JP2003281771A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which can perform recording/ reproduction to a plurality of optical recording media with different substrate thicknesses by using a plurality of light source units with different wavelengths, and of which working distance can be secured. <P>SOLUTION: The optical pickup device performs recording/reproduction on the recording surface 31a of a first optical recording medium 31 with the substrate of thickness t1 by using a first light source 11 of wavelength λ1 and on the recording surface 32a of a second recording medium 32 with the substrate of thickness t2 (t1<t2) by using a second light source 12 of wavelength λ2 (λ1<λ2). The distances from a light emitting point of each light source to the surface of the first optical recording medium and the second optical recording medium are identical. The device includes a coupling lens 14 through which a luminous flux from the first light source or the second light source makes incident and an objective lens 17 which images a luminous flux from the coupling lens in an information recording surface. At least either of the objective lens or the coupling lens has a diffraction conformation that focal distance becomes long in accordance with the length of the wavelength of the incident luminous flux. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for reproducing and / or recording information on two types of optical information recording media having different protective substrate thicknesses by using light beams having different wavelengths.

[0002]

2. Description of the Related Art For example, an optical pickup device using two light sources has been developed so that information can be recorded on or reproduced from a DVD and information can be recorded on or reproduced from a CD. There are various strict requirements for low price and compact structure. On the other hand, a light source unit in which a plurality of light sources having different wavelengths are arranged on a single substrate has been developed, and by using such a light source unit, the structure of the optical pickup device can be simplified and the cost can be reduced.

However, the thickness of the protective substrate (transparent substrate) provided on the information recording surface of each of the above optical information recording media is DV.
D is 0.6 mm and CD is 1.2 mm. When the above-mentioned light source unit is used, the distance from the light source to the information recording surface of each optical information recording medium becomes almost equal. When recording or reproducing, there is a problem that it is difficult to secure a sufficient working distance between the objective lens and the surface of the optical information recording medium.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention uses a light source unit in which a plurality of light sources having different wavelengths are arranged on a single substrate, and a plurality of optical information having different protective substrate thicknesses. An object of the present invention is to provide an optical pickup device capable of performing at least one of recording and reproducing of information on a recording medium and ensuring a sufficient working distance for an optical information recording medium having a thick protective substrate. And

[0005]

In order to achieve the above object, an optical pickup device according to the present invention uses a first light source which emits a light beam having a wavelength λ1 to obtain a first optical information recording medium having a protective substrate thickness t1. Reproduction of information on the information recording surface and / or
Alternatively, recording is performed, and a protective substrate thickness t2 (t1 <t
2) In the optical pickup device for reproducing and / or recording information on the information recording surface of the second optical information recording medium, the first light source and the second light source are the light emitting points of the light sources. A coupling lens, which is arranged such that the distances to the surfaces of the first optical information recording medium and the second optical information recording medium are equal, and into which the light flux from the first light source or the second light source is incident, and the coupling lens. And an objective lens that forms an image of the light flux on the information recording surface, and at least one of the objective lens and the coupling lens has a focal length that increases as the wavelength of the incident light flux increases. It is characterized by having a diffractive structure that is changed to be long.

According to this optical pickup device, when the focal length of the objective lens is increased by the diffractive structure provided on at least one of the objective lens and the coupling lens, as compared with the case where the present invention is not applied, Since the image forming point can be set far from the objective lens for the two optical information recording medium, a sufficient working distance can be secured for the second optical information recording medium having a thick protective substrate. Further, when the focal length of the coupling lens is increased, divergent light is incident on the objective lens, and the image forming point of the second optical information recording medium is changed from the objective lens to the case where the present invention is not applied. Since the distance can be set far away, a sufficient working distance can be secured for the second optical information recording medium having a thick protective substrate. Further, since the distances from the light emitting points of the respective light sources to the surfaces of the first optical information recording medium and the second optical information recording medium are arranged substantially equal to each other, a plurality of light sources having different wavelengths are arranged on a single substrate. It is possible to record / reproduce information on / from a plurality of optical information recording media having different protective substrate thicknesses by using.

