JP2001344778A - Optical pickup - Google Patents

Abstract

(57) [Problem] In an optical pickup integrated with an optical system, a light capable of mounting an optical system with an object-image distance as long as about 20 mm without causing useless weight increase of a movable member. Provide pickup. SOLUTION: Semiconductor laser element and objective lens 101
103 on which an optical system including
5 and a conductive elastic supporting member 104 that movably supports the housing 103, and is disposed in the housing 103 at a position symmetrical with respect to the optical axis of the laser beam with respect to the optical axis. A plurality of sets of drive coils 106a and 106b for driving the housing 103 in the focus direction and the tracking direction by generating a magnetic force between the drive coils 111a and the like are mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical pickup used for reading information from an optical recording medium or recording information on the optical recording medium.

[0002]

2. Description of the Related Art CD (Compact Disk), DVD
2. Description of the Related Art An optical pickup used for recording and reproducing information on and from an optical recording medium such as a (digital versatile disk) is equipped with an objective lens for focusing a laser beam on the optical recording medium, and the objective lens is optically recorded. Generally, a movable member configured to be movable to follow a focus direction and a tracking direction of a medium, and a fixed member that supports the movable member are provided. In recent years, a semiconductor laser element that emits a laser beam, An optical system including the objective lens and the like as a whole mounted on a movable member side (hereinafter, referred to as an “optical system integrated drive type” or simply as an “integrated type”) has been proposed.

In this integrated optical pickup, a so-called optical system separated type optical pickup in which a semiconductor laser element and the like are mounted on a fixed member side and only an objective lens is driven because the entire optical system is mounted on a movable member side. In comparison with the structure, the optical characteristics are not deteriorated when the objective lens is driven, and stable characteristics can be obtained. A conventional optical pickup integrated with an optical system is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-147147.
No. 43 is disclosed. In this optical pickup, the position adjustment in the focus direction and the tracking direction is made possible by providing an elastic member for making the movable member movable in the focus direction and means for enabling rotation in the tracking direction.

[0004]

Generally, an optical system for recording / reproducing a high-density optical recording medium such as a DVD has a large numerical aperture of an objective lens in order to realize a high density. It is necessary to hold down the tilt of the objective lens with respect to the optical recording medium to a small extent, and it is desirable to use an actuator that follows the surface shake of the optical recording medium. However, the optical pickup in the above-described conventional technique has a problem that it is difficult to adjust the position in the tilt direction since the position in the focus direction can be adjusted by using an elastic member such as a leaf spring. Was.

It is preferable that a recording / reproducing apparatus for a high-density optical recording medium such as a DVD can reproduce a conventional optical recording medium such as a CD. It is desirable that recording and reproduction of a medium can be realized by a single optical pickup. Here, a three-beam method is one of the most reliable and widely used tracking error detection methods for reproducing a CD.
Many optical pickups that perform recording and reproduction on a write-once optical recording medium such as DR have a configuration using a differential push-pull method. The tracking error is detected by focusing three spots.

However, in the above-mentioned conventional optical pickup, the operation of the movable member in the tracking direction is a rotating operation. Therefore, the information recording row and the spot on the optical recording medium are different from those of the three-beam method or the differential bush pull method. When a tracking error detection method in which the positional relationship between the spots is important is used, there is a problem that the positional relationship between the information recording sequence and the spot always changes, and the amplitude of the tracking error signal changes.

Further, in an optical pickup integrated with an optical system, since the entire optical system is mounted on a movable portion, a driving current of a semiconductor laser and a driving voltage to a light receiving element substrate for receiving return light from an optical recording medium are provided. It is necessary to perform electrical wiring in order to supply the signal or to send the detection signal of the light receiving element to the processing circuit on the fixed member side. According to the optical pickup in the above-described conventional technology, the focus direction is connected by an elastic member such as a leaf spring, and since it is necessary to rotate in the tracking direction, a member connecting the fixed member side and the movable member side. However, the number of signal wires required for exchanging electrical signals between the movable member and the outside cannot be secured even if the conductive member is made of a conductive material. Therefore, it is necessary to secure the signal wiring from the movable member using a wiring member such as a flexible board, which increases the number of components and may cause the signal wiring member, which is a so-called aerial wiring, to affect the characteristics of the actuator. There are points.

In an optical pickup corresponding to a high-density optical recording medium such as a DVD, the distance between an object and an image of an optical
Generally, the length is increased to about 0 mm. Here, the luminous flux from the semiconductor laser element to the objective lens needs to be arranged so as to pass through the position of the magnetic circuit for position adjustment in the focus direction and the tracking direction, and is provided with only one magnetic circuit. However, in such a configuration, it may be necessary to mount a weight or the like on the movable member to balance the weight, which may increase the weight of the movable member.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is directed to a small-sized optical pickup having an optical system integrated driving type having more stable optical characteristics and having an object-image distance of about 20 mm. The purpose of the present invention is to provide an optical pickup capable of mounting a system.

[0010]

To achieve the above object, an optical pickup according to the present invention comprises a semiconductor laser device for emitting a laser beam, and an objective lens for condensing the laser beam on an optical recording medium. A housing on which an optical system including is mounted, a fixing member, and an elastic supporting member that movably supports the housing from the fixing member, wherein the housing sandwiches an optical axis of the laser beam. The objective lens is driven at least in a focusing direction and a tracking direction by generating magnetic forces between a plurality of magnets disposed at predetermined positions and arranged symmetrically with respect to the optical axis. It is characterized in that a plurality of sets of drive coils are mounted.

In this manner, since it is not necessary to provide a weight or the like for balancing the weight of the housing, which is a movable member, the distance between the object and the image of the optical system can be increased without causing unnecessary weight increase. Optical pickup can be provided. A housing mounted with an optical system including a semiconductor laser element that emits a laser beam, and an objective lens that focuses the laser beam on an optical recording medium, a fixing member,
An elastic support member movably supporting the housing from the fixed member, wherein the housing is disposed at a position symmetrical with respect to the optical axis of the laser beam with the optical axis interposed therebetween, and at a predetermined position. A plurality of magnets for generating a magnetic force between the provided plural sets of driving coils to generate a magnetic flux for driving the objective lens at least in a focus direction and a tracking direction are mounted. It can also be.

The objective lens and the semiconductor laser element may be arranged such that the position of the center of gravity in the optical axis direction of the housing on which the objective lens and the semiconductor laser element are mounted is a point at which the elastic support member supports the housing. May be arranged at both end positions of the housing so as to coincide with the position in the optical axis direction. In addition, the elastic support member is composed of at least six conductive members, and at least two of the elastic support members also serve as wires for supplying power to the semiconductor laser element. When the device is mounted, the drive current can be supplied to the semiconductor laser device via the elastic support member, so that a wiring member such as a flexible substrate is not required.

[0013] Here, the housing is further provided with a light receiving element for receiving return light reflected by the laser beam on the optical recording medium, and the elastic support member is formed of at least six conductive members. That is, a part or the whole thereof may also serve as a wiring for supplying power to the semiconductor laser element, the light receiving element, and the drive coil. According to this configuration, it is easy to use a light receiving / emitting integrated element in which the semiconductor laser element and the light receiving element are integrated.

Further, the plurality of sets of drive coils include a plurality of focus coils for adjusting a position of the casing in a focus direction, and drive currents of the plurality of focus coils are supplied independently. If this is the case, the tilt direction can be easily controlled, and it can be applied to a high-density optical recording medium such as a DVD.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical pickup according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a configuration of a main part of the optical pickup according to the present embodiment. FIG. 2 is a top view of the optical pickup shown in FIG. 1, and FIG.
It is a line sectional arrow view.

