Infrared sensor element, infrared sensor, and position detection system

Abstract

To provide an infrared sensor element that can detect the direction in which an object to be detected is located, while enabling miniaturization. [Solution] The infrared sensor element comprises a pyroelectric element having one main surface facing one direction in the thickness direction and another main surface that overlaps with the first main surface when viewed from the thickness direction and faces the other direction in the thickness direction, a one-side electrode provided on the first main surface, and a other-side electrode provided on the other main surface that overlaps with the first-side electrode when viewed from the thickness direction. When viewed from the thickness direction, the first-side electrode or the other-side electrode has a curved outer edge that is parabolic in shape.

Description

[Technical Field]

[0001] This disclosure relates to an infrared sensor element, an infrared sensor equipped with the infrared sensor element, and a position detection system equipped with the infrared sensor. [Background technology]

[0002] Infrared sensors using pyroelectric elements are known (see, for example, Patent Document 1). Such infrared sensors are used, for example, to detect the presence of objects to be detected, such as the human body.

[0003] In an infrared sensor using a pyroelectric element, for example, infrared radiation emitted from an object to be detected is focused onto the pyroelectric element through a lens, and an image is formed on the pyroelectric element. The part of the pyroelectric element irradiated with infrared radiation is heated, and the temperature of that part changes. When the temperature changes, an electric charge is generated on the surface of that part of the pyroelectric element due to the pyroelectric effect. This charge is output as an electrical signal to the outside of the pyroelectric element. Based on the output electrical signal, the object to be detected is detected.

[0004] For a temperature change to occur in a pyroelectric element, the size and intensity of the image focused on the pyroelectric element must change. When detecting a moving object, the size and intensity of the image focused on a stationary pyroelectric element may change. On the other hand, to detect a stationary object, for example, the pyroelectric element is moved to change the image focused on it.

[0005] Patent Document 2 discloses an infrared sensor that changes the distance between a pyroelectric element and an object to be detected by vibrating the pyroelectric element in the direction of the optical axis of the light-receiving surface of the pyroelectric element. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4702366 [Patent Document 2] Japanese Patent Application Publication No. 8-184492 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, moving a pyroelectric element, as in the infrared sensor disclosed in Patent Document 2, only allows for the detection of the presence or absence of an object within the field of view of the infrared sensor. In other words, it is not possible to obtain additional information such as the direction in which the object is located relative to the infrared sensor.

[0008] To obtain additional information, it is conceivable to create an array of multiple infrared sensors arranged in a planar configuration to achieve higher resolution. However, miniaturizing the arrayed sensor reduces the spacing between the pyroelectric elements of two adjacent infrared sensors, potentially leading to crosstalk due to heat conduction between the elements. In other words, there are limits to the miniaturization of the arrayed sensor. Therefore, it is difficult to obtain sufficient resolution by arranging multiple infrared sensors in a planar configuration.

[0009] The purpose of this disclosure is to provide an infrared sensor element that can detect the direction in which an object to be detected is located while enabling miniaturization. [Means for solving the problem]

[0010] An infrared sensor element according to one aspect of this disclosure is A pyroelectric element having one main surface facing one direction in the thickness direction and another main surface that overlaps with the first main surface when viewed from the thickness direction and faces the other direction in the thickness direction, One side electrode provided on the one main surface, The other main surface is provided with a second electrode which overlaps with the first electrode when viewed from the thickness direction, Viewed from the thickness direction, one electrode or the other electrode has a curved outer edge that is parabolic in shape. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide an infrared sensor element that can detect the direction in which a detection target object is present while enabling miniaturization. [Brief Description of the Drawings]

[0012] [Figure 1] Functional block diagram of a position detection system according to the first embodiment of the present disclosure [Figure 2] Schematic diagram illustrating infrared irradiation from a detection target object to an infrared sensor [Figure 3] Schematic plan view of an infrared sensor element [Figure 4] Schematic bottom view of an infrared sensor element [Figure 5] Schematic cross-sectional view taken along line A-A of FIG. 3 [Figure 6] A schematic cross-sectional view corresponding to the B-B cross-section of FIG. 3, showing the infrared sensor element and a support portion [Figure 7] Flowchart for explaining the operation of the position detection system [Figure 8] Schematic plan view of an infrared sensor element for explaining calculation of an image center position [Figure 9] A schematic cross-sectional view corresponding to the B-B cross-section of FIG. 3, showing a modified example of the infrared sensor element and the support portion [Figure 10] Schematic plan view of a modified example of an infrared sensor element [Figure 11] Schematic plan view of a modified example of an infrared sensor element [Figure 12] Schematic bottom view of a modified example of an infrared sensor element [Figure 13] A schematic cross-sectional view corresponding to the C-C cross-section of FIG. 11, showing a modified example of the infrared sensor element and the support portion [Figure 14] Schematic cross-sectional view taken along line D-D of FIG. 11 [Figure 15] Schematic cross-sectional view taken along line D-D of FIG. 11 [Figure 16] A schematic cross-sectional view corresponding to the C-C cross-section of FIG. 11, showing a modified example of the infrared sensor element and the support portion [Figure 17]A schematic diagram showing the irradiation of infrared rays from the object being detected to the two infrared sensors. [Modes for carrying out the invention]

[0013] An example of this disclosure is described below with reference to the attached drawings. The following description is essentially illustrative and is not intended to limit this disclosure, its applications, or its uses. Furthermore, the drawings are schematic, and the proportions of dimensions, etc., do not necessarily correspond to reality. In addition, the following description uses terms indicating specific directions or positions (e.g., terms including "up," "down," "right," "left," "front," and "back") as needed. However, the use of terms indicating specific directions or positions is for the purpose of facilitating the understanding of this disclosure with reference to the drawings, and the meaning of these terms does not limit the technical scope of this disclosure.

[0014] <First Embodiment> Figure 1 is a functional block diagram of a position detection system according to the first embodiment of this disclosure. Figure 2 is a schematic diagram showing the irradiation of infrared rays from an object to be detected to an infrared sensor.

[0015] As shown in Figure 1, the position detection system 1 comprises an infrared sensor 2 and a lens 6. The infrared sensor 2 outputs an electrical signal based on infrared radiation 7A emitted from a detection target object 7 (see Figure 2), such as a person. In Figure 2 and Figure 17 described later, infrared radiation 7A is indicated by a dashed arrow for ease of explanation.

[0016] As shown in Figures 1 and 2, the infrared sensor 2 comprises an infrared sensor element 4, a drive unit 5, and a control unit 3. The control unit 3 controls the drive unit 5, receives a signal from the infrared sensor element 4, and calculates the image center position k (see Figure 2), as will be described later.

[0017] Figure 3 is a schematic plan view of the infrared sensor element. Figure 4 is a schematic bottom view of the infrared sensor element. Figure 5 is a schematic cross-sectional view showing section AA of Figure 3.

[0018] As shown in Figures 2 to 5, the infrared sensor element 4 comprises a pyroelectric element 41 and one electrode 42 and the other electrode 43 stacked on the pyroelectric element 41 in the thickness direction 101. Note that the one electrode 42 and the other electrode 43 are not shown in Figure 2.

[0019] The pyroelectric element 41 is rectangular in shape. As shown in Figures 3 and 4, the pyroelectric element 41 has one rectangular main surface 41A and another rectangular main surface 41B. As shown in Figure 5, one main surface 41A faces one direction in the thickness direction 101. The other main surface 41B faces the other direction in the thickness direction 101. When viewed from the thickness direction 101, one main surface 41A and the other main surface 41B overlap. Note that the pyroelectric element 41 is not limited to a rectangular parallelepiped. For example, the pyroelectric element 41 may be cylindrical.

