Objective lens for light pick-up device, light pick-up device and optical information recording regenerator
A recording and reproducing device and information recording technology, applied in the field of objective lenses, can solve problems such as high characteristics disadvantage, and achieve the effects of high-speed focusing action, easy injection molding, and simple structure
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no. 1 approach
[0103] First, the first embodiment will be described. image 3 It is a schematic configuration diagram of an optical pickup device (optical information recording and reproducing device) including the present embodiment. This optical pickup device is composed of a red laser 1 as a light source of wavelength λ, an objective lens 2 and an optical information recording medium 3 . A beam splitter 4 is provided between the red laser 1 and the objective lens 2 to deflect the reflected light from the optical information recording medium 3 in the direction of the detector 5 .
[0104] The divergent light from the red laser 1 is incident on the objective lens 2 , and its beam diameter is limited by the diaphragm 6 . In this way, since the imaging magnification becomes limited, the number of parts of the entire optical system can be reduced and the structure can be simplified. The objective lens 2 is double-sided aspherical and consists of plastic material. In the present embodiment, ...
no. 2 approach
[0109] Next, a second embodiment will be described. In this embodiment, with image 3 The first embodiment shown is different in that the surface shape of the effective diameter of the light source side of the objective lens is handled, and the description of the same configuration will be omitted.
[0110] When the focal length of the objective lens 2 becomes shorter, the paraxial curvature radius r1 ( figure 1 ) and the on-axis thickness becomes thinner. Therefore, if the numerical aperture NA is the same, the lens shape is similar, so the peripheral thickness / axial thickness of the objective lens 2 is almost the same, but when viewed in absolute value, the smaller the focal length f becomes, the thinner the peripheral thickness becomes. Although it will be described in the following examples, in an objective lens with a numerical aperture NA of 0.60, if the axial thickness is set to 0.4mm, the edge thickness will be less than 0.1mm, and the moldability of the objective le...
Embodiment 1
[0114] Example 1 relates to an objective lens applicable to the first embodiment described above. In Table 1, the number of lens pairs of the objective lens related to Example 1 is shown. Let the light source be the 0th plane, the first and second planes be the beam splitter, the third plane be the diaphragm, and the fourth and fifth planes be the objective lens. The sixth surface represents the information recording surface of the optical information recording medium. Also, in the following (the table contains the data of the lens), it is intended to put the multiplier that should be multiplied by 10 (for example, 2.5×10 -3 ) is represented by E (for example, 2.5×E-3).
[0115] Table 1
[0116] Example 1
[0117] f(mm) 0.567 ((1-m)NA) 4 ×f×|δn / δT| / λ
[0118] 0.029
[0119] m -0.166667 δW temp(λrms) at +30℃ temperature change 0.019
[0120] NA 0.62 δW height(λrms) at image height 0.02mm 0.028
[0121] λ(nm) 650 d / f 0.794
[0122] δn / δT( / ℃) -0.00012 r1 / (n(1-m)f) 0.37 ...
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