Multi-spectral optical detector with integrated testing

Abstract

The invention relates to a multi-spectral optical probe with integrated testing, comprising a housing having a window. The first channel is disposed within the housing adjacent the window and is sensitive to electromagnetic radiation within a first frequency range. The second channel is disposed within the housing adjacent the window and is sensitive to electromagnetic radiation within a second frequency range different from the first frequency range. The digitizer is operably coupled to the first channel and the second channel and is configured to provide a digital indication of the electromagnetic radiation received by the first channel and the second channel. A processor is coupled to the digitizer to receive the digital indication and generate an output signal based thereon. At least one transmitter is disposed within the housing and operably coupled to the processor. The at least one transmitter is configured to inject a test signal into at least one of the first channel and the second channel to test operation of the at least one first channel and the second channel. A method of operating a multi-channel optical detector is also provided.

Description

Technical Field

[0001] This invention relates to a multi-spectral optical detector with integrated testing. Background Technology

[0002] The process control and monitoring industry supports a wide range of processing industries. Some processing industries may use or handle highly flammable or even explosive materials. Examples of such industries include chemical processing facilities as well as oil extraction and refining. In these environments, fire and explosion are significant hazards. In these highly unstable environments, the use of one or more optical detectors (e.g., optical flame detectors) (which detect any flame in the process environment so that it can be quickly extinguished) is useful and sometimes necessary. Summary of the Invention

[0003] A multi-spectral optical detector includes a housing with a window. A first channel is disposed within the housing adjacent to the window and is sensitive to electromagnetic radiation in a first frequency range. A second channel is disposed within the housing adjacent to the window and is sensitive to electromagnetic radiation in a second frequency range different from the first frequency range. A digitizer is operatively coupled to the first and second channels and configured to provide a digital indication of electromagnetic radiation received by the first and second channels. A processor is coupled to the digitizer to receive the digital indication and, based thereon, generate an output signal. At least one transmitter is disposed within the housing and operatively coupled to the processor. The at least one transmitter is configured to inject a test signal into at least one of the first and second channels to test the operation of the at least one first and second channel. A method of operating the multi-channel optical detector is also provided. Attached Figure Description

[0004] Figure 1 This is a system block diagram of a multi-channel optical sensor, in which the embodiments described herein are particularly useful.

[0005] Figure 2 This is a system block diagram of a multi-channel optical sensor according to an embodiment of the present invention.

[0006] Figure 3 This is a graph showing the signal strength of multiple IR sensors with an internally self-testing optical detector according to an embodiment of the present invention.

[0007] Figure 4 This is a flowchart of a method for operating an optical detector according to an embodiment of the present invention.

[0008] Figure 5 This is a system block diagram of a multi-channel optical sensor according to another embodiment of the present invention.

[0009] Figure 6 This is a system block diagram of a pair of multi-channel optical sensors according to another embodiment of the present invention, operating in a cloud environment. Detailed Implementation

[0010] Figure 1 This is a system block diagram of a multi-channel optical sensor, in which the embodiments described herein are particularly useful. When used in the context of optical flame detection, the multi-channel optical sensor 10 is a device designed to detect the presence of a flame by analyzing emissions on multiple spectral bands or channels. Using multiple channels offers several advantages. First, detection accuracy is improved because different materials have different spectral characteristics when burning. Multi-channel sensors can detect various types of fires by analyzing different portions of the electromagnetic spectrum, including ultraviolet (UV), visible, and infrared (IR) bands. Second, the false alarm rate is reduced by comparing the intensity of emissions on several channels; these sensors can distinguish actual flames from other emission sources (e.g., sunlight, artificial light, or reflections) that might cause false alarms. Third, reliability is improved because multi-channel sensors can operate effectively under various environmental conditions, thereby reducing the risk of detection failure due to factors such as dust, moisture, or other atmospheric obstructions.

[0011] Sensor 10 includes a housing 12 with a lens or window 14 through which the flame 16 can be viewed. The flame 16 emits broad-spectrum infrared radiation. Sensor 10 includes multiple individual IR sensors IR1, IR2, IR3…IR n Each individual sensor is sensitive to a specific range, frequency band, or IR wavelength. Therefore, each individual sensor is essentially tuned or otherwise focused to the relevant flame emission wavelength. IR sensors IR1, IR2, IR3…IR n Each of the components is operatively coupled to a digitizer 18, which includes circuitry for converting analog signals from a single IR sensor into its digital representation. The digitizer 18 is coupled to a processor 20 and configured to provide the processor 20 with digital representations associated with the various IR sensors.

