Thermopile array and signal readout circuit therefor

Abstract

The application relates to a thermoelectric array and a signal readout circuit thereof, the thermoelectric array comprising: a plurality of sensor pixel elements; and a readout circuit comprising a plurality of signal processing channels, each signal processing channel comprising: a preamplifier for amplifying a sensor signal, the preamplifier being a single-stage amplifier; and an analog-to-digital converter connected to an output of the preamplifier, the analog-to-digital converter being a delta-sigma analog-to-digital converter; wherein each signal processing channel is configured to process sensor signals output by i sensor pixel elements, i being a positive integer and not greater than the square root of the number of sensor pixel elements in the thermoelectric array divided by 4. The application effectively reduces the noise bandwidth of the signal channel, thereby effectively improving the signal-to-noise ratio of the signal processing channel, effectively improving the system performance, and significantly improving the thermal temperature resolution; at the same time, because the frequency is reduced, the area and power consumption of the preamplifier and the analog-to-digital converter can be significantly reduced.

Description

Technical Field

[0001] This invention relates to infrared sensing, and more particularly to a thermopile array, and also to a signal readout circuit for a thermopile array. Background Technology

[0002] Far-infrared thermal sensors are finding increasingly diverse applications, ranging from industrial control and consumer electronics to smart buildings and the Internet of Things (IoT). With the booming consumer market, there are higher demands on the quantity and integration of far-infrared thermal sensors, requiring further improvements in sensor size and cost. Thermopile sensors typically consist of a large number of thermocouples connected in series (or occasionally in parallel). The output voltage of a series thermocouple depends on the temperature difference between the thermocouple junction and a reference junction. This principle is known as the Seebeck effect. With technological and market advancements, thermopile infrared sensors have gradually evolved from early single-pixel structures to array-type sensors. In the continuous development of thermopile infrared sensor arrays, the signal processing of thermopile sensors inevitably encounters the following problems:

[0003] The signal processing of mainstream thermopile arrays employs a preamplifier and a high-precision analog-to-digital converter (ADC). Both the preamplifier and the ADC require significant area and power consumption to ensure performance. For small-scale arrays (e.g., 2x2 or 4x4), the sensor pixels are large and the signal is strong, providing sufficient space for the signal processing chip to accommodate the high-performance preamplifier and ADC. However, as the array size increases (>16x16), the pixel size decreases significantly, leaving insufficient space for the signal processing chip to accommodate more signal processing channels. Furthermore, more signal processing channels lead to higher power consumption. In addition to the inherent current loss, the higher current causes self-heating of the chip, which severely affects sensor calibration, thereby significantly reducing the temperature resolution and reliability of the thermopile sensor. The signal readout circuit of a thermopile array typically uses a preamplifier with very high gain, such as greater than 10,000 times. A low-pass filter is usually required after the preamplifier to eliminate high-frequency noise. Then, a high-performance analog-to-digital converter is used to convert the amplified signal into a digital signal for output. To ensure performance, a large area and power consumption are required. Summary of the Invention

[0004] Therefore, it is necessary to provide a thermopile array and its signal readout circuit that is suitable for arrays with a large number of sensor pixels and can take into account power consumption, area and performance.

[0005] A thermoelectric array, comprising: a plurality of sensor pixels; and a readout circuit comprising a plurality of signal processing channels, each signal processing channel comprising: a preamplifier for amplifying a sensor signal, the preamplifier being a single-stage amplifier; and an analog-to-digital converter having an input connected to an output of the preamplifier, the analog-to-digital converter being a delta-sigma analog-to-digital converter; wherein each of the signal processing channels is configured to process the sensor signal output by i sensor pixels, i being a positive integer and i being no greater than a square root of a number of sensor pixels of the thermoelectric array divided by 4 when the number of sensor pixels is no less than 256.

[0006] In one embodiment, the number of signal processing channels is equal to the number of sensor pixels, and each signal processing channel corresponds to one sensor pixel; or the thermoelectric array further comprises at least one multiplexer, each multiplexer having an input connected to more than one sensor pixel and an output connected to one signal processing channel, and different multiplexers being connected to different signal processing channels; for a single multiplexer, the sensor pixels connected to the multiplexer are simultaneously turned on and turned off to combine the sensor signals of the turned-on sensor pixels and send the combined sensor signals to the connected signal processing channel.

