JPH07181082A - Infrared detector - Google Patents

Abstract

PURPOSE:To detect failure of an infrared detector itself conveniently. CONSTITUTION:An infrared radiator 29 is disposed beneath the cold contact 28 of a thermocouple 25 constituting a thermopile through an interlayer isolation film thus coupling the thermocouple 25 and the infrared radiator 29 thermally. A self-diagnostic circuit 33 applies a voltage to the infrared radiator 29 at a predetermined interval or timing. Thermoelectromotive force of the thermocouple 25 is then detected and a decision is made whether the thermocouple 25 functions or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector for measuring infrared rays using a thermal type element.

[0002]

2. Description of the Related Art In the known infrared detecting device,
There are roughly classified into those using a quantum type element and those using a thermal type element. Among them, as an infrared detection device using a thermal type element that does not require cooling unlike a quantum type element, a thermocouple or a resistor is used. A thermopile and a bolometer using each of them have been put to practical use.

10 and 11 are views showing examples of conventional thermopiles and bolometers, respectively (see FIG. 10, "Infrared Optics", Infrared Technology Research Group, p.131).

FIG. 10 is a plan view showing the structure of the thermopile. In the figure, in a thermopile 1, for example, a plurality of thermocouples 3 are radially arranged on a silicon substrate 2, and by connecting the thermocouples 3 in series, hot junctions 4 and The cold junction 5 is formed, and the infrared absorbing film 6 is formed on the hot junction 4. When infrared rays are guided onto the infrared absorption film 6,
The infrared absorption film 6 absorbs infrared rays and the temperature of the hot junction 4 rises, whereby the thermoelectromotive force generated in the thermocouple 3 connected in series is detected through the lead wire 7 and incident on the infrared absorption film 6. Detect the amount of infrared rays.

FIG. 11 is a sectional view showing the structure of a bolometer. In the figure, a bolometer 8 is provided with a resistor 10 arranged on a substrate 9, and infrared rays are incident on this resistor 10 to detect its resistance value via a lead wire 7. Resistor 1
0 is formed of a substance whose resistance value changes according to temperature, such as a thermistor, and the amount of infrared rays incident on the resistor 10 can be detected by detecting the change of the resistance value of the resistor 10.

[0006]

However, in the above-mentioned conventional infrared detecting device, infrared rays are not incident not only when the lead wire 7, the thermocouple 3, and the resistor 10 are abnormal such as disconnection. In that case, there is a characteristic that the output value does not change. Therefore, in the conventional infrared detection device, it is difficult to determine whether the output value cannot be obtained due to an abnormality such as disconnection, or whether the infrared detection device is not irradiated with infrared light, and the failure of the device itself can be simplified. There was a problem that it could not be judged.

An object of the present invention is to propose an infrared detecting device capable of easily detecting a failure of the device itself.

[0008]

The present invention will be described with reference to FIGS. 1, 3, and 9. The invention of claim 1 is a thermal type element 25 whose output voltage changes according to the intensity of incident infrared rays. An infrared radiator 29 that is thermally coupled to the thermal element 25 by being provided via the thermal element 25 and the insulating film 26, and emits infrared rays in accordance with the applied voltage;
By applying a voltage to the infrared radiator 29 and detecting an output voltage from the thermal element 25, the infrared detecting device 20 including a self-diagnosis means 33 for diagnosing whether or not the thermal element 25 operates. The above-mentioned purpose is achieved.

Further, in the invention of claim 2, the thermal type element 52 whose output voltage changes according to the intensity of the infrared rays incident through the transparent member 54 and the transparent member 54, which is installed in accordance with the applied voltage. Whether the thermal element 52 operates by detecting the output voltage from the thermal element 52 while applying a voltage to the infrared radiator 55, which is a substantially transparent member that emits infrared rays, and the infrared radiator 55. The above-described object is achieved by the infrared detection device 50 including a self-diagnosis means for diagnosing.

[0010]

[Action]

-Claim 1-By applying a voltage to the infrared emitter 29 thermally coupled to the thermal element 25 through the insulator 26 and detecting the output voltage from the thermal element 25, the self-diagnosis means 33.
In, it is possible to determine whether or not the thermal device 25 operates, and thus it is possible to determine whether or not infrared rays can be detected.

-Claim 2-Infrared rays obtained by applying a voltage to the infrared radiator 55 are made incident on the thermal type element 52 and the output voltage of the thermal type element 52 is detected. It can be determined whether the mold element 52 is operable, and thus whether infrared radiation can be detected.

