Objective lens for optical head
A technology of objective lens and optical system, which is applied in the field of objective lens and high NA objective lens, and can solve problems affecting data recording/reading operations, etc.
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no. 1 example
[0059] image 3 The objective lens according to the first numerical embodiment is schematically represented. exist image 3 In , the objective lens 10 and the first optical disk D1 are shown. The laser beam is incident on the objective lens 10 as a parallel luminous flux (ie, the object distance is infinite), and is converged onto the data recording surface of the first optical disc D1. Table 2 shows numerical values.
[0060] In the first embodiment, the first surface 11 is divided into a central region RC and a peripheral region RE. The central region RC is defined as a region of 0≦h<1.50 (mm), and the peripheral region RE is defined as a region of 1.50≦h, where h represents the height relative to the optical axis of the objective lens 10 . The central region RC is a continuous surface without a stepped portion, and the peripheral region RE has a diffractive lens structure that changes the dependence of spherical aberration on the wavelength of light passing therethrough...
no. 2 example
[0084] Table 3 shows the numerical structure of the objective lens 10 . The structure of the second embodiment is basically the same as that of the first embodiment except that the structure in the peripheral region RE is different.
[0085] NA 1 =0.60f 1 =3.00λ 1 = 650WD 1 =1.61
OD 1 =∞
first surface
second surface
(0≤h<1.50)
peripheral area
(1.50≤h)
r
1.870
1.870
-8.109
kappa
-0.500
-0.500
0.00
A 4
-2.12×10 -4
2.36×10 -3
1.68×10 -2
A 6
1.47×10 -4
-5.50×10 -4
-2.57×10 -3
A 8
-8.23×10 -5
-5.23×10 -4
2.20×10 -4
A 10
6.09×10 -5
2.12×10 -4
-1.68×10 -4
A 12
-1.92×10 -5
-4.20×10 -5
2.93×10 -5
P 2
---
0.00
---
P 4
---
2.25
---
P 6
---
-1.03
---
P 8
---
0.00
---
P 10
-...
no. 3 example
[0089] Figure 8 A front view of the objective lens 10 according to the third embodiment is shown. Similar to the first and second embodiments, the first surface 11 of the objective lens 10 is divided into a central region RC (0≤h<1.50) and a peripheral region RE (1.50≤h). In the peripheral region RE, a diffractive lens structure that can change the wavelength dependence of spherical aberration on light passing therethrough is formed. Also according to the third embodiment, another diffractive lens structure is formed in the central region RC to compensate for chromatic aberration. The second surface 12 of the objective lens 10 is a rotationally symmetrical aspherical surface without a diffractive lens structure.
[0090] Table 4 shows the numerical structure of the objective lens 10 according to the third embodiment.
[0091] NA 1 =0.60f 1 =3.00λ 1 = 650WD 1 =1.63
OD 1 =∞
first surface
second surface
(0≤h<1.50) ...
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