JPH07174624A - Dual pyroelectric sensor - Google Patents

Abstract

PURPOSE:To equally maintain the effective light receiving areas of paired elements even when the positions of electrode patterns are deviated from each other by forming the electrode main body on one surface of a pyroelectric body larger than that on another surface in one unit pyroelectric element of the paired elements and forming the electrode main body on one surface of a pyroelectric body smaller than that on the another surface in another unit pyroelectric element. CONSTITUTION:The dual pyroelectric sensor 10 is provided with a pair of electrodes 2 and 3 on the surface of a sheet-like pyroelectric body 1 and another pair of electrodes 4 and 5 on the rear surface of the body 1 and the main bodies 2 and 5 of the electrodes 2 and 5 respectively have protruding sections 2'a and 5'a around their overlapping sections upon the main bodies 4a and 3a of the electrodes 4 and 3 facing each other on both sides of the body l and are formed smaller than the main bodies 4a and 3a. In addition, the leading out sections 3b and 4b of the electrodes 3 and 4 are constituted so that they can be led out from the main bodies 3a and 4a in the opposite directions substantially. Therefore, even when the pattern of the electrodes 2 and 4 is slightly deviated in position from that of the electrodes 3 and 5, the offsetting performance of vibration variation or temperature variation or in-phase noise of background radiation, etc., can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual-type pyroelectric sensor composed of a pair of unit pyroelectric elements, and more specifically, the patterns of electrodes provided on the front and back surfaces of a pyroelectric body are relatively The unit has an electrode structure in which the effective light receiving area defined as the overlapping area of electrodes facing each other across the pyroelectric body is not substantially different between the unit pyroelectric elements even if they are misaligned. And a dual pyroelectric sensor having excellent in-phase noise cancellation characteristics.

[0002]

2. Description of the Related Art Optical detection of infrared rays and the like using a pyroelectric element is
It is used in various electronic devices such as remote switches, intruder alarms, and motion sensors. The principle common to these is
For example, grasping a motion such as waving a hand as movement of an infrared radiator to distinguish it from infrared radiation from an object with little movement in the surroundings. It is to determine whether it is the movement of the infrared radiator that is the target by converting into.

However, in an infrared detector composed of a single pyroelectric element, the pyroelectric element reacts to vibrations, changes in ambient temperature, changes in background radiation such as blinking of lights, and so malfunctions are avoided. Absent. Therefore, as described in, for example, US Pat. No. 3,839,640, a proposal for solving the problem of malfunction by forming a dual pyroelectric element by connecting a pair of unit pyroelectric elements in series or in parallel with their polarities opposite to each other Has been done. According to the method of the U.S. Patent, by appropriately selecting an optical system, noise as a cause of malfunctions such as the above-mentioned vibration and changes in background radiation, a pair of unit pyroelectric elements connected in anti-series or anti-parallel are connected. However, the movement of the object to be detected can be differentially detected by a pair of unit pyroelectric elements alternately and extracted as an electric signal. Is.

In order to further develop the technique of the above-mentioned US patent, for example, Japanese Patent Laid-Open No. 61-175583, Japanese Utility Model Laid-Open No. 58-32337, and European Patent No. 0131.
No. 996 and Japanese Utility Model Laid-Open No. 01-152226 have been proposed and have reached the level of practical use. All of these are intended to overcome the difficulty of the direct connection (wire bonding) of the lead wire to the electrode of the thin film, which is a problem in the technology of the U.S. patent. It is a proposal for an extraction electrode that extends over the body and whose tip reaches the edge of the pyroelectric body.

Certainly, the above-mentioned Japanese Patent Laid-Open No. 61-175583.
In the dual pyroelectric elements described in Japanese Patent Publication No. 58-32337, Japanese Utility Model Publication No. 58-32337, and European Patent No. 0131996, a conductive adhesive or the like is used at the edge of the pyroelectric body where the tip of the extraction electrode reaches. The electrical connection with the lead wire can be achieved, and the difficulty of connecting the lead wire is eliminated.

