JP5108927B2 - Optical element actuator - Google Patents

Description

  The present invention is used for an information recording / reproducing apparatus for recording and / or reproducing information on an optical recording medium such as a magneto-optical disk drive, a write-once disk drive, a phase change disk drive, a CD-ROM, a DVD, and an optical card. The present invention relates to an actuator that supports an optical element such as an objective lens, a coupling lens for an optical fiber used for optical communication, or an objective lens of a scanning microscope in a drivable manner.

  For example, in an optical pickup actuator used in an optical apparatus such as the above information recording / reproducing apparatus, an objective lens that is an optical element is supported so as to be drivable in two directions of a focus direction and a tracking direction, and the light spot of the objective lens is It is necessary to be accurately positioned on the recording track of the recording medium. For this reason, as actuators that support the optical element so that it can be driven in two directions, various actuators having high driving sensitivity have been proposed for the purpose of improving recording density and access speed.

  For example, Patent Document 1 proposes an actuator as shown in FIG. This actuator holds the objective lens 10 with a holder 11 and is respectively provided on two attachment surfaces 11f (only one is shown in FIG. 7) arranged opposite to the holder 11 in a tangential direction Z orthogonal to the focus direction X and the tracking direction Y. The flat focus coil 12 and the tracking coil 13 are arranged one by one, and an effective magnetic field is directed to the focus coil 12 and the tracking coil 13 from the magnet 14 arranged opposite to each other via the yoke 15. is there. This prior art uses two sides of the working sides 12a and 12b as effective sides in the focus coil 12, and uses two sides of the working sides 13a and 13b as effective sides in which electromagnetic force is generated in the tracking coil 13. This enhances the response (drive sensitivity) of the actuator.

  Patent Document 2 proposes an actuator as shown in FIG. In order to efficiently generate a driving force in the tracking direction, this actuator wraps the focus coil 22 around the outer periphery of the holder 21 that holds the objective lens 20, and attaches the tracking coil 23 to one side surface of the holder 21. An effective magnetic field is directed to the magnet 22 and the tracking coil 23 through the outer yoke 25a and the inner yoke 25b from the magnets 24a and 24b arranged opposite to each other.

Japanese Utility Model Publication No. 2-30120 Japanese Patent No. 2620221

  However, it has become clear that such conventional actuators have the following disadvantages.

  First, in the actuator as shown in Patent Document 1, the focus coil 12 and the tracking coil 13 are integrally attached to the attachment surface 11f arranged in the tangential direction. Therefore, it is difficult to increase the driving sensitivity.

  In the actuator as shown in Patent Document 2, since the tracking coil 23 is attached to the holder 21 around which the focus coil 22 is wound, the focus coil 22 has only two magnets 24a out of the three magnets 24a and 24b. The focus coil 22 in the portion (the portion extending along the tracking direction Y) to which the tracking coil 23 is attached does not act, and it is difficult to increase the drive sensitivity.

  The present invention has been made to solve the above-described problems, and is an optical element actuator capable of driving an optical element with high sensitivity in two directions of a first direction and a second direction orthogonal to each other. The purpose is to provide.

The present invention relates to an optical element actuator that supports an optical element so as to be drivable in two directions of a focus direction and a tracking direction orthogonal to each other, and uses a side surface disposed so as to surround the central axis along the focus direction as a coil attachment surface. Inside, a holder that holds the optical element with NA of 0.7 to 0.9, a focus coil that is attached to the coil mounting surface of the holder and generates a driving force in the focusing direction, and is attached to the coil mounting surface of the holder A tracking coil that generates a driving force in the tracking direction, a magnetic field generating means that includes a magnet that directs a magnetic field to the focus coil and the tracking coil , and a support member that supports the holder to be drivable in the focus direction and the tracking direction. , wherein the focus co Le is I der those capable of controlling the direction of current in opposite directions through the mutual coil,
The holder fixedly holds the correction lens at the lower end thereof, and has four side surfaces arranged so as to surround the central axis along the focus direction, and each of the side surfaces serves as the coil attachment surface. Attaching only a single focus coil to each of the two first attachment surfaces arranged to face each other across the central axis among the coil attachment surfaces,
Each of the two second mounting surfaces arranged to face each other across the central axis is provided with only a single tracking coil, provided with a light shielding bar, and a light emitting diode and a photodiode, An output difference between the light projected from the light emitting diode to the light receiving surface of the photodiode is obtained by being orthogonal to and intersecting the light incident on the reflection mirror that reflects the light from the laser to the optical element. Thus, the position of the optical element is detected,
The magnetic field generating means is an open magnetic circuit that does not have a yoke constituting a magnetic gap .

