JP2766468B2 - Optical head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical head device for controlling the position of an objective lens in a tracking direction.

[0002]

2. Description of the Related Art An optical disk player optically reads information recorded on a rotationally driven optical disk. At this time, the position of the objective lens is controlled in the tracking direction by the optical head device in order to read the information recorded on the optical disk well.

A conventional example of such an optical head device 1 will be described below with reference to FIG. In the drawing, the focusing direction is indicated as Fo and the tracking direction is indicated as Tr. Further, hereinafter, a direction orthogonal to the focusing direction and the tracking direction is conveniently referred to as a jitter direction, and is indicated as Ji in the figure.

At a position facing the optical disc 2 in the focusing direction, an objective lens 3 supported so as to be displaceable in a tracking direction with respect to a head body (not shown),
Fixed mirrors 4 as fixed deflection means fixed to the head main body are arranged in order. This fixed mirror 4
Since the fixed optical system 5 fixed to the head main body is disposed at a position facing the jitter direction, the fixed optical system 5 and the fixed mirror 4 are relatively fixedly disposed. .

The fixed optical system 5 has a semiconductor laser 6 as a light emitting element, and a collimator lens 7, a polarizing beam splitter 8, a quarter wave plate 9, Are arranged in order. The quarter-wave plate 9 faces the fixed mirror 4, and an imaging lens 10 and a light receiving element 11 are arranged in order on the reflection optical path of the polarization beam splitter 8.

In the optical head device 1 having such a structure, the light beam emitted from the semiconductor laser 6 is deflected in the focusing direction by the fixed mirror 4, converged by the objective lens 3 and made incident on the track of the optical disk 2. The light beam reflected in the focusing direction by the optical disk 2 is converged by the objective lens 3 and deflected by the fixed mirror 4. This light beam is deflected by the polarizing beam splitter 8,
The reading is performed by the light receiving element 11 to detect a tracking error. By controlling the position of the objective lens 3 in the tracking direction in accordance with the detected tracking error, the position of the light beam irradiated on the optical disk 2 is adjusted on the track. For this reason, when information is recorded on the optical disk 2, this information can be satisfactorily recorded on the track, and when information on the optical disk 2 is reproduced, the information can be satisfactorily reproduced from the track.

[0007]

In the optical head device 1 as described above, by controlling the tracking of the objective lens 3, the image forming position can follow the track of the optical disk 2.

However, if tracking control is performed only on the objective lens 3 with the fixed optical system 5 fixed, the fixed optical system 5
Then, an optical axis shift occurs in which the optical axis of the light beam incident on the objective lens 3 is displaced. When the optical head device 1 detects a tracking error by the push-pull method, the optical axis shift becomes a DC (Direct Current) offset of the detection signal, and lowers the accuracy of the tracking control.

Further, as shown in FIG. 20, since the intensity of the laser beam is higher in the center and lower in the periphery, the intensity of the light beam irradiated from the objective lens 3 onto the optical disk 2 decreases when the optical axis shifts. For this reason, when information is recorded on the optical disc 2, information cannot be stably recorded on the track, and when information on the optical disc 2 is reproduced, information cannot be accurately reproduced from the track. In addition, these problems occur irrespective of the tracking error detection method.

An optical head device 12 that solves such a problem is disclosed in Japanese Patent Application Laid-Open No. 4-14628. In this optical head device 12, as shown in FIG. 21, since the objective lens 3 is rotatably supported around the focusing direction, the objective lens 3 is supported movably substantially parallel to the tracking direction. I have. A first mirror 13 for deflecting a light beam entering the focusing direction from the optical disc 2 via the objective lens 3 in the jitter direction, and a fixed optical system 5 for deflecting the light beam entering the jitter direction from the first mirror 13 in the focusing direction. And a second mirror 14 that makes the light incident on the second mirror 14. The center of the optical axis between the second mirror 14 and the fixed optical system 5 coincides with the center of rotation of the objective lens 3, and the objective lens 3, the first mirror 13, and the second mirror 14 rotate integrally. .

In this optical head device 12, since the objective lens 3, the first mirror 13, and the second mirror 14 rotate integrally and the fixed optical system 5 is located on the optical axis of the second mirror 14, The optical axis of the light beam entering the fixed optical system 5 does not shift. However, in this case, since the second mirror 14 and the fixed optical system 5 are arranged in the focusing direction, it is difficult to reduce the size of the optical head device 12 in a direction perpendicular to the optical disk 2.

Also, in the mirror-lens translation type optical head device, since the objective lens and the reflection mirror are displaced integrally, no optical axis shift occurs. However, since the objective lens is supported by a spring so as to be displaceable in the focusing direction with respect to the reflection mirror, the objective lens easily resonates during the tracking operation. In addition, this cannot be applied to an optical head device that structurally executes tracking by rotating an objective lens.

For example, in a mirror-lens translation type optical head device, it is conceivable to rotate the reflection mirror together with the objective lens. However, in this case, the optical axis of the light beam incident on the objective lens is also inclined, and the light-collecting performance is increased. Because of the decrease, the spot formed on the optical disc is deteriorated.

[0014]

According to the first aspect of the present invention,
An objective lens, which is placed opposite to the optical disk, is mounted on a lens holder. This lens holder is elastically supported by a resilient member on a head base so as to be displaceable in a tracking direction and a focusing direction, and fixed optics for emitting laser light in the tracking direction. A movable deflecting means for deflecting the emitted light beam in a direction orthogonal to the focusing direction and the tracking direction is mounted on the lens holder, and the deflected light beam is deflected in the focusing direction to the objective lens. A fixed deflecting unit to be incident is mounted on the head base, and an error detecting unit is provided for detecting tracking and focusing errors from a light beam returned from the optical disk to the fixed optical system. Hold the holder in the tracking direction with respect to the head base. Position control means for controlling and driving the focusing lens is provided, and a movable part is formed by at least the lens holder on which the objective lens and the movable deflecting means are mounted. The center of gravity of the movable part and the principal point of the objective lens In the focusing direction and the focal length of the objective lens were substantially matched. Accordingly, the light beam emitted in the tracking direction from the fixed optical system is deflected by the movable deflecting means in a direction orthogonal to the focusing direction and the tracking direction, and this light beam is deflected in the focusing direction by the fixed deflecting means and passes through the objective lens. It is incident on the optical disc. Since the movable deflecting means moves integrally with the objective lens, the optical axis of the light beam does not shift due to the tracking movement of the objective lens. In addition, when the movable part resonates rotationally about the tracking direction as an axis, the movable deflection means also rotates, so that the angle of the light beam incident on the objective lens also changes. Since the objective lens moves by a distance that cancels out, the position of the light spot formed on the optical disk does not change.

