JPH02101644A - Rotary scanning type optical head device - Google Patents

Abstract

PURPOSE:To attain power saving and the miniaturization of an optical head device by arranging a movable part required for focusing control and tracking control, etc., in the neighborhood of the center axis of the rotation of a rotary drum. CONSTITUTION:The focusing control can be attained by performing the moving control of a collimation lens L1 in a direction of (b) by a driving circuit 20 based on a signal supplied from a focusing servo circuit, and the tracking control can be attained by performing the conversion of the angle of a polarizing beam splitter BS in a direction of (c) by a driving circuit 21 based on the signal supplied from a tracking servo circuit. At this time, since the conversion of the positions or the angles of the collimation lens L1 and the polarizing beam splitter BS are performed almost in the center axis a-a' of the rotation, it is enough to prepare driving devices provided ordinary driving forces as the driving devices 20 and 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical recording/reproducing device using an optical tape as a recording medium, and particularly to a rotary scanning type optical head device.

[Summary of the Invention] In the rotary scanning optical head device of the present invention, a movable part for focus control, tracking control, etc., which is necessary in an optical head device mounted in a rotary drum, is connected to the central axis of rotation of the rotary drum. By placing the movable part in the vicinity of the rotation center axis of the rotating drum,
The centrifugal force accompanying the rotation of the rotating drum, which affects the operation of the movable part, can be reduced.

[Prior art] With the development of technology that uses optical tape as an optical recording medium,
An optical head device is mounted inside the rotating drum, and in particular, as is known as the helical scan method, an optical tape is spirally wound around the rotating drum at a predetermined angle and run, and the rotating drum is rotated. and scan the
Techniques for recording or reproducing are being developed.

An example of a device in which an optical head device is mounted within a rotating drum is disclosed in Japanese Patent Application Laid-Open No. 62-205550.

Such a conventional optical head device mounted in a rotating drum will be described by taking as an example a two-light source, 180-degree opposed head type shown in FIG.

The optical head device shown in FIG. 4 has laser diodes IA and IB installed in a rotating drum D at symmetrical positions and separated from each other at a predetermined interval.
A total reflection prism 2 is installed at an intermediate position. In the beam traveling direction from this total reflection prism 2, collimation lenses 3A, 3B, cratings 4A, 4B, polarizing beam splitters 5A, 5B, 1/
Four wavelength plates 6A, 6B and objective lenses 7A, 7B are provided. The recording or reproducing beams emitted from the laser diodes IA and IB pass through each of the above optical systems and are emitted from the exit ports 8A and 8B to the outside of the rotating drum D, forming a spiral around the rotating drum D in a range of about 180 degrees. The optical tape reaches the optical tape T which is being wound in a shape and is running, and records signals or reads signals recorded on the optical tape.

Further, the reflected light from the optical tape T, which becomes a reproduction signal or a focus and tracking control signal, is transmitted to the objective lens 7.
The light reaches the light receiving lenses 9A, 9B via the light beams A, 7B, the quarter-wave plates 6A, 6B, and the polarizing beam blocks 5A, 5B, and is further irradiated onto the detectors IOA, IOB to be detected. And the outputs of detectors IOA and IOB are
The signal is supplied to a reproduced signal processing circuit and each servo circuit (not shown).

For example, two units of optical heads are configured in the rotating drum D in this way, and as the optical tape T runs, recording or reproducing beams are sequentially emitted from the laser diodes 1A and 1B every 1/2 rotation of the rotating drum D. By emitting the light, a helical scan type optical head device can be achieved.

[Problems to be solved by the invention] By the way, in such a conventional optical head device, the fourth
As shown by 11A and 11B in the figure, objective lenses 8A and 8
A portion B is provided with focus and tracking servo control means using a two-axis mechanism or the like, and focus servo and tracking servo are executed by controlling the movement or angle of the objective lenses 8A and 8B.

However, as a rotary optical head device, the servo control means (actuators) 11A, IIB
If, for example, the objective lenses 8A and 8B are configured to be provided at a position away from the center of rotation and the movement of the objective lenses 8A and 8B is controlled as described above, the following problems will occur.

