Thermal sensor array device, method of measuring temperature gradient, and method of measuring temperature

Abstract

The invention relates to a thermal sensor array device, a method of measuring a temperature gradient, and a method of measuring a temperature. A thermal sensor array device includes a substrate having a cavity formed therein. An infrared absorbing film is suspended above the cavity from a first beam and a second beam, the first beam being thermally coupled to the substrate at one end thereof at a first substrate cold junction (Cj1), and the second beam being thermally coupled to a second substrate cold junction (Cj2) at one end thereof. A thermocouple is disposed over the first and second beams and on the membrane. Thermocouples are arranged on the first and second beams and the membrane as first and second thermopiles. The first and second thermopiles are arranged on the film to measure a sum of a first temperature difference between the first substrate cold junction (Cj1) and the hot junction (Hj) on the film and a second temperature difference between the second substrate cold junction (Cj2) and the hot junction (Hj) on the film. The first thermopile is configured for selective series and anti-series connection to the second thermopile.

Description

Technical Field

[0001] The present invention relates to a certain type of thermal sensor device, which for example includes an infrared absorbing film suspended above a cavity in a substrate. The present invention also relates to a method of measuring a temperature gradient, which is of the type that measures the temperature gradient across the infrared absorbing film of the thermal sensor device. The present invention also relates to a method of measuring temperature, which is of the type that employs measurement of the temperature gradient across the thermal sensor device, for example. Background Art

[0002] In the field of thermal sensors, it is known to employ thermal sensor devices to measure temperature and / or provide images of remote objects in a scene based on light emitted from the target object in the infrared range of the electromagnetic spectrum. Thermal sensor devices typically include an array of sensor pixels (e.g., arranged as a grid), each sensor pixel individually responsive to infrared electromagnetic radiation.

[0003] In practice, although the pixels of an array of such sensor devices are exposed to the same amount of infrared radiation, there are response variations between the sensor pixels. Therefore, it is well known that an infrared camera employing such a sensor device applies corrections to the raw output signals from the array. For example, known correction techniques include generating a table of individual correction factors to be applied to the corresponding outputs of each pixel of the image. However, it is well known that additional variations in the outputs of the sensor pixels of the array may occur in the event of local heating within the sensor device due to normal operation of the sensor device. Such so-called local hot spots may affect the response of one or more sensor pixels of the array. Similarly, external heat sources adjacent to the sensor device (but not part of the scene) may cause temperature variations across the array. When the array is exposed to such heat sources, linear and nonlinear temperature gradients appear across the array. Such temperature gradients result in inconsistent and / or inaccurate measurements.

[0004] Those skilled in the art will appreciate that a temperature gradient extending across the pixels of an array of a sensor device causes the pixels across the array to be heated to different temperatures. Thus, even before being exposed to one or more infrared sources in the scene to be measured, the pixels are already biased by the temperature to which they have been exposed in their respective environments, which may be local and proximal, or within a wider scene. For example, when packaged, the local proximal environment is contained by, for example, a cover, and the local proximal environment contains thermal energy that may affect the measurement made by the pixels. The transfer of thermal energy between the individual local proximal environments and the corresponding pixels may cause the pixels of the sensor device to be heated to different temperatures. Outside the device package, one or more heat-radiating objects near the sensor device (but not the subject to be measured) may "preheat" several pixels of the sensor device so that different pixels will provide different temperature measurements for the same object body to be measured. This may be caused by changes in the thermal resistance and / or the location of the unwanted heat source within the environment. European Patent No. 3118594B1 describes the arrangement of a combination of active pixels and so-called "blind" pixels in a predetermined pattern in order to eliminate the effects of the above-mentioned temperature gradient. German patent publication number DE 102004027393A1 describes arranging a plurality of thermocouples on a sensor membrane in a predetermined manner in order to compensate for temperature gradients. However, the described arrangement employs symmetrically arranged hot and cold junctions, which is not always possible due to space limitations. In such cases, the sensor's unwanted response to the temperature gradient may increase. Furthermore, the described arrangement does not allow for accurate identification of the location of the unwanted heat source.

[0005] It is also known to provide additional thermocouples along with an array of thermal sensor devices, and to use interpolation techniques to determine the temperature gradient across the array of devices. Summary of the invention

[0006] According to a first aspect of the present invention, there is provided a thermal sensor element device, comprising: a substrate having a cavity formed therein; and an infrared absorbing film suspended from a first beam and a second beam above the cavity, the first beam being thermally coupled to the substrate at one end thereof at a first substrate cold junction, and the second beam being thermally coupled to the substrate at one end thereof at a second substrate cold junction; and a plurality of thermocouples disposed above the first beam and the second beam and the infrared absorbing film; wherein the plurality of thermocouples are arranged as a first thermopile and a second thermopile on the first beam and the second beam and the infrared absorbing film; the first thermopile and the second thermopile are arranged on the infrared absorbing film to measure the sum of a first temperature difference and a second temperature difference when in use, the first temperature difference being between the first substrate cold junction and the hot junction on the infrared absorbing film, and the second temperature difference being between the second substrate cold junction and the hot junction on the infrared absorbing film; and the first thermopile is configured to be selectively connected in series and anti-series to the second thermopile.

[0007] The infrared absorbing film may include hot junctions for a plurality of thermocouples.

[0008] Each of the first thermopile and the second thermopile may be respectively configured to measure the sum of temperature differences about the first region of the infrared absorbing film and the second region of the infrared absorbing film when in use.

[0009] Several hot junctions and several cold junctions of the plurality of thermocouples can be configured to provide a first thermopile between the plurality of hot junctions and the plurality of cold junctions; another several hot junctions and another several cold junctions of the plurality of thermocouples can be configured to provide a second thermopile between the plurality of hot junctions and another several cold junctions; at least one of the several cold junctions can be positioned at a first end of the first beam away from the infrared absorbing film; and at least one of the another several cold junctions can be positioned at a second end of the second beam away from the infrared absorbing film.

