A miniature fingerprint sensor using a trapezoidal prism and a holographic optical element

摘要

A fingerprint sensor (11) with a trapezoidal prism (12) and a holographic phase grating (17) which is glued to the base surface (13) of the prism (12) operates to totally internally reflect light (23) from the finger-coverslip (18) interface protecting the exterior surface of the grating (17), diffracting the reflected light to propagate back through the base surface (13) and out the top parallel surface (16) of the prism (12) in a converging beam (20) having an optical axis normally oriented with respect to such parallel base (13) and top surfaces (16) of the prism (12).