[0012] Processor 20 is any suitable device capable of executing programmed steps or functions to provide various characteristics of sensor 10. Examples of such devices include digital signal processors, microcontrollers, field-programmable gate arrays, and application-specific integrated circuits (ASICs). In some examples, processor 20 is a microprocessor. Digitizer 18 provides processor 20 with a digital representation of the IR sensor signals for signal processing. Processor 20 processes the digitized signals from the IR sensors and analyzes the signals from each IR sensor. Processor 20 attempts to identify specific patterns associated with flame flicker and intensity. To analyze the flame flicker frequency, processor 20 typically converts the signal from the time domain to a frequency fast Fourier transform (FFT). By comparing the outputs of multiple IR sensors, processor 20 can distinguish flames from other IR sources such as sunlight, thermomechanical sources, or artificial lighting. This characteristic is achieved by analyzing the intensity and frequency response of each channel. A real flame is characterized by a low-frequency signal with a response of 1-5 Hz, a high-intensity signal at the signal channel, and a low-intensity signal at the reference channel. The expected correlation (frequency response) of the channels is high, but not perfectly correlated, which would indicate an artificial signal. This multi-spectral analysis reduces false alarms. Processor 20 executes the following method: applying this analysis to calculate the integrity of the signal corresponding to the flame intensity, calculating the ratio between channels to understand whether the signal channel is higher than the reference channel. The final part compares the frequency behavior between different channels to measure the correlation between them.

[0013] When the processor 20 confirms the presence of a flame, it generates an output 22, such as triggering an alarm and / or other appropriate actions. The sensor 10 can also initiate automatic safety measures, such as shutting down equipment and / or activating a fire suppression system.

[0014] Traditional multichannel optical sensors are crucial for detecting light emission in various environments. However, these devices typically lack the ability to continuously assess their own operational integrity. Therefore, any malfunction or degradation in their functionality may go undetected until the next manual inspection or maintenance check, potentially leading to undesirable consequences. Furthermore, in various applications, multichannel optical sensors are inherently susceptible to failures caused by unexpected electrical or optical crosstalk between optical channels.

[0015] Optical crosstalk occurs in an IR sensor when unwanted infrared signals from adjacent sensors interfere with the sensor's intended detection signal. This interference can lead to inaccurate readings or false alarms, thereby reducing the sensor's overall accuracy and reliability.

[0016] This type of failure can manifest as unexpected shortcuts or signal interference between channels, leading to impaired sensor performance, incorrect data acquisition, or inaccurate detection or measurement of the expected optical signal. This problem is particularly prevalent in environments requiring dense integration of optical channels, and precise separation of the optical path is crucial for the operational integrity and accuracy of the sensor. Advanced multi-channel optical sensors can accommodate up to 256 optical elements with a physical size of 10 mm, a channel size of 30 micrometers, and a channel spacing of 10 micrometers.

[0017] Due to its small size, any problems during assembly could lead to shortcuts between channels, resulting in incorrect information being received from the sensors.

[0018] Current optical flame detectors are tested using external light sources, which requires additional hardware, occupies space, and allows only a single light source to be used to test all channels. Due to the mechanical tolerances and dimensions of external light sources, this can lead to inaccurate signals reaching each channel. Therefore, while such sensors can be tested to ensure they respond to light, it is generally impossible to analyze the response of each channel individually because all channels are exposed to the same signal level.

[0019] According to embodiments of the present invention, the optical sensor provides an internal self-test feature. In some embodiments, this internal self-test can continuously verify the internal hardware components of the multi-channel optical sensor. This process preferably occurs in real time along with the device's main detection tasks without interrupting or diminishing the device's ability to detect optical signals. However, it is explicitly envisioned that this internal self-test can also be performed periodically and / or in response to user input. Furthermore, embodiments of the present invention include a method for evaluating the integrity and performance of a multi-channel optical sensor by employing multiple different energy sources. The method involves sequentially directing energy from each of these sources into an optical channel, and subsequently recording the response of each channel to the corresponding energy input. A processor 20 then processes the collected response data to determine whether optical crosstalk exists between the channels. By measuring and comparing the responses of each channel to various energy sources, this method ensures accurate differentiation of signals corresponding to each channel, thereby improving the fidelity and reliability of the multi-channel optical sensor system.

