White turbid state diagnostic apparatus

A white turbid state diagnostic apparatus, comprising

• an imager that is installed on a vehicle and observes a periphery of the vehicle via a lens, the imager having a photoelectric convertor that converts a light signal of the observed periphery of the vehicle into an image signal;
• a region detector that detects a region from the image signal, the region being constituted by pixels having brightness values over a predetermined brightness and being in a substantially circular shape having a predetermined area or more;
• a brightness gradient calculator that calculates a brightness gradient on a line which is directed from a predetermined position in a predetermined direction based on brightness values of pixels on the line in the region;
• and
• a white turbid level calculator that calculates a white turbid level of the lens based on the brightness gradient,
• wherein the white turbid level calculator includes:
• a brightness gradient average value calculator that calculates an average value of the brightness gradient calculated on the line to obtain a white turbid level;
• a similarity calculator that calculates a similarity of regions detected from image signals imaged at different timings;
• and
• a certainty determiner that determines a certainty of the white turbid level according to a period where high similarities are continuously calculated,
• wherein the certainty determiner updates the average value of the white turbid levels calculated in the previous processing and stores the updated average value, and
• wherein the certainty determiner calculates an error from the updated average value and the previous average value to determine a certainty of the white turbid level.