[0010] The sum of the first temperature difference and the second temperature difference may be measured between the plurality of cold junctions and the plurality of hot junctions.

[0011] At least a portion of each of the heat junctions may be configured to converge within a predetermined hot end region of the infrared absorbing film.

[0012] The hot junction of the thermocouple may include an interconnection in a predetermined hot end region of the infrared absorbing film.

[0013] The first beam may include a narrow track portion extending toward the infrared absorbing film and integrally forming a portion of the infrared absorbing film; and the second beam may include a narrow track portion extending toward the infrared absorbing film and integrally forming another portion of the infrared absorbing film.

[0014] Adjacent thermocouples of the first thermopile may be separated by a plurality of separation channels that are narrower than the thermocouples.

[0015] The plurality of thermocouples may be an even number of thermocouples.

[0016] The first beam may bridge the substrate and a first side of the infrared absorbing film; and the second beam may bridge the substrate and a second side of the infrared absorbing film.

[0017] A first number of thermocouples between a hot junction of the first thermopile on the infrared absorbing film and at least one of the several cold junctions of the first beam may be greater than a second number of thermocouples between a hot junction of the first thermopile on the infrared absorbing film and at least one of the several cold junctions of the second beam.

[0018] A first number of thermocouples between the hot junction of the second thermopile on the infrared absorbing film and at least one of the other several cold junctions of the second beam may be greater than a second number of thermocouples between the hot junction of the second thermopile on the infrared absorbing film and at least one of the several cold junctions of the first beam.

[0019] According to a second aspect of the present invention, there is provided a thermal sensor array device comprising a thermal sensor element device as set out above in relation to the first aspect of the present invention.

[0020] According to a third aspect of the present invention, a method for measuring a temperature gradient above a thermal sensor device in an array of thermal sensor devices is provided, the method comprising: providing an array of thermal sensor devices, the array of thermal sensor devices comprising the thermal sensor devices as described above with respect to the first aspect of the present invention; receiving infrared electromagnetic radiation incident on the thermal sensor devices; connecting a first thermopile in anti-series to a second thermopile; measuring a difference with respect to the received infrared electromagnetic radiation, the difference constituting a temperature gradient; and storing the measured temperature gradient.

[0021] According to a fourth aspect of the present invention, there is provided a method for measuring temperature, the method comprising: measuring a temperature gradient as described above with respect to the third aspect of the present invention; connecting a first thermopile in series to a second thermopile; measuring a sum value of received infrared electromagnetic radiation; and calculating the temperature by using the temperature gradient to compensate for the sum value.

[0022] Thus, it is possible to provide a thermal sensor device and a method for measuring the temperature gradient across an infrared absorbing film, which provides a more accurate measurement of infrared electromagnetic radiation incident on the thermal sensor elements of the thermal sensor element array. The device and method enable the same thermal sensor device that measures infrared electromagnetic radiation to be used to measure the temperature gradient across itself. When used for calibration purposes, it is possible to measure the temperature distribution above the sensor element array more accurately than using additional thermocouples and simple interpolation techniques. When the gas conductivity in the cover of the sensor device is constant, the incremental temperature measurement function between cold junctions can be used to compensate for changes in the temperature gradient. In this regard, for example, when the power consumption plan, the power value of the thermal energy source across the space of the integrated circuit including the sensor device, and one or more changes related to the way in which the die is attached to the lead frame (such as cracking, delamination or changes in its properties of the bonding agent used) occur, the change in the gradient may occur. Additionally, during production, the method and device allow verification that the bonding agent used to attach the die to the lead frame has been reliably applied during assembly. During operation of the sensor device, measurements according to the method may be performed to check for internal and external thermal influences that may be the cause of a temperature gradient across an array of sensor devices. Such measured temperature gradients may be used to determine degradation of the performance and / or drift of the packaging of the thermal sensor device and / or array of sensor devices. Measurements of the temperature gradient may also be used to determine whether an excessively strong heat source within the scene is set too close to the sensor device, so that the measurements performed are adversely affected. In conjunction with the setting of the maximum permissible temperature gradient, an indication of whether the measurement is trusted may be provided to the user, and thereby the sensor including the sensor device provides greater confidence in its use for critical applications. The sensor device and method also provide the ability to use the sensor device directly for measurements at the start-up of the sensor device without having to wait for the sensor device to reach a thermally stable state. Thus, the sensor device can be used during short time intervals without having to wait for the thermal stability of the sensor device to be reached, and the sensor device can remain powered off when not in use. Support for this mode of use is particularly but not exclusively beneficial for battery-operated applications, in which it is desirable to minimize power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] At least one embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic diagram of a thermal sensor device including an array of thermal sensor elements and constituting an embodiment of the present invention;

[0025] Figure 2 yes Figure 1A schematic diagram of a thermal sensor element of a thermal sensor array device;

[0026] Figure 3 yes Figure 2 Circuit diagram of the thermocouple of the thermal sensor element;

[0027] Figure 4 is a flow chart of a method for measuring temperature gradient;

[0028] Figure 5 yes Figure 1 A schematic diagram of adjacent thermal sensor elements;

[0029] Figure 6 Is to measure temperature and use according to Figure 4 A flow chart of a method for calculating a temperature gradient to compensate for a measured temperature; and

[0030] Figure 7 yes Figure 2 Cross-sectional view of the thermal sensor element along line AA. DETAILED DESCRIPTION

[0031] Throughout the following description, the same reference numerals will be used to identify the same parts.