[0007] In one embodiment, up to 8 sensor pixels are connected to one signal processing channel by one multiplexer.

[0008] In one embodiment, the sensor pixels are arranged in an array, and the number of signal processing channels is at least 4 times the number of rows of the array.

[0009] In one embodiment, no low-pass filter is provided between the analog-to-digital converter and the preamplifier of each signal processing channel.

[0010] In one embodiment, the preamplifier is of a sleeve or folded cascode structure.

[0011] In one embodiment, the closed-loop gain of the preamplifier is 80-500.

[0012] In one embodiment, the preamplifier adopts a chopping-stabilized modulation mode.

[0013] In one embodiment, the analog-to-digital converter adopts a first-order single-bit quantizer feedback structure.

[0014] In one embodiment, the oversampling rate of the analog-to-digital converter is greater than 4096.

[0015] In one embodiment, the integrator in the analog-to-digital converter is an inverter-type integrator.

[0016] In one embodiment, the analog-to-digital converter uses a unit capacitor of no more than 100 fF.

[0017] In one embodiment, the thermopile array, integrated on a chip, also includes two or more ambient temperature sensors, each of which is distributed on the chip.

[0018] In one embodiment, the sensor pixels are arranged to form an array; at least a portion of the preamplifiers in the multi-channel signal processing channel are located in the gaps between adjacent sensor pixels.

[0019] In one embodiment, the preamplifier is located between more than half of the adjacent sensor pixels.

[0020] In one embodiment, the power consumption of each preamplifier within the sensor array is less than the power consumption of each preamplifier outside the sensor array.

[0021] In one embodiment, the array of sensor pixels includes at least one reference pixel in each row or column, and each reference pixel does not receive external temperature signals. The readout circuit further includes a compensation circuit for calibrating the sensor signals output by the sensor pixels with the sensor signals output by the reference pixels in the same row or column.

[0022] A readout circuit for a thermopile array, applied to a thermopile array, includes multiple signal processing channels. Each signal processing channel includes: a preamplifier for amplifying sensor signals, wherein the preamplifier is a single-stage amplifier; and a delta-sigma analog-to-digital converter, the input of which is connected to the output of the preamplifier, wherein the analog-to-digital converter is a delta-sigma analog-to-digital converter. Each signal processing channel processes the sensor signals output from i sensor pixels, where i is a positive integer and, when the number of the plurality of sensor pixels is not less than 256, i is not greater than the square root of the number of sensor pixels in the thermopile array divided by 4.

[0023] In one embodiment, each of the multiplexers is used to connect up to eight sensor pixels of the thermopile array.

[0024] In one embodiment, the number of signal processing channels is at least four times the number of rows in the array.

[0025] In one embodiment, no low-pass filter is provided between the analog-to-digital converter and the preamplifier of each of the signal processing channels.

[0026] In one embodiment, the preamplifier is a sleeve or folded cascode structure.

[0027] In one embodiment, the preamplifier has a closed loop gain of 80-500.

[0028] In one embodiment, the preamplifier uses a chopping stabilized modulation scheme.

[0029] In one embodiment, the analog-to-digital converter uses a first order single bit quantizer feedback structure.

[0030] In one embodiment, the analog-to-digital converter has an oversampling ratio greater than 4096.

[0031] In one embodiment, the integrator in the analog-to-digital converter is an inverter type integrator.

[0032] In one embodiment, the analog-to-digital converter uses a unit capacitance of no more than 100 fF.

[0033] In one embodiment, at least some of the preamplifiers of the plurality of signal processing channels are disposed at interstitial spaces between adjacent sensor pixel elements of the thermopile array.

[0034] In one embodiment, each preamplifier within the sensor array has a power consumption less than each preamplifier outside the sensor array.

