JP2004178720A - Objective optical element for optical pickup device, and the optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device and its objective optical element, which can appropriately record and/or reproduce information to a different optical information recording medium, using a light source with different frequencies, while providing a compact structure. <P>SOLUTION: Both the miniaturization of the optical pickup device and attainment of aberration characteristics are met, by irradiating a light beam with a small emitting angle to an object lens OBJ. More specifically, deterioration in the aberration characteristics can be suppressed, because its magnification in an optical system m1 is larger than the lower bound in the formula (-1/7≤m1≤-1/25), even when the center for the light beam from the light source is deviated or injected with the slope, with respect to the optical axis for an object optical lens OBJ. Because the magnification in the optical system m1 is lower than the upper limit, a sufficient distance can be secured between the object lens OBJ and an optical information recording medium D. <P>COPYRIGHT: (C)2004,JPO

Description

【００６２】
更に、対物レンズの光源側非球面の表面には回折構造が形成されている。この回折構造は、ブレーズ化波長λＢに対する光路差関数Φにより単位をｍｍとして［数２］で表される。この２次係数が回折部分の近軸的なパワーが表される。また、２次以外の係数、例えば４次、６次係数等で球面収差を制御できる。ここで制御できるとは、屈折部分が有する球面収差を回折部分で逆特性の球面収差を持たせてトータルとして球面収差を補正したり、回折部分の波長依存性を利用して、入射波長によって球面収差を補正したりフレアを生じさせたりすることができる。この場合、温度変化時の球面収差も、屈折部分の球面収差の温度変化と回折部分の球面収差変化のトータルと考えることが出来る。
【数２】

【００６３】
（実施例１）
以下に述べる実施例１は、上記実施の形態に適用可能な対物レンズに関するものである。表１に、実施例１の対物レンズにかかるレンズデータを示す。尚、これ以降（表のレンズデータ含む）において、１０のべき乗数（例えば、２．５×１０^−３）を、Ｅ（例えば、２．５×Ｅ―３）を用いて表すものとする。
【表１】

【００６４】
（実施例２）
以下に述べる実施例２も、上記実施の形態に適用可能な対物レンズに関するものである。表２、実施例２の対物レンズにかかるレンズデータを示す。
【表２】

【００６５】
【発明の効果】
本発明によれば、コンパクトな構成を提供しながらも、波長の異なる光源を用いて異なる光情報記録媒体に対して適切に情報の記録及び／又は再生ができる光ピックアップ装置及びその対物光学素子を提供することができる。
【図面の簡単な説明】
【図１】本発明の対物光学素子の一例の断面図である。
【図２】本実施の形態にかかる光ピックアップ装置の概略構成図である。
【符号の説明】
１５ カップリングレンズ
１６ 対物レンズ
１７ 絞り
２０ 第１の光ディスク、第２の光ディスク
３０ 光検出器
１１１ 第１半導体レーザ
１１２ 第２半導体レーザ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical pickup device and an objective optical element thereof, and more particularly, to an optical pickup device capable of recording and / or reproducing information on and from different optical information recording media using a plurality of light sources having different wavelengths, and an object thereof. It relates to an optical element.
[0002]
[Prior art]
For example, optical pickup devices capable of recording and reproducing information on and from different types of optical information recording media, such as DVDs and CDs, have been developed and used for various purposes. In such an optical pickup device, the thickness of the transparent substrate is different between the DVD and the CD, and information is recorded or reproduced using light beams from light sources having different wavelengths. It can be said that it is preferable to use a separate light-converging optical system optimized in accordance with whether a DVD is used or a CD.
[0003]
However, if a plurality of condensing optical systems are provided in the optical pickup device, a switching mechanism and the like are required, so that the configuration becomes complicated and the cost increases. Therefore, in recent years, by using a single objective lens having a diffractive structure on the optical surface, information recording / reproducing is performed on both DVD and CD while simplifying the configuration and reducing the cost. An optical pickup device capable of performing the above has been developed (see Patent Document 1). Also, a light source called two-laser one-package, in which two semiconductor lasers having different wavelengths are arranged on one substrate, is used, and the focal length of the objective lens tends to be shorter due to miniaturization of the optical pickup device. There is.
[Patent Document 1]
JP-A-2001-76367
[0004]
[Problems to be solved by the invention]
By the way, in the optical pickup device, a certain distance is ensured between the objective lens and the DVD or CD so that they do not interfere with each other even if the objective lens and the DVD or CD are relatively inclined due to an assembly error or a variation in component accuracy. In the optical pickup device, it is desirable that the divergent light beam be incident on the objective lens from the viewpoint of securing such a distance and reducing the size of the entire optical system.
[0005]
However, in the optical pickup device, when the light beam is deviated or inclined from the optical axis due to an assembling error or the like and enters the objective lens, there is a problem that the divergent light beam is more likely to deteriorate the aberration characteristic than the parallel light beam. On the other hand, in order to make the parallel light beam incident on the objective lens, a collimator lens for converting the divergent light beam from the light source into a parallel light beam is required, and the optical pickup device cannot be downsized.
[0006]
In addition, if the objective lens is formed of plastic, high-precision and lightweight products with reduced component variations can be mass-produced at low cost, but on the other hand, changes in the refractive index due to temperature changes will deteriorate the aberration characteristics. Some countermeasures are needed.
[0007]
The present invention has been made in view of the problems of the related art, and provides information recording and / or appropriate recording on different optical information recording media using light sources having different wavelengths while providing a compact configuration. An object of the present invention is to provide an optical pickup device capable of reproducing and an objective optical element thereof.
