1. A recognition object detecting apparatus, comprising: an imaging unit which generates image data representing a taken image; and a detection unit which detects a recognition object from the image represented by the image data, wherein the imaging unit has a characteristic in which a relation between luminance and output pixel values varies depending on a to luminance range, and the detection unit binarizes the output pixel values of the image represented by the image data by using a plurality of threshold values to generate a plurality of binary images, and detects the recognition object based on the plurality of binary images.