JPH0875546A - Pyroelectric infrared sensor - Google Patents

Abstract

PURPOSE: To enhance the reliability by stabilizing the driving of a miniature chopper in a pyroelectric infrared sensor employing a piezoelectric actuator. CONSTITUTION: Piezoelectrics 12a, 12b are bonded to shims 11a, 11b, respectively, and the shims are secured, only in the vicinity of a shim hole machining part 21a thereof, to sensor bases 14a, 14b by means of unimorphic element securing pieces 15a, 15b thus constituting the chopper for a unimorphic piezoelectric element. Consequently, the resonance frequency of unimorphic element is lowered and the chopper is driven in the vicinity of resonance frequency. This structure realizes integrated management of the chopper and the fixing part while facilitating replacement of the chopper and suppressing fluctuation in the resonance frequency among individual choppers thus realizing a miniature chopper producing a large displacement while stabilizing the driving.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared sensor for detecting infrared rays emitted from an object in a non-contact manner.

[0002]

2. Description of the Related Art In recent years, pyroelectric infrared sensors have been used in a wide range of fields such as temperature measurement of cooked foods in microwave ovens and position detection of human bodies in air conditioners, and it is expected that demand will increase further in the future. Pyroelectric infrared sensor
It utilizes the pyroelectric effect of a pyroelectric material such as a LiTaO ₃ single crystal. Pyroelectric materials have spontaneous polarization and always generate surface charges, but in the steady state in the atmosphere, they are electrically neutral because they are associated with the charges in the atmosphere. When infrared rays are incident on this pyroelectric body, the temperature of the pyroelectric body changes, and along with this, the charge state of the surface also changes, breaking the neutral state. A pyroelectric infrared sensor measures the amount of incident infrared rays by detecting the charges generated on the surface. An object emits infrared rays according to its temperature, and the position and temperature of the object can be detected by using this sensor. The pyroelectric effect is caused by a change in the incident amount of infrared rays, and it is necessary to change the incident amount of infrared rays when detecting the temperature of an object as a pyroelectric infrared sensor. A chopper is used as this means and detects the temperature of the detection object by forcibly interrupting the incident infrared rays. As a conventional chopper, an electromagnetic motor, a piezoelectric actuator, etc. have been used.

FIG. 4 shows a conventional example of a pyroelectric infrared sensor using an actuator in which a piezoelectric material is bonded to an elastic flat plate as a chopper. Generally, a piezoelectric element is bonded to an elastic flat plate such as metal to form a bonded element and one end is fixed,
Actuators that generate bending motions by utilizing the strain of a piezoelectric body are generally called bimorph type in which the piezoelectric body is bonded to both sides of an elastic plate, and unimorph type in which only one side is bonded. Further, the elastic plate is called a shim, and each member is called as such.

FIG. 4 shows a bimorph type element used as a chopper for a pyroelectric infrared sensor, 61 is a shim,
62a and 62b are piezoelectric bodies, 63 is a shielding plate, 64 is a pedestal,
Reference numeral 65 is a fixture, 66 is wiring for shims, 67a and 67b are wiring for piezoelectric bodies, 68 is an infrared detecting section, 69 is a slit, 7
0 is infrared. On both sides of the shim 61, a piezoelectric body 62a,
62b are bonded to each other, and the three are integrated to form a bimorph type element. Electrodes are printed on the surfaces of the piezoelectric bodies 62a and 62b, and polarization treatment is performed in a direction perpendicular to the bonding surface. The polarization directions of the piezoelectric bodies 62a and 62b are the wiring 66 and the piezoelectric material taken out from the shim. Depending on the direction of the electric field applied between the shim 61 and the piezoelectric bodies 62a, 62b by the wirings 67a, 67b taken out from the body, it is determined that the piezoelectric bodies 62a, 62b always generate strain in opposite directions. To be That is, the direction of the applied electric field and the polarization direction are determined such that when one of the piezoelectric bodies 62a and 62b is distorted in the direction of extension in the polarization direction, the other is contracted in the direction of polarization. The bimorph type element is held by the pedestal 64 and the fixture 65 by simultaneously sandwiching the portion of the shim 61 and the portions of the piezoelectric bodies 62a and 62b. The shim wiring 66 is attached to a portion of the shim 61 where the piezoelectric bodies 62a and 62b are not adhered, and the piezoelectric body wiring 6 is provided on the surfaces of the piezoelectric bodies 62a and 62b.
7a and 67b are attached. A shield plate 63 is attached to the free end of the bimorph element, and a slit 69 is provided in the shield plate 63. Shield plate 6
In the vicinity of 3, the infrared detection unit 68 is arranged so as not to come into contact with the shield plate 63 and the bimorph type element. The shim 61 is formed by the shim wiring 66 and the piezoelectric body wirings 67a and 67b.
When an electric field is applied between the piezoelectric element 62a and the piezoelectric element 62b, the bimorph element generates a bending movement with one end fixed, and the shield plate 63 and the slit 69 attached to the tip end.
Performs reciprocating motion in the moving direction indicated by the arrow in FIG. 4 in accordance with the change in the direction in which the electric field is applied. The reciprocating movement of the slit 69 interrupts the infrared rays 70 incident on the infrared detecting section 68 intermittently.

However, in the bimorph type chopper having the above structure, it is necessary to increase the dimension from the fixed portion to the moving portion at the tip in order to obtain a moving distance sufficient to intermittently block infrared rays. Very high drive voltage is required.

Therefore, as a conventional improvement method, a load is applied to the tip moving portion of the bimorph type element or the unimorph type element to lower the resonance frequency, and the fixing is performed only at the shim portion, whereby the piezoelectric body is brittlely broken. It is possible to obtain a large displacement by driving at a low voltage by preventing the above phenomenon and further lowering the resonance frequency by means such as providing a notch in a shim near the fixed portion as necessary. An example of the structure of the chopper having the above characteristics is shown below.

FIG. 5 is a perspective view showing an example of a conventional improved unimorph type element as a chopper for a pyroelectric infrared sensor, which is formed so that the width of the fixing place of the shim portion becomes narrow. In FIG. 5, 71a and 71b
Is a shim, 72a and 72b are piezoelectric bodies, 73a and 73b are weights, 74 is a sensor pedestal, 75a and 75b are unimorph type element fixtures, 76a and 76b are shim wiring, and 77a and 7a.
Reference numeral 7b is a piezoelectric wire, 78 is an infrared detector, and 79a and 7a.
9b, 79c and 79d are unimorph type element fixing screws, 8
0 is infrared.

FIG. 6 is a perspective view showing the details of the shims 71a and 71b, where 81 is a shielding portion, 82 is a piezoelectric body adhesive portion,
83 is a notch part, 84 is a positioning part, 85a, 85b
Is a fixing hole. The shielding portion 81 and the piezoelectric body bonding portion 82 are bent to form a right angle, and the cutout portion 83 formed such that the width is smaller than that of the piezoelectric body bonding portion 82 from the piezoelectric body bonding portion 82 to the positioning portion 84. And fixing holes 85a and 85b are provided at both ends of the positioning portion 84.

As shown in FIG. 6, the shims 71a and 71b are provided with a notch 83 having a narrow width, and the notch 83 is sandwiched between the sensor pedestal 74 and the unimorph type element fixtures 75a and 75b as shown in FIG. Further, the unimorph type element fixing screws 79a and 79b are respectively fixed in the fixing holes 8
5a, 85b are inserted, positioned and fixed at one end, and arranged so as to face each other in parallel. Further, the piezoelectric bodies 72a and 72b are provided on the surfaces of the shims 71a and 71b which face each other, that is, on the piezoelectric body bonding portion 82.
4, unimorph type element fixtures 75a, 75b and shim 7
The unimorph type piezoelectric actuator is configured by being bonded at a position where it does not come into contact with the shield portions at the tips of 1a and 71b as well as the cutout portion 83. The infrared detector 78 is the sensor base 7
4 is arranged in the vicinity of the free end of the unimorph type element and receives or is blocked by the infrared rays 80. The shield that connects and disconnects the infrared rays 80 is configured by bending the ends of the shims 71a and 71b on the opposite side to the fixed side, and the weights 73a and 73b are adhered to the plane portions of this portion, respectively. The shim wirings 76a and 76b are provided at one location other than the movable portions of the shims 71a and 71b, that is, one location of the positioning section 84, and the piezoelectric body wirings 77a and 77b are provided at the piezoelectric bodies 72a and 72b, respectively. When the electric field is applied between the shim 71a and the piezoelectric body 72a and the shim 71b and the piezoelectric body 72b by the shim wirings 76a and 76b and the piezoelectric body wirings 77a and 77b, the unimorph type element is bent. Raise and move the shield at the tip. Two
The two unimorph type elements are driven in the opposite directions at the same frequency to intermittently block the infrared rays 80.