[0020] As shown in Figures 3 and 5, one electrode 42 is stacked on one main surface 41A of the pyroelectric element 41. In other words, one electrode 42 is provided on one main surface 41A. As shown in Figures 4 and 5, the other electrode 43 is stacked on the other main surface 41B of the pyroelectric element 41. In other words, the other electrode 43 is provided on the other main surface 41B.

[0021] As shown in Figure 3, one main surface 41A of the pyroelectric element 41 has a detection region 41Aa and two non-detection regions 41Ab and 41Ac. The two non-detection regions 41Ab and 41Ac are located on both sides of the main surface 41A in the X-axis direction 103. The detection region 41Aa is located between the two non-detection regions 41Ab and 41Ac in the X-axis direction 103. The X-axis direction 103 is parallel to the main surface 41A and is parallel to the longitudinal direction of the rectangular main surface 41A.

[0022] As shown in Figure 4, the other main surface 41B of the pyroelectric element 41 has a detection region 41Ba and two non-detection regions 41Bb and 41Bc. The two non-detection regions 41Bb and 41Bc are located on both sides of the other main surface 41B in the X-axis direction 103. The detection region 41Ba is located between the two non-detection regions 41Bb and 41Bc in the X-axis direction 103.

[0023] The detection regions 41Aa and 41Ba shown in Figures 3 and 4 are the regions where infrared radiation 7A (see Figure 3) from the object to be detected 7 is irradiated and an image 8 is formed. The non-detection regions 41Ab, 41Ac, 41Bb, and 41Bc are regions used for electrical connection to the outside of the infrared sensor element 4 and for supporting the pyroelectric element 41.

[0024] In Figures 3 and 4, the non-detection regions 41Ab, 41Ac, 41Bb, and 41Bc are the regions enclosed by dashed lines, while the detection regions 41Aa and 41Ba are the regions excluding those enclosed by dashed lines.

[0025] As shown in Figures 3 and 4, when viewed from the thickness direction 101, the detection area 41Aa of one main surface 41A overlaps with the detection area 41Ba of the other main surface 41B. When viewed from the thickness direction 101, the non-detection area 41Ab of one main surface 41A overlaps with the non-detection area 41Bb of the other main surface 41B. When viewed from the thickness direction 101, the non-detection area 41Ac of one main surface 41A overlaps with the non-detection area 41Bc of the other main surface 41B.

[0026] In the configurations shown in Figures 3 and 4, the entire area of ​​detection region 41Aa overlaps with the entire area of ​​detection region 41Ba when viewed from the thickness direction 101, but the configuration is not limited to this. For example, a portion of detection region 41Aa may overlap with a portion of detection region 41Ba when viewed from the thickness direction 101.

[0027] In the configurations shown in Figures 3 and 4, when viewed from the thickness direction 101, the entire area of ​​non-detection region 41Ab overlaps with the entire area of ​​non-detection region 41Bb, and the entire area of ​​non-detection region 41Ac overlaps with the entire area of ​​non-detection region 41Bc. However, the configuration is not limited to this. For example, when viewed from the thickness direction 101, the non-detection region 41Ab does not have to overlap with the non-detection region 41Bb.

[0028] As shown in Figure 3, the one-sided electrode 42 is provided across the detection region 41Aa and the non-detection region 41Ab of the one main surface 41A.

[0029] As shown in Figure 4, the other electrode 43 is provided across the detection region 41Ba and the non-detection region 41Bc of the other main surface 41B.

[0030] As shown in Figures 3 and 4, when viewed from the thickness direction 101, the portion of one electrode 42 provided in the detection region 41Aa overlaps with the portion of the other electrode 43 provided in the detection region 41Ba.

[0031] Viewed from the thickness direction 101, the portion of one electrode 42 provided in the non-detection region 41Ab does not overlap with the portion of the other electrode 43 provided in the non-detection region 41Bc. In other words, viewed from the thickness direction 101, the non-detection region 41Ab of the one main surface 41A where the one electrode 42 is provided is located outside the non-detection region 41Bc of the other main surface 41B where the other electrode 43 is provided.

[0032] When viewed from the thickness direction 101, the non-detection region of one main surface 41A where one electrode 42 is provided may overlap with the non-detection region of the other main surface 41B where the other electrode 43 is provided. For example, one electrode 42 may be provided in the non-detection region 41Ac of one main surface 41A, and the other electrode 43 may be provided in the non-detection region 41Bc of the other main surface 41B.

[0033] As shown in Figure 3, when viewed from the thickness direction 101, the one-sided electrode 42 has two parabolic curved outer edges 42A. Each parabola of the two curved outer edges 42A has a common axis AX. Axis AX is parallel to the Y-axis direction 104. The Y-axis direction 104 is parallel to the short side direction of the rectangular one-sided main surface 41A. In other words, the Y-axis direction 104 is parallel to the one-sided main surface 41A and perpendicular to the X-axis direction 103. In the first embodiment, the two curved outer edges 42A are symmetric with respect to a line LN perpendicular to axis AX, that is, a line LN parallel to the X-axis direction 103, such that the vertices of the two curved outer edges 42A are closest to each other. Note that the two curved outer edges 42A do not have to be symmetric with respect to each other.

[0034] Figure 6 is a schematic cross-sectional view corresponding to the BB cross-section in Figure 3, and shows the infrared sensor element and the support portion.

[0035] As shown in Figure 6, the infrared sensor element 4 is supported by a support portion 91. In the first embodiment, the support portion 91 is made of LTCC (Low Temperature Co-fired Ceramics) and has a first support portion 911 and a second support portion 912 laminated on the first support portion 911. The boundary between the first support portion 911 and the second support portion 912 may be indistinguishable. Therefore, in Figure 6, the boundary is shown with a dashed line. The support portion 91 may be made of a material other than LTCC.

[0036] Conductive pastes 921 and 922, made of copper or the like, are formed on the first support portion 911. The pyroelectric element 41 is mounted on the pastes 921 and 922 with its other main surface 41B facing the pastes 921 and 922. As a result, the other-side electrode 43 formed on the other main surface 41B is in contact with the paste 922.

[0037] Conductive pastes 931 and 932, made of copper or the like, are formed on the second support portion 912. Paste 931 is in contact with paste 921 and one-sided electrode 42. Paste 932 is in contact with paste 922.

[0038] Wirings 94 and 95 are formed on the surface and inside of the support portion 91. Wiring 94 is in contact with the paste 931. Wiring 95 is in contact with the paste 922. Although not shown in Figure 6, wirings 94 and 95 are electrically connected to the outside of the support portion 91 (the control unit 3 shown in Figure 1 in the first embodiment).

[0039] The drive unit 5 shown in Figure 1 drives the infrared sensor element 4. The drive unit 5 is a known actuator, such as a motor. In the first embodiment, the drive unit 5 is a motor comprising a coil and a rotor. The drive unit 5 is mechanically connected to the infrared sensor element 4 or the support unit 91. In accordance with the rotation of the rotor of the drive unit 5, the infrared sensor element 4 and the support unit 91 move along the X-axis direction 103 (see Figure 2). In other words, the drive unit 5 moves the infrared sensor element 4 and the support unit 91 along the X-axis direction 103.

[0040] In the first embodiment, the drive unit 5 is sinusoidally driven by the control unit 3 (see Figure 1). The rotational speed of the rotor changes according to the sinusoidal voltage applied to the coil by the control unit 3. The moving speed of the infrared sensor element 4 changes according to the rotational speed of the rotor.

[0041] As shown in Figure 2, the lens 6 is positioned opposite one main surface 41A of the pyroelectric element 41 in the optical axis direction 102. In the first embodiment, the optical axis direction 102 is parallel to the thickness direction 101 of the pyroelectric element 41. In the first embodiment, the optical axis 6A of the lens 6 passes through position P (see Figure 3) where axis AX and a straight line LN intersect on one main surface 41A. In the first embodiment, one main surface 41A corresponds to the opposing surface. The lens 6 may also be positioned opposite the other main surface 41B of the pyroelectric element 41 in the optical axis direction 102. In this case, the other main surface 41B corresponds to the opposing surface.