[0032] refer to Figure 1 , the thermal sensor array device 100 includes a plurality of thermal sensor elements or devices 102. The plurality of thermal sensor elements 102 are arranged as an n×m pixel array. A first 2×2 cluster 104 of sensor devices includes a first thermal sensor element or device 106, a second thermal sensor element or device 108, a third thermal sensor element or device 110, and a fourth thermal sensor element or device 112. A second adjacent cluster 114 is spaced apart from the first cluster 104 by a first channel 116, and a third adjacent cluster 118 is spaced apart from the second cluster 114 by a second channel 120. Of course, those skilled in the art will appreciate that while the plurality of thermal sensor elements 102 are arranged as clusters of thermal sensor elements, other arrangements are contemplated depending on the precise manufacturing process employed.

[0033] Each sensor element of the plurality of thermal sensor elements 102 is operably coupled to a measurement circuit 122. Although a single signal line is shown between the sensor element and the measurement circuit 122, those skilled in the art will appreciate that there are multiple connections between the measurement circuit and each thermal sensor element, as will be described below, and that a single line is shown for simplicity and clarity.

[0034] Go to Figure 2 and Figure 7, the first thermal sensor element 106, the second thermal sensor element 108, the third thermal sensor element 110, and the fourth thermal sensor element 112 (just like the other thermal sensor elements in the plurality of thermal sensor elements 102 of the pixel array) have similar constructions, and therefore, for the sake of clarity and brevity of description, only the structure of the first thermal sensor element 104 will be described. However, those skilled in the art will appreciate that the structure of the first thermal sensor element 106 is applicable to the other thermal sensor elements in the plurality of thermal sensor elements 102.

[0035] The first thermal sensor element 106 employs any suitable mechanical support structure known in the art. For example, the first thermal sensor element 106 includes a substrate 600 that constitutes a so-called "bulk" material layer (e.g., silicon). A relatively thin shaped structure called a membrane or diaphragm 200 is formed over the bulk material and connected to the substrate via beams 202, 206. The beams constitute narrow track portions extending from the area of ​​the substrate associated with the thermal sensor element 106 to the membrane 200, in this example, the narrow track portions extend from two opposite sides of the area of ​​the substrate associated with the thermal sensor element 106, and intersect the membrane 200 on its opposite sides. The portion of the substrate below the membrane 200 has been removed (e.g., by any suitable known etching technique) to form a cavity 291 below the membrane 200 and the beams 202, 206. A cover structure (not shown) formed of an infrared transmissive material is mounted over the substrate 600 so that the membrane 200 and the beams 202, 206 are encapsulated in a closed cavity (not shown) that is generally hermetically sealed. The pressure within the cavity and the composition of the gas inside the cavity are largely determined by the specific technique used to seal the substrate 600 to the cover structure. Most of the cover structure (except for the openings that serve as holes or windows through which infrared electromagnetic radiation is permitted to propagate) is covered by a layer of non-transparent material.

[0036] In this example, as mentioned above, the beams 202, 206 are disposed between the opposing sides 292, 293 of the membrane 200 and the substrate 600, and are arranged as the first beam 202 at the first side 204 of the substrate 600 adjacent to the cavity 291, and as the second beam 206 at the second side 208 of the substrate 600 adjacent to the cavity 291. In this example, the first beam 202 includes a first thermocouple 210, a second thermocouple 212, a third thermocouple 214, and a fourth thermocouple 216. The second beam 206 includes a fifth thermocouple 218, a sixth thermocouple 220, a seventh thermocouple 222, and an eighth thermocouple 224. In this example, multiple thermocouples share a common beam, but in other examples, other distributions are possible, such as dedicated beams for one or more thermocouples. The first end 226 of the first thermocouple 210, the second thermocouple 212, the third thermocouple 214, and the fourth thermocouple 216 is thermally coupled to the first region of the substrate (not shown), and the first end 228 of the fifth thermocouple 218, the sixth thermocouple 220, the seventh thermocouple 222, and the eighth thermocouple 224 is thermally coupled to the second region of the substrate (not shown). The first region of the substrate is spaced apart from the second region, and in this example, the first region of the substrate and the second region of the substrate are opposite to each other, and the film 200 is located between the first region and the second region of the substrate. The second end 230 of the first beam 202 is formed integrally with the film 200 at the first connection side 232 of the film 200. The second end 234 of the second beam 206 is formed integrally with the film 200 at the second connection side 236 of the film 200. In this example, the first connection side 232 and the second connection side 236 of the film 200 are diagonally opposite to each other.

[0037] In this example, the membrane 200 has a generally rectangular shape. The membrane 200 has a first long side 238 and a second long side 240. The first beam 202 extends substantially parallel to and adjacent to the first long side 238, and the second beam 206 extends substantially parallel to and adjacent to the second long side 240.

[0038] The purpose of the first beam 202 and the second beam 206 and the membrane 200 is to carry the above-mentioned multiple thermocouples, which are arranged as a first thermopile and a second thermopile in this example. In this example, the number of thermocouples in the multiple thermocouples is an even number. The multiple thermocouples are formed by a first deposition of a p-type semiconductor 602 (e.g., p-type polysilicon) on a field oxide layer 604 and are separated from a second deposition of an n-type semiconductor 606 (e.g., n-type polysilicon) by a thin oxide layer 608. A dielectric oxide layer 610 is formed above the n-type polysilicon 606, and a passivation oxide layer 612 is formed above the dielectric oxide layer 610. Then, silicon nitride 614 is disposed above the passivation oxide layer 612. The structure will be referred to as a pn polysilicon layer stack hereinafter. The p-type polysilicon layer 602 and the n-type polysilicon layer 606, the oxide layers 604, 608, 610, 612, and the silicon nitride layer 614 are patterned using any suitable photolithography technique to shape the deposits and expose small areas of the deposited p-type polysilicon layer 602 and the n-type polysilicon layer 606 to permit interconnection of the p-type polysilicon layer 602 and the n-type polysilicon layer 606. Such point interconnection permits thermocouples to be formed and permits multiple thermocouples to be connected together to form a thermopile. The p-type polysilicon layer 602 and the n-type polysilicon layer 606, the oxide layers 604, 608, 610, 612, and the silicon nitride layer 614 overlie the first beam 202 and the second beam 206 and the membrane 200. The p-type polysilicon and n-type polysilicon are deposited so that the surface of the film 200 is covered by shaped portions of n-type polysilicon that substantially cover corresponding portions of p-type polysilicon (with a thin dielectric oxide layer 608 therebetween), while adding a small amount of dielectric oxide 610 to insulate the pn polysilicon layer stacks on either side of each shaped portion, thereby forming a plurality of adjacent polysilicon layer stacks. The channels separating adjacent pn polysilicon layer stacks of the pn polysilicon layer stacks are narrower than the pn polysilicon layer stacks. Thus, a first, second, third, fourth, fifth, sixth, seventh, and eighth pn polysilicon layer stacks are provided.

