JPS6097488A - Counting circuit of number of passing object - Google Patents

Abstract

PURPOSE:To count number of passing objects accurately even when plural objects pass simultaneously. CONSTITUTION:When number of objects, for instance human bodies, that pass in front of an infrared-ray sensor 1 is two, infrared rays 41, 42 from the two bodies are inputted to the infrared-ray sensor 1 between time t1 and t2, and between time t3 and t4, and change of respective charge accumulated in the infrared-ray sensor 1 becomes as shown (2) in the figure. Accordingly, pyroelectric current Ip of waveform as shown by (3) in the figure is given to the gate of a field effect transistor 6, and output corresponding to the pyroelectric current Ip is applied to a positive phase input terminal + of the first comparison amplifier 7 through a capacitor C1, and output V of the amplifier 7 becomes waveform (solid line) as (4) in the figure. The output V is applied to the second comparator 8. A signal obtained by differentiating the output V' by a differentiation circuit 9 is applied to the inversion input terminal of the comparator 8. Accordingly, the output V' becomes as shown by solid lines of (5) in the figure, and a signal level of high output can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a circuit that uses a pyroelectric infrared sensor to count the number of objects such as human bodies passing through the circuit.

(Prior art and its problems) When a pyroelectric infrared sensor is incident with infrared rays, a temperature rise ΔT occurs in the pyroelectric material constituting the infrared sensor in response to the incident infrared rays. It is known that the response speed of the sensor output is slow due to the heat capacity of the pyroelectric material, and that the output timing of the sensor output is delayed by an order of magnitude with respect to the incident timing of infrared rays. When infrared rays are incident on such an infrared sensor, a charge Q given by the following equation (1) is generated, and a pyroelectric current 11+ given by the following equation (2), which is obtained by differentiating this charge Q with respect to time t, is generated. Output.

ΔQ=λ・ΔT (1) I p=d(ΔQ)/dL (2) By the way, as shown in FIG. The infrared rays 4 from the human body 3 are detected by this infrared sensor 1, the pyroelectric current ip from this infrared sensor 1 is amplified by an amplifier 5, and the amplified output V of this amplifier 5 is detected by the infrared sensor 1. A circuit for counting the number of objects passing through the human body 3 using the n1j force as an output for counting the number of objects passing through the body 3 has been considered. FIG. 2 shows each manual waveform and output waveform in this case. Figure 2 shows that the human body is 1 between time [1 and L2].
Figure 2 (1) shows the waveform of infrared ray 4 incident on infrared sensor → 11, and the second
Figure (2) shows the change waveform of the charge ΔQ in the above formula (1),
FIG. 2(3) shows the waveform of the pyroelectric current I in the equation (2), and FIG. 2(4) shows the waveform of the amplified output V of the amplifier 5. In this circuit, the waveform of the amplified output V is created in this slice by utilizing the fact that a valley B occurs below the level L of the slice line in FIG. 2 (4) in response to the passage of the human body 3. The number of passages of the valley B below the level of the line is measured by a measuring means (not shown) to measure the number of human bodies 3 passing through. However, such a circuit has the following problem when the human body 3 passes through the distance of 2 Å or more. FIG. 3 is a waveform diagram corresponding to FIG. 2 when there are two human bodies 3. Fig. 3 (1) is shown in Fig. 2 (1), Fig. 3 (2) is shown in Fig. 2 (2), vJ3 Fig. (3) is shown in Fig. 2 (3), Fig. 3 (4) correspond to FIG. 2 (4), respectively. In Fig. 3, since the intensity of infrared #14 from the three human bodies varies depending on clothing, hairstyle, height, walking position, walking speed, etc., the first time is set to time t1 as shown in Fig. 3 (1). A large level of infrared rays 4 from the human body 3 passing between times t3 and 2 and then a small level of infrared rays 42 from the human body 3 passing between times t3 and L4 are incident on the infrared sensor 1. In such a case, the change curve of the weight Q as shown in Fig. 3 (2) is obtained, and as a result, the pyroelectric current I p
changes as shown in FIG. 3 (3). Then, the waveform of the amplified output ■ of the amplifier 5 will have only one valley B, which is below the level of the slice line, as shown in Figure 3 (4), and the number of human bodies 3 passing through is actually two. There is an inconvenience that it is counted as one person even though there is a person. Another prior art circuit that solves this problem is shown in FIG.

