JP2011124847A - Amplifier of output of resistance-type infrared sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the saturation of an amplification circuit at a temperature drift caused by a change or the like in environmental temperature, in the amplification circuit which amplifies a variable resistance-type infrared detection element that is not temperature-controlled. <P>SOLUTION: The amplification circuit for the variable resistance-type infrared detection element includes a subtraction circuit that subtracts an output of a D-A converter from an output of the amplification circuit in a first stage. The saturation of the amplification circuit is prevented eve if the temperature control of a sensor element is not performed by subtraction-amplifying a drift component at a temperature change of an atmosphere by having a second-stage amplification circuit which amplifies an output from the subtraction circuit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an amplifying apparatus that performs stable amplification by preventing saturation of an amplifying circuit due to drift of a sensor output due to a change in environmental temperature with respect to output amplification from a resistance change type two-dimensional infrared sensor array.

  As a conventional method of amplifying the output of a resistance infrared sensor, a temperature control element such as a Peltier element is used to control the sensor element to a constant temperature, preventing a large drift in sensor output due to environmental temperature changes, and preventing saturation of the amplifier circuit. Temperature control is performed to obtain a constant output.

The resistance-type infrared sensor detects a change in resistance due to a temperature change on the surface of the sensor element due to infrared rays radiated from an object to be measured, and converts it into an electrical signal for output. However, the temperature change of the sensor surface that is changed by infrared rays emitted from the measurement object is very small. For example, if the temperature change of the object is 1 ° C., the temperature change of the sensor element surface is 0.001 ° C. Degree. At this time, when the temperature of the surface of the infrared sensor element fluctuates due to a factor other than infrared input, particularly the environmental temperature, this fluctuation is converted into an electric signal as a drift signal, and the amplifier circuit is saturated. Therefore, it is necessary to always control the temperature around the infrared sensor to be constant. However, in order to maintain the sensor peripheral part at a constant temperature, the current consumption due to the temperature control element is increased, and the cost of the apparatus is increased. Therefore, a method of not performing the temperature control has been devised.
Japanese Patent Laid-Open No. 2000-131148 devises a method for extracting and correcting a temperature drift component from image data captured in a state where infrared rays from the outside are blocked.

JP 2000-131148 A

  In the above conventional technique, if the environmental temperature changes greatly, there is a problem that the amplification circuit for obtaining the correction data is easily saturated and the temperature drift component cannot be extracted.

  The present invention has been made in order to solve the above-described problems. Even in an environment where the environmental temperature changes greatly, the amplification circuit of the amplifier circuit can be controlled without constant control of the sensor ambient temperature. An object of the present invention is to provide an amplifying device that prevents saturation and amplifies a sensor output signal.

In order to achieve the above object, the infrared sensor output amplifying device of the present invention provides the following means.
The output by infrared input from the infrared sensor is input to the first stage amplifier circuit, and the amplification degree is set so that the first stage amplifier circuit is not saturated by the drift signal from the infrared sensor output due to environmental temperature change. ing.
The output from the first amplifying circuit is input to the subtracting circuit, the value obtained by D / A converting the data from the CPU is subtracted by the subtracting circuit, and then input to the second amplifying circuit. The output of the second amplifier circuit is A / D converted and read by the CPU. The CPU compares the output of the second amplifier circuit with the reference frame data, and if there is a difference, the CPU performs an arithmetic process so that the difference data is subtracted in the next frame, and the subtractor circuit via the D / A An infrared sensor output amplifying device that outputs subtraction data to the CPU, performs correction by the CPU so that the output of the second amplifier circuit is always constant, and adds the subtraction data to the read output data from the second amplifier circuit .

The temperature change of the sensor surface that is changed by infrared rays emitted from the measurement object is very small. For example, if the temperature change of the object is 1 ° C., the temperature change of the sensor element surface is about 0.001 ° C. . If the ambient temperature changes by 1 ° C., in the case of a sensor that does not control the temperature to a constant temperature, the temperature of the sensor element surface also changes by 1 ° C., and the output from the sensor element changes the temperature of the measured object by 1 ° C. The temperature drift signal is 1000 times as much as the signal.
In such a state, the amplifier circuit in the prior art is easily saturated with the drift signal.
According to the present invention, it is possible to perform amplification without saturation even if the output signal is from an infrared sensor including a drift signal without controlling the temperature around the infrared sensor with a Peltier element or the like. The problem of increase in current consumption and increase in manufacturing cost due to the mounting of can be solved.

The figure explaining the form of this invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Signals are mixed with digital output and analog output, but the values will be described as equivalent.
The output 100 of the n frame from the infrared sensor is amplified by the first amplifier circuit 1 to become an output 101, and the output 106 from the D / A 6 is subtracted by the subtractor circuit 2 to become the output 102, which is amplified by the second amplifier circuit 3 and the signal This signal 103, which becomes 103, is converted from analog to digital by A / D4, and a digital signal 104 is output to the CPU 5. The CPU 5 performs comparison operation processing with the stored reference frame data, outputs the difference data obtained by dividing the amplification degree of the second amplifier circuit to the D / A 6 as subtraction data at the time of reading n + 1, and adds the difference data. Output 107 is output as n-frame infrared sensor signal data.
Here, the amplification degree of the first amplification circuit 1 is G1, the amplification degree of the second amplification circuit 3 is G2, the output nth frame from the infrared sensor that is sequentially read is used as a reference frame, and the value of the infrared sensor signal 100 is Assuming A, the signal 101 output from the first amplifier circuit is G1 × A. Since the nth frame is a reference frame, the subtraction signal 106 input to the subtraction circuit 2 is 0, and the output 103 obtained by amplifying the output 102 from the subtraction circuit 2 by the second amplification circuit 3 is converted by A / D4. The output 104 is G1 × G2 × A. Next, the CPU stores G1 × G2 × A as reference n-frame subtraction value calculation data, adds difference data to the value of G1 × G2 × A, and outputs the result as n-frame sensor signal data 107. Since n frames are reference frames, the difference is zero.

