Thermocouple-driven thermal imaging sensor with thermal transistors

Abstract

A thermocouple-driven thermal imaging sensor with a thermal transistor is proposed. The thermal imaging sensor includes one or more thermocouples, each thermocouple being configured to provide a sensed voltage based on the difference between the temperature of the hot junction and the temperature of the cold junction of the thermocouple; the thermal imaging sensor further includes one or more sensing transistors, each sensing transistor being driven based on the sensed voltage of one or more corresponding thermocouples and being configured to provide a sensed electrical signal based on its temperature and the corresponding sensed voltage. A thermal imaging device including the thermal imaging sensor and a corresponding signal processing circuit is also proposed, as well as a system including one or more thermal imaging devices.

Description

Technical Field

[0001] The present disclosure relates to the field of thermal imaging. More specifically, the present disclosure relates to thermal imaging sensors. Background Art

[0002] The background of the present disclosure is introduced below by discussing the technology related to its context. However, even when the discussion involves documents, actions, artifacts, etc., it does not imply or indicate that the technology discussed is part of the prior art or common general knowledge in the field related to the present disclosure.

[0003] Thermal imaging sensors are generally used to detect the thermal characteristics of their fields of view (each field of view including one or more material objects). A thermal imaging sensor is capable of sensing the thermal radiation (i.e., electromagnetic radiation generated by the thermal motion of its particles) emitted by every (material) object above absolute zero temperature; since an object essentially behaves as a black body (i.e., the emitted thermal radiation depends only on the corresponding temperature), the sensed thermal radiation represents their temperature. For example, a thermal imaging sensor is used to measure the temperature of objects in the entire field of view (e.g., in a thermal scanner). Optionally, a thermal imaging sensor is used to acquire a thermogram image (or thermogram), each thermogram image representing the temperature distribution of the field of view (defined by the thermal radiation emitted from its different positions); the thermogram image is used in thermal imaging (or thermography) applications to represent any field of view (according to its thermal characteristics) independently of its illumination, i.e., even when invisible to the human eye.

[0004] There are several types of thermal imaging sensors available. For example, uncooled thermal imaging sensors (also referred to as thermal sensors) sense a change in an electrical parameter according to a temperature change related to the amount of absorbed thermal radiation; these thermal imaging sensors can operate at room temperature without any complex and expensive cooling equipment.

[0005] A typical (uncooled) thermal imaging sensor is based on thermally-insulated MOS (TMOS) transistors, whose electrical characteristics strongly depend on temperature. In this case, two TMOS transistor arrays are provided: one array is exposed to thermal radiation and the other array remains blind (e.g., by shielding it with a metal layer). Each TMOS transistor provides a signal depending on its temperature (e.g., a current when its operating point is set by a bias voltage). Then, a differential signal indicating the temperature gradient between each pair of TMOS transistors can be generated by subtracting the signals of each pair of TMOS transistors in the exposed array and the blind array, and the temperature gradient can be calculated from this differential signal (in cases where very precise measurements are required, such as for the temperature of a human body, the actual temperature at the TMOS transistor in the blind array can also be measured, for example, by a separate temperature sensor based on a thermistor).

[0006] A completely different type of thermal imaging sensor is based on a thermopile (TP). A thermopile consists of multiple thermocouples, which are typically connected to each other in series. According to the Seebeck effect, each thermocouple converts the temperature gradient between the hot and cold junctions (generated by thermal radiation) into electrical energy (measuring its amplitude). For example, a thermocouple includes two (electrical) conductors of different materials (with different Seebeck coefficients). The conductors are joined at a point where the temperature must be measured (the hot junction or thermal joint), while their free ends are maintained at a reference temperature (the cold junction or cold joint). When a temperature gradient exists between the hot and cold joints, a corresponding voltage is generated at the cold junction, from which the temperature gradient can be calculated (as described above, in cases where very precise measurements are required, the actual temperature at the cold junction can also be measured, for example, by a separate temperature sensor based on a thermistor). The measured voltage is very small (on the order of μV); multiple thermocouples in a thermopile are connected in series, and then a higher (total) measured voltage is generated, providing better resolution.

[0007] There are several factors that affect the performance of thermal imaging sensors. For example, high sensitivity, low response time, and limited thermal crosstalk between sensing elements are desired. However, the performance of existing thermal imaging sensors (based on TMOS transistors or thermocouples) is not entirely satisfactory; this adversely affects the performance of the corresponding thermal imaging sensors (e.g., expressed in terms of noise equivalent thermal difference or NETD, which is given by the amount of thermal radiation required to match the internal noise to make the signal-to-noise ratio equal to 1). This has hindered the use of thermal imaging sensors in specific fields (e.g., in consumer applications, especially of the mobile type). Summary of the Invention

[0008] To provide a basic understanding of the present invention, a simplified summary of the invention is given herein; however, the sole purpose of this summary is to introduce some concepts of the present disclosure in a simplified form as a prelude to its more detailed description below, and it should not be construed as an identification of its key elements or a delimitation of its scope.

[0009] Generally speaking, the present disclosure is based on the idea of combining a thermal transistor with a thermocouple.

[0010] For example, one aspect provides a thermal imaging sensor. The thermal imaging sensor includes one or more thermocouples, each thermocouple for providing a sensing voltage according to the difference between the temperature of the hot junction and the temperature of the cold junction of the thermocouple; the thermal imaging sensor further includes one or more sensing transistors, each sensing transistor being driven according to the sensing voltage of one or more corresponding thermocouples and for providing a sensing electrical signal according to its temperature and the corresponding sensing voltage.

[0011] Another aspect provides a thermal imaging device including the thermal imaging sensor and a corresponding signal processing circuit.

[0012] On the other hand, a system is provided that includes one or more thermal imaging devices as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The solution of the present invention and its further features and advantages will be best understood by reference to the following detailed description, which is given purely by way of non - limiting indication and is to be read in conjunction with the accompanying drawings (wherein, for simplicity, corresponding elements are denoted by equal or similar references and their explanations are not repeated, and the name of each entity is generally used to denote its type and properties, such as values, contents, and representations). In this regard, it is expressly intended that the drawings need not be drawn to scale (with some details possibly being exaggerated and / or simplified), and that, unless otherwise indicated, they are only used to conceptually illustrate the structures and processes described herein. For example:

[0014] Figure 1 FIG. shows a partially - cutaway view of a (packaged) thermal imaging device in which a solution according to an embodiment of the present disclosure can be applied,

[0015] Figure 2 FIG. shows a schematic cross - sectional view of a thermal imaging sensor in which a solution according to an embodiment of the present disclosure can be applied,

[0016] Figure 3 FIG. shows a simplified circuit pattern of a sensing element of a thermal imaging sensor according to an embodiment of the present disclosure,

[0017] Figures 4A to 4C FIG. shows a schematic view of a specific thermal imaging sensor according to an embodiment of the present disclosure,

[0018] Figure 5 FIG. shows an exemplary structure of a thermal imaging sensor according to an embodiment of the present disclosure,

[0019] Figure 6 FIG. shows another exemplary structure of a thermal imaging sensor according to an embodiment of the present disclosure, and

[0020] Figure 7 FIG. shows a schematic block diagram of a system incorporating a thermal imaging device according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] With particular reference to Figure 1 , a graphical representation of a (packaged) thermal imaging device 100 in which a solution according to an embodiment of the present disclosure can be applied is shown in a partial cross - sectional view.

