JP2001296184A - Infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make surely detectable the temperature distribution of a region to be detected by eliminating detection errors caused by the difference in structure between a heat detection element and a reference element. SOLUTION: A plurality of heat detection elements 10 are formed at a position, where infrared rays enter from a region to be detected in a sensor chip 7, and at the same time, a reference element 20 and a temperature-measuring element 21 are formed at a position where infrared rays do not enter from the region to be detected. Even though the temperature distribution of the region to be detected can be detected by obtaining the difference in output between the heat detection elements 10 and the reference element 20 in a differential amplifier circuit 22, fluctuations caused by the change in an environmental temperature is included in output from the heat detection element 10. Since the temperature-detecting element 21 can detect the temperature change caused by the change in an environmental temperature, the temperature distribution of the region to be detected can be detected accurately, based on the output from the temperature detection element 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detecting device for detecting a temperature distribution in a detection target area based on an output difference between a heat detecting element formed on a substrate and a reference element.

[0002]

2. Description of the Related Art In recent years, for example, an infrared detection device has been provided which has a detection target area in a passenger compartment. It has been proposed to perform security control by detecting intrusion into a vehicle. In other words, by focusing the infrared rays emitted from the human body on the infrared image sensor with a condenser lens,
The presence of a person is determined based on the output from the infrared image sensor, and various controls such as air conditioner, airbag, and security of the vehicle are performed based on the determination result.

[0003]

An infrared detector of this type is disclosed in Japanese Patent Application Laid-Open No. 7-167708. This is a bolometer-type infrared sensor that enables temperature measurement using a change in the resistance value of a metal thin film.

In such a bolometer type (thermal type) infrared sensor, the infrared light condensed by an infrared condensing lens is absorbed by an absorption film covering a metal thin film resistor and converted into heat. Since this metal thin film resistor is formed on a membrane provided with an air gap, it can be thermally insulated from the outside while storing the heat absorbed by the absorbing film. Since the resistance value of the metal thin film resistor changes depending on the temperature, the temperature of the detection target can be detected based on the change amount.

[0005] In this case, in order to accurately detect the temperature of the detection target based on the output from the infrared sensor, it is necessary to correctly detect only the temperature change due to the absorption of the infrared radiation emitted from the detection target. For this reason, this type of bolometer type infrared sensor has a reference element in addition to the sensor element on the same sensor substrate, and obtains the absolute temperature of the detection target using the resistance value of the reference element. I have to. As an example, there is a method in which a difference between the output of the sensor element and the output of the reference element is obtained, and the difference value is amplified and taken out to read out a resistance change amount due to radiation from the detection target. .

Here, if the resistance characteristics of the sensor element and the reference element are exactly the same, and the shapes and forms of the two elements are the same and the temperatures of the elements are exactly the same, the infrared radiation from the detection object causes It is possible to accurately detect only a temperature change.

However, the sensor element and the reference element cannot adopt the same shape and form for the following reasons. That is, when the temperature of the detection target is measured based on the output from one sensor element, the same current is applied to the sensor element and the reference element at the same time, and the voltage generated is read. . From this, for example, when 100 sensor elements are provided for one screen, there is a sufficient energization interval between the sensor elements and self-heating does not accumulate, whereas the reference element is used for each sensor element measurement. Since power is supplied, self-heating occurs. In this case, since the membrane of the reference element has a heat insulating structure, a temperature difference is generated between the reference element and the substrate, which results in a measurement error. In order to avoid this, the reference element is energized only once for each measurement of one screen, and its value is stored in a memory or the like, or stored using a sample-and-hold circuit. Although a method of detecting using the difference from the measured value of each sensor element is conceivable, it requires a new additional circuit and cannot cancel the variation of the energizing current when measuring each sensor element. Minutes become errors and occur. That is, the temperature change on the membrane that occurs when the detection target changes by 1 ° C. is a minute temperature change of less than 0.1 ° C., and the amount of change in the resistance value (= voltage) caused by the change is very small. Therefore, the influence of the error caused by the above factors cannot be ignored. For these reasons, the sensor element and the reference element cannot have the same shape and form.

Therefore, the reference element usually does not have a membrane structure in order to eliminate the influence of self-heating due to repeated energization. In this case, although self-heating is generated by energizing the reference element, the heat is immediately released to the substrate having a large heat capacity because the element is provided in heat conduction with the substrate. There is no temperature change due to self-heating. Thus, current can be supplied for each sensor element measurement, and variations in the current supplied during measurement of each sensor element can be canceled.

