Laminated wave plate and optical pickup device using the same

Abstract

A laminated wave plate that corresponds to a plurality of wavelengths including at least two wavelengths of lambdaA and lambdaB, and includes a first wave plate disposed on an incident side and a second wave plate disposed on an emitting side, the first wave plate and the second wave plate being laminated in such a manner that their optical axes are intersected each other, includes the following equations: GammaA1=360 DEG +360 DEG *2NA; GammaA2=180 DEG +360 DEG *NA; GammaB1=360 DEG *2NB; GammaB2=360 DEG xNB; and NB=(DeltanB / DeltanA)x(lambdaA / lambdaB)x(0.5+NA), in which GammaA1 is a phase difference of the wavelength lambdaA at the first wave plate, GammaA2 is a phase difference of the wavelength lambdaA at the second wave plate, GammaB1 is a phase difference of the wavelength lambdaB at the first wave plate, GammaB2 is a phase difference of the wavelength lambdaB at the second wave plate, theta1 is an in-plane azimuth of the first wave plate, theta2 is an in-plane azimuth of the second wave plate, DeltanA is a birefringent difference that is a difference (neA-noA) between a normal ray refractive index noA and an abnormal ray refractive index neA of the wavelength lambdaA, and DeltanB is a birefringent difference that is a difference (neB-noB) between a normal ray refractive index noB and an abnormal ray refractive index neB of the wavelength lambdaB, under conditions of theta1=-21 DEG, and theta2=45 DEG.

Description

technical field [0001] The present invention relates to a laminated wave plate and an optical pick-up device using the laminated wave plate. Background technique [0002] In an optical pickup device for recording and reproducing optical recording media such as CDs (compact discs: CD-ROMs) and DVDs (digital versatile discs) and optical disks, due to the need for compatibility between CDs and DVDs, , using wavelength plates corresponding to various wavelengths. [0003] For example, Patent Document 1 discloses a wave plate having a phase difference of 1625 nm, and describes the following content: Regarding this wave plate, for laser light with a wavelength of 650 nm, since 1625 nm=325 nm+650 nm×2, it is substantially equal to If expressed in radians, a phase difference of 325nm / 650nm×2π=π is produced. For a laser with a wavelength of 790nm, since 1625nm=835nm+790nm×1, it is essentially expressed in radians, resulting in phase difference. In addition, a wavelength plate hav...

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Problems solved by technology

[0013] On the other hand, the laminated wave plate disclosed in Patent Document 4 has a phase difference compensation function, that is, even if the wavelength of the laser light emitted from the light source has a Deviation can also correct the change of the phase difference caused by the laser light passing through the multilayer wave plate, so the wavelength dependence is improved, but there is the following problem: when it functions as a 1 / 2 wavelength plate, it cannot Rotate the polarization plane of the linearly polarized light of the laser beam incident on the multilayer wave plate by 90°

That is, the polarization plane of the linearly polarized light of the incident light and the polarization plane of the linearly polarized light of the outgoing light are not in an orthogonal relationship, so there is a problem that it is not suitable for converting P-polarized light to S-polarized light or abnormal light Optical system (use) necessary for conversion to normal light, etc.

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