[0042] Lens 6 forms an image of the infrared radiation 7A emitted from the object to be detected 7 onto one main surface 41A of the pyroelectric element 41. At this time, the image 8 (see Figure 3) formed by the infrared radiation passing through lens 6 onto one main surface 41A satisfies the following conditions. In other words, lens 6 is provided such that the image 8 satisfies the following conditions.

[0043] The first condition is that the image 8 is formed in the Y-axis direction 104, extending from one end to the other of the main surface 41A, as shown in Figure 3. The second condition is that the image 8 is formed in the X-axis direction 103, being shorter than the main surface 41A (in the first embodiment, the detection area 41Aa of the main surface 41A). In other words, the image 8 is formed in the region enclosed by the dashed line in Figure 3.

[0044] Note that the position 103 in the X-axis direction of image 8 (the area enclosed by the dashed line in Figure 3) is just one example. The position 103 in the X-axis direction of image 8 can be in various positions depending on the relative position of the lens 6 with respect to the object to be detected 7. The position 103 in the X-axis direction of image 8 can be moved to any position in the detection area 41Aa of one main surface 41A by moving the infrared sensor element 4 by the drive unit 5.

[0045] The arrangement positions of the lens 6 and pyroelectric element 41 shown in Figure 2 may be determined so that the image 8 satisfies the above conditions. Furthermore, lenses 6 with different focal lengths in the X-axis direction 103 and the Y-axis direction 104 may be used so that the image 8 satisfies the above conditions. Also, lenses 6 with changeable aspect ratios in the X-axis direction 103 and the Y-axis direction 104 may be used so that the image 8 satisfies the above conditions.

[0046] The pyroelectric element 41 undergoes a temperature change when infrared radiation 7A emitted from the object to be detected 7 is incident on it. As shown in Figure 2, the infrared radiation 7A emitted from the object to be detected 7 is imaged onto one main surface 41A of the pyroelectric element 41 by the lens 6. In the portion of the pyroelectric element 41 that overlaps with the image 8 formed when viewed from the thickness direction 101, the temperature of the pyroelectric element 41 rises. In response to this temperature change, surface charges are generated on the main surfaces of the pyroelectric element 41 (one main surface 41A and the other main surface 41B) due to the pyroelectric effect. For example, as shown in Figure 5, a positive charge PC is generated on one main surface 41A and a negative charge NC is generated on the other main surface 41B.

[0047] On one side, the surface charge generated on the main surface 41A (for example, the positive charge PC shown in Figure 5) is output as an electrical signal from the one-side electrode 42 to the outside of the infrared sensor element 4 (the control unit 3 shown in Figure 1 in the first embodiment) via the paste 931 and wiring 94 (see Figure 6). On the other side, the surface charge generated on the main surface 41B (for example, the negative charge NC shown in Figure 5) is output as an electrical signal from the other-side electrode 43 to the outside of the infrared sensor element 4 (the control unit 3 shown in Figure 1 in the first embodiment) via the paste 922 and wiring 95 (see Figure 6).

[0048] The control unit 3 shown in Figure 1 is electrically connected to one electrode 42 of the infrared sensor element 4 via the wiring 94 and paste 931 shown in Figure 6. The control unit 3 shown in Figure 1 is also electrically connected to the other electrode 43 of the infrared sensor element 4 via the wiring 95 and paste 922 shown in Figure 6. Furthermore, as shown in Figure 1, the control unit 3 is electrically connected to the drive unit 5 via wiring etc. (not shown).

[0049] As the control unit 3, known configurations may be used, such as a processor that works in cooperation with software to realize a predetermined function, and / or wired logic that cannot be rewritten. The processor is, for example, a CPU (Central Processing Unit) that reads a program stored in memory and executes various processes. The wired logic is, for example, an Application Specific Integrated Circuit (ASIC).

[0050] As will be described later, the control unit 3 performs drive control of the drive unit 5 and calculates the image center position k (see Figure 2).

[0051] Figure 7 is a flowchart illustrating the operation of the location detection system. The detection operation of location detection system 1 will be explained below with reference to Figures 2 and 7.

[0052] The position detection system 1 waits until an electrical signal is input to the control unit 3 (S10:NO). Here, an electrical signal input means, for example, that a voltage equal to or greater than a preset threshold is input to the control unit 3.

[0053] When there is an input voltage (S10:YES), the control unit 3 drives the drive unit 5 with a sinusoidal wave. This is described in detail below. When infrared rays 7A from the object to be detected 7 are incident on the pyroelectric element 41, the pyroelectric element 41 is heated. As a result, surface charges are generated on one main surface 41A and the other main surface 41B of the pyroelectric element 41. The generated surface charges are output as electrical signals to the control unit 3 from the one-side electrode 42 and the other-side electrode 43. When the control unit 3 receives the electrical signal output from the pyroelectric element 41, it applies a sinusoidal voltage of frequency f (Hz) to the coil of the drive unit 5. As a result, the drive unit 5 is driven with a sinusoidal wave at frequency f (Hz). When the drive unit 5 is driven with a sinusoidal wave, the infrared sensor element 4 and the support unit 91 move along the X-axis direction 103 while accelerating and decelerating according to the sinusoidal voltage.

[0054] At this time, the value of the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is determined so that the image 8 (see Figure 3) as viewed from the thickness direction 101 does not lie outside the detection area Aa of the one main surface 41A. In other words, the value of the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is determined so that the image 8 as viewed from the thickness direction 101 does not overlap with the non-detection areas 41Ab and 41Ac of the one main surface 41A. To put it another way, the value of the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is determined so that the relative displacement of the image 8 with respect to the one main surface 41A does not become too large.

[0055] Here, the amplitude of the movement of the infrared sensor element 4, which moves along the X-axis direction 103 in response to the sinusoidal voltage (α in equation (1) described later), should be as large as possible. In other words, the amount of movement of the infrared sensor element 4 along the X-axis direction 103 should be as large as possible. To achieve this, it is desirable that the length of the image 8 along the X-axis direction 103 (twice the w included in equation (1) described later, see Figure 3) be sufficiently shorter than the detection area 41Aa of one of the main surfaces 41A along the X-axis direction 103.

[0056] When the infrared sensor element 4 moves, the position of the image 8 formed on one main surface 41A of the pyroelectric element 41 of the infrared sensor element 4 changes. As a result, the overlapping area between the image 8 and one side electrode 42 changes when viewed from the thickness direction 101, and therefore the electrical signals output from one side electrode 42 and the other side electrode 43 to the control unit 3 change. Specifically, if the overlapping area increases, the value of the electrical signal output from one side electrode 42 and the other side electrode 43 to the control unit 3 increases. On the other hand, if the overlapping area decreases, the value of the electrical signal (e.g., RMS value) output from one side electrode 42 and the other side electrode 43 to the control unit 3 decreases. The control unit 3 calculates the image center position k (see Figure 2) based on this changing electrical signal (S30). The calculation of the image center position k will be explained in detail later.

[0057] In the first embodiment, the control unit 3 calculates the image center position k based on the electrical signals output from one electrode 42 and the other electrode 43. However, the image center position k may also be calculated based on the electrical signal output from one of the two electrodes 42 and the other electrode 43. For example, the control unit 3 may calculate the image center position k based on the electrical signal from the electrode whose overlapping area with respect to the image 8 changes when the infrared sensor element 4 moves (the one electrode 42 in the first embodiment). In a configuration where the other electrode 43 has a curved outer edge, the control unit 3 may calculate the image center position k based on the electrical signal from the other electrode 43.

