JP2002133703A - Optical pickup device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device and an optical disk device satisfying a recordable CD optical system and a highly accurate DVD optical system and capable of reducing the number of constituent optical parts. SOLUTION: This optical pickup device and the optical disk device using thereof is characterized by that it has an optical unit 2 having a semiconductor laser emitting a laser beam A and a semiconductor laser emitting a laser beam B, an objective lens 7 focusing the laser beams A and B on respectively different optical disks 1, and a cylindrical lens 5 converting the laser beams A and B from elliptical beams to circular beams, and the semiconductor lasers are housed in the optical unit 2 so that an optical path length of the laser beams B is longer for a predetermined distance than an optical path length of the laser beam A.

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 recording or reproducing data on or from an optical recording medium. The present invention relates to an optical pickup device and an optical disk device using the optical pickup device.

[0002]

2. Description of the Related Art Optical recording media have been rapidly spread because of the advantages of their large recording capacity and easy handling. At the same time, various types of recording media have been proposed to increase the recording capacity. On the other hand, there has been a growing demand for disk devices that can support these types of recording media. In response to such a demand, Japanese Patent Application Laid-Open No. 10-1543 discloses an optical configuration using two types of light sources having different wavelengths.
For example, an optical pickup disclosed in No. 44 has been proposed.

Further, research on semiconductor lasers has made remarkable progress, and two types of semiconductor lasers having different wavelengths have been developed.
Two-wavelength lasers in one package have also begun to spread. As a technique for applying this two-wavelength laser to an optical pickup, the International Conference on Optical Memory (ISOM2000) has also proposed a technique of detecting with the same photodetector using a two-wavelength laser and a hologram.

[0004] By the way, a representative of the most popular media is C.
D. As for CDs, a medium that can be recorded by a user is also widespread, and has a medium thickness of 1.2 mm and a wavelength of 780 μm. In addition, a representative of media that is currently spreading rapidly is D
VD. DVD is 0.6m thick
m, wavelength 635-670 nm. Therefore, the above 2
It is conceivable to use a wavelength laser as the light source for both media.

[0005]

However, it has not been possible to realize an optical configuration which simultaneously solves the optimum condition of the recordable CD optical system and the optimum condition of the DVD optical system requiring high-precision reproduction. Even if a two-wavelength laser was used only for the light source, the optical pickup could not be completed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and simultaneously solves a recordable CD optical system and a DVD optical system which requires high-precision reproduction. It is an object of the present invention to provide an optical pickup device in which the number is reduced and an optical disk device using the same.

[0007]

SUMMARY OF THE INVENTION The present invention provides a first light source for emitting laser light of a first wavelength and a second light source for emitting laser light of a second wavelength longer than the first wavelength. An optical pickup device comprising: a two-wavelength light source element having the following formulas; and an objective lens for focusing two types of laser beams having different wavelengths onto media having different thicknesses, wherein the two types of laser beams are converted from elliptical beams. An optical pickup device having a cylindrical lens for converting into a circular beam, wherein the second light source is disposed so that the optical path length of the second light source is longer than the optical path length of the first light source by a predetermined distance.

According to the present invention, a recordable CD optical system and a DVD optical system requiring high-precision reproduction are simultaneously satisfied, and the number of optical components is reduced to achieve a simple configuration and a low cost. An optical pickup device and an optical disk device using the same can be provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a first light source for emitting a laser beam of a first wavelength and a laser beam of a second wavelength longer than the first wavelength are used. An optical pickup device comprising: a two-wavelength light source element having a second light source for emitting light; and an objective lens for focusing two types of laser beams having different wavelengths on media having different thicknesses. A cylindrical lens for converting a laser beam from an elliptical beam to a circular beam, wherein the second light source is disposed such that the optical path length of the second light source is longer than the optical path length of the first light source by a predetermined distance. An optical pickup device.

According to the present invention, a recordable CD optical system and a DVD optical system that requires high-precision reproduction are simultaneously satisfied, and the number of optical components is reduced to achieve a simple configuration and a low cost. An optical pickup device can be provided.

