JP2003255221A - Objective for optical pickup, optical pickup and optical information processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an objective for an optical pickup which has large NA (numerical aperture), whose production tolerance is gentle, and by which information can be recorded, reproduced and erased on/from the optical recording medium of a DVD system and a CD system with single lens configuration. <P>SOLUTION: The objective for the optical pickup performs at least one or more of the recording, the reproduction and the erasion of the information on/from the optical recording medium having the thickness of a light radiation side base plate: 0.1 mm on a condition that operating wavelength: 407 nm±10 nm and numerical aperture: 0.85±0.05. Both surfaces of the objective are aspherical and convex, the objective satisfies the specified condition on a refractive index to material on a d-line: nd, an Abbe number: νd, the paraxial radius of curvature of a light source side surface: R1, a working distance: WD, a focal distance: f, and the objective is made of glass mold material, is easily produced and has the specified NA with the single lens configuration. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens for an optical pickup, an optical pickup using the same, and an optical information processing apparatus.

[0002]

2. Description of the Related Art In an optical system used in an information recording / reproducing apparatus for recording or reproducing information on an optical recording medium, in order to increase the density of a recording information signal, an objective lens reduces a spot condensed on the recording medium. Required to do so. Therefore, the wavelength of the semiconductor laser, which is a light source, is shortened, and the numerical aperture (hereinafter, referred to as NA) of the objective lens is increased.

A semiconductor laser as a light source has an oscillation wavelength of 40
Practical application of a semiconductor laser of about 0 nm has been attempted.
As the high NA lens, for example, JP-A-2001-834
No. 10, JP-A-11-202194, and JP-A-11-203711 disclose a high NA lens for a pickup, which is composed of two aspherical lenses. In the high NA objective lens composed of these two lenses, the number of assembling steps is increased, the precision is increased with the increase in the number of lenses, and the weight is increased as compared with the objective lens which is conventionally composed of one lens in the low NA region. Up is a challenge.

Further, in the case of the two-sheet structure, the working distance: WD corresponding to the distance between the objective lens and the information recording medium becomes small, and the information recording medium and the objective lens are damaged by the collision of the information recording medium and the objective lens. Is more likely to occur, resulting in reliability issues. Japanese Patent Laid-Open No. 2001-324673 discloses an objective lens with a NA of 0.7 or more that solves such a problem.

However, these conventional examples have low manufacturing feasibility. In order to achieve high NA and short wavelength with a single objective lens, select a glass type that can be press-molded using an ultra-precision machined mold, and secure wavefront performance at the designed median value. And manufacturing tolerances need to be within a viable range. First, it is necessary to suppress the wavefront aberration at the design median value to 0.01 λ or less.

According to the calculation by the inventor, Japanese Patent Laid-Open No. 2001-3
No. 24673, wavelength used in Example 3, 400 nm, NA: 0.85, f (focal length): 1.765 mm, nd (refractive index of lens material with respect to d-line): 1.71667, νd (Abbe number): 5
In the objective lens for optical pickup of 3.2, the wavefront aberration is 0.037λ, and the feasibility is low. Moreover, even if the wavefront performance of the design median is good, it is difficult to put it into practical use if the feasibility of manufacturing tolerance is low. For example, the thickness deviation is ± 1μ
When m or more, the deterioration amount of the wavefront aberration needs to be about 0.015λ or less. FIG. 20 shows another example of using wavelength: 6
50 nm, NA: 0.75, f: 2.00 mm, nd:
Regarding the objective lens for optical pickup of 1.69330 and νd: 53.17, the relationship between the thickness tolerance and the wavefront aberration is shown, and the above conditions cannot be satisfied.

[0007]

Therefore, it is desired to provide a lens having a small amount of wavefront deterioration due to manufacturing tolerances or an optical pickup capable of suppressing the amount of wavefront deterioration due to manufacturing tolerances.

Further, while the new standard by increasing the NA and shortening the wavelength has been realized in recent years, users have the conventional optical recording media such as CD and DVD. It is desirable that both the optical recording medium and the optical recording medium of the new standard can be handled by the same optical information processing device. The simplest method is to mount a conventional optical pickup and an optical pickup of a new standard optical pickup. But,
With this method, it is difficult to achieve miniaturization and cost reduction.

The present invention is directed to solving the above-mentioned problems of the prior art. It has a single lens structure, has a large NA effective for reducing the diameter of a light spot, and has a narrow manufacturing tolerance. In the optical pickup using the objective lens for the optical pickup, recording, reproduction, and erasing can be performed on a conventional optical recording medium such as a DVD system or a CD system without providing a plurality of optical pickups.
Further, it is an object of the present invention to provide an optical information processing apparatus using the optical pickup, by which the aberration component generated by the manufacturing tolerance can be corrected to realize the reliability of the optical pickup.

[0010]

In order to achieve this object, an objective lens for an optical pickup, an optical pickup and an optical information processing apparatus according to the present invention are provided.
The described objective lens for an optical pickup has a use wavelength: 40
An infinite system for an optical pickup that records, reproduces, or erases information on an optical recording medium with a substrate thickness of 0.1 mm on the light irradiation side by 7 nm ± 10 nm and NA: 0.85 ± 0.05. It is an objective lens for an optical pickup used as a lens, is configured as a single lens, has both aspherical surfaces and convex surfaces, and has a refractive index with respect to a material of d-line:
nd and Abbe number: νd is the following two conditions, νd ≦ 65
And an aspherical glass molded product satisfying 1.55 ≦ nd, and further, in the objective lens for an optical pickup according to claim 2, the center thickness of the lens: t, the paraxial radius of curvature of the side surface of the light source: R1 , Working distance: W
Refractive index of material for D and D lines: nd, focal length: f
However, the following three conditions, 1.0nd-1.0≤R1 / f≤1.0nd-0.8 1.2nd-0.75≤t / f≤1.2nd-0.5-0.35nd + 0.3. 77 ≦ WD / f ≦ −0.35nd +
By satisfying 0.85, it is a single lens structure,
By increasing the number of parts, weight, and assembling accuracy, a glass mold material has realized a thickness deviation of several μm or more that could not be achieved with the conventional NA: 0.85 single-lens objective lens. It is possible to obtain an objective lens with NA: 0.85 that is easy to manufacture.

The objective lens for an optical pickup according to any one of claims 3 to 5 is the objective lens for an optical pickup according to claim 1 or 2, wherein the refractive index with respect to the material of the d-line is:
nd and working distance: WD satisfies the following condition −0.42nd + 0.82 ≦ WD / f ≦ −0.42nd +
0.95 and / or −0.35nd + 0.64 ≦ WD / f ≦ −0.35nd +
An objective lens for an optical pickup that satisfies 0.72 and is used as a finite lens, and has a usable wavelength of 660 nm ± 10 nm,
NA 0.65 ± 0.05, Light irradiation side Substrate thickness: 0.6m
m optical recording medium, and / or wavelength used: 780 nm
± 10 nm, NA 0.50 ± 0.05, substrate thickness on the light irradiation side: At least one or more of information recording, reproduction, and erasing on an optical recording medium having a thickness of 1.2 mm, a usable wavelength: 407 nm, It is possible to obtain an objective lens for a large-capacity optical recording medium with NA: 0.85 and an optical recording medium for DVD or CD.

Further, in the objective lens for an optical pickup according to any one of claims 6 to 7, the aperture limiting means for switching the numerical aperture according to the used wavelength and / or the curvature of the objective lens side between the objective lens and the light source. By using a lens with a strong surface together, wavelength used: 407n
m, NA: 0.85 high capacity optical recording medium, DVD and C
It is possible to focus light on the optical recording medium of D with aberration suppressed.

The optical pickup according to claim 8 is:
Working wavelength: 407 nm ± 10 nm, NA: 0.85 ± 0.
According to 05, at least one of recording, reproducing and erasing of information on an optical recording medium having a light irradiation side substrate thickness of 0.1 mm 1
An optical pickup for performing the above, wherein the objective lens for an optical pickup according to claim 1 or 2 is used as an objective lens for converging a light beam from a light source as a light spot on a recording surface of an optical recording medium. Thus, recording, reproduction, or erasing can be performed corresponding to a high-density optical recording medium.

Further, the optical pickup described in claims 9 to 11 is the same as the optical pickup described in claim 8, wherein the wavelength used is 660 nm ± 10 nm, and the NA is 0.65 ± 0.05.
By the optical irradiation side, the substrate thickness: 0.6 mm, and / or the wavelength used: 780 nm ± 10 nm, NA:
An optical pickup for recording / reproducing / erasing information on / from an optical recording medium having a light irradiation side substrate thickness of 1.2 mm according to 0.50 ± 0.05. As an objective lens for condensing a light spot as a light spot on the recording surface of the optical recording medium.
By using the objective lens for an optical pickup according to any one of 7 above, a usable wavelength: 407 nm, NA: 0.
The large-capacity optical recording medium 85 and the conventional optical recording medium such as DVD or CD can be condensed with aberration suppressed and can be recorded, reproduced, or erased by one pickup.

An optical pickup according to any one of claims 12 to 15 is the optical pickup according to any one of claims 8 to 11, wherein the first correction means corrects an even-order aberration component and an even-order aberration component. A first detecting means for detecting an aberration component is provided, and the first correcting means is arranged between the objective lens and the light source, and is a correcting means for changing the divergence state of the light incident on the objective lens. Further, the first correcting means is disposed between the objective lens and the light source, and is a correcting means that concentrically gives a phase difference level when the light flux is transmitted or reflected, and the first correcting means further comprises: By using the aberration correcting means for correcting the spherical aberration, the correction for suppressing the axially symmetric aberration caused by the manufacturing error of the objective lens and the spherical aberration caused by the substrate thickness error of the optical recording medium. Means Ete, good recording, reproduction, and can provide an optical pickup capable of performing erasure can loosen the manufacturing tolerances of the objective lens.