As shown in the drawings, in the optical pickup according to the present embodiment, a housing 103 which is a movable member on which various optical system parts including an objective lens 101 described later are mounted.
Are connected to and supported by a fixing member 105 via 16 elastic supporting members 104 having conductivity.
5 is fixed on the optical base 102. The housing 103 has four drive coils 106a and 106b for generating electromagnetic driving force for adjusting the position of the objective lens 101.
Are mounted at positions that are line-symmetric with respect to the optical axis of the laser beam described later. Drive coils 106a, 106b
Are focus coils 108a and 108b for driving the entire housing 103 in the focus direction (focus direction) with respect to the optical recording medium 107, and a direction (tracking) for following the information recording sequence of the optical recording medium 107. Tracking coils 109a, 10)
9b, and four magnets 111a, 112a, 111b, 112b arranged on yokes 110a, 110b fixed on the optical base 102 (hereinafter, when the four magnets are collectively expressed, A magnetic circuit for position adjustment is formed by the “magnet 111”) and the drive coils 106a and 106b.

In the optical pickup of this embodiment, the magnetic flux generated by the drive coils 106a and 106b is arranged so as to be orthogonal to the tracking direction, and the magnetic flux generated by the four magnets 111 is also orthogonal to the tracking direction. Are arranged as follows. The windings of the tracking coils 109a and 109b are electrically connected in series and connected to the outside so that a tracking drive current flows through the elastic support member 104, but the focus coils 108a and 108b are electrically connected. It is independent and connected to the outside by two systems of focus drive current supply lines included in the elastic support member 104.

The semiconductor laser element 11 is provided inside the housing 103.
A light receiving / emitting integrated element 115 in which the light receiving element 3 and the light receiving element substrate 114 are integrated, a reflection hologram optical element 116, and a rising mirror 117 are arranged (see FIG. 3). FIG. 4 is a conceptual diagram for explaining the configuration of the reflection hologram optical element 116. The reflection hologram optical element 116 has two hologram areas 116a and 116 divided by a division line 116c parallel to the information recording sequence on the optical recording medium 107.
b, and the return light from the optical recording medium 107 is reflected and diffracted in each area. Reflection type hologram optical element 1
Numeral 16 designates a wavefront conversion function (lens effect) so that the focal lengths of the + 1st-order diffracted light and the -1st-order diffracted light from the same region among the diffracted lights diffracted at the time of reflection are different, and the incident angle at the time of reflection This is a curve pattern in which the dependence is taken into consideration, and the pitch of the diffraction grating is changed so that the diffraction angle is different between the hologram regions 116a and 116b.

FIG. 5 is a perspective view showing the structure of the light receiving / emitting integrated element 115. As shown in the drawing, a semiconductor laser element 113 is mounted on the integrated light emitting / receiving element 115 of the present embodiment, and a focus error is detected between the focal points of the ± 1st-order diffracted light in each of the hologram areas 116a and 116b. And a three-division light receiving element 114a, 1 for tracking error detection.
Light receiving element substrate 1 on which 14b, 114c, 114d are arranged
14 are mounted. The focus error is detected by detecting the spot size change of ± 1st order diffracted light.
The detection method employs a push-pull method for detecting a tracking error based on differential detection in the vertical direction with respect to an information recording column on the optical recording medium 107 corresponding to the hologram areas 116a and 116b of the light beam.

As shown in FIG. 2, in the optical pickup of this embodiment, the magnetic circuit formed by the drive coil 106 and the magnet 111 is divided into two parts with the optical axis interposed therebetween. It is possible to mount an optical system in which the distance between the object image and the information recording surface on the optical recording medium 107 is increased to about 20 mm. In the present embodiment, the objective lens 101 and the integrated light receiving / emitting element 115
And the drive coils 106a and 106b on the housing 103.
Are arranged at both end positions of the casing 103 which are substantially symmetrical with respect to a straight line connecting the center positions of the light receiving and emitting integrated elements 11.
In combination with the weight adjustment of 5, for example, it is not necessary to use an extra weight or the like for designing the position of the center of gravity of the housing 103.

Thus, the center of the driving force generated in the drive coil 106, the center of gravity of the housing 103, and the optical axis of the center of support by the elastic support member 104 without unnecessarily increasing the weight of the housing 103, which is a movable member. Direction (more appropriately,
A direction orthogonal to both the tracking direction and the focus direction, hereinafter referred to as a “front-back direction”. ) Can be realized.

