55. The variability threshold 55 is selected based on the configuration of System 1. The variability threshold 55 is preferably predetermined. The variability threshold 55 can be, for example, 5% to 40% of the typical difference between the signal strength measured in the presence and absence states. The variability threshold 55 can also be determined experimentally or by System 1. The variability threshold 55 can be stored in the presence determination logic 13.

[0072] Therefore, in step 103, the variability of the IR sensor signal 50 is determined. This determination is performed by the signal processing module 11. Any useful dispersion parameter or variability measure can be used and applied to the IR signal 50. For example, the standard deviation, absolute deviation, mean absolute deviation, or variance of the IR sensor signal 50 can be used. The variability 54 can be determined as the difference between the highest and lowest values ​​over a first time period. In one embodiment, the variability 54 of the smoothed signal 51 is determined, rather than the variability 54 of the IR sensor signal 50.

[0073] The variability 54 of the IR sensor signal 50 is determined over a predetermined time period, which may be 3 to 15 cycles. Therefore, in one embodiment, the standard deviation of the IR sensor signal 50 is used to determine the variability 54 of the IR sensor signal 50.

[0074] The higher background noise of the IR signal 50 will result in higher variability 54, and thus a higher standard deviation over the measured time interval.

[0075] When the variability 54 is high, System 1 remains in the second mode. However, when the variability drops below the variability threshold 55, in step 104, System 1 changes its mode from the second mode to the first mode. This occurs... Figure 6a The time interval is 38 seconds, during which we can see how the IR sensor signal 50 begins to stabilize from approximately 31 seconds, triggering the first mode at time 38. Therefore, there may be a delay that requires the variability 54 to remain below the variability threshold 55 for a period of time, such as from 3 to 15 cycles, in order to trigger the transition to the first mode.

[0076] exist Figure 6a In the process, from time point 29 to time point 38, the system is in the present state, i.e., the second mode, and if (step 105) the IR sensor signal 50 becomes lower than the smoothed IR signal 51 (i.e., at some point in time it is lower than the smoothed IR signal 51), then this state can revert to the non-present state. However, this is in... Figure 6a This did not happen in the example. Instead, in Figure 6a In the middle, starting from time point 38, system 1 in the existing state enters the first mode because the IR sensor signal 50 has stabilized to a point where the variability 54 is reduced below the threshold 55 (step 104).

[0077] At time 54, the IR sensor signal 50 falls below the lower threshold 53 because person 16 is leaving the field of view 15. This triggers the absence state and the second mode (step 106). Therefore, the smoothed IR signal 51 now begins to rapidly adjust to the IR sensor signal 50. Simultaneously, the variability 54 of the IR sensor signal 50 is being determined, and when the variability 54 drops below the variability threshold 55, the system reverts to the first mode at time 61.

[0078] Therefore, the system may have four different combinations of states and modes, as shown in Table 1.

[0079]

[0080] Table 1

[0081] Figure 7 Four possible combinations of modes and states are shown, along with the possible transitions between them. Existence states and modes are stored in memory 6 of system 1 as existence state data 12 and mode data 20. Existence determination logic 13 determines the state (existence, non-existence) and mode (first, second).

[0082] System 1 repeatedly samples the IR sensor signal 50 and determines the state and mode. A voltage is supplied from IR sensor 2 to subsystem 3. The IR sensor signal 50 and the smoothed IR signal 51 are determined by signal processing module 11, which provides these signals to presence determination logic 13. Signal processing module 11 also provides the smoothed IR signal 51 to threshold determination logic 10.

[0083] The presence is determined by the presence determination logic 13 using the IR sensor signal 50. This presence determination logic can access thresholds 52 and 53 in the form of threshold data 9 in the memory 6, and access the smoothed IR signal 52.

[0084] The state (presence or absence) is repeatedly updated at a predetermined frequency. Therefore, the smoothed IR signal 51, thresholds 52, 53, and variability 54, as well as the state and mode, are preferably repeatedly updated at a predetermined frequency. In each cycle, the smoothed IR signal 51, thresholds 52, 53, variability, mode, and state can be determined. In some embodiments, variability 54 is not determined in a first mode (because it is not used). In some embodiments, thresholds 52 and 53 are not determined in a second mode (because they are not used). The frequency can be at least once every 5 seconds, more preferably at least once every 1 second, more preferably at least twice per second, and most preferably at least ten times per second. Updates may occur more rapidly in the second mode compared to the first mode.

[0085] Thresholds 52 and 53 can be used by existence determination logic 13 in a period immediately following the period in which they are determined by threshold determination logic 10. In a similar manner, the value of the smoothed IR signal 51 can be compared with the IR sensor signal 50 determined in the next period.

[0086] The smoothed IR signal 51, thresholds 52, 53, and variability 54 can be determined using data from several previous cycles (e.g., from a sliding window of the cycle).

[0087] Parameters that are not needed in a specific mode or state can remain unupdated in that mode or state. In the first state, it is not necessary to determine the variability 54 of the IR sensor signal 50. In the second state, it is not necessary to determine the thresholds 52 and 53. In the first state, it is not necessary to check whether the IR signal 50 crosses the smoothed IR signal 51. In the second mode, it is not necessary to check whether the IR signal 50 crosses the thresholds 52 and 53 (these are not needed initially).

[0088] When system 1 starts, in one embodiment, system 1 can be pre-defined as being in a state selected from a present state and a non-present state. Then, system 1 can change its state based on whether an upper threshold 52 or a lower threshold 53 has been crossed.

[0089] When system 1 is started, in one embodiment, system 1 may be pre-programmed into a mode selected from a first mode and a second mode, wherein the first mode is preferred.