By providing the notch in the shim portion between the piezoelectric member and the fixed portion of the unimorph type element, the resonance frequency can be further reduced as compared with the unimorph type element having the same size and not having the notch. Therefore, it is possible to reduce the size of the chopper and increase the amount of displacement during low frequency driving, as compared with the case where the notch is not provided.

Further, even when holes are formed instead of the notches, the same effect can be obtained.

[0012]

However, a bimorph type or unimorph type chopper having a configuration in which a weight is arranged at the cutout portion and the tip end portion according to the above-mentioned conventional improvement example and the resonance frequency is a bimorph type or unimorph type chopper can be driven in the vicinity of the resonance frequency. Because there is
When the resonance frequency varies among the solids, the difference between the individual displacement amounts becomes large, and it is necessary to finely adjust the resonance frequency of the chopper between the solids.

Further, since the infrared detector and the plurality of choppers are fixed on the sensor pedestal, it is difficult to fix them at the time of assembly, and once assembled, one component is repaired or the resonance frequency of the chopper is adjusted. When doing so, it is difficult to fix the whole part, and other parts hinder the movement or replacement of the target parts, which makes the workability poor.When the whole is disassembled, the resonance frequency changes due to the movement of the chopper fixed position. As a result, the driving characteristics fluctuate and extra adjustment is required. Further, the rigidity of the chopper is low, so that the chopper other than the intended purpose is easily damaged during the work.

In view of the above points, the present invention provides a pyroelectric infrared sensor which has a smaller variation in resonance frequency and which is driven at a frequency near the resonance frequency and which has improved workability during assembly. With the goal.

[0015]

To achieve this object, in the pyroelectric infrared sensor of the present invention, the pedestal for fixing the sensor can be divided so that the chopper is fixed to each of the pedestals, or the chopper has another rigidity. After fixing to the member,
The rigid member is fixed to the sensor base.

[0016]

As a member for fixing the chopper is a base of the infrared detecting portion, and the base can be divided into a plurality of parts so that the chopper is fixed to each of the bases, thereby assembling each chopper and the infrared detecting portion. Fixed, repair,
The resonance frequency of the chopper can be adjusted individually, which facilitates assembly and management of the sensor as a whole, and damage to parts other than the chopper intended for repair and adjustment, especially for other choppers with low rigidity. Damage can be prevented, and replacement work of each component is simplified. Alternatively, even if the chopper is attached to another small member, and the chopper is attached to the infrared detector pedestal by the small member, there is the same action as above, and the sensor unit and the chopper can be managed individually, Workability is improved.

[0017]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention,
It is a perspective view showing an example of a chopper for a pyroelectric infrared sensor using a unimorph type piezoelectric actuator.

In FIG. 1, 11a and 11b are shims and 1
2a and 12b are piezoelectric bodies, 13a and 13b are weights, 14
a and 14b are sensor pedestals, 15a and 15b are unimorph type element fixtures, 16a and 16b are shim wiring, 17a,
Reference numeral 17b is a wiring for attaching a piezoelectric body, 18a and 18b are wirings for a piezoelectric body, 19 is an infrared detecting section, 20 is infrared ray, 21
a and 21b (not shown because they are on the back side in the perspective view) are shim hole processed portions, 22a and 22b are relay boards, and 23a and 23a.
b, 23c and 23d are unimorph type element fixing screws (23
c and 23d are not shown), and 24a and 24b are sensor base fixing screws (24b is not shown).

