JPH11203704A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small optical pickup provided with two converging optical systems. SOLUTION: This optical pickup comprises a semiconductor laser 12 transmitting a light beam, a galvano-mirror 18 deflecting the light beam, a relay lens 14 arranged between them, a first converging optical system converging the light beam from the galvano-mirror 18 on a recording medium 42 arranged on the upper side of the optical pickup and a second converging optical system converging the light beam from the galvano-mirror 18 on a recording medium 44 arranged on the lower side of the optical pickup. The first converging optical system is composed of an imaging lens 22, an erecting mirror 24 and an objective lens 26 and the second converging optical system is composed of an imaging lens 32, an erecting mirror 34 and an objective lens 36. These optical elements are provided in a casing 68 being movably supported and the moving directions of the objective lenses 26 and 36 by the movement of the casing 68 are set to be the tracking direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup for optically recording and reproducing information on a recording medium.

[0002]

2. Description of the Related Art Some optical pickups are provided with two condensing optical systems including an objective lens due to design requirements. The reason why such an optical pickup is designed is, for example, to selectively focus a light beam on each recording layer of a recording medium having recording layers on both sides, or
This is for selectively condensing the light beam on two recording media arranged above and below the optical pickup, or for condensing the light beam on different types of recording media to be exchanged.

[0003] Still another reason is that the access range of the recording medium is divided between the two condensing optical systems, so that the movement amount of the optical pickup is reduced and the access speed is improved.

Such an optical pickup has a mechanism for directing the light beam emitted from the light source unit to one of the two condensing optical systems, in other words, a mechanism for switching the condensing optical system to which the light beam is directed. ing.

For example, Japanese Patent Application Laid-Open No. Hei 5-189797 includes a fixed optical unit for emitting a light beam and a movable optical unit equipped with two condensing optical systems. An optical pickup is disclosed that directs a light beam to one of the focusing optics by translation.

[0006]

The optical pickup is desired to be small and light. However, the above-mentioned optical pickup requires a large space for mechanically moving the fixed optical part, which is small and light. It is a factor that hinders the development.

Further, since the condensing optical system to which the light beam is directed is switched by mechanically moving a relatively large fixed optical unit, it is difficult to obtain high responsiveness.

Further, a mechanism for tracking control is provided for each light collecting optical system separately from a mechanism for directing a light beam to one light collecting optical system. The present invention has been made in view of such a situation, and an object of the present invention is to provide a small-sized optical pickup having two light collecting optical systems.

It is a further object of the present invention to provide an optical pickup which can switch a focusing optical system to which a light beam is directed at high speed. A further object of the present invention is to provide an optical pickup in which a mechanism for directing a light beam to one of the condensing optical systems also serves as a mechanism for tracking control.

[0010]

According to a first aspect of the present invention, there is provided an optical pickup, comprising: a light source for emitting a light beam; a galvano mirror for deflecting the light beam; and a light source disposed between the light source and the galvano mirror. A first relay lens and a plurality of condensing optical systems for condensing a light beam on a recording medium, each of which includes at least a second relay lens and an objective lens, and is provided through the galvanomirror. The light beam is incident on the plurality of condensing optical systems.

An optical pickup according to a second aspect of the present invention is characterized in that the light passing through the galvanomirror selects one of the plurality of condensing optical systems by an optical path selecting means.

An optical pickup according to a third aspect of the present invention is characterized in that the optical path selecting means is the galvanomirror. An optical pickup according to a fourth aspect of the present invention is characterized in that the optical path selecting means is an electro-optical element.

An optical pickup according to a fifth aspect of the present invention is characterized in that the light passing through the galvanomirror is separated into a light beam by a beam splitter and is incident on the plurality of condensing optical systems. An optical pickup according to claim 6 of the present invention is characterized in that a mirror is arranged between the galvanometer mirror and the objective lens.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, an optical pickup according to the first embodiment will be described with reference to FIG. As shown in FIGS. 1A and 1B, the optical pickup includes a semiconductor laser 12 for emitting a light beam, a galvano mirror 18 for deflecting the light beam, and a relay lens disposed between these. (First relay lens) 14. Although the relay lens 14 also functions as a collimating lens, a configuration in which a relay lens and a collimating lens are provided separately may be employed. The galvanomirror 18 is supported so as to be swingable about an axis 18a perpendicular to the paper surface of FIG. 1A, and the direction of the surface is controlled by a drive mechanism (not shown).