In other words, as the drum D rotates at a high speed, a fairly strong centrifugal force acts on the outer circumference of the drum D (for example, if the drum diameter is 75φ and the rotation speed is 3600 rpm, the
500G), therefore, the actuator is of a type that uses a voice coil to control the movement of movable parts such as the objective lens by electromagnetic force generated by the current supplied to the coil. , normal,
Even if it has sufficient performance for use in an optical head device other than a rotary scanning type, the
When loaded, it is recognized that the power is insufficient against the centrifugal force,
It was difficult to make the movable part of the actuator 11 operate normally. Therefore, the actuator is required to have a sufficiently strong driving force (the power of the actuator is approximately +30G greater than the centrifugal force in the part where it is placed), and for this reason, the actuator is quite expensive. There is a problem in that a large optical head is required, which causes an increase in cost, and that the optical head is also forced to be larger and, furthermore, power consumption increases.

In addition, in order to achieve high-density recording and high-speed recording and reproduction, it is desirable to further increase the rotational speed of the rotary drum D (for example, 500 (about 1 to 6000 rpm)), but in such a high-speed rotation state In this case, the centrifugal force becomes even larger, and the actuator that can be mounted on the optical head inside the rotating drum has the problem that it cannot operate properly as a servo mechanism, which is a major obstacle to increasing the rotation speed. It has become.

[Means for Solving the Problems] The present invention has been made in view of the above problems, and the present invention rotates a movable part whose movement is controlled by a drive mechanism such as a servo means using a two-axis actuator. It is arranged in the vicinity of the rotation center axis within the drum.

[Function] By locating the movable part in the vicinity of the rotation center axis of the rotary drum, the strong centrifugal force accompanying the high-speed rotation of the rotary drum will hardly affect changes in the position, angle, etc. of the movable part. It disappears.

[Embodiment] FIG. 1 is a side sectional view of a rotating drum showing an embodiment of the present invention, and schematically shows an internal optical system. Note that this rotating drum D is represented by a dotted chain in the figure) S a - a
The optical tape T rotates around the rotating drum D as the central axis of rotation, and when the optical tape T is loaded, it is wound around the rotating drum D at a predetermined angle and runs.

Inside the rotary drum D, a laser diode LD, a collimation lens L + , a crating G, and a polarizing beam block BS are arranged as an optical head device on the rotation center axis a-a°, and furthermore, in the beam traveling direction, l /
A four-wavelength iQ and an objective lens L2 are provided, and a light receiving lens L3, a cylindrical lens L4, and a detector PD are provided in the traveling direction of the reflected light from the optical tape T, and the above arrangement constitutes a recording/reproducing optical system. There is.

In this embodiment, the objective lens L2 is fixed, and by configuring the collimation lens L1 and the polarizing beam splitter BS as movable parts, focus control is performed in the collimation lens L1, and tracking control is performed in the polarizing beam splitter BS. It has been made possible to do so.

That is, focus control is performed by the driving means 20 based on a signal supplied from a focus servo circuit (not shown).
The tracking control is achieved by controlling the movement of the collimation lens L in the direction indicated in the figure, and further, the driving means 21 adjusts the angle of the polarizing beam splitter BS based on a signal supplied from a tracking servo circuit (not shown). This is achieved by shifting in the middle C direction.

At this time, the positions or angles of the collimation lens L and the polarizing beam splitter BS are not influenced by centrifugal force because they are performed on the rotation center axis a-a°, and the driving means 20.21 For this reason, one with normal driving force is sufficient, but one with high power is necessary.

In this embodiment, the driving means 20 is configured as a two-axis actuator, and the collimation lens L is
By allowing directional movement as well as angular movement in the d direction, both focus and tracking can be controlled using only the collimation lens L.

FIG. 2 shows another embodiment of the present invention. In this embodiment, only the collimation lens L1 is arranged on the rotation center axis a-a°, and therefore the movable part is the collimation lens L1. By using only the lens L1, configuring the driving means 20 by a two-axis actuator, and controlling both focus and tracking only with the collimation lens L1, the influence of centrifugal force on each servo operation can be eliminated.

FIG. 3 shows still another embodiment, in which an optical head device with 180-degree opposed heads using two light sources is mounted on a rotating drum D.

