Patent Publication Number: US-9418532-B2

Title: Infrared detector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119 of the filing date of Chinese Patent Application No. 201410116794.8, for Smart Infrared Detector and Working Method Thereof, which was filed on Mar. 26, 2014, and which is incorporated here by reference. 
     BACKGROUND 
     The present specification relates to infrared detectors. 
     Infrared detectors are often used to measure temperature changes within an area such as a room being monitored. One typical type of infrared detector includes a pyroelectric sensor. When a surface temperature of the pyroelectric sensor&#39;s dielectric changes, the dielectric generates an electric charge. In particular, polarization of the material forming the dielectric surface changes in response to a change in temperature, which generates a voltage across the dielectric. When the surface temperature rises, the polarization strength in the dielectric reduces, which results in a release of charge by the dielectric. The generated charge gradually drifts away from the dielectric surface. Infrared radiation incident upon the dielectric of the pyroelectric sensor continues. When the surface temperature of the dielectric reaches equilibrium, i.e., a constant temperature, it stops releasing a charge, and no signal is output. Thus, the pyroelectric sensor is used to detect temperature changes in an area being monitored. 
     Once a person enters the area being monitored, a change in the temperature of the area occurs. The infrared detector can detect these temperature changes, e.g., based on the pyroelectric sensor. Thus, based on signals outputted by the infrared detector, it can be determined whether or not someone enters the area being monitored. 
     However, conventional infrared detectors can only identify temperature changes and cannot detect when there is a static infrared signal source in the area being monitored. For example, if an elderly person enters the area being monitored and falls down in the area, a conventional infrared detector can only determine if the temperature changes in the area being monitored. Thus, the detector can determine that someone enters or leaves the area being monitored, but cannot determine that a continuous and static infrared signal source exists in the area being monitored. Consequently, the conventional detector would fail to determine that someone fell down in the area being monitored and as a result the detector cannot generate an alarm in response. 
     In some typical scenarios that require nursing care and monitoring, web cameras are often used to monitor the area. The camera is used to capture video images of the area and transmits the video images, for example, to a nursing station. 
     However, cameras generally have high power consumption and are powered by city electricity, which restricts installation and applications of the web cameras. In addition, since the web cameras produce images of the area being monitored, protecting the privacy of persons in the area being monitored restricts their use as well. For example, the web cameras typically cannot be installed in washing rooms and bedrooms. 
     SUMMARY 
     An infrared detector is described in this specification that can detect a static infrared signal source while having low power consumption. 
     In general, one innovative aspect of the subject matter described in this specification can be embodied in infrared detectors that include a pyroelectric sensor; a controller for receiving a trigger signal outputted by the pyroelectric sensor; a thermopile sensor, wherein the controller starts the thermopile sensor after receiving the trigger signal output by the pyroelectric sensor; and an alarm, wherein when the thermopile sensor determines that a difference between a current temperature and a background temperature is larger than a threshold value, the controller controls the alarm to generate an alarm signal. 
     The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. The infrared detector further includes a timer, wherein the controller starts the timer after receiving the trigger signal outputted by the pyroelectric sensor, and starts the thermopile sensor after a counted time is ended. The alarm is a wireless alarm circuit. The wireless alarm circuit is a wireless radio frequency (RF) circuit, a Wi-Fi signal transmitting circuit, or a Bluetooth signal transmitting circuit. The infrared detector further includes a battery module, for supplying power to the pyroelectric sensor and the thermopile sensor. 
     In general, one innovative aspect of the subject matter described in this specification can be embodied in methods that include the actions of using a thermopile sensor of an infrared detector to determine a background temperature of an area being monitored; using a pyroelectric sensor of the infrared detector to determine whether a temperature in the area being monitored has changed; and in response to a determination that the temperature has changed: using a thermopile sensor to determine the temperature in the area being monitored; and comparing the determined temperature to the background temperature; determining whether the difference between the determined temperature and the background temperature satisfies a threshold value; and in response to determining that the difference satisfies the threshold value, generating an alarm. 
     The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. After the pyroelectric sensor determines that the temperature in the area being monitored changed changes, initiating a timer to count down time before using the thermopile sensor, and after the counted time is ended, using the thermopile sensor. Generating the alarm includes using a wireless alarm circuit. The wireless alarm circuit is a wireless radio frequency (RF) circuit, a Wi-Fi signal transmitting circuit, or a Bluetooth signal transmitting circuit. 