[0008]
[Means for Solving the Problems]
The objective optical element of the optical pickup device according to claim 1, wherein a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element. And the condensing optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby recording and recording information. And / or perform reproduction, and collect the light flux from the second light source on the information recording surface of the second optical information recording medium via a protective layer having a thickness t2 (t1 ≦ t2). An objective optical element used for an optical pickup device capable of recording and / or reproducing information by illuminating,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
A common diffraction structure is provided in the common region, and the common diffraction structure is configured such that, according to a wavelength difference between the wavelength λ1 and the wavelength λ2, a light beam of the wavelength λ1 that has passed through the common diffraction structure has the thickness t1. Spherical aberration when the light is condensed on the information recording surface of the first optical information recording medium via the protective layer, and the luminous flux of the wavelength λ2 passing through the common diffraction structure pass through the protective layer having the thickness t2. A function of correcting the difference from the spherical aberration when the light is focused on the information recording surface of the second optical information recording medium so as to be small,
A dedicated diffraction structure is provided in the dedicated region, and the dedicated diffraction structure emits a light beam of the wavelength λ1 that has passed through the dedicated diffraction structure according to an increase in ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The luminous flux having the wavelength λ2 that has passed through the dedicated diffraction structure crosses the optical axis at a position different from a converging spot formed on the information recording surface of the second optical information recording medium in the optical axis direction. .
[0009]
According to the objective optical element of the optical pickup device according to the first aspect, by irradiating the objective optical element with a light beam having a small divergence angle, both miniaturization of the optical pickup device and securing of aberration characteristics are achieved. Let me. More specifically, in the above equation (1), since the optical system magnification m1 is equal to or larger than the lower limit, for example, the center of the light beam from the light source is shifted or inclined with respect to the optical axis of the objective optical element. Even in the case where the light enters, the deterioration of the aberration characteristics can be suppressed. On the other hand, since the magnification m1 of the optical system is equal to or less than the upper limit, a sufficient distance can be secured between the objective optical element and the optical information recording medium. Further, in the present invention, the diffraction structure provided in the common area suppresses deterioration of spherical aberration caused by a difference in thickness between the protective layer of the first optical information recording medium and the protective layer of the second optical information recording medium. In addition, the diffraction structure provided in the dedicated area suppresses deterioration of spherical aberration caused by a change in the refractive index of the objective optical element in response to a rise in ambient temperature, so that different types of optical information recording media can be used. , And can appropriately record and / or reproduce information. Note that "correcting the difference in spherical aberration to be smaller" means that the spherical aberration is corrected to be smaller than in the case where the shared diffraction structure is not provided and only the refractive surface is provided. Meaning.
[0010]
The objective optical element of the optical pickup device according to claim 2, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3)
[0011]
4. The objective optical element of the optical pickup device according to claim 3, wherein the common area is divided into a first annular area and a second annular area centered on the optical axis and divided by a step in an optical axis direction. Wherein the shared diffraction structure is provided in the first annular zone farther from the optical axis, and the second annular zone closer to the optical axis has a refracting surface. And
[0012]
5. The objective optical element of the optical pickup device according to claim 4, wherein an edge of the second ring-shaped region adjacent to the first ring-shaped region is the second ring in the first ring-shaped region. 6. It is characterized by being located on the light source side along the optical axis with respect to the edge adjacent to the band-shaped region.
[0013]
6. The objective optical element of the optical pickup device according to claim 5, wherein a third annular zone having a refracting surface on a side farther from an optical axis is provided adjacent to the first annular zone. The edge of the third annular zone adjacent to the third annular zone in the annular zone of the optical information along the optical axis with respect to the edge of the third annular zone adjacent to the first annular zone. It is characterized by being located on the recording medium side.
[0014]
7. The objective optical element of the optical pickup device according to claim 6, wherein the common diffraction structure has an optical characteristic that, when the light source wavelength changes so as to be longer, causes the light beam passing through the common diffraction structure to have a spherical aberration lower. It is characterized by having.
[0015]
Here, examples of the objective optical element according to the above invention will be described with reference to the drawings. FIG. 1 is a sectional view of the objective optical element OBJ of the present invention. In FIG. 1, an optical surface S1 on the light source side of the objective optical element OBJ has a central second annular zone A2 including the optical axis X, a first annular zone A1 around the central second annular zone A2, and a further peripheral zone. The third annular zone A3 is separated by a step in the optical axis direction. The shared area according to the present invention corresponds to the second annular area A2 and the first annular area A1, and the dedicated area according to the present invention corresponds to the third annular area A3.
[0016]
That is, when information is recorded and / or reproduced on the first optical information recording medium D, as shown in FIG. 1A, the first annular zone A1, the second annular zone A2, and the The light beam passing through the third annular zone A3 forms a converged spot on the information recording surface Dr via the protective layer Dp. On the other hand, when information is recorded and / or reproduced on the second optical information recording medium D, as shown in FIG. 1B, the first annular zone A1 and the second annular zone A2 are separated. The passing light beam forms a condensed spot on the information recording surface Dr via the protective layer Dp. At this time, the luminous flux passing through the third annular zone A3 becomes flare light without forming a converging spot on the information recording surface Dr.
[0017]
Each of the regions A1 to A3 is composed of a refraction surface, and a diffraction structure is formed thereon (however, the region A2 may be only a refraction surface). The first annular region A1 is composed of the second annular region A2 and the second annular region A2. The third annular zone A3 is displaced toward the optical information recording medium D. More specifically, an edge P1 adjacent to the first annular zone A1 in the second annular zone A2 is an edge P2 adjacent to the second annular zone A2 in the first annular zone A1. Are located on the light source side along the optical axis. In addition, the edge P3 of the first annular area A1 adjacent to the third annular area A3 is lighter than the edge P4 of the third annular area A3 adjacent to the first annular area A1. It is located on the optical information recording medium D side along the axis. With such a configuration, an effect of changing the phase difference can be obtained as described in claim 6 or 7 below.