The driving coils 106a and 106
b, the semiconductor laser element 113 and the light receiving element substrate 114
Since all are electrically connected to the elastic support member 104, the housing 103 and the fixing member 1 are provided in addition to the elastic support member 104.
No signal wiring connecting the lines 05 is required, and all the voltage and current can be supplied via the elastic supporting member 104. As the elastic support member 104, a conductive copper alloy such as phosphor bronze, titanium copper, and beryllium copper can be used.

In the present embodiment, the elastic support member 1
Although 16 conductive members are formed as 04, the effect of increasing the number of the conductive members to some extent to increase the resistance to disturbances and the like of the entire device can be obtained. This makes it difficult for the focus direction and the tracking direction to follow each other, and makes it possible to simplify a control circuit provided outside for position control in both directions. This effect can be obtained not only when 16 members are used but also when at least 5 or 6 members are used.

In order to improve the resistance effect against disturbance as described above, the number of the elastic support members 104 is set to be an even number so as to be symmetrical with respect to the optical axis extending in the front-rear direction, or the number of the elastic support members 104 is reduced. As a multiple of 4, it is more preferable to arrange symmetrically in the vertical and horizontal directions with respect to the optical axis. The number of the elastic support members 104 is
It is preferable to supply power to various elements mounted in the housing 103 and to secure a necessary number of signal lines. However, for example, the drive coil 106
a and 106b are not mounted, a magnet is arranged on the housing 103 side to form a magnetic circuit, or only the semiconductor laser element is mounted on the housing 103, and no light receiving element is mounted. By reducing the number of wires required,
It is also possible to reduce the number of elastic support members 104.

Next, the operation of the optical pickup configured as described above will be described. FIG. 6 is a diagram schematically showing a cross section taken along line BB of FIG. 2 and is a diagram for explaining the operation of the optical pickup of the present embodiment. Case 1
The laser beam emitted from the semiconductor laser element 113 mounted on the optical disc 03 passes between the drive coils 106a and 106b, and is condensed on the optical recording medium 107 by the objective lens 101 via the rising mirror 117. You. The return light reflected from the optical recording medium 107 travels backward in the same optical path, is diffracted by the reflection hologram optical element 116, and is received on the light receiving element substrate 114. This light receiving element substrate 1
A servo signal and an information recording signal are detected from the light received at 14, but the details of the signal detection processing are omitted.

In FIG. 6, when the position of the optical recording medium 107 in the focus direction is adjusted, the same drive current I ₁ is supplied to the focus coils 108a and 108b, so that the electromagnetic force F _{1 is} applied between the magnets 111a and 111b.
Is generated, and the housing 103 can be driven in the focus direction. Also, after turning on the focus servo,
In order to make the laser beam follow the information recording sequence on the optical recording medium 107, the current is passed through the tracking coils 109a and 109b, so that the magnets 112a,
An electromagnetic force is generated between the casing 103 and the casing 12b, and the casing 103 can be driven in the tracking direction.

In this embodiment, after the tracking servo is turned on, the tilt of the optical pickup with respect to the optical recording medium 107 is also controlled. This control is performed so that the information recording signal extracted from the light received by the light receiving element substrate 114 is in the best state.
a, 108b to the tilt control components I _2a , I _2b
Are superimposed respectively on the focus coils 108a and 108a.
8b. That is, Thus, since the driving force acting on the focus coil 108a and 108b F _2a, can be divided by the change in F _2b,
It is possible to control the casing 103 to follow the tilt of the optical recording medium 107, thereby ensuring more stable optical characteristics and improving the precision in the tilt direction as in a high-density optical recording medium such as a DVD. Even in an optical recording medium where strict requirements are imposed, good optical characteristics can be realized.

