JPS61177651A - Optical disk device - Google Patents

Abstract

PURPOSE:To execute at a high speed the tracking control by making the construction to be able to oscillate and control the mirror surface of the fixing reflecting mirror. CONSTITUTION:A mirror surface 41 of an oscillating mirror 3' to be able to oscillate and control the mirror surface is oscillated and controlled with a rotary shaft 42 as a center, and a coming-out light flux from a fixing optical system 1 can be oscillated upward and downward in the plane including an optical path B parallel to the radial direction of the light shaft and optical disk media 2 of an objective lens 5. By the oscillation, an optical beam spot irradiated on the necessary track of media 2 is shifted in the radial direction of the medial 2 with the position as a center. Consequently, by the oscillating control, the positioning control on the track of the optical beam spot can be executed. Since the oscillating part of the oscillating mirror 3' can be constituted very small compared with the moving part of a voice coil motor 11, the fine access to follow up the track of the optical beam spot can be easily controlled. Thus, the tracking control can be executed at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc device, and more particularly to a trunk following mechanism of an optical head and a structure that allows both sides of an optical disc medium to be used for reading and writing information.

In recent years, optical disk devices have attracted attention for their high recording density performance.
Improvements in technology have been remarkable. In order to position the optical head, that is, the objective lens, at a desired track position on the optical disk medium, a coarse access mechanism is required to access a large area of the medium surface, and a so-called tracking mechanism is used to correct track deviations including trunk eccentricity. There are fine access mechanisms, all of which utilize drive mechanisms such as voice coil motors.

There are limits to manufacturing technology in reducing the weight of the moving part of a voice coil motor and the carriage connected to the moving part, and the moment of inertia generated by the movement of a mass object makes it particularly difficult to perform fine positioning. Therefore, it is desired to develop a fine access means that does not rely on a voice coil motor.

[Conventional. technology]

Figure 5 shows a perspective view of a conventional optical head positioning mechanism. In the figure, reference numeral 1 denotes a fixed optical system equipped with a light source 12 and an information detection function from a collimating lens 13 to a photodetector 19, and the output optical path A of the fixed optical system 1 is parallel to the radial direction of the optical disk medium 2. A fixed reflecting mirror 3 that reflects light onto the optical path B is provided at a fixed part.

The reflected light reflected onto the optical path B is reflected by the movable reflecting mirror 4 onto an optical path C perpendicular to the surface of the optical disk medium 2.

The movable reflector 4 is fixed to a carriage 8, and the carriage 8
is moved along a guide rail 10 installed in the direction of the optical path B by a plurality of attached rollers 9, and is directly connected to and driven by a voice coil motor 11.

The objective lens 5 is integrally attached to the movable reflecting mirror 4 and the tip of the carriage 8, and focuses the light by aligning its optical axis with the optical path C to form a light beam spot on the surface of the optical disc medium 2. Reference numeral 6 denotes an automatic focus control mechanism for controlling the focus of a light beam spot formed on the surface of the optical disk medium 2, and includes a small voice coil motor. The optical head 7 is composed of an objective lens 5, an automatic focus control mechanism 6, and a movable reflecting mirror 4.

The laser beam emitted from the light source 12 becomes parallel light beams by the collimating lens 13, is adjusted into a circular beam by the circular correction prism 14, and is converted into a circular beam by the polarizing beam splitter 15 and λ
/4 plate 16 (λ is the wavelength of the laser beam) and the fixed reflecting mirror 3
, a moving reflecting mirror 4, and an objective lens 5 to form a light beam spot on a track of the optical disk medium 2.

Further, the reflected light from the optical disk medium 2 travels backward along the incident optical path, is reflected at right angles by the polarizing beam splitter 15, and passes through the cylindrical lens 17 and the condensing lens 18.
The light is received by a photodetector 19. Reference numeral 20 denotes a detection circuit, which houses detection circuits such as a focus detection system, a track position detection system, and a signal detection system.

The detection signal output from the detection circuit 20 is fed back to the automatic focus control mechanism 6 via the control circuit 21 and the flexible parallel cable 22, and a portion is fed back to the voice coil motor 11 to drive the positioning of the optical head 7. conduct.

