JPS60153020A - Light beam deflecting mirror - Google Patents

Abstract

PURPOSE:To reduce external influence of temperature, an external magnetic field, etc., by forming a long hole in both side end parts of a movable body, and fitting a driving coil to one-side opening parts of both long holes. CONSTITUTION:The movable body 12 made of aluminum is supported elastically on a base 26 with a spring 27 which is energized by a thin plate made of stainless steel. A movable body 22, on the other hand, has a mirror 21 mounted at its top surface center part and is provided with short coils 23a and 23b and rectangular long holes 24a and 24b at both sides. Then, driving coils 25a and 25b are attached in one-side opening parts of the long holes 24a and 24b and yokes 29a and 29b of magnetic circuits 28a and 28b provided outside of both sides of the movable body 22 are inserted into the long hole 24a and driving coil 25b. Consequently, external influence of temperature and an external magnetic field is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a light beam deflection mirror used for precise position control of a light spot in an optical disk device or the like.

[Background of the invention]

As shown in FIG. 1, a conventional general mirror of this type has a mirror 1 fixed to a base 5 via an elastic support 2 made of rubber, and a magnet 3 and a coil 4 attached to the mirror 1 and the base 5, respectively. It has a fixed structure and is rotated by the magnetic force acting between the magnet 3 and the coil 4.

The rubber used for the elastic support 2 has a large vibration damping effect, and has a property that the rigidity and vibration damping effect change greatly depending on temperature. For this reason, the deflection mirror has the disadvantage that it cannot be used in a two-stage servo control system developed for high-precision positioning because its main resonance frequency fo and vibration reduction ratio change greatly with temperature. The details (nm + are from the 22nd SICE Jijutsu Zen Performance)
'P541-542, it is described in 3210, so it will be omitted.

In order to stabilize the above-mentioned frequency f, the elastic support 2 should be changed to a material that is not easily affected by temperature, such as Kasadori, but since these materials have a small vibration damping effect, It is necessary to provide a separate vibration damping section. Therefore, electromagnetic induction has been applied as a vibration damping method that is not easily affected by temperature, and examples thereof are shown in FIGS. 2 and 3.

FIG. 2 shows a lens actuator for velocity feedback. This lens actuator is supported by an elastic support 8, and a lens barrel 7 to which a lens 6 is attached has a velocity detection coil 9 and a drive coil. 10, and is also provided with a magnet, an overall support section, an automatic focusing direction w, and a moving section, but these are not shown. Details of this example can be found in Sharp Technology, 21
Since it is described in No., p. 33-40, it will be omitted here.

In the speed feedback method using the lens actuator as described above, in order to prevent the induced current caused by the current flowing through the drive coil 10 from flowing to the speed detection coil 9, it is recommended to install the two coils 10.9 apart. Common. Therefore, it is necessary to use two magnets or to make them larger, which requires two coils, resulting in a significant increase in cost. Also, as mentioned above, it is possible to separate the speed detection coil 9 from the drive coil 10! Since the 11IJ portion had to be made thicker, the weight also increased.

On the other hand, another method for applying electromagnetic induction is the short ring method, an example of which is shown in FIG. The deflection mirror shown in the figure includes a mirror 11 on the upper and lower surfaces of a movable body 12 made of a highly conductive material that has a built-in short coil (not shown), and a planar) J7.
A movable body 12 is elastically supported by a support 13 attached to a base 16, and a magnet 14 attached to a pace 16 is provided so as to face the short coil and drive coil 15. It consists of a structure.

In the deflection mirror configured in this way, as shown in FIG. When the resistance is R, a braking torque T expressed by the following equation (1) is generated, and the angle MLωf:g can be reduced.

However, L, γ: width and length of the movable body 12;
When the magnet 14 is used in an open state, the magnetic flux f! At i degree B, there is no dog, and the braking torque T is also small.

On the other hand, when the magnetic flux density B' of the external magnetic field changes, an eddy current 1' occurs in the movable body 12 in a direction that cancels this change. flows. This eddy current 1'. If the disturbance torque generated by 81 is T', then the eddy current l'. and the disturbance torque T' is expressed by the following equation (21(3)).

In order to reduce the disturbance torque T', the area S should be reduced; however, since the eddy current 1' has a property of flowing around the outer periphery of the movable body 12, the area S is [Objective of the Invention] In view of the above, the present invention provides a vibration characteristic that is resistant to the influence of the external environment such as temperature and external magnetic field, and has stable vibration characteristics. The object of the present invention is to provide a light beam deflection mirror that exhibits the following characteristics.

