JPH1186315A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize outside sizes by simplfying the optical constitution of an optical path where a second lens is not arranged and suppressing the expansion occupied by the optical path, thereby narrowing the width of one side direction of longitudinal and lateral directions of outside sizes. SOLUTION: A first lens 6 acting as a divergent lens for correcting a coupling efficiency 7 of a light beam to be emitted from one side (first light source 2) of a first light source 2 and a second light source 10 to the objective lens 7 is arranged on a common optical path where a first optical path and a second optical path are joined by a beam slitter 5. Moreover, a second lens 12 acting as a collimating lens for making the light beam to be emitted from other side (second light source 10) of the light sources 2, 10 parallel beams by the resultant characteristic with the first lens 6 is arranged thereon. Thus, it is advantageous in the miniaturization of the outsize size by arranging the first lens 6 on the common optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device capable of reading signals from two types of recording media having different recording densities.

[0002]

2. Description of the Related Art As an optical disk in which a signal is optically read using a light beam such as a laser beam,
CDs (Compact Disks) have become widespread, but in response to the need for even larger capacities, the same disk diameter as CDs has been used to ensure mechanical compatibility, and higher density recording has been achieved by using higher density recording than CDs. A standardized high-density disk (DVD) has been proposed for the purpose of illustration.

[0003] In this DVD, a recording signal is read by using a short wavelength semiconductor laser and an optical pickup device having an optical system with high resolution. By the way, in order for the optical pickup device to read both CD and DVD signals, a laser diode and a DVD that emit a light beam having a wavelength suitable for the recording density of the CD are required.
A laser diode that emits a light beam having a wavelength suitable for the recording density of a laser diode is provided with two types of light sources having different wavelengths, and the light source to be used is switched according to the recording density of the disk from which a signal is read. There is a method in which signals can be read from two types of disks having different recording densities by an optical pickup.

In an optical pickup device using these two types of light sources, a recording medium having a wavelength-dependent recording film,
For example, even in the case of a CD-R, a signal can be read by a light beam having an appropriate wavelength, so that it is possible to prevent a situation in which a recorded signal cannot be read due to a remarkable decrease in a signal intensity level obtained by an optical pickup device. it can.

[0005]

By the way, the aforementioned 2
In an optical pickup device using two types of light sources, an optical system commonly used by the two types of light sources is designed with priority given to a DVD having a high recording density. The parallel light is made incident on the objective lens so that the light spot condensed by the objective lens is suitable for DVD. For that reason,
It is necessary to arrange a collimator lens for converting a divergent light beam emitted from the DVD light source into a parallel light between the DVD light source and the objective lens.

In addition, an objective lens set as a DVD optical system used for reading a signal of a DVD is not used as a DVD optical system in order to make the objective lens suitable for a light beam emitted from a light source for a CD. It is necessary to arrange a divergent lens in the optical path for CD, adjust the divergence angle when the light beam emitted from the light source for CD is incident on the objective lens, and correct the coupling efficiency of the light beam to the objective lens. is there.

In such an optical pickup device using two types of light sources and corresponding to two types of recording media having different recording densities, there are many optical components to be used. Since there was a problem in that respect, some measures were desired.

The present invention provides an optical pickup device that solves this problem by devising the arrangement of optical components.

[0009]

According to the present invention, a first light source and a second light source which emit light beams having different wavelengths are used by switching between two kinds of recording media having different recording densities for signal reading. In the optical pickup device described above, the first light source and the second light source are branched by a beam splitter to form a first optical path and a second optical path having different optical axes.
Each is arranged in the optical path. And the first
A divergent lens for correcting the coupling efficiency of the light beam emitted from one of the first light source and the second light source to the objective lens on a common optical path where the optical path and the second optical path are merged by the beam splitter and guided to the objective lens. A working first lens is arranged. A collimator that converts a light beam emitted from the other of the first light source and the second light source into a parallel light in an optical path different from an optical path in which one of the first light source and the second light source is arranged, by a combination characteristic with the first lens. A second lens acting as a lens is arranged. With such an optical arrangement, the first lens acting as a divergent lens is arranged on the common optical path, and the optical configuration of the optical path on which one of the first light source and the second light source is arranged is simplified. The overall size is reduced by suppressing the area required for forming the lever optical path.

Further, the beam splitter is constituted by a prism, the first lens and the second lens are constituted by a flat lens on one side on the side of the beam splitter, and the first lens and the second lens are respectively brought into close contact with the beam splitter. By integrating them, the assembly is simplified and the mounting error of parts is reduced.

[0011]

FIG. 1 is a plan view showing an optical system of an optical pickup device according to an embodiment of the present invention, and FIG. 2 is a side view showing an optical arrangement of an optical element in FIG.

The optical pickup device shown in FIG. 1 has a configuration capable of reading a signal from a CD and a DVD. In the drawing, reference numeral 1 denotes a light that includes a first laser element 2 that emits a laser beam having a wavelength suitable for a CD, for example, 780 nm, and receives a laser beam from the first laser element 2 that is modulated by a disk in the same package. This is an optical composite unit including the detector 3.

