JPH03260924A - Tracking mirror actuator device - Google Patents

Abstract

PURPOSE:To allow a sure tracking mirror actuator operation by forming respectively plural sheets of leaf spring members which support both ends of a movable part into a shape having at least two points of curved parts extended in the direction perpendicular to the turning center line of the movable part. CONSTITUTION:The directions of driving currents are so determined that the directions of the force in the normal direction of the mirror generated in driving coils 4 in a magnetic gap 9 are reversed in the respective driving coils 4, by which the couple of forces is generated in the movable part 5 and the movable part is rotated around the rotating center line C. The curved parts 13a, 13b of the leaf spring member 12 deform curvilinearly at this time. The curved parts 13a, 13b can be made sufficiently longer than the longitudinal length of the leaf spring member and since the parallel curved parts 13a, 13b exist at two point in one sheet of the leaf spring member 12, the 1st order resonance frequency is suppressed to a sufficiently low state even if the thickness of the member is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking mirror actuator device in an optical information recording/reproducing device.

2. Description of the Related Art Generally, in an optical information recording/reproducing apparatus, a minute spot is formed on an information recording medium to record or reproduce information. At this time, some devices are equipped with a movable mirror for performing a tracking operation of the minute spot with respect to the optical information recording medium.

An example of a tracking mirror actuator configuration in this case is shown in Japanese Patent Application Laid-Open No. 62-210418, for example. Figures 7 to 9 show the contents. First, the mirror 1 is supported by a mirror support 2. On both sides of the mirror support 2 in the X direction are driving parts 3.
The movable part 5 is integrated with the drive coil 4 inside.
is configured. The drive unit 3 includes a substantially U-shaped yoke magnetic circuit 7 fixed upright on a fixed base 6, a magnet 8 fixed to the outer inner surface of the yoke magnetic circuit 7, and a magnetic gap formed between the yoke magnetic circuit 7 and the magnet 8. It consists of the drive coil 4 with one side located at 9111.

Furthermore, the movable part 5 has a substantially bilaterally symmetrical shape (although it is also symmetrical in the front-rear direction), and the fixed base 6 is attached to the left and right sides (both sides in the y direction) by one thin plate-like spring part A10.
” It is supported by two people. That is, one end of the thin plate-shaped spring member 10 is fixed to the mirror support 2 (movable part 5), and the other end is fixed to a fixed support part 11 that is erected and fixed to the fixed base 6''. These two thin plate-like spring members 10 are also provided symmetrically on both the left and right sides, but specifically, the center line of the thin plate-like spring member 10 is set on the rotation center line C of the movable part 5. . The center of gravity of the movable part 5 is set near this rotation center line C.

That is, the movable part 5 including the mirror l is supported by two left and right thin plate spring members 10, the center of gravity of the movable part 5 is set near the torsion center line of the thin plate spring members 10, and the support system has low rigidity. The thickness direction of the thin plate-shaped spring portion lO is fixed to match the in-plane direction of the mirror so that the direction of the thin plate-shaped spring portion 10 is equal to the in-plane direction of the mirror, and the direction of high rigidity is equal to the normal direction of the mirror by =3 −. According to this, the position of the light beam is not affected at all in the mirror 1 even if the mirror moves by a minute amount in the mirror in-plane direction, so there is no problem even if the support system has low rigidity. Furthermore, since the rigidity of the support system in the normal direction of the mirror, which is related to the position of the light beam, can be made high, vibrations that degrade the positioning accuracy of the light spot can be suppressed.

The problem to be solved by the invention is to provide such a tracking mirror actuator device.
When examined in more detail, the primary resonance frequency of the movable part 5 usually needs to be set to around 50 Hz. For this reason, when stainless steel material is used for the thin plate spring member 10, the
The thickness will be around m.

Here, since the stainless steel plate inevitably has an error of about ±2 μm in its thickness, the thickness of the thin plate spring member IO is ±2 μm.
There will be a variation of about 10%. On the other hand, the torsional spring travel number of the thin plate spring part 10 is proportional to the cube of the plate thickness, so if there is a variation of about ±10% in the plate thickness, the torsional spring constant will vary by about ±33%. It turns out. Here, the primary resonance frequency, which is proportional to the 1/2 power of the torsional spring constant, has a variation of about ±15%.