[0035] The above thermoelectric array and its readout circuit set sufficient parallel signal processing channels according to the number of sensor pixel elements, the data processing time of a single signal processing channel is significantly improved, the preamplifier and the analog-to-digital converter can meet the requirements by using a lower frequency, the noise bandwidth of the signal channel is effectively reduced, thereby effectively improving the signal-to-noise ratio of the signal processing channel and the performance of the system, and the thermal temperature resolution is significantly improved; at the same time, because of the reduction in frequency, the area and power consumption of the preamplifier and the analog-to-digital converter can be significantly reduced. With the increase in the number of signal processing channels, due to the adoption of sufficient signal processing channels, the integration processing time of the sensor signal output by each sensor pixel element of the signal processing channel is greatly increased, and the noise bandwidth is greatly reduced. The preamplifier mainly functions in noise suppression while preliminarily amplifying the signal and providing a certain driving capability, and the requirement for its amplification precision is reduced. Therefore, in order to control the area of the readout circuit, the preamplifier can adopt a low closed-loop gain structure (for example, a single-stage amplifier), which can greatly reduce the power consumption and area, thereby reducing the design difficulty of the related analog circuit (for example, the preamplifier and the analog-to-digital converter). The working current of the signal processing channel is greatly reduced, thereby effectively overcoming the self-heating problem caused by a large current and greatly reducing the requirement for system temperature calibration. In view of the low closed-loop gain coefficient of the preamplifier, the analog-to-digital converter adopts a delta-sigma architecture, and the low-pass characteristic of the delta-sigma signal transfer function is utilized, so that a low-pass filter does not need to be arranged between the preamplifier and the analog-to-digital converter. BRIEF DESCRIPTION OF DRAWINGS

[0036] For better describing and illustrating the embodiments and / or examples of the inventions disclosed herein, reference can be made to one or more drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the presently described embodiments and / or examples, and the best mode presently understood of these inventions.

[0037] Figure 1 FIG. 1 is a structural schematic diagram of a signal processing channel in an embodiment;

[0038] Figure 2 FIG. 2 is a connection schematic diagram of a signal processing channel and a sensor pixel element in an embodiment;

[0039] Figure 3 FIG. 3 is a schematic diagram of simultaneously selecting a plurality of sensor pixel elements to the same signal processing channel in an embodiment;

[0040] Figure 4a FIG. 4 is a schematic diagram of an embodiment in which a thermoelectric array is provided with two ambient temperature sensors, Figure 4b FIG. 5 is a schematic diagram of an embodiment in which a thermoelectric array is provided with four ambient temperature sensors;

[0041] Figure 5 FIG. 1 is a schematic diagram of a preamplifier disposed within a sensor array in an embodiment. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

[0044] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements can also be present. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] As used in this description, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. The term "comprises" and / or "comprising", as used herein, specifies the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0046] This application provides a thermopile array, specifically a thermopile infrared sensor array, including multiple sensor pixels and a readout circuit (ROIC). The readout circuit includes multiple signal processing channels. Figure 1 This is a schematic diagram of a signal processing channel in one embodiment. Each signal processing channel includes a preamplifier and an analog-to-digital converter. The preamplifier is used to amplify the sensor signal. Figure 1 In the illustrated embodiment, the preamplifier is a single-stage amplifier. The input of the analog-to-digital converter is connected to the output of the preamplifier. Figure 1 In the illustrated embodiment, the analog-to-digital converter (ADC) is a delta-sigma ADC. Each signal processing channel processes the sensor signals output by i sensor pixels (i.e., sensor points), where i is a positive integer, and when the number of sensor pixels in the thermopile array is not less than 256, i is not greater than the square root of the number of sensor pixels in the thermopile array divided by 4. It is understood that the above embodiment mainly targets large-scale arrays; the larger the array size, the larger i becomes. When the number of sensor pixels in the thermopile array is less than 256, i.e., a small-scale array, each signal processing channel can be configured to process the sensor signals output by multiple sensor pixels.

