PURPOSE: To enable the detection of the presence and the amount of rain drops, by providing first and second electrodes at a specified interval on the back of the dielectric body.
CONSTITUTION: Dielectric bodies 7 and 7 are arranged facing respective windows 1a and 1b in a case 1. First and second electrodes 8 and 9 provided on the back of each dielectric body 7 are divided into a plurality of sets each formed in a comb-teetch pattern, for example, 3 sets of unit electrodes 8aW8c and 9aW9c. Then, a rain drop sensor 12 thus obtained can sufficiently detect attached state of rain drops according to changes in the electrostatic capacitance (namely, changes in impedance between the electrodes 8 and 9) practically. The electrostatic capacitance attributed to the rain drops themselves can be ignored. In this case, as the electrostatic capacitance between the electrodes 8 and 9 varies roughly in proportion to the amount of rain drops attached to the dielectric body 7, the amount of rain drops can be detected easily based on the electrostatic capacitance.
OOTA ATSUSHI
MUTO MASAHITO
ARAO UMEO
HAYASHI SHIGERU
KUBOTA KAZUHISA
TOKAI RIKA CO LTD