JPH03150733A - Rotary mirror device - Google Patents

Abstract

PURPOSE:To attain the stable control of the rotational vibrations of a mirror by deforming previously a leaf spring supporting the mirror into a form of a vibration mode of a secondary or more degrees. CONSTITUTION:Each of two leaf springs 47 and 49 is deformed into a form of a secondary deformation mode and fixed to a fixing stage 46 at one of both ends with the other end fixed to a holder 42 respectively. When a drive coil 44 is energized, the torque is produced by an electromagnetic driving mechanism 45 and a mirror 41 is revolved attending on the deformation of both springs 47 and 49 which are caused in a secondary vibration mode. In such a rotary mirror device 40, the resonance peak of the primary mode is secured at about 90Hz and no peak emerges in any area of a frequency higher than 90Hz. Thus a control hand area is increased without deteriorating the stability when the device 40 is used as a tracking actuator of an optical disk device. The same effect is also ensured with the deformation into the vibration modes of a secondary or more degrees.

Description

[Detailed Description of the Invention] [Summary] Regarding a rotating mirror device applied to a tracking actuator of an optical disk device, etc., the difference in frequency between the n-th and (n+1)th-order vibration modes increases as the order increases. With the aim of enabling stable control of the rotational vibration of the mirror, we developed a planar leaf spring that is fixed at one end and supports the mirror at its free end, and a flat spring that supports the mirror on its free end. In a rotating mirror device that includes a drive mechanism that applies torque and rotates and vibrates the mirror while deflecting a waist plate spring, the plate spring is driven by a vibration mode of the second or higher order of the planar plate spring in the rotating mirror device. Incorporate and configure as a shape.

[Industrial application field]

The present invention relates to a rotating mirror device that can be applied to a troughing actuator or the like of an optical disk device.

This type of device is: 1. +1wJ stability is good,
Moreover, it is desirable that the control band be wide.

[Conventional technology]

FIG. 13 shows a conventional example. Reference numeral 1 denotes a mirror, one end of which is supported via leaf springs 2, 3 arranged in a cross shape and a holder 4.

On the free end side of the mirror 1, there is a permanent magnet piece 5 fixed to the mirror 1,
This is surrounded by a fixed coil 6, and arrows A+ and A2
An 'IFi magnetic drive lJ mechanism 7 is provided which applies a torque in the direction.

When a control current based on the tracking i, II control signals is supplied to the coil 6, torque is generated by the electromagnetic drive mechanism 7, and! I! 1 is rotated back and forth (rotational vibration) while bending the leaf spring 2.3.

The above configuration is schematically shown in FIG. 14.

Reference numeral 10 indicates a single leaf spring, which corresponds to the above-mentioned cross-shaped leaf spring structure.

Reading 1 rotates in the directions of arrows A+ and A2 while bending the leaf spring 10, and a laser beam 14 is emitted from the semiconductor laser 11, reflected there, passes through the objective lens 12, and is focused on the optical disk 13. is swung in the direction of arrow B++B2 and tracking control is performed.

When the frequency of rotational vibration at t*1 is gradually increased,
The leaf spring 10 first vibrates in a primary vibration mode as shown in FIG. 15, then in a secondary vibration mode as shown in FIG. 16, and then in a tertiary vibration mode as shown in FIG. .

[Problem to be solved by the invention]

Figure 18 shows the rotation angle of FAl per driving torque (Q/T
) and the frequency f of the rotational vibration of the mirror 1.

, in the figure, 20 is a peak due to the primary vibration mode of the leaf spring 10, 21 is a peak due to the secondary vibration mode, and 22 is a peak due to the tertiary vibration mode.

Figure 19 shows the phase angle between the rotation angle of mirror 1 and the driving torque,
111 shows the relationship between rotational vibration frequency f of No. 111.

From the figure, the phase rotation occurs in the part surrounded by the broken line circle 23 corresponding to the peak 21 due to the second-order vibration mode and the part surrounded by the broken line circle 24 corresponding to the peak 22 due to the third-order vibration mode, It can be seen that the degree of rotation is particularly large in the former case.

Furthermore, the frequency f3 of the third-order vibration mode is several hundred times higher than the frequency f+ of the -th-order vibration mode, which is as high as several thousand Hz, whereas the frequency f2 of the second-order vibration mode is 10 times the frequency f1. It is about 100 Hz, which is low.