[0022] The thermal imaging device 100 is used to detect the thermal characteristics of (material) objects included in its field of view, e.g., a part of the world within the solid angle sensitive to the thermal imaging device; the thermal imaging device 100 can find applications in different fields, e.g., for medical, security, military, industrial, etc. applications. The thermal imaging device 100 includes the following components.

[0023] The uncooled thermal imaging sensor 105 is used to sense the electromagnetic radiation emitted by each object with a temperature above absolute zero, e.g., according to the blackbody radiation law. In some implementations, the thermal imaging sensor 105 is sensitive to infrared (IR) radiation in the (infrared) range from 1.1 μm to 20.0 μm, where infrared radiation is emitted from most objects close to room temperature. Then, the thermal imaging sensor 105 outputs one or more temperature (electrical) signals that indicate the sensed infrared radiation and then indicate the corresponding temperature of the objects in the field of view; in some implementations, the thermal imaging sensor 105 can output a single temperature signal or multiple temperature signals that respectively represent the temperature gradient of the entire field of view or different positions of the field of view relative to a reference (ambient) temperature. The processing unit 110 is coupled to the thermal imaging sensor 105 and is used to process the temperature signals provided by the thermal imaging sensor 105, e.g., by performing analog-to-digital conversion, temperature correction, e.g., when very precise measurements are required, by adding the ambient temperature measured by a separate temperature sensor, e.g., based on a thermistor, etc. The processing unit 110 outputs a temperature indication of the field of view or a (digital) thermal map image of the field of view, e.g., a bitmap of the (digital) values of the basic picture elements (pixels) of the thermal map image, and each (pixel) value defines the brightness of the pixel as a function of the temperature at the corresponding position of the field of view). The thermal imaging sensor 105 and the processing unit 110 are encapsulated in the package 115, which protects them while allowing access to them; e.g., a package 115 of the ceramic type shields infrared radiation, except for the window 120 having a lens (such as silicon), which focuses the infrared radiation onto the (sensing) part of the thermal imaging sensor 105.

[0024] Now referring to Figure 2 , a schematic cross-sectional view of the thermal imaging sensor 105 in which the solution according to an embodiment of the present disclosure can be applied is shown.

[0025] The thermal imaging sensor 105 includes two corresponding arrays of sensing elements 205 and reference elements 210, respectively, for example, a staring array, i.e., a two-dimensional array of 8×8 sensing / reference elements 205, 210 each. As described in detail below, each sensing / reference element 205, 210 provides a sensing / reference (electrical) signal according to its temperature. The sensing elements 205 are exposed to the infrared radiation to be sensed so as to be heated to a temperature associated therewith; in contrast, the reference elements 210 are blind, for example, as described below, shielded from the infrared radiation so as to remain at an (ambient) temperature independent of the infrared radiation. The comparison circuit compares the sensing signal of the sensing elements 205 with the reference signal of the reference elements 210 to obtain a temperature signal; in some implementations, the comparison circuit may compare a common sensing signal provided by all the sensing elements 205 with a common reference signal provided by all the reference elements 210 to obtain a single temperature signal representing the temperature gradient of the entire field of view, or it may compare the sensing signal provided by each sensing element 205 with the reference signal provided by the corresponding reference element 210 to obtain a corresponding temperature signal representing the temperature gradient of the corresponding position of the field of view.

[0026] In an example implementation, the sensing element array 205, the reference element array 210, and the comparison circuit 215 are integrated on a semiconductor on insulator, for example, integrated on an SOI-type die 220 fabricated using standard CMOS process steps and adding MEMS process steps (in order to define the corresponding chip). In some implementations, as described in detail herein, the sensing element array 205 and the reference element array 210 are provided on corresponding suspended membranes. For example, the suspended membranes can be released from the body of the die 220, or they can be released from the front of the die 220 (e.g., by a wet etching process without removing all of the substrate).

[0027] In addition, the thermal imaging sensor 105 includes a (top) semiconductor body, such as a die 225 of silicon. For example, through etching, cavities 230 corresponding to the sensing element array 205 and cavities 235 corresponding to the reference element array 210 are formed in the die 225. In addition, a window 240 is opened (e.g., through etching) through the die 225 to expose a lateral portion of the die 220 where I / O contacts 245 (e.g., pads) of the thermal imaging sensor 105 are provided. The thermal imaging sensor 105 further includes a (bottom) semiconductor body, such as a die 250 of silicon. The die 225 and the die 250 are bonded to the die 220, and the cavities 230, 235 of the die 225 and the die 250 face the die 220. For example, through a glass frit technique of a corresponding glass intermediate layer not shown in the figure, the sensing element 205 array is encapsulated in a vacuum-sealed structure defined by the cavity 230 of the die 220 corresponding to the sensing element 205 and the cavity 255, and the reference element 210 array is encapsulated in a vacuum-sealed structure defined by the cavity 235 of the die 220 corresponding to the reference element 210 and the cavity 260, where the sealed structure prevents heat sinking from the atmosphere and mechanically protects the sensing / reference elements 205, 210.

[0028] The die 225 is substantially transparent to infrared radiation. Thus, the die 220 includes absorption layers 265 in the release membranes 205 and 210 located at the cavities 230 and 235, respectively; the absorption layers 265 are made of an infrared highly absorbent spectral material such as deposited TiN to improve the absorption of infrared radiation to be sensed by the underlying sensing elements 205. A shielding layer 270 of an infrared highly reflective material is provided on the top of the die 225 at the cavity 235 to shield the underlying reference elements 210 from infrared radiation. In addition, the die 250 includes vacuum getters 275 in the cavity 255 and vacuum getters 280 in the cavity 260. The vacuum getters 275, 280 are made of a reactive material layer, such as deposited zirconium-aluminum alloy, capable of removing any residual gas molecules present in the vacuum-sealed cavities 255, 260, for example, chemically or by absorption.

[0029] Now referring to Figure 3 , a simplified circuit diagram of the sensing / reference elements 205, 210 of a thermal imaging sensor according to an embodiment of the present disclosure is shown.

[0030] The sensing / reference elements 205, 210 have a hybrid structure based on a combination of thermocouples 305s, 305r (or more) and (sensing / reference) transistors 310s, 310r (or more). For simplicity, in the following, referring to the sensing element 205, the same factors applicable to the reference element 210 are considered, except that in this case, both the thermocouple 305r and the transistor 310r are shielded from infrared radiation.

[0031] In some embodiments, the thermocouples 305s have a hot junction and a cold junction, the hot junction being arranged to receive the infrared radiation to be sensed, e.g., so as to be heated to a temperature dependent thereon, and the cold junction being maintained at ambient temperature; thus, the thermocouples 305s provide a sensed voltage Vtc according to the difference between the temperature of the hot junction and the temperature of the cold junction and an externally applied voltage Vg. The transistors 310s are also arranged to receive the infrared radiation to be sensed, e.g., so as to be heated to a temperature dependent thereon. In addition, the transistors 310s are coupled to the thermocouples 305s so as to be driven according to their sensed voltage Vtc. Thus, the transistors 310s provide a sensing signal of the sensing element 205 that depends on both the temperature of the transistors 310s and the sensed voltage Vtc.