The optical pickup according to any one of claims 16 to 19 is the optical pickup according to any one of claims 8 to 11, wherein a second correcting means for correcting an odd-order aberration component and the odd-order And a second detecting means for detecting the aberration component of
The correcting means is disposed between the objective lens and the light source, and the incident light incident on the objective lens is inclined and incident with respect to the optical axis of the objective lens, and the second correcting means is disposed between the objective lens and the light source. The manufacturing error of the objective lens is made by the correction means for providing the phase difference level in a stepwise manner when the light flux is transmitted or reflected, and the second correction means is the aberration correction means for correcting the coma aberration. Provided is an optical pickup capable of excellent recording, reproduction, and erasing, which is provided with a correction means for suppressing an asymmetrical aberration caused by the above and a coma aberration caused by the tilt of an optical recording medium. Therefore, the manufacturing tolerance of the objective lens can be relaxed.

Further, the optical information processing apparatus according to claims 20 to 22 has a working wavelength of 407 nm ± 10 nm and a NA of 0.0.
85 ± 0.05 optical recording medium with light irradiation side substrate thickness: 0.1 mm, and working wavelength: 660 nm ± 10 nm, N
A: Light irradiation side substrate thickness: 0.6m due to 0.65 ± 0.05
m optical recording medium, and / or wavelength used: 780 nm
At least one of information recording, reproducing, and erasing is performed using an optical pickup on an optical recording medium having a substrate thickness of 1.2 mm at a light irradiation side of ± 10 nm and NA: 0.50 ± 0.05. An optical information processing apparatus, wherein the optical pickup has a working wavelength of 407 nm ± 10 nm and NA:
For an optical recording medium with a substrate thickness of 0.15 mm and a light irradiation side of 0.85 ± 0.05, the light flux incident on the objective lens is an infinite system, and the wavelength used is 660 nm ± 10 nm and NA is 0.65 ± 0.0.
5, an optical recording medium having a light irradiation side substrate thickness of 0.6 mm, and / or a wavelength used: 780 nm ± 10 nm, NA: 0.0.
50 ± 0.05 The thickness of the substrate on the light irradiation side: For the optical recording medium of 1.2 mm, the incident light flux of the objective lens is a finite system, so that information can be recorded well on the optical recording medium of each wavelength used. , Can be played, and erased.

The optical information processing apparatus according to the twenty-third to twenty-fifth aspects has a usable wavelength of 407 nm ± 10 nm and NA of 0.0.
85 ± 0.05 optical recording medium with light irradiation side substrate thickness: 0.1 mm, and working wavelength: 660 nm ± 10 nm, N
A: Light irradiation side substrate thickness: 0.6m due to 0.65 ± 0.05
m optical recording medium, and / or wavelength used: 780 nm
At least one of information recording, reproducing, and erasing is performed using an optical pickup on an optical recording medium having a substrate thickness of 1.2 mm at a light irradiation side of ± 10 nm and NA: 0.50 ± 0.05. An optical information processing device, wherein an optical pickup has a wavelength of 407 nm ± 10 nm with N
A: 0.85 ± 0.05, wavelength used: 660 nm ±
NA: 0.65 ± 0.05 for 10 nm, NA: 0.5 for used wavelength: 780 nm ± 10 nm
Since the aperture limiting means for limiting the numerical aperture to 0 ± 0.05 is provided, information can be recorded, reproduced, and erased more favorably on the optical recording medium of each used wavelength.

An optical information processing apparatus according to a twenty-sixth aspect is the optical information processing apparatus according to any one of the twentieth to twenty-fifth aspects, wherein the optical pickup is provided with even-order or odd-order aberration correction means. As a result, the aberration is corrected for the optical recording medium of each used wavelength, and the information is satisfactorily recorded,
It can be played and erased.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Generally, the form of the optical recording medium is a disk, and the substrate thickness on the light irradiation side of the optical recording medium: 0.1 mm is a standard value. The "optical system of the optical pickup" is designed based on this standard value, and in the actually used optical recording medium, the light irradiation side substrate thickness has an error with respect to the standard value.

Here, refractive index: nd, Abbe number: νd,
Center thickness of lens: t, paraxial radius of curvature of light source side surface: R
1, working distance: WD, refractive index of material for d-line: nd, focal length: f, Condition 1: νd ≦ 65 Condition 2: 1.55 ≦ nd Condition 3: 1.0nd-1.0 ≦ R1 / f≤1.0nd-0.
8 Condition 4: 1.2nd-0.75≤t / f≤1.2nd-0.
5 Condition 5: −0.35nd + 0.77 ≦ WD / f ≦ −0.35
nd + 0.85 Conditions 1 to 5 are conditions for realizing the "desired performance" of the objective lens for the optical pickup.

The objective lens for an optical pickup used as an infinite system lens is a positive lens for condensing a parallel light flux incident from the light source side. The objective lens for an optical pickup of the present invention has a single lens structure and both surfaces are aspherical. From a certain point of view, a biconvex lens or a meniscus lens can be used as the lens form, but the biconvex lens can reduce the curvature on the light source side, and therefore the biconvex lens is preferable from the viewpoint of manufacturing feasibility.

A light spot having a desired wavelength is formed on a recording surface through a light source having a predetermined wavelength and a substrate having a predetermined thickness.
At the time of forming by, it is necessary to suppress the “upper limit of wavefront aberration allowed to form a good light spot” to 0.04λ (λ: wavelength) or less. This wavefront aberration: 0.04
λ includes wavefront deterioration due to manufacturing errors such as curvature radius deviation, thickness deviation, aspheric shape deviation, surface shift, and tilt of each surface of the first and second surfaces of the lens. Therefore, the upper limit of the wavefront deterioration amount due to each manufacturing error is about 0.015λ.

Further, FIG. 1 shows a lens material which is allowed to realize a wavefront aberration of 0.04λ or less in terms of the relationship between the refractive index: nd and the Abbe number: νd.
When the objective lens for the optical pickup is configured as a “biconvex lens with a surface having a strong curvature facing the light source side”, if the condition 2: 1.55 ≦ nd is not satisfied, the refractive index of the objective lens is too small, When realizing NA, the curvature of the lens surface on the light source side in particular must be increased, making it difficult to form the objective lens surface with high precision, and the cost of the objective lens also increases.

Further, the condition 1: Abbe number: νd: ν
If d ≦ 65 is not satisfied, chromatic aberration due to wavelength variation in the light source becomes too large. It is desirable that the conditions regarding the Abbe number: νd and the refractive index: nd are satisfied especially when the objective lens for the optical pickup is “a biconvex lens with a surface having a strong curvature facing the light source side”.

Further, in the case of being formed as "a biconvex lens having a convex surface with a strong curvature facing the light source side", if the above conditions 3 and 4 are not satisfied, the required numerical aperture is realized and the wavefront aberration: It cannot realize 0.04λ or less.

Paraxial radius of curvature of the above conditions 3 and 4: R1,
Consider the center thickness of the lens: t and the refractive index: nd. Assuming that the light source side surface of the objective lens for the optical pickup is “convex toward the light source side”, increasing the paraxial radius of curvature R1 means reducing the positive refracting power on this surface. In the present invention, the NA of the objective lens for the optical pickup is
However, in order to increase NA, the positive refractive power of the lens must be increased. Therefore, if the paraxial radius of curvature R1 is increased and the NA is increased as described above, the refractive index of the lens material must be increased, and "the refractive index of the lens material: nd is the paraxial curvature Radius: Increases as R1 increases.

On the other hand, when the central thickness t of the lens is increased, the area where the light passes through the surface on the recording medium side is reduced. In the present invention, the object is to increase the NA of the objective lens for the optical pickup, but in order to increase the NA, the positive refractive power of the lens must be increased. Therefore, if the center thickness of the lens: t is increased and the NA is increased as described above, the refractive index of the lens material must be increased, and "the refractive index of the lens material: nd is Central wall thickness: increases as t increases.

Under the condition that the above-mentioned "wavefront aberration: 0.04λ or less" can be achieved, the relationship that the paraxial radius of curvature R1 and the refractive index: nd are satisfied is that "a surface with a strong curvature is on the light source side. Focal length of objective lens for optical pickup formed as "biconvex lens facing toward": f = 1.765 mm, N
Taking A: 0.85 as an example, the result is as shown by a black circle (●) in FIG. Similarly, f = 2.235
mm and NA: 0.85 taken as an example
It becomes like a triangle (Δ) in (a). That is, it falls within the range on the straight line 2a-1 and the straight line 2a-2. Since the refractive index of the material depends on the Abbe number: νd in addition to the refractive index of the d-line: nd, the relationship between R1 and nd cannot be determined to be the highest, but the range between the straight line 2a-1 and the straight line 2a-2 By satisfying the condition 3 of R1 and nd determined by and satisfying νd defined by the condition 1, “wavefront aberration: 0.04λ or less” can be achieved.

Similarly, under the condition that "wavefront aberration: 0.04λ or less" can be achieved, the central wall thickness: t and the refractive index:
nd is satisfied, the focal length of the objective lens for an optical pickup formed as “a biconvex lens with a surface having a strong curvature facing the light source side”: f = 1.765 mm, NA: 0.
If 85 is taken as an example and viewed, it becomes like a black circle (●) in FIG. Similarly, f = 2.235 mm, N
When A: 0.85 is taken as an example, the triangle (Δ) in FIG. 2B is obtained. That is, the straight line 2b-1
And within the range on the straight line 2b-2. The refractive index of the material is d
Since the refractive index of the line: nd depends on the Abbe number: νd, the relationship between R1 and nd cannot be determined to be the highest, but the straight line 2
By satisfying the condition 4 of R1 and nd defined in the range of b-1 and the straight line 2b-2 and satisfying vd defined in the condition 1, "wavefront aberration: 0.04λ or less" can be achieved.

Next, the objective lens for the optical pickup of the present invention secures the working distance: WD necessary for improving the reliability of the optical pickup. The working distance: WD can be increased by increasing the back focus. For that purpose, the refractive index of the objective lens for the optical pickup can be decreased to reduce the refractive power, but this leads to a decrease in NA. Therefore, in order to secure the required working distance: WD while securing the required NA, the NA and nd must be balanced.