  In the present invention, the current flowing through the focus coil can be an added value of the focus servo current and the tilt servo current.

1 is a perspective view showing a recording / reproducing apparatus for an optical disc according to a first embodiment of the present invention. FIG. 2 is a top view of FIG. 1. It is sectional drawing which showed FIG. 1 from the tangential direction. It is a disassembled perspective view of the same form. It is a perspective view which shows the recording / reproducing apparatus for optical discs which is the reference technique of this invention. It is a perspective view which shows the recording / reproducing apparatus for optical discs which is 2nd Embodiment of this invention. It is a perspective view which shows the actuator of the optical element by a prior art. It is a perspective view which shows the actuator of the other optical element by a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 3 are a perspective view showing a recording / reproducing apparatus for an optical disc according to a first embodiment of the present invention, a top view of FIG. 1, and a sectional view showing FIG. 1 from a tangential direction. Is an exploded view.

  This recording / reproducing apparatus is a recording / reproducing apparatus for the phase change recording type optical disc 1 (see FIG. 3), and is in a first direction (focus direction) X and a second direction (tracking) orthogonal to the objective lens 100 as an optical element. (Direction) It is supported so that it can be driven in two directions. As the optical disc 1, an existing one in which the recording surface 1f is covered with a thin cover glass 1c of 0-0.1 (mm) is used.

3 and 4, the objective lens 100 has a high NA of 0.7 to 0.9, and is formed at the upper end of the holder 110 whose central axis O ₁ coincides with the optical axis of the objective lens 100. Fixedly held in the mounting hole. The holder 110 also has a chromatic aberration correction lens 120 fixedly held at the lower end thereof so that the chromatic aberration correction lens 120 functions as a balancer in the focus direction X of the objective lens 100, while the objective lens 100 functions as the focus direction X of the chromatic aberration correction lens 120. It functions as a balancer. In this case, the holder 110 does not need an extra balancer.

  As shown in FIG. 4, the holder 110 includes two first attachment surfaces 111 a and 111 b that are disposed opposite to the holder 110 in the tracking direction Y, and a third direction (tangential direction) orthogonal to the focus direction X and the tracking direction Y. ) In Z, two second mounting surfaces 112a and 112b arranged to face the holder 110 are provided.

  The first mounting surface 111a has two protrusions protruding along the tracking direction Y, and a first flat coil (hereinafter referred to as a focus coil) 131 is positioned on the first mounting surface 111a by these protrusions. The first attachment surface 111a is adhesively fixed in parallel to the entire surface. Similarly, the first attachment surface 111b is formed with two protrusions (not shown) protruding along the tracking direction Y, and a first flat coil (hereinafter referred to as a focus coil) 132 is formed by these protrusions. In a state of being positioned on the first mounting surface 111b, the first mounting surface 111b is bonded and fixed in parallel to the entire surface.

  The second mounting surface 112a has two protrusions protruding along the tangential direction Z, and the second flat coil (hereinafter referred to as tracking coil) 133 is positioned on the second mounting surface 112a by these protrusions. In this state, the second mounting surface 112a is bonded and fixed in parallel to the entire surface. Similarly, the second mounting surface 112b has two protrusions (not shown) protruding along the tangential direction Z, and the second flat coil (hereinafter referred to as tracking coil) 134 is formed by these protrusions. 2 In a state where it is positioned on the mounting surface 112b, it is bonded and fixed in parallel to the entire surface of the second mounting surface 112b.

That is, the focus coils 131 and 132 and the tracking coils 133 and 134 include a total of four focus directions X provided so as to surround the center axis O _{1 of the} holder, that is, to surround the optical axis of the objective lens 100 and to face each other. Are attached in parallel to the first attachment surfaces 111a and 111b and the second attachment surfaces 112a and 112b which are parallel to each other.

  The holder 110 is integrally provided with two fixing portions 115 extending along the focus direction X at two locations on the tracking coil 133 side, and one ends of springs 140a and 140b are bonded and fixed to the fixing portion 115, respectively. Yes. The springs 140a and 140b are obtained by edging a thin plate made of beryllium copper having a thickness of about 0.05 (mm), and an intermediate portion of the springs 140a and 140b surrounds the periphery of the objective lens 100, and will be described later. 141 and the focus coils 131 and 132 are positioned therebetween. The other ends of the springs 140a and 140b are bonded and fixed to spring fixing portions 142a and 142b formed integrally with the spring holder 142 at two locations on the upper and lower ends of the spring holder 142, respectively.

  The spring holder 142 is bonded and fixed in a state of being positioned with respect to the mounting surface 141g of the base 141 by two bosses formed on the mounting surface 142f.

  The base 141 has a substantially cylindrical shape obtained by drawing an iron plate having a thickness of 0.6 (mm). The focus magnet 151 is magnetized with two poles in the focus direction X on each of the inner walls opposed to each other in the tracking direction Y. , 152 are bonded to the inner walls opposed to each other in the tangential direction Z, and tracking magnets 153, 154 magnetized in the tracking direction Y are bonded to each other. In this case, it is convenient to use a magnet with two poles as the magnetic field generating means because a magnetic field having a required magnitude can be easily generated.

  That is, the magnetic pole of the focus magnet 151 (152) faces the two action sides 131a and 131b (132a and 132b) extending in the tangential direction Z of the focus coil 131 (132), and the tracking magnet 153 (154) The magnetic pole faces two action sides 133a and 133b (134a and 134b) extending in the focus direction X of the tracking coil 133 (134).

  As shown in FIG. 3, the base 141 is integrally formed with a spherical portion 141 f for tilt adjustment at the lower end, and the spherical portion 141 f can be tilted with respect to the conical surface 160 f formed on the upper surface of the carriage 160. Abut. As a result, the base 141 is adjusted to the inclination with respect to the carriage 160 and then fixed to the carriage 160 by adhesion. A reflecting mirror 161 is housed on the conical surface 160f of the carriage 160 as shown in FIG.

  Furthermore, the sensor holder 162 is fixed to the outer surface of the base 141 in the tracking direction Y. The sensor holder 162 includes PDs (photodiodes) 163 and LEDs (light-emitting diodes) 164 each having a light-receiving surface that is divided into two in the tracking direction Y at opposite ends in the tangential direction Z.

  The light emitted from the LED 164 is projected onto the light shielding bar 116 disposed at the lower end of the holder 110 and is incident on the light receiving portion of the PD 163. At this time, when the holder 110 moves integrally with the objective lens 100 in the tracking direction Y, the light shielding bar 116 also moves in the tracking direction Y. Therefore, by taking the output difference of the two divided light receiving surfaces on the PD 163, the objective is obtained. The position of the lens 100 in the tracking direction Y can be detected.

  The light emitted from the LED 164 is arranged so as to be orthogonal to and intersect with the light incident on the reflection mirror 161 from the laser. Thereby, space can be used effectively and a recording / reproducing apparatus can be reduced in size.

  As shown in FIG. 3, the recording / reproducing apparatus of the present embodiment reflects light from a laser (not shown) by a reflecting mirror 161, and makes this reflected light enter the objective lens 100 through the chromatic aberration correction lens 120, thereby making the optical disc. A light spot is formed on one recording surface 1f. In the present embodiment, the reflected light from the recording surface 1f of the optical disc 1 is caused to follow the reverse optical path to the objective lens 100, the chromatic aberration correction lens 120, and the reflecting mirror 161, and is incident on the light receiving element via the error detection optical element. Thus, tracking error detection, focus error detection, and RF signal detection can be performed. Since various optical systems have been proposed, the description thereof will be omitted.

  Here, a fine adjustment method of the objective lens 100 will be described.

  First, when the objective lens 100 is finely adjusted in the focus direction X, power is supplied to the focus coils 131 and 132 via the springs 140a and 140b. At this time, the same force in cooperation with the magnetic field from the focus magnets 151 and 152 is applied to the two action sides 131a and 131b of the focus coil 131 and the two action sides 132a and 132b of the focus coil 132 in the focus direction X, respectively. Therefore, the holder 110 can be driven along the focus direction X to finely adjust the objective lens 100 in the focus direction X.

  Next, when the objective lens 100 is finely adjusted in the tracking direction Y, power is supplied to the tracking coils 133 and 134 via the springs 140a and 140b. At this time, the same force cooperating with the magnetic field from the tracking magnets 153 and 154 is generated along the tracking direction Y on the action sides 133a and 133b of the tracking coil 133 and the action sides 134a and 134b of the tracking coil 134, respectively. Therefore, the holder 110 can be driven along the tracking direction Y to finely adjust the objective lens 100 in the tracking direction Y.

In the present embodiment, the first mounting surfaces 111 a and 111 b and the second mounting surfaces 112 a and 112 b provided on the holder 110 so as to surround the optical axis of the objective lens 100 that coincides with the central axis O ₁ of the holder 110 are flat. The focus coils 131 and 132 and the tracking coils 133 and 134 are attached in parallel to the first attachment surfaces 111a and 111b and the second attachment surfaces 112a and 112b, respectively, and magnetic fields are applied to the focus coils 131 and 132 and the tracking coils 133 and 134, respectively. Since the focus magnets 151 and 152 and the tracking magnets 153 and 154 correspond to the magnetic field generation means for directing
A sufficient arrangement space for the focus coils 131 and 132 and the tracking coils 133 and 134 can be secured on the first mounting surfaces 111a and 111b and the second mounting surfaces 112a and 112b.

Further, by disposing the driving coils 131 to 134 on almost the entire outer peripheral surface surrounding the central axis O ₁ of the holder 110, the wasted empty space around the holder 110 is minimized and efficiently used. . Further, the focus driving coils 131 and 132 and the magnets 151 and 152 and the tracking driving coils 133 and 134 and the magnets 153 and 154 are not arranged on the same plane, but are mounted on separate mounting surfaces 111a and 111b perpendicular to each other. , 112a and 112b, a large coil and a magnet can be arranged in each.

  Therefore, according to the present embodiment, since the focus coils 131 and 132 and the tracking coils 133 and 134 can be set to large ones, the respective action sides 131a, 131b, 132a, 132b, 133a, 133b, and 134a can be set. , 134b can be increased in length and volume, and the focus magnets 151, 152 and tracking magnets 153, 154 corresponding to the coils can be increased in accordance with the coils. It can be driven with high sensitivity to the direction.

  In addition, in the present embodiment, since the focus magnet 151 (152) corresponds to the focus coil 131 (132) and the tracking magnet 153 (154) corresponds to the tracking coil 133 (134), the focus magnet 151 (152). Magnetic fields that generate different forces such as the magnetic field from the tracking magnetic field and the magnetic field from the tracking magnet 153 (154) do not interfere with each other.

  For this reason, for example, when the objective lens 100 is finely adjusted in the focus direction X, the magnetic field acting on the focus coil 131 (132) from the tracking magnet 153 (154) is very large even when a current is passed through the focus coil 131 (132). Since there are few, the motion of the objective lens 100 which is not desired can be prevented. On the other hand, in the prior art 2, since the magnetic field of the magnet acting on the tracking coil acts on one surface of the focus coil, a torque rotating around the axis in the tangential direction Z is generated, and the objective lens moves undesirably. .

  Furthermore, in this embodiment, the focus coil 131 (132) and the tracking coil 133 (134) are flattened, and the flat surface is fixed to the holder 110, so that the focus coil 131 (132) and the tracking coil 133 (134) are fixed. Are mounted in parallel to the first mounting surfaces 111a and 111b and the second mounting surfaces 112a and 112b, respectively, so that the rigidity of the focus coil 131 (132) and the tracking coil 133 (134) mounted on the holder 110 is remarkably increased. The resonance frequency of the mode in which the coil itself is deformed becomes very high. In addition, the holder 110 itself has a square block shape and high rigidity, and the central opening is reinforced by the objective lens 100 and the chromatic aberration correction lens 120, and the outer peripheral portion thereof is reinforced by a flat coil, so that the rigidity is increased. The resonance frequency is also increased.

  By the way, the magnetism generating means of the present embodiment constitutes an open magnetic circuit that does not have a yoke that forms a magnetic gap composed of dipole magnetized focus magnets 151 and 152 and tracking magnets 153 and 154. In this case, since there is no need to provide an opening for arranging the yoke in the holder 110, the rigidity of the holder 110 can be increased by the rigidity of the opening.

  Further, in the present embodiment, since the support members are the springs 140a and 140b arranged so as to sandwich the focus coils 131 and 132, the tracking direction width of the holder 110 can be set small without increasing it by the support member.

  Furthermore, in the present embodiment, the base 141 is cylindrical, and there is no inner yoke that directly faces the focus magnet and the tracking magnet. Therefore, the rigidity of the base 141 is not required because a cantilevered yoke is not required. Can be increased.

  FIG. 5 is an exploded perspective view showing a recording / reproducing apparatus for an optical disk which is a reference technique of the present invention.

  Similar to the first embodiment, this recording / reproducing apparatus is a recording / reproducing apparatus for the optical disk 1 of the phase change recording system, and supports the objective lens 100 so as to be drivable in two directions, ie, a focus direction X and a tracking direction Y. Is. For this reason, the same part as 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  The holder 110 includes two first mounting surfaces 111a and 111b disposed to face the holder 110 in the tracking direction Y, and two second mounting surfaces 112a and 112b disposed to face the holder 110 in the tangential direction Z. Have

  In the first mounting surface 111a, the focus magnet 171 is bonded and fixed in parallel to the first mounting surface 111a. Similarly, in the first mounting surface 111b, the focus magnet 172 is bonded and fixed in parallel to the first mounting surface 111b. Has been.

  The tracking magnet 173 is bonded and fixed to the second mounting surface 112a in parallel to the second mounting surface 112a. Similarly, the tracking magnet 174 is bonded to the second mounting surface 112b in parallel to the second mounting surface 112b. It is fixed.

  The base 141 is made of non-magnetic stainless steel to prevent the focus magnets 171 and 172 and the tracking magnets 173 and 174 from being magnetically attracted, and the focus coils 181 and 182 are tracked on the inner walls facing each other in the tracking direction Y, respectively. The tracking coils 183 and 184 are bonded in parallel with the inner wall in the tangential direction, respectively, while being bonded in parallel with the inner wall in the direction, and on the inner walls opposed to each other in the tangential direction Z.

  That is, in contrast to the first embodiment, which is a moving coil configuration in which a coil is disposed on a holder 110 that is a movable part, the present reference technology is a moving magnet configuration in which a magnet is disposed on the holder 110. For this reason, according to this embodiment, the electric power feeding to the holder 110 which is a movable part becomes unnecessary.

  The first embodiment and the reference technique can be used in combination, and by attaching the tracking coil and the focus magnet to the holder 110 and attaching the focus magnet and the tracking coil to the base 141, the focus direction X or Either one of the tracking directions Y may be a moving coil drive, and the other may be a moving magnet drive.

  FIG. 6 is an exploded perspective view showing a recording / reproducing apparatus for an optical disc according to the second embodiment of the present invention.

  Similarly to the first embodiment, this recording / reproducing apparatus is a recording / reproducing apparatus for an optical disk of the phase change recording system, and supports the objective lens 100 so as to be drivable in two directions of the orthogonal focus direction X and tracking direction Y. It is. For this reason, the same part as 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In this embodiment, an insulating layer made of polyimide having a thickness of about 5 (μ: micron) is provided on the surfaces of the springs 140a and 140b, and two wiring patterns made of aluminum are formed on the insulating layer. is there.

  In the present embodiment, since there are four springs 140a and 140b, the total number of wiring patterns is eight, but only six of them are actually used, and the breakdown is the tracking coils 133 and 134. 2 for the focus coil and 2 for the focus coils 131 and 132 respectively. As a result, power can be supplied to the focus coils 131 and 132 independently.

  Here, when a focus servo current is supplied so as to generate the same force in the focus direction X to the focus coils 131 and 132, the objective lens 100 can be finely adjusted in the focus direction X. On the other hand, as shown in FIG. 6, when a tilt servo current is supplied so as to generate a force in the opposite focus direction X to each of the focus coils 131 and 132, a rotation θz around the tangential axis Z occurs, and the objective Since the lens 100 can be tilted around the tangential axis Z, coma and the like can be corrected. If a servo current obtained by adding a focus servo current and a tilt servo current is applied to the focus coils 131 and 132, the objective lens 100 can be tilted around the tangential axis Z while being finely adjusted in the focus direction X. This is more effective for correcting aberrations.

  In other words, in the present embodiment, the focus coils 131 and 132 can control the direction of the current flowing through the coils. Therefore, if the directions of feeding power to the focus coils 131 and 132 are opposite to each other, the objective lens 100 is used. Can be tilted in the tracking direction Y.