However, the temperature of the sensor element actually changes due to the following various factors due to a change in environmental temperature. (1) When the sensor environment temperature changes, the amount of infrared radiation from the condenser lens or the sensor package changes,
Temperature change caused by absorbing the radiation. (2) The membrane is not completely floating with respect to the substrate, and the heat insulating structure referred to here means that the beam that connects the substrate and the membrane has low thermal conductivity. Therefore, when the temperature of the substrate changes due to a change in the sensor environment temperature, the temperature change is transmitted to the membrane through the beam supporting the membrane, and the temperature change occurs.

However, since the reference element does not adopt the membrane structure for the above-mentioned reason, the fact is that the temperature change due to the above (1) and (2) cannot be excluded.

That is, when the sensor environment temperature changes,
The amount of radiation from the condenser lens or the sensor package changes. At this time, the resistance of the sensor element changes due to a temperature change generated by absorbing the infrared radiation from the condenser lens or the sensor package, whereas the reference element generates heat by absorbing the radiation. It does not escape immediately to the substrate and the resistance value does not change. As a result, a resistance value difference occurs between the sensor element and the reference element, and the resistance value difference becomes a detection error.
This is the same even if the reference element has an infrared absorbing film.

When the sensor environment changes, the temperature of the reference element changes the same as that of the substrate, whereas the sensor element has a heat insulating structure with respect to the substrate. However, the temperature change amounts are not always the same. This means that if the substrate and the membrane have the same temperature, both the substrate and the membrane radiate heat at that temperature. At this time, the heat capacity is different between the substrate and the membrane, so that the temperature of the substrate hardly changes. On the other hand, the temperature of the membrane slightly decreases due to heat radiation. As described above, a detection error always occurs unless the sensor element and the reference element have exactly the same shape and form and cannot be measured simultaneously.

Therefore, in a general infrared sensor, the entire sensor (including the sensor itself, the condenser lens or the sensor package) is controlled by a temperature control system such as a Peltier element.
To stabilize the temperature. In this case, if the reference element does not have a membrane structure, it is possible to reduce all the degrees of influence of the above-described error factors.

However, as in a vehicle interior environment, -4
In a place where the environmental temperature changes from 0 ° C. to 80 ° C., it is very difficult to maintain a constant temperature with a temperature control system. Also, even if it could be implemented, the power consumption of the temperature control system is large, and it is desired to use low power consumption for automotive applications (for example, when the engine is stopped or when parking).
Not available.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a configuration for detecting a temperature distribution in a detection target area based on an output difference between a heat detection element and a reference element. It is an object of the present invention to provide an infrared detection device capable of eliminating a detection error due to a difference in structure from an element and reliably detecting a temperature distribution in a detection target region.

[0016]

According to the first aspect of the present invention, when the area to be detected forms an image on the substrate, the temperature of the heat detecting element rises with the absorption of infrared rays from the area to be detected. When the element is energized, the heat detection element outputs a signal corresponding to its own temperature. At this time, the output from the heat detecting element is the sum Z1 + Z2 of the output Z1 corresponding to the temperature rise due to the infrared rays from the detection target area and the output Z2 corresponding to the substrate temperature. Here, since the reference element outputs a signal indicating the temperature of the substrate, the temperature judging means subtracts the output Z2 of the reference element from the output Z1 + Z2 from the heat detecting element to obtain the temperature by infrared rays from the detection target area. It is possible to detect the rise, and thus the absolute temperature of the detection target area.

By the way, since the heat detecting element is provided in a heat insulating structure with respect to the substrate, it varies from the original output under the influence of the environmental temperature change, whereas the reference element is provided with respect to the substrate. Because it is provided heat conductive, it is not affected by environmental temperature changes. For this reason, even if the temperature determination means determines the temperature distribution in the detection target area as described above, the temperature distribution has a shift corresponding to the environmental temperature change.

However, the temperature measuring element is provided in a heat insulating structure with respect to the substrate similarly to the heat detecting element, and the temperature rises due to the incidence of infrared rays other than the area to be detected. It is possible to detect a temperature change in the sensing element due to an environmental temperature change.