[0039] In this regard, a plurality of pn polysilicon layer stacks are provided as follows. A first pn polysilicon layer stack is provided as a first thermocouple 210 and extends over a first region 242 of the membrane 200. Similarly, a second, third, and fourth pn polysilicon layer stacks extend over the first beam 202, respectively, thereby constituting a second thermocouple 212, a third thermocouple 214, and a fourth thermocouple 216 extending to a second region 244, a third region 246, and a fourth region 248 of the membrane 200, respectively. For each of the first, second, third, and fourth pn polysilicon layer stacks, the n-type polysilicon layer does not completely cover the p-type polysilicon layer, and a first small film contact area 250, a second small film contact area 252, a third small film contact area 254, and a fourth small film contact area 256 of the p-type polysilicon layer are not covered by the corresponding n-type polysilicon layer. Similarly, the n-type polysilicon layer of each of the first, second, third and fourth pn polysilicon layer stacks does not completely cover the p-type silicon layer at the first end 226 of the first thermocouple 210, the second thermocouple 212, the third thermocouple 214, and the fourth thermocouple 216, and thus forms a first thermocouple contact area 258, a second thermocouple contact area 260, a third thermocouple contact area 262 and a fourth thermocouple contact area 264.

[0040] The fifth, sixth, seventh, and eighth pn polysilicon layer stacks are provided as fifth thermocouple 218, sixth thermocouple 220, seventh thermocouple 222, and eighth thermocouple 224, respectively, and extend to fifth region 266, sixth region 268, seventh region 270, and eighth region 272, respectively, of film 200. For each of the fifth, sixth, seventh, and eighth pn polysilicon layer stacks, the n-type polysilicon layer does not completely cover the p-type polysilicon layer, and a fifth small film contact area 274, a sixth small film contact area 276, a seventh small film contact area 278, and an eighth small film contact area 280 of the p-type polysilicon layer are not covered by the n-type polysilicon layer. Similarly, the n-type polysilicon layer of each of the fifth, sixth, seventh and eighth pn polysilicon layer stacks does not completely cover the p-type polysilicon layer at the first end 228 of the fifth thermocouple 218, the sixth thermocouple 220, the seventh thermocouple 222 and the eighth thermocouple 224, and thus forms a fifth thermocouple contact region 282, a sixth thermocouple contact region 284, a seventh thermocouple contact region 286 and an eighth thermocouple contact region 288.

[0041] The pn polysilicon layer stack of each of the first region 242, the second region 244, the third region 246, the fourth region 248, the fifth region 266, the sixth region 268, the seventh region 270 and the eighth region 272 of the covering film 200 each includes a corresponding peninsula region, and the first contact region 250, the second contact region 252, the third contact region 254, the fourth contact region 256, the fifth contact region 274, the sixth contact region 276, the seventh contact region 278 and the eighth contact region 280 are respectively positioned at the far ends of the peninsula regions of the first region 242, the second region 244, the third region 246, the fourth region 248, the fifth region 266, the sixth region 268, the seventh region 270 and the eighth region 272 of the film 200. In this example, the distal ends of the peninsular regions of the first region 242, the second region 244, the third region 246, the fourth region 248, the fifth region 266, the sixth region 268, the seventh region 270, and the eighth region 272 of the film 200 converge toward the central region 290 of the film 200. Metal interconnections are employed to couple the p-type polysilicon layer to the n-type polysilicon layer in a predetermined manner, thereby providing a plurality of thermocouples in the central region 290. Thus, the hot junctions Hj converge in the central region 290 constituting the hot end region. The predetermined interconnection pattern of the p-type polysilicon layer and the n-type polysilicon layer independently interconnects the plurality of thermocouples into a first thermopile and a second thermopile.

[0042] In this example, the n-type polysilicon adjacent to the fourth thermocouple contact region 264 is operably coupled to the measurement circuit 122 ( Figure 2276 ). The n-type polysilicon of the fourth pn polysilicon layer stack residing at the tip of the peninsula region of the fourth region 248 of the film 200 is coupled to the p-type polysilicon of the eighth film contact region 280. The p-type polysilicon of the eighth pn polysilicon layer stack at the eighth thermocouple contact region 288 is coupled at the first end 228 to the n-type polysilicon of the pn polysilicon layer stack of the seventh thermocouple 222. The n-type polysilicon at the tip of the peninsula region of the seventh pn polysilicon layer stack deposited on the seventh region 270 of the film 200 is coupled to the p-type polysilicon of the sixth pn polysilicon layer stack at the sixth film contact region 276. The p-type polysilicon of the sixth pn polysilicon layer stack at the sixth thermocouple contact region 284 is coupled at the first end 228 to the n-type polysilicon of the fifth pn polysilicon layer stack of the fifth thermocouple 218. The n-type polysilicon at the tip of the peninsula region of the fifth pn polysilicon layer stack deposited on the fifth region 266 of the film 200 is coupled to the p-type polysilicon of the seventh pn polysilicon layer stack at the seventh film contact region 278. The p-type polysilicon of the seventh pn polysilicon layer stack at the seventh thermocouple contact region 286 is coupled to the n-type polysilicon of the sixth pn polysilicon layer stack of the sixth thermocouple 220 at the first end 228. The n-type polysilicon at the tip of the peninsula region of the sixth pn polysilicon layer stack deposited on the sixth region 268 of the film 200 is coupled to the p-type polysilicon of the first pn polysilicon layer stack at the first film contact region 250. The p-type polysilicon of the first pn polysilicon layer stack at the first thermocouple contact region 258 is coupled to the measurement circuit 122. The above series of interconnections form a number of connected thermocouples, four thermocouples in this example, which together form a first thermopile.