In the above optical pickup device, when each light flux from the first light source and the second light source is configured to enter the objective lens as infinite light from the coupling lens, the wavelength of the incident light flux is The focal length of at least one of the objective lens and the coupling lens can be changed so as to become longer as the length becomes longer.

Further, the light flux from the first light source is made to enter the objective lens as infinite light from the coupling lens, and the light flux from the second light source is made to enter as finite divergent light. The focal length of at least one of the objective lens and the coupling lens can be changed so as to become longer as the wavelength of the luminous flux becomes longer. In this case, it is preferable that the finite optical magnification m by the coupling lens and the objective lens when the light flux from the second light source is incident as finite divergent light satisfies the following expression, and the ring of the diffractive structure in the coupling lens is satisfied. The number of bands can be reduced, and manufacturing becomes easy. -1/12 <m <0

Even when the light fluxes from the first light source and the second light source are made to enter the objective lens as finite divergent light from the coupling lens, as the wavelength of the incident light beam becomes longer. The focal length of at least one of the objective lens and the coupling lens can be changed to be long.

Further, the objective lens has a thickness t of the protective substrate.
By having a spherical aberration correction diffractive structure that corrects the spherical aberration caused by the difference between 1 and t2, the same coupling lens and objective lens are provided for a plurality of optical information recording media having different thicknesses of the protective substrate. Recording and reproduction are possible with the condensing optical system.

Further, another optical pickup device according to the present invention uses the first light source for emitting the light flux of wavelength λ1 to reproduce and reproduce information on the information recording surface of the first optical information recording medium having the protective substrate thickness t1. / Or record the wavelength λ2 (λ
An optical pickup device for reproducing and / or recording information on an information recording surface of a second optical information recording medium having a protective substrate thickness t2 (t1 <t2) by using a second light source that emits a light flux of 1 <λ2). In the above, the first light source and the second light source are arranged such that the distances from the light emitting points of the respective light sources to the surfaces of the first optical information recording medium and the second optical information recording medium are equal, A coupling lens on which a light beam from one light source or the first light source is incident, and a light beam emitted from the coupling lens is incident to form an image on the information recording surface and the protective substrate thickness t1.
And an objective lens having a spherical aberration correction diffractive structure that corrects a spherical aberration caused by the difference between t2 and t2, and at least one of the objective lens and the coupling lens receives the light flux from the second light source. It has a diffractive structure configured to enter the objective lens with finite divergent light when the above is performed.

According to this optical pickup device, due to the diffractive structure provided on at least one of the objective lens and the coupling lens, the luminous flux from the second light source is finitely diverged for recording / reproducing with respect to the second optical information recording medium. Since the light is incident on the objective lens and the image forming point of the second optical information recording medium can be set far from the objective lens, a sufficient working distance can be secured for the second optical information recording medium having a thick protective substrate. Further, since the distances from the light emitting points of the respective light sources to the surfaces of the first optical information recording medium and the second optical information recording medium are arranged substantially equal to each other, a plurality of light sources having different wavelengths are arranged on a single substrate. It is possible to record / reproduce information on / from a plurality of optical information recording media having different protective substrate thicknesses by using. Further, due to the spherical aberration correction diffractive structure, recording / reproducing can be performed with respect to a plurality of optical information recording media having different thicknesses of the protective substrate by a converging optical system including the same coupling lens and objective lens.

Further, the objective lens includes a central area including an optical axis and used for reproducing and / or recording information on both the first optical information recording medium and the second optical information recording medium, It has an optical functional surface located on the peripheral side of the central area and mainly composed of a peripheral area used for reproducing and / or recording information on the first optical information recording medium, and is close to the central area. The spherical aberration correction diffractive structure that does not have an axial refractive power and performs the spherical aberration correction may be provided. As a result, the number of diffractive ring zones of the objective lens can be reduced, which facilitates manufacturing.

Alternatively, the objective lens includes a central region including an optical axis and used for reproducing and / or recording information on both the first optical information recording medium and the second optical information recording medium, It has an optical functional surface located on the peripheral side of the central area and mainly composed of a peripheral area used for reproducing and / or recording information on the first optical information recording medium, and is close to the central area. The spherical aberration correction diffractive structure having an axial refractive power and performing the spherical aberration correction may be provided. In this case, with the same diffractive structure, it is possible to combine the function of securing the working distance and the function of correcting the spherical aberration described above, and the number of ring zones of the diffractive structure of the coupling lens can be reduced, which facilitates manufacturing.