[0032] For example, the transistors 310s are, e.g., n-type thermally-insulated MOS (TMOS) transistors, i.e., MOS transistors fabricated on an (thermally) insulating structure so that their electrical characteristics strongly depend on temperature. In this case, the TMOS transistors 310s have a source terminal S, a drain terminal D, and a gate terminal G for accessing the source region, the drain region, and the gate region, respectively. The thermocouples 305s have a positive terminal P and a negative terminal N that define its cold junction, which is opposite to its hot junction H. The positive terminal P of the thermocouple 305s is coupled to the gate terminal G of the TMOS transistor 310s.

[0033] The source region, drain region, and gate region of the TMOS transistors 310s and the hot junction H of the thermocouple 305S are arranged in a hot zone 315, such as heated by infrared radiation, while the source terminal S, drain terminal D, and gate terminal G of the transistors 310s and the cold junction P-N of the thermocouple 305S are arranged to be maintained at ambient temperature. In operation, the TMOS transistors 310s are biased by applying (biasing) voltages Vs, Vd, Vg to the source terminal S, drain terminal D, and gate terminal G of the TMOS transistors 310s, respectively. In some implementations, the TMOS transistors 310s are biased to subthreshold conditions, e.g., where it is more sensitive to temperature, i.e., the voltage Vgs between its source terminal S and gate terminal G is lower than its threshold voltage Vth; e.g., this result is achieved by setting the voltage Vs to a reference value or ground, setting the voltage Vd to 0.6V, and setting the voltage Vg to 0.21V (relative to ground). In this case, when no infrared radiation reaches the sensing element 205, the sensing voltage Vtc provided by the thermocouple 305s is 0V, and then the gate terminal G of the TMOS transistor 310s receives the same voltage Vg. A corresponding subthreshold current Itm then flows between the drain terminal D and the source terminal S of the TMOS transistor 310s, where the current Itm can be used as a sensing signal for the sensing element 205 and is thus referred to as the sensing current Itm. Conversely, when any infrared radiation reaches the sensing element 205, it heats both the thermocouple 305s and the TMOS transistor 310s. Therefore, the sensing current Itm provided by the TMOS transistor 310s increases according to temperature. At the same time, the sensing voltage Vtc provided by the thermocouple 305s also increases according to temperature, e.g., on the order of 0.5 - 1.0 μV / °C. Therefore, the voltage (Vg + Vtc) applied to the gate terminal G of the TMOS transistor 310s is correspondingly elevated, which causes the sensing current Itm provided by it to further increase accordingly.

[0034] The above solution significantly improves the performance of the sensing element 205, and thus improves the performance of the entire thermal imaging sensor. For example, in this way, the sensitivity can be increased and the response time can be reduced, e.g., by up to an order of magnitude, e.g., from a sensitivity of only a few nA / °C of the TMOS transistors 310s to approximately several tens of nA / °C. This reflects a corresponding improvement in the performance of the thermal imaging device, e.g., in terms of its noise equivalent temperature difference (NETD).

[0035] All of these promote the use of thermal imaging devices in more fields, e.g., in consumer applications, especially in mobile type applications.

[0036] Now referring to Figures 4A to 4C , a schematic diagram showing details of a thermal imaging sensor according to an embodiment of the present disclosure is shown.

[0037] Figure 4A A top view showing a part of the sensing element array is shown. Figure 4B Shows along Figures 4A to 4C A cross-sectional view of a single sensing / reference element 205, 210 in the plane A-A of Figure 4C Shows in Figure 4A The arrangement of the single sensing / reference elements 205, 210 surrounded therein.

[0038] (SOI) The die 220 has a layered structure, including a substrate 405, for example made of a semiconductor material, for example made of single-crystalline silicon; a functional layer 410, for example including an active layer of single-crystalline silicon, a gate oxide layer, a polysilicon layer, one or more metal layers, and one or more insulating material layers (such as silicon dioxide); and a buried insulating layer 415 of an electrically insulating material separating them, for example silicon oxide. The die 220 is micromachined to define a suspended membrane of the functional layer 410 and the insulating layer 415, and the insulating layer 415 houses an array of sensing / reference elements 205, 210, where the suspended membrane is released from the substrate 405. The suspended membrane is patterned to define a grid 420. The grid 420 is defined by regularly spaced row rungs and column rungs that cross each other, for example perpendicularly, to form corresponding frames 425 for the sensing / reference elements 205, 210, such as surrounding holes. For each sensing / reference element 205, 210, the grid 420 then includes a plate 430 suspended from the frame 425. For this purpose, one or more (holding) arms, two in the example under discussion, denoted by reference numerals 435a and 435b, support the plate 430 from the frame 425; the arms 435a, 435b are relatively long, for example having a U-shape, and thin.

[0039] In each sensing / reference element 205, 210, the hot junction H of the thermocouple and the sensing transistor are formed in the plate 430, the thermocouple and the sensing transistor are denoted by reference numerals 305 and 310 respectively, and the cold junction P-N of the thermocouple 305 is formed in the frame 425. More specifically, the thermocouple 305 includes a (first) conductor 440p of a (conductive) material and a (second) conductor 440n of another (conductive) material, such as P+ polysilicon and N+ polysilicon respectively, which extend between the frame 425 and the plate 430 through arms 435b and 435a respectively. At the ends of the conductors 440p and 440n in the plate 430, such as at their corners, they are short-circuited by a metal track such as aluminum to define the hot junction H of the thermocouple 305. The end portions of the conductors 440p and 440n in the frame 425 define the positive terminal P and the negative terminal N of the cold junction of the thermocouple 305 respectively. In addition, another thermocouple (not shown in the figure) can be formed in a similar manner through two regions of a single crystal layer doped with P+ type and N+ type impurities, and this other thermocouple is coupled in series with the thermocouple 305 to form a thermopile. For simplicity, in the following, reference will be made to a single thermocouple 305, and the same considerations apply to the thermopile. The TMOS transistor 310 has a source region and a drain region of, for example, N+ type, and a gate region of, for example, P+ polysilicon, the gate region being insulated from the channel formed therebetween, such as having a honeycomb structure, where the same structure is replicated in a plurality of (e.g., 64) cells, and the cells are connected in series / parallel between them. Corresponding conductors 445s1, 445s2, 445d, and 445g made of a (conductive) material (such as P+ polysilicon and / or N+ polysilicon) extend between the frame 425 and the plate 430 through arms 435a, 435b for connecting the source region, the drain region, and the gate region to the source terminal S, the drain terminal D, and the gate terminal G respectively. The conductors 445s1, 445s2 are replicated to utilize the remaining free conductors in the case where the arms 435a and 435b are symmetric, and each arm has 3 conductors. One or more (thermally) conductive tracks 450 of a conductive material, such as a three-layer metal, such as aluminum, extend along the frame 425 for thermally equalizing the cold junction P-N of the thermocouple 305 with the substrate 405, thereby acting as its heat sink element and for transmitting electrical signals.

