JPS624909Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a track scanning device such as an optical reproduction device.

2. Description of the Related Art A disc player is known in which a laser beam is used to extract a reproduced signal from a disc on which an audio signal or a video signal is recorded in the form of pits. FIG. 1 is a schematic diagram of a conventional optical system of this type of disk player. On disk 1,
The information is recorded as columns of convex or concave pits along the overwound track. The reproduced signal is generated by converting a beam 2 formed by a laser in the pickup through a galvanometer mirror 3 and a focus lens 4, modulating the reflected light with a phase structure along the track of the disk 1, and converting the reflected light into an electrical signal using a photodiode or the like. obtained by converting.

The galvanometer mirror 3 is provided for the purpose of performing tracking by displacing a spot formed by focusing the beam 2 on the disk 1 in the tracking direction (the normal direction of the track or the radial direction of the disk). . A magnet 5 is attached to the galvano mirror 3, and by supplying a tracking error signal to a fixed coil 6 placed close to the magnet, the galvano mirror 3 rotates around an elastic support member 7 such as rubber. It is swayed.

The focus lens 4 is attached to a cylindrical body 11 that is slidably held by a fixed guide sleeve 10, and this cylindrical body is moved between the surface of the disk 1 and the surface of the disk 1 by a linear motor consisting of a coil 12, a magnet 13, and a yoke 14. Focus errors are corrected by driving in the orthogonal direction (focus direction).

The conventional optical system as shown in FIG. 1 uses a focus linear motor and a galvano mirror to focus and track the beam 2, so it is difficult to make the pickup device compact. Furthermore, it becomes difficult to align the optical axes of each device. Furthermore, since the galvanometer mirror 3 is oscillated to move the beam 2 in the tracking direction, the laser beam enters the focus lens 4 at an angle, so an expensive lens with extensive correction for off-axis aberrations is required. There is a problem.

The present invention provides an optical track scanning device that overcomes the above-mentioned problems.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a side view of the optical track scanning device according to the present invention, FIG. 3 is a plan view, and FIG. 4 is a side view of the lens holder (bobbin).

The focus lens 4 is attached to the center of a substantially rectangular parallelepiped lens holder 20. This lens holder 20 is made of a non-magnetic material, and has a hole formed along the optical axis of the focus lens 4 through which the laser beam passes. Further, a pair of holes 22a, 22b with a rectangular cross section are formed parallel to the optical axis, into which a pair of fixed yokes 21a, 21b are inserted. These holes 22a, 22b have E-shaped yokes 21a, 21b.
The central yoke pieces 23a and 23b of each of the holes are inserted through the hole without contacting the inner wall thereof.

A focus coil 25 is wound around the outer peripheral surface of the lens holder 20, as shown in FIG.
Lens holder 20 around which coils 24 and 25 are wound
is supported by a rising portion of an L-shaped base 27 via a pair of upper and lower relay plates 26a and 26b. Both end surfaces of these relay plates 26a, 26b are connected to the lens holder 2 via rubber 28a, 28b having a T-shaped cross section.
0 and the base 27 by adhesive or the like. Therefore, the lens holder 20 is moved in the direction of arrow A in FIG.
It is supported by the base 27 in a state where it can swing in the direction (focusing direction) and in the direction of arrow B in FIG. 3 (tracking direction). Note that butyl rubber or the like can be used as the rubbers 28a and 28b, and silicone rubber is preferably used when temperature characteristics are taken into consideration.

A pair of magnets 30a, 3 are attached to the tips of the yoke pieces on both sides of the E-shaped yokes 21a, 21b.
0b is fixed, and these magnets 30a, 3
The magnetic flux generated from 0b is transferred to the focus coil 24
It passes through the tracking coil 25 in the horizontal direction and is absorbed by the yoke pieces 23a and 23b. The focus coil 24 is wound so as to surround the optical axis as shown in FIG. is displaced in the optical axis direction (focus direction shown in the direction of arrow A). Further, the tracking coil 25 has a coil portion parallel to the optical axis, and the lens holder 20 is displaced in the tracking direction perpendicular to the optical axis by the driving force generated by the driving current and interlinking magnetic flux.

Note that it is desirable that the center of the driving point by the magnetic circuit coincide with the center of gravity of the lens holder 20.
This makes it possible to prevent the relay plates 26a and 26b from twisting, and it is possible to displace the focus lens 4 in the tracking direction while keeping it substantially horizontal. Furthermore, by driving the center of gravity position, displacement sensitivity can be improved.

The displacement of the lens holder 20 in the tracking direction is arcuate as shown by arrow B in FIG.
Since the displacement required for tracking is several μm, there is no problem even if the displacement is not linear. On the other hand, the displacement of the lens holder 20 in the focus direction is a substantially linear gap because the pair of relay plates 26a and 26b are disposed above and below. The quadrilateral formed by the lens holder 20, relay plates 26a, 26b, and base 27 as shown in FIG. 2 is deformed like a parallelogram, and the lens holder 20 is linear in the direction of arrow A. Displaced to. At this time, the optical axis of the focus lens 4 is kept perpendicular to the disk surface.

The mechanical neutral point in the tracking direction can be set by attaching a magnet 31 as shown in FIG. 3 to the lens holder 20. Due to the repulsive force between this magnet 31 and a pair of magnets 30a of the magnetic circuit fixed in the vicinity thereof, the lens holder 20 is fixed at a substantially mechanical neutral position without being biased. According to this structure,
Even if the characteristics of the rubbers 28a and 28b change over time or have hysteresis characteristics, they can be used with the influence reduced.

According to the above embodiment, the pair of relay plates 26a,
26b and the rubbers 28a, 28b alone can achieve free displacement in the focusing direction and the tracking direction, so the structure is extremely simple and can be manufactured at low cost. Furthermore, since the focus servo and tracking servo devices are integrated into one device, the optical scanning system can be downsized and the optical path arrangement of the optical system can be simplified. Furthermore, since the laser beam 2 is not incident on the focus lens 4 at an angle by tracking with the galvanometer mirror 3 as shown in Fig. 1, the focus lens 4 only has aberrations near its optical axis. Therefore, it is possible to reduce the number of lens components and use lower-priced lenses.

Further, since a support method using plate springs is not used, problems of inherent mutual erosion and multiple resonance due to plate springs do not occur, and more precise and stable position control can be performed.

In the above embodiment, the lens holder 20 is displaced in the tracking direction (direction perpendicular to the track), but it may also be displaced in a direction along the track to correct jitter (time axis fluctuation component) of the reproduced signal.

Further, in the embodiment, each relay plate 26a, 26
Although support portions of rubber 28a and 28b are provided at both ends of each of b, only one rubber (for example, rubber 28b on the base 27 side) may be provided.

As described above, the present invention has a support plate (relay plate 26 in the embodiment) parallel to the scanning surface of the disk-shaped recording medium.
The lens holder 20 is supported on the base body (base 27) via a flexible coupling member such as a, 26b) and rubber (rubber 28a, 28b in the embodiment), and The lens holder can be moved. Therefore, the position control structure for the lens in the focusing direction (the above-mentioned orthogonal direction) and the tracking direction (the above-mentioned parallel direction) can be integrated into one structure, and the structure is simple and the optical system can be made more compact. In addition, since it does not use a tracking galvanometer mirror like in the past, the laser beam incident on the objective lens (focus lens) is not tilted, which simplifies the aberration correction of the objective lens and allows for a lower-priced lens system. can be used. Furthermore, there is no problem of supplementary resonance that occurs when a variable displacement support means such as a leaf spring is used, and more precise and stable track scanning control can be performed. In addition, since the optical axis of the lens is one side of a parallelogram using a pair of support plates, the lens does not wobble when controlling the position in the focus direction, making it possible to perform extremely stable control. .

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a conventionally known optical system of a disk planer to which the present invention is applied, Fig. 2 is a side view of an optical track scanning device according to the present invention, and Fig. 3 is a plan view. , FIG. 4 is a side view of the lens holder (bobbin). In addition, in the symbols used in the drawings, 4
... Focus lens, 20 ... Lens holder,
21a, 21b... Yoke, 24... Focus coil, 25... Tracking coil, 26a,
26b... Relay plate, 27... Base, 28a, 2
8b...Rubber, 30a, 30b...Magnet,
It is.

Claims (1)

[Scope of utility model registration request] A lens holder that holds a lens that guides a scanning beam to a track of a disk-shaped recording medium to be scanned for recording or reproduction; a flexible connecting member such as rubber that connects each of the pair of support plates to one or both of the base body or the lens holder, and the lens holder is connected to the recorder. An optical track scanning device comprising electromagnetic drive means provided across both the lens holder and the base body for displacing the medium in a direction perpendicular to and parallel to the scanning plane.