[0090] The following describes the assumption that the system is in a present state, i.e., mode 1, upon startup. If this assumption is correct, when person 16 leaves the field of view 15, the IR sensor signal 50 will cross the lower threshold 53, and system 1 will enter a non-present state.

[0091] However, if the person is not present in field of view 15 at startup, the initial assumption of the presence of person 16 is incorrect. However, the system will self-calibrate in the following manner: If person 16 subsequently enters field of view 15, in a manner similar to... Figure 6a In the case of the condition at 29 seconds, the upper threshold 52 will be exceeded. Then, the system will remain in the present state. The IR signal 50 will eventually stabilize at a new, higher level (similar to...). Figure 6a (In the case of 38 seconds), and at this higher level, new thresholds 52 and 53 will be determined. The system is now correctly calibrated because when the current threshold 53 is exceeded (e.g., Figure 6a At 54 seconds (in the time frame), it will enter a non-existent state. Therefore, the system is self-calibrating.

[0092] It should be understood that this method and system are implemented using a portion of a computer with digital computer equipment. The various embodiments and components described herein, as well as the communication between these components, can utilize digital computer technology for storing and processing digital information and signals, and suitable hardware and software (including, for example, suitable digital processors, digital memories, input devices, output devices, buses, and communication interfaces).

[0093] The methods described herein can be implemented using any suitable combination of software and hardware. For example, while signal processing module 11 has been described as the software unit above, it can also include hardware such as an A / D converter. Any suitable programming language can be used for the described software unit and methods.

[0094] It should be recognized that everything described in conjunction with one embodiment is fully applicable to other embodiments, provided they are compatible. Therefore, the invention is not limited to the described embodiments, but can be varied within the scope of the appended claims.

[0095] Although the invention has been described with reference to specific exemplary embodiments, this description is generally intended to illustrate the inventive concept and should not be construed as limiting the scope of the invention. The scope is generally defined by the claims.

Claims

1. A method for determining the existence of a person, wherein, The method relates to a system that can be in a state of presence or absence, and the method includes: The method further includes receiving an IR sensor signal, the IR sensor signal being a voltage varying over time, and using the IR sensor signal to determine a smoothed IR signal, wherein the smoothed IR signal is adjusted to the IR sensor signal over time at a first rate in a first mode, and adjusted to the IR sensor signal over time at a second rate in a second mode, wherein the first rate is lower than the second rate. In the first mode, an upper threshold is determined as the smoothed IR signal plus an offset value, and a lower threshold is determined as the smoothed IR signal minus the offset value. In this first mode, presence determination is performed by comparing the IR sensor signal with the upper and lower thresholds. The upper threshold is used to determine a transition from the absence state to the presence state, and the lower threshold is used to determine a transition from the presence state to the absence state. In the second mode, presence determination is performed by comparing the IR sensor signal with the smoothed IR signal. Specifically, when the IR sensor signal is higher than the upper threshold or lower than the lower threshold, a switch from the first mode to the second mode occurs. In the second mode, the variability of the IR sensor signal is determined, and When the variability of the IR sensor signal is below the variability threshold, a switch occurs from the second mode to the first mode.

2. The method according to claim 1, wherein, In the first mode, presence determination is performed by comparing the IR sensor signal with the upper threshold and the lower threshold, such that when the IR sensor signal is higher than the upper threshold, a transition from the absence state to the presence state occurs, and when the IR sensor signal is lower than the lower threshold, a transition from the presence state to the absence state occurs. In the second mode, presence detection is performed by comparing the IR sensor signal with the smoothed IR signal, such that when the IR sensor signal is lower than the smoothed IR signal, a transition from the presence state to the absence state occurs, and when the IR sensor signal is higher than the smoothed IR signal, a transition from the absence state to the presence state occurs.

3. The method according to claim 2, wherein, At the start of the method, the system is pre-defined to be in either the present state or the non-present state.

4. The method according to any one of claims 1 to 3, wherein, The IR sensor is a thermopile.

5. The method according to any one of claims 1 to 3, wherein, The presence or absence status is updated at least once per second.

6. The method according to any one of claims 1 to 3, wherein, The presence state is used to wake the access control device from sleep.

7. A system configured to determine whether a person is present in the field of view of an IR sensor, the system comprising a signal processing module, threshold determination logic, and presence determination logic. The signal processing module is configured to receive voltage from the IR sensor and determine the IR sensor signal that varies with time, and to determine the smoothed IR signal, wherein, The smoothed IR signal is modulated into the IR sensor signal over time at a first rate in a first mode, and at a second rate over time in a second mode, wherein the first rate is lower than the second rate, and the system is further configured to determine the variability of the IR sensor signal. Specifically, the threshold determination logic is configured to, in the first mode, determine the upper threshold as the smoothed IR signal plus an offset value, and determine the lower threshold as the smoothed IR signal minus the offset value. In the first mode, presence determination is performed by comparing the IR sensor signal with an upper threshold and a lower threshold, wherein the upper threshold is used to determine a transition from a non-existent state to a present state, and the lower threshold is used to determine a transition from a present state to a non-existent state. The system is configured to perform an existence determination in the second mode by comparing the IR sensor signal with the smoothed IR signal, wherein a switch from the first mode to the second mode occurs when the IR sensor signal is above the upper threshold or below the lower threshold, and a switch from the second mode to the first mode occurs when the variability of the IR sensor signal is below the variability threshold.

8. A power receiving device comprising the system according to claim 7.

9. The power receiving device according to claim 8, wherein the device is an access control device.

10. The power receiving equipment according to claim 8 or 9, wherein, The device is configured to put the device into a power-saving mode when it receives information from the system that no one is present, or to wake the device from the power-saving mode when it receives information from the system that a person is present.

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