[0040] The above structure provides good thermal insulation between the plate 430 and the frame 425, for example, a corresponding low thermal conductivity Gth; in this way, low thermal crosstalk between the sensing / reference elements 205, 210 can be obtained. In addition, in addition to the thermal insulation from the plate 430, the heat dissipation from the frame 425 to the substrate 405 enables good sensitivity of the thermocouple 305 to be obtained.

[0041] The positive / negative terminals P, N of the thermocouple 305 and the source / drain / gate terminals S, D, G of the TMOS transistor 310 can be connected to each other in the frame 425 in various ways according to the corresponding architecture of the thermal imaging sensor.

[0042] Now referring to Figure 5 , an example architecture of a thermal imaging sensor according to an embodiment of the present disclosure is shown.

[0043] In this case, the sensing / reference elements 205, 210 are configured to operate together. In some embodiments, the positive terminal P of each thermocouple 305 that is different from the last thermocouple 305 in its series (e.g., coupled to the thermal junction H in the plate 430 via the conductor 440p through the arm 435a) is coupled to the negative terminal N of the next thermocouple 305 in series (e.g., coupled to the thermal junction H in the plate 430 via the conductor 440n through the arm 435a) in the corresponding frame 425, for example. The source terminals S, drain terminals D, and gate terminals G of all the TMOS transistors 310 are coupled to the common source terminal CS, common drain terminal CD, and common gate terminal CG, respectively, in the corresponding frame 425, for example, via the conductors 455s1, 455s2, 455d, and 455g through the arms 435b, 435b, and 435a to the source region, drain region, and gate region, respectively. The negative terminal N of the first thermocouple 305 in series is the common bias terminal for all the sensing / reference elements 205, 210 for receiving the voltage Vg; the positive terminal P of the last thermocouple 305 is coupled to the common gate terminal CG of the TMOS transistor 310.

[0044] In this way, the thermocouples 305 are connected in series to provide a common sensing voltage that is equal to the sum of their sensing voltages Vtc, which drives all the TMOS transistors 310. Conversely, the TMOS transistors 310 are connected in parallel to provide a common sensing current CItm that is equal to the sum of their sensing currents Itm, flowing between their common source terminal CS and common drain terminal CD. This configuration emphasizes the above advantages of the proposed solution.

[0045] Now referring to Figure 6 , another example architecture of a thermal imaging sensor according to an embodiment of the present disclosure is shown.

[0046] In this case, the sense / reference elements 205, 210 are configured to operate individually. For example, each sense / reference element 205, 210 has the following configuration. The negative terminal N of the thermocouple 305, for example, is coupled to its thermal junction H in the plate 430 via the arm 435a and the conductor 440n, and is the bias terminal of the sense / reference elements 205, 210 for receiving the voltage Vg. The positive terminal P of the thermocouple 305, for example, is coupled to the gate terminal G of the TMOS transistor 310 in the frame 425 via the arm 435a and the conductor 440p, and is coupled to the gate region via the conductor 445g, for example, via the arm 440a. For example, the source terminal S and the drain terminal D of the TMOS transistor 310, which are coupled to the source region and the drain region via the conductors 455s1, 455s2 and 455d respectively through the arms 435b and 435b, receive the bias voltages Vs and Vd respectively in the frame 425.

[0047] In this way, the thermocouple 305 drives the TMOS transistor 310 with its sensed voltage Vtc. Thus, the TMOS transistor 310 provides its sensed current Itm flowing between the source terminal S and the drain terminal D. This configuration independently applies the above advantages to different sense / reference elements 205, 210.

[0048] For example, the sense / reference elements 205, 210 can be continuously enabled at the row level. To this end, the source terminals S of all sense / reference elements 205, 210 are coupled to a reference terminal, for example, for receiving a ground voltage. The drain terminals D of the sense / reference elements 205, 210 in each column of the array are coupled to the corresponding column lines, and the bias terminals of the sense / reference elements 205, 210 in each row of the array are coupled to the corresponding row lines, for example, to the gate terminals G. In the stationary state, all row lines and column lines are biased to ground so that all TMOS transistors 310 do not provide any current. During the sensing operation, all column lines are biased to the voltage Vd. Then the sense / reference elements 205, 210 of the selected row are continuously selected. To this end, the row line of the selected row is biased to the voltage Vg. Thus, the corresponding TMOS transistors 310 provide their sensed current Itm flowing along the corresponding column lines. The sensed current Itm is converted into a voltage by a corresponding sense amplifier, for example, and this voltage is output by the thermal imaging sensor 105.

[0049] Now referring to Figure 7 , a schematic block diagram of a system 700 incorporating a thermal imaging device 100 according to an embodiment of the present disclosure is shown.

[0050] For example, when the thermal imaging device 100 is based on a global or individually operated thermal imaging sensor, the system 700 is a thermal scanner or a smart phone. The system 700 includes several units connected to each other via a bus structure 705 (with one or more levels). For example, a microprocessor (μP) 710 or more provides the logical capabilities of the system 700; a non-volatile memory (ROM) 715 stores the basic code for booting the system 700, and a volatile memory (RAM) 720 is used by the microprocessor 710 as a working memory. The system has a mass memory 725 (e.g., flash E2PROM) for storing programs and data. In addition, the system 700 includes a plurality of controllers for peripheral devices 730, and the peripheral devices 730 include the above-mentioned thermal imaging device 100. For example, in the case of a thermal scanner, the thermal imaging device 100 implements an infrared thermometer (the peripheral device 730 further includes control buttons, a display, etc.); in the case of a smart phone, instead, the thermal imaging device 100 implements an infrared camera (the peripheral device 730 further includes a telephone transceiver, a Wi-Fi WNIC, a touch screen, a GPS receiver, an accelerometer, etc.).

[0051] Naturally, to meet local and specific requirements, those skilled in the art can apply many logical and / or physical modifications and changes to the present disclosure. More specifically, although the present disclosure has been described with a certain degree of particularity with reference to one or more embodiments thereof, it should be understood that various omissions, substitutions, and changes in form and detail, as well as in other embodiments, are possible. For example, different embodiments of the present disclosure can be practiced even without the specific details (such as numerical values) set forth in the previous description to provide a more thorough understanding thereof; conversely, well-known features can be omitted or simplified so as not to obscure the description with unnecessary details. In addition, it is expressly intended that the specific elements and / or method steps described in connection with any embodiment of the present disclosure can be incorporated in any other embodiment as a matter of general design choice. Moreover, items presented in the same group and in different embodiments, examples, or alternatives should not be construed as being in fact equivalent to each other (but they are separate and autonomous entities). In any case, each numerical value should be read as being modified according to the applicable tolerances; for example, unless otherwise stated, terms such as "substantially", "about", "approximately", etc. should be understood to be within 10%, preferably within 5%, and more preferably within 1%. In addition, each numerical range should clearly specify any possible number along the continuum within that range (including its endpoints). Serial numbers or other qualifiers are merely used as labels to distinguish like elements, but they do not in themselves imply any precedence, priority, or order. Terms such as including, having, containing, involving, etc. are intended to have an open, non-exhaustive meaning (i.e., not limited to the stated items), terms based on, dependent on, according to function, etc. are intended to be non-exclusive relationships (i.e., involving possible further variables), the term a / an is intended to mean one or more items (unless otherwise expressly indicated), and the term means (or any means-plus-function formulation) is intended to mean any structure adapted or configured to perform the relevant function.

