JPS6340895A - Moving object detector - Google Patents

Abstract

PURPOSE:To cancel physical changes due to a disturbance factor one another and prevent the malfunction of a detector by providing a pair of differential type infrared sensors, converting the detection signals thereof to absolute values, conducting subtractions and performing level decisions. CONSTITUTION:Two differential type infrared sensors 6 and 7, wherein a pair of detecting elements 6a and 6b and a pair of detecting elements 7a and 7b, respectively, with different polarities from each other are differentially connected to each other, are arranged in parallel in the moving direction of a moving object. When the moving object crosses the detecting area of an optical system, the detecting elements feed out detection signals having time delays due to the movement of the object. These signals are, after amplified, inputted to absolute-value circuits 10 and 11 and subtractions (12) are conducted on the signals converted to absolute values. Then, whether the signals are above a set level is judged and, when they are above the set level, an output circuit 14 is actuated and an alarm is emitted or an automatic door is opened and closed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention detects the presence or absence of a moving object such as a human body within a predetermined detection area and controls the opening/closing of an automatic door or the operation of a security alarm device. The present invention relates to a moving object detection device that can be applied to an activation switch for detecting a moving object.

<Prior art> Various types of moving object detection devices have been put into practical use for detecting moving objects such as human bodies and used as activation switches to control the activation of security alarm devices. A commonly used non-contact detection device is an infrared passive detection device that uses fluctuations in radiated infrared light flux based on the temperature difference between the background and the moving object. This detection device is shown in Figure 6. The radiant energy of a predetermined detection pattern is transmitted to the infrared sensor 2 by an optical system 1 consisting of a mirror or lens.
focus on. The infrared sensor 2 converts changes in the focused radiant energy into an electrical signal, and this electrical signal is sent to the amplifier circuit 3.
After being amplified by the signal level determination circuit 4, it is determined whether the signal level is higher than the detection level or not.If the signal level is higher than the detection level, a signal is output, and this output signal drives the alarm output circuit 5 to trigger the relay. activate and issue an alarm.

Further, as shown in FIG. 7, the infrared sensor 2 is generally of a differential type called a twin type sensor or dual type sensor in which two detection elements 2a and 2b of different polarities are differentially connected. , radiant energy from the floor and wall surfaces in the detection area set by the optical system 1 is constantly detected, and when a human body enters this detection area, the incident energy to the infrared sensor 2 changes,
When this variation exceeds a certain level, an alarm is output.

<Problems to be Solved by the Invention> Incidentally, the above-mentioned infrared detection elements 2a and 2b have noise caused by external factors in addition to the noise inherent in the elements themselves. That is, first, disturbance light from sunlight, illumination light, or car headlights; second, sudden changes in the ambient temperature around the infrared sensor 2 due to sunlight, wind, air conditioners, etc.; and third, radio equipment, electric motors, etc. When electromagnetic wave noise or radio waves caused by lightning induction occur, the infrared sensor 2 reacts as a change in incident energy. The differential infrared sensor 2 described above detects noise caused by such external factors using a pair of detection elements 2a.

They can be removed by canceling each other in 2b.

To be more specific, since the object to be measured in this type of detection device is a moving object, for example, when the moving object moves in the direction of the arrow in FIG. 7, as shown in FIG.
The detection signal AI from the rain detection element 2b and the detection signal B1 from the second detection element 2b are output with a certain time difference, whereas physical changes caused by external factors are equally applied to the rain detection elements 2a and 2b at the same time. As shown in Figure 8 (bl, (C)), elements 2a and 2b simultaneously output outputs A2 and B2, respectively, and since they are connected differentially, voltages with opposite polarities and the same magnitude are generated. By canceling each other out, no output from the sensor 2 should be generated.

However, it is impossible to make each of the detection elements 2a and 2b completely the same shape and performance, and there are considerable variations, and there is a sensitivity difference between the rain detection elements 2a and 2b, and there is also a disturbance It does not necessarily act equally on the rain detection elements 2a and 2b. Therefore, even if it is a differential type, it is impossible to cancel out the signals A2 and B2 due to disturbance noise and make the output completely zero, and in reality, as shown in Figure 8+d), the output is slightly reduced. Therefore, if the disturbance is large, the alarm output circuit 5 will be activated and a false alarm will be issued.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned conventional problems and to solve them, and has a very simple and inexpensive structure that offsets physical changes caused by disturbance factors. The object of the present invention is to provide a moving object detection device that can reduce the signal output to almost zero.

<Means for Solving the Problems> In order to achieve the above object, the moving object detection device of the present invention includes a differential infrared sensor formed by differentially connecting a pair of infrared detection elements to each other, and a predetermined and an optical system that focuses infrared energy emitted from the detection area on the detection element, in which at least one pair of differential infrared sensors is provided, and each sensor is The detection elements are arranged in a line along the moving direction of the moving object to be detected, and an absolute value circuit is connected to each sensor, and the difference between the absolute value outputs of the paired absolute value circuits is calculated. The present invention is characterized in that it includes a subtraction circuit that performs calculations, and a level discrimination circuit that compares the difference signal of the subtraction circuit with a detection level.

<Function> Since at least two pairs of differential infrared sensors each having a pair of detection elements 2 are differentially connected are provided, when a physical change due to a disturbance factor is applied, each pair of each sensor is The detection elements cancel each other out, and each sensor outputs a small signal due to variations in each pair of detection elements. Each of these signals is converted into an absolute value by an absolute value circuit, and then subtracted by a subtraction circuit to cancel each other out. That is, noise caused by external factors is canceled out twice by the pair of detection elements in each sensor and the subtraction circuit, and the output from the subtraction circuit becomes almost zero, so that no malfunction occurs as a detection device.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

As shown in FIG. 1 and FIG. 2 showing one embodiment, a pair of detection elements 6a and 6b having different polarities.

6. Differential infrared sensor formed by differentially connecting 7a and 7b.
As shown in FIG. ,
Arrange 6b, 7a, and 7b in a line. As the infrared sensor 6.7, it is preferable to use a pyroelectric element, a thermistor bolometer, a thermocouple (thermo panel), etc.
As a form, two pairs of four differentially connected detection elements 6a, 6b, 7a, 7b may be arranged in a line inside the same package, and in this case, four detection elements 6a, 6b
, 7a, 7b are polarized as +, -1+, - or +
, -1-10. Furthermore, the differential connection of the two detection elements 6a, 6b, 7a+7b may be either series connection or parallel connection.

The optical system 8 detects the radiant energy of a predetermined detection area on each of the detection elements 6a, 6b, ? a, 7b, and one case is provided corresponding to each infrared sensor 6.7, and each detection element 5a, 5b, 7a.

7b may be provided, or the detection area may be made into a multi-area by using a split optical system such as a split mirror, or may be made into a single area by using a single optical system. .

Then, in each infrared sensor 6.7, a detection signal in which a change in incident energy is converted into an electrical signal is amplified by amplifier circuits 8 and 9, respectively, and then converted into an absolute value by an absolute value circuit 10.11. . This double absolute value circuit 10.
The output signal of 11 is subtracted by the subtraction circuit 12, and the level discrimination circuit 13 discriminates whether the output signal level of the subtraction circuit 12 is higher than the detection level. An operating signal is output from the output circuit 14 to drive the output circuit 14.

Next, the operation of the apparatus of the embodiment will be explained with reference to FIGS. 3 to 5.

First, when a moving object, such as a human body, crosses the detection area, the detection signals from each detection element 6a, 6b, 7a, and 7b are emitted by the time delay caused by the movement, as shown in FIG. In this figure, each detection element 6a, 6b, 7a.

The case where the polarity of 7b is set to +, -, 10, - is shown. Then, each infrared sensor 6.7 outputs a signal as shown in FIG. .11 and from each absolute value circuit 10.11 as shown in FIG. 3(g).