According to a second aspect of the present invention, an objective lens disposed opposite to an optical disk is mounted on a lens holder, and the lens holder is elastically supported on a head base by an elastic member so as to be displaceable in a tracking direction and a focusing direction. A fixed optical system that emits laser light in the tracking direction; and a movable deflecting unit that deflects the emitted light beam in a direction orthogonal to the focusing direction and the tracking direction is mounted on the lens holder. Fixed deflection means for deflecting the light in the focusing direction to be incident on the objective lens is mounted on the head base, and error detecting means for detecting errors in tracking and focusing from the light flux returned from the optical disc to the fixed optical system. The lens holder in response to this detection error. Position control means for controlling drive in the tracking direction and the focusing direction is provided to the base, forming a movable portion by at least said lens holder and objective lens and the movable deflecting means is mounted,
The position of the center of gravity of the movable portion, the objective lens, and the movable deflecting means are sequentially positioned in the direction orthogonal to the tracking direction and the focusing direction, and the position of the center of gravity of the movable portion in the direction orthogonal to the tracking direction and the focusing direction. The distance between the object and the principal point of the objective lens and the focal length of the objective lens are set to be approximately two to one. Accordingly, the light beam emitted in the tracking direction from the fixed optical system is deflected by the movable deflecting means in a direction orthogonal to the focusing direction and the tracking direction, and this light beam is deflected in the focusing direction by the fixed deflecting means and passes through the objective lens. It is incident on the optical disc. Since the movable deflecting means moves integrally with the objective lens, the optical axis of the light beam does not shift due to the tracking movement of the objective lens. In addition, when the movable part resonates rotationally about the tracking direction as an axis, the movable deflection means also rotates, so that the angle of the light beam incident on the objective lens also changes. Since the objective lens moves by a distance that cancels out, the position of the light spot formed on the optical disk does not change.

According to a third aspect of the present invention, an objective lens disposed opposite to an optical disk is mounted on a lens holder, and this lens holder is elastically supported on a head base by an elastic member so as to be displaceable in a tracking direction and a focusing direction. A fixed optical system that emits a laser beam, and a movable deflecting unit that deflects the emitted light beam only twice and emits the light beam in a direction orthogonal to the tracking direction and the focusing direction is attached to the lens holder. A fixed deflecting means for deflecting the luminous flux in the focusing direction and making it incident on the objective lens is mounted on the head base, and errors for tracking and focusing errors are respectively detected from the luminous flux returned from the optical disc to the fixed optical system. Detecting means for moving the lens holder in response to the detection error. Position control means for controlling and driving the lens in a tracking direction and a focusing direction, and a movable part is formed by at least the lens holder on which the objective lens and the movable deflecting means are mounted, and a center of gravity of the movable part is provided. The distance in the focusing direction between the position and the principal point of the objective lens, the focal length of the objective lens,
It was almost doubled. Accordingly, the light beam emitted from the fixed optical system is deflected by the movable deflecting device only an even number of times and emitted in the direction orthogonal to the tracking direction and the focusing direction, and this light beam is deflected in the focusing direction by the fixed deflecting device, and Through the optical disk. Since the movable deflection means moves integrally with the objective lens,
The optical axis of the light beam does not shift due to the tracking movement of the objective lens. In addition, when the movable part resonates rotationally about the tracking direction as an axis, the movable deflection means also rotates, so that the angle of the light beam incident on the objective lens also changes. Since the objective lens moves by a distance that cancels out, the position of the light spot formed on the optical disk does not change.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, the center position of the resilient support, the center position of the control drive, and the position of the center of gravity of the movable portion are substantially matched.
Therefore, since the stress of the control drive and the reaction force of the resilient support act on the position of the center of gravity of the movable part, the rotational resonance is less likely to occur.

According to a fifth aspect of the present invention, in the first aspect of the invention, the center of gravity of the movable portion is located on the optical axis of the objective lens. Therefore, even if rotational resonance occurs in the movable part, the objective lens is not displaced in the focusing direction.

According to a sixth aspect of the present invention, in the first, second, or third aspect, a weight for adjusting the position of the center of gravity of the movable portion is mounted on the lens holder. Therefore, the position of the center of gravity of the movable portion can be freely adjusted with a simple structure.

[0020]

FIG. 1 shows a first embodiment of the present invention.
This will be described below with reference to FIG. Regarding the optical head device 21 exemplified here, the same portions as those of the optical head device 1 described above as a conventional example are denoted by the same names and reference numerals, and detailed description thereof will be omitted.

First, the optical head device 21 of the present embodiment
Also has a fixed optical system 5 composed of a laser light source, a light receiving element, a beam splitter, and the like, and as shown in FIG. 22 are arranged.
A fixed mirror 4 which is a fixed deflection means is disposed at a position facing the movable mirror 22 in the jitter direction.
The objective lens 3 is arranged at a position facing the fixed mirror 4 in the focusing direction.

More specifically, as shown in FIG. 1 and the like, the fixed mirror 4, the fixed optical system 5, and the yoke 23 are fixed to a head base (not shown) movable in the tracking direction. A rectangular parallelepiped lens support 24 is mounted on the yoke 23. The lens support portion 24 has four spring shafts 25, which are elastic members, protruding from four corners of the surface in the jitter direction. The spring shafts 25 move the lens holder 26 in the tracking direction and the focusing direction. It is elastically supported to be displaceable. The lens holder 26 is formed in a box shape that is elongated in the jitter direction, and the support protrusion 2 protrudes from substantially the center in the jitter direction on both sides in the tracking direction.
7 is connected to the spring shaft 25.