[0052] For example, one embodiment provides a thermal imaging sensor for sensing thermal radiation. However, the thermal imaging sensor can be used to sense any thermal radiation (e.g., in the frequency ranges of infrared, terahertz, microwave, etc.) for any purpose (e.g., for measuring the temperature of an object, obtaining a thermal map image, detecting the presence of an object, detecting motion, etc.).

[0053] In one embodiment, the thermal imaging sensor includes one or more thermocouples. However, the thermocouples can be any number and arranged in any manner (e.g., in a two-dimensional matrix, a linear vector, etc.).

[0054] In one embodiment, each thermocouple has a hot junction configured to receive thermal radiation (and thus be heated to a temperature dependent on the thermal radiation) and a cold junction configured to be maintained at a temperature independent of the thermal radiation, the cold junction being adapted to provide a sensed voltage dependent on the difference between the temperature of the hot junction and the temperature of the cold junction. However, the thermocouple can be of any type (e.g., polysilicon / polysilicon, polysilicon / metal, silicon / metal, etc.).

[0055] In one embodiment, the thermal imaging sensor includes one or more sensing transistors. However, the sensing transistors can be of any number and arranged in any manner (e.g., the same or different relative to the thermocouples).

[0056] In one embodiment, the sensing transistors are arranged to receive thermal radiation (and thus be heated to a temperature dependent on the thermal radiation). However, the sensing transistors can be arranged in any manner for this purpose (e.g., together with the corresponding thermocouples, separated from the thermocouples, etc.).

[0057] In one embodiment, the sensing transistors are coupled to the corresponding one or more thermocouples so as to be driven in accordance with the corresponding sensed voltage. However, the sensing transistors can be coupled to the thermocouples in any manner (e.g., the corresponding thermocouple or group of thermocouples coupled to each sensing transistor, all thermocouples coupled to all sensing transistors, etc.) and driven in any manner (e.g., directly, via a voltage-current converter, via an amplifier, etc.).

[0058] In one embodiment, the sensing transistors are adapted to provide a sensed electrical signal in accordance with their temperature and the corresponding sensed voltage. However, the sensed electrical signal can be of any type (e.g., current, voltage, etc.).

[0059] In one embodiment, the thermal imaging sensor includes one or more reference transistors. However, the reference transistors can be of any number and arranged in any manner (e.g., the same or different relative to the sensing transistors, driven or not driven by further thermocouples, etc.).

[0060] In one embodiment, each reference transistor is configured to shield thermal radiation (and thus be maintained at a temperature independent thereof), the reference transistor being adapted to provide a reference electrical signal dependent on its temperature. However, the reference transistors can be shielded in any manner (e.g., all shielded together, shielded individually, etc.), and each reference electrical signal can be of any type (e.g., the same or different relative to the sensed electrical signal).

[0061] In one embodiment, the thermal imaging sensor includes a comparison circuit for providing one or more temperature electrical signals indicative of thermal radiation. However, the temperature electrical signals can be any number (e.g., a single signal across the entire thermal imaging sensor, a single signal for each sensing transistor or group of sensing transistors, etc.).

[0062] In one embodiment, the temperature electrical signal is provided based on a comparison between a sensing electrical signal of a sensing transistor and a reference electrical signal of a reference transistor. However, the temperature electrical signal can be provided based on any comparison (e.g., by comparing a common sensing electrical signal of all sensing transistors with a single reference electrical signal, comparing the sensing electrical signal of each sensing transistor or group of sensing transistors with a corresponding reference electrical signal, etc.).

[0063] Additional embodiments provide additional advantageous features, which can however be completely omitted in a basic implementation.

[0064] For example, in one embodiment, the thermal imaging sensor includes one or more additional thermocouples. However, further thermocouples can be any number and arranged in any manner (identical or different with respect to the thermocouples).

[0065] In one embodiment, each additional thermocouple has an additional hot junction and an additional cold junction, and the hot junction and the cold junction are adapted to provide an additional sensing voltage based on a difference between a temperature of the additional hot junction and a temperature of the additional cold junction. However, further thermocouples can be of any type (identical or different with respect to the thermocouples).

[0066] In one embodiment, the additional thermocouples are arranged to shield thermal radiation so as to remain at a temperature independent of thermal radiation. However, further thermocouples can be shielded in any manner (identical or different with respect to the reference transistors).

[0067] In one embodiment, each of the reference transistors is coupled to a corresponding one or more additional thermocouples so as to be driven based on the corresponding additional sensing voltage, and thereby further provide a corresponding reference electrical signal based on the corresponding additional sensing voltage. However, the reference transistors can be coupled to other thermocouples in any manner so as to be driven in any manner (identical or different with respect to the sensing transistors).

[0068] In one embodiment, the thermal imaging sensor includes one or more sensing elements, each sensing element including at least one thermocouple and at least one sensing transistor. However, the sensing element may include any number of thermocouples (e.g., a single thermocouple, a thermopile formed by connecting multiple thermocouples in series, etc.) and any number of sensing transistors (e.g., a single sensing transistor, having a singular structure or a cell structure formed by connecting any number of cells in series and / or in parallel, any number of sensing transistors connected in series and / or in parallel, etc.).

[0069] In one embodiment, the thermal imaging sensor includes a corresponding one or more reference elements, each reference element including at least one reference transistor. However, the number of reference transistors corresponding to each sensing element can be any number (e.g., the same as or different from the sensing transistors of the sensing element).

[0070] In one embodiment, the sensing elements are integrated on the body of an insulating-type semiconductor. However, the body can be of any type (e.g., SOI, SOS, and more generally even not of the semiconductor-on-insulator type, such as having an epitaxial layer grown on a substrate) and provided in any way (e.g., in the form of a raw wafer, packaged as a bare die, etc.). The thermal imaging sensor can be fabricated using any technology, with different numbers and types of masks and having different process steps / parameters. In addition, the above solutions can be part of an integrated device design. The design can also be created using a hardware description language; moreover, if the designer does not fabricate the chip or mask, the design may be transferred to others by physical means.

[0071] In one embodiment, the body includes a substrate. However, the substrate can be of any type (e.g., silicon, germanium, having any type and concentration of dopants, etc.).

[0072] In one embodiment, the body includes a functional layer of semiconductor material. However, the functional layer can be of any type (e.g., the same as or different from the substrate).

[0073] In one embodiment, the body includes an insulating layer inserted between the substrate and the functional layer. However, the insulating layer can be of any type (e.g., silicon oxide, silicon nitride, etc.).

[0074] In one embodiment, the body is patterned to define a grid (of the functional layer and the insulating layer) hanging from the substrate. However, the grid can have any shape, size, and structure; the result can be achieved in any way (e.g., applying MEMS, NEMS, etc. process steps after, before, and / or during the integration of the sensing elements, etc.).