Further, the diffractive structure can be provided only on the coupling lens, and considering the entire focusing optical system, only the coupling lens needs to be devised, which facilitates the manufacturing and reduces the manufacturing cost. Connect

Further, the diffractive structure can be provided only in the objective lens, and when considering the whole focusing optical system, only the objective lens needs to be devised, which facilitates the manufacture,
This leads to a reduction in manufacturing costs.

Further, by providing the diffractive structure on both the coupling lens and the objective lens, the diffractive power can be distributed to both, so that the number of diffractive ring zones and the diffractive power can be reduced. Manufacturing by molding becomes easy.

Further, it is possible to use a light source unit in which the first light source and the second light source are provided on the same substrate and are unitized, and the structure of the optical pickup device can be simplified.

Further, the first light source emits a light beam having a wavelength of 655 nm, the second light source emits a light beam having a wavelength of 785 nm, and the diffractive structure and / or the spherical aberration correcting diffractive structure emits the first light information. Change rate of image forming point position (μm) in the vicinity of wavelength 655 nm on the information recording surface of the recording medium
/ Nm) is preferably 0.5 to 2.0.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an optical pickup device according to an embodiment of the present invention.

The optical pickup device shown in FIG.
1b CD with a thickness of 1.2 mm (second optical disc 32)
And a DVD (first disc having a thickness of 0.6 mm of the protective substrate 32b).
For both of the optical disks 31), information is recorded and recorded on the information recording surfaces 31a and 32a of the first optical disk 31 and the second optical disk 32, respectively, by the light fluxes of 655 nm and 785 nm, respectively, from the first and second light sources. And / or configured for playback.

As shown in FIG. 1, the optical pickup device has a D
A first semiconductor (first light source) laser 11 for emitting a light beam having a wavelength of 655 nm for VD as shown by the solid line in the figure, and a CD
A second semiconductor laser (second light source) 12 for emitting light having a wavelength of 785 nm as shown by a broken line in the figure, and each light source 11,
Coupling lens 14 that makes both light fluxes from 12 substantially parallel by refraction to become infinite light, and objective lens 17 that images the infinite light from coupling lens 14 on information recording surfaces 31a and 32a of optical disks 31 and 32, respectively. And

The first semiconductor laser 11 and the second semiconductor laser 12 are arranged on the same substrate 10a and integrated as a light source unit 10. Therefore, the distance from the emission point of the first semiconductor laser 11 to the surface of the first optical disk 31 and the emission point of the second semiconductor laser 12 from the second point
The distance to the surface of the optical disc 32 is almost equal.

A beam splitter 13 for transmitting the light beams from the light sources 11 and 12 is arranged between the light sources 11 and 12 and the coupling lens 14, and a beam splitter 13 is provided between the coupling lens 14 and the objective lens 17. A quarter wave plate 15 and a diaphragm 16 are arranged. In addition, each optical disc 31,
The light flux reflected from the information recording surfaces 31a and 32a of 32 changes its optical path by the beam splitter 13 and goes to the photodetector 20.

The objective lens 17 has a flange portion 17a on its outer circumference, and the objective lens 17 can be easily attached to the optical pickup device by the flange portion 17a. Since the flange portion 17a has a surface extending in a direction substantially perpendicular to the optical axis of the objective lens 17, it is possible to easily mount the flange portion 17a with higher accuracy. The objective lens 17 is driven by the biaxial actuator 21 in the focusing direction and the tracking direction.

Further, on the optical surface of the objective lens 17, there is formed a ring-shaped diffractive structure which changes so that the focal length of the objective lens becomes longer as the wavelength of the incident light beam becomes longer. In addition, the protective substrate 31 of each optical disc 31, 32
A ring-shaped diffractive structure for spherical aberration correction that corrects spherical aberration caused by the difference in thickness between b and 32b includes the optical axis of the objective lens 17 for both the first optical disc 31 and the second optical disc 32. It is formed in a central area used for reproducing and / or recording information.

