1. An irregular pattern detector, comprising: a first optical system having a light source; a transparent light guide body including an incident face receiving an incident light from the light source of the first optical system, a detection face provided to face the incident face and for placing a subject having an irregular pattern thereon, a curved surface reflecting scattering light from the detection face, an optical absorbing face provided to face the curved surface and having an opening part outputting the reflection light from the curved surface; and a second optical system for guiding the light from the opening part of the optical absorbing face of the transparent light guide body to a camera device.