1. A recognition object detecting apparatus, comprising: means for generating image data representing a taken image; and means for detecting a recognition object from the image represented by the image data, wherein the generating means has a characteristic in which a relation between luminance and output pixel values varies depending on a luminance range, and the detecting means 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.