[0006]

However, the above three publications raise new problems to be solved unintentionally by the lead electrodes provided to eliminate the difficulty of connecting lead wires.
This is because if the electrode patterns provided facing the front and back surfaces of the pyroelectric body are misaligned during electrode formation, the overlap area (effective light receiving area) of the front and back electrodes including the extraction electrode is two unit pyroelectric elements ( (Also referred to as pair elements) are not equal. If there is a difference in the effective light receiving area of the pair of elements, the in-phase noise described above cannot be completely canceled out, resulting in a detector having poor noise canceling characteristics. Actually, in the manufacturing stage of the pyroelectric infrared detector, the common-mode noise canceling performance of the detector is not necessarily as high as expected, and there are variations in the characteristics between manufacturing lots. .

On the other hand, the above-mentioned Japanese Utility Model Laid-Open No. 01-152226 discloses one solution to the problem of inconsistency in the effective light receiving area due to the above-mentioned deviation in electrode formation. According to this publication, the desired area uniformity is achieved by making the extraction directions of the extraction electrodes extending from the electrode body the same. However, in this pyroelectric element, when the paired elements are connected in anti-parallel, the extraction electrode is inevitably routed around the pyroelectric body, and it is necessary to increase the area of the pyroelectric body to be used. Furthermore, the extraction electrode has a high risk of disconnection.

In the present invention, it is not necessary to extend the lead-out portion of the electrode for a long time.
Even if the electrode pattern is formed on both sides of the pyroelectric body with a slight misalignment as in the case of No. 996,
A pyroelectric sensor in which the effective light receiving area of the pair element is kept equal,
The purpose is to propose a simple electrode structure different from that of Japanese Utility Model Laid-Open No. 01-152226.

[0009]

DISCLOSURE OF THE INVENTION The inventor has found that in one unit pyroelectric element of a pair element, the electrode body on one surface of the pyroelectric body is formed to be larger than the electrode body on the other surface, and conversely, on the other hand. In the electric device, an inversion idea was obtained from the technical idea of European Patent 0131996, in which the electrode body on one surface of the pyroelectric body was formed smaller than the electrode on the other surface, and the present invention was completed.

That is, the dual pyroelectric sensor of the present invention comprises a sheet-shaped pyroelectric body, a pair of first and second electrodes provided on one surface of the pyroelectric body, and the pyroelectric body of the pyroelectric body. A pair of third and fourth electrodes provided on the other surface, wherein each of the first to fourth electrodes is a lead of an electrode body for providing an effective light receiving area and a lead of another electric circuit. A lead portion that is integrally drawn from the electrode body and extends to make a wire connection, and a first electrode, a third electrode, and a pyroelectric body interposed between the first electrode and the third electrode Dual pyroelectric element in which the first unit pyroelectric element is configured, and the second unit pyroelectric element is configured by the second electrode, the fourth electrode, and the pyroelectric body interposed between these electrodes. A sensor, wherein the electrode pattern provided on the one surface is an electrode provided on the other surface Even if the electrodes are formed so as to be relatively displaced with respect to the pattern, the effective light receiving area defined as the overlapping area of the electrodes facing each other with the pyroelectric body interposed therebetween is between the first and second unit pyroelectric elements. , The electrode body of the first electrode has a protruding portion around the overlapping portion with the electrode body of the opposing third electrode, and the electrode body of the fourth electrode has an opposing portion. There is a protruding portion around the overlapping portion of the second electrode with the electrode body,
Moreover, the lead-out portions of the second and third electrodes are characterized in that the directions in which they are pulled out from the electrode body and start to extend are substantially opposite to each other.

In the dual pyroelectric sensor of the present invention, it is preferable that the areas of the electrode bodies of the second and third electrodes and the width of the lead portion are substantially the same.
Further, the tip portion of the lead-out portion of the first electrode is led out of the fourth electrode so that the first unit pyroelectric element is connected in parallel to the second unit pyroelectric element with their polarization directions reversed. The tip portion of the second electrode and the edge portion of the pyroelectric body are substantially opposed to each other with the pyroelectric body interposed therebetween, and the tip portion of the lead portion of the second electrode is separated from the tip portion of the lead portion of the third electrode by the pyroelectric body. It is further preferable that the edges substantially face each other with the pyroelectric body interposed therebetween.