The working distance: WD and the refractive index of the lens material which are allowed under the condition that NA: 0.85 can be realized and the wavefront aberration is suppressed to 0.04λ or less.
The relationship with nd is investigated under the condition that the focal length of the objective lens for the optical pickup formed as “a biconvex lens having a surface with a strong curvature facing the light source side”: f = 1.765 mm, NA: 0.85. When viewed, it looks like a black circle (●) in FIG. Similarly, when it is obtained and viewed under f = 2.235 mm and NA: 0.85, it becomes like a triangle (Δ) in FIG. That is, it falls within the range on the straight line 2c-1 and the straight line 2c-2. Refractive index of material is d-line refractive index: nd
Besides, since it depends on the Abbe number: νd, the relation between WD and nd cannot be determined to be the highest, but the straight line 2c-1 and the straight line 2c
-By satisfying condition 5 of WD and nd defined in the range above -2 and satisfying vd defined in condition 1, a wavefront aberration of 0.04λ or less can be achieved. From the viewpoint of the working distance and the weight of the objective lens, the effective diameter of the light source side surface of the objective lens is appropriately in the range of φ3 mm to φ4 mm.

If the above conditions 3 to 5 are not satisfied, even if the aspherical shape of the lens surface on the light source side or the optical recording medium side is adjusted, N
When A: 0.85, the wavefront aberration cannot reach 0.04λ or less.

In this way, by satisfying the above conditions 1 and 2, it is possible to realize an objective lens for an optical pickup having a numerical aperture in a required range and a wavefront aberration of 0.04λ or less. Further, by satisfying the conditions 3 to 5, the feasibility in manufacturing can be further improved.

As the first embodiment of the present invention, two concrete examples of the objective lens for the optical pickup will be given. Here, in order to avoid complication, components having equivalent functions corresponding to the respective constituent members shown in FIGS. 3 (a) and 4 (a) are designated by the same reference numerals, 1 is a wavelength selection aperture, and 2 is a wavelength selection aperture.
Is an objective lens for an optical pickup, and 3 is a light irradiation side substrate (thickness: 0.1 mm) of an optical recording medium. Light source side (not shown, but located on the left side of FIGS. 3A and 4A)
The laser beam from is as a “parallel beam” and the aperture of the wavelength selection aperture 1 (aperture diameter: φ = 3 mm, or 4 m
m), enters the objective lens 2, is converged by the objective lens 2 and is transmitted through the light irradiation side substrate 3 of the optical recording medium to the recording surface (on the right side surface of the light irradiation side substrate 3). Match)
To form a light spot.

Further, the aspherical shape of the lens surface has a coordinate in the optical axis direction: X, a coordinate in the direction orthogonal to the optical axis: Y, a paraxial radius of curvature:
R, conic constant: K, higher coefficient: A, B, C, D, E,
A well-known aspherical expression is expressed by (Equation 1) using F, ...

[0038]

## EQU1 ## X = (Y ² / R) / [1 + √ {1- (1 + K)
Y / R ² } + AY ⁴ + BY ⁶ + CY ⁸ + DY ¹⁰ + EY ¹² + F
Y ¹⁴ + GY ¹⁶ + HY ¹⁸ + JY ²⁰ + ... R, K, A, B, C, D ,.

First, the objective lens for the optical pickup according to the first embodiment has a working wavelength of 407 nm and an NA of 0.8.
5, f: 1.765 mm, nd: 1.69350, νd:
53.2, and (Table 1) shows specific data.

[0040]

[Table 1] The symbols in the table are as follows. "OBJ" means an object point (semiconductor laser as a light source), but the objective lens 2 for the optical pickup is an "infinite system", and the radius of curvature is RDY and the thickness is "INFINITY" of THI.
(Infinity) means that the light source is at infinity. Further, “STO” is the surface of the wavelength selection aperture 1, its radius of curvature: RDY is “INFINITY”, and thickness:
THI is set to "0" in design. Unless otherwise specified, the unit of the quantity having the dimension of length is “mm”.

"S1" means the light source side surface of the objective lens for the optical pickup, and "S2" means the optical recording medium side surface. The objective lens 2 in Example 1 has a wall thickness of 2.381463 m.
m, and the thickness 0.425496 mm described on the right side of the radius of curvature in the column of S2 is "working distance: W
D "is shown.

"S3" is a light source side surface of the light irradiation side substrate 3 of the optical recording medium, and "S4" is a surface corresponding to the recording surface. The distance between these surfaces S3 and S4, that is, the light irradiation side substrate thickness. Is 0.1 mm, nd: 1.516330, νd: 64.
It is 1. "EPD: entrance pupil diameter" represents the aperture diameter (3 mm) of the wavelength selection aperture 1, and "WL: wavelength" represents the used wavelength (407 nm).

In the display of the aspherical coefficient, for example, "D: 0.305477E-03" means "D =
0.305477 × 10 ⁻³ ”. The same applies to the display of each table below.

FIG. 3A shows an arrangement state of the wavelength selection aperture 1, the optical pickup objective lens 2, and the light irradiation side substrate 3 according to the first embodiment. 3B and 3C, astigmatism and spherical aberration of the optical pickup objective lens 2 of Example 1 (the ordinate scale is a value obtained by normalizing the entrance pupil radius to 1). Indicates. Both aberrations are corrected very well. The axial median wavefront aberration is 0.002.
It is 2λ.

Further, FIG. 3D shows the amount of aberration deterioration when the center thickness deviation of the lens occurs. The broken line indicates the wavelength used: 650 nm, NA: 0.75, f: 2.00 m
Corresponding to the amount of aberration deterioration due to the deviation of the center thickness in the conventional objective lens of m, nd: 1.69330, and vd: 53.17, the solid line shows the same amount of deterioration of the first embodiment. Compared with a conventional objective lens, even if there is a thickness deviation of about ± 1 μm, the wavefront deterioration is 0.006λ or less, which is in a range where manufacturing is sufficiently possible.

As described above, the objective lens of the first embodiment is
Approximate radius of curvature on light source side: R1 = 1.375595 mm, f
= 1.765 mm, nd = 1.69350, νd = 53.
2, WD = 0.425496 mm, so R
1, t, WD, f, nd, νd are the conditions 1 to 5 described above.
Within the range that satisfies.

Next, the objective lens for the optical pickup in the second embodiment is different from the first embodiment in the focal length: f, NA: 0.85, f = 2.353 mm, nd =
1.69350 and vd = 53.2. (Table 2)
Specific data is shown in accordance with (Table 1).

[0048]

[Table 2] FIG. 4A shows an arrangement state of the wavelength selection aperture 1, the optical pickup objective lens 2, and the light irradiation side substrate 3 according to the second embodiment. 4B and 4C, astigmatism and spherical aberration of the optical pickup objective lens 2 of Example 2 (the scale on the vertical axis is a value obtained by normalizing the entrance pupil radius to 1). Indicates. Both aberrations are corrected very well.
On the axis, the wavefront aberration of the median design value is 0.0043λ.

As described above, the objective lens of the second embodiment is
R1 = 1.8331 mm, f = 2.353 mm, nd =
1.69350, vd = 53.2, WD = 0.58845
Since it is 9 mm, R1, t, WD, f, nd, ν
d is within the range satisfying the above conditions 1 to 5 as in the first embodiment.

Subsequently, the wavelength used in the present invention: 407 nm ±
Light irradiation side substrate thickness at 10 nm, NA: 0.85 ± 0.05:
Conditions for realizing desired performance for conventional optical recording media such as DVDs and CDs by using an objective lens for 0.1 mm optical recording media optical pickups are as follows: Condition 6: -0.42nd + 0.4. 82 ≦ WD / f ≦ −0.42
nd + 0.95 Condition 7: −0.35 nd + 0.64 ≦ WD / f ≦ −0.35
nd + 0.72, and the meaning of condition 6 is the same as the meaning of condition 7.

In order to focus the light on the DVD type optical recording medium, "use wavelength: 660 nm ± 10 nm, NA 0.65
It is necessary to be an objective lens for an optical pickup capable of condensing on an optical recording medium with a light irradiation side substrate thickness of 0.6 mm at ± 0.05.

Similarly, in order to focus the light on the CD type optical recording medium, "use wavelength: 780 nm ± 10 nm, NA 0.5
It is necessary to be an objective lens for an optical pickup capable of condensing on an optical recording medium having a substrate thickness of light irradiation side of 0 ± 0.05 and 1.2 mm.

When the objective lens of the present invention is used as an infinite system objective lens under the above-mentioned wavelength and substrate thickness conditions of the DVD system and the CD system, the difference in substrate thickness (0.1 mm, 0.6 m).
m, 1.2 mm), wavelength difference (407 nm, 660 n
m, 780 nm) and spherical aberration occurs. In order to suppress the spherical aberration, it is possible to correct the incident light flux to the objective lens by diverging light when recording, reproducing or erasing on the DVD system or the CD system. That is, it is used as a finite objective lens when recording, reproducing and erasing on a DVD system or a CD system. Also,
Even if incident light is incident in a divergent state, a slight amount of spherical aberration remains, but this can be suppressed by disposing a coupling lens having a surface with a strong curvature on the objective lens side between the light source and the objective lens. Also, the difference in NA (0.85,
0.65, 0.50) can be solved by using an element whose aperture can be limited according to the wavelength used.

[Use wavelength: which satisfies the above conditions 1 to 5]
407 nm ± 10 nm, NA: 0.85 ± 0.05, and light irradiation side substrate thickness: 0.1 mm for optical recording medium optical pickup objective lens ”,“ working wavelength: 660 nm ± 10 nm,
NA: 0.65 ± 0.05, light irradiation side substrate thickness: 0.6 mm
As an objective lens for an optical pickup capable of condensing on an optical recording medium (DVD system), the working distance allowed under the condition that the spherical aberration caused by the difference in the substrate thickness and the used wavelength is minimized: Examining the relationship between WD and the refractive index of the lens material: nd, when the focal length is f = 1.8 to 1.9 mm, a black circle (●) in FIG. 5A is obtained. Similarly, f = 2.4 to 2.5
When mm and NA: 0.85 are taken as an example, see FIG.
It becomes like a triangle (Δ) in (a). That is, straight line 5
It falls within the range on a-1 and the straight line 5a-2. Since the refractive index of the material depends on the Abbe number: νd in addition to the d-line refractive index: nd, the relation between WD and nd cannot be determined to be the highest.
WD and nd determined in the range of the straight line 5a-1 and the straight line 5a-2
By satisfying the condition 6 of 4 and satisfying νd defined by the condition 1, spherical aberration caused by the difference in the substrate thickness and the used wavelength can be suppressed to the minimum.