[Summary of the invention]

In order to achieve the above object, the present invention provides a movable body configured by coupling a mirror, a short coil made of a conductive material, and a drive coil with a coupling member, a support body that elastically supports this movable body, and a movable body configured by connecting a mirror, a short coil made of a conductive material, and a drive coil, a support body that elastically supports the movable body, and and a magnetic circuit installed opposite to a drive coil, in which elongated holes are provided at both ends of the movable body, and a drive coil is attached to an opening on one side of both of the holes. The yokes of the magnetic circuits provided on both sides of the movable body are respectively inserted into the elongated hole and the drive coil, and the magnetization directions of both magnetic circuits are made to oppose each other.

[Embodiments of the invention]

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

In FIGS. 5 and 6, a movable body 22 made of aluminum is elastically supported on a base 26 by a cross-shaped spring 27 formed of a thin plate made of stainless steel. Further, the movable body 22 is equipped with a mirror 21 at the center of its upper surface.
Short coils 23a, 23b and a rectangular long hole 24a are provided on both sides.

24b are provided respectively. Its long hole 24a.

Drive coils 25a and 25b are attached to the opening on one side (lower side in the figure) of 24b, respectively, and a movable body 220 is attached to the front long hole 24a and the drive coil 25a, and between the long hole 24b and the drive coil 25b. Yokes 29a and 29b of magnetic circuits 28a and 28b provided outside on both sides are inserted, respectively.

The reason why the movable body was made of 22-core aluminum as mentioned above is summarized in the following two points.

Generally, when using a short ring type deflection mirror in an optical disk device, the main resonant frequency fo of the deflection mirror is set to 5.
It is often set to about 0H2.

Now, when the moment of inertia of the movable body is J1, the spring constant of the elastic support part is J1, and the viscous damping coefficient is C, the main resonance frequency f and the vibration damping ratio ζ are expressed by the following equations (4) and (5). .

In the short ring method, the braking B2 shown in the above equation (1)
z2γ2 Since the torque coefficient (2~-□) corresponds to the above C, (
Equation 5) is expressed by Equation (6) below.

2 B” t” r” ζ=□ ・・・・・・・・・(6) 2v'JKR In other words, it is necessary to keep fo'ff constant and make ζ as thick as possible, but in order to do so ( 6) Formula F)
It is sufficient to reduce J and K by a certain ratio, and to reduce R, while increasing B, t, and γ. To satisfy this requirement, a metal with low density and low specific resistance, such as aluminum, is suitable, so the movable body 22 was made of aluminum.

Direction Ba of the magnetic field of the magnetic circuits 28a, 28b.

Bb are in opposite directions, that is, facing each other, as shown in FIG. 7, and the drive coils 25a and 25b are connected so that the currents 14a and ldl+ in the magnetic gap are in the same direction. , drive coils 25a, 25b
When driving currents 14m and ldb flow through the coils 25a and 25b, opposite forces are generated in the movable body 2.
Add rotational torque to 2.

As shown in FIG. 6, when the movable body 22 rotates and vibrates in the direction of arrow P centering on the intersection point
When is constant, it is expressed as K-(2πfo)''r, so the above equation (6) becomes the following equation (7).

In the case where the magnetic circuit 14 is open as in the conventional example shown in FIG. 3, and in the case where the magnetic circuit 28a is opened as in the present embodiment.

Comparing the case where 28b is used in an open/closed circuit, the value of 72 is approximately the same value, so the magnetic circuit 28a.

Making 28b an open/closed circuit is advantageous in increasing the vibration damping ratio ζ by increasing the magnetic flux densities Ba and Bb in the magnetic gap. The long hole 24a.

By reducing the shape and dimensions of 24b, for example, the width a as shown in FIG. 8, the influence of the external magnetic field is reduced, and the deformation that occurs in movable body 22 due to drive coils 25a and 25b can be reduced.

On the other hand, the dimension d between the elongated holes 24a, 24b and the front and rear surfaces of the movable body 22 needs to be increased to some extent from the viewpoint of suppressing deformation of the movable body 22 to a small extent.

Further, the cross-sectional area of the short coil portions 23a and 23b needs to be increased to some extent in order to reduce the resistance R of the method.
If the width of the ends of 3a and 23b is increased, the magnetic gap g (Fig. 6) becomes thicker and the magnetic flux densities Ba and Bb decrease, so it is necessary to keep the width smaller. The thickness h of the movable body 22 is made larger than the width to ensure a cross-sectional area. This is because the force generated by the drive coils 25a and 25b is a force in the thickness direction of the movable body 22.
This is effective for suppressing the deformation of 2.

