Patent ID: 7733049

Claim:
A raindrop quantity sensing apparatus comprising: a raindrop sensor that outputs a measurement signal, which corresponds to a quantity of raindrops in a predetermined area in a wiping range of a wiper blade on a windshield; a change computing means for computing an amount of change in a measured value of the measurement signal of the raindrop sensor in a raindrop quantity sensing execution time period, wherein the change computing means sets a time period, during which the wiper blade moves in a sensing range of the raindrop sensor, as a raindrop quantity sensing prohibited time period, and the change computing means sets a time period, during which the wiper blade moves outside of the sensing range, as a raindrop quantity sensing execution time period: a difference computing means for computing a difference between a predetermined reference value and an initial measured value of the measurement signal of the raindrop sensor, wherein the initial measured value of the measurement signal of the raindrop sensor is measured at a beginning of the raindrop quantity sensing execution time period; and a determining means for determining the quantity of raindrops on the windshield based on the amount of change, which is computed by the change computing means, and the difference, which is computed by the difference computing means: wherein the determining means determines the quantity of raindrops on the windshield based on: an increasing tendency or decreasing tendency of the amount of change, which is computed by the change computing means; and an increasing tendency or decreasing tendency of the difference, which is computed by the difference computing means.