The optical pickup has a first condensing optical system for condensing a light beam from the galvanomirror 18 on a recording medium 42 arranged above the optical pickup, and a recording medium arranged below the optical pickup. And a second condensing optical system for condensing light on the medium 44.

The first condensing optical system includes a galvanomirror 18
Lens (second relay lens) 22 for converting the light beam from the light into parallel light, and imaging lens 2
It comprises a rising mirror 24 for reflecting the light beam from the mirror 2 upward and an objective lens 26 for condensing the light beam from the rising mirror 24.

Similarly, the second condensing optical system includes an imaging lens (second relay lens) 32 for converting the light beam from the galvanomirror 18 into parallel light and a light beam from the imaging lens 32 directed downward. The mirror comprises a rising mirror 34 for reflecting light and an objective lens 36 for condensing a light beam from the rising mirror 34.

Further, the optical pickup comprises a prism 52
, A light amount monitoring photodiode 54, a hologram 56, an error detection photodiode 58, a Wollaston prism 60, and a photodetector 62.

The prism 52 converts a part of the light beam from the semiconductor laser 12 into a light amount monitoring photodiode 5.
4 and the return light beam from the recording media 42 and 44 to the Wollaston prism 60. The Wollaston prism 60 splits the light beam in a direction perpendicular to the plane of the paper, and the split light beam enters the photodetector 62.

The hologram 56 guides the return light beam passing through the prism 52 toward the error detecting photodiode 58. As shown in FIG. 1C, the photodetector 62 is configured by a photodiode having four light receiving units. The outputs of the light receiving section of the photodetector 62 are a,
When represented by b, c, and d, the reproduced signal is (a + c)-(b +
d), the tracking error signal is (a + b)-
(C + d). The tracking error signal and the focus error signal are also obtained by the error detection photodiode 58.

The above-described optical elements are provided on one housing 68, for example, a swingably supported swinging member or a translationally supported moving body. At this time, the direction of movement of the objective lenses 26 and 36 due to swinging and translation is set to a direction crossing the tracks formed on the recording media 42 and 44 substantially orthogonally, that is, a tracking direction.

The divergent light beam emitted from the semiconductor laser 12 is converted into a convergent light beam by the relay lens 14, and then the imaging lens 22 or the imaging lens 3 by the galvanomirror 18.
It is reflected towards 2. In other words, relay lens 1
The light beam from 4 is selectively moved to one of the first condensing optical system and the second condensing optical system by swinging the galvanomirror 18 largely (for example, 5 to 10 °) around the axis 18a. Oriented. That is, galvanometer mirror 1
8, two focusing optical systems are selected.

The two focusing optics are substantially the same,
Since the action on the light beam is the same, only the first condensing optical system will be typically described below. The light beam directed to the first condensing optical system is changed into parallel light by the imaging lens 22, reflected upward by the rising mirror 24, and turned into the objective lens 26.
As a result, a light spot is formed on the surface of the recording medium 42.

The recording medium 42 is relatively moved with respect to the objective lens 26, during which focus control and tracking control are performed. The focus control is performed by moving the relay lens 14 along the optical axis, and the tracking control is performed by moving the galvanometer mirror 18 to the axis 18.
This is performed by shaking a little (eg, 1 to 2 °) around a.

As described above, in this optical pickup, the condensing optical system for guiding the light beam is selected by swinging the galvanomirror 18 greatly, and the galvanomirror 1
The tracking adjustment is performed by shaking 8 small.

Therefore, the plurality of recording media 42 and 44 can be selectively accessed, the switching can be performed in a short time, and an optical pickup having a small device configuration can be obtained. Also,
Since the imaging lens 22 is arranged between the galvanomirror 18 and the objective lens 26 and the imaging lens 32 is arranged between the galvanomirror 18 and the objective lens 36, the angle range of the galvanomirror 18 can be widened.
That is, regarding the imaging lens 22 (or 32), the galvanometer mirror 18 and the objective lens 26 (or 36)
Are located at substantially conjugate positions. Therefore, even if the tracking adjustment is performed by swinging the galvanometer mirror 18, the movement of the light beam at the front focal position of the objective lens 26 (or 36) is very small. Therefore, the offset of the track error signal at the time of tracking adjustment is very small. Therefore, since the two objective lenses 26 and 36 are positioned on the same recording track, the moving range of the optical pickup in the tracking direction is reduced.

If the parallel light is made incident on the galvanometer mirror 18 and the parallel light is made incident on the objective lens, if the galvanomirror is shaken and the tracking is adjusted, the light beam incident on the objective lens moves greatly. . This has the disadvantage that the offset of the track error signal becomes very large.

Since the galvanomirror doubles as a selecting means for selectively directing light to a plurality of condensing optical systems and a tracking means for finely moving a light spot on a recording medium in a tracking direction, The configuration is simplified,
It is small, lightweight and inexpensive.

Since a plurality of focusing optical systems are selected according to the direction of reflection of the total reflection mirror of the galvanometer mirror, the light is separated using, for example, a half mirror, and the separated light is sent to the plurality of focusing optical systems. On the other hand, there is no light amount loss reaching one condensing optical system. Therefore, a large output is obtained from the objective lens.

When a swing arm type seek mechanism for rotating the casing 68 about an axis perpendicular to the paper surface is used, the rotation center can be around the galvanomirror.
In that case, a galvanometer mirror having heavy parts such as a magnet and a yoke can be arranged near the center of rotation,
The swing arm has a small moment of inertia and high drive sensitivity.

Each condensing optical system has one imaging lens (second relay lens). For this reason, by adjusting the position of each imaging lens in the optical axis direction, it is possible to adjust the focus in the focus direction according to each objective lens.

Next, an optical pickup according to a second embodiment will be described with reference to FIG. FIG. 2 shows a portion different from the first embodiment. In the drawing, members indicated by the same reference numerals as those already used in the description of the first embodiment are equivalent members. Is shown.

As shown in FIG. 2, in this optical pickup, an imaging lens 22 and a rising mirror 24 are provided.
A flat mirror 72 that turns the light beam inward is disposed between the imaging lens 32 and a flat mirror 74 that turns the light beam inward between the imaging lens 32 and the rising mirror 34.

In other words, the first condensing optical system further includes a deflecting optical element or a plane mirror 72 disposed between the imaging lens 22 and the rising mirror 24, and the second condensing optical system. The system further includes a deflecting optic or flat mirror 74 disposed between the imaging lens 32 and the raising mirror 34.

As a result, compared to the first embodiment, the two mirrors 24 and 34 are arranged closer to each other. Therefore, the two objective lenses 26 and 36 are located close to each other in an arrangement relationship where they are projected on a plane parallel to the paper surface.

As a result, this optical pickup requires a smaller amount of movement to access the track formed on the recording medium than the optical pickup of the first embodiment, and thus the apparatus can be downsized. There is an advantage that can be promoted.

Next, an optical pickup according to a third embodiment will be described with reference to FIG. FIG. 3 shows a portion different from the first embodiment. In the drawing, members indicated by the same reference numerals as those already used in the description of the first embodiment are equivalent members. Is shown.

As shown in FIG. 3, this optical pickup converts an optical beam from the galvanomirror 18 into parallel light and deflects it toward the rising mirror 24 disposed inside, and a galvanomirror. It has an imaging lens 84 that converts the light beam from 18 into parallel light and deflects it toward the rising mirror 34 disposed inside.

In other words, the first condenser optical system further includes a deflection optical element provided integrally with the imaging lens, and the second condenser optical system is provided integrally with the imaging lens. And a deflection optical element. An imaging lens equipped with such a deflection optical element,
For example, it is produced by forming a diffraction grating (preferably composed of a hologram) on the surface of the imaging lens.

As a result, compared to the first embodiment, the two rising mirrors 24 and 34 are arranged closer. Therefore, the two objective lenses 26 and 36 are located close to each other in an arrangement relationship where they are projected on a plane parallel to the paper surface.

As a result, this optical pickup requires a smaller amount of movement to access the track formed on the recording medium than the optical pickup of the first embodiment, and thus the apparatus can be downsized. There is an advantage that can be promoted.

Further, as compared with the second embodiment, there is an advantage that the number of parts can be reduced and the structure can be reduced in weight. This is advantageous for reducing manufacturing costs and improving responsiveness.

An optical pickup according to a fourth embodiment will be described with reference to FIG. In FIG. 4, members denoted by the same reference numerals as those already used in the first embodiment indicate the same members.

As shown in FIGS. 4A and 4B, in this optical pickup, a fixed mirror 92 is provided on the optical path between the galvanometer mirror 18 and the imaging lens 32. The fixed mirror 92 is preferably located near the focal point of the light beam to reduce its size.

The orientation of the fixed mirror 92 is selected so that the optical path between the fixed mirror 92 and the rising mirror 34 is parallel to the optical path between the galvanometer mirror 18 and the rising mirror 24. .

Further, the optical path length from the galvanometer mirror 18 to the rising mirror 34 via the fixed mirror 92 is set equal to the optical path length from the galvanometer mirror 18 to the rising mirror 24.

In this optical pickup, the optical path between the galvanometer mirror 18 and the rising mirror 24 and the fixed mirror 9
Since the optical path between the mirror 2 and the rising mirror 34 is parallel to each other, the two rising mirrors 24 and 34 can be arranged at a very narrow interval as compared with the first embodiment. . As a result, a smaller optical pickup can be obtained.

In this optical pickup, the selection of the focusing optical system and the tracking control are both performed in the same manner as in the first embodiment. That is, selection of the condensing optical system is performed by swinging the galvanometer mirror 18 large (for example, 5 to 10 degrees), and tracking control is performed by swinging the galvanometer mirror 18 small (for example, 1 to 2 degrees).

An optical pickup according to a fifth embodiment will be described with reference to FIG. In FIG. 5, members denoted by the same reference numerals as those already used in the first embodiment indicate the same members.

As shown in FIGS. 5A and 5B, in this optical pickup, a first galvanomirror 94 and a second galvanomirror are provided downstream of the relay lens 14 along its axis. 96 are provided.

The first galvanomirror 94 is 45 ° ± 5 °.
5 has an optical characteristic of reflecting a light ray incident at an angle of 0 ° and transmitting a light ray incident at an angle of 0 ° ± 5 °.
(A) is supported so as to be swingable about an axis perpendicular to the paper surface. Further, the first galvanometer mirror 94 is switched by a driving mechanism (not shown) between a state in which the relay lens 14 is inclined by about 45 ° and a state in which the axis is substantially perpendicular to the axis of the relay lens 14.

When the surface of the first galvanomirror 94 is inclined by about 45 ° with respect to the axis of the relay lens 14, the first galvanomirror 94 reflects the light beam from the relay lens 14 toward the imaging lens 22. I do. Also,
When the surface of the first galvanomirror 94 is substantially perpendicular to the axis of the relay lens 14, the first galvanomirror 9
4 transmits the light beam from the relay lens 14.

The second galvanometer mirror 96 reflects the light beam transmitted through the first galvanometer mirror 94 toward the imaging lens 32. Second galvanometer mirror 96
5A is supported so as to be swingable about an axis perpendicular to the paper surface of FIG. 5A, and its reference state is such that the optical path between the first galvanometer mirror 94 and the rising mirror 24 and the second Is inclined by about 45 ° with respect to the axis of the relay lens 14 so that the optical path between the galvanometer mirror 96 and the rising mirror 34 is parallel to each other.

The optical path length from the first galvanomirror 94 to the rising mirror 24 and the second galvanomirror 9
The optical path lengths from 4 to the rising mirror 34 via the reflection mirror 96 are set to be equal to each other.

In this optical pickup, the optical path between the first galvanometer mirror 94 and the rising mirror 24 and the optical path between the second galvanometer mirror 96 and the rising mirror 34 are parallel to each other. Two mirrors 24
And 34 can be arranged at a much smaller interval than in the first embodiment, and a smaller optical pickup can be obtained.

In this optical pickup, the selection of the condensing optical system is performed by making the first galvanometer mirror 94 large (about 45 °).
This is done by shaking. That is, the surface of the first galvanomirror 94 is set at about 45 degrees with respect to the axis of the relay lens 14.
By tilting, the first condensing optical system (the imaging lens 22, the rising mirror 24, and the objective lens 2)
6) is selected, and the surface of the first galvanomirror 94 is made substantially orthogonal to the axis of the relay lens 14 so that
The second condensing optical system (the imaging lens 32, the rising mirror 34, and the objective lens 36) is selected.

The tracking control is performed by swinging the first galvanomirror by a small amount (for example, 1 to 2 °) with respect to the first focusing optical system, and by controlling the second focusing optical system. This is performed by shaking the second galvanomirror small (eg, 1 to 2 °).

Next, an optical pickup according to a sixth embodiment will be described with reference to FIG. The optical pickup of FIG. 6 switches the light beam to the first focusing optical system and the second focusing optical system by using a liquid crystal element as an electro-optical element instead of a galvanomirror and a polarization element as a polarizing optical element. This is performed by a combination with a beam splitter. In the drawings, members indicated by the same reference numerals as those already used in the description of the first embodiment indicate equivalent members.

As shown in FIG. 6, this optical pickup comprises a liquid crystal element 6 for controlling the plane of polarization of a transmitted laser beam.
3. It has a liquid crystal element driving circuit 64 as driving means, a polarizing beam splitter 65 that transmits or reflects laser light depending on the state of the polarization plane of the light beam, and a total reflection mirror 66. The beam splitter 65 changes the P-polarized light by 20%, for example.
It is designed to reflect and reflect S-polarized light by 80%.

The divergent light beam emitted from the semiconductor laser 12 is converted by the relay lens 14 into a convergent light beam. The light beam emitted from the semiconductor laser 12 is assumed to be S-polarized linearly polarized light. The light beam is reflected and deflected by the galvanometer mirror 18 toward the liquid crystal element 63.

Which one of the two condensing optical systems guides the light beam is selected depending on whether the liquid crystal driving circuit 64 drives the liquid crystal element 63 or not. When guiding the light beam to the first condensing optical system including the imaging lens 22, the rising mirror 24, and the objective lens 26, the liquid crystal element 63 is not driven. In this case, the light beam incident as S-polarized light has its polarization plane rotated by 90 degrees inside the liquid crystal element and is emitted as P-polarized light. Here, the reflection surface of the polarization beam splitter 65 reflects the P-polarized component by 20% (RP
= 20%), 80% transmission, 80% reflection of S-polarized component (R
If S = 80%) and 20% transmission are designed, most of the P-polarized light beam emitted from the liquid crystal element 63 passes through the polarization beam splitter 65 and is guided to the first condensing optical system. I will

This light beam is converted into parallel light by the imaging lens 22, reflected upward by the rising mirror 24, and condensed by the objective lens 26 on a recording medium opposed thereto. If the recording medium is a magneto-optical disk, the light beam has a polarization plane of ± θk depending on the state of the recording mark formed on the recording medium during reflection.
(Car rotation angle). The return light beam reflected by the recording medium returns to the polarization beam splitter 65 by going backward in the optical path up to that point, and is reflected by the polarization beam splitter 65. Then, the polarization component is separated by the Wollaston prism 60, and the light is detected. The signal reaches the detector 62 and a signal is detected.

On the contrary, when a light beam is guided to the second focusing optical system, a voltage is applied to the liquid crystal element 63 (the liquid crystal element 63).
Is driven). In this case, the S-polarized light beam exits as S-polarized light, is reflected by the polarization beam splitter 65, is reflected by the mirror 66, and is guided to the imaging lens 32. The light beam is converted into parallel light by the imaging lens 32, reflected downward by the rising mirror 34, and condensed by the objective lens 36 on a recording medium (magneto-optical disk) opposed thereto. If the recording medium is a magneto-optical disk, the light beam
At the time of reflection, the polarization plane is rotated by ± θk (Kerr rotation angle) depending on the state of the recording mark formed on the recording medium.
The return light beam reflected by the recording medium returns to the polarization beam splitter 65 by traveling backward through the optical path up to that point, passes through the polarization beam splitter 65, and is separated by the Wollaston prism 60 into polarization components. A signal is detected.

