| 摘要 |
PURPOSE:To reduce the number of parts and to make the constitution of an entire device small in size and light in weight by providing an optical path separation means having a semi-transmission type diffraction grating consisting of modulation pitches formed on one surface and a transmission type diffraction grating formed on the other surface on the optical path of light projected from a laser light source. CONSTITUTION:A dual type grating 25 functioning as the optical path separation means is provided on the optical path of the light projected from a semiconductor laser 24. The light projected from the laser light source 24 is reflected by the semi-transmission type diffraction grating 26a consisting of the modulation pitches of the optical path separation means 25, collimated by a collimating lens 27 and irradiates an optical information recording medium 29 through a condensing lens 28. Then, the reflected light is conducted to the means 25 again and transmitted through the diffraction grating 26a of the modulation pitches of the means 25 to be separated to 0th-order light and 1st-order light. Namely, the dual type grating 25 can be substituted for a beam splitter and a beam shaping prism, etc. Thus, the number of the parts is drastically reduced. |