[0020] Figure 2 This is a system block diagram of a multi-channel optical sensor according to an embodiment of the present invention. Sensor 100 has some similarities to sensor 10, and similar components are similarly numbered. Sensor 100 includes a sensor housing 12, which contains various IR sensors, such as IR1, IR2, IR3, and IR42 shown. nEach of the various IR sensors is operatively coupled to a digitizer 18, which provides a digital representation of the signals from the IR sensors to a processor 20. However, sensor 100 includes an internal illumination source operatively coupled to processor 20, such that processor 20 controls the illumination source. In the illustrated embodiment, the internal illumination source is in the form of a plurality of transmitters 102, 104, 106, and 108. Figure 2 As shown, the transmitters are located adjacent to each IR sensor. More specifically: transmitter 102 is located adjacent to sensor IR1; transmitter 104 is located adjacent to sensor IR2; transmitter 106 is located adjacent to sensor IR3; and transmitter 108 is located adjacent to sensor IR4. n Each transmitter can be configured to have an emission wavelength that matches its corresponding IR sensor. Alternatively, one or more transmitters can have an emission spectrum wider than their corresponding IR sensors. In some cases, the transmitter can be a broad-spectrum transmitter, such as an incandescent lamp or a strobe lamp. In some embodiments, the proximity of the transmitter to each corresponding IR sensor can be achieved by mounting discrete transmitters on a circuit board adjacent to each discrete IR sensor. In other embodiments, the IR transmitter can be mounted on the same silicon substrate as the IR sensor (i.e., a composite silicon assembly with multiple transmitters and IR sensors). In other embodiments, the IR transmitter can be disposed within each corresponding IR sensor.

[0021] All transmitters 102, 104, 106, and 108 are operatively coupled to processor 20, such that processor 20 controls the operation of each individual transmitter. Therefore, processor 20 can power transmitter 102 and determine whether sensor IR1 has an acceptable response or detection to the emitted radiation. Furthermore, processor 20 can detect whether any other IR sensor senses the emission from transmitter 102, which would indicate crosstalk. This crosstalk could be due to illumination from transmitter 102 reaching an IR sensor different from sensor IR1, and / or it could indicate an electrical fault that allows a signal from sensor IR1 to appear as a signal from another IR sensor (e.g., sensor IR2). In either case, this detection is an indication of a fault that processor 20 can provide locally and / or to remote devices.

[0022] Figure 3 This is a graph showing the signal strength of multiple IR sensors with an internally self-testing optical detector according to an embodiment of the present invention. Figure 3 The sensor's response to illumination from corresponding integrated energy sources (e.g., emitters 102, 104, 106, and 108) is shown. During normal sensor operation, the energy within housing 12 (e.g., Figure 2(As shown) emits light energy, which is generated by IR sensors IR1, IR2, IR3 and IR4. n Receiving and detecting.

[0023] The embodiments described herein typically include one or more emitters integrated within the housing of a multichannel sensor device and located near a corresponding channel / detector within the device. Preferably, each emitter is operatively paired with a corresponding channel / detector. Activation of the emitters is preferably performed sequentially to facilitate measurement of each channel's response to its associated emitter. Analyzing the response of each channel / detector allows for the calculation and compensation of the sensitivity of each channel / detector, ensuring that sensitivity does not decrease over time. This configuration ensures the continued accuracy and reliability of the multichannel sensor system, maintaining its ability to perform critical detection functions without degradation.

[0024] Figure 4 This is a flowchart of a method for operating an optical detector according to an embodiment of the present invention. Method 150 begins at block 152, where processor 20 uses one or more internal emission sources (e.g., emitters 102, 104, 106, and 108) to trigger or otherwise initiate a self-test. Method 150 continues at block 154, where processor 20 activates one or more channels / IR ​​sensors under test, as shown at block 154a. In some embodiments, the channels / IR ​​sensors are activated sequentially. However, in other embodiments, multiple channels / IR ​​sensors can be activated simultaneously, provided that the channels / detectors are spaced far enough apart that (optical and / or electrical) crosstalk is impossible. Next, processor 20 controls one or more emitters 102, 104, 106, 108 to inject a predefined test signal into each channel / IR detector to simulate one or more real-world operating scenarios, as shown at block 154b. The predefined test signal is an important feature because it allows processor 20 to distinguish the channel response from ambient and / or flame signals. Next, in box 154, digitizer 18 measures or otherwise converts the IR sensor’s response to the injected test signal and provides it to processor 20, as shown in box 154c.

[0025] In block 156, processor 20 compares the response of each channel / IR detector to a predefined expected response for each test signal. The deviation between the measured channel response and the expected channel response is analyzed to identify potential sensor faults or system inaccuracies. In some embodiments, the deviation of a single channel from the expected response can be simply compared to a predefined threshold (i.e., 10%), and if the deviation exceeds the predefined threshold, processor 20 can generate a sensor fault and / or initiate error handling, as shown in block 158. In another example, if the deviation exceeds the predefined threshold, processor 20 can do so by ignoring or otherwise mitigating the impact of the faulty channel on overall detector operation. In another example, processor 20 can also proceed to block 158 and indicate a sensor fault if processor 20 detects a response in a channel / IR sensor that is not the expected receiver of the injected test signal. Furthermore, in future system operation, the responses of the channel / IR sensors can be ignored or otherwise mitigated. If all channel / IR detectors provide a response to the injected test signal that matches the expected response or matches within a selected amount, processor 20 determines that the system is functioning correctly and passes control to block 160, where normal system operation continues. Method 150 ends at block 162, but can be repeated or iterated continuously or at selected intervals, as shown in line 164.

[0026] As described above, the embodiments disclosed herein typically provide one or more power sources disposed within the housing of an optical detection device to simultaneously measure channel responses during normal operation (i.e., in the background), thereby allowing for accurate detection of optical crosstalk and / or electrical crosstalk. This allows the multi-channel optical sensor to continuously self-evaluate the optical sensor according to various embodiments without interrupting normal detection capabilities. Therefore, the embodiments described herein allow the device to identify and report faults in real time, thereby ensuring the operational integrity of the multi-channel optical sensor is always maintained.

[0027] The response of each channel / IR sensor is characterized by measuring the channel / IR sensor and comparing that response with other channel / IR sensors. The unique processing of the channel / IR sensor's response to a predefined test signal facilitates the detection of subtle anomalies that can indicate impending failure or performance degradation.

[0028] The embodiments described herein typically include an integrated hardware and software system that combines hardware modifications and software enhancements to achieve internal self-test functionality. It is believed that such a system will be compatible with existing optical inspection frameworks and provide seamless operation within them. Furthermore, the internal self-test can operate autonomously without external input or activation, thereby ensuring uninterrupted optical inspection.

[0029] Figure 5 This is a system block diagram of a multi-channel optical sensor according to another embodiment of the present invention. Sensor 200 and sensor 100 (e.g.) Figure 2 The embodiments shown have some similarities, and similar components are similarly numbered. Embodiments of the invention are particularly suitable for battery-powered devices. Given that the embodiments typically add the additional functionality of providing power to one or more transmitters (e.g., transmitters 102, 104, 106, and 108) within the housing 12, devices using the disclosed embodiments may consume battery power faster than existing devices. Therefore, the optical detector 200 includes an energy harvester 202 operatively coupled to the processor 20. The energy harvester 202 is configured to generate power for the sensor 200 from an ambient energy source available to the sensor 200. In one example, the energy harvester 202 includes one or more solar cells that convert sunlight into electricity. In another example, the energy harvester includes a thermoelectric generator that converts the thermal difference between two surfaces into electricity. In another example, the energy harvester may include a vibration generator that converts vibrational motion into electricity. In yet another example, the energy harvester 202 includes a wind turbine configured to drive the generator using wind power. Finally, the embodiments include any combination of the various forms of energy harvesting listed above.

[0030] Figure 6 This is a system block diagram of a pair of multi-channel optical sensors according to another embodiment of the present invention, operating in a cloud environment. Figure 6 Each sensor 250 shown includes a communication module 252 coupled to the processor 20 and operatively coupled to the cloud computing system 300. The communication module 252 allows the processor 20 to communicate with remote devices (e.g., the cloud computing system 300). This communication can take any suitable form, but is preferably wireless. Examples of wireless communication include, but are not limited to: the wireless HART process communication protocol (IEC 62591); cellular communication protocols such as GPRS, UMTS, CDMA2000, LTE, LTE-M, NB-IoT, WiMax, 5G NR; WiFi standards such as IEEE 802.11b / g / n / a / ac / ax / be; and the LoRaWAN protocol (ITU-T Y.4480). Advanced data analytics, predictive maintenance, and remote monitoring capabilities can be achieved using cloud-based analytics (e.g., analytics provided by cloud resources 300). This cloud-based analytics can also enable more complex diagnostics, trend analysis, and preventative actions based on aggregated data from multiple sensors 250.

