Pyroelectric sensor array and pyroelectric infrared detection device

1. A pyroelectric sensor array attachable on a circuit board, the pyroelectric sensor array comprising:

a pyroelectric board having a connection surface configured to be placed on the circuit board; and

a plurality of pyroelectric elements formed on the pyroelectric board, the pyroelectric elements containing a peripheral pyroelectric element arranged at a peripheral portion of the pyroelectric board in a predetermined arranging direction and a central pyroelectric element arranged at a central portion of the pyroelectric board, each of the pyroelectric elements having two adjacent connection electrodes formed on the connection surface, an electrostatic capacity between the two connection electrodes of the peripheral pyroelectric element being larger than an electrostatic capacity between the two connection electrodes of the central pyroelectric element.

2. The pyroelectric sensor array according to claim 1 , wherein a length of a part which generates the electrostatic capacity between the two connection electrodes of the peripheral pyroelectric element is longer than a length of a part which generates the electrostatic capacity between the two connection electrodes of the central pyroelectric element.

3. The pyroelectric sensor array according to claim 1 , wherein a distance between parts which generate the electrostatic capacity between the two connection electrodes of the peripheral pyroelectric element is shorter than a distance between parts which generate the electrostatic capacity between the two connection electrodes of the central pyroelectric element.

4. The pyroelectric sensor array according to claim 1 , wherein:

the two connection electrodes face each other in a first direction in parallel to the connection surface; and

in a second direction which is perpendicular to the first direction and in parallel to the connection surface, a length of each of the two connection electrodes of the peripheral pyroelectric element is longer than a length of each of the two connection electrodes of the central pyroelectric element.

5. The pyroelectric sensor array according to claim 4 , wherein, a distance in the first direction between the two connection electrodes of the peripheral pyroelectric element is shorter than a distance in the first direction between the two connection electrodes of the central pyroelectric element.

6. The pyroelectric sensor array according to claim 1 , wherein:

the two connection electrodes face each other in a second direction in parallel to the connection surface; and

each of the two connection. electrodes of the peripheral pyroelectric element includes a comb-like pattern extending toward the opposite connection electrode along the second direction, the comb-like pattern of one of the two connection electrodes and the comb-like pattern of a remaining one of the two connection electrodes face each other in a first direction which is perpendicular to the second direction and in parallel to the connection surface.

7. The pyroelectric sensor array according to claim 1 , wherein;

the two connection electrodes face each other in a first direction in parallel to the connection surface;

each of the two connection electrodes includes an extension pattern which extends from the connection electrode so as to encircle the connection electrode, the extension patterns partially facing each other in the first direction; and

a length of a facing part of the extension pattern of the peripheral pyroelectric element is longer than a length of a facing part of the extension pattern of the central pyroelectric element.

8. The pyroelectric sensor array according to claim 7 , wherein, a distance in the first direction between the facing parts of the extension patterns of the peripheral pyroelectric element is shorter than a distance in the first direction between the facing parts of the extension patterns of the central pyroelectric element.

9. The pyroelectric sensor array according to claim 1 , wherein an electric shielding is provided between the two connection electrodes.

10. The pyroelectric sensor array according to claim 9 , wherein the electric shielding is formed so as to encircle each of the connection electrodes.

11. The pyroelectric sensor array according to one of c claim 1 , wherein:

the pyroelectric board is shaped in a plate-like shape which extends in two directions perpendicular to each other;

the arranging direction is one of the two directions; and

the peripheral pyroelectric element is arranged in the vicinity of an end portion in the arranging direction while the central pyroelectric element is arranged in the vicinity of a middle portion in the arranging direction.

12. The pyroelectric sensor array according to claim 1 , wherein:

the pyroelectric board is shaped in a dome-like shape;

the arranging direction is a radius direction of the pyroelectric board; and

the peripheral pyroelectric element is arranged in the vicinity of a rim portion in the arranging direction while the central pyroelectric element is arranged in the vicinity of a central portion in the arranging direction.

13. A pyroelectric infrared detection device comprising the pyroelectric sensor array according to claim 1 and a circuit board attached with the pyroelectric sensor array, wherein:

the circuit board includes a mount portion on which the connection surface of the pyroelectric sensor array is placed, a plurality of potential detection circuits provided on outside of the mount portion, a ground portion, a plurality of conductive patterns and a plurality of ground conductive patterns; and

the conductive pattern electrically connects one of the two connection. electrodes and the potential detection circuit with each other while the ground conductive pattern electrically connects a remaining one of the two connection electrodes and the ground portion with each other.

14. The pyroelectric infrared detection device according to claim 13 , wherein a length of a conductive pattern which electrically connects the connection electrode of the peripheral pyroelectric element and the potential detection circuit with each other is shorter than a length of a conductive pattern which electrically connects the connection electrode of the central pyroelectric element and the potential detection circuit with each other.

15. The pyroelectric infrared detection device according to claim 13 , wherein a distance between a conductive pattern, which electrically connects the connection electrode of the central pyroelectric element and the potential detection circuit with each other, and each of the other conductive pattern and the ground conductive pattern is longer than a distance between a conductive pattern, which electrically connects the connection electrode of the peripheral pyroelectric element and the potential detection circuit with each other, and each of the other conductive pattern and the ground conductive pattern.