Generally, considering the specifications of the control system, it is necessary to suppress the variation in the primary resonance frequency of the movable part 5 within a range of approximately ±10%. However, the thickness of the thin plate spring member 10 alone is ±
If there is a variation of 15%, other factors (e.g.
Variation in the moment of inertia of the moving part, thin plate spring member lO
Considering the influence of variations in length, width, etc.), in reality, the negative-order resonance frequency has a variation of about ±20%, making it impossible to satisfy the specifications of the control system.

In this regard, the variation in the plate thickness of the thin plate spring member 10 is limited to ±5%.
If it can be suppressed within a range of about 5%, the variation in the primary resonance frequency due to this influence can be suppressed to about ±7.6%, which satisfies the specifications of the control system. Let's consider whether such a configuration is possible. First, when the plate thickness of the thin plate spring member 10 is 40 μm, the torsional spring constant is 2 if the configuration as shown in FIGS. 7 to 9 is maintained.
゛ = 8 times, and the -order resonance frequency becomes 8 degrees = 2.8 times, and it cannot be set around 50 Hz. Therefore, the longitudinal direction (y direction) of the thin plate spring member 10
It is necessary to increase the length, shorten the length in the width direction (Z direction), and decrease the torsional spring constant. However, if the length of the thin plate-like spring member 10 in the longitudinal direction is increased, the device becomes larger. Moreover, if the width direction is shortened, the shear stress [kg-f/cn+] acting on the thin plate spring member 10 becomes large, causing a problem of exceeding the allowable stress of the thin plate spring member IO.

Means for Solving the Problem Forming a minute spot on an optical information recording medium and performing 1'i! f
An optical information recording/reproducing device for recording or reproducing information, the optical ti! f report DW, the mirror for performing the tracking operation of the minute spot with respect to the body is supported by the mirror support, and the drive unit is moved in the same direction around the rotation center line. In a tracking mirror actuator device mounted on a movable movable t'fl(t),
In the invention according to claim 1, each mirror has at least two bent portions extending in a direction perpendicular to the rotation center line of the movable portion, and has a thickness direction aligned with the in-plane direction of the mirror. The left and right sides of the movable part are supported with respect to the fixed part by thin plate-like springs γfI+ The left and right sides of the movable part are supported by at least three thin plate-like spring members each having a bent part and arranged radially around the rotation center line with respect to the fixed part.

The thin plate-shaped spring member supporting both ends of the working movable part has a shape that extends in a direction perpendicular to the rotation center line of the movable part and has at least two bent parts, so that the plate thickness can be reduced. Even if the thickness is increased, the primary resonance frequency can be kept low. Therefore, variations in the primary resonance frequency due to variations in the thickness of the thin plate-shaped spring member are small, and reliable tracking mirror actuator operation can be performed.

In particular, as in the invention as claimed in claim 2, by supporting at least three or more thin plate-like spring members arranged radially around the rotation center line, the rigidity in directions other than the rotation direction is sufficiently increased. Harmful movement of the movable part in directions other than the rotational direction can be suppressed.

Embodiment An embodiment of the invention set forth in claim 1 will be described with reference to FIGS. 1 to 3. Same as the part shown in Figures 7 to 9 -m! Minutes are indicated using the same symbols.

Although the structure of the tracking mirror actuator is the same, the shape of the thin plate-like spring member that supports the movable part 5 has been devised. First, two thin plate-like spring members 12 are provided on each of the left and right sides of the movable portion 5 in a vertically symmetrical arrangement (in the Z direction). These thin plate springs f+ll+J ] 2 are all approximately U-shaped in the lit body, and have two parallel locations extending in a direction perpendicular to the rotation center line C of the movable part 5, which is the same straight line. Bent part 13
a and 13b, and these bent portions 13a and 13b are connected to each other with the point farthest from the center line C of rotation 1 as a connecting portion 13c, and one bent portion 13a is connected to the portion closest to the rotation center line C. The side is fixed to the mirror support 2 (movable part 5), and the other bent part 13b (It!l is fixed to the fixed support part 11
is fixed. That is, the mirror support 2 and the fixed support part 11 are not supported in a short-circuit manner at the shortest distance by the thin plate spring member, but are supported in a roundabout manner by the crank shaped thin plate spring member 12. There is. Further, the thickness direction of these thin plate-like spring members 12 is in the in-plane direction of the mirror 1. Note that even in this embodiment, the movable part 5
The center of gravity of is set near the rotation center line C.