When reproducing the first optical disk (DVD) 31, the light flux emitted from the first semiconductor laser 11 is transmitted through the beam splitter 13 and the coupling lens 14 as shown by the solid line in FIG. Becomes This parallel light flux passes through the quarter-wave plate 15 and the diaphragm 16 and then passes through the objective lens 1
7, the light is focused on the information recording surface 31a via the protective substrate 31b of the first optical disc 31. And the information recording surface 3
The light flux modulated and reflected by the information pit at 1 a is again passed through the objective lens 17, the diaphragm 16, the quarter-wave plate 15, and the coupling lens 14, and then the beam splitter 1
It is reflected by 3 and is given astigmatism by the cylindrical lens 18, and is incident on the photodetector 20 via the concave lens 19 and recorded on the first optical disc 31 using the signal output from the photodetector 20. A read signal of the information obtained is obtained. In addition, focus shape detection and track detection are performed by detecting a change in the shape of the spot on the photodetector 20 and a change in the amount of light due to a change in the position. While moving the objective lens 17 in the focusing direction so that the image is formed on the information recording surface 31a of the first optical disc 31,
The objective lens 17 is moved in the tracking direction so that the light flux from the first semiconductor laser 11 is imaged on a predetermined track. Information can be recorded on the first optical disc 31 in the same manner.

Next, when reproducing the second optical disk (CD) 32, the light flux emitted from the second semiconductor laser 12 passes through the beam splitter 13 and the coupling lens 14, as indicated by the broken line in the figure. Becomes a parallel light flux. The parallel light flux passes through the quarter-wave plate 15 and the diaphragm 16 and is focused by the objective lens 17 on the information recording surface 32a via the protective substrate 32b of the second optical disc 32. Then, the light flux modulated by the information pits and reflected by the information recording surface 32a is again the objective lens 17, the diaphragm 16, and the quarter-wave plate 1.
5, through the coupling lens 14, is reflected by the beam splitter 13, is given astigmatism by the cylindrical lens 18, is incident on the photodetector 20 via the concave lens 19, and is output from the photodetector 20. The read signal of the information recorded on the second optical disc 32 is obtained by using the signal. Further, focus change and track detection are performed by detecting a change in the shape of the spot on the photodetector 20 and a change in the amount of light due to a change in position, and based on this detection, the biaxial actuator 21 causes the biaxial actuator 21 to emit a light beam from the second semiconductor laser 12. The second
The objective lens 17 is moved in the focusing direction so as to form an image on the information recording surface 32a of the optical disc 32, and the objective lens 17 is moved in the tracking direction so as to form the light beam from the second semiconductor laser 12 on a predetermined track. To move. Information can be recorded on the second optical disc 32 in the same manner.

At the time of reproduction / recording on the second optical disk 32 described above, a diffractive structure is formed on the optical surface of the objective lens 17 so that the focal length of the objective lens becomes longer as the wavelength of the incident light beam becomes longer. Therefore, when a light beam having a long wavelength from the second semiconductor laser 112 enters the objective lens 17, the focal length becomes long, and the light beam is transmitted by the biaxial actuator 21 to the information recording surface 32a of the optical disc 32.
When the image is formed on the upper surface, the objective lens 17 and the second optical disk 32
Distance to the surface 32c (working distance)
Becomes longer, and the surface 32c of the second optical disc 32 becomes substantially the same as the position of the surface 31c of the first optical disc 31 during reproduction. Therefore, a sufficient working distance can be secured even when reproducing / recording on the second optical disc 32 having a thick protective substrate, which is preferable. Further, the possibility of contact between the objective lens 17 and the surface 32c of the second optical disc 32 is reduced, and the reliability of reproduction / recording is improved.

As described above, according to the present embodiment, by using the light source unit in which two light sources having different wavelengths are formed on the same substrate, the optical pickup device can have a simple structure and the light source unit can be used. Even if the optical information recording medium with a thick protective substrate is reproduced with a long wavelength light flux,
A sufficient working distance can be secured when recording, and a highly reliable optical pickup device can be realized.

