Optical head device and optical information recording and reproducing device

EXAMPLE 1

[0105] fp=10.0 [0106] R11=−8.48 [0107] R12=14.3 [0108] R21=33.2 [0109] R22=−9.02 [0110] E1=2.0 [0111] d1=1.2 [0112] d2=1.2 [0113] n1=1.74188 [0114] n2=1.71791 [0115] EFF=3.0

[0116] Here, since the focal length of the convex lens is 10 mm, the distance from the convex lens to the first surface of the objective lens is also set to 10 mm, assuming that the aperture of the objective lens lies in the first surface of the objective lens. See FIG. 3.

[0117] The amount of third-order spherical aberration corrected when the convex lens is moved by ±0.5 mm is about 0.18 λ: RMS. In the following description, when the convex lens is moved toward the light source, the amount of movement is designated as negative, and when the convex lens is moved toward the objective lens, the amount of movement is designated as positive.

[0118] The height of the light ray incident on the spherical aberration correcting optical system, which corresponds to the peripheral ray or marginal ray incident on th

EXAMPLE 2

[0121] fp=20.0 [0122] R11=−23.11 [0123] R12=24.93 [0124] R21=81.09 [0125] R22=−12.036 [0126] E1=2.5 [0127] d1=1.2 [0128] d2=2.0 [0129] n1=1.74188 [0130] n2=1.52801 [0131] EFF=3.0

[0132] Here, since the focal length of the convex lens is 20 mm, the distance from the convex lens to the first surface of the objective lens is also set to 20 mm, assuming that the aperture of the objective lens lies in the first surface of the objective lens. See FIG. 4.

[0133] The amount of third-order spherical aberration corrected when the convex lens is moved by ±1.5 mm is about 0.15 λ: RMS. In the following description, when the convex lens is moved toward the light source, the amount of movement is designated as negative, and when the convex lens is moved toward the objective lens, the amount of movement is designated as positive.

[0134] The height of the light ray incident on the spherical aberration correcting optical system, which corresponds to the peripheral ray or marginal ray incident

EXAMPLE 3

[0137] fp=8.0 [0138] R11=−6.914 [0139] R12=5.35 [0140] R21=71.645 [0141] R22=−4.414 [0142] E1=3.0 [0143] d1=0.8 [0144] d2=1.5 [0145] n1=1.75747 [0146] n2=1.52331 [0147] EFF=3.7

[0148] The second surface of the second lens is aspherical, and its aspherical shape is also expressed by (equation 1). See FIG. 5. [0149] k2=−0.1710231 [0150] A2, 4=2.839637×10−5

[0151] Here, since the focal length of the convex lens is 8 mm, the distance from the convex lens to the first surface of the objective lens is also set to 8 mm, assuming that the aperture of the objective lens lies in the first surface of the objective lens.

[0152] The amount of third-order spherical aberration corrected when the convex lens is moved by ±0.25 mm is about 0.25 λ: RMS. In the following description, when the convex lens is moved toward the light source, the amount of movement is designated as negative, and when the convex lens is moved toward the objective lens, the amount of movement is designated as positive.