In such a configuration, the direction of the drive current is determined so that the direction of the horn in the mirror normal direction (X direction) generated in the drive coil 4 in the magnetic gap 9 is opposite in each drive coil 4. As a result, a force couple is generated in the movable part 5, and the movable part 5 rotates about the rotation center line C. At this time, the bent portions 13a and 13b of the thin plate-like spring member 12 of this embodiment are bent and deformed.

These bent portions 13a and 13b can be made sufficiently longer than the length in the longitudinal direction of the thin plate-like spring member 10 shown in FIG. Because of the bent portions 13a and 13b, the primary resonance frequency can be kept sufficiently low even if the plate thickness is increased.

Next, an embodiment of the invention according to claim 2 will be described with reference to FIGS. 4 to 7. Basically, it is the same as the previous embodiment, but in this embodiment, four thin plate-like spring members 12 are provided at both left and right ends of the movable part 5 radially with respect to the rotation center line C of the movable part 5. They are arranged in an x-shape. This is to increase the rigidity of the thin plate spring member. That is, in the case of the above embodiment, the thin plate spring member 12
Yes.

Although the rigidity in the X direction is sufficiently large, the rigidity in the X direction is extremely small, and the movable part 5 rotates around the Z axis, causing the tracking direction of the light beam deflected by the mirror 1 to change from the original tracking direction. There is a possibility that it will shift. In this regard, in this embodiment, since the four thin plate spring members 12 are arranged radially with respect to the rotation center line C, the rigidity of the thin plate spring members 12 is It can be made large enough in the direction.

In this embodiment, -11=12 four thin plate spring members 12 are provided on one side of the movable part 5, but in short, three or more thin plate spring members 12 are provided.
The second thin plate-like spring member 12 may be arranged radially with respect to the rotation center line C.

Effects of the Invention As described above, the present invention provides at least two bent portions in which a plurality of thin plate spring members each supporting both ends of the movable portion extend in a direction perpendicular to the rotation center line of the movable portion. Since the shape is such that the primary resonance frequency can be kept low even if the plate thickness is increased, the variation in the primary resonance frequency due to variation in the plate thickness of the thin plate spring member can be minimized. The tracking mirror actuator can be operated reliably, and in particular, according to the invention as claimed in claim 2, at least three or more thin plate-like spring members are arranged radially around the rotation center line. It is possible to sufficiently increase the rigidity in directions other than the rotational direction and suppress harmful movements of the movable parts in directions other than the rotational direction.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the invention as claimed in claim 1;
FIG. 2 is a side view of the vicinity of the thin plate spring member, FIG. 3 is a front view of the vicinity of the thin plate spring member, FIG. 4 is a perspective view showing an embodiment of the invention as claimed in claim 2, and FIG. 5 is a thin plate Figure 6 is a side view of the thin plate-shaped spring member (1);
The figure is a perspective view showing a conventional example, FIG. 8 is a side view of the thin plate-like spring portion, and FIG. 9 is a front view of the vicinity of the thin plate-like spring member. ■...Mirror, 2...Mirror support body, 3...Drive part, 5...Movable part, 11...Fixed part, 12...Thin plate-shaped spring member, 13a, 13b... Bent part, C...
Rotation center line, %, 3 feed, J3c 1 8 bleaching

Claims (1)

[Claims] 1. An optical information recording/reproducing device that records or reproduces information by forming a minute spot on an optical information recording medium, in which a tracking operation of the minute spot is performed on the optical information recording medium. In a tracking mirror actuator device in which a mirror is supported on a mirror support and is mounted on a movable part that has a substantially bilaterally symmetrical structure and can be rotated about a center line of rotation, the mirror is supported by a mirror support and has a drive part. The left and right sides of the movable part are connected to the fixed part by two thin plate spring members each having at least two bent parts extending in a direction perpendicular to the mirror and having a thickness direction aligned with the in-plane direction of the mirror. A tracking mirror actuator device, characterized in that the tracking mirror actuator device is supported against an object. 2. In an optical information recording and reproducing device that records or reproduces information by forming a minute spot on an optical information recording medium, a mirror is supported for performing a tracking operation of the minute spot on the optical information recording medium. In a tracking mirror actuator device, which is mounted on a movable part that is supported by the body and has a drive part and has a substantially bilaterally symmetrical structure and can be rotated about a center line of rotation, the actuator device extends in a direction perpendicular to the center line of rotation of the movable part. The left and right sides of the movable part are supported with respect to the fixed part by at least three thin plate-like spring members each having at least two bent parts and arranged radially around the rotation center line. A tracking mirror actuator device characterized by: