JPH07198482A - Pyroelectric infrared sensor system - Google Patents

Abstract

PURPOSE:To obtain the pyroelectric infrared sensor system in which a reference voltage is supplied to a signal processing circuit only by an electric operation and whose measuring time is shortened by a method wherein a power-supply voltage which is supplied to an impedance transformation circuit is lowered or stopped. CONSTITUTION:An impedance transformation circuit 2 impedance-transforms the output signal of a pyroelectric heat-detection element 1. A signal amplifier circuit 3 amplifies the output signal of the transformation circuit 2, and it is constituted of an initial stage 14, of a final stage 16, of a plurality of intermediate stages 15 and of reference-voltage generators 6. A signal processing circuit 5 processes the output signal of the amplifier circuit 3, and it takes out information. A switching element 7 is opened in a mode in which a reference voltage is taken into, and it stops the supply of electric power to the transformation circuit 2 from a power supply 4 so that the output signal of the element 1 is not transmitted to the amplifier circuit 3. The output signal of the amplifier circuit 3 in this state keeps a stable DC potential. As a result, when a switching element 8 is set to continuity, the reference voltage is branchedd at a reference-voltage intake terminal for the processing circuit 5. Thereby, the reference voltage can be taken into only by an electric operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared sensor for detecting a thermal environment and human body behavior.

[0002]

2. Description of the Related Art Recently, a system for measuring a thermal image and a temperature distribution by using a pyroelectric infrared sensor has been developed. In these systems, it is necessary to quantitatively process and measure the amplitude of the output signal of the pyroelectric heat detection element group amplified by the signal amplification circuit. Particularly, when the processing of the output signal is performed digitally, analog / digital conversion (hereinafter referred to as A / D conversion) is required, and the A / D conversion requires a reference voltage that serves as a reference for electrical processing. Become. In addition, the reference voltage may be required even when analog processing is performed. In the conventional sensor system, the reference potential required for the above-mentioned signal processing is obtained by mechanically blocking the infrared rays incident on the pyroelectric heat detecting element group with a chopper. This method does not require a mechanism only to generate the reference voltage, but it requires the reference voltage to be taken in serially with the main measurement, which lengthens the overall measurement time or requires the sensor mechanism to move. However, there are drawbacks such as the burden of software for controlling the sensor system increasing.

[0003]

SUMMARY OF THE INVENTION In the present invention, the mechanical operation as described above is not required, and the power supply to the impedance conversion circuit for impedance-converting the output signal of the pyroelectric thermal detection element group is stopped. By removing the signal component from the output of the signal amplification circuit by making the output signal not transmitted to the circuit in the subsequent stage, the reference potential is measured only by the electrical operation, and the measurement time is shortened or the system The advantage is that the control software is simplified.

[0004]

In order to solve the above problems, the present invention provides a plurality of pyroelectric heat detecting element groups and a chopper for limiting the amount of infrared rays incident on the pyroelectric heat detecting element groups. And an impedance conversion circuit for impedance-converting the output signal of the pyroelectric heat detection element group, and amplifying the output signal of the impedance conversion circuit, or a single stage, or
It has a signal amplifier circuit composed of a plurality of stages of amplifier circuits connected in series, and a signal processing circuit for processing an output signal of the signal amplifier circuit.

The signal processing circuit further comprises means for supplying a reference voltage as a reference for signal processing.

Further, the reference voltage is supplied to the signal processing circuit by lowering or stopping the power supply voltage supplied to the impedance conversion circuit.

Further, the supply of the reference voltage to the signal processing circuit is realized by lowering or stopping the power supply voltage supplied to the amplification circuit of any amplification stage other than the final stage of the signal amplification circuit.

Further, the reference voltage is supplied to the signal processing circuit by short-circuiting the input terminal of the amplification circuit of any amplification stage of the signal amplification circuit to the ground potential by using a switch element.

Further, the reference voltage of the amplification circuit of any amplification stage of the signal amplification circuit is used as a reference voltage for signal processing to realize the reference voltage supply to the signal processing circuit.

Further, it has a reference voltage circuit only for supplying the reference voltage, and the circuit realizes the reference voltage supply to the signal processing circuit.

In the pyroelectric heat detecting element group,
A reference voltage is supplied to the signal processing circuit by using an output signal of a signal amplifier circuit that amplifies the output signal of the element as a reference voltage and has a piezoelectric element that shields infrared rays from entering. It is characterized in that noise unique to the pyroelectric sensor is used for correction.

[0012]

The present invention relates to a reference voltage required for digital processing in a device for quantitatively processing the output signal of a pyroelectric infrared sensor for the purpose of non-contact measurement of the surface temperature of an object. Is supplied only by electric operation.

[0013]

EXAMPLE An example of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a first embodiment of the present invention. In FIG. 1, 1 is an arbitrary element in the pyroelectric thermal image detecting element group, and 2 is an impedance conversion circuit for impedance-converting an output signal of the pyroelectric thermal detecting element. Reference numeral 3 is a signal amplifier circuit for amplifying the output signal of the impedance conversion circuit, and reference numeral 3 is an amplifier circuit at the first stage, an amplifier circuit at the last stage 16, and a plurality of intermediate stage amplifier circuits
5 and a reference voltage generator 6. However, if 14 and 16 or only 14 can provide a sufficient gain, 3 is not necessarily required in a plurality of stages. Reference numeral 4 is a power supply that supplies power to the impedance conversion circuit and the signal amplification circuit, and reference numeral 5 is a signal processing circuit that processes the output signal of the signal amplification circuit and extracts information. Reference numeral 7 is a switch element for controlling the power supply to the impedance conversion circuit, which is opened in the mode for taking in the reference voltage to stop the power supply to 2 and prevent the output signal of 1 from being transmitted to 3 in the subsequent stage. . The output signal of 3 in this state maintains a stable DC potential, so that the switching element 8 is turned on, thereby
It is branched to the reference voltage input terminal of. If the reference voltage can be fetched in terms of software or circuit out of 5, 8 is not always necessary.

FIG. 2 is a diagram showing a second embodiment of the present invention. Reference numeral 9 is a switch element for controlling power supply to 2 or 14 or 15, or all of them. 2 or 1
The power supply to 4 or 15 is stopped, the transmission of the output signal to 16 is stopped, and the mode for taking in the reference voltage is formed as in the first embodiment.

FIG. 3 is a diagram showing a third embodiment of the present invention. The switch element 10 short-circuits the output signal of 2 to the ground potential through the resistance element to stop the transmission of the signal to the latter stage 3 and forms a mode for taking in the reference voltage as in the first embodiment. 10 is not only between 2 and 14 but also 1
The same applies when connecting between 4 and 15 and between 15 and 16.

FIG. 4 is a diagram showing a fourth embodiment of the present invention. The switch element 11 controls the transmission line of the signal from 14 to 15, and when 11 is released,
The signal transmission to the circuit is stopped and the mode for taking in the reference voltage is formed as in the first embodiment.

FIG. 5 is a diagram showing a fifth embodiment of the present invention. It is branched from the reference voltage of the arbitrary amplification circuit of 3 and used for taking in the reference voltage of 5.

FIG. 6 is a diagram showing a sixth embodiment of the present invention. The reference voltage generated from the reference voltage generation circuit 12 is used as the reference voltage of 5, and 12 can be supplied by a circuit in which the power supply voltage is simply divided by a resistor, and the accuracy and stability are improved. In this case, it is also possible to convert the impedance with an operational amplifier or the like before supplying.

FIG. 7 is a diagram showing a seventh embodiment of the present invention. Reference numeral 13 is a pyroelectric type heat detection element which is optically shielded from the outside, and its output signal is inputted to the reference voltage terminal 5 via 2 and 3. Since 13 is shielded and does not output a signal due to a change in infrared rays, the amplified output signal can be used as a reference voltage. In addition, the piezoelectric noise generated by physically vibrating the pyroelectric heat detection element group and the temperature noise due to the change in ambient temperature are accurate and stable for the temperature measurement system using the pyroelectric heat detection element group. In the present embodiment, noise having the same amplitude and the same phase as that of 1 is generated in 13 as well, so that the output thereof is used to correct the noise component, and the accuracy and stability of the system are improved. Can be improved.

