JP3127285B2 - Pyroelectric infrared detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared detecting apparatus for detecting the presence of an object such as a human body 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, a pyroelectric infrared sensor generates an output only when a temperature change is given, and becomes undetectable without a temperature change. For example, if there is a person in the room, but only moving in a small area such as a finger or mouth and the whole is still, there is no change in the infrared energy radiated from the human body, which makes it impossible to detect the human body That results. Therefore, in general, a chopper plate is disposed in front of the pyroelectric infrared sensor to make a continuous change in infrared energy from a human body, thereby enabling continuous detection.

[0003]

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

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

[0005]

In order to achieve the above object, a pyroelectric infrared detector according to the present invention comprises an infrared sensor, a Fresnel lens for condensing infrared light emitted from an object to be detected on the infrared sensor, and a Fresnel lens. Output is generated from a zoom lens disposed in front of the lens, driving means for driving the zoom lens, and an infrared sensor.
The zoom lens in the non-zoom position during
When the output from the sensor stops, the zoom lens
Control means for controlling the driving means so as to drive the nozzle .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One 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 on the front surface of a pyroelectric infrared sensor 1. The Fresnel lens 2 is composed of a plurality of micro lenses, and the optical axis of each micro lens is all directed to the infrared sensor 1. The Fresnel lens 2 forms a filter having a convex front end using a plastic that transmits only specific infrared rays radiated from an object to be detected such as a human body, and a plurality of micro lenses are integrally formed in the front end of the filter. It is provided in.

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

A zoom lens 4 is disposed in front of the Fresnel lens 2. Zoom lens 4 is composed of a fixed lens 4A and the moving lens 4B, a zoom driving circuit 50 constituting the drive means 5 that drive 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 moving gear 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 infrared energy radiated from an object to be detected such as a human body is weak, and the temperature difference changes when the ambient temperature changes. The fluctuation of the ambient temperature sensed by 3 is corrected by the temperature correction circuit 7, and this 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 a terminal 31.

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

[0013] As an example of the driving conditions, the driving's over beam lens 4 when it is not generated the output from the infrared sensor 1
Move.

Next, the operation will be described. As shown in FIG. 1, for example, when a detection target such as a human body enters a room, infrared rays emitted from the detection target pass through the zoom lens 4 and the Fresnel lens 2 and are collected on the infrared sensor 1. Is done. The infrared light incident on the infrared sensor 1 is converted into heat on the surface of the sensing element, and a surface charge is generated by a pyroelectric effect. The generated surface charge is amplified by the amplifier circuit 6 and output as an electric signal from the terminal 11 via the temperature correction circuit 7, and at the same time, is input to the control circuit 8 to confirm the presence of the object to be detected. When the detected object that has entered the room is in a stationary state as a whole, no temperature change is given to the infrared sensor 1 and no output is generated. Thus no input signal to the control circuit 8 from the temperature compensation circuit 7, and generates a stop signal in the control circuit 8 receives the stop of the signal, that to drive the zoom lens 4 by the stop signal.

That is, when the object to be detected is a person, the person often performs minute movements such as moving his arm or head even when lying down. At the time of zooming, when a stop signal is generated from the control circuit 8, a zoom signal is output from the zoom drive circuit 50, and a drive motor (not shown) is driven by this signal, and as shown in FIG. The lens is moved in a direction to widen the distance from the fixed lens 4A, and a portion where a minute operation is performed is zoomed. In this zoom state, the minute movement as described above is enlarged, and the infrared rays A and B emitted from the moving part are transmitted through the zoom lens 4 and the Fresnel lens 2 and are collected on the infrared sensor 1. It is sensed by the infrared sensor 1 as a temperature change,
The output is generated again, and subsequently, the moving lens 4B moves backward and returns to the home position ( non-zoom position ). That is, while resulting output from the infrared sensor 1, a zoom lens 4 is in place and becomes no longer occur the output, and outputs a zoom signal from the control circuit 8, that drive the zoom lens 4.

In this embodiment, when the output from the infrared sensor 1 is no longer generated, the zoom lens 4 is zoomed to generate the infrared output again. If zooming is performed at fixed time intervals regardless of the presence or absence of output from the infrared sensor 1, intermittent zooming is performed at fixed time intervals, especially when the entire body remains stationary, such as a bedridden elderly person. A signal is given, and zooming, in which the zoom lens 4 reciprocates between the zoom position and the home position, is performed intermittently, so that a temperature change occurs each time and an infrared output is generated. If zooming is performed constantly, the zoom lens 4 is repeatedly moved back and forth between the zoom position and the fixed position, so that infrared output is continuously generated as long as the person is there.

[0017]

According to the present invention, since the zoom lens is zoomed, even if the object to be detected such as a human body is stationary as a whole, it performs a minute operation which cannot be detected conventionally. A part of the object to be detected is zoomed and its movement is enlarged, and the infrared sensor detects temperature changes.This makes it possible to detect infrared radiation with high accuracy and has a simple configuration. The device can be provided at low cost.

[Brief description of the drawings]

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Infrared sensor 2 Fresnel lens 4 Zoom lens 5 Driving means 8 Control means (control circuit)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01J 5/00-5/62 G01J 1/00-1/46 G01V 8/12 G03B 27/34

Claims (1)

(57) [Claims] 1. An infrared sensor, a Fresnel lens for condensing infrared light emitted from an object to be detected on the infrared sensor, a zoom lens disposed in front of the Fresnel lens, and driving the zoom lens driving means for, while the output from the infrared sensor has occurred the zoom
The infrared lens to the non-zoom position
The above zoom lens when the output from the
Control means for controlling the driving means so as to drive the device. [0001]