[0047] The aforementioned thermopile array, with a sufficient number of parallel signal processing channels based on the number of sensor pixels, significantly improves the data processing time of a single signal processing channel. The preamplifier and analog-to-digital converter (ADC) can operate at lower frequencies, effectively reducing the noise bandwidth of the signal channels and thus significantly improving the signal-to-noise ratio (SNR) of the signal processing channels, thereby enhancing system performance and significantly improving thermal temperature resolution. Simultaneously, due to the lower frequency, the area and power consumption of the preamplifier and ADC can be significantly reduced. With the increase in signal processing channels, the integration processing time for the sensor signal output from each sensor pixel is greatly increased due to the sufficient number of channels, resulting in a substantial reduction in noise bandwidth. The preamplifier's primary function is noise suppression while providing initial signal amplification and some driving capability; therefore, the amplification accuracy requirement is reduced. To control the area of ​​the readout circuit, the preamplifier can adopt a low closed-loop gain structure (e.g., a single-stage amplifier), significantly reducing power consumption and area, thereby reducing the design difficulty of related analog circuits (e.g., preamplifier and ADC). The operating current of the signal processing channels is significantly reduced, effectively overcoming the self-heating problem caused by high current and significantly reducing the requirements for system temperature calibration. Given the low closed-loop gain of the preamplifier, the analog-to-digital converter adopts a delta-sigma architecture. Taking advantage of the low-pass characteristics of the delta-sigma signal transfer function, no low-pass filter is needed between the preamplifier and the analog-to-digital converter.

[0048] An exemplary analog signal conditioning circuit is composed of a high performance preamplifier (PGA) plus a low pass filter (LPF) and a high performance analog-to-digital converter (ADC), whose cost is inversely proportional to its performance.

[0049] When the thermopile pixel is low, the exemplary signal conditioning circuit can switch the multiple signals to a single or a few signal processing channels through a multiplexer (MUX) method, at the cost of sacrificing the processing time of a single pixel element, in other words, increasing the noise bandwidth of a single pixel, which leads to insufficient performance when the pixel array is large. The initially available thermopile infrared sensor array on the market has only one or a few pixels (for example, 8x8 pixels or 16x16 pixels), and each pixel is relatively large (for example, 150-300umx150-300um). Therefore, there is enough space on the sensor chip to accommodate a small number of amplifiers or low pass filters on the chip next to the thermopile sensor array. Thermopile sensor arrays with a larger number of pixels require the size of the pixels to be reduced to 100μm in length or even to 25μm. However, the pixel units generate signals proportional to their surface area. This means that if the pixel size is halved, the signal strength that needs to be further processed is reduced to one quarter. In principle, the size of the thermopile unit (thermopile pixel) can be reduced, and more and more pixels can be integrated on the sensor chip. For example, 16x16, 32x32, 64x64, 128x128 or higher thermopile pixels are implemented on the sensor chip. The signal voltage of each thermopile pixel will need to be multiplexed using M*N addressing and multiplexer (MUX) switching, i.e., routed to a common serial signal line, or through a common serial interface, to each row or each column. As the integration increases, the pixel pitch of the array sensor will decrease significantly, and the output impedance of the sensor will increase significantly, the signal strength will decrease significantly, and the device and circuit noise will significantly reduce the system signal-to-noise ratio (SNR). Compared with the earlier single-point thermopile sensor, the array sensor increases the number of signals to be processed as the array size increases, thereby significantly increasing the performance requirements of the signal processing circuit in terms of bandwidth, gain, etc.

[0050] Figure 2 Figure 1 is a schematic diagram of the connection between the signal processing channel and the sensor pixel element in an embodiment. In this embodiment, the sensor pixel elements are arranged in an MxN array. To ensure the thermal temperature resolution and conversion rate of the thermopile array, at most 8 sensor pixel elements are connected to a signal processing channel through a multiplexer (Multiplexer), and the same sensor pixel element is only connected to one signal processing channel, and the number of signal processing channels is at least 4 times the number of rows.

[0051] In another embodiment, the multiplexer can not be provided, the number of signal processing channels is equal to the number of sensor pixel units, and the signal processing channels correspond one by one to the sensor pixel units, that is, each signal processing channel processes the sensor signal of one sensor pixel unit. The absence of the multiplexer can save the chip area occupied by the multiplexer and simplify the design.

[0052] Due to the adoption of a large number of signal processing channels, the data processing time of a single signal processing channel is significantly improved. For an exemplary 32*32 thermoelectric array, the array maintains a conversion rate of 15 frames, and the single signal processing channel switches the input signal through the multiplexer, and the conversion rate of the preamplifier and the analog-to-digital converter must be higher than 15*32*32=15kHz. If the scheme of one independent signal processing channel corresponding to each sensor pixel unit is adopted, the conversion rate of the preamplifier and the analog-to-digital converter only needs to be 15Hz to meet the system requirements. Due to the increase in conversion time, the noise bandwidth of the signal processing channel is significantly reduced (from 15kHz to 15Hz), thereby effectively improving the signal-to-noise ratio of the signal processing channel. At the same time, because the frequency is reduced, the area and power consumption of the preamplifier and the analog-to-digital converter can be significantly reduced.

