JP2885105B2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in an optical disk reproducing apparatus such as a CD (compact disk) player and an LD (laser disk) player or an optical disk recording / reproducing apparatus.

[0002]

2. Description of the Related Art Hitherto, an optical pickup for detecting a signal from an optical disk and performing tracking control and focus control on the optical disk has been proposed. This optical pickup is configured as shown in FIG.
That is, the divergent laser light is incident on the beam splitter 4 from the laser diode 3, the divergent laser light reflected by the beam splitter 4 is incident on the collimating lens 5, and the divergent laser light is collimated by the After that, the light is focused by the objective lens 2 to form an image of the light beam on the disk 1.
The light beam reflected by the light source passes through the objective lens 2, the collimator lens 5, and the beam splitter 4 again, and is incident on the photodiode 7.
The detection signal is calculated to detect the signal recorded on the disk 1 and the tracking error signal and the focus error signal for performing the tracking control and the focus control.

An optical system in which the diverging laser light is collimated by the collimator lens 5 and enters the objective lens 2 is called an infinite optical system.

As shown in FIG. 11, among the above-described optical configurations, a configuration without a collimating lens 5 (finite optical system) has been proposed.

Next, although not shown, in FIGS. 11 and 13, the optical pickup body is provided with the above-described coils for tracking control and focus control, respectively, and detects the detection signal from the photodiode 7. The tracking error signal and the focus error signal obtained by the calculation are supplied. Therefore, the tracking control for the disk 1 is performed by moving the optical pickup with respect to the disk 1 in the horizontal direction by the electromagnetic force of the tracking coil, as shown by the arrow X in FIGS. The focus control is performed by moving the optical pickup with respect to the disk 1 in the vertical direction by the electromagnetic force of the focusing coil, as shown by the arrow Z in FIGS.

In the conventional optical pickup, if the optical axis of the signal reproducing beam is inclined with respect to the optical disk reproducing surface, optical aberration occurs, crosstalk increases, and the reproducing signal deteriorates. Further, in the optical disk recording / reproducing apparatus, if the optical axis of the signal reproducing beam is inclined with respect to the optical disk reproducing surface, the recording signal is degraded, and pit formation errors may occur.

Further, in the conventional optical pickup of a finite optical system shown in FIG. 11, since the beam light emitted from the laser diode 3 enters the objective lens 2 as divergent light, the objective lens 2 is moved in the tracking direction. When moved in the (X direction), as shown in FIG. 12, a tilt image D is generated between the axis connecting the light emitting point and the image forming point and the axis of the objective lens, and astigmatism as optical aberration increases. There was an inconvenience that a design margin, that is, a tolerance could not be obtained.

In order to solve this problem, a method of tilting the objective lens has been proposed in recent years. For example, JP-A-3-6
In Japanese Patent No. 6913, as shown in FIG. 10, two pairs of astigmatism correcting means 11 are all fixed to the same height on the side surface of the movable portion in the circumferential direction of the disk.
By tilting in the direction, the astigmatism caused by the objective lens 2 is reduced.

A conventional optical pickup will be described below with reference to Japanese Patent Application Laid-Open No. 3-66913.

FIG. 10 shows a perspective view and a sectional view of a main part of a conventional optical pickup. In FIG. 10, reference numeral 8 denotes a main body of the movable portion (illustration of magnets, yokes, etc. is omitted). As shown in FIG.
The copper coil is wound to form the focusing coil 9. The focusing coil 9 is provided with the photodiode 7 shown in FIG.
An electric current based on the signal obtained by calculating the detection signal is supplied, thereby moving the main body 8 in the vertical direction. Reference numeral 10 denotes a tracking coil.
Two pieces are respectively arranged on the front side and the opposite side of the main body 8. The effective magnetic flux of the tracking coil 10 is as shown by a dashed line. This tracking coil 10
Then, a current based on the signal obtained by calculating the detection signal from the photodiode 7 shown in FIG. 11 is supplied to move the main body 8 in the track direction (X direction) with respect to the disk 1. .

A correction coil 11 is arranged in front of the main body 8 and above the opposite side. This correction coil 11
Then, a current is applied to the tracking coil 10 to
A predetermined current is made to flow in accordance with the amount of movement when moving. At this time, the effective magnetic flux of the correction coil 11 becomes as indicated by a dashed line, and the direction of the electromagnetic force F1 of one correction coil 11 is downward, and the electromagnetic force F2 of the other correction coil 11 is
Is upward. Therefore, the main body 8 is tilted (R
Direction), that is, the objective lens 2 can be tilted.

