JP2006058228A - Multi-element thermopile module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in a combination of a multi-element thermopile module and a plano-convex single lens that produces unevenness and blurring due to detection area in association with the focal distance, that focusing is difficult when using the plano-convex single lens, that a heat sink or the like is required in temperature detection for an abrupt temperature change, and that there is requirement for increasing the accuracy of detected temperature. <P>SOLUTION: Each element light-receiving section is placed at a distance deviation averaged position, with respect to each light-receiving section from a focal point of the plano-convex lens. A antireflection part and an aperture function are provided. The window shape has the same curvature as the plano-convex lens. Thermistors, having the same B constant and resistance, are mounted inside and outside the thermopile. In the multi-element thermopile chip, the circumference of the element is provided with heat insulation with a heat sink. A temperature calculation correction technique is provided to select by target detected temperature accuracy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multi-element thermopile module that detects the temperature of an object having infrared rays.

  In general, a multi-element type thermopile module composed of a multi-element thermopile sensor, an operational amplifier, a multiplexer, a memory, a resistor, a capacitor, a microcomputer, and the like uses an optical system (lens, mirror, etc.) to create a detection area. The focal length is indispensable for the optical system. The focal length can be arbitrarily set in the optical design. When this optical system is actually combined with a multi-element light-receiving element and a plano-convex single lens, a light-receiving part whose focal lengths do not match is generated due to the arrangement of the light-receiving parts of the multi-element light-receiving element.

  As a result, in the detection area projected from the multi-element type thermopile module, the area is clearly projected in the projection area where the focal length is the same, and the blurred area is projected in the projection area where the focal length is not the same. An unbalanced phenomenon that was said to have occurred.

When measuring temperature using these multi-element type thermopile modules, the temperature of an object is measured by self-temperature correction of the thermistor provided with the electromotive force of the thermopile in the thermopile sensor. However, when the temperature environment in which the multi-element type thermopile module is used changes suddenly, there is a difference between the thermopile thermal time constant and the thermistor thermal time constant. In order to prevent these problems, the temperature measurement accuracy at the time of sudden environmental temperature change was maintained by using a technique for increasing the heat capacity with a heat sink or a technique technique for intentionally delaying the temperature follow-up, which is provided with an air insulation layer.
Japanese Patent Application No. 2004-1387

Regarding the combination of a multi-element type thermopile module and a plano-convex single lens, it is difficult to match all the focal lengths of the multi-element light receiving unit because the plano-convex single lens that is the optical system has a single curvature and a single focal point. In the conventional method, the focal length of the central portion of the element coincides, but the farther away from the central portion of the element, the more the focal length shifts and defocuses, resulting in non-uniform detection area. The area was blurred.
In order to eliminate the focal length mismatch, it is necessary to limit the visual field of the optical system with a compound eye. As a result, difficulty in optical design, an increase in cost, and a decrease in yield due to the directionality between the compound-eye optical system and the multi-element light receiving unit become problems.
In addition, when using a plano-convex single lens, the curved side of the plano-convex single lens is exposed from the can window part, but since the top surface of the can is flat, the plano-convex single lens is formed by the end face of the window inside the can. Therefore, it is difficult to suppress the inclination of the plano-convex single lens.
Further, in the temperature measurement accuracy at the time of a sudden temperature change, a method of providing a heat sink as shown in FIG. 22 is often used in order to intentionally delay the temperature tracking of the thermopile portion. This is to increase the heat capacity of the thermopile itself by providing a heat sink so that it is not affected by changes in environmental temperature. As another method, there is also a method of providing an air insulation layer around the thermopile, but both of the above have space restrictions for providing a heat sink and an air insulation layer. It was an issue.
Further, the temperature calculation from the thermopile output and the thermistor output is carried out by an ASIC or the like, but recently there are many demands for further improvement in detection temperature accuracy.