In this example, a laser diode LD, a collimation lens L1, a grating G, and a laser diode LD make up a first optical system.
', a collimation lens L1' and a grating G° are arranged on the rotational center axis a-a', and a total reflection prism is placed between the first and second optical systems on the rotational center axis a-a'. P is arranged. Then, changing beam splitters BS and BS' are installed in the beam traveling direction in the first and second optical systems, respectively.
, quarter wavelength plates Q, Q', objective lenses L2, L2°,
Light receiving lenses L8, L3°, cylindrical lenses L, . . . L4, and detectors PD, PD' are arranged in the traveling direction of the reflected light from the optical tape T, forming a two-unit recording/reproducing optical system.

In this embodiment, the movable parts for each servo control are collimation lenses L1, Llo, and total reflection prism P, and the collimation lens L is controlled by driving means 20 and 20.

Focus servo is achieved by controlling the position of Llo, and tracking control is achieved by controlling the angle of the total reflection prism P using the driving means 21, 21'.

In addition, when tracking control is performed using the total reflection prism P, the total reflection prism P is formed by dividing it into 21 parts and 25 parts, so that the angle change can be controlled independently for tracking control of each optical system. Alternatively, in the case of a recording/reproducing system in which each optical system is sequentially used every 1/2 revolution of the rotating drum D, beams are not emitted from both laser diodes LD and LD' at the same time. Therefore, the angle shift for tracking control of each optical system may be sequentially performed every 1/2 revolution of the rotary drum D, without having to divide the optical system into 21 parts and a P part.

Further, as in the embodiment shown in FIG. 1, by employing a two-axis actuator for the driving means 20.20', it is also possible to perform not only focus control but also tracking control in the collimation lenses L1 and L1'.

As shown in the embodiments shown in FIGS. 1 to 3 above, the movable part whose position or angle is changed in order to perform focus servo and tracking servo is connected to the rotation center axis a-a of the rotary drum D. In other words, by making the component placed on the central axis of rotation a-a' a movable part, the movable part will not be centrifugal even if the rotary drum D rotates at high speed. It is hardly affected by force (therefore, there is no need for a large output drive means such as an actuator to drive the movable part).

Furthermore, there is no problem in reducing the size of the rotating head and increasing the rotational speed, and as a result, it becomes possible to provide a rotating head that can achieve high-speed and high-density recording. It is something.

In addition, the optical system alignment and the shape of the rotating drum, etc.
It goes without saying that various embodiments other than those shown in the embodiments are conceivable as long as the movable part is disposed in the vicinity of the rotation center axis.

[Effects of the Invention] As explained above, in the rotary scanning optical head device of the present invention, the movable parts necessary for the optical head device for, for example, focus control, tracking control, etc. are located in the vicinity of the rotation center axis of the rotary drum. Since the movable parts are arranged in the same direction, the movable parts are hardly affected by the centrifugal force caused by the rotation of the rotary drum, and therefore the driving means for driving the movable parts does not need to have a large output (this also reduces power consumption). This has the effect of reducing the size and cost of the optical head device, and furthermore, even if the rotating drum rotates at a higher than normal speed, the movable part can easily maintain normal operation. This has a very excellent effect in that it is possible to realize an optical head device that can be used.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a sectional view showing another embodiment of the invention, FIG. 3 is a sectional view showing still another embodiment of the invention, and FIG. The figure is a partially cutaway view showing a conventional rotary scanning optical head device. 20.21 is a driving means, LD is a laser diode, Ll
is a collimation lens, L2 is an objective lens, L3 is a light receiving lens, L is a cylindrical lens, G is a grating, BS is a polarizing beam splitter, Q is a quarter wavelength, PD is a detector, P is a total reflection prism, and D is a total reflection prism. Rotating drum, T is optical tape. Procedural amendment 1゛) (I″1 shot)

Claims (1)

[Claims] An optical tape is wound at a predetermined angle around a rotating drum equipped with an optical head device, and data is recorded on the optical tape or data recorded on the optical tape is played back by rotating and scanning the optical tape as it runs. A rotary scanning type optical head device capable of providing a rotary scanning type optical head device, characterized in that a movable part necessary for focus control, tracking control, etc. in the optical head device is arranged in the vicinity of the rotation center axis of the rotary drum. Optical head device.