KR100716942B1 - Optical pickup device - Google Patents

Abstract

An optical pickup apparatus is disclosed. The disclosed optical pickup apparatus includes: first and second light sources for generating laser light having different wavelengths; An objective lens for focusing the laser light from the light source onto the media; A first photodetector and a second photodetector for receiving laser light from the first and second light sources reflected from the media, respectively; A collimating lens positioned on an optical path through which at least a relatively short wavelength laser light travels, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; And satisfies an expression expressed as -1.5> f / fn when f is the total focal length of the collimating lens and fn is the focal length of the negative lens. The present invention gives compatibility to existing DVD-based discs for the so-called HD (High Definition) DVD optical pickup using a blue light source near 400nm and an objective lens having a numerical aperture of 0.6 or more, which has not yet been standardized.

Optical pickup device

Description

Optical pickup device

1 is a diagram showing a change in emission wavelength according to a change in output for each temperature band of a case accommodating a laser diode.

2 is a diagram showing variation in refractive index according to wavelength variation of optical materials.

3 is a schematic configuration diagram of a conventional objective lens for chromatic aberration correction.

4 is a schematic structural diagram of a first embodiment according to the optical pickup of the present invention.

5 is a schematic structural diagram of a second embodiment according to the optical pickup of the present invention.

6 is a schematic structural diagram of a third embodiment according to the optical pickup of the present invention.

7 is a schematic structural diagram of a fourth embodiment according to the optical pickup of the present invention.

8 is an optical path diagram of a light source of 400 nm in the optical pickup device according to the present invention,

FIG. 9 is an aberration diagram for the optical path diagram shown in FIG. 8.

FIG. 10 is an optical path diagram of a light source of 650 nm in the optical pickup apparatus according to the present invention, and FIG. 11 is an aberration diagram thereof.

FIG. 12 is an aberration diagram for light sources of 400 nm and 401 nm in the optical path diagram shown in FIG. 8.

13 is an optical path diagram of an optical pickup using a conventional general collimating lens.

14 is an aberration diagram according to the optical path diagram shown in FIG. 13.

15 is an optical path diagram of an optical pickup apparatus using a collimating lens according to the present invention.

FIG. 16 is an aberration diagram according to the optical path diagram shown in FIG. 15.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus applied to a high density information recording / reproducing apparatus, and more particularly, to an optical pickup apparatus capable of reducing chromatic aberration generated when using a blue light source.

In an apparatus for recording arbitrary information on an optical disc or reproducing the information recorded therein by using a condensed spot by a laser light and an objective lens in an optical pickup, the recording capacity is determined by the size of the spot to be condensed. In general, the size S of the condensing spot is proportional to the wavelength λ and is inversely proportional to the numerical aperture (NA) as in Equation 1 below.

S ∝ λ / NA

Therefore, in order to obtain a higher information recording density than the recording density of information obtained from a current CD (Compact Disc) or a DVD (Digital Versatile Disc), it is necessary to further reduce the size of spots formed on the optical disc. In order to reduce the size of the spot, as shown in Equation 1, the light of the laser beam should be shortened and the numerical aperture NA of the objective lens should be greatly enlarged. In order to record information with high density, a short wavelength laser light source such as a blue laser should be used, and the numerical aperture of the objective lens should be maintained at 0.6 or more.

1 is a diagram showing a change in emission wavelength according to the output change for each case temperature range. 2 is a diagram showing variation in refractive index according to wavelength variation of optical materials.

Referring to FIG. 1, it can be seen that when the output increases due to the characteristics of the laser diode, the wavelength of the emitted light also increases. However, it can be seen that the refractive index variation of the optical optical material in the short wavelength region is very steep in the vicinity of the 400 nm wavelength band as compared to the wavelength of 780 nm applied to the CD and 650 nm applied to the DVD as shown in FIG.

When recording information on an optical disc, first, the desired position is found by the reproduction output to confirm the address, and then the recording mark is formed on the optical disc by increasing the power by the recording output. However, the optical spot is defocused by the chromatic aberration of the optical system due to this instantaneous output fluctuation, and a considerable time is delayed in controlling the servo circuit to compensate for the defocus. In addition, when the HF (High Frequency) module is used to reduce the noise of the laser diode caused by the light returning from the optical disk to the light source, the wavelength line width of the light source is increased, which causes chromatic aberration in the optical component, especially the objective lens. This increases and the playback signal deteriorates. In addition, as shown in FIG. 1, the wavelength becomes longer due to the increase in the temperature of the pick-up apparatus, and a change in the chromatic aberration value with respect to the wavelength deviation of the laser unit must be considered.

In the case of 0.6mm thick DVD optical pickup using a red light source and an objective lens with a NA of 0.6, various methods using a 650nm light source and a single objective lens have been adopted to ensure compatibility with a CD-based 1.2mm thick disk. Presented. For example, a so-called annular shielding method that prevents light in the middle region between the circular axis and the paraxial region from reaching the disk, a method of controlling the aperture ratio of the actual optical pickup using a liquid crystal shutter, and two disks having different thicknesses using holograms, respectively There is a HOE method for separating the light to have a focus on. However, in the case of CD-R (Compact Disc Recordable), since the reflectance of red light is drastically reduced, in this case, the adoption of a 780 nm light source is inevitable, and thus, one objective lens has compatibility with 780 nm and 650 nm light. A DVD infinity / CD finite optical system, an annular lens system, and the like have been proposed. In particular, in the case of a CD finite optical system, a limiting numerical aperture and a method of injecting divergent light into the objective lens are applied to correct an aberration according to the objective lens and the disk thickness.

In order to record and reproduce information denser than a DVD, an optical pickup apparatus using a light source with a shorter wavelength is required. An example of this is a so-called optical pickup for HD (High Definition) DVD, in which case a laser light of a shorter wavelength than the 650 nm laser light applied to the DVD should be applied. However, as shown in FIG. 2, since a very steep refractive index change of the optical material is shown in a wavelength band shorter than 650 nm, a large amount of aberration is generated. Therefore, for this purpose, an optical system capable of effectively reducing chromatic aberration is required. The optics also need to maintain compatibility with existing DVDs as well as HD-DVDs.

DVD-R discs for write-once also have a low reflectance for light other than red light, and therefore, a 650 nm light source is inevitable for compatibility. However, in the objective lens for 400 nm, the aberration is not sufficiently removed by controlling the degree of divergence of the light incident on the objective lens for 650 nm.

Recently, studies on so-called HD DVD (High Density Digital Versatile Disc) using shorter wavelengths than the DVD, for example, around 400 nm, have been studied. An important task in this research is the effective chromatic aberration correction method. That is, as shown in FIG. 2, all materials exhibit a very sharp refractive index change around 400 nm. Such a sharp change in refractive index causes a large amount of aberration, especially chromatic aberration, in the optical system, thereby dramatically reducing optical quality.

3 shows the structure of an objective lens having a chromatic aberration correcting function disclosed in Japanese Patent Laid-Open No. Hei 10-123410.

Referring to FIG. 3, the conventional objective lens has a configuration of two groups of two, a first lens 3 and a second lens 4. That is, the first lens 1 for correcting chromatic aberration is provided between the disk 6, which is the media, and the second lens 4, which focuses light. According to this structure, the numerical aperture can be increased to 0.7 or more, so that it can be used as an optical system component for media capable of high-density information recording.

However, the objective lens of such a structure not only has a long optical distance by the two lenses, but also a large change in the light quality sensitive to a change in relative position between both lenses.

It is a first object of the present invention to provide a compatible optical pickup apparatus using laser light having two different wavelengths in a short wavelength band.

It is a second object of the present invention to provide a compatible optical pickup apparatus capable of effectively correcting the occurrence of aberration caused by a sudden change in refractive index of an optical material.

A third object of the present invention is to provide a DVD to which 650 nm laser light is applied and a compatible optical pickup apparatus capable of applying shorter laser light around 400 nm.

In order to achieve the above object, according to the first type of the present invention,

First and second light sources for generating laser light having different wavelengths;

An objective lens for focusing the laser light from the light source onto the media;

A first photodetector and a second photodetector for receiving laser light from the first and second light sources reflected from the media, respectively;

A collimating lens positioned on an optical path through which at least a relatively short wavelength laser light travels, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped,

 When the total focal length of the collimating lens is f, and the focal length of the negative lens is fn, an optical pickup apparatus is provided that satisfies an expression represented by -1.5> f / fn.

In order to achieve the above object, according to the second type of the present invention,

An objective lens facing the media;

A first light source positioned on an optical axis of the objective lens;

A light splitter provided between the objective lens and the first light source;

A second light source positioned on a traveling path of reflected light branched from the light splitter;

A first photodetector for receiving light from the first light source reflected from the media;

A second photodetector for receiving light from a second light source reflected from the media;

A collimating lens positioned between the light splitter and the objective lens, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped,

 When the total focal length of the collimating lens is f, and the focal length of the negative lens is fn, an optical pickup apparatus is provided that satisfies an expression represented by -1.5> f / fn.

In order to achieve the above object, according to the third type of the present invention,

An objective lens facing the media;

A first light source positioned on an optical axis of the objective lens;

First, second, and third light splitters provided on the optical axis between the objective lens and the first light source with a predetermined distance from the first light source side;

A second light source positioned on a traveling path of reflected light branched from the first light splitter and providing laser light to the media through the first light splitter;

A first photodetector positioned on a traveling path of the reflected light branched from the third optical splitter and receiving laser light from the first light source reflected from the media;

A second photodetector positioned on a traveling path of reflected light branched from the second light splitter and receiving laser light from a second light source reflected from the media;

A collimating lens positioned between the second light splitter and the third light splitter, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped,

 When the total focal length of the collimating lens is f, and the focal length of the negative lens is fn, an optical pickup apparatus is provided that satisfies an expression represented by -1.5> f / fn.

In order to achieve the above object, according to the fourth type of the present invention,

An objective lens facing the media;

A first light source positioned on an optical axis of the objective lens;

First, second, and third light splitters provided on the optical axis between the objective lens and the first light source with a predetermined distance from the first light source side;

A second light source positioned on a traveling path of reflected light branched from the first light splitter and providing laser light to the media through the first light splitter;

A first photodetector positioned on a traveling path of the reflected light branched from the third optical splitter and receiving laser light from the first light source reflected from the media;

A second photodetector positioned on a traveling path of reflected light branched from the second light splitter and receiving laser light from a second light source reflected from the media;

A collimating lens positioned between the objective lens and the third light splitter, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped,

When the total focal length of the collimating lens is f, and the focal length of the negative lens is fn, an optical pickup apparatus is provided that satisfies an expression represented by -1.5> f / fn.

In front of at least one of the photodetectors, a focusing lens for focusing the light reflected from the media to the photodetector is further provided between the light splitter and the laser beam incident on each detector.

In addition, the wavelength selective filter for adjusting the numerical aperture between the optical element adjacent to the objective lens is preferably further provided.

The first light source may generate blue laser light at about 400 nm, and the second light source may generate red laser light at around 650 nm.

In the optical pickup apparatus of the present invention, the focal lengths of the lenses from the first light source side are f1, f2, ... fn, respectively, and the Abbe number of the optical material of each part is denoted by v1, When v2, ... vn, satisfying the inequality represented by -0.005 <1 / (f1 · v1) + 1 / (f2 · v2) + ,,, + 1 / (fn · vn) <0.0005 desirable.
Here, chromatic aberration is proportional to Σ1 / (fi / vi) (see WJ Smith: 'Modern Optical Engineering' McGraw-Hill Book Co. p.334 (12.1) and p.342 (12.12)).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

Referring to FIG. 4, the first light source 600 is positioned at an end portion on the optical axis of the objective lens 200 facing the media 100. Between the objective lens 200 and the first light source 600 is a wavelength selective filter 300 for adjusting the numerical aperture, the collimating lens 400 and the light splitter 500 to characterize the present invention.

The light splitter 500 passes the laser light from the first light source and reflects the laser light from the second light source 700 to be described later. The second light source 700 is positioned on the reflected light propagation path of the light splitter 500.

The wavelength selective filter 300 is optional, and is installed when the numerical aperture of the first light source 600 and the second light source 700 is required, for example, the first light source 600 is When the blue laser light having a 400 nm wavelength is generated, the numerical aperture required is 0.7, and the second light source 700 generates the laser light having a red color having a 650 nm wavelength, and the required numerical aperture is 0.6, the wavelength The selective filter 300 narrows the aperture so that the numerical aperture is 0.6 for the 650 nm laser light and allows all to pass for the 400 nm wavelength laser light.

The first light source 600 and the second light source 700 is applied to the existing transmission and reception device having a photodetector. That is, the emission of the laser light and the reception of the reflected laser light are performed together.

Meanwhile, the collimating lens 400 which characterizes the present invention includes a positive lens 401 having a positive power and a negative lens 402 having a negative power. In this case, when the total focal length of the collimating lens 103 is f and the focal length of the negative lens is fn, the expression represented by -1.5> f / fn is satisfied.

The collimating lens 400 makes laser light from the first and second light sources 601 and 701 into parallel light and simultaneously corrects chromatic aberration.

Example 2

Referring to FIG. 5, a first light source 601 is positioned at an end portion on an optical axis of the objective lens 200 facing the media 100. Between the objective lens 200 and the first light source 601, the wavelength selective filter 300 for adjusting the numerical aperture, the collimating lens 400, and the first, second, third light to characterize the present invention Dividers 501, 502, 503 are positioned at predetermined intervals.

The third light splitter 503 passes the laser light from the first light source and reflects the laser light from the second light source 700 described later. The second light source 700 is positioned on the reflected light propagation path of the third light splitter 501.

The second light splitter 502 passes all the light from the first and second light sources 601 and 701 and reflects the laser light from the second light source 701 among the light reflected from the media 100. Let's do it. Reflected light from the media reflected by the second light splitter 502 is focused to the second light detector 702 through the second focusing lens 802.

The third light splitter 502 passes all the light from the first and second light sources 601 and 701, and among the light reflected from the media 100, the laser light from the first light source 701 Reflect. The reflected light from the media reflected by the first light splitter 501 is focused to the first light detector 602 through the first focusing lens 801.

The wavelength selective filter 300 is also optional, and is installed when the numerical aperture of the first light source 601 and the second light source 701 is required, for example, the first light source 601. When the blue laser light of the 400 nm wavelength is generated, the numerical aperture required for this is 0.7, and the second light source 701 generates the laser light of the red series of the 650 nm wavelength, and the numerical aperture required for this is 0.6. The wavelength selective filter 300 narrows the aperture so that the numerical aperture is 0.6 for the laser light of the 650 nm wavelength, and allows all to pass through for the laser light of the 400 nm wavelength.

The collimating lens 400 characterizing the present invention includes a positive lens 401 having a positive power and a negative lens 402 having a negative power. In this case, when the total focal length of the collimating lens 103 is f and the focal length of the negative lens is fn, the expression represented by -1.5> f / fn is satisfied.

The collimating lens 400 makes laser light from the first and second light sources 601 and 701 into parallel light and simultaneously corrects chromatic aberration.

Third embodiment

Referring to FIG. 6, a first light source 601 is positioned at an end portion on an optical axis of the objective lens 200 facing the media 100. Between the objective lens 200 and the first light source 601, the wavelength selective filter 300 and the first, second, and third light splitters 501, 502, and 503 for adjusting the numerical aperture are provided at predetermined intervals. Place it. Between the first light splitter 501 and the second light splitter 502, a collimating lens 400 characterizing the present invention is located.

The third light splitter 503 passes the laser light from the first light source 601 and reflects the laser light from the second light source 700 described later. The second light source 700 is positioned on the reflected light propagation path of the third light splitter 501.

The second light splitter 502 passes all the light from the first and second light sources 601 and 701 and reflects the laser light from the second light source 701 among the light reflected from the media 100. Let's do it. Reflected light from the media reflected by the second light splitter 502 is focused to the second light detector 702 through the second focusing lens 802.