[0043] Additionally, the second thermopile is formed according to the following interconnections. The n-type polysilicon of the third pn polysilicon layer stack of the third thermocouple 214 at the first end 226 is operatively coupled to the measurement circuit 122 ( Figure 2246 of the membrane 200 is coupled to the n-type polysilicon of the eighth pn polysilicon layer stack at the first end 228. The n-type polysilicon of the eighth pn polysilicon layer stack residing at the tip of the peninsula region of the eighth region 272 of the film 200 is coupled to the p-type polysilicon of the third film contact region 254. The p-type polysilicon of the third pn polysilicon layer stack at the third thermocouple contact region 262 is coupled at the first end 226 to the n-type polysilicon of the second pn polysilicon layer stack of the second thermocouple 212. The n-type polysilicon of the second pn polysilicon layer stack residing at the tip of the peninsula region of the second region 244 of the film 200 is coupled to the p-type polysilicon of the fourth film contact region 256, and the p-type polysilicon of the fourth pn polysilicon layer stack at the fourth thermocouple contact region 264 is coupled to the measurement circuit 122.

[0044] refer to Figure 3, and considering the p-type polysilicon layer and the n-type polysilicon layer of the pn polysilicon layer stack as circuit components, the first thermopile 300 includes a first end of the n-type polysilicon layer 303 of the fourth pn polysilicon layer stack, which is coupled to the measurement circuit 122 via the first terminal 302, and a second end of the n-type polysilicon layer 303 of the fourth pn polysilicon layer stack is coupled to a first end of the p-type polysilicon layer 304 of the eighth pn polysilicon layer stack. A second end of the p-type polysilicon layer 304 of the eighth pn polysilicon layer stack is coupled to a first end of the n-type polysilicon layer 306 of the seventh pn polysilicon layer stack, and a second end of the n-type polysilicon layer 306 of the seventh pn polysilicon layer stack is coupled to a first end of the p-type polysilicon layer 308 of the sixth pn polysilicon layer stack. A second end of the p-type polysilicon layer 308 of the sixth pn polysilicon layer stack is coupled to a first end of the n-type polysilicon layer 310 of the fifth pn polysilicon layer stack, and a second end of the n-type polysilicon layer 310 of the fifth pn polysilicon layer stack is coupled to a first end of the p-type polysilicon layer 312 of the seventh pn polysilicon layer stack. A second end of the p-type polysilicon layer 312 of the seventh pn polysilicon layer stack is coupled to a first end of the n-type polysilicon layer 314 of the sixth pn polysilicon layer stack, and a second end of the n-type polysilicon layer 314 of the sixth pn polysilicon layer stack is coupled to a first end of the p-type polysilicon layer 316 of the first pn polysilicon layer stack. A second end of the p-type polysilicon layer 316 of the first pn polysilicon layer stack is coupled to the measurement circuit 122 via a second terminal 318.

[0045] The second thermopile 320 includes a first end of an n-type polysilicon layer 322 of a third pn polysilicon layer stack, the first end of the n-type polysilicon layer 322 of the third pn polysilicon layer stack is coupled to the measurement circuit 122 via a third terminal 324, and a second end of the n-type polysilicon layer 322 of the third pn polysilicon layer stack is coupled to a first end of a p-type polysilicon layer 326 of a second pn polysilicon layer stack. A second end of the p-type polysilicon layer 326 of the second pn polysilicon layer stack is coupled to a first end of an n-type polysilicon layer 328 of the first pn polysilicon layer stack, and a second end of the n-type silicon layer 328 of the first pn polysilicon layer stack is coupled to a first end of a p-type polysilicon layer 330 of a fifth pn polysilicon layer stack. A second end of the p-type polysilicon layer 330 of the fifth pn polysilicon layer stack is coupled to a first end of the n-type polysilicon layer 332 of the eighth pn polysilicon layer stack, and a second end of the n-type polysilicon layer 332 of the eighth pn polysilicon layer stack is coupled to a first end of the p-type polysilicon layer 334 of the third pn polysilicon layer stack. A second end of the p-type polysilicon layer 334 of the third pn polysilicon layer stack is coupled to a first end of the n-type polysilicon layer 336 of the second pn polysilicon layer stack, and a second end of the n-type polysilicon layer 336 of the second pn polysilicon layer stack is coupled to a first end of the p-type polysilicon layer 338 of the fourth pn polysilicon layer stack. A second end of the p-type polysilicon layer 338 of the fourth pn polysilicon layer stack is coupled to the measurement circuit 122 via a fourth terminal 340.

[0046] As from Figure 3 It can be seen that the number of thermocouple elements (p-type polysilicon layer or n-type polysilicon layer) between the hot junction Hj and the second cold junction Cj2 of the first thermopile 300 is greater than the number of thermocouple elements between the hot junction Hj and the first cold junction Cj1 of the first thermopile 300. Similarly, the number of thermocouple elements between the hot junction Hj and the first cold junction Cj1 of the second thermopile 320 is greater than the number of thermocouple elements between the hot junction Hj and the second cold junction Cj2 of the second thermopile 320.

[0047] In this example, the measurement circuit 122 is configured to selectively connect the second terminal 318 to the third terminal 324 and measure the summed voltage across the first terminal 302 and the fourth terminal 340, or to connect the second terminal 318 to the fourth terminal 340 and measure the differential voltage across the first terminal 302 and the third terminal 324. The connection of the second terminal 318 to the third terminal 324 connects the first thermopile 300 in series to the second thermopile 320. The connection of the second terminal 318 to the fourth terminal 340 connects the first thermopile 300 to the second thermopile 320 in a so-called “anti-series” or “reverse series” manner, wherein the connection of the second thermopile 320 to the first thermopile 300 is such that the polarity of the second thermopile 320 is opposite to the polarity of the first thermopile 300.

[0048] In operation ( Figure 4 ), the first ends 226 of the first thermocouple 210, the second thermocouple 212, the third thermocouple 214 and the fourth thermocouple 216 and the first ends 228 of the fifth beam 218, the sixth beam 220, the seventh beam 222 and the eighth beam 224 (all of which are in thermal contact with the substrate) constitute the first cold junction Cj1 and the second cold junction Cj2, respectively. The central region 290 of the film 200 where the junction is formed constitutes the hot junction Hj. Separately, the thermocouple elements 304, 306, 308, 310, 312, 314 of the first thermopile 300 are arranged on the film 200 and the second beam 206 for measuring the temperature difference between the second cold junction Cj2 and the hot junction Hj, and the thermocouple elements 303, 316 of the first thermopile 300 are arranged on the film 200 and the first beam 202 for measuring the temperature difference between the first cold junction Cj1 and the hot junction Hj. Thermocouple elements 322, 326, 328, 334, 336, 338 of the second thermopile 320 are arranged on the membrane 200 and the first beam 202 for measuring the temperature difference between the first cold junction Cj1 and the hot junction Hj, and the thermocouple elements 330, 332 of the second thermopile 320 are arranged on the membrane 200 and the second beam 206 for measuring the temperature difference between the second cold junction Cj2 and the hot junction Hj. Thus, the first thermopile 300 and the second thermopile 320 are configured to measure the sum of a first temperature difference, the first temperature difference being between the first cold junction Cj1 and the hot junction Hj on the membrane 200, and the second temperature difference being between the second cold junction Cj2 and the hot junction Hj on the membrane 200.

[0049] After providing a plurality of thermal sensor elements 102 as a pixel array in the manner described above (step 400), for example, a method for measuring a temperature gradient above a thermal sensor element (e.g., a first thermal sensor element 106 of the thermal sensor array device 100) includes: powering up the thermal sensor array device 100 (step 402); and exposing the thermal sensor array device 100 to an infrared electromagnetic radiation source in a scene. Thus, the infrared electromagnetic radiation is received by one or more of the plurality of thermal sensor elements 102 (e.g., the first thermal sensor element 106) (step 404).

[0050] To measure the temperature gradient across the first thermal sensor element 106, the first thermopile 300 is coupled in anti-series to the second thermopile 320 by the measurement circuit 122 (step 406), and the measurement circuit 122 measures (step 408) the voltage across the first terminal 302 and the third terminal 324 of the first thermopile 300 and the second thermopile 320, respectively, thereby measuring the voltage difference across the anti-series circuit of the thermocouples. The measurement circuit then uses the measured voltage difference to calculate (step 410) the temperature gradient across the first cold junction Cj1 and the second cold junction Cj2. The measured temperature gradient is then stored by the measurement circuit 122 (step 412).

[0051] It should be noted that the first thermopile 300 and the second thermopile 320 have spatial asymmetry so as to measure a voltage difference proportional to the temperature difference between the cold junctions when the first thermopile 300 and the second thermopile 320 are connected in anti-series (because the spatial asymmetry ensures that a voltage difference is generated when the anti-series connection and the temperature gradient exist). The sensor element layout ensures that the voltage difference signal is not erroneously generated when there is no temperature gradient.

[0052] In this example, the above-mentioned differential voltage measurement is performed for all thermal sensor elements of the pixel array, and the temperature gradient with respect to all thermal sensor elements is also calculated. This enables the measurement circuit 122 to process the individual temperature gradients of adjacent thermal sensor elements in order to calculate (step 414) the local temperature gradients in the x-direction and the y-direction with respect to the pixel array, as will be described in further detail below.

[0053] However, first, the voltage difference V measured with respect to a given thermal sensor element (eg, the first thermal sensor element 106) is Δ be considered. V Δ =V TPA -V TPB =S(T hj -T cj1 )+(n-1)S(T hj -T cj2 )-(n-1)S(Thj -T cj1 )-S(T hj -T cj2 ) =-(n-2)S(T hj -T cj1 )+(n-2)S(T hj -T cj2 ) =(n-2)S(T hj -T cj2 -T hj +T cj1 ) =(n-2)S(T cj1 -T cj2 ) (1)

[0054] Among them, V TPA is the voltage measured between the first terminal 302 and the second terminal 318, V TPB is the voltage measured between the third terminal 324 and the fourth terminal 340, S is the difference between the Seebeck coefficients of the n-type polysilicon layer and the p-type polysilicon layer, T hj is the temperature at the hot junction Hj, T cj1 is the temperature of the first cold junction Cj1, T cj2 is the temperature at the second cold junction Cj2, and n is the number of thermocouples per beam.

[0055] As described above, the above calculation is used to calculate the voltage difference for each thermal sensor element of the pixel array. In this regard, and with reference to Figure 5 , for clarity and brevity of description, four exemplary thermal sensor elements will now be considered to illustrate the calculation of local temperature gradients in the x and y directions.

[0056] In this regard, the measurement circuit 122 calculates a first voltage difference V with respect to the first thermal sensor element 106 from the first cluster 104. Δ12 , with respect to the second voltage difference V of the fifth thermal sensor element or device 124 from the second cluster 114 △13 , with respect to a third voltage difference V of the sixth thermal sensor element or device 126 from the third cluster 118 △43 , and a fourth voltage difference V about the seventh thermal sensor element or device 130 from the fourth cluster 132 Δ42. The cold junctions of the first thermal sensor element 106 and the fifth thermal sensor element 124 adjacent to the first channel 116 are at the same temperature, and are therefore regarded as one cold junction, namely, the first cold junction Cj1. The cold junctions of the first thermal sensor element 106 and the seventh thermal sensor element 130 adjacent to the second channel 120 are at the same temperature, and can therefore also be regarded as one cold junction, namely, the second cold junction Cj2. The cold junctions of the fifth thermal sensor element 124 and the sixth thermal sensor element 126 adjacent to the second channel 120 are at the same temperature, and can therefore also be regarded as one cold junction, namely, the third cold junction Cj3. The cold junctions of the sixth thermal sensor element 126 and the seventh thermal sensor element 130 adjacent to the first channel 116 are at the same temperature, and can therefore also be regarded as one cold junction, namely, the fourth cold junction Cj4.

[0057] To calculate the temperature gradients in the x-direction and the y-direction with respect to the first cluster 104, the second cluster 114, the third cluster 118, and the fourth cluster 132, only the first voltage difference V Δ12 , the second voltage difference V Δ13 , and the fourth voltage difference V Δ42 The first voltage difference V Δ12 The second voltage difference V △13 is related to the temperature difference between the first cold junction Cj1 and the third cold junction Cj3, and the fourth voltage difference V △42 It is related to the temperature difference between the fourth cold junction Cj4 and the second cold junction Cj2.

[0058] As described above, the first voltage difference V between the first cold junction Cj1 and the second cold junction Cj2 Δ12 It is given by the following expression: V Δ12 =(n-2)S(T cj1 -T cj2 ) (1)

[0059] Similarly, the second voltage difference V between the first cold junction Cj1 and the third cold junction Cj3 is Δ13 Given by a similar equation: V Δ13 =(n-2)S(T cj1 -T cj3 ) (2)

[0060] In addition, a fourth voltage difference V between the fourth cold junction Cj4 and the second cold junction Cj2 is Δ42 Given by a similar equation: V Δ42 =(n-2)S(T cj4 -T cj2 ) (3)

[0061] Rearranging equation (1), it is possible to obtain an expression for the temperature difference between the first cold junction Cj1 and the second cold junction Cj2:

[0062] Similarly, rearranging equations (2) and (3), the expression for the temperature difference Cj3 between the first cold junction Cj1 and the third cold junction, and the expression for the temperature difference between the fourth cold junction Cj4 and the second cold junction Cj2 can be obtained respectively:

[0063] By calculating the temperature difference between the second cold junction Cj2 and the third cold junction Cj3, the temperature gradient in the x direction is calculated. is possible:

[0064] where Δx is the distance between adjacent clusters in the x-direction. To calculate the temperature gradient in the y-direction Similarly, the temperature difference between the first cold junction Cj1 and the fourth cold junction Cj4 is calculated:

[0065] Where Δy is the distance between adjacent clusters in the y direction. Calculation of the temperature gradient between clusters of thermal sensor elements in the x and y directions enables the overall temperature gradient over the pixel array to be calculated and stored.

[0066] The stored temperature gradients can be used for various applications, including offset temperature measurements by individual thermal sensor elements of the pixel array. Once a local temperature gradient map for a collection of clusters of thermal sensor elements has been generated, the measurement circuit 122 determines (step 416) whether further temperature gradients need to be measured, and if so, repeats the above steps (steps 406 to 414), otherwise the process stops.

[0067] refer to Figure 6 , and taking the measurement of the temperature of one or more objects in the scene as an example, the measurement circuit 122 measures (step 500) the local temperature gradient in the above manner before measuring the temperature of the object in the scene. Once the temperature gradient map has been generated, the measurement circuit 122 connects the first thermopile 300 in series to the second thermopile 320 by connecting the second terminal 318 to the third terminal 324 (step 502).

[0068] Thereafter, the measurement circuit 122 measures (step 504) the summed voltage V across the first terminal 302 and the fourth terminal 340. Σ With respect to the first thermal sensor element 106, the summed voltage VΣ The relationship with temperature is as follows: V ∑ =V TPA +V TPB =S(T hj -T cj1 )+(n-1)S(T hj -T cj2 )+(n-1)S(T hj -T cj1 )+S(T hj -T cj2 ) =nS(T hj -T cj1 )+nS(T hj -T cj2 ) =2nS(T hj -T cj ) (9)

[0069] Where T cj is the temperature of the first cold junction T cj1 The temperature of the second cold junction T cj2 The average between the summing voltage V ∑ , the measurement circuit 122 uses equation (9) to calculate (step 506) a temperature corresponding to the infrared electromagnetic radiation received by the first thermal sensor element 106. This process is also performed for the other thermal sensor elements in the plurality of thermal sensor elements 102.

[0070] Thereafter, the temperature measured by the first thermal sensor element 106 is compensated (step 508) by the local temperature gradient calculated with respect to the pixel cluster between which the first thermal sensor element 106 resides. For example, from the summed voltage V calculated according to equation (9) ∑ Subtract the first voltage difference V calculated according to equation (1) Δ12 A small part of.

[0071] Compensated temperature measurements are also calculated for other thermal sensor elements in the plurality of thermal sensor elements 102. If further temperature measurements of the thermal sensor array device 100 are required (step 510), the above process (steps 500 to 508) is repeated. Otherwise, the measurement process stops.

[0072] In addition to using the calculated local temperature gradient in the process of measuring temperature using the thermal sensor array device 100 "during an application," such as when measuring the temperature of one or more objects in a scene during use, measurements of the local temperature gradient may be performed as part of a calibration process for the thermal sensor array device 100 prior to use of the thermal sensor array device 100 for an application.