Each of the shims 11a and 11b is provided with a bent portion perpendicular to the surface at one end and shim hole processed portions 21a and 21b, and a wide portion is again provided at the tip of the shim hole processed portions 21a and 21b. In this portion, the shim wirings 16a and 16b are soldered to the shims 11a and 11b. Weights 13a and 13b are attached to the bent portions of the shims 11a and 11b, respectively, and contribute to the reduction of the resonance frequency of the chopper together with the shim hole processing portions 21a and 21b. Weights 13a, 1
3b is arranged to be substantially symmetrical with respect to the widthwise centers of the shims 11a and 11b. The shims 11a and 11b are attached to the sensor pedestal 14 near the shim holes 21a and 21b.
a, 14b and unimorph type element fixing tools 15a, 15b, and unimorph type element fixing screws 23a, 2
3b, 23c, 23d is fixed at one end with screws,
The sensor pedestal 14a has holes (not shown), and the sensor pedestal 14b has screw holes (not shown), which are fixed together by the sensor pedestal fixing screws 24a and 24b.
The two parts of the sensor pedestals 14a and 14b where the choppers are fixed have steps, and when the choppers are fixed, the choppers are arranged so that their movable ends have steps. The shims 11a and 11b are arranged such that the surfaces on the bent sides face each other in parallel, and the piezoelectric bodies 12a and 12b have the bent portions of the shims 11a and 11b and the shim hole processing portion 21 on the respective facing surfaces.
A unimorph type element, which is a chopper, is configured by being adhered so as not to contact a and 21b. Piezoelectric body 12a,
On the surface of 12b, wirings 17a, 1 for mounting the piezoelectric body
7b is the shim hole processing portion 21a, 2 of the shim 11a, 11b.
1b is soldered in the area close to 1b, and the sensor base 1
Relay boards 22a attached to the end faces of 4a, 14b,
The piezoelectric body mounting wirings 17a and 17b are electrically connected to the piezoelectric body wirings 18a and 18b via 22b. The piezoelectric bodies 12a and 12b are pre-polarized so that the surfaces not bonded to each other are positive. An infrared detector 19 is arranged on the sensor bases 14a and 14b so as to be electrically insulated from the sensor bases 14a and 14b. Wirings for shims 16a and 16b and wiring for piezoelectric body 18
When an electric field is applied to the piezoelectric bodies 12a and 12b by the a and 18b, the piezoelectric bodies 12a and 12b are deformed, and the movable portions of the chopper are bent and deformed, and the weights 13a and 13b.
The attached tip part of is displaced. When the same electric field is applied to each of the two choppers, the tip portions of the two choppers are always displaced in opposite directions, and the tip portions open and close in the opening / closing direction of the arrow in FIG. Infrared rays 20 that enter the infrared detector 19 are blocked or blocked,
Functions as a chopper for a pyroelectric infrared sensor.

FIG. 2 is a perspective view for explaining the shape of the shim used in the chopper in detail. In FIG. 2, 31 is a bent portion, 32 is a piezoelectric bonding portion, 33 is a shim hole processed portion, 34 is a fixed portion, 35a and 35b are fixing holes, and 36a and 36b are grooved portions.

A bent portion 31 and a shim hole processing portion 33 are integrally formed at both ends of the piezoelectric body bonding portion 32, and are formed on the surface of the piezoelectric body bonding portion 32 in the bending direction. By bonding the piezoelectric body, attaching a weight to the upper surface of the bent portion 31 if necessary, and fixing one end at or near the shim hole processed portion 33,
A chopper having a movable portion at the bent portion 31 at the tip is configured. When the fixing is performed below the shim hole processed portion 33, the only members that directly fix the drive portion of the chopper are the two small members on both sides in the width direction of the shim hole processed portion 33. Fixing hole 35 provided in the fixing portion 34
a, 35b, chopper sensor pedestals 14a, 14
Then, the sensor pedestals 14a and 14b are integrated in the grooved portions 36a and 36b.

In the chopper of the type which is driven near the resonance frequency, such as the chopper having the above-mentioned structure, an extremely large displacement can be obtained due to the influence of resonance, but the amount of displacement at the resonance point is unstable and a constant drive characteristic is obtained. Hard to get. Therefore, the chopper is driven at a frequency lower by 5 to 15% than the resonance frequency. Specifically, the length of the piezoelectric bronze shim is about 12 mm and the resonance frequency is about 2 mm.
For the unimorph type chopper of 2 Hz, the drive frequency of 20 Hz with the resonance frequency reduced by 10% is selected. In this case, it is possible to obtain a displacement of 1.2 mm or more by applying a voltage of 80 V as an alternating current only in the polarization direction of the piezoelectric body and by applying an electric field in the direction opposite to the polarization so as not to cause polarization breakdown. is there. By using this drive frequency, the instability of resonance can be avoided and the effect of displacement expansion due to resonance can also be achieved, so a large displacement amount can be obtained. On the contrary, the same effect can be obtained when the driving is performed by shifting the frequency to the side higher than the resonance frequency, but the lower driving frequency is preferable in order to increase the sensitivity of the infrared detecting section of the sensor.

