FOG DETECTOR

PROBLEM TO BE SOLVED: To improve determination accuracy of the presence or absence of fog.SOLUTION: A fog detector 1 connected to a camera 2 loaded on a vehicle to detect the presence or absence of fog on an external field of the vehicle includes: an image input unit 11 for acquiring a plurality of images inputted from the camera 2 at a predetermined interval; a power spectrum calculation unit 12 for calculating a plurality of power spectra by respectively applying Fourier transform processing to the plurality of images; a normalization processing unit 13 for respectively normalizing the plurality of power spectra; a DC component extraction unit 14 for extracting DC components from respective normalized power spectra and generating time series data; and a fog determination unit 15 for determining the presence or absence of fog based on the time series data.