Laser expander design of highly efficient Blu-ray disc pickup head

We present a collimator design with a horizontal beam expander for a Blu-ray Disc pickup head. The design transforms the shape of a laser diode beam from an elliptical into circular which achieves higher efficiency in the pickup head system. In this research, we suggest two ways to do the beam expander. One way is to use two cylindrical lenses, and the other is to use two prisms.