In FIG. 4, the sensor output of the infrared sensor 1 is applied to the positive phase side input terminal 10 of the first comparison amplifier 7 via the field effect transistor 6, and the output of the first comparison amplifier 7 is applied to the positive phase side input terminal 10 of the first comparison amplifier 7. It is applied to the positive phase side input terminal 10. A differentiating circuit 9 including a capacitor C2 is connected to the output side of the second comparison amplifier 8. Therefore, when two human bodies pass by as in the case of Fig. 3, the output of the second comparator amplifier 8 is differentiated by the differentiating circuit 9I, and the differential output ■゛ as shown in Fig. 3 (5) is obtained. can get. In response to the rise and fall of the output level to the differential output v' filtered waveform #rJ2 comparison amplifier 8 shown in FIG. 3 (5), the slice #! There are two valleys B1 and B2 that are below the level of L, and therefore, if you count the number of valleys B1 and B-2 that are below the level of the differential output V' waveform slice line, you can accurately calculate The process ends with counting the number of human bodies passing through. However, in the conventional circuit shown in FIG. 4, a new problem occurs as described below. In other words, the problem is that as shown in Fig. 2, the number of human bodies passing through is one, and the infrared rays level from this human body is large.When the output of the second comparison amplifier 8 is differentiated, the difference is Since the circuit 9 responds to the rise and fall of the output, the differential output V' waveform changes greatly as shown in FIG. B3. Two B4's occur, so that the number of human bodies passing through is actually one, but it is counted as two.

(Objective of the invention) The present invention provides a method for reducing the number of objects, such as a human body, passing
It is an object of the present invention to enable accurate counting of the number of passing objects even if the number is larger than that.

(Configuration and Effects of the Invention) In order to achieve the above object, the present invention provides a pyroelectric infrared sensor that detects infrared rays from an object such as a human body, an amplifier that amplifies the sensor output of this infrared sensor, and this amplifier. In the circuit for counting the number of passing objects, the circuit includes a differentiating circuit for differentiating an amplified output of the differentiating circuit, and the differential output of the differentiating circuit is used as an output for counting the number of objects passing through. Therefore, according to the present invention, when the number of passing objects is one, the level of infrared rays incident on the infrared sensor is large, and therefore the level of infrared rays incident on the amplifier is Even if the change in the human power level becomes large, the output level of the amplifier is suppressed by the amplification characteristic control circuit. This prevents the valley part corresponding to the falling edge from being below the level of the slice line.Also, when the number of passing objects is two or more, the infrared level from the first object is high, and the infrared level from the next object is high. When the output level of the amplifier is small, the suppression of the output level of the amplifier is small and the change is differentiated by the differentiating circuit, so the trough portion of the differentiated output waveform occurs corresponding to the number of passes. Therefore, the circuit of the present invention can accurately count the number of passing objects.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings. FIG. 5 is a circuit diagram of this embodiment, and parts corresponding to those in FIG. 4 are given the same reference numerals. The circuit of this embodiment includes a pyroelectric infrared sensor 1 that detects infrared rays from an object such as a human body, and a first comparator amplifier 7 that amplifies the sensor output of this infrared sensor via a field effect transistor 6.
A second comparison amplifier 8 further amplifies the first comparison amplification output V of the first comparison amplifier 7, and a second comparison amplifier 8 of the second comparison amplifier 8.
A differentiating circuit 9 for differentiating the comparison amplified output is used. C1 is a capacitor for compensating for each temperature drift F of the infrared sensor 1 and the field effect transistor 6, and this capacitor C1 and a resistor R1 connected between the positive phase side input terminal of the first comparator amplifier 7 and ground. It is preferable to set the value of the element constant to a sufficiently large value. Capacitor C2 in the differentiator circuit 9
The resistor R2, which is connected between and ground, is for stabilizing the circuit.

