JP2983459B2 - Passive infrared detector shield device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of passive infrared detection. The passive type refers to a method of detecting electromagnetic waves or light rays generated by thermal energy of an object itself. In particular, the presence or absence of a human body that has entered a predetermined area by converting far-infrared rays emitted by the human body into electric energy. Applied to devices that detect

[0002]

2. Description of the Related Art Light energy containing a large amount of far infrared rays emitted by the human body (36.degree. C.) is extremely weak and needs to be amplified with a high gain after being collected and photoelectrically converted. Therefore, it is important to perform amplification with a high S / N ratio by blocking external noise generated by lightning, automobile engines, communication equipment, lighting equipment, and the like.

Conventionally, a shield device has been used to block external noise. However, as shown in FIG. 5, a circuit including a photoelectric conversion element 22 and a first-stage amplifier 23 is used.
The ground line G of the circuit inside the shield case 21 and the circuit outside the shield case 21 is commonly connected, and the shield case 21 is connected to the ground line G.

[0004]

Although the shielding device shown in the prior art has the ability to shield external noise caused by lightning, automobile engines, etc., the present invention further increases the shielding ability. It is an object of the present invention to provide a shield device.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems
In particular, the shield device of the passive infrared detector of the present invention is
Weak light energy such as electric infrared detector
Photoelectric conversion element that converts to energy and output of the photoelectric conversion element
The amplification circuit that amplifies the
In the covered device, the photoelectric conversion element and the amplification circuit
The ground line (G ₁ ) is one point of the above shield case
(P) and the ground of the subsequent circuit.
The drain (G ₂ ) is separated from one point (P) of the shield case.
At the other point (Q) of the shield case located between
It is characterized by being connected. Ma
In this configuration, the other point (Q) is a shield.
On the opposite side of the point (P) above the center of the case
Preferably.

[0006]

FIG. 1 is a perspective view showing the appearance of an embodiment of the present invention, and FIG. 2 is a circuit diagram thereof. Printed wiring board 1
, A pair of pyroelectric infrared detecting elements 2.2, a pair of amplifying ICs 3.3, and a circuit element such as a diode, a resistor, and a capacitor, which constitute a circuit, are arranged.
Constructed, the pair of output terminals 5.5, the power supply terminal 6, and a ground line G ₁ of the terminal 7 of the printed wiring board 1 is provided with. Shield case 4 covering this substrate 1
Is a box shape as a whole in which an opening 8 is formed on the front surface of the pyroelectric infrared detecting element 2.2, and a metal film such as an aluminum plate or a tin plate, or a metal film formed on a plastic surface by sputtering or the like. And is fixed to the printed wiring board 1.

The following circuit section B connected to the preceding circuit section A includes a comparator for comparing the outputs of the pair of amplifying ICs 3.3, a discrimination circuit for discriminating whether or not the object is a detection object, and a detection object. a switching circuit for outputting a detection signal when it is determined to be, and has a common power supply line 9 and the ground line G _2. In some cases, a transmission antenna for outputting the detection signal by wireless communication is provided.

The ground line terminal 7 of the preceding circuit section A is
A point Q on the opposite side of the shield case 4 which is connected to a point P of the shield case 4 and is located on the opposite side of the center of the shield case with respect to the point P, is connected to the ground line G ₂ of the subsequent circuit section B. The power terminal 6 of the section A is directly connected to the power line of the subsequent circuit section B. Further, the shield case 4 is connected to the ground line G ₁ of the previous stage circuit portion A.

As shown in FIG. 3, when the point P is on one side 11 of the shield case 4, the other point Q is preferably selected on the opposite side 12, as shown in FIG. The other point Q can be selected as one of the two sides 13 and 14 adjacent to the side 11.

FIG. 4 shows a circuit diagram of another embodiment of the present invention. In this embodiment, a single photoelectric conversion element 15 and two stages of amplifying ICs 16 and 17 in series and their associated circuits constitute a front stage circuit section A, and the ground line G _{1 of} that section is connected to a point P of the shield case 4. It is connected to the ground line G ₂ in the subsequent stage through between the point Q. It is not an indispensable constituent requirement that the entire front-stage circuit section A is covered with the shield case 4. In general, external noise due to lightning, automobile engines, aircraft engines, etc., includes electromagnetic waves of very high frequency components, which are guided to a subsequent circuit section B having a large area including a transmission antenna to become electric noise, It is considered that this invades the pre-stage circuit unit A and is amplified by the pre-stage amplification circuit having a high gain to cause erroneous detection. Therefore, with the configuration as in the present invention, the shield case itself functions as a high-impedance element against electric noise of high frequency components, and greatly attenuates when entering the front-stage circuit unit A from the rear-stage circuit unit B. It is speculated that this is not the case.

[0011]

The following test results were obtained using a pseudo-noise source for confirming the effects of the present invention. Test 1: 430MHz used for amateur radio
The radio wave was continuously transmitted, and the electric field strength of the radio wave was gradually increased. In the conventional example, the malfunction detection signal was output when the electric field strength was 15.8 V / m, whereas in the present embodiment, even if the electric field strength was increased to 57.5 V / m,
There was no malfunction. This means that the 430 MHz UHF
This indicates that noise resistance of 11 dB or more with respect to the electromagnetic wave noise in the band was obtained.

Test 2: A test was performed using an air discharge defined by the IEC (International Electrotechnical Commission) standard. In the conventional example, when the discharge voltage was 10 kV, any of the devices including the former circuit part and the latter circuit part was used. While such a circuit element was destroyed and became inoperable, in the example of the present invention, no malfunction was observed even at a discharge voltage of 20 kv (the maximum value of the testable range).

As described above, according to the present invention, the noise resistance can be improved by simply using the conventional shield case and changing its wiring position without adding circuit elements such as high-frequency coils, capacitors, and resistors. A surprisingly improved, and therefore high-density and reliable passive human body detection device can be obtained.

[Brief description of the drawings]

FIG. 1 is an external view of an embodiment of the present invention.

FIG. 2 shows a circuit diagram of an embodiment of the present invention.

FIG. 3 is an explanatory view of a modified example of points P and Q of the shield case 4 of the present invention.

FIG. 4 shows a circuit diagram of another embodiment of the present invention.

FIG. 5 shows a conventional circuit example.

[Explanation of symbols]

1 ... preliminary circuit portion of the printed circuit board 2 .... pyroelectric infrared detection element 4 ... shield case 7 ... pre-stage circuit unit ground line terminals G ₁ ... preliminary circuit of Ground line G ₂ ····· Ground line of subsequent circuit part P ···· One point of shield case Q ······ Other point of shield case

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01J 1/02 G01J 1/42-1/44 G01J 5/02 G01V 9/04 G08B 13/19-13 / 191 G08B 17/00 H04N 5/335 H05K 9/00

Claims (2)

(57) [Claims] And 1. A photoelectric conversion element for converting the weak light energy such as a pyroelectric infrared detection element to electrical energy, an amplifier circuit for amplifying the output of the photoelectric conversion elements, is shielded with the external world by the shield case In the device, the ground line (G ₁ ) of the photoelectric conversion element and the amplifier circuit is connected to the seal.
Connected to one point (P) of the
The ground line (G ₂ ) of the circuit of
Other than the above shield case located at a distance from one point (P)
A shield device for a passive infrared detector, wherein the shield device is connected to one point (Q) . Wherein said another one point (Q) is, that across the central portion of the shield case on the opposite side of the one point (P)
And wherein, passive infrared detectors shield apparatus according to claim 1.