A tracking coil 28 is mounted on the support projection 27 of the lens holder 26 in the tracking direction, and a focusing coil 29 is mounted on both end surfaces of the lens holder 26 that are orthogonal to the jitter direction. . A tracking magnet 30 and a focusing magnet 31 are fixed to the yoke 23, and these magnets 30, 31 are connected to the coils 28, 31.
29 respectively. The tracking magnet 30 is magnetized to opposite polarities on both sides of the tracking coil 28, and the focusing magnet 3
Numeral 1 is magnetized with opposite polarities in the vertical direction.

The objective lens 3 is mounted in the center of the upper surface of the lens holder 26 perpendicular to the focusing direction, and the movable mirror 22 is mounted on the inner surface of the lens holder 26 perpendicular to the jitter direction. A concave portion 32 is formed on a side surface of the lens holder 26 facing the movable mirror 22, and the movable mirror 22 and the fixed optical system 5 face each other via the concave portion 32.

An error detection circuit (not shown) is connected to the light receiving element of the fixed optical system 5, and is provided with error detection means for detecting tracking and focusing errors. A coil drive circuit (not shown) connected to the error detection circuit applies a predetermined drive power to the coils 28 and 29 in response to the detection error, so that the lens holder 26 is connected to the head base here. On the other hand, position control means for controlling and driving in the tracking direction and the focusing direction is provided.

In the optical head device 21 of the present embodiment,
As described above, the lens holder 2 on which the objective lens 3, the movable mirror 22, and the coils 28 and 29 are mounted.
6 is resiliently supported by the spring shaft 25 so as to be freely displaceable, so that a movable portion 33 is formed here. The center position of the resilient support of the movable portion 33, the center position of the control drive, and the center of gravity G substantially coincide with each other, and the center of gravity G of the movable portion 33 is located on the optical axis of the objective lens 3. The distance “L” between the center of gravity G of the movable portion 33 and the principal point 34 of the objective lens 3 in the focusing direction matches the focal length “f” of the objective lens 3.

The center position of the movable portion 33 for resiliently supporting is the center of a plurality of locations where the movable portion 33 is resiliently supported. More specifically, the spring shaft 25 and the lens These are the centers of the four contact points with the supporting projections 27 of the holder 26. The center position of the control drive of the movable portion 33 is the center of a portion for applying the stress of the position control of tracking and focusing to the movable portion 33, and more specifically, the center of the pair of tracking coils 28. And the center of the pair of focusing coils 29.

In such a configuration, in the optical head device 21 of the present embodiment, the light beam emitted in the tracking direction from the fixed optical system 5 is deflected in the jitter direction by the movable mirror 22. The light beam deflected in the jitter direction by the movable mirror 22 is deflected in the focusing direction by the fixed mirror 4 and is imaged on a track of the optical disk 2 by the objective lens 3.

The light beam reflected by the optical disk 2 in the focusing direction is transmitted through the objective lens 3 and then deflected in the jitter direction by the fixed mirror 4. The light beam deflected in the jitter direction is transmitted by the movable mirror 22. The light is deflected in the tracking direction and read by the fixed optical system 5.

Since errors in tracking and focusing are detected from the read result of the fixed optical system 5, driving power is applied to the tracking and focusing coils 28 and 29 in response to these errors, The position of the lens holder 26 is controlled in the tracking direction and the focusing direction. As a result, the objective lens 3 mounted on the lens holder 26 follows the track of the optical disc 2, and the information recorded on this track is read by the fixed optical system 5.

At this time, the optical head device 2 of the present embodiment
1, when the objective lens 3 is displaced in the tracking direction as described above, the optical axis of the objective lens 3 is changed to the fixed mirror 4
Although the movable mirror 22 is displaced integrally with the objective lens 3 with respect to the optical axis of the light beam incident from the lens, the light beam incident on the fixed mirror 4 from the movable mirror 22 is also displaced integrally with the objective lens 3. As the lens 3 moves parallel to the tracking direction in the same manner as the lens 3, the optical axis shift from the fixed optical system 5 to the objective lens 3 via the movable mirror 22 and the fixed mirror 4 does not occur.

Therefore, in the optical head device 21 according to the present embodiment, even when a tracking error is detected by the push-pull method, no DC offset occurs in this detection signal, so that tracking control can be performed with good accuracy. I can do it. Further, since the light amount of the light beam irradiated on the optical disk 2 does not fluctuate due to the intensity distribution of the laser light and the light amount of the light beam detected by the fixed optical system 5 does not fluctuate, the recording and reproduction of information on the optical disk 2 Can be executed with high accuracy.

The displacement of the lens holder 26 in the tracking direction as described above is a fine adjustment operation for causing the objective lens 3 to follow the minute displacement of the track due to the rotation of the optical disk 2, and moves between the tracks of the optical disk 2. In the seek operation, the entire optical head device 21 is transported in the tracking direction by a head transport mechanism (not shown).

Although the movable mirror 22 integrally displaces the objective lens 3 with the movable mirror 22 as described above, it is possible to prevent the optical axis from being shifted due to the tracking error. There is a concern about occurrence of a jitter error due to rotational resonance centered on the axis. That is, when the movable portion 33 rotates by an angle “θ” about the tracking direction as an axis due to resonance around the center of gravity G,
Since the movable mirror 22 also rotates the angle “θ” in the same direction,
As shown in FIGS. 5 and 6, the light flux emitted from the fixed optical system 5 and incident on the objective lens 3 by reflection from the movable mirror 22 and the fixed mirror 4 has an angle “θ” in the jitter direction from the original optical axis direction. "Tilting. Then, the imaging position of the objective lens 3 having the focal length “f” is displaced in the jitter direction by “fθ”, and this results in a jitter error in the reading result of the optical disc 2.

However, the optical head device 2 of the present embodiment
In 1, the distance “L” in the focusing direction between the center of gravity G of the movable section 33 and the principal point 34 of the objective lens 3 matches the focal length “f” of the objective lens 3, so that the movable section as described above is used. No jitter error occurs due to the rotational resonance of 33. That is, since the rotational resonance of the movable portion 33 is generated with the center of gravity G as the center of rotation, when the movable portion 33 rotates counterclockwise by an angle “θ” in the drawing, the objective lens 3 is in the jitter direction. Move leftward in the figure by “Lθ”. In such a case, as described above, the light beam incident on the objective lens 3 is tilted by “θ” to the right in the figure, which is the jitter direction, so that the image forming position is rightward with respect to the objective lens 3 in the figure. It moves by “fθ”. However, since the objective lens 3 moves leftward by “Lθ” in the figure, the image formation position on the optical disk 2 is not displaced by the cancellation.

That is, the above-described optical head device 21
Since the objective lens 3 and the movable mirror 22 are integrally moved to prevent the optical axis from being shifted by the tracking control, the objective lens 3 and the movable mirror 22 may rotate and resonate integrally. Is separated from the center of gravity G by the same distance as the focal length “f”, the change in the imaging position due to the change in the angle of the light beam can be offset by the change in the position of the objective lens 3, and the image is formed on the optical disk 2. The displacement of the light spot can be prevented.

In the above-described optical head device 21, since the center position of the resilient support of the movable portion 33, the center position of the control drive, and the center of gravity G substantially coincide with each other, the stress of the control drive and the resilient support Even when the reaction force acts on the movable portion 33, rotational resonance hardly occurs. Furthermore, since the position G of the center of gravity of the movable part 33 is located on the optical axis of the objective lens 3, even if rotational resonance occurs in the movable part 33, the objective lens 3 is not displaced in the focusing direction. Focusing control is easy.

In the optical head device 21 described above,
Although the objective lens 3 and the movable mirror 22 are moved together to prevent the optical axis from being shifted by the tracking control, the displacement of the imaging position due to the resonance of the movable part 33 is canceled by the movement of the objective lens 3. It seems that the optical axis shift occurs due to the movement of the objective lens 3. However, while the optical axis shift due to the tracking control occurs at a rate of about 0.4 (mm), the movement of the objective lens 3 with respect to resonance is performed at a rate of about several μm. No.

A second embodiment of the present invention will be described below with reference to FIGS. In addition, regarding the optical head device 41 illustrated here, the optical head device 2 described above is used.
The same parts as those in 1 are denoted by the same names and reference numerals, and detailed description is omitted.

First, the optical head device 41 of the present embodiment
As shown in FIGS. 8 to 10, a fixed mirror 4 is mounted on a head base (not shown) movable in the tracking direction.
The fixed optical system 5 and the yoke 42 are fixed, and four spring shafts 25 as elastic members protrude from a lens support 43 mounted on the yoke 42. The lens holder 44 resiliently supported by these spring shafts 25 so as to be freely displaceable in the tracking direction and the focusing direction has support projections 45 projecting from substantially the center in the jitter direction on both sides in the tracking direction. The spring shaft 25 is connected to the support projection 45 of the spring.

The lens holder 44 has a rectangular through-hole 46 opened in the focusing direction at substantially the center thereof, and a pair of tracking coils 47 and one focusing coil 48 are mounted inside the through-hole 46. ing. As shown in FIG. 11, the focusing coil 48 is wound in a large rectangular shape corresponding to substantially half of the through hole 46 of the lens holder 44, and the tracking coil 47 is formed by a pair of small diameter flat members. It is connected in the direction. A pair of magnets 49 having opposite polarities are fixed to the yoke 42, and these magnets 49 face the coils 47 and 48.

The objective lens 3 is mounted on the upper surface of the lens holder 44 orthogonal to the focusing direction.
The movable mirror 22 is mounted on an end of the lens holder 44 in the jitter direction. A counter weight 50 is detachably mounted on the end opposite to the movable mirror 22. The lens holder 44 on which various components are mounted is elastically supported by the spring shaft 25 so as to be displaceable. Therefore, the movable portion 51 is formed here.

The position of the center of gravity of the movable portion 51 is adjusted by the counter weight 50, and here, the center position of the resilient support and the center position of the control drive exactly match. In the movable section 51, the center of gravity G, the objective lens 3 and the movable mirror 22 are sequentially located in the jitter direction, but as shown in FIG. The distance in the jitter direction is set to twice the focal length “f” of the objective lens 3.

In such a configuration, also in the optical head device 41 of the present embodiment, the movable mirror 22 is displaced integrally with the objective lens 3 similarly to the above-described optical head device 21, so that the movable optical system There is no optical axis shift that enters the objective lens 3 via the mirror 22 and the fixed mirror 4. For this reason, even when a tracking error is detected by the push-pull method, no DC offset occurs in the detection signal, so that tracking control can be performed with good accuracy. Further, since the light amount of the light beam irradiated on the optical disk 2 does not fluctuate due to the intensity distribution of the laser light and the light amount of the light beam detected by the fixed optical system 5 does not fluctuate, the recording and reproduction of information on the optical disk 2 Can be executed with high accuracy.

As described above, the displacement of the optical axis caused by the tracking error can be prevented by the movable mirror 22 integrally displacing the objective lens 3. However, in such a structure, the movable section 51 is moved in the focusing direction. There is a concern that a tracking error may occur due to rotational resonance having the axis as a center. In other words, when the movable part 51 rotates by an angle “θ” about the focusing direction due to resonance around the center of gravity G, the movable mirror 22 also rotates by an angle “θ” in the same direction, as shown in FIG. The light beam emitted from the fixed optical system 5 and incident on the objective lens 3 by reflection from the movable mirror 22 and the fixed mirror 4 is inclined at an angle “2θ” in the tracking direction from the original optical axis direction. Then, since the image forming position of the objective lens 3 having the focal length "f" is displaced in the tracking direction by "2fθ", the tracking control becomes unstable, and a tracking error occurs in the data reading of the optical disc 2.