In such a configuration, an amplification characteristic control circuit 10 for controlling the amplification characteristic of the first comparison amplifier 7 is disconnected when the negative phase side input terminal and the output terminal of the first comparison amplifier 7 are opened. This amplification characteristic control circuit 10 has a plurality of amplification control elements, for example, resistors R4, R5, R6.
R6 includes conductive elements with different conduction levels, such as diodes D1. D2. ZD is provided, and as the input level increases, the diodes are made conductive one after another, and the resistors R4 and R are connected.
By making the 5°R6 function as an amplification control element, the output level is successively suppressed.

Among these resistors, the mi resistor R4 is not provided with a diode, the second resistor R5 is provided with a first diode D1, and the third resistor R6 is provided with a series circuit of a second diode D2 and a Zener diode ZD. will be provided. Therefore, the output level of the first comparator amplifier 7 is low, and therefore the respective diodes DI, D2 . When ZD cannot be made conductive, its amplification characteristics are determined by the resistor R3 and the first resistor R4 connected to its negative phase side input terminal.

The degree of amplification H at this time is H=R4/R3. Next, when the output level increases and the first diode D1 becomes conductive, the amplification characteristics change between the resistor R3, the first resistor R4, and the second diode D1.
It is determined by the resistor R5, and the amplification degree H at this time is T1=
R4/, R5/R3.

Here, the symbol 〃 is the sum of the parallel resistances of R4 and R5, and the same applies below. Furthermore, the output level increases, and not only the first diode D1 but also the second diode D2
When the Zener diode ZD and ZD become conductive, their amplification characteristics are determined by the resistors R4, R5, and R6. The amplification degree H at this time is H=R4//R5#R6/R3. Such amplification characteristics are shown in FIG. The horizontal axis of the tJS6 diagram represents the input level, and the vertical axis represents the output level. As is clear from FIG. 6, the output level of the second comparator amplifier 8 exhibits a polygonal characteristic as the input level increases.

In the figure, the broken line I indicates the diodes DI, D2. This is when all of ZD are conductive, and the broken line 1 is when only diode D1 is conductive.

Next, the operation will be explained.

(A) Infrared sensor 1 in the case of an object passing in the n;
The infrared sensor 1 is manually operated between the two. The charge Q accumulated in the infrared sensor 1-1 is as shown in tPJ2 diagram (2). Therefore, a pyroelectric current I+] having a waveform as shown in FIG. 2(3) is applied to the gate of the field effect transistor 6 to which the infrared sensor 1 is connected. This pyroelectric current 1p
The output corresponding to 2 is applied to the positive phase side input terminal of the first comparator amplifier 7 via the capacitor C1. The first comparator amplifier 7 outputs an amplified output {circle around (4)} having a waveform shown in FIG. 2 (4) in response to the input level applied to the input terminal on the positive phase side.

Here, the time t at which the sensor output in FIG. 2 (1) falls
In the case of 2 or more, the amplified output V was as shown by the solid line a in the conventional example, but in the case of the embodiment, it changes as shown by the chain line A, and the amplified output 2 does not become large. This is because when the infrared ray level drops significantly after the human body passes through, and therefore the pyroelectric current It) changes greatly, the diodes DI, D2, etc. of the amplification characteristic control circuit 10 become conductive one after another, and the amplification characteristic of the first comparison amplifier 7 changes. This is because it changes as shown by broken line 1 in FIG.

Therefore, the differentiating circuit 9 that differentiates the amplified output of the second comparison amplifier 8 outputs a differential output V' that changes as shown by the chain line C in FIG. 2 (5), and the valley B3. Among B4', one trough B3 which is lower than the level of slice line 1- occurs between times t1 and t2 when the sensor output from the infrared sensor 1 is given, and does not occur after this time L2.

Thereby, if the output of the differentiating circuit 9 is used as an output for counting the number of passing objects, it is possible to accurately count the number of passing objects.

(B) When there are two objects passing in front of the infrared sensor 1, for example, two human bodies; each infrared ray 41 from the two people has a waveform as shown in FIG. 3 (1).
, 42 between times t1 and L2, and between times t3 and 14
and are input to the infrared sensor 1 respectively. Figure 3 (2) shows the changes in each charge Q accumulated in the infrared sensor 1.
become that way. Therefore, a pyroelectric current 1p having a waveform as shown in FIG. 3(3) is applied to the gate of the field effect transistor 6 to which the infrared sensor 1 is connected. An output corresponding to this pyroelectric current I I+ is given to the positive phase side input terminal of the first comparator amplifier 7 via the capacitor C1.

The first comparator amplifier 7 outputs an amplified waveform as shown in FIG. 3 (4) in response to the input level applied to the positive phase input terminal.
Output. Here, in the conventional example, the amplified output ■ when the level of infrared rays falls in FIG. , as shown by the solid line, and after time L3, unlike the conventional example, it changes as shown by the chain line d. The reason for this is the same as above.

However, in this case, since the level of infrared rays between time points 3 and 4 is small, the input level to the first comparison amplifier 7 is also small, and therefore the amplification degree of the first comparison amplifier 7 is controlled, for example, by amplification characteristic control. This is determined by the broken line (■) in FIG. 6, in which only the first diode D1 of the circuit 10 is conductive.

Therefore, the output waveform of the differentiating circuit 9 that differentiates the output of the second comparator amplifier 8 has a slightly higher level than the solid line of the conventional example in FIG. 3 (5), but it is similar to the chain line e in FIG. changes below the level of the slice line. As a result, both the valleys B1 and B2' of the output waveform of the differentiating circuit 9 become below the level of the slice line, and no valley below the level of the slice line occurs after time L4. Thereby, if the output of the differentiating circuit 9 is used as an output for counting the number of passing objects, it is possible to accurately count the number of passing objects.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the principle of a circuit for counting the number of objects passing by an infrared sensor, and FIGS. 2 and 3 are waveform diagrams for explaining the operation of the circuit for counting the number of objects passing through. When the number of passages is one, the figure shows the case where there are two passages. Figure 4 is a circuit diagram for counting the number of passages in the conventional example, and Figure 5 is a circuit diagram for counting the number of passages in the embodiment of the present invention. The circuit diagram and FIG. 6 are diagrams showing the amplification characteristics of the first comparison amplifier according to the embodiment. □ 1 is an infrared sensor, :( is a human body to be counted, 7
1 is the first comparison amplifier, 8 is the second comparison amplifier, 9 is the differential circuit, 1 () is the amplification characteristic control circuit Applicant: Denji Tateishi Co., Ltd. Applicant: HORIBA Co., Ltd. Agent Patent attorney Oka 1) Kazuhide 1 Figure 2 Mutj3 bt. Figure 3 41 Figure 5 Figure 6

Claims (4)

[Claims] (1) It includes a pyroelectric infrared sensor that detects infrared rays from an object such as a human body, an amplifier that amplifies the sensor output of this infrared sensor, and a differentiating circuit that differentiates the amplified output of this amplifier, and the differentiating circuit In the circuit for counting the number of passing objects, the differential output of which is used as an output for counting the number of passing objects, the amplifier is provided with an amplification characteristic control circuit that suppresses the output level when the input level change is in a direction large. A circuit for counting the number of passing objects. (2) In the circuit for counting the number of passing objects according to claim 1, the amplification characteristic control circuit includes a plurality of amplification control elements, and the amplification control elements have different conduction levels. I) Passage of an object such as a human body that sequentially suppresses the output level by providing a conduction element and sequentially turning on the conduction element as the input level change increases to function the amplification control element. Piece counting circuit. (3) The circuit for counting the number of objects passing through, such as a human body, wherein the amplification control element is a diode. (4) The circuit for counting the number of passing objects as set forth in claim 3, wherein the diode includes a Zener diode.