JPS58177533A - Reader for information track - Google Patents

Abstract

PURPOSE:To obtain capacity necessary for tracking in an electromagnet method as a moving means by fitting a magnetic ring around an objective opposite to a fixed magnet which operates the objective. CONSTITUTION:A couple of leaf springs 19 and 20 are arranged opposite to the optical axis of the objective 16 and one of those leaf springs is weighted to prevent resonance and buckling which may occur during the tracking or focusing of the objective 16. In concrete, the leaf spring 19 is made a little bit thicker than the other leaf spring 20. In another way, one of the leaf springs 19 and 20 is made different in plate thickness, shape, material from the other plate material in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for reading information by projecting a profile light spot onto an information track recorded on a recording medium in a spiral manner or concentrically. This type of information reading apparatus is well known. be.

A recording medium having an information track is, for example, called a video disk, and encoded video signals and audio signals are recorded as optical information such as optical transmission characteristics, reflection characteristics, and phase characteristics.

While the video disc is rotating at high speed, laser light emitted from a laser light source is focused and projected onto the video disc to read optical information.

Such recording media are characterized by a very high information density, so that the width of each information track is very narrow and the spacing between successive information tracks is also very narrow. Therefore, the diameter of the reading light spot is also extremely small.

In order to accurately read the original information from an information track with such a narrow width and pitch, it is necessary to minimize the deviation in the relative position between the reading light spot and the information track, that is, the tracking error. To this end, tracking control has traditionally been performed to detect the relative positional deviation between the reading light spot and the information track, and to displace the reading light spot in the width direction of the information track based on this tracking error signal. There is a method of displacing the optical axis of the objective lens in a direction perpendicular to the information trunk based on the tracking margin (M) by means of an elastic member supported by the objective lens.

In this method, a thin plate-shaped elastic member is generally used for supporting the objective lens.

In this way, as a driving device using an elastic member not supported by the objective lens, there are a method using an electromagnet, a method using a piezoelectric element, and the like.

However, in order to improve the tracking response characteristics, it is necessary to make the lens as large as possible and as lightweight as possible.

In the device, in addition to such a tracking difference, there is also a 7-occurring difference in which the light spot is not correctly focused on the information track, and in order to correct this 7-occurring error, it is necessary to displace the sealed tube lens in the direction of its optical axis. A 7-force force means is also required. Generally, the tracking mechanism is placed above the 7-focusing mechanism from a functional standpoint, so the tracking mechanism needs to be small and lightweight in order to perform the 7-focusing correction well. It can be said that the above-mentioned electromagnetic method as a moving means can obtain the force necessary for tracking, and is also suitable for being small and lightweight.

Therefore, the present invention can obtain the power required for tracking using the electromagnetic method as a moving means required for this type of information track reading device, and can also more appropriately obtain the function and effect suitable for weight reduction in type I). The purpose of this product is to provide an information track reading device that uses a light spot to read information on a disk. The present invention is constructed by fitting magnetic rings arranged opposite each other to the lens frame of the objective lens.

The structure of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and is a front view with half of the plane in longitudinal section.

FIG. 2 is a schematic plan view showing the top surface of FIG. 1.

FIG. 3 is an enlarged sectional rkJ diagram of the cost part of the present invention.

A ring-shaped permanent magnet 2 fixed to the outer frame 1 and a ring-shaped yoke 3.4 are integrally constructed. A fill holding cylinder 6 is disposed inside the yoke 3.4, and its base end 6& is a cylindrical holding part 7 in which an elastic member, that is, a leaf spring 19, which will be described later, is installed.
It is fitted and installed. Further, a movable filter 8 is wound around the outer part of the fill holding cylinder 6 and faces the permanent magnet 2. The upwardly extending end s6b of this coil holding cylinder 6 holds a #lh coiled spring 9 whose periphery is held by a spacer 11 disposed within the outer frame 1. Further, the inner periphery of a spiral spring 10 formed in a circular shape is held on the outer periphery of the proximal end 6& which is fitted and attached to the holding member 7, and the outer periphery is held by a spacer 12 disposed within the outer frame 1. ing.

Above the spiral spring 9, a holding frame 13 is mounted, and a fixed image 14 and a fixed magnet 15 are integrally mounted thereon. A fixed coil 17 for driving an objective lens 16 is wound around the fixed imager 14. The objective lens 16 is integrally fixed to the lens frame 18, and the fixed magnet 1 is attached to the outer periphery of the objective lens 16.
The tips of a pair of leaf springs 19 and 20 are arranged at intervals between the outer ring of the mirror frame 18 and the inner periphery of the magnetic ring 1121, on which a ring-shaped magnetic ring 21 is fitted and mounted opposite to the ring-shaped magnetic ring 21. The insert is stuck.