As described above, depending on whether the liquid crystal element 63 is driven or whether a voltage is applied or not, the light beam is directed to one of the first condensing optical system and the second condensing optical system. Attached.

The recording medium is moved relative to the objective lens, during which focus control and tracking control are performed. Focus control is performed by the image lens 22
Alternatively, the tracking control is performed by moving 32 along the optical axis, while the tracking control is performed by the galvanomirror 18.
Is performed by shaking.

Therefore, a plurality of recording media can be selectively accessed, and the switching can be performed in a very short time of switching the driving voltage of the liquid crystal element 63, and an optical pickup with a small device configuration can be obtained. Also, only one galvanomirror for tracking control is required for two recording surfaces.

The polarizing beam splitter 65 may be arranged anywhere as long as it is located between the imaging lenses 22 and 32 and the galvanometer mirror 18. Further, another optical system, for example, an optical system for detecting the angle of the galvanomirror 18 may be provided between the galvanomirror 18 and the polarization beam splitter 65. Further, the liquid crystal element 63 may be arranged anywhere as long as it is located between the polarization beam splitter 65 and the semiconductor laser 12 as a light source. For example, in order to configure a smaller optical pickup, the galvanomirror 18 And the relay lens 14.

The liquid crystal drive circuit 64 may switch between applying and not applying a DC voltage to the liquid crystal element, or switching between applying and not applying an AC voltage. When an AC voltage is applied, a rectangular wave or a sine wave may be used. Instead of applying no voltage, a very low voltage (a voltage equal to or lower than the threshold value) may be applied.

The electro-optical element is not limited to a liquid crystal element. For example, a device in which a comb-shaped electrode is formed on the exit surface of an electro-optical material of lithium niobate single crystal may be used. The polarizing optical element can also be used instead of the polarizing beam splitter as long as its reflectance and transmittance change depending on the state of the polarization plane. The reflectance of the polarizing beam splitter is 0 ≦ RP ≦ 50% ≦ RS ≦ 100%
May be freely selected within the range.

When a high-power laser beam is required, such as in a read-only disk, the electro-optical element can be omitted. As described above, according to the present embodiment, by using the electro-optical element and the polarizing optical element for directing the light beam to one of the two condensing optical systems, the condensing optical system to which the light beam is directed is extremely An optical pickup that can be switched at a high speed can be obtained. Further, regardless of which focusing optical system is used, the tracking control can be performed by one galvanomirror, and the angle at which the galvanomirror is swung for the tracking control can be made constant.

The present invention is not limited to the above-described embodiment at all, but includes all embodiments carried out without departing from the gist thereof. In the embodiment, the optical pickup including two objective lenses for condensing the light beams on different recording media arranged vertically is described. May be applied to an optical pickup provided with two objective lenses to collect light. As such an optical pickup, there is an optical pickup having an objective lens of high magnification and low magnification, for example, an optical pickup having an objective lens for CD and an objective lens for DVD. Further, the number of the condensing optical systems is not limited to two, but may be three or more. Further, an optical pickup having a plurality of condensing optical systems having objective lenses opposed to both surfaces of one recording medium may be used.

The present invention can be applied to any optical pickup that optically records and / or reproduces information, regardless of its type. For example, the present invention can be applied to an optical pickup for a read-only optical disk and an optical pickup for a recordable magneto-optical disk. Further, the present invention can also be applied to an optical pickup using a near-field recording technique, which has recently attracted attention.

The present invention includes the following inventions. (1) A light source for emitting a light beam, a galvanometer mirror for deflecting the light beam, one relay lens located between the light source and the galvanometer mirror, and a light source for condensing the light beam on a recording medium. Two condensing optical systems, two condensing optical systems each including a relay lens and an objective lens, an electro-optical element for controlling the plane of polarization of the light beam, and a drive control for the electro-optical element Driving means, comprising a polarizing optical element that transmits or reflects the light beam, under the control of the driving means, the light beam is directed to which of the two condensing optical system is selected, An optical pickup, wherein a position of a light spot formed on the recording medium is moved by deflection of the light beam by the galvanomirror.

