| 摘要 |
An optical pickup which appropriately detects reflected light and return light reflected back from an information recording medium even if a laser light B 1 emitted from a light source varies in wavelength. The transmittances of a half mirror to the laser light B 1 emitted from the light source, and to the reflected light Bwr, Ber or the return light Brr reflected back from the information recording medium are preset according to a predetermined condition, i.e., Tpc(lambdac)/Tp(lambda)=(1-Ts(lambda)/(1-Tsc(lambdac))x(Tsc(lambdac)/Ts(lambda)). Here, lambda is a predetermined wavelength emitted from a semiconductor laser as the light source, Ts(lambda) is a transmittance to the laser light B 1 with a predetermined polarization, Tp(lambda) is a transmittance to the reflected light Bwr, Ber or the return light Brr reflected back from the information recording medium when the laser light B 1 with the predetermined wavelength lambda is emitted, Tsc(lambdac) is a transmittance to the laser light B 1 with a wavelength lambdac when the semiconductor laser varies in wavelength characteristic, and Tpc(lambdac) is a transmittance to the reflected light Bwr, Ber or the return light Brr reflected back from the information recording medium when the laser light B 1 with the wavelength lambdac is emitted.
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