In order to solve the problem of the unbalance of the projected detection area definition for each element, the present invention receives light from each element so that the average position of the distance from the focal position of the plano-convex single lens to the distance from each light receiving unit becomes equal. The portion is arranged and does not deviate from the normal focal length.
Moreover, in order to suppress infrared reflection of the inner wall of the thermopile itself, the inner wall of the can is subjected to an antireflection treatment.
In addition, in order to prevent reflection inside the can of infrared light incident through the plano-convex single lens, and to make the infrared light incident on the thermopile element into a linear light, the anti-reflection treatment part located between the plano-convex single lens and the thermopile element. It is characterized by having an aperture function.
Also, when installing and aligning a plano-convex single lens on a can, the shape of the can window is the same curvature shape and size as the plano-convex single lens, increasing the holding position accuracy of the plano-convex single lens and focusing position accuracy Is characterized by high accuracy.
Also, in the case of a sudden temperature change, the self-temperature correction thermistor mounted inside the thermopile cannot follow the temperature change depending on the conditions, so it is the same as the self-temperature correction thermistor mounted outside the thermopile. A thermistor with B constant and resistance value is mounted.
In addition, the structure of the multi-element thermopile chip is designed to follow the same temperature as the thermistor inside the thermopile by thermally insulating the periphery of the element with a heat sink so that each element is not affected by heat and conduction from other elements. It is characterized by improved temperature detection performance.
Also, in order to further improve the detection temperature accuracy in addition to the normal temperature calculation, two or more programs with different detection temperature calculation correction methods (formulas) are provided in advance in the detection temperature calculation microcomputer. It is characterized by selecting according to accuracy.

The present invention provides a plano-convex single lens when combining an optical system of a multi-element thermopile module composed of a general multi-element thermopile, an operational amplifier, a multiplexer, a memory, a resistor, a capacitor, a microcomputer, and the like with a plano-convex single lens. Each element light receiving unit is arranged at an average position of the distance from the focal point of the lens to each light receiving unit, and the projected area definition for each element can be made equal by not deviating from the normal focal length. .
Further, by combining the inner wall of the can with an antireflection treatment and an aperture function, reflection inside the can can be suppressed.
Further, by making the can window portion have the same curvature shape and size as the plano-convex single lens, it is possible to improve the holding position accuracy of the plano-convex single lens and to adjust the focal position with high accuracy.
In addition to the inside of the thermopile, the thermistor with the same B constant and resistance value as the inside of the thermopile is mounted outside the thermopile to prevent the detection deviation of the detected temperature against the abrupt temperature change. Things are possible.
In addition, by thermally insulating the structure of the multi-element thermopile chip for each element with a heat sink, it is possible to follow the same temperature as a thermistor placed on the same stem, which was the cause of detection temperature deviation. , Thermopile cold junction and thermistor temperature tracking can be made the same and temperature measurement accuracy can be improved.
In addition to the normal temperature calculation, two or more programs with different detection temperature calculation correction methods (formulas) are provided in advance in the detection temperature calculation microcomputer, and can be selected according to the actual use purpose detection temperature accuracy. The detection temperature accuracy can be improved.

The present invention has realized a multi-element type thermopile module that does not complicate the optical system, and does not cause an increase in cost and a decrease in yield, and can achieve the same level of projection area definition for each element.
Further, by providing the inner wall of the can with an antireflection treatment or an antireflection polycarbonate part, it was possible to suppress infrared reflection inside the can. Furthermore, infrared reflection was able to be suppressed more by providing an aperture function.
In addition, by making the can window part the same curvature shape and size as the plano-convex single lens, the joint between the can and the plano-convex single lens is just fit, and the holding position accuracy of the plano-convex single lens is improved, and the focus is high. I was able to adjust the position.
In addition to the inside of the thermopile, even when there is a sudden temperature change, the same B constant, resistance thermistor and peripheral circuit as the inside of the thermopile are added, and the manufacturing method of the multi-element thermopile chip is changed. Improved temperature measurement performance.
In addition to the normal temperature calculation, two or more programs with different detection temperature calculation correction methods (formulas) are provided in advance in the detection temperature calculation microcomputer, and can be selected according to the actual use purpose detection temperature accuracy. Improved detection temperature accuracy.