Therefore, the temperature determining means can reliably determine the temperature distribution of the detection target area based on the output from the temperature measuring element in addition to the output from the heat detecting element and the reference element.

According to the second aspect of the present invention, as shown in FIG. 8, in the correlation storage means, the heat detection element difference output (Z1 '+) corresponding to the temperature of the substrate at a predetermined reference temperature is detected.
Since the correlation between Z3) and the temperature measurement element difference output (Z3) is stored, the heat detection element difference output stored in the correlation storage means corresponding to the temperature measurement element difference output from the comparison means is a detection target. When the area is at the reference temperature, the value is to be output from the comparing means. In this case, the difference dZ1 'between the heat detection element difference output from the comparison means and the heat detection element difference output stored in the correlation storage means corresponding to the temperature measurement element difference output is the actual temperature of the detection target area and the reference dZ1'. Since the difference from the temperature is indicated, the temperature determining means calculates the difference dZ1 ′.
Can be used to determine the temperature distribution in the detection target area.

According to the third aspect of the present invention, when the temperature of the detection target area is constant, the differential output of the heat detecting element and the differential output of the temperature measuring element output from the comparing means with respect to the temperature change of the substrate. Therefore, in at least two temperature states of the substrate, the correlation can be easily obtained based on the difference output of the heat detecting element and the difference output of the temperature measuring element obtained by the comparing means.

According to the fourth aspect of the present invention, each of the plurality of temperature measuring elements provided around the heat detecting element is configured to output an average of their outputs to the comparing means.
Even if a temperature distribution difference occurs in the substrate, the influence of the temperature distribution difference can be suppressed.

According to the fifth aspect of the present invention, the outputs from the plurality of temperature measuring elements provided around the heat detecting element indicate the temperature distribution difference of the heat detecting element. By correcting the output from the heat detecting element, it is possible to avoid the influence of the temperature distribution difference of the heat detecting element.

According to the sixth aspect of the present invention, the reference voltage from the reference voltage generating circuit output from the comparing means does not fluctuate due to a temperature change. Therefore, when the reference voltage fluctuates when passing through the analog circuit, drift occurs. It can be determined that it has occurred. Therefore, by disabling the drift voltage in the analog circuit, it is possible to prevent the influence of the drift in the analog circuit.

According to the seventh aspect of the present invention, since the inner peripheral surface of the package accommodating the substrate is made of a material having a high thermal conductivity, even if the temperature of the inner peripheral surface of the package rises, the temperature rises uniformly. Thereby, the infrared rays are uniformly radiated to the substrate, so that it is possible to prevent the heat distribution from being generated for each of the heat detecting elements, and it is possible to enhance the accuracy of determining the temperature of the detection target area obtained by the temperature determining means.

According to the eighth aspect of the present invention, the package for accommodating the substrate has a simple heat insulating structure, so that even if the environmental temperature changes, the influence of the temperature change can be suppressed. it can.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment in which the present invention is applied to a human body detecting device for a vehicle will be described below with reference to FIGS. In FIG. 2 showing the vehicle interior, a human body detection device 1 is arranged on the ceiling of the vehicle interior. The human body detection device (corresponding to an infrared detection device) 1 is integrated with a map lamp (not shown) and includes first to third infrared image sensors 2 to 4. These infrared image sensors 2 to 4 have a detection target area around the driver's seat, around the passenger seat, and around the rear seat (or luggage compartment). Further, as shown in FIG. 3, a temperature calibrator 5 is provided so as to be located in the field of view of each of the infrared image sensors 2 to 4. This temperature calibrator 5
Is constituted by an LED that generates heat by energization, a PTC thermistor that maintains a constant temperature by self-heating, or a Peltier element that is controlled to a constant temperature by energization control. It is provided to correct the output deviation.

FIG. 4 schematically shows a cross section of the infrared image sensors 2 to 4. In FIG. 4, the infrared image sensors 2 to 4 have a sensor chip (corresponding to a substrate) 7 fixed to the inner bottom surface of the sensor package 6 and a condenser lens 8 mounted on an opening of the sensor package 6.
The condensing lens 8 forms an image of the detection target area on the sensor chip 7. The sensor chip 7 is connected to an external electric circuit through a plurality of pins 9.

Here, the sensor package 6 has a high thermal conductivity material 6a made of copper or aluminum from the inner peripheral surface.
It is formed by sequentially laminating a low thermal conductivity material 6b and a high thermal conductivity material 6c.