In this way, by using the movable reflector 4 and the fixed reflector 3 on the optical path B, and by moving most of the parts of the optical system mounted on the carriage 8 to the fixed part, the weight of the carriage 8 is reduced. The fine access function can be driven by one voice coil motor 11.

′ [Problem to be solved by the invention] There is a manufacturing limit to reducing the weight of the movable parts of the voice coil motor, and the moment of inertia generated by the movement of the limited mass causes the optical head to lose weight. There is a drawback that overshoot becomes a hindrance, making it impossible to increase the speed of control particularly over small distances, and this is an attempt to optically increase the speed of tracking control by using a reflector that can be driven minutely.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a fixed reflecting mirror that reflects the emitted light beam from a fixed optical system including a light source and an information detection function in a direction parallel to the radial direction of the optical disk medium surface; A movable reflector that vertically reflects the reflected light onto the optical disk medium surface, and an objective lens that is driven in the radial direction integrally with the movable reflector and focuses the vertically reflected light onto the optical disk medium surface. In the device positioning optical system according to the present invention, the mirror surface of the fixed reflecting mirror is attached so as to be swing controllable, and the positioning optical system is provided on at least one side of the optical disc medium. This is achieved by

[Effect]

That is, in the positioning optical system, if the mirror surface of the fixed reflector is controlled to minutely swing so that the position of the light beam spot irradiated onto the optical disk medium surface moves minutely in the radial direction of the optical disk medium surface, this will cause the optical Most of the track following operation of the beam spot is performed by controlling the voice coil motor, and minute track eccentricity that cannot be followed by this can be followed by controlling the mirror surface of the fixed reflecting mirror. Moreover, by symmetrically installing this positioning optical system on both the front and back surfaces of the optical disk medium, the conventional optical disk medium that could only be used on one side can be improved to use both sides.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. Furthermore, the configuration
In order to make the description of the operation easier to understand, the same parts are designated by the same reference numerals throughout the design, and repeated description thereof will be omitted.

FIG. 1 shows a perspective view of essential parts of an optical disc device according to the present invention. In the figure, guide rails 10.10'' are disposed oppositely above and below the optical disk medium 2 in the radial direction, and rollers 9.9''
are attached to the top and bottom of the carriage 8, and the guide rails 1
The carriage 8 is supported by rolling on a height of 0.10'.

The carriage 8 is directly connected to a voice coil motor 11 for driving, and the voice coil motor 11 and the guide rail 10.1
0" and the fixed reflector support metal fittings 31 are respectively attached to the base 3.
The structure is fixed to 0.

3° is a structure in which the mirror surface of the fixed reflecting mirror 3 shown in FIG. 5 can be controlled to swing, and is hereinafter referred to as a swinging mirror. 1 is basically the same as FIG. 5 except for the swinging mirror 3'. Note that the internal configuration of the fixed optical system 1, the control section 21, and the parallel cable 22 shown in FIG. 5 are omitted.

The mirror surface 41 of the oscillating mirror 3° is controlled to oscillate around the rotation axis 42, and the light flux emitted from the fixed optical system 1 is directed to include the optical axis of the objective lens 5 and the optical path B parallel to the radial direction of the optical disk medium 2. It can swing up and down within a plane. Due to this swinging, the light beam spot irradiated onto a desired track of the optical disc medium 2 moves in the radial direction of the optical disc medium 2, centering on that position. Therefore, if swing control is possible, positioning control of the light beam spot on the track becomes possible.

FIG. 2 shows a cross-sectional structural diagram of the oscillating mirror. In the figure, a cylindrical bobbin 43 is integrally formed on the back surface of a mirror surface 41 of the swinging mirror 3 with a rotating shaft 42 in between, and a movable coil 44 is wound around the outer periphery of the bobbin 43. A required air gap is provided around the moving coil 44 to create a magnetic circuit 45, and a permanent magnet 45 is installed so that the magnetic path passes vertically through the moving coil 44.
Insert and configure.