Thus, the switching of the focusing optical system and the tracking are performed by one galvanomirror, so that the optical pickup can be made compact. (2) The optical pickup according to (1), wherein the electro-optical element is a liquid crystal element, and the polarizing optical element is a polarization beam splitter.

Thus, the optical pickup can be configured at a low cost. (3) The polarizing optical element is located between the galvanomirror and the two condensing optical systems, and the electro-optical element is located between the polarizing optical element and the light source. The optical pickup according to item (1), which is characterized in that:

As a result, the optical path reflected by the galvanomirror becomes one, so that the size of the galvanomirror can be reduced. (4) The driving means selects which of the two condensing optical systems the light beam is directed to by applying or not applying a voltage between the electrodes of the electro-optical element. The optical pickup according to item (2), which is characterized in that: Thus, the optical path can be switched by electrical control, and thus the optical path can be switched at high speed.

[0077]

In the optical pickup according to the first aspect of the present invention, a plurality of second relays are provided for one first relay lens.
And a galvanomirror was placed between them. Therefore, the offset of the tracking error signal when performing the tracking operation with the galvanomirror tilted is small. Therefore, a stable servo can be obtained with a wide tracking range.

In the optical pickup according to the second aspect of the present invention, since the light passing through the first relay lens is made incident on only one condensing optical system, an inexpensive laser with low light loss and low power is used. And the emission power of the objective lens can be increased.

In the optical pickup according to the third aspect of the present invention, since the optical path selecting means and the galvanomirror are used, the configuration can be simplified and the size and weight can be reduced. In the optical pickup according to the fourth aspect of the present invention, since the optical path selecting means is constituted by the electro-optical element, the optical path is not mechanically displaced, so that the selecting operation speed is high.

In the optical pickup according to the fifth aspect of the present invention, since the optical path selecting means is constituted by the beam splitter, the cost of the optical system can be reduced. In the optical pickup according to the sixth aspect of the present invention, since the mirror is arranged between the galvanometer mirror and the objective lens, the distance between the plurality of objective lenses can be adjusted. When the interval is reduced, the driving range of the mechanism for seeking the objective lens can be reduced.

[Brief description of the drawings]

FIG. 1A is a plan view schematically showing a configuration of an optical pickup according to a first embodiment of the present invention;
(B) is a side view, and (C) is a view of the photodetector viewed from the optical axis direction.

FIG. 2 is a diagram schematically showing a part of a configuration of an optical pickup according to a second embodiment of the present invention.

FIG. 3 is a diagram schematically showing a part of a configuration of an optical pickup according to a third embodiment of the present invention.

FIG. 4A is a plan view schematically showing a configuration of an optical pickup according to a fourth embodiment of the present invention;
(B) is a side view thereof.

FIG. 5A is a plan view schematically showing a configuration of an optical pickup according to a fifth embodiment of the present invention;
(B) is a side view thereof.

FIG. 6 is a plan view schematically showing a configuration of an optical pickup according to a sixth embodiment of the present invention.

[Description of Signs] 12 Semiconductor laser 14 Relay lens 18 Galvano mirror 22 Imaging lens 26 Objective lens 32 Imaging lens 36 Objective lens

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhide Matsubayashi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (6)

[Claims] 1. An optical pickup for optically recording and reproducing information on and from a recording medium, comprising: a light source for emitting a light beam; a galvanometer mirror for deflecting the light beam; and a position between the light source and the galvanometer mirror. A plurality of focusing optical systems for focusing a light beam on a recording medium, each including at least a second relay lens and an objective lens. An optical pickup characterized in that the transmitted light beam enters the plurality of condensing optical systems. 2. The optical pickup according to claim 1, wherein one of the plurality of condensing optical systems is selected by a light path selecting means for the light passing through the galvanomirror. 3. The optical pickup according to claim 2, wherein said optical path selecting means is said galvanomirror. 4. The optical pickup according to claim 2, wherein said optical path selecting means is an electro-optical element. 5. The optical pickup according to claim 1, wherein the light passing through the galvanomirror is split by a beam splitter and is incident on the plurality of condensing optical systems. 6. The optical pickup according to claim 1, wherein a mirror is arranged between the galvanometer mirror and the objective lens.