[0018]
8. The objective optical element of the optical pickup device according to claim 7, wherein at the best image plane position, the light beam of the wavelength λ1 that has passed through the first annular zone and the wavelength that has passed through the second annular zone. 9. The light flux of λ1 is characterized in that the phase is different by 2π × i (i: integer).
[0019]
9. The objective optical element of the optical pickup device according to claim 8, wherein at the best image plane position, the luminous flux having the wavelength λ1 having passed through the first annular zone and the wavelength having passed through the third annular zone. The light flux of λ1 is characterized in that the phase is different by 2π × i (i: integer).
[0020]
10. The objective optical element of the optical pickup device according to claim 9, wherein a diffractive structure is provided in all of the common areas.
[0021]
The objective optical element of the optical pickup device according to claim 10, wherein a first light source having a wavelength of λ1, a second light source having a wavelength of λ2 (λ1 <λ2), a condensing optical system including a magnification conversion element and an objective optical element. And the condensing optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby recording and recording information. And / or perform reproduction, and collect the light flux from the second light source on the information recording surface of the second optical information recording medium via a protective layer having a thickness t2 (t1 ≦ t2). An objective optical element used for an optical pickup device capable of recording and / or reproducing information by illuminating,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
The common area is divided into a plurality of annular refraction surfaces having steps in the optical axis direction, and each surface is divided into a first surface, a second surface,... ) Surface, at least the edge of the n-th surface (n is a natural number of 2 or more, n ≦ k) closer to the optical axis of the orbicular refraction surface is the same as the (n−1) th orbicular refraction surface. The edge of the n-th surface which is located on the optical information recording medium side along the optical axis and farthest from the optical axis is (n + 1) ) With respect to the edge near the optical axis of the orbicular refraction surface of the surface [where n = k, the surface of the dedicated area], on the optical information recording medium side along the optical axis;
The light beam of the wavelength λ1 that has passed through the n-th surface is focused on a position different from the best image plane position in the optical axis direction,
The light beam of the wavelength λ1 that has passed through the dedicated area forms a first condensed spot on the information recording surface of the first optical information recording medium, and the light beam of the wavelength λ2 that has passed through the dedicated area is Without forming a second converging spot on the information recording surface of the two-optical information recording medium,
A diffraction structure for temperature correction is formed in the dedicated area, and the luminous flux having the wavelength λ1 that has passed through the diffraction structure for temperature correction is increased in accordance with an increase in the ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The light beam having the wavelength λ2 that has passed through the temperature-correcting diffraction structure crosses the optical axis at a position different from the second condensed spot in the optical axis direction.
[0022]
According to the objective optical element of the optical pickup device described in claim 10, by irradiating the objective optical element with a light beam having a small divergence angle, it is possible to achieve both miniaturization of the optical pickup device and securing of aberration characteristics. Let me. More specifically, in the above equation (1), since the optical system magnification m1 is equal to or larger than the lower limit, for example, the center of the light beam from the light source is shifted or inclined with respect to the optical axis of the objective optical element. Even in the case where the light enters, the deterioration of the aberration characteristics can be suppressed. On the other hand, since the magnification m1 of the optical system is equal to or less than the upper limit, a sufficient distance can be secured between the objective optical element and the optical information recording medium.
[0023]
Further, the present invention will be described by taking FIG. 1 as an example. The second annular zone A2 is the first surface, the first annular zone A1 is the second surface, and the third annular zone A3 is the third surface. Therefore, if n = 2, the edge P2 of the second annular surface refracting surface closer to the optical axis is closer to the edge P1 of the first annular surface refracting surface farther from the optical axis. The edge P3 located on the optical information recording medium D side along the optical axis and farther from the optical axis of the second annular refraction surface is closer to the optical axis of the third annular refraction surface. Is located on the optical information recording medium D side along the optical axis with respect to the edge portion P4, so that the effect of changing the phase difference can be obtained.
[0024]
The objective optical element of the optical pickup device according to claim 11, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3)
[0025]
The objective optical element of the optical pickup device according to claim 12, wherein, at the best image plane position, the light beam of the wavelength λ1 passing through the n-th surface and the light beam of the wavelength λ1 passing through the (n−1) -th surface. The light beam is characterized in that the phase differs by 2π × i (i: integer).
[0026]
14. The objective optical element of the optical pickup device according to claim 13, wherein a first light source having a wavelength of λ1, a second light source having a wavelength of λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element. And the condensing optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby recording and recording information. And / or perform reproduction, and collect the light flux from the second light source on the information recording surface of the second optical information recording medium via a protective layer having a thickness t2 (t1 ≦ t2). An objective optical element used for an optical pickup device capable of recording and / or reproducing information by illuminating,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
At least a part of the common area is configured such that a light beam of the wavelength λ1 that has passed through the common area passes through the protective layer having the thickness t1 according to a wavelength difference between the wavelength λ1 and the wavelength λ2. The spherical aberration when condensed on the information recording surface of the information recording medium and the luminous flux having the wavelength λ2 that has passed through the common diffraction structure are transmitted through the protective layer having the thickness t2 of the second optical information recording medium. It has the function of correcting so that the difference from the spherical aberration when condensed on the information recording surface is small,
At least a portion of the dedicated area increases when the light beam of the wavelength λ1 that has passed through the dedicated diffraction structure is condensed on the information recording surface of the first optical information recording medium in accordance with an increase in ambient temperature. Having a function of suppressing the spherical aberration to occur in accordance with a wavelength change of the light beam of the wavelength λ1,
The light beam of the wavelength λ2 that has passed through the dedicated area crosses the optical axis at a position different from a converging spot formed on the information recording surface of the second optical information recording medium in the optical axis direction. The operation and effect of the present invention is the same as the operation and effect described in claim 1 or 9.
[0027]
The objective optical element of the optical pickup device according to claim 14, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3)
[0028]
The objective optical element of the optical pickup device according to claim 15, wherein the magnification conversion optical element is a coupling lens.