  FIG. 1 is a configuration diagram of a multi-element thermopile module on which a multi-element thermopile sensor, an operational amplifier, a multiplexer, a memory, a resistor, a capacitor, a microcomputer, etc. of the present invention are mounted. FIG. The distance relationship with a lens focus position is shown. The multi-view type light receiving element in FIG. 2 is a matrix array type having a total of 16 elements of 4 × 4 in length, and a planoconvex single lens using a silicon base substrate (focal length f = 1). .95) was used.

  The embodiment of the present invention will be specifically described below with reference to FIG.

  The multi-element type thermopile module of the present invention is different from the conventional multi-element type thermopile module because when there is a combination of a conventional multi-element type thermopile module and a plano-convex single lens, there is only one focal position. The focal length is adjusted with reference to the light receiving elements 2 and 3 in FIG. FIG. 3 shows a distance relationship between the conventional multi-element light receiving unit and the plano-convex single lens focal position. The distance relationship between the light-receiving elements 1, 2, 3, and 4 and the plano-convex single lens focal point position is as follows: light-receiving element 1 = light-receiving element 4> light-receiving element 2 = light-receiving element 3. As the light receiving elements 1 and 4 are projected out of the focal distance, the detection area is defocused and the detection area is blurred. The actual area was expanding.

  On the other hand, in the present invention, as shown in FIG. Place a single lens. In this way, the detection area is deliberately blurred by detecting the focal point of the plano-convex single lens by aligning the focal position of the plano-convex single lens with the average position deviation of the distance between the original plano-convex single lens and each multi-element light receiving unit. The area is made uniform.

  Comparison verification of visual field characteristics in the multi-element type thermopile module and the conventional multi-element type thermopile module in which the plano-convex single lens in the present invention thus configured and the focal position are intentionally set at the deviation average position Went.

  As a verification condition, an amplification circuit with a small heat source of 60 ° C. and an amplification factor of 1000 times is prepared, and measurement is performed by moving the small heat source at a small heat source moving pitch of 10 mm at a distance of 200 mm between the small heat source and the multi-element thermopile module. went. The results are shown in FIG. 4 for the multi-element thermopile module of the present invention and in FIG. 5 for the conventional multi-element thermopile module.

From this result, it was confirmed that the multi-element type thermopile module of the present invention has the same level of projected area definition for each projected element as compared with the conventional multi-element type thermopile module.
4 and 5 plot the results of the 16 matrix light receiving elements 1 to 4, but the remaining light receiving elements 5 to 16 have the same effect.

  This time, the test was conducted with a 16 matrix array type thermopile, but it is possible to give the same performance to a thermopile of a matrix type, a staggered type, an in-line type, etc. having two or more elements. is there.

  In FIG. 6, the infrared stray light transmitted from the plano-convex single lens to the inside of the can of the thermopile sensor of the above embodiment is transmitted through the can through the infrared reflected from the inner wall of the can and the ambient temperature change around the thermopile sensor. An example in which an antireflection treatment is performed to suppress secondary radiant infrared heat will be described. In the antireflection treatment of the embodiment shown in FIG. 6, a cylinder made of polycarbonate was press-fitted into the inner wall of the thermopile sensor. The tube was black. A multi-element type thermopile module equipped with this black cylinder was verified in the same manner as described above. The result is shown in FIG. The detection area projected by the thermopile sensor of the present invention having a black cylinder became sharper and sharper than the thermopile sensor having no black cylinder on the inner wall of the can. In particular, it can be seen that there is almost no output due to heat detection outside the detection area of the design.

  In addition, this black cylinder was made into an aperture shape. As shown in FIG. The aperture shape was the same or smaller aperture diameter than the condensing optical path trajectory of the plano-convex single lens and the thermopile light receiving element. Further, only one aperture position is provided at an intermediate distance of the focal length of the plano-convex single lens. This black cylinder was provided on the inner wall of the thermopile sensor in the same manner as described above, and the same verification was performed. The result of verification similar to the above is shown in FIG. Sharper and clearer than the normal black tube.

From this result, it was confirmed that the detection area was formed more clearly in the multi-element type thermopile module of the present invention in which reflection of infrared rays inside the can was suppressed.
In addition, the above is the result at the focal length f = 1.95 of the plano-convex single lens. In addition, the plano-convex single lens is prepared at a 0.5 mm interval from the focal length f = 1.0 to 6.0. The same verification was performed. As a result, the same effect as that at f = 1.95 was obtained.

FIG. 10 is a can shape diagram in which the can window portion of the thermopile sensor of the present invention is processed into the same curvature shape as a plano-convex single lens. The can window portion shape of the present invention can be bonded to the curvature shape of a plano-convex single lens so as to be just-fit bonded to the conventional can window portion shape of FIG. As a result, it was possible to suppress the inclination and positional deviation of the plano-convex single lens and create a regular focal length. The result is shown in FIG. The data in FIG. 12 shows the maximum and minimum values by measuring the distance from the flat surface of the plano-convex single lens at four points up, down, left, and right from the can collar. From this result, the can of the present invention produced using a can having the same curvature shape as the plano-convex single lens curvature shape of the can window portion of the present invention compared to the conventional can window shape is more flat. It was confirmed that the convex single lens has little tilt. As a result, it was possible to improve the accuracy of the focal length of the plano-convex single lens.
Moreover, the same effect was acquired also in the can shape shown in FIG.

  FIG. 14 is a circuit diagram in which a thermistor is mounted inside and outside the thermopile sensor of the present invention, and FIG. 15 is a schematic configuration diagram. The wiring pattern on the wiring board and the mounting electronic component in FIG. 14 are omitted because the figure becomes complicated. The internal thermistor and the external thermistor are thermistors having the same B constant and resistance value electrical performance. Using the multi-element type thermopile module of these configurations, the detection temperature performance when a sudden temperature change occurred was verified. As verification conditions, the target temperature and the temperature measurement performance were confirmed under the conditions of an environmental temperature of 0 to 20 degrees and a maximum temperature change gradient of 10 ° C./min. The heat source serving as the target temperature in this case showed almost the same temperature change as the environmental temperature, and the temperature of the temperature measurement target surface was monitored with a thermocouple. The verification result is shown in FIG. As the thermopile, a 16 matrix array type was used, but in FIG. Only 6 outputs were plotted. From this result, it can be seen that the external thermistor shows a tracking that approximates the temperature change of the target temperature (environment temperature) thermocouple with respect to the internal thermistor. FIG. 17 shows the result of expressing the result of FIG. 16 in the non-contact temperature measurement calculated from the thermopile module. The temperature measurement was calculated in three ways: one that quoted only the internal thermistor value, one that cited only the external thermistor value, and one that summed the internal and external thermistor values and quoted the value divided by 2.

From this result, it was found that, in the usage environment where the verification condition of the rapid temperature change of this time can occur, the quote calculation of (internal thermistor value + external thermistor value) / 2 can perform the most accurate temperature measurement. However, the usage environment varies depending on the environment in which the multi-element thermopile module is actually used, its application, the module cover, and the like. For the quotation of these internal thermistor values only, external thermistor values only, (internal thermistor value + external thermistor value) / 2, the best combination can be selected according to actual use conditions.
Further, the present invention can obtain the same effect even if the thermopile is not a multi-element but a single element.

  FIG. 18 shows a thermopile element using a method of thermally insulating each element with a heat sink and an internal configuration diagram in the multi-element thermopile of the present invention. FIG. 19 shows a thermopile element in a conventional multi-element thermopile and an internal configuration diagram. In the figure, a multiplexer is originally mounted, and wire bonding is performed to each terminal, etc., but it is omitted because the figure becomes complicated.