For this reason, although the vibration in the tertiary vibration mode is unlikely to become an obstacle in control, the vibration in the secondary vibration mode becomes an obstacle in v4il, making it difficult to control the mirror vibration stably 1tiIIII, that is, tracking stably.

The present invention focuses on the fact that the difference in frequency between the n-th and (n+1)th-order vibration modes increases as the order increases, and provides a rotating mirror device that enables stable tilIIO of rotational vibration of a mirror. The purpose is to

(Means for Solving the Problems) FIG. 1 shows the basic configuration of the present invention. In the figure, parts corresponding to those shown in FIG. 14 are given the same reference numerals.

Reference numeral 30 denotes a leaf spring, which is deformed during assembly into a shape corresponding to the shape of the secondary vibration mode shown in FIG.

[Effect]

Torques in the directions of arrows A+ and A2 are applied by the electromagnetic drive mechanism 7, and the mirror IG and the i-plate spring 30 are rotated while being bent.

Since the leaf spring 30 has the above-described shape, the -th vibration mode becomes as shown in FIG. 2, which is the second vibration mode in the device shown in FIG. 14. The second-order vibration mode becomes as shown in FIG. 3, and becomes the third-order vibration mode in the apparatus shown in FIG. 14.

Therefore, the relationship between the rotational angle (θ/T) of 11 per drive torque and the frequency f of the rotational vibration of tllll is as shown in FIG.

31 is a peak due to the first-order deformation mode, and its frequency f+8 is approximately 100 Hz.

32 is a peak due to the second-order deformation mode, and its frequency f2a is quite high at several 1,000 Hz.

Therefore, as shown in Fig. 4, the frequency characteristic associated with the driving torque has a negative peak 31 at a low frequency f'+a of several 100 Hz, and no peak at higher frequencies in a frequency band close to this. The curve becomes gradually smoother, and has a small peak 32 at a fairly high frequency f2a. That is, the higher-order mode resonance does not appear near the first-order mode resonance.

That is, the higher-order mode resonance does not appear near the first-order mode resonance.

As a result, the relationship between the phase angle φ between the rotation angle of the mirror 1 and the driving torque and the frequency r of the rotational vibration of the mirror 111 becomes as shown in FIG. However, it does not occur at higher frequencies, and only a small phase rotation occurs at frequencies corresponding to the considerably high frequency f2a.

As a result, when the above-mentioned rotating mirror device is used as a tracking 7 controller of an optical disk device, the control band can be widened without impairing stability, and it has excellent high-speed performance.

〔Example〕

Figures 6 and 7 show a rotating mirror bag M which is an embodiment of the present invention.
40 is shown.

Reference numeral 41 denotes a mirror, which is fixed on a plate-shaped holder 42.

43 is a permanent magnetic G piece, which is fixed to one end side of the holder 42. A fixed drive coil 44 is installed on the fixed side and surrounds the permanent 11 stone piece 43. This permanent magnet piece 43 and fixed drive coil 44 constitute an electromagnetic drive mechanism 45, which generates torque in the directions of arrows A+ and A2h.

46 is a fixed base.

Reference numeral 47 designates a bifurcated first leaf spring, which is deformed into a shape corresponding to the shape of the secondary deformation mode, like the leaf spring 10 shown in FIG. The other end is fixed to the lower surface of the holder 42.

A second leaf spring 49 is deformed in the same manner as the first leaf spring 47 and is fixed to the fixing base 46 and the holder 42.

The width of the pair of arm portions 47a and 47b of the first leaf spring 47 is W.
, the width of the second leaf spring 48 is 2xw.

1st. The second leaf springs 47 and 49 are cross-shaped.

In addition, the above 1. As shown in FIG. 8, the second leaf spring 47.49 has a structure in which a viscoelastic damping material 52 made of silicone rubber is sandwiched between metal plate members 50.51.

When the drive coil 44 is energized, torque is generated by the electromagnetic drive mechanism 45, and the mirror 41 moves as shown in FIGS. 9(A) and 9(B).
As shown in FIG. 4, the leaf springs 47 and 49 are rotated with deformation. The deformation of the leaf springs 47, 49 occurs according to the second-order vibration mode.

FIG. 10 shows the measurement results of the relationship between the rotation angle (θ/[) of the mirror 41 per driving torque and the rotation frequency f of the mirror 41 in the rotating mirror device 40 of the above embodiment.

As can be seen from the figure, a peak due to resonance of the primary mode of the device 40 appears at approximately 90 Hz, but no peak appears in a higher frequency range.