[0029]
The objective optical element of the optical pickup device according to claim 16 is an objective lens.
[0030]
The objective optical element of the optical pickup device according to claim 17 is formed of plastic.
[0031]
The objective optical element of the optical pickup device according to claim 18, wherein the first light source and the second light source are arranged on the same substrate as in a two-laser one-package unit.
[0032]
20. The objective optical element of the optical pickup device according to claim 19, wherein the first light source and the second light source are arranged at an equal distance from the magnification conversion element along an optical axis. I do.
[0033]
The optical pickup device according to claim 20, comprising: a first light source having a wavelength of λ1, a second light source having a wavelength of λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element. The condensing optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby recording and / or reproducing information. The light beam from the second light source is condensed on the information recording surface of the second optical information recording medium via a protective layer having a thickness t2 (t1 ≦ t2). In an optical pickup device capable of recording and / or reproducing information,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
A common diffraction structure is provided in the common region, and the common diffraction structure is configured such that, according to a wavelength difference between the wavelength λ1 and the wavelength λ2, a light beam of the wavelength λ1 that has passed through the common diffraction structure has the thickness t1. Spherical aberration when the light is condensed on the information recording surface of the first optical information recording medium via the protective layer, and the luminous flux of the wavelength λ2 passing through the common diffraction structure pass through the protective layer having the thickness t2. A function of correcting the difference from the spherical aberration when the light is focused on the information recording surface of the second optical information recording medium so as to be small,
A dedicated diffraction structure is provided in the dedicated region, and the dedicated diffraction structure emits a light beam of the wavelength λ1 that has passed through the dedicated diffraction structure according to an increase in ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The luminous flux having the wavelength λ2 that has passed through the dedicated diffraction structure crosses the optical axis at a position different from a converging spot formed on the information recording surface of the second optical information recording medium in the optical axis direction. . The operation and effect of the present invention are the same as those of the first aspect.
[0034]
22. The optical pickup device according to claim 21, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3)
[0035]
23. The optical pickup device according to claim 22, wherein the common area is provided with a first annular area and a second annular area centered on the optical axis, each of which is divided by a step in an optical axis direction, The common diffraction structure is provided in the first annular zone farther from the optical axis, and the second annular zone closer to the optical axis has a refracting surface.
[0036]
24. The optical pickup device according to claim 23, wherein an edge of the second annular zone adjacent to the first annular zone is adjacent to the second annular zone of the first annular zone. It is characterized by being located on the light source side along the optical axis with respect to the edge to be formed.
[0037]
25. The optical pickup device according to claim 24, wherein a third annular zone having a refracting surface on a side far from the optical axis is provided adjacent to the first annular zone, and wherein the first annular zone is provided. The edge portion adjacent to the third annular region in the optical information recording medium side along the optical axis with respect to the edge portion of the third annular region adjacent to the first annular region. It is characterized by being located.
[0038]
26. The optical pickup device according to claim 25, wherein the common diffraction structure has an optical characteristic that when the light source wavelength changes so as to be longer, the spherical aberration of the light flux passing through the common diffraction structure is further reduced. And
[0039]
27. The optical pickup device according to claim 26, wherein, at the best image plane position, the light flux of the wavelength λ1 passing through the first annular zone and the light flux of the wavelength λ1 passing through the second annular zone. Is characterized in that the phases are different by 2π × i (i: integer).
[0040]
28. The optical pickup device according to claim 27, wherein, at the best image plane position, the light flux of the wavelength λ1 passing through the first annular zone and the light flux of the wavelength λ1 passing through the third annular zone. Is characterized in that the phases are different by 2π × i (i: integer).
[0041]
An optical pickup device according to a twenty-eighth aspect is characterized in that a diffraction structure is provided in all of the common areas.
[0042]
The optical pickup device according to claim 29, comprising: a first light source having a wavelength of λ1, a second light source having a wavelength of λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element. The condensing optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby recording and / or reproducing information. The light beam from the second light source is condensed on the information recording surface of the second optical information recording medium via a protective layer having a thickness t2 (t1 ≦ t2). In an optical pickup device capable of recording and / or reproducing information,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
The common area is divided into a plurality of annular refraction surfaces having steps in the optical axis direction, and each surface is divided into a first surface, a second surface,... ) Surface, at least the edge of the n-th surface (n is a natural number of 2 or more, n ≦ k) closer to the optical axis of the orbicular refraction surface is the same as the (n−1) th orbicular refraction surface. The edge of the n-th surface which is located on the optical information recording medium side along the optical axis and farthest from the optical axis is (n + 1) ) With respect to the edge near the optical axis of the orbicular refraction surface of the surface [where n = k, the surface of the dedicated area], on the optical information recording medium side along the optical axis;
The light beam of the wavelength λ1 that has passed through the n-th surface is focused on a position different from the best image plane position in the optical axis direction,
The light beam of the wavelength λ1 that has passed through the dedicated area forms a first condensed spot on the information recording surface of the first optical information recording medium, and the light beam of the wavelength λ2 that has passed through the dedicated area is Without forming a second converging spot on the information recording surface of the two-optical information recording medium,
A diffraction structure for temperature correction is formed in the dedicated area, and the luminous flux having the wavelength λ1 that has passed through the diffraction structure for temperature correction is increased in accordance with an increase in the ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The light beam having the wavelength λ2 that has passed through the temperature-correcting diffraction structure crosses the optical axis at a position different from the second condensed spot in the optical axis direction. The operational effects of the present invention are the same as those of the tenth aspect.
[0043]
31. The optical pickup device according to claim 30, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3)
[0044]
The optical pickup device according to claim 31, wherein, at the best image plane position, the light beam of the wavelength λ1 passing through the n-th surface and the light beam of the wavelength λ1 passing through the (n-1) th surface are: The phase is different at 2π × i (i: integer).