FIG. 5 schematically shows the structure of the sensor chip 7 of each of the infrared image sensors 2 to 4. In FIG. 5, the sensor chip 7 is formed by assembling, for example, 15.times.10 two-dimensional matrices of heat detecting elements 10 made of platinum resistance, and collects infrared rays emitted from the periphery of the seat. The light is condensed by the lens 8 to form an image on the heat detection element 10 as a thermal image. In this case, the condenser lens 8 is, for example, 750 × 500 at a position separated by 500 mm.
It is designed so that a range of mm can be condensed on the entire heat detecting element 10. Therefore, if the number of the thermal detection elements 10 of the infrared image sensors 2 to 4 is 15 × 10, the range (detection resolution) that can be detected by one thermal detection element 10 is 50.
mm square. In the infrared image sensors 2 to 4, a signal generation circuit 11 and a selection circuit 12 are provided around the heat detection element 10.

As shown in FIG. 5, the heat detecting element 10 is formed by forming an SiO.sub.2 thin film 10a, a metal thin film resistance portion 10b, and an absorption film 10c on a Si substrate 7a forming the main part of the sensor chip 7, and then forming the metal thin film resistance portion. By removing the back surface side of 10b by etching, the metal thin-film resistance portion 10b is
A is formed in a membrane structure located with an air gap from a.

FIG. 6 schematically shows the electrical configuration of the sensor chip 7 of each of the infrared image sensors 2 to 4. In FIG. 6, the heat detecting element 10 is selectively selected through an FET 13 by an X ring counter 12 a and a Y ring counter 12 b constituting a selection circuit 12. A signal detection and processing circuit shown in FIG. 1 (corresponding to a temperature judging means)
By taking in sequentially, the temperature distribution of the detection target area set in each of the infrared image sensors 2 to 4 can be detected.

That is, in FIG. 7 schematically showing the entire configuration, the signal detection / processing circuit 14 comprises a signal amplifier 15, a signal processing circuit 16, and a data transmission circuit 17, and the signal processing circuit 16 Sensor 2
4, thermal image data is created based on the detected temperature distribution. Here, the signal processing circuit 16
As will be described later, a correlation for determining the temperature of the detection target area is stored in a memory (corresponding to a correlation storage unit) 18.

The various system control circuits 19 control predetermined vehicle systems such as an air conditioner, an airbag, and security based on the thermal image data supplied from the signal detection / processing circuit 14.

Here, FIG. 1 shows the infrared image sensors 2 to
4 schematically shows the sensor chip 7. In FIG. 1, a reference element 20 and a temperature measuring element 21 are formed on the sensor chip 7 in addition to the heat detecting element 10 (omitted in FIGS. 5 and 6). In this case, the heat detecting element 10 is formed at a position where infrared rays from the detection target area is incident, whereas the reference element 20 and the temperature measuring element 21 are formed at a position where infrared rays from the detection target area are not incident. ing. The reference element 20 is formed so as to conduct heat to the sensor chip 7, and detects the temperature of the sensor chip 7 when the temperature becomes the same as the temperature of the sensor chip 7. Therefore, in the differential amplifier circuit (corresponding to the comparison means) 22, the difference between the output from the heat detecting element 10 and the output from the reference element 20 in accordance with the switching of the switch 23 (hereinafter, referred to as the heat detecting element difference output). Is obtained and output, the signal detection / processing circuit 14 can detect a temperature change due to infrared rays from the detection target area, and furthermore, a temperature distribution in the detection target area.

As will be described later, the signal detection / processing circuit 14 cannot accurately determine the temperature distribution in the detection target area based on the difference between the outputs from the heat detection element 10 and the reference element 20. , Temperature measuring element 21
It is a feature of the present invention to determine the temperature distribution of the detection target area including the output from the temperature measuring element 21.

Next, the operation of the above configuration will be described. In a state where the occupant is seated in the passenger compartment, the infrared rays emitted from the occupant are transmitted to the infrared image sensors 2 to 4 of the human body detecting device 1.
And reaches the heat detecting element 10 of the sensor chip 7 through the condenser lens 8 provided in the sensor chip 7.

