Information processing apparatus and optial head incorporated therein

The present invention provides a suitable portable computer, such as a book-sized computer, and a portable recording / reproducing apparatus compact thin optical disk memory. In the optical disc, the diameter of the objective lens is limited and a beam shaping prism, a beam splitter, a mirror and a quarter-wave plate is made into a unitary structure such that the optical axis of the optical head is easy to adjust and to ensure high precision assembly.