[0042]
[0043] The pyroelectric sensor including the structure of the light shield 110 of the first embodiment will be described.
[0044] Figure 8 A represents the appearance of the hood 110, Figure 8 B represents an example of the size of the opening pattern 112 of the light shield 110.
[0045] The light-shielding cover 110 includes a sheet portion 111 for blocking infrared rays; an opening pattern 112 composed of a plurality of through holes formed in the sheet portion 111; and a mounting portion 113. The light shield structure includes a sheet portion 111 and an opening pattern 112.
[0046] For example, the light shield 110 (perforated metal plate) is formed by pressing a metal plate.
[0047] On the detection surface of the pyroelectric sensor, the arrangement direction of the two pyroelectric elements of the pyroelectric sensor is set as the x direction, and the direction perpendicular to the x direction on the detection surface is set as the y direction. The opening pattern 112 is sufficiently inclined relative to the prior art opening pattern, and the ratio of the irradiation range of the two pyroelectric elements 91R and 91L is changed with respect to the movement of the moving object in each direction in the x direction and the y direction.
[0048] When the opening pattern is symmetrical with respect to the x-direction axis and the y-direction axis passing through the center of the pyroelectric sensor, sometimes the ratio of the irradiation range of the two pyroelectric elements 91R and 91L does not occur for the movement of the moving object in the x or y direction. Variety. Here, "the center of the pyroelectric sensor" refers to the point where the pyroelectric element 91R and the pyroelectric element 91L arranged on the detection surface form a point symmetry. "The opening pattern is about the x-direction axis passing through the center of the pyroelectric sensor. "Axisymmetric and y-direction" means "set the direction perpendicular to the x-direction and y-direction as the z-direction, and the opening pattern is symmetrical with respect to the x'-axis and y'-axis. The x'-axis and y'-axis are The x-direction and y-direction axes of the sensor center respectively move up the z-direction to the axis of the opening pattern forming surface". For example, in the opening pattern of the light shield 93, the ratio of the irradiation range of the two pyroelectric elements 91R and 91L does not change with respect to the movement of the moving object in the y direction. Therefore, the opening pattern 112 is formed asymmetrically with respect to the x-direction axis and the y-direction axis passing through the center of the pyroelectric sensor. In addition, the opening pattern is formed such that the area ratio of the opening pattern divided by the x-direction axis (x' axis) and the area ratio of the opening pattern divided by the y-direction axis (y' axis) are both 1:1.
[0049] For example, the opening pattern is symmetrical with respect to the center point of the pyroelectric sensor. Here, the so-called "symmetrical with respect to the center of the pyroelectric sensor" means "point symmetrical with respect to the point o', which is to extend the center of the pyroelectric sensor in the z direction (slide) to the opening pattern The point that forms the face".
[0050] In this embodiment, the opening pattern 112 is composed of eight through holes 112-1 to 112-8.
[0051] The three through holes 112-1 to 112-3 constitute a first through hole row extending in the y direction, and the three through holes 112-5 to 112-7 constitute a second through hole row extending in the y direction. The through holes 112-4 are arranged on the side of the first through hole row that does not have the second through hole row. The through holes 112-8 are arranged on the side of the second through hole row that does not have the first through hole row. Two through holes 112-2 and 112-7 are formed in a row extending in the x direction, and two through holes 112-3 and 112-6 are formed in a row extending in the x direction. The three through holes 112-4, 112-1, and 112-2 are arranged at the vertex positions of the equilateral triangle. The three through holes 112-8, 112-5, and 112-6 are arranged at the vertex positions of the equilateral triangle.
[0052] In other words, the three through-holes 112-1 to 112-3 are sequentially arranged at equal intervals to form a first through-hole row extending in the y direction. The three through holes 112-5 to 112-7 are formed so as to be point-symmetrical with respect to the center of the pyroelectric sensor, and the three through holes 112-1 to 112-3 form a second through hole row. The through holes 112-2 and 112-7 are adjacent in the x direction, and the through holes 112-3 and 112-6 are adjacent in the x direction. Viewed from the center of the pyroelectric sensor, the through holes 112-4 are formed outside the first through hole row. In addition, the three through holes 112-4, 112-1, and 112-2 are arranged at the vertex positions of the equilateral triangle. The through hole 112-8 is formed so as to be point-symmetrical with the through hole 112-4 with respect to the center of the pyroelectric sensor.
[0053] For example, the distance in the x-direction between the first through hole row and the second through hole row is 0.5 mm, the diameter of each through hole is 0.5 mm, and the distance between the centers of the through holes constituting the apex of an equilateral triangle is 0.9 mm. These distances and/or diameters may be appropriately set by the distance between the sheet portion 111 and the pyroelectric element (for example, 1.1 mm), the position and size of the pyroelectric element, and the like. In addition, as a pyroelectric element, there are PZT (lead zirconate titanate)-based pyroelectric ceramics and the like. PZT-based pyroelectric ceramics are ceramics that become a solid solution of lead titanate (PbTiO3) and lead zirconate (PbZrO3).
[0054] Picture 9 A schematic diagram showing a structure including the opening pattern 112. Picture 10 Indicates the position of the non-sensing area 102 generated by the opening pattern 112, Picture 10 A represents the positional relationship between the non-sensing area 102 and the two pyroelectric elements 91R and 91L when the moving object is on the front of the pyroelectric sensor. Picture 10 B represents the positional relationship between the non-sensing area 102 and the two pyroelectric elements 91R and 91L when the moving object moves in the x direction (left direction) relative to the pyroelectric sensor, Picture 10 C represents the positional relationship between the non-sensing area 102 and the two pyroelectric elements 91R and 91L when the moving object moves in the y direction (upward direction) relative to the pyroelectric sensor. For simplification, the illuminated part is not represented as a circular shape, but as an area where the illuminated part exists.