According to a second aspect of the present invention, there is provided an optical pickup device for reproducing information recorded on an optical disk or recording information, wherein a first laser emitting a first wavelength laser beam is emitted. Light source and a second light source longer than the first wavelength.
A two-wavelength light source element having a second light source that emits laser light of a different wavelength, an objective lens that focuses two types of laser light having different wavelengths on media having different thicknesses, and two types of laser light And a cylindrical lens that converts two types of laser light from an elliptical beam to a circular beam, and the two-wavelength light source element has a larger optical path length of the second light source than the optical path length of the first light source. An optical pickup device wherein an optical path length is increased by a predetermined distance and a second light source is arranged.

In particular, the two-wavelength light source element is such that the second light source is arranged in the direction away from the collimator lens along the optical axis of the optical system by a predetermined distance from the optical path length of the first light source, and Is set in the range of 25 μm to 45 μm.

Further, the two-wavelength light source element accommodates the joint surface of the first light source and the joint surface of the second light source in parallel with each other, so that the curved surface axis of the cylindrical lens is in a direction perpendicular to the joint surface. This is one in which a two-wavelength light source element and a cylindrical lens are arranged.

According to the present invention, a recordable CD optical system and a DVD optical system requiring high-precision reproduction are simultaneously satisfied, and the number of optical components is reduced to achieve a simple configuration and a low cost. An optical pickup device can be provided.

According to a sixth aspect of the present invention, there is provided an optical disk device using the optical pickup device according to any one of the first to fifth aspects. According to the present invention, a compact and inexpensive CD optical system and D
An optical disk device that can be used together with a VD optical system can be provided.

An embodiment of the present invention will be described below with reference to the drawings. For simplicity of explanation and easy understanding, description will be made using a DVD as an example of a high-density recording medium and a CD as an example of a low-density recording medium.
The DVD has a medium thickness of 1.2 mm and a thickness from the lower surface (front surface) to the recording layer of 0.6 mm. On the other hand, both the thickness of the medium and the thickness from the lower surface (front surface) to the recording layer of the CD are 1.2.
mm.

(Embodiment 1) FIG. 1 is a plan view of an optical pickup device according to Embodiment 1 of the present invention, and FIG. 2 is an enlarged view of a main part of the optical system of FIG. 1 and 2, reference numeral 1 denotes an optical disk, and a lower surface (front surface)
A high-density optical disk (DVD) having a thickness from about 0.6 mm to a recording surface and a low-density optical disk (CD) having a thickness from about 1.2 mm to a recording surface can be used.

Reference numeral 2 denotes an optical unit. Optical unit 2
Accommodates a two-wavelength semiconductor laser in which two types of semiconductor lasers having different wavelengths are housed in one package.
The light source of the first wavelength is the first semiconductor laser 21, which emits laser light A having a wavelength of 635 to 670 nm. Also,
The light source having the second wavelength is the second semiconductor laser 22, which emits a laser beam B having a wavelength of 780 nm. Further, a two-wavelength semiconductor laser, a diffraction grating for generating three beams from the laser beam B, a return light separating element for guiding reflected light from the optical disc 1 to a detector, and a diffraction grating are integrally formed.

Reference numeral 3 denotes a light receiving element. A light receiving element for detecting the optical output of the two-wavelength semiconductor laser and a light receiving element for detecting the reflected light from the optical disk 1 are housed.

Reference numeral 4 denotes a collimator lens. The diffused light emitted from the two-wavelength semiconductor laser is converted into substantially parallel light. In order to satisfy the condition of the recordable CD optical system, the collimator lens 4 is set to have a short focal length and is arranged as close as possible to the optical unit 2 (that is, the light source). In this way, the emitted light before being diffused can be converged, so that the light output of the semiconductor laser can be used without waste and the utilization efficiency can be improved.

5 is a cylindrical lens (cylindrical lens)
To shape the beam light of the elliptical pattern into a circular pattern.

Reference numeral 6 denotes an aperture filter. The objective lens 7 is shared to control the diameter of a passing light beam in order to satisfy both standards of a CD disk and a DVD disk.
That is, laser light A (wavelength for DVD 635-670 nm)
Is transmitted in the entire region, and a numerical aperture (hereinafter abbreviated as NA) of 0.6 is realized. On the other hand, the laser light B (wavelength for CD: 780 nm) is transmitted in the central region and reflected (light-absorbed) in the peripheral region. Thus, NA 0.45 (NA
0.5 in some cases).