[0012]

However, in the above-mentioned conventional configuration, an electromagnetic force F3 for driving the main body portion 8 in the tracking direction is generated in the vertical portion of the correction coil 11 and causes disturbance in the tracking direction. There was a problem of becoming unstable.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an excellent optical pickup capable of obtaining a stable tracking control characteristic even when the optical axis is corrected.

[0014]

In order to achieve this object, an optical pickup according to the present invention comprises a pair of flat tilt coils arranged on two circumferential sides of an objective lens holder, and the pair is arranged on the same side. One of the flat tilting coils formed is disposed on the optical disk side with respect to the vertical center of the magnetic circuit, and the other is disposed on the opposite side of the magnetic circuit with respect to the optical disk.

[0015]

According to the present invention, unnecessary driving force in the tracking direction can be canceled by the upper flat tilting coil and the lower flat driving coil among the pair of flat tilting coils by the above-described configuration, and the objective lens holder can be used. Even when tilted, stable control characteristics can be obtained.

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the optical pickup according to the present invention. FIG. 1 is a perspective view of the optical pickup, and FIG. 2 is a perspective view of a main part of a tilting coil of the optical pickup. It is.

In FIG. 1, reference numeral 101 denotes an objective lens of an optical system, and its periphery is fixed and held by an objective lens holder 102. A focus coil 103 is wound around a side surface of the objective lens holder 102. 10
Reference numeral 4 denotes a flat tracking coil, in which two flat tracking coils 104 are arranged on one side in the circumferential direction (Y direction) of the objective lens holder 102, and two flat tracking coils 104 are mounted on the other side parallel to this. Each is arranged in pairs. Reference numeral 105 denotes a tilt coil, and a pair of tilt coils 105 are arranged on one side surface of the objective lens holder 102 in the circumferential direction (Y direction).
Among them, the inner circumference side (X direction plus side) of the optical disk is arranged on the upper side, and the outer circumference side (X direction minus side) is arranged on the lower side. The tilting coil 105 is also provided on the other side parallel to this.
Are similarly arranged in a pair. 108 is a magnet, U
The magnetic circuit is fixed to one side surface of the character yoke 109 and sandwiches the focus coil 103, the flat tracking coil 104, and the tilt coil 105. 1
Reference numeral 06 denotes a support member, one end of which is connected to the objective lens holder 102.
Of the objective lens 101 and the objective lens holder 10
2. A movable portion including a focus coil 103, a flat tracking coil 104, and a tilt coil 105 is supported so as to be movable in a focus direction (Z direction), a tracking direction (X direction), and an optical axis tilt direction (R direction). Coil 103, flat tracking coil 104,
Power is also supplied to the tilt coil 105. Reference numeral 110 denotes a yoke base, which is fixed on an optical base (not shown).

The operation of the optical pickup of the present invention will be described below. When a current based on a signal obtained by calculating a detection signal of the photodiode 7 in FIG. 11 is applied to the focus coil 103, a focus driving force is generated in the focus coil 103 by an electromagnetic action with a magnetic circuit, and the movable part is moved in the focus direction (Z direction). Direction). For this reason, the focus of the light beam irradiated on the optical disk through the objective lens 101 can be adjusted accurately. The effective magnetic flux of the flat tracking coil 104 is within a range surrounded by a dashed line.
When a current based on a signal obtained by calculating the detection signal of the photodiode 7 is applied, a tracking driving force is generated by an electromagnetic action with the magnetic circuit, and the movable portion is moved in parallel in the tracking direction (X direction). Therefore, the objective lens 10
The tracking of the light beam irradiating the optical disk through the optical disk 1 can be adjusted accurately. Further, a predetermined current corresponding to the amount of movement when the movable portion is moved in the tracking direction is caused to flow through the tilt coil 105. At this time, the effective magnetic flux of the tilting coil 105 is as shown by a dashed line, and the direction of the electromagnetic driving force F101 is downward, and the electromagnetic driving force F102 of the other tilting coil 105 is upward. Therefore, the movable portion can be tilted in the optical axis tilt direction R.

Here, an unnecessary electromagnetic driving force F103 is applied to the tilt coil 105 in the vertical direction on the plus side in the X direction.
4 occur on the negative side in the X direction, and each can cancel each other.