However, the optical head device 4 of the present embodiment
In FIG. 1, the movable mirror 22, the objective lens 3, and the center of gravity G of the movable part 51 are located in order in the jitter direction, and the distance between the center of gravity G and the principal point 34 of the objective lens 3 in the jitter direction and the objective Since the relationship with the focal length “f” of the lens 3 is two-to-one, the tracking error due to the rotational resonance of the movable part 51 does not occur. That is, since the rotational resonance of the movable portion 51 occurs around the center of gravity G, the resonance causes the movable portion 51 to move the counterclockwise angle “θ” in the drawing.
When rotated, the objective lens 3 moves by “2fθ” to the left in the drawing, which is the tracking direction, as shown in FIG. FIG. 13 shows a state where the objective lens 3 is viewed from the lens support 43 side in the jitter direction.

In such a case, as described above, the light beam incident on the objective lens 3 is inclined by “2θ” to the right in the drawing, which is the tracking direction. It will move rightward by “2fθ”. However, since the objective lens 3 moves to the left in the figure by “2fθ”, the image formation position on the optical disc 2 does not shift due to the offset.

That is, the optical head device 41 described above
Since the objective lens 3 and the movable mirror 22 are integrally moved to prevent the optical axis from being shifted by the tracking control, the objective lens 3 and the movable mirror 22 may rotate and resonate integrally. The distance in the jitter direction between the objective lens 3 and the principal point 34 is the focal length “f” of the objective lens 3.
Therefore, the change in the image formation position due to the change in the angle of the light beam can be offset by the change in the position of the objective lens 3, and the displacement of the light spot formed on the optical disk 2 can be prevented.

In the above-described optical head device 41, since the center position of the resilient support of the movable portion 51, the center position of the control drive, and the center of gravity G substantially coincide with each other, the stress of the control drive and the resilient support are provided. Even when the reaction force acts on the movable portion 51, rotational resonance hardly occurs. Furthermore, since the position G of the center of gravity of the movable portion 51 is adjusted by mounting the separate counterweight 50,
The position of the center of gravity G can be adjusted easily and accurately. For example, the movable mirror 2 is mounted on an existing optical head device (not shown).
It is also possible to manufacture the optical head device 41 by adding 2 and the counterweight 50.

A third embodiment of the present invention will be described below with reference to FIGS. Regarding the optical head device 61 exemplified here, the same portions as those of the above-described optical head device 21 are denoted by the same names and reference numerals, and detailed description is omitted.

First, the optical head device 61 of the present embodiment
In this case, as shown in FIGS. 14 and 15, the fixed optical system 5 is arranged to emit a light beam in the jitter direction, and a first movable mirror 62 as a first movable deflection unit is arranged on the optical axis. ing. The first movable mirror 62 is inclined by 45 ° with respect to the jitter direction and the tracking direction, and a second movable mirror 63 as a second movable deflecting means is provided at a position facing the first movable mirror 62 from the tracking direction. Is arranged.

Since the second movable mirror 63 is also inclined by 45 ° with respect to the jitter direction and the tracking direction, the first and second movable mirrors 62 and 63 are opposed to each other at right angles, and The mirror 63 faces the fixed mirror 4 from the jitter direction. That is, since the first and second movable mirrors 62 and 63 deflect the light beam incident from the fixed optical system 5 toward the fixed mirror 4 by two reflections, the movable deflection deflects the light beam even number of times. Means are formed.

As shown in FIG. 16, a leaf spring 64 is mounted on the yoke 24 as a pair of elastic members that can bend in the focusing direction. Are rotatably supported by a pair of torsion bars 66 which are a pair of elastic members communicating in the focusing direction. Since the leaf spring 64 and the lens holder 65 protrude in the jitter direction, the objective lens 3 attached to the tip of the lens holder 65
Is supported movably in parallel with the focusing direction and rotatably supported so as to move substantially in parallel with the tracking direction.

The first and second movable mirrors 62 and 63 are
Since the light beam incident from the fixed optical system 5 is reflected twice, a movable deflection means for deflecting the light beam only an even number of times is formed here. Since the first and second movable mirrors 62 and 63 are formed integrally below the lens holder 65, the first and second movable mirrors 62 and 63 are moved integrally with the objective lens 3 here. A movement interlocking mechanism is formed.

As shown in FIG. 14, the optical head device 61 of this embodiment has an axis O, which is the center of rotation of the lens holder 65, and a position Q, at which the light beam of the second movable mirror 63 is incident. A is the distance in the jitter direction from the point A, B is the distance in the tracking direction between the axis O and the point P where the light beam of the first movable mirror 62 is incident, and the axis O is the optical axis of the objective lens 3. Assuming that the distance in the jitter direction from the center is R, R = 2A-B is satisfied. Here, since each of the first and second movable mirrors 62 and 63 is inclined by 45 ° with respect to the tracking direction and the jitter direction, the rotation center axis O and the first and second movable mirrors are If the distance in the jitter direction from the intersection C of 62 and 63 is A ', then A' = AB / 2, and R = 2A '.

Further, the optical head device 6 of the present embodiment
1, the objective lens 3 and the movable mirror 6
The lens holder 65 on which the components 2, 63 and the like are mounted is resiliently and resiliently supported by the leaf spring 64 and the torsion bar 66, so that the movable portion 67 is formed here. Then, the position G of the center of gravity of the movable portion 67 and the objective lens 3
Of the objective lens 3 in the focusing direction is twice as long as the focal length “f” of the objective lens 3.

In such a configuration, in the optical head device 61 of this embodiment, the light beam emitted in the jitter direction from the fixed optical system 5 is deflected in the tracking direction by the first The light is deflected in the jitter direction by the mirror 63. The light beam in the jitter direction is deflected in the focusing direction by the fixed mirror 4, converged by the objective lens 3, and enters the track of the optical disk 2.

The light beam reflected in the focusing direction by the optical disk 2 is converged by the objective lens 3 and deflected by the fixed mirror 4 in the jitter direction.
The light beam in the jitter direction is deflected in the tracking direction by the second movable mirror 63, deflected in the jitter direction by the first movable mirror 62, and read by the fixed optical system 5.

Since a tracking error is detected based on the result of reading by the fixed optical system 5, the lens holder 65 is rotated in the tracking direction in accordance with the tracking error, so that the objective lens 3 is positioned on the track of the optical disk 2. The recorded information is read by the fixed optical system 5 following the tracking.