     The subject matter described in this specification can be implemented in particular embodiments so as to realize one or more of the following advantages. An infrared sensor is provided that can detect both changes in temperature within an area being monitored as well as detect static infrared sources. As a result, the infrared detector can improve monitoring of an area to detect static sources particularly in cases of monitoring individuals particularly those under nursing care while minimizing the impact on individual privacy. 
     The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an example structure of an infrared detector. 
         FIG. 2  is a flow chart of an example process for using an infrared detector. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     This specification describes an infrared detector. The infrared detector is configured to include both a pyroelectric sensor and a thermopile sensor. The infrared detector can be used to monitor particular regions. For example, the infrared detector can be used to detect activities of persons in a specific area being monitored such as a particular room, thereby being applicable to circumstances that involve monitoring of vulnerable individuals, e.g., nursing. 
       FIG. 1  is a block diagram of an example structure of an infrared detector  100 . The infrared detector  100  includes a controller  10 , a pyroelectric sensor  11 , a thermopile sensor  12 , a timer  13 , a wireless radio frequency (RF) circuit  14 , and a rechargeable battery  15 . 
     The controller  10  controls operations of the pyroelectric sensor  11  and the thermopile sensor  12 , and receives signals sent by the pyroelectric sensor  11  and the thermopile sensor  12 . Moreover, the controller  10  controls the wireless RF circuit  14  to generate an alarm signal when triggered. 
     The pyroelectric sensor  11  is used to determine whether anyone enters an area being monitored such that the temperature changes. When someone enters the area being monitored and causes temperature changes, e.g., when a movable infrared signal source enters the area being monitored, a surface temperature of the pyroelectric sensor&#39;s  11  dielectric changes and the dielectric releases some electric charge. The pyroelectric sensor  11  is triggered and sends a trigger signal to the controller  10 . 
     The thermopile sensor  12  includes a plurality of thermocouple sensors coupled in series or in parallel. The thermopile sensor  12  is used to monitor a static temperature in the area being monitored. In particular, the thermopile sensor  12  detects a static infrared signal source, converts the detected temperature into an electrical signal, and determines the temperature in the area being monitored based on the electrical signal. In some implementations, the thermopile sensor  12  enters a sleeping mode in which it does not maintain a working status continuously to save the electrical energy consumed by the infrared detector  100 . 
     The timer  13  starts counting down a specified amount of time under the control of the controller  10 . Once the counted time was elapsed, the timer  13  outputs a break request signal (BRS) to the controller  10 . The break request signal informs the controller  10  that the counted time is ended. The specific amount of time set by the timer  13  may be a time set within the controller  10 . Additionally, in some implementations, the timer is built as part of the controller  10 . 
     The wireless RF circuit  14  provides the alarm for the infrared detector  100 . The wireless RF circuit  14  sends an alarm signal, in response to a command from the controller  10 , in a form of a wireless RF signal to a backend control center, e.g., a backend computer or server. After receiving the alarm signal, the control center informs the authorized individuals of the alarm. For example, in a nursing context, the controlling center can inform a nursing staff to provide help to the person associated with the alarm. 
     Alternatively, in some other implementations, the alarm is a wireless alarm circuit in another form, e.g., a Wi-Fi signal transmitting circuit, or a BLUETOOTH signal transmitting circuit. These alarm circuits send wireless signals to the backend control center. In addition, the alarm may be a sound and light alarm circuit integrated with the infrared detector, e.g., a light emitting diode (LED) or buzzer to provide a local audible alarm. The individuals around the infrared detector  100  respond to the alarm generated by the sound and light alarm circuit of the infrared detector  100 . 
     The rechargeable battery  15  provides a battery module for the infrared detector  100  and is used to supply power to the controller  10 , the pyroelectric sensor  11 , and the thermopile sensor  12 . Since the pyroelectric sensor  11  and the thermopile sensor  12  consume low levels of electrical energy, a typical rechargeable battery  15  can supply a stable low-voltage direct current (DC) to satisfy the operational requirements of the pyroelectric sensor  11  and the thermopile sensor  12 . 
       FIG. 2  is flow chart of an example process  200  for using an infrared detector, e.g., infrared detector  100  of  FIG. 1 . The infrared detector is activated  202 . For example, a battery, e.g., rechargeable battery  15 , supplies power to a controller, a pyroelectric sensor, and a thermopile sensor of the infrared detector. The controller can be the controller  10 , the pyroelectric sensor can be the pyroelectric sensor  11 , and the thermopile sensor can be the thermopile sensor  12  of  FIG. 1 . The thermopile sensor of the infrared detector collects a background temperature in an area being monitored, and outputs the collected temperature data to the controller. The controller stores the background temperature data. Then, the thermopile sensor enters a sleeping status ( 204 ). 
     The pyroelectric sensor determines whether anyone enters the area being monitored causing a temperature change in the area. If it is determined that someone enters the area being monitored, the pyroelectric sensor is triggered, and outputs a trigger signal to the controller ( 206 ). If it is determined that someone has not entered the area being monitored, the thermopile sensor terminates the working status ( 220 ). 
     The controller initiates a timer, e.g., the timer  13  of  FIG. 1 , to start counting down the specified time ( 208 ). The controller determines whether the counted time is ended ( 210 ). If it is determined that the counted time has ended, yes branch of  210 , the controller starts the thermopile sensor. The thermopile sensor collects a temperature in the area under detection, converts the temperature into an electrical signal, and outputs it to the controller ( 212 ). If the counter time has not ended, no branch of  210 , the timer continues to count down and the determination is repeated. In some implementations, a subsequent detection of someone entering the area by the pyroelectric sensor resets the timer. 
     The controller compares the collected current temperature in the area being monitored with the background temperature ( 214 ). The controller determines whether any static infrared signal source exists in the area being monitored based on a comparison result ( 216 ). If the controller determines that the current temperature of the area being monitored is inconsistent with the background temperature, or a difference there-between is larger than a threshold value, yes branch of  216 , it is determined that a static infrared signal source exists in the area under detection. Consequently, the controller triggers an alert response ( 218 ). For example, the alert response can be an alarm provided by a wireless RF circuit, e.g., wireless RF circuit  14  of  FIG. 1 , which transmits an alarm signal to a control center. 
     If the controller determines that the temperature in the area under detection has not changed or that the difference between the current temperature in the area under detection and the background temperature is smaller than a threshold value, no branch of  216 , the controller determines that no static infrared signal source exists in the area under detection, the thermopile sensor terminates the working status, and the timer is reset to zero ( 220 ). 
     The infrared detector includes both the pyroelectric sensor and the thermopile sensor in the same package. As a result, the infrared detector can determine whether a movable infrared signal source exists in the area being monitored as well as determine whether a static infrared signal source exists in the area being monitored. The infrared detector can determine, for example, whether a person falls down in the area being monitored. In addition, unlike a camera device, the thermopile sensor does not capture images, e.g., photographic images, which protects the privacy of those in the area being monitored. As such, the infrared detector can be installed in washing rooms, bedrooms, etc., and can be used to monitor those needing special care, e.g., those under nursing care. 
     Furthermore, the pyroelectric sensor and the thermopile sensor have low electrical energy consumption, and can therefore be constructed such that they only need a rechargeable battery instead of being plugged in or directly wired to a building electrical supply. Thus, the installation of the infrared detector is versatile. 
     In some alternative implementations, after the pyroelectric sensor is triggered, the set time of the timer may be adjusted depending upon an actual usage circumstances, or set manually. Alternatively, when the controller determines whether a static infrared signal source exists in the area being monitored, a threshold value for a difference between the background temperature and the current temperature may be set manually, e.g., based on particular criteria and environmental conditions. 
     The infrared detector described above can further be used for other applications including in advertisement boards or advertisement boxes. For example, the thermopile sensor first inspects a background temperature in an area under detection in front of an advertisement board or advertisement box. Then, the pyroelectric sensor determines whether anyone passes by, that is, the sensor detects whether the temperature in the area being monitored changes or not. If the temperature changes, the thermopile sensor detects the temperature in the area being monitored once again after a preset time period elapsed, and determines whether the current temperature is consistent with the background temperature. If not, it determines that someone stays in front of the advertisement board or advertisement box. In this case, the controller, used for controlling the advertisement board or advertisement box, controls the advertisement board or advertisement box to operate, e.g., powering on a screen to display images, characters, cartoons, or turning over a displaying board, etc. 
     Thus, when a person quickly walks by the front area of the advertisement board or advertisement box, the advertisement board or advertisement box does not display the advertising content or only shows a static advertising content. Only when someone stays in front of the advertisement board or advertisement box, the advertisement board or advertisement box operates, which reduces electrical energy consumed by the advertisement board or advertisement box. 
     It should be noted that, the infrared sensor described in this specification is not limited to be above implementations, and changing of the type of an alarm, the type of a timer, and the type of a rechargeable battery all fall within the protection scope as claimed. While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.