[0045]
An optical pickup device according to claim 32, comprising: a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element. The condensing optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby recording and / or reproducing information. The light beam from the second light source is condensed on the information recording surface of the second optical information recording medium via a protective layer having a thickness t2 (t1 ≦ t2). In an optical pickup device capable of recording and / or reproducing information,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
At least a part of the common area is configured such that a light beam of the wavelength λ1 that has passed through the common area passes through the protective layer having the thickness t1 according to a wavelength difference between the wavelength λ1 and the wavelength λ2. The spherical aberration when condensed on the information recording surface of the information recording medium and the luminous flux having the wavelength λ2 that has passed through the common diffraction structure are transmitted through the protective layer having the thickness t2 of the second optical information recording medium. It has the function of correcting so that the difference from the spherical aberration when condensed on the information recording surface is small,
At least a portion of the dedicated area increases when the light beam of the wavelength λ1 that has passed through the dedicated diffraction structure is condensed on the information recording surface of the first optical information recording medium in accordance with an increase in ambient temperature. Having a function of suppressing the spherical aberration to occur in accordance with a wavelength change of the light beam of the wavelength λ1,
The light beam of the wavelength λ2 that has passed through the dedicated area crosses the optical axis at a position different from a converging spot formed on the information recording surface of the second optical information recording medium in the optical axis direction. The operation and effect of the present invention are the same as the operation and effect of the invention described in claim 1 or 10.
[0046]
The optical pickup device according to claim 33, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3)
[0047]
35. The optical pickup device according to claim 34, wherein the magnification conversion optical element is a coupling lens.
[0048]
36. The optical pickup device according to claim 35, wherein the objective optical element is an objective lens.
[0049]
37. The optical pickup device according to claim 36, wherein the objective optical element is formed from plastic.
[0050]
38. The optical pickup device according to claim 37, wherein the first light source and the second light source are arranged on the same substrate.
[0051]
39. The optical pickup device according to claim 38, wherein the first light source and the second light source are arranged at an equal distance from the magnification conversion element along an optical axis.
[0052]
In this specification, “optical system magnification” refers to a so-called lateral magnification which is a ratio between the size of an object and the size of an image.
[0053]
As used herein, the term "diffraction structure" refers to a portion provided with a relief on the surface of an optical element, for example, an objective lens, to condense or diverge a light beam by diffraction. As the shape of the relief, for example, formed on the surface of the optical element as a substantially concentric annular zone centered on the optical axis, each annular zone is shaped like a sawtooth when its cross section is viewed on a plane including the optical axis. Is known, but includes such a shape, and such a shape is particularly called “diffraction ring zone”.
[0054]
In the present specification, in the narrow sense, the objective lens is a light condensing function that is arranged to face the optical information recording medium at the position closest to the optical information recording medium when the optical information recording medium is loaded in the optical pickup device. And, in a broad sense, together with the lens, a lens operable at least in the optical axis direction by an actuator.
[0055]
In the present specification, the second optical information recording medium (also referred to as a second optical disk) refers to, for example, various CD-type optical disks such as CD-R, CD-RW, CD-Video, and CD-ROM. The first optical information recording medium (also referred to as a first optical disk) includes a DVD-ROM, a DVD-Video used for reproduction only, a DVD-RAM, a DVD-R, a DVD-RW and the like which also perform reproduction / recording. And various DVD-type optical disks. Further, in the present specification, the term “thickness t” of the transparent substrate includes t = 0.
[0056]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a schematic configuration diagram of the optical pickup device according to the embodiment of the present invention. The optical pickup device shown in FIG. 2 includes a first semiconductor laser 111 that is a first light source used for recording / reproducing information on a first optical disc (for example, a DVD) and a second optical disc ( For example, a second semiconductor laser 112 which is a second light source used for recording / reproducing information on / from a CD) is disposed on the same substrate 113.
[0057]
First, when information is recorded or reproduced on the first optical disk, a laser beam is emitted from the first semiconductor laser 111. The emitted light flux passes through the polarization beam splitter 120 and the coupling lens 15 as a magnification conversion element, and becomes a divergent light flux close to a parallel light flux. This light beam is stopped down by the stop 17 and is focused on the information recording surface 22 via the transparent substrate 21 of the first optical disc 20 by the objective lens 16 which is an objective optical element.
[0058]
The light flux modulated and reflected by the information pits on the information recording surface 22 passes through the objective lens 16, the diaphragm 17 and the coupling lens 15 again, enters the polarization beam splitter 120, is reflected there, and is reflected by the cylindrical lens 180. A point aberration is given, and the light enters the light receiving surface of the photodetector 30 via the concave lens 50. Using the output signal from the photodetector 30, a recording or reproduction signal of information recorded on the first optical disc 20 is obtained.
[0059]
On the other hand, when reproducing the second optical disc, the second semiconductor laser 112 emits a laser beam. The emitted light beam passes through the transparent substrate 21 of the second optical disc 20 via the polarization beam splitter 120, the coupling lens 15, the stop 17, and the objective lens 16, similarly to the light beam from the first semiconductor laser 111. The light is focused on the information recording surface 22.
[0060]
The light flux modulated and reflected by the information pits on the information recording surface 22 is received again by the photodetector 30 via the objective lens 16, the diaphragm 17, the coupling lens 15, the polarization beam splitter 120, the cylindrical lens 180, and the concave lens 50. Incident on the surface. Similarly, a recording or reproduction signal of information recorded on the second optical disc 20 is obtained using an output signal from the photodetector 30.
[0061]
Hereinafter, an example suitable for the above-described embodiment will be described.
Both surfaces of the objective lens are aspherical surfaces represented by [Equation 1]. Here, Z is the axis in the optical axis direction, h is the height from the optical axis, r is the paraxial radius of curvature, κ is the cone coefficient, and A _2i Is an aspheric coefficient.