By passing a direct current through the movable coil 44, the mirror surface 41 is tilted about the rotating shaft 42, and the tilt can be accurately controlled by the direct current. Moreover, the total mass of the mirror surface 41, rotating shaft 42, bobbin 43, and moving coil 44 can be configured to be extremely small compared to the moving parts of conventional voice coil motors, so Microaccess can be easily controlled.

In this embodiment, in FIG. 1, the X amount of the movable part of the voice coil motor including the carriage 8 and the automatic focus control mechanism 6 is 150 gr, and the mechanical resonance frequency in the direction of carriage movement including the automatic focus control mechanism 6 is approximately 3KH2. The band of the voice coil motor control system was increased to 400 Hz, several times that of conventional devices. In addition, the optical disk medium 2
For a rotation speed of 180 rpm, the track following error due to voice coil motor control is approximately 2 μm, and as a result of compensating for this error by controlling the oscillating mirror 3°, the track following error can be reduced to 0.
．． It became possible to reduce the thickness to 1 μm or less.

FIG. 3 shows a configuration diagram of a double-sided usage method of an optical disc device. In the figure, the configuration of the positioning optical system consisting of an objective lens 5, an automatic focus control mechanism 6, and a movable reflector 4, which are provided on the lower side by extending the upper arm of the carriage 8, is placed at a symmetrical position on the upper side with the optical disk medium in between. An objective lens 5°, an automatic focus control mechanism 6', and a movable reflector 4'' are installed opposite to the carriage 8, and a swinging mirror 3'' and a fixed optical system 1' are provided on the base 30, so that both sides of the optical disk medium can be It can be used without replacing or reversing.

In this case, there is an increase in the mass of the carriage 8 and an increase in the number of mounted parts, but both are small increases, and since the small access can be easily corrected by controlling the swinging mirror, the influence of the moment of inertia is small.

FIG. 4 shows a block diagram of the applied example of FIG. In the figure,
Reference numeral 50 denotes a switching reflector which is connected to a switching drive unit 51 and can be switched to a position corresponding to the movable reflector 4 or a 4° optical path B or B'. A swinging mirror 3' is interposed between the switching reflector 50 and the fixed optical system 1 to perform minute access control. Note that an optical switch using a magneto-optic effect or the like may be used instead of the switching reflector 50.

〔Effect of the invention〕

As described above in detail, according to the optical disk device of the present invention, minute access in positioning the optical head can be corrected by controlling the oscillating mirror, and as a result, the fine access in the positioning of the optical head can be corrected by controlling the swinging mirror. This has the effect of increasing the number of parts mounted on the carriage and making it possible to record and reproduce data on both sides of the optical disc device.

[Brief explanation of drawings]

Fig. 1 is a perspective view of essential parts of an optical disc device according to the present invention, Fig. 2 is a cross-sectional structural diagram of an oscillating mirror, Fig. 3 is a configuration diagram of a double-sided usage method of an optical disc device, and Fig. 4 is an application of Fig. 3. FIG. 5 shows a perspective view of a conventional optical head positioning mechanism. In the figure, 1 is a fixed optical system, 2 is an optical disk medium, and 3 is a fixed optical system.
is a fixed reflector, 3゛ and 3'' are swinging mirrors, 4 is a movable reflector, 5 is an objective lens, 7 is an optical head, 8 is a carriage,
11 indicates a voice coil motor. Figure 1 t 4+) 1112m Figure 4

Claims (1)

[Claims] a fixed reflecting mirror that reflects the emitted light beam from a fixed optical system having a light source and an information detection function in a direction parallel to the radial direction of the optical disk medium surface; and a movable reflecting mirror that reflects the reflected light vertically to the optical disk medium surface. , a positioning optical system comprising an objective lens that is driven in the radial direction integrally with the movable reflector and focuses the vertically reflected light onto the optical disk medium surface, the mirror surface of the fixed reflector is oscillated; 1. An optical disc device, wherein the positioning optical system is attached so as to be dynamically controllable, and the positioning optical system is provided on at least one side of the optical disc medium.