| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical recording and reproducing device which is capable of obtaining regenerative signals of a good signal-to-noise ratio and can always exactly reproduce information from the respective recording layers of a recording medium having the plural recording layers in a thickness direction. SOLUTION: The optical recording and reproducing device which records or reproduces the information by irradiating the recording medium 7 having the plural recording layers 6 in a thickness direction with light from a light source 1 through an objective lens 5 has a beam splitter 2 which is arranged between the optical path between the light source 1 and the objective lens 5 and separates the light made incident on the objective lens 5 from the light source 1 and the return light emitted through the objective lens 5 from the recording medium 7, a pinhole 14 which is arranged in the optical path of the return light separated by the beam splitter 2, a first photodetecting section 11 which receives the return light past the pinhole 14, a second photodetecting section 12 which does not receive the return light from the recording medium 7 and a differential arithmetic circuit which computes the output difference between the first photodetecting section 11 and the second photodetecting section 12. |
