Windshield wiper controller, optical raindrop detector and detection method thereof

A windshield wiper controller, adapted to be disposed on an inner surface of a windshield, the windshield wiper controller comprising:

• a light source;
• a light control unit configured to control the light source to emit light with a first brightness value and a second brightness value;
• a light guide comprising an incident surface, a detection surface and an ejection surface, wherein the detection surface is configured to be attached to the inner surface, and the light source is configured to emit incident light into the light guide via the incident surface and a plurality of microstructures are formed on the ejection surface configured to reflect the incident light to become scattered light toward the detection surface;
• an image sensor configured to receive reflected light formed by raindrops outside the windshield reflecting the scattered light to penetrate the light guide and eject from the ejection surface and to generate a first image frame corresponding to the first brightness value and a second image frame corresponding to the second brightness value;
• a processing unit configured to calculate a differential image of the first image frame and the second image frame and to output a wiper control signal according to the differential image;
• and
• a control unit configured to control a wiper according to the wiper control signal.

A detection method of an optical raindrop detector, the optical raindrop detector comprising a light source, a light guide, an image sensor and a processing unit, the light guide comprising an incident surface, a detection surface and an ejection surface, a plurality of microstructures being formed on the ejection surface, the detection method comprising:

• controlling the light source to emit light with a first brightness value and a second brightness value;
• using the image sensor to capture, at a sampling frequency, reflected light formed by raindrops in front of the detection surface reflecting scattered light, which is formed by the microstructures reflecting incident light emitted by the light source into the light guide and ejecting from the detection surface, to penetrate the light guide and eject from the ejection surface to generate a first image frame corresponding to the first brightness value and a second image frame corresponding to the second brightness value;
• using the processing unit to calculate a differential image of the first image frame and the second image frame;
• and
• using the processing unit to compare the differential image with an intensity threshold to identify rain intensity.