Incidentally, in the section of means and action for solving the above problems for explaining the constitution of the present invention, the drawings of the embodiments are used for the purpose of making the present invention easy to understand. It is not limited to.

[0013]

【Example】

First Embodiment FIG. 1 is a plan view showing the configuration of the first embodiment of the infrared detection device according to the present invention, and FIGS. 2 and 3 are sectional views thereof. The infrared detector of the present embodiment detects the amount of infrared rays by a thermopile provided with a plurality of thermocouples.

In the figure, the infrared detecting element 20 is constructed so that the infrared rays incident on the element 20 can be detected by connecting the output terminals 21 and 22 to a predetermined measuring circuit, and further through an alarm output terminal 23. An alarm signal is output to notify that the infrared detecting element 20 has an abnormality.

Explaining the configuration in detail, two types of metal thin films, polysilicon, etc. are formed on a silicon substrate 24 to form two sets of thermocouples 25 on the substrate 25, and both ends of each thermocouple 25 are formed. Each of the hot junctions 27 is a conductor.
By forming the cold junction 28 and the cold junction 28, these two sets of thermocouples 25 are connected in series. Two thermocouples 25
The voltage between both ends of is output to the outside by the output terminals 21 and 22.

Reference numeral 29 denotes an infrared radiator, which is made of a material that emits infrared rays by itself generating heat by Joule heat, and is made of, for example, polysilicon or aluminum. In this embodiment, as shown in FIG. 3, the thermocouple 25 and the infrared radiator 29 are both the silicon substrate 2
4 is directly formed on the thermocouple 25. The cold junction 28 extends from the upper part of the thermocouple 25 toward the infrared radiator 29, and is formed so as to cover the infrared radiator 29 through the interlayer insulating film 26. ing.

Reference numeral 31 is an infrared absorbing film, which is an interlayer insulating film 3
It is formed so as to cover the upper side of the hot junction 27 of the thermocouple 25 via 0. Infrared rays to be measured are introduced into the infrared absorption film 31 by introducing means (not shown).

On the silicon substrate 24, a cavity 32 is formed on the back surface of the formation position of the hot junction 27 by a technique such as anisotropic etching. In the cavity 32, heat from the infrared absorption film 31 is applied to the silicon substrate 24. A heat separation region that thermally separates the hot contacts 27 and the cold contacts 28 from each other is configured so as to be less likely to be conducted to the whole, more specifically, the portion where the cold contacts 28 are formed.

Reference numeral 33 is a self-diagnosis circuit equipped with, for example, a microcomputer. To the self-diagnosis circuit 33, both ends of two sets of thermocouples 25 connected in series and both ends of an infrared radiator 29 are connected. . Self-diagnosis circuit 3
3 indicates whether or not infrared rays can be correctly detected by executing a predetermined self-diagnosis processing procedure to energize the infrared radiator 29 and detect the thermoelectromotive force of the thermocouple 25 at the time of power-on and operation. Judgment is made and an alarm signal is output from the alarm output terminal 23 if necessary (details will be described later).

Next, the operation of this embodiment will be described with reference to the flow charts of FIGS. 4 and 5 and FIGS. 4 and 5 are flowcharts showing the operation of the self-diagnosis circuit 33 at power-on and measurement, respectively.

The self-diagnosis circuit 33 includes an infrared detecting element 20.
When the entire power is turned on, execution of the program shown in the flowchart of FIG. 4 is started. First, in step S1, the infrared radiator 29 is energized to heat the infrared radiator 29, thereby starting the heating of the cold junction 28. The infrared rays from the infrared radiator 29 are preferably stronger than the infrared rays incident on the infrared absorption film 31 in order to shorten the determination time. Then, in step S2, the thermocouple 25 which is the detection element is used.
The output of is detected and it is determined whether or not the correct output is obtained.

If the thermocouple 25 can detect infrared rays correctly, the infrared radiator 29 heats the cold junction 28 side, and the hot junction 27 is thermally separated from the cold junction 28 by the heat separation area 32. The cold junction 28
Only the temperature on the side rises. Therefore, the thermoelectromotive force of the opposite polarity to the case where infrared rays are detected by the thermocouple 25 is generated by the thermocouple 2.
5, the self-diagnosis circuit 33 can detect the thermoelectromotive force of the opposite polarity to determine whether or not the thermocouple 25 can correctly detect infrared rays.