  The difference between the multi-element thermopile of the present invention and the conventional multi-element thermopile lies in the thermopile chip inside the multi-element thermopile. In the conventional thermopile chip, the surface (111) is exposed by anisotropic wet etching, and the heat sink is formed with an oblique angle. When the number of elements is increased, a gap between adjacent elements is narrow, so that a heat sink cannot be provided for each element. Therefore, when infrared rays are incident on the element light receiving unit, heat is received from other adjacent element light receiving units, and an excessive signal is output.

On the other hand, the multi-element thermopile of the present invention can form a vertical heat sink around each element light receiving portion by adopting plasma etching.
As shown in FIG. 18, each light receiving element is thermally insulated by a heat sink, so that the thermopile element is mounted on the same stem as the thermistor, and the cold junction of the thermopile element can follow the same temperature as the thermistor. is there.

FIG. 20 shows detected temperature performance data of a thermopile module equipped with the multi-element thermopile of the present invention. The verification conditions are omitted because they are the same as those in the third embodiment. The thermistor value used was quoted from the thermistor mounted inside the thermopile.
As a result, it was confirmed that the multi-element thermopile of the present invention followed the rapid environmental temperature change compared to the conventional multi-element thermopile.

FIG. 21 shows a block diagram of a multi-element type thermopile module equipped with a microcomputer for detecting temperature calculation of the present invention.
A detection temperature correction method (formula) is provided in advance in the detection temperature calculation microcomputer, and selection is performed according to the actual use purpose detection temperature accuracy.
In the multi-element type thermopile module, data of four points of heat sources a, b, c, d set at different temperatures are collected and stored as data a1, b1, c1, d1. Based on the four-point data of a1, b1, c1, and d1, the detection temperature calculation correction method (formula) is calculated.

The concept of detected temperature correction for the four methods (formulas) will be described below.
(1) Formula Based on the four-point data of a1, b1, c1, and d1 that detected heat sources set at different temperatures, a primary approximation formula was created in the microcomputer, and the detected temperature data that actually detected the object To correct.
(2) Formula Based on the four-point data of a1, b1, c1, and d1 that detected heat sources set at different temperatures, a quadratic approximate expression was created in the microcomputer, and the detected temperature at which the target was actually detected Correct the data.
(3) Formula Based on the four-point data of a1, b1, c1, and d1 that detected heat sources set at different temperatures, (A) Create a first-order approximation formula from the two-point data of a1 and b1, b1, c1 When (B) primary approximation formula is created from the two points of data, and (C) primary approximation formula is created from the two points data of c1 and d1, and three formulas are created in the microcomputer, and the target is actually detected If the detected temperature is less than or equal to b1, apply formula (A), if the detected temperature is between b1 and c1, apply formula (B), and if the detected temperature is greater than or equal to c1, apply formula (C). Perform temperature correction.
(4) Formula Create a first-order approximation formula from the two-point data of a1, d1, based on the four-point data of a1, b1, c1, d1 that detected the heat sources set at different temperatures, and actually detect the object The detected temperature data is corrected.
The detection temperature accuracy can be improved by selecting, setting and using the best matching method (formula) according to the actual use purpose detection temperature accuracy.
This time, the calculation is performed by the multi-element type thermopile module. However, the same effect can be obtained in the single-element type thermopile module.