[0075] In one embodiment, for each sensing element, the grid includes a frame, a plate, and one or more arms that support the plate from the frame. However, the frame and the plate can be of any size and shape (e.g., square, rectangular, etc., the same or different from each other), the arms can be of any number and at any position (e.g., at the boundaries, corners, etc. of the plate), and they can have any length, width, and shape (e.g., U-shaped, S-shaped, straight, etc.).

[0076] In one embodiment, the sensing transistors of the sensing element are formed in the plate. However, the sensing transistors can be arranged in the plate in any manner (e.g., taking up most of it, in the center, in the lateral part, etc.).

[0077] In one embodiment, the thermocouple of the sensing element includes a first conductor (made of a first conductive material), and the first conductor extends from the first terminal of the cold junction in the frame through one of the arms to the plate. However, the first conductor can be of any material (e.g., deposited polysilicon / metal, implanted / diffused dopant), and it can extend to the plate in any manner (e.g., along one or more boundaries, to the center, etc.).

[0078] In one embodiment, the thermocouple of the sensing element includes a second conductor (made of a second conductive material different from the first conductive material), and the second conductor extends from the second terminal of the cold junction in the frame through one of the arms to the plate. However, the second conductor can be of any material, and it can extend to the plate in any manner (e.g., the same as or different from the first conductor) and through any arm (e.g., the same as or another one as the first conductor).

[0079] In one embodiment, the first conductor and the second conductor are short-circuited to the hot junction on the plate. However, the first conductor and the second conductor can be short-circuited at any position (e.g., at the corners, boundaries, center, etc. of the plate) and in any manner (e.g., through any connecting element, such as metal, polysilicon, etc., directly, etc.).

[0080] In one embodiment, the thermal imaging sensor includes a plurality of sensing elements. However, the sensing elements can be of any number and arranged in any manner (e.g., in a two-dimensional matrix, a linear vector, etc.).

[0081] In one embodiment, the sensing transistors of the sensing element are coupled to provide a common sensing electrical signal based on the sum of their sensed electrical signals. However, the sensing transistors can be coupled in any manner (e.g., in parallel to provide a common sensing current, in series to provide a common sensing voltage, etc.).

[0082] In one embodiment, the thermocouples of the sensing elements are coupled in series to provide a common sensing voltage for driving all the sensing transistors based on the sum of their sensed voltages. However, the common sensing voltage can drive the sensing transistors in any manner (see above).

[0083] In one embodiment, the comparison circuit is adapted to provide one of the temperature electrical signals based on a comparison between a common sensing signal and a common reference signal provided by a reference element. However, the single temperature electrical signal can be provided in any manner (see above).

[0084] In one embodiment, each sensing transistor has a first conductive terminal and a second conductive terminal for providing a respective sensing electrical signal that is a sensing current. However, the first / second conductive terminals can be of any type (e.g., source / drain terminals in a MOS transistor, emitter / collector terminals in a BJT transistor, etc.).

[0085] In one embodiment, the first conductive terminal and the second conductive terminal of the sensing transistor are respectively coupled in parallel to a common first conductive terminal and a common second conductive terminal for providing a common sensing electrical signal that is a common sensing current. However, the first / second conductive terminals can be coupled in parallel in any manner (e.g., through one or more conductors, accessing each of them through the same or different arms, etc.).

[0086] In one embodiment, each sensing transistor has a control terminal for controlling the sensing transistor. However, the control terminal can be of any type (e.g., gate terminal in a MOS transistor, base terminal in a BJT transistor, etc.).

[0087] In one embodiment, the control terminals of the sensing transistors are coupled in parallel to a common control terminal for receiving a common sensing voltage. However, the control terminals can be coupled in parallel in any manner (e.g., through the same or different arms with respect to the first / second conductive terminals, accessing each of them through one or more conductors, etc.).

[0088] In one embodiment, the second terminal of each thermocouple different from the last thermocouple is coupled to the first terminal of the next thermocouple in the corresponding frame. However, this connection can be made in any manner (e.g., with tracks of polysilicon, metal, and the like, directly, etc.).

[0089] In one embodiment, the first terminal of the first thermocouple defines a bias terminal for receiving a bias voltage of the thermal imaging sensor. However, the first thermocouple and the bias terminal can be arranged in any position (e.g., a corner of the gate, a boundary, etc.), and the bias voltage can have any value for biasing the sensing transistor in any manner (e.g., to subthreshold conditions, to on conditions, etc.).

[0090] In one embodiment, the second terminal of the last thermocouple is coupled to the control terminal of each sensing transistor through a respective one of the arms. However, the last thermocouple can be arranged at any position (e.g., corners of the gate, boundaries, etc.), and it can be coupled to the control terminal of each sensing transistor in any way (e.g., through the same arm of its first conductor and / or through another arm with any number of conductors, etc.).

[0091] In one embodiment, in each sensing element, the sensing transistor is coupled to the thermocouple to be driven according to the respective sensed voltage. However, the sensed voltage can drive the sensing transistor in any way (see above).

[0092] In one embodiment, the comparison circuit is adapted to provide one of the corresponding temperature electrical signals for each sensing element based on a comparison between the sensing signal of the sensing transistor of the sensing element and the reference signal of the corresponding reference element. However, the temperature electrical signal can be provided in any way (see above).

[0093] In one embodiment, in each sensing element, the second terminal of the thermocouple is coupled to the control terminal of the sensing transistor through one of the arms. However, this coupling can be obtained in any way (e.g., through the same arm of the first conductor of the thermopile and / or through any number of conductors of another arm, etc.).

[0094] In one embodiment, the sensing transistor is a TMOS transistor. However, the TMOS transistor can be of any type (e.g., NMOS, PMOS, etc.).

[0095] One embodiment provides a thermal imaging device. However, the thermal imaging device can be of any type (e.g., thermal scanner, camera, motion sensor, etc.).

[0096] In one embodiment, the thermal imaging device includes the above thermal imaging sensor and a signal processing circuit, which is coupled to the thermal imaging sensor to process the temperature signal. However, the signal processing circuit can apply any number and type of processing operations (e.g., partial, different, and additional processing operations relative to the processing operations mentioned above); in addition, the signal processing circuit can be of any type (e.g., integrated on any type of separate body, the same or different relative to one of the thermal imaging sensors, and the thermal imaging sensor in the same body, etc.), and the thermal imaging sensor and the processing circuit can be coupled in any way (e.g., in a common package, on a common chip, on a PCB, etc.).

[0097] One embodiment provides a system including at least one of the above thermal imaging devices. However, the system may include any number of thermal imaging devices, and it may be of any type (e.g., for ensuring social distancing, controlling air conditioning, monitoring food transportation, detecting hotspots, assisting people, controlling access, etc.).

[0098] Generally, similar considerations apply if the thermal imaging sensor, thermal imaging device, and system each have different structures or include equivalent components (e.g., different materials) or have other operating characteristics. In any case, each of its components can be separated into more elements, or two or more elements can be combined into a single element; in addition, each component can be replicated to support parallel execution of the corresponding operations. Furthermore, unless otherwise stated, any interaction between different components generally does not need to be continuous, and it can be direct or indirect through one or more intermediaries.

