OPTICAL HEAD

PURPOSE:To reduce the length of an optical head in the optical axis direction of an objective by shifting together the objective, the semiconductor laser of a light source and an optical system including a photodetector. CONSTITUTION:An optical head contains a semiconductor laser 21 which forms a light source, a polarized beam splitter 22, a 1/4 wavelength plate 24, a rectangular prism 25, an objective 26, a photodetector 28 which detects the laser light reflected by the splitter 22, etc. in one body. Such an optical system is shifted toward the optical axis of the lens 26 as well as in the direction rectangular to said optical axis for purposes of focusing and tracking respectively. Therefore it is possible to reduce the size of the objective 26 as well as the distance between the objective 26 and the prism 25 in comparison with the case where only the objective 26 is shifted. As a result, the length of the optical head can be reduced in the optical axis direction of the objective 26.