[0073] During operation, the measurement of the temperature gradient can be used to check for internal and external thermal influences that generate the temperature gradient. In the event that the source external to the thermal sensor array device 100 is too strong, in another example, a maximum temperature gradient can be set for the thermal sensor array device 100, and the thermal sensor array device 100 can be configured to provide a warning signal when the maximum temperature gradient is exceeded for one or more thermal sensor elements to indicate that the temperature measurement of the pixel array may be unreliable. Such monitoring of the temperature gradient can be performed at the start-up of the thermal sensor array device 100, or periodically during field use. In an example implementation, when adjacent thermal sensor elements (e.g., the first thermal sensor element 106, the second thermal sensor element 108, the fourth thermal sensor element 112, the fifth thermal sensor element 124, and / or the seventh thermal sensor element 130) measure a local gradient (such as a voltage difference) that exceeds a predetermined voltage difference or temperature gradient threshold set according to the compensation capability of the measurement circuit 122, the temperature measurement made using the thermal sensor array device 100 can be considered unreliable. In such cases, the warning signal may be provided using any suitable means, such as an audible alarm or a message such as presented on a display of a temperature measurement device including the thermal sensor array device 100 .

[0074] Although the above examples involve a particular layout of pixels, those skilled in the art will appreciate that each cluster may include any number of individual thermal sensor elements. Additionally, although each cluster in the above examples is generally rectangular in shape, the clusters may be shaped differently.

Claims

1. A thermal sensor element device, comprising: a substrate having a cavity formed therein; as well as an infrared absorbing film suspended above the cavity from a first beam and a second beam, the first beam being thermally coupled at one end thereof to the substrate at a first substrate cold junction and the second beam being thermally coupled at one end thereof to the substrate at a second substrate cold junction; as well as a plurality of thermocouples, wherein the plurality of thermocouples are arranged above the first beam, the second beam and the infrared absorbing film; wherein, The plurality of thermocouples are arranged as first and second thermopiles on the first and second beams and the infrared absorbing film; The first thermopile and the second thermopile are arranged on the infrared absorbing film to measure, in use, a sum of a first temperature difference between a cold junction of the first substrate and a hot junction on the infrared absorbing film and a second temperature difference between a cold junction of the second substrate and the hot junction on the infrared absorbing film; and The first thermopile is configured for selective series and anti-series connection to the second thermopile.

2. The device according to claim 1, wherein The infrared absorbing film includes heat junctions of the plurality of thermocouples.

3. A device as claimed in claim 1 or 2, wherein: Each of the first thermopile and the second thermopile is configured to measure, when in use, a sum of temperature differences about a first region of the infrared absorbing film and a second region of the infrared absorbing film, respectively.

4. The device according to claim 2, wherein The plurality of hot junctions and the plurality of cold junctions of the plurality of thermocouples are configured such that the first thermopile is provided between the plurality of hot junctions and the plurality of cold junctions; Another plurality of hot junctions and another plurality of cold junctions of the plurality of thermocouples are configured such that the second thermopile is provided between the plurality of hot junctions and the another plurality of cold junctions; At least one of the plurality of cold junctions is positioned at a first end of the first beam distal from the infrared absorbing film; and At least one of the other plurality of cold junctions is positioned at a second end of the second beam distal from the infrared absorbing film.

5. The device of claim 4, wherein: A sum of the first temperature difference and the second temperature difference is measured between the plurality of cold junctions and the plurality of hot junctions.

6. The device according to claim 1, wherein At least a portion of each of the heat junctions is configured to converge within a predetermined hot end region of the infrared absorbing film.

7. The device of claim 1, wherein: The first beam includes a narrow track portion extending toward the infrared absorbing film and integrally forming a portion of the infrared absorbing film; and The second beam includes a narrow track portion extending toward the infrared absorbing film and integrally forming another portion of the infrared absorbing film.

8. The device of claim 1, wherein: Adjacent thermocouples of the first thermopile are separated by a plurality of separation channels that are narrower than the thermocouples.

9. The device of claim 1, wherein: The plurality of thermocouples is an even number of thermocouples.

10. The device of claim 1, wherein: The first beam bridges the substrate and a first side of the infrared absorbing film; and The second beam bridges the substrate and a second side of the infrared absorbing film.

11. The device according to claim 4 or 5, wherein A first number of thermocouples between a hot junction of the first thermopile on the infrared absorbing film and at least one of the plurality of cold junctions of the first beam is greater than a second number of thermocouples between a hot junction of the first thermopile on the infrared absorbing film and at least one of the other plurality of cold junctions of the second beam.

12. The device of claim 1, wherein: A first number of thermocouples of the second thermopile between the hot junction on the infrared absorbing film and at least one of the other several cold junctions of the second beam is greater than a second number of thermocouples of the second thermopile between the hot junction on the infrared absorbing film and at least one of the several cold junctions of the first beam. 13 . A thermal sensor array device, comprising the thermal sensor element device according to claim 1 .

14. A method of measuring a temperature gradient over a thermal sensor device of an array of thermal sensor devices, the method comprising: Providing an array of thermal sensor devices, the array of thermal sensor devices comprising the thermal sensor device according to claim 1; receiving infrared electromagnetic radiation incident on the thermal sensor device; connecting the first thermopile in anti-series to the second thermopile; measuring a difference in the received infrared electromagnetic radiation, said difference constituting said temperature gradient; as well as The measured temperature gradient is stored.

15. A method for measuring temperature, the method comprising: Measuring the temperature gradient as claimed in claim 14; connecting the first thermopile in series to the second thermopile; Measuring the total value of received infrared electromagnetic radiation; as well as The temperature is calculated by compensating the sum value using the temperature gradient.

Images