If step S2 is denied, the program proceeds to step S3 to output an abnormal alarm signal from the alarm output terminal 23, and then proceeds to step S4 to stop energization of the infrared radiator 29 and end the operation. To do. Step S3
When the output value is smaller than a predetermined prescribed value, the self-diagnosis circuit 33 judges that the connection of the lead wire, the thermocouple 25, etc. is defective, and outputs an alarm signal, while the output value is 0. At this time, it is determined that the thermocouple 25 or the like is broken, and an alarm signal is output. On the other hand, if step S2 is positive, the program proceeds to step S4 to stop energization of the infrared radiator 29 and end the self-diagnosis operation.

In this way, when the infrared rays are incident on the infrared absorption film 31 when no abnormality is detected when the power is turned on, the infrared absorption film 31 is heated by the infrared rays, and the heat of the infrared absorption film 31 is applied to the hot junction 27. Conduct to. Here, since the heat separation area 32 is formed on the back surface of the hot junction 27 to thermally separate the hot junction 27 and the cold junction 28, the heat of the infrared absorption film 31 is hardly conducted to the cold junction. , The temperature of the hot junction 27 rises with respect to the cold junction 28.
As a result, a thermoelectromotive force is generated in the thermocouple 25, and this thermoelectromotive force is taken out through the output terminals 21 and 22 to detect the infrared intensity.

During normal operation, the self-diagnosis circuit 33
Executes the program shown in the flowchart of FIG. 5 in a constant cycle to detect an abnormality. First, in step S5, it is determined whether or not the output value of the thermocouple 25, which is the detection element, is 0. If the determination is negative, the processing procedure is ended. On the other hand, if step S5 is positive, step S5
After incrementing the time counter included in the self-diagnosis circuit 33 at 6, it is determined at step S7 whether or not the count value of the time counter exceeds a predetermined value. And
If the determination is negative, the processing procedure is ended, and if the determination is affirmative, the processing procedure similar to the flowchart of FIG. 4 is executed in step S8. In step S8, it is determined whether or not the output value of the thermocouple 25 is equal to or greater than a predetermined number of times 0 during the period that is set back from the current time by the set time set in the clock counter. If it is, it is possible that some abnormality has occurred, so step S
Moving to 8, it is determined whether or not there is an abnormality.

Therefore, according to this embodiment, the cold junction 28 is heated by the infrared radiator 29 and the thermoelectromotive force from the thermocouple 25 is detected to detect the presence or absence of abnormality of the thermocouple 25 or the like. Since this is done, it is possible to easily detect a failure in the device itself, such as an abnormality in the thermocouple 25. Further, this abnormality detection is executed as needed during normal operation in addition to power-on, so an alarm can be issued in response to an abnormality that occurred during use, and usability can be improved accordingly. .

Further, by arranging the infrared radiator 29 on the cold junction 28 side and heating the cold junction 28, the infrared detecting element 20 having high characteristics and reliability can be formed. That is, since the thermal isolation region 32 is formed on the substrate 24 near the hot junction 27, the mechanical strength of the substrate is weaker than that of the other portions. It is preferable to form the heat separation region 32.
In addition, in order to obtain a large thermoelectromotive force and efficiently conduct the heat of the infrared absorption film 31, it is necessary to arrange a large number of thermocouples 25 in the heat separation region 32 in close proximity to each other. Therefore, if an element other than the thermocouple 25, that is, the infrared radiator 29 is formed in the heat separation region 32, the characteristics and reliability of the infrared detection device 20 may be deteriorated by that amount, but the substrate on the cold junction 28 side. 24 does not have such a restriction, the infrared radiator 29 can be arranged and the abnormality of the detection device 20 can be detected without lowering the characteristics and reliability.

The disconnection failure of the thermocouple 25 is often caused by the destruction of the thin film in the heat separation area 32, and the infrared radiator 2 formed avoiding the heat separation area 32.
Since the reliability of 9 is sufficiently higher than that of the thermocouple 25, the possibility that the infrared radiator 29 does not operate normally is sufficiently low.

Further, in this embodiment, since the cold junction 28 covers the upper side of the infrared radiator 29, the cold junction 28 and the infrared radiator 29 are thermally heated via the relatively thin interlayer insulating film 26. Can be combined, which allows
The cold junction 28 can be efficiently heated, and the presence / absence of abnormality can be determined in that short time. Further, the power required for heating can be reduced. In particular, the thickness of the interlayer insulating film 26 is about 1 μm at the most, which is preferable because the cold junction 28 and the infrared radiator 29 can be sufficiently close to each other as compared with the distance on the plane between the layers which is limited by the layout rule. . In addition, these cold junctions 2
It is possible to secure a large area where 8 and the infrared radiator 29 face each other, and from this aspect, it is possible to efficiently heat the cold junction 28.

