A small, thin device for reading a pattern with projections comprising a prism provided with a sensing face where an object having a pattern with projections is placed and an incident face inclined with respect to the sensing face at a first angle and adapted to output the light falling on the incident face and reflected from the sensing face, a first optical system having a light source and adapted to direct light from the light source to the incident face of the prism in such a way that the optical axis of the light is generally parallel to the sensing face, and a second optical system adapted to direct the light outputted from the prism to an imaging device.