(Equation 1)

[0062]
Further, a diffraction structure is formed on the surface of the aspherical surface on the light source side of the objective lens. This diffractive structure is represented by [Equation 2] with a unit of mm by an optical path difference function Φ with respect to the blazed wavelength λB. This second-order coefficient represents the paraxial power of the diffraction portion. Further, the spherical aberration can be controlled by a coefficient other than the second order, for example, a fourth order or sixth order coefficient. Controllable here means that the spherical aberration of the refraction part is corrected by adding the spherical aberration of the inverse characteristic to the diffraction part, and the spherical aberration is corrected as a whole. Aberrations can be corrected and flares can be generated. In this case, the spherical aberration at the time of temperature change can be considered as the total of the temperature change of the spherical aberration of the refraction part and the spherical aberration change of the diffraction part.
(Equation 2)

[0063]
(Example 1)
Example 1 described below relates to an objective lens applicable to the above embodiment. Table 1 shows lens data of the objective lens of Example 1. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ^-3 ) Is represented using E (for example, 2.5 × E-3).
[Table 1]

[0064]
(Example 2)
Example 2 described below also relates to an objective lens applicable to the above embodiment. Table 2 shows lens data concerning the objective lens of Example 2.
[Table 2]

[0065]
【The invention's effect】
According to the present invention, there is provided an optical pickup device and an objective optical element which can appropriately record and / or reproduce information on different optical information recording media using light sources having different wavelengths while providing a compact configuration. Can be provided.
[Brief description of the drawings]
FIG. 1 is a sectional view of an example of an objective optical element of the present invention.
FIG. 2 is a schematic configuration diagram of an optical pickup device according to the present embodiment.
[Explanation of symbols]
15 Coupling lens
16 Objective lens
17 Aperture
20 1st optical disk, 2nd optical disk
30 Photodetector
111 1st semiconductor laser
112 Second semiconductor laser

Claims (38)

A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element, wherein the condensing optical system includes the first light source Is focused on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1, whereby information can be recorded and / or reproduced. Recording and / or reproducing information by condensing a light beam from the second light source on an information recording surface of a second optical information recording medium via a protective layer having a thickness of t2 (t1 ≦ t2). An objective optical element used in an optical pickup device capable of
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
A common diffraction structure is provided in the common region, and the common diffraction structure is configured such that, according to a wavelength difference between the wavelength λ1 and the wavelength λ2, a light beam of the wavelength λ1 that has passed through the common diffraction structure has the thickness t1. Spherical aberration when the light is condensed on the information recording surface of the first optical information recording medium via the protective layer, and the luminous flux of the wavelength λ2 passing through the common diffraction structure pass through the protective layer having the thickness t2. A function of correcting the difference from the spherical aberration when the light is focused on the information recording surface of the second optical information recording medium so as to be small,
A dedicated diffraction structure is provided in the dedicated region, and the dedicated diffraction structure emits a light beam of the wavelength λ1 that has passed through the dedicated diffraction structure according to an increase in ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The luminous flux having the wavelength λ2 that has passed through the dedicated diffraction structure crosses the optical axis at a position different from a converging spot formed on the information recording surface of the second optical information recording medium in the optical axis direction. Objective optical element for optical pickup device. The objective optical element of the optical pickup device according to claim 1, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3) The common area is provided with a first annular area and a second annular area centered on the optical axis, each of which is separated by a step in the optical axis direction, and wherein the first annular area is located farther from the optical axis. The objective of the optical pickup device according to claim 1, wherein the common diffraction structure is provided in an annular zone, and the second annular zone near the optical axis has a refractive surface. Optical element. An edge of the second annular zone adjacent to the first annular zone is along an optical axis with respect to an edge of the first annular zone adjacent to the second annular zone. The objective optical element of the optical pickup device according to claim 3, wherein the objective optical element is located on a light source side. A third annular zone having a refracting surface on a side far from the optical axis is provided adjacent to the first annular zone, and is adjacent to the third annular zone in the first annular zone. The edge portion is located on the optical information recording medium side along an optical axis with respect to an edge portion of the third annular region adjacent to the first annular region. 5. The objective optical element of the optical pickup device according to 4. 6. The common diffraction structure according to claim 1, wherein, when the light source wavelength changes so as to be longer, the light beam passing through the common diffraction structure has an optical characteristic that makes spherical aberration lower. An objective optical element of the optical pickup device described in the above. At the best image plane position, the luminous flux of the wavelength λ1 passing through the first annular zone and the luminous flux of the wavelength λ1 passing through the second annular zone are 2π × i (i: integer). 7. The objective optical element of the optical pickup device according to claim 3, wherein the phases are different. At the best image plane position, the light flux of the wavelength λ1 passing through the first annular zone and the light flux of the wavelength λ1 passing through the third annular zone are 2π × i (i: integer). The objective optical element of the optical pickup device according to claim 5, wherein phases are different. 9. The objective optical element according to claim 1, wherein a diffractive structure is provided in all of the common areas. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element, wherein the condensing optical system includes the first light source Is focused on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1, whereby information can be recorded and / or reproduced. Recording and / or reproducing information by condensing a light beam from the second light source on an information recording surface of a second optical information recording medium via a protective layer having a thickness of t2 (t1 ≦ t2). An objective optical element used in an optical pickup device capable of
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
The common area is divided into a plurality of annular refraction surfaces having steps in the optical axis direction, and each surface is divided into a first surface, a second surface,... ) Surface, at least the edge of the n-th surface (n is a natural number of 2 or more, n ≦ k) closer to the optical axis of the orbicular refraction surface is the same as the (n−1) th orbicular refraction surface. The edge of the n-th surface which is located on the optical information recording medium side along the optical axis and farthest from the optical axis is (n + 1) ) With respect to the edge near the optical axis of the orbicular refraction surface of the surface [where n = k, the surface of the dedicated area], on the optical information recording medium side along the optical axis;
The light beam of the wavelength λ1 that has passed through the n-th surface is focused on a position different from the best image plane position in the optical axis direction,
The light beam of the wavelength λ1 that has passed through the dedicated area forms a first condensed spot on the information recording surface of the first optical information recording medium, and the light beam of the wavelength λ2 that has passed through the dedicated area is Without forming a second converging spot on the information recording surface of the two-optical information recording medium,
A diffraction structure for temperature correction is formed in the dedicated area, and the luminous flux having the wavelength λ1 that has passed through the diffraction structure for temperature correction is increased in accordance with an increase in the ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The objective optical element of the optical pickup device, wherein the light beam of the wavelength λ2 that has passed through the temperature correction diffraction structure crosses the optical axis at a position different from the second condensed spot in the optical axis direction. . The objective optical element of the optical pickup device according to claim 10, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3) At the best image plane position, the light beam of the wavelength λ1 passing through the n-th surface and the light beam of the wavelength λ1 passing through the (n-1) th surface have a phase of 2π × i (i: integer). The objective optical element of the optical pickup device according to claim 10, wherein the objective optical element is different. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element, wherein the condensing optical system includes the first light source Is focused on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1, whereby information can be recorded and / or reproduced. Recording and / or reproducing information by condensing a light beam from the second light source on an information recording surface of a second optical information recording medium via a protective layer having a thickness of t2 (t1 ≦ t2). An objective optical element used in an optical pickup device capable of
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
At least a part of the common area is configured such that a light beam of the wavelength λ1 that has passed through the common area passes through the protective layer having the thickness t1 according to a wavelength difference between the wavelength λ1 and the wavelength λ2. The spherical aberration when condensed on the information recording surface of the information recording medium and the luminous flux having the wavelength λ2 that has passed through the common diffraction structure are transmitted through the protective layer having the thickness t2 of the second optical information recording medium. It has the function of correcting so that the difference from the spherical aberration when condensed on the information recording surface is small,
At least a portion of the dedicated area increases when the light beam of the wavelength λ1 that has passed through the dedicated diffraction structure is condensed on the information recording surface of the first optical information recording medium in accordance with an increase in ambient temperature. Having a function of suppressing the spherical aberration to occur in accordance with a wavelength change of the light beam of the wavelength λ1,
The light beam of the wavelength λ2 passing through the dedicated area crosses the optical axis at a position different from a converging spot formed on an information recording surface of the second optical information recording medium in an optical axis direction. Objective optical element of the pickup device. The objective optical element of the optical pickup device according to claim 1, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength λ2 is m2.
| M1-m2 | <0.5 (3) 15. The objective optical element of the optical pickup device according to claim 1, wherein the magnification conversion optical element is a coupling lens. 16. The objective optical element of the optical pickup device according to claim 1, wherein the objective optical element is an objective lens. 17. The objective optical element of the optical pickup device according to claim 1, wherein the objective optical element is formed of plastic. 18. The objective optical element of the optical pickup device according to claim 1, wherein the first light source and the second light source are arranged on a same substrate. 19. The optical pickup device according to claim 1, wherein the first light source and the second light source are arranged at an equal distance from the magnification conversion element along an optical axis. Objective optical element. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element, wherein the condensing optical system includes the first light source Is focused on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1, whereby information can be recorded and / or reproduced. Recording and / or reproducing information by condensing a light beam from the second light source on an information recording surface of a second optical information recording medium via a protective layer having a thickness of t2 (t1 ≦ t2). Optical pickup device,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
A common diffraction structure is provided in the common region, and the common diffraction structure is configured such that, according to a wavelength difference between the wavelength λ1 and the wavelength λ2, a light beam of the wavelength λ1 that has passed through the common diffraction structure has the thickness t1. Spherical aberration when the light is condensed on the information recording surface of the first optical information recording medium via the protective layer, and the luminous flux of the wavelength λ2 passing through the common diffraction structure pass through the protective layer having the thickness t2. A function of correcting the difference from the spherical aberration when the light is focused on the information recording surface of the second optical information recording medium so as to be small,
A dedicated diffraction structure is provided in the dedicated region, and the dedicated diffraction structure emits a light beam of the wavelength λ1 that has passed through the dedicated diffraction structure according to an increase in ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
The luminous flux having the wavelength λ2 that has passed through the dedicated diffraction structure crosses the optical axis at a position different from a converging spot formed on the information recording surface of the second optical information recording medium in the optical axis direction. Optical pickup device. 21. The optical pickup device according to claim 20, wherein the following formula is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength [lambda] 2 is m2.