The longer the length t (Fig. 5) of the magnetic gap g is, the more desirable it is in terms of increasing the vibration damping ratio ζ.
It is not possible to increase the length t to such a length that the elasticity of the short coil portions 23a and 23b is below the minimum allowable value.

On the other hand, when a magnetic field is uniformly applied from the outside and the magnetic field changes, currents in opposite directions flow through the short coil parts 23a and 23b, so forces in the same direction are generated in the short coil parts 23a and 23b, making them movable. An attempt is made to translate the body 22 in its thickness direction, but the movable body 22 is moved by the cross-shaped spring 2.
Since it is symmetrical with respect to 7, no rotational movement occurs. In addition, since the rigidity of the cross-shaped spring 27 in the translational direction is sufficiently high, the amount of translational movement can be suppressed to a sufficiently small value.
Don't worry about the issue■.

In this embodiment, as shown in FIG. 6, drive coils 25a,
The portion of the movable body 22 to which the movable body 25b is attached is counterboreed, and the drive coil 25a is attached to this processed portion.

25b is glued. For this reason, the drive coil 25a,
A sheared surface with strong adhesive strength can be secured against the force generated in the coils 25b, and the positioning of the coils 25a and 25b can be facilitated.

In addition, since the intersection point X of the cross-shaped spring 27 coincides with the center of gravity of the movable body 22 in the thickness direction, the movable part consisting of the mirror 21, the movable body 22, and the drive coils 25a, 2 and 5b, which are formed symmetrically, rotates. The center can be aligned with the center of gravity.

As shown in FIG. 8, this embodiment described above is mounted on a head 30 for an optical disk device, and a light beam 32 incident on an objective lens 31 is deflected by a mirror 21 into a light beam 32a. As a result, even if acceleration is applied to the base 26 of the deflection mirror, the angle of the mirror 21 does not change because no rotational torque is applied to the deflection mirror because the center of rotation and the center of gravity of the movable part coincide as described above. .

In this case, if the area surrounded by the loop of the drive coils 25a, 25b increases, the mutual inductance with the short ring portion will increase, and the phase delay of displacement with respect to the drive current will also increase, so the loop area is made as small as possible.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to exhibit stable imaging characteristics with less influence from the external environment such as temperature and external magnetic field.

In addition, the vibration damping ratio ζ (≧0.
Since the deflection that satisfies 2) has been achieved, it has become possible to improve the optical spot positioning accuracy and increase the density of the optical disk device using a two-stage servo control system.

[Brief explanation of the drawing]

Figures 1 to 3 are perspective views showing conventional examples of original beam deflection mirrors, Figure 4 is an explanatory diagram of the short ring system, and Figures 5 and 6 are examples of an uninvented light beam deflection mirror. A perspective view and a side view showing an example, FIG. 7 is a back view of the movable part of the same embodiment, and FIG. 8 is an explanatory diagram of the usage state of the present embodiment. 21...Mirror, 22...Movable body, 23a, 23b
... Short coil, 24a, 24b --- Long hole, 2
5a. 25b... Drive coil, 27... Cruciform spring, 28
a. 28b...Magnetic circuit, 29a, 29b...Yoke. Part 1: Two countries'! J3 drawing 40 hole 5 mouth 1 concave 26 17L f 7th leap g mouth

Claims (1)

[Claims] 1. A movable body configured by combining a mirror, a short coil made of a conductive material, and a drive coil with a coupling member, a support that elastically supports this movable body, and the short coil and drive coil. In a light beam deflection mirror consisting of a coil and a magnetic circuit installed opposite to each other, elongated holes are provided at the inner ends of the movable body, and driving coils are respectively attached to the openings on the 10,000 side of both of the holes. An original beam deflection mirror characterized in that yokes of magnetic circuits provided on both sides of the movable body are respectively inserted into the elongated hole and the drive coil, and the magnetization directions of the two magnetic circuits are opposed to each other. 2. The light beam deflection mirror according to claim 1, wherein the movable body and the short coil are made of a material with low density and high tetraelectricity. 3. A patent characterized in that the short coil portion is provided within the magnetic gap of the closed magnetic circuit, and the dimension of the cross section of the short coil portion in the direction of the magnetic field is smaller than the dimension in the direction perpendicular to the direction of the magnetic field. The light beam deflection mirror 04 according to claim 1, wherein the movable body is elastically supported by a cross-shaped spring made of a metal plate, and the rotation center of the movable body is provided near the rotation center of the cross-shaped spring. The light beam deflection mirror according to claim 1, characterized in that: