Compact optical head using a holographic optical element for CD players

A small-size lightweight optical head using a holographic optical element (HOE) for optical disk systems has been developed. This optical head consists of only four optical elements. The HOE has the three optical functions required for an optical head: splitting the reflected beam; focusing error detection; and tracking error detection. A new optical configuration has been designed for this optical head to remove the influence of wavelength variation in the light source. The offset signal in the tracking error signal, which causes unstable operation, has been reduced by introduction of the holograms which are used only for detecting tracking error.