(A signal converted into an absolute value is output as shown by hl, and is subtracted by the subtracting circuit 12, resulting in a signal output as shown in FIG. 3(i). This output signal is as shown in FIG. 5. , it is determined whether or not the detection level is higher than the detection level shown by the dashed-dotted line preset in the level determination circuit 13, and as shown in the figure, if the detection level is higher than the detection level, the level determination circuit 13 outputs an activation signal. The output circuit 14 is activated to issue an alarm output or open/close an automatic door.

In addition, when a sudden temperature change occurs on the lens surface or mirror cover surface of the optical system 1 due to disturbance light, wind, etc., each detection element 6a, 6b, 7a, 7b responds to the change in incident energy. react, each detection element 6a, 6b, ? a, 7
Detection signals are simultaneously outputted from terminal b as shown in FIGS. 4(al to d).

These simultaneously output detection signals cancel each other out, and as shown in FIG.
, 7b, a small signal is output. These output signals are respectively amplified by amplifier circuits 8.9 and then converted into absolute values by absolute value circuits 10.11.
．． 11 to Fig. 4(g).

(As shown in hl, it is output as a small signal of the same polarity, and this hundred output signal is subtracted by the subtraction circuit 12, so
The signal output of the subtraction circuit 12 is almost constant as shown in FIG. Therefore, even if the disturbance is large, the output signal level of the subtraction circuit 12 will not exceed the detection level of the level discrimination circuit (and malfunctions can be reliably prevented).

It should be noted that the present invention is not limited only to the above embodiments, and it goes without saying that various embodiments are possible without departing from the scope of the claims. For example, in the embodiment described above, two infrared sensors 6.7 are provided, but more than two infrared sensors 6.7 may be provided. However, the number needs to be a multiple of 2. Alternatively, one of the absolute value circuits 10 may convert the values into positive absolute values, and the other absolute value circuit 11 may convert the values into negative absolute values, and the calculation may be performed such that the results are added and subtracted as a result.

<Effects of the Invention> As detailed above, according to the moving object detection device of the present invention, at least two pairs of differential infrared sensors are provided, and the detection signals of both sensors are converted into absolute values and then subtracted. Therefore, energy that is input at the same time, such as noise due to disturbance factors, can be canceled out twice by each infrared sensor and the subtraction circuit, and this noise can be almost eliminated, and large disturbances can be canceled out. It is also possible to suppress malfunctions to below the detection level to reliably prevent malfunctions.

[Brief explanation of drawings]

1 to 5 show an embodiment of the moving object detection device of the present invention, FIG. 1 is a block diagram, FIG. 2 is an explanatory diagram of the infrared sensor in FIG. 1, and FIG. 3 (al.
- (1) is a waveform diagram of the operating voltage of each part when a moving object is detected, Fig. 4 (al - (1) is a waveform diagram of the operating voltage of each part when disturbance noise is detected, and Fig. 5 is a waveform diagram of the operating voltage of each part when a moving object is detected. Figure 6 is a block diagram of the conventional device. Figure 7 is an illustration of the infrared sensor in Figure 1. Figure 8 (a)
-(d) are waveform diagrams of operating voltages of various parts in FIG. 1. 6.7 - Differential infrared sensor 6a, 6b, 7a, 1b - Infrared detection element 8 - Optical system 10.11 - Absolute value circuit 12 - Subtraction circuit 13 - Level discrimination circuit

Claims (1)

[Claims] (1) An infrared passive type sensor that uses a differential infrared sensor consisting of a pair of infrared detection elements differentially connected to each other and an optical system that focuses infrared energy emitted from a predetermined detection area onto the detection element. In the configuration, at least one pair of the differential infrared sensors is provided, and
The sensors are arranged so that the detection elements are arranged in a line along the moving direction of the moving object to be detected, and an absolute value circuit is connected to each sensor, and
A moving object detection device comprising: a subtraction circuit that calculates the difference between the absolute value outputs of the pair of absolute value circuits; and a level discrimination circuit that compares the difference signal of the subtraction circuit with a detection level. .