Next, referring to FIG. 2, a description will be given of an optical pickup device in which finite divergent light is made incident on the objective lens from the coupling lens when reproducing / recording the second optical disc 32. FIG. 2 is a diagram showing another example of the optical pickup device according to the present embodiment.

In FIG. 1, both optical disks 31 and 32 are reproduced.
In contrast to the structure in which the coupling lens makes infinite light incident on the objective lens at the time of recording, the optical pickup device of FIG. 2 makes it possible to reproduce / record an optical disk 31 having a thin protective substrate with a light flux having a short wavelength. While the coupling lens allows infinite light to be incident on the objective lens, the optical disc 32 having a thick protective beam and a long wavelength light beam is used.
When reproducing and recording, the finite divergent light is made incident on the objective lens from the coupling lens.

That is, on the optical surface of the coupling lens 24 shown in FIG. 2, a ring-shaped diffractive structure is formed so as to be emitted as finite divergent light when the wavelength of the incident light beam becomes long. The focal length of at least one of the coupling lens 24 and the objective lens 17 becomes longer when reproducing / recording the optical disc 32. The optical pickup device of FIG. 2 has the same configuration as that of FIG. 1 except for the coupling lens 24, and the same effect as that of FIG. 1 can be obtained.

In FIG. 2, the second optical disc 32
In order to increase the focal length of at least one of the coupling lens 24 and the objective lens 17 when reproducing / recording, the coupling lens 24 and the objective lens 1
You may make it provide a diffractive structure to both 7. Also,
In FIG. 2, a finite divergent light may be incident on the objective lens from the coupling lens even when reproducing / recording the optical disk 31 having a thin protective substrate with a light beam having a short wavelength.

[0035]

EXAMPLES Next, the present invention will be explained more specifically by Examples 1 to 5 in which an objective lens and a coupling lens are combined, but the present invention is not limited to these examples. In this embodiment, the first optical information recording medium is D
VD (reference wavelength is 655 nm) and the second optical information recording medium is CD (reference wavelength is 785 nm). The objective lens and the coupling lens of Example 1 are applicable to the optical pickup device of FIG. 1, and the objective lens and the coupling lens of Examples 2 to 5 are applicable to the optical pickup device of FIG.

When the optical surfaces of the objective lens and the coupling lens of this embodiment are aspherical surfaces, each aspherical surface has an aspherical shape expressed by the following mathematical formula 1. . However, Z is an axis in the optical axis direction, h is an axis perpendicular to the optical axis, r is a paraxial radius of curvature, κ is a conic coefficient, and A is an aspherical surface coefficient.

[0037]

[Equation 1]

The diffractive structure formed on the coupling lens and the objective lens is generally expressed by the following equation 2 using the optical path difference function ΦB and the unit of radian.

[0039]

[Equation 2]

<Example 1>

In the first embodiment, infinite light is incident on the objective lens from the coupling lens for both DVD and CD, and FIG. 3 (a) shows an optical path diagram for DVD.
FIG. 3B shows an optical path diagram for a CD. Table 1 shows lens data of Example 1.

[0042]

[Table 1]

In the first embodiment, the action of extending the focal length in the case of CD is performed only by the diffraction structure of the objective lens, and the coupling lens is a refracting surface. The spherical aberration due to the difference in the thickness of the protective substrate is corrected by the diffractive structure of the DVD / CD common area of the objective lens.

<Example 2>

In the second embodiment, infinite light is incident on the objective lens from the coupling lens for DVD and finite divergent light is incident on CD, and FIG. 4 (a) shows an optical path diagram in the case of DVD. An optical path diagram for a CD is shown in (b). Table 2 shows lens data of Example 2.

[0046]

[Table 2]

In the second embodiment, the action of extending the working distance due to the incident divergent light in the case of CD is performed by both the diffractive structures of the coupling lens and the objective lens. Correction of spherical aberration due to the difference in the thickness of the protective substrate
The diffraction structure is used in the VD / CD common area.

<Example 3>

In the third embodiment, infinite light is made incident on the objective lens from the coupling lens for DVD, and finite divergent light is made incident on CD. FIG. 5A shows an optical path diagram in the case of DVD. An optical path diagram for a CD is shown in (b). Table 3 shows lens data of Example 3.