[0058] After calculating the image center position k, the control unit 3 determines whether or not to stop the drive unit 5, as detailed below (S40-S90).

[0059] The control unit 3 repeatedly calculates the image center position k until there is no electrical signal input from the infrared sensor element 4 (S40:NO, S30). Here, "no electrical signal input" means, for example, that the voltage input to the control unit 3 is below a preset threshold.

[0060] When the control unit 3 stops receiving an electrical signal from the infrared sensor element 4 (S10: YES), it starts counting time (S50). The time count is performed, for example, by a counter built into the control unit 3.

[0061] When the counter count exceeds a preset time, that is, when the set time has elapsed since the input of an electrical signal from the infrared sensor element 4 to the control unit 3 ceases (S60: YES), the control unit 3 stops applying a sinusoidal voltage to the coil of the drive unit 5. As a result, the drive unit 5 stops (S70). After that, the control unit 3 resets the count (S80) and terminates the detection operation.

[0062] On the other hand, if the counter count is less than the set time (S60: NO), and there is an electrical signal input from the infrared sensor element 4 to the control unit 3 (S90: YES), the control unit 3 resets the counter (S100). After that, the control unit 3 resumes calculating the image center position k based on the input electrical signal (S30).

[0063] In the flowchart of Figure 7, the position detection system 1 starts its detection operation triggered by the input of an electrical signal to the control unit 3, and stops the detection operation if no electrical signal is input to the control unit 3 for a set time. However, the detection operation of the position detection system 1 is not limited to this. For example, the position detection system 1 may perform detection operations continuously. Alternatively, for example, the position detection system 1 may perform detection operations at predetermined intervals.

[0064] Figure 8 is a schematic plan view of an infrared sensor element used to explain the calculation of the image center position. The calculation of the image center position k performed by the control unit 3 will be explained below with reference to Figure 8. Note that the infrared sensor element 4A shown in Figure 8 has one parabolic curved outer edge portion 42A. In this respect, it differs from the infrared sensor element 4 (see Figure 3) which has two parabolic curved outer edges portion 42A.

[0065] The image center position k of the image 8 formed on one main surface 41A by infrared rays 7A emitted from the object to be detected through the lens 6 is the position of the center of the image 8 with respect to the axis AX of the parabola in the X-axis direction 103. In other words, the image center position k is the distance between the center position 8A of the image 8 and the axis AX of the curved outer edge 42A, which is a parabola, in the X-axis direction 103.

[0066] When viewed from the thickness direction 101, the overlapping portion between the one electrode 42 and the image 8 (shown as hatched in Figure 8) moves along the X-axis direction 103 as the pyroelectric element 41 moves. As a result, the area S(t) of that portion changes. The area S(t) is expressed by the following equation (1).

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[0067] In equation (1), the meaning of each symbol is as follows: t is time. α is the amplitude of the infrared sensor element 4 as it moves in response to the applied sinusoidal voltage. β is the parabolic function equation of the curved outer edge, y = βx 2 This is the coefficient of the parabola when +γ is used. In the parabola, x is a variable indicating the position 103 in the X-axis direction, y is a variable indicating the position 104 in the Y-axis direction, and γ is the intercept. w represents half the length of image 8 in the X-axis direction (103). k is the position of the image center. θ = 2πf. f is the frequency of the sinusoidal voltage.

[0068] It is difficult to know the exact value of w, which represents half the length of 103 in the X-axis direction of image 8, but this is not a problem because it cancels out in the numerator and denominator of equation (6).

[0069] The infrared sensor element 4A shown in Figure 8 has one parabolic curved outer edge 42A. On the other hand, the infrared sensor element 4 shown in Figure 3 has two parabolic curved outer edges 42A. Therefore, in the infrared sensor element 4, the area S(t) can be expressed as, for example, twice the value of equation (1).

[0070] The following are examples of specific values ​​for the infrared sensor element 4A shown in Figure 8. The length L of the long side of the pyroelectric element 41 shown in Figure 8. l The length is 5 mm, and the length of the shorter side is L S The diameter is 2 mm. The parabola function equation on one main surface 41A of the pyroelectric element 41 is y = βx 2 The coefficient β of +γ is 0.21 mm, and the intercept of the function equation is 0.1 mm. The amount of infrared light that reached the pyroelectric element 41 from the object being detected 7 is 0.4386 W / m 2 In this case, the length of the image 8 formed on one main surface 41A of the pyroelectric element 41 in the X-axis direction 103, i.e., 2w, is 0.5 mm. Also, the frequency of the sinusoidal voltage is 10 Hz, and the amplitude α of the infrared sensor element 4 that moves in accordance with the sinusoidal voltage is 0.2 mm.

[0071] Expanding equation (1) yields equation (2).

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[0072] The change in area S(t) with respect to time is expressed by equation (3) by differentiating equation (2).

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[0073] Focusing on the spectrum, the product of the change in area S(t) with respect to time and the thermal properties of the pyroelectric element 41 is proportional to the output voltage of the infrared sensor element 4. This relationship is expressed by the following equations (4) and (5).

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[0074] In equations (4) and (5), the meaning of each symbol is as follows: H(θ) represents the thermal characteristics of the pyroelectric element 41 at frequency f. H(2θ) represents the thermal characteristics of the pyroelectric element 41 at twice the frequency f. F V is the voltage component of the electrical signal output from the infrared sensor element 4 to the control unit 3 at frequency f. S This is the voltage component of the electrical signal output from the infrared sensor element 4 to the control unit 3 at a frequency twice the frequency f.

[0075] Dividing the left and right sides of equations (4) and (5) yields equation (6).

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[0076] From equation (6), the image center position k is expressed by the following equation (7).

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[0077] In equation (7), α is known, as previously mentioned, the amplitude of the infrared sensor element 4 when it moves in response to the applied sinusoidal voltage. The thermal characteristics H(θ) and H(2θ) are known values ​​because they depend on the material and shape of the pyroelectric element 41, which are determined by the design, and the drive frequency controlled by the control unit 3. The thermal characteristics H(θ) and H(2θ) do not depend on the width of the image 8 or the amount of infrared light, which are determined by the object to be detected 7. For example, if the pyroelectric element 41 is made of ceramics, then in equation (7), H(2θ) / H(θ) can be calculated as 1 / 2.

[0078] The control unit 3 calculates the image center position k from equation (7).

[0079] The control unit 3 identifies whether the image center position k is located on the right or left side of axis AX, for example, as follows:

[0080] For example, the infrared sensor element 4 may further include an optical sensor for detecting the position of the image 8. In this case, the control unit 3 may identify, based on the signal output from the sensor, whether the image center position k is located to the right or left of the axis AX of the parabola at the center of the image 8.

[0081] Furthermore, for example, a motor that rotates in a direction corresponding to the positive or negative voltage applied from the control unit 3 may be used as the drive unit 5.

[0082] For example, when the voltage applied from the control unit 3 is positive, the motor rotates clockwise, and when the voltage applied from the control unit 3 is negative, the motor rotates counterclockwise. When such a motor is used, the control unit 3 can identify the direction of movement of the infrared sensor element 4 according to the positive or negative voltage value of the sinusoidal voltage applied to the coil of the drive unit 5. For example, the control unit 3 determines that the infrared sensor element 4 is moving to the left when the applied voltage value is positive, and determines that the infrared sensor element 4 is moving to the right when the applied voltage value is negative. In other words, the control unit 3 determines that the image 8 is moving to the right relative to the pyroelectric element 41 when the applied voltage value is positive, and determines that the image 8 is moving to the left relative to the pyroelectric element 41 when the applied voltage value is negative.

[0083] As mentioned above, when the overlapping area between the image 8 viewed from the thickness direction 101 and the one-sided electrode 42 increases, the value of the electrical signal output from the infrared sensor element 4 to the control unit 3 increases, and when the overlapping area decreases, the value of the electrical signal decreases.

[0084] Based on the above, the control unit 3 can determine whether the image center position k is located to the right or left of the axis AX of the parabola at the center of the image 8, in the following manner.

[0085] When the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is positive, and the value of the electrical signal from the infrared sensor element 4 to the control unit 3 is increasing, the control unit 3 determines that the image 8 is to the right of axis AX, that is, that the object to be detected 7 is to the left of axis AX.

[0086] Furthermore, when the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is positive, if the value of the electrical signal from the infrared sensor element 4 to the control unit 3 decreases, the control unit 3 determines that the image 8 is to the left of axis AX, that is, that the object to be detected 7 is to the right of axis AX.

[0087] Furthermore, when the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is negative, and the value of the electrical signal from the infrared sensor element 4 to the control unit 3 is increasing, the control unit 3 determines that the image 8 is to the left of axis AX, that is, that the object to be detected 7 is to the right of axis AX.

[0088] Furthermore, when the sinusoidal voltage applied from the control unit 3 to the coil of the drive unit 5 is negative, and the value of the electrical signal from the infrared sensor element 4 to the control unit 3 decreases, the control unit 3 determines that the image 8 is to the right of axis AX, that is, that the object to be detected 7 is to the left of axis AX.

[0089] In the first embodiment, when infrared rays 7A are irradiated from the object to be detected 7 toward the pyroelectric element 41, the irradiated portion of the pyroelectric element 41 is heated. The irradiated portion of the pyroelectric element 41 is the portion of the pyroelectric element 41 that extends in the direction of light irradiation from the region where the image 8 is formed on one main surface 41A. At this time, an electric charge is generated on the surface of the overlapping portion of the irradiated portion of the pyroelectric element 41 that overlaps with the one-sided electrode 42 and the other-sided electrode 43 when viewed from the thickness direction 101. When one of the pyroelectric element 41 and the object to be detected 7 moves relative to the other, the position of the overlapping portion of the pyroelectric element 41 changes. According to the first embodiment, the one-sided electrode 42 has a parabolic curved outer edge portion 42A. Therefore, when the position of the overlapping portion changes due to the relative movement, the rate of change of the area of ​​the overlapping portion as viewed from the thickness direction 101 corresponds to the parabolic shape. This characteristic of the rate of change of area can be used to calculate the direction in which the object to be detected 7 is located relative to the infrared sensor element 4.

[0090] Thus, in the first embodiment, the direction in which the object to be detected 7 is located relative to the infrared sensor element 4 can be calculated by a single infrared sensor element 4. Therefore, the infrared sensor element 4 can be miniaturized.

[0091] According to the first embodiment, an electrical signal based on a charge generated on one main surface 41A is extracted from one electrode 42 provided in a non-detection region 41Ab included in the one main surface 41A. An electrical signal based on a charge generated on the other main surface 41B is extracted from the other electrode 43 provided in a non-detection region 41Bc included in the other main surface 41B. In other words, the two electrical signals are extracted from different surfaces. Therefore, compared to a configuration in which the two electrical signals are extracted from the same surface, the possibility of short circuits between the two electrodes (one electrode 42 and the other electrode 43) corresponding to each of the two electrical signals can be reduced.

[0092] According to the first embodiment, when viewed from the thickness direction 101, the non-detection region 41Ab of the one main surface 41A where the one-side electrode 42 is provided is in a different position from the non-detection region 41Bc of the other main surface 41B where the other-side electrode 43 is provided. In other words, the two electrical signals are taken from different positions when viewed from the thickness direction 101. Therefore, compared to a configuration in which the two electrical signals are taken from the same position when viewed from the thickness direction 101, the possibility of short circuits between the two electrodes (one-side electrode 42 and the other-side electrode 43) corresponding to each of the two electrical signals can be reduced.

[0093] According to the first embodiment, the lens 6 is provided such that the image 8 formed on one main surface 41A is formed across the entire length of the main surface 41A in the Y-axis direction 104. Therefore, the curved outer edge 42A can be contained within the range of the image 8 in the Y-axis direction 104.

[0094] According to the first embodiment, the lens 6 is provided such that the image 8 formed on one main surface 41A is shorter than the one main surface 41A (more specifically, the detection area 41Aa of the one main surface 41A) in the X-axis direction 103. Therefore, the image 8 can be formed within the one main surface 41A in the X-axis direction 103. Furthermore, by limiting the movement distance of the pyroelectric element 41 to within the difference between the length of the one main surface 41A in the X-axis direction 103 and the length of the image 8 formed on the one main surface 41A in the X-axis direction 103, it is possible to prevent the image 8 moving along the X-axis direction 103 from being located outside the one main surface 41A.

[0095] According to the first embodiment, the pyroelectric element 41 is moved by the drive unit 5. This allows the position of the image 8 formed on one main surface 41A of the pyroelectric element 41 to be changed. Based on the change in the position of the image 8, the object to be detected 7 can be detected.

[0096] According to the first embodiment, the pyroelectric element 41 moves along the X-axis direction 103. That is, the pyroelectric element 41 moves so as to intersect with a parabola that forms the curved outer edge 42A and has an axis AX parallel to the Y-axis direction 104. Therefore, when one of the pyroelectric element 41 and the object to be detected 7 moves relative to the other, the rate of change of the area of ​​the charge-generating region as seen from the thickness direction 101 can be made to correspond to the parabolic shape.

[0097] According to the first embodiment, the curved outer edge portion 42A has a parabolic shape with an axis AX parallel to the Y-axis direction 104, and the pyroelectric element 41 moves along the X-axis direction 103 based on sinusoidal drive. As a result, multiple voltage output components can be obtained for the frequency of the sinusoidal drive-based movement of the pyroelectric element 41 from the change in area of ​​the overlapping portion of the irradiated portion of the pyroelectric element 41 that overlaps with one electrode 42 and the other electrode 43 when viewed from the thickness direction 101. The image center position k can be calculated from these multiple voltage output components.

[0098] <Variation> In the first embodiment, an example was described in which one main surface 41A of the pyroelectric element 41 has a detection region 41Aa and two non-detection regions 41Ab and 41Ac, and the other main surface 41B of the pyroelectric element 41 has a detection region 41Ba and two non-detection regions 41Bb and 41Bc. However, the number of non-detection regions on each of the one main surface 41A and the other main surface 41B is not limited to two. Furthermore, each of the one main surface 41A and the other main surface 41B does not have to have any non-detection regions. In other words, each of the one main surface 41A and the other main surface 41B may have only a detection region.

[0099] In the first embodiment, a configuration was described in which the control unit 3 is electrically connected to one electrode 42 via wiring 94 and paste 931, and to the other electrode 43 via wiring 95 and paste 922. However, the control unit 3 and the one electrode 42 and the other electrode 43 may be electrically connected by other configurations.

[0100] For example, the control unit 3 may be electrically connected to one electrode 42 and the other electrode 43 by wire bonding. Figure 9 is a schematic cross-sectional view corresponding to the BB cross-section of Figure 3, and is a schematic cross-sectional view showing a modified example of the infrared sensor element and the support part. In the following description of the configuration shown in Figure 9, common parts with the configuration shown in Figure 6 are denoted by the same reference numerals, and their explanations are generally omitted. In Figure 9, the one electrode 42 of the infrared sensor element 4 is electrically connected to the wiring 94 via a wire 96 instead of paste 931. As a result, the one electrode 42 is electrically connected to the control unit 3 via the wire 96 and the wiring 94.