Hereinafter, the details of the tilt control will be described more specifically. Address area (CAPA) arranged in a staggered manner off the track center, for example, DVD
In the case of an optical recording medium having a signal, when the focus servo and the tracking servo are turned on, a signal when passing through a portion deviated to the left with respect to the light spot passing direction of the address areas arranged in a staggered manner. The center of the track is detected by comparing the amplitude with the signal amplitude when the signal passes through a portion shifted to the right.

By controlling the signal amplitude to be equal, it is possible to cause the light spot to follow the center of the track, but under this control, the entire optical system is displaced as a unit, and there is an objective lens shift. Therefore, the tracking error signal level is proportional only to the tilt component. Therefore, the tracking error signal is sent to the actuator as a tilt signal, and a tilt control (servo) operation is performed so that the change of the tracking error signal in the staggered address area indicates a symmetrical change.

Here, there is a certain relationship between the tilt signal and the disc tilt amount, and the disc tilt amount and the tilt amount of the objective lens at which the optical spot on the optical recording medium is optically best. There is a certain relationship between them. Further, considering the sensitivity of the actuator to the drive signal in the tilt operation, the tilt control components I _2a and I _2b to be superimposed on the drive current to the focus coils 108a and 108b are uniquely determined from the detected tilt signal. Therefore, tilt control can be performed. The above relationship can be acquired in advance, for example, when exchanging a disk, and stored in a table.

On the other hand, the following control can be performed on an optical recording medium having no staggered address area such as the DVD. That is, since the optical pickup of the present embodiment is of an optical system integrated drive type, an objective lens offset component of the tracking signal does not occur in principle. Accordingly, since the tracking error signal level is proportional to only the tilt component, the same control as in the case of the DVD or the like can be performed using this signal as a tilt control component.
However, the accuracy of track center detection seems to be higher in the case of a DVD or the like having the above-mentioned staggered address area.

In addition, if the best condition of the information recording signal is detected without depending on the optical recording medium, the information recording signal is monitored to minimize the so-called jitter or to reduce the amplitude of the AC component of the information recording signal. There is also a method of performing tilt control so that the maximum value is obtained. In the present embodiment, the drive coils 106a and 106b are mounted on the housing 103, and the magnet 1 is mounted on the optical base 102 via the yoke 110.
Although the configuration is such that the drive coil 11 is mounted, the drive coil may be mounted on the optical base side and the magnet may be mounted on the movable member (housing) side as described above. With this configuration, it is not necessary to supply a drive current to the drive coil via the elastic support member 104, so that the number of elastic support members 104 can be reduced.

The wavelength of the semiconductor laser device 113 mounted on the housing 103 is in the infrared wavelength band (λ = 800 nm band).
However, a red wavelength band (λ = 650 nm band) or a blue wavelength band (λ = 400 nm band) may be used, and one semiconductor laser element having emission points of two or more wavelength bands may be used. it can. When the semiconductor laser device is used, for example, by using an object lens corresponding to two or more wavelengths as an objective lens, a CD-ROM and a DV
A single optical pickup, such as D, can cope with recording and reproduction of various types of optical recording media. Furthermore, two or more types of individual semiconductor laser elements having different wavelengths may be mounted (may be mounted in a hybrid).

Further, in the above embodiment, the two focus coils 108a and 108b are configured to be electrically independent from each other so as to adjust the position in the tilt direction.
The two focus coils may be electrically connected in series. This is because the tilt control mechanism for supporting a high-density optical recording medium is omitted, but it can support a conventional high-density optical recording medium.

The optical system is not limited to a finite optical system, but may be an infinite optical system using a collimator lens. Further, in the above-described embodiment, the case where the distance between the object and the image is set to about 20 mm has been described. However, this is because the distance between the object and the image must be about 20 mm in the DVD system from the current design technology. Even if it becomes possible to make the object-image distance shorter than the current state, it is naturally possible to apply the present invention.