With the above construction, when the infrared detector is repaired from the sensor pedestal, the chopper can be separated from the infrared detector without removing it from the fixed portion, and the extra parts hinder the work. And the risk of damaging the chopper during work is reduced. In addition, when the chopper is removed from the pedestal, the resonance frequency of the chopper is likely to change and the characteristics are less stable, but if the chopper is removed together with the pedestal, fluctuations in the resonance frequency can be prevented.
Further, when the resonance frequency of the chopper is adjusted for each individual, it can be performed only by the chopper and the pedestal, which facilitates work and management.

Although the unimorph type element is used as the chopper in this embodiment, the same effect can be obtained by using the bimorph type element. Needless to say, if the resonance frequency of the chopper is in the vicinity of the driving frequency without the weight or the hole of the shim, it is possible to perform the driving without using these.

(Embodiment 2) Another embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows the second aspect of the present invention.
FIG. 7 is a perspective view showing an example of a chopper for a pyroelectric infrared sensor using a unimorph type piezoelectric actuator in the example of FIG.

In FIG. 3, 41a and 41b are shims and 4
2a and 42b are piezoelectric bodies, 43a and 43b are weights, 44 is a sensor pedestal, 45a and 45b are unimorph type element fixtures A, 46a and 46b are shim wirings, 47a and 47b are piezoelectric body mounting wirings (47b is a drawing (Not shown), 48a, 4
8b is a piezoelectric wiring, 49 is an infrared detecting part, 50 is infrared, 51a and 51b are notched parts (51b are not shown), 52a and 52b are relay boards (52b is not shown), 53a and 53b, 53c and 53d are fixing screws A
(53c and 53d are not shown), 54a, 54b and 54
c and 54d are fixing screws B (54c and 54b are not shown), and 55a and 55b are unimorph type element fixing tools B.

Each of the shims 41a and 41b is provided with a bent portion perpendicular to the surface at one end thereof and cutout portions 51a and 51b, and a wide portion is again provided at the tip of the cutout portions 51a and 51b. Wiring for shim in part 4
6a and 46b are soldered to the shims 41a and 41b. Weights 43a and 43b are attached to the bent portions of the shims 41a and 41b, respectively.
The cutouts 51a and 51b and the combined chopper contribute to the reduction of the resonance frequency. The weights 43a and 43b are arranged to be substantially symmetrical with respect to the widthwise centers of the shims 41a and 41b. Unimorph type element fixture A45
a, 45b are provided with through holes (not shown), unimorph type element fixtures B55a, 55b are provided with female screw holes (not shown) and through holes, and shims 41a, 41b are provided with cutouts 5.
Unimorph type element fixture A4 near 1a and 51b
5a, 45b and unimorph type element fixture B55a, 55
It is sandwiched by b and fixed by fixing screws A53a, 53b and 53c, 53d. Further, the sensor pedestal 44 is provided with a female screw hole (not shown),
The unimorph type element fixtures B55a, 55b are provided with fixing screws B54a, 54b, and 54 for the sensor base 44.
The chopper is fixed to the sensor pedestal 44. Two portions of the sensor pedestal 44 where the chopper is fixed have steps, and when the chopper is fixed, the chopper is arranged such that each movable end has a step. The shims 41a and 41b are arranged so that the surfaces on the bent sides face each other in parallel, and the piezoelectric body 42 is provided on each of the facing surfaces.
The a and 42b are adhered so as not to contact the bent portions of the shims 41a and 41b and the cutout portions 51a and 51b to form a unimorph type element which is a chopper. On the surfaces of the piezoelectric bodies 42a and 42b, the piezoelectric body mounting wirings 47a and 47b are soldered at the portions near the notches 51a and 51b of the shims 41a and 41b, and further mounted on the sensor pedestal 44. , 52
The piezoelectric body mounting wirings 47a and 47b are electrically connected to the piezoelectric body wirings 48a and 48b through the line b.
The piezoelectric bodies 42a and 42b are pre-polarized so that the surfaces not bonded to each other are positive. An infrared detector 49 is arranged on the sensor base 44 so as to be electrically insulated from the sensor base 44. Shim wiring 46
When an electric field is applied to the piezoelectric bodies 42a and 42b by a and 46b and the piezoelectric body wirings 48a and 48b, the piezoelectric bodies 42a and 4b
2b is deformed, the movable portion of the chopper is bent and deformed, and the tip end portions to which the weights 43a and 43b are attached are displaced. When the same electric field is applied to each of the two choppers, the tip portions of the two choppers are always displaced in opposite directions, so that the tip portions of the two choppers enter or block the infrared rays 50 entering the infrared detecting section 49. Functions as a chopper for infrared sensors.