[0031] Although the invention has been described with reference to preferred embodiments, those skilled in the art will recognize that modifications in form and detail may be made without departing from the spirit and scope of the invention.

Claims

1. A multi-spectral optical detector comprising: a housing having a window; a first channel disposed within the housing proximate the window and sensitive to electromagnetic radiation in a first frequency range; a second channel disposed within the housing proximate the window and sensitive to electromagnetic radiation in a second frequency range different from the first frequency range; a digitizer operably coupled to the first channel and the second channel, the digitizer configured to provide a digital indication of electromagnetic radiation received by the first channel and the second channel; a processor coupled to the digitizer to receive the digital indication and based thereon to generate an output signal; and at least one emitter disposed within the housing and operably coupled to the processor, the at least one emitter configured to inject a test signal into at least one of the first channel and the second channel to test operation of at least one first channel and second channel. The at least one emitter comprises a plurality of emitters, wherein a first emitter of the plurality of emitters is disposed proximate the first channel and a second emitter of the plurality of emitters is disposed proximate the second channel.

2. The multi-spectral optical detector of claim 1, wherein, The first emitter has an emission wavelength in the first frequency range.

3. The multi-spectral optical detector of claim 2, wherein, The second emitter has an emission wavelength in the second frequency range.

4. The multi-spectral optical detector of claim 3, wherein, 5. The multi-spectral optical detector of claim 1, further comprising at least one additional channel disposed within the housing proximate the window and sensitive to electromagnetic radiation in at least one additional frequency range different from the first frequency range and the second frequency range. The at least one emitter comprises a plurality of emitters, wherein a first emitter of the plurality of emitters is disposed proximate the first channel and a second emitter of the plurality of emitters is disposed proximate the second channel, and at least one additional emitter is disposed proximate each respective at least one additional channel.

6. The multi-spectral optical detector of claim 5, wherein, The multi-spectral optical sensor comprises more than 200 additional channels in addition to the first channel and the second channel, each additional channel sensitive to electromagnetic radiation in a different range, and wherein optical elements of the channels are mounted within a physical dimension of 10 millimeters.

7. The multi-spectral optical detector of claim 1, wherein, The first channel and the second channel are spaced apart by about 10 microns.

8. The multi-spectral optical detector of claim 1, wherein, The processor is configured to identify cross-talk between the first channel and the second channel and to provide an indication of cross-talk.

9. The multi-spectral optical detector of claim 1, wherein, The multi-channel optical detector is a flame detector and the first frequency range and the second frequency range are directed to spectral characteristics of a flame.

10. The multi-channel optical detector of claim 1, wherein, The processor is configured to control the at least one emitter to perform a self-test.

11. The multi-channel optical detector of claim 1, wherein, The processor is configured to perform the self-test as a background task.

12. The multi-channel optical detector of claim 11, wherein, The test signal is a predefined test signal.

13. The multi-channel optical detector of claim 1, wherein, ​ 14. The multi-channel optical detector of claim 1, further comprising an energy harvester disposed within the housing and coupled to the processor, the energy harvester configured to generate electrical power from ambient potential energy proximate the multi-channel optical detector.

15. The multi-channel optical detector of claim 14, wherein, The energy harvester is configured to generate electrical power from at least one of: solar radiation, thermal energy, motion, and wind.

16. The multi-channel optical detector of claim 1, further comprising a communication circuit coupled to the processor and configured to communicate with a remote device.

17. The multi-channel optical detector of claim 16, wherein, The processor is configured to provide channel response information to the remote device for remote analysis.

18. A method of operating a multi-channel optical detector, the method comprising: activating a plurality of channels of the optical detector; injecting a test signal into each activated channel using an emitter disposed within the multi-channel optical detector; measuring a response of each channel to the injected test signal; and comparing the measured response of each channel to an expected response and generating a self-test diagnostic output based on the comparison.

19. The method of claim 18, wherein, Activating the plurality of channels and injecting the test signal are performed sequentially for each of the plurality of channels.

20. The method of claim 18, wherein, The test signal is a predefined test signal.

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