In the optical head device 61 of this embodiment,
As described above, the objective lens 3 is moved in the tracking direction by the rotation of the lens holder 65, and the first and second movable mirrors 62 and 63 also rotate together with the objective lens 3. Since the first and second movable mirrors 62 and 63 deflect the light beam by two reflections, the angle of the light beam incident on the fixed mirror 4 does not change even if the lens holder 65 rotates about the axis O.

That is, when the lens holder 65 has a small angle θ
When the objective lens 3 is rotated only by this distance, the light beam incident on the objective lens 3 from the fixed optical system 5 via the first and second movable mirrors 62 and 63 becomes
It moves parallel by about 2A'θ in the tracking direction. At the same time, the objective lens 3 moves by about Rθ in the tracking direction, but since R = 2A ′, the objective lens 3 is located on the displaced optical axis. In other words, no optical axis shift occurs in the light beam entering the objective lens 3 from the fixed optical system 5, and no optical axis shift occurs in the light beam entering the fixed optical system 5 from the objective lens 3.

This will be described in detail below. Here, the process in which the light emitted from the fixed optical system 5 is incident on the objective lens 3 will be described as an example, but this is the same as the process in which the reflected light from the optical disk 2 is incident on the fixed optical system 5 if the order is reversed. It is.

First, the first and second movable mirrors 62 and 63
In the initial state, each is inclined by 45 ° with respect to the tracking direction and the jitter direction. Therefore, as shown in FIG. 14, when the light beam emitted from the fixed optical system 5 in the jitter direction is incident on the point P of the first movable mirror 62, the light beam reflected here is parallel to the tracking direction and the second Movable mirror 6
The light beam is incident on the point Q of No. 3, and the reflected light beam is incident on the fixed mirror 4 in parallel with the jitter direction.

When the lens holder 65 rotates counterclockwise by a small angle θ about the axis O, the first and second movable mirrors 62 and 63 rotate by a small angle θ and in the tracking direction. And in the jitter direction. When the first and second movable mirrors 62 and 63 move parallel to the fixed optical system 5 by Δy in the tracking direction, the light flux reflected by the first and second movable mirrors 62 and 63 and emitted to the fixed mirror 4 Moves in parallel in the tracking direction by 2 △ y.

On the other hand, even if the first and second movable mirrors 62 and 63 move parallel to the fixed optical system 5 by Δx in the jitter direction, they are reflected and fixed by the first and second movable mirrors 62 and 63. The light beam emitted to the mirror 4 does not move. Also,
Even if the first and second movable mirrors 62 and 63 rotate around the intersection c by the angle θ, the light beam reflected by the first and second movable mirrors 62 and 63 and emitted to the fixed mirror 4 does not move. .

That is, when the lens holder 65 rotates about the axis O by the angle θ, the light beam incident on the objective lens 3 moves in the tracking direction by 2 △ y. Here is 2 △
Since y = (2A−B) θ = 2A′θ, the moving distance of the light beam is 2A′θ. On the other hand, as shown in FIG. 14, the center of the optical axis of the objective lens 3 moves in the tracking direction by Rθ due to the rotation of the angle θ, and the distance of this movement is Rθ = 2.
Since it is A'θ, this coincides with the movement distance of the light beam.

That is, in the optical head device 61 of this embodiment, the lens holder 65 is used for tracking control.
Is rotated by the angle θ, the optical axis of the light beam incident on the objective lens 3 moves by 2A′θ in the tracking direction.
Since the objective lens 3 also moves in the tracking direction by 2A'θ, no optical axis shift occurs in the light beam incident on the objective lens 3. Similarly, the light flux reflected by the optical disk 2 and returned to the fixed optical system 5 via the objective lens 3 and the first and second movable mirrors 62 and 63 does not have an optical axis shift.

For this reason, in the optical head device 61 of this embodiment, even when a tracking error is detected by the push-pull method, no DC offset occurs in this detection signal, so that tracking control can be performed with good accuracy. I can do it. Furthermore, since the intensity of the light beam irradiated on the optical disk 2 does not fluctuate due to the intensity distribution of the laser light, and the intensity of the light beam detected by the fixed optical system 5 does not fluctuate, the reproduction or recording of information on the optical disk 2 is performed. Can be executed with high accuracy.

In addition, the optical head device 6 of this embodiment
In No. 1, since it is not necessary to arrange a large number of optical elements in the focusing direction in order to prevent the optical axis of the light beam from shifting,
It is possible to reduce the size of the device in the focusing direction. Further, the objective lens 3 and the first and second movable mirrors 6
2 and 63 are provided on the lens holder 65 and move together, so that the objective lens 3 is
There is no resonance with 63.

However, there is a concern that the movable portion 67 resonates around the center of gravity G and a jitter error occurs in the read result of the optical disk 2. When the movable part 67 rotates by an angle “θ” around the tracking direction due to resonance around the center of gravity G, the movable mirrors 62 and 63 also rotate by an angle “θ” in the same direction, as shown in FIG. The luminous flux emitted from the fixed optical system 5 and incident on the objective lens 3 by reflection from the movable mirrors 62 and 63 and the fixed mirror 4 is
The angle is inclined by “2θ” in the jitter direction from the original optical axis direction. Then, the imaging position of the objective lens 3 having the focal length “f” is displaced in the jitter direction by “2fθ”, and this results in a jitter error in the read result of the optical disc 2.

However, the optical head device 6 of the present embodiment
In 1, the distance “L” in the focusing direction between the center of gravity G of the movable section 67 and the principal point 34 of the objective lens 3 is twice the focal length “f” of the objective lens 3. No jitter error occurs due to rotational resonance. That is, since the rotational resonance of the movable part 67 is generated with the center of gravity G as the center of rotation, when the movable part 67 rotates counterclockwise in FIG. 18 by the angle “θ” due to this resonance, as shown in FIG. The lens 3 has “L” on the left side in the figure, which is the jitter direction.
In such a case, as described above, the light beam incident on the objective lens 3 is inclined by “2θ” to the right in the figure, which is the jitter direction, so that the image forming position is relative to the objective lens 3. However, the objective lens 3 moves rightward in the figure by “2fθ”, but the objective lens 3 moves leftward in the figure by “Lθ = 2f”.
θ ”, the image formation position on the optical disk 2 is not displaced by this offset.