The third light splitter 502 passes all the light from the first and second light sources 601 and 701 and reflects the laser light from the first light source 701 among the light reflected from the media 100. Let's do it. The reflected light from the media reflected by the first light splitter 501 is focused to the first light detector 602 through the first focusing lens 801.

The wavelength selective filter 300 is also optional, and is installed when the numerical aperture of the first light source 601 and the second light source 701 is required, for example, the first light source 601. When the blue laser light of the 400 nm wavelength is generated, the numerical aperture required for this is 0.7, and the second light source 701 generates the laser light of the red series of the 650 nm wavelength, and the numerical aperture required for this is 0.6. The wavelength selective filter 300 narrows the aperture so that the numerical aperture is 0.6 for the laser light of the 650 nm wavelength, and allows all to pass through for the laser light of the 400 nm wavelength.

The collimating lens 400 characterizing the present invention includes a positive lens 401 having a positive power and a negative lens 402 having a negative power. In this case, when the total focal length of the collimating lens 103 is f and the focal length of the negative lens is fn, the expression expressed as -1.5> f / fn is satisfied.

The collimating lens 400 makes laser light from the first and second light sources 601 and 701 into parallel light and simultaneously corrects chromatic aberration.

Fourth embodiment

Referring to FIG. 7, a first light source 601 is positioned at an end portion on an optical axis of the objective lens 200 facing the media 100. Between the objective lens 200 and the first light source 601, the wavelength selective filter 300 and the first, second, and third light splitters 501, 502, and 503 for adjusting the numerical aperture are provided at predetermined intervals. Place it. Between the second light splitter 502 and the second light splitter 503, a collimating lens 400 characterizing the present invention is located.

The third light splitter 503 passes the laser light from the first light source 601 and reflects the laser light from the second light source 700 described later. The second light source 700 is positioned on the reflected light propagation path of the third light splitter 501.

The second light splitter 502 passes all the light from the first and second light sources 601 and 701 and reflects the laser light from the second light source 701 among the light reflected from the media 100. Let's do it. Reflected light from the media reflected by the second light splitter 502 is focused to the second light detector 702 through the second focusing lens 802.

The third light splitter 502 passes all the light from the first and second light sources 601 and 701 and reflects the laser light from the first light source 701 among the light reflected from the media 100. Let's do it. The reflected light from the media reflected by the first light splitter 501 is focused to the first light detector 602 through the first focusing lens 801.

The wavelength selective filter 300 is also optional, and is installed when the numerical aperture of the first light source 601 and the second light source 701 is required, for example, the first light source 601. When the blue laser light of the 400 nm wavelength is generated, the numerical aperture required for this is 0.7, and the second light source 701 generates the laser light of the red series of the 650 nm wavelength, and the numerical aperture required for this is 0.6. The wavelength selective filter 300 narrows the aperture so that the numerical aperture is 0.6 for the laser light of the 650 nm wavelength, and allows all to pass through for the laser light of the 400 nm wavelength.

The collimating lens 400 characterizing the present invention includes a positive lens 401 having a positive power and a negative lens 402 having a negative power. In this case, when the total focal length of the collimating lens 103 is f and the focal length of the negative lens is fn, the expression represented by -1.5> f / fn is satisfied.

The collimating lens 400 makes laser light from the first and second light sources 601 and 701 into parallel light and simultaneously corrects chromatic aberration.

