Abstract: An automatic antiglare mirror for a vehicle with its reflectivity being variably controlled by an electrochromic element includes a rear light detection circuit for detecting quantity of light in the rear of the vehicle, a coloration amount control circuit for controlling an amount of coloration the electrochromic element and a response speed control circuit for controlling response speed of the electrochromic element. The coloration amount control circuit performs control of the amount of coloration in such a manner that, when quantity of rear light is smaller, the amount of coloration of the electrochromic element is smaller whereas, when the quantity of rear light is larger, the amount of coloration of the electrochromic element is larger.

Abstract: In a device for driving an EC antiglare mirror in which reflectivity is variably controlled by an EC element, a surrounding light quantity detection circuit detects quantity of light surrounding a vehicle. A rear light quantity detection circuit detects quantity of light in the rear of the vehicle. An oscillation circuit is constructed so that duration of an "H" level of an oscillation signal and duration of an "L" level of the oscillation signal are individually controlled. An inversion period control circuit variably controls duration of one of the "H" and "L" levels of the oscillation signal generated by the oscillation circuit in response to light quantity detected by the surrounding light quantity detection circuit and also variably controls duration of the other level in response to light quantity detected by the rear light quantity detection circuit.