With the above configuration, the infrared detector and the infrared detector 2
Can manage two choppers independently. The resonance frequency of the chopper changes depending on the fixed position, which affects the drive characteristics, and adjustment may be required when the resonance frequency varies between solids.However, according to the above configuration, the chopper unit moves with the fixed part. Because it is possible, the work is easy. Further, each chopper can be managed in a fixed state, and choppers having the same resonance frequency can be stored at all times, so management is easy, and chopper replacement and the like can be performed smoothly.

Further, since the left and right choppers having the same shape with exactly the same length can be constructed by simply mounting them at different positions, mass productivity of the choppers is good.

Although a plurality of choppers are used in this embodiment, this is not necessary when the area for opening and closing the infrared rays can be achieved by a single chopper, and even in this case, the same effects as described above regarding chopper management and resonance frequency stability can be obtained. It goes without saying that there is.

[0031]

As described above, the present invention is a chopper in which only the shim portion of a unimorph type element or a bimorph type element is fixed, and a part of the shim is machined to reduce the resonance frequency to near the driving frequency. In the above, by making each pedestal that directly fixes the chopper separable, it is possible to easily adjust, replace, and repair the resonance frequency of multiple choppers, and it is possible to always use a chopper whose resonance frequency is stable between solids. It is possible to stabilize the driving characteristics when the sensor is attached. In addition, assembly at the time of mass production becomes easy, and productivity is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of the configuration of a pyroelectric infrared sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a shim shape in the embodiment of the present invention.

FIG. 3 is a perspective view showing an example of a configuration of a pyroelectric infrared sensor according to an embodiment of the present invention.

FIG. 4 is a perspective view showing an example of a conventional pyroelectric infrared sensor.

FIG. 5 is a perspective view showing an example of an improved pyroelectric infrared sensor in a conventional example.

FIG. 6 is a perspective view showing an example of a shim shape of a chopper in a conventional example.

[Explanation of symbols]

 11a, 11b Shims 12a, 12b Piezoelectric bodies 13a, 13b Weights 14a, 14b Sensor pedestal 19 Infrared detector

Claims (2)

[Claims] 1. A flat elastic member as a means (hereinafter referred to as a chopper) for entering / blocking infrared rays of a pyroelectric infrared sensor for detecting an object by injecting infrared rays emitted from an object into a pyroelectric sensor section. On the other hand, a flat plate-shaped piezoelectric body polarized in a direction perpendicular to the elastic member surface is bonded on one or both sides of a plane to form a bonded element, and one end of the bonded element is fixed by a fixing member. Then, by applying an electric field to the bonding element to cause the bonding element to bend and move, the other end of the bonding element is a movable part, and the fixed part of the bonding element is the elastic member. A chopper in which only a part of the member is fixed, and a hole or a notch is provided in the elastic member between the fixed portion and the bonding portion of the elastic member is used. It has a plurality of parts and has a structure in which the pedestal part for arranging the infrared detecting part is separable into at least two parts, and the individual choppers are fixed directly to the respective separated parts of the pedestal. Pyroelectric infrared sensor. 2. A flat elastic member as a means (hereinafter referred to as a chopper) for entering / blocking infrared rays of a pyroelectric infrared sensor for detecting an object by allowing infrared rays emitted from the object to enter the pyroelectric sensor section. On the other hand, a flat plate-shaped piezoelectric body polarized in a direction perpendicular to the elastic member surface is bonded on one or both sides of a plane to form a bonded element, and one end of the bonded element is fixed by a fixing member. Then, by applying an electric field to the bonding element to cause the bonding element to bend and move, the other end of the bonding element is a movable part, and the fixed part of the bonding element is the elastic member. A chopper in which only a part of the member is fixed to the rigid member, and a hole or a notch is provided in the elastic member between the fixing portion and the bonding portion of the elastic member, A pyroelectric infrared sensor having a plurality of the choppers, wherein the rigid member is fixed to a pedestal portion on which an infrared detection section is arranged, whereby the chopper is fixed to the pedestal portion.