The reason why the peaks due to the resonance of the secondary mode and the tertiary mode of the 5A position 40 are suppressed is due to the l/I vibration effect of the leaf spring 47, 49 itself.

FIG. 11 shows the measurement results of the relationship between the phase angle φ between the rotation angle of the mirror 41 and the driving torque and the frequency of rotation of the mirror 41 in the rotating mirror device 40 described above.

It can be seen from the figure that a phase lag occurs at a portion corresponding to the peak in FIG. 10, and that phase lag is maintained at frequencies higher than that.

As a result, when the rotating mirror device 40 described above is used as a tracking unit for an optical disk, the control band can be widened without sacrificing stability, and excellent high speed performance can be achieved.

FIG. 12 shows a rotating mirror bag 2ff6 which is another embodiment of the present invention.
Indicates 0. In the figure, the same reference numerals are given to the parts that substantially correspond to the constituent parts shown in FIGS. 6 and 7, and the explanation thereof will be omitted.

Reference numeral 61 denotes a leaf spring, whose upper center in the longitudinal direction is fixed on the fixed base 46 by a clamp plate 62 and a pin 63;
A plate spring portion 61a extends to both sides.

61b are both previously deformed into the secondary deformation mode, and their tips are fixed to the lower surface of the holder 42 by the pin 64.

This rotating mirror device 60 also has characteristics similar to the rotating mirror device 40 shown in FIG.

Alternatively, a configuration may be adopted in which the leaf spring is incorporated in a shape corresponding to the shape of the tertiary deformation mode.

Further, the leaf spring may be formed into a shape corresponding to secondary or higher deformation modes by bending a flat plate, or may be formed into the above shape by pressing or the like in advance and then assembled as is.

[Effects of the Invention] As described above, according to the present invention, - the next imaging mode is the order corresponding to the predetermined deformation mode and becomes the mode of the order in the conventional device; The resonance frequency of the next higher order is considerably higher than the frequency of the above-mentioned -order vibration mode, and there is no other resonance frequency near the frequency of the -order vibration mode. This stabilizes the frequency characteristics without compromising stability.
It can cover a wide range and achieve excellent high speed.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the principle configuration of the present invention. Figure 2 is a diagram showing the primary vibration mode of the rotating mirror device in Figure 1. Figure 3 is a diagram showing the secondary vibration mode of the rotating mirror device in Figure 1. Figure 4 is a diagram showing the frequency characteristics of the rotation angle per drive torque of the rotating mirror device in Figure 1, Figure 5 is a diagram showing the frequency characteristics of the phase of the rotating mirror device in Figure 1, and Figure 6 is a diagram showing the frequency characteristics of the rotation angle per drive torque of the rotating mirror device in Figure 1. is an exploded perspective view of one embodiment of the present invention, FIG. 7 is a front view of one embodiment of the present invention, FIG. 8 is a diagram showing the structure of a leaf spring, and FIG. 9 is a view of the rotating mirror device of FIG. 7. 10 is a diagram showing the frequency characteristics of the rotation angle per drive torque of the device in FIG. 7, FIG. 11 is a diagram showing the frequency characteristics of the phase of the device in FIG. 7, and 12 is a diagram showing the rotational vibration state. 13 is a diagram showing a conventional example; FIG. 14 is a diagram showing a schematic configuration of the 5A position in FIG. 13;
Fig. 5 is a diagram showing the primary vibration mode of the device in Fig. 14, Fig. 16 is a diagram showing the secondary vibration mode of the device in Fig. 14, and Fig. 17 is a diagram showing the tertiary vibration mode of the device in Fig. 14. , FIG. 18 is a diagram showing the rotation angle frequency characteristic of the device shown in FIG. 14, and FIG. 19 is a diagram showing the phase frequency characteristic of the device shown in FIG. 14. In the figure, 1.41 is a mirror, 7.45 is a 'Pi magnetic drive drive mechanism, 0.47.49.61 is a leaf spring, 40.60 is a rotating mirror device, 50.51 is a metal plate, and 52 is a viscoelastic control. The vibration material, 61a, 61b GL leaf spring portion is shown.

Claims (1)

[Claims] A planar leaf spring (30) fixed at one end and supporting a mirror (1) on its free end side, and a drive mechanism (7) that applies torque to the mirror based on a control signal. In a rotating mirror device that rotationally vibrates the mirror while bending the leaf spring, the leaf spring is incorporated in a shape of a second or higher vibration mode of the planar leaf spring in the rotating mirror device. A rotating mirror device characterized by having a configuration consisting of: