Slider for optical head

Details Slider for optical head Slider for optical head

1999-09-30

2001-11-20

Klimowicz, William (Department: 2652)

Dynamic information storage or retrieval

Detail of optical slider per se

C369S013010, C369S112040

Reexamination Certificate

active

06320841

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a slider for an optical head used for recording and/or reproducing information signals for a recording medium by exploiting a proximity optical field.
2. Description of the Related Art
For realizing a higher recording density of a recording medium, such as an optical disc, a technique has been proposed in which the proximity optical field is utilized for recording/reproducing the recording medium. In this technique, the numerical aperture NA of the optical system adapted for collecting light on the recording medium in recording/reproduction is adapted to be not less than unity (
1
) by exploiting the proximity optical field. This renders it possible to raise the recording density of the recording medium.
FIG. 1
shows an illustrative slider for an optical head used in recording/reproduction by exploiting the proximity optical field.
A slider for an optical head
100
includes an optical system employing a so-called solid immersion lens. The slider for the optical head
100
includes a slider member
105
, supported by a suspension
103
, a first optical lens
107
and a second optical lens
109
. Both the first and second optical lenses
107
,
109
are mounted on the slider member
105
. When a recording medium
111
, such as an optical disc, is run in rotation, the slider member
105
is uplifted by an air stream flowing between the recording medium
111
and the slider member
106
so as to be floated over the recording medium
111
.
Of the optical lenses, loaded on the slider member
105
, the first optical lens
107
arranged on the light incident side, is of the numerical aperture NA=0.6, while the second optical lens
109
, arranged on the recording medium
111
, is a semi-spherical lens with the refractive index n=2. Thus, an optical system combined from the first optical lens
107
and the second optical lens
108
, is of the numerical aperture NA=1.2, thus achieving the numerical aperture NA>1.
In recording/reproduction, the recording medium
111
is run in rotation to float the slider member
105
to maintain the interval of tens of a nm between the recording medium facing surface of the second optical lens
109
and the recording medium
111
. The recording/reproducing light is caused to fall from the first optical lens
107
so as to be focussed on the recording medium facing surface of the second optical lens
109
. At this time, evanescent light leaks from the recording medium facing surface of the second optical lens
109
. This evanescent light, leaking from the recording medium facing surface of the second optical lens
109
, is coupled to the recording medium
111
. This evanescent light is used for recording/reproduction. Thus, with the numerical aperture NA>1, it becomes possible to use an extremely fine light spot to perform recording/reproduction.
Meanwhile, in order to perform recording/reproduction as described above, the interval between the recording medium facing surface of the second optical lens
109
and the recording medium
111
needs to be sufficiently small as compared to the light wavelength. Thus, in this slider for the optical head
100
, the slider member
105
is used to enable the interval between the recording medium facing surface of the second optical lens
109
and the recording medium
111
to be maintained at a sufficiently small value. There are a large number of prior art techniques for floating the head a minor amount. The slider for the optical head
100
exploits this technique routinely used in the field of hard disc devices.
In the slider for the optical head
100
, shown in
FIG. 1
, the optical axes and the relative distance of the first optical lens
107
and the second optical lens
109
need to be aligned accurately, thus raising the problem of manufacture difficulties.
Also, in the present slider for the optical head
100
, the recording medium facing surface of the second optical lens
109
constitutes a so-called air bearing surface (ABS) along with the recording medium facing surface of the slider member
105
. Thus, with the present slider for the optical head
100
, it is necessary to load the second optical lens
109
on the slider member
105
and to grind the recording medium facing surfaces thereof. However, with the conventional slider for the optical head
100
, the second optical lens
109
and the slider member
105
are formed of different materials, such that it is difficult to grind these members to form the desired ABS surface to a high accuracy.
The recording medium facing surface of the slider member
105
is formed with a pattern of irregularities in order to control the air stream flowing between the slider member
105
and the recording medium
111
to realize stable floating. However, with the slider for the optical head
100
, since the second optical lens
109
is exposed to the recording medium facing surface, the degree of freedom in designing the pattern of irregularities is lowered.
If the recording medium
111
is a magneto-optical disc, a magnetic field is required in recording/reproduction, so that a magnetic coil needs to be arranged in the vicinity of the light focussing point. This magnetic coil needs to be arranged so that the light focussing point will be at the center of the magnetic coil, while the magnetic coil needs to be buried in the slider member
105
so as not to disturb the floating of the slider member
105
. However, since the second optical lens
109
is exposed to the recording medium facing surface, limitations are imposed on the burying position to lower the degree of freedom in designing. Although it may be contemplated to bury the magnetic coil in the second optical lens
109
, it is difficult to bury the magnetic coil in the optical lens, thus increasing the manufacturing cost.
Thus, in the slider for the optical head
100
, the optical axes and the relative distance of the first optical lens
107
and the second optical lens
109
need to be aligned accurately, thus raising manufacture difficulties. Also, the ABS surface is difficult to machine accurately, while the degree of freedom in designing is low. Moreover, limitations are imposed on the arraying position of the magnetic coil to lower the freedom in designing.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a slider for an optical head for recording/reproducing a recording medium by exploiting the proximity optical field in which manufacture is facilitated and the degree of freedom in designing is high.
According to the present invention, there is provided a slider for the optical head including a slider member for running on a recording medium during recording and/or reproduction for the recording medium in a state of being floated over or in a state of being contacted with the recording medium, and an optical lens connected to the slider member. The slider member is connected and optically unified to the optical lens so that the numerical aperture NA of an optical system made up of the slider member and the optical lens is not less than unity. The focal point plane of the light incident from a side of the optical lens is on a recording medium facing surface of the slider member.
At least the portion of the slider member on which falls the light incident from a side of the optical lens preferably has the refractive index not less than that of the optical lens. In the slider for the optical head, the slider member and the optical lens are connected to each other by bonding with an adhesive. The magnitude of the refractive index of the adhesive is preferably not less than the magnitude of the numerical aperture NA of an optical system comprised of the slider member and the optical lens. The optical head may be provided with a magnetic coil buried in the slider member for encircling the position of the focal pint of the light incident from the side of the optical lens. The optical lens used for the slider for the optical head is preferably a catadioptric lens.
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