JPH08261834A - Pyroelectric type infrared detector - Google Patents

Abstract

PURPOSE: To provide a pyroelectric type infrared detector with a simple structure at a lower cost, which permits the detecting of infrared rays radiated from a subject at a high accuracy even when a part of the subject moves finely or the subject is at rest as a whole. CONSTITUTION: A Fresnel lens 2 is arranged on the front of an infrared senior 1 to condense infrared rays radiated from a subject to the infrared sensor 1. A lens 4 for zooming is arranged in front of the Fresnel lens 2. The lens 4 for zooming is made to zoom by a drive means to reciprocate in a specified range. The zooming of the lens 4 for zooming is made when the output from the infrared sensor 1 fails, at a fixed time interval or constantly. As one example of the drive means, a zooming drive circuit is provided and controlled by a control circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared detecting device for detecting the presence of an object to be detected such as a human body by using a pyroelectric infrared sensor.

[0002]

2. Description of the Related Art Conventionally, pyroelectric infrared detectors have been widely used as means for detecting the presence of a human body or the like.
As is well known, the pyroelectric infrared sensor produces an output only when a temperature change is given, and cannot be detected if there is no temperature change. For example, if there is a person in the room but the person is moving in a small area such as a finger or mouth and is stationary as a whole, there is no change in the infrared energy emitted from the human body and therefore the human body cannot be detected. It happens that. Therefore, generally, a chopper plate is arranged in front of the pyroelectric infrared sensor to forcibly change the infrared energy from the human body to enable continuous detection.

[0003]

However, with the chopper mechanism, for example, a stepping motor must be driven through a drive circuit to rotate the chopper plate. For this reason, the apparatus becomes large in size, the configuration becomes complicated, and the cost becomes high.

Therefore, an object of the present invention is to detect a detected object such as a human body with high accuracy even if the detected object such as a human body is moving in a minute range or is stationary as a whole. An object is to provide a possible pyroelectric infrared detection device with a simple structure at low cost.

[0005]

In order to achieve the above object, a pyroelectric infrared detection device of the present invention comprises an infrared sensor, a Fresnel lens for condensing infrared rays emitted from an object to be detected on the infrared sensor, and a Fresnel. The zoom lens is provided in front of the lens, and the driving means for zooming the zoom lens is provided.

The above zoom lens is preferably reciprocally movable within a predetermined range.

The zooming of the zoom lens is preferably carried out when the output from the infrared sensor is no longer produced, at regular time intervals, or at all times.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a Fresnel lens 2 is provided in front of a pyroelectric infrared sensor 1. The Fresnel lens 2 is composed of a plurality of microlenses, and the optical axes of the respective microlenses are all directed toward the infrared sensor 1. The Fresnel lens 2 uses a plastic that transmits only specific infrared rays radiated from an object to be detected, such as a human body, to form a filter having a convex front end, and a plurality of microlenses are integrated in the front end of the filter. It was installed in.

A pyroelectric infrared sensor 1 is disposed at the focal position of the Fresnel lens 2, and a temperature sensor (thermistor in this embodiment) 3 for sensing the ambient temperature is disposed in the vicinity of this sensor. There is.

A zoom lens 4 is arranged in front of the Fresnel lens 2. The zoom lens 4 is composed of a fixed lens 4A and a movable lens 4B, and a zoom drive circuit 50 that constitutes a drive means 5 for zooming the zoom lens 4 is provided.

A drive motor (not shown) is rotationally driven by the output of the zoom drive circuit 50, and the movable lens 4B is moved forward and backward by the rotation of the drive gear of this motor to perform zooming.

The output of the infrared sensor 1 is amplified by the amplifier circuit 6 because the infrared energy radiated from the object to be detected such as a human body is weak, and when the ambient temperature changes, the temperature difference also changes. The temperature correction circuit 7 corrects the fluctuation of the ambient temperature sensed by 3, and the output is mixed with the output of the amplifier circuit 6 and output from the terminal 11. The ambient temperature detected by the temperature sensor 3 is output from the terminal 31.