if Radius of curvature thickness Glass Object plane INFINITY 0.100000 s1 INFINITY 0.250000 BK7 s2 INFINITY 5.929508z 2.122789z s3 INFINITY 6.000000 BK7 s4 INFINITY 3.000000 s5 -4.081133 1.000000 FDS1 s6 30.164147 2.000000 TAC8 s7                                              -3.467121 5.000000  K:-0.200770INFINITY A: 0.445555E-03 B: -0.119205E-03 C: 0.316310E-04 D:-. 267022E-05 s8 1.770182 1.802215 BACD5  K: -0.721945 A: 0.537259E-02 B:-. 183575E-03 C:-. 855000E-04 D: -0.121341E-04 s9 -11.452471 1.272566z 1.389972z  K:-179.717593 A: 0.222258E-02 B:-. 194835E-03 C:-. 172951E-04 D: 0.399488E-05 s10 INFINITY 0.600000 'CG' s11 INFINITY 0.000000 Top INFINITY 0.000000 Aspheric expression (See Equation 1) Abbe number at refractive index / d line v    Wavelength 650nm 400nm Dispersion BK7 1.514520 1.530849 / 64.2 FDS1 1.911294 2.012371 / 20.9 TAC8 1.725425 1.752798 / 54.7 BACD5 1.586422 1.606048 / 61.3 'CG' 1.581922 1.623343 / 31.0 Incident pupil diameter (mm) 4.0 Wavelength (nm) 400nm, 650nm Collimating Lens Single Focal Length (mm) Collimating Lens Total Focal Length (mm) -3.499 / 4.239 at 400nm 19.995 at 400nm Objective lens focal length (mm) 2.667 at 400nm ∑1 / (fi / vi) -0.0032

Table 1 above is designed for a collimating lens having a focal length of about 20 mm and an objective lens having a numerical aperture of 0.75 when the wavelength of the laser light is 400 nm. According to this embodiment, the amount of defocus in the media for the wavelength variation ± 5 nm is within the depth of focus ± 0.36 μm, and the axial optical distance OPD at 650 nm shows 0.012λ ₆₅₀ .

8 is an optical path diagram for a 400 nm light source, and FIG. 9 is an aberration diagram thereof.

FIG. 10 is an optical path diagram for a 650 nm light source, and FIG. 11 is an aberration diagram thereof.

FIG. 12 is an aberration diagram for light sources of 400 nm and 401 nm in the optical path diagram shown in FIG. 8.

FIG. 13 shows an optical path diagram of an optical pickup using a conventional general collimating lens, and FIG. 14 is an aberration diagram according thereto.

15 is an optical path diagram of an optical pickup using a collimating lens according to the present invention, and FIG. 16 is an aberration diagram according thereto.

As shown in FIG. 13 and FIG. 14, the conventional collimating lens used for a light source having a long wavelength of 500 nm or more is a structure in which the power of the negative lens is not so large, and thus, chromatic aberration in the short wavelength light source of 500 nm or less cannot be effectively corrected. . The focal length of each lens in Fig. 13 is -15.646 / 8.999 / 2.667, and the Abbe number is 43.0 / 53.9 / 61.3, thus, Σ1 / (fi · vi) = 0.0067. As shown in Fig. 14, the aberration for the light of 400 nm is not so great, but the aberration changes very rapidly for the light of 405 nm. Therefore, conventional collimating lenses cannot be used for light in such a short wavelength band.

However, as shown in Figs. 15 and 16, according to the present invention, the aberration change at 400 nm and 405 nm is not large. This makes it possible to effectively correct the aberration by increasing the power of the negative lens in the collimating lens of the present invention, thus making it possible to bring the spot in the media within the depth of focus to the wavelength change of light.

Here, in order to correct the effective chromatic aberration for light of short wavelength as described above, when the total focal length of the collimating lens is f and the focal length of the negative lens is fn, the expression -1.5> f / fn satisfies the equation. It is necessary.

Furthermore, in the optical pickup apparatus of the present invention, the focal lengths of the lenses from the light source side are f1, f2, ... fn, respectively, and the Abbe number of d-line of the optical material of each component is v1, v2, respectively. , ... vn, it is desirable to satisfy the inequality expressed as -0.005 <1 / (f1 · v1) + 1 / (f2 · v2) + ,,, + 1 / (fn · vn) <0.0005 Do.

The present invention gives compatibility to existing DVD-based discs for the so-called HD (High Definition) DVD optical pickup using a blue light source near 400nm and an objective lens having a numerical aperture of 0.6 or more, which has not yet been standardized.

This is made possible by effectively correcting the chromatic aberration of the blue series short wavelength laser light by the collimating lens which characterizes this invention.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined only by the appended claims.

