An optical head to access data on an optical recording medium, which has two data storage densities, includes two sets of optical path systems to provide two optical paths that are crossed. Each optical path system includes a laser light generation unit, a light guiding unit, a converging objective lens and a photo detector. The light guiding unit is located on the optical path of the laser light generation unit, to direct the laser light to pass through the converging objective lens and focus on the data side of the optical recording medium to carry optical data signals from the data side. The laser light returns to the light guiding unit and travels along the optical path and is received by the photo detector.