In the heat detecting element 10, incident infrared light is converted into heat by absorbing it with the absorbing film 10c, and the heat increases the temperature of the metal thin-film resistance portion 10b to change the resistance value. The temperature distribution of the detection target area can be detected by sequentially inputting the detection output (sensor signal) from the heat detection element 10 to the signal detection / processing circuit 14.

The signal detection / processing circuit 14 generates thermal image data of each detection target area by taking in detection outputs from all the heat detection elements 10 of each of the infrared image sensors 2 to 4. That is, the infrared image sensor 2
4 generates thermal image data based on the detected temperature distribution.

By the way, the output from the heat detecting element 10 is
The sum Z of the output Z1 corresponding to the temperature rise due to infrared rays from the detection target area and the output Z2 corresponding to the temperature of the sensor chip 7
1 + Z2. Here, the reference element 20 is provided on the sensor chip 7 so as to conduct heat.
Is detected in the differential amplifier circuit 22, the output Z1 + Z2 from the heat detecting element 10 and the output Z from the reference element 20 are switched according to the switching of the switch 23.
By calculating and outputting the difference from 2, it is possible to detect the temperature rise due to infrared rays from the detection target area, and thus the absolute temperature of the detection target area.

However, since the heat detecting element 10 is provided in a heat-insulating structure with respect to the sensor chip 7, the heat detecting element 10 fluctuates from the original output under the influence of the environmental temperature change. Is provided so as to conduct heat to the sensor chip 7, so that it is not affected by an environmental temperature change. For this reason, even if the signal detection / processing circuit 14 detects the temperature distribution of the detection target area based on the difference between the outputs from the heat detection element 10 and the reference element 20 as described above, the temperature distribution is Output fluctuations due to temperature changes remain included.

In this case, as the environmental temperature change received by the heat detecting element 10, the amount of infrared radiation from the condenser lens or the sensor package changes, and the temperature change generated by absorbing the radiation and the sensor chip 7. This is a temperature difference between the metal thin-film resistance portion 10b and the sensor chip 7 due to a difference in heat capacity when heat from the substrate is transferred to the metal thin-film resistance portion 10b through the beam supporting the metal thin-film resistance portion 10b.

Therefore, in the present embodiment, a temperature measuring element 21 having a membrane structure identical to that of the heat detecting element 10 is formed on the sensor chip 7, and the output from the temperature measuring element 21 Reference element 2
By calculating a difference from the output from 0 and outputting the difference (hereinafter, referred to as a temperature measurement element difference output), the signal detection / processing circuit 14 can determine the difference based on the heat detection element difference output and the temperature measurement element difference output. The temperature distribution in the detection target area can be accurately detected.

That is, the output from the heat detecting element 10 is the output Z1 corresponding to the temperature rise due to infrared rays from the detection target area.
Z1 + Z, the output Z2 corresponding to the temperature of the sensor chip 7 and the output Z3 corresponding to the temperature change accompanying the environmental temperature change.
2 + Z3. Further, the output from the reference element 20 is an output Z2 according to the temperature of the sensor chip 7 because no infrared light from the detection target area enters. Therefore, the differential output of the heat detecting element from the differential amplifier circuit 22 is
The sum Z1 + Z3 of the output Z1 corresponding to the temperature rise due to the infrared rays from the detection target area and the output Z3 corresponding to the temperature change accompanying the environmental temperature change.

On the other hand, the output from the temperature measuring element 21 is the sum of the output Z2 corresponding to the temperature of the sensor chip 7 and the output Z3 corresponding to the temperature change accompanying the environmental temperature change. Therefore,
The temperature measurement element difference output from the differential amplifier circuit 22 becomes an output Z3 corresponding to the temperature change accompanying the environmental temperature change.

Here, under the condition that the temperature of the detection target area is constant, a proportional relationship holds that when the temperature measurement element difference output Z3 rises, the heat detection element difference output Z1 + Z3 rises by the rise. become. Thus, if the detection target area has a predetermined reference temperature and the heat detection element difference output corresponding to the temperature rise due to infrared rays from the detection target area is Z1 ′ (= constant), the heat detection element difference output is Z1 ′. + Z3 (see FIG. 8), when the relationship between the temperature measurement element difference output Z3 and the heat detection element difference output Z1 '+ Z3 is established, the temperature of the detection target area may be regarded as the reference temperature. it can.

