Patent ID: 8275179

Claim:
A fingerprint image capturing apparatus comprising: a prism having an imaging plane on which a finger having valleys and ridges is placed, a bottom plane parallel to the imaging plane and a reflective plane intercepting the imaging plane and the bottom plane at an angle α; a light source for generating a light with an incident angle of approximately 0° with respect to a surface normal of the imaging plane; a lens for capturing light reflected from the reflective plane; an image sensor for generating an image of the valleys and ridges of the finger; and an adjuster for adjusting the reflective plane to change the value of α in such a way to meet the following equation: α>45+(arc sin ( n 1 /n 2 ))/2, where n 1 is a refraction index of medium filled between the valleys of the finger and the imaging plane, and n 2 is refraction index of the prism.