Reference numeral 7 denotes an objective lens. Now, when a parallel light beam enters the objective lens 7, the laser light A is focused to a depth of 0.6 mm from the disk surface, and the laser light B is focused to a depth of 1.2 mm from the disk surface. Provide a function to focus. Thus, even if the wavelength of the light source and the thickness of the medium up to the recording layer are different, it can function properly. That is, the objective lens 7 functions as a so-called special objective lens.

The objective lens 7 is fixed to the lens holder 8 by bonding or the like. One end of a wire 15 is fixed to the lens holder 8, and the lens holder 8 is slightly displaced by four wires 15 in a focus direction (vertical direction on the paper surface) and a tracking direction (lateral direction on the paper surface, that is, in a radial direction of the optical disc 1). Supported as possible. The other end of the wire 15 is fixedly supported by the suspension holder 14. Embodiment 1
Here, the lens holder 8, the wire 15 and the suspension holder 14 are integrally formed.

The lens holder 8 has a frame type structure having a circular space and a substantially rectangular opening, and the above-mentioned objective lens 7 is fixed to the circular space by an adhesive or the like. On the other hand, a focus coil 16 for driving the objective lens 7 in the focus direction and a tracking coil 17 for driving in the tracking direction are fixed to the substantially rectangular opening by means such as bonding.

A yoke 18 is fixed to the carriage 10 together with the suspension holder 14. York 1
A magnet 19 is further fixed to 8. Thus, the focus coil 16 and the tracking coil 17 are arranged in the magnetic field formed by the magnet 19. Therefore, by supplying electricity to the focus coil 16 or the tracking coil 17 via the wire 15, the objective lens 7 can be slightly displaced in the focus direction or the tracking direction.

When the objective lens 7 needs to be displaced over the inner and outer circumferences of the optical disk 1, the carriage 10 is moved in the radial direction. A support shaft 11 and a guide shaft 12 are arranged in parallel on both sides of the carriage 10, and both ends of the carriage 10 are slidably supported by the support shaft 11 and the guide shaft 12. Then, the carriage 10 moves in the radial direction of the optical disc 1 by being driven in the radial direction by a carriage moving means (not shown). From the above optical unit 2 to the magnet 1
The whole up to 9 is collectively referred to as an optical pickup device.

Next, the relationship between the first and second semiconductor lasers 21 and 22 and the cylindrical lens 5 will be described with reference to FIG. First, FIG. 2A is a schematic diagram of a radiation pattern of a semiconductor laser. Generally, when laser light is emitted from the center (active layer) of the bonding surface 23 of the first and second semiconductor lasers 21 and 22, the laser beam has a narrow divergence angle in the direction (x) parallel to the bonding surface, It has a wide divergence angle in the direction (y) perpendicular to the bonding surface. Therefore, the distribution pattern (far field pattern, far field pattern) of the light beam cross-sectional intensity at a position sufficiently distant from the light emitting point (the active layer at the center of the bonding surface 23).
ern; hereinafter abbreviated as FFP) is an elliptical pattern that is narrow in the x direction and wide in the y direction.

FIG. 2B is an explanatory view of a light beam having the paper surface in the x direction. Therefore, the first and second semiconductor lasers 2
The joining surfaces 23 of 1 and 22 are combined so as to be parallel to each other, and housed (arranged and mounted) in the optical unit 2.
Then, the optical unit 2 and the cylindrical lens 5 are arranged such that the virtual curved axis of the cylindrical curved surface forming the cylindrical lens 5 is in the direction (y) perpendicular to the joint surface.

Thus, the first and second semiconductor lasers 21,
Both the laser light A and the laser light B emitted from 22 are converted into a parallel light beam by the collimator lens 4. However, the radiation pattern is a parallel light beam having a narrow divergence angle. Then, through the cylindrical lens 5, x
Expand beam in direction. As a result, the x-direction pattern of the laser light A emitted from the cylindrical lens 5 is y
Enlarged in the same way as the axial direction, and the cylindrical lens 5
Is emitted as a parallel light beam from the emission surface of.

On the other hand, FIG. 2 (c) is an explanatory view of a light beam having the paper surface in the y direction. Similarly, the laser light A and the laser light B emitted from the first and second semiconductor lasers 21 and 22 are both converted into parallel light by the collimator lens 4. At this time, the patterns of both laser beams already have a sufficient spread angle. Therefore, the cylindrical lens 5 functions as a light guide member that is simply parallel to the y direction. As a result, both the laser light A and the laser light B emitted from the cylindrical lens 5 enter the aperture filter 6 in a circular pattern.

The case where different wavelengths of the laser light A (wavelength for DVD: 635 to 670 nm) and the laser light B (wavelength for CD: 780 nm) will be described for the entire optical system configured as described above. Now, for the sake of simplicity, it is assumed that the first semiconductor laser 21, the collimator lens 4, and the cylindrical lens 5 are set to the optical conditions of the laser beam A.

As generally referred to as chromatic aberration, the refractive index of an optical system depends on the wavelength, and the longer the wavelength, the smaller the refraction angle. Therefore, when the laser light B having a long wavelength is applied to the above-described optical conditions, the laser light B transmitted through the collimator lens 4 becomes a slightly divergent light, and an elliptic pattern remains after transmitting through the cylindrical lens 5.

Therefore, in the embodiment of the present invention, the second semiconductor laser 22 is arranged in a direction away from the collimator lens 4 along the optical axis direction of the optical system.
FIG. 2C illustrates the above configuration,
The semiconductor laser 22 is arranged in the direction away from the collimator lens 4 along the optical axis direction of the optical system by a shift amount L. In other words, the optical path length of the long wavelength optical system is set longer by a predetermined distance (L) with respect to the short wavelength optical system. More specifically, a two-wavelength semiconductor laser is housed inside the optical unit 2 described above. At this time, mounting is performed so that the virtual light emitting points of both light sources have the above-mentioned shift amount L, respectively.

Thus, since the laser beam B is longer than the focal length of the collimator lens 4, the collimator lens 4 can maintain a predetermined refraction angle even with a long-wavelength light beam. Beam shaping can be satisfied. As a result, it is possible to satisfy a CD optical system and a DVD optical system at the same time without using a complicated optical lens such as an achromatic lens, and realize a simple configuration in which the number of optical components is greatly reduced. it can.

FIG. 3 is a diagram for explaining the influence of the shift amount L on the aberration. In FIG. 3, as described above, when the second semiconductor laser 22 of the laser beam B is relatively moved with the first semiconductor laser 21 of the laser beam A as a reference position,
It shows the total aberration. The moving direction is defined as + in the direction away from the collimator lens 4. The astigmatism (astigma) changes in proportion to the shift amount L from the above-described action, and the total aberration including the astigmatism and the wavefront aberration becomes the minimum value when the shift amount is 35 μm. When the practical allowable aberration range of the optical pickup device is set to 20 mλ, the allowable shift amount L is required to be 25 to 45 μm.

The operation of the optical pickup device according to Embodiment 1 of the present invention configured as described above will be described. 1 and 2, the DVD optical system has a high-density recording medium and small and precise medium information to be detected (recording pits of an optical disk). Therefore, the laser beam A is converted into a parallel light beam by the collimator lens 4 and then the FFP elliptical beam is converted into a circular beam by the cylindrical lens 5. Further, NA is matched by the aperture filter 6 (as described above, the laser beam A has no limitation on the beam diameter). In addition, a reflecting mirror (not shown) is arranged below the objective lens 7 so that a beam substantially parallel to the optical disk 1 is incident on the objective lens 7. In this way, the laser beam A of the short-wavelength circular beam is narrowed down to a minimum spot by the effect of the special objective lens of the objective lens 7, and focused on a 0.6 mm recording layer from the disk surface.

Next, the laser beam B of the CD optical system is emitted from the collimator lens 4 having a short focal length.
Is converted to a parallel light beam as much as possible. Thus,
It is possible to irradiate a recording medium by efficiently using the optical power required for recording. Further, the laser light B converts the FFP elliptical beam into a circular beam by the cylindrical lens 5. At this time, the second semiconductor laser 22, which is the light source of the laser light B, is arranged in the direction away from the collimator lens 4 along the optical axis direction of the optical system by the shift amount L, so that the laser light B is the same as the laser light A. By maintaining a predetermined angle of refraction by the collimator lens 4, the cylindrical lens 5 can satisfy the beam shaping condition. Further, the NA is matched by the aperture filter 6, and the light is similarly incident on the objective lens 7. Therefore, the light output of the second semiconductor laser 22 can be used without waste and the utilization efficiency can be improved. In this way, by the effect of the special objective lens of the objective lens 7, the laser light B having a long wavelength is focused on a spot having a high optical power, and focused on a recording layer 1.2 mm from the disk surface.

As described in detail above, according to the present invention, the optical path length of the long wavelength optical system is set longer by a predetermined amount (L) with respect to the short wavelength optical system, so that the collimator lens 4 and the cylindrical lens 5 , The CD optical system and the DVD optical system can be satisfied at the same time. Therefore, it is possible to provide an optical pickup device having a simple configuration in which the number of constituent parts of the optical components is significantly reduced, and an optical disk device using the optical pickup device can be reduced in size and cost.
Further, it is possible to provide an optical disk device that can be used for both the CD optical system and the DVD optical system.

[0040]

According to the present invention, an optical pickup device in which a recordable CD optical system and a DVD optical system requiring high-precision reproduction are simultaneously solved and the number of optical components is reduced, and Compact, inexpensive, and CD using
An optical disk device that can be used for both an optical system and a DVD optical system can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view of an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the optical system of FIG. 1;

FIG. 3 is a view for explaining the influence of a shift amount L on aberration.

[Explanation of symbols]

 Reference Signs List 1 optical disk 2 optical unit 3 light receiving element 4 collimator lens 5 cylindrical lens 6 aperture filter 7 objective lens 8 lens holder 9 missing number 10 carriage 11 support shaft 12 guide shaft 13 missing number 14 suspension holder 15 wire 16 focus coil 17 tracking coil 18 yoke 19 magnet Reference Signs List 20 missing number 21 first semiconductor laser 22 second semiconductor laser 23 bonding surface (active layer)

Continued on the front page (72) Inventor Fumikawa Furukawa 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd.F-term (reference) 5D119 AA01 AA04 AA41 BA01 DA01 DA05 EC45 EC47 FA05 FA08 JA08 JA43 JC07 LB04

Claims (6)

[Claims] 1. A two-wavelength light source device comprising: a first light source for emitting a laser light of a first wavelength; and a second light source for emitting a laser light of a second wavelength longer than the first wavelength. And an objective lens for focusing two types of laser beams having different wavelengths onto media having different thicknesses, wherein the two types of laser beams are converted from an elliptical beam to a circular beam. An optical pickup device having a lens, wherein the second light source is disposed such that the optical path length of the second light source is longer than the optical path length of the first light source by a predetermined distance. 2. An optical pickup device for reproducing information recorded on an optical disk or recording information, comprising: a first light source for emitting a laser beam of a first wavelength; and a second light source longer than the first wavelength. A two-wavelength light source element having a second light source that emits laser light of a different wavelength, an objective lens that focuses two types of laser light having different wavelengths on media having different thicknesses, and the two types of lasers A collimator lens that converts light into a parallel light beam; and a cylindrical lens that converts the two types of laser light from an elliptical beam to a circular beam. An optical pickup device, wherein the second light source is disposed by increasing the optical path length of the second light source by a predetermined distance. 3. The apparatus according to claim 2, wherein the two-wavelength light source element is arranged in a direction in which the second light source is moved away from the collimator lens along the optical axis of the optical system by a predetermined distance from the optical path length of the first light source. The optical pickup device according to claim 2, wherein: 4. The apparatus according to claim 2, wherein said predetermined distance is set in a range of 25 μm to 45 μm.
An optical pickup device according to item 1. 5. The two-wavelength light source element receives a joint surface of the first light source and a joint surface of the second light source in parallel with each other, and sets a curved surface axis of the cylindrical lens in a direction perpendicular to the joint surface. The optical pickup device according to any one of claims 2 to 4, wherein the two-wavelength light source element and the cylindrical lens are arranged such that: 6. An optical disk device for recording or reproducing data on or from optical recording media having different recording densities, wherein the optical pickup device according to claim 1 is used. Optical disk device.