[0020]

According to the present invention, by electrically interrupting the transmission line of the output signal from the pyroelectric heat detecting element group,
It is possible to take in the reference voltage to the signal processing circuit only by electrical operation, thereby shortening the measuring time of the temperature measuring system and simplifying the control software. In addition, by using a reference voltage supply circuit that has an optically shielded pyroelectric heat detection element, it is possible to correct the piezoelectric noise and temperature noise generated from the pyroelectric heat detection element group, thus improving system accuracy and stability. It is possible to improve the property.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

[Fig. 2] The same configuration diagram

[FIG. 3] The same configuration diagram

[Fig. 4] The same configuration diagram

[Fig. 5] The same configuration diagram

FIG. 6 is the same configuration diagram

[Fig. 7] The same configuration diagram

[Explanation of symbols]

 1 Pyroelectric heat detection element 2 Impedance conversion circuit 3 Signal amplification circuit 4 Power supply 5 Signal processing circuit 6 Reference voltage generator 7 Switch element 1 8 Switch element 2 9 Switch element 3 10 Switch element 4 11 Switch element 5 12 Reference voltage generation Circuit 13 Optically shielded pyroelectric thermal detection element 14 First stage amplifier circuit 15 Intermediate stage amplifier circuit 16 Last stage amplifier circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isamu Okuda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A plurality of pyroelectric heat detecting element groups, a chopper for limiting the amount of infrared rays incident on the pyroelectric heat detecting element group, and an impedance of an output signal of the pyroelectric heat detecting element group. An impedance conversion circuit for conversion, and a single stage for amplifying the output signal of the impedance conversion circuit, or
A pyroelectric infrared sensor system having a signal amplification circuit composed of a plurality of stages of amplification circuits connected in series and a signal processing circuit for processing an output signal of the signal amplification circuit. 2. The pyroelectric infrared sensor system according to claim 1, further comprising means for supplying a reference voltage serving as a reference for signal processing to the signal processing circuit. 3. The pyroelectric infrared sensor system according to claim 2, wherein the reference voltage is supplied to the signal processing circuit by lowering or stopping the power supply voltage supplied to the impedance conversion circuit. 4. The reference voltage supply to the signal processing circuit is realized by reducing or stopping the power supply voltage supplied to the amplification circuit of any amplification stage other than the final stage of the signal amplification circuit. Pyroelectric infrared sensor system. 5. The reference voltage supply to the signal processing circuit is realized by short-circuiting the input terminal of the amplification circuit of an arbitrary amplification stage of the signal amplification circuit to the ground potential by using a switch element. Pyroelectric infrared sensor system. 6. A signal line for connecting the impedance conversion circuit and the signal amplification circuit, or a signal line for connection between amplification circuits of arbitrary amplification stages is opened by using a switch element, and thereby the signal processing circuit is opened. The pyroelectric infrared sensor system according to claim 2, which realizes the reference voltage supply. 7. The pyroelectric according to claim 2, wherein a reference voltage is supplied to the signal processing circuit by using a reference voltage of an amplification circuit of an arbitrary amplification stage of the signal amplification circuit as a reference voltage for signal processing. Infrared sensor system. 8. The pyroelectric infrared sensor according to claim 2, further comprising a reference voltage circuit only for supplying a reference voltage, and the reference voltage circuit realizes the reference voltage supply to the signal processing circuit. system. 9. The pyroelectric heat detection element group has an element shielded from infrared rays so that the output signal of a signal amplification circuit for amplifying the output signal of the element is used as a reference voltage. Thus, the reference voltage supply to the signal processing circuit is realized, and the noise peculiar to the pyroelectric sensor such as piezoelectric noise is used for correction, and the pyroelectric infrared sensor system according to claim 2.