  In particular, in the present embodiment, tilt servo can be applied around the tangential axis θz using a tilt sensor of the optical disc 1 or a track crosstalk signal of a reproduction signal. In this case, since the coma aberration can be corrected by tilting the objective lens 100, the aberration of the light spot is improved and good recording / reproduction is possible.

  Note that the present embodiment can also be used in combination with the reference technique, and either the focus direction X or the tracking direction Y may be a moving coil drive and the other may be a moving magnet drive. Further, not only the focus coils 131 and 132 but also the tracking coils 133 and 134 or both the focus coils 131 and 132 and the tracking coils 133 and 134 may be capable of controlling the direction of current flowing through the coils.

The above description is only a preferred embodiment of the present invention, and various modifications can be made by those skilled in the art within the scope of the claims. For example, in the first and second embodiments, the center axis O _{1 of the} holder coincides with the optical axis of the objective lens 100 so that fine adjustment of the objective lens 100 is facilitated. It is not necessary to make ₁ coincide with the optical axis of the objective lens 100. In addition, although the two-pole magnetized magnets are opposed to each other on the two sides of the focus coil and the tracking coil, a single-pole magnet may be opposed to only one side.

Further, the first and second mounting surfaces 111a, 111b, 112a, 112b provided on the holder 110 cause the holder 110 to generate an equal force in the same direction on the two focus or tracking coils or the two focus or tracking magnets. If it is an arrangement that surrounds the central axis O ₁ , it is not always necessary to arrange it oppositely in the focus direction X or the tracking direction Y.

  For this reason, in the present embodiment, the objective lens actuator used in the optical disk recording / reproducing apparatus is illustrated, but the optical element is not limited to the objective lens, and may be a collimator lens, an LD (laser diode), or the like. The apparatus can also be applied to a collimating lens actuator that is coupled to a fiber of an optical communication device.

DESCRIPTION OF SYMBOLS 1 Optical disk 100 Objective lens 110 Holder 111a, 111b 1st attachment surface 112a, 112b 2nd attachment surface 115 Fixing part 116
120 Chromatic aberration correction lens 131, 132 Focus coil 133, 134 Tracking coil 140a, 140b Spring 141 Base 141f Spherical surface 141g Base mounting surface 142 Spring holder 142a, 142b Spring fixing part 151, 152 Focus magnet 153, 154 Tracking magnet 160 Carriage 161 Reflection Mirror 162 Sensor holder 163 PD (photodiode)
164 LED (Light Emitting Diode)
171 and 172 Focus magnets 173 and 174 Tracking magnets 181 and 182 Focus coils 183 and 184 Tracking coils

Claims (2)

In an actuator of an optical element that supports the optical element so as to be drivable in two directions of a focus direction and a tracking direction orthogonal to each other,
A side surface arranged so as to surround the central axis along the focus direction is used as a coil mounting surface, a holder for holding the optical element with NA of 0.7 to 0.9, and a coil mounting surface of the holder. A focus coil that generates a driving force in the focusing direction, a tracking coil that is attached to the coil mounting surface of the holder and generates a driving force in the tracking direction, and a magnetic field that includes a magnet that directs the magnetic field to the focusing coil and the tracking coil comprising a generating unit, and a support member for drivingly supporting the holder in the focusing direction and the tracking direction,
The focus coil is capable of controlling the directions of currents flowing through the coils in opposite directions ,
The holder fixedly holds the correction lens at the lower end thereof, and has four side surfaces arranged so as to surround the central axis along the focus direction, and each of the side surfaces serves as the coil attachment surface. Attaching only a single focus coil to each of the two first attachment surfaces arranged to face each other across the central axis among the coil attachment surfaces,
Each of the two second mounting surfaces arranged to face each other across the central axis is provided with only a single tracking coil, provided with a light shielding bar, and a light emitting diode and a photodiode, An output difference between the light projected from the light emitting diode to the light receiving surface of the photodiode is obtained by being orthogonal to and intersecting the light incident on the reflection mirror that reflects the light from the laser to the optical element. Thus, the position of the optical element is detected,
The actuator of an optical element, wherein the magnetic field generating means is an open magnetic circuit having no yoke constituting a magnetic gap . 2. The optical element actuator according to claim 1, wherein the current flowing through the focus coil is an added value of a focus servo current and a tilt servo current.

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