JPH09292277A - Infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the position of an object with a simple structure without using an infrared ray shielding means such as a chopper. SOLUTION: In this device, infrared rays from four detecting areas 7a-7d are converged onto corresponding thermistors 1a-1d by infrared ray condensers 8a-8d, and the change of resistance values of the thermistors 1a-1d is detected by a signal processing circuit 6, whereby the presence of an object in each detecting area 7a-7d is detected. This device has a differential amplifier 5 for forming bridge circuits by the thermistors 1a-1d and detecting the difference in intermediate potential of the bridge circuits, and a switching circuit 4 capable of changing the combination of the thermistors 1a-1d. The combination of the thermistors 1a-1d is changed by the switching circuit 4, whereby the presence of the object 9 in the detecting areas 7a-7d is detected on the basis of the differential signals in the respective combination states of the thermistors 1a-1d in the signal processing circuit 6.

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 detection area in which an object emitting infrared rays, such as a human body, exists.

[0002]

2. Description of the Related Art Conventionally, there have been known infrared detectors capable of detecting a position, in which pyroelectric elements are connected in an array or in which a plurality of thermopiles are connected, and infrared rays incident on the pyroelectric elements or thermopile. The output signal changes according to the change in the amount, and the position detection can be performed based on the change in the output signal.

[0003]

However, since the infrared detecting device using the pyroelectric element outputs a signal only when the incident amount of infrared rays changes, continuous infrared ray incident can be detected. There wasn't. Therefore, it is necessary to shield infrared rays by using a chopper or the like, which causes a problem that the structure becomes complicated.

Further, the infrared detector using the thermopile has a problem that a highly accurate amplifier is required because the output signal thereof is extremely small.

The present invention has been made in view of the above points, and it is an object of the present invention to detect the position of an object with a simple structure without using an infrared ray shielding means such as a chopper. An object is to provide an infrared detection device.

[0006]

According to the first aspect of the present invention,
An infrared light receiving element is formed by forming thermistors having the same resistance value at the same temperature on four thin films that are thermally insulated from each other on a semiconductor substrate. An infrared detector that detects the presence of an object in each detection area by focusing the infrared rays from the detection area on the corresponding thermistor and detecting the change in the resistance value of the thermistor in the signal processing circuit. In the switching circuit, the thermistor is provided with a difference amplifier for forming a bridge circuit and detecting a difference between intermediate potentials of the bridge circuit, and a switching circuit capable of changing a combination of the thermistors forming the bridge circuit. In the signal processing circuit, by changing the combination of each thermistor, It is characterized in that to detect the presence of an object in the sensing area based on the difference signal in each state of the combined saw.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a schematic configuration of an infrared detection device according to an example of an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a plane and a cross section of the schematic configuration of an infrared detection device according to the above. . Reference numerals 1a to 1d are thermistors whose resistance values change with infrared rays, and are set to have the same resistance value at the same temperature. The thermistors 1 a to 1 d are formed on the four thin films 2 a to 2 d which are formed on the semiconductor substrate 2 and are thermally insulated from each other, and constitute the infrared detection element 1. Note that 11 to 16 are connection terminals. Thermistors 1a and 1b and Thermistor 1
c and 1d are respectively connected in series, and thermistors 1a to 1d
Are arranged so as to form a bridge circuit. A power source 3 supplies power to the bridge circuit composed of the thermistors 1a to 1d. Reference numeral 4 is a switching circuit for changing the combination of the thermistors 1a to 1d and changing the connection relationship between the power supply 3 and the bridge circuit. 5 is a differential amplifier, the thermistor 1
The potential difference between the potential at the connection point 12 of a and 1b and the potential at the connection point 15 of the thermistors 1c and 1d is amplified. Reference numeral 6 denotes a signal processing circuit which takes in the potential difference signal output from the differential amplifier 5 and outputs a switching signal to the switching circuit 4 and also the thermistor 1a.
The potential difference signal when the combination of 1d to 1d is changed is also detected, and the thermistors 1a to 1d having a change in resistance value are detected.

FIG. 3 is a schematic diagram showing the correspondence between the thermistors 1a to 1d constituting the infrared detecting element 1 and the detection areas 7a to 7d. Infrared rays emitted from an object such as the human body 9 existing in each of the detection areas 7a to 7d are detected by the detection area 7a.
Infrared condensing lenses 8a-8 arranged corresponding to 7d
The light is focused on the thermistors 1a to 1d by d. That is, as shown in FIG. 3, the infrared rays emitted from the human body 9 present in the detection area 7c are condensed on the thermistor 1c by the infrared condenser lens 8c.

Next, the operation of this embodiment will be described. now,
It is assumed that the switching circuit 4 is set in the state as shown in FIG. 1 and that NTC thermistors are used as the thermistors 1a to 1d. Since the thermistors 1a to 1d are set to have the same resistance value if the temperature of the installation environment is the same, the thermistors 1a to 1d show the same resistance value unless the installation environment is kept at room temperature and infrared rays are irradiated. Therefore, in this case, the bridge circuit is balanced and the output of the differential amplifier 5 is zero.
It is. Here, as shown in FIG. 3, if the human body 9 enters the detection area 7c, the infrared rays emitted from the human body 9 are irradiated to the thermistor 1c via the infrared condenser lens 8c, and the temperature of the thermistor 1c rises. However, the resistance value decreases as the temperature rises. In this case, the bridge circuit is unbalanced, a positive power source is applied to the connection terminal 16, and only the resistance value of the thermistor 1c becomes lower than the resistance values of the other thermistors, so that the output of the differential amplifier 5 is the thermistor. It becomes a positive value by the amount corresponding to the amount of change in the resistance value of 1c. In the signal processing circuit 6, when the output signal of the differential amplifier 5 is taken in, a control signal for switching the switch is sent to the switching circuit 4, and the switching circuit 4
The switch of is changed. Due to the switching of the switch of the switching circuit 4, the positive power source is applied to the connection terminal 14 and the negative power source is applied to the connection terminal 16 in this state, and when the resistance value of the thermistor 1c is low, the difference is small. The output of the dynamic amplifier 5 has a negative value corresponding to the amount of change in the resistance value of the thermistor 1c. The output signal of the differential amplifier 5 in this case is also taken into the signal processing circuit 6. In the signal processing circuit 6, when the output signal of the differential amplifier 5 is output as a positive value, it is output as H (high level), and when it is output as a negative value, it is output as L (low level) and a value of 0. By determining the threshold value in consideration of the amplification factor and the offset voltage so as to be M (middle level), it is possible to determine the three-stage output signal of the differential amplifier 5. Then, the combination of the two output signals of the differential amplifier 5 obtained by switching the switching circuit 4 determines which detection region 7a the human body 9 is in.
It is possible to detect whether it exists in ~ 7d.
In this case, that is, when the human body 9 exists in the detection area 7c, the output signal of the differential amplifier 5 becomes (H, L). The output signal of the differential amplifier 5 is (L, H) when the human body 9 is in the detection area 7d, and the output signal of the differential amplifier 5 is (L, H) when the human body 9 is in the detection area 7a. L, L), and when the human body 9 exists in the detection area 7b, the output signal of the differential amplifier 5 becomes (H, H). Further, when the human body 9 does not exist in any of the detection areas 7a to 7d, the output signal of the differential amplifier 5 becomes (M, M).

As described above, the detection areas 7a to 7d in which the human body 9 exists can be detected based on the combination of L and H of the output signals of the differential amplifier 5.

[0011]

As described above, according to the first aspect of the present invention, thermistors having the same resistance value at the same temperature are formed on the four thin films thermally insulated from each other formed on the semiconductor substrate. The infrared light receiving element is configured by forming each of them, and the infrared light collecting lens collects the infrared light from the four detection areas on the corresponding thermistor, and the signal processing circuit detects the change in the resistance value of the thermistor. In the infrared detection device configured to detect the presence of an object in each detection area, a bridge circuit is formed by the thermistor, and a difference amplifier for detecting a difference in intermediate potential of the bridge circuit is provided, and the bridge circuit is provided. The thermistor is equipped with a switching circuit that can change the combination of the thermistors that make up the circuit. By changing the above, the signal processing circuit detects the presence of an object in each detection area based on the difference signal in each state of each thermistor combination, so use an infrared light shielding means such as a chopper. In other words, an infrared detection device capable of detecting the position of an object with a simple configuration can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of an infrared detection device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic view of a plane and a cross section in XY showing a schematic configuration of the infrared detection element according to the above.

FIG. 3 is a schematic diagram showing a correspondence relationship between each thermistor constituting the infrared detection element and a detection region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Infrared detection element 1a-1d Thermistor 2 Semiconductor substrate 2a-2d Thin film 3 Power supply 4 Switching circuit 5 Differential amplifier 6 Signal processing circuit 7a-7d Detection area 8a-8d Infrared condensing lens 9 Human body 11-16 Connection terminals

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[Procedure amendment]

[Submission date] September 2, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (1)

[Claims] 1. An infrared light receiving element is formed by forming thermistors having the same resistance value at the same temperature on four thin films formed on a semiconductor substrate and thermally insulated from each other. An optical lens is used to focus the infrared rays from the four detection areas on the corresponding thermistors, and the signal processing circuit detects the change in the resistance value of the thermistor to detect the presence of an object in each detection area. In the infrared detection device described above, a bridge circuit is formed by the thermistor, and a differential amplifier that detects a difference in intermediate potential of the bridge circuit is provided, and a switching circuit that can change a combination of the thermistors that form the bridge circuit is provided. However, by changing the combination of the thermistors in the switching circuit, An infrared detection device characterized in that the presence of an object in each detection region is detected based on a difference signal in each state of a combination of thermistors.