1. An image capturing device comprising: a housing having an aperture; a two-dimensional sensor that captures an object outside of the housing through the aperture; a reference pattern arranged in the housing for being captured together with the object by the two-dimensional sensor; an image forming element arranged on both a first optical path between the two-dimensional sensor and the reference pattern and a second optical path between the two-dimensional sensor and the object, the image forming element forming an image of the reference pattern on a sensor surface of the two-dimensional sensor; and a transparent member arranged on the second optical path, the transparent member having a refractive index that causes an image of the object, formed by the image forming element, to be positioned on the sensor surface on the two-dimensional sensor.