It is a block diagram of the multi-element type thermopile module by this invention. It is a distance relation figure of the multi-element light-receiving part by the present invention and the plano-convex single lens focal position. It is a distance relationship figure of the conventional multi-element light-receiving part and a plano-convex single lens focal position. It is a visual field characteristic data of the multi-element type thermopile module of this invention. There is visual field characteristic data of a conventional multi-element type thermopile module. It is an internal structure figure of the multi-element type thermopile module of this invention which comprised the cylinder made from a polycarbonate for reflection prevention. It is a visual field characteristic data of the multi-element type thermopile module of this invention which comprised the cylinder made from polycarbonate for reflection prevention. It is an internal structure figure of the multi-element type thermopile module of this invention which made the cylinder made from a polycarbonate for reflection prevention aperture shape. It is a visual field characteristic data of the multi-element type thermopile module of this invention which made the cylinder made from a polycarbonate for reflection prevention aperture shape. It is a can shape figure which processed the can window part of the present invention into the same curvature shape as a plano-convex single lens. It is a conventional can shape diagram. This is lens tilt data when a plano-convex single lens is arranged in the present invention and a conventional can shape. It is a can shape figure which processed the can shape of the present invention into the same curvature shape as a plano-convex single lens. It is a circuit diagram at the time of mounting the thermistor inside and outside the thermopile of the present invention. It is a schematic block diagram at the time of mounting the thermistor inside the thermopile of this invention, and the exterior. It is the detection temperature performance data of the internal thermistor of this invention, and an external thermistor. Non-contact temperature measurement data calculated by quoting the thermistors of the present invention, the thermistor of the present invention, and the thermistors of (internal thermistor + external thermistor) / 2. FIG. 4 is a diagram showing a thermopile element using a method of thermally insulating each element with a heat sink in the multi-element thermopile of the present invention, and an internal configuration diagram. It is the thermopile element in the conventional multi-element thermopile, and an internal block diagram. It is the detection temperature data at the time of the rapid environmental temperature change of the thermopile module which mounts the thermopile multi-element using the method of thermally insulating each element of this invention with a heat sink. It is a schematic block diagram of the multi-element type thermopile module which mounts the microcomputer of this invention. It is an external view of the thermopile module provided with the conventional heat sink.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermopile sensor 2 Wiring board 3a, 3b Circuit configuration electronic component 4 Can 5 Plano-convex single lens 6 Focal position 7 Focal length locus 8 Multi-element thermopile chip 9 Stem 10 Anti-reflection black tube 11 Aperture-shaped anti-reflection black tube 12 A can 13 having a window processed into a curvature similar to a plano-convex single lens 14 A can processed into a curvature similar to a plano-convex single lens 14 Internal thermistor 15 External thermistor 16 Multiplexer 17 Element thermopile chip 18 Operational amplifier 19 Microcomputer 20 Heat sink 21 Connector terminal

Claims (7)

  When combining the optical system of a multi-element type thermopile module with a plano-convex single lens, each element light-receiving unit is disposed at an average position of the distance from the focal point of the plano-convex single lens to each light-receiving unit. A multi-element type thermopile module characterized in that the projected area definition of each element can be made to the same level by not deviating from the focal length.   The multi-element type thermopile according to claim 1, wherein the inner wall of the can of the thermopile sensor itself is subjected to an antireflection treatment to prevent reflection of the infrared can inside the thermopile sensor through a plano-convex single lens. module.   The anti-reflective processing part is provided with an aperture function in order to prevent reflection inside the can of infrared light incident through the plano-convex single lens and to make the infrared light incident on the thermopile element into linear light. The multi-element type thermopile module according to claim 1 or 2.   The shape of the thermopile sensor can window that is joined and held with a plano-convex single lens, and the size is the same as that of the plano-convex single lens. The multi-element type thermopile module according to any one of claims 1 to 3, wherein the multi-element type thermopile module has high accuracy.   5. A thermistor for self-temperature correction of a multi-element type thermopile module, wherein the thermistor having the same B constant and resistance value is mounted inside and outside the can of the thermopile sensor itself. The multi-element type thermopile module described in any one of the above.   6. The temperature detection performance in a sudden temperature change is improved by thermally insulating each element with a heat sink in a multi-element thermopile chip. The multi-element type thermopile module described in 1.   Two or more programs with different detection temperature calculation correction methods (formulas) are pre-installed in the detection temperature calculation microcomputer mounted on the multi-element thermopile module, and selected according to the actual use purpose detection temperature accuracy. The multi-element type thermopile module described in any one of Claims 1-6.

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