JPH08320257A - Infrared detecting device - Google Patents

Abstract

PURPOSE: To provide an infrared detecting device in which the measuring time can be shortened with a simple structure. CONSTITUTION: Four thermistors Th1 -Th4 are bridge-connected to constitute a bolometer bridge 1. The series circuit of the bolometer bridge 1 and a resistor Ra is connected to both ends of a DC power source 2. This device has a bridge- to-bridge voltage detecting circuit 3 for detecting the voltage between bridges of the bolometer bridge 1, and a resistor end-to-end voltage detecting circuit 4 for detecting the voltage between both ends of the resistor Ra. Namely, the detection of the voltage between bridges of the bolometer bridge 1 and the detection of the voltage between both ends of the resistor Ra by the resistor end-to-end voltage detecting circuit 4 can be simultaneously performed, and the measuring time can be shortened with a simple structure.

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 detecting the amount of incident infrared rays by a bolometer bridge using a thermistor.

[0002]

2. Description of the Related Art Conventionally, an infrared detector for detecting an incident infrared ray amount by a bolometer bridge using a thermistor has been sometimes applied to a radiation thermometer capable of measuring the temperature of an object in a non-contact manner. When measuring the temperature of the object by the infrared detection device, the measurement of the amount of infrared rays emitted from the object and incident on the bolometer bridge, and the temperature measurement of the bolometer bridge based on the resistance change of the thermistor due to the incident infrared rays. It was necessary to make two measurements of That is, in a circuit configuration in which a bolometer bridge 1 formed by connecting thermistors Th _{1 to} Th ₄ as bolometers and resistors Rb _{1 to} Rb ₃ as shown in FIG. The voltage between the bridge of the circuit is detected by the voltage detection circuit 10
Between the bolometer bridges 1 in the circuit configuration in which the bolometer bridges 1 are connected to both ends of the DC power supply 2 as shown in FIG. It was necessary to perform two measurements, that is, the measurement of the amount of incident infrared rays by detecting the voltage by the inter-bridge voltage detection circuit 11.

[0003]

However, in the above-mentioned conventional configuration, in order to perform two measurements, the circuit configuration shown in FIG. 4 and the circuit configuration shown in FIG. 5 are separately provided, or two circuit configurations are provided. It is necessary to provide a switching means for switching the circuit configuration, and there is a problem that the circuit configuration becomes complicated or that it takes time to finally measure the temperature of the object because two measurements are performed sequentially.

The present invention is intended to solve the above problems, and an object of the present invention is to provide an infrared detection device capable of shortening the measurement time with a simple structure.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 is an infrared detector for detecting an incident infrared ray amount by a bolometer bridge using a thermistor, which comprises a bolometer bridge and a resistor part. A series circuit is connected to both ends of a DC power supply, and an inter-bridge voltage detection circuit that detects the inter-bridge voltage of the bolometer bridge and a resistance-both-end voltage detection circuit that detects the two-end voltage of the resistor section are provided. .

According to a second aspect of the present invention, in the first aspect of the present invention, the resistance portion whose resistance value can be varied, and the control circuit which varies the resistance value of the resistance portion according to the detection output of the voltage across the resistance detection circuit. And is provided.

[0007]

According to the first aspect of the present invention, the series circuit of the bolometer bridge and the resistor section is connected to both ends of the DC power supply to detect the inter-bridge voltage of the bolometer bridge, and the voltage across the resistor section. Since a voltage detection circuit across the resistor to detect the temperature is provided, when measuring the temperature of the object in a non-contact manner, the infrared amount measurement by the voltage detection circuit between bridges and the temperature measurement of the bolometer bridge by the voltage detection circuit across the resistance are performed. Can be performed simultaneously, and the temperature measurement time of the object can be shortened with a simple configuration.

According to the second aspect of the invention, since the resistance portion whose resistance value can be varied and the control circuit which varies the resistance value of the resistance portion according to the detection output of the voltage across the resistance detection circuit are provided. It is possible to reduce the influence of the ambient temperature at the time of measurement on the thermistor forming the bolometer bridge, and improve the accuracy of temperature measurement of the object.

[0009]

【Example】

(Embodiment 1) FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention. Since the basic configuration is common to that of the conventional example, the same parts are designated by the same reference numerals and their description will be omitted. The description will be omitted, and only the characteristic parts of this embodiment will be described.

In this embodiment, a series circuit of a bolometer bridge 1 and a resistor Ra is connected to both ends of a DC power source 2, and a voltage between the bridges of the bolometer bridge 1 (ab in FIG.
It is characterized in that the inter-bridge voltage detection circuit 3 for detecting the inter-bridge voltage and the resistance voltage detection circuit 4 for detecting the voltage across the resistor Ra are provided. The bridge-to-bridge voltage detection circuit 3 and the resistance-both-ends voltage detection circuit 4 have a well-known configuration for measuring a voltage between two points. Since the configurations are not the gist of the present invention, the description thereof will be omitted.

That is, according to the configuration of this embodiment, the inter-bridge voltage detection circuit 3 detects the inter-bridge voltage of the bolometer bridge 1 and the resistance end-to-end voltage detection circuit 4 detects the end-to-end voltage of the resistor Ra at the same time. be able to. Next, the principle of non-contact measurement of the temperature of the object using the infrared detection device of this embodiment will be described.

[0012] First, a thermistor Th ₁ ... resistance R constituting the bolometer bridge 1, related as the following equation between the thermistor Th ₁ ... temperature. R = R ₀ exp {B (1 / T-1 / T ₀ )} where B: B constant of the thermistor R ₀ : Resistance value of the thermistor Th _{1 at the} temperature T ₀ Therefore, the voltage across the resistor Ra at this time Is V ₁ , the voltage between bolometer bridges is V ₂ , the power supply voltage is V ₃ , and the resistance value of the thermistor Th ₁ is R ₁ , the temperature T of _one thermistor (for example, thermistor Th ₁ ) that constitutes the bolometer bridge 1. ₁ is expressed by the following equation.

[0013]

(Equation 1)

However, R ₁ = (V ₃ / V ₁ -1) Ra (R
a is the resistance value of the resistance Ra), and the temperature change of the thermistor Th ₁ due to the incident infrared rays from the surroundings other than the object is very small, so that the influence of the incident infrared rays on the resistance value change of the thermistor Th ₁ can be almost ignored. Now, when infrared rays emitted from an object whose temperature is to be measured are incident on one thermistor Th ₁ which constitutes the bolometer bridge 1, the temperature of the thermistor Th ₁ is changed by the incident infrared rays and the resistance value thereof is R ₁ To R ₂ . Here, the temperature of the thermistor Th ₁ is T ₂ , and the temperatures of the other thermistors Th _{2 to} Th ₄ to which infrared rays are not incident are T ₂ .
Letting ₁ and its resistance value be R ₁ , the temperature T ₂ of the thermistor Th ₁ on which infrared rays are incident is expressed by the following equation.

[0015]

(Equation 2)

[0016] _{However, R 2 / R 1 = (} V 1 -2V 2 -
V ₃₎ is _{/ (V 1 + 2V 2 -V} 3). On the other hand, the infrared ray amount Q radiated to the thermistor Th ₁ is emissivity ε, Stefan-Boltzmann constant σ, measured area (irradiated area)
Let S be the temperature of the object and Ta be the temperature of the object. Q = εσS The (Ta ⁴ -T ₁ ^4), the following expression of relation is established when the heat capacity of the thermistor Th ₁ and C.

[0017] _{^{εσS (Ta 4 -T 1 4)}} = C (T 2 -T 1) Therefore, the temperature Ta of the object from these equations can be obtained by the following equation.

[0018]

(Equation 3)

The operations corresponding to the above equations are shown in the figure.
No arithmetic processing means (for example, a microcomputer
Do) According to the above configuration, infrared detection
When measuring the temperature of an object using the device, the incident infrared
Measurement of dose Q (voltage V across resistor Ra₁Measurement)
Temperature measurement of the meter bridge 1 (voltage between bridges V₂of
(Measurement) and can be performed at the same time.
The simple configuration can reduce the temperature measurement time of the object.
You can In order to improve the detection accuracy,
Voltage between bridges of bridge 1 ₂Higher is desired
For that purpose, the voltage applied to the bolometer bridge 1 is
Source voltage V₃The bolometer bridge
The resistance value of the resistor Ra connected in series to the di1 is the thermistor.
Th₁It is desirable that it is smaller than the resistance value of.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
It is a circuit block diagram showing. The basic configuration of this embodiment is
It is common with the first embodiment, and the same reference numerals are used for the common parts.
The explanation is omitted and the characteristic parts of this embodiment are described.
Only explained. Generally, in infrared detectors,
Configure bolometer bridge 1 to increase output sensitivity
Thermistor Th₁... is the temperature variation of the resistance as much as possible.
The one that has a large variation is used. Therefore, the atmosphere of the measurement environment
Thermistor Th depending on air temperature₁The temperature change of the resistance value of
The voltage across the resistance is detected against changes in ambient temperature.
The detection output of the output circuit 3 will also change greatly.
It For example, the thermistor Th ₁Resistance value R of₁1% of
The detection output V of the voltage across the resistor 3 with respect to the change ₁
Change ΔV₁Is expressed by the following equation.

[0021]

(Equation 4)

Therefore, the difference ΔV _{1 with} respect to the resistance ratio between the resistance value Ra of the resistance Ra and the resistance value R ₁ of the thermistor Th ₁ ...

