| 摘要 |
PURPOSE:To contrive miniaturization and cost reduction of the device by splitting reflected light into different luminous fluxes in the state of polarization, converging them into two light spots and performing specified dealing. CONSTITUTION:The beam flux passed through a beam splitter 22 and a 1/2- waveform plate 25 is made incident via a convergent lens 27 upon a polarization separating element 30 provided with a polarizing plate 30c having the same crystal orientation as a prism 30b in addition to a prism 30a and the prism 30b (Wollaston polarizing prism) whose crystal axes are orthogonal to each other. The luminous flux passed through the element 30 is made to exit in different directions with a normal ray of light and an abnormal ray of light, and hence because of a difference between the two rays of light in refractive index as well, equivalent optical thickness is changed, so that converging positions of the two rays of light are different. Consequently, a light receiving parts 29 of a photodetector 28 are positioned for one luminous flux in terms of the polarizing direction in a position prior to converging and for the other luminous flux in a divergent luminous flux after converging. Thus, only one beam splitter element is required for an optical head, thus miniaturizing the device and lightening weight. |