-Second Embodiment- FIG. 6 is a plan view showing the configuration of the second embodiment of the infrared detecting apparatus according to the present invention. 6, parts that are the same as or correspond to those in FIG. 1 are assigned the same reference numerals, and the description of the configuration is omitted, and the parts that differ from FIG. 1 will be mainly described.

The infrared detector 35 of this embodiment is different from that of FIG. 1 in that the infrared radiator 29 is formed on the side of the hot junction 27, and the hot junction 27 is provided so as to cover the infrared radiator 29. It is at a point extending toward the infrared radiator 29.

The operation of this embodiment will be described. The self-diagnosis circuit 36 executes a predetermined abnormality detection processing procedure at power-on and during normal operation, as in the first embodiment.
As a result, it is determined whether the thermocouple 25 can operate properly, and a warning signal is generated if necessary. At this time, in this embodiment, since the infrared radiator 29 is formed on the hot junction 27 side, when the infrared radiator 29 is energized, thermoelectromotive force of the same polarity as when infrared rays are incident on the infrared absorption film 31 is generated. Occurs in pair 25. Therefore, the self-diagnosis circuit 36
Whether or not there is an abnormality in the device 35 is determined by determining whether or not a signal similar to a normal infrared detection signal is input by energizing the infrared radiator 29.

As described above, in the present embodiment, the presence or absence of abnormality of the device 35 is detected by heating the hot junction 27 with the infrared radiator 29 and detecting the thermoelectromotive force. Also according to the above, it is possible to obtain the same effects as those of the first embodiment described above.

Particularly, in the present embodiment, unlike the above-mentioned first embodiment, the polarity of the thermoelectromotive force of the thermocouple 25 when the infrared radiator 29 is energized is the polarity of the thermoelectromotive force of the thermocouple 25 at the time of infrared detection. Since the polarity is the same, no special circuit is required in the self-diagnosis circuit 36. That is, when an amplifier or an input circuit having a polarity is used for input, when the polarity of the input signal is inverted, the behavior does not always be the same as when it is not. Therefore, when the polarity of the thermocouple 25 is reversed as in the first embodiment, it is necessary to devise the circuit configuration so that it can be handled without problems even if the polarity of the input signal is reversed. If the input signal is not inverted, there is no need for such a device.

-Third Embodiment- FIG. 7 is a plan view showing the structure of a third embodiment of the infrared detector according to the present invention, and FIG. 8 is a sectional view thereof. The infrared detector of the present embodiment detects the amount of infrared rays with a bolometer. 7 and 8, parts that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and the description of the structure is omitted, and the parts that differ from FIG. 1 will be mainly described.

In FIGS. 7 and 8, an infrared detector 40 is formed by forming an infrared radiator 29 formed on a heat separation region of the substrate 24 and an interlayer insulating film 26 above the infrared radiator 29. And a resistor 41. A plurality of infrared radiators 29 are linearly formed on the substrate 24,
The resistor 41 is arranged in a zigzag pattern so as to be orthogonal to the linear infrared radiators 29. Both ends of the resistor 41 are connected to the output terminals 21 and 22, while both ends of the infrared radiator 29 are connected in parallel to the self-diagnosis circuit 42.

The operation of this embodiment will be described. The self-diagnosis circuit 42 executes a predetermined abnormality detection processing procedure at power-on and during normal operation, as in the first embodiment.
As a result, it is determined whether the resistor 41 can operate correctly, and a warning signal is generated if necessary. At this time, when the infrared radiator 29 is energized, the resistance 41 changes in the same resistance value as when the infrared rays are incident on the infrared absorption film 31. Therefore, the self-diagnosis circuit 36 detects a change in the resistance value of the resistor 41 due to energization of the infrared radiator 29, and determines that infrared rays can be correctly detected when the resistance value changes to a specified value. If the resistance is abnormally high,
An alarm is generated when it is judged that the leader line is broken. Therefore, also according to this embodiment, the same operational effects as those of the above-described first and second embodiments can be obtained.

[Fourth Embodiment] FIG. 9 is a sectional view showing the structure of a fourth embodiment of the infrared detector according to the present invention. In the figure, infrared detection device 5
Reference numeral 0 denotes an infrared detection element 52 arranged on the bottom surface of a cylindrical casing 51, and infrared rays incident from a window 54 which is a transparent member according to claim 2 provided on the front end surface of the casing 51 to the infrared detection element 52. A lens 53 for condensing light and a sealing plate 55 for sealing the window 54 are provided.