Therefore, the correlation between the differential output of the temperature measuring element and the differential output of the heat detecting element when measuring the detection target area of the reference temperature is stored in advance, and when the correlation is established, the temperature of the detection target area becomes It can be determined that the temperature is the reference temperature.

However, since the temperature of the detection target area is usually different from the reference temperature, the above correlation is rarely established. Here, assuming that the output change from the heat detecting element 10 due to the temperature of the detection target area deviating from the reference temperature is dZ1, the differential output of the heat detecting element is dZ1.
+ Z1 '+ Z3 (see FIG. 8). In this case, dZ1 increases as the difference between the temperature of the detection target area and the reference temperature increases. Therefore, by determining dZ1, it is possible to determine the temperature deviation of the detection target area with respect to the reference temperature, and thus the temperature of the detection target area. it can.

However, in the present embodiment, signal detection and
The processing circuit 14 obtains a correlation between the differential output of the heat detecting element and the differential output of the temperature measuring element when the detection target area of the reference temperature is measured as follows, and calculates the temperature distribution of the detection target area based on the correlation. The judgment was made (see FIG. 9).

(1) The temperature of the detection target area is equal to the reference temperature T0.
And the temperature difference of the heat detection element A0 and the temperature measurement element difference output B0 when the temperature of the sensor chip 7 is Ts0. (2) Thermal detection element difference output A1 when the temperature of the detection target area is the reference temperature T0 and the temperature of the sensor chip 7 is Ts1
And the temperature measurement element difference output B1 are measured. That is, the differential output of the heat detecting element and the differential output of the temperature measuring element are obtained at two environmental temperatures Ts0 and Ts1, respectively.

(3) The correlation coefficient K is obtained from the differential output A0, A1 of the heat detecting element and the differential output B0, B1 of the temperature measuring element. (4) The correlation coefficient K of each heat detection element 10 is obtained by performing the above (1) to (3) for each heat detection element 10 and stored in the memory 18. (5) At the time of actual measurement, the difference output A2 of the heat detecting element and the difference output B2 of the temperature measuring element are measured.

(6) From the temperature measurement element difference output B2 and the correlation coefficient K, a heat detection element difference output A3 when the detection target area of the reference temperature T0 is measured under the current measurement conditions is obtained. (7) Thermal detection element difference output A2 and thermal detection element difference output A
The deviation of the temperature of the detection target region from the reference temperature T0 from the difference from the reference temperature T0, and the temperature distribution of the detection target region are determined.

According to such an embodiment, the sensor chip 7 when measuring the detection target area at the predetermined reference temperature is used.
The correlation coefficient K between the difference output of the heat sensing element and the difference output of the temperature measurement element according to the temperature of the sensor is obtained and stored, and the difference output of the heat detection element and the difference output of the temperature measurement element for each heat detection element 10 at the time of measurement. Since the temperature distribution of the detection target area is determined based on the stored correlation coefficient K, even if the temperature of the heat detecting element 10 and the temperature of the reference element 20 are different due to the environmental temperature change, the influence is eliminated. As a result, the temperature distribution in the detection target area can be accurately detected.

Further, in each heat detecting element 10, only the correlation coefficient K when the detection target area is at the reference temperature is stored, and the temperature distribution of the detection target area is determined based on the correlation coefficient K. As compared with a configuration in which a plurality of correlation coefficients are stored when the temperatures of the detection target regions are different, the capacity for storing the correlation coefficients can be significantly reduced.

Further, since the sensor package 6 in each of the infrared image sensors 2 to 4 has a simple heat insulating structure, even if the environmental temperature changes, it is not greatly affected by the temperature change. When the temperature of a part of the outer peripheral surface of the sensor package 6 rises, the temperature of the high thermal conductivity material 6c on the outer peripheral surface uniformly increases, and then the high thermal conductivity material 6a passes through the low thermal conductivity material 6b. Since the heat is transmitted and becomes uniform in the high thermal conductivity material 6a, the temperature of the inner peripheral surface of the sensor package 6 becomes uniform. Therefore, the temperature distribution of the sensor chip 7 is made uniform,
The accuracy of determining the temperature distribution in the detection target area can be improved.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
10 and 11 will be described with reference to FIGS. 10 and 11. The same parts as those in the first embodiment will be denoted by the same reference numerals, description thereof will be omitted, and different parts will be described. This second
The embodiment is characterized in that the sensor chip 7 is provided with a plurality of temperature measuring elements.