[0053] The conventional thermoelectric array signal readout circuit has a very high requirement for the performance of the preamplifier and the analog-to-digital converter in the case of a small number of channels. Whether CDS (correlated double sampling) or chopping (chopping modulation) technology is adopted, the design difficulty will be greatly increased, and the system requirements cannot be met due to factors such as area and power consumption. The adoption of sufficient parallel signal processing channels in the present application effectively reduces the noise bandwidth of the signal channel, thereby effectively improving the system performance, and the thermal temperature resolution is significantly improved. In addition, the adoption of sufficient parallel channels reduces the design difficulty of the related analog circuit, and the power consumption and area are greatly reduced, which is beneficial to large-scale array (>16*16) integration.

[0054] In one embodiment, the thermoelectric array includes at least one multiplexer, the input end of each multiplexer is connected to one or more sensor pixel units, the output end is connected to a signal processing channel, and different multiplexers are connected to different signal processing channels. For a single multiplexer, the connected sensor pixel units are simultaneously turned on and turned off at the same time to combine the sensor signals of the turned-on sensor pixel units and send them to the connected signal processing channel to enhance the signal strength.

[0055] Figure 3This is a schematic diagram illustrating how multiple sensor pixels are simultaneously selected to the same signal processing channel in one embodiment. At the same time, the multiplexer switches open or close simultaneously, allowing sensor signals from multiple sensor pixels to be combined and sent to a single signal processing channel. The signal-to-noise ratio can be improved through a combination of series and parallel thermopile configurations. Figure 3 In the embodiments shown, each multiplexer does not have a requirement for the number of connected sensor pixels; the number can be determined based on the actual needs of the system.

[0056] In one embodiment, the preamplifier employs a telescopic or folded-cascode structure to achieve high open-loop gain. In one embodiment, the closed-loop gain (preamplifier gain factor) of the preamplifier is set to be adjustable between 80 and 500. In another embodiment, given the low closed-loop gain factor of the preamplifier, a single-stage structure is used to significantly reduce power consumption and area.

[0057] Traditionally, high-gain analog amplifiers used for signal amplification require multi-stage amplifiers with large area requirements. Furthermore, these amplifiers consume significant power. This translates to increased power loss and self-heating, leading to an overall increase in measurement error for thermopile arrays. In contrast, the embodiments of this application employ a single-stage preamplifier structure, which significantly reduces area and power consumption, facilitating large-scale signal channel integration.

[0058] In one embodiment, to reduce preamplifier noise, the preamplifier employs chopper-stabilized (CHS) modulation. Compared to CDS (correlated double sampling) technology, CHS offers better low-frequency noise suppression and is more suitable for low-frequency baseband signal processing.

[0059] An exemplary thermopile employs an integrating or slope-type analog-to-digital converter (ADC) for data conversion. While this structure is relatively simple, its accuracy is highly dependent on design and manufacturing processes, and it occupies a large area and is extremely slow, making it difficult to meet system requirements. Given the low closed-loop gain of the preamplifier in this embodiment, in one instance, a NYQUIST ADC, such as an integrating / slope-type ADC or a charge-balance ADC, is not used after the preamplifier; instead, a high-precision delta-sigma architecture is used for ADC conversion. Utilizing the low-pass characteristic of the delta-sigma signal transfer function, a low-pass filter is not required between the preamplifier and the ADC.

