1. An input apparatus, comprising: an infrared camera; an image capture unit configured to sequentially capture a plurality of temperature distribution images photographed at predetermined time intervals by the infrared camera; and an input recognition unit configured to detect, from among the plurality of temperature distribution images captured by the image capture unit, pairs of skin temperature image portions each corresponding to a temperature of skin of a person, to recognize, from among the pairs of skin temperature image portions detected, pairs of skin temperature image portions as pairs of detection target images, from among which motions are observed, and to recognize an operation input based on states of the motions of the pairs of detection target images, wherein the input recognition unit is configured to detect the pairs of skin temperature image portions from among the plurality of temperature distribution images by comparing temperature values of pixels of each of the plurality of temperature distribution images with each other with respect to a first threshold and a second threshold which are set to define a temperature range of the skin of the person, and wherein the input recognition unit is further configured to generate a pair of binary images each containing the pairs of skin temperature image portions by binarizing the plurality of temperature distribution images based on whether or not the temperature values of the pixels of each of the plurality of temperature distribution images fall within the temperature range defined by the first threshold and the second threshold, generate a difference image of the pairs of detection target images in the pairs of skin temperature image portions, from among which the motions are observed, by determining a difference between the pair of binary images of the plurality of temperature distribution images, and judge, by using the difference image, the states of the motions of the pairs of detection target images.