That is, when the temperature of the sensor chip 7 changes gradually as a whole, since the resistance values of the heat detecting element 10 and the temperature measuring element 21 match, as in the first embodiment described above. Although it is possible to determine the temperature of the detection target area by using the focusing lens 8 as shown in FIG.
Alternatively, when a difference occurs in the amount of infrared radiation from the sensor package 6 or when a temperature distribution difference occurs in the sensor chip 7, a temperature difference occurs for each heat detection element 10. Such a temperature difference of the heat detecting element 10 causes an error in a heat detecting element difference output corresponding to the heat detecting element 10, and becomes a detection error of the temperature distribution of the detection target area.

Therefore, in the present embodiment, as shown in FIG. 11, a plurality (four in this embodiment) of infrared rays from the detection target area around the heat sensing element 10 of the sensor chip 7 are not incident. The correlation coefficient K is obtained by forming the temperature measuring element 21 and outputting the average of the outputs to the differential amplifier circuit 22 to obtain the differential output of the heat detecting element. That is, the correlation coefficient K indicates a correlation corresponding to the average temperature of the heat detection element 10.

According to such an embodiment, the correlation coefficient K is obtained based on the average of the outputs from the plurality of temperature measuring elements 21 formed around the heat detecting element 10, so that the sensor chip 7, even if a temperature distribution difference occurs, it is possible to accurately detect the temperature distribution in the detection target region by suppressing the influence thereof.

Incidentally, the temperature distribution of the sensor chip 7 may be determined based on the outputs from the plurality of temperature measuring elements 21 and the output from the heat detecting element 10 may be weighted based on the temperature distribution. That is, when the sensor chip 7 has a temperature distribution in the left-right direction, for example, the left side has a high temperature and the right side has a low temperature, the output from the heat sensing element 10 located on the left side of the heat sensing element 10 is located on the left side. The output from the temperature measuring element 21 is weighted and corrected. In addition, heat detection element 1
0, the output from the heat detecting element 10 located on the right side is:
The output from the temperature measuring element 21 located on the right side is weighted and corrected. Accordingly, even when a temperature distribution occurs in the sensor chip 7, the accuracy of the output from the heat detection element 10 can be increased, and the detection accuracy of the temperature distribution in the detection target region can be increased.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is characterized in that the influence of temperature drift in the signal detection / processing circuit 14 is prevented.

That is, in each of the above embodiments, signal detection and
Since the processing circuit 14 uses an analog signal, there is a possibility that a drift occurs with a change in temperature and an error occurs during measurement.

Therefore, in the present embodiment, as shown in FIG. 12, a reference voltage generating circuit (corresponding to reference voltage generating means) 31 for generating a reference voltage which does not change with temperature.
And the reference voltage generation circuit 31 supplies the reference voltage and 0
The V potential is output to the differential amplifier circuit 22 according to the switching of the switches 23 and 32. As a result, the reference voltage from the reference voltage generation circuit 31 passes through the signal detection / processing circuit 14 similarly to the heat detection element differential output and the reference element differential output. When drift occurs, the reference voltage that has passed through the signal detection / processing circuit 14 also fluctuates.

However, in the signal detection / processing circuit 14, the reference voltage from the reference voltage generation circuit 31 is measured, for example, once after obtaining the differential output of the heat detection elements from all the heat detection elements 10, and at this time, Since the drift voltage can be obtained from the output fluctuation amount, the influence of the drift can be reduced by correcting the differential output of the heat detecting element based on the drift voltage at this time.

The present invention is not limited to each of the above embodiments, and a dedicated differential amplifier circuit for calculating the difference between the output from the temperature measuring element 21 and the output from the reference element 20 is provided. Is also good.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a sensor chip of an infrared image sensor according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a vehicle interior showing an arrangement position of a human body detection device and a detection target area.

FIG. 3 is a perspective view of a human body detection device.

FIG. 4 is a cross-sectional view of an infrared image sensor.

FIG. 5 is a cross-sectional view of a sensor chip of the infrared image sensor.

FIG. 6 is a schematic diagram showing an electrical configuration of the infrared image sensor.

FIG. 7 is a schematic diagram showing the overall configuration.

FIG. 8 is a diagram showing a relationship between a temperature measurement element difference output and a heat detection element difference output.