[0036]

As described above, according to the optical pickup of the present invention, the housing on which the optical system including the semiconductor laser element and the objective lens is mounted, the fixing member, and the housing from the fixing member. In the optical system integrated drive type optical pickup including an elastic supporting member movably supported, the housing is disposed at a predetermined position symmetrically with respect to the optical axis of the laser beam with the optical axis interposed therebetween. Since a plurality of sets of drive coils for driving the objective lens at least in the focusing direction and the tracking direction by mounting a magnetic force between the plurality of magnets and the plurality of magnets are mounted, a housing as a movable member is provided. Without increasing the weight of the body,
There is an effect that it is possible to provide an optical pickup in which the distance between object images of the optical system is increased to about 20 mm.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a main part of an optical pickup according to an embodiment of the present invention.

FIG. 2 is a top view of the optical pickup shown in FIG.

FIG. 3 is a cross-sectional view taken along line AA of FIG.

FIG. 4 is a conceptual diagram illustrating a configuration of a reflection hologram optical element 116.

FIG. 5 is a perspective view showing a configuration of a light emitting and receiving integrated element 115.

FIG. 6 is a diagram schematically showing a cross section taken along line BB of FIG. 2, and is a diagram for explaining an operation of the optical pickup according to the embodiment of the present invention.

[Explanation of symbols]

101 Objective lens 102 Optical base 103 Housing 104 Elastic support member 105 Fixed member 106, 106a, 106b Drive coil 107 Optical recording medium 108, 108a, 108b Focus coil 109, 109a, 109b Tracking coil 110, 110a, 110b Yoke 111, 111a, 111b Magnets 112a, 112b Magnets 113 Semiconductor laser elements 114 Light receiving element substrates 114a to 114d Three-division light receiving elements 115 Light receiving / emitting integrated elements 116 Reflection type hologram optical elements 117 Start-up mirrors

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutoshi Onozawa 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics Corporation Incorporated (72) Inventor Hideyuki Nakanishi 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics 5D118 CD02 CD03 CD04 CG39 DB02 DC03 EA02 ED05 EE06 FA27 FA30 FB10 FB12

Claims (6)

[Claims] A housing mounted with an optical system including a semiconductor laser element for emitting a laser beam, and an objective lens for condensing the laser beam on an optical recording medium; a fixing member; An elastic support member movably supporting the housing, wherein the housing is provided at a predetermined position symmetrically with respect to an optical axis of the laser beam with the optical axis interposed therebetween. An optical pickup comprising a plurality of sets of drive coils for driving the objective lens at least in a focusing direction and a tracking direction by generating a magnetic force between the magnets and the magnets. 2. A housing on which an optical system including a semiconductor laser element for emitting a laser beam, and an objective lens for condensing the laser beam on an optical recording medium is mounted, a fixing member, and a fixing member. An elastic support member movably supporting the housing, wherein the housing is provided at a predetermined position symmetrically with respect to an optical axis of the laser beam with the optical axis interposed therebetween. A plurality of magnets for generating a magnetic force between each set of drive coils to generate a magnetic flux for driving the objective lens at least in a focus direction and a tracking direction are mounted. Optical pickup. 3. The object lens and the semiconductor laser device, wherein the center of gravity of the housing on which the objective lens and the semiconductor laser device are mounted in the optical axis direction is a support point of the housing by the elastic support member. 3. The optical pickup according to claim 1, wherein the optical pickup is disposed at both ends of the housing so as to coincide with the position in the optical axis direction. 4. 4. The semiconductor device according to claim 1, wherein the elastic support member comprises at least six conductive members, and at least two of the elastic support members also serve as wires for supplying power to the semiconductor laser device. From 3
An optical pickup according to any one of the above. 5. A light receiving element for receiving return light of the laser beam reflected on an optical recording medium is mounted on the housing, and the elastic support member is composed of at least six conductive members. 2. The optical pickup according to claim 1, wherein a part or the whole thereof also serves as a wiring for supplying power to the semiconductor laser element, the light receiving element, and the drive coil. 6. The plurality of sets of drive coils include a plurality of focus coils for adjusting a position of the housing in a focus direction, and drive currents of the plurality of focus coils are supplied independently of each other. The optical pickup according to claim 5, wherein