Therefore, in the information track reading device having the above-mentioned configuration, by supplying the 7 force signal to the coil 8, the objective lens 16 can be displaced in the optical axis direction by the action of the spiral spring 9.10. can.

In addition, by supplying a tracking signal to the coil IT, 17', the plate spring 19.20 is actuated to move the objective lens 16 in the direction of the arrow (shown in FIG. 2), that is, orthogonal to the optical axis of the objective lens 16. It can be displaced in the direction of

However, when the rice spring 19.20tt swings the objective lens 16 in a direction perpendicular to the optical axis, a harmful resonance effect occurs.

Therefore, in conventional devices of this type, in order to prevent the occurrence of this resonance effect, damping of this vibration was performed using a magnetic fluid, but the characteristics of the magnetic fluid are accompanied by temperature changes, and the amount of damping is not sufficient, so it is not possible to use the best method. No damping effect could be expected.

In addition, when the leaf springs 19 and 20 are displaced in the 7-occurring direction, that is, in the optical axis direction at high speed, if the plate springs 19 and 20 are of the same thickness as in the past, the plate thickness is extremely thin, so a buckling phenomenon easily occurs, and the 7-occurring signal and the objective Disturbances were likely to occur in the mutual characteristics with the amount of displacement of the lens 16.

The biggest cause of such defects is that the leaf springs 19.20 constituting the elastic member of the objective lens 16 described above are constructed with the same structural requirements, and the leaf springs 19.20 are made of the same thickness. When configured, the We lens 16 can be used for tracking or 7
It was found that resonance and buckling phenomena occur during excavation.

Therefore, as described above, by weighting one of the pair of leaf springs 19 and 20 disposed opposite to the optical axis of the objective lens 16, the tracking of the objective lens 16 or the The structure is such that resonance and buckling phenomena that occur during excavation can be prevented.

As a specific example, the leaf spring 1
This is done by making the plate thickness of leaf spring 9 slightly thicker than that of the other leaf spring 20, for example, 0.02 mm.
: 0.03 proverb, 0.03m : 0.04m, 0.
04m I O, 05mm or 0.02m + 0
．． 04m5+, 0.025 m, s O, 035mm
The thickness of one of the leaf springs 19 and 20 can be changed with respect to the other (for example, one leaf spring can be made of a multi-layered material). By changing the shape, etc.) or by changing the shape, it is possible to make both leaf springs 1
9.20 can be implemented by mutually changing the materials, and by appropriately combining the conditions such as plate thickness, wall thickness, shape, and material, and within the scope of other aspects that do not depart from the idea of this invention. It is possible to obtain the desired effect by making various changes.

Although no specific example was given for the case where the elastic member is composed of three or more elastic members, in that case, any one of the plurality of elastic members or a plurality of elastic members may be used. By selecting and weighting the members, it is possible to achieve similar effects.

Therefore, by weighting one of the elastic members of the pair of elastic members disposed opposite to the optical axis of the objective lens, the tracking of the objective lens and the force-singing action can be performed reliably. It is.

Since the leaf spring 19 is thicker than the leaf spring 20 used, it is strong and prevents buckling, so the other leaf spring 20 is supported by the leaf spring 19 and does not buckle. In the tracking action, the leaf spring 20 is supported by the leaf spring 19 in the same manner as the upper part 1, and no resonance occurs, so that a reliable action is performed.

Now, with regard to the leaf springs 19 and 20 in the information track reading device of the present invention described above, the above-mentioned effects can be particularly obtained, but in addition, as is clear from the above embodiments, the objective lens In adopting the electromagnetic method in this Kaede information track reading device, the magnetic llA 21, which is disposed opposite to the fixed magnet 15 that operates the 16, is fitted into the lens frame 18 of the objective lens 16. In addition to being able to achieve the effect of being compact and lightweight by incorporating all configurations, the desired effect of the electromagnetic method can be very appropriately achieved.

[Brief explanation of drawings]

Fig. 1 is a front view of an embodiment of the present invention with the other side vertically 1, and Fig. 2 is 1b! A schematic plan view rk1 showing the top surface of J and FIG. 3 are enlarged sectional views of essential parts of the present invention. 1... Outer frame 2... Permanent magnet 3.4... Gasket 6... Coil holding cylinder T... Holding member 8... Moving coil 9.10... Spiral spring 11. 12--Fist spacer- 13...Yoke holding frame 14...Fixed cylinder 15...Fixed magnet 16...Objective lens 17...Fixed coil 18...Mirror frame 19.20...・Plate spring 21... Magnetic ring patent applicant Olympus Optical Industry Co., Ltd. Figure 1 112 Figure 11315! I

Claims (1)

[Claims] (1) An information track reading device that reads information on a disk using a light spot, which is constructed by fitting a magnetic ring placed opposite a fixed magnet that operates an objective lens into the lens frame of the objective lens. An information track reading device characterized by: