Abstract: A detecting device for road monitoring which detects traveling states of vehicles on a road (traffic stagnation, stopping of vehicles, etc.) or fallen objects on a road is provided. Luminance change detecting unit prepares background image data by taking a time average of luminance for each picture element, and detects image portions where inputted image data is different in luminance from the prepared background image data. Hue change detecting unit prepares background image data by taking a time average of hue for each picture element, and detects image portions where inputted image data is different in hue from the prepared background image data.

Abstract: A charge injection circuit for injecting a charge to a signal processing circuit has a photo-voltaic element for generating a photocurrent when an infrared light is received, a field effect transistor used for injecting the charge to the signal processing circuit, and an impedance conversion circuit for feeding back an output of the field effect transistor to a substrate potential of the photo-voltaic element. The impedance conversion circuit has a gain which is greater than zero and less than or equal to one.