[0060] In view of the parallel use of a large number of signal channels, the frequency range of the single signal processing channel of the present application is greatly reduced, thereby greatly reducing the noise bandwidth requirements of the preamplifier and the analog-to-digital converter. In one embodiment, to save area and power consumption, the analog-to-digital converter is implemented using a first-order single-bit quantizer feedback structure. Using a feedback structure can simplify circuit design. As a comparative example, the conditioning circuit uses a 2nd-order or higher delta-sigma architecture to complete the analog-to-digital conversion, which is relatively complex and not conducive to large-scale integration of the thermocouple array readout circuit. The simplified first-order delta-sigma ADC significantly reduces area and power consumption, facilitating large-scale signal channel integration. In one embodiment, the oversampling rate of the analog-to-digital converter is greater than 4096. At this oversampling rate, the performance of the analog-to-digital converter depends on the in-band low-frequency noise floor (irrelevant to the signal quantization noise ratio SQNR), and the signal-to-noise ratio of MOD1 is infinitely close to that of a high-order modulator, but the area and power consumption are significantly better than those of a high-order modulator.

[0061] At an oversampling rate of OSR>4096, the influence of thermal noise of the sampling capacitor is significantly reduced according to the following formula:

[0062] E 2 T = (1 / OSR) x kT / C

[0063] where E 2 T represents the thermal noise energy of the sampling capacitor, and its unit is V 2 , OSR is the oversampling rate, k is the Boltzmann constant, T is the temperature in Kelvin, and C is the capacitance value. In one embodiment, to reduce power consumption and area cost, the analog-to-digital converter uses a unit capacitance of no more than 100 fF.

[0064] In one embodiment, in view of the use of a high-oversampling-rate analog-to-digital converter, the requirements for the integrator inside the analog-to-digital converter are greatly reduced. To save power and area, an inverter-type integrator can be used instead of an operational transconductance amplifier (OTA) type integrator as a comparative example. In one embodiment, the inverter-type integrator is suitable for low-voltage (<1.2V) applications.

[0065] In one embodiment, the thermoelectric array is integrated on a chip. The thermoelectric array includes two or more ambient temperature sensors, each of which is arranged at a different location on the chip. The sensor chip includes high-precision ambient temperature sensors built-in, and the output of each ambient temperature sensor is converted to digital by a separate signal processing channel and used for later system non-linear calibration. In one embodiment, for a larger array (> 32*32), 2 or 4 identical ambient temperature sensors are used inside the chip, and are arranged at the opposite corners (2 ambient temperature sensors) or the four corners (4 ambient temperature sensors) of the chip. The output of each ambient temperature sensor is processed in parallel, and is used for sensor signal calibration of the sensor pixel elements in the region corresponding to the location of the ambient temperature sensor. For example, for the case of 2 ambient temperature sensors, each ambient temperature sensor is used for calibration of the sensor pixel elements on one side of the chip. See Figure 4a For the case of 4 ambient temperature sensors, each ambient temperature sensor is used for calibration of one quarter of the sensor pixel elements. See Figure 4b A sensor chip with only one ambient temperature sensor as a comparative example cannot accurately measure the temperature difference in each region, which has a serious impact on system temperature calibration and results in a significant decrease in the accuracy of the final output of the system. In the embodiments of the present application, multiple ambient temperature sensors are used for large-scale arrays, and each ambient temperature sensor is used for calibration of the pixel signals in a region, which can effectively reduce the sensor errors caused by self-heating and significantly improve the temperature resolution.

[0066] In one embodiment, the sensor pixel elements of the thermoelectric array are arranged in an array, and at least some of the preamplifiers of the signal processing channels are arranged in the gaps between adjacent sensor pixel elements. See Figure 5In this design, the preamplifiers in the readout circuit (ROIC) are placed between the pixels (pixels) of the thermopile array; specifically, preamplifiers are positioned between most (e.g., more than half) of adjacent sensor pixels. This approach firstly fully utilizes the spacing between pixels, effectively reducing chip area costs and facilitating integration; secondly, because the preamplifiers in the signal processing channel are close to the signal source (pixels), noise problems such as signal crosstalk between pixels are effectively prevented. In one embodiment, only the low-power preamplifiers can be placed in the gaps between adjacent sensor pixels, while the high-power preamplifiers can be placed outside the sensor array. That is, the power consumption of each preamplifier within the sensor array is less than the power consumption of each preamplifier outside the sensor array, thereby avoiding the impact of preamplifier heat on the sensing of the sensor pixels to a certain extent. In the layout of the exemplary monolithically integrated thermopile infrared sensor array and ASIC (Application-Specific Integrated Circuit) product, the readout circuit (ROIC) is located around the perimeter of the sensor array, occupying a large chip area. Furthermore, the signal processing channels are far from the pixels, leading to signal interference and attenuation; for example, long signal traces can significantly affect the weak signals from the thermopile pixels. However, the integration method in this application, where some ROIC circuits are located in the gaps between adjacent sensor pixels, fully utilizes the spacing between array pixels, effectively reducing area costs while overcoming crosstalk noise and other problems associated with weak signals during transmission.