[0012]

In the dual pyroelectric sensor of the present invention, the electrode body on one side of the pyroelectric body is formed larger than the electrode body on the other side in one unit pyroelectric element constituting the dual pyroelectric sensor, and conversely the other unit pyroelectric element is formed. In the element, the electrode body on one surface of the pyroelectric body is formed smaller than the electrode on the other surface. Due to such a reverse configuration of the electrode body, even if the lead-out direction of the lead-out portions of the four electrodes is directed to the gap region separating the first and second unit pyroelectric elements, the positional deviation of the electrode pattern is effective. The light receiving area does not cause a significant difference between the elements. And
The anti-parallel connection with the electric circuit in the subsequent stage can be easily performed without extending the lead portion for a long time.

[0013]

Embodiments of the dual pyroelectric sensor of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a dual pyroelectric sensor, and FIG. 2 shows an electrode pattern provided on the back surface side indicated by a dotted line with reference to a pattern of electrodes provided on the front surface side of the sheet-shaped pyroelectric body. FIG. 3 is a plan view showing the dual pyroelectric sensor when the dual pyroelectric sensor is formed by being displaced from the position where there is no misalignment in the lower right direction in the figure, and FIG. 3 is a circuit diagram showing an example of an electric circuit provided in the subsequent stage of the dual pyroelectric sensor. is there.

Reference numeral 10 in the figure denotes a dual pyroelectric sensor of the present invention. The dual pyroelectric sensor 10 includes a sheet-shaped pyroelectric body 1 and one surface of the pyroelectric body 1 (in this embodiment, pyroelectric body 1). A pair of electrodes (first electrode 2 and second electrode 3) provided on the body 1) and the other surface of the pyroelectric body 1 (the same as the back surface).
And a pair of electrodes (third electrode 4 and fourth electrode 5) provided in. The first to fourth electrodes 2, 3, 4 and 5 are for connecting lead wires to the electrode bodies 2a, 3a, 4a and 5a for providing an effective light receiving area and other electric circuits, respectively. In addition, the lead-out portions 2b and 3 that are integrally drawn from the electrode body and extend onto the pyroelectric body 1.
b, 4b, 5b, and a first electrode 2 and a third electrode 4
And the pyroelectric body interposed between these electrodes constitute a first unit pyroelectric element, and the pyroelectric element interposed between the second electrode 3 and the fourth electrode 5 and these electrodes. The body constitutes a second unit pyroelectric element. Pyroelectric body 1
For example, it is polarized so as to be oriented from the back surface side to the front surface side, and has electrical characteristics that cause spontaneous polarization in response to thermal changes. In addition, in FIGS. 1 and 2,
The electrodes 2 and 3 provided on the front surface side of the pyroelectric body 1 are shown by solid lines, and the electrodes 4 and 5 provided on the back surface side are shown by dotted lines.

The lead-out portions 2b, 3b, 4b, 5b are
In order to easily and securely connect a lead wire to an electric circuit at a subsequent stage, for example, an impedance conversion circuit 20 as shown in FIG. 3, the tip end portions 2b 'and 3b' are drawn out from the electrode body and then bent at a substantially right angle. , 4b ', 5b' are made wider than the other parts of the lead-out portion and reach the edge of the pyroelectric body 1. Here, if an example of the lead wire connection with the electric circuit of the latter stage is shown, first, the dual pyroelectric sensor 1
0 is adhered and fixed to a fixed substrate such as alumina or plastic, and then a lead wire to an electric circuit is provided on the same fixed substrate, the tip of which is the tip portion 2b ', 3b' of the lead-out portion.
There is a method of fixing so as to be near 4b 'and 5b', and conducting both the lead wire and the tip portion with a conductive bonding agent such as low melting point solder or conductive adhesive.

Further, the first unit pyroelectric element and the second unit pyroelectric element are connected in parallel with their polarization directions reversed, that is, so-called
In order to simplify and facilitate the antiparallel connection shown in FIG.
The leading end portion 2b 'of the lead-out portion of the electrode is substantially opposite to the leading end portion 5b' of the lead-out portion of the fourth electrode at the edge portion of the pyroelectric body 1 with the pyroelectric body interposed therebetween. The leading end portion 3b 'of the lead-out portion is substantially opposite to the leading end portion 4b' of the lead-out portion of the third electrode at the edge portion of the pyroelectric body 1 with the pyroelectric body interposed therebetween.