FIG. 9 is a diagram showing a method of obtaining a correlation coefficient K;

FIG. 10 is a schematic diagram of an infrared image sensor showing infrared light incident on a sensor chip according to a second embodiment of the present invention.

FIG. 11 is a diagram corresponding to FIG. 1;

FIG. 12 is a diagram corresponding to FIG. 1, showing a third embodiment of the present invention;

[Explanation of symbols]

1 is a human body detecting device (infrared ray detecting device), 2 to 4 are infrared ray image sensors, 7 is a sensor chip (substrate), 10 is a heat detecting element, 14 is a signal detecting / processing circuit (temperature determining means), 18 is a memory ( Correlation storage means), 20 is a reference element, 21 is a temperature measurement element, 22 is a differential amplifier circuit (comparison means), and 31 is a reference voltage generation circuit (reference voltage generation means).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01J 1/44 G01J 1/44 D 5/02 5/02 C 5/04 5/04 5/10 5 / 10 B (72) Inventor Hiroshi Ando 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Co., Ltd. (72) Inventor Sadasuke Kimura 1-1-1, Showa-cho, Kariya-shi, Aichi F term (reference) 2G065 AA04 AB02 BA12 BA34 BC05 BC14 CA21 DA20 2G066 AC13 BA09 BB11 BC11 CA01 CA08 3D054 EE11 FF16

Claims (8)

[Claims] 1. A plurality of heat detecting elements which are provided with a heat insulating structure on a substrate so that infrared rays from a detection target area are incident thereon, and output a signal indicating their own temperature in response to energization; A reference element that is provided so as to conduct heat, and outputs a signal indicating the temperature of the substrate in response to energization at the same time as energization to each of the heat detection elements; and an output from the heat detection element and the reference element. And a temperature determining means for determining a temperature distribution of the detection target area based on the infrared ray detection device. A temperature measuring element that outputs a signal indicating its own temperature in accordance with the temperature measuring element, wherein the temperature determining means outputs the signal from the temperature measuring element in addition to the heat detecting element and the reference element. To determine the temperature distribution in the detection target area based infrared detecting apparatus according to claim. 2. The temperature judging means obtains a heat detection element difference output indicating a difference between an output from each of the heat detection elements and an output from the reference element, and outputs an output from the temperature measurement element and the reference from the reference. A comparison means for obtaining a temperature measurement element difference output indicating a difference from an output from the element; and a heat detection element difference output and a temperature obtained by the comparison means according to a temperature state of the substrate at a predetermined reference temperature in a detection target area. Correlation storage means for storing a correlation with the measurement element difference output, and a heat detection element difference output indicated by the correlation stored in the correlation storage means corresponding to the temperature measurement element difference output obtained by the comparison means. 2. The infrared detection device according to claim 1, wherein the temperature of the detection target area is determined based on a difference between the difference output of the heat detection element and the difference output obtained by the comparison means. 3. The correlation stored in the correlation storage means is a heat detection element difference output and a temperature measurement element difference obtained by the comparison means in a detection target area at a reference temperature and at least two temperature states of the substrate. 3. The infrared detecting device according to claim 2, wherein the infrared detecting device is obtained based on the output. 4. A plurality of the temperature measuring elements are provided around the heat detecting element, and the temperature judging means judges a temperature distribution in a detection target area based on an average of outputs from the heat detecting elements. The infrared detecting device according to any one of claims 1 to 3, wherein 5. A plurality of the temperature measuring elements are provided around the heat detecting element, and the temperature judging means obtains a temperature distribution difference of the heat detecting element based on an output from the temperature measuring element. The infrared detection device according to any one of claims 1 to 4, wherein the temperature distribution of the detection target area is determined according to the temperature distribution difference. 6. A reference voltage generating means for outputting a reference voltage which does not fluctuate due to a temperature change to said comparing means, wherein a reference voltage output from said comparing means from said reference voltage generating means passes through an analog circuit. 6. The infrared detecting device according to claim 1, wherein the drift voltage is determined and the drift voltage in the analog circuit is invalidated. 7. The package accommodating the substrate, wherein an inner peripheral surface is made of a material having high thermal conductivity.
7. The infrared detection device according to any one of claims 1 to 6. 8. The infrared detecting device according to claim 7, wherein the package accommodating the substrate is made of a high thermal conductivity material, a low thermal conductivity material, and a high thermal conductivity material from an inner peripheral surface.