[0101] In the first embodiment, an example was described in which the infrared sensor 2 is equipped with a drive unit 5, and the position of the object to be detected 7 is detected by changing the position of the image 8 due to the movement of the infrared sensor element 4 by the drive unit 5. However, when the object to be detected 7 is moving, even if the infrared sensor element 4 is stationary, the image 8 moves relative to the infrared sensor element 4, so the object to be detected 7 can be detected. In other words, when the object to be detected 7 is moving, the object to be detected 7 can be detected even if the infrared sensor 2 is not equipped with a drive unit 5.

[0102] The shapes of the one-sided electrode 42 and the other-sided electrode 43 are not limited to those shown in Figure 3. For example, the one-sided electrode 42 and the other-sided electrode 43 may have the shapes shown in Figure 10. Figure 10 is a schematic plan view of a modified example of the infrared sensor element. In the description of the infrared sensor element 4B shown in Figure 10, commonalities with the infrared sensor element 4 shown in Figure 3 are given the same reference numerals, and their explanations are generally omitted, with explanations provided as needed.

[0103] In the one-sided electrode 42 of the infrared sensor element 4B shown in Figure 10, the two curved outer edges 42A are symmetrical with respect to the line LN such that their respective vertices are furthest apart. This is a difference from the one-sided electrode 42 shown in Figure 3.

[0104] In the first embodiment, an example was described in which one side electrode 42 has two curved outer edges 42A, but the curved outer edges 42A of one side electrode 42 are not limited to two.

[0105] In the first embodiment, an example was described in which one electrode 42 has a curved outer edge portion 42A, but the other electrode 43 may also have a curved outer edge portion. Both the one electrode 42 and the other electrode 43 may have curved outer edges portions. In this case, it is desirable that the curved outer edge portion of the one electrode 42 and the curved outer edge portion of the other electrode 43 overlap each other when viewed from the thickness direction 101.

[0106] In the first embodiment, one electrode 42 is provided in the non-detection region 41Ab of one main surface 41A, and the other electrode 43 is provided in the non-detection region 41Bc of the other main surface 41B. In this case, electrical signals are output to the outside from both the one main surface 41A and the other main surface 41B. Therefore, as shown in Figure 6, the pyroelectric element 41 is supported by the support portion 91 so as to be sandwiched from both sides in the thickness direction 101.

[0107] However, the electrical signal may be output to the outside from only one of the main surfaces 41A and 41B. In this case, the pyroelectric element 41 can be supported by the support portion 91 from only one side in the thickness direction 101. Such a configuration will be explained below with reference to Figures 11 to 15. In the explanation of the infrared sensor element 4C shown in Figures 11 to 15, commonalities with the infrared sensor element 4 shown in Figures 3 to 6 are given the same reference numerals, and their explanations are generally omitted, and will be explained as necessary.

[0108] Figure 11 is a schematic plan view of a modified infrared sensor element. Figure 12 is a schematic bottom view of a modified infrared sensor element.

[0109] As shown in Figure 11, one electrode 42 is provided in the detection region 41Aa of the one main surface 41A, while it is not provided in the non-detection regions 41Ab and 41Ac.

[0110] One electrode 42 has two parabolic curved outer edges 42Aa and 42Ab. Viewed from the thickness direction 101, the two curved outer edges 42Aa and 42Ab overlap with the detection region 41Ba of the other main surface 41B, but do not overlap with the non-detection regions 41Bb and 41Bc of the other main surface 41B. The parabolas of the two curved outer edges 42Aa and 42Ab share a common axis AX. The two curved outer edges 42Aa and 42Ab are parallel to each other. Curved outer edge 42Aa is an example of a first curved outer edge. Curved outer edge 42Ab is an example of a second curved outer edge.

[0111] As shown in Figure 12, the other electrode 43 has a first electrode 431 and a second electrode 432. The first electrode 431 and the second electrode 432 are separated from each other. In other words, the first electrode 431 and the second electrode 432 are electrically insulated from each other.

[0112] The first electrode 431 is provided across a portion of the detection area 41Ba and the non-detection area 41Bb of the other main surface 41B. In the infrared sensor element 4C, the non-detection area 41Bb of the other main surface 41B is an example of a first non-detection area. Viewed from the thickness direction 101, the first electrode 431 overlaps with the portion of the one-side electrode 42 that has a curved outer edge 42Aa.

[0113] The second electrode 432 is provided across a portion of the detection area 41Ba of the other main surface 41B (the portion where the first electrode 431 is not provided) and the non-detection area 41Bc of the other main surface 41B. In the infrared sensor element 4C, the non-detection area 41Bc of the other main surface 41B is an example of a second non-detection area. Viewed from the thickness direction 101, the second electrode 432 overlaps with the portion of the one-side electrode 42 that has a curved outer edge portion 42Ab.

[0114] Figure 13 is a schematic cross-sectional view corresponding to the CC cross-section of Figure 11, and is a schematic cross-sectional view showing a modified example of the infrared sensor element and support part. In the following description of the configuration shown in Figure 13, commonalities with the configuration shown in Figure 6 are denoted by the same reference numerals, and their explanations are generally omitted.

[0115] As shown in Figure 13, the first electrode 431 of the infrared sensor element 4C is in contact with the paste 921, and the second electrode 432 of the infrared sensor element 4C is in contact with the paste 922. In the configuration shown in Figure 13, pastes 931 and 932 are not provided. Wiring 94 is in contact with paste 921. Wiring 95 is in contact with paste 922. As a result, the first electrode 431 is electrically connected to the control unit 3 via paste 921 and wiring 94, and the second electrode 432 is electrically connected to the control unit 3 via paste 922 and wiring 95.

[0116] The generation of surface charge in the infrared sensor element 4C will be explained below with reference to Figures 14 and 15. Figures 14 and 15 are schematic cross-sectional views showing the DD cross-section of Figure 11.

[0117] When an image 8 is formed in the region including the DD cross-section in Figure 11 by infrared radiation emitted from the object to be detected 7 (see Figure 2), surface charges are generated on the main surfaces of the pyroelectric element 41 (one main surface 41A and the other main surface 41B) due to the pyroelectric effect, as shown in Figure 14. For example, a positive charge PC is generated on the one main surface 41A and a negative charge NC is generated on the other main surface 41B.

[0118] On the one hand, surface charge generated on the main surface 41A (for example, the positive charge PC shown in Figure 14) is not output to the outside of the infrared sensor element 4C. On the other hand, surface charge generated on the main surface 41B can be output to the outside of the infrared sensor element 4C. However, in the state shown in Figure 14, where a positive charge PC is generated on one main surface 41A and a negative charge NC is generated on the other main surface 41B, no potential difference is generated between the two main surfaces 41A and 41B. Therefore, surface charge generated on the other main surface 41B is not output to the outside of the infrared sensor element 4C.

[0119] However, as the image 8 formed on the detection region 41Aa of one main surface 41A moves, the surface charge generated on the other main surface 41B is output to the outside of the infrared sensor element 4C. This will be described in detail below. For example, as shown in Figure 11, when the image 8 formed on the detection region 41Aa moves from the position indicated by reference numeral 8B to the position indicated by reference numeral 8C, the area of ​​the overlapping portion between the image 8 and the one-side electrode 42, viewed from the thickness direction 101, decreases in the upper part of the paper in Figure 11. On the other hand, when the image 8 formed on the detection region 41Aa moves from the position indicated by reference numeral 8B to the position indicated by reference numeral 8C, the area of ​​the overlapping portion between the image 8 and the one-side electrode 42, viewed from the thickness direction 101, increases in the lower part of the paper in Figure 11. In the upper part of the paper in Figure 11, the second electrode 432 (see Figure 12) overlaps with the one-side electrode 42, viewed from the thickness direction 101. In the lower part of Figure 11, the first electrode 431 (see Figure 12) overlaps with the one-sided electrode 42 when viewed from the thickness direction 101.