The electrode body 2a of the first electrode is opposed to the electrode body 4a of the third electrode with the pyroelectric body 1 interposed therebetween.
In addition to having a protruding portion 2a 'around the overlapped portion with the
The lead-out portions 3b and 4b of the electrode bodies 3a and 4a, which have a protruding portion 5a 'around the overlapping portion of the electrode with the electrode body 3a and are small in size, start to be extended from the electrode body. The directions (hereinafter, referred to as pull-out directions) are substantially opposite to each other. The electrode main body 3a and the electrode main body 4a have substantially the same area, and their shapes are generally rectangular, but may be any other shape.

The "reverse direction" in the present invention means the opposite direction, or the center line (C in FIG. 1) of the gap that divides the first unit pyroelectric element and the second unit pyroelectric element. It means that the direction is symmetrical. Here, the opposite direction and the symmetric direction include the case where the parallel movement is applied to the opposite direction and the symmetric direction, respectively.

The lead-out portions 3b and 4b are preferably drawn out from either the left or right ends of the respective electrode bodies 3a and 4a, and particularly, to the right side from the electrode body 3a of the second electrode located on the left side, It is preferable that the third electrode on the right side is led out to the left side from the electrode body 4a. In this preferable mode, the lead-out portions 3b and 4b are developed between the gaps, and the lead-out portion can be formed short. The lead-out portion is not pulled out vertically from the electrode body but is pulled out obliquely, the line width is not constant along the lead-out direction, and the lead-out portion is enlarged or reduced, or divided into a plurality of portions. May be. Therefore, it is desirable that the line widths at the bases of the lead-out portions are the same in the lead-out portions 3b and 4b, but they can be formed differently as long as the effect of the present invention is exhibited.

In the figure, the lead-out portions 2b and 5b of the first and fourth electrodes, in which the electrode body is formed large, are substantially opposite to each other in the directions in which they are pulled out from the electrode body and start to extend. , And is developed between the gaps.
According to such a preferred embodiment, the length of the lead-out portions 2b, 5b can be shortened, and the beauty of the pattern can be enjoyed due to the symmetrical shape. For example, the lead-out portions 2b, 5b can be formed from the lower end portions of the respective electrode bodies 2a, 5a. It may be formed by pulling out downward in the same direction. In short, since the electrode main body is formed large in the first and fourth electrodes, the lead-out portion does not matter in the lead-out direction or the lead-out position.

Taking an intruder alarm device using a dual type pyroelectric sensor as an example, generally, the electrode dimensions are about 1 mm in width and 2 mm in length, which are extremely small, and the electrode interval (the gap) is that of the intruder. 0.8 so that motion can be detected differentially
It is between mm and 1.0 mm. In the case of this example, the line widths of the lead-out portions 2b, 3b, 4b, 5b are naturally selected to be smaller than the above-mentioned size, and it is unavoidable that the line width is made smaller in order to reduce the size of the device. Therefore, the fact that the length of the lead-out portion is short is advantageous because there is little risk that the thin lead-out portion will be broken during the process of being assembled into the apparatus.

The protruding portions 2a ', 5a' are small-sized electrode bodies 4a, 5a 'even if positional deviation occurs in any direction (up, down, left and right) when forming an electrode pattern.
It is preferable that the electrode 3a is designed so as not to protrude from the areas of the electrode bodies 2a and 5a in which 3a is formed large. One example of such a design is that, in the state of FIG. 1 where there is no positional deviation, the protruding portion is provided with the same width all around the electrode body that is formed small, and the width is set to be equal to or greater than the positioning accuracy of the electrode forming device. is there.

The sheet-shaped pyroelectric material 1 of the present invention is not particularly limited, and in addition to a polymer-based pyroelectric material film represented by polyvinylidene fluoride, a modified zirconic acid supplied in a thin plate shape. Ceramic pyroelectric materials such as lead titanate are used. In particular, the present invention exerts a remarkable effect in a polymer-based pyroelectric material having a small dielectric constant and a small heat capacity, and is suitable. In the present invention, when polyvinylidene fluoride is called,
The present invention is not limited to vinylidene fluoride homopolymers, but includes, for example, inferior amounts of monomers containing a predominant amount of vinylidene fluoride and copolymerizable therewith, such as vinyl fluoride, ethylene trifluoride, ethylene tetrafluoride, and trifluoride. It also includes copolymers with modified ethylene chloride, propylene hexafluoride and the like.