As described above, according to the present embodiment, a pair of tilt coils 105 are arranged on one side surface in the circumferential direction (Y direction) of the objective lens holder 102, and the tilt coils 105 in the The circumferential side (X direction plus side) is placed on the upper side, and the outer circumferential side (X direction minus side) is placed on the lower side,
Unnecessary electromagnetic driving forces F103 and F104 generated at the time of tilt driving can be canceled by arranging the pair of tilting coils 105 on the other side parallel to the above, similarly.
The driving force does not leak in the tracking direction.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. 3, 4, 5, 6,
FIG. 7 shows a second embodiment of the optical pickup of the present invention. FIG. 3 is a perspective view of the optical pickup, and FIG.
FIG. 5 is a schematic view of a main part of the optical pickup in a case where there is no optical axis deviation of the inclination detecting means, and FIG. 5 is a schematic view of a main part of the optical pickup in a case where the optical axis deviation of the inclination detecting means occurs.
Is a configuration diagram of the tilt control circuit, and FIG. 7 is a principle diagram of tilt drive.

In FIGS. 3, 4, 5, 6, and 7, components having the same functions as those in FIGS. 1 and 2 are denoted by the same reference numerals. The difference from the configuration of FIG. 1 is that the objective lens holder 102 has two diagonal sides in the circumferential direction (Y direction).
System tilt coil 205a and tilt coil 205
The tilt coil 205a is disposed on one side surface of the objective lens holder 102 in the circumferential direction so that the tilt coil 205a
05b is disposed on the lower side on the outer peripheral side (minus side in the X direction), and the tilt coil 2
05b is disposed on the upper side on the inner circumference side (plus side in the X direction) of the optical disk, and the tilt coil 205a is disposed on the lower side on the outer circumference side (minus side in the X direction). 210a and the circumferential tilt detector 210b are arranged in pairs, and the radial tilt detector 21
0a and a tilt control circuit 130 that calculates a radial tilt signal detected from the circumferential tilt detector 210b and supplies a current to the tilt coils 205a and 205b. is there.

The radial tilt detector 210a and the circumferential tilt detector 210b are connected to the objective lens 1 of the light emitted from the objective lens 101 and condensed and reflected on the optical disk 212.
Diffracted light that does not return to 01 can be received.

The operation of the optical pickup configured as described above will be described. Of the light emitted from the objective lens 101 and focused on the optical disk 212, diffracted light that does not return to the objective lens 101 impinges on the radial tilt detector 210a and the circumferential tilt detector 210b. As shown in FIG. 4, when the objective lens 101 and the optical disk 212 are parallel, a pair of the radial tilt detector 210a and the circumferential tilt detector 210 are paired.
The light amounts received at b are equal. However, as shown in FIG. 5, when the objective lens 101 and the optical disk 212 are not parallel, a difference occurs in the amount of light received by the pair of the radial tilt detector 210a or the circumferential tilt detector 210b. , A radial inclination detection signal and a circumferential inclination detection signal are generated.

The radial tilt detection signal and the circumferential tilt detection signal are input to the tilt control circuit 130 to generate an addition signal and a subtraction signal of the radial tilt detection signal and the circumferential tilt detection signal. Then, based on the addition signal, the upper tilt coil 2 on one side of the objective lens holder 102 is provided.
An electric current is applied to the lower tilt coil 205a on the lower side of the other side 05a. At this time, the effective magnetic flux of the tilt coil is as shown by a dashed line.
5a generates F31 in which the electromagnetic driving force F21 based on the radial inclination detection signal and the electromagnetic driving force F22 based on the circumferential inclination detection signal are added. Further, based on the subtraction signal, a current flows through the lower tilt coil 205b on one side and the upper tilt coil 205b on the other side. Then, the tilt coil 205b generates an F32 obtained by subtracting the electromagnetic driving force F21 based on the radial inclination detection signal and the electromagnetic driving force F22 based on the circumferential inclination detection signal. By balancing the two tilt coils 205a and 205b, the objective lens holder 102 can be inclined in the radial direction R and the circumferential direction T.

As described above, the two tilt coils 2
05a and 205b are arranged diagonally on the side surface of the objective lens holder 102 in the circumferential direction (Y direction), and a pair of the radial tilt detector 210a and the circumferential tilt detector 210b are arranged on the upper surface of the objective lens holder 102. A tilt control circuit 130 that calculates a radial tilt signal detected from the radial tilt detector 210a and a circumferential tilt signal detected from the circumferential tilt detector 210b, and supplies a current to the tilt coil 205. By doing so, not only the radial direction R but also the optical axis inclination in the circumferential direction T can be corrected.

Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. 8 and 9 show a third embodiment of the optical pickup of the present invention. FIG. 8 is a perspective view of the optical pickup, and FIG. 9 is a sectional view of a main part of a magnetic circuit of the optical pickup.

In FIGS. 8 and 9, components having the same functions as those in FIGS. 1 to 7 are denoted by the same reference numerals.
1 and 2 is that the tracking coil 2
Reference numeral 04 denotes a point that is wound around the side surface of the objective lens holder 102 in the radial direction (X direction).

