| 摘要 |
PURPOSE:To securely detect a heat source by arranging a reflecting shield plate which reflects an infrared ray between a pyroelectric infrared sensor element and a Fresnel lens so that the space between a couple of elements is partitioned. CONSTITUTION:The reflecting shield plate 8 made of aluminum is provided almost in the middle between the 1st element 4 and 2nd element 5 of the sensor element 3. Then, when a heat source moves from a detection area (a) to a detection area (b), the heat source is in the detection area A of the element 4 itself, so the infrared ray enters the element 4, but no infrared ray enters the element 5. Consequently, there is a difference generated between the output levels of the elements 4 and 5 and a differential output E1 is obtained from the sensor element 3. Similarly, no differential output is obtained in heat-source movement sections bd and gh, a differential output 2E1 is obtained in movement sections de and ef, and a differential output E1 is obtained in a section hi. Thus, a detectable area is created newly at the overlap of the areas A and B by the reflecting shield plate 8 and more effective detection becomes possible. |