In the present invention, the electrode provided on the side on which radiation is incident is preferably a translucent electrode, and examples of such a translucent electrode include gold, platinum, silver, nickel, chromium, aluminum, Semi-transparent film such as copper (thickness is 3
˜20 mμ). On the other hand, the electrode on the side facing the translucent electrode can be a normal non-translucent metal vapor deposition film. The transparent electrode can be formed on the surface of the pyroelectric body by a conventional method such as vapor deposition or sputtering.

Next, an example of an electric circuit provided after the dual pyroelectric sensor will be described with reference to FIG. The electric circuit 20 is an impedance conversion circuit using a field effect transistor (FET) 21 having a drain electrode D, a source electrode S, and a gate electrode G. In the dual pyroelectric sensor 10, the first unit pyroelectric element (right side in the drawing) and the second unit pyroelectric element (left side in the drawing) are in a so-called anti-parallel connection in which the polarization direction p is reversed, and The leading end portion 3b '(4b') of the lead portion is connected to the gate electrode G via the lead wire,
The tip portion 2b ′ (5b ′) of the other lead-out portion is connected to the ground 24. In FIG. 3, reference numeral 22 is a power supply terminal for supplying + B voltage to the drain electrode D, and 23 is a source electrode S.
Output terminals Rg and Rs for extracting the detection voltage from are gate resistance and source resistance, respectively.

Infrared detection by the dual pyroelectric sensor 10 connected in antiparallel shown in the drawing will be described. As for the movement of an infrared radiator such as a human body, for example, the first unit pyroelectric element first receives infrared rays and then the human body. Is received by the second unit pyroelectric element by the movement of the second unit pyroelectric element, and the light is captured alternately by the pair of unit pyroelectric elements. Then, the gate potential slightly changes according to the change of the received infrared ray, and as a result, the FET
Of the source resistance Rs
A response voltage can be obtained between the terminals 23 and 24 by flowing.

On the other hand, the response of the dual pyroelectric sensor 10 to noise such as vibration, temperature change or background radiation is
These noises act equally on the pair of unit pyroelectric elements (in-phase), and the spontaneous polarization of the sensor has an opposite phase as shown in FIG. 3, so that the gate potential does not change due to cancellation. That is, the dual pyroelectric sensor 10 of FIG.
Are those that respond only to differential (not in-phase) stimuli.

However, this in-phase noise canceling effect can be enjoyed only when the characteristics are uniform among the unit pyroelectric elements forming the pair element, and as the characteristics of the unit pyroelectric element, the effective light receiving area, That is, the overlapping area of the electrodes on the front and back sides (area including the lead-out portion) is the most important factor. If the effective light receiving areas are not equal among the unit elements, the sensor responds to strong noise, and malfunctions cannot be avoided.

The effective light receiving area of this embodiment will be described below with reference to FIGS. The overlap areas of the first and second unit pyroelectric elements are the area of the smaller electrode bodies 4a and 3a and the area of the hatched portions of the lead portions 4b and 3b drawn from the smaller electrode bodies, respectively. Is the sum of In this embodiment, the electrode bodies 4a and 3a have substantially the same area, and the line widths at the bases of the lead-out portions 4b and 3b and the widths (in FIG. 1) of the protruding portions 2a 'and 5a' are substantially the same between the pair of elements. Are the same. Therefore, in FIG. 1 in which the electrode patterns on the front and back sides are not displaced, the areas of the shaded portions are also equal, and the effective light receiving areas of the two unit pyroelectric elements are substantially the same.

In FIG. 2, in which the electrode pattern (dotted line) on the back surface side is formed by being displaced from the position in FIG. 1 to the lower right direction in the figure, the areas of the electrode bodies 4a and 3a are kept the same. Although the shaded area is longer than that in FIG. 1, the two unit pyroelectric elements are increased by the same length, and the effective light receiving areas of both are also equal. In this embodiment, if the electrode pattern on the back surface is displaced to the right, the shaded portion becomes longer than that in FIG. 1, and conversely, if the electrode pattern is displaced to the left, the shaded portion becomes shorter. The same effective light receiving area is ensured between the elements. Actual Kaihei 01-152226
Comparing this example with FIG. 5 of the conventional example described in Japanese Patent Publication, in one of the two unit pyroelectric elements, the electrode body on one surface of the pyroelectric body is formed larger than the electrode body on the other surface, On the other hand, on the other hand, the excellent effect secured by the present invention in which the electrode body on one surface of the pyroelectric body is formed smaller than the electrode on the other surface is clear.