The operation of the optical pickup configured as described above will be described. The effective magnetic flux of the tracking coil 204 is in a range surrounded by a dashed line in FIG. 8. When an appropriate current is applied to the flat tracking coil 204, a tracking driving force F 41 is generated by an electromagnetic action with a magnetic circuit, and the objective lens holder is moved. Translates in the tracking direction.
Here, the magnetic circuit is viewed from the side as shown in FIG. 9, and the magnetic flux density distribution in the air gap of the magnetic circuit is non-uniform. Therefore, when the upper and lower horizontal portions are within the effective magnetic flux as in the case of a flat tracking coil, a driving force is generated in the up and down direction. However, since the horizontal portion of the tracking coil 204 is not in the effective magnetic flux, no upward or downward electromagnetic driving force is generated by the upper and lower horizontal portions.
Therefore, even when the objective lens holder 102 moves in the focus direction, no tilt driving force in the radial direction R due to the imbalance of the electromagnetic driving force in the vertical direction is generated.

As described above, by winding the tracking coil 204 around the side surface of the objective lens holder 102 in the radial direction (X direction), even if the objective lens holder 102 moves in the focusing direction, the tracking coil 204 does not need to move. No tilt driving force is generated, the first embodiment, the second embodiment
In addition to the effects of the embodiment, a stable tilt servo can be obtained.

[0032]

As described above, according to the present invention, a pair of flat tilting coils are arranged on two circumferential sides of the objective lens holder, and one of the pair of flat tilting coils on the same side is connected to an electromagnetic circuit. Of the pair of flat tilting coils, the upper flat tilting coil and the lower flat driving coil of the pair of flat tilting coils. Thus, unnecessary driving force in the tracking direction can be canceled, and an excellent optical pickup having stable tracking control characteristics can be realized even when the objective lens holder is tilted.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of a main part of a tilting coil of the optical pickup according to the first embodiment of the present invention.

FIG. 3 is a perspective view of an optical pickup according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of a main part of the optical pickup according to a second embodiment of the present invention when there is no optical axis shift of the inclination detecting means of the optical pickup;

FIG. 5 is a schematic diagram of a main part of the optical pickup according to a second embodiment of the present invention in a case where an optical axis shift has occurred in the inclination detecting means of the optical pickup;

FIG. 6 is a configuration diagram of a tilt control circuit of an optical pickup according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating the principle of tilt drive of an optical pickup according to a second embodiment of the present invention.

FIG. 8 is a perspective view of an optical pickup according to a third embodiment of the present invention.

FIG. 9 is a sectional view of a main part of a magnetic circuit of an optical pickup according to a third embodiment of the present invention.

FIG. 10 is a perspective view and a sectional view of a main part of a conventional optical pickup.

FIG. 11 is a configuration diagram of a conventional finite optical system.

FIG. 12 is a diagram illustrating occurrence of astigmatism;

FIG. 13 is a configuration diagram of a conventional infinite optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Objective lens 102 Objective lens holder 103 Focus coil 104 Flat tracking coil 105 Tilting coil 106 Support material 107 Support material fixing part 108 Magnet 109 U-shaped yoke 110 Yoke base

Claims (3)

(57) [Claims] At least an objective lens for condensing coherent light on an information recording medium, an objective lens holder for holding the objective lens, a focus coil for driving the objective lens holder in the direction of the information recording medium,
A tracking coil that is driven in a direction perpendicular to the information track of the information recording medium; and an optical axis of coherent light that is fixed in pairs on a side surface of the objective lens holder in the information track direction and is collected by the objective lens. A flat tilting coil that corrects the tilt of the optical axis with the information recording medium, and a magnet that forms an electromagnetic circuit with these coils. One of the pair of flat tilting coils is closer to the information recording medium than the vertical center of the electromagnetic circuit. An optical pickup characterized in that the other is fixed to the side opposite to the information recording medium from the center of the electromagnetic circuit. 2. A tilt detecting means for detecting a tilt between the coherent light and an objective lens or an information recording medium, a radial tilt signal for correcting an optical axis tilt in a direction orthogonal to an information track of the information recording medium, and an information track. 2. The optical pickup according to claim 1, further comprising a tilt drive circuit for generating an arithmetic signal with a circumferential tilt signal for correcting an optical axis tilt in a direction parallel to the tilt drive circuit. 3. The optical pickup according to claim 1, wherein the tracking coil is wound around an information track direction of the information recording medium on a side surface of the objective lens holder.