The infrared detecting element 52 may be a well-known element having an infrared detecting function, and no special one is necessary. The sealing plate 55 is formed, for example, by processing a silicon (Si) or germanium (Ge) substrate to have a predetermined thickness, transmits infrared rays, and generates infrared rays by energizing through an electrode 56 formed in the periphery. It is designed to be able to do. The sealing plate 55 and the electrode 56 are electrically connected by a method similar to IC bonding, for example. More specifically, a vapor deposition film of aluminum is formed on the surface of the sealing plate 55, and an aluminum or gold wire is bonded to the vapor deposition film to electrically connect the sealing plate 55 and the electrode 56. . When the resistance of the silicon substrate or the like is high, impurities may be doped to form a low resistance layer on a part of the substrate to form a path through which a current flows.

The operation of this embodiment will be described. The self-diagnosis circuit 56 energizes the sealing plate 55 at a predetermined interval when the power is turned on and during normal operation, whereby the sealing plate 55 emits infrared rays. This infrared light is condensed by the lens 53 and enters the infrared detection element 52, and if the infrared detection device 50 operates normally, the infrared detection element 52 outputs a specified value determined by the energization amount of the sealing plate 55. Detected by. As a result, the self-diagnosis circuit 56 determines whether or not infrared rays can be correctly detected by monitoring the output signal of the infrared detection element 52 and determining whether or not the output of the specified value can be obtained, and determines that there is an abnormality. If it does, the alarm output terminal 23
Generates an alarm signal from.

Therefore, according to this embodiment as well, it is possible to obtain the same effects as the above-mentioned embodiments. In particular,
According to this embodiment, there is an advantage that the conventionally used infrared detecting element can be applied as it is.

In this embodiment, the sealing plate 55 is used as an infrared radiator, but instead of or in addition to this,
The lens 53 may be used as an infrared radiator. Further, in this embodiment, the infrared light is collected by the lens, but the infrared light may be collected by the reflecting mirror, and in this case, the reflecting mirror may be used as the infrared radiator.

In the relationship between the embodiment described above and the claims, the thermocouple 25, the resistor 41, and the infrared detecting element 5
2 is a thermal device, and self-diagnostic circuits 33, 36, 42, 56
Indicates a self-diagnosis means, the window 54 constitutes a transparent member, and the sealing plate 55 constitutes an infrared radiator. The details of the infrared detection device of the present invention are not limited to the above-described embodiment, and various modifications are possible.

[0044]

As described in detail above, according to the present invention, the abnormality of the infrared detecting device is detected by detecting the voltage output from the thermal element by the infrared ray from the infrared radiator by the self-diagnosis means. Therefore, the abnormality of the device itself can be easily detected.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of an infrared detection device that is a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of FIG.

FIG. 3 is a sectional view taken along the line BB ′ of FIG.

FIG. 4 is a flowchart for explaining the operation of the first embodiment.

5 is a flowchart similar to FIG.

FIG. 6 is a plan view showing the configuration of an infrared detection device that is a second embodiment of the present invention.

FIG. 7 is a plan view showing the configuration of an infrared detection device that is a third embodiment of the present invention.

FIG. 8 is a cross-sectional view taken along the line CC ′ of FIG.

FIG. 9 is a plan view showing the configuration of an infrared detection device that is a fourth embodiment of the present invention.

FIG. 10 is a plan view showing a thermopile that is an example of a conventional infrared detection device.

FIG. 11 is a sectional view showing a bolometer which is another example of a conventional infrared detection device.

[Explanation of symbols]

 20, 35, 4, 50 Infrared detector 24 Substrate 25 Thermocouple 26 Interlayer insulating film 27 Hot junction 28 Cold junction 29 Infrared radiator 31 Infrared absorbing film 32 Thermal separation area 33, 36, 42, 56 Self-diagnosis circuit 41 Resistor 52 infrared detection element 53 lens 54 window 55 sealing plate

Claims (2)

[Claims] 1. A thermal type element whose output voltage changes according to the intensity of incident infrared rays, and a thermal type element which is thermally coupled to the thermal type element by being provided via an insulating film and applied. An infrared radiator that emits infrared rays according to a voltage, and a voltage is applied to the infrared radiator, and the output voltage from the thermal element is detected to diagnose whether the thermal element operates. An infrared detector comprising a self-diagnosis means. 2. A thermal type element whose output voltage changes according to the intensity of infrared rays incident through the transparent member, and a substantially transparent member which is installed on the transparent member and emits infrared rays according to the applied voltage. And a self-diagnosis means for diagnosing whether or not the thermal element operates by detecting the output voltage from the thermal element while applying a voltage to the infrared radiator. Infrared detector characterized by.