[0120] Due to the aforementioned increase or decrease in area caused by the movement of image 8, different charges are generated in the areas where the area has increased and the areas where the area has decreased. For example, as shown in Figure 15, in the area where the area has decreased, a negative charge NC is generated on one main surface 41A and a positive charge PC is generated on the other main surface 41B. On the other hand, in the area where the area has increased, a positive charge PC is generated on one main surface 41A and a negative charge NC is generated on the other main surface 41B. As a result, a potential difference of opposite polarity is generated in the areas where the area has increased and the areas where the area has decreased. Therefore, the negative charge NC generated in the area where the area has increased is output as an electrical signal from the first electrode 431 to the outside of the infrared sensor element 4C (control unit 3) via the paste 921. On the other hand, the positive charge PC generated in the area where the area has decreased is output as an electrical signal from the second electrode 432 to the outside of the infrared sensor element 4C (control unit 3) via the paste 922.

[0121] Based on the above, in the infrared sensor element 4C, the surface charge generated on the other main surface 41B is output to the outside, while the surface charge generated on the one main surface 41A is not output to the outside. In this respect, it differs from the infrared sensor element 4, in which the surface charge generated on both the one main surface 41A and the one main surface 41B is output to the outside.

[0122] According to the configuration shown in Figures 11 to 15, the electrical signal based on the charge generated on one main surface 41A and the electrical signal based on the charge generated on the other main surface 41B are both extracted from the non-detection regions 41Bb and 41Bc of the other main surface 41B. When a support portion 91 is provided to support the infrared sensor element 4C and extract the aforementioned electrical signals, the support portion 91 only needs to support the infrared sensor element 4C from the other main surface 41B side, and it is not necessary to support the infrared sensor element 4C from the one main surface 41A side.

[0123] As shown in Figure 6, in a configuration where electrical signals are extracted from both the one main surface 41A and the other main surface 41B, the extraction of electrical signals can be facilitated by providing a step in the support portion 91. On the other hand, as shown in Figure 13, in a configuration where electrical signals are extracted from only one of the two main surfaces 41A and the other main surface 41B (only the other main surface 41B in the configuration shown in Figure 13), the extraction of electrical signals can be facilitated even without a step in the support portion 91.

[0124] Such an example is shown in Figure 16. Figure 16 is a schematic cross-sectional view corresponding to the CC cross-section of Figure 11, and is a schematic cross-sectional view showing a modified example of the infrared sensor element and the support part. In the configuration shown in Figure 16, a space equal to the thickness of the pastes 921 and 922 can be formed between the support part 91 and the pyroelectric element 41. In the configuration shown in Figure 16, since the support part 91 does not have a step, it is easy to use a substrate made of glass epoxy or the like as the support part 91. In the configuration shown in Figure 16, the length (in other words, height) in the thickness direction 101 can be reduced compared to the configuration shown in Figure 6. Also, in the configuration shown in Figure 6, an inexpensive support part 91 without a step can be used.

[0125] <Second Embodiment> Figure 17 is a schematic diagram showing the irradiation of infrared rays from the object to be detected to the two infrared sensors. The difference between the position detection system according to the second embodiment and the position detection system 1 according to the first embodiment is that it is equipped with two infrared sensors 21 and 22. The differences from the first embodiment will be explained below. Similarities with the position detection system 1 according to the first embodiment are given the same reference numerals, and their explanations will be omitted in principle, and will be explained as necessary.

[0126] As shown in Figure 17, the infrared sensor 2 of the position detection system according to the second embodiment comprises two infrared sensors 21 and 22. The position detection system also comprises lenses 61 and 62 corresponding to each of the infrared sensors 21 and 22.

[0127] Each of the two infrared sensors 21 and 22 has the same configuration as the infrared sensor 2 of the position detection system 1 according to the first embodiment.

[0128] The infrared sensor element 4 of the infrared sensor 21 and the infrared sensor element 4 of the infrared sensor 22 are arranged side by side in the X-axis direction 103. The lens 61 is arranged to face the infrared sensor element 4 of the infrared sensor 21 in the optical axis direction 102. The lens 62 is arranged to face the infrared sensor element 4 of the infrared sensor 22 in the optical axis direction 102. The lens 61 and the lens 62 are arranged side by side in the X-axis direction 103. One main surface 41A of the pyroelectric element 41 of the infrared sensor 21 and one main surface 41A of the pyroelectric element 41 of the infrared sensor 22 are located on the same virtual plane. The one main surface 41A of the pyroelectric element 41 of the infrared sensor 21 and the one main surface 41A of the pyroelectric element 41 of the infrared sensor 22 are an example of facing surfaces.

[0129] The control unit 3 (see FIG. 1) is electrically connected to each of the two infrared sensors 21 and 22.

[0130] The control unit 3 calculates the image center position k1 in the infrared sensor 21 based on the electric signal output from the infrared sensor 21 to the control unit 3. The control unit 3 calculates the image center position k2 in the infrared sensor 22 based on the electric signal output from the infrared sensor 22 to the control unit 3.

[0131] The control unit 3 calculates the difference between the two calculated image center positions k1 and k2. In FIG. 17, since the image center positions k1 and k2 are located on opposite sides of the optical axis 6A, the difference k between the image center positions k1 and k2 d is k d =k1-(-k2)=k1+k2.

[0132] The control unit 3 calculates the distance L along the optical axis direction 102 between the centers C1, C2 of the lenses 61, 62 and the detection target object 7 by the following equation (8). [Equation]

[0133] In equation (8), k d D1 is the difference between the image center positions k1 and k2. D1 is the distance along the optical axis direction 102 between the centers C1 and C2 of lenses 61 and 62 and the pyroelectric element 41. D2 is the distance along the X axis direction 103 between the optical axis 61A of lens 61 and the optical axis 62A of lens 62. In other words, D2 is the distance along the X axis direction 103 between the axis AX of the parabola constituting the curved outer edge of the infrared sensor 21 and the axis AX of the parabola constituting the curved outer edge of the infrared sensor 22. The control unit 3 controls k d Based on D1 and D2, the distance L is calculated.

[0134] According to the second embodiment, the distance between the infrared sensor 2 and the object to be detected 7 can be calculated.

[0135] The infrared sensor element, infrared sensor, and position detection system described above can also be expressed as follows.

[0136] (1) An infrared sensor element according to one aspect of the present disclosure is A pyroelectric element having one main surface facing one direction in the thickness direction and another main surface that overlaps with the first main surface when viewed from the thickness direction and faces the other direction in the thickness direction, One side electrode provided on the one main surface, The other main surface is provided with a second electrode which overlaps with the first electrode when viewed from the thickness direction, Viewed from the thickness direction, one electrode or the other electrode has a curved outer edge that is parabolic in shape.

[0137] (2) In the infrared sensor element of (1), Each of the aforementioned main surfaces may have a detection area and a non-detection area. When viewed from the thickness direction, the detection area of ​​one main surface and the detection area of ​​the other main surface may overlap. The one-sided electrode is provided across the detection region and the non-detection region of the one main surface, and may have the curved outer edge portion provided in the detection region of the one main surface. The other electrode may be provided across the detection area and the non-detection area of ​​the other main surface. Viewed from the thickness direction, the portion of the one electrode provided in the detection region of the one main surface may overlap with the portion of the other electrode provided in the detection region of the other main surface.

[0138] (3) In the infrared sensor element of (2), Viewed from the thickness direction, the non-detection region of the one main surface on which the one electrode is provided may be located outside the non-detection region of the other main surface on which the other electrode is provided.