[0099] A thermal imaging sensor (105) for sensing thermal radiation, wherein the thermal imaging sensor (105) can generally be summarized as including one or more thermocouples (305s), each thermocouple having a hot junction (H) arranged to receive thermal radiation and thus be heated to a temperature associated therewith and a cold junction (P-N) arranged to be maintained at a temperature independent thereof, the cold junction (P-N) being adapted to provide a sensed voltage according to the difference between the temperature of the hot junction (H) and the temperature of the cold junction (P-N); one or more sensing transistors (310s), each sensing transistor being arranged to receive thermal radiation and thus be heated to a temperature dependent on the thermal radiation and being coupled to a corresponding one or more thermocouples (305s) to be driven according to the corresponding sensed voltage, the sensing transistors (310s) being adapted to provide a sensed electrical signal according to their temperature and the corresponding sensed voltage; one or more reference transistors (310r), each being arranged to shield thermal radiation and thus be maintained at a temperature independent thereof, the reference transistors (310r) being adapted to provide a reference electrical signal dependent on their temperature; and a comparison circuit (215) for providing one or more temperature electrical signals indicative of thermal radiation based on a comparison between the sensed electrical signal of the sensing transistors (310s) and the reference electrical signal of the reference transistors (310r).

[0100] The thermal imaging sensor (105) may include one or more additional thermocouples (305r), each thermocouple having an additional hot junction (H) and an additional cold junction (P-N), the thermocouple being adapted to provide an additional sensed voltage based on a difference between a temperature of the additional hot junction (H) and a temperature of the additional cold junction (P-N), the additional thermocouples (305r) being arranged to be shielded from thermal radiation so as to remain at a temperature independent of thermal radiation, and each reference transistor (310r) may be coupled to a corresponding one or more additional thermocouples (305r) so as to be driven based on the corresponding additional sensed voltage, thereby providing a corresponding reference electrical signal further dependent on the corresponding additional sensed voltage.

[0101] The thermal imaging sensor (105) may include one or more sensing elements (205), each sensing element including at least one thermocouple (305s) and at least one sensing transistor (310s), and the thermal imaging sensor (105) may include a corresponding one or more reference elements (210), each reference element including at least one reference transistor (310r).

[0102] The sensing elements (205) may be integrated on a body (220) of an insulating-type semiconductor, wherein the body (220) may include a substrate (405), a functional layer (410), and an insulating layer (415), the insulating layer being interposed between the substrate (405) and the functional layer (410), the body (220) being patterned to define a grid (420) of the functional layer (410) and the insulating layer (415) hanging from the substrate (405), wherein for each sensing element (205), the grid (420) may include a frame (425), a plate (430), and one or more arms (435a, 435b) supporting the plate (430) from the frame (425), wherein the sensing transistor (310s) of the sensing element (205) is formed in the plate (430), and wherein the thermocouple (305s) of the sensing element (205) may include a first conductor (440P) of a first conductive material and a second conductor (440n) of a second conductive material different from the first conductive material, the first conductor extending from a first terminal (P) of the cold junction in the frame (425) through one of the arms (435a, 435b) to the plate (430), the second conductor extending from a second terminal (N) of the cold junction in the frame (425) through one of the arms (435a, 435b) to the plate (430), the first conductor (440p) and the second conductor (440N) being short-circuited to the hot junction (H) at the plate (430).

[0103] The thermal imaging sensor (105) may include a plurality of sensing elements (205). The sensing transistors (310s) of the sensing elements (205) are coupled to provide a common sensing electrical signal based on the sum of their sensed electrical signals. The thermocouples (305s) of the sensing elements (205) are coupled in series to provide a common sensing voltage based on the sum of their sensed voltages for driving all the sensing transistors (310s). The comparison circuit (215) may be adapted to provide one of the temperature electrical signals based on a comparison between the common sensing signal and the common reference signal provided by the reference element (210).

[0104] Each sensing transistor (310s) may have a first conductive terminal (S) and a second conductive terminal (D) for providing a corresponding sensed electrical signal, which is a sensed current. The first conductive terminal (S) and the second conductive terminal (D) of the sensing transistors (310s) are respectively coupled in parallel to a common first conductive terminal (S) and a common second conductive terminal (D) to provide a common sensing electrical signal as a common sensed current. And each sensing transistor (310s) may have a control terminal (G) for controlling the sensing transistor (310s). The control terminals (G) of the sensing transistors (310s) are coupled in parallel to a common control terminal (G) for receiving a common sensing voltage.

[0105] The second terminal (N) of each thermocouple (305s) different from the last thermocouple in the thermocouples (305s) may be coupled to the first terminal (P) of the next thermocouple in the thermocouples (305s) in the corresponding frame (425). The first terminal (P) of the first thermocouple in the thermocouples (305s) defines a bias terminal for receiving a bias voltage (Vg) of the thermal imaging sensor (105). The second terminal (N) of the last thermocouple (305s) is coupled to the control terminal (G) of each sensing transistor (310s) through a corresponding one of the arms (435a, 435b).

[0106] The thermal imaging sensor (105) may include a plurality of sensing elements (205). In each sensing element (205), the sensing transistor (310s) is coupled to the thermocouple (305s) to be driven according to the corresponding sensed voltage. And the comparison circuit (215) may be adapted to provide one of the corresponding temperature electrical signals for each sensing element (205) based on a comparison between the sensing signal of the sensing transistor (310s) of the sensing element (205) and the reference signal of the corresponding reference element (210).

[0107] In each sensing element (205), the second terminal (N) of the thermocouple (305s) may be coupled to the control terminal (G) of the sensing transistor (310s) through one of the arms (435a, 435b).

[0108] The sensing transistors (310s) can be TMOS transistors (310s).

[0109] The thermal imaging device (100) can generally be summarized as including a thermal imaging sensor (105) and signal processing circuitry (110), the signal processing circuitry (110) being coupled to the thermal imaging sensor (105) for processing temperature signals.

[0110] A system (700) can generally be summarized as including at least one thermal imaging device (100).

[0111] The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to adopt concepts of the various embodiments to provide yet another embodiment.

[0112] These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments and the full scope of equivalents to which these claims are entitled. Thus, the claims are not limited by the present disclosure.

Claims

1. A thermal imaging sensor for sensing thermal radiation, wherein the thermal imaging sensor comprises: One or more thermocouples, each thermocouple having a hot junction and a cold junction, the hot junction being configured to be heated to a temperature in response to the thermal radiation, the cold junction being configured to be maintained at a temperature independent of the thermal radiation, each thermocouple being configured to provide a sensed voltage based on a difference between the temperature of the hot junction and the temperature of the cold junction; One or more sensing transistors, each sensing transistor being configured to be heated to a temperature in response to the thermal radiation and being coupled to a corresponding one or more of the thermocouples configured to be driven based on a corresponding sensed voltage, each sensing transistor being configured to provide a sensed electrical signal based on the temperature of the sensing transistor and the corresponding sensed voltage; One or more reference transistors, each reference transistor being configured to be shielded from the thermal radiation and having a temperature independent of the thermal radiation, each reference transistor being configured to provide a reference electrical signal based on the temperature of the reference transistor; And A comparison circuit configured to provide one or more temperature electrical signals based on a comparison between the sensed electrical signals of the one or more sensing transistors and the reference electrical signals of the one or more reference transistors, the one or more temperature electrical signals indicating the thermal radiation.