The zoom drive circuit 50 is controlled by the control circuit 8 to generate an output. The output of the temperature correction circuit 7 is supplied to the control circuit 8 and a signal corresponding to a zoom drive condition is input from a terminal 81. I can do it.

As an example of the driving conditions, various driving conditions such as zooming when the output from the infrared sensor 1 is no longer generated, zooming at a constant time interval regardless of the presence or absence of output, or constant zooming are available. is there.

Next, the operation will be described.

As shown in FIG. 1, when an object to be detected, such as a human body, enters the room, infrared rays emitted from the object to be detected pass through the zoom lens 4 and the Fresnel lens 2 and the infrared sensor 1 is detected. F is collected. The infrared rays incident on the infrared sensor 1 are converted into heat on the surface of the sensing element, and surface charges are generated by the pyroelectric effect. The generated surface charge is
The signal is amplified by the amplifier circuit 6 and is output from the terminal 11 as an electric signal through the temperature correction circuit 7, and at the same time, is input to the control circuit 8 to confirm the presence of the detected object. When the object to be detected entering the room is in a stationary state as a whole, the infrared sensor 1 is not given a temperature change and no output is generated. As a result, no signal is input from the temperature correction circuit 7 to the control circuit 8, and upon receipt of this signal stop, the control circuit 8 generates a stop signal, and the stop signal causes the zoom lens 4 to zoom.

That is, when the object to be detected is a person, the person often makes a minute movement such as moving his arm or head even when lying down. At the time of zooming, a stop signal is generated from the control circuit 8 to output a zoom signal from the zoom drive circuit 50, and a drive motor (not shown) is driven by this signal to drive the moving lens 4B as shown in FIG. The lens is moved in a direction to widen the gap with the fixed lens 4A, and zoomed to a portion that is performing a minute movement. In this zoom state, the minute movement as described above is magnified, so that the infrared rays A and B emitted from the moving part are transmitted through the zoom lens 4 and the Fresnel lens 2 and focused on the infrared sensor 1. It is detected by the infrared sensor 1 as a temperature change,
Output is generated again, and then the moving lens 4B retracts and returns to the fixed position (no zoom state). That is, the zoom lens 4 is in a fixed position while the infrared sensor 1 is producing an output, and when the output is not produced, a zoom signal is output from the control circuit 8 to zoom the zoom lens 4.

In this embodiment, when the output from the infrared sensor 1 is stopped, the zoom lens 4 is zoomed so that the infrared output is generated again. If the zooming is performed at a constant time interval regardless of whether or not there is an output from the infrared sensor 1, the zoom is intermittently performed at a constant time interval even when the overall stationary state continues, such as a bedridden old man. A signal is given and zooming in which the zoom lens 4 reciprocates between a zoom position and a fixed position is intermittently performed, so that a temperature change occurs each time and infrared output is generated. Further, if the zooming is always performed, the zoom lens 4 is repeatedly moved back and forth between the zoom position and the fixed position, so that infrared light is continuously generated as long as a person is there.

[0020]

As described above, according to the present invention, the zoom lens is zoomed. Therefore, even when the detected object such as a human body is stationary as a whole, a small movement which cannot be detected by the conventional method is performed. A part of the detected object is zoomed and its movement is magnified, and the infrared sensor detects the temperature change by this, so it is possible to detect the emitted infrared rays with high accuracy, and with a simple configuration The device can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of the present invention.

FIG. 2 is a cross-sectional view showing the operation of the zoom lens.

[Explanation of symbols]

 1 infrared sensor 2 Fresnel lens 4 zoom lens 5 driving means

Claims (3)

[Claims] 1. An infrared sensor, a Fresnel lens for condensing infrared rays emitted from an object to be detected on the infrared sensor, a zoom lens arranged in front of the Fresnel lens, and a zoom lens for zooming. A pyroelectric infrared detection device, comprising: a driving unit that drives the pyroelectric infrared detection device. 2. The pyroelectric infrared detection device according to claim 1, wherein the zoom lens is configured to reciprocate within a predetermined range. 3. The zoom lens according to claim 1, wherein zooming of the zoom lens is performed when an output from the infrared sensor is no longer generated, at a constant time interval, or at all times. Pyroelectric infrared detector.