[0139] (4) In the infrared sensor element of (1), The other main surface may have a detection area, a first non-detection area, and a second non-detection area. The aforementioned one-sided electrode may have the curved outer edge portion. The curved outer edge portion of the one-side electrode is The first curved outer edge portion, which overlaps with the detection area of ​​the other main surface when viewed from the thickness direction, It may also have a second curved outer edge portion that overlaps with the detection area of ​​the other main surface when viewed from the thickness direction and is parallel to the first curved outer edge portion. The other electrode is, A first electrode is provided extending from a part of the detection area of ​​the other main surface to the first non-detection area of ​​the other main surface, and overlaps with the portion of the one-side electrode having the first curved outer edge when viewed from the thickness direction, The device may also include a second electrode that is electrically insulated from the first electrode, extends across a portion of the detection area of ​​the other main surface and a second non-detection area of ​​the other main surface, and overlaps with the portion of the one-side electrode having the second curved outer edge when viewed from the thickness direction.

[0140] (5) An infrared sensor in one aspect of the present disclosure is (1) to (4) one infrared sensor element, A drive unit for moving the pyroelectric element, The system includes a control unit that controls the aforementioned drive unit.

[0141] (6) In the infrared sensor in (5), The control unit may drive the drive unit with a sinusoidal wave.

[0142] (7) The position detection system of the positional configuration of the present disclosure is (6) The infrared sensor, The system comprises a lens provided facing either the one principal surface or the other principal surface in the optical axis direction parallel to the thickness direction, The lens is provided such that the image formed by infrared radiation emitted from the object to be detected on the opposing surface of the one main surface and the other main surface facing the lens is formed from one end of the opposing surface to the other in the Y-axis direction, which is parallel to the opposing surface and parallel to the axis of the parabola constituting the curved outer edge, and is formed to be shorter than the opposing surface in the X-axis direction, which is parallel to the opposing surface and perpendicular to the Y-axis direction. The control unit, The drive unit is driven sinusoidally to move the pyroelectric element along the X-axis direction. Based on the electrical signals output from at least one of the one electrode and the other electrode due to the movement of the pyroelectric element, the image center position is calculated, which is the position in the X-axis direction relative to the axis of the parabola of the center of the image formed on the opposing surface by infrared radiation emitted from the object to be detected through the lens.

[0143] (8) In the position detection system of (7), It may also be equipped with two of the aforementioned infrared sensors. The opposing surfaces of the two infrared sensors may be located on the same plane. The control unit, The image center position may be calculated for each of the two infrared sensors. The distance between the center of the lens and the object to be detected, along the optical axis, may be calculated based on the difference between the two calculated image center positions, the distance along the optical axis between the center of the lens and the pyroelectric element, and the distance along the X axis between the axis of the parabola constituting the curved outer edge of one of the two infrared sensors and the axis of the parabola constituting the curved outer edge of the other of the two infrared sensors.

[0144] Furthermore, by appropriately combining any of the various embodiments described above, the effects of each embodiment can be achieved.

[0145] Although the present invention has been fully described in relation to preferred embodiments with reference to the drawings as appropriate, various modifications and alterations will be obvious to those skilled in the art. Such modifications and alterations should be understood to be included within the scope of the invention as defined in the appended claims, as long as they do not fall outside that scope. [Explanation of symbols]

[0146] 1. Location detection system 2. Infrared sensor 3. Control Unit 4. Infrared sensor element 41 Pyroelectric element 41A One main surface (opposing surface) 41Aa Detection area 41Ab Non-detection area 41Ac Non-detection area 41B Other main surface 41Ba detection area 41Bb Non-detection area (1st non-detection area) 41Bc Non-detection area (2nd non-detection area) 42 One-sided electrode 42A Curved outer edge 42Aa Curved outer edge (first curved outer edge) 42Ab Curved outer edge (second curved outer edge) 43 Other side electrode 431 1st electrode 432 2nd electrode 5 Drive Unit 6 lenses 7. Detectable objects 8 statue 101 Thickness direction 102 Optical axis direction 103 X-axis direction 104 Y-axis

Claims

1. A pyroelectric element having one main surface facing one direction in the thickness direction and another main surface that overlaps with the first main surface when viewed from the thickness direction and faces the other direction in the thickness direction, One side electrode provided on the one main surface, The other main surface is provided with a second electrode which overlaps with the first electrode when viewed from the thickness direction, An infrared sensor element having a curved outer edge that is parabolic in shape, as viewed from the thickness direction.

2. Each of the aforementioned main surfaces has a detection area and a non-detection area. Viewed from the thickness direction, the detection area of ​​one main surface and the detection area of ​​the other main surface overlap. The one-sided electrode is provided across the detection region and the non-detection region of the one main surface, and has the curved outer edge portion provided in the detection region of the one main surface. The other electrode is provided across the detection area and the non-detection area of ​​the other main surface. The infrared sensor element according to claim 1, wherein, when viewed from the thickness direction, the portion of the one electrode provided in the detection region of the one main surface overlaps with the portion of the other electrode provided in the detection region of the other main surface.

3. The infrared sensor element according to claim 2, wherein, when viewed from the thickness direction, the non-detection region of the one main surface on which the one electrode is provided is located outside the non-detection region of the other main surface on which the other electrode is provided.

4. The other main surface has a detection area, a first non-detection area, and a second non-detection area. The aforementioned one-sided electrode has the curved outer edge portion, The curved outer edge portion of the one-side electrode is The first curved outer edge portion, which overlaps with the detection area of ​​the other main surface when viewed from the thickness direction, It has a second curved outer edge portion that overlaps with the detection area of ​​the other main surface when viewed from the thickness direction and is parallel to the first curved outer edge portion, The other electrode is, A first electrode is provided extending from a part of the detection area of ​​the other main surface to the first non-detection area of ​​the other main surface, and overlaps with the portion of the one-side electrode having the first curved outer edge when viewed from the thickness direction, The infrared sensor element according to claim 1, comprising: a second electrode that is electrically insulated from the first electrode, extends over a part of the detection area of ​​the other main surface and a second non-detection area of ​​the other main surface, and overlaps with the portion of the one-side electrode having the second curved outer edge when viewed from the thickness direction.

5. An infrared sensor element according to any one of claims 1 to 4, A drive unit for moving the pyroelectric element, An infrared sensor comprising a control unit for controlling the aforementioned drive unit.

6. The infrared sensor according to claim 5, wherein the control unit drives the drive unit with a sinusoidal wave.

7. The infrared sensor according to claim 6, The system comprises a lens provided facing either the one principal surface or the other principal surface in the optical axis direction parallel to the thickness direction, The lens is provided such that the image formed by infrared radiation emitted from the object to be detected on the opposing surface of the one main surface and the other main surface facing the lens is formed from one end of the opposing surface to the other in the Y-axis direction, which is parallel to the opposing surface and parallel to the axis of the parabola constituting the curved outer edge, and is formed to be shorter than the opposing surface in the X-axis direction, which is parallel to the opposing surface and perpendicular to the Y-axis direction. The control unit, The drive unit is driven sinusoidally to move the pyroelectric element along the X-axis direction. A position detection system that calculates the image center position, which is the position in the X-axis direction relative to the axis of the parabola of the center of an image formed on the opposing surface through the lens by infrared radiation emitted from an object to be detected, based on an electrical signal output from at least one of the one electrode and the other electrode due to the movement of the pyroelectric element.

8. Equipped with two of the aforementioned infrared sensors, The opposing surfaces of the two infrared sensors are located on the same plane. The control unit, The image center position is calculated for each of the two infrared sensors. The position detection system according to claim 7, which calculates the distance between the center of the lens and the object to be detected along the optical axis direction based on the difference between the two calculated image center positions, the distance along the optical axis direction between the center of the lens and the pyroelectric element, and the distance along the X axis direction between the axis of the parabola constituting the curved outer edge of one of the two infrared sensors and the axis of the parabola constituting the curved outer edge of the other of the two infrared sensors.

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