JP3340484B2 - Collimating lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collimator lens suitable for an optical system using a semiconductor laser as a light source, such as a magneto-optical disk drive.

[0002]

2. Description of the Related Art The emission wavelength of a semiconductor laser used as a light source of an optical disk device shifts due to a change in output power or a change in temperature. For this reason, if the chromatic aberration of the optical system is not corrected, the focusing position of the light beam changes due to the shift of the wavelength, and there is a possibility that an error occurs in reading and writing of information. Therefore, it is necessary for the collimating lens provided in the optical system to sufficiently correct axial chromatic aberration.

[0003]

However, the conventional collimating lenses disclosed in JP-A-2-48886, JP-A-63-31767 and the like are premised on use in the visible light wavelength range. In the near-infrared region, which is one of the wavelength ranges of semiconductor lasers, sufficient axial chromatic aberration cannot be corrected depending on the selection of the glass material.

[0004] Further, with the miniaturization of the entire optical disk device or the increase in access speed, it is desired that the entire optical system is also reduced in size and weight, and the cost must be low.

Furthermore, in order to shorten the optical path of the optical system, it is necessary to provide each optical function component during the convergence and divergence of the collimator lens. It is necessary that good performance be obtained even when the cover glass of the semiconductor laser located at is relatively thick.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a small and lightweight structure, which can sufficiently correct chromatic aberration even in the near-infrared wavelength region of a semiconductor laser. It is another object of the present invention to provide a collimating lens having excellent performance even when an optical functional component such as a relatively thick cover glass is provided in the divergent or convergent light within the working distance.

[0007]

In order to achieve the above object, a collimating lens according to the present invention has a biconvex positive first lens and a double-convex first lens attached to the first lens in order from the side where light beams become parallel. The negative second lens of the combined meniscus is arranged and configured to satisfy the following conditions (1) to (7).

Nd1 = 1.69350 (1) nd2 = 1.80518 (2) νd1 = 53.2 (3) νd2 = 25.4 (4) 0.70 <r1 / f <0.725 … (5) −0.50 <r2 / f <−0.45 (6) d2 / d1 = 0.57 (7) where nd1 is the refractive index of the first lens at d-line, nd2 : Refractive index of the second lens at the d-line, νd1: Abbe number of the first lens at the d-line, νd2: Abbe number of the second lens at the d-line, r1: radius of curvature of the front side (parallel beam side) of the first lens R2: radius of curvature of the bonding surface of the first lens and the second lens; d1: center thickness of the first lens on the optical axis; d2: center thickness of the second lens on the optical axis; f: focal length of the entire system It is.

Alternatively, in a similar configuration, the following conditions (1), (3) and (8)-(12) are satisfied.

Nd1 = 1.69350 (1) nd2 = 1.78470 (8) νd1 = 53.2 (3) νd2 = 26.3 (9) 0.705 <r1 / f <0.73 ... (10) -0.48 <r2 / f <-0.43 (11) d2 / d1 = 0.71 (12)

Conditions (1), (2), (5), (6),
When (8), (10), and (11) are not satisfied, correction of spherical aberration and coma (sine condition) is insufficient or a problem, and satisfactory aberration correction cannot be performed.

Further, conditions (3), (4), (7),
If the conditions (9) and (12) are not satisfied, the correction of the axial chromatic aberration becomes insufficient, and the lens cannot be used in actual use.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The collimating lens of the embodiment is, for example, shown in FIG.
As shown in FIG. 1, a biconvex positive first lens and a meniscus negative second lens bonded to the first lens are arranged in this order from the side on the left side where the light flux is parallel.
This is a collimating lens for optical recording / reproducing which has two groups.

In each embodiment, the F number is 2.0 to 5.
0 (NA 0.1 to 0.25), and the half angle of view ω is 0 ° to
1.5 °. The focal length f of the entire system is normalized to 1. In the following examples, the axial chromatic aberration is almost 0, and other aberrations are sufficiently corrected.

In addition, within the range of NA shown in the embodiment, good performance can be obtained even if the NA does not always coincide with the NA in the embodiment. Also, by performing scaling for other focal lengths, equivalent performance can be obtained.

[0017]

FIG. 1 shows a lens configuration of a collimating lens according to a first embodiment. The specific numerical configuration is shown in Table 1. In the table, FNO. Is the F number, f is the focal length, ω is the half angle of view, r is the radius of curvature, d is the lens thickness or air gap, n is the refractive index at d-line (588 nm), ν is the Abbe number , N1 are the refractive indices at a wavelength of 780 nm . During divergent light is a working distance of co Limay <br/> Trends
Is Kabagara scan of semiconductors lasers are provided.

FIG. 2 shows spherical aberration SA, sine condition SC, and wavelength 76.
The graph shows chromatic aberration and astigmatism (S: sagittal, M: meridional) represented by spherical aberration at 0 nm, 780 nm, and 800 nm.

[0019]

[Table 1]

[0020]

Second Embodiment FIG. 3 shows a second embodiment of the present invention. The specific numerical configuration is shown in Table 2. FIG. 4 shows various aberrations due to this configuration.

[0021]

[Table 2]

[0022]

Third Embodiment FIG. 5 shows a third embodiment of the present invention. Table 3 shows a specific numerical configuration. FIG. 6 shows various aberrations due to this configuration.

[0023]

[Table 3]

[0024]

Fourth Embodiment FIG. 7 shows a fourth embodiment of the present invention. Table 4 shows a specific numerical configuration. FIG. 8 shows various aberrations due to this configuration.

[0025]

[Table 4]

[0026]

Fifth Embodiment FIG. 9 shows a fifth embodiment of the present invention. Table 5 shows a specific numerical configuration. FIG. 10 shows various aberrations due to this configuration.

[0027]

[Table 5]

[0028]

Sixth Embodiment FIG. 11 shows a sixth embodiment of the present invention. Table 6 shows a specific numerical configuration. FIG. 12 shows various aberrations due to this configuration.

[0029]

[Table 6]

[0030]

Seventh Embodiment FIG. 13 shows a seventh embodiment of the present invention. The specific numerical configuration is shown in Table 7. FIG. 14 shows various aberrations due to this configuration.

[0031]

[Table 7]

[0032]

Embodiment 8 FIG. 15 shows an eighth embodiment of the present invention. The specific numerical configuration is shown in Table 8. FIG. 16 shows various aberrations due to this configuration.

[0033]

[Table 8]

[0034]

Ninth Embodiment FIG. 17 shows a ninth embodiment of the present invention. Table 9 shows a specific numerical configuration. FIG. 18 shows various aberrations due to this configuration.

[0035]

[Table 9]

[0036]

Tenth Embodiment FIG. 19 shows a tenth embodiment of the present invention. Table 10 shows a specific numerical configuration. FIG.
Indicates various aberrations due to this configuration.

[0037]

[Table 10]

[0038]

Embodiment 11 FIG. 21 shows Embodiment 11 of the present invention. Table 11 shows a specific numerical configuration. FIG.
Indicates various aberrations due to this configuration.

[0039]

[Table 11]

[0040]

Twelfth Embodiment FIG. 23 shows a twelfth embodiment of the present invention. Table 12 shows a specific numerical configuration. FIG.
Indicates various aberrations due to this configuration.

[0041]

[Table 12]

[0042]

As described above, according to the present invention, the biconvex positive first lens and the meniscus negative second lens are used.
By configuring bonded lens and the two lenses of the combination of low-cost glass material, a relatively small, yet lightweight, well be the aberration correction, without collimating lenses axial chromatic aberration Can be provided.

[Brief description of the drawings]

FIG. 1 is a lens diagram of a collimating lens according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating various aberrations caused by the configuration of FIG. 1;

FIG. 3 is a lens diagram of a collimating lens according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating various aberrations caused by the configuration of FIG. 3;

FIG. 5 is a lens diagram of a collimating lens according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating various aberrations caused by the configuration of FIG. 5;

FIG. 7 is a lens diagram of a collimating lens according to a fourth embodiment of the present invention.

8 is a diagram illustrating various aberrations caused by the configuration illustrated in FIG. 7;

FIG. 9 is a lens diagram of a collimating lens according to Embodiment 5 of the present invention.

FIG. 10 is a diagram illustrating various aberrations caused by the configuration in FIG. 9;

FIG. 11 is a lens diagram of a collimator lens according to Embodiment 6 of the present invention.

FIG. 12 is a diagram illustrating various aberrations caused by the configuration in FIG. 11;

FIG. 13 is a lens diagram of a collimating lens according to a seventh embodiment of the present invention.

14 is a diagram illustrating various aberrations caused by the configuration in FIG. 13;

FIG. 15 is a lens diagram of a collimator lens according to Embodiment 8 of the present invention.

16 is a diagram of various aberrations caused by the configuration of FIG. 15;

FIG. 17 is a lens diagram of a collimating lens according to Embodiment 9 of the present invention.

18 is a diagram of various aberrations caused by the configuration in FIG. 17;

FIG. 19 is a lens diagram of a collimator lens according to Embodiment 10 of the present invention.

20 is a diagram of various aberrations caused by the configuration of FIG. 19;

FIG. 21 is a lens diagram of a collimating lens according to Embodiment 11 of the present invention.

FIG. 22 is a diagram illustrating various aberrations caused by the configuration in FIG. 21;

FIG. 23 is a lens diagram of a collimator lens according to Embodiment 12 of the present invention.

24 is a diagram of various aberrations caused by the configuration of FIG. 23;

Claims (2)

(57) [Claims] 1. A biconvex positive first lens and a meniscus negative second lens bonded to the first lens are arranged in this order from the side where the light flux becomes parallel. A collimating lens characterized by satisfying. nd1 = 1.69350 (1) nd2 = 1.80518 (2) νd1 = 53.2 (3) νd2 = 25.4 (4) 0.70 <r1 / f <0.725 (7) 5) -0.50 <r2 / f <-0.45 (6) 0.54 <d2 / d1 <0.60 (7) where nd1 is the refractive index of the first lens at d-line, nd2: refractive index of the second lens at the d-line, νd1: Abbe number of the first lens at the d-line, νd2: Abbe number of the second lens at the d-line, r1: curvature of the front side (parallel beam side) of the first lens Radius, r2: radius of curvature of the bonding surface of the first lens and the second lens, d1: center thickness of the first lens on the optical axis, d2: center thickness of the second lens on the optical axis, f: focal point of the entire system Distance. 2. A biconvex positive first lens and a meniscus negative second lens bonded to the first lens are arranged in this order from the side where the light beams become parallel. A collimating lens characterized by satisfying. nd1 = 1.69350 (1) nd2 = 1.78470 (8) νd1 = 53.2 (3) νd2 = 26.3 (9) 0.705 <r1 / f <0.73 (10) -0.48 <r2 / f <-0.43 (11) 0.68 <d2 / d1 <0.74 (12) where nd1 is the refractive index of the first lens at d-line, and nd2 is the second. Refractive index of d-line of two lenses, νd1: Abbe number of d-line of first lens, νd2: Abbe number of d-line of second lens, r1: radius of curvature of front side (parallel beam side) of first lens, r2 : Radius of curvature of the first lens and second lens bonding surfaces, d1: center thickness of the first lens on the optical axis, d2: center thickness of the second lens on the optical axis, f: focal length of the entire system .