2. The thermal imaging sensor according to claim 1, wherein the thermal imaging sensor comprises one or more reference thermocouples, each reference thermocouple having a hot junction and a cold junction, the reference thermocouple being configured to provide a sensed voltage based on a difference between the temperature of the hot junction of the reference thermocouple and the temperature of the cold junction of the reference thermocouple, the reference thermocouple being configured to be shielded from the thermal radiation and having a temperature independent of the thermal radiation, and each reference transistor in the reference transistors being coupled to one or more reference thermocouples and being configured to be driven according to the corresponding sensed voltage of the one or more reference thermocouples and to provide a reference electrical signal based on the reference sensed voltage of the one or more reference thermocouples.

3. The thermal imaging sensor according to claim 1, wherein the thermal imaging sensor comprises one or more sensing elements, each sensing element comprising at least one of the one or more thermocouples and at least one of the one or more sensing transistors, and wherein the thermal imaging sensor comprises one or more reference elements corresponding to the one or more sensing elements, each reference element comprising at least one of the one or more reference transistors.

4. The thermal imaging sensor according to claim 3, wherein the sensing element is integrated on a body having a substrate, a functional layer, and an insulating layer, the insulating layer being interposed between the substrate and the functional layer, and the body being patterned to define a grid of the functional layer and the insulating layer suspended from the substrate, wherein for each of the one or more sensing elements, the grid includes a frame, a plate, and one or more arms coupling the plate to the frame, wherein the sensing transistor of the sensing element is formed in the plate, and wherein the thermocouple of the sensing element includes a first conductor of a first conductive material and a second conductor of a second conductive material different from the first conductive material, the first conductor extending from a first terminal of the cold junction in the frame through one of the arms to the plate, the second conductor extending from a second terminal of the cold junction in the frame through one of the arms to the plate, and the first conductor and the second conductor being short-circuited to the hot junction at the plate.

5. The thermal imaging sensor according to claim 3, wherein the thermal imaging sensor includes a plurality of sensing elements, the sensing transistors of the sensing elements being coupled to provide a common sensing electrical signal based on the sum of the sensing electrical signals of the plurality of sensing elements, and the thermocouples of the plurality of sensing elements being coupled in series to provide a common sensing voltage based on the sum of the sensing voltages of the thermocouples for driving all of the sensing transistors, and wherein the comparison circuit is configured to provide a temperature electrical signal based on a comparison between the common sensing signals.

6. The thermal imaging sensor according to claim 5, wherein each of the sensing transistors has a first conductive terminal and a second conductive terminal for providing a corresponding sensing current as the sensing electrical signal, the first conductive terminal and the second conductive terminal of the sensing transistor being respectively coupled in parallel to a common first conductive terminal and a common second conductive terminal for providing a common sensing current as the common sensing electrical signal, and wherein each of the sensing transistors has a control terminal for controlling the sensing transistor, the control terminals of the sensing transistors being coupled in parallel to a common control terminal, the common control terminal being coupled to receive the common sensing voltage.

7. The thermal imaging sensor according to claim 6, wherein a second terminal of a first thermocouple is coupled to a first terminal of a second thermocouple in a corresponding frame, the first terminal of the first thermocouple being a bias terminal for receiving a bias voltage of the thermal imaging sensor, and the second terminal of the second thermocouple being coupled to the control terminal of each of the sensing transistors through a corresponding one of the arms.

8. The thermal imaging sensor according to claim 4, wherein the thermal imaging sensor includes a plurality of sensing elements, and in each of the sensing elements, the sensing transistor is coupled to the thermocouple and is driven based on the sensing voltage of the thermocouple, and wherein the comparison circuit is configured to provide a corresponding one of the temperature electrical signals in the temperature electrical signals for each of the sensing elements according to a comparison between the sensing signal of the sensing transistor of the sensing element and the reference signal of a corresponding reference element.

9. The thermal imaging sensor according to claim 8, wherein in each of the sensing elements, the second terminal of the thermocouple is coupled to the control terminal of the sensing transistor through one of the arms.

10. The thermal imaging sensor according to claim 1, wherein the sensing transistor is a thermally insulated MOS (TMOS) transistor.

11. A thermal imaging sensor, comprising: a body including a film and a first cavity, the film being located on a first surface of the body, the first cavity being located in the body and below the film, the film including: a frame portion, a plate portion, a first arm portion, and a second arm portion, the first arm portion coupling the plate portion to the frame portion, and the second arm portion coupling the plate portion to the frame portion; a first conductive track extending from a first joint on the frame portion through the first arm portion to a second joint on the plate portion; a second conductive track extending from a third joint on the frame portion through the second arm portion to the second joint on the plate portion, the first conductive track and the second conductive track being coupled to each other through the second joint; a transistor located on the plate portion, the transistor including a source region, a drain region, and a channel region; a third conductive track extending from a first point on the frame through the first arm portion to the source region of the transistor; a fourth conductive track extending from a second point on the frame through the second arm portion to the drain region of the transistor.

12. The sensor according to claim 11, wherein the source region, the drain region, and the channel region of the transistor are located in a region of the plate portion configured to receive thermal radiation.

13. The sensor according to claim 11, wherein the second joint is located on a region of the plate portion configured to receive thermal radiation.

14. The sensor according to claim 11, including a fifth conductive track extending from a third point on the frame through one of the first arm portion or the second arm portion to the channel region of the transistor.

15. The sensor according to claim 14, wherein the third point on the frame is coupled to one of the first joint or the third joint on the frame.

16. The sensor according to claim 11, wherein the channel region includes a honeycomb structure.

17. The sensor according to claim 11, wherein the transistor is a thermally insulated MOS transistor.

18. A thermal imaging sensor, comprising: a first body, including: A first film and a second film, located on a first surface of the first body, the first film including a first thermocouple and a first thermally-insulated MOS transistor, and the second film including a second thermocouple and a second thermally-insulated MOS transistor; and A first cavity and a second cavity, respectively located in the first body and below the first film and the second film, the first cavity being separated from the second cavity; A second body, coupled to the first body by the first surface of the first body, the second body having a third cavity and a fourth cavity, the third cavity facing the first film, the fourth cavity facing the second film, the third cavity being separated from the fourth cavity; and A shielding layer, located on the second body, away from the first body, and overlapping with the fourth cavity, the shielding layer being configured to prevent thermal radiation from reaching the second film.

19. The sensor according to claim 18, comprising a third body, the third body being coupled to the first body by a second surface of the first body, the second surface being opposite to the first surface, wherein each of the first cavity and the second cavity extends into the third body.

20. The sensor according to claim 19, comprising a comparison circuit device configured to compare an electrical signal of the first thermally-insulated MOS transistor with an electrical signal of the second thermally-insulated MOS transistor.

Images