[0067] In one embodiment, the thermopile array further includes multiple reference pixels. The array formed by arranging the sensor pixels includes at least one reference pixel in each row or column. The reference pixels are used for background noise compensation and temperature calibration. Specifically, the size and shape of each reference pixel are completely identical to those of the normal temperature-sensing pixels (i.e., each sensor pixel), but they do not receive external temperature signals. The readout circuit of the thermopile array also includes a compensation circuit for calibrating the sensor signals output by the sensor pixels with the sensor signals output by the reference pixels in the same row or column. Since the reference pixels are located in the array matrix, their low-frequency noise characteristics and susceptibility to internal chip temperature are similar to those of other temperature-sensing pixels in the same row or column. By subtracting the output of the reference pixels from the output of other temperature-sensing pixels through an analog front-end (AFE) or by performing an ADC conversion followed by digital subtraction, the influence of low-frequency noise and internal chip temperature changes on the temperature-sensing pixels can be removed or reduced. This can be used for background noise suppression and temperature compensation of the thermopile array.

[0068] In the description of the specification, the description of the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are contained in at least one embodiment or example of the present application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0069] The technical features of the above-described embodiments can be combined arbitrarily, and for the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present application.

[0070] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A thermopile array, characterized in that, include: Multiple sensor pixels; and The readout circuit includes multiple signal processing channels, each of which includes: A preamplifier is used to amplify sensor signals; the preamplifier is a single-stage amplifier. An analog-to-digital converter (ADC) is provided, with its input terminal connected to the output terminal of the preamplifier. The ADC is a delta-sigma ADC. Each of the signal processing channels is used to process the sensor signals output by i sensor pixels, where i is a positive integer and when the number of the plurality of sensor pixels is not less than 256, i is not greater than the square root of the number of sensor pixels in the thermopile array divided by 4. The thermopile array also includes at least one multiplexer. The input of each multiplexer is connected to one or more of the sensor pixels, and the output is connected to one of the signal processing channels. Different multiplexers are connected to different signal processing channels. For a single multiplexer, the sensor pixels connected to it are simultaneously selected and turned off, so as to combine the sensor signals of the selected sensor pixels and send them to the connected signal processing channel. The sensor pixels are arranged to form an array; among the preamplifiers of the multi-channel signal processing channels, the preamplifier with lower power consumption is located in the gap between adjacent sensor pixels, and the preamplifier with higher power consumption is located outside the sensor array.

2. The thermopile array according to claim 1, characterized in that, No low-pass filter is provided between the analog-to-digital converter and the preamplifier of each of the aforementioned signal processing channels.

3. The thermopile array according to claim 1, characterized in that, The preamplifier is a sleeve-type or folded common source and common gate structure.

4. The thermopile array according to claim 3, characterized in that, The closed-loop gain of the preamplifier is 80~500.

5. The thermopile array according to claim 3 or 4, characterized in that, The preamplifier employs a chopper-stabilized modulation method.

6. The thermopile array according to claim 1, characterized in that, The analog-to-digital converter adopts a first-order single-bit quantizer feedback structure.

7. The thermopile array according to claim 1 or 6, characterized in that, The oversampling rate of the analog-to-digital converter is greater than 4096, and the integrator in the analog-to-digital converter is an inverter-type integrator.

8. The thermopile array according to claim 1, characterized in that, The thermopile array is integrated on a chip, and the thermopile array also includes two or more ambient temperature sensors, which are distributed on the chip.

9. The thermopile array according to claim 1, characterized in that, It also includes multiple reference pixels. The array formed by arranging the sensor pixels includes at least one reference pixel in each row or column. Each reference pixel does not receive external temperature signals. The readout circuit also includes a compensation circuit for calibrating the sensor signal output by the sensor pixel with the sensor signal output by the reference pixel in the same row or column.

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