[0050]

[Table 3]

In the third embodiment, the function of extending the working distance due to the incident divergent light in the case of CD is performed only by the diffractive structure of the coupling lens. The spherical aberration due to the difference in the thickness of the protective substrate is corrected by the diffractive structure of the DVD / CD common area of the objective lens.

<Example 4>

The fourth embodiment is similar to the third embodiment in that infinite light is incident on the objective lens from the coupling lens for DVD and finite divergent light is incident on CD.
The optical path diagram in the case of D is similar to that in FIG. 5A, and the optical path diagram in the case of CD is similar to that in FIG. 5B. Example 4 in Table 4
The lens data of is shown.

[0054]

[Table 4]

In the fourth embodiment, the action of extending the working distance due to the incident divergent light in the case of CD is performed only by the diffractive structure of the coupling lens. The spherical aberration due to the difference in the thickness of the protective substrate is corrected by the diffractive structure of the DVD / CD common area of the objective lens.

<Example 5>

In Example 5, infinite light is incident on the objective lens from the coupling lens for DVD and finite divergent light is incident on CD, and FIG. 6A shows an optical path diagram in the case of DVD. An optical path diagram for a CD is shown in (b). Table 5 shows lens data of Example 5.

[0058]

[Table 5]

In Example 5, the action of extending the working distance due to divergent light incidence in the case of CD is performed only by the diffractive structure of the coupling lens. The spherical aberration due to the difference in the thickness of the protective substrate is corrected by the diffractive structure of the DVD / CD common area of the objective lens.

Table 6 shows each structure of the coupling lens and the objective lens in the above Examples 1 to 5.

[0061]

[Table 6]

As shown in Table 6, in Example 1, the axial thickness of the objective lens is 0.2 mm thinner than the conventional one, and the distance (working distance) WD _CD from the lens surface vertex of the objective lens to the CD surface is 0. Extend by 1 mm and extend by 0.1 mm by the paraxial power of the diffractive structure of the objective lens, distance W
The _CD is stretched to 1.53 mm. In the conventional structure, the axial thickness of the objective lens is 1.72 mm,
Distance _{WD CD} to the surface is is 1.33 mm, the distance even when the axial thickness of the objective lens thin 0.2 mm _{WD CD} was 1.43 mm.

In the second embodiment, the axial thickness of the objective lens is thinner than that of the conventional one by 0.2 mm, the distance WD _CD from the apex of the objective lens surface to the CD surface is extended by 0.1 mm, and the objective lens diffraction structure is changed. With paraxial power and finite divergent light incidence, the distance is further extended by 0.1 mm, and the distance WD _CD is extended to 1.53 mm.

In Example 3, the axial thickness of the objective lens is made 0.25 mm thinner than the conventional one, the distance WD _CD from the apex of the lens surface of the objective lens to the CD surface is extended by 0.125 mm, and further finite divergent light incidence is performed. It is extended by 0.075 mm and the distance WD _CD is extended to 1.53 mm.

In Example 4, the axial thickness of the objective lens is made thinner by 0.2 mm than in the conventional case, the distance WD _CD from the lens surface vertex of the objective lens to the CD surface is extended by 0.1 mm, and further finite divergent light incidence is performed. It is extended by 0.1 mm and the distance WD _CD is extended to 1.53 mm.

In the fifth embodiment, the axial thickness of the objective lens is the same as the conventional one, and the distance WD _CD from the objective lens to the CD surface is extended by 0.2 mm when the finite divergent light is incident to 1.53 mm.
I am trying.

Further, in the above Tables 1 to 5, f1 represents the focal length of the information recording surface of the DVD due to the refractive power of the objective lens, f2 represents the focal length of the information recording surface of the CD, and NA1 represents NA1. The image side numerical aperture of the objective lens in the case of DVD is represented, and NA2 represents the image side numerical aperture in the case of CD.

In Examples 1 and 2, the objective lens is DVD /
Having a paraxial refractive power in the shared area of the CD, the diffractive structure provided in the shared area of the DVD / CD both extends the focal length of the objective lens and corrects spherical aberration due to the difference in the thickness of the protective substrate. Also serves as. Further, in Examples 3, 4 and 5, the objective lens is a diffractive structure provided in the DVD / CD shared area without having a paraxial refractive power in the DVD / CD shared area, and is caused by the difference in the thickness of the protective substrate. Corrects spherical aberration.

As shown in FIG. 6, in the case of CD, the finite optical magnification m _CD by the objective lens is −1/12 <m _CD
It is within the range of <0. In addition, the rate of change in the image forming point position ΔI near the wavelength of 655 nm on the information recording surface of the DVD
_DVD / Δλ (μm / nm) is within the range of 0.5 to 2.0.

Further, in the above table or figure, E (or e) is used to express the power of 10, and, for example, E-02
It may be expressed as (= 10 ⁻² ).

Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to these and various modifications can be made within the scope of the technical idea of the present invention. . For example, a DVD is used as a first optical information recording medium (first optical disc) having a thin protective substrate for reproducing / recording information using a first light source having a short wavelength, and a DVD having a long wavelength is used as a second optical information recording medium.
Although a CD has been described as an example of the second optical information recording medium (second optical disc) having a thick protective substrate for reproducing and recording information using a light source, the present invention is applied only to these optical information recording media. It is not a thing, for example, the wavelength used is 4
It is also applicable to a DVD and a higher density optical disc having a protective substrate thickness of about 0.1 mm at about 00 nm.

[0072]

According to the optical pickup device of the present invention,
Using a light source unit in which a plurality of light sources with different wavelengths are arranged on a single substrate, it is possible to record and / or reproduce information on a plurality of optical information recording media with different thicknesses of the protective substrate, and to protect A sufficient working distance can be secured for an optical information recording medium having a thick substrate.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical pickup device according to the present embodiment.

FIG. 2 is a diagram showing a schematic configuration of another optical pickup device according to the present embodiment.

3A is an optical path diagram in the case of a DVD in Embodiment 1, and FIG. 3B is an optical path diagram in the case of a CD.

FIG. 4 (a) is an optical path diagram for a DVD in Example 2 and FIG. 4 (b) is an optical path diagram for a CD.

5 (a) is an optical path diagram for a DVD in Examples 3 and 4, and FIG. 5 (b) is an optical path diagram for a CD.

6A is an optical path diagram in the case of a DVD in Example 5, and FIG. 6B is an optical path diagram in the case of a CD.

[Explanation of symbols]

10 Light source unit 10a substrate 11 First semiconductor laser, first light source 12 Second semiconductor laser, second light source 14,24 Coupling lens 17 Objective lens 31 first optical disk, first optical information recording medium 31a Information recording surface 31b Protective substrate 32 second optical disk, second optical information recording medium 32a Information recording surface 32b protection board

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kohei Ota             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             Inside the company F-term (reference) 2H049 AA03 AA18 AA57 AA64                 2H087 KA13 PA02 PA17 PB02 QA02                       QA07 QA14 QA21 QA34 QA41                       RA05 RA12 RA13 RA42 RA46                 5D119 AA05 AA11 AA22 AA41 BA01                       BB01 BB02 BB03 DA01 DA05                       EA02 EA03 EB02 EC01 EC45                       EC47 FA05 FA08 FA28 JA01                       JA09 JA44 JA64 JB01 JB02                       JB03 JB05 JB10                 5D789 AA05 AA11 AA22 AA41 BA01                       BB01 BB02 BB03 DA01 DA05                       EA02 EA03 EB02 EC01 EC45                       EC47 FA05 FA08 FA28 JA01                       JA09 JA44 JA64 JB01 JB02                       JB03 JB05 JB10

Claims (14)

[Claims] 1. Information is reproduced and / or recorded on an information recording surface of a first optical information recording medium having a protective substrate thickness t1 by using a first light source which emits a light beam having a wavelength λ1 and a wavelength λ2 (λ1 An optical pickup device for reproducing and / or recording information on an information recording surface of a second optical information recording medium having a protective substrate thickness t2 (t1 <t2) using a second light source that emits a luminous flux of <λ2). The first light source and the second light source are arranged such that the distances from the light emitting points of the respective light sources to the surfaces of the first optical information recording medium and the second optical information recording medium are equal to each other, The objective lens includes a coupling lens on which a light flux from the light source or the second light source is incident, and an objective lens on which the light flux emitted from the coupling lens is incident and focuses the light flux on the information recording surface. At least one of the fine the coupling lens, the optical pickup device characterized by having a diffraction structure to vary such that the focal length increases as the wavelength of the light beam incident increases. 2. The light according to claim 1, wherein each of the light fluxes from the first light source and the second light source is configured to enter the objective lens as infinite light from the coupling lens. Pickup device. 3. The light flux from the first light source is made to enter the objective lens as infinite light from the coupling lens, and the light flux from the second light source is made to enter as finite divergent light. The optical pickup device according to claim 1. 4. The optical pickup device according to claim 3, wherein the finite optical magnification m by the objective lens when the light flux from the second light source enters as finite divergent light satisfies the following expression. -1/12 <m <0 5. The light source according to claim 1, wherein each of the light fluxes from the first light source and the second light source is configured to enter the objective lens as finite divergent light from the coupling lens. Optical pickup device. 6. The objective lens has a spherical aberration correcting diffractive structure for correcting spherical aberration caused by the difference between the protective substrate thicknesses t1 and t2. The optical pickup device described in. 7. Information is reproduced and / or recorded on an information recording surface of a first optical information recording medium having a protective substrate thickness t1 by using a first light source which emits a light beam having a wavelength λ1 and a wavelength λ2 (λ1 An optical pickup device for reproducing and / or recording information on an information recording surface of a second optical information recording medium having a protective substrate thickness t2 (t1 <t2) using a second light source that emits a luminous flux of <λ2). The first light source and the second light source are arranged such that the distances from the light emitting points of the respective light sources to the surfaces of the first optical information recording medium and the second optical information recording medium are equal to each other, A coupling lens on which a light flux from the light source or the first light source is incident, and a light flux emitted from the coupling lens is incident to form an image on the information recording surface and the protective substrate thicknesses t1 and t2. An objective lens having a spherical aberration correction diffractive structure that corrects the spherical aberration caused by, and at least one of the objective lens and the coupling lens has a finite divergence when a light beam from the second light source is incident. An optical pickup device comprising a diffractive structure configured to cause light to enter the objective lens. 8. The first objective lens including an optical axis,
A central area used for reproducing and / or recording information on both the optical information recording medium and the second optical information recording medium, and the first optical information recording mainly located on the peripheral side of the central area. The spherical aberration which has an optical functional surface consisting of a peripheral region used for reproducing and / or recording information on the medium, and which has no paraxial refractive power in the central region and corrects the spherical aberration. The optical pickup device according to claim 6, further comprising a diffractive structure for correction. 9. The first objective lens includes an optical axis and includes the first objective lens.
A central area used for reproducing and / or recording information on both the optical information recording medium and the second optical information recording medium, and the first optical information recording mainly located on the peripheral side of the central area. For spherical aberration correction, having an optical functional surface consisting of a peripheral region used for reproducing and / or recording information on a medium, and having a paraxial refractive power in the central region for correcting the spherical aberration. The optical pickup device according to claim 6, further comprising a diffractive structure. 10. The optical pickup device according to claim 1, wherein the diffractive structure is provided on the coupling lens. 11. The optical pickup device according to claim 1, wherein the diffractive structure is provided on the objective lens. 12. The optical pickup device according to claim 1, wherein the diffractive structure is provided on both the coupling lens and the objective lens. 13. The optical pickup device according to claim 1, wherein the first light source and the second light source are provided on the same substrate and are unitized. 14. The first light source emits a light beam having a wavelength of 655 nm, the second light source emits a light beam having a wavelength of 785 nm, and the diffractive structure and / or the spherical aberration correcting diffractive structure emits the first optical information. The wavelength 65 on the information recording surface of the recording medium
The imaging point position change rate (μm / nm) near 5 nm is 0.
14. The optical pickup device according to claim 1, wherein the optical pickup device has a configuration of 5 to 2.0.