[0023]

[Table 1]

As described above, when the output voltage V ₁ of the voltage detecting circuit 3 across the resistance greatly changes due to the change of the ambient temperature of the measurement environment, and the resistance value R ₁ of the thermistor Th ₁ increases according to the change of the ambient temperature, becomes small variation [Delta] V ₁ of the output voltage V _1, the detection sensitivity of the infrared detection device is reduced. Therefore, in the present embodiment, in order to prevent the detection sensitivity from being lowered due to the change in the ambient temperature of the measurement environment as described above, a plurality of resistors Ra _{1 having} different resistance values are used instead of the resistor Ra 1 of the first embodiment. a resistor array 5 comprising the to Ra ₄ are connected in parallel, a bolometer and a switching circuit 6 for selectively switching coupled to bolometer bridge 1 at least one of the resistors Ra ₁ to Ra ₄ of these resistor arrays 4 Switching is performed by the switching circuit 6 according to the detection output of the resistor voltage detection circuit 3 that detects the voltage across the resistor Ra ₁ that is connected to the bridge 1 in series and that is switched and connected to the bolometer bridge 1 by the switching circuit 6. It is characterized in that a control circuit 7 for controlling is provided.

In this embodiment, the output voltage V ₁ of the voltage across the resistor 3 which changes in response to a change in the resistance value of the thermistor Th ₁ ... The control circuit 7 compares V ₁ with a preset reference voltage and depending on the comparison result.
Controls the switching circuit 6 to control the bolometer bridge 1
The resistors Ra _{1 to} Ra ₄ connected to are switched so that ΔV ₁ is kept substantially constant with respect to changes in the ambient temperature of the measurement environment.

FIG. 3 is a circuit diagram showing an example of the control circuit 7. The voltage dividing resistors r _{1 to} r ₃ for dividing the power supply voltage V _DD to obtain the reference voltages Vr ₁ and Vr ₂ and the voltage detection circuit across the resistors. It is provided with comparators CP ₁ and CP _{2 for} comparing the output voltage V ₁ of _No. 3 with reference voltages Vr ₁ and Vr ₂ , respectively. Here, the reference voltages Vr ₁ and Vr ₂ are expressed by the following equations, respectively.

Vr ₁ = (r ₂ + r ₃ ) / (r ₁ + r ₂ + r ₃ ) · V _DD Vr ₂ = r ₃ / (r ₁ + r ₂ + r ₃ ) · V _DD And this control circuit 7 measures If the output voltage V _{1 of the} voltage across the resistance detection circuit 3 becomes higher than the reference voltage Vr ₁ due to the increase of the ambient temperature in the environment, the output of the comparator CP ₁ becomes H level and the switching circuit 6 is switched to control the resistance. The resistance value of the array 5 is decreased, and conversely, the ambient temperature in the measurement environment is lowered, so that the output voltage V _{1 of the} voltage across the resistance detection circuit 3 becomes the reference voltage Vr ₂
If it becomes smaller, the output of the comparator CP ₂ goes to L level, and the switching circuit 6 is switched and controlled to increase the resistance value of the resistor array 5.

According to the above configuration, the control circuit 7 switches and controls the switching circuit 6 on the basis of the change in the output voltage V ₁ of the voltage across the resistance detection circuit 3 due to the ambient temperature of the measurement environment and is connected to the bolometer bridge 1. Since the resistance value of the resistance array 5 is variable, the influence on the bolometer bridge 1 with respect to the change in the ambient temperature of the measurement environment can be reduced, and the measurement accuracy can be improved when the temperature is measured for the object. .

[0029]

According to the first aspect of the present invention, there is provided an infrared detecting device for detecting an incident infrared ray amount by a bolometer bridge using a thermistor, wherein a series circuit of the bolometer bridge and the resistor section is connected to both ends of a DC power source. Since the inter-bridge voltage detection circuit that detects the inter-bridge voltage of the bridge and the resistance both-end voltage detection circuit that detects the both-end voltage of the resistance part are provided, the inter-bridge voltage is measured when the temperature of the object is measured in a non-contact manner. The infrared amount measurement by the detection circuit and the temperature measurement of the bolometer bridge by the resistance voltage detection circuit can be performed at the same time, and there is an effect that the measurement time of the temperature of the object can be shortened with a simple configuration.

According to the second aspect of the present invention, since the resistance portion whose resistance value can be changed and the control circuit which changes the resistance value of the resistance portion according to the detection output of the resistance voltage detection circuit are provided, the bolometer is provided. There is an effect that the influence of the ambient temperature at the time of measurement on the thermistor forming the bridge can be reduced and the accuracy of temperature measurement of the object can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a main part of the same.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is a circuit diagram showing another example of the above.

[Explanation of symbols]

1 bolometer bridge 2 DC power supply 3 voltage detection circuit between bridges 4 voltage detection circuit between resistors Th _{1 to} Th ₄ thermistor Ra resistance

Claims (2)

[Claims] 1. An infrared detection device for detecting an incident infrared ray amount by a bolometer bridge using a thermistor, wherein a series circuit of a bolometer bridge and a resistor section is connected to both ends of a DC power source to detect a voltage between bridges of the bolometer bridge. An infrared detecting device, comprising: a voltage detecting circuit between bridges, and a voltage detecting circuit across a resistor for detecting a voltage across a resistor portion. 2. The resistance unit, wherein the resistance value can be varied, and a control circuit for varying the resistance value of the resistance unit according to the detection output of the voltage across the resistance detection circuit. 1. The infrared detection device according to 1.