Similarly, "working wavelength: 407 nm ± 10 nm, NA: 0.85 ± 0.05" satisfying the above conditions 1 to 5
"Light-irradiation side substrate thickness: 0.1 mm for optical recording medium optical pickup objective lens", "Working wavelength: 780 nm ± 10
nm, NA 0.50 ± 0.05, Light irradiation side Substrate thickness: 1.2
mm "optical pickup objective lens that can be focused on an optical recording medium" (CD system), with an acceptable working distance under conditions that minimize spherical aberration caused by differences in substrate thickness and wavelength used. When the relationship between WD and the refractive index of the lens material: nd is examined and seen, in the example of the focal length: f = 1.8 to 1.9 mm, a black circle (●) in FIG. 5B is obtained. Similarly, f = 2.4 to 2.5
Taking mm and NA: 0.85 as an example, the triangle (Δ) in FIG. 5B is obtained.

That is, it falls within the range on the straight line 5b-1 and the straight line 5b-2. Refractive index of material is d-line refractive index: nd
Besides, since it depends on the Abbe number: νd, the relationship between WD and nd cannot be determined to be the highest, but the straight line 5b-1 and the straight line 5b
-By satisfying the condition 7 of WD and nd defined in the above range and satisfying vd defined in the condition 1, spherical aberration caused by the difference in the substrate thickness and the used wavelength is minimized. it can.

In this way, by satisfying the above-mentioned condition 6 or condition 7, the "working wavelength: 407 nm ±
Light irradiation side substrate thickness at 10 nm, NA: 0.85 ± 0.05:
"Infinite optical pickup for recording, reproducing and / or erasing information on a 0.1 mm optical recording medium", recording, reproducing and erasing conventional optical recording media such as DVDs or CDs. It is possible to realize an optical pickup capable of realizing at least any one of the above.

In the second embodiment, recording, reproduction and erasing are performed on a large capacity optical recording medium having a used wavelength of 407 nm and an NA of 0.85 and a conventional optical recording medium such as a DVD system or a CD system. Two concrete examples of the so-called compatible objective lens for a compatible optical pickup will be given below. 6 (a) and 7 (a), as in FIGS. 3 (a) and 4 (a) of the first embodiment, they have the same functions and corresponding functions. Reference numerals are given, 1 is a wavelength selection aperture, 2 is an objective lens, 3 is a light irradiation side substrate (thickness is 0.6 mm for DVD system, 1.2 m for CD system)
m), 4 is a light source, and 5 is a coupling lens having a concave shape.

The light emitted from the light source 4 passes through the coupling lens 5 and passes through the aperture (aperture diameter: φ = 3.24570 mm) of the wavelength selection aperture 1 as a “divergent light beam” and enters the objective lens 2. The objective lens 2 forms a condensed light beam, which is transmitted through the light irradiation side substrate 3 of the optical recording medium to form a light spot on the recording surface (matching the right side surface of the light irradiation side substrate 3).

Further, the aspherical shape of the lens surface has a coordinate in the optical axis direction: X, a coordinate in the direction orthogonal to the optical axis: Y, a paraxial radius of curvature:
R, conic constant: K, higher coefficient: A, B, C, D, E,
A well-known aspherical expression is expressed by (Equation 2) using F, ...

[0061]

## EQU2 ## X = (Y ² / R) / [1 + √ {1- (1 + K)
Y / R ² } + AY ⁴ + BY ⁶ + CY ⁸ + DY ¹⁰ + EY ¹² + F
Y ¹⁴ + GY ¹⁶ + HY ¹⁸ + JY ²⁰ + ... R, K, A, B, C, D ,.

As Example 3, a case where the objective lens 2 in Example 1 of the first embodiment is used in a DVD system will be described. The objective lens for this optical pickup is used wavelength: 660 nm, NA: 0.65, f: 2.
4230 mm, nd: 1.51680, νd: 64.2
And (Table 3) shows specific data.

[0063]

[Table 3] The symbols in the table are as follows. “OBJ” means an object point (semiconductor laser as a light source), the objective lens 2 is used as a “finite system” in a DVD system, RDY means a radius of curvature, and THI means a thickness. Further, “STO” is the surface of the wavelength selection aperture 1, its radius of curvature is “INFINITY”, and its thickness is “0” in design. Also, unless otherwise specified, the unit of the quantity having the dimension of length is “mm”.

“S2” means the light source side surface of the coupling lens 5, and “S3” means the optical recording medium side surface. In addition, "S
“5” means the light source side surface of the objective lens 2, and “S7” means the optical recording medium side surface.

The thickness of the objective lens 2 in the third embodiment is 3.174078 mm, and the thickness of 0.501457 mm described on the right side of the radius of curvature in the column of "S6" indicates "working distance: WD".

"S7" is a light source side surface of the light irradiation side substrate 3 of the optical recording medium, and "S8" is a surface corresponding to the same recording surface. The distance between these surfaces S7 and S8, that is, the light irradiation side substrate thickness. Is 0.6 mm, nd: 1.516330, νd: 64.1.
Is. "EPD: Entrance pupil diameter" is the wavelength selection aperture 1
Represents the opening diameter (3.24570 mm), and "WL: wavelength" represents the used wavelength (660 nm).

FIG. 6A shows the arrangement of the wavelength selection aperture 1, the objective lens 2 for the optical pickup, the light irradiation side substrate 3, the coupling lens 5, and the light source 4 according to the third embodiment. In addition, in FIG. 6B, the objective lens 2 described in Example 1 is used with a wavelength of 660 nm and a substrate thickness of 0.6 m.
As for the relationship between the optical system configuration and the wavefront aberration when the light is focused as m, NA: 0.65, is incident on an infinite system state, is incident on a finite state, and is coupled via a coupling lens. Shows the wavefront aberration performance when the light is made incident in a finite system state. In the form of Example 3 shown in FIG. 6A, the aberration is corrected extremely well.

As described above, the objective lens 2 of Example 3
Is nd: 1.69350, νd: 53.2, f: 2.4
Since it is 299 mm and WD: 0.501457 mm,
The WD, f, nd, and νd are within a range that satisfies the above-mentioned conditions 1, condition 2, and condition 6.

As Example 4 of the second embodiment, the objective lens for the optical pickup has a CD wavelength of 7:
80 nm, and (Table 4) shows specific data (Table 3).
It is shown after.

[0070]

[Table 4] FIG. 7A shows the wavelength selection aperture 1 according to the fourth embodiment, the optical pickup objective lens 2, the light irradiation side substrate 3,
The arrangement state of the coupling lens 5 and the light source 4 is shown. Moreover, in FIG. 7B, the objective lens 2 described in the first embodiment is used.
, Wavelength used: 780 nm, substrate thickness: 1.2 mm, N
A: The relationship between the optical system configuration and the wavefront aberration when condensed as 0.50 is:
Shows the wavefront aberration performance in the case of incident in the finite system state, and in the case of incident in the finite system state via the coupling lens. In the form of the fourth embodiment shown in FIG.
Aberrations are very well corrected.

As described above, the objective lens 2 of Example 4
Are nd: 1.69350, νd: 53.2, f: 2.
Since it is 4445 mm and WD: 0.236004 mm, the WD, f, nd, and νd are within the range satisfying the conditions 1, 2 and 7.

Furthermore, the third and fourth embodiments can be realized at the same time.

FIG. 8 is a block diagram showing a schematic structure of an optical pickup according to the third embodiment of the present invention. The third embodiment uses the objective lens described in Examples 1 and 2 of the first embodiment.

The essential parts of the optical pickup shown in FIG. 8 are a semiconductor laser 101, a collimator lens 102, a polarization beam splitter 103, a deflection prism 104, and a quarter wavelength plate 1.
05, an objective lens 106 for an optical pickup, a detection lens 108, and a light receiving element 109.

The laser beam emitted from the semiconductor laser 101 is converted into a substantially parallel beam by the collimator lens 102, transmitted through the polarization beam splitter 103, the optical path is bent 90 degrees by the deflecting prism 104, and passes through the objective lens 106. Then, the light is converted into a condensed light flux, is irradiated onto the optical recording medium 107 (light irradiation side substrate thickness: 0.1 mm), and is transmitted through the light irradiation side substrate to form a light spot on the recording surface.

A quarter wavelength plate 105 is arranged in front of the objective lens 106, and converts linearly polarized light from the light source side into circularly polarized light. The light beam reflected by the optical recording medium 107 becomes a “return light beam”, travels backward in the optical path at the time of irradiation, and enters the polarization beam splitter 103 through the objective lens 106, the quarter-wave plate 105, and the deflection prism 104. To do.

The return light beam incident on the quarter-wave plate 105 is circularly polarized light in the opposite direction to the outward path, and when transmitted through the quarter-wave plate 105, it becomes linearly polarized light which is orthogonal to the polarization direction of the outward path and is polarized. It is reflected by the beam splitter 103.
The return light flux reflected by the polarization beam splitter 103 is
The light enters the light receiving element 109 via the detection lens 108.

The light receiving element 109 has a light receiving surface appropriately divided according to the method of generating a servo signal. A tracking signal / focusing signal is generated based on the photoelectric output from each light receiving surface, and a reproduction signal is generated together with these signals when reproducing information. Further, these signals are output to a control circuit (not shown).

FIG. 9A is a block diagram showing a schematic structure of the optical pickup according to the fourth embodiment of the present invention.
Here, components having equivalent functions corresponding to those of the constituent members described in FIG. 8 showing the third embodiment are designated by the same reference numerals and shown, and the same applies to each of the following drawings.

The fourth embodiment uses the objective lens described in Examples 3 and 4 of the second embodiment. The optical pickup shown in FIG. 9A has a usable wavelength: 407n.
It is possible to record, reproduce, or erase both a large-capacity optical recording medium of m, NA: 0.85, and a DVD type optical recording medium of working wavelength: 660 nm, NA: 0.65.

First, used wavelength: 407 nm, NA: 0.
A case of recording, reproducing, or erasing on the 85 high-capacity optical recording medium will be described. In FIG. 9A, 101 is a semiconductor laser having a wavelength of 407 nm, which is a light source. The linearly polarized divergent light emitted from the semiconductor laser (light source) 101 is made into substantially parallel light by a collimator lens 102, and a polarization beam splitter is used. 103 and the dichroic prism 203, and the deflection prism 104 changes the optical path to 90 degrees.
Is deflected, passes through the quarter-wave plate 105, becomes circularly polarized light, passes through the wavelength selection aperture 204, and the objective lens 1
It is incident on 06 and is condensed as a minute spot on the optical recording medium 107. Information is recorded, reproduced, or erased by this spot.

The light reflected from the optical recording medium 107 passes through the objective lens 106 and the quarter-wave plate 105 to become circularly polarized light in the opposite direction to the outward path, again becomes substantially parallel light and becomes linearly polarized light orthogonal to the outward path. Then, the light is reflected by the polarization beam splitter 103, converged by the detection lens 108, and reaches the light receiving element 109. An information signal and a servo signal are detected from the light receiving element 109.

Next, used wavelength: 660 nm, NA: 0.
The case of recording, reproducing, or erasing on the 65 DVD optical recording medium will be described. 2. Description of the Related Art In recent years, a hologram unit in which a light emitting / receiving element is installed in one can (container) and a light beam is separated using a hologram has been generally used for a DVD optical pickup.

In FIG. 9C, reference numeral 201 denotes a hologram unit formed by integrating the chip of the semiconductor laser 201a, the hologram 201b, and the light receiving element 201c. The divergent light having a wavelength of 660 nm emitted from the semiconductor laser 201a of the hologram unit 201 passes through the hologram 201b and is coupled by the coupling lens 202 as shown in FIG. 9 (a).
Deflection prism 1 by dichroic prism 203
04, the light path is deflected by 90 degrees by the deflection prism 104, passes through the quarter-wave plate 105 to be circularly polarized light, passes through the wavelength selection aperture 204, enters the objective lens 106, and is optically recorded. It is condensed as a minute spot on the medium 107. Information is reproduced, recorded, or erased by this spot.

In particular, the wavelength selection aperture 204 limits the passing light flux so that the light having the used wavelength: 660 becomes NA: 0.65. That is, as shown in FIG. 9B, the wavelength selection aperture 204 is a concentric aperture limiting means and does not act on light with a wavelength of 407 nm, and light with a wavelength of 660 nm satisfies NA: 0.65. Only the central part for transmitting is transmitted.

The light reflected from the optical recording medium 107 is deflected by the deflection prism 104, reflected by the dichroic prism 203, made into convergent light by the coupling lens 202, and converted into a semiconductor laser by the hologram 201b shown in FIG. 9C. Light receiving element 2 in the same can as 201a
The light is diffracted in the 01c direction and is received. Light receiving element 201c
From, an information signal and a servo signal are detected.

FIG. 10A is a block diagram showing a schematic structure of the optical pickup according to the fifth embodiment of the present invention. In the fifth embodiment, used wavelength: 407 nm, NA:
Large-capacity optical recording medium of 0.85 and used wavelength: 660n
This is an optical pickup capable of recording, reproducing, or erasing both a DVD-based optical recording medium with m, NA: 0.65 and a CD-based optical recording medium with a working wavelength: 780 nm, NA: 0.50.

The difference from the third embodiment is that two semiconductor lasers 201 having different wavelengths, DVD and CD, are used.
a, 301a chip, and a light receiving element 201c for receiving reflected light from each of the DVD and CD optical recording media.
Two light receiving elements 301c and light receiving elements 201c and 301c for reflecting light from the DVD and CD optical recording media.
A hologram unit 301 composed of a hologram 301b for focusing on each of the above, and a DVD system and a CD system as shown in FIG.
Wavelength: 660 nm, wavelength:
This is the point that the wavelength selection aperture 304 for limiting the light of 780 nm is used, and the passing optical path and the like are the same as those in the fourth embodiment.

FIG. 11 is a block diagram showing a schematic structure of the optical pickup according to the sixth embodiment of the present invention. The difference between the sixth embodiment and the third to fifth embodiments is that a correction unit 401 for correcting even-order aberration components caused by manufacturing tolerances of the objective lens is provided.

Manufacturing errors of a glass mold lens having aspherical surfaces on both sides include paraxial curvature radius deviation of each surface, aspherical surface shape deviation of each surface, thickness deviation, material variation, shift between surfaces, shift between surfaces. Tilt can be mentioned. Among these, the paraxial radius of curvature deviation, thickness deviation, and material variation of each surface are factors that cause even-order aberrations. If there are even-order aberrations, the shape of the light spot formed on the recording surface deteriorates.

The optical pickup having the even-order aberration detecting means and the even-order aberration correcting means of the sixth embodiment is shown in FIG.
As shown in FIG. 5, the semiconductor laser 101 has an emission wavelength of 407 nm ± 10 nm, and the objective lens 106 is any one of the objective lenses described in Examples 1 and 2 of the first embodiment. To be

In FIG. 11, 401 is an even-order aberration correction means, 402 is an even-order aberration detection means for detecting a lens manufacturing error, and the aberration detection means 402 is a simplified illustration of the actual configuration. .

Now, if there is a lens manufacturing error, even-order aberrations occur and the shape of the light spot formed on the recording surface deteriorates. The aberration thus generated distorts the wavefront of the returning light beam, and thus the light beam traveling toward the light receiving element 109 via the detection lens 108 also has aberration.

FIG. 12A shows this state. When even-order aberrations are generated in the return light flux that enters the detection lens 108 from the left side, with respect to the reference wavefront of the return light flux,
There is a "wavefront delay" in the optical axis symmetry, and the position where the delayed wavefront is focused with respect to the focusing point when the reference wavefront is focused is defocused. Therefore, the "state of occurrence of wavefront aberration" can be known by extracting the difference between the delayed wavefront and the advanced wavefront to detect the focus state.

For example, the aberration detecting means 402 shown in FIG.
As an element for shifting the timing by an optical path separating means such as a hologram or a beam splitter, or a liquid crystal shutter, and an area A and an area B as shown in FIG.
Using the light receiving element 109 whose light receiving area is divided as
By examining the received light output of each of the areas A and B, it is possible to detect even-order aberrations in the return light flux.

Since the even-order aberrations detected by the aberration detecting means 402 are caused by the manufacturing error of the lens, the detected aberration and the lens manufacturing error have a correlation with each other. The lens manufacturing error can be known by detecting the aberration of the returning light flux as described above. By correcting even-order aberrations based on this lens manufacturing error, it becomes possible to form an appropriate light spot on the recording surface. In the sixth embodiment, the detected aberration is given as an “aberration signal” obtained by appropriately combining photoelectric output signals from the respective areas A and B of the light receiving element 109.

Further, the aberration correcting means 401 in the sixth embodiment is composed of two lenses and a distance adjusting means (not shown) for adjusting the distance between these lenses. One of the two lenses is a positive lens and the other is a negative lens. In the example shown in FIG. 11, the negative lens is arranged on the light source side, but the positive lens may be arranged on the light source side.

When the distance between the positive and negative lenses constituting the aberration correction means 401 is changed, even-order aberrations occur in the light beam passing through the aberration correction means 401 toward the objective lens 106 side. It suffices to cancel even-order aberrations that occur due to manufacturing errors of the objective lens 106.

It is assumed that the wavefront aberration which gives an even-order aberration generated by the manufacturing error of the objective lens 106 detected by the aberration detecting means 402 is as shown in FIG. 12C, for example. FIG. 12D shows the wavefront aberration as a two-dimensional curve. With respect to such a wavefront aberration, when the distance between the positive and negative lenses in the light beam entering the objective lens 106 from the light source side is changed to change the divergence state of the incident light to the objective lens, FIG. Such a wavefront aberration is obtained as the corrected wavefront aberration, and is significantly smaller than the original wavefront aberration.

Further, as a concrete correction reference, the above-mentioned "aberration signal" when the objective lens 106 has a substantially designed center value and no aberration occurs with the distance between the two lenses in the aberration correction means 401 as a reference value. When the objective lens 106 actually used is assembled and an aberration occurs, the distance between the lenses may be adjusted so that the aberration signal becomes zero.

Note that one or both of the positive lens and the negative lens which compose the aberration correction means 401 may be composed of a plurality of lenses.

FIG. 13A is a block diagram showing a schematic structure of the optical pickup in the seventh embodiment of the present invention. The seventh embodiment differs from the sixth embodiment in that
This is that the even-order aberration correction means 401 is an even-order aberration correction means 501 including a liquid crystal element and a voltage control means (not shown) for driving the liquid crystal element.

The liquid crystal element, as shown in FIG.
At least one transparent electrode is divided into concentric circles, and it is configured so that a voltage can be independently applied between the electrode part of each concentric circle band and the common electrode.By controlling this voltage, the liquid crystal of each electrode part is controlled. Refractive index of: n can be freely changed from n1 to n2.

When the refractive index: n is changed, the optical path difference of the light passing through each region: Δn · d (Δn is the refractive index change, d
Is the cell thickness of the liquid crystal), that is, the wavelength is λ and the phase difference is Δn · d (2π / λ).

It is assumed that the wavefront aberration which gives an even-order aberration generated by the manufacturing error of the objective lens 106 detected by the aberration detecting means 502 is as shown in FIG. 12C, for example. The wavefront aberration is shown as a two-dimensional curve by the solid line in the upper part of FIG.

In response to such wavefront aberration, the objective lens 1
When the voltage applied to each concentric band electrode of the liquid crystal element is adjusted so that the phase difference shown by the broken line in the lower part of FIG. The "wavefront aberration" can be canceled by the delay of the wavefront at each part of the light flux that is generated. FIG. 14B shows the sum of the solid line (wavefront aberration) and the broken line (wavefront delay due to the liquid crystal element) in FIG. 14A, that is, the corrected wavefront aberration. It is much smaller than the original wavefront aberration (upper part of FIG. 14A).