The optical composite unit 1 has a diffraction grating 4 of a hologram element for splitting an optical path in a front portion of a package where the first laser element 2 and the photodetector 3 are installed. The optical axis of the laser beam returned from the disk is bent, and the laser beam is applied to a photodetector 3 arranged on an optical axis different from that of the first laser element 2.

The first laser element 2 of the optical composite unit 1
Is emitted from the optical composite unit 1 through the diffraction grating 4, and the optical axis is bent by a prism type beam splitter 5 composed of a filter having wavelength selectivity.
After the divergence angle is adjusted by the first lens 6 of the convex lens arranged in close contact with the mirror, the light is reflected by the rising mirror 7 so that the optical axis is perpendicular to the disk surface and is incident on the objective lens 8. The light is converged by the objective lens 8 and irradiated onto the signal surface of the disk D.

An aperture setting plate 9 for setting the aperture diameter of the objective lens 8 is disposed in front of the objective lens 8.
The luminous flux of the laser beam incident on the objective lens 8 is restricted by the aperture diameter set by the aperture setting plate 9.

The laser beam modulated and reflected by the signal surface of the disk D returns to the objective lens 8, returns to the beam splitter 5 via the aperture setting plate 9, the rising mirror 7, and the first lens 6, and receives the laser beam. The light is reflected by the beam splitter 5 and returned to the optical composite unit 1 due to the wavelength.

The laser beam returned to the optical composite unit 1 is received by the photodetector 3 after the optical axis is bent by the diffraction grating 4. Thus, the laser beam corresponding to the CD emitted from the first laser element 2 disposed in the optical composite unit 1 is received by the photodetector 3 in the optical composite unit 1, and the CD is detected by the photodetector 3. And the control signals used for the focusing control and the tracking control corresponding to the CD are obtained.

On the other hand, a laser unit 10 having a second laser element is arranged on an optical path which is branched by a beam splitter 7 and has an optical axis different from the optical path in which the first laser element 2 is arranged. The laser unit 10
The second laser element provided in the device emits a laser beam having a wavelength suitable for DVD, for example, 650 nm.

The laser beam emitted from the second laser element of the laser unit 10 is reflected by the surface of the half mirror 11 and condensed by the second lens 12 of the convex lens arranged in close contact with the beam splitter 5. The light enters the beam splitter 5. The laser beam incident on the beam splitter 5 goes straight as it is because of the wavelength of the laser beam, and is further condensed via the first lens 6.

Thereafter, the laser beam enters the objective lens 8 along the same path as the laser beam from the first laser element 2 and is converged on the signal surface of the disk D by the objective lens 8.

The laser beam modulated and reflected by the signal surface of the disk D returns to the objective lens 8, returns to the beam splitter 5 via the aperture setting plate 9, the rising mirror 7, and the first lens 6. Go straight through the splitter 5 and further through the second lens 12 the half mirror 11
Return to

The laser beam returned to the half mirror 11 passes through the half mirror 11 and reaches the photodetector 13, where the laser beam is received. As described above, the laser beam corresponding to the DVD emitted from the second laser element of the laser unit 10 is received by the photodetector 13, the recording signal of the DVD is obtained by the photodetector 13, and the DVD corresponding to the DVD is obtained. Each control signal used for the focusing control and the tracking control is obtained.

By the way, the aperture setting plate 9 is adapted to act as an aperture having a different size depending on the laser element to be used. When a laser beam emitted from the first laser element 2 is used, the aperture setting plate 9 is opened. The caliber is first
It is set appropriately in accordance with the CD in consideration of the wavelength of the laser beam emitted from the laser element 2.

On the other hand, when a laser beam emitted from the second laser element of the laser unit 10 is used, the aperture diameter of the aperture setting plate 9 matches the wavelength of the laser beam emitted from the second laser element. DVD
It is set appropriately according to. Therefore, when a laser beam emitted from the first laser element 2 is used, the light spot for reading the recording signal of the disk has a light spot diameter and a focal depth suitable for a CD, and the light spot from the second laser element of the laser unit 10 When a emitted laser beam is used, a light spot for reading a recording signal of a disk has a light spot diameter and a focal depth suitable for a DVD.

The first lens 6 is arranged on a common optical path where the optical path where the optical composite unit 1 is arranged and the optical path where the laser unit 10 is arranged are joined by the beam splitter 5 and guided to the objective lens. , First
Each laser beam emitted from each of the laser element 2 and the second laser element is passed.

The first lens 6 includes a first laser element 2
It is set so as to act as a divergent lens for correcting the coupling efficiency of the laser beam emitted from the objective lens 8 to the objective lens 8.

On the other hand, the second lens 12 is arranged on the optical path where the laser unit 10 branched by the beam splitter 5 is arranged, and only the laser beam emitted from the second laser element is passed.

The second lens 12 is set so as to act as a collimator lens for converting a laser beam emitted from the second laser element of the laser unit 10 into parallel light by a combination characteristic with the first lens 6.

The first lens 6 and the second lens 12 are
The sides facing the beam splitter 5 are each formed of a plane, and are integrated with the beam splitter 5 by bonding. Therefore, the beam splitter 5
The divergent lens and the collimator lens can be installed at the same time by installing, which is advantageous in terms of the assembly work of the optical system and the accuracy of mounting the parts.

Further, it is not necessary to dispose any other optical components in the optical path where the optical composite unit 1 is disposed, and the optical composite unit 1 can be disposed close to the beam splitter 5, so that the vertical and horizontal dimensions of the external dimensions can be reduced. Is advantageous in reducing the width in one direction, and the external dimensions can be reduced. In this case, the second lens 12 is arranged on the optical path in which the laser unit 10 that passes through the beam splitter 5 and is aligned with the common optical path is arranged. It is possible to reduce the amount of overhang on the optical path side that is not arranged in the optical path that is bent with respect to the common optical path to be reflected and that is bent with respect to the common optical path, which is advantageous for miniaturization of the external dimensions.

When it is desired to reduce the amount of overhang on the optical path side that passes through the beam splitter 5 and is on a straight line with the common optical path, a high-density optical path that is bent with respect to the common optical path reflected by the beam splitter 5 is used. The laser unit 10 that emits a wavelength corresponding to the DVD on the side may be disposed, and the second lens 12 may be disposed in close contact with the folded optical path side of the beam splitter 5.

Further, in the embodiment, the first lens 6 and the second lens 12 are respectively brought into close contact with the beam splitter 5 to be integrated. However, even if the first lens 6 and the second lens 12 are not integrated, the first lens 6 is disposed in the common optical path. Therefore, there is no need to dispose any other optical element in the optical path where the optical composite unit 1 is disposed, which is advantageous in reducing the external dimensions.

[0033]

As described above, the present invention acts as a divergent lens on the common optical path where the first optical path and the second optical path where the first light source and the second light source are respectively arranged are merged by the beam splitter. The first lens is arranged, and the second lens that acts as a collimator lens due to the combined characteristics with the first lens is arranged on one of the first optical path and the second optical path. The optical configuration of the optical path that is not performed can be simplified, the amount of overhang occupied by the optical path can be suppressed, and it is advantageous to reduce the width of the external dimension in one of the vertical and horizontal directions, and the external dimensions can be reduced in size.

Further, according to the present invention, the beam splitter is constituted by a prism, and the first lens and the second lens are constituted by lenses having a flat surface on one side, so that the first lens and the second lens are respectively brought into close contact with the beam splitter. Since the beam splitter is installed, the divergent lens and the collimator lens can be installed at the same time by installing the beam splitter, which is advantageous in terms of the work of assembling the optical system and the accuracy of mounting components.

In this case, by arranging the second lens on an optical path which passes through the beam splitter and is in line with the common optical path, the second lens is folded with respect to the common optical path reflected by the beam splitter. Since it is not necessary to arrange the optical path in the bent optical path, the amount of protrusion in the optical axis direction orthogonal to the common optical path can be reduced, which is advantageous for miniaturization of external dimensions.

[Brief description of the drawings]

FIG. 1 is a plan optical arrangement diagram showing an optical system of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is an optical arrangement view from the side showing an overlapping portion of the optical elements in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical composite unit 2 1st laser element 3 Photodetector 5 Beam splitter 6 1st lens 8 Objective lens 10 Laser unit 12 2nd lens 13 Photodetector

Claims (3)

[Claims] A first light source and a second light source that emit light beams having different wavelengths from each other; and a light source that emits a light beam incident on an objective lens is selectively switched between the first light source and the second light source. An optical pickup device for reading signals of at least two types of recording media having different recording densities, wherein the first light source and the second light source are branched into a first optical path and a second optical path of different optical paths having different optical axes. A beam splitter for disposition, a first lens disposed on a common optical path where the first optical path and the second optical path are joined by the beam splitter and guided to an objective lens, and on the first optical path and the second optical path. A second lens disposed on one of the
The first lens is a divergent lens that corrects a coupling efficiency of a light beam emitted from a light source disposed on an optical path where the second lens is not disposed, of the first optical path and the second optical path, to an objective lens. And the second lens emits light from a light source disposed in the optical path on which the second lens is disposed, of the first optical path and the second optical path, due to the combined characteristics with the first lens. An optical pickup device, which functions as a collimator lens that converts a beam into parallel light. 2. The beam splitter is constituted by a prism, the first lens and the second lens are constituted by lenses having flat surfaces on the side of the beam splitter, and the first lens and the second lens are respectively constituted by the beam splitter. 2. The optical pickup device according to claim 1, wherein said optical pickup device is integrated with said optical pickup. 3. The optical pickup according to claim 1, wherein the second lens is disposed in an optical path of the first optical path and the second optical path, which is transmitted through a beam splitter and guided to the common optical path. apparatus.