Claims (21)

First and second light sources for generating laser light having different wavelengths; An objective lens for focusing the laser light from the light source onto the media; A first photodetector and a second photodetector for receiving laser light from the first and second light sources reflected from the media, respectively; A collimating lens positioned on an optical path through which at least a relatively short wavelength laser light travels, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped, And an expression expressed as -1.5 > f / fn when the total focal length of the collimating lens is f and the focal length of the negative lens is fn. The method of claim 1, And a wavelength selective filter on an optical axis adjacent to the objective lens. The method of claim 1, And the first light source, the first light detector, and the second light source and the second light detector are adjacent to the same optical axis. The optical pickup apparatus of any one of claims 1 to 3, wherein the first light source generates blue laser light, and the second light source generates red laser light. The method according to any one of claims 1 to 3, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. The method of claim 4, wherein When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. An objective lens facing the media; A first light source positioned on an optical axis of the objective lens; A light splitter provided between the objective lens and the first light source; A second light source positioned on a traveling path of reflected light branched from the light splitter; A first photodetector for receiving light from the first light source reflected from the media; A second photodetector for receiving light from a second light source reflected from the media; A collimating lens positioned between the light splitter and the objective lens, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped,  And an expression expressed as -1.5 > f / fn when the total focal length of the collimating lens is f and the focal length of the negative lens is fn. 8. The optical pickup apparatus of claim 7, further comprising a wavelength selective filter for adjusting the numerical aperture between the objective lens and the collimating lens. The optical pickup apparatus of claim 7 or 8, wherein the first light source generates blue laser light, and the second light source generates red laser light. The method according to claim 7 or 8, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. The method of claim 9, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe numbers on the d line of the optical material of each component are v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. An objective lens facing the media; A first light source positioned on an optical axis of the objective lens; First, second, and third light splitters provided on the optical axis between the objective lens and the first light source with a predetermined distance from the first light source side; A second light source positioned on a traveling path of reflected light branched from the first light splitter and providing laser light to the media through the first light splitter; A first photodetector positioned on a traveling path of the reflected light branched from the third optical splitter and receiving laser light from the first light source reflected from the media; A second photodetector positioned on a traveling path of reflected light branched from the second light splitter and receiving laser light from a second light source reflected from the media; A collimating lens positioned between the second light splitter and the third light splitter, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped,  And an expression expressed as -1.5 > f / fn when the total focal length of the collimating lens is f and the focal length of the negative lens is fn. 13. The optical pickup apparatus of claim 12, further comprising a wavelength selective filter for adjusting the numerical aperture between the objective lens and the collimating lens. The optical pickup apparatus of claim 12 or 13, wherein the first light source generates blue laser light, and the second light source generates red laser light. The method according to claim 12 or 13, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. The method of claim 14, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. An objective lens facing the media; A first light source positioned on an optical axis of the objective lens; First, second and third light splitters arranged on the optical axis between the objective lens and the first light source at a predetermined distance from the first light source side; A second light source positioned on a traveling path of reflected light branched from the first light splitter and providing laser light to the media through the first light splitter; A first photodetector positioned on a traveling path of the reflected light branched from the third optical splitter and receiving laser light from the first light source reflected from the media; A second photodetector positioned on a traveling path of reflected light branched from the second light splitter and receiving laser light from a second light source reflected from the media; A collimating lens positioned between the objective lens and the third light splitter, the collimating lens including a negative lens having a negative power and a positive lens having a positive power; Equipped, And an expression expressed as -1.5 > f / fn when the total focal length of the collimating lens is f and the focal length of the negative lens is fn. 18. The optical pickup apparatus of claim 17, further comprising a wavelength selective filter for adjusting the numerical aperture between the objective lens and the collimating lens. 19. The optical pickup apparatus of claim 17 or 18, wherein the first light source generates blue laser light, and the second light source generates red laser light. The method of claim 17 or 18, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005. The method of claim 19, When the focal lengths of the lenses from the first light source side are respectively f1, f2, ... fn, and the Abbe number of d-line of the optical material of each component is v1, v2, ... vn, respectively,- An optical pickup device satisfying an inequality expressed by 0.005 <1 / (f1 · v1) + 1 / (f2 · v2) +,, and + 1 / (fn · vn) <0.0005.

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