The wavelength used is 407 nm ± 10 nm,
As a problem of an optical pickup that records, reproduces, or erases on an optical recording medium with NA: 0.85, there is the occurrence of spherical aberration due to the deviation of the substrate thickness of the optical recording medium. That is, the spherical aberration accompanying the deviation of the substrate thickness increases in proportion to the fourth power of NA and the first power of the wavelength, but the manufacturing error of the substrate thickness is ± 10 μm.
Since m is unacceptable for an optical pickup, it is necessary to correct the aberration associated with the thickness deviation of the optical recording medium. As means for correcting such substrate thickness deviation, Japanese Patent No.
502884, JP 2000-131603, JP 3067665, and JP 9-1287.
No. 85, etc. are known, and even-order aberrations due to the lens manufacturing error are corrected by sharing with a conventionally known spherical aberration correcting means for correcting a substrate thickness error. It is also possible.

Further, the aberration correction means 401 and 501 in the sixth and seventh embodiments have been described by taking as an example the configuration in which the aberration detection signal is generated and fed back on the light receiving element, but the invention is not limited to this. It is also possible to adopt a configuration in which the reference position of the aberration correction means is adjusted while observing the transmitted light of the objective lens at the time of assembly.

Further, the timing of correcting the aberration caused by the lens manufacturing error may be performed when the power is turned on, or when the optical recording medium is attached, the aberration may be corrected together with the spherical aberration caused by the thickness deviation of the optical recording medium. Alternatively, it may be performed at any time during the recording, reproducing and erasing operations of the optical recording medium.

Aberration correction means is used at a wavelength of 407.
nm ± 10 nm, NA: record 0.85 optical recording medium,
The optical pickup is not limited to the optical pickup for reproducing or erasing, and may be arranged in the optical path on the way of the optical pickup for compatibility with the DVD system and the CD system shown in FIGS. 9A and 10A. good.

FIG. 15 is a block diagram showing a schematic structure of the optical pickup according to the eighth embodiment of the present invention. The difference between the eighth embodiment and the third to fifth embodiments is that
The point is that a correction unit 601 for correcting an odd-order aberration component generated due to the manufacturing tolerance of the objective lens is provided.

Manufacturing errors of a glass mold lens having aspherical surfaces on both sides include paraxial curvature radius deviation of each surface, aspherical surface shape deviation of each surface, thickness deviation, material variation, shift between surfaces, shift between surfaces. Tilt can be mentioned. Among these, the shift and tilt between the respective surfaces are factors that generate odd-order aberrations. Odd-order aberrations deteriorate the shape of the light spot formed on the recording surface.

The optical pickup having the odd-order aberration detecting means and the odd-order aberration correcting means of the eighth embodiment is shown in FIG.
As shown in FIG. 5, the semiconductor laser 101 has an emission wavelength of 407 nm ± 10 nm, and the objective lens 106 is any one of the objective lenses described in Examples 1 and 2 of the first embodiment. To be

In FIG. 15, 601 is an odd-order aberration correction means, 602 is an odd-order aberration detection means for detecting a lens manufacturing error, and the aberration detection means 602 is a simplified illustration of the actual configuration. .

Now, if there is a lens manufacturing error, odd-order aberrations occur and the shape of the light spot formed on the recording surface deteriorates. The aberration thus generated distorts the wavefront of the returning light beam, and thus the light beam traveling toward the light receiving element 109 via the detection lens 108 also has aberration.

FIG. 16A shows this state, and when an odd-order aberration is generated in the return light flux which enters the detection lens 108 from the left side, with respect to the reference wavefront of the return light flux,
The optical axis has a "wavefront delay" antisymmetrically, and an unbalanced side lobe is formed at the position where the delayed wavefront is focused with respect to the focusing point when the reference wavefront is focused. Therefore, the "state of occurrence of wavefront aberration" can be known by extracting the difference between the delayed wavefront and the advanced wavefront to detect the focus state.

For example, the aberration detecting means 602 shown in FIG.
As an optical path separation means such as a hologram or a beam splitter, or an element for shifting the timing by a liquid crystal shutter or the like, as shown in FIG.
Using the light receiving element 109 whose light receiving area is divided as
By examining the received light output of each of the areas A and B, it is possible to detect the aberration in the return light flux.

Since the odd-order aberrations detected by the aberration detecting means 502 are originally caused by the lens manufacturing error, the detected aberration and the lens manufacturing error have a correspondence relationship with each other. The lens manufacturing error can be known by detecting the aberration of the returning light flux as described above. By correcting the odd-order aberrations based on this lens manufacturing error, it becomes possible to form an appropriate light spot on the recording surface. In the eighth embodiment, the detected aberration is given as an “aberration signal” obtained by appropriately combining photoelectric output signals from the respective areas A and B of the light receiving element 109.

Aberration correcting means 601 in the eighth embodiment shown in FIG. 15 uses an optical axis of the objective lens by using a four-axis actuator capable of tilt control around two axes in addition to the two-direction control of the objective lens for focus / tracking. Is composed of an objective lens tilt adjusting means for adjusting the tilt from the optical axis of the optical system.

When the tilt of the objective lens is changed by the four-axis actuator constituting the aberration correction means 601, odd-order aberrations are generated in the light beam passing through the aberration correction means 601 toward the objective lens 106 side. It suffices to cancel the odd-order aberrations caused by the manufacturing error of the objective lens due to the aberrations.

It is assumed that the wavefront aberration which gives an odd-order aberration generated by the manufacturing error of the objective lens 106 detected by the aberration detecting means 602 is as shown in FIG. 16C, for example. FIG. 16D shows the wavefront aberration as a two-dimensional curve.

For such wavefront aberration, the objective lens 1
When the inclination of the objective lens is changed with respect to the light beam incident on the light source side in 06, the wavefront aberration as shown in FIG. 16E is obtained as the corrected wavefront aberration. It is much smaller than the original wavefront aberration.

Further, as a concrete correction reference, the "aberration signal" is set to 0 when the inclination of the objective lens in the aberration correction means 601 is used as a reference value and the aberration does not occur at a substantially designed median value. If the objective lens actually used is assembled and an aberration occurs, the inclination of the objective lens may be adjusted so that the aberration signal becomes zero.

The aberration correcting means is not limited to the four axes, but may be a three-axis actuator for controlling only focus, track, and tilt in the one-axis direction. In this case, the correction capability is lower than that of the four axes. Needless to say.

FIG. 17A is a block diagram showing a schematic structure of the optical pickup in the ninth embodiment of the present invention. The ninth embodiment differs from the eighth embodiment in that
The odd-order aberration correction means 601 is an odd-order aberration correction means 701 composed of a liquid crystal element and a voltage control means (not shown) for driving the liquid crystal element.

The liquid crystal element, as shown in FIG.
At least one of the transparent electrodes 31 to 38 is horizontally and vertically symmetrically divided so that a voltage can be independently applied between each electrode portion and the common electrode. By controlling this voltage, each electrode portion is controlled. Refractive index of liquid crystal: n from n1 to n
You can change up to 2.

When the refractive index: n is changed, the optical path difference of the light beam passing through each region: Δn · d (Δn is the change in the refractive index, d
Is the cell thickness of the liquid crystal), that is, the wavelength is λ and the phase difference is Δn · d (2π / λ).

It is assumed that the wavefront aberration which gives an odd-order aberration generated by the manufacturing error of the objective lens 106 detected by the aberration detecting means 702 is as shown in FIG. 16C, for example. A solid line in FIG. 18A shows this wavefront aberration as a two-dimensional curve.

For such wavefront aberration, the objective lens 1
When the voltage applied to each electrode of the liquid crystal element is adjusted so that the phase difference shown by the wavy line in FIG. The "wavefront aberration" can be canceled by the delay of the wavefront. FIG. 18B is a solid line (wavefront aberration) and a broken line (wavefront delay due to the liquid crystal element) in FIG. 18A.
, The wavefront aberration after correction is shown. It is much smaller than the original wavefront aberration (the solid line portion in FIG. 18A).

A problem of the optical pickup is the occurrence of coma aberration due to the tilt shift of the optical recording medium. That is, it is necessary to allow for a tilt of about ± 1 degree when the substrate is operating, but this is not acceptable as an optical pickup, so it is necessary to correct coma aberration due to tilt of the optical recording medium. As means for correcting such coma aberration due to tilt, Japanese Patent Laid-Open Nos. 10-91990 and 200 are known.
There are known ones such as 1-110075, Japanese Patent No. 3142251, and Japanese Patent Laid-Open No. 9-128785. Therefore, it is also possible to correct odd-order aberrations due to the lens manufacturing error by sharing the same with conventionally known recording medium tilt coma aberration correcting means.

Further, as the aberration correction means 601 and 701 in the eighth and ninth embodiments, the configuration in which the aberration detection signal is generated and fed back on the light receiving element has been described, but the present invention is not limited to this, and it is not limited to this. There is also a configuration in which the reference position of the aberration correction means is adjusted while observing the transmitted light of the objective lens during assembly.

Further, the timing of correcting the aberration caused by the lens manufacturing error may be performed when the power is turned on, or when the optical recording medium is attached, the aberration may be corrected together with the coma aberration caused by the tilt of the optical recording medium. Alternatively, it may be performed at any time during the recording, reproducing and erasing operations of the optical recording medium.

Aberration correction means is used at a wavelength of 407.
nm ± 10 nm, NA: record 0.85 optical recording medium,
The optical pickup is not limited to the optical pickup for reproducing or erasing, and may be arranged in the optical path on the way of the optical pickup for compatibility with the DVD system and the CD system shown in FIGS. 9A and 10A. good.

In particular, the coma aberration caused by the tilt of the substrate is N
It increases in proportion to the cube of A, the substrate thickness to the 1st power, and the wavelength to the -1th power, but it is not necessary for the CD generation and required for the DVD generation. "Use wavelength: 407 nm, substrate thickness: 0.1 m
Since the influence of coma aberration is smaller in the generation of m, NA: 0.85 ”than the generation of the DVD system, there is a high possibility that it will be unnecessary.