Next, when reading the frame n + 1, if the drift signal Ad1 is superimposed on the value A of the signal 100 from the infrared sensor, the previous n frame is the reference frame and the subtraction signal is 0. The output 103 of 3 is G1 × G2 × (A + Ad1). This value is compared with the stored reference n frame subtraction value calculation data G1 × G2 × (A) to obtain a difference G1 × G2 × Ad1. Then, G1 × G2 × (A + Ad1) is added with difference data 0 subjected to subtraction processing when n + 1 frame is read, and G1 × G2 × (A + Ad1) is output as infrared sensor n + 1 frame signal data 107.
When reading the next n + 2 frame, the CPU 5 outputs a value G1 × Ad1 obtained by dividing the difference G1 × G2 × Ad1 obtained in the n + 1 frame by the amplification degree G2 of the second amplifier circuit 3 to the D / A6 as an output 105. The D / A 6 converts the signal 105 from digital to analog and outputs a subtraction signal 106. When the drift signal Ad2 is further superimposed on the n + 2 frame, the output signal 100 from the infrared sensor becomes A + Ad1 + Ad2, and the CPU 5 secondly amplifies the output signal 102 from the subtraction circuit 2 of the n + 2 frame obtained by subtracting G1 × Ad1 by the subtraction circuit. Data G1 × G2 × (A + Ad2) obtained by analog-digital conversion of the output 103 amplified by the circuit 3 by A / D4 is obtained. The CPU 5 adds the difference G1 × G2 × Ad1 calculated to obtain the subtraction value to the output data, and outputs G1 × G2 × (A + Ad1 + Ad2) as the infrared sensor n + 2 frame signal data 107. At the same time, comparison operation is performed with n frame subtraction value calculation data G1 × G2 × A to obtain subtraction data G1 × (Ad1 + Ad2) / G2 when n + 3 frame data is acquired.

By repeating such processing, even when the drift signal superimposed on the infrared sensor output is superimposed on A, A + Ad1, A + Ad1 + Ad2, and A + Ad1 + Ad2 + Ad3, it is input to the second amplifier circuit by performing subtraction processing. The signals are G1 × (A), G1 × (A + Ad1), G1 × (A + Ad2), G1 × (A + Ad3), and can be amplified while preventing saturation of the second amplifier circuit, and the subtraction data is added. Therefore, even if the drift signal is included in G1 × G2 × (A), G1 × G2 × (A + Ad1), G1 × G2 × (A + Ad1 + Ad2), and G1 × G2 × (A + Ad1 + Ad2 + Ad3), an infrared sensor is used. A value obtained by amplifying the output can be obtained.
When the output voltage from the infrared sensor is 1 μV, if the temperature changes by 1 ° C., 1000 mV of 1 mV is superimposed as a drift signal and amplified by a 100,000 times amplification circuit, the drift signal alone becomes 100 V, and the amplifier Is saturated and the correct value cannot be obtained. However, if the first stage amplification is 1000 times and the second stage is 100 times the amplification circuit of 100,000 times, when the drift signal of 1 mV is superimposed on the infrared output of 1 μV, the output of the first amplification circuit is This 1V is subtracted by the subtracting circuit, and 1 mV is amplified by the second amplifying circuit to give an output of 0.1V. The CPU can obtain the amplified infrared signal 100.1V by multiplying the subtracted 1V by the amplification degree 100 of the second amplifier circuit.

DESCRIPTION OF SYMBOLS 1 1st amplifier circuit 2 Subtraction circuit 3 2nd amplifier circuit 4 A / D converter 5 Arithmetic unit CPU
6 D / A converter 100 Analog output signal 101 from infrared sensor Analog amplified signal 102 from first amplifier Analog output 103 from subtractor circuit 103 Amplified signal 104 from second amplifier circuit Digital data 105 from A / D converter Digital data from device CPU 106 Analog signal from D / A converter

Claims (1)

  An amplifying apparatus that prevents saturation of an amplifying circuit due to a temperature drift due to a change in environmental temperature of output data from a resistance change type infrared sensor that is not temperature-controlled, between a first amplifying circuit and a second amplifying circuit The nth frame of the sensor output sequentially read is used as a reference frame, the output of the second amplification circuit of the reference frame is A / D converted, and the value is stored as reference data. When the CPU performs a comparison operation with the output value of the second amplifier circuit and a difference occurs due to a change in environmental temperature, the CPU calculates the value to be subtracted by the subtractor circuit, and reads the next n + 2 frame. Is converted to an analog signal, input to the subtractor circuit, and the drift generated between frame n and frame n + 1 is subtracted by the subtractor circuit so that the second amplifier circuit is not saturated by temperature drift. An infrared sensor signal characterized in that the difference between frame n and frame n + 1 is added to the data obtained by A / D converting the signal obtained from the amplifier circuit and output as amplified infrared sensor signal data of n + 3 frames. Amplification equipment.

Images