| M1-m2 | <0.5 (3) The common area is provided with a first annular area and a second annular area centered on the optical axis, each of which is separated by a step in the optical axis direction, and wherein the first annular area is located farther from the optical axis. 22. The optical pickup device according to claim 20, wherein the common diffraction structure is provided in an annular zone, and the second annular zone near the optical axis has a refractive surface. An edge of the second annular zone adjacent to the first annular zone is along an optical axis with respect to an edge of the first annular zone adjacent to the second annular zone. The optical pickup device according to claim 22, wherein the optical pickup device is located on a light source side. A third annular zone having a refracting surface on a side far from the optical axis is provided adjacent to the first annular zone, and is adjacent to the third annular zone in the first annular zone. 23. The optical recording medium according to claim 22, wherein the edge is located on the optical information recording medium side along an optical axis with respect to an edge of the third annular area adjacent to the first annular area. 24. The optical pickup device according to 23. 25. The common diffraction structure according to claim 20, wherein, when the light source wavelength changes so as to be longer, the light beam passing through the common diffraction structure has an optical characteristic of making spherical aberration lower. An optical pickup device as described in the above. At the best image plane position, the luminous flux of the wavelength λ1 passing through the first annular zone and the luminous flux of the wavelength λ1 passing through the second annular zone are 2π × i (i: integer). The optical pickup device according to any one of claims 22 to 25, wherein phases are different. At the best image plane position, the light flux of the wavelength λ1 passing through the first annular zone and the light flux of the wavelength λ1 passing through the third annular zone are 2π × i (i: integer). 26. The optical pickup device according to claim 24, wherein the phases are different. The optical pickup device according to any one of claims 20 to 27, wherein a diffraction structure is provided in all of the common areas. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element, wherein the condensing optical system includes the first light source Is focused on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1, whereby information can be recorded and / or reproduced. Recording and / or reproducing information by condensing a light beam from the second light source on an information recording surface of a second optical information recording medium via a protective layer having a thickness of t2 (t1 ≦ t2). Optical pickup device,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
The common area is divided into a plurality of annular refraction surfaces having steps in the optical axis direction, and each surface is divided into a first surface, a second surface,... ) Surface, at least the edge of the n-th surface (n is a natural number of 2 or more, n ≦ k) closer to the optical axis of the orbicular refraction surface is the same as the (n−1) th orbicular refraction surface. The edge of the n-th surface which is located on the optical information recording medium side along the optical axis and farthest from the optical axis is (n + 1) ) With respect to the edge near the optical axis of the orbicular refraction surface of the surface [where n = k, the surface of the dedicated area], on the optical information recording medium side along the optical axis;
The light beam of the wavelength λ1 that has passed through the n-th surface is focused on a position different from the best image plane position in the optical axis direction,
The light beam of the wavelength λ1 that has passed through the dedicated area forms a first condensed spot on the information recording surface of the first optical information recording medium, and the light beam of the wavelength λ2 that has passed through the dedicated area is Without forming a second converging spot on the information recording surface of the two-optical information recording medium,
A diffraction structure for temperature correction is formed in the dedicated area, and the luminous flux having the wavelength λ1 that has passed through the diffraction structure for temperature correction is increased in accordance with an increase in the ambient temperature, on the information recording surface of the first optical information recording medium. Having a function of suppressing the spherical aberration that increases when light is condensed on the basis of a change in the wavelength of the light beam having the wavelength λ1;
Further, the light beam of the wavelength λ2, which has passed through the temperature-correcting diffraction structure, crosses the optical axis at a position different from the second condensed spot in the optical axis direction. 30. The optical pickup device according to claim 29, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam having the wavelength λ2 is m2.
| M1-m2 | <0.5 (3) At the best image plane position, the light beam of the wavelength λ1 passing through the n-th surface and the light beam of the wavelength λ1 passing through the (n-1) th surface have a phase of 2π × i (i: integer). 31. The optical pickup device according to claim 29, wherein the optical pickup device is different. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including a magnification conversion element and an objective optical element, wherein the condensing optical system includes the first light source Is focused on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1, whereby information can be recorded and / or reproduced. Recording and / or reproducing information by condensing a light beam from the second light source on an information recording surface of a second optical information recording medium via a protective layer having a thickness of t2 (t1 ≦ t2). Optical pickup device,
The optical system magnification m1 of the objective optical element with respect to the light beam of the wavelength λ1 is:
−1 / 7 ≦ m1 ≦ −1 / 25 (1)
The filling,
In the optical pickup device, an optical system magnification M1 from the first light source to the first optical information recording medium with respect to the light beam of the wavelength λ1 is:
| M1 | <| M1 | (2)
The filling,
On at least one surface of the objective optical element, a light beam from the first light source and a light beam from the second light source pass in common, and the information recording surface of the first optical information recording medium and the second A common area for forming a converging spot on the information recording surface of the optical information recording medium, and a light beam from the first light source passes therethrough to form a converging spot on the information recording surface of the first optical information recording medium. However, even if a light beam from the second light source passes, a dedicated area that does not form a focused spot is provided on the information recording surface of the second optical information recording medium,
At least a part of the common area is configured such that a light beam of the wavelength λ1 that has passed through the common area passes through the protective layer having the thickness t1 according to a wavelength difference between the wavelength λ1 and the wavelength λ2. The spherical aberration when condensed on the information recording surface of the information recording medium and the luminous flux having the wavelength λ2 that has passed through the common diffraction structure are transmitted through the protective layer having the thickness t2 of the second optical information recording medium. It has the function of correcting so that the difference from the spherical aberration when condensed on the information recording surface is small,
At least a portion of the dedicated area increases when the light beam of the wavelength λ1 that has passed through the dedicated diffraction structure is condensed on the information recording surface of the first optical information recording medium in accordance with an increase in ambient temperature. Having a function of suppressing the spherical aberration to occur in accordance with a wavelength change of the light beam of the wavelength λ1,
The light beam of the wavelength λ2 passing through the dedicated area crosses the optical axis at a position different from a converging spot formed on an information recording surface of the second optical information recording medium in an optical axis direction. Pickup device. 33. The optical pickup device according to claim 32, wherein the following expression is satisfied when an optical system magnification of the objective optical element with respect to the light beam of the wavelength [lambda] 2 is m2.
| M1-m2 | <0.5 (3) 34. The optical pickup device according to claim 20, wherein the magnification conversion optical element is a coupling lens. The optical pickup device according to any one of claims 20 to 34, wherein the objective optical element is an objective lens. The optical pickup device according to any one of claims 20 to 35, wherein the objective optical element is formed of plastic. 37. The optical pickup device according to claim 20, wherein the first light source and the second light source are arranged on a same substrate. The optical pickup device according to any one of claims 20 to 37, wherein the first light source and the second light source are arranged at an equal distance from the magnification conversion element along an optical axis. .

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