Therefore, as shown in FIG. 9A, the DVD
System generation, "using wavelength: 407 nm, substrate thickness: 0.1
mm, NA: 0.85 ”generation, the optical pickup device that records, reproduces, and erases together functions as a coma-aberration correction means associated with the tilt of the substrate during recording, reproducing, and erasing in the DVD system generation. Wavelength: 407n
m, substrate thickness: 0.1 mm, NA: 0.85 "generation recording / reproducing / erasing may be configured to function as means for correcting a lens manufacturing error.

FIG. 19 is a transparent perspective view showing a schematic structure of the optical information processing apparatus according to the tenth embodiment of the present invention.
The optical information processing device 10 is a device that records, reproduces, or erases information on or from the optical recording medium 20 by using the optical pickup 11. Embodiment 1
0, the optical recording medium 20 has a disk shape and is stored in the cartridge 21 of the protective case. The optical recording medium 20, together with the cartridge 21, is inserted and set in the optical information processing device 10 from the insertion port 12 in the direction of the "disk insertion", rotated by the spindle motor 13, and the optical pickup 11 records, reproduces, or erases information. Done.

The optical pickup 11 may be any one of claims 20 to 20.
The optical pickup described in 26 can be appropriately used,
The optical information processing device can satisfactorily record, reproduce, and erase information on the optical recording medium having the used wavelength.

[0138]

As described above, according to the present invention,
With a single lens structure, there are no problems such as an increase in the number of parts, an increase in weight, and an increase in the accuracy of assembly. The NA: 0.85 objective lens of the conventional one-lens structure does not achieve several μm.
The above thickness deviation makes it possible to realize an objective lens for an optical pickup with NA: 0.85 which is easy to manufacture with a glass mold material. An optical pickup using this can handle high-density information processing and can be used in DVD-type and It is possible to focus light on a conventional optical recording medium such as a CD system with aberration suppressed, and each optical recording medium can be compatible with one optical pickup. Further, it occurs due to a manufacturing error of an objective lens. Axisymmetric aberration, spherical aberration caused by substrate thickness error of optical recording medium, anti-axisymmetric aberration caused by manufacturing error of objective lens, coma caused by tilt of optical recording medium An optical pickup having a configuration in which a correction unit for suppressing aberrations and the like is shared and capable of reliable and excellent recording, reproduction, and erasing without increasing the number of parts, and an optical recording medium of each of the above-mentioned used wavelengths. It is possible to realize an objective lens for an optical pickup, an optical pickup, and an optical information processing device capable of satisfactorily recording, reproducing, and erasing information on the body.

[Brief description of drawings]

FIG. 1 shows a lens material having a refractive index of nd and an Abbe number of νd.
Diagram of the relationship with

2A is a paraxial radius of curvature and a refractive index, FIG. 2B is a center thickness and a refractive index of a lens, and FIG. 2C is a condition for achieving a working distance and a wavefront aberration of a refractive index of 0.04λ or less. Diagram showing the relationship in

FIG. 3 is a diagram illustrating an arrangement state of a wavelength selection aperture, an optical pickup objective lens, and a light irradiation side substrate of Example 1 in Embodiment 1 of the present invention, (b) is astigmatism, (c) is spherical aberration, and FIG. 3D is a diagram showing the amount of aberration deterioration when the center thickness deviation of the lens occurs.

FIG. 4 is an arrangement state of a wavelength selection aperture, an optical pickup objective lens, a light irradiation side substrate of Example 2 in Embodiment 1 of the present invention, (b) is astigmatism, (c) is spherical aberration, FIG. 3D is a diagram showing the amount of aberration deterioration when the center thickness deviation of the lens occurs.

FIG. 5A is a diagram showing a relationship between a working distance of a DVD type and a CD type of FIG. 5B and a refractive index of a lens material.

FIG. 6A is an arrangement state of a wavelength selection aperture, an optical pickup objective lens, a light irradiation side substrate, a coupling lens, and a light source of Example 3 in Embodiment 2 of the present invention, and FIG. 6B is a DVD system. Showing the relationship between the optical system configuration and the wavefront aberration of

FIG. 7 (a) is an arrangement state of a wavelength selection aperture, an optical pickup objective lens, a light irradiation side substrate, a coupling lens, and a light source of Example 4 in Embodiment 2 of the present invention, and (b) is a CD system. Showing the relationship between the optical system configuration and the wavefront aberration of

FIG. 8 is a block diagram showing a schematic configuration of an optical pickup according to a third embodiment of the present invention.

9A is a block diagram showing a schematic configuration of an optical pickup according to a fourth embodiment of the present invention, FIG. 9B is a wavelength selection aperture, and FIG. 9C is an enlarged view of a hologram unit.

10A is a block diagram showing a schematic configuration of an optical pickup according to a fifth embodiment of the present invention, and FIG. 10B is a diagram showing wavelength aperture restriction of a wavelength selection aperture.

FIG. 11 is a block diagram showing a schematic configuration of an optical pickup according to a sixth embodiment of the present invention.

FIG. 12A is an even-order aberration generated in a detection lens,
(B) is a divided area of the light receiving element, (c) is a three-dimensional curve of wavefront aberration, (d) is a two-dimensional curve of wavefront aberration, and (e) is a diagram showing a two-dimensional curve after correction.

13A is a block diagram showing a schematic configuration of an optical pickup according to a seventh embodiment of the present invention, and FIG. 13B is a diagram showing a transparent electrode of a liquid crystal element which is an aberration correcting unit.

14A is a diagram showing wavefront aberration before correction, and FIG. 14B is a diagram showing wavefront aberration after correction.

FIG. 15 is a block diagram showing a schematic configuration of an optical pickup according to an eighth embodiment of the present invention.

16A is an odd-order aberration generated in the detection lens, FIG.
(B) is a divided area of the light receiving element, (c) is a three-dimensional curve of wavefront aberration, (d) is a two-dimensional curve of wavefront aberration, and (e) is a diagram showing a two-dimensional curve after correction.

FIG. 17A is a block diagram showing a schematic configuration of an optical pickup according to a ninth embodiment of the present invention, and FIG. 17B is a diagram showing a transparent electrode of a liquid crystal element which is aberration correction means.

FIG. 18A is a diagram showing wavefront aberration before correction, and FIG. 18B is a diagram showing wavefront aberration after correction.

FIG. 19 is a transparent perspective view showing a schematic configuration of an optical information processing device according to a tenth embodiment of the present invention.

FIG. 20 is a diagram showing the relationship between the thickness tolerance and the wavefront aberration of the conventional objective lens.

[Explanation of symbols]

1,204,304 Wavelength selection aperture 2,106 Objective lens 3 substrates 4 light sources 5,202,302 Coupling lens 10 Information recording / reproducing apparatus 11 Optical pickup 12 insertion slot 13 Spindle motor 14 carriage 20,107 Optical recording medium 21 cartridges 22 shutter 31-38 transparent electrode 101, 201a, 301a Semiconductor laser 102 collimating lens 103 Polarizing beam splitter 104 deflection prism 105 1/4 wave plate 108 Detection lens 109, 201c, 301c Light receiving element 201,301 Hologram unit 201b, 301b hologram 203,303 Dichroic prism 401, 501 Even-order aberration correction means 402, 502 Even-order aberration detecting means 601 and 701 Odd-order aberration correction means 602, 702 Odd-order aberration detecting means

Continued front page    F term (reference) 2H087 KA13 PA01 PA17 PB01 QA02                       QA07 QA14 QA34 RA05 RA12                       RA13                 5D119 AA01 AA39 AA40 DA01 DA05                       DA07 EC04 JA44 JB01 JB02                       JB03 JB06                 5D789 AA01 AA39 AA40 DA01 DA05                       DA07 EC04 JA44 JB01 JB02                       JB03 JB06

Claims (26)

[Claims] 1. The wavelength of light used: 407 nm ± 10 nm, the numerical aperture: 0.85 ± 0.05, and the substrate thickness on the light irradiation side is 0.1 m.
An objective lens for an optical pickup used as an infinite lens for an optical pickup that performs at least one of recording, reproduction, and erasing of information on an optical recording medium of m. Also, it is a convex surface, the refractive index for the material of the d-line: nd and the Abbe number:
An objective lens for an optical pickup, wherein νd is an aspherical glass molded product satisfying the following two conditions νd ≦ 65 1.55 ≦ nd. 2. The objective lens for an optical pickup according to claim 1, wherein the lens center thickness: t, the paraxial radius of curvature of the light source side surface: R1, the working distance: WD, the refractive index of the material with respect to the d-line: nd, Focal length: f is the next 3
Condition 1.0nd-1.0≤R1 / f≤1.0nd-0.8 1.2nd-0.75≤t / f≤1.2nd-0.5-0.35nd + 0.77≤WD / f≤ -0.35nd +
An objective lens for an optical pickup, characterized by satisfying 0.85. 3. The objective lens for an optical pickup according to claim 1, wherein the refractive index for the material of the d-line is n.
d and working distance: WD satisfies the following condition −0.42nd + 0.82 ≦ WD / f ≦ −0.42nd +
It is an objective lens for an optical pickup which satisfies 0.95 and is used as a finite system lens, and has a working wavelength of 660 nm ± 10 nm and a numerical aperture of 0.65 ±.
An objective lens for an optical pickup, characterized in that at least one or more of recording, reproducing, and erasing information is performed on an optical recording medium having a substrate thickness of 0.6 mm on a light irradiation side: 0.6 mm. 4. The objective lens for an optical pickup according to claim 1, wherein the refractive index for the material of the d-line is n.
d and working distance: WD satisfies the following condition −0.35nd + 0.64 ≦ WD / f ≦ −0.35nd +
An objective lens for an optical pickup that satisfies 0.72 and is used as a finite system lens, with a working wavelength of 780 nm ± 10 nm and a numerical aperture of 0.50 ±
An objective lens for an optical pickup, characterized in that at least one of information recording, reproduction, and erasing is performed on an optical recording medium having a substrate thickness of 1.2 mm on a light irradiation side: 1.2 mm. 5. The objective lens for an optical pickup according to claim 1, wherein the refractive index of the material of the d-line is n.
d and working distance: WD is the following condition −0.42nd + 0.82 ≦ WD / f ≦ −0.42nd +
Depending on the objective lens for the optical pickup that satisfies 0.95 and is used as a finite lens, the wavelength used is: 660 nm ± 10 nm,
Numerical aperture: 0.65 ± 0.05, substrate thickness on light irradiation side: 0.
6 mm optical recording medium, and the following condition -0.35nd + 0.64≤WD / f≤-0.35nd +
Depending on the objective lens for the optical pickup that satisfies 0.72 and is used as a finite system lens, the wavelength used is: 780 nm ± 10 nm,
Numerical aperture: 0.50 ± 0.05, substrate thickness on light irradiation side: 1.
An objective lens for an optical pickup, wherein at least one of recording, reproducing, and erasing of information is performed on each of 2 mm optical recording media. 6. The objective lens for an optical pickup according to claim 3, further comprising aperture limiting means for switching a numerical aperture according to the wavelength used. 7. The optical pickup according to claim 3, wherein a lens having a surface having a strong curvature is used together on the objective lens side between the objective lens and the light source. Objective lens. 8. The light irradiation side substrate thickness: 0.1 m according to a working wavelength: 407 nm ± 10 nm and a numerical aperture: 0.85 ± 0.05.
An optical pickup for performing at least one of information recording, reproduction, and erasing on an optical recording medium of m, for converging a light flux from a light source as a light spot on the recording surface of the optical recording medium. The objective lens of claim 1,
Alternatively, an optical pickup using the objective lens for optical pickup described in 2. 9. The optical pickup according to claim 8, wherein the wavelength used is 660 nm ± 10 nm, and the numerical aperture is 0.6.
An optical pickup that records, reproduces, and / or erases information on / from an optical recording medium having a substrate thickness of 0.6 mm on the light irradiation side according to 5 ± 0.05. An optical pickup using the objective lens for an optical pickup according to claim 3, 5, 6 or 7 as an objective lens for converging a light spot on a recording surface of an optical recording medium. 10. The optical pickup according to claim 8, wherein the wavelength used is 780 nm ± 10 nm, and the numerical aperture is 0.5.
An optical pickup for recording / reproducing / erasing information on / from an optical recording medium having a substrate thickness of 1.2 mm according to 0 ± 0.05. An optical pickup using the objective lens for an optical pickup according to claim 4, 5 or 6 as an objective lens for converging a light spot on a recording surface of an optical recording medium. 11. The optical pickup according to claim 8, wherein the wavelength used is 660 nm ± 10 nm, and the numerical aperture is 0.6.
Optical recording medium with light irradiation side substrate thickness: 0.6 mm by 5 ± 0.05, and wavelength used: 780 nm ± 10 nm, numerical aperture: 0.50 ± 0.05, light irradiation side substrate thickness: 1.2 m
An optical pickup which records, reproduces and / or erases information with respect to an optical recording medium of m, and collects a light beam from a light source as a light spot on the recording surface of the optical recording medium. As an objective lens for
An optical pickup using the objective lens for an optical pickup according to any one of items 1 to 7. 12. The optical pickup according to claim 8, further comprising a first correction unit that corrects an even-order aberration component and a first detection unit that detects an even-order aberration component. An optical pick-up characterized by having it. 13. The correction means is arranged between the objective lens and a light source and changes the divergence state of the light incident on the objective lens.
The optical pickup described in 2. 14. The first correction means is arranged between the objective lens and the light source, and when the light flux is transmitted or reflected,
13. The optical pickup according to claim 12, wherein the optical pickup is a concentric circle correction means. 15. The aberration correcting means for correcting spherical aberration, wherein the first correcting means is an aberration correcting means.
15. The optical pickup according to any one of items 14 to 14. 16. The optical pickup according to any one of claims 8 to 11, wherein a second correction unit corrects an odd-order aberration component and a second detection unit detects the odd-order aberration component. An optical pickup characterized by having and. 17. The correction means is arranged between the objective lens and a light source, and the second correction means is a correction means for injecting the incident light of the objective lens at an angle with respect to the optical axis of the objective lens. The optical pickup according to claim 15. 18. The second correction means is arranged between the objective lens and the light source, and when the light flux is transmitted or reflected,
The optical pickup according to claim 15, wherein the optical pickup is a correction means that gives a phase difference level stepwise. 19. The aberration correcting means for correcting coma aberration, wherein the second correcting means is an aberration correcting means.
18. The optical pickup according to claim 17. 20. Light irradiation side substrate thickness: 0.1 according to working wavelength: 407 nm ± 10 nm and numerical aperture: 0.85 ± 0.05
mm optical recording medium, and wavelength used: 660 nm ± 10
nm, numerical aperture: 0.65 ± 0.05, at least one or more of information recording, reproducing, and erasing is performed using an optical pickup on an optical recording medium having a substrate thickness of 0.6 mm on the light irradiation side. An optical information processing device, wherein the optical pickup is used with a wavelength of 407 nm ± 10 n.
m, numerical aperture: 0.85 ± 0.05, light irradiation side substrate thickness: 0.
For an optical recording medium of 1 mm, the incident light flux incident on the objective lens is an infinite system, wavelength used: 660 nm ± 10 nm, numerical aperture:
An optical information processing apparatus characterized in that the light flux incident on the objective lens is a finite system with respect to an optical recording medium having a substrate thickness of 0.65 ± 0.05 and a light irradiation side substrate thickness of 0.6 mm. 21. The wavelength of light used: 407 nm ± 10 nm, and the numerical aperture: 0.85 ± 0.05.
mm optical recording medium, and wavelength used: 780 nm ± 10
nm, numerical aperture: 0.50 ± 0.05, at least one of information recording, reproduction, and erasing is performed using an optical pickup on an optical recording medium having a substrate thickness of 1.2 mm on the light irradiation side. An optical information processing device, wherein the optical pickup is used with a wavelength of 407 nm ± 10 n.
m, numerical aperture: 0.85 ± 0.05, light irradiation side substrate thickness: 0.
For an optical recording medium of 1 mm, the light flux incident on the objective lens is an infinite system, wavelength used: 780 nm ± 10 nm, numerical aperture:
An optical information processing apparatus, wherein the light flux incident on the objective lens is a finite system for an optical recording medium having a substrate thickness on the light irradiation side of 0.50 ± 0.05 and 1.2 mm. 22. The wavelength of light used: 407 nm ± 10 nm, and the numerical aperture: 0.85 ± 0.05.
mm optical recording medium, and wavelength used: 660 nm ± 10
nm, numerical aperture: 0.65 ± 0.05, optical recording medium with light irradiation side substrate thickness: 0.6 mm, and wavelength used: 780
nm ± 10 nm, numerical aperture: 0.50 ± 0.05, optical recording medium with light irradiation side substrate thickness: 1.2 mm, at least one of information recording, reproduction and erasing using an optical pickup. An optical information processing device for performing the optical pickup, wherein: the optical pickup is used at a wavelength of 407 nm ± 10 n.
m, numerical aperture: 0.85 ± 0.05, light irradiation side substrate thickness: 0.
For an optical recording medium of 1 mm, the incident light flux incident on the objective lens is an infinite system, wavelength used: 660 nm ± 10 nm, numerical aperture:
Optical recording medium with light irradiation side substrate thickness: 0.6 mm at 0.65 ± 0.05, wavelength used: 780 nm ± 10 nm, numerical aperture: 0.50 ± 0.05, light irradiation side substrate thickness: 1. 2 mm
An optical information processing apparatus, wherein the objective lens incident light flux is a finite system with respect to the optical recording medium. 23. The substrate thickness on the light irradiation side: 0.1, with a working wavelength of 407 nm ± 10 nm and a numerical aperture of 0.85 ± 0.05.
mm optical recording medium, and wavelength used: 660 nm ± 10
nm, numerical aperture: 0.65 ± 0.05, at least one or more of information recording, reproducing, and erasing is performed using an optical pickup on an optical recording medium having a substrate thickness of 0.6 mm on the light irradiation side. An optical information processing device, wherein the optical pickup has a wavelength used: 407 nm ± 10 n
The numerical aperture is 0.85 ± 0.05 for m, and the numerical aperture is 0.65 for wavelength used: 660 nm ± 10 nm.
An optical information processing device comprising an aperture limiting means for limiting the numerical aperture to ± 0.05. 24. The wavelength of light used: 407 nm ± 10 nm, the numerical aperture: 0.85 ± 0.05, and the substrate thickness on the light irradiation side: 0.1.
mm optical recording medium, and wavelength used: 780 nm ± 10
nm, numerical aperture: 0.50 ± 0.05, at least one of information recording, reproduction, and erasing is performed using an optical pickup on an optical recording medium having a substrate thickness of 1.2 mm on the light irradiation side. An optical information processing device, wherein the optical pickup has a wavelength used: 407 nm ± 10 n
The numerical aperture for m is 0.85 ± 0.05, and the numerical aperture for wavelength used is 780 nm ± 10 nm: 0.50
An optical information processing device comprising an aperture limiting means for limiting the numerical aperture to ± 0.05. 25. The wavelength of light used: 407 nm ± 10 nm, the numerical aperture: 0.85 ± 0.05, and the substrate thickness on the light irradiation side is 0.1.
mm optical recording medium, and wavelength used: 660 nm ± 10
nm, numerical aperture: 0.65 ± 0.05, optical recording medium with light irradiation side substrate thickness: 0.6 mm, and wavelength used: 780
nm ± 10 nm, numerical aperture: 0.50 ± 0.05, and optical recording medium with a light irradiation side substrate thickness: 1.2 mm, at least one of information recording, reproduction, and erasing using an optical pickup. An optical information processing device for performing the following, wherein the used wavelength is 407 nm ± 10 n.
The numerical aperture is 0.85 ± 0.05 for m, and the numerical aperture is 0.65 for wavelength used: 660 nm ± 10 nm.
An optical information processing device, characterized in that it has an aperture limiting means for limiting the numerical aperture as ± 0.05 to a working wavelength of 780 nm ± 10 nm and a numerical aperture of 0.50 ± 0.05. 26. The optical information processing apparatus according to claim 20, wherein the optical pickup is provided with even-order or odd-order aberration correction means.