That is, the optical head device 61 described above
Since the objective lens 3 and the movable mirrors 62 and 63 are moved together to prevent the optical axis from being shifted by the tracking control, the objective lens 3 and the movable mirrors 62 and 63 may rotate and resonate integrally. By changing the objective lens 3 away from the center of gravity G by a distance twice as long as the focal length "f", a change in the imaging position due to a change in the angle of the light beam can be offset by a change in the position of the objective lens 3, and 2 can be prevented from being displaced.

The optical head device 61 of the present embodiment
Since the first and second movable mirrors 62 and 63 are formed integrally with the lens holder 65 on which the objective lens 3 is mounted, the structure is simple, and productivity can be improved and the size and weight can be easily reduced. The response can be improved by reducing the mass of the portion. For example, when the lens holder 65 is made of metal, the first and second movable mirrors 62 and 63 can be formed by precisely forming a concave portion having an inner angle of a right angle.

Here, for simplicity of explanation, a structure in which the first and second movable mirrors 62 and 63 are opposed to each other at a right angle and inclined by 45 ° with respect to the tracking direction and the jitter direction has been exemplified. However, the present invention is not limited to the above-described method. If the movable deflecting unit deflects the light beam only an even number of times, the optical axis of the objective lens 3 can be prevented from being shifted. For example,
The first and second movable mirrors 62 and 63 may be inclined at a predetermined angle from the beginning with respect to the tracking direction and the jitter direction, and the inner angles of the first and second movable mirrors 62 and 63 may not be right angles. good.

Further, although the movable deflecting means is formed by the first and second movable mirrors 62 and 63 here, it can be formed by one triangular prism (not shown). Since such a triangular prism can rotate the polarization plane of the light beam reciprocating between the fixed optical system 5 and the optical disk 2 by 90 °, the quarter-wave plate 9 is omitted from the fixed optical system 5. Is also possible.

[0076]

According to the first aspect of the present invention, a movable deflecting means for deflecting a light beam emitted from a fixed optical system in a direction orthogonal to a focusing direction and a tracking direction is mounted on a lens holder, and the deflected light beam is transmitted to the lens holder. A fixed deflecting means for deflecting in the focusing direction and entering the objective lens is mounted on the head base, and a movable part is formed by a lens holder on which at least the objective lens and the movable deflecting means are mounted. Since the distance in the focusing direction from the principal point of the lens and the focal length of the objective lens are substantially matched, there is no optical axis shift in the light beam entering the objective lens from the fixed optical system via each deflecting means. The tracking error can be detected well even by the push-pull method, and the intensity fluctuation due to the laser light intensity distribution can be prevented. In addition, even if the movable portion rotates and resonates in a direction perpendicular to the tracking direction and the focusing direction and the angle of the light beam incident on the objective lens changes, the distance that offsets the change in the imaging position due to the tilt of the light beam. Since the objective lens only moves, the position of the light spot imaged on the optical disk does not shift, and the occurrence of a jitter error can be prevented.

According to a second aspect of the present invention, a movable deflecting means for deflecting a light beam emitted from a fixed optical system in a direction orthogonal to a focusing direction and a tracking direction is mounted on a lens holder, and the deflected light beam is focused in the focusing direction. The fixed deflecting means for deflecting the light into the objective lens is mounted on the head base, and at least a movable part is formed by a lens holder on which the objective lens and the movable deflecting means are mounted. The movable deflecting means are sequentially positioned in the direction orthogonal to the tracking direction and the focusing direction, and the distance between the center of gravity of the movable part in the direction orthogonal to the tracking direction and the focusing direction, the principal point of the objective lens, and the By making the focal length approximately two-to-one, light enters the objective lens from the fixed optical system via each deflecting means. Since the optical axis does not shift in the bundle, the tracking error can be detected well even by the push-pull method, the intensity fluctuation due to the laser light intensity distribution can be prevented, and the movable part rotates in the tracking direction. Even if the angle of the light beam incident on the objective lens changes due to resonance, the objective lens moves by a distance that offsets the change in the imaging position due to the inclination of the light beam, so that the position of the light spot imaged on the optical disk is changed. It is possible to prevent a tracking error from occurring without displacement.

According to a third aspect of the present invention, an objective lens arranged to face an optical disk is mounted on a lens holder, and this lens holder is elastically supported on a head base by an elastic member so as to be displaceable in a tracking direction and a focusing direction. A fixed optical system that emits laser light is provided, and a movable deflecting unit that deflects the emitted light beam twice and emits the light beam in a direction orthogonal to the tracking direction and the focusing direction is attached to the lens holder. A fixed deflecting means for deflecting the luminous flux in the focusing direction and making it incident on the objective lens is attached to the head base, and error detecting means for detecting errors of tracking and focusing from the luminous flux returned from the optical disc to the fixed optical system are provided, The tracking method for the lens holder with respect to the head base in response to this detection error Position control means for controlling and driving the object and the focusing direction. A movable part is formed by a lens holder on which at least the objective lens and the movable deflecting means are mounted, and focusing between the position of the center of gravity of the movable part and the principal point of the objective lens is performed. Since the distance in the direction is almost twice as long as the focal length of the objective lens, there is no optical axis shift in the light beam entering the objective lens from the fixed optical system via each deflecting means. The system can also detect well and prevent fluctuations in intensity due to the intensity distribution of the laser beam.Moreover, the movable part rotates and resonates in the direction orthogonal to the tracking direction and the focusing direction, causing Even if the angle of the incident light beam changes, the objective lens moves by a distance that offsets the change in the imaging position due to the inclination of the light beam. , The position of the light spot imaged on the optical disk without displacement, it is possible to prevent occurrence of jitter error.

According to the fourth aspect of the present invention, since the center position of the resilient support, the center position of the control drive, and the position of the center of gravity of the movable portion are substantially matched, the stress of the control drive and the reaction force of the resilient support are provided. Acts on the position of the center of gravity of the movable part, so that the occurrence of rotational resonance of the movable part can be reduced.

According to the fifth aspect of the present invention, since the center of gravity of the movable portion is located on the optical axis of the objective lens, the objective lens is not displaced in the focusing direction even if rotational resonance occurs in the movable portion. The control can be executed easily and accurately.

According to the sixth aspect of the present invention, since the weight for adjusting the position of the center of gravity of the movable portion is attached to the lens holder, the position of the center of gravity of the movable portion can be freely adjusted with a simple structure.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an optical head device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a positional relationship between components of the optical head device.

FIG. 3 is a plan view showing the optical head device.

FIG. 4 is a vertical sectional side view showing a main part of the optical head device.

FIG. 5 is a schematic diagram showing a state in which a light beam incident on a fixed mirror as a fixed deflection unit from a movable mirror as a movable deflection unit is rotated.

FIG. 6 is a schematic diagram showing a state where a light spot at which an objective lens forms an image on an optical disc is displaced.

FIG. 7 is a schematic diagram showing a state in which the rotation of the light beam and the movement of the objective lens cancel each other.

FIG. 8 is an exploded perspective view showing an optical head device according to a second embodiment of the present invention.

FIG. 9 is a plan view showing the optical head device.

FIG. 10 is a vertical sectional side view showing a main part of the optical head device.

FIG. 11 is a perspective view showing a tracking coil and a focusing coil.

FIG. 12 is a schematic diagram illustrating a state in which a light beam incident on a fixed mirror from a movable mirror is rotated.

FIG. 13 is a schematic diagram showing a state where a light spot at which an objective lens forms an image on an optical disc is displaced.

FIG. 14 is a plan view showing an optical head device according to a third embodiment of the present invention.

FIG. 15 is a side view showing the optical head device.

FIG. 16 is a perspective view showing an optical head device.

FIG. 17 is a schematic diagram showing a state where a movable section is inclined.

FIG. 18 is a schematic diagram showing a state in which rotation of a light beam and movement of an objective lens cancel each other.

FIG. 19 is a side view showing a positional relationship between components of an optical head device according to a conventional example.

FIG. 20 is a schematic diagram showing an intensity distribution of a light beam.

FIG. 21 is a perspective view showing a positional relationship between components of another conventional optical head device.

[Explanation of symbols]

 Reference Signs List 2 optical disk 3 objective lens 4 fixed deflecting means 5 fixed optical system 21, 41, 61 optical head device 22, 62, 63 movable deflecting means 25, 64, 66 elastic members 26, 44, 65 lens holder 33, 51, 67 movable part 34 principal points 50 weights

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/09-7/095 G11B 7/135

Claims (6)

(57) [Claims] An object lens opposed to an optical disk is mounted on a lens holder, and this lens holder is elastically supported on a head base by an elastic member so as to be freely displaceable in a tracking direction and a focusing direction, and a laser beam is emitted in a tracking direction. A movable deflecting means for deflecting the emitted light beam in a direction orthogonal to the focusing direction and the tracking direction is attached to the lens holder, and the deflected light beam is deflected in the focusing direction. Fixed deflection means for causing the light to enter the objective lens is attached to the head base, and error detection means for detecting errors in tracking and focusing from the light flux returned from the optical disc to the fixed optical system are provided. Correspondingly, track the lens holder against the head base. Position control means for controlling and driving in a king direction and a focusing direction is provided, and a movable part is formed by at least the lens holder on which the objective lens and the movable deflecting means are mounted. The center of gravity of the movable part and the objective lens An optical head device wherein a distance in a focusing direction from a principal point of the objective lens and a focal length of the objective lens are substantially matched. 2. An objective lens, which is disposed opposite to an optical disk, is mounted on a lens holder, and the lens holder is elastically supported by a resilient member on a head base so as to be displaceable in a tracking direction and a focusing direction. A movable deflecting means for deflecting the emitted light beam in a direction orthogonal to the focusing direction and the tracking direction is attached to the lens holder, and the deflected light beam is deflected in the focusing direction. Fixed deflection means for causing the light to enter the objective lens is attached to the head base, and error detection means for detecting errors in tracking and focusing from the light flux returned from the optical disc to the fixed optical system are provided. Correspondingly, track the lens holder against the head base. Position control means for controlling and driving in a king direction and a focusing direction is provided, and a movable part is formed by at least the lens holder on which the objective lens and the movable deflecting means are mounted, and a center of gravity of the movable part and the objective lens And the movable deflecting means are sequentially positioned in a direction orthogonal to the tracking direction and the focusing direction, and a distance between a center of gravity of the movable portion in a direction orthogonal to the tracking direction and the focusing direction and a principal point of the objective lens. And the focal length of the objective lens is substantially two-to-one. 3. An objective lens disposed opposite to an optical disk is mounted on a lens holder, and the lens holder is elastically supported on a head base by an elastic member so as to be freely displaceable in a tracking direction and a focusing direction, and emits a laser beam. A fixed optical system is provided, and movable deflecting means for deflecting the emitted light beam only twice and emitting the light beam in a direction orthogonal to the tracking direction and the focusing direction is attached to the lens holder, and the deflected light beam is focused in the focusing direction. A fixed deflecting means for deflecting the light into the objective lens is attached to the head base, and error detecting means for detecting errors of tracking and focusing from a light beam returned from the optical disc to the fixed optical system are provided. Track the lens holder with respect to the head base in response to a detection error. Position control means for controlling and driving in a focusing direction and a focusing direction, a movable portion is formed by at least the lens holder on which the objective lens and the movable deflecting means are mounted, and a center of gravity of the movable portion and the objective lens An optical head device wherein a distance in a focusing direction from a principal point of the optical head is approximately twice a focal length of the objective lens. 4. The optical head device according to claim 1, wherein the center position of the movable portion, the center position of the resilient support, the center position of the control drive, and the position of the center of gravity are substantially matched. 5. The optical head device according to claim 1, wherein the center of gravity of the movable portion is located on the optical axis of the objective lens. 6. The lens holder according to claim 1, wherein a weight for adjusting the position of the center of gravity of the movable portion is mounted on the lens holder.
Or the optical head device according to 3.