Tip portions 2b ', 3b', 4 of the drawer portion
In the vicinity of b ′ and 5b ′, there is an overlap of the electrodes of the lead portions. However, since this light receiving region is a region where the front and back electrodes are short-circuited by the lead wire, the spontaneous polarization generated there is canceled and there is no problem.

In FIG. 3, C1 and C2 are bypass capacitors for cutting a strong high frequency current such as UHF band wireless communication which enters the impedance conversion circuit 20 through the power supply terminal 22 and the output terminal 23, respectively. Considering such high frequency induction current, the circuit of FIG. 3 is preferably housed in one shield case.

The dual pyroelectric sensor of the present invention has been described above based on the embodiments. However, the present invention is not limited to the pyroelectric sensor in which only one dual type pyroelectric element is incorporated, and also includes a pyroelectric sensor in which a plurality of dual elements are arranged at intervals in an array.

According to the present invention, even if the electrode patterns are slightly displaced from each other on both sides of the pyroelectric body, the effective light-receiving area of the two unit pyroelectric elements constituting the dual pyroelectric sensor is the element. Since they are substantially the same, it is possible to obtain a sensor excellent in noise canceling performance against common-mode noise such as vibration, temperature change, or background radiation.

[Brief description of drawings]

FIG. 1 is a plan view showing a dual pyroelectric sensor of the present invention.

FIG. 2 is a diagram showing a pattern of electrodes provided on the back surface side, which is indicated by a dotted line, from the position where there is no deviation in FIG. FIG. 6 is a plan view showing the dual pyroelectric sensor when the dual pyroelectric sensor is formed by being displaced.

FIG. 3 is a circuit diagram showing an example of an electric circuit provided in a subsequent stage of a dual pyroelectric sensor.

[Explanation of symbols]

 1: Sheet-shaped pyroelectric body 2, 3, 4, 5: Electrode 2a, 3a, 4a, 5a: Electrode body 2b, 3b, 4b, 5b: Lead-out portion 2a ', 5a': Overhanging portion 10: Dual pyroelectric sensor 20: Impedance conversion circuit 21: Field effect transistor (FET)

Claims (3)

[Claims] 1. A sheet-shaped pyroelectric material, a pair of first and second electrodes provided on one surface of the pyroelectric material, and a third electrode provided on the other surface of the pyroelectric material. And a fourth pair of electrodes, each of the first to fourth electrodes,
The electrode body has an electrode body for providing an effective light receiving area, and a lead-out portion integrally extended from the electrode body for connecting a lead wire to another electric circuit. The first unit pyroelectric element is constituted by the third electrode and the pyroelectric body interposed between these electrodes, and the pyroelectric element interposed between the second electrode, the fourth electrode and these electrodes is formed. A dual pyroelectric sensor in which a second unit pyroelectric element is constituted by the body, wherein the pattern of electrodes provided on the one surface is relative to the pattern of electrodes provided on the other surface. Even if the electrodes are formed so as to be misaligned with each other, the effective light-receiving area defined as the overlapping area of the electrodes facing each other with the pyroelectric body interposed therebetween is the first
In order not to be substantially different between the second unit pyroelectric element and the second unit pyroelectric element, the electrode body of the first electrode has a protruding portion around the overlapping portion with the electrode body of the opposing third electrode, and The electrode body of the second electrode has a protruding portion around the overlapping portion of the opposing second electrode with the electrode body, and the lead portions of the second and third electrodes extend and extend from the electrode body. A dual pyroelectric sensor, wherein the starting directions are substantially opposite to each other. 2. The areas of the electrode bodies of the second and third electrodes are substantially the same, and the widths of the lead-out portions of the second and third electrodes are substantially the same. Dual pyroelectric sensor. 3. The tip portion of the lead-out portion of the first electrode is formed into a fourth unit so that the first unit pyroelectric element is connected in parallel to the second unit pyroelectric element with their polarization directions reversed. The tip portion of the lead portion of the electrode and the edge portion of the pyroelectric body are substantially opposed to each other with the pyroelectric body interposed therebetween, and the tip portion of the lead portion of the second electrode and the tip portion of the lead portion of the third electrode are the same as those of the pyroelectric body. The dual pyroelectric sensor according to claim 1, wherein the dual pyroelectric sensor is substantially opposed to the edge of the electric body with the pyroelectric body interposed therebetween.