Integrated optical unit employing two-wavelength laser diode for digital versatile disc/compact disc optical pickup

We have developed an integrated optical unit employing a two-wavelength laser diode for a digital versatile disc (DVD)/ compact disc (CD) optical pickup. In this paper, we propose a new design method to share a holographic optical element for 780 and 650 nm light beams in an integrated optical unit.: To share the holographic optical element, we have introduced an additional aberration to reduce the focusing error signal offset of the 780 nm light beam. Moreover, we have introduced the phase-shift differential push-pull (PS-DPP) method for, both the 650 and 780nm light beams. We have evaluated the performance of this integrated optical unit and confirmed that the performance of this unit is sufficient for both DVD and CD systems.